JP2001192296A - Method of honing processing of single crystal wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honing processing method for a single crystal wafer, which is capable of improving the processing yield and the yield in device process. SOLUTION: This method for honing processing comprises integrally arranging an ultraviolet curing film with a protective film on the main surface to be processed of a single crystal wafer, then heating the single crystal wafer to peel off the protective film, lowering the temperature of the single crystal wafer to a temperature lower than that at which the protective film is peeled, exposing the film to light, developing to form a fine hole pattern and finally subjecting to honing processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for honing a single crystal wafer to be processed, such as a surface acoustic wave substrate, and more particularly, to forming fine irregularities on the back surface in order to effectively suppress obstacle waves of surface acoustic waves. The present invention relates to an improvement in a honing processing method for a single crystal wafer to be processed, which is suitable for a method.

[0002]

2. Description of the Related Art For example, an elastic wave surface device is constructed by using a LiTaO ₃ single crystal wafer or a LiNbO ₃ single crystal wafer exhibiting piezoelectricity as a substrate and providing an interdigital transducer on one principal surface. In this configuration, although the surface acoustic wave is excited and received by the transducer, an unnecessary wave (disturbance wave) such as a bulk wave is also excited and received at the same time. By the way, since the bulk wave causes spurious interference in the frequency characteristic, in order to remove the spurious interference, a groove is formed on the back surface of the surface wave substrate by dicer cutting or mask honing, or the entire back surface is randomly formed. Roughening (surface roughness R
a: 2 μm or more).

[0003]

However, although the above-mentioned method has a certain effect, an acoustic wave surface device (filter) requiring strict characteristics still cannot sufficiently solve the problem of the bulk wave. The problem remains. In other words, in the case of the surface acoustic wave filter, the obstacle of the bulk wave excited at the same time is large, and it is difficult to cope with the design. Forming the unevenness causes a decrease in mechanical strength, and as a result, a reduction in the yield of the wafer or a reduction in the yield of the device process. In particular, recently, there has been a demand for automation and a high degree of device accuracy accompanying the use of a stepper in a device process, and this requirement is premised on a high flatness of the wafer. For this reason, high accuracy is also required in a processing method for forming large irregularities on the back surface of the substrate (wafer), and the back surface is formed by honing through an uneven hole pattern mask made of an ultraviolet curable resin layer. Means for making the surface uneven have been tried, but the processing yield at the time of honing is poor and has not been put to practical use. In particular, at the time of the honing processing, the peripheral portion of the processing surface of the single crystal wafer is apt to be deformed, so that the mechanical strength of the single crystal wafer is reduced, and the processing yield and the yield of the device process are reduced. There is.

[0004] On the other hand, the following problems are recognized when the above-mentioned ultraviolet curable resin layer (film) is subjected to selective ultraviolet exposure and development to form a required fine hole pattern. That is, after a UV curable resin film with a protective film is adhered to the surface to be processed of the single crystal wafer, the protective film is peeled off and subjected to a selective UV exposure treatment. If the adhesion is reduced so that the mold resin film is easily damaged and peeled off, the hole diameter of the hole pattern formed by the exposure and development processing will vary, and as a result, the processing yield of the single crystal wafer will be reduced. There is a problem that it causes a decrease and a decrease in the yield of the device process.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a honing method for a single crystal wafer which can greatly improve a processing yield and a device process yield.

[0006]

According to a honing method for a single crystal wafer according to the present invention, an ultraviolet curing film with a protective film is integrally disposed on a main surface to be processed of the single crystal wafer. After the wafer is heated and the protective film is peeled off, the temperature of the single crystal wafer is lowered from the temperature at the time of the peeling, exposure and development are performed, and a fine hole pattern is formed, followed by honing. It is characterized by the following.

According to the present invention, the peeling temperature of the protective film attached to the ultraviolet-curable film prior to the selective exposure and development of the ultraviolet-curable film is set to be lower than the temperature at the time of exposure. This is based on the knowledge that when a high temperature is selected and set, substantially uniform uneven surface processing can be easily and reliably achieved in the subsequent honing processing.

According to the method for honing a single crystal wafer according to the present invention, an ultraviolet curable film functioning as a protective film or a mask can be peeled off without any damage, and as a result, the pattern can be removed. High-precision uneven surface without collapse (grooves and holes with no variation in diameter)
Honing with the required flatness can be achieved with good reproducibility and always and easily. FIG. 1 shows an example of the relationship between the peeling temperature of the protective film prior to exposure of the ultraviolet curable film and the yield rate by the honing process, and FIG. 2 shows an example of the relationship between the exposure temperature and the yield by the honing process. It is.

[0009]

Embodiments of the present invention will be described below.

Example 1 First, both sides were wrapped to a thickness of 0.52 mm and an outer diameter of 76 mm.
Prepared of 128 ° Y LiNbO ₃ wafer, a LiNbO ₃ backside protective film with UV curable urethane resin film wafer (mask material) is adhered (bonded) by thermal compression bonding. Next, the protective film is peeled off after keeping the temperature at 50 ° C for 30 minutes in a warmer, and the back side is selectively exposed to ultraviolet light for several tens of seconds with the temperature lowered to 20 ° C, and then developed with an alkaline solution. By processing, a hole pattern having a diameter of 250 μm was formed at a pitch of 500 μm.

[0011] Thereafter, the LiN
Alundum No. 240 was sprayed from a honing nozzle through a UV curable urethane resin film mask formed on the bO ₃ wafer surface to perform honing for 10 minutes. After the processing, the UV-curable urethane resin film mask was dissolved and removed, and the processed surface was observed. As a result, the diameter and the depth were 270 μm and 100 μm, respectively.
m holes were uniformly formed.

