JPH0655285A - Laser beam machining method and equipment using this method - Google Patents

Abstract

PURPOSE:To surely cut without giving thermal shock to the whole body to be machined by preliminarily heating a target position locally of the body to be machined with a laser beam of low level, and then executing cutting of the objective part with a laser beam of high level. CONSTITUTION:A laser beam 12 of a low level being not reached to cutting from a laser beam oscillator 13 irradiates the part preliminarily made to a target by focusing, and the temperature of the part being made as the target is increased and preliminarily heated. Due to this pre-heating, the temperature of the target part is increased, then the laser beam 12 of a high level is emitted from a laser beam source and the objective part is cut. Therefore, the target part can be only locally heated with the pre-heating, and a fusing possible part 10A can be made to the change of phase in a liquid like. So, the fusing possible part 10A can be surely cut, even if it is existed in a deep part of the IC. Further, the pre-heating is executed with the laser beam 12, only the target part is locally heated and the thermal shock is not given to whole of the body to be machined 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method and a laser processing apparatus using this processing method which can be used, for example, in an IC manufacturing site.

[0002]

2. Description of the Related Art In the field of integrated memory, a redundant portion is provided in order to remedy a defective memory cell, and a line in which a defective cell is generated is replaced with a line in the redundant portion so that it can be used as a good product. There is a way to treat.
A laser processing apparatus has been conventionally put into practical use in order to carry out this remedy. A laser beam is converged by a laser processing apparatus and irradiated to a fusing part (fuse or the like) provided in the IC, the fusing part in the IC is cut, and a relief treatment is performed.

[0003]

The storage capacity of the memory is increasing day and night, and the degree of integration of ICs is becoming higher and higher. Conventionally, the portion to be cut, which is provided to perform the relief treatment, is provided relatively close to the surface of the IC. However, due to the effect of this high density, the portion to be cut tends to gradually move to the deep portion. . As the fusing part to be cut is moved to the deep part of the IC, the accuracy of the cutting process is lowered, and it is questioned whether or not the relief treatment can be executed.

As one method for solving this problem, there is considered a method in which the entire workpiece is preheated and the cutting is performed by a laser beam in a state where the temperature of the fusingable portion is raised. However, in order to heat the entire work piece, the work piece is mounted, the work piece is moved in the X-Y axis directions, and a moving table is provided to irradiate a desired position of the work piece with a laser beam. In addition, the heating device will have to be installed. When the heating device is mounted on the moving table, heat is also applied to the moving table and the accuracy of the moving position is deteriorated. There is also a drawback that it takes time to heat the entire workpiece to reach a desired temperature. Further, since the whole of the object to be processed is heated, there is a drawback that a portion which does not require heating is also heated and a thermal shock is given. The object of the present invention is that the cutting process can be surely executed even if the portion to be cut is provided in the deep portion of the IC, and the thermal processing does not give a thermal shock to the whole body to be processed. XY
An object of the present invention is to provide a laser processing method that does not apply heat to a moving table and a laser processing apparatus that uses this processing method.

[0005]

According to the present invention, a low-level laser beam or other low-level light that does not reach the cutting process from a laser oscillator or other auxiliary light source is focused and irradiated on a target portion in advance. Then, the temperature of the target portion is raised and preheating is performed. The temperature of the target portion is raised by this preheating, and then a high-level laser beam is emitted from the laser beam source to cut the target portion.

According to this laser processing method, only the target portion can be locally heated by preheating, and the meltable portion can be changed into a liquid phase. Therefore, even if the meltable portion exists deep in the IC, it can be surely cut. Since the laser beam or the light from the auxiliary light source preheats, only the target portion can be locally heated. Therefore, it is not necessary to give a thermal shock to the entire object to be processed, and it is not necessary to apply heat to the XY moving table that constitutes the laser processing apparatus. As a result, it is possible to maintain the positioning accuracy of the work piece in a good state without deteriorating the positioning accuracy of the XY moving table.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a waveform diagram for explaining a laser processing method according to the present invention. The horizontal axis t represents time, and the vertical axis E represents laser beam energy. In the present invention, the workpiece is irradiated with the laser beam A for preheating having the energy E ₁ that does not melt the target portion, and preheating is performed.
After the preheating, a laser beam B for cutting having energy E ₂ necessary for cutting is irradiated within a time period (about 1 ms) in which the temperature of the object to be processed does not decrease, and the target portion is cut.

