JP2000340571A - Manufacture of wafer of high planarity degree - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent melting of the rear face treatment layer of a semiconductor wafer by a method, wherein after polishing surface of the semiconductor wafer, the polished face of the wafer is cleaned and then is mirror-polished and thereafter subjecting it to a prescribed rear face treatment to the rear face of the semiconductor wafer. SOLUTION: A silicon ingot is sliced into silicon wafers (S101). After chamfering the periphery of each wafer (S102), the wafer is lapped (S103). Next, the silicon wafer is etched (S104) and is cleaned with an RCA series cleaning liquid (S105), and then the surface is polished (S106). The surface-polished silicon wafer is cleaned with alkaline cleanings (S107), and the cleaned silicon wafer is applied with a prescribed rear face treatment (S108). Thereafter, the silicon wafer is subjected to WHT (heat treatment) (S109). Then, the rear face of the silicon wafer is mirror-polished (S110) and is cleaned (S111), to manufacture a silicon wafer of high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high flatness wafer, and more particularly, to a high flatness wafer in which a high flatness semiconductor wafer is obtained by grinding and polishing the surface of a semiconductor wafer after etching. And a method for producing the same.

[0002]

2. Description of the Related Art An example of a conventional method for manufacturing a silicon wafer will be described with reference to a flowchart of FIG. First, in a slicing step (S301), a silicon wafer is sliced from an ingot. Next chamfering process (S3
In 02), an outer peripheral portion of the silicon wafer is chamfered. In the subsequent lapping step (S303), lapping is performed on both the front and back surfaces of the silicon wafer using a lapping machine. Then, in the next etching step (S3
In step 04), the wrapped wafer is immersed in a predetermined etchant (mixed acid or alkali + mixed acid) to remove distortion in the lapping process, distortion in the chamfering step, and the like. Thereafter, this silicon wafer is bonded to a polishing board using wax, and the wafer surface is mirror-polished (S305).
Then, after removing the wax and the like attached to the back surface of the silicon wafer, a final finish cleaning step (S306) is performed.

However, in such a conventional method of manufacturing a silicon wafer, as described above, after lapping the silicon wafer, acid etching is performed using a mixed acid. As a result, the etching rate was relatively high, and at the time of acid etching, the silicon wafer and the acidic solution strongly reacted, and a relatively large amount of bubbles were generated. Due to these effects and the like, there is a problem that undulations are likely to occur on the wafer surface. There is also a problem that the taper generated by lapping is further emphasized by etching. Moreover, the problem of the surface flatness was not so much improved in the subsequent polishing step.

[0004] As a prior art for solving these problems,
For example, there is known a "supporting substrate for bonding and a method of manufacturing the same" in Japanese Patent Application Laid-Open No. 10-22186, which was filed by the applicant of the present application first and subsequently published. According to this conventional technique, the surface of a silicon wafer that has been cleaned after etching is ground using a vitrified grinding wheel having abrasive grains higher than # 2000, and then, after cleaning, the wafer ground surface is mirror-polished. . By grinding the surface of the etched wafer before mirror polishing,
The undulation of the wafer surface and the sagging of the outer peripheral portion of the wafer caused by the etching can be removed.

[0005]

However, in the manufacturing process of the silicon wafer, the back surface of the silicon wafer may be subjected to a back surface process such as sandblasting, polyback sealing, LTO (deposition of a low-temperature oxide film), or the like. is there. At this time, in the related art, no technical study has been made as to which step in the wafer manufacturing process this back surface processing process should be incorporated. Therefore, it has been described that the above-described back surface treatment may be performed before the grinding step. However, when the experiment of grinding after the back surface treatment was repeated, a certain fact was found. That is, the back surface treatment layer formed on the back surface of the wafer and provided with fine irregularities by, for example, sandblasting may be damaged by washing after grinding (usually RCA washing using an alkaline washing solution). was there.
Therefore, the processing effect on the back side of this wafer is reduced by half,
In the worst case, there was a possibility that it would completely disappear. On the other hand, at the time of the above-mentioned grinding, there is also a fear that the wafer is attracted to the wafer holding portion of the grinding apparatus and the back surface (processed surface) of the wafer is damaged.

