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Incremental Structure for Electrical Determination of Mask Alignment

IP.com Disclosure Number: IPCOM000085451D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Genin, DJ: AUTHOR [+3]

Abstract

A set of structures formed by one semiconductor mask is designed in "incremental positions" with respect to a corresponding set of structures formed by a second mask. This allows some measurable parameter to vary (preferably symmetrically) across the set and such that some value of the parameter, e.g., the center of symmetry, shifts across the set with changing mask registration, thereby permitting determination of that registration.

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Incremental Structure for Electrical Determination of Mask Alignment

A set of structures formed by one semiconductor mask is designed in "incremental positions" with respect to a corresponding set of structures formed by a second mask. This allows some measurable parameter to vary (preferably symmetrically) across the set and such that some value of the parameter, e.g., the center of symmetry, shifts across the set with changing mask registration, thereby permitting determination of that registration.

For example, the speed of high-performance lateral transistors is very dependent on both CCB (collector-base capacitance) and CCS (collector- substrate capacitance). CCB is determined primarily by the vertical structure, whereas CCS, which is composed of three parts, one of which is dependent upon the relative horizontal position of the subcollector to the surrounding isolation, is not. Thus, the horizontal component (due to the intersection of the sidewalls of the two diffusions) is very sensitive to the location of the subcollector relative to the isolation. Measurements of CCS on any standard device are uncertain, due to the lack of knowledge of the precise location of the four sides of the interacting diffusions.

The structure in Fig. 1 enables electrical measurements which indicate the degree of alignment between masks on different levels of the fabrication process. The structure is particularly adapted for subcollector-to-isolation breakdown voltage measurement.

The design is such that nDelta = a - Delta or n = (a -

Delta)/Delta , where (a - Delta) is the maximum separ...