US 5,395,802 A · Process for making semiconductor acceleration sensor having anti-etching layer

Abstract

A semiconductor acceleration transducer is fabricated so that the semiconductor beam and the piezoelectric transducing element are accurately positioned relative to each other, and the impact resistance is improved. The fabrication process comprises a wafer preparing step for forming a buried layer between a substrate of a first conductivity type and an epitaxial layer of a second conductivity type, a doping step for forming a diffusion region of the first conductivity type in the epitaxial layer, and an etching step for removing unwanted portions of the substrate and the diffusion region from the bottom of the substrate to shape the beam supporting portion serving as a seismic mass. The buried layer is formed at such a position that the shape and position of the beam is determined by the buried layer. The buried layer may be a second conductivity type layer to determine the contour of the beam by stopping the etching process or may be a first conductivity type layer which is etched away to determine the contour of the beam with its diffusion contour.

Claims25

Dependent claims

A fabricating process for fabricating a semiconductor acceleration sensor including a beam portion and a mass portion supported by said beam portion, said fabricating process comprising:

a preparing step of forming first and second buried regions of a second conductivity type between a semiconductor substrate of a first conductivity type and an epitaxial layer of the second conductivity type formed on a first major surface of said semiconductor substrate;
a resistor forming step of forming a diffused resistor region of the first conductivity type in a surface of said epitaxial layer;
an anti-etching film forming step of selectively forming an anti-etching film on a second major surface of said semiconductor substrate;
and
an etching step of forming the beam portion and the mass portion by selectively etching said semiconductor substrate from said second major surface of said substrate by using said anti-etching film as a pattern;
wherein said first and second buried regions formed by said preparing step are separated by said epitaxial layer, and said etching step is performed until said epitaxial layer is exposed between said first and second buried regions, thereby reducing effects caused by alignment errors.

3 more elements

A fabricating process for fabricating a semiconductor acceleration sensor including a beam portion and a mass portion supported by said beam portion, said fabricating process comprising:

a preparing step of forming a buried layer of a first conductivity type between a semiconductor substrate of the first conductivity type and an epitaxial layer of a second conductivity type on a first major surface of said semiconductor substrate;
a resistor forming step of forming a diffused resistor region of the first conductivity type by doping, said diffused resistor region extending into said epitaxial layer from a surface of said epitaxial layer;
an anti-etching film forming step of selectively forming an anti-etching film on a second major surface of said semiconductor substrate;
and
an etching step of forming the beam portion and the mass portion by selectively etching away said semiconductor substrate and said buried layer from said second major surface of said substrate by using said anti-etching film as a pattern;
wherein, in said etching step, said buried layer is etched away until said epitaxial layer is bared, thereby reducing effects caused by alignment errors.

3 more elements

Dependencies are inferred from the claim text.

Process for making semiconductor acceleration sensor having anti-etching layer

Life of this patent

Process for making semiconductor acceleration sensor having anti-etching layer

Life of this patent

Abstract

Claims25