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Structure for Electrical Measurement of Overlay Between P+ Layer and Isolation Disclosure Number: IPCOM000038718D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Feb-01

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Yee, PL Martin, B Ritchie, RJ [+details]


The method electrically measures the centerline overlay of P+ diffusion to isolation in semiconductor devices. This was previously accomplished by means of manual optical measurements. An isolation defined LPNP is the measurement device used which consists of a symmetric lateral PNP with emitter 1 (Fig. 1) and collector 2 with a diffusion window a┬╣aspect ratio (1/w) made up of length 5 and width 3,4. This is specifically adjusted and is especially sensitive to variations in dimension w1 3 or w2 4. It has very small, but always equal, contacts 10. The illustration depicts the P+ diffusion 6 mask level, the isolation 7 mask level, the base 8 mask level, and the reach through 9 mask level. Nominally, w1 - w2.