JPH07236989A - Device for laser beam processing - Google Patents

Abstract

PURPOSE:To continuously execute the precise processing without any mistakes by obtaining the difference between the positional data where the position of a plurality of specific points on the surface of a work is preliminarily and precisely measured and the data on the position of the specific points of a new work, and making the alarm signal when the difference in the data exceeds the allowable value. CONSTITUTION:A reflected light detecting part 35 receives the positional data of the specific points of three or more positioning marks 40, and stores them in a storing means 52. An arithmetic means 53 operates the distance of movement and the rotational angle of a beam positioner 30 or a wafer stage 12 based on the measured positional data and the data on the reference value of the point. The operated results are stored in the storing means 52, and the signal is transmitted to the beam positioner 30 or the wafer stage 12 to modify the position. A comparing means 54 compares the difference in the data, and judges whether or not the alarm is made, and alarm is provided when a judgement is made that the positional accuracy of the device is deviated from the allowable value.

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 which can be used for defect relief and fine processing at a manufacturing site of, for example, an IC memory, and more particularly to a technique for aligning a workpiece. As described above, although the present invention is a technique of position accuracy of a high precision laser processing device,
The memory repair technology will be mainly described.

[0002]

2. Description of the Related Art The progress of semiconductor manufacturing technology is remarkable,
The memory capacity of the C memory is increasing day by night, and the integration density of ICs is becoming higher and higher. Along with this, the circuit pattern is miniaturized, the size of the defect is also miniaturized, and the number of defects is dramatically increased. Therefore, securing the yield is an important issue. Therefore, a repair (defect repair) technique has been widely used in which a spare redundant cell is configured in advance in an IC chip and a normal memory cell has a defect and is switched to the redundant cell. A laser processing device is used as the means.

The repair technology uses laser processing equipment.
A laser beam is converged and irradiated to a fusing part such as a fuse provided in a chip of an IC memory, and the fusing part in the IC chip is cut and repaired.

An example of a conventional repair technique will be outlined with reference to the drawings. FIG. 2 is a process flow diagram before and after repair.
Before the repair process, preliminary testing is performed in the wafer state using an IC tester, and the address of the repairable chip and its defective data line is checked for each wafer to obtain data.
In the laser processing apparatus, using the above-mentioned measurement data for the wafer, the predetermined fuses of predetermined chips are blown one after another.
When the repair is completed, all chips are tested by this testing to determine whether they are good or bad, and IC chips are selected.

FIG. 3 is a block diagram of a laser processing apparatus. The workpiece 10 (hereinafter referred to as “wafer 10”) is stored in a predetermined position on the loader side of the loader / unloader 11 and is pre-aligned (rough alignment in X, Y, θ directions), and then is transferred from the loader to the wafer stage 12. It is automatically transported. Wafer alignment (intermediate alignment in X, Y, and θ directions) is performed by the TV camera 14 on the way,
Move to the working area.

In the wafer alignment detection optical system 13, alignment illumination light is illuminated from the illumination light source 15, focused on the wafer 10 by the objective lens 20 through the mirror 17, half mirrors 18 and 19, and the reflected light is reflected by the half mirror. The image is formed through 18, the mirror 21, and the lens 22, and the image is recognized by the television camera 16. By this image recognition, the positional deviation of the wafer 10 in the X, Y, and θ directions is calculated, and the calculated data is sent to the wafer stage 12 and aligned at a predetermined position.

The beam positioner 30 is a mechanism for positioning the laser beam at a predetermined fuse position in the chip with high speed and high accuracy. For example, the XY stage drives the XY stage at high speed with a linear motor. The X / Y stage position is detected by an optical linear scale. In this method, the objective lens 20 is mounted on the beam positioner 30. The movable range of the beam positioner 30 is slightly larger than the chip size.

When the wafer 10 is aligned at a predetermined position on the wafer stage 12, the laser oscillator 31 initially emits a weak laser beam, for example, a continuous wave laser beam, and the laser processing optical system 32, the mirrors 33 and 19 are emitted. The laser light is focused on the wafer 10 by the objective lens 20 through. The position of the fuse is confirmed by the reflected light, and the fuse is blown by the next strong laser light, for example, pulsed laser light having accumulated energy. That is, first, a weak laser beam is scanned in the vicinity of the chip alignment target, the reflectance is detected by one or two sensors, the target position is calculated, and the relative positional relationship between the target and the fuse given in advance is also calculated. Then, the emission port of the beam positioner 30 is moved to the fuse position, laser light of cutting power is irradiated, and the beam is cut. Scanning of the laser light near the target and movement to the fuse position are performed by movement of the beam positioner 30.

