JPH03131005A - Laser trimming device - Google Patents

Abstract

PURPOSE:To obtain a laser trimming device with a high-speed and highly accurate laser trimming capacity without reducing trimming treatment capacity by enabling laser irradiation light from a laser oscillator to be gathered and by forming a plurality of cut traces to a resistor on a substrate to be machined. CONSTITUTION:Laser beam irradiated from laser oscillator 1 enters a scan optic system 2 and is gathered near a resistance film 4 on a substrate to be machined 3 thorugh a beam scanner 21 and a f-theta lens 22. When laser trimming is actually performed, while resistance of a resistor to be machined is measured by a resistance measuring equipment 5 and it is checked to see whether the trimming target value is exceed or not, beam position is moved by a position coordinates signal 11 from a controller 6 for performing laser shot and cutting is made from the outside of the resistance film in order. Then, by stopping oscillation of laser when the resistance of the resistor to be machined exceeds the trimming target value, the trimming is completed, thus achieving a further accurate trimming without sacrificing machining speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser processing machine, and more particularly to a laser trimming device that uses a laser beam to cut out a part of a resistive film on a substrate and adjust it to a desired resistance value. Regarding.

[Prior Art] Generally, when performing laser trimming of a resistor on a substrate, the resistance value of the processed resistor is measured using a resistance measuring device, and the focus position of the laser beam is adjusted to the resistive film ( resistor)
While sequentially moving from the outside to the inside, the laser shot is repeated to cut into the resistive film.
The laser shot is stopped when the measured resistance value exceeds the trimming target value.

At this time, from the point of view of processability, etc., the laser beam is a pulsed beam output light with a constant period, so the bite size, that is, the distance between the previous laser shot position and the next laser shot position, is used. Trimming will proceed discontinuously.

Therefore, the resistance value also changes discontinuously in steps corresponding to the bite size for each shot.

Even at the end of trimming, the amount of change in resistance value equivalent to one shot inevitably remains as a variation.

This determines the limit of trimming accuracy.

The amount of change in resistance value per shot tends to increase rapidly as the depth of the cut increases.

Correspondingly, the amount of variation increases rapidly, resulting in poor trimming accuracy and, in many cases, the desired resistance value accuracy cannot be obtained.

[Problems to be Solved by the Invention] Conventionally, the following two measures have been taken to improve trimming accuracy in such cases.

The first improvement measure is to reduce the bite size, but when the bite size is set small, the number of shots increases and excessive laser power is applied to the resistive film. Due to this increase in thermal influence, there is a drawback that machining accuracy cannot be improved to the extent that it is proportional to the bite size. Therefore, it is necessary to reduce the byte size even more,
In this case, due to the relationship with workability, it becomes necessary to simultaneously slow down the processing speed, resulting in a disadvantage that processing capacity is significantly reduced.

The second improvement measure is to change the cut shape.

Instead of a simple linear cut, there are methods such as adding an L-shaped cut that can reduce the change in resistance value per bite size, or adding a second cut for fine adjustment.
It is possible to improve processing accuracy.

However, since the cut length is generally longer and the calculation control is more complicated, the processing time is increased accordingly.

As described above, there is a problem in that no matter which method is used, a decrease in processing capacity is unavoidable.

Furthermore, there is a problem in that the resistance value determined by ΔN at the end of laser trimming is different from the final resistance value after one hour has elapsed. This phenomenon is called over-trimming or drift.

This is caused by changes in physical properties due to the residual effects of thermal processing during trimming, the occurrence of microcracks, or a delay in the response of the resistance measuring device, but it is especially noticeable when attempting to trim a high resistance. This is a major obstacle in ensuring trimming accuracy.

The amount of over-trimming varies considerably from resistor to resistor, and there are many parts that cannot be removed even using high-speed response measuring instruments, so the main cause is residual thermal effects such as changes in physical properties and the occurrence of micro-cracks. This is thought to be due to. In other words, the resistive material is elevated or scattered at the center of the beam due to the laser shot, but
The surrounding area gradually returns to room temperature after being melted or heated due to insufficient processing energy.

In the case of high-resistance materials, if the physical properties of the molten part change significantly and trimming is performed at high speed, the next laser shot may be applied before the laser shot has sufficiently cooled down and returned to a steady state. It is thought that this is because the amount of over-trimming becomes large due to the cumulative effect of heat.

