US20080045009A1 - Method and apparatus for simultaneously removing multiple conductive materials from microelectronic substrates - Google Patents

Abstract

A method and apparatus for simultaneously removing conductive materials from a microelectronic substrate. A method in accordance with one embodiment of the invention includes contacting a surface of a microelectronic substrate with an electrolytic liquid, the microelectronic substrate having first and second different conductive materials. The method can further include controlling a difference between a first open circuit potential of the first conducive material and a second open circuit potential of the second conductive material by selecting a pH of the electrolytic liquid. The method can further include simultaneously removing at least portions of the first and second conductive materials by passing a varying electrical signal through the electrolytic liquid and the conductive materials. Accordingly, the effects of galvanic interactions between the two conductive materials can be reduced and/or eliminated.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is related to the following pending U.S. patent applications, all of which are incorporated herein by reference: Ser. No. 09/651,779 (Attorney Docket 10829.8515US), filed Aug. 30, 2000; Ser. No. 09/651,808 (Client Docket 00-0036), filed Aug. 30, 2000; Ser. No. 09/653,392 (Client Docket 00-0130), filed Aug. 31, 2000; Ser. No. 09/888,084 (Attorney Docket 10829.8515US01), filed Jun. 21, 2001; Ser. No. 09/887,767 (Attorney Docket 10829.8515US02), filed Jun. 21, 2001; and Ser. No. 09/888,002 (Attorney Docket 10829.8515US03) filed Jun. 21, 2001. Also incorporated herein by reference are the following U.S. patent applications filed simultaneously herewith: 10/______ (Attorney Docket 10829.8515US06); 10/______ (Attorney Docket 10829.8515US07); 10/______ (Attorney Docket 10829.8515US08); 10/______ (Attorney Docket 10829.8672); and 10/______ (Attorney Docket 10829.8673).
TECHNICAL FIELD
• The present disclosure is directed toward methods and apparatuses for simultaneously removing multiple conductive materials from microelectronic substrates.
BACKGROUND
• Microelectronic substrates and substrate assemblies typically include a semiconductor material having features, such as memory cells, that are linked with conductive lines. The conductive lines can be formed by first forming trenches or other recesses in the semiconductor material and then overlaying a conductive material (such as a metal) in the trenches. The conductive material is then selectively removed to leave conductive lines or vias extending from one feature in the semiconductor material to another.
• FIG. 1 is a partially schematic illustration of a portion of amicroelectronic substrate10 having a conductive line formed in accordance with the prior art. Themicroelectronic substrate10 includes an aperture or recess16 in anoxide material13. Abarrier layer14, formed from materials such as tantalum or tantalum compounds, is disposed on themicroelectronic substrate10 and in theaperture16. Aconductive material15, such as copper, is then disposed on thebarrier layer14. Thebarrier layer14 can prevent copper atoms from migrating into the surroundingoxide13.
• In a typical existing process, two separate chemical-mechanical planarization (CMP) steps are used to remove the excess portions of theconductive material15 and thebarrier layer14 from themicroelectronic substrate10. In one step, a first slurry and polishing pad are used to remove theconductive material15 overlying thebarrier layer14 external to theaperture16, thus exposing thebarrier layer14. In a separate step, a second slurry and a second polishing pad are then used to remove the barrier layer14 (and the remaining conductive material15) external to theaperture16. The resultingconductive line8 includes theconductive material15 surrounded by a lining formed by thebarrier layer14.
• One drawback with the foregoing process is that high downforces are typically required to remove copper and tantalum from themicroelectronic substrate10. High downforces can cause other portions of themicroelectronic substrate10 to become dished or eroded, and/or can smear structures in other parts of themicroelectronic substrate10. A further drawback is that high downforces typically are not compatible with soft substrate materials. However, it is often desirable to use soft materials, such as ultra low dielectric materials, around the conductive features to reduce and/or eliminate electrical coupling between these features.
SUMMARY
• The present invention is directed toward methods and apparatuses for simultaneously removing multiple conductive materials from a microelectronic substrate. A method in accordance with one aspect of the invention includes contacting a surface of a microelectronic substrate with an electrolytic liquid, the microelectronic substrate having a first conductive material and a second conductive material different than the first. The method can still further include controlling an absolute value of a difference between a first open circuit potential of the first conductive material and a second open circuit potential of the second conductive material by selecting a pH of the electrolytic liquid. The method can further include simultaneously removing at least portions of the first and second conductive materials by passing a varying electrical signal through the electrolytic liquid and the conductive materials while the electrolytic liquid contacts the microelectronic substrate.
• In a further aspect of the invention, wherein the first conductive material includes tungsten and the second conductive material includes copper, the method can include controlling an absolute value of a difference between the first open circuit potential and the second open circuit potential to be about 0.50 volts or less by selecting the pH of the electrolytic liquid to be from about 2 to about 5. The conductive materials can be removed simultaneously by passing an electrical signal from a first electrode spaced apart from the microelectronic substrate, through the electrolytic liquid to the first and second conductive materials and from the first and second conductive materials through the electrolytic liquid to a second electrode spaced apart from the first electrode and spaced apart from the microelectronic substrate.
