JPS6342128A - Photo processing - Google Patents

Abstract

PURPOSE:To contrive a reduction in a cost and an increase in productivity by a method wherein pulse laser light having a wavelength of 400 nm or less is irradiated on a surface to be processed on a substrate through a mask, which is provided part from the surface to be processed and has a prescribed pattern drawn thereon, and the surface to be processed is selectively removed. CONSTITUTION:An initial optical beam 20 has 350 mj as it has 15 mm X 20 mm and its efficiency is 3%, this beam is formed into a long area or a large area by a beam expander 2 and moreover, is focused by a synthetic quartz lens 4 in such a way that the aperture groove width on a surface to be processed beams 5 mm in case no mask is used. A mask 3 consisting of a quartz plate is used and such a heat-resisting light-shielding material 3' as chrome and MoSi2 is selectively provided on the lower side of this mask. Here, focused light 12 is irradiated on the surface 10 to be processed. By such a way, a 5-mm long and 5-mm wide slitlike beam 22 is irradiated on a material 11 to be processed on the substrate 10 in a plane form to perform a processing and a pattern is formed.

Description

Detailed Description of the Invention "Industrial Field of Application J The present invention is directed to the processing of a surface of a substrate used for a solar cell, a display device, etc., preferably a thin metal film or a transparent conductive film, using a photoresist. The present invention relates to a selective processing method in which a predetermined pattern is directly drawn using only a mask without using a mask.

``Conventional technology j Regarding optical processing without using photoresist, YAG laser light (wavelength 1.06 μm) is used as a laser processing technology.
m) method is mainly used.

In this wavelength-based laser processing method, a spot-shaped beam is irradiated onto the workpiece, and this beam is scanned in the processing direction to form a chain of points. Therefore, the scanning speed of this beam and the energy density required for processing interact in a very subtle way, in addition to the thermal conductivity and sublimation property of the workpiece. Therefore, while improving productivity during industrialization, there is a drawback that there is a small margin for guaranteeing optimal products.

Furthermore, the optical energy of the laser beam is 1.23 eV (
1,06 μm), and the duration of the pulse is more than 80 ns. However, on the other hand, a workpiece formed on an insulating substrate with extremely low thermal conductivity, such as a glass substrate, such as a metal or a transparent conductive film (hereinafter referred to as CTF), generates heat that is an order of magnitude higher than that of the substrate. Since it has conductivity, the irradiated heat propagates in the lateral direction of the thin film, and while the pulsed light is being irradiated, it is not possible to locally make only the irradiated part extremely high temperature. In addition, in the laser processing method using the Q switch of YAG laser, the pulsed light has an average of 0.5 to IW (light diameter 50 μm, focal length 40 m).
m, pulse frequency 3 KHz, pulse duration 100 ns) at a scanning speed of 30 to 60 cm.
/min and must be processed. As a result, although the CTF can be processed using this stronger than necessary laser beam, microcracks are generated in the substrate provided below, for example, a glass substrate.

``Problem to be solved by the invention'' In this processing method using a YAG laser, a spot beam is repeatedly scanned and applied, so the minute crank generated on the base substrate has a shape similar to the circumference of the laser beam. It has been made into a "scale" shape.

In addition, the long laser beam during this pulse tends to cause swelling around the processed area, and especially for thin metal films, the irradiation time is short enough to directly vaporize the solid, so heat propagates in the lateral direction. As a result, a molten state occurs, and the surface tension at the time of melting causes the thin films to stick together and solidify further, resulting in a "bulge" at the edge of the area irradiated with the laser beam. Therefore, compared to a method using photoresist, the edges of the pattern are not sharply cut.

In addition, in the method using a Q switch of a YAG laser, the peak value output tends to vary over a long period of use, and it is necessary to check it on a monitor each time it is used.

Furthermore, it has been completely impossible to selectively form a large number of fine patterns having a width of 10 to 50 μΦ on the same plane.

Furthermore, since the CTF material in the processed area was not sufficiently pulverized after irradiation, etching had to be performed using a CTF etching solution.

The present invention is based on the “Patent Application No. 59-211 filed by the inventor.
769 (October 8, 1981, 1II) Optical Processing Method" was further improved.

Means for Solving Problem J The present invention solves the above problem, and uses irradiation light of 400 nm or less (energy of 3.1 eV or more).
irradiate with a pulse laser with a wavelength of 40 ns or less in pulse width, and create a beam spot of 50 μι instead of a beam spot of 20 to 50 μΦ.
m~1511II+ width, length 60~2cm (for example, 100μ x 30cm or 10m shoes x 151,
The energy density per unit area is set to be a density sufficient to process the surface to be processed), and the same location is irradiated with one or several pulses to simultaneously and instantaneously process the entire surface of the pattern. Thus, 400n11 shown in the present invention
By focusing pulsed light of the following wavelengths (pulse width 40 ns or less) and irradiating it onto the workpiece surface, the absorption efficiency of light energy on the workpiece surface is more than 100 times that of a YAG laser (1,06 μm). As a result, the machining speed was increased by more than 10 times.

