DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1-5, 9-10, 12-15, 18 and 20 are rejected under 35 U.S.C. 103 as being unpatentable over Walmsley et al. (NPL – Micro-G Silicon Accelerometer Using Surface Electrodes) in view of Guo (US 7736931 B1).
Considering claim 1, Walmsley discloses a MEMS structure comprising:
- a mechanical layer that extends parallel to a reference device plane, wherein:
- the mechanical layer includes a static electrode (Stator Electrode) and a movable electrode (Proof Mass Electrode) configured to move relative to the static electrode and parallel to the reference device plane (Figure 1, Page 972, III Next Generation Sensor).
- the static electrode and the movable electrode form a capacitor having capacitance that varies based on an overlap between the static electrode and the movable electrode (Page 972, III Next Generation Sensor, “Motion of the proof mass in response to external acceleration changes the area of overlap and thus the capacitance between the electrodes”),
- the mechanical layer includes a first silicon layer and a second silicon layer (Page 972, III Next Generation Sensor, “Three silicon wafers are bonded together to form a sealed cavity around a proof mass”),
- the movable electrode is in the first silicon layer and the static electrode is in the second silicon layer (Figure 1), and
- the movable electrode is separated from the static electrode by a first gap in an interface between the first silicon layer and the second silicon layer (Figure 1).
The invention by Walmsley utilizes thin film bonding material between the first and second layers of the mechanical layer, and thus fails to disclose that the first and second silicon layers are in part directly bonded to one another.
However, Guo discloses an accelerometer having a mechanical layer that includes a first silicon layer 108 (Figures 10-13; Column 5, lines 42-56) and a second silicon layer 124 (Figures 5, 9 and 10; Column 6, lines 20-33) which are in part directly bonded to one another (Figure 10; Column 7, line 57 - Column 8, line 2).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to utilize silicon layers that are directly bonded to one another, as taught by Guo, in the invention by Walmsley. The motivation for doing so, as understood in the art, is to provide enhanced thermal stability by matching the coefficients of thermal expansion of the two mechanical layers, thus reducing thermal induced strain on the accelerometer package.
Considering claim 2, Walmsley discloses that the overlap of the static electrode and the movable electrode corresponds to projections of the static electrode and the movable electrode onto the reference device plane (Figure 1; Page 972, III Next Generation Sensor).
Considering claim 3, Walmsley discloses that the movable electrode and the static electrode include one or more comb fingers that extend parallel to the reference device plane (Figure 2; Page 972).
Considering claim 4, Walmsley discloses a substrate layer (Figure 1, Stator wafer).
Considering claim 5, Walmsley discloses that the one or more comb fingers of the movable electrode extend from one or more beams suspended from the substrate layer or the mechanical layer by one or more spring elements that enable back and forth movement of the one or more beams beam parallel to the reference plane (Figures 1-2; Page 972, III Next Generation Sensor, “flexural suspension is defined by etching through the MEMS wafer” and “high aspect ratio flexures”).
Considering claim 9, Walmsley discloses a cap layer (Cap Wafer) bonded to the second silicon layer, such that the movable electrode (MEMS Wafer) is separated from the cap layer by a second gap patterned into the interface between the second silicon layer and the cap layer (Figure 1; Page 972).
Considering claim 10, Walmsley discloses that the capacitance of the capacitor is configured to detect an acceleration parallel to the reference device plane (Page 972, III Next Generation Sensor, “The sensor is a variable capacitor, using surface electrodes between the MEMS wafer and the stator wafer. Motion of the proof mass in response to external acceleration changes the area of overlap and thus the capacitance between the electrodes”).
Considering claim 12, Walmsley discloses a MEMS structure including a mechanical layer that extends parallel to a reference device plane, the MEMS structure comprising:
- a static electrode (Stator Electrode) and a movable electrode (Proof Mass Electrode) configured to move relative to the static electrode and parallel to the reference device plane (Figure 1, Page 972, III Next Generation Sensor);
- a capacitor formed by the static and movable electrodes having capacitance that varies based on an overlap between the static electrode and the movable electrode (Page 972, III Next Generation Sensor, “Motion of the proof mass in response to external acceleration changes the area of overlap and thus the capacitance between the electrodes”);
- a first silicon layer and a second silicon layer (Page 972, III Next Generation Sensor, “Three silicon wafers are bonded together to form a sealed cavity around a proof mass”);
- wherein the movable electrode is in the first silicon layer and the static electrode is in the second silicon layer (Figure 1), and
- wherein the movable electrode is separated from the static electrode by a first gap between the first silicon layer and the second silicon layer (Figure 1).
