Doc Code: PA..
`PTO/AIA/82A (07-13)
`Document Description: Power of Attorney
`Approved for use through 01/31/2018. OMB 0651-0035
`U.S, Patent and Trademark Office; U.S, DEPARTMENT OF COMMERCE
`Under the Paperwork Reduction Act of 1995, no persons are required to respond to a collection of information unless it displays a valid OMB control number.
`
`TRANSMITTAL FOR POWER OF ATTORNEY TO ONE OR MORE
`REGISTERED PRACTITIONERS
`
`NOTE: This form is to be submitted with the Power of Attorney by Applicant form (PTO/AIA/82B) to identify the application to which the
`Power of Attorney is directed, in accordance with 37 CFR 1.5, unless the application number and filing date are identified in the Power of
`If neither form PTO/AIA/82A nor form PTO/AIA82B identifies the application to which the Power of Attorney is
`Attorney by Applicant form.
`directed, the Power of Attorney will not be recognized in the application.
`
`Application Number
`
`Filing Date
`
`02-Jul-2019
`
`First Named Inventor
`
`Peter John COUSINS
`
`Title
`
`FRONT CONTACT SOLAR CELL WITH FORMED EMITTER
`
`Art Unit
`
`Examiner Name
`
`Attorney Docket Number
`
`|10031.004212
`
`SIGNATURE of Applicant or Patent Practitioner
`/Patrick D. Benedicto/
`Signature
`PATRICK D. BENEDICTO
`
`Name
`
`Title (if Applicant is a
`juristic entity)
`
`|Attorney of Record
`
`Date (Optional)
`
`Registration
`Number
`
`140,909
`
`Applicant Name (if Applicant is a juristic entity)
`SunPower Corporation
`NOTE: This form must be signed in accordance with 37 CFR 1.33. See 37 CFR 1.4(d) for signature requirements and certifications. If
`more than one applicant, use multiple forms.
`*Total of 4
`forms are submitted.
`
`This collection of information is required by 37 CFR 1.131, 1.32, and 1.33. The information is required to obtain or retain a benefit by
`the public which is to file (and by the USPTO to process) an application. Confidentiality is governed by 35 U.S.C. 122 and 37 CFR
`1.11 and 1.14. This collection is estimated to take 3 minutes to complete, including gathering, preparing, and submitting the completed
`application form to the USPTO. Time will vary depending upon the individual case. Any comments on the amount of time you require
`to complete this form and/or suggestions for reducing this burden, should be sent to the Chief Information Officer, U.S. Patent and
`Trademark Office, U.S. Department of Commerce, P.O. Box 1450, Alexandria, VA 22313-1450. DO NOT SEND FEES OR
`COMPLETED FORMS TO THIS ADDRESS. SEND TO: Commissioner for Patents, P.O. Box 1450, Alexandria, VA 22313-1450.
`
`ifyou need assistance in completing the form, call 1-800-PTO-9199 and select option 2.
`
`

