US 5,665,620 A · Method for forming concurrent top oxides using reoxidized silicon in an EPROM

Abstract

A stack of oxide (16) and silicon nitride (18) is grown/deposited over a patterned polysilicon line, which typically acts as a bottom capacitor plate. A thin layer of amorphous or polycrystalline silicon (20) is deposited over the blanket silicon nitride film. The thickness of the deposited silicon layer must be optimized according to the final amount of oxide desired over the silicon nitride, which will be roughly twice the thickness of the deposited silicon film. The oxide/nitride/silicon stack is then patterned and etched, stopping either at or underneath the bottom oxide. Any subsequent cleaning in potentially oxide-etching chemistries (including HF) is done with the protective silicon deposit on top of the silicon nitride. The entire structure is then thermally oxidized, transforming the deposited silicon into silicon oxide (30). Where the structure has been cleared down to the substrate by etching, a second gate oxide is simultaneously formed.

Claims20

Dependent claims

A method for forming a semiconductor device, comprising the steps of:

providing a semiconductor substrate;
forming a silicon layer overlying the semiconductor substrate;
forming a first dielectric layer overlying the silicon layer;
forming a second dielectric layer overlying the first dielectric layer;
forming an amorphous silicon layer overlying the second dielectric layer;
etching the amorphous silicon layer to form a patterned amorphous silicon layer;
forming an exposed portion of the semiconductor substrate, wherein the exposed portion of the semiconductor substrate is formed after the patterned amorphous silicon layer been formed;
and
thermally oxidizing the patterned amorphous silicon layer to convert the patterned amorphous silicon layer into a thermal oxide layer overlying a portion of the second dielectric layer and thermally oxidizing the exposed portion of the semiconductor substrate to form a first gate dielectric layer, wherein the patterned amorphous silicon layer and the exposed portion of the semiconductor substrate are thermally oxidized at the same time.

6 more elements

Dependencies are inferred from the claim text.

Method for forming concurrent top oxides using reoxidized silicon in an EPROM

Life of this patent

Method for forming concurrent top oxides using reoxidized silicon in an EPROM

Life of this patent

Abstract

Claims20