Conventionally, methods have been used to reduce the bite size or change the cut shape depending on the required trimming accuracy, but either method increases processing time and reduces the processing capacity of the trimming device. It is causing deterioration.

By the way, the demand for a laser trimming device that can perform high-speed and high-precision trimming is becoming stronger year by year.
For example, there is a demand for high-precision trimming at a high speed exceeding several dozen pieces per second, and conventional laser trimming devices cannot meet this demand.

Therefore, one object of the present invention is to realize a laser trimming device that can perform high-speed, high-precision laser trimming without reducing trimming processing performance.

[Means for Solving the Problems] A trimming device according to the present invention includes a scanning optical device that collects a laser beam emitted from a laser oscillator and scans it at a predetermined period.

The present invention is characterized in that it has a control means for driving and controlling the laser oscillator in synchronization with a predetermined cycle, and is configured to form a plurality of cutting trajectories on the resistor on the substrate to be processed.

Furthermore, the scanning optical means includes a first scanning means that receives the laser emitted light and scans in a predetermined direction at a predetermined period, and receives the emitted light from the first scanning means and deflects the emitted light. It also has a condensing means for condensing light.

The above-mentioned scanning optical means receives the laser emitted light and scans it at a predetermined period along a predetermined circumference.
The scanning device may include a scanning device, and a focusing device that receives the emitted light from the first scanning device, deflects the emitted light, and condenses the emitted light.

[Function] According to the laser trimming device of the present invention, shots are made alternately on a plurality of cut trajectories, and trimming of a plurality of cuts is performed nine times in parallel.

Trimming using this double line cut allows highly accurate trimming without sacrificing processing speed in the following respects.

Figure 2 shows the locus of cuts made to the resistive film, where the single-dot line shows the locus of the straight-line cut conventionally used for boat fishing, and the solid line shows the locus of the double-track cut according to the present invention. . In addition, Fig. 3 shows the analytically determined relationship between the cut depth and the resistance value corresponding to the cut locus, where the one-dot line represents the change in resistance value due to the conventional single-line cut, and the solid line represents the change in resistance value due to the conventional single-line cut. It shows the change in resistance value due to cutting.

In conventional single wire cut trimming, trimming is performed along the trajectory shown by the dotted line in Figure 2, and the change in resistance value at that time is as shown by the dotted line in Figure 3, and the resistance value suddenly increases at the end of trimming. It is on a rising trend. Therefore, as mentioned above, the variation in machining accuracy increases,
And stability deteriorates. On the other hand, in the double line cut of the present invention.

While laser shots are performed alternately on a plurality of cutting trajectories, the trajectories shown by solid lines in FIG. 2 are trimmed in parallel. This results in a change in resistance value as shown by the solid line in FIG. As shown in Figure 3, the same resistance value R
If you try to get t.

The depth of the cut will be as shown at point a and point b, and the double line cut will be shallower. Therefore, the effects of changes in physical properties due to residual thermal effects and the occurrence of microcracks are reduced, and variations can be reduced and stability improved accordingly.

Furthermore, when comparing the rate of change in resistance value with respect to the cut length at the end of trimming, the two are almost the same, as shown by the slopes of the curves at points a and b in FIG. But if the byte size is the same.

In the double wire cut of the present invention, the same change in resistance value is obtained in two shots, so the change in resistance value per shot is halved, and the variation is correspondingly improved. On the other hand, if we compare the conditions that allow the same amount of variation in resistance value, it means that the double line cut of the present invention can be trimmed by doubling the bite size, and in this way the bite size can be made larger. Therefore, processing accuracy is improved by reducing unnecessary heating during laser shot. Additionally, the processing time is also faster as the cut length is shorter.

Furthermore, since laser shots are performed alternately even at the same shot time interval, the shot time interval is twice as long for each cut.

Therefore, for at least one cut, the resistance value can be measured after the laser-processed part has cooled down to a more stable state.

As a result, the amount of over-trimming can be reduced, making it possible to perform trimming with higher precision.

Comparing cases where this resistor is actually used in a circuit, 1. With the double wire cut of the present invention, the power is distributed at two locations, so the concentration of power generated at the tip of each cut is considerably lower, 1. Local heat generation is reduced. This has the advantage of improving long-term stability during use.