`

`Doc Code: PA..
`PTOSAIAB2B (87-13)
`Document Description: Power of Attorney
`Appraved tor use through 11/30/2014, OMB 0654-0051
`U.S. Patent and Trademark Otfing, U.S. OEPARTMENT OF COMMERCE
`Under the Papenvork Reduction Act of 1995, ne persons ate required to respond to a collection of information unless it displays a valid OMB contral number
`
`ane
`
`Bim
`
`POWER OF ATTORNEY BY APPLICANT
`
`{ heraby revoke all previous powers of attorney given inthe application identified in either the attached transmittal letter ar
`the boxes below,
`
`Application Number
`
`Filing Date
`
`(Note: The boxes above may be left blank if information is provided on form PTO/AIAI82A.)
`i hereby appoint the Patent Praciitioner(s) associated with the following Customer Number as my/our aitorney(s) ar agent(s), and
`{o transact all businessin the United States Patent and Trademark Office connecied therewith for the application referencedin
`ihe altached transmitial letter (form PTO/AIA/32A) or identified above:
`74254
`oR
`[| i hereby appoint Practitioner(s} named in the attached list (form PTO/AIA/820) as my/our atlamey(s) of agent(s), and to transact
`ail business in the United States Patent and Trademark Office connected therewith for the patent application referanced in the
`attached transmittal letter (form PTO/AIA/S2A) or identified above. (Note: Complete form PTOVAIAB2C.}
`Please recognize or change the correspondance address fer the application identified in the attached transmittal
`letter or the boxes above to:
`[|
`The address associated with ihe above-mentioned Customer Number
`OR
`[| The address
`
`with Customer Number:
`
`associated
`
`OR
`Firm or
`individual Name
`
`Address.
`
`City
`Country
`| Email
`Telephone
`i
`lam the Applicant (ifthe Applicant is a juristic entity, list the Applicant name in the box}:
`
`|
`
`| State.
`
`iZip
`
`SUNPOWER CORPORATION
`
`inventor or Joint inventor (title not required below}
`[| Legal Represontative of a Deceased or Legally incapacitated Inventor (title not required below)
`Vi
`Assignee or Person to Whom the Inventor is Under ari Obligation to Assign (provide signer's title if applicant is a juristic entity)
`im Person Who Otherwise Shows Sufficient Proprietary interest (e.g., a patition under 37 CFR 1.48(b\(2) was granted in the
`application or is concurrently being filed with this document} (provide signer's title { applicant is a juristic entity}
`SIGNATURE of Applicant for Patent
`titeis suppligd belay) is authorized is act on behalf of the applicant (e.g., where the applicantis a juristic entity).
`ae
`_[ Date (Optional)
`| si eeed. ¢
`iy
`
`(whose
`
`The undersigned
`Signature
`DAVID PETRIM
`Name
`HEAD IP COUNSEL, SUNPOWER CORPORATION
`Tite
`NOTE: Signature - This form must be signed by the applicant in accordance with 37 CFR 1.33, See 37 CFR 1.4 for signature requirements
`and certifications, If more than one applicant, use multinle forms.
`[Fro of
`forms are submiltied.
`"hs collection of infannationis required by 37 CER 4.4131, $92, and 1.33, Tha information js required fo obtain or retain a benefit by the public vehich is to Re (and by the
`USPTO to process} an application. Confidentialityis governed by 35 U.S.C. 122 and 37 CFR 1.11 and 1.14. This collection is estimated to take 3 minutes to complete,
`indluding gathering, preparing, and submitting the completed application form to the USPTO. Time will vary depending upon the idividual case. Any comments on the ammunt
`of time you require to complete this form andine suggestions tor reducing this burden, should de sant to the Chief tnfaymation Ovicer, U.S. Patent and Trademark Olfice, U.S,
`Department of Commarca, P.O. Box 1450, Alexandria, VA 22915-1480, BO NOT SEND FEES OR COMPLETED FORMS TO THIS ADDRESS. SEND TO: Commissioner
`for Patents, P.O. Hox 1450, Alexandria, VA 22343-1456.
`if you need assistance in completing the farm, call 1-800-PTO-9199 and select optian 2.
`
`1
`
`

`

`Attorney Docket No. 10031.004212
`
`FRONT CONTACT SOLAR CELL WITH FORMED EMITTER
`
`Inventor: Peter John Cousins
`
`5
`
`10
`
`REFERENCE TO RELATED APPLICATIONS
`
`This application is a continuation of U.S. Application No. 14/504,771, filed on
`
`October 2, 2014, which is a continuation of U.S. Application No. 13/495,577, filed on
`June 13, 2012, now U.S. Patent No. 8,878,053, which is a divisional of U.S. Application
`No. 12/070,742, filed on February 20, 2008, now U.S. Patent No. 8,222,516. The just-
`mentioned disclosures are incorporated herein by reference in their entirety.
`
`BACKGROUND OF THE INVENTION
`
`1.
`
`Field of the Invention
`
`15
`
`The present invention relates generally to solar cells, and more particularly but
`
`not exclusively to solar cell fabrication processes and structures.
`
`2.
`
`Description of the Background Art
`
`Solar cells are well known devices for converting solar radiation to electrical
`
`20
`
`energy. They may be fabricated on a semiconductor wafer using semiconductor
`processing technology. A solar cell includes P-type and N-type diffusion regions that
`form a junction. Solar radiation impinging on the solar cell creates electrons and holes
`
`that migrate to the diffusion regions, thereby creating voltage differentials between the
`
`diffusion regions.
`
`In a backside contact solar cell, both the diffusion regions and the
`-1-
`
`

`

`Attorney Docket No. 10031.004212
`
`metal contacts coupled to them are on the backside of the solar cell. The metal
`
`contacts allow an external electrical circuit to be coupled to and be powered by the solar
`
`cell.
`
`In a front contact solar cell, at least one of the metal contacts making an
`electrical connection to a diffusion region is on the front side of the solar cell. The front
`
`5
`
`side of the solar cell, which is opposite the backside, faces the sun during normal
`
`operation to collect solar radiation. While backside contact solar cells have an aesthetic
`
`advantage over front contact solar cells
`
`di
`due to the absence of metal contacts on the
`
`front side, and are thus preferred for residential applications, aesthetics is not a major
`
`10
`
`requirement for power plants and other applications where power generation is the main
`
`concern. Disclosed herein are structures for a relatively efficient and cost-effective front
`
`contact solar cell and processes for manufacturing same.
`
`SUMMARY
`
`15
`
`A bipolar solar cell includes a backside junction formed by an N-type silicon
`substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An
`antireflection layer may be formed on a textured front surface of the silicon substrate. A
`negative polarity metal contact on the front side of the solar cell makes an electrical
`
`connection to the substrate, while a positive polarity metal contact on the backside of
`
`20
`
`the solar cell makes an electrical connection to the polysilicon emitter. An external
`
`electrical circuit may be connected to the negative and positive metal contacts to be
`powered by the solar cell. The positive polarity metal contact may form an infrared
`
`reflecting layer with an underlying dielectric layer for increased solar radiation collection.
`-2-
`
`

