Method for manufacturing a silicon sensor and a silicon sensor

• US 20040074301A1
• Filed: 11/24/2003
• Published: 04/22/2004
• Est. Priority Date: 03/21/2001
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: VTI Technologies Oy (Murata Manufacturing Co Limited)
• Inventors: Kuisma, Heikki, Lahdenpera, Juha
• Granted Patent: US 6,998,059 B2
• Time in Patent Office: Days
• US Class Current: 73/514.38
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81C 1/00182 Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: B81C 2201/0133 Wet etching
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 2015/0817 for pivoting movement of the mass, e.g. in-plane pendulum

Abstract

The invention relates to a method for manufacturing a silicon sensor structure and a silicon sensor. According to the method, into a single-crystal silicon wafer (10) is formed by etched opening at least one spring element configuration (7) and at least one seismic mass (8) connected to said spring element configuration (7). According to the invention, the openings and trenches (8) extending through the depth of the silicon wafer are fabricated by dry etch methods, and the etch process used for controlling the spring constant of the spring element configuration (7) is based on wet etch methods.

Claims

1. A method for manufacturing a silicon sensor structure, the method comprising the steps of forming by etched openings into a single crystal silicon wafer (10) at least one spring element configuration (7) and at least one seismic mass (8) connected to said spring element configuration (7),

characterized in that

the openings and trenches (8) extending through the depth of the silicon wafer are fabricated by dry etch methods, and

the etch process used for controlling the spring constant of the spring element configuration (7) is based on wet etch methods.

2. The method of claim 1, characterized in that the angle α

between the longitudinal axis of the spring element (7) and the equivalent 110 crystal orientation in the plane of the silicon wafer selected to be different from zero, advantageously greater than 15°

, and typically being 25°

to 65°

, advantageously about 45°

.

3. The method of claim 1 or 2, characterized in that the ratio L1/L between the length L of the spring element (7) to the longitudinal dimension L1 thereof in the direction of the {111} crystal plane is selected to be smaller than 0.45.

4. The method of any one of foregoing claims, characterized in that the wet etch step is carried out using alkine etch processes that are anisotropic in regard to different crystal orientations.

5. The method of any one of foregoing claims, characterized in that the etching of the structures in orientations other than those perpendicular to the wafer plane is limited by making into the substrate such vertical trenches (8) that are aligned substantially in different orientations than the 110 orientation of the silicon wafer and are protected at their sidewalls against etch attack.

6. The method of claim 3, characterized in that both the dry etch and the wet etch processes are anisotropic.

7. A silicon sensor structure manufactured from a single crystal silicon wafer (10) so as to comprise

a frame (10),

at least one elongated spring element (7) connected at its one end to the frame (10), and

at least one seismic mass (6) connected to the other end of the spring element (7),

characterized in that

an intersection line (11) of inclined {111} crystal planes is formed at the ends of the spring element (7) or at least in a close vicinity thereof.

8. The sensor structure of claim 7, characterized in that the sensor structure is made from a single-crystal (100) silicon wafer, whereby all inclined crystal planes are {111} crystal planes.

9. The sensor structure of claim 7 or 8, characterized in that the intersection line (11) of the {111} crystal planes is oriented at least substantially parallel with the longitudinal axis of the spring element (7).