WO1988010514A1 - Stabilization of intraconnections and interfaces - Google Patents
Stabilization of intraconnections and interfaces Download PDFInfo
- Publication number
- WO1988010514A1 WO1988010514A1 PCT/US1987/001518 US8701518W WO8810514A1 WO 1988010514 A1 WO1988010514 A1 WO 1988010514A1 US 8701518 W US8701518 W US 8701518W WO 8810514 A1 WO8810514 A1 WO 8810514A1
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- WO
- WIPO (PCT)
- Prior art keywords
- electrode
- metallic
- semiconductor
- nickel
- ions
- Prior art date
Links
- 230000006641 stabilisation Effects 0.000 title abstract description 6
- 238000011105 stabilization Methods 0.000 title abstract description 6
- 150000001455 metallic ions Chemical class 0.000 claims abstract description 23
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000004065 semiconductor Substances 0.000 claims abstract description 15
- 238000007598 dipping method Methods 0.000 claims abstract description 7
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 7
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 239000011651 chromium Substances 0.000 claims abstract description 5
- 230000008021 deposition Effects 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 18
- 239000002253 acid Substances 0.000 claims description 14
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 12
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 6
- 229910001453 nickel ion Inorganic materials 0.000 claims description 6
- 239000000758 substrate Substances 0.000 claims description 6
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- 150000002500 ions Chemical class 0.000 claims description 3
- 230000000087 stabilizing effect Effects 0.000 claims description 3
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 claims description 2
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 claims description 2
- 239000004094 surface-active agent Substances 0.000 claims description 2
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 claims 1
- 239000000470 constituent Substances 0.000 claims 1
- 229910044991 metal oxide Inorganic materials 0.000 claims 1
- 238000000151 deposition Methods 0.000 abstract description 4
- 229910052751 metal Inorganic materials 0.000 abstract description 4
- 239000002184 metal Substances 0.000 abstract description 4
- 238000001465 metallisation Methods 0.000 abstract description 3
- 229910017052 cobalt Inorganic materials 0.000 abstract description 2
- 239000010941 cobalt Substances 0.000 abstract description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 abstract description 2
- 238000001035 drying Methods 0.000 abstract description 2
- 150000002739 metals Chemical class 0.000 abstract description 2
- 239000000126 substance Substances 0.000 abstract description 2
- 238000005382 thermal cycling Methods 0.000 description 16
- 230000009467 reduction Effects 0.000 description 12
- 229910052782 aluminium Inorganic materials 0.000 description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 10
- 229910021417 amorphous silicon Inorganic materials 0.000 description 10
- 238000012360 testing method Methods 0.000 description 9
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 9
- 229910001887 tin oxide Inorganic materials 0.000 description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- 229910052710 silicon Inorganic materials 0.000 description 7
- 239000010703 silicon Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 4
- 239000013068 control sample Substances 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 238000002791 soaking Methods 0.000 description 4
- 230000002459 sustained effect Effects 0.000 description 4
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 3
- 239000004327 boric acid Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000000637 aluminium metallisation Methods 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 206010072082 Environmental exposure Diseases 0.000 description 1
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 235000019333 sodium laurylsulphate Nutrition 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/20—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof such devices or parts thereof comprising amorphous semiconductor materials
- H01L31/208—Particular post-treatment of the devices, e.g. annealing, short-circuit elimination
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
- H01L31/042—PV modules or arrays of single PV cells
- H01L31/0445—PV modules or arrays of single PV cells including thin film solar cells, e.g. single thin film a-Si, CIS or CdTe solar cells
- H01L31/046—PV modules composed of a plurality of thin film solar cells deposited on the same substrate
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- This invention relates to the stabilization of intraconnected devices, i.e., those with internal connection, and, more particularly, to the stabilization of the intraconnected energy sensitive devices such as solar cells.
- Energy sensitive devices such as amorphous silicon solar cells are vulnerable to various kinds of degradation that affect their performance.
- One important kind of degradation results in panel deterioration and arises because of thermal soaking or cycling of the electrical contact between a back electrode, usually aluminum, and a front electrode, usually conductive tin oxide in the common panel configuration of intraconnected elements of glass, ti oxide, PIN amorphous silicon and aluminum.
