US20130309874A1 - Method and apparatus for liquid treatment of wafer-shaped articles - Google Patents

Abstract

An apparatus for treating a wafer-shaped article, comprises a spin chuck for holding a wafer-shaped article in a predetermined orientation, a liquid dispenser for dispensing a treatment liquid onto a downwardly facing surface of a wafer-shaped article when positioned on the spin chuck, and a gas dispenser for dispensing a gas within a gap defined between the downwardly-facing surface of the wafer-shaped article and an upper surface of the spin chuck.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The invention relates generally to methods and apparatus for liquid treatment of wafer-shaped articles, such as semiconductor wafers, wherein one or more process liquids are dispensed onto a surface of the wafer-shaped article.
• 2. Description of Related Art
• Semiconductor wafers are subjected to various surface treatment processes such as etching, cleaning, polishing and material deposition. To accommodate such processes, a single wafer may be supported in relation to one or more treatment fluid nozzles by a chuck associated with a rotatable carrier, as is described for example in U.S. Pat. Nos. 4,903,717 and 5,513,668.
• Alternatively, a chuck in the form of a ring rotor adapted to support a wafer may be located within a closed process chamber and driven without physical contact through an active magnetic bearing, as is described for example in International Publication No. WO 2007/101764 and U.S. Pat. No. 6,485,531.
• Ordinarily, treatment fluids, especially etching liquids, are dispensed from above onto the upper surface of a rotating wafer which faces away from the chuck. In some instances, as described for example in International Publication No. WO 2009/027194, gas is directed to the opposite back surface, which faces the chuck, to provide a gas cushion between the wafer and the chuck which secures the wafer using the Bernoulli-Effect and/or limits treatment liquid dispensed on the front surface of the wafer from flowing around the wafer's edge to the back surface of the wafer. As is further described in International Publication No. WO 2009/027194, a rinsing liquid may be directed to the back surface of the wafer to remove residues of treatment liquid that may have reached the peripheral region of the back surface of the wafer.
• With increasing miniaturization of devices and features fabricated on semiconductor wafers, processing those wafers in an uncontrolled open environment becomes more problematic. For example, when wafers undergo wet processing in stations that are open to the surrounding air, the oxygen content of the air causes unwanted corrosion of copper on the front side of the wafer.
• During processing of a single wafer in an open environment the oxygen from the air can diffuse through the liquid layer on the wafer to the wafer surface, leading to copper oxidation and therefore copper loss. This effect is enhanced where the liquid layer is very thin, e.g. at the wafer edge.
• Furthermore, mechanical and fluid forces acting across the surface of a wafer during processing in an uncontrolled open environment can lead to pattern collapse, distortion or other damage to various devices and features fabricated on the surface of the wafer.
• Pattern collapse can occur, for example, when the surface tension of a liquid moving radially outwardly across the surface of a rotating wafer applies a damaging or destructive force to the submicroscopic structures formed on the wafer surface. The problem of pattern collapse becomes more serious as the diameter of semiconductor wafers increases and as the aspect ratio of the submicroscopic structures increases.
• The application and removal of treatment liquids in an uncontrolled open environment also leads to the creation of watermarks on the surface of the wafer.
SUMMARY OF THE INVENTION
• The present inventors have developed new and improved processes and apparatus for providing a process liquid for liquid treatment of wafer-shaped articles, in which the process liquid is directed to the back surface of a wafer-shaped article, within a space formed between the back surface of the article and a chuck that supports the article during processing, wherein the back surface of the article is maintained in a controlled environment during the liquid treatment.
• The present inventors have surprisingly discovered that the present method and apparatus effectively reduce the above-described negative consequences associated with oxygen, as well as reducing pattern loss and formation of watermarks.
• Thus, the invention in one aspect relates to an apparatus for treating a wafer-shaped article, comprising a spin chuck for holding a wafer-shaped article in a predetermined orientation wherein a lower surface of the wafer-shaped article, when positioned on the spin chuck, is downwardly-facing and spaced a predetermined distance from an upper surface of the spin chuck, thereby defining a gap between the lower surface of the wafer-shaped article and the upper surface of the spin chuck, a lower gas dispenser located and configured for dispensing gas at least to an annular region of the gap defined by the upper surface of the spin chuck and the lower surface of a wafer-shaped article when positioned on the spin chuck, and at least one lower liquid dispenser located and configured for dispensing liquid onto a downwardly facing surface of a wafer-shaped article when positioned on the spin chuck, wherein the at least one lower liquid dispenser is operatively connected to at least two different liquid sources for subsequently dispensing two different liquids onto a downwardly facing surface of a wafer-shaped article when positioned on the spin chuck.
