JPH10328873A - Laser beam machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved laser beam machining device capable of efficiently cutting a fuse in a semiconductor device. SOLUTION: This device is provided with plural laser light sources 1A, 1B capable of generating with independent and arbitrary timing and a condensing optical system 4 for converging a laser beam to a wafer 8 as plural spot beams 5A, 5B. In addition, the device is provided with a stage 6 for scanning the wafer 8 and a mechanism 12 for adjusting the mutual space between the beams. By moving the movable mirror 3B of this beam space adjusting mechanism 12, the mutual space is adjusted for the beams 5A, 5B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus for performing processing by applying a laser beam to a workpiece. In particular, the present invention relates to a laser processing apparatus improved so as to efficiently cut a fuse in a semiconductor device.

[0002]

2. Description of the Related Art An example of fuse processing in a semiconductor device will be described. In a semiconductor device, there is a case where a wiring portion called a fuse for cutting a laser beam is provided. For example, in DRAM,
A fuse is attached to each memory cell column at the time of manufacture, and a spare memory cell column is arranged. The fuse of the memory cell column that has been found defective during inspection is cut off to isolate the cell column in the device. At the same time, a spare memory cell column is replaced with a spare column by cutting a fuse for designating an address of a defective column, thereby improving the yield of DRAM (see Japanese Patent Application Laid-Open No. 1-224189). In a gate array, a specific program is built into a device by cutting a part of a fuse in a circuit called a program link and selectively leaving a part of the fuse. Laser repair for the former,
The latter is called laser trimming.

[0003] A fuse in such a semiconductor device is generally formed of a thin line made of polysilicon or aluminum (a width of 0.8 to 1.5 μm, a thickness of 0.3 to 1.0 μm,
The cut length is 3 to 10 μm). YA to this fuse
A laser beam from a processing laser light source such as a G laser is condensed and irradiated, and the material constituting the fuse is heated and evaporated with light energy to remove the fuse. The fuse is usually made of a transparent SiO ₂ film (0.
2 to 0.5 μm). As for the position data of the fuse to be blown, data from a tester, which is another device for inspecting a defective portion, is input to the laser repair device via a medium such as online communication or FD. In the laser repair device, the wafer is placed on an XY table and positioned, and the fuses are sequentially cut while automatically aligning the position of the fuse to be cut with the focal point of the laser beam.

FIG. 7 is a plan view schematically showing how a fuse in a semiconductor device is cut using a conventional laser processing apparatus. In the figure, rows of fuses 20 are shown vertically in two rows on the left and right. Each fuse 20 extends linearly in the horizontal direction of the figure, and has two vertical lines 23, 23 '.
Are arranged along. Both lines 23, 23 'are parallel. The fuse marked with X in the figure is to be blown (or blown). The laser beam 21 is focused and irradiated on the center of the fuse 20 to be cut. The diameter of the laser beam 21 is, for example, 3 to 5 μm. The interval L between the fuse rows is generally constant in the same device, and is several tens to several hundreds μm.

The wafer stage is driven so that the center line 23 of each laser beam 20 runs below the laser beam converging point, and the laser is oscillated when the fuse 20 to be cut has just come to the converging point. The fuse 20 is cut. When the processing of the fuse array along the line 23 is completed, the stage is advanced by the interval L, and the fuse array along the line 23 'is processed next. The machining path at this time is indicated by a white arrow 22.

[0006]

With the recent increase in memory integration, the number of fuses for memory cell rescue has increased dramatically, and the number of fuses to be processed has become enormous. There is also a demand for reducing the area occupied by the rescue fuses for high integration, and the fuse pitch tends to be narrowed. However, there is a limit to increasing the oscillation frequency (about several kHz) of the processing laser while maintaining the energy required for processing. Therefore,
Since it is difficult to increase the moving speed between the fuses defined by the same frequency more than the current level, the cutting processing capability of the laser repair device naturally has its limit.

