JPH1128592A - Laser beam machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of machining precision caused by temp. variation of a material to be machined. SOLUTION: In a laser beam machining device, a temp. adjusting mechanism 18 for keeping the temp. at the constant, is arranged in a holder 2 for holding the material to be machined (wafer 1). Further, a temp. adjusting mechanism 19 for keeping the temp. at the constant, is arranged in a waiting part 14 for waiting the wafer before machining. Then, the temp. of the wafer 1 set to the holder 2 is adjusted to the setting temp. value. Consequently, the wafer is not gradually displaced caused by the temp. difference and the machining can be executed while keeping the precision.

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 fine processing by irradiating a predetermined position on a wafer on which semiconductor devices are formed with a laser. In particular, the present invention relates to a laser processing apparatus improved to prevent a reduction in processing accuracy due to a change in temperature of a workpiece.

[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.

A fuse in such a semiconductor device is generally a thin line made of polysilicon or aluminum. A laser beam from a processing laser light source such as a YAG laser is condensed and irradiated to the fuse, and the material constituting the fuse is heated and evaporated by light energy to remove the fuse, thereby cutting the fuse. The fuse is usually formed under 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 apparatus, 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.

[0004] Such a laser processing apparatus for processing semiconductor devices is installed in an enclosure for blocking laser light harmful to the human body. The loading and unloading of the wafer into and out of the laser processing apparatus is performed through a carrier chamber having double doors at the front and rear. Due to such a closed structure, heat is trapped in the laser processing machine, and the temperature inside the machine becomes higher than outside air. In order to release the heat, a plurality of exhaust fans are provided inside the machine to maintain a thermal balance inside the machine. It should be noted that the outside air referred to here does not mean the air outside but the air outside the enclosure of the laser processing apparatus, generally inside the factory building.

[0005]

In the conventional structure, even if the thermal equilibrium in the machine can be maintained, the temperature in the machine becomes higher than that in the outside air and becomes equilibrium. Therefore, when a wafer left at an outside air temperature is transferred into the machine and laser processing is performed, the wafer expands during the processing. as a result,
There has been a problem that the processing position coordinates calculated in the first alignment measurement are shifted during the processing, and it is not possible to accurately perform processing at a predetermined position.

[0006] In particular, in recent years, the size of the wafer has been remarkably increased.
For example, in the case of an 8-inch (200 mm) wafer, assuming that the thermal expansion coefficient of silicon is 2.6 ppm, a temperature change of 1 ° C. at the outermost circumference of 8 inches results in 0.2 m × 2.6 ppm × 1 ° C.
= 0.5 .mu.m, and a displacement of about 0.8 .mu.m on a 12-inch (300 mm) wafer, directly leading to a deterioration in processing accuracy.

In addition, when the outside air temperature fluctuates, the change in the internal temperature does not immediately follow, so that a wafer having a large temperature difference from the internal temperature is processed, and the problem of deterioration of the processing accuracy is disadvantageous. It was more likely to occur. Further, the laser processing may require about one hour per wafer, and even if there is a sudden temperature change that affects the internal temperature during the processing, accuracy deterioration is caused. Was.

In order to eliminate the dimensional change of the wafer due to the temperature change, there is a solution in which a temperature control chamber is installed in the apparatus and the temperature inside the apparatus is controlled, but the cost is increased due to additional equipment such as a temperature controller. There was a problem that would.

The present invention has been made in view of such conventional problems, and has as its object to provide a laser processing apparatus capable of preventing a reduction in processing accuracy due to a temperature change of a workpiece. I do.

[0010]

Means for Solving the Problems In order to solve the above problems, a laser processing apparatus of the present invention is directed to a laser processing apparatus for irradiating a workpiece with a laser to process the workpiece; Is provided with a temperature control mechanism for keeping the temperature constant. Alternatively, in a laser processing apparatus that performs processing by irradiating a workpiece with a laser, a temperature control mechanism that maintains a constant temperature is provided in a standby unit that waits for the workpiece before processing.

That is, a temperature control mechanism is provided in the wafer holder and / or the wafer standby section during wafer transfer, and the temperature of the wafer installed therein is set to a set value. Therefore, the processing can be performed with high accuracy without the wafer being gradually displaced by the temperature difference in the machine. Specific examples of the temperature control mechanism include a device in which a temperature-controlled liquid medium flows through a flow path and a device using a Peltier element.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view showing the overall arrangement of a laser processing apparatus and its peripheral devices according to one embodiment of the present invention.
FIG. 2 is a schematic plan view showing the overall arrangement of the laser processing apparatus of the embodiment of FIG. 1 and its peripheral devices. The laser processing apparatus main body of this embodiment includes a stage 3 movable in a horizontal plane on which a wafer holder 2 holding a workpiece 1 (a wafer in this example) is mounted, and a processing for injecting a processing laser to the workpiece 1. It comprises an optical system 4. The stage 3 on which the wafer holder 2 holding the workpiece 1 is mounted is a processing optical system 4
The workpiece 1 is moved directly below the objective lens 5, and at that position, the processing optical system 4 emits a processing beam to perform laser processing.

