MEMS microphone and manufacturing method for making same

The present invention provides a manufacturing method for MEMS structure. The method includes steps of: S1: providing a substrate, including a structural layer and a silicon-based layer overlapped with the structural layer; S2: carrying out a main etching process for etching out a cavity hole from an end of the silicon-based layer, which is far away from the structural layer, in a direction toward the structural layer until the cavity hole contacts the structural layer; and S3: carrying out an over-etching process for deepening the cavity hole and control an included angle α between a side wall of the cavity hole and the structural layer to be larger than 10° but smaller than 90°. The invention also provides a MEMS structural and a MEMS microphone manufactured by the method.

FIELD OF THE PRESENT DISCLOSURE

The invention relates to the technical field of the manufacturing of silicon microphones, particularly to a manufacturing method of MEMS structure, MEMS structure, and a silicon microphone.

DESCRIPTION OF RELATED ART

Bosch process is a deep silicon etching process which repeats isotropic etching cycles and then deposits a protection film. Generally, SF6 plasma etching silicon and a C4F8 plasma deposition protection layer are used. The Bosch process and the deposition protection layer are used. The wall of etched silicon generates a fan shape. For industry, the silicon etching rate is slow; thus, the volume is limited when deeply etch Si. To get a higher yield, the method is designed to try best to etch as fast as possible but doesn't concern the fan shape and size, however, the fan shape, particularly, the fan shape which contacts a structure layer influences the result of the test of a mechanical stability structure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring toFIG. 1, an embodiment of the invention provides a manufacturing method for a MEMS structure, which comprises of the following steps:

S1. Provide a substrate, including a structural layer1and a silicon-based layer2overlapped with the structural layer1(as shown inFIG. 2).

Wherein, the structural layer1can be made from silicon, nitride, polysilicon and other materials.

S2. Carry out a main etching process. Etch out a cavity hole3from the end of the silicon-based layer2, which is far away from the structural layer1, in the direction to the structural layer1until the cavity hole3contacts the structural layer1, as shown inFIG. 3.

Wherein, once the deepest part A of the cavity hole3contacts the structural layer1, the main etching process ends.

S3. Carry out an over-etching process. Deepen the cavity hole3and control an included angle α between a side wall of the cavity hole3and the structural layer1to be larger than 10° but smaller than 90°, as shown inFIG. 4.

In the invention, the cavity hole3is deeper than 100 μm.

The included angle α between the cavity hole3and the structural layer1can be controlled by controlling the etching rate, etc, in the over-etching process.

Both of S2and S3use Bosch process for etching. Of course, the Bosch process is not necessary. However, the Bosch process is preferred in the preferred embodiments of the invention so as to both get high verticality of the side wall and ensure the etching rate.

It should be noted that in S2, the main etching process includes the circulation operation of etching and deposition of a protection layer. In S3, the over-etching process also includes the circulation operation of etching and deposition of the protection layer.

As shown inFIG. 5, the invention also provides a MEMS structure100which comprises of a structural layer1and a silicon-based layer2, wherein, the silicon-based layer2is provided with the cavity hole3which penetrates the silicon-based layer2. The cavity hole3is deeper than 100 μm. The included angle α between the cavity hole3and the structural layer1is larger than 10° but smaller than 90°. It has to explain that the cavity hole is a closed hole with a closed side wall, as shown inFIG. 5(a). The cavity hole3can also be a non-closed hole of which the side wall is not closed, as shown inFIG. 5(b). Wherein,FIG. 5(a)shows the specific structure of the MEMS structure100when the included angle is close to 10°, andFIG. 5(b)shows the specific structure of the MEMS structure100when the included angle is close to 90°. When the included angle is between 10° to 90°, the MEMS structure100has high reliability.

It has to explain that the included angle α above is the included angle between the plane where the structural layer1is and the tangent line of the side wall of the intersection of the structural layer1and the cavity hole3.

Please refer toFIG. 6; the invention also provides a silicon microphone200which uses the MEMS structure100. When the MEMS structure100is applied in the silicon microphone, the structural layer1can be used as a back plate or a diaphragm. In the specific embodiments provided by the invention, the structural layer1is used as a first back plate, the silicon microphone200also comprises of an insulation layer20arranged on the structural layer1, a second back plate21arranged on the insulation layer20and a diaphragm22included between the second back plate21and the insulation layer20.

Compared with the prior art, the manufacturing method of MEMS structure, the MEMS structure and the silicon microphone which are provided by the invention have the following advantage: the structural reliability of the microphone is effectively improved by controlling the included angle between the side wall of the cavity hole and the structural layer to be larger than 10° but smaller than 90°.

One of ordinary skill in the art understands that the above embodiments are specific embodiments for the realization of the present invention, and in practical applications, various changes can be made to them in form and detail without deviating from the spirit and scope of the invention.