RU2787710C1 - Method for visual control of integrated microcircuit crystals - Google Patents

Abstract

FIELD: integrated circuits and semiconductor devices production.

SUBSTANCE: scope of the proposed invention is the production of integrated circuits and semiconductor devices manufactured by lithography. This effect is achieved by the fact that, unlike the known methods of visual control of integrated circuit crystals, which consist in orienting the crystals with the working surface up, examining the appearance of crystals under a metallurgical stereomicroscope in a bright and dark field according to the criteria of appearance, rejecting crystals that do not meet the criteria of external type, in the proposed method, the crystals are preliminarily oriented in such a way that the long axis of the crystal is parallel to the line connecting the centers of the eyepieces of the metallurgical stereomicroscope, and the images of the crystal area with the smallest dimensions and the highest density of elements are to the right below the operator.

EFFECT: increasing the reliability of visual control and labor productivity.

1 cl, 5 dwg

Description

The scope of the invention is the production of integrated circuits and semiconductor devices manufactured by lithography.

There are known methods of visual control of crystals of integrated circuits, which consist in orienting the crystals with the working surface up, examining the appearance of crystals under the metallurgical stereomicroscope in a bright and dark field according to the appearance criteria, rejecting crystals that do not meet the appearance criteria, and transferring suitable crystals for further processing ( see, for example, US Standard MIL-STD-883 Department of Defense Test Method Standard, Microcircuits // Santa Cruz Institute for Particle Physics (SCIPP): [website] - 2002. - URL: http://scipp.ucsc. edu/groups/fermi/electronics/mil-std883.pdf [accessed 06/15/2022], or OCT 11 073.013-2008 "Integrated microcircuits. Test methods. Visual control methods. Part 4" // EastBond. Micro welding equipment: [website ].- 2022. - URL: https://eastbond.ru/wp-content/uploads/2021/06/OST-l1-073.013-2008.-IMS.-Metody-ispytanij-vizualnyj-kontrol.-Chast-4 .pdf [accessed 06/15/2022]).

The magnification of a metallographic stereomicroscope depends on the degree of integration of the microcircuit: if the design norm (the minimum size of microcircuit elements) is 3 μm, then a magnification of 120× is sufficient for visual inspection of integrated circuit crystals, but if the design norm is 1 μm, then a magnification of 250× is necessary. The use of a metallographic stereo microscope is due to the fact that such microscopes have vertical illumination (bright field), which allows you to control the spread in the thickness of translucent and transparent layers of the microcircuit: silicon oxide, silicon nitride, polycrystalline silicon.

The method of visual control of crystals of integrated circuits is designed to control crystals and bases of semiconductor microcircuits, including crystals of the third and higher degrees of integration with metallization, protected and not protected by a dielectric film, and to control the quality of the assembly of microcircuits. Visual control of the appearance of the crystals on the plate and (or) after the operation of separating the plates into crystals is carried out under a microscope with a magnification of 80×, 100×, 200× with direct illumination of the object. Metallization defects can be checked in the dark field of a microscope.

Criteria for rejection of microcircuits with internal free volume, without protection of crystals with polymeric materials:

- cracks on the edge of the crystal, directed to the metallization or the active region of the circuit;

- chips related to metallization;

- stratification of the crystal;

- metallization with traces of electrical destruction (burnout of metallization at the p-p junction of a transistor, diode, melting and burning out of aluminum, corrosion of an aluminum film with the formation of chemical reaction products, characterized by a decrease in relief or swelling of the protective film), delamination of metallization.

All requirements of the standards regarding the quality of the oxide should apply equally to any other passivating materials used in the manufacture of microcircuits.

The dark field of a metallographic stereomicroscope makes it possible to control the quality of metallization. Stereomicroscopes allow you to visually determine the delamination of the layers of the microcircuit, for example, the metallization layer. To control the appearance of integrated circuits, operators are selected for color perception, the same vision of both eyes, attentiveness and the distance between the eyes, corresponding to the distance between the eyepieces of the microscope.

With such visual control, the number of errors, as a rule, is 3-5%, therefore, to eliminate errors, 10% of good crystals from the batch are additionally controlled by another operator (line inspector of the quality department). In addition, the IC chips in the cassette can be upside down, resulting in control delays and decreased productivity.

The closest known is the method of visual control of integrated circuit crystals, widely used in industry, which consists in orienting the crystals with the working surface up, examining the appearance of crystals under a metallurgical stereomicroscope in a bright and dark field according to the appearance criteria, rejecting crystals that do not meet the appearance criteria, (see, for example, the technological map YuF0.734.819 TK12 used in industry). The orientation of the crystals with the working surface upwards eliminates delays in control.

The disadvantage of this method of visual control of integrated circuit crystals, as in the previous case, are errors in visual control, which are explained by a decrease in the operator's attention and fatigue.

The technical result of the invention is to increase the reliability of visual control and productivity.

This technical result is achieved by the fact that, unlike the known methods of visual control of integrated circuit crystals, which consist in orienting the crystals with the working surface up, examining the appearance of crystals under the metallurgical stereomicroscope in a bright and dark field according to the criteria of appearance, rejecting crystals that do not meet the criteria of external type, in the proposed method, the crystals are preliminarily oriented in such a way that the long axis of the crystal is parallel to the line connecting the centers of the eyepieces of the metallurgical stereomicroscope, and the images of the crystal region with the smallest dimensions and the highest density of elements are located to the lower right of the operator

In the proposed method, the crystals are preliminarily oriented so that the long axis of the crystal is parallel to the line connecting the centers of the eyepieces of a metallurgical stereomicroscope. Since the zone of the best human vision when viewed through the eyepieces of a stereomicroscope has a length to width ratio of 3.5:2, the controlled crystal completely falls into the zone of the operator's best vision, which increases the reliability of visual control.

