JP2004214398A - Method of manufacturing semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor wafer by which a damage hardly occurs at the outer periphery part of a semiconductor wafer due to contact of a wafer holding hole with an inner peripheral wall in the case of wafer flat work. <P>SOLUTION: On the outermost peripheral surface of a silicon wafer W, a protective coat Wa is formed. Thus, even when the outermost peripheral surface of the silicon wafer W is brought into contact with the inner peripheral wall of the wafer holding hole 12 during wrapping, what the outermost peripheral surface actually brought into contact with is the protective coat Wa. Thus, the damage due to wearing hardly occurs at the outer periphery part of a semiconductor wafer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor wafer, for example, a method for manufacturing a semiconductor wafer for preventing damage generated on an outer peripheral portion of a semiconductor wafer due to contact with an inner wall of a wafer holding hole of a lap carrier during lapping.
[0002]
[Prior art]
A conventional standard semiconductor wafer processing process will be described with reference to FIG.
First, in a slicing step (S501), a silicon wafer is sliced from a block-cut ingot. In the next chamfering step (S502), the outer peripheral portion of the silicon wafer is chamfered. In the subsequent lapping step (S503), a lapping liquid having a mixture of alumina abrasive grains, a dispersant, and water is supplied by a lapping device having a pair of upper and lower lapping plates, and the front and back surfaces of the silicon wafer are wrapped. Here, the processing has a margin of about 40 to 80 μm on both sides of the wafer.
[0003]
Subsequently, the silicon wafer is immersed in a predetermined etching solution (mixed acid or alkali + mixed acid) to remove distortion in the lapping process, distortion in the chamfering step, and the like (S504). In this case, usually, one side is etched at 10 to 20 μm, and both sides are etched at 20 to 40 μm.
In the next PCR (Polishing Corner Rounding) step (S505), the outer peripheral portion of the silicon wafer is subjected to PCR processing in a state where the front and back surfaces of the silicon wafer are attracted to the chuck. In the PCR processing, the chamfered surface is mirror-finished with a polishing cloth.
[0004]
In the subsequent primary polishing step (S506), the surface of the silicon wafer is primarily polished using a single-side polishing apparatus. At this time, the surface of the silicon wafer is polished by about 10 μm. Thereby, the unevenness of the silicon wafer after the etching is removed, and the flatness is improved.
In the subsequent polishing step (S507), the wafer surface (device forming surface) is polished with a polishing amount of 1 μm or less using a single-side polishing apparatus. Then, they are subjected to final cleaning and inspection, and are shipped to a device maker of an order receiving party.
[0005]
Here, the lapping process by the lapping device will be specifically described with reference to FIGS.
FIG. 6 is a schematic plan view of a lapping device according to a conventional means. FIG. 7 is an enlarged cross-sectional view showing a state cut along the line S7-S7 in FIG.
The conventional lapping apparatus 100 forms a plurality of wafer holding holes 102 in a carrier (wafer holding plate) 101 and holds a silicon wafer W in each wafer holding hole 102. Then, a lapping liquid containing alumina abrasive grains is supplied to the silicon wafer W from above, and the front and back surfaces of each silicon wafer W are simultaneously wrapped.
That is, a carrier 101 having an outer gear 103 on its outer periphery is rotatably and revolvably provided between a rotatable sun gear 110 and an internal gear 111, and the front and back of a silicon wafer W held by the carrier 101. Both surfaces (upper and lower surfaces) are wrapped by being pressed and slid by the upper surface plate 106 and the lower surface plate 107.
[0006]
[Problems to be solved by the invention]
However, according to such a conventional lapping method, when the silicon wafer W is held in the wafer holding hole 102, there is a slight gap between the inner peripheral wall of the wafer holding hole 102 of the carrier 101 and the outer peripheral portion of the silicon wafer W. A gap appears. Therefore, during double-side polishing, the outermost peripheral portion of the silicon wafer W may come into contact with the inner peripheral wall of the carrier 101, causing rubbing and damaging the outermost peripheral portion of the silicon wafer W.