• In preferred embodiments of the apparatus according to the present invention, the spin chuck further comprises a peripheral series of upwardly projecting gripping elements positioned so as to be engageable with a peripheral edge of a wafer-shaped article to be held by the spin chuck, each of the upwardly projecting gripping elements being pivotable about an axis parallel to an axis of rotation of the spin chuck.
• In preferred embodiments of the apparatus according to the present invention, the lower gas dispenser comprises a plurality of annularly arranged gas nozzles.
• In preferred embodiments of the apparatus according to the present invention, the lower gas dispenser comprises an annular gas nozzle.
• In preferred embodiments of the apparatus according to the present invention, the at least one lower liquid dispenser comprises two lower liquid dispensers, each terminating at a same liquid nozzle.
• In preferred embodiments of the apparatus according to the present invention, the at least one lower liquid dispenser comprises two lower liquid dispensers, each terminating at a different liquid nozzle.
• In preferred embodiments, the apparatus according to the present invention further comprises an upper dispenser positioned and configured for dispensing liquid or gas onto an upwardly facing surface of a wafer-shaped article when positioned on the spin chuck.
• Preferably, the different liquid sources include an etching liquid source and a rinsing liquid source.
• In preferred embodiments of the apparatus according to the present invention, the at least one lower liquid dispenser comprises two lower liquid dispensers, each terminating at a different liquid nozzle, and the different liquid sources include an etching liquid source and a rinsing liquid source.
• In another aspect, the present invention provides a process for treating a wafer-shaped article, comprising positioning a wafer-shaped article on a spin chuck in a predetermined orientation wherein a lower surface of the wafer-shaped article is downwardly-facing and spaced a predetermined distance from an upper surface of the spin chuck thereby defining a gap between the lower surface of the wafer-shaped article and the upper surface of the spin chuck, dispensing a treatment liquid onto the lower surface of the wafer-shaped article while rotating the wafer-shaped article, and dispensing a gas at least to an annular region of the gap defined by the lower surface of the wafer-shaped article and the upper surface of the spin chuck.
• In preferred embodiments of the process according to the present invention, the steps of dispensing a treatment liquid and dispensing a gas are at least partly performed concurrently.
• In preferred embodiments of the process according to the present invention, the treatment liquid is an etching liquid.
• Preferably, the etching liquid is dilute hydrogen fluoride.
• In preferred embodiments of the process according to the present invention, the process further comprises dispensing a rinsing liquid onto the lower surface of the wafer-shaped article while rotating the wafer-shaped article, and dispensing a gas into the gap defined by the lower surface of the wafer-shaped article and the upper surface of the spin chuck.
• In preferred embodiments of the process according to the present invention, the steps of dispensing a rinsing liquid and dispensing a gas are at least partly performed concurrently.
BRIEF DESCRIPTION OF THE DRAWINGS
• Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which:
• FIG. 1 is a schematic representation of an apparatus according to an embodiment of the present invention;
• FIG. 2 is a schematic diagram of an apparatus according to an embodiment of the present invention.
• FIG. 3 is a vertical and axial cross sectional view of the apparatus ofFIG. 2;
• FIG. 4 depicts a plurality of liquid nozzles for use in an embodiment of the present invention.
• FIG. 5 depicts plural valved liquid conduits for use in an embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• InFIG. 1, an apparatus according to the invention comprises a rotatable chuck1 adapted to support a semiconductor wafer W for single wafer wet processing. For example, chuck1 may include grippingfingers2 extending upwardly from anupper surface3 which engage the peripheral edge of a wafer W to position the wafer a fixed distance above the chuck'ssurface3. Thus, in use, agap4 exists between the lower (back) surface of a wafer and theupper surface3 of the chuck1.
• A treatment liquid dispenser comprisesliquid conduit5 which extends axially through a central bore in chuck1 to aliquid nozzle6 located at or withingap4.Liquid conduit5 andliquid nozzle6 are adapted to conduct one or more treatment liquids to the back surface of a wafer, preferably while the wafer W and chuck1 are rotating. Additional liquid conduits may extend through chuck1 to a commonliquid nozzle6 or to additional liquid nozzles located at or withingap4, as is further described below.
• A gas dispenser includesconduit7 which extends axially through a central bore in chuck1, preferably but not necessarily about theliquid conduit5, terminating with a gas distributor configured to dispense gas withingap4.
