JPS61194745A - Laser treatment equipment - Google Patents

Abstract

PURPOSE:To prevent the parts except the desired part from being damaged, by melting and evaporizing the desired part by the ultra-violet laser beam after melting and eliminating in order the materials deposited on the desired part. CONSTITUTION:On the silicon substrate 11, the isolation film 12 composed of silicon dioxide is formed, on which the wiring structure 13 composed of polysilicon is formed. When this wiring structure 13 is melted, the defective memory cell is converted to the redundant memory cell. On the wiring structure 13, the interlaminar insulation film 14 composed of silicon dioxide and the final protection film 15 of silicon nitride are formed. When the laser beam is irradiated on the wafer 2, the final protection film 15 and the interlaminar insulation film 14 are heated, melted and eliminated, because of the absorption indexes of the final protection film 15 and the interlaminar isolation film 14 are high for the ultra-violet ray laser beam 10. Accordingly, the wiring structure 13 is melted and cut by the ultra-violet ray laser beam in the opened space, and the damage of the parts except the desired part caused by the increase of internal presence and the thermal expansion of said port can be prevented.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is effective when applied to a laser processing technique, particularly a technique for heating and fusing a part of a wiring structure formed on a wafer in the manufacture of semiconductor devices using laser energy. Regarding technology.

[Background Art] For example, in the manufacture of semiconductor memories, as the capacity of the memory increases, the probability of defects occurring in individual memory cells inside the semiconductor element increases, and the probability of defects occurring in individual memory cells within the semiconductor element increases. A decrease in yield is inevitable.

Therefore, as a method for repairing a semiconductor device in which the number of defective memory cells that have occurred is less than a predetermined number, a predetermined number of extra memory cells, that is, redundant memory cells, are built into the semiconductor device in advance, and the outside of the semiconductor device is Therefore, a so-called focus relief process is performed in which the defective memory cell is switched to a redundant memory cell by, for example, cutting the wiring structure to form an open circuit.

In this case, the defective memory cell is discovered through inspection after the final protective film is formed on the semiconductor element, and an open circuit is formed by cutting the wiring structure made of polysilicon, etc. on the semiconductor element from the outside. For example, the above-mentioned SRI can be applied to a wiring structure such as polysilicon formed under a final protective film such as a silicon nitride film or a silicon oxide film.
It is conceivable to irradiate a laser beam with a high transmittance to na, for example in the visible range, to melt and evaporate only the wiring structure under the illumination film and cut it.

However, when using the above visible laser beam, the wiring structure is melted and evaporated while being sealed in a protective film formed on the wiring structure, so thermal expansion due to heating and increase in internal pressure cause The inventors of the present invention have discovered that there are drawbacks such as cracking and damage to the base and substrate other than the wiring structure, which causes a decrease in the reliability of the semiconductor element.

Note that the literature that explains how to rescue defective memory cells in semiconductor memory is Kogyo Kenkyukai Co., Ltd., 1933.
"Electronic Materials" June 1980 issue, published June 1, 1980, P2
There are 7 to P33.

[Object of the Invention] An object of the present invention is to provide a laser processing technique that can process an object to be processed without damaging it.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the Invention] A brief overview of typical inventions disclosed in this application is as follows.

In other words, by using an ultraviolet laser that has a high absorption rate even for substances deposited on the target part of the object, the substances deposited on the top of the target part are sequentially melted and removed, and then the target part is removed. This method melts and evaporates the target part and avoids the process of melting and evaporating the target part using laser energy in a closed state, thereby preventing damage to parts other than the target part of the object due to an increase in internal pressure at the target part. This is to prevent

[Embodiment] FIG. 1 is a perspective view schematically showing a bit relief device which is an embodiment of the present invention.

A plurality of semiconductor memory elements including, for example, a large number of memory cells (not shown) and a predetermined number of redundant memory cells (not shown) are formed on an XY table 1 that is movable within a predetermined plane. A wafer 2 (workpiece) is positioned.

Further, an illumination section 3 is provided above the XY table 1, and the illumination section 3 illuminates the surface of the wafer 2 through a half mirror 4 and a lens 5, and the illumination light 6 reflected from the surface of the wafer 2 is , is guided to an image observation section 7 by a half mirror 4, and is configured so that a pattern such as a wiring structure formed on the wafer 2 can be recognized.

Further, a laser mirror 8 is provided between the half mirror 4 and the lens 5, and an ultraviolet laser source 9 of 360 r+m or less is provided on the upper side of the XY table l.
, an ultraviolet laser beam 10 having a predetermined wavelength, e.g. third harmonic, emitted from a YAG laser, excimer laser, N2 laser source, etc.
A predetermined portion of a wafer 2 fixed on a table 1 is irradiated with a spot of a predetermined diameter, and the predetermined portion of the wafer 2 is heated with laser energy.

