US20060270233A1 - Vapor deposition of benzotriazole (BTA) for protecting copper interconnects - Google Patents

Abstract

A method of protecting an interconnect is provided. The method includes forming an integrated circuit structure having an interconnect, and depositing vaporized benzotriazole on the interconnect.

Description

TECHNICAL FIELD OF THE INVENTION
• This invention relates in general to protecting copper interconnects during wafer fabrication, and, more particularly, to vapor deposition of benzotriazole (BTA) for protecting copper interconnects.
BACKGROUND OF THE INVENTION
• Integrated circuits often include copper interconnects formed in one or more metalization layers. During wafer fabrication processes to form such integrated circuits, exposed copper interconnects may be oxidized and corroded in humid, chemically or thermally harsh environments, or environments containing oxygen. A film or coating of benzotriazole (BTA) is often applied to exposed surfaces of copper interconnects using wet dipping techniques to prevent oxidation or corrosion of the copper interconnects. The film or coating of BTA is often non-uniform and non-continuous and thus may provide only partial protection of the surfaces of the copper interconnects.
SUMMARY OF THE INVENTION
• According to one embodiment, a method of protecting an interconnect is provided. The method includes forming an integrated circuit structure having an interconnect, and depositing vaporized benzotriazole on the interconnect.
• According to another embodiment, an integrated circuit structure is provided. The integrated circuit structure includes a first interconnect having a first surface, and a first layer of benzotriazole formed on the first surface of the first interconnect. The first layer of benzotriazole is formed using vapor deposition of benzotriazole on the first surface of the first interconnect.
• According to yet another embodiment, a system for protecting an interconnect is provided. The system includes a vapor deposition chamber operable to receive an integrated circuit structure having an interconnect, and to allow vaporized benzotriazole to be deposited on the interconnect.
• Various embodiments of the present invention may benefit from numerous advantages. It should be noted that one or more embodiments may benefit from some, none, or all of the advantages discussed below.
• One advantage is that since benzotriazole (BTA) exists in single molecules in the vapor state, rather than in clusters of molecules (as in the liquid state), a thin, uniform and continuous film or coating of BTA may be formed on the outer surface of copper interconnects. Such thin, uniform and continuous film or coating of BTA provides enhanced surface protection of the underlying copper interconnects, which is important for producing high-quality wafers.
• Another advantage is that by applying BTA in the vapor state, much less BTA may be used as compared with previous wet dipping techniques. Thus, negative environmental effects associated with the use of BTA may be reduced.
• Yet another advantage is that applying BTA in the vapor state may reduce the frequency of maintenance for etch stop nitride (NIT) deposition equipment. BTA layers formed by wet dipping are often non-uniform and thus difficult to remove uniformly and completely. As a result, when depositing a nitride etch stop layer adjacent the wafer after removal of the BTA layer, condensation of BTA residue may occur within the nitride deposition chamber, which may require frequent cleaning of the nitride deposition chamber. This may result in down time of the equipment. In contrast, the thin, uniform and continuous BTA layers created by applying BTA in the vapor state are significantly easier to remove uniformly and completely. This may result in less BTA condensation within the nitride deposition chamber, which reduces the required frequency of cleaning the nitride deposition chamber, thus reducing down time of the equipment.
• Other advantages will be readily apparent to one having ordinary skill in the art from the following figures, descriptions, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• For a more complete understanding of the present invention and for further features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
• FIG. 1 illustrates a system for polishing, cleaning and depositing benzotriazole (BTA) vapor onto a wafer according to one embodiment of the present invention;
• FIG. 2 illustrates an example partial cross-section of a wafer to be processed by the system ofFIG. 1;
• FIG. 3 illustrates an example system for the creation and control of BTA vapor to be delivered into the vapor deposition chamber of the system shown inFIG. 1;
• FIG. 4 illustrates application of liquid BTA to a wafer using a traditional “wet dipping” technique;
• FIG. 5 illustrates vapor deposition of BTA on a wafer according to an embodiment of the present invention;
