JP2003007659A - Method of manufacturing silicon semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To finish an etching epitaxial wafer and a mirror-surface wafer in a high planarity shape over the entire surface from a (high luminance) etching wafer by eliminating shape defects on the wafer periphery due to etching or polishing process works. SOLUTION: Non-flat etching defective peripheral portions of a wafer due to deviation of inner and outer peripheral portions of the wafer in etching and the etching quantity difference, caused by the etching solution feed rate difference or non-flat polishing defective peripheral portions of the wafer, due to its biting into the polishing cloth in mirror-surface working are ground off mechanically, to leave only the inner portion of the wafer superior in flatness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a silicon semiconductor wafer having excellent flatness even with a large diameter wafer. More specifically, the present invention relates to a method for manufacturing a silicon semiconductor wafer when a wafer cut out from a single crystal silicon ingot is sequentially subjected to predetermined processing to be finished as an etching wafer or a mirror surface wafer.

[0002]

2. Description of the Related Art Usually, a wafer (slice wafer) cut out from a single crystal silicon ingot undergoes chamfering processing, lapping processing, and then chemical etching (hereinafter referred to as etching) processing, so that the mechanical processing distortion of the surface is caused. Are removed, and then, mirror polishing is performed to finish a mirror wafer or the like. Regarding the etching process, the wafer after lapping is kept at a constant interval in a storage jig that is generally called a drum and is rotatable about the longitudinal direction.
About 50 to 100 sheets are stored and held, and the storage jig is dipped in an etching solution composed of a mixed acid obtained by mixing hydrofluoric acid, nitric acid, and acetic acid at a predetermined ratio for a certain period of time to perform etching. The reaction at this time is extremely intense, and a large amount of reaction heat is generated from the contact portion between the wafer surface and the etching solution, so that heat is collected in the central portion of the stored and held wafer, and a uniform etching action does not proceed. Therefore, the etching liquid in the bath is circulated and flowed while being kept at a constant temperature such as by cooling, and the wafer itself is also oscillated along with the storage jig to uniformly etch the entire wafer surface to obtain an etched wafer with excellent flatness. It is devised to be able to. On the other hand, in the mirror polishing of wafers, a plurality of wafers are attached and held by a wax to a holding plate, and the holding plate is pressed against the rotating metal surface plate to which the polishing cloth is attached while flowing the polishing slurry. The wafer polishing surface is brought into close contact with the polishing cloth and is moved and polished. Also in this case, in order to maintain good flatness of the wafer after polishing, use a sticking plate whose quality is controlled, such as periodic surface correction, and a coating method that forms a uniform wax film. The technique of improving the accuracy of sticking a wafer to a plate by adopting, and pressing the cloth against a cloth for polishing while keeping the entire surface of the wafer flat and highly accurate has been used in a necessary situation.

[0003]

However, the wafers that have been subjected to etching processing or polishing processing by such a conventional manufacturing method have the following problems, respectively. First of all, regarding etching processing, when processing is performed with a cutting machine such as an inner peripheral blade or a wire saw at the time of slicing into a wafer from an ingot, not only the beginning and end of cutting but also the middle of cutting Also, a large impact force is applied to the cutting surface centering around the vicinity of the contact between the wafer and the cutting edge, and a large stress is repeatedly applied to destroy the crystal structure, which remains as internal strain. This phenomenon appears more prominently in the outer peripheral portion of the wafer than in the inner portion of the wafer, but after the lapping process following slicing and chamfering, the strain at the time of cutting near the outer peripheral edge remains, and when etching with mixed acid, wrapping occurs. Processing strain is also applied, and the etching rate (etching speed) near the outer periphery where there is a large amount of strain is faster, and the amount of etching on the inner and outer peripheries varies, causing distortion (referred to as "etching sag"). Further, since the degree of contact with the unreacted etching solution at the outer peripheral portion of the wafer is higher than that at the inner portion, the reaction proceeds further and the above phenomenon is promoted. This etching sag will adversely affect the flatness of the wafer after etching. In particular, an etching epitaxial wafer which is produced by using an etching wafer as a substrate (usually a mirror surface wafer is often used as a substrate, but in recent years, it is produced by directly vapor-depositing a high-intensity etching wafer for the purpose of supplying a low-cost epi wafer. ) Has a large etching allowance because it is processed to have high brightness, and compared with regular products (for mirror polishing),
The flatness becomes worse. Further, in the polishing process, when the wafer attached to the holding plate is pressed by the cloth and moves in the slurry, the polishing cloth is an elastic body, so that the periphery of the wafer bites into the polishing cloth in a state that it bites into the polishing cloth. Since the contact surface pressure is higher than that of the inner polishing surface of the wafer, and more of the slurry is supplied to the outer peripheral portion of the wafer than the inside of the wafer, polishing progresses beyond the inside of the wafer, and as a result The thickness of the outer peripheral portion becomes thinner than that of the inside of the wafer (referred to as “drainage around polishing”), and the flatness of the entire wafer deteriorates. By eliminating the defects in the outer circumference of the wafer caused by the etching and polishing processes described above, it is possible to finish the etching epitaxial wafer and mirror-finished wafer made of the (high-brightness) etching wafer with high flatness over the entire surface. Was a challenge.