- a further complicating factor is the interdiffusion of silicon and aluminum at the back contact interface, namely between n-type amorphous silicon and aluminum. This type o cell degradation is continuous and non-reversible, under thermal cycling. It seriously curtails the useful lifetime of the solar panels in the field.
- a succession of layers are deposited, one on top of the other, on a suitable substrate.
- glass is a commonly used substrate on which a transparent conductive tin oxide layer is deposited.
- Individual electrodes are created by patterning the tin oxide. This is followed by the deposition of P, I, and N type of amorphous silicon based alloys.
- the semiconductor layers are opened to expose a thin line of the underlying tin oxide.
- the final step is the deposition of the back contact, for example aluminum, to produce an intraconnected solar panel.
- the most common technique for the last step is vacuum metallization.
- Another object of the invention is to reduce the degradation that occurs during the thermal cycling of interconnectors, particularly solar cells.
- Still another object of the invention is to reduce interdiffusion at contact interfaces, particularly in solar cells between a semiconductor and a metal contact.
- energy sensitive panels after first initial electrode formation but before subsequent metallizing, are dipped in solutions containing specific chemicals, followed by rinsing and drying. Then the final electrode is deposited by metallizing.
- the front electrode (conductive tin oxide) equipped panels are dipped in an acid solution, such as 30% phosphoric, for a prescribed period, such as about 30 seconds, rinsed in deionized water, and then dipped in a metallic ion solution.
- the metallic ion solution is desirably of nickel, cobalt, chromium, and related metals.
- a suitable metallic ion solution is of nickel sulfate, boric acid and ammonium chloride.
- the time is prescribed, e.g., again for 30 seconds, rinsed in dionized water, dried with a rinse, for example isopropanol, and then subjected to back electrode deposition.
- At least one of the solutions prefferably include a surfactant, such as sodium lauryl sulfate, to provide
- a surfactant such as sodium lauryl sulfate
- concentrations are illustrative only. Lower or higher concentrations are also suitable. For low concentrations, (2% nickel ion) a longer dipping time might be required. For higher concentrations, i.e., about 11% nickel ion and 1.5% each of boric acid and ammonium chloride, there is a reduction in cost effectiveness for the manufacturing process.
- Figures 1A through ID are graphs comparing untreated panels with those in accordance with the invention for various normalized photovoltaic factors over prescribed periods of thermal cycling;
- Figures 2A and 2B are graphs showing the effect on various normalized parameters of untreated panels in comparison with panels that have been treated in accordance with the invention.
- Figures 3A through 3D are graphs illustrating the effect of thermal cycling on untreated panels in comparison with variously treated panels in accordance with the invention.
- Figure 1A illustrates the effect of thermal cycling on contact resistance for untreated panels and those treated in accordance with the invention.
- Figure IC compares fill factor of the treated and untreated panels. It is apparent from Figure IC that the untreated panels sustained a reduction in fill factor by 50% whereas the treated panels have reduction in fill factor of 20%.
- Figure ID A further example of the invention is illustrated in Figure ID, where the untreated panel sustained a reduction in short circuit current by 55%- after six days of thermal cycling. By contrast treated panels sustained a reduction in short circuit current of about 10% after six days of thermal cycling at elevated temperatures. (150°C.)
- FIG. 2A A further illustration of the advantages of the present invention is provided by the test results summarized in Figures 2A through 2D.
- a control and treated solar panel were heated at 120 Centigrade and the photovoltaic parameters of the panels were measured as a function of time.
- the contact resistance (between Al and SnOfact) of the control panel (indicated with "C" test points) increased by a factor of 8.5 after 300 hours at 120 Centigrade.
- the panel, treated according to the present invention showed hardly any change in the Al/SnO_ contact resistance after thermal cycling at 120°C. for the same period (300 hrs.) . These are indicated by points "N" in Fig. 2A. Similar stabilizing effects of the method of the present invention on other photovoltaic parameters after heating for 300 hours at 120°C. are depicted in Figs. 2B-D.
