Formation of CIGS absorber layer materials using atomic layer deposition and high throughput surface treatment

• US 20050186342A1
• Filed: 09/18/2004
• Published: 08/25/2005
• Est. Priority Date: 02/19/2004
• Status: Active Grant

• Current Assignee: Aeris Capital Sustainable IP, Ltd.
• Original Assignee: Nanosolar Incorporated
• Inventors: Leidholm, Craig, Roscheisen, Martin R., Sager, Brian M.
• Granted Patent: US 7,858,151 B2
• Time in Patent Office: Days
• US Class Current: 427/248.100
• CPC Class Codes: C23C 16/405 of refractory metals or yttrium
• CPC Class Codes: C23C 16/45544 characterized by the apparatus
• CPC Class Codes: C23C 16/458 characterised by the method used for supporting substrates in the reaction chamber
• CPC Class Codes: C23C 16/4581 characterised by material of construction or surface finish of the means for supporting the substrate
• CPC Class Codes: C23C 16/545 for coating elongated substrates
• CPC Class Codes: C25D 17/02 Tanks; Installations therefor
• CPC Class Codes: C25D 7/0614 Strips or foils
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/0322 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
• CPC Class Codes: H01L 31/0392 including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate textured substrates H01L31/02366
• CPC Class Codes: H01L 31/03926 comprising a flexible substrate
• CPC Class Codes: H01L 31/1864 Annealing
• CPC Class Codes: H01L 31/1876 Particular processes or apparatus for batch treatment of the devices
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

An absorber layer may be formed on on a substrate using atomic layer deposition reactions. An absorber layer containing elements of groups IB, IIIA and VIB may be formed by placing a substrate in a treatment chamber and performing atomic layer deposition of a group IB element and/or one or more group IIIA elements from separate sources onto a substrate to form a film. A group VIA element is then incorporated into the film and annealed to form the absorber layer. The absorber layer may be greater than about 25 nm thick. The substrate may be coiled into one or more coils in such a way that adjacent turns of the coils do not touch one another. The coiled substrate may be placed in a treatment chamber where substantially an entire surface of the one or more coiled substrates may be treated by an atomic layer deposition process. One or more group IB elements and/or one or more group IIIA elements may be deposited onto the substrate in a stoichiometrically controlled ratio by atomic layer deposition using one or more self limiting reactions.

Claims

1. A method for forming an absorber layer containing elements of groups IB, IIIA and VIA, comprising the steps of:

placing a substrate in a treatment chamber;

performing atomic layer deposition of a group IB element from a first source and a first group IIIA element from a second source and/or a second group IIIA element from a third source onto the substrate to form a film;

annealing the film; and

incorporating one or more group VIA elements into the film to form the absorber layer;

wherein the absorber layer has a thickness greater than about 25 nm.

2. The method of claim 1 wherein the absorber layer is between about 25 nm and about 5000 nm thick.

3. The method of claim 1 wherein the absorber layer is between about 25 nm and about 3000 nm thick.

4. The method of claim 1 wherein the absorber layer is between about 100 nm and about 2000 nm thick.

5. The method of claim 1 wherein the absorber layer is between about 500 nm and about 2000 nm thick.

6. The method of claim 1 wherein the absorber layer is between about 1000 nm and about 2000 nm thick.

7. The method of claim 1 wherein the substrate is coiled in the treatment chamber.

8. The method of claim 7 wherein the atomic layer deposition is carried out in a stoichiometrically controlled ratio using one or more self-limiting reactions involving precursor gases of the group IB and group IIIA elements in a mix ratio that translates into a deposition ratio of the group IB and IIIA elements on the substrate, and/or by an atomic layer deposition sequence involving two or more self-limiting single species deposition reactions with precursor gases of the group IB and group IIIA elements;

and incorporating an element of group VIA into the absorber layer.

9. The method of claim 7 wherein the element of group VIA is selenium or sulfur.

10. The method of claim 7 wherein incorporating the element of group VIA into the absorber layer includes exposing the film to selenium vapor, sulfur vapor, H₂Se or H₂S one or more other selenium- or sulfur-containing compounds, or combinations or mixtures of two or more of these.

11. The method of claim 7 wherein incorporating the element of group VIA into the absorber layer involves one or more precursors gases containing one or more elements of group VIA.

12. The method of claim 11 wherein the element of group VIA is incorporated into the absorber film through a sequence of atomic layer deposition steps.

13. The method of claim 11 wherein the sequence of atomic layer deposition steps includes the use of one or more metal organic precursors containing selenium or sulfur, H₂Se or H₂S one or more other selenium- or sulfur-containing compounds, or combinations or mixtures of two or more of these.