`

`Attorney Docket No. 10031.004212
`
`n
`These and other features of the present invention will be readily apparent to
`
`persons of ordinary skill in the art upon reading the entirety of this disclosure, which
`
`includes the accompanying drawings and claims.
`
`‘5
`
`DESCRIPTION OF THE DRAWINGS
`
`FIG.
`
`1 schematically shows a cross-section of a solar cell in accordance with an
`
`embodiment of the present invention.
`
`FIG. 2 is a plan view schematically showing the front side of the solar cell of FIG.
`
`10
`
`FIG. 3 is a plan view schematically showing the backside of the solar cell of FIG.
`
`FIG. 4, which comprises FIGS. 4A-4M, schematically illustrates the fabrication of
`the solar cell of FIG. 1 in accordance with an embodiment of the present invention.
`
`The use of the same reference label in different figures indicates the same or like
`components. The figures are not drawn to scale.
`
`15
`
`DETAILED DESCRIPTION
`
`In the present disclosure, numerous specific details are provided, such as
`
`examples of apparatus, process parameters, materials, process steps, and structures,
`
`20
`
`to provide a thorough understanding of embodiments of the invention. Persons of
`
`ordinary skill in the art will recognize, however, that the invention can be practiced
`
`-3-
`
`

`

`Attorney Docket No. 10031.004212
`
`without one or more of the specific details.
`
`In other instances, well-known details are
`
`not shown or described to avoid obscuring aspects of the invention.
`
`FIG.
`
`1 schematically shows a cross-section of a solar cell 100 in accordance with
`
`an embodiment of the present invention. The solar cell 100 has a front side where a
`
`‘5
`
`metal contact 102 is located and a backside on a same side as the metal contact 110.
`
`The front side faces the sun during normal operation to collect solar radiation.
`
`In the example of FIG. 1, the solar cell 100 includes a backside junction formed
`
`by a P-type doped polysilicon emitter 108 serving as a P-type diffusion region and an N-
`type silicon substrate 101 servings as an N-type diffusion region. The N-type silicon
`
`10
`
`substrate 101 may comprise a long lifetime (e.g., 2 to 5ms) N-type silicon wafer and
`a
`may havea thickness of about 100 to 250 um as measured from the backside surface
`to a tip of the textured front side surface of the substrate. The front side surface of the
`
`substrate 101 is randomly textured (labeled as 113) and includes N-type doped regions
`
`105 and 106 formed in the substrate. The N-type doped region 105 provides low front
`
`15
`
`surface recombination and improves lateral conductivity whilst not compromising the
`
`blue response of the solar cell. The region 106, which may be a phosphorus diffusion,
`
`provides low contact resistance and minimizes contact recombination. The region 106
`
`is also referred to as an "N-dot” because, in one embodiment, it forms a dot-shape to
`
`minimize the area of heavily diffused regions on the front surface. The N-type doped
`
`20
`
`region 105 may have a sheet resistance of 100 to 500 QO/sq, whilst the n-type doped
`
`region 106 may have a sheet resistance of 10 to 50 O/sq.
`
`An antireflective coating (ARC) of silicon nitride layer 103 is formed on the
`textured front side surface of the substrate 101. The texture front side surface and the
`-4-
`
`