- the acid dip which is the initial step in the practice of the process has a cleansing effect on the panels and prepares the panels for the metallic ion dip.
- the preliminary acid dip taken alone, provides an improvement over the untreated control panels, but its effect is not nearly as . significant as that of the metallic ion dip taken alone.
- the contact resistance of the untreated panel increased by a factor of 11.5 after 50 hours of thermal cycling at 150 Centigrade.
- the panels treated with the acid dip alone (phosphoric acid) with test points indicated by the designation "P” showed an increase in contact resistance after 50 hours by a factor of 2.5.
- the phosphoric acid has a concentration in the range from 10 to 100 per cent.
- a desirable phosphoric acid concentration is 30 per cent.
- the dipping time is approximately in the range from 10 to 30 seonds, with 30 seconds being particularly desirable.
- the metal ion dip nickel
- the test points indicated by "N” the increase in contact resistance was just by a factor of 1.5.
- the better performance of the panels which are dipped in metallic ions alone may be attributable to the ability of the adsorbed metallic ion on the amorphous silicon and the exposed front electrode (Sn0 2 ) to significantly limit interdiffusion on aluminum and silicon at the semiconductor metal interface, and the promotion of better contact between Al and Sn Q 2) .
- the acid and metallic ion solution can be mixed so that only one dip is used instead of two separate dips.
- the boric acid in the metallic ion solution is desirable in acting as a buffer.
- other ions can be used, such as chromium and related metallic components.
Abstract
Stabilization of energy sensitive semiconductive devices by forming initial electrodes which are exposed through an overlying layer of semiconductor, dipping the exposed electrodes in solutions containing specified chemicals, such as metallic ion solutions of nickel, cobalt, chromium and related metals, followed by rinsing, drying and the final deposition of an overlying electrode by metallization.
Description
Stabilization of Intraconnections and Interfaces
This invention relates to the stabilization of intraconnected devices, i.e., those with internal connection, and, more particularly, to the stabilization of the intraconnected energy sensitive devices such as solar cells.
Energy sensitive devices such as amorphous silicon solar cells are vulnerable to various kinds of degradation that affect their performance. One important kind of degradation results in panel deterioration and arises because of thermal soaking or cycling of the electrical contact between a back electrode, usually aluminum, and a front electrode, usually conductive tin oxide in the common panel configuration of intraconnected elements of glass, ti oxide, PIN amorphous silicon and aluminum.
A further complicating factor is the interdiffusion of silicon and aluminum at the back contact interface, namely between n-type amorphous silicon and aluminum. This type o cell degradation is continuous and non-reversible, under thermal cycling. It seriously curtails the useful lifetime of the solar panels in the field.
In the general practice of manufacturing amorphous silicon solar cells, a succession of layers are deposited, one on top of the other, on a suitable substrate. For example, glass is a commonly used substrate on which a transparent conductive tin oxide layer is deposited. Individual electrodes are created by patterning the tin oxide. This is followed by the deposition of P, I, and N type of amorphous silicon based alloys. The semiconductor layers are opened to expose a thin line of the underlying tin oxide. The final step is the deposition of the back contact, for example aluminum, to produce an intraconnected solar panel. The most common technique for the last step is vacuum metallization.
When amorphous silicon is opened to expose the underlying tin oxide, it is likely that the site thus created will not provide a good contact on subsequent metallization and subjection to thermal cycling. Further, under the same conditions of outdoor thermal cycling or soaking, there is a gradual interdiffusion between silicon and aluminum as indicated by accelerated testing.
Accordingly, it is an object of the invention to improve the stabilization of the intraconnections in devices, particularly the intraconnections in solar cells.
Another object of the invention is to reduce the degradation that occurs during the thermal cycling of interconnectors, particularly solar cells.
Still another object of the invention is to reduce interdiffusion at contact interfaces, particularly in solar cells between a semiconductor and a metal contact.
Summary of the Invention In accordance with the present invention, energy sensitive panels, after first initial electrode formation but before subsequent metallizing, are dipped in solutions containing specific chemicals, followed by rinsing and drying. Then the final electrode is deposited by metallizing.