On the other hand, Japanese Patent Application Laid-Open No. 3-297588 proposes a laser processing apparatus having a plurality of laser light sources and capable of simultaneously processing a plurality of processing portions by applying a laser beam to each of the plurality of processing portions. Then, a proposal has been made to adjust the interval between a plurality of laser beams (optical axes). However, this proposal is vague, and there is no disclosure of a specific beam interval adjusting mechanism.

The present invention relates to a laser processing apparatus improved so that a fuse in a semiconductor device can be efficiently cut, and has a high processing capability capable of coping with further higher integration of a semiconductor device in the future. The purpose is to provide.

[0009]

According to a first aspect of the present invention, there is provided a laser processing apparatus comprising: a plurality of processing laser light sources; and the plurality of processing laser light sources oscillating independently and at an arbitrary timing. And a condensing optical system that condenses each laser beam emitted from these processing laser light sources on the workpiece as a plurality of spot beams.
A scanning mechanism for relatively scanning the workpiece and the spot beam; and a beam interval adjusting mechanism for adjusting an interval between the plurality of spot beams. The beam interval adjusting mechanism includes a movable mirror. The mirror receives and reflects at least one of the laser beams emitted from the processing laser light source, and adjusts a mutual interval between the plurality of spot beams by moving the mirror. I do. With this configuration, the beam interval can be adjusted reliably and easily, and a plurality of fuse arrays can be processed at once by a plurality of processing lasers and a desired fuse can be selectively processed. Decrease and increase throughput.

[0010] A laser processing apparatus according to a second aspect of the present invention comprises: a plurality of processing laser light sources; a power supply capable of oscillating the plurality of processing laser light sources independently and at an arbitrary timing;
A condensing optical system for condensing each laser beam emitted from these processing laser light sources as a plurality of spot beams on a workpiece, a scanning mechanism for relatively scanning the workpiece and the spot beam, And a beam interval adjusting mechanism for adjusting the interval between the plurality of spot beams. The optical path length of the laser beam from the processing laser light source to the workpiece does not change even when the beam interval adjusting mechanism operates. It is characterized by the following. Therefore, even if the laser light in the beam interval adjusting mechanism is not parallel light, the imaging relationship does not change when the beam interval changes. Therefore, the degree of freedom in the arrangement of the beam interval adjusting mechanism is increased, and the design and manufacture of the laser processing apparatus are facilitated.

Further, a laser processing apparatus according to a third aspect of the present invention comprises: a plurality of processing laser light sources; a power source capable of oscillating the plurality of processing laser light sources independently and at an arbitrary timing; A focusing optical system for focusing each emitted laser beam on the workpiece as a plurality of spot beams; a scanning mechanism for relatively scanning the workpiece and the spot beam; A beam spacing adjusting mechanism for adjusting the mutual spacing; and wherein the beam spacing adjusting mechanism adjusts a laser beam chief ray incident on the beam spacing adjusting mechanism and a beam spacing even when the movable mirror is deflected. It has an automatic centering function in which the relative angle of the laser beam chief ray emitted from the mechanism does not change. In this case, the position of the laser beam does not change much due to the deflection of the movable mirror, and the beam interval can be adjusted with high accuracy.

A laser processing apparatus according to a fourth aspect of the present invention is a laser processing apparatus, comprising: condensing a laser beam on a plurality of processing portions arranged on a plurality of parallel lines at a certain interval (processing line interval); A laser processing apparatus for processing a processing portion;
A plurality of processing laser light sources, a power supply capable of oscillating the plurality of processing laser light sources independently and at an arbitrary timing, and a laser beam emitted from each of these processing laser light sources as a plurality of spot beams on a workpiece. A focusing optical system for focusing, a scanning mechanism for relatively scanning the workpiece and the spot beam, and a beam interval adjusting mechanism for adjusting an interval between the plurality of spot beams;
Means for automatically recognizing a beam interval; and a beam interval control unit for driving the beam interval adjusting mechanism so that the beam interval matches the processing line interval. In this case, the actual beam interval can be measured and the beam interval can be feedback controlled.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing an overall configuration of a laser processing apparatus according to one embodiment of the present invention. This laser processing apparatus includes two laser light sources 1A such as YAG lasers,
1B. These laser light sources are independently oscillated at arbitrary timings by a command from the control unit 11. The power source of the laser is not shown.

