Ex Parte Breitwisch et alDownload PDFPatent Trial and Appeal BoardApr 17, 201412243809 (P.T.A.B. Apr. 17, 2014) Copy Citation UNITED STATES PATENT AND TRADEMARK OFFICE _________ BEFORE THE PATENT TRIAL AND APPEAL BOARD __________ Ex parte MATHEW J. BREITWISCH, ERIC A. JOSEPH, CHUNG H. LAM, BIPIN RAJENDRAN, and ALEJANDRO G. SCHROTT __________ Appeal 2012-000264 Application 12/243,809 Technology Center 2800 ___________ Before ADRIENE LEPIANE HANLON, CATHERINE Q. TIMM, and JAMES C. HOUSEL, Administrative Patent Judges. HANLON, Administrative Patent Judge. DECISION ON APPEAL Appeal 2012-000264 Application 12/243,809 2 A. STATEMENT OF THE CASE The Appellants appeal under 35 U.S.C. § 134 from the final rejection of claims 1-10. We have jurisdiction under 35 U.S.C. § 6(b). We AFFIRM. The subject matter on appeal is directed to a method for forming a memory cell structure for phase change memory. The Appellants disclose: In phase change memory, information is stored in materials that can be manipulated into different phases. Each of these phases exhibit different electrical properties which can be used for storing information. The amorphous and crystalline phases are typically two phases used for bit storage (1’s and 0’s) since they have detectable differences in electrical resistance. Specifically, the amorphous phase has a higher resistance than the crystalline phase. Spec. ¶ [0002]. According to the Appellants, “[o]ne issue with phase change memory is the energy required to melt the phase change material.” Spec. ¶ [0004]. To reduce this energy requirement, the Appellants employ a stress liner to impart stress on the phase change material. The increased stress on the phase change material is said to lower its melting point during phase change and thus reduce the energy required for melting. Spec. ¶ [0019]. The Appellants disclose that the stress liner material “may be comprised of a variety of materials such as tensile silicon nitride and compressive silicon nitride” and the phase change material may be a chalcogenide, such as germanium- antimony-tellurium (GST). Spec. ¶¶ [0003], [0025], [0026]. Appeal 2012-000264 Application 12/243,809 3 Claim 1 is reproduced below from the Claims Appendix of the Appeal Brief dated January 27, 2011 (“Br.”).1 1. A method for forming a memory cell structure, the method comprising: [1] forming a bottom electrode within a substrate, the bottom electrode being electrically conducting; [2] depositing a dielectric layer over the bottom electrode, the dielectric layer being electrically insulating; [3] forming a via within the dielectric layer and substantially over the center of the bottom electrode, the via including at least one sidewall; [4] depositing a stress liner along the at least one sidewall of the via such that the stress liner imparts stress on material proximate the stress liner; [5] depositing a phase change material within the via and a volume enclosed by the stress liner, wherein the stress imparted by the stress liner lowers the melting point of the phase change material; and [6] forming a top electrode above the phase change material, the top electrode being electrically conducting. The claims on appeal stand rejected as follows: claims 1-9 under 35 U.S.C. § 103(a) as unpatentable over Lung2 in view of Philipp3; and claim 10 under 35 U.S.C. § 103(a) as unpatentable over Lung in view of Philipp and further in view of Richter.4 The Appellants argue the patentability of claims 1-9 as a group and do not present separate arguments in support of the patentability of claim 10. Br. 11. Thus, for purposes of this appeal, claims 2-9 stand or fall with the patentability of 1 Italics and numbering added. 2 US 2008/0191186 A1, published August 14, 2008. 3 US 2007/0249086 A1, published October 25, 2007. 4 US 2008/0182346 A1, published July 31, 2008. Appeal 2012-000264 Application 12/243,809 4 claim 1, and the patentability of claim 10 will be considered based on the arguments advanced in support of the patentability of claim 1. 