JPS635891A - Laser trimming device - Google Patents

Abstract

PURPOSE:To improve the processing capacity by providing a scan unit for moving a laser light onto a memory IC to be worked, and also, providing a trigger generating unit for blowing a target fuse. CONSTITUTION:A scan unit 1 for loading a wafer stage 2 and a memory IC wafer 3 to be worked is provided, and also, the unit 1 is controlled by a scan unit controller 5 so that a laser optical system 4 passes through successively on plural target fuse coordinates of the IC wafer 3. When an output 13 of a position detector 6 of the unit 1 has coincided with a latching circuit output 12 of a trigger generating unit 8, a trigger signal 15 is inputted to a laser controller 14, and a target fuse is blown by generating a laser pulse from an oscillator 16. A scan is executed without stopping the unit 1, therefore, acceleration and deceleration become unnecessary, and the processing capacity is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser trimming device, particularly a laser trimming device for glue dundancy, which uses a laser to blow out fuses of defective addresses in highly integrated memory ICs and replaces them with spare addresses. Regarding.

[Prior Art] Conventionally, this type of laser trimming apparatus has a laser oscillator, a wafer stage on which a memory IC wafer to be processed is placed, and a laser optical system from the laser oscillator to image formation on the wafer. a scanning unit that moves the laser optical system to an arbitrary position on the memory IC wafer to be processed; a detector that detects the coordinates of the laser optical system on the memory IC wafer to be processed; and a trigger generation unit that generates a trigger signal to the laser oscillator when the laser optical system comes to rest on the target fuse coordinates.

The scanning unit moves the laser optical system to the target fuse coordinates of the target chip based on the intra-wafer coordinates of the chip to be processed and the fuse coordinates to be cut within the chip, which are obtained by measuring each chip on the wafer with a memory tester. Then, the laser optical system is stopped at the target fuse coordinates by the position control unit, and when the laser optical system is stopped at the target fuse coordinates, the trigger generation unit issues a trigger signal to the laser oscillator to generate a laser pulse and blow the target fuse. Usually, there are a plurality of fuses to be cut in one chip, so after one fuse is blown, the scan unit moves to the next fuse and processes it in the same way.

[Problems to be Solved by the Invention] The conventional laser trimming device described above uses a scanning unit to move the laser optical system to the coordinates of each fuse to be cut, and a position control unit to stop the laser optical system on the target fuse coordinates. When the target fuse is stationary on the target coordinates, the trigger generation unit issues a trigger signal to the laser oscillator to oscillate a laser pulse to blow the target fuse, so in order to blow the second fuse after blowing the first fuse, First, after the first fuse is blown, the scan unit is accelerated, moved at a constant speed toward the second fuse coordinate, decelerated in the vicinity of the second fuse coordinate, and moved toward the second fuse coordinate. After accurate positioning of the laser optical system, the second fuse is blown by the subsequent laser pulse oscillation. FIG. 3 is a time chart of the speed of the scan unit after the first fuse is blown until the second fuse is blown in a conventional laser trimming device. The time Ta required from blowing the first fuse 'l to blowing the second fuse 2 is equal to the time 3Ti required for accelerating the scanning unit and the movement at a constant speed toward the coordinates of the second fuse. Time used for 4TC
1. The time required for deceleration of the scanning unit near the second fuse coordinate, 5Td, and the time required for accurate positioning of the laser optical system on the second fuse coordinate, 6T.
It is S. Assuming that the distance between the first and second fuses is L, the acceleration of the scan unit when accelerating is αi, the maximum speed of the scan unit is V1, and the acceleration of the scan unit when decelerating is αd, the first fuse is blown 1. The time Ta required to blow the second fuse after blowing 2 is as follows: Ta=Ti+Tc+Td±Ts =L/V+V/ (2・αi) +V/(2・αd)+Ts ・・・・・・■ becomes.

Generally, in order to improve the throughput of a laser trimming device, it is necessary to shorten the time required to move the scan unit. To do this, a large torque motor or the like is used to increase the acceleration α1. Measures are taken to increase αd and maximum maximum speed. However, there are limits to the acceleration and maximum speed that can be achieved due to dimensions, precision, etc. Furthermore, since the scan unit itself has mass, it is difficult to eliminate the time TS required for accurate positioning of the laser optical system on the fuse coordinates. Therefore, there is a limit to the improvement in the throughput of conventional laser trimming devices.

[Differences between the invention and the prior art] In contrast to the conventional laser trimming device described above, in the present invention, the scanning unit does not stand still but moves at a constant speed over the fuse, and when it is located on the target fuse coordinates, the scanning unit is activated by the trigger generation unit. It has a structure that emits a trigger signal to the laser excavator to excavate the laser pulse and fuse the target fuse, causing the scanning unit to accelerate,
It has the original content of eliminating the time Ti and Td required for deceleration and the time TS required for accurate positioning of the laser optical system on the target fuse coordinates.