In one practice of the invention, the front electrode (conductive tin oxide) equipped panels are dipped in an acid solution, such as 30% phosphoric, for a prescribed period, such as about 30 seconds, rinsed in deionized water, and then dipped in a metallic ion solution. The metallic ion solution is desirably of nickel, cobalt, chromium, and related metals. A suitable metallic ion solution is of nickel sulfate, boric acid and ammonium chloride. The time is prescribed, e.g., again for 30 seconds, rinsed in dionized water, dried with a rinse, for example isopropanol, and then subjected to back electrode deposition. It is advantageous for at least one of the solutions to include a surfactant, such as sodium lauryl sulfate, to provide
The concentrations are illustrative only. Lower or higher concentrations are also suitable. For low concentrations, (2% nickel ion) a longer dipping time might be required. For higher concentrations, i.e., about 11% nickel ion and 1.5% each of boric acid and ammonium chloride, there is a reduction in cost effectiveness for the manufacturing process.
Description of the Drawings
Other aspects of the invention will!become apparent after considering several illustrative embodiments, taken in "•conjunction with the drawings in which:
Figures 1A through ID are graphs comparing untreated panels with those in accordance with the invention for various normalized photovoltaic factors over prescribed periods of thermal cycling;
Figures 2A and 2B are graphs showing the effect on various normalized parameters of untreated panels in comparison with panels that have been treated in accordance with the invention; and
Figures 3A through 3D are graphs illustrating the effect of thermal cycling on untreated panels in comparison with variously treated panels in accordance with the invention.
Detailed Description
With reference to the drawings. Figure 1A illustrates the effect of thermal cycling on contact resistance for untreated panels and those treated in accordance with the invention.
In Figure 1A the untreated panels ("control") are represented by various test positions designated by *'C". It is seen that after six days of thermal cycling at 150 Centigrade, the contact resistance of the interconnect for a standard panel rose by a factor of 22. In the case of panels that are treated with a preliminary acid solution followed by dipping in a metallic ion solution, i|n
SUBSTITUTE SHEET
accordance with the invention, after six days of thermal cycling at 150 Centigrade, the contact resistance had increased by a factor of 1.8. This represents a significant improvement by comparison with the substantial increase in contact resistance that characterized the untreated panels. (Percentage of light converted to electrical power)
Similarly, in the case of efficiency (percentage of light converted to power) of the untreated panels versus the treated panels, the untreated panel, again with test points represented by "C", showed a reduction in efficiency by a factor of 10 after six days of thermal cycleing at 150° Centigrade. By contrast, the panels treated in accordance with the invention, with test points indicated by "N" showed a reduction in efficiency by a factor of 1.6. Here again, there is a significant improvement in stabilizing efficiency. It will be appreciated that the thermal cycling tests conducted at 150° Centigrade represent significantly accelerated aging and although practiced over a period of six days correspond in actual environmental- exposure to a substantially increased period of time on the order of a number of years.
In further example of the advantage provided by the invention, Figure IC compares fill factor of the treated and untreated panels. It is apparent from Figure IC that the untreated panels sustained a reduction in fill factor by 50% whereas the treated panels have reduction in fill factor of 20%. A further example of the invention is illustrated in Figure ID, where the untreated panel sustained a reduction in short circuit current by 55%- after six days of thermal cycling. By contrast treated panels sustained a reduction in short circuit current of about 10% after six days of thermal cycling at elevated temperatures. (150°C.)
In another example of thermal cycling of treated and untreated panels, two solar panels with individual cell structures formed by layers of g _lass, tin oxide,r PIN amorphous silicon and aluminum were heated at 150° Centigrade for 22 hours. Upon subjecting the two panels,
SUBST!TUT_- SHEET
one the control and the other stabilized in accordance with the invention, to scanning Auger analysis it was found that silicon could be detected through the aluminum grain boundary of the control panel. By contrast, silicon was detected only to a distance of about 750 angstroms form the aluminum-amorphous silicon interface of the stabilized panel. This AES (Auger) depth profile was not corrected for the interface broadening effects of the sputter profiling technique. Accordingly, the actual aluminum-silicon interface is narrower than indicated by the above analysis. The same type of analysis also revealed that nickel is adsorbed by both the tin oxide surface and the amorphous silicon surface in separate experiments.
