Ex Parte Chan et alDownload PDFPatent Trial and Appeal BoardOct 30, 201711494413 (P.T.A.B. Oct. 30, 2017) Copy Citation United States Patent and Trademark Office UNITED STATES DEPARTMENT OF COMMERCE United States Patent and Trademark Office Address: COMMISSIONER FOR PATENTS P.O.Box 1450 Alexandria, Virginia 22313-1450 www.uspto.gov APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO. 1098.P0008US 2057 EXAMINER KING, DOUGLAS ART UNIT PAPER NUMBER 2824 MAIL DATE DELIVERY MODE 11/494,413 07/27/2006 79662 7590 James M. Wu JW Law Group 84 W. Santa Clara Street Suite 820 San Jose, CA 95113 Vei-Han Chan 10/31/2017 PAPER Please find below and/or attached an Office communication concerning this application or proceeding. The time period for reply, if any, is set in the attached communication. PTOL-90A (Rev. 04/07) UNITED STATES PATENT AND TRADEMARK OFFICE BEFORE THE PATENT TRIAL AND APPEAL BOARD Ex parte VEI-HAN CHAN,1 Louis Kordus, Narbeh Derhacobian, and Jason Golbus Appeal 2016-004795 Application 11/494,413 Technology Center 2800 Before JEFFREY T. SMITH, MARKNAGUMO, and JEFFREY R. SNAY, Administrative Patent Judges. NAGUMO, Administrative Patent Judge. DECISION ON APPEAL Vei-Han Chan, Louis Kordus, Narbeh Derhacobian, and Jason Golbus (“Chanâ€) timely appeal under 35 U.S.C. § 134(a) from the Final Rejection2 of all pending claims 1—20. We have jurisdiction. 35 U.S.C. § 6. We affirm. 1 The real party in interest is identified as Agate Logic Incorporated (Appeal Brief, filed 23 June 2014 (“Br.â€), 3.) 2 Office action mailed 23 January 2014 (“Final Rejectionâ€; cited as “FRâ€). Appeal 2016-004795 Application 11/494,413 OPINION A. Introduction3 The subject matter on appeal relates to methods of programming (independent claims 1, 7, and 13) a phase change device (“PCDâ€) (independent claim 17). The devices of interest are based on chalcogenic compounds (i.e., compounds that are based on S, Se, and Te) that can be transformed between an amorphous state and a crystalline state. (Spec. 1 [0002].) The amorphous state is obtained by heating the material above its melting point, followed by rapid cooling. (Id.) In contrast, the crystalline state is obtained by gradual cooling from the melt. (Id.) Generally, the amorphous and crystalline states have different electrical conductivities (typically, the amorphous state has high electrical resistance while the crystalline state has low electrical resistance) or different optical properties. (Id. at [0003].) Thus, a memory device, such as a rewritable compact disk (CD) or digital video disk (DVD), may be realized. Notwithstanding these examples, in which the heating is accomplished, typically, via exposure to a laser beam, the devices of interest in this appeal heat the phase-change material by passing pulses of electrical current through the material. (Id.) According to the '413 Specification, prior art methods use a short, high magnitude rectangular “reset†pulse to induce the amorphous phase, followed by a longer, lower magnitude “set†pulse to induce the crystalline 3 Application 11/494,413, Method and apparatus for programming phase change devices, filed 27 July 2006. We refer to the “'413 Specification,†which we cite as “Spec.†2 Appeal 2016-004795 Application 11/494,413 phase without heating the material to the amorphizing temperature Tm. {Id. at 3 [0006].) However, the increased duration of the programming pulses is said to slow the programming speed, and cell-to-cell variations of the optimum crystallizing temperature are said to result in reduced dynamic range of high and low resistance devices and increased variability of resistance values. {Id. at 4 [0008].) In particular, the prior art methods are said to be incapable of distinguishing between “soft†devices, which are set by lower current pulses, and “hard†devices, which require higher current pulses to be set, as shown in Figure 4, reproduced below.4 a-ftCv’ 5 r5 t i r i! : \ , i \ ' \ j , ; t >2 (Knit} f | <2 Citp*w( (Figure 4 shows the variation in the set current for soft and hard cells} Thus, the current I2(min) necessary to set a soft PCD to the low resistance state is insufficient to set a typical or a hard PCD. On the other hand, the current 12(max) necessary to set a hard device in the crystalline, low resistance state, is sufficient to leave a soft or typical PCD in the amorphous high resistance state. Moreover, the programming characteristics of the memory devices are said to change over the lifetime of the device, but the fixed magnitude pulses of the prior art methods are unable to afford the flexibility required to adapt to those changes. {Id.) 4 The Specification reveals that “program devices at the soft and hard tails of the population . . . typically constitute only about 1% of the entire device population on a given chip.