| 摘要 |
A self-aligned, maskless method of forming a p-well is accomplished by implanting a fast p-type diffuser into a p+ buried layer, prior to epitaxial growth. This way the p-well is self-aligned with the p+ buried layer because one mask is used to define both, and the need for a separate p-well mask is eliminated. The fast diffuser, such as aluminum (Al), diffuses toward the silicon surface during the various thermal steps of the process such as epitaxial growth, field oxidation, sinker diffusion, and final drive-in, etc. The dosage of aluminum used and the parameters of the thermal drive determines the p-well doping level. Similarly, an n-well can also be formed in an n-type buried layer in a self-aligned fashion.
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