Laser light 2 emitted from laser light source 1A
A is totally reflected downward on the total reflection mirror 3A.
The laser light 2B emitted from the laser light source 1B strikes the movable mirror 3B of the beam interval adjusting mechanism 12, and is totally reflected downward. Here, the optical axes of the laser beams 2A and 2B are parallel, and the mirrors 3A and 3B are arranged in parallel.
Therefore, the optical axes of both laser beams reflected from the mirrors 3A and 3B are also parallel. The position of the movable mirror 3B can be changed to the left and right in the figure, and the distance L 'between the optical axes of the laser light reflected downward by the mirrors 3A and 3B is variable.
A specific example of the structure of the beam interval adjusting mechanism will be described later.

The laser beams reflected by the mirrors 3A and 3B pass through a common (single) objective lens 4 disposed below the mirrors and are condensed to form a spot beam 5
A and 5B are emitted to the processed portion on the surface of the processed object (wafer 8). The optical axis interval L between the two spot beams 5A and 5B is several tenths of the optical axis interval L 'before the objective lens. The beam diameter of both spot beams 5A and 5B is 5
It is about μm.

The wafer 8 is placed on the wafer stage 6 via a chuck (not shown). Wafer stage 6
Are the optical axis direction (Z direction) and the optical axis vertical direction (X, Y, θ).
Direction). The position of the stage is accurately monitored by a position measurement system configured around the interferometer 10 (resolution of several tens nm). A beam position measurement mark 7 is arranged on the stage 6.
This mark 7 is composed of fine lines of a substance having a high reflectivity.
When the stage 6 is scanned and the beams 5A and 5B hit the mark 7, high-level reflected light is emitted, and this is detected by a detector 9 arranged on the side of the objective lens 4. Thereby, the relative positional relationship between each of the beams 5A and 5B and the stage 6 can be grasped. As a result, both beams 5
The control unit 11 calculates an interval L between A and 5B, and the control unit 11 recognizes the beam interval. The control unit 11 adjusts the beam interval adjustment mechanism 12 so that the predetermined interval between the fuse arrays and the beam interval match.

FIG. 2 is a perspective view showing an example of a beam interval adjusting mechanism. A total reflection mirror 3B inclined at 45 ° to the horizontal is slidably arranged in a guide groove (not shown), and an actuator 12X is connected to the movable mirror 3B. It is movable in the optical axis direction of the incident laser beam 2B. As the actuator 12X, a combination of a stepping motor and a feed screw or a piezo actuator can be used. The stroke of the actuator 12X is 5
10mm (250-500μ in terms of spot beam spacing)
m) and the positioning accuracy is preferably about ± 1 μm (± 0.05 μm in terms of spot beam interval conversion).

By driving the drive unit 12X in this manner, the total reflection mirror 3B moves to the position shown by the dotted line, the reflection position of the processing laser beam 2B changes, and the incident position on the objective lens 4 also changes. Change. As a result, the processing laser beam 5B in FIG. 1 moves as indicated by the dotted line, and the interval L between the processing laser beams 5A and 5B can be changed. Therefore, the interval L between the processing laser beams 5A and 5B can be measured by the method using the position measurement mark. L can be adjusted.

