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Electrically Measuring Misalignment Between Masking Levels on an Integrated Circuit Chip

IP.com Disclosure Number: IPCOM000085458D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 4 page(s) / 168K

Publishing Venue

IBM

Related People

Dennison, RT: AUTHOR [+2]

Abstract

The structures shown in Figs. 1-4 give the misalignment between the indicated masking steps, using electrical measurements. All structures use differential measurements between pairs of devices which are identical in all respects except orientation. The orientation is adjusted to give maximum difference in a particular parameter (breakdown voltage, resistance) as a function of misalignment. This will become clear as the structures are described.

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Electrically Measuring Misalignment Between Masking Levels on an Integrated Circuit Chip

The structures shown in Figs. 1-4 give the misalignment between the indicated masking steps, using electrical measurements. All structures use differential measurements between pairs of devices which are identical in all respects except orientation. The orientation is adjusted to give maximum difference in a particular parameter (breakdown voltage, resistance) as a function of misalignment. This will become clear as the structures are described.

The structure shown in Figs. 1A and 1B gives B-to-A misalignment indication using collector-to-isolation breakdown voltage measurements. The upper and lower diodes give vertical (Y) alignment indication, while the left and right diodes give horizontal (X) alignment indication. Note that the B-to-A spacing on one edge of each diode is very narrow (2 microns nominal). The X and Y diode pairs are orientated so that a B-to-A misalignment increases this B-to-A spacing of one diode, while decreasing it for the other. Thus, the breakdown voltage of one diode increases while the other decreases. The difference in breakdown voltage gives the magnitude and sense of misalignment.

The structure shown in Figs. 2A and 2B gives D-to-B misalignment using epi resistance measurements. The resistor is formed by the intersection of D and B masks. Any misalignment between D and B modifies the epi resistor value. This can be seen in Fig. 2B which shows a magnified cross section of a single resistor. As the alignment changes, the nearer ROI and P-isolati...