• In the embodiment shown inFIG. 1, the gas distributor comprises a plurality ofbranch conduits29 fluidly connected toconduit7 and leading to an annulargas distribution chamber34, which in turn is fluidly connected togap4 through a plurality ofgas nozzles36.Nozzles36 can be uniformly or randomly distributed over theupper surface3 of chuck1. Preferably,nozzles36 are annularly arranged and located at thesurface3 of chuck1 at least 2 cm outwardly from the central axis of the spin chuck and at least 5 mm inwardly from the edge of a wafer when positioned on the spin chuck. Alternatively, a single annular gas nozzle may be provided, in which case the annular gas nozzle preferably is located at least 4 cm outwardly from the central axis of the spin chuck and at least 1 cm inwardly from the edge of a wafer when positioned on the spin chuck.
• Adispenser8 is optionally provided opposite theupper surface3 of chuck1 such that gas and/or liquid may be dispensed onto the upper (front) surface of a wafer W mounted on chuck1.
• Liquid conduit5,gas conduit7 and optionallydispenser8 may be configured to operate selectively, and preferably concurrently, during a wafer treatment process. Accordingly, a treatment liquid delivered byliquid nozzle6 can effectively be bounded from below by gas which is delivered vianozzles36 and optionally from above by gas which is concurrently delivered viadispenser8, such that a layer of treatment liquid dispersed over the back surface of a wafer W can be maintained within a controlled local environment.
• Suitable gases include those which are inert to the wafer undergoing treatment and the devices and features fabricated thereon. For example, Nitrogen (N₂), IsoPropyl Alcohol (IPA) vapor, and combinations thereof may be provided.
• Treatment liquids will depend upon the given treatment process being conducted, and generally include any treatment liquid suitable for conducting a surface treatment processes. For example, etching liquids such as diluted hydrogen fluoride (dHF) may be conducted vialiquid conduit5. Rinsing liquids such as deionized (DI) water and/or IPA also may be conducted vialiquid conduit5.
• Referring toFIGS. 2 and 3, a further embodiment of the present invention comprises aspin chuck21 for holding and rotating a wafer W and anon-rotating nozzle head20. The spin chuck has abase body10, which is mounted onto arotating support plate41.
• Thesupport plate41 is connected to a rotating hollow shaft42 (rotor), which is part of ahollow shaft motor40. The hollow shaft motor has anouter stator40 and an inner rotor. Thestator40 is connected to amachine frame part43,44 with aframe plate43 and a connectingpart44. The cylinder-likenon-rotating nozzle head20 is connected to the connectingpart44.
• Thenozzle head20 therefore leads through thehollow shaft42 and thesupport plate41 leaving a small gap (preferably 0.05-0.5 mm) to the inner wall of thehollow shaft42. This gap between thehollow shaft42 and thenozzle head20 is sealed by anannular duct47, which is connected to a suction device (not shown).
• Thebase body10 of the spin chuck, which is mounted onto therotating support plate41, has an inner hole leaving a small gap (preferably 0.05-0.5 mm) to thenon-rotating nozzle head20.
• Acover plate12 is mounted onto thebase body10, whereby an inwardly opengas distribution chamber34 is generated. Thecover plate12 has a central plate11, which is mounted to the cover plate. The central plate11 is shaped in order to correspond to the shape of the nozzle head, wherein the central plate does not touch the nozzle head leaving a small gap G2 between thenozzle head20 and the central plate11 with a distance in a range of 0.05 and 0.5 mm. The inner hole of the central plate11 corresponds to thenozzle26 leaving a gap G3 with a distance d in a range of 0.05 and 0.5 mm.
• At the bottom of the gas distribution chamber34 aplate13 is mounted to thebase plate10 leaving a chamber between thebase plate10 and theplate13 for thetooth gear16. Thetooth gear16 is rotatable connected to thebase plate10 by thebearing17. The chamber for thetooth gear16 thus does not have a connection to thegas distribution chamber34.
• Thespin chuck21 comprises six cylindrically shaped holdingelements14 with eccentrically mountedgripping pins14a. The gripping pins14aare rotated about the holding elements' cylinder axis by atooth gear16. Thetooth gear16 is rotated against the base-body10 of the spin chuck by holding the tooth gear by a vertically movable rod18 (penetrating through a not shown slit in the base-body) while slightly rotating the base-body with the hollow-shaft motor40. Thereby thecylindrical holding elements14 are rotated and thegripping pins14aturn into open position. Thetooth gear16 drives the tooth gears15, which are part of the holdingelements14. After a wafer has been placed within the grippingpins14a, the base body is turned back and the tooth gear turns into close position driven by springs (not shown). Thereby the grippingpins14acontact the wafer's edge and securely grip the wafer.
• Thenozzle head20 comprises three lines (liquid line24,gas line28, and vacuum line46), which are parallel to the rotational axis of the spin chuck. Theliquid line24 leads to thenozzle26 for treating the wafer surface, which faces the spin chuck.