This is a clear indication of the capability of the present invention to retard also the interdiffusion of aluminum and silicon at the interface between a metallic electrode and a layer of silicon.
A further illustration of the advantages of the present invention is provided by the test results summarized in Figures 2A through 2D. For the graphs of these figures, a control and treated solar panel were heated at 120 Centigrade and the photovoltaic parameters of the panels were measured as a function of time. As indicated in Figure 2A the contact resistance (between Al and SnO„) of the control panel (indicated with "C" test points) increased by a factor of 8.5 after 300 hours at 120 Centigrade.
However, the panel, treated according to the present invention, showed hardly any change in the Al/SnO_ contact resistance after thermal cycling at 120°C. for the same period (300 hrs.) . These are indicated by points "N" in Fig. 2A. Similar stabilizing effects of the method of the present invention on other photovoltaic parameters after heating for 300 hours at 120°C. are depicted in Figs. 2B-D.
It has been theorized that the acid dip which is the initial step in the practice of the process has a cleansing effect on the panels and prepares the panels for the metallic ion dip.
As indicated in Figures 3A through 3D, the preliminary acid dip, taken alone, provides an improvement over the untreated control panels, but its effect is not nearly as . significant as that of the metallic ion dip taken alone. Thus, in Figure 3A the contact resistance of the untreated panel increased by a factor of 11.5 after 50 hours of thermal cycling at 150 Centigrade. -By significant contrast, the panels treated with the acid dip alone (phosphoric acid) with test points indicated by the designation "P", showed an increase in contact resistance after 50 hours by a factor of 2.5. The phosphoric acid has a concentration in the range from 10 to 100 per cent. A desirable phosphoric acid concentration is 30 per cent. The dipping time is approximately in the range from 10 to 30 seonds, with 30 seconds being particularly desirable. However, in the case of the metal ion dip (nickel) the test points indicated by "N", the increase in contact resistance was just by a factor of 1.5.
Similarly, in the case of efficiency, as before there was a significant reduction (75%) for the control sample. This is in contrast with a reduction by 30% for the acid cleansed samples, and the slight reduction of 10% for the metallic ion solution. The results of Figure 3B are also confirmed by Figure 3C where the fill factor for the control sample was reduced by 50% but the fill factor for the cleansing acid bath was reduced by 25%, while the nickel ion bath produced substantially no change, (about 5% reduction) even after 50 hours of thermal soaking in 150 C.
Finally, in the case of Figure 3D the short circuit current sustained a significant reduction for the control sample but was virtually unchanged (or marginally reduced) , for both the acid and the nickel baths, with the nickel (ion) bath producing virtually no change and being superior to the phosphoric acid cleansing bath taken alone.
The results summarized by Figures 3A through 3D refer to the treatment, and in the case of the control sample, the lack of treatment before aluminum metallization. After
aluminum metallization all of the samples were heated at 150 Centigrade and the various parameters were measured as a function of time and plotted as normalized parameters.
It is seen from Figures 3A through 3D that the untreated panel degrades very rapidly but the metal ion and the acid dipped panels show superior stability in the face of thermal cycling and soaking at 150 C.
The better performance of the panels which are dipped in metallic ions alone may be attributable to the ability of the adsorbed metallic ion on the amorphous silicon and the exposed front electrode (Sn02) to significantly limit interdiffusion on aluminum and silicon at the semiconductor metal interface, and the promotion of better contact between Al and SnQ2) .
It is to be noted that the acid and metallic ion solution can be mixed so that only one dip is used instead of two separate dips. The boric acid in the metallic ion solution is desirable in acting as a buffer. In addition, other ions can be used, such as chromium and related metallic components.
The foregoing detailed description is for illustration only and it will be apparent that other adaptations of the invention will occur to those of ordinary skill in the art.
Claims
1. The method of stabilizing semiconductor devices with interconnections, which comprises the steps of:
(a) providing the device with a first electrode which is exposed through an overlying layer of semiconductor;
(b) dipping the device in acid solution;
(c) further dipping the device in a metallic ion solution; and
(d) providing a further contact to the first contact.