• A method in accordance with another aspect of the invention includes providing a microelectronic substrate having a first conductive material and a second conductive material different than the first. The method can further include disposing on the microelectronic substrate an electrolytic liquid having a pH that controls a difference between a first open circuit potential of the first conductive material and a second open circuit potential on the second conductive material. The method can further include simultaneously removing at least portions of the first and second conductive materials by passing a variable electrical signal through the electrolytic liquid and the conductive materials while the electrolytic liquid contacts the microelectronic substrate.
• An electrolytic liquid in accordance with another embodiment of the invention can include a liquid carrier and an electrolyte disposed in the liquid carrier. The electrolyte can be configured to transmit electrical signals from an electrode to the first and second conductive materials of the microelectronic substrate. A pH of the electrolytic liquid can be from about 2 to about 5.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a partially schematic, cross-sectional view of a portion of a microelectronic substrate having multiple conductive materials processed in accordance with the prior art.
• FIGS. 2A-2C are partially schematic, cross-sectional illustrations of a portion of a microelectronic substrate having multiple conductive materials processed in accordance with an embodiment of the invention.
• FIG. 3 is a partially schematic, cross-sectional view of a portion of a microelectronic substrate having multiple conductive materials processed in accordance with another embodiment of the invention.
• FIG. 4 is a partially schematic illustration of an apparatus for electrolytically removing conductive materials from a microelectronic substrate in accordance with an embodiment of the invention.
• FIG. 5 is a partially schematic illustration of an apparatus for electrolytically removing conductive materials from a microelectronic substrate in accordance with another embodiment of the invention.
• FIG. 6 is a partially schematic illustration of an apparatus for electrolytically, chemically-mechanically and/or electrochemically-mechanically removing conductive material from a microelectronic substrate in accordance with still another embodiment of the invention.
• FIG. 7 is a partially schematic, isometric view of a portion of an embodiment of the apparatus shown inFIG. 6.
• FIG. 8 is a partially schematic, isometric illustration of a portion of an apparatus for removing conductive material from a microelectronic substrate in accordance with yet another embodiment of the invention.
• FIG. 9 is a schematic illustration of a waveform for electrolytically processing a microelectronic substrate in accordance with still another embodiment of the invention.
DETAILED DESCRIPTION
• The present disclosure describes methods and apparatuses for removing conductive materials from a microelectronic substrate. The term “microelectronic substrate” is used throughout to include a substrate upon which and/or in which microelectronic circuits or components, data storage elements or layers, and/or micro-mechanical elements are fabricated. Features in the substrate can include submicron features (having submicron dimensions ranging from, for example, 0.1 micron to 0.75 micron) such as trenches, vias, lines and holes. It will be appreciated that several of the details set forth below are provided to describe the following embodiments in a manner sufficient to enable a person skilled in the relevant art to make and use the disclosed embodiments. Several of the details and advantages described below, however, may not be necessary to practice certain embodiments of the invention. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect toFIG. 2A-9.
• One approach for addressing some of the drawbacks described above with reference toFIG. 1 is to remove conductive materials from the microelectronic substrate with electrolytic processes. Accordingly, a voltage is applied to the conductive material in the presence of an electrolytic liquid to remove the conductive material. However, many existing electrolytic liquids cannot simultaneously remove copper and tantalum, once the tantalum barrier layer has been exposed. Accordingly, chemical-mechanical planarization (CMP) techniques are typically used to remove the exposed tantalum barrier layer and the adjacent copper material. However, this approach typically re-introduces the high downforces that the initial electrolytic process was intended to avoid. Accordingly, another approach has been to replace the tantalum barrier layer with a tungsten barrier layer. However, tungsten (and tungsten compounds) typically form a galvanic couple with copper, which results in one or the other of these materials corroding and dissolving at an uncontrolled rate. The following disclosure describes methods and apparatuses for overcoming this drawback.
• FIG. 2A is a partially schematic, cross-sectional side view of amicroelectronic substrate210 prior to electrolytic processing in accordance with an embodiment of the invention. In one aspect of this embodiment, themicroelectronic substrate210 includes asubstrate material213, such as an oxide or a low dielectric constant material. Thesubstrate material213 includes asubstrate material surface217 having anaperture216 formed by conventional processes, such as selective etch processes. A firstconductive material218 is disposed on thesubstrate material213 and can form abarrier layer214 along the walls of theaperture216. A secondconductive material209, such as a blanket fill material, can be disposed on the firstconductive material218 to form afill layer219. In one embodiment, the firstconductive material218 can include tungsten (W) or a tungsten compound, such as tungsten nitride (WN_x), and the secondconductive material209 can include copper or copper alloys such as alloys that include at least 50% copper. In other embodiments, these conductive materials can include other elements or compounds. In any of these embodiments, the firstconductive material218 and the secondconductive material209 can collectively define aconductive portion211 of themicroelectronic substrate210.
