Method of fabricating a micromechanical sensor

• US 5,616,514 A
• Filed: 06/06/1995
• Issued: 04/01/1997
• Est. Priority Date: 06/03/1993
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Waldvogel, Winfried, Muchow, Joerg, Offenberg, Michael, Muenzel, Horst
• Primary Examiner(s): Breneman, R. Bruce
• Assistant Examiner(s): Paladugu, Ramamohan Rao
• Application Number:
  US08/470,373
• Time in Patent Office: 665 Days
• Field of Search: 437/89, 437/90, 117/84, 257/415, 257/417, 257/418, 73/517 B
• US Class Current: 438/50
• CPC Class Codes: G01H 11/06 by electric means
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 2015/0817 for pivoting movement of the mass, e.g. in-plane pendulum
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

A micromechanical sensor includes a support of silicon substrate having an epitaxial layer of silicon applied on the silicon substrate. A part of the epitaxial layer is laid bare to form at least one micromechanical deflection part by an etching process. The bared deflection part is made of polycrystalline silicon which has grown in polycrystalline form during the epitaxial process over a silicon-oxide layer which has been removed by etching. In the support region and/or at the connection to the silicon substrate, the exposed deflection part passes into single crystal silicon. By large layer thicknesses, a large working capacity of the sensor is possible. The sensor structure provides enhanced mechanical stability, processability, and possibilities of shaping, and it can be integrated, in particular, in a bipolar process or mixed process (bipolar-CMOS, bipolar-CMOS-DMOS).

Claims

1. A method of manufacturing a micromechanical sensor comprising the steps of:

providing a support of silicon substrate;

applying a silicon-oxide layer onto the silicon substrate at a position where a micromechanical deflection part is to be formed;

producing contact window openings on the silicon substrate adjacent to the silicon-oxide layer;

depositing an epitaxial layer of silicon on the silicon-oxide layer and on the contact window openings, the epitaxial layer growing in polycrystalline form on the silicon-oxide layer and in single crystal form on the contact window openings, thereby providing a direct connection to the silicon substrate; and

removing the silicon-oxide layer during an etching process.

2. The method according to claim 1, further comprising the step of, prior to the removing step, forming lateral structural limitations of at least one deflection part by etching through the polycrystalline epitaxial layer in narrow etch pits to form trenches using an anisotropic plasma etching technique.

3. The method according to claim 1, further comprising the step of applying a poly-start layer to the silicon-oxide layer prior to the epitaxy.

4. The method according to claim 1, further comprising the step of, prior to the applying step, depositing HF-resistant dielectric layers on the silicon substrate for passivation.

5. The method according to claim 4, wherein the HF-resistant dielectric layers are made of nitride.

6. The method according to claim 1, further comprising the step of doping the silicon-oxide layer.

7. The method according to claim 1, further comprising the step of removing the silicon-oxide layer with hydrofluoric acid.

8. The method according to claim 1, further comprising the step of producing integrated electronic circuits, for evaluation of a deflection of the deflection part, on the silicon support.

9. A method of manufacturing a micromechanical structure, comprising the steps of:

providing a silicon substrate support;

applying an etching-layer onto the silicon substrate support;

depositing a layer of polysilicon on the etching layer via an epitaxial process; and

etching the etching-layer during an etching process.

10. The method according to claim 9, further comprising the step of, prior to the etching step, forming a lateral structural limitation having at least one deflection part by etching through the polysilicon layer in narrow etch pits to form trenches using an anisotropic plasma etching technique.

11. The method according to claim 10, further comprising the step of stopping the etching when the etching-layer is etched below a part of the lateral structural limitation.

12. The method according to claim 9, further comprising the step of applying a poly-start layer to the etching layer prior to depositing the layer of polysilicon.

13. The method according to claim 9, further comprising the step of, prior to the applying step, depositing HF-resistant dielectric layers on the silicon substrate support for electric passivation.

14. The method according to claim 13, wherein the HF-resistant dielectric layers are made of nitride.

15. The method according to claim 9, wherein the etching layer includes silicon dioxide, and wherein the etching step includes removing the silicon dioxide etching layer with hydrofluoric acid.

16. The method according to claim 10, further comprising the step of producing at least one integrated electronic circuit, for evaluation of a deflection of the deflection part, on the silicon substrate support.