The invention set forth in claim 1 of the present invention is intended to obtain an etched epitaxial wafer having a high flatness over the entire surface except for "etching sagging" after etching. The second aspect of the present invention is intended to obtain a mirror-finished wafer having a high flatness over the entire surface except for the "polishing peripheral sagging" after the polishing process. Claim 3
In addition to the object of the invention described in claim 1 or 2, the described invention is intended to obtain a mirror-finished wafer having high cleanliness and high flatness. In addition to the object of the invention described in claim 1 or 2, the invention according to claim 4 is aimed at the grinding process capable of efficiently performing the mirror chamfering process without lowering the grinding process efficiency. Is.

[0005]

[Means for Solving the Problems] Means taken by the present invention for solving the above problems are as follows. Claim 1
Then, in a method of manufacturing a silicon semiconductor wafer in which a wafer cut out from a single crystal silicon ingot is sequentially subjected to predetermined processing to finish it as an etching wafer, after performing chemical etching processing, etching sagging occurs due to this etching processing. A method for manufacturing a silicon semiconductor wafer is adopted, which is characterized by grinding and removing the outer peripheral portion of the wafer. According to a second aspect of the present invention, in a method for manufacturing a silicon semiconductor wafer in which a wafer cut out from a single crystal silicon ingot is sequentially subjected to predetermined processing to be finished into a mirror-finished wafer, after chemical etching is performed and mirror-polishing is performed, A method of manufacturing a silicon semiconductor mirror-finished wafer, characterized in that the outer peripheral portion of the wafer in which polishing sag is generated by grinding is removed by this mirror-polishing process. According to a third aspect of the present invention, the method for manufacturing a silicon semiconductor wafer according to the first or second aspect is characterized in that after the outer peripheral portion of the wafer is ground and removed, the new outer peripheral edge is mirror-chamfered. To do. A fourth aspect of the present invention is the method of manufacturing a silicon semiconductor wafer according to the first or second aspect, wherein the outer peripheral portion of the wafer is ground with a grinding tool having a grinding wheel count of # 600 to # 1200.

[0006]

The following effects are brought about by adopting the method according to claim 1. The non-flat “etching sag” part on the outer circumference of the wafer caused by the deviation of the inner and outer circumferences of the wafer during etching processing and the difference in the etching amount caused by the difference in the supply of the etching solution (noticeable for high-brightness wafers where the etching margin is large) By mechanically removing, only the inside of the wafer, which has a very good flatness, remains, and as a result, the flatness of the entire surface is improved by eliminating the shape defect of the outer periphery of the wafer due to etching processing, and the entire surface is highly flat. An etched epitaxial wafer is obtained. Adopting the method according to claim 2 produces the following effects. By mechanically removing the non-flat "polishing peripheral sag" portion of the wafer outer periphery that occurs due to the biting into the polishing cloth during mirror surface processing, only the inside of the wafer with excellent flatness remains,
As a result, the flatness of the entire surface is improved by eliminating the defective shape of the outer periphery of the wafer due to the polishing process, and a mirror-finished wafer having a high flatness on the entire surface can be obtained. Adopting the method according to claim 3 produces the following effects. After grinding and removing the outer peripheral portion of the wafer, mirror chamfering processing is performed on the new outer peripheral portion to improve the surface roughness of the outer periphery of the wafer and eliminate dust from the chamfered portion. As a result, particles are hardly generated on the entire wafer, and as a result, a mirror-finished wafer having high cleanliness and high flatness can be obtained. Adopting the method according to claim 4 produces the following effects. By grinding the outer periphery of the wafer with # 600 to # 1200, the grinding efficiency does not drop extremely due to clogging of the grinding tool,
Since the ground surface does not become rough, the burden of subsequent mirror chamfering is small and the machining time is shortened. As a result, it is possible to perform grinding without lowering the grinding efficiency and without affecting the mirror chamfering. . It should be noted that with fine abrasive grains exceeding # 1200, the grinding efficiency is extremely reduced due to clogging, etc.
If the grain size is less than 0.5, the grinding surface will be rough and the burden on the subsequent chamfering will be large, and it will take a long processing time to be impractical.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Each embodiment of the present invention will be described below. [Embodiment 1] In this embodiment 1, a wafer to be used as a substrate for an etching epitaxial wafer is manufactured after etching is performed. When the outer peripheral portion of the wafer in which etching sag has occurred is removed by grinding. Is shown.