• To form an isolated conductive line within theaperture216, the firstconductive material218 and secondconductive material219 external to theaperture216 are typically removed. In one embodiment, the secondconductive material209 is removed using a CMP process. In other embodiments, an electrochemical-mechanical polishing (ECMP) process or an electrolytic process is used to remove the secondconductive material209. An advantage of electrolytic and ECMP processes is that the downforce applied to themicroelectronic substrate210 during processing can be reduced or eliminated. Apparatuses for performing these processes are described in greater detail below with reference toFIGS. 4-9. In any of these embodiments, the result after completing this portion of the process is amicroelectronic substrate210 having the secondconductive material209 external to theaperture216 and external to thebarrier layer214 removed, as is shown inFIG. 2B.
• Referring now toFIG. 2B, a process in accordance with one embodiment of the invention includes simultaneously, electrolytically removing the portions of the secondconductive material209 and the firstconductive material218 that extend beyond thesubstrate material surface217 after the initial removal process described above with reference toFIG. 2A. Accordingly, in one aspect of this embodiment, anelectrolytic liquid231 can be disposed on themicroelectronic substrate210 and a pair of electrodes220 (shown as a first electrode220aand asecond electrode220b) can be positioned in electrical communication with theelectrolytic liquid231. The electrodes220 can be coupled to a variable signal transmitter221 (such as a variable current source) to provide a varying electrical signal to both the firstconductive material218 and the secondconductive material209. These conductive materials can be simultaneously removed via an electrolytic process
• In a further aspect of this embodiment, the pH of theelectrolytic liquid231 is selected to control the difference between the open circuit potential of the firstconductive material218 and the open circuit potential of the secondconductive material209. As used herein, the difference in open circuit potentials between the firstconductive material218 and the secondconductive material209 refers to the difference in electrical potential that would result when measuring the voltage difference between the firstconductive material218 and the secondconductive material209 in the presence of theelectrolytic liquid231, but in the absence of any current applied by thesignal transmitter221. In a particular aspect of this embodiment, for example, when the firstconductive material218 includes tungsten and the secondconductive material209 includes copper, the pH of theelectrolytic liquid231 can be selected to be from about 2 to about 5 to produce a difference in open circuit potential of from about 0.50 volts to about −0.50 volts. In other words, the absolute value of the difference in open circuit potential can be about 0.50 volts or less. In other embodiments, the absolute value of the difference in open circuit potential can be about 0.25 volts or less, for example, 0.15 volts or less. In still further embodiments, the pH of theelectrolytic liquid231 can have other values to produce near-zero open circuit potential differentials for other combinations of firstconductive materials218 and secondconductive materials209. For example, in one embodiment, theelectrolytic liquid231 can have a pH of from about 0 to about 7.
• In any of the foregoing embodiments, the first and secondconductive materials218,209 can be removed simultaneously without necessarily being removed at the same rates. For example, in one embodiment for which the firstconductive material218 includes tungsten or a tungsten compound and the secondconductive material209 includes copper, the copper can be removed at about four times the rate at which the tungsten or tungsten compound is removed. In other embodiments, the first and secondconductive materials218,209 can be removed at rates that vary by greater or lesser amounts.
• In one embodiment, the pH of theelectrolytic liquid231 can be controlled by disposing an acid in theelectrolytic liquid231. Accordingly, theelectrolytic liquid231 can include a liquid carrier (such as deionized water) and an acid such as nitric acid, acetic acid, hydrochloric acid, sulfuric acid, or phosphoric acid. In other embodiments, theelectrolytic liquid231 can include other acids. In addition to reducing the pH of theelectrolytic liquid231, the acid can provide ions to enhance the electrolytic action of theelectrolytic liquid231. In any of these embodiments, theelectrolytic liquid231 can also optionally include an inhibitor, such as benzotriazole (BTA) to produce more uniform material removal. Theelectrolytic liquid231 can also include oxidizers, such as hydroxylamine, peroxide or ammonium persulfate. In another embodiment, the oxidizers can be eliminated, for example, when the electrolytic action provided by the electrodes220 is sufficient to oxidize theconductive materials218 and209.
• In any of the foregoing embodiments, the firstconductive material218 and the secondconductive material209 external to therecess216 can be removed, producing amicroelectronic substrate210 having an embeddedconductive structure208, as shown inFIG. 2C. In one embodiment, theconductive structure208 can include a conductive line and in other embodiments,conductive structure208 can include a via or other feature in themicroelectronic substrate210. In any of these embodiments, the foregoing processes can provide aconductive structure208 having a smoothexternal surface207 that includes smooth external surface portions for both the firstconductive material218 and the secondconductive material209.
• One feature of an embodiment of the method described above with reference toFIGS. 2A-2C is that the pH of theelectrolytic liquid231 can be selected to reduce or eliminate the open circuit potential differential between the firstconductive material218 and the secondconductive material209. An advantage of this feature is that the likelihood for a galvanic reaction, which can preferentially pit, dissolve, or otherwise remove one of the conductive materials more readily than the other, can be reduced and/or eliminated. Accordingly, the resultingexternal surface207 that includes the firstconductive material218 and the secondconductive material209 can be clean and uniform, as shown inFIG. 2C. Another advantage of this feature is that the firstconductive material218 and the secondconductive material209 can be removed simultaneously without requiring high downforces which can damage structures and features of themicroelectronic substrate210.