The laser that performs this processing is required to have a high output, and the entire laser processing apparatus and peripheral equipment are shielded by an enclosure 6 so that emitted laser light and the like do not harm the human body. ing. The enclosure 6 of the laser beam machine has a structure in which the opening is limited to the opening and the exit of the wafer carrier, and the opening is locked during processing, so as to be in a closed state. 1 and 2, a wafer carrier 7 containing unprocessed wafers is placed on a wafer carrier table 9 in a carrier chamber 8 by an operator. Thereafter, the carrier door 10 is locked by the locking means 11 in a state where the operator closes the carrier door 10 of the carrier chamber 8 and transmits a processing start command to the processing machine. Even if the laser beam is irradiated at this time, the laser beam does not leak out of the cover.

The wafer transfer device 12 extracts wafers one by one from the wafer carrier 7 and transfers the wafers to the wafer holder 2. Next, the wafer is aligned, the installation position of the wafer is measured, the processing position coordinates are calculated, and the laser processing machine starts processing. The process of transferring a wafer from a wafer carrier to a wafer holder will be specifically described. The wafer extracted from the wafer carrier 7 by the wafer transfer device 12 is transferred to the pre-alignment unit 13. At this location, the wafer is subjected to alignment before stage installation, such as positioning the orientation flat position in a predetermined direction, so-called pre-alignment. Thereafter, the wafer is transferred onto the wafer holder 2 by the wafer transfer device 12, and fine alignment for precisely measuring a processing position is performed.

In the transfer of the wafer, in order to reduce the processing time, the processed wafer is immediately replaced. For this reason, there may be a case where a waiting place 14 for waiting the wafer after the completion of the pre-alignment is provided.

As described above, a safety structure is ensured so that the laser does not leak to the outside during processing. When the processing is completed and all the processed wafers have been collected in the wafer carrier 7, the lock is released and the wafer carrier 7 can be taken out from the carrier chamber 8. If it becomes necessary to take out the wafer carrier 7 during processing, the operator sends a command to take out the carrier halfway to the processing machine, and releases the lock of the carrier chamber 8. At this time, the carrier room 8
The shutter 16 provided in the opening 15 between the wafer transfer device 12 and the wafer carrier 12 is closed, so that the laser beam does not leak even if the carrier door 10 is opened during processing, so that the laser safety is not impaired. ing.

The wafer holder is provided with a temperature control means 18, and the wafer is processed while being constantly maintained at a constant temperature. After the wafer to be processed next is pre-aligned by the pre-alignment unit 13, it waits at the standby place 14 until the processing of the first wafer is completed. The temperature control means 19 is also installed in the standby place 14, and the wafer is already at the set temperature before being transferred to the wafer holder 2,
When the processing of the first wafer is completed, the wafer is replaced with the wafer at the standby position 14 and the processing is executed.

[0018]

As is apparent from the above description, according to the present invention, since the processing is performed while the temperature of the wafer is always kept constant by the temperature control means, the wafer is transferred from the outside air having different temperatures into the processing machine. In addition, a processing error due to expansion or contraction of the wafer during processing does not occur, and high-precision processing is performed. Further, even when the outside air temperature fluctuates due to long-time processing, since the wafer temperature is kept constant by the temperature control means, the processing is performed without generating a processing error due to the temperature. Further, since a temperature controller for controlling the entire internal temperature is not required, an effect of reducing the cost of the entire laser processing apparatus can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an overall arrangement of a laser processing apparatus and peripheral devices according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing the overall arrangement of the laser processing apparatus and its peripheral devices according to the embodiment shown in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Wafer 2 Wafer holder 3 Stage 4 Optical system 5 Objective lens 6 Enclosure 7 Wafer carrier 8 Carrier chamber 9 Carrier table 10 Door 11 Locking means 12 Wafer transfer device 13 Prealignment unit 14 Standby place 15 Opening 16 Shutter 17 Fan 18, 19 Temperature Adjusting means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B23K 31/00 B23K 31/00 J

Claims (3)

[Claims] 1. A laser processing apparatus for processing a workpiece by irradiating the workpiece with a laser; a holder for holding the workpiece;
A laser processing apparatus provided with a temperature control mechanism for maintaining a constant temperature. 2. A laser processing apparatus for processing a workpiece by irradiating a laser with a laser, wherein a temperature control mechanism for maintaining a constant temperature is provided in a standby unit for waiting the workpiece before processing. Laser processing equipment. 3. The laser processing apparatus according to claim 1, wherein a temperature control mechanism for maintaining a constant temperature is provided in a standby unit for waiting a workpiece before processing.