It has been established that in the process of visual control of crystals of integrated circuits, the operator's gaze moves from the upper left corner of the crystal to the lower right corner, and then to the center, while the upper right and lower left edges of the crystal are missed. Despite the fact that the operator's gaze falls primarily on the upper left corner of the crystal, this area is not considered carefully for a long time. The operator's gaze moves on to encompass the rest of the crystal. Areas in the lower right corner of the crystal or just above the lower right corner towards the middle of the crystal are given more attention by the operator, therefore, areas of the crystal with the highest density of topology elements should be placed in this area, since it is unlikely that the operator's gaze will return to the upper left corner of the crystal again . Thus, the operator's gaze moves along the crystal, starting from the upper left corner of the crystal to the lower right corner along its diagonal. When the operator's gaze passes the diagonal in the opposite direction (from right to left), then his movement slows down.

The essence of the invention is illustrated by figures.

Figures 1-5 show an example of the implementation of the invention in the process of manufacturing integrated circuits and semiconductor devices manufactured by lithography.

In the figure 1: crystals of integrated circuits of a rectangular shape, pasted on an adhesive film on the hoop;

figure 2: crystals of integrated circuits of a rectangular shape in a cassette;

figure 3: chips of integrated circuits of a square shape in a cassette;

figure 4: a crystal of the transistor KT664, manufactured using the "island base" technology, square;

in figure 5: a crystal of a powerful analog integrated circuit of a rectangular shape.

Item designation:

1 - crystals of integrated circuits;

2 - adhesive film on the hoop;

3 - line of separation of crystals;

4 - cassette;

5 - recesses in the cassette for placing crystals;

6 - emitter;

7 - base;

8 - powerful transistors;

9 - contact pads;

10 - control scheme.

Plates with crystals were made for visual control of integrated circuit crystals. Next, the electrical parameters of the crystals were checked at the probe control unit and the crystals were sorted: the location of the defective crystals on the plates was recorded in the computer memory. On a plate, depending on its diameter and the size of integrated circuit crystals, there can be up to 30-40 thousand crystals. Then the plates were glued onto the adhesive film 2, fixed on the hoop, and cut into crystals 1 along the separation line 3 (see: Fig. 1). Further, using data on the location of defective crystals, these crystals were removed by a robot from the adhesive film. Since the location of the crystals on the plate does not change when an adhesive film is used, suitable crystals glued onto the adhesive film on the hoop can be used for visual inspection directly on the hoop. Since many consumers for hybrid devices need small amounts of crystals (100-1000 pieces), then in the process of visual inspection of integrated circuit crystals, stackers of crystals from an adhesive film into special cassettes are used (see: Fig. 2-3). In this case, the linear dimensions of the recesses 5 in the cassette for placing crystals 4 are less than or equal to the diagonal of the crystals, which excludes a change in the orientation of the crystals in the recesses during their transportation.

When visually inspecting square crystals of semiconductor devices, for example, KT664 transistor crystals manufactured using the “island base” technology (see: Fig. 4), they are oriented so that the emitter of 6 transistors is at the top left in the microscope eyepiece, and the base of 7 transistors is bottom right, since it is the base that has an extensive chain of contacts. This is due to the fact that in the process of visual control of integrated circuit crystals, the operator's gaze moves from the upper left corner of the crystal (emitter) to the lower right corner (base), and then to the center, while the upper right and lower left edges of the crystal are skipped.

When visually inspecting rectangular crystals, for example, crystals of powerful analog integrated circuits (see Fig. 5), consisting of powerful transistors 8, contact pads 9 and control circuits 10, the crystals are arranged in such a way that powerful transistors with a wide metallization covering the elements of the transistor , were on the left, and control circuits, consisting of small elements and tires, were on the right. This is due to the fact that in the process of visual inspection of integrated circuit crystals, the operator's gaze moves from the upper left corner of the crystal (powerful transistors) to the lower right corner (control circuit), and then to the center, while the upper right and lower left edges of the crystal are skipped.

If the chips of integrated circuits have a topology, the elements of which differ little from each other, then when visually inspecting the chips of integrated circuits on each chip, the operator’s gaze moves in the same way and you can choose the direction of visual inspection that is most convenient for the operator, which allows you to reduce the number of unnoticed defects and increase productivity labor.

The proposed invention was tested (see: table 1). KT664 transistor crystals made using the “island base” technology were used as square crystals of semiconductor devices (see: Fig. 4). As rectangular crystals, crystals of a powerful analog integrated circuit were used (see: Fig. 5). The crystals were loaded into the appropriate cassettes (see: Fig. 2 and Fig. 3). The tests were carried out three times on different batches of crystals. To assess the reliability of the check, the crystals were rechecked by another operator (line inspector of the quality department).

The results of visual inspection of crystals show that the number of errors in visual inspection of crystals according to the invention is less than in visual inspection of crystals with random orientation, and the time spent by the operator for visual inspection of crystals according to the invention is less than in visual inspection of crystals with random orientation .

Claims (1)

A method for visual control of crystals of integrated circuits, which consists in orienting the crystals with the working surface up, examining the appearance of crystals under the metallurgical stereomicroscope in a bright and dark field according to the criteria for appearance, rejecting crystals that do not meet the criteria for appearance, characterized in that the crystals are preliminarily oriented in this way , so that the long axis of the crystal is parallel to the line connecting the centers of the eyepieces of the metallurgical stereomicroscope, and the images of the crystal region with the smallest dimensions and the highest density of elements are located to the lower right of the operator.

Images