• In the embodiments described above with reference toFIGS. 2A-2C, the first andsecond electrodes220a,220bare spaced apart from themicroelectronic substrate210 as they remove conductive materials from themicroelectronic substrate210. An advantage of this arrangement is that the conductive material removal process can be relatively uniform. In other embodiments, one or more of the electrodes can be positioned in direct contact with themicroelectronic substrate210. For example, as shown inFIG. 3, afirst electrode320acan be positioned in a spaced apart orientation relative to themicroelectronic substrate210, and asecond electrode320bcan be connected to a rear surface of themicroelectronic substrate210. A conductive path308 (such as an internal via) between the rear surface and theconductive portion211 of the microelectronic substrate can complete the circuit between theelectrodes320a,320b, allowing thesignal transmitter221 to remove conductive material in a manner generally similar to that described above. In still another embodiment, thesecond electrode320bcan be connected directly to themicroelectronic substrate210. Such arrangements can be used when material removal nonuniformities which may result from the direct contact between the electrode and the microelectronic substrate are remote from regions that might be adversely affected by such nonuniformities.
• FIGS. 4-9 illustrate apparatuses for electrolytically, chemically-mechanically, and/or electrochemically-mechanically removing material from microelectronic substrates to perform the processes described above with reference toFIGS. 2A-3. Beginning withFIG. 4, anapparatus460 can electrolytically remove conductive material from themicroelectronic substrate210 in accordance with an embodiment of the invention. In one aspect of this embodiment, theapparatus460 includes liquid support, such as avessel430 containing an electrolytic liquid orgel431. Asupport member440 supports themicroelectronic substrate210 relative to thevessel430 so that theconductive portion211 of themicroelectronic substrate210 contacts theelectrolytic liquid431. In another aspect of this embodiment, thesupport member440 can be coupled to asubstrate drive unit441 that moves thesupport member440 and thesubstrate210 relative to thevessel430. For example, thesubstrate drive unit441 can translate the support member440 (as indicated by arrow “A”) and/or rotate the support member440 (as indicated by arrow “B”).
• Theapparatus460 can further include afirst electrode420aand asecond electrode420b(referred to collectively as electrodes420) supported relative to themicroelectronic substrate210 by asupport arm424. In one aspect of this embodiment, thesupport arm424 is coupled to anelectrode drive unit423 for moving theelectrodes420 relative to themicroelectronic substrate210. For example, theelectrode drive unit423 can move theelectrodes420 toward and away from theconductive portion211 of themicroelectronic substrate210, (as indicated by arrow “C”), and/or transversely (as indicated by arrow “D”) in a plane generally parallel to theconductive portion211. In other embodiments, theelectrode drive unit423 can move theelectrodes420 in other fashions, or theelectrode drive unit423 can be eliminated when thesubstrate drive unit441 provides sufficient relative motion between thesubstrate210 and theelectrodes420.
• In either embodiment described above with reference toFIG. 4, theelectrodes420 can be coupled to asignal transmitter421 withleads428 for supplying electrical current to theelectrolytic liquid431 and theconductive portion211. In operation, thesignal transmitter421 can supply an alternating current (signal phase or multi-phase) to theelectrodes420. The current passes through theelectrolytic liquid431 and reacts electrochemically with theconductive portion211 to remove material (for example, atoms or groups of atoms) from theconductive portion211. Theelectrodes420 and/or themicroelectronic substrate210 can be moved relative to each other to remove material from select regions of theconductive portion211, or from the entireconductive portion211.
• In one aspect of an embodiment of theapparatus460 shown inFIG. 4, a distance D₁between theelectrodes420 and theconductive portion211 is set to be smaller than a distance D₂between thefirst electrode420aand thesecond electrode420b. Furthermore, theelectrolytic liquid431 generally has a higher resistance than theconductive portion211. Accordingly, the alternating current follows the path of least resistance from thefirst electrode420a, through theelectrolytic liquid431 to theconductive portion211 and back through theelectrolytic liquid431 to thesecond electrode420b, rather than from thefirst electrode420adirectly through theelectrolytic liquid431 to thesecond electrode420b. In one aspect of this embodiment, the resistance of theelectrolytic liquid431 can be increased as the thickness of theconductive portion211 decreases (and the resistance of theconductive portion211 increases) to maintain the current path described above. In another embodiment, a low dielectric material (not shown) can be positioned between thefirst electrode420aand thesecond electrode420bto decouple direct electrical communication between theelectrodes420 that does not first pass through theconductive portion211.
• FIG. 5 is a partially schematic, side elevation view of anapparatus560 that includes asupport member540 positioned to support themicroelectronic substrate210 in accordance with another embodiment of the invention. In one aspect of this embodiment, thesupport member540 supports themicroelectronic substrate210 with theconductive portion211 facing upwardly. Asubstrate drive unit541 can move thesupport member540 and themicroelectronic substrate210, as described above with reference toFIG. 4.Electrodes520, including first andsecond electrodes520aand520b, are positioned above theconductive portion211 and are coupled to acurrent source521. Asupport arm524 supports theelectrodes520 relative to thesubstrate210 and is coupled to anelectrode drive unit523 to move theelectrodes520 over the surface of theconductive portion211 in a manner generally similar to that described above with reference toFIG. 4.