37 C.F.R. § 41.37(c)(1)(vii). B. DISCUSSION The Examiner finds that Lung discloses a method for forming a memory cell structure comprising, inter alia, the steps of depositing sidewall spacers (910) along at least one sidewall of a via (step [4] of claim 1) and depositing a phase change material (1000), such as a chalcogenide, within the via (step [5] of claim 1). The Examiner finds the sidewall spacers (910) and the phase change material (1000) are in direct contact with one another in the via (Fig. 11) but finds that Lung does not expressly disclose that the sidewall spacers impart stress on the phase change material as recited in claim 1. Ans. 4.5 The Examiner finds that Philipp discloses a stress liner (208, 130) formed as sidewall spacers around a phase change memory material (206, 128). Ans. 4. The Examiner does not find that Philipp expressly discloses that the stress liner imparts stress on the phase change memory material. Nonetheless, the Examiner finds that Philipp discloses “the same materials for the stress liner and phase change material (tensile or compressive silicon nitride and chalocogenides) (par. 0039, 0043, Philipp) . . . formed in the same location in the substantially same structure as those in the current application (par. 0025, 0003).” Ans. 9-10. Thus, the Examiner finds the stress liner of Philipp “would perform the same function as claimed” (i.e., lower the melting point of the phase change material) in both Philipp and Lung as modified by Philipp. Ans. 10; see also Ans. 5. 5 Examiner’s Answer dated May 11, 2011. Appeal 2012-000264 Application 12/243,809 5 The Appellants do not dispute that it would have been obvious to combine the teachings of Lung and Philipp as proposed by the Examiner. Rather, relying on paragraph [0062] of Philipp, the Appellants argue that stress layer 208 operates to suppress a transition in phase change material 206 to a high temperature crystalline state. Thus, the Appellants contend that “Philipp appears to disclose that the stress layer increases[, rather than decreases,] the melting temperature of the phase change material.” Br. 10. In response, the Examiner makes the following findings: The melting point is the temperature at which a transition occurs from solid to liquid (or, in this case, amorphous) state. In Philipp, this is temperature T1. The suppressed transition to a high temperature crystalline state, as taught by Philipps [sic], is a transition from one solid phase (low temperature crystalline phase) to another solid phase (high temperature crystalline phase), and is designated as T2. This occurs at a different (higher) temperature than the melting temperature T1, as can be seen in fig. 3 of Philipps [sic]. Thus, although Philipps [sic] discloses that a transition to a high temperature crystalline state is suppressed (T2 is made higher), Philipps [sic] does not disclose that this raises the melting temperature T1. Ans. 9. These findings are supported by the record. See, e.g., Philipp ¶ [0050]. The Appellants also argue: Philipp discloses that when switching between memory/phase states of a phase change material, “the local temperature is generally raised above the melting temperature (approximately 600 degrees Celsius) to achieve a highly random atomic structure, and then rapidly cooled to ‘lock’ the atomic structure in the amorphous state.[”] Philipp, par. [0005] (emphasis added). Thus, according to Philipp, transitioning between phase states requires melting the phase change material. Br. 10. Appeal 2012-000264 Application 12/243,809 6 A review of the Appellants’ Specification reveals that the Appellants also disclose that transitioning between phase states requires melting the phase change material. See Spec. ¶ [0021] (“altering the phase change material’s state requires heating the material to a melting point and then cooling the material to one of the possible states”). For example, the Appellants disclose that “[m]elting and abruptly cooling the phase change material quenches the phase change material into the amorphous state.” Spec. ¶ [0021]. Thus, this argument is not persuasive of reversible error. In sum, the Appellants have failed to demonstrate harmful error in the Examiner’s rejection of claim 1. Therefore, the § 103(a) rejections are sustained. C. DECISION The decision of the Examiner is affirmed. No time period for taking any subsequent action in connection with this appeal may be extended under 37 C.F.R. § 1.136(a)(1). AFFIRMED cdc Copy with citationCopy as parenthetical citation