Furthermore, the present invention uses excimer laser light.

Therefore, the initial light irradiation surface has a rectangular shape, and the intensity is approximately uniform within the irradiation surface. For this reason, a so-called beam expander that expands the width of the light is used to increase the rectangular area or to increase the area. Thereafter, the laser beam is focused in the X or Y direction by another optical system.

Furthermore, in order to make arbitrary patterns such as IC (integrated circuit) chips on-board (instead of mounting epoxy packaged chips on the board, the chip is mounted directly on the board to reduce size and cost). form a pattern.

As a result, depending on the pattern shape of this mask, for example, 1
A pattern within an irradiation area of 0.00 μm x 30 cm to 10 mm x 15 mm can be created with clear edges around the irradiation area.

"Operation" The first aspect of the present invention is to form a predetermined pattern at a predetermined position by irradiating the same location with pulsed light once or several times through a mask. Further, by a repeat method in which the same pattern as this pattern is repeatedly formed next to the substrate or on other parts, the pattern is directly drawn on the substrate without using a photoresist.

The second aspect of the present invention is to construct a large-area predetermined mask on a substrate. This mask and the substrate having the surface to be processed are fixed and moved little by little while being irradiated with a laser beam strong enough to directly write, and finally the pattern patterned on the mask over the entire surface is This method involves drawing directly onto the processed surface of a conductive thin film with high thermal conductivity on a small insulating substrate.

As a result, it is possible to selectively remove slit-shaped grooves of only chromium, nickel or CTF without damaging the underlying substrate, and at the same time, it is possible to remove vacuum or clean air between the mask and the workpiece. Alternatively, by injecting nitrogen, flying objects generated by laser beam irradiation of the workpiece can be prevented by actively falling downward without adhering to the lower surface of the mask.

In addition, powdery residues remaining on the processed part after forming the coating can be sufficiently removed by ultrasonic cleaning using a cleaning solution such as alcohol or acetone, and can be used for so-called resist coating, etching of the processed material, and resist removal. This eliminates the need for many processes and the use of polluting materials.

In addition, since the mask is spaced apart from the workpiece, there is less damage to the mask. In addition, since the laser light is at the position where the mask is placed before it is sufficiently focused, even if the energy density is high enough to process the workpiece, it will not cause any damage to the mask. You can choose no energy density.

Embodiment 1" FIG. 1 shows a system diagram of laser processing of the present invention using an excimer laser. Excimer laser (1) (wavelength 248n
m, Eg = 5.0 eV). The initial light beam (20) then has 15 ml x 20 mm and has an efficiency of 3χ and thus 350 mJ. Furthermore, this beam was enlarged to a longer area ratio or larger area using a beam expander (2), that is, expanded to 15 mm x 300 mm (FIG. 2 (21)).

An energy density of 5.6 x 10-''mJ/mm2 was obtained with this device.

Further, a lens (4) made of synthetic quartz was used to condense the light as much as possible to 5 mm in the open groove on the processed surface when no mask was used. A quartz plate mask (3) was used. A heat-resistant light-shielding material (3') such as chromium or MoSi2 is selectively provided under the mask to form a mask. Here the focused light (12)
The surface to be processed (10) is irradiated with more light.

In this way, a slit-shaped beam (22) having a length of 5 TIIm and a width of 5 mm was irradiated onto the workpiece (11) on the substrate (10) in a planar manner to form a pattern (5).

The surface to be processed is chrome on glass (thickness 500~10
An excimer laser (manufactured by Questec Inc.) was used for the substrate (10) having 0.00 people).

The pulse width is 20 ns, the repetition frequency is 1 to 100 Hz, for example 10 Hz, and the workpiece is a thin metal film on a glass substrate, and since this chromium is sublimable, the irradiated area is I was able to remove it sufficiently.

After this, ultrasonic cleaning with acetone aqueous solution (frequency 29K)
Hz) for about 1 to 10 minutes to remove this CTF.

Residues adhering to the chrome substrate were removed.

The underlying soda glass was not damaged in any way. Figure 2 explains the state of the laser beam in Figure 1. That is, the state irradiated with laser light becomes a rectangle (20) in FIG. 2(A). This is expanded with an expander (21) to obtain the image shown in FIG. 2(B). Further, the light is condensed by a condenser lens, a part of the light is removed by a photomask, and a beam of predetermined size (FIG. 2(C)) is irradiated onto the surface to be formed.