• In one aspect of the embodiment shown inFIG. 5, theapparatus560 further includes anelectrolyte vessel530 having asupply conduit537 with anaperture538 positioned proximate to theelectrodes520. Accordingly, anelectrolytic liquid531 can be deposited locally in aninterface region539 between theelectrodes520 and theconductive portion211, without necessarily covering the entireconductive portion211. Theelectrolytic liquid531 and the conductive material removed from theconductive portion211 flow over thesubstrate210 and collect in anelectrolyte receptacle532. The mixture ofelectrolytic liquid531 and conductive material can flow to areclaimer533 that removes most of the conductive material from theelectrolytic liquid531. Afilter534 positioned downstream of thereclaimer533 provides additional filtration of theelectrolytic liquid531, and apump535 returns the reconditionedelectrolytic liquid531 to theelectrolyte vessel530 via areturn line536.
• In another aspect of an embodiment shown inFIG. 5, theapparatus560 can include asensor assembly550 having asensor551 positioned proximate to theconductive portion211, and asensor control unit552 coupled to thesensor551 for processing signals generated by thesensor551. Thecontrol unit552 can also move thesensor551 relative to themicroelectronic substrate210. In a further aspect of this embodiment, thesensor assembly550 can be coupled via afeedback path553 to theelectrode drive unit523 and/or thesubstrate drive unit541. Accordingly, thesensor551 can determine which areas of theconductive portion211 require additional material removal and can move theelectrodes520 and/or themicroelectronic substrate210 relative to each other to position theelectrodes520 over those areas. Alternatively, (for example, when the removal process is highly repeatable), theelectrodes520 and/or themicroelectronic substrate210 can move relative to each other according to a pre-determined motion schedule.
• FIG. 6 schematically illustrates anapparatus660 for electrolytically, chemically-mechanically and/or electrochemically-mechanically polishing themicroelectronic substrate210 in accordance with an embodiment of the invention. In one aspect of this embodiment, theapparatus660 has a support table680 with a top-panel681 at a workstation where an operative portion “W” of apolishing pad683 is positioned. The top-panel681 is generally a rigid plate to provide a flat, solid surface to which a particular section of thepolishing pad683 may be secured during polishing.
• Theapparatus660 can also have a plurality of rollers to guide, position and hold thepolishing pad683 over the top-panel681. The rollers can include asupply roller687, first and secondidler rollers684aand684b, first andsecond guide rollers685aand685b, and a take-uproller686. Thesupply roller687 carries an unused or preoperative portion of thepolishing pad683, and the take-uproller686 carries a used or postoperative portion of thepolishing pad683. Additionally, the first idler roller684aand thefirst guide roller685acan stretch thepolishing pad683 over the top-panel681 to hold thepolishing pad683 stationary during operation. A motor (not shown) drives at least one of thesupply roller687 and the take-uproller686 to sequentially advance thepolishing pad683 across the top-panel681. Accordingly, clean preoperative sections of thepolishing pad683 may be quickly substituted for used sections to provide a consistent surface for polishing and/or cleaning themicroelectronic substrate210.
• Theapparatus660 can also have acarrier assembly690 that controls and protects themicroelectronic substrate210 during polishing. Thecarrier assembly690 can include asubstrate holder692 to pick up, hold and release themicroelectronic substrate210 at appropriate stages of the polishing process. Thecarrier assembly690 can also have asupport gantry694 carrying adrive assembly695 that can translate along thegantry694. Thedrive assembly695 can have anactuator696, adrive shaft697 coupled to theactuator696, and anarm698 projecting from thedrive shaft697. Thearm698 carries thesubstrate holder692 via aterminal shaft699 such that thedrive assembly695 orbits thesubstrate holder692 about an axis E-E (as indicated by arrow “R₁”). Theterminal shaft699 may also rotate thesubstrate holder692 about its central axis F-F (as indicated by arrow “R₂”).
• Thepolishing pad683 and a polishing liquid689 define a polishing medium682 that electrolytically, chemically-mechanically, and/or electro-chemically-mechanically removes material from the surface of themicroelectronic substrate210. In some embodiments, thepolishing pad683 may be a nonabrasive pad without abrasive particles, and the polishing liquid689 can be a slurry with abrasive particles and chemicals to remove material from themicroelectronic substrate210. In other embodiments, thepolishing pad683 can be a fixed-abrasive polishing pad in which abrasive particles are fixedly bonded to a suspension medium. To polish themicroelectronic substrate210 with theapparatus660, thecarrier assembly690 presses themicroelectronic substrate210 against a polishingsurface688 of thepolishing pad683 in the presence of the polishingliquid689. Thedrive assembly695 then orbits thesubstrate holder692 about the axis E-E and optionally rotates thesubstrate holder692 about the axis F-F to translate thesubstrate210 across the polishingsurface688. As a result, the abrasive particles and/or the chemicals in the polishing medium682 remove material from the surface of themicroelectronic substrate210 in a chemical and/or chemical-mechanical polishing process.
• In a further aspect of this embodiment, the polishing liquid689 can include an electrolyte for electrolytic processing or ECMP processing. In another embodiment, theapparatus660 can include anelectrolyte supply vessel630 that delivers an electrolyte separately to the polishingsurface688 of thepolishing pad683 with aconduit637, as described in greater detail below with reference toFIG. 7. In either embodiment, theapparatus660 can further include acurrent supply621 coupled to electrodes positioned proximate to thepolishing pad683. Accordingly, theapparatus660 can electrolytically remove material from themicroelectronic substrate210.
