Method of producing a semiconductor device of SiC

A method for producing a micro structure containing a free hanging structure, such as a diaphragm, cantilever or beam, on a SiC-substrate comprising layers of SiC, characterised in

• that the SiC-substrate is formed with a first layer (2;
• 9) of p-type SiC, a second layer of p-type SiC and a third layer (4;
• 13) of n-type SiC, the second layer (3;
• 8) being located between the first and the third layer (2, 4;
• 9, 13), and the second layer (3;
• 8) having a doping concentration which is higher than the doping concentration of the first layer (2;
• 9),
• that a passage (5;
• 12, 14) is formed in the substrate for allowing a selective etching solution to come into contact with the second layer (3;
• 8),
• that the substrate is placed in a selective etching solution containing fluorine ions and having an oxidising effect on SiC, and
• that a positive potential is applied to the second layer (3;
• 8) via the first layer (2;
• 9) so as to etch said second layer (3;
• 8) in the etching solution for the formation of an interspace (7;
• 16) between the first layer (2;
• 9) and the third layer (4;
• 13), whereby said free hanging structure (17) is formed by said third layer (4;
• 13).

A method for producing a piezo-resistive pressure sensor, characterized in that the method comprises the following steps:

• forming a first layer (8) of p-type SiC on a substrate (9) of p-type SiC by epitaxial growth or ion implantation, said layer (8) being formed with a doping concentration which is higher than the doping concentration of the substrate (9),
• forming a second layer (13) of n-type SiC on the first layer (8) by epitaxial growth or ion implantation,
• forming a passage (12, 14) in the second layer (13) for allowing a selective etching solution to come into contact with the first layer (8),
• placing the so formed structure (15) in a selective etching solution containing fluorine ions and having an oxidising effect on SiC,
• applying a positive potential to the first layer (8) via the substrate so as to etch said first layer in the etching solution for the formation of an interspace (16) between the substrate (9) and the second layer (13), whereby a diaphragm (17) is formed by said second layer (13),
• forming a third layer (18) of SiC on the diaphragm (17) and the exposed parts of the substrate (9) by epitaxial growth, and
• etching the third layer (18) to form a piezo resistor (19) of the third layer material on the diaphragm (17) and to form a sealing (20) of the third layer material between the diaphragm (17) and the substrate (9) so as to seal the cavity (16) formed between the diaphragm (17) and the substrate (9).

A method for producing a MEMS device of SiC having a free hanging structure, such as a diaphragm, cantilever or beam, characterised in that the method comprises the following steps:

• forming a first layer (8) of p-type SiC on a substrate (9) of p-type SiC by epitaxial growth or ion implantation, said layer (8) being formed with a doping concentration which is higher than the doping concentration of the substrate (9),
• forming a second layer (13) of n-type SiC on the first layer (8) by epitaxial growth or ion implantation,
• forming at least one passage (12, 14) in the second layer (13) for allowing a selective etching solution to come into contact with the first layer (8),
• placing the so formed sample (15) in a selective etching solution containing fluorine ions and having an oxidising effect on SiC, and
• applying a positive potential to the first layer (8) via the substrate (9) so as to etch said first layer (8) in the etching solution for the formation of an interspace (16) between the substrate (9) and the second layer (13), whereby said free hanging structure (17) is formed by said second layer (13).