Method for anodizing silicon substrates for surface type acceleration sensors
AssigneeKabushiki Kaisha Tokai Rika Denki Seisakusho
InventorsHitoshi Iwata, Makoto Murate
Life of this patent
Estimating the term…
Abstract
An epitaxial growth layer, an oxide film, and a passivation film are formed on a silicon substrate. Except for an opening formed on a part of the passivation film, the upper surface of the passivation film is covered with a metal protective film made of tungsten (W). With the silicon substrate immersed in a high-concentration hydrofluoric aqueous solution, anodization is performed with the silicon substrate as an anode and the metal protective film as a counter electrode.
Claims14
A method for manufacturing a surface-type acceleration sensor comprising the steps of:
- forming a first p-type silicon layer on a predetermined area of a surface of a p-type single crystal silicon substrate by adding impurities;
- embedding the first p-type silicon layer below an epitaxial growth layer by forming the epitaxial growth layer, which is made of n-type single crystal silicon, on an upper surface of the first p-type single crystal silicon substrate;
- forming a second p-type silicon layer for forming an opening in the epitaxial growth layer by adding impurities;
- forming a deformation gage, which is made of p-type silicon, on an upper surface of the epitaxial growth layer;
- forming a wiring pattern connected to the deformation gage;
- forming a passivation film over the wiring pattern when the second p-type silicon layer is exposed;
- forming an HF-resistant metal protective film on a surface of the passivation film and the epitaxial growth layer, but not on the second p-type silicon layer;
- forming an HF-resistant metal silicide film on the interface between the metal protective film and the epitaxial growth layer when the metal protective film is formed;
- performing anodization to convert the first and second p-type silicon layers into a porous silicon layer;
- and
- removing the porous silicon layer by alkali etching to form a beam that is made of the epitaxial growth layer.
A method for anodizing a silicon substrate having a first portion to be made porous and a second portion that excludes the first portion, the method comprising the steps of:
- forming an HF-resistant metal protective film on a surface of the second portion of the silicon substrate;
- forming an HF-resistant metal silicide film on the interface between the metal protective film and the silicon substrate when the metal protective film is formed;
- immersing the substrate in a solution containing HF;
- and
- applying a voltage to the silicon substrate when the silicon substrate is immersed in the solution containing HF, and when a positive terminal of a DC power source is connected to the silicon substrate.
Dependencies are inferred from the claim text.