`

`Attorney Docket No. 10031.004212
`
`silicon nitride layer 103 help improve solar radiation collection efficiency. A passivating
`oxide 124 may comprise silicon dioxide thermally grown to a thickness of about 10 to
`
`250 Angstroms on the front side surface of the substrate 101.
`
`‘5
`
`In one embodiment, the polysilicon emitter 108 is formed on a tunnel oxide layer
`107. The polysilicon emitter 108 may be formed by forming a layer of polysilicon using
`a
`Chemical Vapor Deposition (CVD), such as Low Pressure CVD (LPCVD) or Plasma
`Enhanced CVD (PECVD), and thermal anneal. The polysilicon emitter 108 may have a
`sheet resistance of 100 O/sq, and a thickness of 1000 to 2000 Angstroms. The tunnel
`
`oxide layer 107 may comprise silicon dioxide thermally grown to a thickness of about 10
`to 50 Angstroms on the backside surface of the substrate 101. A metal contact 110
`
`10
`
`electrically connects to the polysilicon emitter 108 through contact holes 123 formed
`through a dielectric comprising a silicon dioxide layer 109. The metal contact 110
`a
`provides a positive polarity terminal to allow an external electrical circuit to be coupled
`
`to and be powered by the solar cell 100. The silicon dioxide layer 109 provides
`
`15
`
`electrical isolation and allows the metal contact 110 to serve as an infrared reflecting
`
`layer for increased solar radiation collection.
`
`In one embodiment, the metal contact 110
`
`comprises silver having a conductance of about 5-25 mQ.cm and a thickness of about
`
`15-35um.
`
`On the front side of the solar cell 100, the metal contact 102 electrically connects
`
`20
`
`to the region 106 through a contact hole 120 formed through the silicon nitride layer
`103. The metal contact 102 provides a negative polarity terminal to allow an external
`
`electrical circuit to be coupled to and be powered by the solar cell 100.
`
`In one
`
`embodiment, the metal contact 102 comprises silver having a sheet resistance of about
`-5-
`
`

`

`Attorney Docket No. 10031.004212
`
`5mQ.cm and a thickness of about 15um. The pitch between adjacent metal contacts
`
`102 may be about 1 to
`
`4
`
`4mm.
`
`In one embodiment, the metal contacts 102 are spaced
`
`at 400 to 1000 um along each metal contact 102 (see FIG. 2).
`
`In the example of FIG. 1, the edge isolation trench 111 is formed through the
`
`5
`
`silicon dioxide layer 109, the polysilicon emitter 108, and a portion of the substrate 101
`
`to provide edge electrical isolation.
`
`FIG. 2 is a plan view schematically showing the front side of the solar cell 100.
`
`In
`
`the example of FIG. 2, two bus bars 201 run parallel on the front side of the substrate
`
`10
`
`101. The contact holes 120, in which the metal contacts 102 are formed, may each
`have a diameter of about 50 to 200 um. A plurality of metal contacts 102 is formed
`perpendicular to the bus bars 201. Each metal contact 102 may have a width of about
`
`60-120um.
`
`FIG. 3 is a plan view schematically showing the backside of the solar cell 100.
`
`In
`
`the example of FIG. 3, two bus bars 301, which are electrically coupled to metal
`
`15
`
`contacts 110, run parallel on the backside.
`
`In practice, the bus bars 201 and 301 will be
`
`electrically connected to corresponding bus bars of adjacent solar cells to form an array
`
`of solar cells.
`
`Solar cells have gained wide acceptance among energy consumers as a viable
`a
`
`renewable energy source. Still, to be competitive with other energy sources, a solar cell
`
`20
`
`manufacturer must be able to fabricate an efficient solar cell at relatively low cost. With
`
`this goal in mind, a process for manufacturing the solar cell 100 is now discussed with
`reference to FIGS. 4A-4M.
`
`6
`
`

`

`Attorney Docket No. 10031.004212
`
`FIG. 4, which comprises FIGS. 4A-4M, schematically illustrates the fabrication of
`the solar cell 100 in accordance with an embodiment of the present invention.
`
`In FIG. 4A, an N-type silicon substrate 101 is prepared for processing into a solar
`cell by undergoing a damage etch step. The substrate 101 is in wafer form in this
`
`5
`
`example, and is thus typically received with damaged surfaces due to the sawing
`
`process used by the wafer vendor to slice the substrate 101 from its ingot. The
`
`substrate 01 may be about 100 to 200 microns thick as received from the wafer
`aT
`
`vendor.
`
`In one embodiment, the damage etch step involves removal of about 10 to 20
`
`um from each side of the substrate 101 using a wet etch process comprising potassium
`hydroxide. The damage etch step may also include cleaning of the substrate 101 to
`
`10
`
`remove metal contamination.
`
`15
`
`20
`
`In FIG. 4B, tunnel oxides 402 and 107 are formed on the front and back surfaces,
`
`respectively, of the substrate 101. The tunnel oxides 402 and 107 may comprise silicon
`
`dioxide thermally grown to a thickness of about 10 to 50 Angstroms on the surfaces of
`the N-type silicon substrate 101. A layer of polysilicon is then formed on the tunnel
`oxides 402 and 107 to form the polysilicon layer 401 and the polysilicon emitter 108,
`
`respectively. Each of the polysilicon layer 401 and the polysilicon emitter 108 may be
`1000 to 2000 Angstroms by CVD.
`
`formed to a thickness of about
`
`aT
`
`In FIG. 4C, a P-type dopant source 461 is formed on the polysilicon emitter 108.
`As its name implies, the P-type dopant source 461 provides a source of P-type dopants
`for diffusion into the polysilicon emitter 108 in a subsequent dopant drive-in step. A
`
`dielectric capping layer 462 is formed on the P-type dopant source 461 to prevent
`
`|
`
`dopants from escaping from the backside of the solar cell during the drive-in step.
`-7-
`
`In
`
`