FIG. 3 is a schematic side view showing another example of the beam interval adjusting mechanism. This beam interval adjusting mechanism 12 '
Has a right-angle movable mirror 51 in which two reflecting surfaces 51A and 51B intersect at right angles, and a fixed mirror 53 having a reflecting surface 53A facing in parallel with one of the two reflecting surfaces 51B. That is, the right-angle movable mirror 51 has reflection surfaces 51A and 51B that intersect at right angles, and one surface 51A is inclined by 45 ° with respect to the horizontal incident light 55, and reflects the incident light 55 downward. . The light reflected on the surface 51A then strikes the other surface 51B and is reflected horizontally rightward (reflected light 57). The reflected light 57 is then reflected downward by the fixed mirror 53 arranged parallel to the reflection surface 51B.

Here, the state where the right-angle movable mirror 51 is moved downward by S while maintaining its posture is a state drawn by a two-dot chain line. The incident light 55 is reflected downward by the reflection surface 51A 'lowered by S, and the reflection position is:
This is the point that went to the right by S. The light reflected downward is then reflected by the surface 51B 'and goes horizontally to the right (reflected light 5
9). This reflected light 59 is lower than the original reflected light 57 by 2S. The reflected light 59 strikes the fixed mirror 53 and is reflected downward, but its position has moved rightward by 2S from the original position.

Here, the optical path length of the laser light passing through the beam interval adjusting mechanism 12 'before and after the movement of the movable mirror 51 will be examined. It is obvious that the optical path lengths of both lights do not change in the vertical direction in the figure. Therefore, when the light is reflected on the surface 51A or 51A ', the reflected light 59 of the two-dot chain line has a shorter optical path length by S at the time when the light is reflected from the surface 51A or 51A'. The path length of the reflected light 59 is longer than that of the reflected light 59 by S. Therefore, the optical path length of the laser beam passing through the beam interval adjusting mechanism 12 'is
Has not changed before and after the movement.

For this reason, even if the laser beam in the beam interval adjusting mechanism is not parallel light, the imaging relationship does not change when the beam interval changes, so that the arrangement of the beam interval adjusting mechanism can be increased, and the design of the laser processing apparatus can be increased.・ Production becomes easy. In the beam interval adjusting mechanism 12 as shown in FIG. 2, it is necessary to insert a collimator lens between the laser light source 1B and the beam interval adjusting mechanism 12 so that the laser light impinging on the movable mirror 3B becomes parallel light. However, if a collimator lens is simply used to convert the light into parallel light, the energy density of the laser is increased to secure the energy required for cutting the fuse, which may damage the mirror. In the present embodiment, since the optical path length does not change, it is possible to easily design the laser beam so as to spread the laser beam and reduce the energy density to such a degree that the mirror is not damaged.

As shown in FIG. 4, the beam interval adjusting mechanism of this embodiment is configured such that the laser beam chief ray 55 incident on the beam interval adjusting mechanism 12 'and the beam interval adjusting mechanism even when the movable mirror 51 shakes. It also has a characteristic that it has an automatic alignment function in which the relative angle of the laser beam chief ray 59 emitted from the laser beam does not change. FIG. 4 is a side view showing a state in which the attitude of the right-angle movable mirror is swung up and down by the beam interval adjusting mechanism of FIG. In FIG. 4, the right-angle movable mirror 51 is provided with an incident light 55.
It is assumed that the camera is swung so as to be directed downward by θ around an axis that is perpendicular and horizontal to the optical axis of FIG. At this time, the angle at which the incident light 55 strikes the surface 51A 'is θ
Only shallower. The light reflected by the surface 51A '
The angle corresponding to 1B 'becomes deeper by θ. However, the surface 51
Since B ′ is rotated by θ below the original surface 51B, the angle at which the reflected light is received is shallower by θ, and the reflected light 59 from the resultant surface 51B ′ is parallel to the original reflected light 57. Becomes Therefore, the light reflected downward from the fixed mirror 53 is also parallel.

That is, the position of the light traveling downward from the beam interval adjusting mechanism 12 'is shifted by the above-mentioned deflection of the movable mirror 51, but the angle is not changed. Even if the position is displaced, the interval between the two beams can be measured, and the result can be fed back so that the desired beam interval can be obtained. On the other hand, if the angle is changed, telecentricity collapses, and particularly when a thick fuse is processed, the processed shape is undesirably collapsed. Therefore,
A mechanism having an automatic centering function such that the angle of the laser beam emitted from the beam interval adjusting mechanism does not change even when the movable mirror 51 swings as in the present embodiment is desirable.

