UNITED STATES PATENT AND TRADEMARK OFFICE BEFORE THE BOARD OF PATENT APPEALS AND INTERFERENCES

Transcription

1 UNITED STATES PATENT AND TRADEMARK OFFICE BEFORE THE BOARD OF PATENT APPEALS AND INTERFERENCES Ex parte ELIZABETH G. PAVEL, MARK N. KAWAGUCHI, and JAMES S. PAPANU Appeal Technology Center 1700 Decided: August 28, 2009 Before ADRIENE LEPIANE HANLON, CHUNG K. PAK, and TERRY J. OWENS, Administrative Patent Judges. PAK, Administrative Patent Judge. DECISION ON APPEAL Appellants appeal under 35 U.S.C. 134(a) from the Examiner s decision finally rejecting claims 1 through 7, 9 through 11, and 13 through 23 (Final Office Action, mailed November 13, 2007), the only claims pending in the application. We have jurisdiction under 35 U.S.C. 6(b).

2 We REVERSE. STATEMENT OF THE CASE The subject matter on appeal is directed to a method for monitoring and detecting optical emission endpoint(s), for photoresist stripping and removal of residue from a substrate (Spec. 1, para. 0002). Details of the appealed subject matter are recited in representative claims 1 and 14 reproduced from the Claims Appendix to the Appeal Brief ( App. Br. ), filed April 14, 2008: 1. A method, comprising: positioning a substrate comprising a photoresist layer into a processing chamber; processing the photoresist layer using a multiple step plasma process; and monitoring the plasma for a hydrogen optical emission and an oxygen optical emission during the multiple step plasma process; wherein the multiple step plasma process comprises: removing a bulk of the photoresist layer using a bulk removal step; and switching to an overetch step in response to the monitored hydrogen optical emission or the monitored oxygen optical emission. 14. A method of etching a photoresist layer comprising: positioning a substrate comprising a photoresist layer into a processing chamber; processing the photoresist layer using a multiple step plasma process; and monitoring the plasma for both by-product optical emission and a reactant optical emission during the multiple step plasma process; wherein the multiple step plasma process comprises: removing a bulk of the photoresist layer using a bulk removal step; and switching to an overetch step in response to the monitored by-product optical emission. 2

3 The Examiner relies on the following evidence to establish unpatentability of the claims on appeal (Examiner s Answer ( Ans. ), mailed June 13, 2008): Tsang US 5,262,279 Nov. 16, 1993 Ishihara US 2001/ A1 Oct. 4, 2001 Powell US 2002/ A1 Sep. 26, 2002 Hallock US 2002/ A1 Oct. 17, 2002 Appellants request review of the following Examiner s rejections (page 3 of Reply Brief ( Reply Br. ), filed August 13, 2008): 1. Claims 1, 5 through 7, 9 through 11, 13, 14, and 17 through 23 under 35 U.S.C. 103(a) as unpatentable over Ishihara in view of Tsang and Powell; and 2. Claims 2 through 4, 15, and 16 under 35 U.S.C. 103(a) as unpatentable over Ishihara, Tsang, Powell and Hallock. In rejecting the claims on appeal under 35 U.S.C. 103, the Examiner relies on Ishihara for teaching a multiple step plasma process comprising monitoring the intensity of light emission of hydrogen or oxygen during the removal or modification of a deteriorated region of a photoresist layer on a semiconductor substrate with a high density plasma, switching to an ashing step in response to the monitored intensity of light emission caused by hydrogen or oxygen, and ashing and removing the modified and/or remaining resist in the presence of an oxygen plasma (Ans. 3-4 and 6). According to the Examiner, the claimed step for removing a bulk of the photoresist layer reads on Ishihara s first step of modifying or removing the deteriorated region on a photoresist layer (Ans. 4, 6, and 11). 3

