WAFER CLEANING METHOD AND APPARATUS THEREFORE

Abstract

The present invention relates to a method for treating the surface of a wafer with multiple liquids, comprising rotating the surface of the wafer and discharging different liquid streams onto the rotating surface in a sequence from separate outlets, wherein the discharge of liquid streams which are contiguous in the sequence overlaps during a transition phase, and wherein during the transition phase the liquid streams merge after exiting said outlets to form a merged liquid stream before impacting the rotating surface. The invention also provides a liquid dispensing device incorporating a housing holding two or more liquid delivery tubes, wherein the tubes' outlets are inwardly angled towards one another, such that in use liquid streams delivered from the outlets of the two or more liquid delivery tubes merge to form a merged liquid stream.

Claims

1. A method for treating the surface of a wafer with multiple liquids, comprising rotating the surface of the wafer and discharging different liquid streams onto the rotating surface in a sequence from separate outlets, wherein the discharge of liquid streams which are contiguous in the sequence overlaps during a transition phase, and wherein during the transition phase the liquid streams merge after exiting said outlets to form a merged liquid stream before impacting the rotating surface.

2. The method according to claim 1, wherein said outlets are angled towards one another so as to form the merged liquid stream.

3. The method according to claim 1, wherein the true flowpath intersection angle between the merging liquid streams is 10° to 40°.

4. The method according to claim 1, wherein the true flowpath intersection height of the merging liquid streams is between 2-100 mm.

5. The method according to claim 1, wherein said sequence comprises alternating active steps and rinsing steps.

6. The method according to claim 5, wherein the method involves treating the surface of a semiconductor wafer, in which the sequence of steps involves one or more cycles of the following: (A) an optional rinsing step; (B) a step to remove organic and/or particulate contaminants; (C) an optional rinsing step; (D) an optional step to remove a surface oxide layer; (E) an optional rinsing step; (F) a step to remove ionic contaminants; and (G) an optional rinsing step; or a variant of the above with the order of steps (A), (F), (G), (B), (C), (D), (E).

7. The method according to claim 6, wherein the method involves one or more cycles of the following steps: (A) optionally, rinsing the surface with water discharged from a first outlet; (B) treating the surface with a solution comprising a mixture of ammonia and hydrogen peroxide discharged from a second outlet; (C) optionally, rinsing the surface with water, preferably discharged from the first outlet; (D) optionally, treating the surface with hydrofluoric acid; (E) optionally, rinsing the surface with water, preferably discharged from the first outlet; (F) treating the surface with a solution comprising a mixture of acid (for example, sulphuric or hydrochloric acid) and hydrogen peroxide discharged from a third outlet; and (G) optionally, rinsing the surface with water, preferably discharged from the first outlet; or a variant of the above with the order of steps (A), (F), (G), (B), (C), (D), (E); wherein the sequence includes at least one of rinsing steps (A), (C), (E) and (G) per cycle.

8. A liquid dispensing device suitable for carrying out a method according to claim 1, comprising a housing holding two or more liquid delivery tubes, wherein the tubes' outlets are inwardly angled towards one another, such that in use liquid streams delivered from the outlets of the two or more liquid delivery tubes merge to form a merged liquid stream.

9. The liquid dispensing device according to claim 8, comprising: said housing, defining an internal chamber opening at an exit port; a spacer, located within the internal chamber of the housing; and said two or more liquid delivery tubes, passing along the spacer within the internal chamber of the housing, and extending to the exit port; wherein the two or more liquid delivery tubes are bent around the spacer so that the tubes' outlets are inwardly angled towards one another, such that in use liquid streams delivered from the outlets of the two or more liquid delivery tubes merge to form a merged liquid stream.

10. The liquid dispensing device according to claim 7, wherein the housing and spacer clamp the two or more liquid delivery tubes in position, and the internal chamber of the housing narrows at or towards the exit port so as to bend the liquid delivery tubes around the spacer and thereby orient the tubes' outlets into said inwardly angled configuration.

11. The liquid dispensing device according to claim 9, wherein the spacer has one or more channels which accommodate the liquid delivery tubes.

12. The liquid dispensing device according to claim 9, wherein the housing comprises a main body and a detachable cap, wherein the detachable cap includes said exit port.

13. The liquid dispensing device according to claim 8, wherein the straight flowpath intersection angle of the tubes' outlets is 10° to 40°.

14. A kit of parts for assembling a liquid dispensing device according to claim 9, comprising: said housing; and one or more of said spacers, preferably at least two spacers having a different number of channels for accommodating liquid delivery tubes.

15. A cleaning apparatus for carrying out a method according to claim 1, comprising: a cleaning chamber; a wafer holder in the cleaning chamber; means for rotating the wafer holder; and a liquid dispensing device according to ay one of claims 8 to 13 comprising a housing holding two or more liquid delivery tubes, wherein the tubes' outlets are inwardly angled towards one another, such that in use liquid streams delivered from the outlets of the two or more liquid delivery tubes merge to form a merged liquid stream.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0120] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0121] FIG. 1 shows a perspective view of a liquid dispensing device according to the present invention;

[0122] FIGS. 2A and 2B are cross-sections of the liquid dispensing device of FIG. 1, the two figures showing views orthogonal to one another;

[0123] FIGS. 3A, 3B and 3C are schematic views showing a liquid delivery sequence in accordance with the method of the present invention;

[0124] FIG. 4 is a schematic view of delivery from a liquid dispensing device according to the present invention to illustrate deviation between the straight flowpath intersection angle and the true flowpath intersection angle;

[0125] FIG. 5 is a flow chart showing the implementation of an RCA clean in accordance with the method of the present invention;

[0126] FIGS. 6A and 6B are perspective views of the top and bottom of a three-tube spacer;

[0127] FIG. 7 is a schematic view of the bottom of a two-tube spacer;

[0128] FIGS. 8A, 8B, 8C show a detachable cap of the liquid dispensing device of the present invention, and are respectively a top perspective view, a bottom perspective view, and a cross-section view.