[Means for solving the problems] The laser trimming device of the present invention includes a laser excavator,
a wafer stage on which a memory IC wafer to be processed is placed; a laser optical system from the laser excavator to image formation on the wafer that forms a laser beam onto the wafer;
A scan unit of the wafer stage or the laser optical system that moves the laser beam imaged by the laser optical system to an arbitrary position on the processed memory IC wafer, and a detector that detects the position coordinates of the scan unit. and a trigger generation unit that issues a trigger signal to the laser oscillator when the laser optical system is positioned on the target use coordinates of the processed memory IC wafer.

[Example] Next, an example of the present invention will be described with reference to the drawings.

(Example 1) FIG. 1 shows a first example of the present invention. A wafer stage 2 and a memory IC wafer 3 to be processed are mounted on a scanning unit 1, and the scanning unit 1 scans the memory IC wafer 3 to be processed so that a laser optical system 4 sequentially passes over a plurality of target fuse coordinates. It is controlled by a unit controller 5. -Generally;
Most of the address switching fuses of memory ICs using redundancy technology are arranged in a line in the X direction or Y direction within the chip, and their coordinates are known in advance. Therefore, the scan unit controller 5
The above-mentioned control of the scanning unit 1 can be easily realized by using a CPU or the like based on fuse arrangement information given in advance. X of scan unit 1
.

A sensor 7 of a position detector 6 (for example, a laser interferometer) is located on the Y axis, and the position detector 6 constantly outputs the coordinates of the scan unit 1. In the trigger generation unit 8, the coordinates of the target fuse are latched into the target coordinate latch circuit 10 by the controller 9.

- The output circuit 11 outputs a trigger signal @15 to the laser controller 14 when the output 12 of the target coordinate latch circuit 10 and the output 13 of the position detector 6 match. The laser controller 14 outputs a Q-switched drive signal 17 to, for example, an Nd YAG Qswitched cw laser oscillator 16 in response to a trigger signal 15, and the laser oscillator 16 generates a laser pulse.

This laser pulse is imaged onto the target fuse by the laser optical system 4 and blows the fuse.

Naturally, the time from when the minus number detection circuit 11 detects the coincidence between the output of the position detection circuit 6 and the output 12 of the target coordinate latch circuit 10 until the laser pulse is generated from the laser oscillator 16 is shorter than that of the conventional technology. Since it is sufficiently small compared to the moving speed of the scan unit 1 that can be realized by
The laser pulse is precisely imaged onto the target fuse.

(Embodiment 2) FIG. 2 shows a second embodiment of the present invention. A memory IC wafer 18 to be processed is mounted on a wafer stage 17 . The laser optical system 19 is mounted on a scan unit 20, and the scan unit 20 is controlled by a scan unit controller 21 so that the laser optical system 19 sequentially passes over the coordinates of a plurality of fuses to be blown on the memory IC wafer 17 to be processed. Ru. X of scan unit 20.

A sensor 23 (for example, an encoder) of a position detector 22 is located on the Y axis, and the position detector 22 constantly outputs the coordinates of the laser optical system 19. The trigger generation circuit 24 is CP
The CP LJ 25 always takes in the output 26 of the position detector 22, and outputs a trigger signal 28 to the laser controller 27 when it matches the target fuse coordinate given in advance.

The laser controller 27 is triggered by the trigger signal 28.
For example, a Q-switched drive signal 30 is output to a Nd YAG Qswitched cw laser oscillator 29, and the laser oscillator 28 generates a laser pulse. This laser pulse is imaged onto the target fuse by the laser optical system 19 and melts the fuse.

[Effects of the Invention] As described above, the laser trimming device of the present invention scans the processed memory IC wafer with the scan unit without stopping on the target fuse coordinates, and when the laser optical system is located on the target fuse coordinates, Blow out the target fuse with a laser pulse. In the laser trimming device of the present invention, the maximum speed of the scanning unit is V, and the distance between the first fuse and the second fuse is L.
Then, the time required from blowing 1 of the first fuse to blowing 2 of the second fuse is Tb
is Tb=L/V .
2・αd) ・・・・・・ Shortened by ■.

As described above, the laser trimming apparatus according to the present invention can realize processing with clearly higher throughput than conventional laser trimming apparatuses.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention, and FIG. 3 is a time chart showing the scanning unit speed of a conventional laser trimming apparatus. 1.20...Scan unit 2.17...Wafer stage 4.19...Laser optical system 6.22...Position detector

Claims (1)

[Claims] (1) A laser trimming device for cutting defective address relief fuses of memory ICs includes a laser oscillator, a wafer stage on which a memory IC wafer to be processed is placed, and a laser beam from the laser oscillator that focuses laser light onto the wafer. a laser optical system up to image formation; a scanning unit for the wafer stage or the laser optical system that moves the laser beam imaged by the laser optical system to an arbitrary position on the processed memory IC wafer; and the scanning unit. The invention is characterized by comprising a position detector that detects the position of the unit, and a trigger generation unit that issues a trigger signal to the laser oscillator when the laser optical system is located on the target fuse coordinates of the processed memory IC wafer. Laser trimming device.