4 The Examiner admits that Ishihara does not teach the claimed overetch step and the claimed hydrogen and oxygen optical emission monitoring during Ishihara s first step (Ans. 4-7). To remedy these deficiencies, the Examiner relies on Tsang for teaching the use of the claimed overetch step for removing residual resist material and Powell for teaching the use of the claimed hydrogen and oxygen optical emission monitoring for stopping an etching process (Ans. 4-9). The Examiner then concludes that it would have been obvious to employ the claimed overetch step taught by Tsang, in lieu of Ishihara s ashing step for removing the rest of the photoresist layer and employ the claimed hydrogen and oxygen optical emission monitoring technique taught by Powell, in lieu of the hydrogen or oxygen light emission intensity monitoring used during Ishihara s deteriorated region removal or modifying step (Ans. 4-7). Hallock is further relied upon to explain the formation of a harden crust layer on Ishihara s photoresist layer (Ans. 9). Appellants contend that the Examiner reversibly erred in finding, inter alia, Ishihara s first step of removing or modifying a deteriorated region on a photoresist layer constitutes the claimed bulk removal step. ISSUES Have Appellants identified reversible error in the Examiner s finding that Ishihara s first step of removing or modifying a deteriorated region on a photoresist layer constitutes the claimed step for removing a bulk of the photoresist layer? On this record, we answer this question in the affirmative. 4

5 FINDINGS OF FACT ( FF ) Claim Interpretation 1. The Specification states (Spec. 6, para. 0024) that: [O]ne chemistry or recipe can be used for photoresist crust removal and a second chemistry or recipe can be used for bulk photoresist removal. Similarly, the bulk photoresist can be removed until another emission change occurs, then a third chemistry or recipe can be used to remove residue that remains from the stripping process. 2. The Specification states that the crust layer is typically one to several thousand angstroms thick and is located on top of the bulk photoresist (Spec. 2, para. 0004). Rejections 3. Ishihara teaches a multiple step plasma process comprising initially modifying a deteriorated region on a photoresist layer on a semiconductor substrate with a high density plasma (due to ion implantation), switching to an ashing step in response to, inter alia, the monitored light emission caused by hydrogen or oxygen, and ashing and removing the modified resist in the presence of an oxygen plasma (pp. 6-7, paras ). 4. Ishihara also teaches (p. 7, paras. 0159, 0160, 0162 and 0164) (emphasis added) that: [0159] If during the ion implantation the substrate surface is inclined and the wafer is rotated, the deteriorated region will also be formed on the side wall of the resist 27. 5

6 [[0160] Then, the resist is modified by effecting the plasma processing with the oxygen-, hydrogen-, and fluorine-containing gases according to the same step as the first step described above. The region deteriorated by the ion implantation may be removed at the same time as this processing or may be only modified without being removed. [0162] Then, the process transfers to the second step to effect the plasma processing with oxygen gas to remove the remaining resist.... [0164] According to the present embodiment, the ion implanted resist can be removed well and rapidly without over etching of the gate electrode or polycrystal silicon and the film comprised of silicon oxide on the source /drain regions. 5. Ishihara further teaches that deteriorated regions are also known to be located on the surface of a photoresist layer (p. 1, paras and 0013). 6. Tsang teaches (col. 7, ll ) that: The use of the endpoint detector 59 to monitor the light intensity associated with the energy released by CH 3 * radicals returning to ground state has provided a precise, reliable and reproducible method of detecting the completion of the stripping of photoresist layer 28. After the endpoint is reached, there may be a thin layer of residual photoresist on some areas of polyimide layer 26. Therefore, a short, timed overetch is employed to ensure complete removal of photoresist layer 28. As discussed above, several factors are believed to cause the plasma to selectively strip the photoresist. 6