`

`Attorney Docket No. 10031.004212
`
`one embodiment, the P-type dopant source comprises BSG (borosilicate glass)
`deposited to a thickness of about 500 to 1000 Angstroms by atmospheric pressure CVD
`(APCVD) and has a dopant concentration of 5 to 10% by weight, while the capping layer
`462 comprises undoped silicon dioxide formed to a thickness of about 2000 to 3000
`Angstroms also by APCVD.
`
`‘5
`
`In FIG. 4D, the edge isolation trench 111 is formed near the edge of the
`substrate 101 on the backside. The trench 111 is relatively shallow (e.g., 10 pm deep
`
`into the substrate 101) and provides edge electrical isolation.
`
`In one embodiment, the
`
`trench 111 is formed by cutting through the capping layer 462, the P-type dopant source
`
`10
`
`461, the polysilicon emitter 108, the tunnel oxide 107, and into a shallow portion of the
`
`substrate 101 using a laser.
`
`In FIG. 4E, exposed regions on the front surface of the substrate 101 is randomly
`
`textured to form the textured surface 113.
`
`In one embodiment, the front surface of the
`
`substrate 101 is textured with random pyramids using a wet etch process comprising
`
`15
`
`potassium hydroxide and isopropyl alcohol.
`
`In FIG. 4F, an N-type dopant source 412 is formed on regions of the textured
`
`surface 113 where contact holes 120 (see FIG. 1) will be subsequently formed to allow
`subsequently formed metal contacts 102 to electrically connect to the substrate 101. As
`its name implies, the N-type dopant source 412 provides a source of N-type dopants for
`
`20
`
`diffusion into the front side of the substrate 101.
`
`In one embodiment, the N-type dopant
`
`source 412 is formed by inkjet printing the dopant material directly onto the substrate
`
`101.
`
`8
`
`

`

`Attorney Docket No. 10031.004212
`
`In one embodiment, the N-type dopant source 412 comprises silicon dioxide
`doped with phosphorus. Only one N-type dopant source 412 is shown in FIG. 4F for
`
`In practice, there are several dot-shaped N-type dopant sources
`clarity of illustration.
`412, one for each region where a contact hole 120 is to be formed (see FIG. 2). This
`
`‘5
`
`allows formation of several dot shaped N-type doped regions 106 (see FIG. 1) after a
`
`subsequently performed drive-in step now discussed with reference to FIG. 4G.
`
`In FIG. 4G, a dopant drive-in step is performed to diffuse N-type dopants from
`
`the N-type dopant source 412 into the substrate 101 to form the N-type dope region
`
`106, to diffuse P-type dopants from the P-type dopant source 461 to the polysilicon
`
`10
`
`emitter 108, and to diffuse N-type dopants into the front side of the substrate 101 to
`
`form the N-type doped region 105. Silicon dioxide layer 109 represents layers 461 and
`
`462 after the drive-in step. The polysilicon emitter 108 also becomes a P-type doped
`
`layer after the drive-in step. The N-type doped region 105 may be formed by exposing
`the sample of FIG. 4G to phosphorus in a diffusion furnace, for example. The use of the
`
`15
`
`N-type dopant source 412 allows for a more controlled and concentrated N-type
`
`diffusion to the N-type doped region 106. The thin thermal silicon dioxide layer 124 may
`
`be grown on the textured surface 113 during the drive-in process.
`
`The drive-in step to dope the polysilicon emitter 108 on the backside and to form
`the N-type doped regions 105 and 106 on the front side may be formed in-situ, which in
`the context of the present disclosure means a single manual (i-e., by fabrication
`
`20
`
`personnel) loading of the substrate 101 in a furnace or other single chamber or multi-
`
`chamber processing tool.
`
`In one embodiment, the drive-in step is performed in a
`
`g
`
`