More specifically, first, a silicon ingot having a diameter of 155 mm is sliced into a wafer by a cutting machine such as a wire saw, and then the sliced wafer is shaped and chamfered as necessary. (Use # 800 whetstone). Next, lapping is performed by a four-axis lapping machine using loose abrasive grains of FO # 1500, and the thickness of the wafer is adjusted to a constant value based on the specifications.

Then, the wrapped wafer is subjected to an etching process. This etching liquid is hydrofluoric acid (H
F50%), nitric acid (HNO ₃ 70%), acetic acid (CH ₃ COO
H 100%) was mixed in a volume ratio of 1: 2: 1 to form a mixed acid (4
0 ° C.) and soak for 80 seconds to chemically remove about 90 μm on both sides of the wafer. As a result, the gloss of the wafer becomes 99%. (Glossiness: synonymous with relative reflectance and brightness when the mirror surface of the mirror-finished wafer is 100%) At this time, the etching solution is agitated and circulated, and the wafer is rotating at 30 rpm.

The etched wafer manufactured in this manner is set in a peripheral grinding device, and the outer peripheral portion (distorted portion) of the wafer in which "etching sagging" has occurred due to the etching process is ground and removed.

Specifically, a # 800 diamond wheel rotating at 1500 rpm is brought into contact with the outer peripheral edge of the wafer rotating at 30 rpm, and a coolant is supplied to the contact processing portion for the purpose of reducing friction and cooling. , Remove by grinding. Outer diameter is 150m
Since the range of the "etching sag (distortion portion)" in an m-sized etching wafer is 1 to 2 mm from the outer peripheral edge, in this Example 1, an etching wafer having a diameter of 155 mm was ground to a diameter of 150 mm. , An etching wafer for an epitaxial substrate with high flatness was produced.

[Embodiment 2] In Embodiment 2, a wafer which has been subjected to etching processing as described in Embodiment 1 is subjected to polishing processing to manufacture a mirror surface wafer, and polishing is performed by this mirror surface polishing processing. The case where the peripheral portion of the wafer where the peripheral sagging has occurred is removed by grinding, and then mirror chamfering is performed.

More specifically, the lapping process is completed for a silicon ingot having a diameter of 206 mm as in the first embodiment.
Next etching treatment Immerse in an etching solution of the same composition for 30 seconds to remove about 30 μm on both sides of the wafer. The glossiness is over 40%. In the next polishing step, multiple wafers that were attached to the ceramic attachment plate with wax were applied to the nonwoven fabric polishing cloth while supplying the slurry of the main component of colloidal silica (average particle size 20 nm) to a surface pressure of 100 g / Polishing was performed for 10 minutes under the conditions of cm ² and relative velocity of wafer cross of 1.5 m / s. The polishing amount (removal allowance) at this time was about 8 μm.

Subsequently, the back surface (etching surface) of this wafer is adsorbed and held, and the outer peripheral portion of the wafer in which polishing peripheral sagging has occurred due to the mirror polishing is ground and removed under the same conditions as in the first embodiment. Since the range of "dip around the polishing" in the wafer having the outer diameter of 200 mm after the polishing is about 1.5 to 2.5 mm from the outer peripheral edge, the wafer having the diameter of 206 mm after the polishing is finished in this Example 2. 200 mm diameter
It was ground until.

After that, a new peripheral edge of the wafer after the grinding was subjected to mirror chamfering by tape polishing while supplying a slurry to produce a mirror surface wafer with high flatness.

