Method of preparing a silicon nitride based substrate for semiconductor components
A process of producing a substrate is described. The process involves mixing intensively a starting mixture comprising silicon power, Si 3 N 4 , an silicon-organic polymer, and optionally an anhydrous organic pressing oil, thereby forming an intermediate mixture. The intermediate mixture is then shaped by a method selected from dry pressing, slip casting, hot pressing, extrusion casting, or tape casting, thereby forming an intermediate shaped article. The intermediate shaped article is then crosslinked and pyrolyzed in an inert atmosphere, thereby forming a crosslinked and pyrolyzed shaped article. The crosslinked and pyrolyzed shaped article is next nitrided, resulting in the formation of a nitrided shaped article, which may be optionally sintered, thereby forming the substrate. The substrates of the present invention may be used in the fabrication of semiconductor components, such as thin film solar cells.
1 - 7 . (canceled)
8 . A process for producing a substrate comprising,
(i) as crystalline phases,
silicon nitride (Si 3 N 4 )
silicon carbide (SiC), and
silicon oxynitride (Si 2 N 2 O), and
(ii) sintering additives in a total concentration of less than 20% by weight, which additives form a liquid phase during production and are present in the substrate in a form selected from the group consisting of an amorphous secondary phase, and as complex additional crystalline phases,
wherein said substrate has,
a crystalline silicon content of ≦5%, based on the sum of the crystalline phases which are present,
a shrinkage during production of <5%, and
an open porosity of <15% by volume,
said process comprising,
(a) mixing intensively a starting mixture comprising silicon power, Si 3 N 4 , an silicon-organic polymer, and optionally an anhydrous organic pressing oil, thereby forming an intermediate mixture,
(b) shaping said intermediate mixture by a method selected from the group consisting of dry pressing, slip casting, hot pressing, extrusion casting, and tape casting, thereby forming an intermediate shaped article,
(c) crosslinking and pyrolyzing said intermediate shaped article in an inert atmosphere, thereby forming a crosslinked and pyrolyzed shaped article,
(d) nitriding said crosslinked and pyrolyzed shaped article, thereby forming a nitrided shaped article, and
(e) optionally sintering said nitrided shaped article, thereby forming said substrate.
9 . The process of claim 8 wherein said intermediate mixture is in the form of a solids suspension comprising an organic solvent in which the silicon-organic polymer is dissolved, and said shaping step is performed by means of tape casting.
10 . The process of claim 9 wherein said intermediate mixture further comprises organic additives in addition to the silicon-organic polymer.
11 . The process of claim 8 wherein the nitriding step is conducted at temperatures of less than 1500° C., under a N 2 pressure of 1 bar.
12 . The process of claim 8 wherein the nitriding step is conducted at temperatures of less than 1500° C., under a N 2 pressure of from 1 to 100 bar.
13 . A process for producing semiconductor components comprising providing a substrate comprising:
(i) as crystalline phases,
silicon nitride (Si 3 N 4 ),
silicon carbide (SiC), and
silicon oxynitride (Si 2 N 2 O); and
(ii) sintering additives in a total concentration of less than 20% by weight, which additives form a liquid phase during production and are present in the substrate in a form selected from the group consisting of an amorphous secondary phase, and as complex additional crystalline phases,
wherein said substrate has,
a crystalline silicon content of ≦5%, based on the sum of the crystalline phases which are present,
a shrinkage during production of <5%, and
an open porosity of <15% by volume.
14 . A process for producing thin-film solar cells comprising providing a substrate comprising:
(i) as crystalline phases,
silicon nitride (Si 3 N 4 ),
silicon carbide (SiC), and
silicon oxynitride (Si 2 N 2 O); and
(ii) sintering additives in a total concentration of less than 20% by weight, which additives form a liquid phase during production and are present in the substrate in a form selected from the group consisting of an amorphous secondary phase, and as complex additional crystalline phases,
wherein said substrate has,
a crystalline silicon content of ≦5%, based on the sum of the crystalline phases which are present,
a shrinkage during production of <5%, and
an open porosity of <15% by volume.
15 - 19 . (canceled)