Honing was performed on 100 LiNbO ₃ wafers with the ultraviolet-curable urethane resin film having the above-mentioned structure, and no damage was caused by shape collapse or the like. Further, these wafers were polished. Where I did
95 good products were obtained, and the polishing yield was also good. In addition, a TV IF filter was fabricated using these wafers, and the characteristics were evaluated. The noise of the bulk wave was reduced to -50 dB, and the device yield was 97%.

Example 2 One side having a lapping process on both sides having a thickness of 0.52 mm and an outer diameter of 76 mm.
A 28 ° Y LiNbO ₃ wafer was prepared, and an ultraviolet-curable urethane resin film (mask material) with a protective film was adhered (bonded) to the back surface of the LiNbO ₃ wafer by thermocompression bonding. Then
After keeping the temperature at 50 ° C for 60 minutes in an incubator, the protective film was peeled off and the back side was selectively exposed to ultraviolet light for several tens of seconds with the temperature lowered to 25 ° C, and then developed with an alkaline solution. A hole pattern having a diameter of 250 μm was formed at a pitch of 500 μm.

Thereafter, using a honing machine with an electrostatic removal blower, Alundum No. 240 is sprayed from a honing nozzle through a UV-curable urethane resin film mask formed on the surface of the LiNbO ₃ wafer for 10 minutes. did.

After the processing, the UV-curable urethane resin film mask was dissolved and removed, and the processed surface was observed.
A hole with a depth of 100 μm and a depth of 100 μm was formed uniformly.

When honing was performed on 100 LiNbO ₃ wafers having the above-described structure and having a UV-curable urethane resin film, no damage was caused by deformation or the like, and the wafers were further polished. Where I did
93 good products were obtained, and the polishing yield was also good. In addition, a TV IF filter was fabricated using these wafers, and the characteristics were evaluated. The noise of the bulk wave was reduced to -50 dB, and the device yield was 93%.

Example 3 In Example 2, the protective film was peeled off after keeping the temperature at 80 ° C. for 10 minutes in an incubator, and the temperature was lowered to 10 ° C., and the back side was selectively irradiated with ultraviolet light for several tens of seconds. After exposure, develop with an alkaline solution and 250μm in diameter at 500μm pitch
Hole pattern was formed.

Thereafter, using a honing machine with an electrostatic removal blower, Alundum No. 240 is sprayed from a honing nozzle through a UV-curable urethane resin film mask formed on the surface of the LiNbO ₃ wafer, and the honing process is performed for 10 minutes. did.

After the processing, the UV-curable urethane resin film mask was dissolved and removed, and the processed surface was observed.
A hole with a depth of 100 μm and a depth of 100 μm was formed uniformly.

When honing was performed on 100 LiNbO ₃ wafers having the above-described UV-curable urethane resin film and having a urethane resin film, no breakage due to shape collapse occurred, and these wafers were further polished. Where I did
94 non-defective products were obtained, and the polishing yield was also good. In addition, a TV IF filter was fabricated using these wafers, and the characteristics were evaluated. The noise of the bulk wave was reduced to -50 dB, and the device yield was 93%.

Comparative Example In Example 1, an ultraviolet-curable urethane resin film (mask material) with a protective film was adhered (bonded) to the back surface of the LiNbO ₃ wafer by thermocompression bonding.
The protective film was peeled off after keeping the temperature at 30 ° C for 30 minutes. In this state (at 35 ° C), the back side was selectively exposed to ultraviolet light for several tens of seconds, and then developed with an alkaline solution to 500 µm Hole patterns with a variation of 280 to 290 μm in diameter were formed at the pitch.

When honing was performed on 100 LiNbO ₃ wafers having the above-described UV-curable urethane resin film and having a urethane resin film, phenomena such as residual adhesion and re-adhesion of the protective film occurred. The treatment yielded only 62 good products.
In addition, a TV IF filter was created using these wafers, and the characteristics were evaluated.
The device yield was 53%.

In the above embodiment, a single crystal wafer is used.
Although the LiNbO ₃ wafer is illustrated, a LiTaO ₃ wafer, a Si wafer, or the like may be used.

[0024]

As can be seen from the above description, according to the method for honing a single crystal wafer according to the present invention, it is possible to perform a required surface roughening process with high processing accuracy and high yield. That is, irregularities contributing to the reduction or prevention of the generation of the bulk wave which is an obstacle can be formed on the back surface of the surface acoustic wave substrate with high accuracy and high yield. In other words, it is possible to form a concave-convex pattern that contributes to the reduction or prevention of the generation of bulk waves that become obstacles when a device is formed, without impairing the mechanical strength of a surface acoustic wave substrate, etc. Not only can it be adapted to an automated stepper, but it can also contribute to a significant improvement in the characteristics and manufacturing yield of devices to be finally formed.

[Brief description of the drawings]

FIG. 1 is a curve diagram showing an example of a relationship between a peeling temperature of a protective film and a yield by honing in a method for processing a single crystal wafer according to the present invention.

FIG. 2 is a curve diagram showing an example of a relationship between an exposure temperature after peeling of a protective film and a yield by honing in the method for processing a single crystal wafer according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/18 H01L 41/18 101A 41/22 41/22 Z

Claims (2)

[Claims] An ultraviolet curable film with a protective film is integrally disposed on a main surface to be processed of a single crystal wafer, and after heating the single crystal wafer to peel off the protective film, the single crystal is removed. A honing method for a single crystal wafer, comprising lowering the temperature of the wafer from the temperature at the time of peeling, performing exposure and development processes, forming a fine hole pattern, and performing honing. 2. The method according to claim 1, wherein the single crystal wafer is LiTaO ₃ or LiTaO _3.
Honing method of a single crystal wafer according to claim 1, characterized in that the NbO _3.