• FIG. 7 is a partially exploded, partially schematic isometric view of a portion of theapparatus660 described above with reference toFIG. 6. In one aspect of the embodiment shown inFIG. 6, the top-panel681 houses a plurality of electrode pairs, each of which includes afirst electrode720aand asecond electrode720b. Thefirst electrodes720aare coupled to afirst lead728aand thesecond electrodes720bare coupled to asecond lead728b. The first andsecond leads728aand728bare coupled to the current supply621 (FIG. 6). In one aspect of this embodiment, thefirst electrodes720acan be separated from thesecond electrodes720bby anelectrode dielectric layer729athat includes Teflon™ or another suitable dielectric material. Theelectrode dielectric layer729acan accordingly control the volume and dielectric constant of the region between the first andsecond electrodes720aand720bto control the electrical coupling between the electrodes.
• Theelectrodes720aand720bcan be electrically coupled to the microelectronic substrate210 (FIG. 6) by thepolishing pad683. In one aspect of this embodiment, thepolishing pad683 is saturated with anelectrolytic liquid731 supplied by thesupply conduits637 throughapertures738 in the top-panel681 just beneath thepolishing pad683. Accordingly, theelectrodes720aand720bare selected to be compatible with theelectrolytic liquid731. In an another arrangement, theelectrolytic liquid731 can be supplied to thepolishing pad683 from above (for example, by disposing theelectrolytic liquid731 in the polishingliquid689, rather than by directing the electrolytic liquid upwardly through the polishing pad683). Accordingly, theapparatus660 can include apad dielectric layer729bpositioned between thepolishing pad683 and theelectrodes720aand720b. When thepad dielectric layer729bis in place, theelectrodes720aand720bcan be isolated from physical contact with theelectrolytic liquid731 and can accordingly be selected from materials that are not necessarily compatible with theelectrolytic liquid731.
• FIG. 8 is an isometric view of a portion of anapparatus860 having electrodes820 (shown as afirst electrode820aand asecond electrode820b), and a polishing medium882 arranged in accordance with another embodiment of the invention. In one aspect of this embodiment, the polishingmedium882 includes polishingpad portions883 that project beyond theelectrodes820aand820b. Eachpolishing pad portion883 can include a polishingsurface888 and a plurality offlow passages884 coupled to a fluid source (not shown inFIG. 8) with aconduit837. Eachflow passage884 can have anaperture885 proximate to the polishingsurface888 to provide anelectrolytic liquid831 proximate to an interface between themicroelectronic substrate210 and the polishingsurface888. In one aspect of this embodiment, thepad portions883 can includerecesses887 surrounding eachaperture885. Accordingly, theelectrolytic liquid831 can proceed outwardly from theflow passages884 while themicroelectronic substrate210 is positioned directly overhead and remains spaced apart from the electrodes820. In other embodiments, thepolishing pad portions883 can be applied to other electrodes, such as those described above with reference toFIGS. 4 and 5 to provide for mechanical as well as electromechanical material removed.
• The foregoing apparatuses described above with reference toFIGS. 4-8 can be used to electrolytically, chemically-mechanically and/or electrochemically-mechanically process themicroelectronic substrate210. When the apparatuses are used to electrolytically or electrochemically-mechanically process themicroelectronic substrate210, they can provide a varying electrical current that passes from the electrodes, through the conductive material of themicroelectronic substrate210 via the electrolytic liquid. For example, as shown inFIG. 9, the apparatus can generate a high-frequency wave904 and can superimpose a low-frequency wave902 on the high-frequency wave904. In one aspect of this embodiment, the high-frequency wave904 can include a series of positive or negative voltage spikes contained within a square wave envelope defined by the low-frequency wave902. Each spike of the high-frequency wave904 can have a relatively steep rise-time slope to transfer charge through the dielectric material to the electrolytic liquid, and a more gradual fall-time slope. The fall-time slope can define a straight line, as indicated by high-frequency wave904, or a curved line, as indicated by high-frequency wave904a. In other embodiments, the high-frequency wave904 and the low-frequency wave902 can have other shapes depending, for example, on the particular characteristics of the dielectric material and the electrolytic liquid, the characteristics of themicroelectronic substrate210, and/or the target rate at which conductive material is to be removed from themicroelectronic substrate210.
• The methods described above with reference toFIGS. 2A-3 may be performed with the apparatuses described above with reference toFIGS. 4-9 in a variety of manners in accordance with several embodiments of the invention. For example, in one embodiment, a single apparatus can be used to electrolytically remove first the secondconductive material209 and then the first and secondconductive materials218,209 simultaneously. Alternatively, one apparatus can initially remove the second material209 (e.g., via CMP) and the same or another apparatus can subsequently remove both the first and secondconductive materials218,209. In either embodiment, both the first an secondconductive materials218,209 can be removed simultaneously when they are exposed. In one aspect of both embodiments, the downforce applied to themicroelectronic substrate210 can be reduced or eliminated during electrolytic processing. In another aspect of these embodiments, a selected downforce can be applied to themicroelectronic substrate210 during electrolytic processing to supplement the electrolytic removal process with a mechanical removal process. The electrolytic removal process can also be supplemented with a chemical removal process in addition to or in lieu of the mechanical removal process.
• From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Claims (26)