FIG. 2 shows an example of a laser processing apparatus. Reference numeral 10 in the figure denotes a workpiece. The workpiece 10 is mounted on an XY moving table 11 and is accurately moved in the XY directions so that the irradiation point of the laser beam 12 can be moved to an arbitrary position on the workpiece 10. The laser beam 12 is emitted from the laser oscillator 13, passes through the mirror 14, the beam splitter 15, and the objective lens 16, and is irradiated onto the workpiece 10. The objective lens 16 is focused on the target position of the workpiece 10. That is, for example, the dissolvable portion 10A provided deep inside the IC shown in FIG. 3 is focused and energy is concentrated on the dissolvable portion 10A. Due to this energy concentration, the meltable portion 10A can be preheated and cut without damaging the wiring patterns L ₁ , L ₂ , and L ₃ formed at positions different from the meltable portion 10A.

The beam splitter 15 can be constituted by a half mirror, and a part of the laser beam emitted from the laser oscillator 13 is detected by an incident light amount detector 17 and is given to an AD converter 19 through a buffer amplifier 18 for AD conversion. The converted output is given to the controller 21, and the controller 21 controls the oscillation intensity of the laser oscillator 13. Further, the beam splitter 15 splits the reflected light from the workpiece 10, measures the reflected light amount with the reflected light amount detector 22, inputs a voltage signal proportional to the reflected light amount to the AD converter 23 through the buffer amplifier 23, and The AD conversion output is given to the controller 21, and the oscillation intensity of the laser oscillator 13 is also controlled by the amount of reflected light.

In the laser processing apparatus according to the present invention, the sequence controller 21A provided in the controller 21 controls the laser oscillator 13 so as to emit the cutting laser beam B within a predetermined time following the preheating laser beam A. To do. By emitting the laser beam A for preheating and the laser beam B for cutting in this way, the target fusing part 10A by the laser beam A for preheating (FIG. 3)
Can be preheated to raise the temperature, and the cutting laser beam B is emitted following this preheating to reliably cut the fusing possible portion 10A.

FIG. 4 shows a modified embodiment of the present invention. In this example, the case where the auxiliary light source 25 is used as the light source for preheating is shown. Therefore, in this case, the mirror 14 uses a half mirror. As the auxiliary light source 25, an infrared light source or a white light source can be used. Further, in this example, a structure is shown in which a shutter 26 is provided between the auxiliary light source 25 and the mirror 14, and the shutter 26 is controlled to be opened and closed to provide the workpiece 10 with energy required for preheating. Therefore, in this case, the auxiliary light source 25 may be maintained in the continuous light emitting state. A shutter can also be provided on the laser oscillator 13 side. When a shutter is provided on the laser oscillator 13 side, the laser oscillator 13 can be a continuous laser oscillator instead of a laser oscillator that oscillates a pulsed laser beam.

FIG. 5 shows still another embodiment of the present invention.
In this embodiment, the temperature detector 27 of the workpiece 10 is provided,
The surface temperature of the workpiece 10 is measured during preheating, and it is detected that the surface temperature of the workpiece 10 reaches a predetermined temperature,
A case in which this detection signal is given to the controller 21 and the laser beam B for cutting is emitted from the laser oscillator 13 to perform cutting processing is shown.

As the temperature detector 27, for example, an infrared sensor can be used. A part of the reflected light incident on the reflected light amount detector 22 is branched by the beam splitter 28 to the temperature detector 27. By providing the temperature detector 27 as in this embodiment, the proper state of preheating can be detected. Therefore, it is possible to increase the accuracy of the cutting process without performing the cutting process in the state where the preheating is insufficient.

FIG. 6 shows still another embodiment of the present invention.
In this example, a film thickness meter 29 is provided in addition to the temperature detector 27. When the film thickness meter 29 is provided, the workpiece 10
The film thickness of the transparent insulating film deposited on the surface of the substrate can be measured in advance, and the energy of the preheating laser beam A and the cutting laser beam B can be controlled according to the film thickness of the insulating film. it can.