At this time, the pattern of the mask is shown in Figure 2 (D-1) (this Figure 2 (D-1) is enlarged compared to Figure 2 (C) to make the wiring easier to see). Like, (23
-1) pattern is patterned on a thin film on a substrate. Furthermore, after this, by moving the substrate to the left and repeating the process, the same pattern can be formed using the same pattern of the mask (23-2). This figure (FIG. 2 CD-1) is an example of an IC chip pattern.

Further, FIG. 2 (D-1) shows a case where the adjacent area (23-2) has the same pattern as the original area (23-1).

On the other hand, FIG. 2 (D-2) shows a case where different patterns are to be drawn in a large area. In this case, the mask and the substrate are fixed, and the laser beam is repeated in steps (23-1) and (23-2). In this case, the mask needs to be large enough to cover the entire area. be.

In this drawing, the cross wiring with the chip location (30) and the lead (33) is located at (31) and (32).
Alternatively, after patterning between (31°) and (32'), a method is used in which each is wire-bonded for air isolation. This wire bonding process
This may be performed in the same process as the wire bonding between the chip (30) and the wiring L% (33).

Embodiment 2 This embodiment is shown in FIG. That is, the initial laser beam light (20) in FIG. 1 is shown in FIG. 3(A). This is enlarged using a beam expander and shown in Figure 3 (B).
get. Furthermore, a cylindrical lens is used to condense the light to 20 to 200 μm, for example, 100 μm, in order to have enough energy to directly write the surface to be processed with the same length and width as the final pattern in the horizontal direction. (C) Obtain (22).

FIG. 3(C) shows the size of the beam on the surface to be processed. At the same time as shown in FIG. 2 (D-2), all the patterns to be patterned on the surface of the substrate to be processed are placed in one mask from above (22-1).
(22-2) ... (22-3) The mask and substrate are moved little by little. Alternatively, the mask and substrate are fixed and the laser beam is moved.

Following this movement, a mask pattern could be formed directly on the metal thin film on the substrate.

In this example, the positions of this substrate and mask were set under vacuum (
The degree of vacuum was 10 −3 torr or less), and pulsed light with a wavelength of 400 nm or less was applied. The wavelength is 248 nm (KrF
). Pulse width Ion seconds, average output 2.3mJ/m
The nickel on the surface to be processed was then vaporized, and the remaining metal leads could be insulated by this opening without damaging the underlying insulator.

The rest is the same as in Example 1.

"Effect" When trying to form a pattern determined by a photomask pattern on a workpiece on a substrate according to the present invention,
It was possible to do this in about 5 minutes when the total area was 2 cm x 30 cm.

As a result, the number of steps is 7 compared to patterning using photoresist using the conventional mask alignment method.
The process required only two steps (light irradiation and cleaning), and the working time could be reduced to 5 to 10 minutes, achieving low cost and high productivity.

That is, in the present invention, the photomask is disposed at a position sufficiently distant from the surface to be processed, and the photoresist is not used in close contact with the surface to be processed, so that the life of the mask is long. There are no processes such as photoresist coating, primer, exposure, etching, and peeling. Furthermore, since a mask is used, any pattern can be formed.

As shown in FIGS. 2(I)-1) and (D-2), the present invention has a metal lead wiring having a width of 30 to 100 μm,
It typically has a width of 50 μm, and can form sufficient leads on the substrate by rough patterning, which is more than 10 times the width of the 0.3 to 3 μm width used in VLSIs, and the process is simplified. It is possible to reduce the price.

Furthermore, in the optical system of the present invention, an integrator, a condenser lens, and a projection lens may be inserted between the beam expander and the surface to be processed in order to make the optical system more accurate.

[Brief explanation of drawings]

FIG. 1 shows an outline of the optical processing method of the present invention. FIG. 2 shows the variation of the light pattern of the present invention. FIG. 3 shows another manufacturing process of the present invention.

Claims (1)

[Claims] By irradiating a processed surface of a substrate with a pulsed laser beam having a wavelength of 1,400 nm or less through a mask provided at a distance from the processed surface and on which a predetermined pattern is drawn,
An optical processing method characterized in that a processed surface of the thin film having a pattern having the same shape as the pattern is formed on a substrate by selectively removing the processed surface. 2. The optical processing method according to claim 1, wherein the surface to be processed on the substrate is made of a metal of an insulating substrate or a thin film of a transparent conductive film. 3. An optical processing method according to claim 1, characterized in that predetermined patterns are formed on the processed surface of the thin film at different positions on the same substrate. 4. An optical processing method according to claim 1, characterized in that a predetermined pattern of a mask is formed on the surface of the thin film to be processed by moving a laser beam onto the same substrate.