The flatness (flatness) of the wafer manufactured as in Example 2 above was measured and evaluated, and a comparison with the conventional product is shown in Table 1 below.

[Table 1]

As the site flatness of the evaluation parameter, the difference in the unevenness of the wafer surface in the area of 25 mm × 25 mm was compared. In addition, the measuring machine is made by ADE, Inc.
"ULTRA SCAN 9600" was used.

Therefore, it can be easily understood from the above Table 1 that the flatness of the wafer manufactured as in Example 2 is significantly improved as compared with the conventional product. By the way,
The wafer manufactured as in Example 2 has improved flatness to a level at which it can be used as a reference wafer for a measuring machine.

In the embodiment shown above, the wafer (slice wafer) cut out from the silicon ingot was subjected to the chamfering process and then the etching process or the polishing process. However, the present invention is not limited to this. It may be omitted without chamfering in a step prior to processing.

[0020]

As described above, according to the first aspect of the present invention, the wafer is caused by the difference in the etching amount caused by the deviation of the inner and outer circumferences of the wafer during etching and the difference in the supply of the etching solution. By mechanically removing the non-flat "etching sag" on the outer circumference, only the inside of the wafer, which has a very good flatness, remains, so that there is no defect in the outer circumference of the wafer due to etching processing, and the flatness of the entire surface is eliminated. In the production of an etching epitaxial wafer using the etching wafer as a substrate, an etching epitaxial wafer having a high flatness over the entire surface can be obtained. Further, in the wafer manufacturing process, the chamfering process, which is a process prior to the etching process, can be omitted, and the manufacturing process is simplified accordingly.

According to the second aspect of the present invention, the non-flat "polishing peripheral sag" portion on the outer periphery of the wafer caused by biting into the polishing cloth during mirror finishing is mechanically removed.
Since only the inside of the wafer having a very excellent flatness remains, the flatness of the entire surface can be improved by eliminating the defective shape of the outer periphery of the wafer due to the polishing process, and a mirror-finished wafer having a high flatness on the entire surface can be obtained. Further, in the wafer manufacturing process, the chamfering process, which is a process prior to the polishing process, can be omitted, and the manufacturing process can be simplified accordingly.

According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, by grinding and removing the outer peripheral portion of the wafer, mirror chamfering processing is performed on the new outer peripheral portion. The surface roughness of the outer peripheral part of the wafer is improved, and a mirror surface similar to the surface of the wafer is obtained. Since dust is not generated from this chamfered part, the generation of particles on the entire wafer is almost eliminated, and therefore high cleanliness is achieved. In addition, a mirror-finished wafer having a high flatness can be obtained.

In addition to the effect of the invention of claim 1 or 2, the invention of claim 4 grinds the outer peripheral portion of the wafer with # 600 to # 1200, so that the grinding tool is clogged and the grinding efficiency is extremely high. In addition, since the grinding surface does not become rough, the burden on the subsequent mirror chamfering is small and the processing time is shortened, so it is possible to perform grinding that does not reduce the grinding efficiency and does not interfere with mirror chamfering. Becomes

Claims (4)

[Claims] 1. A method for manufacturing a silicon semiconductor wafer in which a wafer cut out from a single crystal silicon ingot is sequentially subjected to predetermined processing to finish an etched wafer. In the method of manufacturing a silicon semiconductor wafer, chemical etching is performed and then etching sag is caused by the etching. A method of manufacturing a silicon semiconductor wafer, which comprises grinding and removing an outer peripheral portion of a wafer in which the above-mentioned problem occurs. 2. A method for manufacturing a silicon semiconductor wafer in which a wafer cut out from a single crystal silicon ingot is subjected to predetermined processing in order to finish it into a mirror-finished wafer. In the method of manufacturing a silicon semiconductor wafer, after chemical-etching processing is followed by mirror-polishing processing, A method for manufacturing a silicon semiconductor mirror-polished wafer, characterized in that an outer peripheral portion of a wafer where polishing sag is generated is ground and removed by the mirror-polishing process. 3. The method for manufacturing a silicon semiconductor wafer according to claim 1, wherein after polishing and removing the outer peripheral portion of the wafer, mirror chamfering is performed on the new outer peripheral edge. 4. The method for manufacturing a silicon semiconductor wafer according to claim 1, wherein the outer peripheral portion of the wafer is ground with a grinding tool having a grinding wheel count of # 600 to # 1200.