[0009]

As described above, in the repair technique in the laser processing apparatus, precise alignment is an important point because a minute point is irradiated with laser light. Therefore, there has been a term of position accuracy in the specifications of laser processing devices, and the position accuracy of recent specifications is 0.
It is about 5 μm. Since it is such a minute interval that cannot be visually determined, in order to suppress the position accuracy to about 0.5 μm, use a special wafer or special jig with a special adjustment method, and measure it only if you have been specially trained. Or it cannot be judged or adjusted. The position accuracy is a numerical value peculiar to the device which is a precision device. However, this positional accuracy may shift due to changes over time.

On the other hand, the operator of the repair technique tends to completely trust the laser processing apparatus in terms of positioning because the laser processing apparatus automatically performs alignment. Even if the positional accuracy of the apparatus deviates slightly, it is often considered that it is specific to the wafer of the lot, because it is cleared by the size and thickness of the wafer, or the warp and distortion. In fact, in many cases, there is a misalignment unique to the wafer. However,
Even if the initial use is right, the positional accuracy of the device may deviate due to the change over time as the number of times of use overlaps. Even in such a case, if the operator believes that the device is correct and irradiates the laser beam, the operator may cause a blow failure of the fuse.

According to the present invention, when the positional accuracy shift caused by the laser processing apparatus is caused as described above, an alarm signal is automatically generated before making a mistaken operation, so that the apparatus can be used. (EN) A laser processing apparatus which is interrupted, informs an alarm to an operator, and gives an instruction to perform adjustment and adjustment of position accuracy again.

[0012]

In order to achieve the above-mentioned object, the present invention is, in the above-mentioned conventional apparatus, data and position of target position detection by a weak laser beam performed by a beam positioner before irradiation of a cutting laser beam. It is configured to compare the specified value data measured at the time of accuracy adjustment and generate an alarm signal if the specified value data deviates by more than a certain value. Here, the constant value varies depending on the type of IC, for example, the degree of integration, the pattern, the structure, etc.
With a certain IC memory, an alarm may be issued when the deviation from the specified value data is 2% or more. The details will be described below.

The positioning of the IC wafer or IC chip is generally corrected by the X-direction scale factor, the Y-direction scale factor, and the X-direction rotation angle and the Y-direction rotation angle in the coordinates of the substrate. Here, the scale factor is a magnification with respect to a unit length, and the X-direction rotation angle is a line drawn in the X-axis direction and how many times it is deviated from. The Y-direction rotation angle also refers to the angle of deviation from the Y-direction line. A positioning mark is always printed on the IC wafer or the IC chip. Image recognition by the television camera or target position detection by the detection unit is first performed using this positioning mark.

In the system control section of the laser processing apparatus, the image recognition or the calculation of the target position in the detection section is performed by comparing the measured data with, for example, reference value data obtained at the time of position accuracy adjustment, The position is calculated by calculating whether or not the position is deviated, and sending the difference data to the wafer stage or the beam positioner to correct the position. Therefore,
It is advisable to constantly monitor the position correction data that is the difference data, and generally generate an alarm signal when the gradually changing data becomes abnormal data that deviates from a certain value. Examples will be described below.

[0015]

EXAMPLE FIG. 1 shows an example of the present invention. The parts corresponding to those in FIG. 3 are designated by the same reference numerals. In addition, this embodiment is an example in which the alignment mark 40 of the wafer 10 is used to perform the alignment. The wafer 10 is wafer-aligned on the wafer stage 12 at a predetermined position. next,
System control unit 50 mainly composed of a computer
A weak laser beam is emitted from the laser oscillator 31 by the control signal from the control means 51. The weak laser light is reflected by the mirror 34,
It is converged on the wafer 10 by the objective lens 20 through the half mirrors 33 and 19. The weak laser light is reflected on the wafer 10, and the position thereof is detected in the reverse direction through the objective lens 20, the half mirrors 19 and 33 by the reflected light detection unit 35. At this time, a weak laser beam is slightly scanned to select a specific point.