7 7. Powell teaches monitoring the optical emissions of the plasma at a plurality of wavelengths to determine changes in reaction by-products produced during an etching process and stopping the etching process based on the optical emissions of wavelengths reflective of undesired byproducts. (pp. 4, 5, and 8, paras. 0030, 0036, 0038, 0041, and 0059). 8. Powell teaches monitoring the oxygen and hydrogen optical emission during the semiconductor chamber cleaning and conditioning processes (pp. 1 and 7, paras and 0051, and Fig. 11). 9. The Examiner relies on Hallock to teach that the implantation of boron, phosphorus or arsenic ion causes the formation of a harden crust layer (Ans. 9; See also Hallock, para and Fig. 1). PRINCIPLES OF LAW During examination, claims terms are generally given their broadest reasonable construction in light of the specification as it would be interpreted by one of ordinary skill in the art. In re Am. Acad. of Sci. Tech. Ctr., 367 F.3d 1359, 1364 (Fed. Cir. 2004); see also In re Fout, 675 F.2d 297, 300 (CCPA 1982)( Claims must always be read in light of the specification. Here, the specification makes plain what appellants did and did not invent. ). However, when the meaning of the claim term is implied, such meaning is given. Phillips v. AWH Corp., 415 F.3d 1303, 1321 (Fed. Cir. 2005)( [T]he specification acts as a dictionary when it expressly defines terms used in the claims or when it defines terms by implication. ); Irdeto Access, Inc. v. Echostar Satellite Corp., 383 F.3d 1295, 1300 (Fed. Cir. 2004)( Even when guidance is not provided in explicit definitional format, the specification may define claim terms by implication 7

8 such that the meaning may be found in or ascertained by a reading of the patent documents. ). Indeed, our reviewing court stated in Phillips v. AWH Corp., 415 F.3d at 1315: The specification is always highly relevant to the claim construction analysis. Usually, it is dispositive; it is the single best guide to the meaning of a disputed term. ANALYSIS The multiple step plasma process recited in claims 1 and 14 requires: removing a bulk of the photoresist layer using a bulk removal step; and switching to an overetch step in response to the monitored hydrogen optical emission or the monitored oxygen optical emission. Although the Specification does not expressly define the meaning of a bulk of the photoresist layer, it provides a clear guidance as to the meaning of such term as correctly argued by Appellants at page 6 of the Appeal Brief and page 4 of the Reply Brief. Specifically, the Specification states (Spec. 6, para. 0024) that: [O]ne chemistry or recipe can be used for photoresist crust removal and a second chemistry or recipe can be used for bulk photoresist removal. Similarly, the bulk photoresist can be removed until another emission change occurs, then a third chemistry or recipe can be used to remove residue that remains from the stripping process. The Specification further states at page 2, paragraph 4, that the crust layer is typically one to several thousand angstroms thick and is located on top of the bulk photoresist. Thus, it is clear from the Specification that the claimed 8

9 bulk of the photoresist layer is a majority of the photoresist layer located below a relatively thin crust (surface) layer. Having properly interpreted the claims on appeal, we now evaluate the propriety of the Examiner s 103(a) rejections. As is apparent from the above, the Examiner s 103 rejections is premised upon the Examiner s finding that Ishihara s first step of modifying or removing the deteriorated region on a photoresist layer constitutes the claimed step for removing a bulk of the photoresist layer. However, as correctly pointed out by Appellants at page 6 of the Appeal Brief and page 4 of the Reply Brief, the deteriorated region taught by Ishihara, like the crust layer, is located only on the surface of a photoresist layer. Thus, it cannot be said that Ishihara s first step of modifying or removing the deteriorated region on a photoresist layer constitutes the claimed step for removing a bulk of the photoresist layer. Accordingly, even if we agree with the Examiner that the features taught by Tsang, Powell, and Hallock are combinable in the manner proposed by the Examiner, we determine that the combination would not result in the claimed invention within the meaning of 35 U.S.C. 103(a). CONCLUSION Appellants have identified reversible error in the Examiner s obviousness determination. The decision of the Examiner rejecting the claims on appeal is reversed. REVERSED tc 9

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