DETAILED ACTION
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
Election/Restrictions
Applicant’s election without traverse of Invention I (etching system), drawn to claim(s) 13-19 and 21-33 in the reply filed on 01/26/2026 is acknowledged.
Claim Rejections - 35 USC § 112
The following is a quotation of the first paragraph of 35 U.S.C. 112(a):
(a) IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.
The following is a quotation of the first paragraph of pre-AIA 35 U.S.C. 112:
The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention.
Claim 25 is rejected under 35 U.S.C. 112(a) or 35 U.S.C. 112 (pre-AIA ), first paragraph, as failing to comply with the written description requirement. The claim(s) contains subject matter which was not described in the specification in such a way as to reasonably convey to one skilled in the relevant art that the inventor or a joint inventor, or for applications subject to pre-AIA 35 U.S.C. 112, the inventor(s), at the time the application was filed, had possession of the claimed invention.
Regarding claim 25:
Claim 25 recites “the controller is configured to, prior to determining the pre-etch surface topography for the work piece, induce removal of…”. It is noted that the specification as originally filed does NOT provide support for this limitation. The controller is merely disclosed to control the measurement apparatus 102 and the localized etch back apparatus 104 [fig 1 & 0013]. It is noted that the claimed removal is NOT disclosed to take place in the disclosed apparatuses.
Claim Rejections - 35 USC § 103
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
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.
Claim(s) 13-18, 21-24, 26, and 28-33 is/are rejected under 35 U.S.C. 103 as being unpatentable over Fulford et al (US 6,746,616) in view of Gaff et al (US 2011/0143462).
Regarding claim 13:
Fulford teaches an etching system (system, 100) [fig 1 & col 3-4, lines 60-4] comprising: a measurement apparatus (metrology tool, 110) configured to receive a work piece (102) [fig 1 & col 3-4, lines 60-4]; a localized etch back apparatus (etcher, 108) configured to etch back the upper surface of the work piece to thin the work piece (wafer 102 is exposed to an etchant) [fig 1, 3 & col 3-4, lines 60-4 and col 6, lines 20-33], the localized etch back apparatus (108) comprising: a work piece support (chuck, 300) configured to support the work piece (102), wherein a face of the work piece support (top of 300) includes a plurality of temperature control zones (zones associated with 303-305) with a plurality of temperature control elements (303-305), respectively [fig 1, 3 & col 6, lines 20-33, 40-52]; and a plasma source (structure to generate plasma) configured to generate ions to etch the work piece (employs plasma etching) while the work piece (102) is supported on the work piece support (300) [fig 1, 3 & col 6, lines 20-33].
Fulford does not specifically disclose the measurement apparatus is configured to determine a plurality of pre-etch surface heights at a plurality of sites on an upper surface of the work piece; and a localized etch back apparatus downstream of the measurement apparatus.
Gaff teaches a measurement apparatus (off-board inspection tool) is configured to determine a plurality of pre-etch surface heights (pre-etch critical dimensions) at a plurality of sites on an upper surface of the work piece (plurality of device die locations) [0015]; and a localized etch back apparatus (plasma etching system) downstream of the measurement apparatus (the substrate is subsequently supported on the on the substrate support of the plasma etching system) [abstract & 0004].
It would have been obvious to one skilled in the art before the effective filing date to modify the measurement apparatus of Fulford to be configured to determine a plurality of pre-etch surface heights upstream of the localized etch back apparatus, as in Gaff, to compensate for the particular amount of error in the pre-etch critical dimensions at the work piece location [Gaff – 0013].
Although taught by the cited prior art, the claim limitations “configured to determine a plurality of pre-etch surface heights at a plurality of sites on an upper surface of the work piece”, “configured to etch back the upper surface of the work piece to thin the work piece”, and “configured to generate ions to etch the work piece while the work piece is supported on the work piece support” are merely intended use and are given weight to the extent that the prior art is capable of performing the intended use. A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex parte Masham, 2 USPQ2d 1647 (Bd. Pat. App. & Inter. 1987).