`

`Attorney Docket No. 10031.004212
`
`diffusion furnace. The preceding sequence of steps leading to the drive-in step allows
`
`for in-situ diffusion, which advantageously helps in lowering fabrication cost.
`
`It is to be noted that the step of using an N-type dopant source 412 to diffuse
`
`dopants into the N-type doped region 106 may be omitted in some applications. That is,
`in an alternative process, the formation of the N-type dopant source 412 in FIG. 4F may
`
`5
`
`be omitted.
`
`In that case, the N-type doped regions 105 and 106 will be both doped by
`
`introduction of an N-type dopant in the diffusion furnace during the drive-in step. All
`
`other process steps disclosed herein remain essentially the same.
`
`In FIG. 4H, the antireflective coating of silicon nitride layer 103 is formed over the
`
`10
`
`textured surface 113 after removal of the N-type dopant source 412. Besides being an
`
`antireflective coating, the silicon nitride layer 103 also advantageously serves as a
`
`dielectric, enabling the selective contacts to be formed on the front surface to reduce
`
`‘front surface recombination. The silicon nitride layer 103 may be formed to a thickness
`
`of about 450 Angstroms by PECVD, for example.
`
`15
`
`In FIG. 41, a front contact mask 420 is formed on the silicon nitride layer 103 to
`
`create a pattern 421 defining the contact holes 120 (see FIG. 1). The mask 420 may
`
`comprise an acid resistance organic material, such as a resist, and formed using a
`
`printing process, such as screen printing or inkjet printing.
`
`In FIG. 4J, a back contact mask 422 is formed on the silicon dioxide layer 109 to
`
`20
`
`create patterns 423 defining the contact holes 123 (see FIG. 1). Similar to the mask
`
`420, the mask 422 may comprise an organic material formed using a printing process.
`
`-10-
`
`

`

`Attorney Docket No. 10031.004212
`
`In FIG. 4K, contact holes 120 and 123 are formed by removing exposed portions
`1:
`
`of the silicon nitride layer 103 and the silicon dioxide 109 in a contact etch step.
`
`In one
`
`embodiment, the contact holes 120 are formed by using a selective etch process that
`
`removes exposed portions of the silicon nitride layer 103 and stops on the substrate
`
`‘5
`
`101. The same etch process removes exposed portions of the silicon dioxide 109 and
`
`stops on the polysilicon emitter 108.
`BOE (buffered oxide etch).
`
`In one embodiment, the etch process comprises a
`
`In FIG. 4L, the metal contact 110 is formed on the silicon dioxide layer 109 to fill
`
`the contact holes 123 and make electrical connection to the polysilicon emitter 108.
`
`10
`
`The metal contact 110 may be formed using a printing process. The metal contact 110
`
`may comprise silver, which, together with the silicon dioxide layer 109, makes an
`
`excellent backside infrared reflector. Other metals may also be used as a metal contact
`
`110, such as aluminum, for example.
`
`In FIG. 4M, the metal contact 120 is formed on the silicon nitride layer 103 to fill
`
`15
`
`the contact holes 120 and make electrical connection to the substrate 101. The metal
`
`contact 120 may comprise silver and formed using a printing process.
`a
`
`a
`Formation of the metal contacts 110 and 102 may be followed bya firing step.
`The firing step is applicable when using screen printed silver paste as metal contacts,
`but not when using other processes or metals. The solar cell 100 may then be visually
`
`20
`
`inspected and tested.
`
`While specific embodiments of the present invention have been provided, it is to
`
`be understood that these embodiments are for illustration purposes and not limiting.
`
`Many additional embodiments will be apparent to persons of ordinary skill in the art
`-11-
`
`

`

`Attorney Docket No. 10031.004212
`
`reading this disclosure.
`
`-12-
`
`

`

`Attorney Docket No. 10031.004212
`
`CLAIMS
`
`What is claimed is:
`
`1.
`
`‘5
`
`A solar cell, comprising:
`a substrate;
`a first tunnel dielectric disposed over the substrate;
`an emitter disposed over the first tunnel dielectric;
`a
`a front electrode disposed over a front surface of the substrate; and
`a back electrode disposed over a back surface of the substrate.
`
`10
`
`2.
`
`The solar cell of claim 1, wherein the emitter is a polysilicon emitter.
`
`The solar cell of claim 1, wherein the substrate is a monocrystalline silicon
`3.
`substrate.
`
`15
`
`4.
`
`The solar cell of claim 1, wherein the first tunnel dielectric is a tunnel oxide.
`
`The solar cell of claim 1, wherein the emitter is disposed over the back
`5.
`the substrate.
`
`of
`
`surface
`
`20
`
`6. __The solar cell of claim 1, further comprising a second tunnel dielectric disposed
`on an opposite side of the substrate than the first tunnel dielectric.
`
`7.
`
`The solar cell of claim 1, wherein the back electrode includes silver.
`
`25
`
`The solar cell of claim 1, further comprising an antireflective layer disposed over
`8.
`the front surface of the substrate.
`
`30
`
`Asolar cell, comprising:
`a substrate;
`an emitter over a back surface of the substrate;
`-13-
`
`

