JPH01289592A - Laser beam machine - Google Patents

Abstract

PURPOSE:To enable a positioning of high accuracy and high speed even if a comparatively inexpensive XY stage is used by making the objective lens part equivalent to the reference light side of a laser measuring machine movable. CONSTITUTION:The laser light 9 of two wavelength output of f1, f2 is separated by the polarizing prism of the interferometer 4 inside and the f1 measures the movement of an XY stage by the interferometer made in the space with the mirror 6 fitted to the XY stage 8. On the other hand, f2 is made incident on the interferometer made between the total reflection mirror 3 fitted to an objective lens 1 by the total reflection mirror 3 as a reference light. The position variation of the objective lens can be detected at the reference light side even in case of the objective lens 1 being relatively slipped to the XY stage 8 by a temp. change, etc., and the relative position of the objective lens 1 and XY stage 8 can always be measured correctly by reading the difference in the positional changes of f1 and f2 sides.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser processing device, and particularly to a laser trimmer,
The present invention relates to a laser processing device for fine patterns such as memory repair.

Description of the Related Art [Prior Art] Conventionally, there have been two methods of configuring this type of laser processing apparatus, as seen in memory repair apparatuses.

In other words, a small stroke laser beam positioner that can move the processing laser spot at relatively high speed and with high precision;
Low precision large stroke XY for step feeding the board
There are two methods: one method consists of a stage, and the other method consists of a large stroke XY stage that fixes the position of the processing laser spot and can position the entire substrate with high accuracy with respect to the laser spot. The former method is a method that has been adopted by conventional laser trimmers, and the latter method is a method that has been adopted by exposure apparatuses.

[Problem to be solved by the invention]

Of the two conventional configuration methods mentioned above, @'s method has low accuracy in feeding the board chip by chip.
An alignment operation is required to align the laser spot and the chip pattern for each chip, and although processing within the chip can be performed at high speed, there is a problem that alignment takes time.

On the other hand, the latter method has high accuracy, but uses an XY stage with a large stroke, so there is a problem in that the moving speed of the stage is low. However, the latter method allows alignment of the entire substrate at once and without stopping the stage.

By controlling the processing point so that it passes through the processing laser spot position one after another, throughput is also improved, and because a laser length measuring device is used on the position side, the former method is better. Compared to conventional methods, essentially high-precision machining has been achieved.

For this reason, the latter method is attracting more attention in the processing of increasingly finer IC wafer patterns.

This method uses a fixed-position laser spot and a high-precision, large-stroke XY stage.

Although it is excellent for processing fine patterns, it has problems in that it is difficult to manufacture a precision XY stage and it is expensive.

The method of configuring a high-precision XY stage involves placing a high-precision XY stage on top of a stage that performs large movements with low precision.

There is a two-stage configuration with a fine movement stage that moves over a small distance, and a method that achieves high precision with a single stage.

In both methods, a laser length measuring device is generally used to measure nine positions. Both of these two methods of configuring the XY stage have complicated structures and are difficult to manufacture, making them expensive.

The present invention is an attempt to solve these problems of the conventional apparatus, and provides a laser processing apparatus that is capable of high-precision, high-speed positioning even when using a low-precision XY stage.

[Means to solve the problem]

According to the present invention, a means for condensing a laser beam onto a surface of a workpiece, a stage on which the workpiece is placed and moved two-dimensionally;
There is obtained a laser processing apparatus having a laser length measuring device as a position measuring means of the stage, characterized in that the light focusing means is provided with means capable of relative movement with the stage. .

[Principle of the invention]

In the present invention, a laser length measuring device is used for position measurement.

A method is used to measure the relative position of an L-shaped mirror provided on the XY stage side and a reference beam mirror provided on the processing optical section side. This is a method commonly used in exposure equipment, etc., as a means to correct relative positional deviations caused by temperature changes between a fixed projection optical system and an XY stage. The position is corrected by

The principle of this method will be explained with reference to FIG.

The laser length measuring device that is most commonly used today uses a two-wavelength output laser with orthogonal polarization directions and slightly different wavelengths, one of which is used as a reference beam, and the other with a reflective Changes in position are read by counting the beats between reflected light that enters an interferometer constructed between the body and a fixed interference unit, and undergoes a Doppler shift due to the movement of the object.

In FIG. 1, a laser beam 9 with a two-wavelength output f1f2 is separated by a polarizing prism in an interferometer 4, and +fl is separated by a polarizing prism in an interferometer 4. Measure movement. On the other hand, 1 f2 enters the interferometer 4 constructed between the total reflection mirrors 3 attached to the objective lens 1 through the total reflection mirror 3 as a reference beam. In this method, the objective lens section 1
Even if the objective lens shifts relative to the XY stage 8 due to temperature changes, etc., the position change of the objective lens can be detected on the reference light side, and the difference between the position change on the +f1 side and the f2 side is read by the detector 5.

The relative position between the objective lens 1 and the XY stage 8 can always be accurately measured.

In the present invention, this principle is adopted as is, an inexpensive and low-precision XY stage is used as the XY stage, and an XY moving mechanism is provided in the objective lens section in order to determine the relative position with respect to the objective lens with high precision. Therefore, in addition to the movement of the low-accuracy XY stage capable of high-speed positioning, the weight of the movable objective lens section whose position is required to be changed using the reference beam f2 is reduced.

By enabling high-speed movement, it becomes possible to achieve high-speed, high-precision positioning while using a low-cost, low-precision stage.