[0006]

An object of the present invention is to provide a method of manufacturing a high flatness wafer in which a back surface treatment layer formed on the back surface of a semiconductor wafer is not melted by cleaning after grinding, and the back surface of the semiconductor wafer is not easily damaged during grinding of the wafer surface. Its purpose is to provide.

[0007]

According to the first aspect of the present invention, there is provided a semiconductor device comprising: a step of grinding a surface of a semiconductor wafer after etching; a step of cleaning the ground surface of the wafer after grinding; Performing a predetermined back surface treatment on the back surface of the wafer, the method for manufacturing a high flatness wafer, wherein the back surface treatment process is performed after performing a grinding process on the semiconductor wafer surface. is there. Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer. The usage of the wafer is not limited. For example, SO
A wafer for a bonded wafer such as an I (Silicon on Insulator) or a dielectric isolation wafer may be used. The surface of the semiconductor wafer having a high flatness as referred to herein means that the flatness of the site, for example, the difference in height SBIR (SiteBack-side Ide) based on the back surface at a site having an area of 25 mm × 25 mm.
al Range) is 0.40 μm or less.

In this case, the grinding is preferably performed by using a high-count grinding wheel capable of grinding the silicon surface, which is a hardly damaged wafer surface. As a grindstone used for grinding, for example, # 1500
To # 3000 resinoid grinding wheels. Note that the resinoid grinding wheel is a wheel in which diamond abrasive grains are bonded using a high-quality synthetic resin as a bonding material. As described above, since grinding with small damage is performed before polishing, high flatness can be obtained on the wafer surface after grinding. Moreover,
Since the polishing amount can be reduced, high throughput can be obtained. The grinding damage in this case is, for example, 2 μm.
m or less. If the damage is large, the amount of subsequent surface polishing increases.

As a cleaning liquid used for cleaning performed after the grinding, for example, alkaline KOH that dissolves the surface of a silicon wafer can be used. For example, it is an alkaline solution that dissolves the surface of a silicon wafer. During this cleaning, the wafer surface layer is 0.05 to 1.0 μm
Even if removed, the flatness of the semiconductor wafer is maintained.
If the amount of erosion of the wafer surface due to cleaning is less than 0.05 μm, the dropped abrasive grains may remain on the wafer surface. If the thickness exceeds 1.0 μm, the roughness increases and the shape of the back surface of the wafer changes.

[0010] The back surface treatment of the semiconductor wafer is not limited. For example, sand blasting, polysilicon back seal (Polysilicon Back Seal), LTO (Low Tempe)
ratureOxidation) processing. Note that the sand blasting is a processing method in which abrasive grains such as Si oxide are sprayed on the back surface of the wafer to cause mechanical damage, and this is used as a gettering site. Polysilicon back seal processing is a processing method in which a polycrystalline silicon film is deposited on the back surface of a wafer and grain boundaries of the polycrystalline silicon are used as gettering sites. In addition, LTO
The processing is a processing method for forming an oxide film on the back surface of the wafer before performing the epitaxial process for the purpose of preventing auto doping. WHT (Wafer H) for heat treatment of wafer
eat Treatment) is one type of this backside treatment.

According to a second aspect of the present invention, the back surface treatment includes a sand blast treatment, a polysilicon layer deposition treatment,
2. The method for manufacturing a high flatness wafer according to claim 1, wherein the method is any one of an oxide film deposition process and a donor killer heat treatment. Further, the invention according to claim 3 is characterized in that the grinding step comprises:
The method for producing a high flatness wafer according to claim 1 or 2, wherein the method is performed using a resinoid bond grinding wheel of # 1500 to # 3000 manufactured by Disco Corporation. As a resinoid bond grinding wheel manufactured by Disco Corporation, for example, a resinoid bond # 2000 high-count grinding wheel having a product name of “IF-01-1-4 / 6-B-M01” can be used.

