JPH1190659A - Laser repairing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately cut a fuse, even if the pitch of adjacent fuses becomes short due to the high integration of the device, by using as a laser beam source a harmonic of specific times as high as YAG or YLF laser. SOLUTION: A harmonic of three times or four times as high as YAG or YLF laser is used. A laser beam outgoing from YAG laser 61 passes through a nonlinear crystal 63 to become a fundamental laser and a harmonic of two times higher. Further, the laser beam 61, passing again through a nonlinear crystal 65, turns to a fundamental beam, harmonics of two times higher and of three times higher. Since a dichroic mirror 67 reflects the fundamental beam and the harmonic of two times higher, the laser beam 61 becomes only the harmonic of three times higher. A machining laser beam 1' emitted from a machining laser beam source 1 is adjusted in the light quantity by a quantity-of- light adjusting part 2, and the cross section shape is formed by a variable aperture 3. The machining laser beam 1' is reflected by the dichroic mirror 4 and converged on the machining point of a work 7 by an objective lens 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defective memory cell in which a defective memory cell is replaced with a spare memory cell by cutting a fuse by a laser when a memory cell in the semiconductor memory chip has a defect. The present invention relates to a laser repair device used to rescue a chip. In particular, the present invention relates to a laser repair apparatus improved so that fuses can be cut accurately even when the pitch between adjacent fuses becomes shorter due to higher integration of devices.

[0002]

2. Description of the Related Art 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 a DRAM, a fuse is attached to each memory cell column at the time of design / manufacture, a spare memory cell column is arranged, and the fuse of the memory cell column that is found defective during inspection is cut off. The column is isolated in the device, and the spare memory cell column is replaced with the spare column by cutting a fuse for designating the address of the defective column, thereby improving the yield of the DRAM (Japanese Patent Laid-Open No. 1-2224189). No.).

A fuse in such a semiconductor device is generally formed of a thin line made of polysilicon or aluminum (example of current dimensions, width 0.8 to 1.5 μm, pitch 3 to 3 μm).
5 μm, thickness 0.3-1.0 μm, cut length 3-10 μm
). 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.

A conventional laser repair device used for such a fuse processing uses a fundamental wave (infrared light) or a second harmonic (visible light, YAG laser (wavelength 1047 nm)) or a YAG laser (wavelength 1047 nm) as a processing laser. Wavelength 1/2).

[0005]

With the recent high integration of memory devices, the number of fuses for memory cell rescue has increased drastically. In order to make effective use of the chip area, the number of fuses has increased due to the increase in fuse pitch. Supplemented by reduction. It is expected that the reduced fuse pitch will be 1-2 μm in the future. On the other hand, the current minimum irradiation beam size of the fundamental wave and the second harmonic laser is 1.5 to 1.5 due to the effect of diffraction.
The limit is about 2 μm.

FIG. 3 is a cross-sectional view schematically showing how a fuse having a fuse pitch of 1 μm is processed using a conventional laser having a beam size. In the figure, three fuses 31, 30, 31 'having a width of 0.5 μm are arranged at a pitch of 1.0 μm. This central fuse 30 is to be machined with a laser beam 32 of about 2 μm square. Thus, when the pitch of the fuses 30 and 31 is 1 to 2 μm,
When the fuse 30 miniaturized by the reduction is processed by the current laser, the size of the irradiation beam 32 is large.
The laser also hits the adjacent fuse 31, and in some cases, the adjacent fuse 31 is also processed (cut), so that the chip cannot be rescued.

The present invention has been made in view of such a problem, and provides a laser repair apparatus capable of cutting a fuse accurately even when the pitch of adjacent fuses is shortened due to high integration of devices. The purpose is to do.

[0008]

In order to solve the above problems, a laser repair apparatus according to the present invention comprises a processing laser light source,
A laser repair apparatus including: an irradiation optical system that focuses laser light emitted from the light source on a portion to be processed; and a mechanism that adjusts a focus position of the laser light to a fuse of a semiconductor device to be processed; As the processing laser light source,
A third or fourth harmonic of a YAG laser is used. Alternatively, use YLF instead of YAG laser.
The same effect can be expected by using the third harmonic or the fourth harmonic of the laser.

By using a third harmonic or a fourth harmonic of a YAG laser or a YLF laser, the size of a laser beam to be irradiated can be reduced to 1 μm or less. As a result, fuses arranged at a pitch of about 1 μm can be cut without affecting adjacent fuses.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram illustrating a configuration of a laser repair device according to one embodiment of the present invention. The laser repair device of FIG. 1A includes a processing laser light source 1, a light amount variable unit 2,
A processing laser irradiation optical system including a variable aperture 3 and the like;
It has an observation optical system including an observation light source 10, an objective lens 6, a CCD camera 12, and the like. The processing laser light source 1 is YAG
This is a laser light source such as a laser, and the wavelength or the pulse time width can be changed by a specific structure described later.

The laser light 1 ′ emitted from the processing laser light source 1 is incident on the light quantity variable section 2. The light amount variable section 2 is provided with a plurality of ND filters having different transmittances, and the laser light amount is adjusted by selectively interposing these filters in the optical path. Alternatively, the amount of light can be adjusted by interposing a polarizing filter in the optical path and rotating the filter. The laser light that has exited from the light amount variable unit 2 enters the variable aperture 3 and is shaped by the aperture 3. Both the light amount variable section 2 and the variable aperture 3 are controlled by the control section 9.