DETAILED DESCRIPTION OF THE INVENTION

[0129] FIG. 1 shows a liquid dispensing device 1 according to the present invention. The device incorporates a tubular housing 2 having a main section 3 and a detachable cap 4. The housing contains a spacer 5 (shown in subsequent figures), secured in place by screw 6, as well as three PFA tubes 7 (shown in subsequent figures) connected to liquid reservoirs (not shown).

[0130] FIGS. 2A and 2B are cross-sectional views of the interior of the housing 2 along the planes indicated by I-I and II-II in FIG. 1 respectively. The housing encases a spacer 5 and tubes 7, the latter of which protrude through the open end of the detachable cap 4 at an angle, due to an inward taper provided on the interior surface of the detachable cap 4 and corresponding tapered outer surface of the spacer 5.

[0131] FIGS. 3A-C show operation of the device shown in FIGS. 1-2. In FIG. 3A a first washing step is carried out by delivering a flow of liquid 10 from first tube 11 onto rotating wafer 12. Next, in FIG. 3B the device enters a transition period in which flow of liquid 10′ is delivered from second tube 11′ whilst maintaining delivery of the first liquid 10 from the first tube 11. The liquids 10 and 10′ and form a single flow which impacts the rotating wafer at its centre point. Finally, in FIG. 3C the flow of liquid 10′ continues with the flow of liquid 10 stopped, to effect a second washing step.

[0132] FIG. 3B shows dotted lines indicated the theoretical flowpath of liquids 10 and 10′ assuming that the liquid is ejected from the tubes 11 and 11′ along a straight path. The point “P” at which the flowpaths intersect corresponds to the straight flowpath intersection height, which in this case is 10 mm above the surface of rotating wafer 12. The straight flowpath intersection angle represented by θ.sub.S is 26°. The true flowpath intersection angle θ.sub.T in this case is approximately the same as that calculated based on straight flows, since the liquid flow rate and proximity to the surface of the rotating wafer 12 mean that there are no significant deviations from straight flow. This is in contrast to the situation shown in FIG. 4, where the combination of a lower flow rate and steeper nozzle angle means that the straight flowpath angle θ.sub.S is greater than the true flowpath angle θ.sub.T, and similarly the true intersection height is lower than that anticipated based on straight flowpath height.

[0133] FIG. 5 shows implementation of an RCA clean using the three tube liquid dispensing device shown in FIGS. 1-4, in which deionised water is dispensed from the first tube, an aqueous mixture of ammonia and hydrogen peroxide in deionised water is dispensed from the second tube, and an aqueous mixture of sulphuric acid and hydrogen peroxide in deionised water is dispensed from the third tube. The shaded regions indicate transition phases, during which liquid is delivered simultaneously from the relevant tubes.

[0134] FIGS. 6A and 6B show the spacer component of FIG. 2 in greater detail. The spacer 20 includes three channels 21 for receiving liquid delivery tubes (not shown). The spacer includes a collar 22, having a diameter comparable to the inner chamber of the housing in order to stably position the spacer horizontally within the housing. The collar is provided with a screw thread on its outer surface (not shown) to engage with a corresponding screw thread within the housing. The collar also has an upper abutment surface 23 which abuts the mouth region of the tubular section 3 of the housing in use (see FIG. 2) to vertically position the spacer within the housing and prevent the housing being pushed too far within the housing, and a lower abutment surface which abuts a corresponding stop surface in the detachable cap. Below the collar, a tapered section 24 is provided which fits within the corresponding inwardly tapered chamber of the housing, which bends the tubes into position. Above the collar, scalloped sections 25 (that is, the “empty” regions between channels) help to minimise friction during insertion of the spacer into the housing, and generally reduce the amount of material used to manufacture the spacer. The spacer 20 also incorporates an anchor section 26, with a screw hole 27 which can be used to secure the spacer to the housing using a screw, as shown in FIG. 2A. FIG. 7 is an alternative spacer 30, having only two channels 31 for receiving liquid delivery tubes (not shown), the other features being identical to those shown for spacer 20.

[0135] FIGS. 8A-C show the features of the detachable cap 40 in greater detail. FIG. 8A is a cross-sectional view of the cap 40. The cap includes an upper chamber 41 with a diameter corresponding to the collar 22 of spacer 20. The surface of the upper chamber includes a screw thread (not shown) which screws onto a corresponding screw thread provided on the collar of a spacer, to hold the cap in place. The cap also has a lower chamber 42, having a frusto-conical shape terminating at an open exit port 43. The lower chamber has a cone angle of ˜22°, which guides the liquid delivery tubes into their inwardly angled configuration in conjunction with the tapered section of the spacer. Between the upper chamber 41 and lower chamber 43 is an intermediate chamber 44, having a larger diameter to allow for the outward bulging of the plastic liquid delivery tubes as they are bent into position, and to avoid chafing of the tubes. FIGS. 8B and 8C respectively show a view of the cap into the upper chamber 41 and lower chamber 42, illustrating the narrower cross section at the exit port 43.

[0136] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0137] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0138] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0139] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0140] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0141] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/−10%.