[0012]

According to the present invention, the surface of the etched wafer is ground, and then the ground surface of the wafer is cleaned. At this time, abrasive grains that have fallen off the grinding wheel during grinding and adhere to the wafer surface are washed away. Next, a predetermined back surface treatment is performed on the washed semiconductor wafer, and thereafter, the front surface of the wafer after the back surface treatment is mirror-polished. As described above, since the wafer back surface treatment is performed after the wafer surface is ground, during cleaning after the grinding, the cleaning liquid having an etching action may damage the wafer back surface treatment layer formed on the back surface side of the semiconductor wafer. Can be avoided.
In addition, the semiconductor wafer thus subjected to the grinding process is an etched wafer that has not been subjected to the back surface treatment,
That is, it is a semiconductor wafer having no abrasive grains attached to the front and back surfaces of the wafer at the time of back surface treatment, and no fine irregularities (generated during sandblasting) formed on the back surface of the wafer. Therefore, when the semiconductor wafer is held by the wafer holding portion of the grinding device and is ground during the wafer grinding, even if the back surface of the wafer is scratched, the scratch can be removed by the subsequent alkali cleaning. In addition, the abrasive grains falling off the grinding wheel can be removed by the washing with the alkaline solution or the like. In addition, contamination in grinding can be removed. Therefore, it is possible to prevent the semiconductor wafer from being damaged due to these abrasive grains.

In particular, according to the third aspect of the present invention, the grinding of the surface of the semiconductor wafer is performed by using #
This is performed using a resinoid bonded grinding wheel of No. 1500 to # 3000. This grinding wheel is a high-count resinoid bonded grinding wheel capable of grinding the silicon surface, which is an undamaged surface. Therefore, the wafer surface which has been etched and has no damage can be ground with this high-count grinding wheel with little damage (for example, a damage depth of about 2 μm) and without surface damage. In addition, grinding can be performed at a higher throughput as compared with electric field dress grinding.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing a method for manufacturing a high flatness wafer according to one embodiment of the present invention. As shown in FIG. 1, in this embodiment, generally, through each of the steps of slicing, chamfering, lapping, etching, cleaning, grinding, cleaning, backside processing, WHT, polishing, and cleaning, a high flatness is obtained. A silicon wafer is produced.
Hereinafter, each step will be described in detail.

The silicon ingot pulled up by the CZ method has a thickness of 860 μm in the slicing step (S101).
It is sliced into an 8-inch silicon wafer of about m. Next, this sliced wafer is subjected to a chamfering step (S
In 102), the periphery is chamfered to a predetermined shape using a chamfering grindstone. As a result, the peripheral portion of the silicon wafer is formed into a predetermined rounded shape (for example, a MOS type chamfered shape). Next, the chamfered silicon wafer is wrapped in a lapping step (S103). In this lapping step, the silicon wafer is placed between lap plates kept parallel to each other, and a lap liquid, which is a mixture of alumina abrasive grains, a dispersant, and water, is placed between the lap plate and the silicon wafer. Pour in. Then, by rotating and sliding under pressure, both sides of the wafer are mechanically wrapped. The lap amount of the silicon wafer is about 40 to 80 μm including the front and back surfaces of the wafer.

Next, the chamfered silicon wafer is etched (S104). Specifically, the silicon wafer is immersed in a mixed acid solution (normal temperature to 50 ° C.) in which hydrofluoric acid and nitric acid are mixed. After that, the silicon wafer is RCA
A cleaning step (S105) of cleaning with a system cleaning liquid is performed. Then, the surface of the silicon wafer was coated with a resinoid bonded grinding wheel manufactured by Disco Corporation, product name “IF-0”.
(1-1-4 / 6-B-M01) (S1
06). This grinding wheel is a special grinding wheel developed for processing a high-count and undamaged surface of # 2000. The product name of this grinding device is "DFG840".

The amount of grinding at this time is about 2 to 10 μm. As a result, when the surface of the wafer is polished in a later step, the polishing amount is 2 to 8 μm, which is reduced to about half of the conventional value. As described above, since the grinding is performed by using a grinding wheel having a high number, damage to the wafer is reduced (2 μm).
m or less) and can be ground without exposing the surface. As described above, the silicon wafer subjected to the grinding process is an etched wafer that has not yet been subjected to the back surface treatment, that is, a silicon wafer having no fine irregularities (for example, generated during sandblasting) formed on the back surface of the wafer. It is.