[Example] Next, one embodiment of the present invention will be explained using examples.

Referring to FIG. 1, the laser trimming device is shown.

Laser oscillator 1, scanning optical system 2, and resistance measuring device 5
and a controller 6.

The laser oscillator 1 is a small Nd laser that can provide high peak output:
A solid-state laser using a YAG (neodymium yttrium aluminum garnet) crystal, which emits a pulsed light beam in response to a pulse signal from the controller 6.

The scan optical system 2 includes a biaxial beam scan 21 and an f-θ lens 22, and the beam scanner 2
1 is a position coordinate signal 11 sent from the controller 6
Accordingly, the mirror is rotated to deflect the direction of the incident laser beam, and then the f-θ lens 22 focuses the incident beam on a position on the substrate 3 to be processed corresponding to the deflection angle.

A resistance measuring device 5 is connected to the electrodes at both ends of the resistive film 4 on the substrate 3 to be processed, and the resistance value of the resistive film 4 is measured by this. Further, the resistance measuring device 5 sends an end signal 12 indicating the end of trimming to the controller 6 when the resistance value changes as the trimming progresses and exceeds the trimming target value.

The laser beam emitted from the laser oscillator 1 is as follows.

enters the scanning optical system 2, beam scanner 21 and f
The light passes through the −θ lens 22 and is focused near the resistive film 4 on the substrate 3 to be processed. When laser trimming is actually performed, the resistance value of the resistor to be processed is measured using the resistance measuring device 5, and the beam position is determined using the position coordinate signal 11 from the controller 6 while monitoring whether it exceeds the trimming target value. Move it and perform a laser shot to make incisions from the outside of the resistive film. Then, when the resistance value of the resistive film to be processed exceeds the trimming target value, the laser oscillation is stopped to complete the trimming.

The above-mentioned trimming operation has been performed conventionally, and in the present invention, a resonant galvanometer scanner that scans the beam with a predetermined amplitude and a predetermined period is added to the scanning optical system as a third scanning means. , laser shots are performed alternately on a plurality of cutting trajectories.

Referring to FIG. 4, the scanning optical system 2 used in the present invention is a biaxial galvanometer type beam scanner 2.
In addition to 3 and 24, a resonant galvanometer scanner 25 is added as a third scanning means, which can scan the beam at high speed with a constant amplitude and a constant cycle.

In the scanning optical system 2 shown in FIG. 4, the two beam scanners 23 and 24 move their positions (polarize the light) twice in one period in synchronization with the period of the resonant galvanometer scanner 25.

In other words, if a laser shot is performed when the deflection angle reaches the maximum, trimming of two cut trajectories can proceed at the same time.

Specifically, when the deflection angle of the mirror of the resonant galvanometer 25 is expressed by ±θ and the focal length of the f-θ lens 22 is expressed by f, the interval between the two cut trajectories is as shown in equation (1).

D-4・f・θ...(1) Therefore,
If the required spacing is D=0.5mm, then f=200
In the case of am, the necessary deflection angle is ±0.036 degrees,
Therefore, if the resonant galvanometer scanner 25 is operated with a deflection angle of ±0.036 degrees and twice the laser shot period, for two cut trajectories with an interval of 0.5 degrees,
Trimming of double track cuts can be performed in parallel while performing laser shots alternately. As a result, as described above, trimming with higher precision becomes possible without sacrificing processing speed.

In addition, for such a small swing angle, a resonant galvanometer can scan up to about 10 kllz, and therefore can also handle a laser shot of 20 kllz, which is sufficient to achieve the high speed that is the objective of the present invention. I'm satisfied with that.

In addition, in the configuration of this embodiment, the resonant galvanometer 2
Since the deflection direction of the beam due to No. 5 is fixed, it is necessary to arrange the beam so that the deflection direction is substantially perpendicular to the trimming direction. Therefore, when trimming in other directions or arbitrary directions, as a modification of this embodiment, the mounting direction of the resonant galvanometer 25 can be changed.

Alternatively, it is necessary to add a similar resonant galvanometer as a fourth scanning means.

In the laser trimming apparatus according to the second embodiment of the present invention, a rotating machine type beam scanner is used in the scanning optical system 2 instead of a resonant type galvanometer.