The reflected light detecting section 35 obtains position (coordinate) data of specific points of the positioning marks 40 of three or more points and stores the position data in the storage means 52. Storage means 5
In 2, all reference value data of the positioning mark 40, for example, reference value data obtained at the time of position accuracy adjustment are all stored.

The calculating means 53 calculates the moving distance and the rotation angle of the beam positioner 30 or the wafer stage 12, that is, the scale factor and the rotation angle in the X and Y directions, based on the measured position data and the reference value data at that point. . The calculation result is stored in the storage means 52 and a signal is transmitted to the beam positioner 30 or the wafer stage 12 for position correction. Further, the calculation means 53 calculates the mutual relation of the position correction data to check the deviation of the position accuracy of the device.

An example of a device position checking method will be described.
One is a method in which a slight absolute value movement of the beam positioner 30 or the entire wafer stage 12 is set, and judgment is made by a relative value of the X axis and the Y axis. For example, an alarm signal is generated when the difference between the X-axis and Y-axis scale factor deviations is 2% or more. The alarm signal may be determined to be when the difference between the X-axis rotation angle and the Y-axis rotation angle is 2% or more. Alternatively, an alarm signal may be issued in the case of a logical product of the two. Alternatively, the data at the time of the first wafer in the wafer manufacturing lot may be used as a reference to compare the data with subsequent wafers, and if the difference becomes 0.1% or more, it may be determined to be an alarm. In essence, it is advisable to determine the degree of deviation of the device based on the positional accuracy unique to the device, the processing accuracy of the workpiece, the processing efficiency, and the like.

The comparison means 54 is means for comparing the difference between the above two data and determining whether or not an alarm is issued. An alarm is generated when it is determined that the position accuracy of the device has deviated from the allowable value.

The alarm means 55 is means for notifying an alarm and interrupting the processing. To inform the alarm, a sound may be emitted, a lamp may be turned on, or a display department may display.

The control means 51 controls not only the system controller 50, but also the laser oscillator 31 and the reflected light detector 3.
5. Control of the system is performed by exchanging signals with the beam positioner 30, the wafer stage 12, etc., but the control of the present invention is also performed.

Up to now, the discovery of the deviation of the position accuracy of the laser processing apparatus due to the change with time has been described focusing on the repair technology of the IC memory, but the present invention is not limited to the laser processing apparatus of the IC memory. It should be additionally noted that the invention is an invention for finding a deviation in the positional accuracy of a precise laser processing device.

[0023]

As described above, the present invention automatically calculates and finds the deviation of the position accuracy of the high-precision laser processing device which is more than the allowable value due to the change with time, in accordance with the situation,
Since the alarm is issued, the operator of the processing apparatus can continuously perform precision processing without making any mistakes, so that its technical and economic effects are great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a conventional process flow diagram before and after repair.

FIG. 3 is a basic block diagram of a conventional laser processing apparatus.

[Explanation of symbols]

 10 Wafer 11 Loader / Unloader 12 Wafer Stage 13 Wafer Alignment Detection Optical System 14 TV Camera 15 Illumination Light Source 16 TV Camera 17 Mirror 18, 19 Half Mirror 20 Objective Lens 30 Beam Positioner 31 Laser Oscillator 32 Laser Processing Optical System 33 Half Mirror 34 Mirror 35 Reflected light detector 40 Alignment mark

Claims (1)

[Claims] 1. A position data of a workpiece (10), comprising a laser oscillator (31), emitting weak light and receiving the reflected light by a reflected light detector (35) before performing laser processing. In the laser processing apparatus for performing laser processing by correcting the position of the workpiece (10) to the correct position based on the position data, and a new position data obtained by precisely measuring a plurality of specific points on the surface of the workpiece (10) in advance. Storage means (52) for storing the data of the positions of the plurality of specific points of the work piece (10) measured by the reflected light detection unit (35), the position data precisely measured in advance and the reflected light detection unit ( Comparing with the data measured in 35), the calculating means (53) for obtaining the difference data of the both, the comparing means (54) for judging whether the difference data is within a preset allowable value, the comparison The judgment by means (54) is And alarm means for generating an alarm signal when a volume value outside (55), the laser processing apparatus characterized by comprising a control means of the system (51) for controlling the above.