Next, the silicon wafer whose surface has been ground is washed with an alkaline washing solution (S).
107). As this cleaning liquid, 10-50% KOH
A solution is employed. As a result of this cleaning, diamond abrasive grains that have fallen off the grinding wheel during grinding and adhered to the wafer surface are washed away. Also, other contamination during grinding is removed. By this cleaning, the wafer surface is melted by 0.5 μm.

Next, a predetermined back surface treatment is performed on the washed semiconductor wafer (S108). Here, sandblasting is employed for the back surface treatment. That is, mechanical damage is given to the back surface of the silicon wafer by spraying abrasive grains of silicon oxide on the back surface of the silicon wafer. The silicon wafer whose back surface has been treated in this way is put into a heating furnace and subjected to WHT (Wa).
fer Heat Treatment) processing (S109). That is, heating is performed in a heating furnace at 650 ° C. for 10 minutes. At this time, if an abnormal defect occurs in the wafer in a grinding step or the like, the abnormality is emphasized during the heat treatment. Therefore, it is easy to determine the quality of the silicon wafer.

Subsequently, the surface of the silicon wafer is mirror-polished (S110). The polishing amount at this time is S
It is only necessary to remove the damage in the grinding step of 106.
Therefore, 2 to 8 μm is sufficient. Subsequently, a cleaning step (S111) is performed. Specifically, the cleaning is performed in an alkaline system. Through such a manufacturing process, a high-quality silicon wafer in which the wafer back surface treatment layer is not damaged by the cleaning liquid is manufactured.

FIG. 2 is a graph showing the degree of erosion in the back surface treatment of the silicon wafer according to this embodiment in comparison with the conventional example. The flatness is indicated by SBIR. FIG. 2 shows that the flatness of the silicon wafer according to this embodiment is improved over that of the conventional example. The flatness is measured by a known method using a known device.

[0022]

According to the present invention, since the back surface treatment step of the semiconductor wafer is performed after the wafer surface is ground, the back surface treatment layer formed on the back surface of the wafer at the time of cleaning after the grinding is melted. There is no damage, and there is no damage due to the suction of the back surface processed during the wafer surface grinding.

In particular, according to the third aspect of the present invention, the step of grinding the surface of the semiconductor wafer is performed using a resinoid bond grinding wheel # 1500 to # 3000 manufactured by Disco Corporation. The surface of the wafer can be ground with little damage and without exposing the surface. In addition, grinding can be performed with higher throughput than in electric field dress grinding.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for manufacturing a high flatness wafer according to one embodiment of the present invention.

FIG. 2 is a graph showing the degree of erosion in back surface treatment of a silicon wafer according to one embodiment of the present invention as compared with a conventional example.

FIG. 3 is a flowchart showing a method for manufacturing a high flatness wafer according to a conventional means.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshiro Kawamoto 1-5-1, Otemachi, Chiyoda-ku, Tokyo F-term (reference) 5F043 AA02 AA14 BB02 BB27 DD30 EE40 FF07

Claims (3)

[Claims] 1. A step of grinding a surface of a semiconductor wafer after etching, a step of cleaning the ground surface of the wafer after grinding, a step of mirror polishing, and a step of performing a predetermined back surface treatment on the back surface of the semiconductor wafer. A method of manufacturing a high flatness wafer, comprising: performing the back surface treatment step after performing a grinding step on a semiconductor wafer surface. 2. The back surface treatment is a sand blast treatment,
2. The method for manufacturing a high flatness wafer according to claim 1, wherein the method is any one of a polysilicon layer deposition process, an oxide film deposition process, and a donor killer heat treatment. 3. The method for manufacturing a high flatness wafer according to claim 1, wherein the grinding step is performed using a resinoid bonded grinding wheel # 1500 to # 3000 manufactured by Disco Corporation.