Regarding claim 14:
Modified Fulford teaches a controller (controller, 112) configured to individually heat or cool the plurality of temperature control elements (303-305) to heat or cool the plurality of temperature control zones (zones associated with 303-305), to a first plurality of temperatures, while the plasma source generates the ions to etch the work piece (during plasma etching) [Fulford - fig 1, 3 & col 6, lines 20-33 and 39-65], wherein the first plurality of temperatures (etching temperature of each device die location) are based on the measured plurality of pre-etch surface heights (measured pre-etch critical dimensions) [Gaff – 0013].
Regarding claims 15-16:
Fulford teaches the work piece support (300) comprises a generally planar surface whereon the work piece resides (see fig 3) [fig 3 & col 6, lines 39-65]; and wherein the generally planar surface contacts an entirety of a backside surface of the work piece (see fig 3) [fig 3 & col 6, lines 39-65].
Regarding claim 17:
Fulford teaches one or more temperature sensors (temperature sensors, 310-314), wherein the one or more temperature sensors (310-314) are configured to measure a temperature of the work piece at a respective location associated with each of the plurality of temperature control elements (310-314 are deployed in each of the zones associated with the heaters 303-305) [fig 3 & col 6-7, lines 66-6].
Regarding claim 18:
Fulford teaches the plurality of temperature control elements (303-305) are configured to heat some temperature control zones of the plurality of temperature control zones (zones associated with 304-305) while concurrently cooling other temperature control zones of the plurality of temperature control zones (cooler could be readily substituted for 303 to create similar temperature variation) [fig 3 & col 6, lines 53-65].
Regarding claim 21:
Fulford teaches an etching system (system, 100) [fig 1 & col 3-4, lines 60-4], comprising: a work piece support (chuck, 300) configured to support the work piece (102), wherein a face of the work piece support (top of 300) includes a plurality of temperature control zones (zones associated with 303-305) [fig 1, 3 & col 6, lines 20-33, 40-52]; a measurement apparatus (metrology tool, 110) [fig 1 & col 3-4, lines 60-4]; a controller (controller, 112) configured to heat a first zone of the temperature control zones (zone associated with 304 or 305) based on the measured plurality of surface heights or thicknesses (measured depth at block 602) and concurrently cool a second zone of the temperature control zones (cooler could be used in zone associated with 303) based on the measured plurality of surface heights or thicknesses (measured depth at block 602), such that the first zone has a first temperature different from a second temperature of the second zone (creating a temperature variation and attendant variation in the relative etch rates) [Fulford - fig 1, 3, 6 & col 6, lines 20-33 and 39-65 and col 7-8, lines 65-50].
Fulford does not specifically disclose the measurement apparatus configured to determine a pre-etch surface topography for the work piece by measuring a plurality of pre-etch surface heights or thicknesses at a plurality of sites on the work piece, wherein the plurality of sites on the work piece correspond to the plurality of temperature control zones on the face of the work piece support; the controller configured to control the temperature control zones based on the measured plurality of pre-etch surface heights or thicknesses; and wherein the controller is configured to carry out a first dry etch while the first zone has the first temperature different from the second temperature of the second zone of the temperature control zones.
Gaff teaches a measurement apparatus (off-board inspection tool) configured to determine a pre-etch surface topography for the work piece (pre-etch critical dimensions) by measuring a plurality of pre-etch surface heights or thicknesses at a plurality of sites on the work piece (measured critical device parameters at a plurality of device die locations), wherein the plurality of sites on the work piece (device die location) correspond to the plurality of temperature control zones on the face of the work piece support (etching temperature of the device die location can be tuned by the heater zones) [0013-0015]; a controller (controller unit) configured to control the temperature control zones (heater zones) based on the measured plurality of pre-etch surface heights or thicknesses (pre-etch critical dimensions) [0013-0015]; and wherein the controller (controller unit) is configured to carry out a first dry etch (plasma etching) while the first zone has the first temperature different from the second temperature of the second zone of the temperature control zones (by tuning the power of each heater zone under control of the controller unit) [0013-0015].