The invention by Walmsley utilizes thin film bonding material between the first and second layers of the mechanical layer, and thus fails to disclose that the first and second silicon layers are in part directly bonded to one another.
However, Guo discloses an accelerometer having a mechanical layer that includes a first silicon layer 108 (Figures 10-13; Column 5, lines 42-56) and a second silicon layer 124 (Figures 5, 9 and 10; Column 6, lines 20-33) which are in part directly bonded to one another (Figure 10; Column 7, line 57 - Column 8, line 2).
Therefore, it would have been obvious to one of ordinary skill in the art to utilize silicon layers that are directly bonded to one another, as taught by Guo, in the invention by Walmsley. The motivation for doing so, as understood in the art, is to provide enhanced thermal stability by matching the coefficients of thermal expansion of the two mechanical layers, thus reducing thermal induced strain on the accelerometer package.
Considering claim 13, Walmsley discloses that the overlap of the static electrode and the movable electrode corresponds to projections of the static electrode and the movable electrode onto the reference device plane (Figure 1; Page 972, III Next Generation Sensor).
Considering claim 14, Walmsley discloses that the movable electrode and the static electrode include one or more comb fingers that extend parallel to the reference device plane (Figure 2; Page 972).
Considering claim 15, Walmsley discloses a substrate layer (Figure 1, Stator wafer), wherein the one or more comb fingers of the movable electrode extend from one or more beams suspended from the substrate layer or the mechanical layer by one or more spring elements that enable back and forth movement of the one or more beams beam parallel to the reference plane (Figures 1-2; Page 972, III Next Generation Sensor, “flexural suspension is defined by etching through the MEMS wafer” and “high aspect ratio flexures”).
Considering claim 18, Walmsley discloses a cap layer (Cap Wafer) bonded to the second silicon layer, such that the movable electrode (MEMS Wafer) is separated from the cap layer by a second gap patterned into the interface between the second silicon layer and the cap layer (Figure 1; Page 972).
Considering claim 20, Walmsley discloses a method for manufacturing a MEMS structure having a static electrode and a movable electrode configured to form a capacitor with a capacitance that varies based on movement of the movable electrode in relation to the static electrode and parallel to a reference device plane, the method including:
- patterning a recess to a first silicon wafer (Figure 1; Page 972, III Next Generation Sensor, “The proof mass and flexural suspension is defined by etching through the MEMS wafer);
- bonding the first silicon wafer to a second wafer (Figure 1, MEMS wafer bonded to Stator wafer);
- patterning static electrodes to the second silicon wafer (Figures 1 and 2; Pages 971, 972, II. First Generation Sensors “variable capacitor is formed by patterning interdigitated or comb electrodes in the device layer between the proof mass and surrounding fixed structure”, and III. Next Generation Sensors, “The sensor is a variable capacitor, using surface electrodes between the MEMS wafer and the stator wafer”).
- patterning movable electrodes to the first silicon wafer (Figures 1 and 2; Pages 971, 972, II. First Generation Sensors “variable capacitor is formed by patterning interdigitated or comb electrodes in the device layer between the proof mass and surrounding fixed structure”, and III. Next Generation Sensors, “The sensor is a variable capacitor, using surface electrodes between the MEMS wafer and the stator wafer”); and
- bonding a capping wafer (Cap Wafer) to the first silicon wafer (MEMS wafer).
The invention by Walmsley utilizes thin film bonding material between the first and second silicon layers, and thus fails to disclose that the first and second silicon layers are in part directly bonded to one another and that the second silicon layer is bonded to a handle wafer.
However, Guo discloses an accelerometer a first silicon layer 124 (Figures 5, 9 and 10; Column 6, lines 20-33) and a second silicon layer 108 (Figures 10-13; Column 5, lines 42-56) that are in part directly bonded to one another (Figure 10; Column 7, line 57 - Column 8, line 2), wherein the second silicon wafer 108 is bonded to handle wafer 112 (Figure 3; Column 5, lines 46-48).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to utilize silicon layers that are directly bonded to one another, as taught by Guo, in the invention by Walmsley. The motivation for doing so, as understood in the art, is to provide enhanced thermal stability by matching the coefficients of thermal expansion of the two mechanical layers, thus reducing thermal induced strain on the accelerometer package.