• A second liquid line (not shown) may be provided as essentially the mirror image ofliquid line24, such thatnozzle head20 includes two parallel liquid lines each of which terminates at thesame nozzle26. Thus, for example, etching liquid may be directed vialiquid line24 andnozzle26 to the back surface of a wafer during an etching process, whereas a rinsing liquid may be directed via the second liquid line andnozzle26 during a rinsing process.
• Thegas line28 is part of the non-rotating part of the gas supply line for providing gas togap4. In the upper part of the nozzle head thegas line28 splits into fourbranches29. Thebranches29 of the gas line end in an annular non-rotatinggas distribution chamber30. The non-rotatinggas distribution chamber30 opens into the rotatinggas distribution chamber34 through twelveopenings32.
• An annularly arranged plurality ofgas nozzles36 is coaxially arranged with respect to the rotational axis.Gas nozzles36 may be oriented outwardly or inwardly relative to the rotational axis from the gas distribution chamber to the surface of the spin chuck.
• More than 80% of gas, which has been supplied from the non-rotatinggas distribution chamber30 into the rotatinggas distribution chamber34, is dispensed through theopenings36 for providing gas to thegap4 between the wafer and thecover plate12.
• The rest of the gas, which has been introduced into the rotatinggas distribution chamber34, is used for purging the gaps G1, G2, and G3 between thenon-rotating nozzle head20 and thespin chuck21.
• G1 is the gap between thenozzle head20 and thebase body10 of the spin chuck. Gas, which has been introduced into gap G1 is removed through theannular duct47, which is connected to thesuction line46.
• G2 is the gap between the upper part of thenozzle head20 and the lower side of the central plate11 and G3 is the gap between thenozzle26 and the central hole of the central plate11.
• For collecting spun off liquid a collecting chamber (annual duct—not shown) is concentrically arranged around the spin chuck. For spinning liquid into different vertically arranged annual ducts the stationary frame and the collecting chamber can be axially shifted against each other (as disclosed for instance in U.S. Pat. No. 4,903,717).
• Nozzle head20 inFIGS. 2 and 3 may be provided in various configurations whereby one or more desired process liquids can be delivered to the back surface of a wafer undergoing treatment and a gas can be delivered to the gap formed between the back surface of the wafer and the upper surface of the spin chuck. For example, as is generally depicted inFIG. 4,nozzle head20 may comprise pluralliquid nozzles26a-26d, each of which is fluidly connected to a corresponding liquid line, such that different process liquids can be selectively dispensed.
• Also,nozzle head20 may comprise aliquid line24 which is selectively fluidly connected to a plurality of process liquid supplies, such as an etchant supply and a rinse supply. For example, referring toFIG. 5,liquid supply conduit48 includes a selectivelyoperable valve48awhich, when open, conducts an etching liquid supply such as dHF toliquid line24.Liquid supply conduit49 includes a selectivelyoperable valve49awhich, when open, conducts a rinsing liquid such as DI water toliquid line24.
• Although not depicted in the drawings, process modules of this type, even when open to the surrounding ambient, are typically closely surrounded by exhaust levels and collector levels that serve to recover liquid flung radially outwardly off of the spinning wafer, as well as to vent gasses safely away from the process module.
• An example of a series of operations performed using the apparatus ofFIG. 1 will now be described.
• A semiconductor wafer W is positioned relative to chuck1 so as to form agap4 between the wafer W and theupper surface3 of chuck1, after which wafer W and chuck1 are rotated. An etching treatment of the back side of the wafer W is conducted. During the etching treatment, dHF is conducted to the back side of the wafer W vialiquid nozzle6 and a mixture of IPA in nitrogen gas is conducted togap4 viagas distribution chamber34 andnozzles36. Optionally, a mixture of IPA in nitrogen gas is concurrently conducted to the front surface of wafer W viadispenser8.
• After etching, a water rinse treatment is conducted. During the water rinse treatment, heated DI water, e.g., about 72° C., is conducted to the back side of the wafer W vialiquid nozzle6 and a mixture of IPA in nitrogen gas is conducted togap4 viagas distribution chamber34 andnozzles36. Optionally, heated DI water, e.g., about 72° C., is concurrently conducted to the front surface of wafer W viadispenser8.
• After water rinsing, an IPA rinse treatment is conducted. During the IPA rinse treatment, heated liquid IPA, e.g., about 72° C., is conducted to the back side of the wafer W vialiquid nozzle6 and a mixture of IPA in nitrogen gas is conducted togap4 viagas distribution chamber34 andnozzles36. Optionally, heated liquid IPA, e.g., about 72° C., is concurrently conducted to the front surface of wafer W viadispenser8.
• After IPA rinsing, a drying treatment is conducted. During the drying treatment, a mixture of IPA in nitrogen gas is conducted togap4 viagas distribution chamber34 andnozzles36. Optionally, a mixture of IPA in nitrogen gas is concurrently conducted to the front surface of wafer W viadispenser8.
• While the present invention has been described in connection with various illustrative embodiments thereof, it is to be understood that those embodiments should not be used as a pretext to limit the scope of protection conferred by the true scope and spirit of the appended claims.