`

`Attorney Docket No. 10031.004212
`
`a first dielectric between the emitter and back surface;
`a front electrode disposed on a front surface of the solar cell; and
`a back electrode disposed on a back surface of the solar cell.
`
`5
`
`10.
`
`The solar cell of claim 9, wherein the emitter is a polysilicon emitter.
`
`The solar cell of claim 9, wherein the substrate is a monocrystalline silicon
`11.
`substrate.
`
`10
`
`12.
`
`The solar cell of claim 9, wherein the first dielectric is an oxide.
`
`The solar cell of claim 9, further comprising a second dielectric disposed on an
`13.
`opposite side of the substrate than the first dielectric.
`
`15
`
`14.
`
`The solar cell of claim 9, wherein the back electrode includes silver.
`
`15.
`
`20
`
`Amethod of fabricating a solar cell, the method comprising:
`forminga first tunnel dielectric on a front surface of a substrate;
`a
`forming a second tunnel dielectric on a back surface of the substrate;
`forming an emitter over the first or second tunnel dielectric;
`forming a front side electrode on a front surface of the solar cell; and
`forming a back side electrode on a back surface of the solar cell.
`
`16.
`
`The method of claim 15, wherein said forming the emitter comprises forming a
`polysilicon emitter.
`
`25
`
`|The method of claim 15, wherein said forming the emitter comprises forming a
`17.
`first silicon layer on the second tunnel dielectric.
`
`30
`
`The method of claim 17, further comprising forming a second silicon layer on the
`18.
`first tunnel dielectric.
`
`-14-
`
`

`

`Attorney Docket No. 10031.004212
`
`|The method of claim 18, wherein forming the first and second silicon layers
`19.
`comprises forming first and second polysilicon layers, respectively.
`
`‘5
`
`The method of claim 15, wherein said forming the second tunnel dielectric
`20.
`comprises forming an oxide.
`
`-15-
`
`

`

`Attorney Docket No. 10031.004212
`
`ABSTRACT
`
`A bipolar solar cell includes a backside junction formed by an N-type silicon substrate
`and a P-type polysilicon emitter formed on the backside of the solar cell. An
`antireflection layer may be formed on a textured front surface of the silicon substrate. A
`negative polarity metal contact on the front side of the solar cell makes an electrical
`connection to the substrate, while a positive polarity metal contact on the backside of
`
`5
`
`the solar cell makes an electrical connection to the polysilicon emitter. An external
`
`electrical circuit may be connected to the negative and positive metal contacts to be
`
`powered by the solar cell. The positive polarity metal contact may form an infrared
`
`10
`
`reflecting layer with an underlying dielectric layer for increased solar radiation collection.
`
`-16-
`
`

`

`Nate
`
`123
`
`Nye
`
`ww
`
`:
`
`FIG1
`123
`
`‘wo
`
`-~
`
`123
`
`'
`
`‘00
`
`|
`
`|
`
`11
`
`109
`7~—108
`
`107
`
`W—106
`
`N
`
`102
`
`Ku
`
`LOL
`
`124
`
`103
`
`105
`
`113
`
`100
`
` OOL
`cébcdlGol
`
`101
`
`60l-—~
`
`BOL2
`
`

`

`100
`
`AY
`
`201
`
`102
`
`
`
`201
`
`a
`
`106
`
`A 06
`
`102
`
`
`
`\
`\
`
`
`106
`
`N
`
`\
`
`\
`
`K
`
`fs
`
`\
`
`\
`
`N
`
`N
`
`fs
`
`\
`
`\
`\
`
`\
`
`\420
`120
`
`FIG. 2
`FIG. 2
`
`‘S
`
`~N
`
`120
`120
`
`120
`120
`
`vA
`
`/
`
`ua
`
`REC Exhibit 1018, Page 20 of 295
`
`
`
`

`

`100
`
`~
`
`— 110
`
`410
`
`301
`301
`
`
`
`
`301
`
`FIG. 3
`FIG. 3
`
`REC Exhibit 1018, Page 21 of 295
`
`

`

`101
`
`FIG. 4A
`
`101
`101
`
`
`FIG. 4B
`FIG. 4B
`
`401
`404
`
`i
`
`02
`—~—AQ?2
`
`107
`
`—107C.
`
`108
`108
`
`401
`
`101
`
`
`
`— a
`
`46
`
`
`
`FIG. 4C
`
`46 1
`11° 462
`
`101
`
`FIG. 4D
`
`02
`
`107
`
`108
`
`401
`
`02
`
`107
`
`08
`
`REC Exhibit 1018, Page 22 of 295
`
`

