RU1821315C - Method of device for retouching defect - Google Patents

Abstract

Usage: in microelectronics in the manufacture of photomasks of integrated circuits, thin-film elements of printed circuit boards, etc. SUMMARY OF THE INVENTION: the laser beam is pre-aligned with the image of the defect in the plane of the screen, then in the processing plane the laser beam, by virtue of the reversibility law, appears to be aligned with the defect. For this purpose, a selective mirror transparent to the visible range is introduced into the device. This mirror is mounted in the center of the screen. The laser beam reflected from it is directed along the optical axis of the visual channel. 2 s.p. f-ly. 1 ill.

Description

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The invention relates to microelectronics and can be used in the manufacture of photomasks of integrated circuits (ICs), thin-film elements, printed circuit boards, and the like.

The aim of the invention is to increase productivity while maintaining accuracy.

The goal is achieved in that in the method of retouching a defect, including forming a laser beam, pointing it at the defect, subsequent processing of the defect, before pointing the laser beam at the defect, a defect image is formed in the center of the screen and the laser beam is combined with the obtained image.

A significant difference of the proposed method is that the laser beam is pre-aligned with the image of the defect in the plane of the screen, then the laser beam in the processing plane, by virtue of the law of reversibility, is combined with the defect. This eliminates the need to form a diaphragm illumination, simplifies the design of the system, eliminates the need for additional quotation operations, provides high reproducibility and repeatability of the results, which increases the productivity of the process while maintaining high friction characteristics.

This goal is achieved in that in a device for retouching a defect containing an energy channel including a laser, a telescopic system, a diaphragm and a visual defect observation channel including a screen, and a lens that is common to the visual and energy channels, the optical axis of the energy channel passes

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through the center of the screen, in which a selective mirror is mounted, transparent for the visible range and reflecting laser radiation, the size of the selective mirror is determined from the ratio

Rz.

D3-D G

T5

(1)

de D - aperture size; an increase in the optical system of the visual channel; -F2 focal length of the output lens of the telescopic system; Рz is the focal length of the lens.

In the prototype, the visual and energetic channels are partially combined. The guidance channel combined with the energy channel includes illumination of the diaphragm, which is both the diaphragm of the guidance channel and the diaphragm of the energy channel.

In the proposed device, the combination of the optical axes of the energy and visual channels is implemented in the plane of the screen. A selective mirror transparent to the visible range is mounted in the center of the screen, the laser beam reflected from it is directed along the optical axis of the visual channel. The size of the selective mirror should be no less than the size of the laser beam passing through the center of the screen so as not to exert a vinyl effect.

The known relation for the Kepler telescopic system has the form

Do F 6rn

(2)

where D0Di are the diameters of the entrance and exit pupils, respectively:

Fo6i and FOK are the focal lengths of the lens and eyepiece.

If you set an aperture of size D in the rear focal plane of the lens of the telescopic system and follow the progress of the optical beam to the lens O (common for the visual and energy channels), then the spot size d in the focal plane of the lens O will be related to the size of the aperture according to formula (2) the ratio

d-d

F3 tv

(3)

where -F2 is the focal distance of the output lens of the telescopic system;

Pz1 is the focal length of the lens O.

If the increase in the visual channel Г has already been set (for example, in the case of reconstruction based on the finished photo projector) and the optical axis of the energy channel passes through the center of the screen, then the size of the laser beam in the plane of the screen is determined by the relation

Oe (4) From here we obtain the expression for the size of the laser beam in the plane of the screen

 {| (5)

The operability of relation (5) is confirmed experimentally. The error is not more than 10%.

Evaluation of the size of the laser beam in the plane of the screen by the formula (5) allows us to limit the geometric dimensions of the selective mirror mounted in the center

Screen Re Da D3 -D G

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Installing a selective mirror of the required size in the center of the screen allows implementing the defect retouching method proposed above, which ensures high reproducibility of results and eliminates additional quotation operations,

retaining high accuracy.

By placing the image of the defect in the center of the screen, thereby combining the generated laser beam with the defect in the processing plane. The guidance channel is completely excluded.

In devices with partially aligned optical channels, there is a rigid connection between the overall dimensions of the energy and visual channels. If the visual channel has already been modeled, then integrating the energy channel (for example, into a finished photo projector) is extremely difficult, and sometimes simply impossible. The proposed solution allows for dimensional calculations of the energy channel not to depend on the distance between the screen and the entrance pupil of the lens of the visual channel.