Claims (15)

What is claimed is:

1. Apparatus for treating a wafer-shaped article, comprising:

a spin chuck for holding a wafer-shaped article in a predetermined orientation wherein a lower surface of the wafer-shaped article, when positioned on the spin chuck, is downwardly-facing and spaced a predetermined distance from an upper surface of the spin chuck, thereby defining a gap between the lower surface of the wafer-shaped article and the upper surface of the spin chuck;

a lower gas dispenser located and configured for dispensing gas at least to an annular region of the gap defined by the upper surface of the spin chuck and the lower surface of a wafer-shaped article when positioned on the spin chuck, and

at least one lower liquid dispenser located and configured for dispensing liquid onto a downwardly facing surface of a wafer-shaped article when positioned on the spin chuck, wherein the at least one lower liquid dispenser is operatively connected to at least two different liquid sources for subsequently dispensing two different liquids onto a downwardly facing surface of a wafer-shaped article when positioned on the spin chuck.

2. The apparatus according toclaim 1, wherein said spin chuck further comprises a peripheral series of upwardly projecting gripping elements positioned so as to be engageable with a peripheral edge of a wafer-shaped article to be held by the spin chuck, each of the upwardly projecting gripping elements being pivotable about an axis parallel to an axis of rotation of the spin chuck.

3. The apparatus according toclaim 1, wherein the lower gas dispenser comprises a plurality of annularly arranged gas nozzles.

4. The apparatus according toclaim 1, wherein the lower gas dispenser comprises an annular gas nozzle.

5. The apparatus according toclaim 1, wherein the at least one lower liquid dispenser comprises two lower liquid dispensers, each terminating at a same liquid nozzle.

6. The apparatus according toclaim 1, wherein the at least one lower liquid dispenser comprises two lower liquid dispensers, each terminating at a different liquid nozzle.

7. The apparatus according toclaim 1, further comprising an upper dispenser positioned and configured for dispensing liquid or gas onto an upwardly facing surface of a wafer-shaped article when positioned on the spin chuck.

8. The apparatus according toclaim 1, wherein the different liquid sources include an etching liquid source and a rinsing liquid source.

9. The apparatus according toclaim 6, wherein the different liquid sources include an etching liquid source and a rinsing liquid source.

10. A process for treating a wafer-shaped article, comprising:

positioning a wafer-shaped article on a spin chuck in a predetermined orientation wherein a lower surface of the wafer-shaped article is downwardly-facing and spaced a predetermined distance from an upper surface of the spin chuck thereby defining a gap between the lower surface of the wafer-shaped article and the upper surface of the spin chuck;

dispensing a treatment liquid onto the lower surface of the wafer-shaped article while rotating the wafer-shaped article; and

dispensing a gas at least to an annular region of the gap defined by the lower surface of the wafer-shaped article and the upper surface of the spin chuck.

11. The process according toclaim 10, wherein the steps of dispensing a treatment liquid and dispensing a gas are at least partly performed concurrently.

12. The process according toclaim 10, wherein the treatment liquid is an etching liquid.

13. The process according toclaim 11, wherein the etching liquid is dilute hydrogen fluoride.

14. The process according toclaim 12, further comprising:

dispensing a rinsing liquid onto the lower surface of the wafer-shaped article while rotating the wafer-shaped article; and

dispensing a gas into the gap defined by the lower surface of the wafer-shaped article and the upper surface of the spin chuck.

15. The process according toclaim 14,

wherein the steps of dispensing a rinsing liquid and dispensing a gas are at least partly performed concurrently.

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