Mos Electronics Corporation

Nan-Hsiung Tsai

Yun-Sheng Hwang

A resistor located above the semiconductive substrate of an integrated circuit chip can be made smaller than prior art resistors because no area is allocated for resistor contacts. During manufacture, a resistive strip having the width of the intended resistor is formed. A photoresist mask protects the top and sides of the resistive strip where the resistor is located, and etching exposes the ends but not the top and sides of the resistor. Contact to the resistor occurs at the upwardly extending (usually near vertical) end surfaces of the resistor.

Resistor with side wall contact

A process of forming a self-aligned oxide layer covering conductive structures such as MOS transistor gates above a semiconductive substrate while portions of the substrate such as source/drain regions are exposed involves forming side wall spacers against the gates, applying refractory metal to the exposed surface, heating the refractory metal so that it forms refractory silicide at regions where the refractory metal contacts the substrate, removing the unreacted refractory metal, and oxidizing the exposed refractory silicide with a low temperature wet oxidation which causes faster oxide growth above the highly doped gates than above the lightly doped source/drain regions. Subsequent etching of the differentially grown oxide layer exposes the source/drain regions while leaving protected the gate regions. Since no mask was needed for forming and patterning the gate-covering oxide, no misalignment can occur and thus no space need be allowed in the circuit layout for misalignment. In one embodiment, spacing between adjacent MOS transistor gates is reduced from 2.4 microns to 1.2 microns.

Process of making self-aligned contact using differential oxidation

A method for forming substrate contacts in an integrated circuit structure uses a layer of conductive material, preferably polycrystalline silicon, applied to the surface of the semiconductor structure to make electrical contact with exposed portions of the substrate. The polycrystalline silicon layer is then coated with a nitride layer. A via mask which is opaque over the region where a contact will be formed produces a photoresist stud smaller that the original via mask. The photoresist stud is used to pattern the nitride to remain only over the contact region. Following this, the polycrystalline silicon is oxidized except at the nitride mask, forming a bird's beak beneath edges of the nitride. The resulting contact is smaller than the photolithographic limit of the via mask and thus allows for smaller space allocated for contact regions and smaller total structure.

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Cupertino, CA, United States of America

Nan-Hsiung Tsai