14. The method of claim 13 wherein the one or more metal organic precursors containing selenium or sulfur include dimethyl selenide, dimethyl diselenide, or diethyl diselenide.

15. The method of claim 14 wherein incorporating the element of group VIA takes place either on a monolayer by monolayer basis, or periodically, with an exposure period substantially longer than a monolayer deposition cycle, or at the end of an absorber layer deposition sequence.

16. The method of claim 1 wherein performing atomic layer deposition includes after exposing the substrate to one or more precursors of copper, indium, and/or gallium, and/or aluminum, and/or selenium, and/or sulfur.

17. The method of claim 16 wherein the precursors include one or more Cu(I) compounds, one or more Cu(II) compounds, CuCl, copper iodide, or other copper halides, one or more copper diketonates, Cu(II)-2,2,6,6,-tetramethyl-3,5,-heptanedionate (Cu(thd)₂)), Cu (II) 2,4-pentanedionate, Cu(II) hexafluroacetylacetonate (Cu(hfac)₂), Cu(II) acetylacetonate (Cu(acac)₂), Cu(II) dimethylaminoethoxide, one or more copper ketoesters, one or more organocopper precursors containing Si or Ge, one or more other organocopper precursors and combinations or mixtures of the above, indium chloride, indium iodide, one or more other indium halides, dimethylindium chloride, trimethylindium, indium 2,4-pentanedionate (indium acetylacetonate), indium hexafluoropentanedionate, indium methoxyethoxide, indium methyk(trimethylacetyl)acetate, indium trifluoropentanedionate, one or more organoindium precursors containing Si or Ge, one or more other organoindium precursors, and combinations or mixtures of the above, diethylgallium chloride, gallium triiodide, one or more other gallium halides, Ga (III) 2,4-pentanedionate, Ga (III) ethoxide, Ga(III) 2,2,6,6,-tetramethylheptanedionate, tris(dimethylaminogallium), gallium (I) salts, gallium chloride, gallium fluoride, gallium iodide, gallium acetate, other gallium (I)-based organometallic precursors, one or more organogallium precursors containing Si or Ge, one or more other organogallium precursors and combinations or mixtures of the above, aluminum chloride, aluminum iodide, or other halides, dimethylaluminum chloride, one or more aluminum butoxides, aluminum di-s-butoxide ethylacetoacetate, aluminum diisopropoxide ethylacetoacetate, aluminum ethoxide, aluminum isopropoxide, aluminum hexafluoropentanedionate, Al(III) 2,4,-pentanedionate, AI(III) 2,2,6,6-tetramethyl3,5-heptanedionate, aluminum trifluroacetate, trisisobutylaluminum, aluminum silicate, one or more organoaluminum or organometallic precursors containing Si or Ge, one or more other organoaluminum or other organometallic precursors and combinations or mixtures of the above.

18. The method of claim 17 further comprising, after exposing the substrate to the one or more organometallic precursors of copper, indium, and/or gallium, and/or aluminum, and/or selenium, and/or sulfur, exposing the substrate to one or more reducing agents or proton-donor compounds.

19. The method of claim 18 wherein the one or more reducing agents or proton donor compounds include water (H₂O), hydrogen peroxide (H₂O₂), methanol, ethanol, isopropyl alcohol, one or more butyl alcohols, one or more other alcohols, carbon monoxide (CO), Oxygen gas (O₂), formalin, or combinations or mixtures of two or more of these.

20. The method of claim 1 wherein performing atomic layer deposition of one or more group IB elements and one or more group IIIA elements includes an atomic layer deposition sequence involving two or more self-limiting single species deposition reactions with precursor gases of the group IB and group IIIA elements and varying the sequence of exposure pulses of the precursor gases.

21. The method of claim 1 wherein performing atomic layer deposition of the group IB and group IIIA elements includes varying the concentration of the group IB and group IIIA elements in the absorber layer as a function of depth.

22. The method of claim 21 wherein performing atomic layer deposition of one or more group IB elements and one or more group IIIA elements includes an atomic layer deposition sequence involving two or more self-limiting single species deposition reactions with precursor gases of the group IB and group IIIA elements and varying a duration of exposure of the substrate to the precursor gases or varying the sequence of deposition reactions to vary the concentration of the group IB and group IIIA elements in the absorber layer as a function of depth.