• FIG. 6 illustrates a system for polishing, cleaning and depositing BTA vapor onto a wafer according to an alternative embodiment of the present invention; and
• FIG. 7 illustrates a system for polishing, cleaning and depositing BTA vapor onto a wafer according to yet another alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
• Example embodiments of the present invention and their advantages are best understood by referring now toFIGS. 1 through 7 of the drawings, in which like numerals refer to like parts.
• FIG. 1 illustrates asystem10 for polishing, cleaning and depositing vaporized benzotriazole (BTA) onto an integrated circuit structure, or wafer,12 during the fabrication of the integrated circuit or a component of an integrated circuit according to one embodiment of the present invention.System10 includes a number of staging areas (such as tanks or chambers, for example) for performing various functions or processes, including awet tank14, a chemical mechanical planarization (CMP)chamber16, a post-CMPclean chamber18, and one or morevapor deposition chambers20. Althoughstaging areas14,16,18 and20 are shown separately inFIG. 1, it should be understood that one or more of such staging areas may be at least partially combined or may be further subdivided.
• Wafer12 may include one or more metalization layers, each comprising one or more low-K dielectric materials and one ormore copper interconnects22.Wafer12 comprises anouter surface24 which may be exposed to the surrounding environment during various portions of the fabrication process. Portions ofouter surface24 may comprise outer or exposedsurfaces26 of one or more of thecopper interconnects22. It should be understood that theouter surface24 ofwafer12 may vary throughout the fabrication process as various fabrication processes are performed and as additional metalization layers are added towafer12.
• FIG. 2 illustrates an example cross-section of a portion ofwafer12.Wafer12 includes atransistor structure27 covered by a firstdielectric material28, and afirst metalization layer29 comprising acopper interconnect22 formed in a seconddielectric material31. As discussed above,wafer12 comprisesouter surface24, a portion of which comprisesouter surface26 ofcopper interconnect22.
• Returning toFIG. 1,wafer12 may be received intowet tank14, which may include liquid, or molten, benzotriazole (BTA) solution. In one embodiment,wet tank14 includes BTA diluted by de-ionized water. Withinwet tank14, BTA may be applied to theouter surface24 ofwafer12.
• Wafer12 may proceed toCMP chamber16, in which a chemical mechanical planarization (CMP) process may be performed to polish theouter surface24 ofwafer12. BTA solution may be applied to wafer12 withinCMP chamber16 during at least a portion of the CMP process. Wafer12 may then proceed back towet tank14, in which a new layer of liquid BTA solution may be applied to theouter surface24 ofwafer12.
• Wafer12 may then proceed to post-CMPclean chamber18, in whichwafer12 may be cleaned to remove various residue, such as slurry residue and metallic contamination, for example. Such cleaning processes may comprise any of a variety of post-CMP hood clean processes, such as a citric clean (CIT) process, for example.
• Wafer12 may then proceed to one or morevapor deposition chambers20. In some embodiments, such as the embodiment shown inFIG. 1, a singlevapor deposition chamber20 is used for applying vaporized isopropyl alcohol (IPA)30 as well as vaporized benzotriazole (BTA)32 to theouter surface24 ofwafer12. In one embodiment, IPAvapor30 and BTAvapor32 may be applied to wafer12 simultaneously.
• In some embodiments, a low pressure dry (LPD) process using IPAvapor30 may be performed onwafer12, with the addition of BTAvapor32 to the IPAvapor30. In one such embodiment,vapor deposition chamber20 comprises a spin dryer.
• In the example embodiment shown inFIG. 1, IPAvapor30 is received intovapor deposition chamber20 from anIPA chamber34 and BTAvapor32 is received intovapor deposition chamber20 from a BTAchamber36.IPA chamber34 may comprise liquid IPA, which is heated to form IPA vapor. The IPA vapor may be carried intovapor deposition chamber20 by one or more inert carrier gasses, such as Argon, Nitrogen and/or Helium, for example.
• Similarly,BTA chamber36 may comprise liquid BTA, which is heated to form BTA vapor. The BTA vapor may be carried intovapor deposition chamber20 by one or more inert carrier gasses, such as Argon, Nitrogen and/or Helium, for example.BTA chamber36 and various systems and methods for producingBTA vapor32 are discussed in greater detail below with reference toFIG. 3.
• FIG. 3 illustrates asystem50 for the creation and control ofBTA vapor32 to be delivered intovapor deposition chamber20, as indicated by arrow A inFIG. 1, according to one embodiment of the present invention.System50 comprisesBTA chamber36, aBTA reservoir52,gas lines54, and a number ofpressure regulators56,mass flow controllers58,irreversible valves60,pressure relief valves62, athrottle valve63 and acontrol valve64.