Further, the irradiation position of the ultraviolet laser beam 10 on the wafer 2 is determined by maintaining, for example, the positional relationship between the half mirror 4 and the laser mirror 8 in a predetermined state, and placing, for example, a line of sight within the field of view of the image observation unit 7. By providing this, the image observation section 7 can recognize the pattern along with the pattern formed on the wafer 2.

Next, the operation of this embodiment will be explained.

First, the wafer 2 is placed on the XY table 1 in a predetermined state.

Next, the surface of the wafer 2 placed on the XY table 1 is illuminated by the illumination unit 3, and the XY table 1 is moved as appropriate while observing the pattern such as the wiring structure formed on the wafer 2 by the image observation unit 7. The target portion on the wafer 2 is moved to a position where the ultraviolet laser beam 10 is irradiated.

Next, irradiation of a predetermined portion of the wafer 2 with the ultraviolet laser beam IO emitted from the YAG laser source 9 is started.

In this case, the portion of the wafer 2 that is irradiated with the ultraviolet laser beam 10 has a structure as shown, for example, in a cross-sectional view in FIG. 2(a).

That is, on the isolation film 12 formed on the silicon substrate 11 and made of silicon dioxide, for example,
For example, a wiring structure 13 made of polysilicon is formed, and when this wiring structure 13 is blown out, an open circuit is formed, and a defective memory cell is switched to a predetermined redundant memory cell.

Further, on this wiring structure 13, an interlayer insulating film 14 made of, for example, silicon dioxide and a final protective film 15 made of silicon nitride are formed.

Then, the ultraviolet laser beam 10 is irradiated onto the wafer 2.
The silicon nitride film 15 is removed before reaching the target wiring structure 13.
and the silicon dioxide film 14, but the final protective film 1
5 and the ultraviolet laser beam 1 on the interlayer insulating film 14
Since the absorption rate of 0 is high, the final protective film 15 and interlayer insulating film 14 deposited on the wiring structure 13 absorb the laser energy and are sequentially heated and melted and removed. The fusing process using the beam 10 is performed in an open state to the outside, as shown in FIG. 2(b).

As a result, the process in which the wiring structure 13 is heated by irradiation with the ultraviolet laser beam 10 and melted and evaporated at a high temperature is prevented from being performed in a state where the wiring structure 13 is sealed by the final protective film 15, the interlayer insulating film 14, etc. For example, due to an increase in internal pressure or thermal expansion, the isolation film 12
The wiring structure 13 is exposed to the ultraviolet laser beam 10 without cracking or other damage to the silicon substrate 11 or the like.
, the wiring structure 13 constitutes an open circuit,
A defective storage cell is switched to a redundant storage cell.

After a predetermined period of time has elapsed, the irradiation of the ultraviolet laser beam 10 is stopped.

By repeating the above series of operations, bit relief processing for a predetermined semiconductor memory element on the wafer 2 is performed.

[Effect (1): In a laser processing apparatus that heats a workpiece with laser energy, an ultraviolet laser that has a high absorption rate even for a substance deposited on the target part of the workpiece,
In particular, since a substance with a wavelength of 360 nm or less is used, the substance deposited on the upper part of the target area is sequentially melted and removed, and then the target area is melted and evaporated, and the target area is heated, melted, and evaporated using laser energy in a sealed state. This prevents damage to parts of the object other than the target part due to an increase in internal pressure or thermal expansion in the target part.

(2) As a result of (1) above, the reliability of semiconductor devices is prevented from deteriorating and the yield of products is improved.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, sources of ultraviolet laser beams that generate ultraviolet light of 360 nIW or less are not limited to YAG lasers.
For example, an excimer laser or a nitrogen gas laser may be used.

Further, although the lens indicated by reference numeral 5 in FIG. 1 uses a refractive lens, a reflecting mirror may also be used.

[Field of Application] In the above explanation, the invention made by the present inventor was mainly applied to the field of application, which is the field of application, which is the bit relief technology of semiconductor memory, but it is not limited to this, and for example, , can be widely applied to laser processing technology, etc.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing a bit relief device according to an embodiment of the present invention, and FIGS. 2(a) and 2(b) are sectional views of the wiring structure of a wafer. ■...XY table, 2...Wafer (workpiece),
3... Illumination section, 4... Half mirror 15... Lens, 6... Illumination light, 7... Image observation section, 8... Laser mirror, 9... Ultraviolet laser source, lO ...Ultraviolet laser beam, 11...Silicon substrate, 12...
Isolation film, 13... Wiring structure, 14...
Interlayer insulating film, 15... final protective film. Figure 2

Claims (1)

[Scope of Claims] 1. A laser processing apparatus for heat-treating a workpiece with laser energy, characterized in that it uses an ultraviolet laser. 2. The laser processing apparatus according to claim 1, wherein the object to be processed is a wafer. 3. The laser processing device according to claim 2, wherein the laser processing device is a bit relief device used for manufacturing semiconductor devices.