†(Spec. 5 [0010].) Thus, the “typical†PCDs comprise the vast majority, -99%, of devices on a chip. 3 Appeal 2016-004795 Application 11/494,413 Chan seeks patent protection for a method and device for programming such phase-change memory devices that are said to overcome these problems. In embodiment 805 shown in Figure 8, below, right, a “programming current pulse (i.e., ‘set’ pulse)†is applied to a PCD at step 804. (Spec. 10 [0028].) The programming pulse generator is ther> deselected and a verily m circuit is selected at step 805. The verify circuit measures the resistance of the PCD without affecting the set state. (Id.) If the resistance is not in the desired range (e.g., it is too high) (808), and if the maximum number of set pulses in the first set of programming pulses has not been applied (810), another first-sequence pulse (steps 802, 804) is applied. (Id. at 11 [0029].) -frf SUCCESS; ENP FIGURE 8 (Fig. 8 shows a flow chart of a PCD programming process} 5 Throughout this Opinion, for clarity, labels to elements or steps are presented in bold font, regardless of their presentation in the original document. 4 Appeal 2016-004795 Application 11/494,413 If the maximum number of first-sequence pulses has been applied, and the preselected maximum programming time has not been exceeded, a pulse from a subsequent sequence may be selected and applied (steps 800-804). (Id.) PCDs that cannot be set can be labeled as defective. (Id. at [0030].) A train of sequences of programming and verifying pulses is illustrated in Figure 11, below. voltage /current 1100 1t02 1104 (Figure 11 shows three sequences of set pulses with verily pulses} The magnitude of a current pulse may be adjusted via a current generator coupled with one or more current mirrors, as illustrated in Figure 9 (not reproduced here). (Spec. 12 [0032].) Claim 1 is representative and reads: A method of programming a phase change device, comprising: [1] applying [804] a first programming pulse generated by a pulse generator having a first magnitude and first pulse duration to a phase change device (“PCDâ€) 5 Appeal 2016-004795 Application 11/494,413 if[ 810] a counter configured to count number of set programming pulse applied is less than a predefined maximum allowable number of set programming pulses', [2] after incrementing said counter, [806] deselecting said pulse generator from coupling to said PCD and coupling said PCD to a verily circuit which subsequently passes a test current through said PCD; [3] determining [808] whether a programmed resistance of said PCD is in accordance with a predetermined target resistance specification based on said test current generated by the verily circuit; [4] identifying [810] whether said counter exceeds a predefined maximum allowable number of set programming pulses, if [808] said programmed resistance is not in accordance with said predetermined target resistance specification; [5] [802] deselecting said verify circuit from coupling to said PCD and coupling said PCD to said pulse generator, if [810] said counter is less than said predefined maximum allowable number of set programming pulses; [6] [800] adjusting a control device associated with one or more current mirrors to generate a second programming pulse; and [7] [804] applying said second programming pulse having a second magnitude and second pulse duration to said PCD if [810] said counter is less than said predefined maximum allowable number of set programming pluses [sic] and if [808] said programmed resistance associated with said PCD is not in accordance with said predetermined target resistance specification. (Claims App., Br. 48-49; some indentation, paragraphing, emphasis, and bracketed labels to Figure 8 and to arguments in the Brief added.) In light of the definition of “programming pulses†as “set pulses†(Spec. 10 [0028]), it appears to be assumed that the memory devices (i.e., individual memory locations) are all initially reset (to the amorphous 6 Appeal 2016-004795 Application 11/494,413 high resistance state), and that the programming pulses are “set†pulses that result in the transition to the crystalline, low resistance phase. Moreover, it appears that a series of programming pulses must be to some extent additive in their phase-changing (crystallizing) effect. It may be noted further that rather than specifying a maximum time period for applying pulses, claim 1 specifies a maximum number of pulses. The Examiner maintains the following grounds of rejection6,7: A. Claims 1—19 stand rejected under 35 U.S.C. § 103(a) in view of the combined teachings of Lowrey,8 Hollmer,9 and Scheuerlein.10 Al. Claim 20 stands rejected under 35 U.S.C. § 103(a) in view of the combined teachings of Lowrey, Hollmer, Scheuerlein, and Ma.11 6 Examiner’s Answer mailed 30 July 2014 (“Ans.â€). 7 Because this application was filed before the 16 March 2013, effective date of the America Invents Act, we refer to the pre-AIA version of the statute. 8 Tyler A. Lowrey and Ward D. Parkinson, Method and system to store information, 2004/0114419 (2004) (issued as U.S. Patent No. 6,813,177 B2 (2 November 2004)). 9 Shane Hollmer and Pau-Ling Chen, Auto adjusting window placement scheme for an NROM virtual ground array, U.S. Patent No. 6,222,768 B1 (2001). 10 Roy E. Scheuerlein, Structure and method for biasing phase change memory array for reliable writing, U.S. Patent Application Publication 2006/0157679 Al (20 July 2006), based on an application filed 19 January 2005. 11 Herman Ma, Phase change based memory device and method for operating same, U.S. Patent Application Publication 2005/0088872 Al (28 April 2005). 