In order to operate the film thickness meter 29, a white light source 31 is provided for film thickness measurement. The light from the white light source 31 is applied to the workpiece 10 through the half mirror 14, and the film thickness is detected by the reflected light. Examples of the film thickness measuring method include a microscopic interference film thickness measuring method and a quenching method ellipsometry.
By providing the temperature detector 27 and the film thickness meter 29 as in this embodiment, the laser beam A for preheating and the laser beam B for cutting are provided according to the thickness of the insulating film deposited on the surface of the workpiece 10. Since each energy is adjusted, it is possible to prevent an accident in which cutting cannot be reached because the temperature of the workpiece 10 does not rise to a predetermined temperature during preheating due to the thick insulating film. it can.

[0016]

As described above, according to the present invention, there is a portion to be cut and processed in the IC, and even if the portion to be cut and processed is provided at a deep portion for high density, the optical Since the preheating is performed by irradiating, and the portion to be cut is liquefied in advance by this preheating, and the cutting laser beam B is irradiated in this state to perform the cutting, the cutting can be surely performed.

Since it is preheated by the energy of light, heat is not applied to the XY moving table 11 which constitutes the laser processing apparatus. As a result, the accuracy of the movement stop position of the X-Y moving base 11 is not deteriorated, and the work for cutting the portion to be cut can be surely performed at the focal position of the laser beam 12. When the temperature detector 27 is provided as in the embodiment shown in FIG. 5, it is possible to monitor the temperature of the workpiece by preheating. Therefore, in this case, a thick insulating film happens to be formed on the surface of the object to be processed 10. Due to this insulating film, cutting may be performed without the temperature of the target portion rising to the predetermined temperature, and the cutting may not be achieved. It can be prevented from occurring. Therefore, when the temperature detector 27 is provided, the processing reliability can be further improved.

[Brief description of drawings]

FIG. 1 is a waveform diagram for explaining a laser processing method according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a laser processing apparatus according to the present invention.

FIG. 3 is a sectional view for explaining the operation of the laser processing apparatus according to the present invention.

FIG. 4 is a block diagram showing a modified embodiment of the present invention.

FIG. 5 is a block diagram showing a modified embodiment of the present invention.

FIG. 6 is a block diagram showing a modified embodiment of the present invention.

[Explanation of symbols]

 10 Workpiece 11 XY Moving Stage 12 Laser Beam 13 Laser Oscillator 14 Mirror (or Half Mira) 15 Beam Splitter 16 Objective Lens 17 Incident Light Amount Detector 18,23 Buffer Amplifier 19,24 AD Converter 25 Auxiliary Light Source 26 Shutter 27 Temperature detector

Claims (4)

[Claims] 1. A laser oscillator is provided, a laser beam emitted from this laser oscillator is applied to a workpiece, and energy is applied to the workpiece via the laser beam.
In a laser processing method that performs processing such as cutting a target body, a low-level preheating light is given to the workpiece in advance, and the target position of the workpiece is locally preheated by this low-level laser beam. Then, after this preheating, a high-level laser beam is applied to perform a cutting process on a target portion. 2. A laser oscillator is provided, a workpiece is irradiated with a laser beam emitted from the laser oscillator, and energy is given to the workpiece through the laser beam.
In a laser processing apparatus for performing processing such as cutting a target body, the laser oscillator is controlled by a controller to emit a low-level laser beam and a high-level laser beam, and the workpiece is processed by the low-level laser beam. A laser processing apparatus that locally preheats the target position of, and emits a high-level laser beam after the preheating to cut the target portion. 3. A laser oscillator and an auxiliary light source that emits a low-level light whose energy is smaller than that of a laser beam emitted by the laser oscillator, and the target position of the workpiece is locally irradiated by the light of the auxiliary light source. A laser processing apparatus which preheats to a target, and after the preheating, emits a laser beam from the laser oscillator to cut a target portion. 4. The laser processing apparatus according to claim 2 or 3, wherein a temperature detector for measuring the temperature of the object to be processed by measuring the amount of light reflected from the object to be processed is provided. A laser processing apparatus that detects that the temperature has risen to a predetermined temperature, and by this detection emits a high-level laser beam from a laser oscillator to cut a target portion.