JP3382218B2 - Honing method for single crystal wafer - Google Patents

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 in particular, it has fine irregularities formed on the back surface thereof in order to effectively suppress disturbance waves of the surface acoustic wave. The present invention relates to an improvement in a honing processing method for a single crystal wafer to be processed, which is suitable for the above.

[0002]

2. Description of the Related Art For example, a surface acoustic wave device is constructed by using a piezoelectric LiTaO ₃ single crystal wafer or a LiNbO ₃ single crystal wafer as a substrate and providing an interdigital transducer on one main surface. In this configuration, the surface acoustic wave is excited and received by the transducer, but at the same time, unnecessary waves (obstacle waves) such as bulk waves are also received and received. By the way, since the bulk wave causes spurious interference in frequency characteristics, in order to remove this 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-described method has some effect, the surface acoustic wave device (filter) that requires strict characteristics cannot sufficiently eliminate the obstacle of the bulk wave. The problem remains. In other words, in the case of a surface acoustic wave filter, the bulk wave that is excited at the same time has a large obstacle, and since it is difficult to deal with the design, we try to eliminate the bulk wave obstacle by the shape of the back surface of the substrate. Forming the unevenness causes a decrease in mechanical strength, resulting in a decrease in the yield of wafers or a decrease in the yield of device processes. In particular, recently, automation and a high degree of device precision have been demanded accompanying the stepperization of the device process, and a high flatness of the wafer is a prerequisite for this demand. For this reason, high precision is required even in the processing method of forming large unevenness on the back surface of the substrate (wafer), and the back surface is subjected to honing processing through the uneven hole pattern mask made of the ultraviolet curing resin layer. Means for making unevenness have also been tried, but the processing yield during honing is poor and it has not been put to practical use. In particular, at the time of the honing process, the peripheral portion of the processed surface of the single crystal wafer is likely 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.

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

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

[0006]

A method for honing a single crystal wafer according to the present invention comprises an ultraviolet curable film with a protective film integrally disposed on a main surface of a single crystal wafer to be processed, After the wafer is heated and the protective film is peeled off, the temperature of the single crystal wafer is lowered below the temperature at the time of peeling, exposure and development processes are performed to form a fine hole pattern, and then honing is performed. It is characterized by

Further, according to the present invention as described above, the peeling temperature of the protective film attached to the ultraviolet curable film prior to the selective exposure and development treatment of the ultraviolet curable film is set to be higher than the peeling temperature. This is also based on the finding that when the high temperature is selected and set, it is possible to easily and surely achieve substantially uniform uneven surface processing in the subsequent honing processing.

According to the method for honing a single crystal wafer according to the present invention, the ultraviolet curable film functioning as a protective film or a mask can be peeled off without any damage, resulting in a pattern. High-precision uneven surface that does not collapse (grooves and holes with no variation in diameter)
With good reproducibility, it is possible to always and easily achieve the honing process having the required flatness. FIG. 1 shows an example of the relationship between the peeling temperature of the protective film prior to the exposure of the UV-curable film and the yield rate by honing, and FIG. 2 shows an example of the relationship between the exposure temperature and the yield by honing. Is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

Example 1 First, both sides were lapped to a thickness of 0.52 mm and an outer diameter of 76 mm.
A 128 ° Y LiNbO ₃ wafer was prepared and a UV-curable urethane resin film (mask material) with a protective film was adhered (adhered) to the back surface of the LiNbO ₃ wafer by thermocompression bonding. Next, after keeping the temperature at 50 ° C for 30 minutes in a warmer, peel off the protective film, and while lowering it to 20 ° C, selectively expose the back side with UV light for several tens of seconds, and then develop with an alkaline solution. After processing, a hole pattern having a diameter of 250 μm was formed at a pitch of 500 μm.

Thereafter, the LiN is prepared by conventional means.
Alundum No. 240 was sprayed from a honing nozzle through a mask made of an ultraviolet curable urethane resin film formed on the surface of the bO ₃ wafer to perform a honing process for 10 minutes. After the above processing, the mask made of UV-curable urethane resin film was dissolved and removed, and the processed surface was observed. As a result, the diameter of the wafer periphery was 270 μm and the pattern was 100 μm without any pattern deformation.
The holes of m were formed uniformly.

