JPH07162017A - Manufacture of semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To remove an etching unevenness, which is generated at the time of an electrochemical etching using a four-electrode method. CONSTITUTION:Trenches 7 and 8 are respectively formed in a superposed region 6 and a fixed part 5 and after that, diffused regions 1 and 9 are respectively formed in the trenches 7 and 8 and wirings 3 are provided to make the region 6 have continutity with the part 5 through the surface of a wafer, whereby a potential in the region 6 can be independently set. As a result, even if the region 6 is insulated from its periphery, the region 6 can be etched while a prescribed bias voltage is applied to the part 5 during an electrochemical etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing method for detecting acceleration.

[0002]

2. Description of the Related Art In an acceleration sensor using silicon anisotropic etching technology, the accuracy of the thickness of a beam portion that supports a weight that is displaced depending on the magnitude of acceleration determines its sensitivity, and variations in the thickness of the beam portion cause sensor characteristics. It is known that there will be variations in. Therefore, as a means of determining the beam thickness, "International Conference Transducer 87 (TRANSDUSERS'87)" of 1987.
B. Kloeck et al., Pp. 116-119, entitled "Quad Electrochemical Etching Method for Silicon Thin Film Formation (A Novel).
Four Electrode Electroche
medical Etch-stop Methode f
or Silicon Membrane Forma
The anodic oxidation etching (electrochemical etching) method referred to as the quadrupole method is known. This method uses a substrate in which n-type silicon is epitaxially grown on a p-type substrate and is shown in FIG. In this manner, the fixed portion 5 made of p-type silicon and the n-type epitaxial layer 2 are etched in an etching solution while applying a reverse bias.By using this method, anisotropic etching is performed from the p-type silicon side. Since the etching can be automatically stopped at the pn junction surface, the beam thickness can be determined with a small variation by predetermining the thickness of the epitaxial layer.

[0003]

However, in the conventional etching method, during the anisotropic etching of silicon,
Due to the progress of the etching around the weight region 6, the weight region 6 is electrically cut off, and a state in which a predetermined reverse bias voltage is not applied occurs. Due to this, there is a problem that uneven etching occurs and the beam thickness becomes non-uniform.

An object of the present invention is to provide a method of manufacturing a semiconductor acceleration sensor which is always free from uneven etching.

[0005]

According to the present invention, in a semiconductor acceleration sensor having a laminated structure having two or more types of conductivity, a beam is applied while applying a voltage to a weight region composed of a second conductive region. It is characterized in that the conductive region is provided in the weight region through the first conductive region for the applied voltage. At least one of a trench structure and a diffusion region is provided as the conduction region.

With the above structure in which the weight region is electrically connected to the surface, the potential of the weight region can be set independently, so that a predetermined bias voltage can be applied to the weight portion during electrochemical etching even if the weight region is insulated from the surroundings. .

[0007]

EXAMPLE 1 FIG. 1 shows a sectional view of a semiconductor acceleration sensor of the present invention. According to the present invention, trenches 7 and 8 are formed on the weight region 6 and the fixed portion 5 by a silicon etching technique, and then the trenches 7 and 8 are diffused to form the diffusion region 1.
And the diffusion region 9 is formed so as to contact the weight region 6 and the fixed portion 5, respectively. The depths of the trenches 7 and 8 are not necessarily required to penetrate the epi layer 2 as long as the diffusion region 1 can contact the weight region 6 and the fixing portion 5.

By forming such a structure, it becomes possible to establish electrical continuity between the weight region 6 and the fixed portion 5 from the wafer surface, so that the wiring 3 extends from the fixed portion 5 to the weight region 6.
By providing the weight region 6, even if the weight region 6 is isolated from the fixed portion 5 by silicon anisotropic etching, the weight region 6 and the fixed portion 5 can be continuously electrically connected. As a result,
By applying a predetermined bias voltage to the fixed portion 5, it is possible to remove the unevenness of etching.

(Embodiment 2) FIG. 2 shows a second embodiment. In order to establish electrical continuity from the surface to the weight region, the diffusion region 1 is formed to a depth at which it contacts the weight region.
In FIG. 3 as well, the trench 7 is similarly formed to a depth reaching the weight region 6 in order to establish electrical conduction from the surface to the weight region 6.

FIG. 3 shows another embodiment of the present invention, in which a trench 7 or a diffusion region 1 is formed as a structure for electrically connecting the weight region 6 from the surface.

[0011]

As in the present invention, by biasing the weight region 6 during the electrochemical etching, the uneven etching can be removed and the beams can be formed uniformly.
Further, by applying a predetermined voltage to the weight region, the weight region can be formed more accurately.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor acceleration sensor of a first invention.

FIG. 2 is a sectional view of a semiconductor acceleration sensor of a second invention.

FIG. 3 is a sectional view of a semiconductor acceleration sensor of a third invention.

FIG. 4 is a sectional view of a conventional semiconductor acceleration sensor.

[Explanation of symbols]

 1 Diffusion Region 2 Epitaxial Layer 3 Wiring 4 Beam (Epitaxial Layer) 5 Fixed Part (Wafer Substrate) 6 Weight (Wafer Substrate) 7 Trench 8 Trench 9 Diffusion Region 10 Insulating Film

Claims (3)

[Claims] 1. A semiconductor acceleration sensor having a laminated structure having two or more types of conductivity, wherein a beam is formed while applying a voltage to a weight region composed of a second conductive region. Acceleration sensor manufacturing method. 2. The method for manufacturing a semiconductor acceleration sensor according to claim 1, further comprising: providing a conductive region for applying a voltage to the weight region via the first conductive region. 3. The method for manufacturing a semiconductor acceleration sensor according to claim 2, wherein at least one of a trench structure and a diffusion region is provided to establish conduction in the weight region.