Claims 6-8 and 16-17 are rejected under 35 U.S.C. 103 as being unpatentable over Walmsley et al. (NPL – Micro-G Silicon Accelerometer Using Surface Electrodes) in view of Guo (US 7736931 B1), as applied to claims 5 and 15, respectively, above, and further in view of Liukku et al. (US 2015/0316581 A1).
Considering claim 6, Walmsley, as modified by Guo, discloses a square proof mass, having a plurality of comb sets, separated by trenches from an outer substrate, thus establishing an outer frame, whereby two-dimensional movement is enabled by positioning flexure suspensions on at least two perpendicular surfaces of the frame, but the combination fails to explicitly disclose four beams and oppositely supported first and second electrode comb sets.
However, Walmsley, as modified by Guo, fails to explicitly disclose that the one or more beams are part of a rectangular frame of four beams, and one beam of the frame supports movable comb fingers of a first electrode comb set and an opposite beam of the frame supports movable comb fingers of a second electrode comb set.
However, Liukku teaches a capacitive MEMS device having a rotor frame 15 flexibly suspended, via spring structures 4,4a,4b over a stator 1 and attached to a substrate 2, whereby the rotor frame 15 is a four-beam rectangular frame having first and second electrode comb sets 7 supported by opposite beams (Figure 1; [0046-54]).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to utilize the four-beam frame structure of Liukku having opposite beams supporting respective first and second comb electrodes sets, in the invention by Walmsley, as modified by Guo. The motivation for doing so is to provide better common-mode rejection and increased sensitivity, as is generally understood in the art of differential output accelerometers.
Considering claim 7, Walmsley discloses that the static comb fingers of the first electrode comb set and static comb fingers of the second electrode comb set are separately coupled to a voltage source and are separated from opposing movable comb fingers by the first gap to form two capacitors configured for differential detection (Figure 3, Page 973, IV Electronics). Additionally, while not relied upon at this time, Applicant’s Admitted Prior Art, in [0033] of the originally filed specification, renders this limitation obvious as well.
Considering claim 8, Walmsley discloses that each movable comb finger is configured to overlap two static comb fingers to form two capacitors that respond in opposite phase to motions of the frame (Figure 3, this is the concept relied upon for the measurement of acceleration).
Considering claim 16, Walmsley, as modified by Guo, discloses a square proof mass, having a plurality of comb sets, separated by trenches from an outer substrate, thus establishing an outer frame, whereby two-dimensional movement is enabled by positioning flexure suspensions on at least two perpendicular surfaces of the frame, but the combination fails to explicitly disclose four beams and oppositely supported first and second electrode comb sets.
However, Walmsley, as modified by Guo, fails to explicitly disclose that the one or more beams are part of a rectangular frame of four beams, and one beam of the frame supports movable comb fingers of a first electrode comb set and an opposite beam of the frame supports movable comb fingers of a second electrode comb set.
However, Liukku teaches a capacitive MEMS device having a rotor frame 15 flexibly suspended, via spring structures 4,4a,4b over a stator 1 and attached to a substrate 2, whereby the rotor frame 15 is a four-beam rectangular frame having first and second electrode comb sets 7 supported by opposite beams (Figure 1; [0046-54]).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to utilize the four-beam frame structure of Liukku having opposite beams supporting respective first and second comb electrodes sets, in the invention by Walmsley, as modified by Guo. The motivation for doing so is to provide better common-mode rejection and increased sensitivity, as is generally understood in the art of differential output accelerometers.
Considering claim 17, Walmsley discloses that the static comb fingers of the first electrode comb set and static comb fingers of the second electrode comb set are separately coupled to a voltage source and are separated from opposing movable comb fingers by the first gap to form two capacitors configured for differential detection (Figure 3, Page 973, IV Electronics), wherein each movable comb finger is configured to overlap two static comb fingers to form two capacitors that respond in opposite phase to motions of the frame (Figure 3, this is the concept relied upon for the measurement of acceleration). Additionally, while not relied upon at this time, Applicant’s Admitted Prior Art, in [0033] of the originally filed specification, renders this limitation obvious as well.