• BTA chamber36 is operable to heat, and thereby vaporize, liquid (molten)BTA66 to formBTA vapor32.BTA chamber36 may include a temperature loop72 operable to measure and/or control the temperature ofliquid BTA66 withinBTA chamber36, so as to control the rate of vaporization, the concentration ofBTA vapor32 withinBTA chamber36, and/or the pressure withinBTA chamber36. In some embodiments,BTA chamber36 may be heated to particular temperatures within the range from 50 to 300 degrees Celsius. In one embodiment, the temperature ofBTA chamber36 may be controlled so as to obtain a desired concentration ofBTA vapor32 relative to other gasses withinBTA chamber36.
• One or more carrier gasses68 (such as Argon, Nitrogen and/or Helium, for example) are introduced intoBTA chamber36 viapath70.Carrier gasses68 may pick up, or entrain,BTA vapor32 withinBTA chamber36 and carryBTA vapor32 towardvapor deposition chamber20 viapath74. In one embodiment,carrier gasses68 are bubbled throughliquid BTA66 inBTA chamber36 to pick up, or entrain,BTA vapor32. The combination ofcarrier gasses68 andBTA vapor32 is indicated inFIG. 3 as combinedgasses76.Additional carrier gasses68 may be introduced into combinedgasses76 viapath78 in order to dilute or otherwise control the concentration ofBTA vapor32 within combinedgasses76.Combined gasses76 may continue alongpath78 toward vapor deposition chamber20 (seeFIG. 1), as indicated by arrow A inFIG. 3.
• Exhaust lines80 and82 may be coupled toBTA chamber36 to allowBTA vapor32,carrier gasses68 or combinedgasses76 to escape fromBTA chamber36, so as to control or regulate the temperature or pressure withinBTA chamber36. For example,exhaust lines80 and/or82 may be used to obtain a desired concentration ofBTA vapor32 relative to other gasses (such ascarrier gasses68, for example) withinBTA chamber36. As shown inFIG. 1, apump83 is coupled toexhaust line82 to pump vapor or gasses away fromBTA chamber36.
• BTA reservoir52 is operable to store liquid (molten)BTA66 and/orBTA vapor32. One ormore carrier gasses68 may be introduced intoBTA reservoir52 viapath84.Carrier gasses68 may pick up, or entrain,BTA vapor32 withinBTA reservoir52 to form combinedgasses76 as described above in connection withBTA chamber36. For example, in one embodiment,carrier gasses68 are bubbled throughliquid BTA66 inBTA reservoir52 to pick up, or entrain,BTA vapor32.
• BTA reservoir52 is coupled toBTA chamber36 and is operable to communicateliquid BTA66,BTA vapor32 and/or combinedgasses76 intoBTA chamber36 viapath86, so as to replenishBTA chamber36 withliquid BTA66, or to control or regulate the concentration ofBTA vapor32 withinBTA chamber36, for example. In one embodiment,liquid BTA66 and orBTA vapor32 may be communicated betweenBTA reservoir52 andBTA chamber36 in order to obtain a desired concentration ofBTA vapor32 withinBTA chamber36.
• LikeBTA chamber36,BTA reservoir52 may be heated and the temperature controlled in order to control the rate of vaporization, the concentration ofBTA vapor32 withinBTA reservoir52, and/or the pressure withinBTA reservoir52. In some embodiments,BTA reservoir52 may be heated to particular temperatures within the range from 50 to 300 degrees Celsius.
• BTA reservoir52 may be operable to automatically refillBTA chamber36 as theliquid BTA66 and/orBTA vapor32 withinBTA chamber36 falls below a predetermined level, or to prevent theliquid BTA66 and/orBTA vapor32 withinBTA chamber36 from falling below a predetermined level.
• In some embodiments, allgas lines54 andcarrier gasses68 are heated in order to preventBTA vapor32 withingas lines54 from condensing into the liquid phase.
• ApplyingBTA vapor32 toouter surface24 ofwafer12, as described above with reference toFIGS. 1 through 3, provides several advantages as compared with applying liquid BTA toouter surface24. First, the vapor deposition of BTA provides a more continuous and more uniform film of BTA on the exposed surfaces26 of copper interconnects22 as compared with applying liquid BTA towafer12.
• For example,FIG. 4 illustrates the application of liquid BTA towafer12 using a traditional “wet dipping” technique. In the liquid state,BTA molecules90 naturally formmolecule clusters92.Molecule clusters92 may attach to an exposedsurface26 of acopper interconnect22 in a non-uniform and non-continuous manner. In addition,molecule clusters92 may attach to the exposedsurface26 in such a manner that they blockother molecule clusters92 from attaching to exposedsurface26, thus resulting in portions of exposedsurface26 remaining uncovered by BTA molecules. This can result in a discontinuous and/or non-uniform BTA film.
• FIG. 5 illustrates vapor deposition of BTA, or in other words, application ofBTA vapor32, such as described above with reference toFIGS. 1 and 3. As shown inFIG. 5, BTA exists asindividual molecules90 in the vapor state. Thus, whenBTA vapor32 is applied towafer12,individual BTA molecules90 may attach to the exposedsurface26 of acopper interconnect22, which may result in a thin, uniform and continuous BTA film orcoating94. Such thin, uniform andcontinuous BTA coating94 provides enhanced surface protection of copper interconnects22, which is important for producing high-quality wafers12 having few defects and little corrosion.
