Polysilicon-to-substrate contact processing
AssigneeNCR Corporation
InventorMurray L. Trudel
Life of this patent
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Abstract
A process for forming polysilicon-to-substrate contacts. The process permits the use of a polysilicon-to-substrate contact mask and eliminates the exposure of the substrate in the contact regions to the polysilicon etch. The polysilicon contact-forming conductors are formed from a layer of polysilicon by etching partially through the layer to leave a residual layer surrounding and defining the conductors; converting the residual polysilicon to oxide; and selectively etching the oxide. The result is a damage-free substrate contact region exhibiting reduced junction leakage current.
Claims11
A process for forming at least a contact between a doped region of a silicon substrate and a layer of polysilicon formed on the substrate, comprising:
- forming a polysilicon-etch-resistant mask on the polysilicon layer and exposing a selected portion of the layer to define a conductor pattern;
- etching partially through the selected portion;
- oxidizing the residual polysilicon;
- etching the oxidized residual polysilicon to remove the oxidized residual polysilicon without etching the silicon substrate;
- and
- doping the contact region formed between the polysilicon conductor and the semiconductor substrate.
In a process for forming an integrated circuit comprising a silicon substrate having impurity regions forming active and passive components and interconnections therein, wherein contacts are formed connecting selected regions of the substrate to polysilicon conductors terminating at the selected regions, the improvement comprising:
- forming (1) a layer of polysilicon on the silicon substrate and (2) a separate monitor layer of polysilicon of the same thickness as the polysilicon layer on a non-silicon layer;
- determining the time, t.sub.c, required to etch through the polysilicon monitor layer;
- etching the polysilicon layer in the presence of a polysilicon-etch-resistant mask formed on the polysilicon defining a conductor pattern therein, and for a time sufficiently less than t.sub.c to form the polysilicon conductors bounded by a residual thickness of the polysilicon layer;
- converting the residual polysilicon to silicon oxide;
- removing the oxidized residual polysilicon by applying an etchant that selectively etches silicon oxide;
- and
- forming ohmic contact between the conductors and the underlying impurity regions of the substrate by doping through the polysilicon conductors.
An improved process for forming at least a contact between a silicon substrate and a layer of polysilicon formed on the substrate, the improvement comprising:
- forming a polysilicon-etch-resistant mask on the polysilicon layer and exposing a selected portion of the layer to define a conductor pattern;
- etching partially through the selected portion;
- oxidizing the residual polysilicon;
- and
- removing the oxidized residual polysilicon using a selective etchant that etches the oxidized residual polysilicon and not silicon.
Dependencies are inferred from the claim text.