Referring to FIG. 5, the single-rotator type beam scanner 26 is composed of a motor with a mirror mounted at a slight angle from a right angle to the single-rotation axis, and by rotating the motor, the beam focusing position can be reduced. It can move in a circular motion.

To give a specific example, with the same parameters as in the first embodiment, if the mirror is attached by tilting the corner by 0.036 degrees, it will form a circle with a diameter of 0.5 mm on the machined surface. With this configuration, the other two beam scanners 23 and 24 move their positions in synchronization with the rotation period of the one-rotator type beam scanner 26,
If you perform laser shots twice in one cycle, that is, when the beam is oscillating in a direction perpendicular to the trimming direction, you can trim two cut trajectories at the same time.

As in the first embodiment, trimming with higher precision is possible without sacrificing processing speed.

Note that with this configuration, the laser shot can be performed only when the beam is deflected in a direction perpendicular to the trimming direction, even if the trimming direction has changed.

Simply the phase relationship of the laser shot to the rotation of the motor,
That is, since it is only necessary to change the time relationship, a laser trimming device capable of trimming in any direction can be constructed.

By the way, in the present invention, high-speed trimming is achieved, but if low-speed trimming is acceptable, the first
Alternatively, the same effect can be achieved by simply controlling the two-axis beam scanners 23 and 24 to vibrate in a direction other than the trimming direction without adding the third scanning means as in the second embodiment. It is possible to obtain effective effects.

In each of the above embodiments, the laser oscillator 1 is Nd:
Although a YAG laser is used, other lasers can be used as long as they have a peak output of the same level or higher.

Furthermore, the scanning optical system 2 may be a combination other than a biaxial beam scanner and an f-theta lens; for example, a combination of a biaxial linear motor and an ordinary condensing lens is also possible.

If the controller 6 uses a microcomputer,
Beam position control, measuring instrument control, etc.

Necessary control functions can be easily achieved. Moreover, this control function can also be constructed by assembling a logic circuit using only electronic circuits.

[Effects of the Invention] As explained above, in the laser trimming device of the present invention, while alternately shooting a plurality of cuts,
Trimming of the double track cut is being carried out in parallel, and as a result, the depth of cut is shallower than before, which reduces the effects of changes in physical properties due to residual thermal effects and the occurrence of microcracks.

Since the bite size can be increased, excess heating during laser shot is reduced. Moreover, when looking at each cut, the shot time interval is doubled, and the resistance value can be measured in a more stable state.

Therefore, compared to trimming with a single straight cut,
Higher precision trimming is possible without sacrificing machining speed.

Another case is when the double line cut according to the present invention is used.

Since the power concentration generated at the cutting tip is considerably low and the local heat generation is reduced, there is an advantage that long-term stability during use can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a laser trimming device according to an embodiment of the present invention, FIG. 2 is a diagram showing a trimming locus, FIG. 3 is a diagram showing the relationship between cut length and resistance value change, and FIG.
5 and 5 are configuration diagrams of scanning optical systems used in the first and second embodiments of the present invention, respectively. 1... Laser oscillator, 2... Scanning optical system, 5.
...Resistance measuring device, 6... Controller, 25... Resonance type galvanometer scanner, 26... Rotating machine type beam scanner. Figure 1 Cut depth full width

Claims (3)

[Claims] 1. Focusing a laser beam emitted from a laser oscillator onto a substrate to be processed, trimming a resistor on the substrate to be processed,
A laser trimming device for adjusting the resistance value of the resistor to a predetermined resistance value includes a scanning optical means for condensing the laser emitted light and scanning at a predetermined synchronization, and a scanning optical means for scanning the laser oscillator at the period. What is claimed is: 1. A laser trimming device comprising: control means for synchronously controlling the drive, and forming a plurality of cut loci on the resistor. 2. In claim 1, the scanning optical means includes a first scanning means that receives the laser emitted light and scans in a predetermined direction at the predetermined period; 1. A laser trimming device comprising a condenser that receives emitted light, deflects the emitted light, and condenses the emitted light. 3. In claim 1, the scanning optical means includes a first scanning means that receives the laser emitted light and scans at the predetermined period along a predetermined circumference; 1. A laser trimming device comprising a condensing means that receives the emitted light from the means, deflects the emitted light, and condenses the emitted light.