23. The method of claim 21 wherein the sequence of deposition reactions produces a concentration of the one or more group IIIA elements that is relatively higher at and near a front region and a back region of the absorber layer, and relatively lower in a central region of the absorber layer, resulting in a “

saddle”

profile for the concentration of the one or more group IIIA elements as a function of depth within the absorber layer.

24. The method of claim 23 wherein the one or more group IIIA elements includes gallium (Ga) and/or Indium.

25. The method of claim 24 wherein the sequence of deposition reactions produces a Ga concentration that is relatively low at or near a back region and a central region of the absorber layer but higher at a front end, while an Indium concentration is highest in a the central region of the absorber layer and lesser at both the back and front regions.

26. The method of claim 25 wherein the one or more group IB elements have a relatively higher concentration at and near the back of the absorber layer in a relatively lesser concentration in the central and front regions of the absorber layer.

27. The method of claim 26 wherein the one or more group IB elements include copper (Cu).

28. The method of claim 27 wherein performing atomic layer deposition of one or more group IB elements and/or one or more group IIIA elements onto the substrate includes depositing gallium by atomic vapor deposition.

29. The method of claim 1 wherein performing atomic layer deposition of one or more group IB elements and one or more group IIIA elements includes the use of a precursor gas of group IB and a precursor gas of group IIIA do not react with each other in the gas phase during deposition.

30. The method of claim 1 wherein performing atomic layer deposition includes the use of one or more precursor gases from the group of halides of copper, indium and/or gallium.

31. The method of claim 1, further comprising flash-heating the absorber layer.

32. The method of claim 31 wherein flash heating the absorber layer includes raising a temperature of the absorber layer at a rate of between about 5 C.°

/sec and about 150 C.°

/sec.

33. The method of claim 32, further comprising incorporating an element of group VIA into the absorber layer occurs before and/or during the flash heating of the absorber layer.

34. The method of claim 33 wherein flash heating the absorber layer includes heating the absorber layer to an average plateau temperature of between about 200°

C. and about 600°

C.

35. The method of claim 33 wherein the flash heating lasts between about 2 minutes and about 10 minutes.

36. The method of claim 1, further comprising the step of depositing an electrode layer on the substrate by atomic layer deposition before depositing the group IB, and/or group IIIA elements.

37. The method of claim 36 wherein the electrode layer includes molybdenum.

39. The method of claim 36 further comprising the step of forming an adhesion layer between the substrate and the electrode layer.

40. The method of claim 39 wherein forming the adhesion layer includes, before depositing the electrode layer, depositing a layer of vanadium, chromium, tungsten or silicon dioxide on the substrate.

41. The method of claim 40 wherein depositing the layer of vanadium, chromium, tungsten or silicon dioxide includes atomic layer deposition using one or more precursors from the group of tungsten chloride or other halides, tungsten ethoxide, tungsten silicide, and organotungsten precursors containing Si or Ge, other organotungsten precursors and combinations or mixtures of the above, vanadium chloride, vanadium iodide or other vanadium halides, vanadium tri-n-propoxide oxide, vanadium triisopropoxide oxide, vanadium trisisobutoxide, vanadium III 2,4-pentanedionate, vanadium IV oxide bis(2,4-pentanedionate), vanadium IV oxide bis(heacafluoropentanedionate), vanadium IV oxide bis(benzoylacetonate), organovanadium precursors containing Si or Ge, other organovanadium precursors and combinations or mixtures of the above, chromium chloride, chromium iodide, or other chromium halides, chromium III benzoylacetonate, chromium (III) heaxafluropentanedionate, chromium III isopropoxide, chromium III 2,4-pentanedionate, chromium III 2,2,6,6-tetramethylheptanedionate, chromium III trifluoropentanedionate, chromium II acetate, chromium III acetate, chromium III 2-ethylheaxonate, organochromium precursors containing Si or Ge, other organochromium precursors and combinations or mixtures of the above, organometallic precursors containing Si or Ge or other organometallic precursors, other halides and combinations or mixtures of the above.

42. The method of claim 36 further comprising, depositing a window layer on the absorber layer.

43. The method of claim 42 wherein the window layer includes Cadmium Sulfide (CdS).

44. The method of claim 43 wherein depositing the window layer includes the use of one or more precursors selected from the group of cadmium chloride, cadmium iodide, or other halides, cadmium 2,4-pentanedionate, cadmium acetate, cadmium formate, dimethylcadmium, organocadmium precursors containing Si or Ge, other organocadmium precursors, organometallic precursors containing Si or Ge, other organometallic precursors and combinations or mixtures of the above.

45. The method of claim 43 wherein depositing the window layer on the absorber layer includes depositing the window layer and the absorber layer in the same chamber without removing the substrate between depositions.