Note that, for example, the beam 5A on the wafer,
The setting resolution of 5B is 0.05 μm, and the optical axis adjustment mechanism 1
If the magnification up to 2 is several tens of times, the resolution required for the movable total reflection mirror 3B is only about 1 μm, and the mechanism can be easily designed by using an encoder.

Next, with reference to FIG. 5, an operation example of cutting a fuse of a semiconductor device using the laser processing apparatus of the present embodiment will be described. FIG. 5 shows a row of two right and left fuses 30. Each fuse 30 extends linearly in the horizontal direction in the figure, and is arranged along two vertical lines 33 and 33 '. Both lines 33, 33 'are parallel.
The fuses marked with X in the figure are to be blown (or blown).

In the present embodiment, the left fuse row 33 and the right fuse row 33 'are processed at once by using two laser beams. That is, the interval between the spot beams 5A and 5B in FIG. 1 is adjusted to the interval L between the fuse arrays 33 and 33 ', the left fuse array 33 is sent below the focal point of the spot beam 5A, and the right fuse array 33 is sent. 'Are sent in parallel under the focal point of the spot beam 5B. Then, when the fuses 30 to be cut (those marked with a cross) come below each of the condensing points, the laser light source is oscillated by a command from the control unit, and a spot beam is applied to the fuses 30 to cut sequentially. Go. ON / OFF of left and right spot beam
Are independent as described above, so it is naturally possible to cut only one of the fuses arranged on the left and right. The machining path at this time is indicated by a white arrow 32.

Since the fuse interval in a chip formed on one wafer is the same, the beam interval may be adjusted once before starting the processing, and the fuse interval is the same for each device. Therefore, readjustment is not required when processing the same device. As described above, in the present embodiment having two laser light sources, the stage movement distance can be reduced to half of the conventional case, and the processing capacity increases.

Next, a laser processing apparatus according to another embodiment of the present invention will be described. FIG. 6 is a block diagram schematically showing an overall configuration of a laser processing apparatus according to another embodiment of the present invention. In the laser processing apparatus of this embodiment, in addition to the processing laser light sources 1A and 1B, helium-neon laser light sources 13A and 13B for alignment are separately provided. The alignment laser beams 14A and 14B emitted from the laser light sources 13A and 13B are basically coaxially multiplexed with the processing laser beams 2A and 2B in the dichroic mirrors 3A 'and 3B', respectively.
And is projected onto the wafer 8.

[0030] By the same method as in Example, using a beam position measuring mark 7, the error distance D _A of the processing laser light 5A and the alignment laser beam 15A, and the error interval of the processing laser beam 5B and the alignment laser beam 15B to previously obtain a D _B, carried out by an optical axis adjusting mechanism 12 in the subsequent fuse spacing L adjustments alignment laser beam 15A, 15B apart from D _a, the value obtained by correcting the distance D _B, the working laser beam 5A, What is necessary is just to adjust the interval of 5B to be equal to the fuse interval L. In other words, the alignment laser measures the position between the chips in the wafer, measures the offset between the alignment laser and the processing laser, and performs processing by correcting the offset and the position information obtained from the alignment laser. is there. Subsequent fuse processing is the same as in the previous embodiment.

[0031]

As is apparent from the above description, according to the present invention, a plurality of processing beams are adjusted in advance in accordance with an arrangement interval of a plurality of fuses (non-processing portions), and the processing beams are oscillated independently. As a result, desired fuse processing can be performed, so that the amount of stage movement is reduced and the processing capability of the processing apparatus can be increased. Therefore, it is possible to provide a laser processing apparatus having a high processing capability capable of coping with further higher integration of semiconductor devices in the future.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an overall configuration of a laser processing apparatus according to one embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a beam interval adjusting mechanism.