• In addition, by applying BTA in the vapor state, much less BTA may be used as compared with previous wet dipping techniques. Thus, any negative environmental effects associated with the use of BTA may be reduced.
• Also, applying BTA in the vapor state may reduce the frequency of maintenance for etch stop layer (such as silicon nitride (NIT), silicon carbide, or others, for example) deposition tools. In situations in which an etch stop layer is deposited over theouter surface24 ofwafer12, the BTA layer or film which was deposited onouter surface24 must first be removed, such as by using a sputtering process for example. To apply the etch stop layer,wafer12 is placed in a deposition chamber. If the BTA film was applied using liquid BTA, condensation of BTA or sputtered BTA residue may occur within the nitride deposition chamber during the deposition of the etch stop layer due to the removal of the non-uniform BTA. Such condensate or sputtered residue must be frequently cleaned from the etch stop deposition chamber, which may result in excessive down time of the equipment.
• However, the thin, uniform andcontinuous BTA coating94 onouter surface24 created by applying BTA in the vapor state is significantly easier to remove uniformly and completely. This may result in less BTA residue within the nitride deposition chamber, which reduces the required frequency of cleaning the etch stop deposition chamber, thus reducing down time of the equipment.
• FIG. 6 illustrates asystem100 for polishing, cleaning and depositing vaporized benzotriazole onto awafer12 according to an alternative embodiment of the present invention.System100 is substantially similar tosystem10 shown inFIG. 1; however,system100 comprises a pair ofvapor deposition chambers20, namely, an IPAvapor deposition chamber102 for performing the IPA cleaning process and a separateBTA deposition chamber104 for depositingBTA vapor32 onto theouter surface24 ofwafer12. In some embodiments, IPAvapor deposition chamber102 comprises a low-pressure dryer, or spin dryer.
• IPA vapor30 may be received into IPAvapor deposition chamber102 fromIPA chamber34. Similarly,BTA vapor32 may be received into BTAvapor deposition chamber104 fromBTA chamber36. BTA vapor32 (or combined gasses76) may be created, controlled and delivered into BTAvapor deposition chamber104, as indicated by arrow A inFIG. 3. As discussed above,IPA vapor30 and/orBTA vapor32 may be carried into IPAvapor deposition chamber102 and BTAvapor deposition chamber104, respectively, using one or more inert carrier gasses, such as Argon, Nitrogen and/or Helium, for example.
• FIG. 7 illustrates asystem200 for polishing, cleaning and depositing benzotriazole vapor onto awafer12 according to another alternative embodiment of the present invention.System200 is substantially similar tosystems10 and100 shown inFIGS. 1 and 6, respectively; however, thevapor deposition chamber20 ofsystem200 receives bothIPA vapor30 andBTA vapor32 from an IPA/BTAvapor formation chamber202. As discussed above,IPA vapor30 and/orBTA vapor32 may be carried intovapor deposition chamber20 using one or more inert carrier gasses, such as Argon, Nitrogen and/or Helium, for example.
• IPA/BTAvapor formation chamber202 is operable to produce bothIPA vapor30 andBTA vapor32 to deliver intovapor deposition chamber20. In one embodiment, IPA/BTAvapor formation chamber202 receives and heats liquid IPA and liquid (molten) BTA to formIPA vapor30 andBTA vapor32. In another embodiment, IPA/BTAvapor formation chamber202 comprisesheated IPA vapor30 and/or liquid IPA, receives liquid BTA, and heats the solution to formIPA vapor30 andBTA vapor32. In yet another embodiment, IPA/BTAvapor formation chamber202 comprisesheated BTA vapor32 and/or liquid BTA, receives liquid IPA, and heats the solution to formIPA vapor30 andBTA vapor32.
• It should be understood that some or all of the systems and methods described above for applyingBTA vapor32 onto theouter surface24 ofwafer12 may be applied at one or more times and onto one or moreouter surfaces24 during the fabrication ofwafer12. For example, particular wafers may include a plurality of metalizationlayers having interconnects22 formed therein, andBTA vapor32 may be applied to the outer surface of one or more such metalization layers during the fabrication of such wafers. In this manner, surfaces of copper interconnects22 within various metalization layers which are exposed at particular times during the fabrication process may be protected by aBTA coating94 formed by applyingBTA vapor32 as discussed above.
• Although embodiments of the invention and their advantages are described in detail, a person skilled in the art could make various alterations, additions, and omissions without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (18)