〔Example〕

Next, one embodiment of the present invention will be explained according to examples.

FIG. 2 is a block diagram of an embodiment of the present invention.

In this embodiment, the objective lens is moved to correct the accuracy of the XY stage. Therefore, the moving distance of the objective lens is within a very small range. - For example, if the XY stage accuracy is ±10 μm over the entire movement range, the movement range of the objective lens section is approximately ±20 μm.

In FIG. 2, a HeNθ laser generator 101 for length measurement
The laser beam emitted is divided into Y-axis and Y-axis beams. After being split, the Y-axis laser beam enters a total reflection mirror 107 and is split into two wavelengths inside an interferometer 109. The laser beam of one wavelength is transmitted to the Ll mirror 114 fixed to the XY stage moving part.
The laser beam of one other wavelength is reflected by the total reflection mirror 105 and used to measure the displacement of the X-coordinate reference mirror 111 fixed to the objective lens 102. After the XY stage 115 moves and stops with accuracy within the stage's ability, it is moved using the X-axis piezo element 106, which is the objective lens side drive mechanism, to compensate for the error from the relative distance between the target XY stage and the objective lens. Remove by letting

On the Y-axis side, similarly, the divided laser beam enters the Y-axis interference needle 110 by the total reflection mirror 108.

Two wavelengths are divided, one wavelength is used to measure the distance between L and the mirror 114, and the other wavelength is reflected by the total reflection mirror 106 and reflected by the mirror 1 attached to the objective lens 102.
It is used to measure the displacement between 12 and 12. Position correction in the Y-axis direction exceeding the accuracy of the XY stage is performed by moving the objective lens 102 with the Y-axis piezo element 104.

With the above method, although the accuracy of the XY stage is low, the overall positioning accuracy can be reduced to 0.3 by correcting the movement of the objective lens.
It can be increased to approximately μm (2σ). Furthermore, since the piezo element has a fast response speed, high-speed positioning is possible.

FIG. 3 is a block diagram of a second embodiment of the present invention. A length measuring laser beam incident on a total reflection mirror 202 from a direction perpendicular to the plane of the paper is separated into two wavelengths by an interferometer 203. The laser beam of one wavelength is placed on the stage 209 of the XY stage 210.
It is used to measure the movement of the L-shaped mirror 205 fixed to the.

The other wavelength is reflected by the total reflection mirror 201.

It is used to measure the movement of the reference beam mirror 204 attached to the objective lens 206 at the tip of the beam positioner 207.

Although FIG. 3 only shows the X-axis portion of the XY position measurement system, the Y-axis portion also has a similar configuration.

This example shows a case where the present invention is applied to a laser trimmer having a beam positioner. The XY stage 210 only performs step feeding between chips of the wafer 208. Therefore, although it moves at high speed, the accuracy of one positioning is ±10μ.
A stage with a low precision of about m is used. On the other hand, cutting and trimming of circuits, fuses, etc. within the chip is performed on the beam positioner 207 side. The possible range of the beam positioner 207 is 20X2Qmm' which can cover the chip size.
However, by using a linear motor as a drive source and reducing the weight of the movable parts, high-speed and highly accurate positioning is possible.

When the wafer 208 is stepped chip by chip,
Although the positional accuracy of the Y stage alone is low, the relative position of the objective lens at the tip of the beam positioner with respect to the XY stage is accurately known by the laser length measuring device. Also, the laser beam is always focused on the optical axis of the objective lens.

This makes it possible to position the focused spot of the radar with respect to the pattern on the wafer with high precision.

As explained above, in the embodiment shown in FIG. 3, laser processing with a higher throughput can be achieved while maintaining the same level of high accuracy as compared to the example shown in FIG.

〔Effect of the invention〕

As described above, in a laser processing apparatus equipped with a laser length measuring device, by making the objective lens section corresponding to the reference light side of the laser length measuring device movable, large and low-precision movements can be performed on the XY stage side. This is because high accuracy and small movements can be performed on the objective lens (beam positioner) side.

High accuracy even when using a relatively inexpensive XY stage.

This has the effect of realizing a laser processing device capable of high-speed positioning.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of distance measurement using a laser length measuring device.
FIG. 2 is a block diagram of a first embodiment of the present invention, and FIG. 6 is a block diagram of a second embodiment of the present invention. Explanation of symbols: 1 is the objective lens, 2 is the mirror for the objective lens, 3 is the total reflection mirror, and 4 is the interferometer. 5 is a detector, and 6 is a mirror for the XY stage. 7 is a substrate, 8 is an XY stage, and 9 is a laser beam. 101 is a HeNe V-za, 102 is an objective lens, 10
3 is an X-axis piezo resistor, and 104 is a Y-axis piezo element. 105 to 108 are total reflection mirrors, 109 is an X-axis interference needle, 110 is a Y-axis interference needle, 111 is an objective lens X-coordinate reference mirror, 116 is a stage, 114 is an L-shaped mirror, and 115 is an XY stage Each of them is hailing. Fig. 1 1 Objective lens 5 Detector 2
Objective lens mirror 6-XV stage mirror 3 Total reflection mirror 71 & plate 4 Thousand pedometer 8-XY stage 9 Laser beam Fig. 2

Claims (1)

[Claims] 1. A laser processing apparatus having a means for condensing laser light onto a surface of a workpiece, a stage on which the workpiece is placed and moves two-dimensionally, and a laser length measuring device as a means for measuring the position of the stage, A laser processing apparatus characterized in that the light condensing means is provided with means capable of moving relative to the stage.