FIG. 3 is a schematic side view showing another example of the beam interval adjusting mechanism.

4 is a side view showing a state in which the attitude of a right-angle movable mirror is swung up and down by the beam interval adjusting mechanism of FIG. 3;

FIG. 5 illustrates an operation example of cutting a fuse of a semiconductor device using the laser processing apparatus of the present embodiment.

FIG. 6 is a block diagram schematically showing an overall configuration of a laser processing apparatus according to another embodiment of the present invention.

FIG. 7 is a plan view schematically showing how a fuse in a semiconductor device is cut using a conventional laser processing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Laser light 3 Mirror 4 Objective lens 5 Spot beam 6 Stage 7 Position measurement mark 8 Wafer 9 Detector 10 Interferometer 11 Controller 12 Beam interval adjusting mechanism 13 Laser light source for alignment 14 Laser 15 Alignment laser light 20, 30 Fuse 21 laser beam 22 path 23 center line 51 right-angle movable mirror 53 fixed mirror 55 incident light 57,
59 Reflected light

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI // H01L 21/82 H01L 21/82 F

Claims (7)

[Claims] 1. A plurality of processing laser light sources, a power supply capable of oscillating the plurality of processing laser light sources independently and at an arbitrary timing, and a laser beam emitted from each of these processing laser light sources A focusing optical system that focuses as a plurality of spot beams, a scanning mechanism that relatively scans the workpiece and the spot beam, a beam interval adjustment mechanism that adjusts the interval between the plurality of spot beams, The beam interval adjusting mechanism includes a movable mirror, and the mirror receives one of the laser beams emitted from the processing laser light source, reflects the laser beam, and moves the mirror to move the mirror. A laser processing apparatus for adjusting an interval between spot beams. 2. A plurality of processing laser light sources, a power source capable of oscillating the plurality of processing laser light sources independently and at an arbitrary timing, and a laser beam emitted from each of these processing laser light sources. A focusing optical system that focuses as a plurality of spot beams, a scanning mechanism that relatively scans the workpiece and the spot beam, a beam interval adjustment mechanism that adjusts the interval between the plurality of spot beams, A laser processing apparatus wherein the optical path length of laser light from the processing laser light source to the workpiece does not change even when the beam interval adjusting mechanism is operated. 3. The laser processing apparatus according to claim 1, wherein the optical path length of the laser beam from the processing laser light source to the workpiece does not change even when the beam interval adjusting mechanism is operated. 4. The beam interval adjusting mechanism changes the relative angle between a laser beam chief ray incident on the mechanism and a laser beam chief ray emitted from the mechanism even when the movable mirror shakes. 2. The laser processing apparatus according to claim 1, wherein the laser processing apparatus has an automatic centering function. 5. The beam interval adjusting mechanism according to claim 1, further comprising a right-angle movable mirror having two reflecting surfaces intersecting at right angles, and a fixed mirror having a reflecting surface facing in parallel with one of the two reflecting surfaces. 5. The laser processing apparatus according to 2, 3, or 4. 6. A laser processing apparatus that processes laser light by condensing laser light on a large number of processing portions arranged on a plurality of lines parallel to each other at a certain interval (processing line interval). A plurality of processing laser light sources; a power supply capable of oscillating the plurality of processing laser light sources independently and at an arbitrary timing; and a plurality of laser light beams emitted from these processing laser light sources being applied to a workpiece. A focusing optical system for focusing as a spot beam, a scanning mechanism for relatively scanning the workpiece and the spot beam, and a beam interval adjusting mechanism for adjusting an interval between the plurality of spot beams. Means for automatically recognizing a beam interval; and a beam interval control unit for driving the beam interval adjusting mechanism so as to adjust the beam interval to the processing line interval. Laser processing equipment. 7. The laser processing apparatus according to claim 6, wherein the processed portion is a fuse arranged in a known arrangement on a semiconductor device.