1-14. (canceled)

15. An integrated circuit structure, comprising:

a first interconnect having a first surface; and

a first layer of benzotriazole formed on the first surface of the first interconnect, the first layer of benzotriazole being formed using vapor deposition of benzotriazole on the first surface of the first interconnect.

16. The integrated circuit structure of claim0, wherein the first layer of benzotriazole comprises a substantially uniform distribution of benzotriazole molecules.

17. The integrated circuit structure of claim0, first comprising:

a first metalization layer, wherein the first interconnect is formed in the first metalization layer;

a second metalization layer;

a second interconnect formed in the second metalization layer, the second interconnect having a first surface; and

a second layer of benzotriazole formed on the first surface of the second interconnect, the second layer of benzotriazole being formed using vapor deposition of benzotriazole on the first surface of the second interconnect.

18. A system for protecting an interconnect, comprising:

a vapor deposition chamber operable to receive an integrated circuit structure having an interconnect and deposit vaporized benzotriazole onto the interconnect.

19. The system ofclaim 18, further comprising:

a benzotriazole chamber operable to heat liquid benzotriazole to form vaporized benzotriazole.

20. The system ofclaim 19, wherein the vapor deposition chamber is further operable to receive vaporized benzotriazole from the benzotriazole chamber.

21. The system ofclaim 19, further comprising:

a benzotriazole reservoir coupled to the benzotriazole chamber, the benzotriazole reservoir operable to store benzotriazole and communicate benzotriazole to the benzotriazole chamber to control the amount of benzotriazole within the benzotriazole chamber.

22. The system ofclaim 19, wherein:

the benzotriazole chamber is operable to receive an inert carrier gas and allow the inert carrier gas to combine with the vaporized benzotriazole; and

the vapor deposition chamber is further operable to apply the combined vaporized benzotriazole and inert carrier gas onto the integrated circuit structure.

23. The system ofclaim 22, wherein the benzotriazole chamber is operable to control the concentration of the vaporized benzotriazole relative to the inert carrier gas to obtain a desired concentration of vaporized benzotriazole.

24. The system ofclaim 19, wherein:

the benzotriazole chamber is operable to allow a carrier gas to bubble through liquid benzotriazole to form a combination of vaporized benzotriazole and the carrier gas; and

the vapor deposition chamber is further operable to apply the combined vaporized benzotriazole and inert carrier gas onto the integrated circuit structure.

25. The system ofclaim 18, wherein the vapor deposition chamber comprises a vacuum chamber operable to receive liquid benzotriazole to create vaporized benzotriazole.

26. The system ofclaim 18, further comprising:

a chemical mechanical polish (CMP) chamber for performing a CMP cleaning process on the integrated circuit structure;

a wet tank for applying liquid benzotriazole to the integrated circuit structure; and

a cleaning chamber for performing a post-CMP cleaning process on the integrated circuit structure prior to the vapor deposition of benzotriazole on the interconnect.

27. The system ofclaim 18, wherein the vapor deposition chamber is further operable to deposit vaporized isopropyl alcohol onto the interconnect.

28. The system ofclaim 27, wherein the vaporized benzotriazole and the vaporized isopropyl alcohol are received into the vapor deposition chamber separately.

29. The system ofclaim 27, wherein the vapor deposition chamber is operable to all of the vaporized benzotriazole and the vaporized isopropyl alcohol to be deposited onto the interconnect simultaneously.

30. The system ofclaim 18, further comprising:

a vapor formation chamber operable to receive liquid benzotriazole and liquid isopropyl alcohol, and heat the liquid benzotriazole and liquid isopropyl alcohol to form vaporized benzotriazole and vaporized isopropyl alcohol; and

wherein the vapor deposition chamber is further operable to receive the vaporized benzotriazole and vaporized isopropyl alcohol such that the vaporized benzotriazole and vaporized isopropyl alcohol may be applied to the integrated circuit structure.

31. The system ofclaim 18, further comprising an isopropyl alcohol deposition chamber for applying vaporized isopropyl alcohol to the integrated circuit structure.

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