1-73. (canceled)

74. A method for processing a semiconductor substrate, comprising:

contacting a surface of the semiconductor substrate with an electrolytic liquid, the surface containing a first conductive material and a second conductive material different than the first conductive material;

selecting a pH of the electrolytic liquid to suppress or eliminate a galvanic reaction between the first and second conductive materials in the presence of the electrolytic liquid; and

passing a varying electrical signal through the electrolytic liquid and the first and second conductive materials while suppressing or eliminating the galvanic reaction.

75. The method ofclaim 74, further comprising simultaneously removing at least portions of the first and second conductive materials while passing the varying electrical signal through the electrolytic liquid and the first and second conductive materials.

76. The method ofclaim 74 wherein selecting a pH of an electrolytic liquid includes selecting a pH of the electrolytic liquid based at least in part on compositions of the first and second conductive materials.

77. The method ofclaim 74 wherein the first conductive material includes tungsten and the second conductive material includes copper, further wherein reducing a galvanic reaction between the first and second conductive materials includes selecting a pH of the electrolytic liquid to be from about 2 to about 5.

78. The method ofclaim 77, further comprising simultaneously removing at least portions of tungsten and copper while passing the varying electrical signal through the electrolytic liquid and the first and second conductive materials.

79. The method ofclaim 77, further comprising removing at least portions of a conductive layer that includes at least 50% copper.

80. The method ofclaim 74 wherein the first conductive material includes tungsten and the second conductive material includes copper, further wherein reducing a galvanic reaction between the first and second conductive materials includes controlling the pH to be from about 2 to about 5.