It would have been obvious to one skilled in the art before the effective filing date to modify the measurement apparatus and controller of Fulford to be configured to measure a plurality of pre-etch surface heights and to carry out a first dry etch based on the measured plurality of pre-etch surface heights or thicknesses, respectively, as in Gaff, to compensate for the particular amount of error in the pre-etch critical dimensions at the work piece location [Gaff – 0013].
Although taught by the cited prior art, the claim limitations “configured to determine a pre-etch surface topography for the work piece by measuring a plurality of pre-etch surface heights or thicknesses at a plurality of sites on the work piece, wherein the plurality of sites on the work piece correspond to the plurality of temperature control zones on the face of the work piece support” are merely intended use and are given weight to the extent that the prior art is capable of performing the intended use. A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex parte Masham, 2 USPQ2d 1647 (Bd. Pat. App. & Inter. 1987).
Regarding claim 22:
Fulford teaches multiple zones of the plurality of temperature control zones are heated while other multiple zones of the plurality of temperature control zones are cooled during the first dry etch (more than three zones may be employed according to the level of zone control deemed appropriate and coolers may be readily substituted in any of the zones) [col 6, lines 40-52].
Regarding claim 23:
Fulford teaches the measurement apparatus (110) is further configured to determine a post-etch surface topography for the work piece by measuring a plurality of post-etch surface heights at the plurality of sites on the work piece (measuring the depth achieved by the etch process at a plurality of locations) [fig 1, 6 & col 7-8, lines 65-6].
Regarding claim 24:
Fulford teaches the measurement apparatus (110) is further configured to determine whether a plurality of measured post-etch surface heights (depth achieved by the etch process at a plurality of locations) in the post-etch surface topography fall within a predetermined acceptable range (preselected depth) [fig 1, 6 & col 7-8, lines 65-25]; and when the plurality of measured post-etch surface heights in the post-etch surface topography fall outside the predetermined acceptable range (preselected depth), then the controller (112) is configured to heat and cool the plurality of temperature control zones, respectively, to a second plurality of temperatures, respectively (modifies the temperature of the zone accordingly by increasing/reducing the appropriate heater/cooler), wherein the second plurality of temperatures are based on the measured plurality of post-etch surface heights, respectively (depth achieved by the etch process at a plurality of locations), and carrying out a second dry etch while the plurality of temperature control zones are at the second plurality of temperatures, respectively (the desired temperature of a zone may be iteratively adjusted until a uniform etch depth is observed in each zone) [fig 1, 6 & col 8, lines 26-50].
Although taught by the cited prior art, the claim limitations “configured to determine whether a plurality of measured post-etch surface heights in the post-etch surface topography fall within a predetermined acceptable range” are merely intended use and are given weight to the extent that the prior art is capable of performing the intended use. A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex parte Masham, 2 USPQ2d 1647 (Bd. Pat. App. & Inter. 1987).
Regarding claim 26:
The claim limitations “wherein the work piece is a part of a three-dimensional integrated circuit including at least two semiconductor substrates” do not impart any additional structure. Expressions relating the apparatus to contents thereof during an intended operation are of no significance in determining patentability of the apparatus claim. Ex parte Thibault, 164 USPQ 666, 667 (Bd. App. 1969). Furthermore, inclusion of material or article worked upon by a structure being claimed does not impart patentability to the claims. In re Young, 75 F.2d 996, 25 USPQ 69 (CCPA 1935) (as restated in In re Otto, 312 F.2d 937, 136 USPQ 458, 459 (CCPA 1963)).
Regarding claim 28:
Fulford teaches the controller (112) is configured to heat and cool the plurality of temperature control zones (modifies the temperature of the zone accordingly by increasing/reducing the appropriate heater/cooler) by predicting a temperature distribution of the work piece at the plurality of sites based on heating or cooling (may be derived theoretically, or may be determined empirically) [fig 1, 6 & col 8, lines 26-50].