46. The method of claim 45 wherein the window layer is deposited by atomic layer deposition, chemical surface deposition or liquid-based atomic layer epitaxy.

47. The method of claim 46, further comprising depositing a transparent electrode layer on the window layer by atomic layer deposition in the same chamber without removing the substrate between depositions.

48. The method of claim 47 wherein the transparent electrode layer includes Zinc Oxide (ZnO).

49. The method of claim 48 wherein depositing the transparent electrode includes the use of one or more precursors selected from the group of zinc chloride, zinc iodide, other zinc halides, dimethyl zinc, diethyl zinc, zinc N,N-dimethylaminoethoxide, zinc methoxyethoxide, zinc 2,4-pentanedionate, zinc 2,2,6,6-tetramethyl-3,5-heptanedionate, zinc acetate, zinc bis(hexamethyldisilazide), and organozinc or organometallic precursors containing Si or Ge, other organozinc or organometallic precursors and combinations or mixtures of the above.

50. An optoelectronic device having an absorber layer containing elements of groups IB, IIIA and VIB, wherein the absorber layer is deposited on a substrate by the method of claim 1.

51. The device of claim 50 wherein a concentration of the one or more group IIIA elements is relatively higher at or near a front region and a back region of the absorber layer, and relatively lower in a central region of the absorber layer, resulting in a “

saddle”

profile for the concentration of the one or more group IIIA elements as a function of depth within the absorber layer.

52. The device of claim 51 wherein the one or more group IIIA elements includes gallium (Ga) and/or aluminum (Al) and/or Indium.

53. The device of claim 50 wherein a concentration of one or more group IVA elements is slightly higher relative to the group IB element proximate the front region of the absorber layer.

54. The device of claim 50 wherein the one or more group IIIA elements includes gallium (Ga) and/or Indium, wherein the sequence of deposition reactions produces a Ga concentration is relatively low at and near a back region and a central region of the absorber layer but higher at a front end, while an Indium concentration is highest in the central region of the absorber layer and lesser at both the back and front regions.

55. The device of claim 54 wherein the one or more group IB elements include copper (Cu).

56. The device of claim 50, further comprising a transparent electrode disposed such that the absorber layer is between the transparent electrode and the substrate, wherein the transparent electrode includes a transparent conductive oxide, zinc oxide, a conductive polymer or Poly-3,4-Ethylenedioxythiophene (PEDOT).

38. The method of claim 38 wherein depositing the electrode includes the use of one or more precursors from the group of molybdenum chloride, molybdenum iodide, other halides of molybdenum, MoCl₅, molybdenum ethoxide, molybdenum VI oxide bis(2,4-pentandedionate), molybdenum hexacarbonyl, molybdenum disilicide, organomolybdenum precursors containing Si or Ge, other organomolybdenum precursors and combinations or mixtures of the above.

57. A method for forming an absorber layer containing elements of groups IB, IIIA and VIA, comprising the steps of:

performing atomic layer deposition of a group IB element from a first source and a first group IIIA element from a second source and a second group IIIA element from a third source onto a substrate to form a film;

annealing the film; and

incorporating one or more group VIA elements into the film to form the absorber layer.

58. The method of claim 57 wherein the absorber layer is between about 1 nm and about 5000 nm thick.

59. The method of claim 57 wherein the group VIA element is sulfur or selenium.

60. The method of claim 59 wherein incorporating an element of group VIA into the absorber layer includes exposing the film to selenium vapor, sulfur vapor, H₂Se or H₂S one or more other selenium- or sulfur-containing compounds, or combinations or mixtures of two or more of these.

61. The method of claim 57 wherein performing atomic layer deposition of one or more group IB elements and one or more group IIIA elements includes varying the concentration of the group IB and group IIIA elements in the absorber layer as a function of depth.

62. The method of claim 61 wherein performing atomic layer deposition of one or more group IB elements and one or more group IIIA elements includes an atomic layer deposition sequence involving two or more self-limiting single species deposition reactions with precursor gases of the group IB and group IIIA elements and varying a duration of exposure of the substrate to the precursor gases or varying the sequence of deposition reactions to vary the concentration of the group IB and group IIIA elements in the absorber layer as a function of depth.

63. The method of claim 61 wherein the sequence of deposition reactions produces a concentration of the one or more group IIIA elements that is relatively higher at and near a front region and a back region of the absorber layer, and relatively lower in a central region of the absorber layer, resulting in a “

saddle”

profile for the concentration of the one or more group IIIA elements as a function of depth within the absorber layer.