2. The method of claim 1 wherein said device is rinsed after the acid step.
3. The method of claim 1 wherein the acid dip contains phosphoric acid.
4. The method of claim 3 wherein the phosphoric acid has a concentration in the range from 10 to 100%, and the dipping time is approximately in the range of 10 to 30 seconds.
5. The method of claim 1 wherein the metallic ion solution contains nickel ions.
6. The method of claim 5 wherein the nickel ion solution is nickel sulfate and has a nickel ion concentration of about 11%.
7. The method of claim 1 wherein said device is rinsed after being dipped in the metallic ion solution.
8. The method of claim 7 wherein the device is dried with an isopropanol rinse after the second rinsing.
9. The method of claim 1 wherein the metallic ion is chromium.
10. A semiconductor device with interconnected electrodes comprising a substrate; a first electrode on said substrate; an amorphous semiconductor on said first electrode; metallic ions on said first electrode and said amorphous semiconductor; and a second electrode on said semiconductor extending into contact with said first electrode at the interface of said first electrode and said metallic ions.
11. The apparatus of claim 10 wherein the metallic ions are nickel.
12. The apparatus of claim 10 wherein the metallic ions are chromium.
13. The apparatus of claim 12 wherein said apparatus is a solar panel comprising said substrate with a plurality of discrete transparent conductive first electrodes on the substrate; said amorphous semiconductor comprising a layer on the transparent electrodes; a plurality of second electrodes on said semiconductor layer and opposite the transparent electrodes; and an interface between each separate transparent electrode and the opposite conducting electrode with metallic ions at said interface; thereby to enhance the thermal stability of said device.
14. The device of claim 13 wherein said metallic ion is adsorbed upon said first electrode and said amorhpous semiconductor to promote contact stability with said first electrode and interface stability between the amorphous semiconductor and the second electrode.
15. The method of claim 1 wherein the device is a constituent of a solar panel with a front electrode of conductive metallic oxide which underlies a layer of amorphous semiconductor.
16. The method of claim 7 wherein the rinses are combined.
17. The method of claim 1 wherein the acid solution and the metallic ion solution are combined to provide a single bath.
18. The method of claim 7 wherein last stage of rinsing is followed by metallic deposition, to provide the final contacting element.
19". The method of claim 1 wherein at least one of the solutions includes a surfactant, to promote contact between the surface and the ions.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US06/859,504 US4675466A (en) | 1986-04-05 | 1986-04-05 | Stabilization of intraconnections and interfaces |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/859,504 US4675466A (en) | 1986-04-05 | 1986-04-05 | Stabilization of intraconnections and interfaces |
Publications (1)
Publication Number | Publication Date |
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WO1988010514A1 true WO1988010514A1 (en) | 1988-12-29 |
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PCT/US1987/001518 WO1988010514A1 (en) | 1986-04-05 | 1987-06-22 | Stabilization of intraconnections and interfaces |
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Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4316049A (en) * | 1979-08-28 | 1982-02-16 | Rca Corporation | High voltage series connected tandem junction solar battery |
US4528065A (en) * | 1982-11-24 | 1985-07-09 | Semiconductor Energy Laboratory Co., Ltd. | Photoelectric conversion device and its manufacturing method |
US4667058A (en) * | 1985-07-01 | 1987-05-19 | Solarex Corporation | Method of fabricating electrically isolated photovoltaic modules arrayed on a substrate and product obtained thereby |
-
1987
- 1987-06-22 WO PCT/US1987/001518 patent/WO1988010514A1/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4316049A (en) * | 1979-08-28 | 1982-02-16 | Rca Corporation | High voltage series connected tandem junction solar battery |
US4528065A (en) * | 1982-11-24 | 1985-07-09 | Semiconductor Energy Laboratory Co., Ltd. | Photoelectric conversion device and its manufacturing method |
US4667058A (en) * | 1985-07-01 | 1987-05-19 | Solarex Corporation | Method of fabricating electrically isolated photovoltaic modules arrayed on a substrate and product obtained thereby |
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