When 100 pieces of LiNbO ₃ wafers with the UV-curable urethane resin film having the above-mentioned structure were subjected to honing processing, no damage such as deformation was caused, and further, these wafers were polished. Where I did
95 good products were obtained and the polishing yield was also good. Moreover, when an IF filter for TV was created 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 1 having a thickness of 0.52 mm and an outer diameter of 76 mm, both sides of which were lapped
A 28 ° Y LiNbO ₃ wafer was prepared, and a UV-curable urethane resin film with a protective film (mask material) was adhered (adhered) to the back surface of the LiNbO ₃ wafer by thermocompression bonding. Then
After incubating at 50 ° C for 60 minutes in a warmer, peel off the protective film, lower the temperature to 25 ° C, and selectively expose the back side with UV light for several tens of seconds, then develop with an alkaline solution. As a result, a hole pattern with a diameter of 250 μm was formed at a pitch of 500 μm.

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

After the processing, the mask made of the UV-curable urethane resin film was melted and removed, and the processed surface was observed.
Holes of μm and depth of 100 μm were uniformly formed.

When 100 pieces of LiNbO ₃ wafers with a UV-curable urethane resin film having the above-mentioned structure were subjected to honing processing, no damage such as deformation was caused, and further, these wafers were polished. Where I did
93 good products were obtained, and the polishing yield was also good. In addition, when an IF filter for TV was created 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, after the temperature was kept at 80 ° C. for 10 minutes in a warmer, the protective film was peeled off and the temperature was lowered to 10 ° C., and the back side was selectively exposed to ultraviolet rays for several tens of seconds. After exposure, develop with alkaline solution and 250μm diameter with 500μm pitch
Hole pattern was formed.

Then, using a honing machine with an electrostatic elimination blower, Alundum No. 240 was sprayed from a honing nozzle through a mask made of a UV-curable urethane resin film formed on the surface of the LiNbO ₃ wafer to perform a honing process for 10 minutes. did.

After the processing, the mask made of the UV-curable urethane resin film was melted and removed, and the surface to be processed was observed.
Holes of μm and depth of 100 μm were uniformly formed.

When 100 pieces of LiNbO ₃ wafers with the UV-curable urethane resin film having the above-mentioned constitution were subjected to honing processing, no damage such as deformation was caused, and further, these wafers were subjected to polishing treatment. Where I did
94 good products were obtained, and the polishing yield was also good. In addition, when an IF filter for TV was created 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 the above-mentioned Example 1, a UV-curable urethane resin film with a protective film (mask material) was adhered (adhered) to the back surface of the LiNbO ₃ wafer by thermocompression bonding, and then a thermostat 35 was used.
After incubating at ℃ for 30 minutes, peel off the protective film, and in this state (hold at 35 ℃), selectively expose the back side with UV light for several tens of seconds, then develop with an alkaline solution to 500 μm. A hole pattern with a diameter of 280 to 290 μm and a variation in pitch was formed.

When 100 pieces of LiNbO ₃ wafers with the UV-curable urethane resin film having the above-mentioned constitution were subjected to the honing process, the phenomenon such as the sticking or sticking of the protective film occurred, and the wafers were polished. When the treatment was applied, only 62 good products were obtained.
In addition, using these wafers, we created an IF filter for TV and evaluated the characteristics. As a result, the bulk wave noise was -50 dB.
And the device yield was 53%.

In the above embodiment, a single crystal wafer is used.
Although the LiNbO ₃ wafer is shown as an example, a LiTaO ₃ wafer, a Si wafer or the like may of course 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 the required uneven surface-fabricating processing with high processing accuracy and yield. That is, it is possible to form unevenness on the back surface of the surface acoustic wave substrate with high accuracy and with high yield, which contributes to the reduction or prevention of the generation of bulk waves that become an obstacle. In other words, it is possible to accurately form a concavo-convex pattern that contributes to the reduction or prevention of the generation of bulk waves, which is an obstacle to the device, without impairing the mechanical strength of the surface acoustic wave substrate or the like. Not only can it be used as an automated stepper, it will also contribute to a significant improvement in the characteristics and manufacturing yield of the finally formed device.

[Brief description of 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 the relationship between the exposure temperature after peeling of the protective film and the yield due to honing in the method for processing a single crystal wafer according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 41/18 H01L 41/18 101A 41/22 41/22 Z (58) Fields investigated (Int.Cl. ⁷ , DB name) C30B 29/30 B24B 33/00 H01L 21/304 601 H01L 21/304 621 H01L 41/18 H01L 41/22

Claims (2)

(57) [Claims] 1. An ultraviolet curable film with a protective film is integrally arranged on a main surface of a single crystal wafer to be processed, and the single crystal wafer is heated to peel off the protective film, and then the single crystal. A honing method for a single crystal wafer, which comprises subjecting a wafer temperature to a temperature lower than the temperature at the time of peeling, exposing and developing the wafer to form a fine hole pattern, and then honing. 2. The single crystal wafer is LiTaO ₃ or Li
The method for honing a single crystal wafer according to claim 1, which is NbO ₃ .