Implementation of the proposed defect retouching method allows to ensure high reproducibility of results, eliminate a number of quotation operations, expand the design capabilities of the device, use production equipment more efficiently, which increases the productivity of the process while maintaining high accuracy characteristics.

The drawing shows an optical diagram of the device.

The device contains an energy channel, consisting of a laser 1. telescopic system 2, having two lenses with focal lengths Fi1 and -Fa, aperture 3, mounted in the rear focal plane of the first lens of the telescopic system, directing mirrors A, 6, mirror 4 directing there is a laser beam in the center of the screen 10, a selective mirror 5, which reflects laser radiation and is transparent to light, the size of which is consistent with that calculated according to formula (1), of a lens 7 focusing the laser beam in the plane of placement of object 8, a visual channel defect observation, consisting of a illuminator 9 (91 in transmitted light 911 in reflected), a coordinate table for placing an object 8, a lens 7 in common with the energy channel, type 6 guiding mirrors and a screen 10 in the center of which a selective mirror is mounted 5.

The device operates as follows.

The lens (for example, a photomask) is placed on the coordinate table 8. Illuminator (9) in transmitted (91) l because it illuminates the object in reflected (911) light. The image of the defect is projected by the lens 7 and the guide mirror 6 onto the screen 10. The defect detected on the object by moving the coordinate table is placed in the center of the field of view of the lens so that the image of the defect coincides with the crosshair in the center of the screen 10. Turn on the laser (1). The formation of a laser beam in a spot of a certain size in the processing plane is carried out using a telescopic system 2, aperture 3, guiding mirrors 4, 5. 6, lens 7. A pre-irradiated laser beam with a mirror 4 is directed to a selective mirror 5, mounted in the center screen, thereby combining the laser beam with the image of the defect. The laser beam reflected by the selective mirror 5 is mirrored by the mirror 6 into the input window of the lens 7. The lens 7 focuses the laser beam on the defect. The defect evaporates. The laser is turned off.

As an example of a specific implementation of or (the above-mentioned device, we consider a laser technological installation for retouching FS microelectronics, implemented on the basis of an EM577 photo projector with an increase in Г 150х. Nitrogen laser LGI-503 was used as a power source. A telescopic system with focal lengths was installed at the laser output window the distance of the first lens FI 50 mm and the second lens -F2 ™ 160 mm, from the rear focal plane of the first lens, a replaceable diaphragm of size D 100 μm; 20 mkm is strengthened. Optical axis of the energy channel ala via guide

The mirror mounted behind the telescopic system was directed toward the center of the screen. In the center of the screen, the side of a cathetus with a size of 5 mm was glued to the floor with a prize of 5 holes, on the hypotenuse of which a selective mirror DS - 4 mm was attached (according to formula (1), the size of the selective mirror should be at least 1 mm), reflecting 95% at the wavelength of the nitrogen laser 0.34

0 microns and transparent in the visible range. A 8.2 mm F2 lens formed in the treatment plane a spot of size d 5 μm; 10 microns. The guidance accuracy was no less than (XS um. Which corresponds to the characteristics of the best 5 devices for laser retouching FS.

Thanks to the defect retouching method used, a number of additional adjustment operations were eliminated, and

0 high reproducibility of results, simplified design.

The proposed optical scheme is implemented on the finished design of the visual channel (photo projector), which demonstrates

5 a significant expansion of the design capabilities of the device.

The proposed method of retouching a defect and a device for its implementation can improve the performance of the process

0 while maintaining accuracy characteristics.

Formulas of the invention

1. A method for retouching a defect, including 5 obtaining an image of the defect on the screen, forming a laser beam, pointing it at the defect and processing the defect, characterized in that, in order to increase productivity while maintaining the accuracy of processing during laser beam guidance, the image of the defect placed in the center of the screen, the laser beam is aligned with the image and then sent to the defect. 5

2. A device for retouching a defect containing an energy channel including a laser, a telescopic system and, a diaphragm, and a visual observation channel

0 defect, including the screen and the lens, common to the visual and energy channels, it is necessary that, in order to increase productivity while maintaining accuracy characteristics, the optical axis of the energy channel is aligned with the center of the screen, and the device is equipped with a selective mirror transparent for the visible range and reflecting laser radiation, which is fixed in the center of the optical system of the visual wound with a diameter of D3-OG, where D is the channel: -P2-focal output

aperture diameter. G is the coefficient of magnification of the telescopic system; The focal length of the lens. 5

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