The laser beam that has exited the variable aperture 3 strikes a dichroic mirror 4 disposed at the intersection of the optical axes of the processing optical system and the observation optical system, and is largely reflected downward. The laser light reflected from the dichroic mirror 4 is
The light enters the objective lens 6 and is focused by the lens 6 on a processing point on a workpiece (wafer) 7. A part of the laser light passing through the dichroic mirror 4 is converted into a light amount monitor 5 '.
Incident on. The light amount monitor 5 ′ calculates the energy of the laser beam applied to the workpiece 8 using the average peak value of a predetermined number of pulses, and supplies the calculation result to the control unit 9.

A wafer 7 to be processed is placed on a stage 8. The stage 8 is controlled by the control unit 9
Scanning is performed in the optical axis direction (Z direction) and in the plane perpendicular to the optical axis (X, Y, θ directions).

A light amount monitor 5 is placed at an end of the stage 8. The setting of the irradiation energy is performed as follows. First, energy is monitored by the light amount monitor 5 on the stage 8,
The control unit 9 adjusts the light amount variable unit 2 so that the irradiation energy becomes appropriate energy for the workpiece 7 stored in the storage unit 9 '. The energy during processing is monitored by the light amount monitor 5 ', and the control unit 9 measures energy stability and the like.

Next, the observation optical system in the laser repair device shown in FIG. This laser repair device includes an observation light source 10 such as a halogen lamp. The observation light 10 ′ emitted from the light source 10 is
1, the light is reflected downward and illuminates the workpiece 7 through the dichroic mirror 4 and the objective lens 6 described above.
The observation light reflected from the workpiece 7 passes through the objective lens 6, the dichroic mirror 4, and the half mirror 11, and
An image of the surface of the workpiece is formed on the photoelectric conversion surface of the D camera 12. The image of the workpiece surface is displayed on the TV monitor 13 and processed by an image processing device (not shown) to be used for alignment or the like.

FIG. 1B is a block diagram showing a specific configuration example of the processing laser light source of FIG. YAG laser 51
Two nonlinear crystals 53 and 55 are arranged in series on the optical path of the laser light emitted from. These nonlinear crystals 53 and 55 are LBO, BBO, or the like, and generate double harmonics incident thereon. Therefore, the second harmonic is included in the light that has passed through the first-stage nonlinear crystal 53, and the fundamental wave is reflected by the dichroic mirror 54 disposed on the exit side of the first stage, and only the second harmonic is reflected. Pass through and enter the second-stage nonlinear crystal 55. The light that has passed through the nonlinear crystal 55 contains the fourth harmonic, the second harmonic is reflected by the dichroic mirror 57 disposed on the exit side of the second stage, and only the fourth harmonic passes. And is emitted from the processing laser light source.

As a specific configuration for generating the third harmonic, for example, as shown in FIG.
Two nonlinear crystals 63 and 65 are arranged in series on the optical path of the laser light emitted from. The light passing through the first-stage nonlinear crystal 63 includes a fundamental wave and a second harmonic, and the fundamental wave and the second harmonic are incident on the second-stage nonlinear crystal 65. The light that has passed through the nonlinear crystal 65 includes the fundamental wave, the second harmonic, and the third harmonic, and the dichroic mirror 67 disposed on the output side of the second stage generates the fundamental wave and the second harmonic. Only the third harmonic is reflected and can be emitted from the processing laser light source.

FIG. 2 is a cross-sectional view schematically showing processing of a fuse having a fuse pitch of 1 μm using the processing laser light source of the present invention. In the figure, three fuses 21, 20, 21 'having a width of 0.5 μm are arranged at a 1.0 μm pitch. This central fuse 20 is about to be processed by a laser beam 22 of about 1 μm square. In the present embodiment, the third or fourth harmonic of the YAG laser or the third or fourth harmonic of the YLF laser is used as the processing laser light source. Even when the pitch is as narrow as 1 to 2 μm, the size of the irradiation beam 22 can be reduced to 1 μm or less. Absent.

[0019]

As is clear from the above description, the beam size can be increased by using the third or fourth harmonic of the YAG laser or the third or fourth harmonic of the YLF laser as the processing laser light source. Can be reduced to 1 μm or less, so that a laser repair apparatus capable of coping with a reduction in fuse pitch in the future can be provided.

[Brief description of the drawings]

FIG. 1A is a block diagram showing a configuration of a laser repair device according to one embodiment of the present invention. (B) shows FIG.
FIG. 3 is a block diagram showing a specific configuration example of the processing laser light source of FIG.

FIG. 2 is a cross-sectional view schematically showing processing of a fuse having a fuse pitch of 1 μm using a processing laser light source according to the present invention.

FIG. 3 is a cross-sectional view schematically showing processing of a fuse having a fuse pitch of 1 μm using a conventional laser having a beam size.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Processing laser light source 1 'Processing laser light 2 Light amount variable part 3 Variable aperture 4 Dichroic mirror 5, 5' Light amount monitor 6 Objective lens 7 Workpiece 8 Stage 9 Control part 9 'Storage part 10 Observation light source 10' Observation light 11 Half Mirror 12 CCD camera 13 TV monitor 20, 30 Desired processed fuse 21, 21 ', 31, 31' Adjacent fuse 22 Irradiation beam in the present invention 32 Irradiation beam in conventional method

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01S 3/109 H01L 21/82 F

Claims (2)

[Claims] 1. A processing laser light source, an irradiation optical system for condensing laser light emitted from the light source on a portion to be processed, and a mechanism for adjusting a laser light condensing position to a fuse of a semiconductor device to be processed. A laser repair device comprising: a third harmonic or a fourth harmonic of a YAG laser as the processing laser light source. 2. A processing laser light source, an irradiation optical system for condensing laser light emitted from the light source on a portion to be processed, and a mechanism for adjusting a laser light condensing position to a fuse of a semiconductor device to be processed. A laser repair device comprising: a third harmonic or a fourth harmonic of a YLF laser as the processing laser light source.