7 Appeal 2016-004795 Application 11/494,413 B. Discussion The Board’s findings of fact throughout this Opinion are supported by a preponderance of the evidence of record. Chan’s arguments for patentability are largely directed to limitations indicated by the bracketed single digits recited in claim 1, reproduced supra. Thus, claims 2—15 stand or fall with claim 1. (Br. 41.) Nominally separate arguments are presented for claims 16 and 17 (id. at 41—46), which we address separately, but separately rejected claim 20 stands or falls with claim 17 (id. at 46). The Examiner finds that Lowrey describes a method of programming a phase change device by applying one or more sets of programming pulses having varying magnitudes and durations, as shown in Figure 3, reproduced below as annotated by the Examiner (FR 3). A (Lowrey Figure 3 shows a set of PCD programming pulses} 8 Appeal 2016-004795 Application 11/494,413 The Examiner finds further that the resistance of the phase change material may be measured after each of programming pulses 200-207. {Id. at 2, citing Lowrey 3 [0027] and 4 [0043].) Indeed, as Chan points out (Br. 27— 28), Lowery discloses the amplitude and duration of each of the programming pulses in Figure 3, and the resistance of the phase change material after each programming pulse (Lowery 4 [0039]—[0040]). The Examiner finds that Lowrey does not describe a counter of set programming pulses, and thus Lowrey does not compare the number of set programming pulses to a predefined maximum allowable number of set programming pulses. (FR 4,11. 1—5.) The Examiner finds, however, that Hollmer teaches this known technique for ending a verification of a memory device in Figure 5 (not reproduced here), checking if the pulse count has reached the maximum value at (s5), providing a pulse (s6) and incrementing the pulse counter (s7), and repeating until the pulse count reaches the maximum value. {Id. at 4, 1st full para.)12 The Examiner reasons that it would have been obvious to incorporate such a pulse-count controlled scheme in the programming method described by Lowery. {Id.) The Examiner also finds that Lowery does not describe a mechanism for generating the second programming pulse, and does not describe a control device associated with one or more current mirrors. {Id. at last para.) The Examiner finds that such a technique is described by Scheuerlein in 12 When the maximum count value is reached, an automatic adjustment to the reference current level from a reference memory cell is performed (s8— sl2) (Hollmer col. 10,11. 53—66), subject to a maximum current adjustment (s9), beyond which, the device is deemed to have failed (slO) {id. at 11. 53-60). 9 Appeal 2016-004795 Application 11/494,413 Figure 8 (not reproduced here), in which a pulse current is adjusted via current mirror 70. The Examiner concludes that it would have been obvious to use such a known system to control the magnitude of the current programming pulses provided by Lowrey, which, as shown in Figure 3, supra, vary in both magnitude and duration. (FR 5, 1st full para.) Chan argues that Lowery cannot render the claimed subject matter obvious because, with respect to element [1], “Lowrey does not mention and/or disclose any condition(s) before application of signals.†(Br. 21, last para.). With regard to Hollmer, Chan argues that “the number of set programming pulse applied is not the same or equivalent to the number of repetitions allotted for verification.†(Id. at 38, 1st full para.) “As can be seen,†Chan continues, “Hollmer has never disclosed that its pulse counter can be used to count number of set programming pulse applied.†{Id.) With regard to Scheuerlein, Chan urges that “Scheuerlein . . . has never disclosed a method of adjusting one or more current mirrors to generate a (i.e., second) programming pulse.†{Id. at 35.) Moreover, Chan adds, “Lowrey has never disclosed ‘adjusting a control device ... to generate a second programming pulse,’ as recited in Claim 1.†(Id.) Chan concludes the rejection must be reversed. These arguments are not persuasive of harmful error in the appealed rejection because they address the teachings of the references individually, not in combination, as applied by the Examiner. In particular, Chan does not challenge in any substantial way the Examiner’s reasoning that the routineer would have found it obvious to compare the number of identical pulses in each of the distinct sequences of pulses having different durations and magnitudes suggested by Lowrey in Figure 3 to a preset number of pulses 10 Appeal 2016-004795 Application 11/494,413 based on the verification procedure taught by Hollmer. Both Lowrey and Hollmer provide for the use of multiple pulses to change the state of a memory device, and both provide criteria for determining when the state has been changed. Adding a predetermined limit on the number of pulses applied to change the state of the memory, as suggested by Hollmer, would have been, on the present record, a logical extension to the method described by Lowrey. Nor has Chan explained satisfactorily why it would not have been obvious to use the current mirror disclosed by Scheuerlein to provide pulses having different magnitudes as the pulses in each sequence taught by Lowrey. Regarding element [2], Chan urges that “Lowrey has never disclosed that generator 160 is deselected and/or circuit (150) passes a test current.