Taiwan Semiconductor Manufacturing Comp. Ltd.

Yao-Chi Chang

Tao-Sheng Chang

Jeff Lu

Kao-Ming Lu

STI structures with step height control are produced using a relatively thin nitrogen-containing layer formed over a substrate. The nitrogen-containing layer may consist of SiN and SiON films with a combined thickness of 900 angstroms or less. Trench openings are formed to extend through the nitrogen-containing layer and into the substrate. Chemical vapor deposition is used to form a dielectric such as an oxide within the trench openings and over the top surface of the nitrogen-containing layer. A polishing operation is used to partially polish the CVD dielectric layer leaving a reduced thickness over the nitrogen-containing layer, and then a dry etch is used to remove the dielectric from over the nitrogen-containing layer and uniformly recede the top surface of the dielectric within the trench. Dishing effects are avoided. The nitrogen-containing layer is removed to produce STI structures with step heights of less than 500 angstroms.

Method for forming STI structures with controlled step height

A method for dry etching a feature to control an etching depth using endpoint detection and a sacrificial hardmask including providing a substrate for etching a feature opening into said substrate, said substrate provided with at least a first dielectric layer overlying the substrate; providing at least a second dielectric layer including a sacrificial hardmask at a predetermined thickness over the at least a first dielectric layer; photolithographically patterning and etching in a first dry etching process through a thickness of the at least a second dielectric layer and the at least a first dielectric layer to expose the substrate for dry etching the feature opening; and, dry etching in a second dry etching process the substrate and the sacrificial hardmask layer to endpoint detection of an underlying layer with respect to the sacrificial hardmask layer to thereby etch through a predetermined thickness of the substrate.

Method for STI etching using endpoint detection

A method for forming sidewall spacers with square shoulders on polysilicon gates and the structure formed by the method are disclosed. In the method, a polysilicon gate is first formed on a silicon substrate wherein the gate has a silicon nitride pad on top. A conformal silicon nitride layer is then blanket deposited on top of the structure followed by the deposition of a silicon oxide layer on top of the conformal silicon nitride layer. The silicon oxide layer is then planarized until a top of the conformal silicon nitride layer is exposed. The conformal silicon nitride layer and the silicon nitride pad are then wet etched away to expose the polysilicon gate by using the silicon oxide layer as a mask. After a photoresist layer is coated and etched-back such that only a cavity formed by the silicon oxide layer, the polysilicon gate and the conformal silicon nitride layer is filled with the photoresist, the silicon oxide layer is wet etched away by an etchant such as HF. The square-shouldered sidewall spacers are then formed by first anisotropically etching the first silicon nitride layer not masked by the photoresist layer and then by a wet etching step to remove the photoresist layer.

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Tainan, Taiwan

Yao-Chi Chang