| 摘要 |
The present invention provides a fabrication process for fabricating a MOS substrate structure having a predetermined thickness of thermally grown oxide on top of a silicon nitride film. A poly-crystalline or amorphous silicon film is deposited onto the nitride film at a desirable fabrication stage requiring a robust oxide layer. The thickness of the silicon film is determined by the desired thickness of the thermal oxide according to pre-determined oxidation rate characteristics between the silicon film material and the oxidant in dry oxygen, or steam form. Typically, the thickness of the oxide grown is approximately 1.75 to 2.00 times the thickness of the silicon film. Care must be taken during subsequent processing to prevent excessive oxide removal. The present invention allows the use of cleaning solutions that are tailored to reduce etching of silicon, which is an easier task than reduce oxide etching. The oxidized silicon film is more robust against etching during HF and SCI or APM cleaning. There is less oxide film loss during cleaning, resulting in more reproducible results. The oxidized silicon film may be used to reduce loss of isolation or field oxide during subsequent processes by exercising the reduced etching rate of hydrofluoric acid (HF) or SCI mixtures.
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