`

`A13
`143
`
`
`10
`104
`
`461
`
`107
`07
`
`
`108
`462
`11
`agp 462
`“108
`
`FIG. 4E
`FIG. 46
`
`101
`
`461s
`
`11
`
`462
`
`113
`
`105
`
`/124
`
`14
`
`104
`
`FIG. 4G
`
`FIG. 4F
`
`
`
`412
`
`107
`
`“108
`
`412
`
`N 06
`
`107
`108
`109
`
`REC Exhibit 1018, Page 23 of 295
`
`

`

`105
`
`Mn
`
`113, 103,AA
`
`AN 106
`
`11
`
`420.
`
`103
`113
`105——*
`
`11
`
`420
`
`103
`4137
`105
`
`11
`
`101
`
`FIG. 4H
`
`421
`
`101
`
`FIG.
`
`107
`108
`109
`
`420
`
`“106
`
`107
`08
`1 09
`
`421.
`
`420
`
`ONE
`
`4106
`
`107
`108
`109
`
`423
`
`422
`
`101
`
`JL423
`
`FIG. 4J
`
`

`

`105
`
`113.
`
`10
`
`101
`
`11
`
`120
`
`106
`
`107
`108
`mt_109
`
`123
`
`123
`
`FIG. 4K
`
`es W “A \
`
`101
`
`120
`
`/
`
`106
`
`107
`108
`109
`
`123
`
`~110
`FIG. 4b
`
`123
`
`105
`
`113.
`
`103
`
`120
`
`102
`
`ww
`
`101
`
`Soe
`
`123
`
`“110
`FIG. 4M
`
`106
`
`107
`L 08
`109
`
`\
`123
`
`

`

`Electronic Patent Application Fee Transmittal
`
`Application Number:
`
`Filing Date:
`
`Title of Invention:
`
`FRONT CONTACT SOLAR CELL WITH FORMED EMITTER
`
`First Named Inventor/Applicant Name:
`
`Peter John COUSINS
`
`Filer:
`
`Attorney Docket Number:
`
`Filed as Large Entity
`
`Filing Fees for Utility under 35 USC 111(a)
`
`Patrick D. Benedicto/Jina Mangaoang
`
`10031.004212
`
`Description
`
`Fee Code
`
`Quantity
`
`Amount
`
`sa
`
`b-Total
`USD($)
`
`in
`
`Basic Filing:
`
`UTILITY APPLICATION FILING
`
`UTILITY SEARCH FEE
`
`UTILITY EXAMINATION FEE
`
`1011
`
`1111
`
`1311
`
`Pages:
`
`Claims:
`
`Miscellaneous-Filing:
`
`LATE FILING FEE FOR OATH OR DECLARATION
`
`1051
`
`Petition:
`
`1
`
`1
`
`1
`
`1
`
`300
`
`660
`
`760
`
`300
`
`660
`
`760
`
`160
`
`160
`
`

`

`Description
`
`Fee Code
`
`Quantity
`
`Amount
`
`Sub-Total in
`USD(S)
`
`Patent-Appeals-and-Interference:
`
`Post-Allowance-and-Post-Issuance:
`
`Extension-of-Time:
`
`Miscellaneous:
`
`Total in USD ($)
`
`1880
`
`

`

`Electronic Acknowledgement Receipt
`
`EFS ID:
`
`Application Number:
`
`36474505
`
`16460035
`
`International Application Number:
`
`Confirmation Number:
`
`5633
`
`Title of Invention:
`
`FRONT CONTACT SOLAR CELL WITH FORMED EMITTER
`
`First Named Inventor/Applicant Name:
`
`Peter John COUSINS
`
`Customer Number:
`
`74254
`
`Filer:
`
`Patrick D. Benedicto/Jina Mangaoang
`
`Filer Authorized By:
`
`Patrick D. Benedicto
`
`Attorney Docket Number:
`
`Receipt Date:
`
`Filing Date:
`
`Time Stamp:
`
`Application Type:
`Payment information:
`Submitted with Payment
`File Listing:
`Document
`Number
`
`Document Description
`
`10031.004212
`
`02-JUL-2019
`
`13:34:09
`
`Utility under 35 USC 111{a)
`
`no
`
`File Name
`
`File Size(Bytes)/
`Multi
`Message Digest | Part/.zip|
`1256147
`
`Pages
`(if appl.)
`
`1
`
`Application Data Sheet
`
`$0123US3_ADSaia0014.pdf
`
`no
`
`8
`
`6ecch61634ca65ec8b243 b9235 2db8Sbc0by
`06636
`
`Warnings:
`
`

`

`Information:
`
`2
`
`Power of Attorney
`
`PowerOfAttorney.pdf
`
`674498
`
`97a7
`
`2004718
`
`e72e
`
`no
`
`2
`
`yes
`
`23
`
`$0123US3_CONT.pdf
`
`Warnings:
`Information:
`
`3
`
`Warnings:
`Information:
`
`Multipart Descri