Method of producing a buried boss diaphragm structure in silicon
AssigneeLucas NovaSensor
InventorsLee A. Christel, Theodore J. Vermeulen
Life of this patent
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Abstract
A method of micromachining silicon to form relatively thick boss areas and relatively thin flexure areas. The method includes the provision of a deep diffusion of n-type dopant atoms in the vicinity of the desired thick boss structures on a p-type silicon substrate. A layer having a thickness equal to the desired thickness of a flexure area is epitaxially grown of n-type doped silicon over the previously doped p-type substrate. Finally, the p-type doped silicon is etched away by a suitable etchant leaving relatively thick boss areas joined by relatively thin flexure areas.
Claims10
A process for forming silicon material having a boss section and a flexure section, said boss section thicker than said flexure section, said process comprising the steps of:
- providing a substrate of one type doped silicon material;
- diffusing another type dopant material into said substrate so as to provide another type doped silicon material at a depth (x-y) from a surface of said one type doped silicon material, said diffusing located only in the regions of the boss section, where x is the boss section thickness and y is the flexure section thickness;
- epitaxially growing a layer of said another type doped silicon on said substrate to said flexure section thickness y over the surface of said substrate;
- and
- etching away one type doped silicon material with a one type doped silicon etchant leaving said boss section having a thickness x and said flexure section having a thickness y.
A method of chemical machining of silicon material to provide a boss section joined by a flexure section from a substrate of p-type doped silicon material, said boss section thicker than said flexure section, said method comprising the steps of:
- diffusing n-type dopant material into said substrate so as to provide an n-type material at a depth (x-y) from a surface of the p-type material, said diffusing being provided only in the regions of the boss section, where x is the boss section thickness and y is the flexure section thickness;
- epitaxially growing a layer of n-type doped silicon on said substrate to said flexure section thickness y;
- and
- etching away p-type doped silicon material with a p-type doped silicon etchant leaving said boss section having a thickness x and said flexure section having a thickness y.
A method of chemical machining of silicon material with a boss section joined by a flexure section from a substrate of boron doped silicon material having a resistivity of from 4 to 6 ohms-cm, said boss section thicker than said flexure section, said method comprising the steps of:
- (1) providing a mask of silicon dioxide on said substrate over said flexure section;
- (2) diffusing phosphorus dopant material into said substrate so as to provide a phosphorus doped silicon material at a depth (x-y) from a surface of the substrate, said diffusing being provided only in the regions of the boss section, where x is the boss section thickness and y is the flexure section thickness, said diffusing step including the steps of:
- implantation of phosphorus dopant ions in said substrate;
- and
- annealing said substrate so as to eliminate crystal lattice defects and to at least partially diffuse said phosphorus dopant ions;
- (3) epitaxially growing a layer of phosphorus doped silicon on said substrate to said flexure section thickness y over the surface of the boron doped silicon substrate and the areas of diffusion phosphorus doped silicon;
- and
- (4) etching away boron doped silicon material with a potassium hydroxide etchant leaving said boss section having a thickness x and said flexure section having a thickness y.
Dependencies are inferred from the claim text.