Regarding claim 29:
The claim limitations “wherein the pre-etch surface topography includes a first site having a first height and a second site having a second height on one side of the first site, the first height being greater than the second height; and wherein the first dry etch reduces the first height of the first site to a third height and reduces the second height of the second site to a fourth height, wherein the third height is less than the fourth height” do not impart any additional structure. Expressions relating the apparatus to contents thereof during an intended operation are of no significance in determining patentability of the apparatus claim. Ex parte Thibault, 164 USPQ 666, 667 (Bd. App. 1969). Furthermore, inclusion of material or article worked upon by a structure being claimed does not impart patentability to the claims. In re Young, 75 F.2d 996, 25 USPQ 69 (CCPA 1935) (as restated in In re Otto, 312 F.2d 937, 136 USPQ 458, 459 (CCPA 1963)).
Regarding claim 30:
Fulford teaches the controller is configured to carry out a second dry etch after the first dry etch (etching process performed by the etcher 108 may be employed on a wafer-to-wafer basis) to provide an etched-back surface topography of substantially uniform height (to produce a desired, uniform etching) [fig 1, 6 & col 8, lines 51-61].
The claim limitations “wherein each of the first site and the second site has a fifth height in the etched-back surface topography and where the fifth height is less than the third height” do not impart any additional structure. Expressions relating the apparatus to contents thereof during an intended operation are of no significance in determining patentability of the apparatus claim. Ex parte Thibault, 164 USPQ 666, 667 (Bd. App. 1969). Furthermore, inclusion of material or article worked upon by a structure being claimed does not impart patentability to the claims. In re Young, 75 F.2d 996, 25 USPQ 69 (CCPA 1935) (as restated in In re Otto, 312 F.2d 937, 136 USPQ 458, 459 (CCPA 1963)).
Regarding claims 31-32:
The claim limitations “wherein the work piece has a total thickness ranging from approximately 0.5 microns to approximately 9 microns, and a total thickness variation or height variation being less than 0.3 microns and greater than 100 angstroms” and “wherein the work piece is a semiconductor wafer” do not impart any additional structure. Expressions relating the apparatus to contents thereof during an intended operation are of no significance in determining patentability of the apparatus claim. Ex parte Thibault, 164 USPQ 666, 667 (Bd. App. 1969). Furthermore, inclusion of material or article worked upon by a structure being claimed does not impart patentability to the claims. In re Young, 75 F.2d 996, 25 USPQ 69 (CCPA 1935) (as restated in In re Otto, 312 F.2d 937, 136 USPQ 458, 459 (CCPA 1963)).
Regarding claim 33:
Fulford teaches an etching system (system, 100) [fig 1 & col 3-4, lines 60-4], comprising: a measurement apparatus (metrology tool, 110) configured to receive a work piece (102) [fig 1 & col 3-4, lines 60-4]; a localized etch back apparatus (etcher, 108) configured to etch back the upper surface of the work piece to thin the work piece (wafer 102 is exposed to an etchant) [fig 1, 3 & col 3-4, lines 60-4 and col 6, lines 20-33], the localized etch back apparatus (108) comprising: a work piece support (chuck, 300) configured to support the work piece (102), wherein a face of the work piece support (top of 300) includes a plurality of temperature control zones (zones associated with 303-305) with a plurality of temperature control elements (303-305), respectively [fig 1, 3 & col 6, lines 20-33, 40-52]; and a plasma source (structure to generate plasma) configured to generate ions to etch the work piece (employs plasma etching) while the work piece (102) is supported on the work piece support (300) [fig 1, 3 & col 6, lines 20-33].
Fulford does not specifically disclose the measurement apparatus is configured to determine a plurality of pre-etch surface heights at a plurality of sites on an upper surface of the work piece; and a localized etch back apparatus downstream of the measurement apparatus.