Claims 11 and 19 are rejected under 35 U.S.C. 103 as being unpatentable over Walmsley et al. (NPL – Micro-G Silicon Accelerometer Using Surface Electrodes) in view of Guo (US 7736931 B1), as applied to claims 1 and 12, respectively, above, and further in view of Geiger et al. (US 9709596 B2).
Considering claim 11, Walmsley discloses applying opposing carrier signals to the stationary stators to nullify alignment offset errors. While it is assumed this will generate motion, even minutely, of the movable electrodes, Walmsley fails to explicitly disclose that this is the result. Accordingly, the invention by Walmsley, as modified by Guo fails to disclose that the capacitance of the capacitor is configured to actuate the movable electrode into a motion parallel to the reference device plane.
However, Geiger teaches the use of a “reset voltage”, whereby voltage applied to stationary electrodes will actuate movement of the movable electrodes to return an inertial mass to a neutral position and/or provide closed-loop control (Column 2, lines 31-44; Column 7, line 63 – Column 8, line 6).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to actuate the movable electrode into a motion parallel to the reference device plane through capacitance between the stationary and movable electrodes, as taught by Geiger, in the invention by Walmsley, as modified by Guo. According to Geiger, the closed-loop control of the positioning of the electrodes relative to one another is placed into effect by applying a voltage to the electrodes, thus providing the alignment control suggested by Walmsley.
Considering claim 19, Walmsley discloses applying opposing carrier signals to the stationary stators to nullify alignment offset errors. While it is assumed this will generate motion, even minutely, of the movable electrodes, Walmsley fails to explicitly disclose that this is the result. Accordingly, the invention by Walmsley, as modified by Guo fails to disclose that the capacitance of the capacitor is configured to actuate the movable electrode into a motion parallel to the reference device plane.
However, Geiger teaches the use of a “reset voltage”, whereby voltage applied to stationary electrodes will actuate movement of the movable electrodes to return an inertial mass to a neutral position and/or provide closed-loop control (Column 2, lines 31-44; Column 7, line 63 – Column 8, line 6).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to actuate the movable electrode into a motion parallel to the reference device plane through capacitance between the stationary and movable electrodes, as taught by Geiger, in the invention by Walmsley, as modified by Guo. According to Geiger, the closed-loop control of the positioning of the electrodes relative to one another is placed into effect by applying a voltage to the electrodes, thus providing the alignment control suggested by Walmsley.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure.
Andermo (RE 34741) discloses a general parallel plate surface electrode displacement measurement transducer.
Ashizawa et al. (US 2021/0331913 A1) discloses parallel silicon layers separated by an insulator and having opposing and relatively movable electrodes patterned thereon, whereby relative movement changes the measured capacitance between the electrodes.
Tocchio et al. (US 2017/0108530 A1) discloses vertical comb moveable electrodes extending inwardly from a four-beam frame flexibly suspended above a stationary comb electrode set.
Jin et al. (US 2012/0293907 A1) discloses parallel substrates having a top movable electrode set flexibly suspended above a lower stationary set of electrodes, whereby the frame of the movable electrodes is directly attached to the lower surface upon which the stationary electrodes are present.
Fasen et al. (US 7142500 B2) discloses a MEMS two-layer capacitive position sensor, using surface plate electrodes, that allows parallel relative movement between the two layers, whereby differential capacitance and opposing phase electrical signals are used.
Hartwell et al. (US 6504385 B2) discloses a MEMS multilayer capacitive motion sensor that uses surface plate electrodes and parallel relative motion.
Ichikawa et al. (US 6041653 A) discloses a glass cap layer and a glass base layer sandwiching a flexibly suspended silicon layer having thereon patterned movable electrodes, the movable electrodes suspended over stationary electrodes, whereby relative lateral movement caused by acceleration is detected as a change in capacitance between the opposing electrodes.
Walmsley et al. (US 8661901 B2) discloses a MEMS three-layer silicon capacitive accelerometer, wherein a cap wafer is bonded to a silicon proof mass wafer having movable electrodes patterned therein, and a lower electronics wafer having an upper array of electrodes opposing the movable electrodes of the proof mass wafer that is bonded to the silicon proof mass wafer, whereby relative movement of the movable electrodes relative to the stationary electrodes causes a change in capacitance, thus indicating acceleration. Walmsley also discloses “wafer-to-wafer bonding” and voltage induced electrical nullification to compensate for misalignments.
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/JONATHAN M DUNLAP/Primary Examiner, Art Unit 2855 March 7, 2026