RU2523752C1 - Method of detecting hidden defects on lsi reading arrays - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method includes opening windows on a silicon wafer with non-defective reading LSI in the protective oxide layer to metal-coated areas of MOS transistor sources, depositing an indium layer, forming indium regions in form of bands insulated from each other and directed perpendicular to the drain buses which short-circuit MOS transistor sources with each other in each band, monitoring operation of a multiplexer to detect drains with hidden defects by short-circuiting the indium bands on the wafer and then forming indium microcontacts. Defects are searched for only within that band where leakage is detected.

EFFECT: shorter time for determining coordinates of a defect since there is no need to check all sources belonging to a given drain bus where the defect is detected.

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Description

The invention relates to the testing of matrix readout LSIs - MOS multiplexers.

Currently, a widely used method for the manufacture of hybrid IR MFPs by inverted mounting of crystals of a photosensitive element and a silicon MOS multiplexer using indium microcontacts. After docking, electrical defects in the MOS multiplexer are often manifested. For example, the electrical connection between the input contacts and the output buses of the MOS multiplexer (the source is the drain bus of the key MOS transistor) in the cell of the photo readout matrix. It is impossible to determine the coordinates (row and column numbers) of such a defect without special testing measures before docking.

It is known that to identify the aforementioned defect, a continuous In layer is used, shorting all the sources of MOS transistors onto a substrate [patent for invention No. 2415493. A method for detecting latent defects of a matrix or linear silicon MOS multiplexer. Akimov V.M., Vasilieva L.A., Esina Yu.V., Klimanov E.A., Liseikin V.P.]. The drain bus number is easily determined visually on a monitor or oscilloscope, or in software. The second coordinate of the hidden defect is determined after the creation of indium microcontacts.

The specified method for detecting defects has a significant drawback. So, the determination of the second coordinate of a hidden defect takes a long time, because in some cases, to search for a drain-source short-circuit, it is necessary to conduct probe monitoring of all the sources of a given drain, which significantly reduces the performance of the hidden-defect monitoring operation.

The objective of the invention is to reduce the time required to determine the coordinates of a hidden defect such as a drain-source short-circuit by forming an indium layer in the form of discrete regions - stripes perpendicular to the drain buses, in which the crystal is sequentially tested for defects in the MOS multiplexer.

The technical result is a decrease in the detection time of defects, is achieved by the fact that:

- a layer of indium is applied to the metallized sites of the sources opened in the oxide;

- using photolithographic processing, indium regions are formed in the form of strips that are oriented perpendicular to the direction of the waste tires without shorting them to the substrate;

- they control the functioning of the multiplexer and fix the presence of hidden source-drain short circuits by alternately connecting indium bands to the substrate;

- indium microcontacts are formed from indium bands by photolithography;

- an operation is carried out to determine the latent defect of the drain-source within only the band where this leak is recorded, thereby reducing the time of detection of the defect, because there is no need to check all the sources belonging to this stock bus in which a defect is detected.

The sequence of the technological chain of the proposed method is illustrated in figures 1-4, where

1 - a fragment of a silicon wafer with a suitable crystal MOS multiplexer;

2 - a layer of protective oxide;

3 - contact windows to the metallized sites of the sources of MOS transistors;

4 - stock tires;

5 - layer of indium;

6 - indium regions in the form of stripes formed perpendicular to the stock tires without shorting to the substrate;

7 - contact pads for monitoring the operation of the MOS multiplexer;

8 - indium microcontacts.

A method for detecting latent defects of MOS multiplexers is carried out in the following sequence:

- on a silicon wafer with suitable MOS multiplexers and with open windows to the sources in the protective oxide layer (Fig. 1), an indium layer is sprayed (Fig. 2);

- photolithographic processing is performed on the indium layer to obtain indium regions in the form of strips that short the sources of MOS transistors between each other in each region in the direction perpendicular to the stock buses — the rows of the matrix (Fig. 3), the number of bands is usually determined as an integer closest to the value of the square root of the number of columns of the MOS multiplexer matrix;

- the functioning of suitable MOS multiplexers is monitored with the identification of latent defects - source-drain short circuits. Electrical control consists in sequentially shorting indium strips on a substrate while simultaneously detecting the occurrence of drain-source leaks;

- photolithographic processing is carried out along the indium layer to form microcontacts (figure 4);

- operations are carried out to determine hidden sink-source defects by means of a probe search for a defect within only the band where the drain-source leak is detected.

Claims (1)

A method for detecting latent defects of matrix readout LSIs, namely, that a silicon wafer with suitable readout LSIs opens windows in the oxide protective layer to the metallized areas of the sources of MOS transistors, an indium layer is deposited, areas of shorting of the sources of MOS transistors with an indium layer are formed, and suitable crystals are controlled with the detection of latent defects, indium microcontacts are formed and defects are searched, characterized in that in order to reduce the search time for a defect in the ind region They are formed in the form of strips isolated from each other, oriented in the direction perpendicular to the drain buses, which short-circuit the sources of MOS transistors with each other, the multiplexer is monitored to detect drains with hidden defects by shorting indium strips on the substrate, followed by the formation of indium microcontacts and the search for defects within one strip of microcontacts from these indium bands.

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