Gaff teaches a measurement apparatus (off-board inspection tool) is configured to determine a plurality of pre-etch surface heights (pre-etch critical dimensions) at a plurality of sites on an upper surface of the work piece (plurality of device die locations) [0015]; and a localized etch back apparatus (plasma etching system) downstream of the measurement apparatus (the substrate is subsequently supported on the on the substrate support of the plasma etching system) [abstract & 0004].
It would have been obvious to one skilled in the art before the effective filing date to modify the measurement apparatus of Fulford to be configured to determine a plurality of pre-etch surface heights upstream of the localized etch back apparatus, as in Gaff, to compensate for the particular amount of error in the pre-etch critical dimensions at the work piece location [Gaff – 0013].
Although taught by the cited prior art, the claim limitations “configured to determine a plurality of pre-etch surface heights at a plurality of sites on an upper surface of the work piece”, “configured to etch back the upper surface of the work piece to thin the work piece”, and “configured to generate ions to etch the work piece while the work piece is supported on the work piece support” are merely intended use and are given weight to the extent that the prior art is capable of performing the intended use. A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex parte Masham, 2 USPQ2d 1647 (Bd. Pat. App. & Inter. 1987).
Furthermore, the claim limitations “wherein the work piece, after being processed by the localized back etch apparatus, comprises: a first integrated circuit structure including a first semiconductor substrate and a first interconnect structure, the first interconnect structure includes a dielectric structure, and a plurality of metal lines stacked over one another and connected to one another through contacts and vias in the first interconnect structure; a second integrated circuit structure including a second interconnect structure disposed over the first interconnect structure, and a second semiconductor substrate disposed over the second interconnect structure; and wherein the second semiconductor substrate has a total thickness ranging from approximately 0.5 microns to approximately 9 microns, and a total thickness variation or height variation being less than 0.3 microns and greater than 100 angstroms” do not impart any additional structure. Expressions relating the apparatus to contents thereof during an intended operation are of no significance in determining patentability of the apparatus claim. Ex parte Thibault, 164 USPQ 666, 667 (Bd. App. 1969). Furthermore, inclusion of material or article worked upon by a structure being claimed does not impart patentability to the claims. In re Young, 75 F.2d 996, 25 USPQ 69 (CCPA 1935) (as restated in In re Otto, 312 F.2d 937, 136 USPQ 458, 459 (CCPA 1963)).
Claim(s) 19 and 27 is/are rejected under 35 U.S.C. 103 as being unpatentable over Fulford et al (US 6,746,616) in view of Gaff et al (US 2011/0143462) as applied to claims 13-18, 21-24, 26, and 28-33 above, and further in view of Yoshimizu et al (US 2019/0035636).
The limitations of claims 13-18, 21-24, 26, and 28-33 have been set forth above.
Regarding claim 19:
Modified Fulford does not specifically teach a nozzle configured to be positioned over a site of the plurality of sites; and a dispensing system configured to dispense a liquid etchant through the nozzle.
Yoshimizu teaches a nozzle (nozzle, 80) configured to be positioned over a site of the plurality of sites (wet etching can be applied in a desired position on the wafer) [fig 6B & 0051]; and a dispensing system (source of EL) configured to dispense a liquid etchant (EL) through the nozzle (80) [fig 6B & 0051].
It would have been obvious to one skilled in the art before the effective filing date to modify the etching system of modified Fulford to further comprise a nozzle and dispensing system, as in Yoshimizu, to obtain the composite effect of plasma treatment and wet etching thereby enabling selective etching by plasma-oxidizing the surface of the work piece [Yoshimizu – 0049-0050].
Although taught by the cited prior art, the claim limitations “configured to be positioned over a site of the plurality of sites based on the surface height of that site” and “configured to dispense a liquid etchant through the nozzle to etch the site while other sites of the plurality of sites are free from the liquid etchant” are merely intended use and are given weight to the extent that the prior art is capable of performing the intended use. A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex parte Masham, 2 USPQ2d 1647 (Bd. Pat. App. & Inter. 1987).