81. The method ofclaim 74 wherein contacting the surface of the semiconductor substrate includes contacting the semiconductor substrate with an electrolytic liquid that includes at least one of an oxidizer, a corrosion inhibitor and a pH control agent.

82. The method ofclaim 74, further comprising removing at least portions of the first and second conductive materials from the semiconductor substrate and changing a resistance of the electrolytic liquid as the first and second conductive materials are removed from the semiconductor substrate.

83. The method ofclaim 74, further comprising removing at least portions of the first and second conductive materials from the semiconductor substrate and increasing a resistance of the electrolytic liquid as the first and second conductive materials are removed from the semiconductor substrate.

84. The method ofclaim 74, further comprising contacting the semiconductor substrate with a polishing pad and moving at least one of the polishing pad and the semiconductor substrate relative to the other while passing the varying electrical signal through the electrolytic liquid and the first and second conductive materials.

85. A method for processing a semiconductor substrate, comprising:

contacting the semiconductor substrate with an electrolytic liquid, the semiconductor substrate having a first conductive material and a second conductive material different than the first conductive material;

controlling a pH of the electrolytic liquid to suppress or eliminate the galvanic reaction between the first and second conductive materials in the presence of the electrolytic liquid; and

simultaneously removing at least portions of the first and second conductive materials from the semiconductor substrate while the galvanic reaction between the first and second conductive materials is suppressed or eliminated.

86. The method ofclaim 85 wherein the first conductive material includes at least one of tungsten and WN_xand the second conductive material includes copper, further wherein controlling a pH of the electrolytic liquid includes controlling a pH of the electrolytic liquid to be from about 2 to about 5.

87. The method ofclaim 85 wherein the first conductive material includes tungsten and the second conductive material includes copper, further wherein controlling a pH of the electrolytic liquid includes controlling a pH of the electrolytic liquid to be from about 2 to about 5, and wherein simultaneously removing at least portions of the first and second conductive materials includes passing a variable electrical current through the electrolytic liquid and the conductive materials while engaging a polishing pad with the semiconductor substrate and moving at least one of the semiconductor substrate and the polishing pad relative to the other while passing the electrical signal through the first and second conductive materials via two electrodes spaced apart from the semiconductor substrate.

88. The method ofclaim 87 wherein passing an electrical signal includes passing an electrical signal from a first electrode spaced apart from the semiconductor substrate, through the electrolytic liquid to the first and second conductive materials and through the electrolytic liquid to a second electrode spaced apart from the first electrode and spaced apart from the semiconductor substrate.

89. The method ofclaim 87 wherein passing an electrical signal includes passing an electrical signal from a first electrode spaced apart from the semiconductor substrate, through the electrolytic liquid to the first and second conductive materials and to a second electrode positioned in contact with the semiconductor substrate.

90. The method ofclaim 85 wherein simultaneously removing at least portions of the first and second conductive materials includes removing tungsten and copper.

91. The method ofclaim 85 wherein simultaneously removing at least portions of the first and second conductive materials includes removing the first conductive material at a first rate and removing the second material at a second rate different than the first rate.

92. The method ofclaim 85 wherein simultaneously removing the first conductive material and the second conductive material includes simultaneously removing a barrier layer material and a blanket fill material.

93. A method for processing a semiconductor substrate having a tungsten containing portion and a copper containing portion, comprising:

selecting a pH of an electrolytic liquid based at least in part on compositions of the tungsten containing portion and the copper containing portion such that a galvanic reaction of the tungsten containing portion and the copper containing portion is suppressed in the presence of the electrolytic liquid;

contacting the semiconductor substrate with an electrolytic liquid having the selected pH; and

simultaneously removing at least part of the copper containing portion and the tungsten containing portion by passing a varying electrical signal through the electrolytic liquid and the copper containing and tungsten containing portions while the electrolytic liquid contacts the microelectronic substrate and while the galvanic reaction is suppressed or eliminated.

94. The method ofclaim 93 wherein removing at least part of the copper containing portion includes removing at least part of a conductive line or a conductive via, and wherein removing at least part of the tungsten containing portion includes removing at least part of a barrier layer.

95. The method ofclaim 93 wherein removing at least part of the copper containing portion includes removing at least part of a portion having about 50% or more copper.

96. The method ofclaim 93 wherein removing at least part of the tungsten containing portion includes removing at least part of a portion having WN_x.

97. The method ofclaim 93 wherein simultaneously removing at least part of the copper containing portion and part of the tungsten containing portion includes removing at least part of the tungsten containing portion at a first rate and removing at least part of the copper containing portion at a second rate about four times greater than the first rate.

98. The method ofclaim 93, further comprising contacting the microelectronic substrate with a polishing pad and moving at least one of the polishing pad and the microelectronic substrate relative to the other while simultaneously removing at least part of the copper containing portion and the tungsten containing portion.

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