†(Br. 23, end of first full para.) Moreover, in Chan’s view, Lowrey does not disclose that the deselection of the pulse generator from coupling to the PCD and the coupling of a verily circuit to the PCD occurs after incrementing a pulse counter. As the Examiner explains in more detail in the Examiner’s Answer, the writing and reading described by Lowrey at [0027] and [0028] do not occur at the same time. (Ans. 3, last para.) Given the generality of the description of “coupling†and “decoupling†in the '413 Specification, the Examiner reasons, those terms are interpreted broadly, as “active†and “inactive,†respectively. {Id. at 4, 1 st para.) As for the test current, the Examiner finds that Lowrey distinguishes between the current required to determine the resistance and the current required to induce a change in the resistance. {Id. at 4, 2d para., citing Lowery [0026] and [0043].) The preponderance of the evidence of record supports the Examiner’s findings 11 Appeal 2016-004795 Application 11/494,413 and the conclusions based on those findings. Accordingly, we find no merit in Chan’s objections with respect to element [2], Regarding element [3], Chan urges that Lowrey discloses a method of changing the resistance of memory cells by applying signals 200—207, but doesn’t disclose “determining whether a programmed resistance of said PCD is in accordance with a predetermined target resistance ...†as recited in claim 1. (Br. 26, 1st para.) We perceive no merit in this objection. Lowrey teaches, in paragraph [0043], as quoted by Chan (Br. 25), that “[t]he resistance of the phase change material of memory cell 140 may be measured to determine if the target resistance is reached after application of signals 200-207.†Particularly in light Lowrey’s disclosure of the resistance of the cell after each application (Lowrey [0039]—[0040]), cited by Chan (Br. 27—28), as well as other disclosures, such as Lowrey [0030]—[0032], which describe iterative phase changing pulses followed by readings of resistance, we have no difficulty concluding that it would have been obvious to measure the resistance of the PCD after every programming pulse. Likewise, we perceive no merit in Chan’s insistence that Lowrey “has never disclosed the claimed element of ‘identifying whether said counter . . . if said programed resistance is not in accordance with said predetermined target resistance specification.†(Br. 28., last full para.) This aspect of element [4] of claim 1 appears to be identical to the “target resistance†mentioned in Lowrey [0043]. Moreover, Chan does not explain satisfactorily why, in view of the maximum pulse number described by Hollmer, it would not have been obvious to provide a maximum number of 12 Appeal 2016-004795 Application 11/494,413 programming pulses in any of the sets of programming pulses applied by Lowrey. Chan objects that the Examiner erred in holding element [5] obvious because “Lowrey has never disclosed the term(s) or equivalent or ‘deselecting said verify circuit from coupling said PCD and coupling said PCD to said pulse generator if said counter is less than (Br. 30, last full para.) This issue is parallel to element [2], and we find it unpersuasive of harmful error for parallel reasons. Finally, Chan urges that the Examiner erred in holding the control device associated with one or more current mirrors (element [6]) and applying the second programming pulse (with a second magnitude and a second pulse duration) (element [7]) obvious. (Br. 31—36.) We find no persuasive merit in Chan’s contentions, given that Lowrey discloses, in Figure 3, additional sets of programming pulses having different magnitudes and durations. Chan’s arguments {id. at 38, 1st full para.) regarding claim 1613 (Claims App., Br. 54) are essentially cumulative with the arguments against element [7], and we find them no more persuasive of harmful error. Chan’s arguments regarding claim 17 essentially repeat the arguments discussed supra, that Lowrey and Hollmer do not render obvious counting 13 Claim 16 depends from claim 13, and requires that the second sequence of programming pulses have at least one having “a different magnitude and/or duration†than at least one pulse of the first sequence. 13 Appeal 2016-004795 Application 11/494,413 the number of set pulses applied (id. at 44), and that Lowrey does not disclose a control circuit capable of controlling PCD connection in response to PCD behavior (id. at 45). Both these arguments, as discussed supra, were addressed satisfactorily by the Examiner. We are thus not persuaded of harmful error in the rejection of claim 17 and the claims that depend from it. We have considered Chan’s lengthy Reply,14 but find it essentially repetitive of the arguments set out in the principal Brief, and therefore not persuasive of harmful error. C. Order It is ORDERED that the rejection of claims 1—20 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). AFFIRMED 14 Reply Brief filed 30 September 2014 (“Replyâ€). 14 Copy with citationCopy as parenthetical citation