Regarding claim 27:
Modified Fulford does not specifically teach a nozzle configured to be positioned over a first site of the plurality of sites.
Yoshimizu teaches a nozzle (nozzle, 80) configured to be positioned over a first site of the plurality of sites (wet etching can be applied in a desired position on the wafer) [fig 6B & 0051].
It would have been obvious to one skilled in the art before the effective filing date to modify the etching system of modified Fulford to further comprise a nozzle, as in Yoshimizu, to obtain the composite effect of plasma treatment and wet etching thereby enabling selective etching by plasma-oxidizing the surface of the work piece [Yoshimizu – 0049-0050].
Although taught by the cited prior art, the claim limitations “configured to be positioned over a first site of the plurality of sites based on a surface height of the first site, the nozzle configured to dispense a liquid etchant to etch the first site while some of the plurality of sites are free from the liquid etchant” are merely intended use and are given weight to the extent that the prior art is capable of performing the intended use. A claim containing a “recitation with respect to the manner in which a claimed apparatus is intended to be employed does not differentiate the claimed apparatus from a prior art apparatus” if the prior art apparatus teaches all the structural limitations of the claim. Ex parte Masham, 2 USPQ2d 1647 (Bd. Pat. App. & Inter. 1987).
Claim(s) 25 is/are rejected under 35 U.S.C. 103 as being unpatentable over Fulford et al (US 6,746,616) in view of Gaff et al (US 2011/0143462) as applied to claims 13-18, 21-24, 26, and 28-33 above, and further in view of Drab (US 2018/0114713) and Cheng et al (US 2017/0301611).
The limitations of claims 13-18, 21-24, 26, and 28-33 have been set forth above.
Regarding claim 25:
Modified Fulford does not specifically teach the controller is configured to, prior to determining the pre-etch surface topography for the work piece, induce removal of at least 95% of an initial thickness of the work piece to provide the work piece with a reduced thickness of between 2 micrometers and 10 micrometers, wherein the work piece with the reduced thickness includes the pre-etch surface topography whereby a total height or thickness variation of the work piece ranges between 0.1 micrometers and 0.5 micrometers.
Drab teaches a method of manufacturing an integrated circuit, comprising bonding a handle substrate 14 to an integrated circuit layer 12 that is formed over a substrate 13 (Fig. 3, [0024]), then removing the substrate 13 to expose the integrated circuit layer 12 (Fig. 4A), wherein the removal comprises first removing a substantial portion of the substrate 13, such as 90% of the substrate 13 (Fig. 5A), then finally removing the remaining of the substrate, wherein the removing may be performed by etching, grinding and polishing ([0025]). Drab further teaches that the remaining of the substrate after the first removal may be 10 µm or less ([0025]).
Therefore, it would have been obvious to one of ordinary skill in the art before effective filing date of the invention, in routine experimentations, to modify the controller of modified Fulford to remove at least 95% of the work piece to a thickness of 10 µm or less during the first removal to nearly completely expose the first major surface through a thin layer of work piece remainder, as in Drab, to enable formation of a CMOS IC [Drab – 0025, 0031].
Fulford modified by Gaff and Drab is silent about the details of the polishing process or a total thickness variation of the initial thickness after the polishing before the etching method.
Cheng teaches a method for polishing a silicon substrate for thinning the silicon substrate, the method produces a substrate having a total thickness variation less than 0.5 micrometer ([0025]).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the invention, in routine experimentations, to use the polishing method taught by Cheng for the preliminary thinning step in the invention of modified Fulford because modified Fulford teaches to perform said polishing but is silent about the details, and Cheng teaches that such polishing method would be effective [Cheng – 0025].
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. Chen et al (US 2004/0182822) teaches an etching system [fig 1].
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/Benjamin Kendall/Primary Examiner, Art Unit 2896
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