[0007]
Therefore, as a result of intensive research, if the outermost peripheral surface of the semiconductor wafer is protected by a protective film, the protective film does not actually contact the inner peripheral wall of the wafer holding hole in flattening processing such as wrapping. It becomes. As a result, they have found that the outermost peripheral portion of the wafer is less likely to be damaged by rubbing, and have completed the present invention.
[0008]
[Object of the invention]
An object of the present invention is to provide a method of manufacturing a semiconductor wafer in which the outer peripheral portion of the semiconductor wafer is less likely to be damaged due to contact with the inner peripheral wall of the wafer holding hole in the flattening process of the semiconductor wafer.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a protective film forming step of forming a protective film on at least the outermost peripheral surface of a chamfered semiconductor wafer, and the semiconductor wafer having the protective film is inserted into a wafer holding hole formed in a wafer holding plate. A semiconductor wafer manufacturing method comprising: a wafer flattening step of holding and flattening the semiconductor wafer; and a protective film removing step of removing the protective film from the flattened semiconductor wafer.
[0010]
As the semiconductor wafer, a silicon wafer, a gallium arsenide wafer, or the like can be used.
The formation range of the protective film on the exposed surface of the semiconductor wafer may be only the outermost peripheral surface of the wafer. Alternatively, only the outer peripheral surface (chamfered surface) of the semiconductor wafer may be used. This is because, for example, the lap carrier follows the chamfered shape as it is used, so that the inner wall surface shape is broken. Therefore, in order to protect the chamfered surface, it is effective to protect the chamfered surface with a protective film. Further, the entire exposed surface of the semiconductor wafer may be used. The outermost peripheral surface of the wafer referred to here is a portion of the outer peripheral surface (chamfered surface) of the semiconductor wafer that protrudes most outward.
Examples of the flattening process of the semiconductor wafer include a lap process of simultaneously lapping both front and back surfaces of a semiconductor wafer held in wafer holding holes of a wafer holding plate by upper and lower lap plates. In addition, there is a double-head grinding process for simultaneously grinding both front and back surfaces of a semiconductor wafer held in a wafer holding hole by upper and lower grinding wheels. Furthermore, double-side polishing in which both the front and back surfaces of the semiconductor wafer held in the wafer holding holes by the upper and lower polishing cloths are simultaneously polished may be mentioned.
[0011]
In short, in various types of wafer flattening processing, all the flattening processing by an apparatus having a wafer holding plate having a wafer holding hole is included. As the wafer flattening device provided with the wafer holding plate, for example, various flattening devices having a planetary gear structure can be adopted. Further, between the upper surface plate and the lower surface plate, the semiconductor wafer in the wafer holding hole formed in the wafer holding plate is rotated in the corresponding wafer holding hole, and circular movement without rotation of the wafer holding plate. And a sun-gear-type flattening apparatus that performs the above.
The thickness of the protective film is appropriately selected according to the material of the protective film. For example, when the protective film is a wax, the thickness is 1 to 10 μm, and when the protective film is a silicon oxide film, the thickness is 0.05 to 0.1 μm.
[0012]
The method for forming the protective film is not limited. For example, in the case of a protective film made of wax and a protective film made of resin, a semiconductor wafer is immersed in paste-like wax or paste-like resin. Alternatively, the semiconductor wafer may be brushed with wax or resin. On the other hand, when the protective film is a silicon oxide film, the semiconductor wafer is inserted into a thermal oxidation furnace, and a heat treatment is performed under a predetermined condition, for example, in an oxygen gas atmosphere. When the protective film is a silicon nitride film, nitrogen gas is supplied into the thermal oxidation furnace instead of oxygen gas.
The method of removing the protective film differs depending on the material of the protective film. For example, in the case of a protective film made of wax, ozone water, a cleaning agent dedicated to wax removal, or a mixed solution of alkali (NaOH, KOH, NH ₄ OH) and hydrogen peroxide water is used. In the case of a protective film made of silicon oxide, for example, an HF solution is used. Further, an HF solution or the like is used for removing the protective film made of silicon nitride.
[0013]
The invention according to claim 2 is the method for manufacturing a semiconductor wafer according to claim 1, wherein the material of the protective film is any one of wax, resin, silicon dioxide, and silicon nitride.
[0014]
The invention according to claim 3 is the method for manufacturing a semiconductor wafer according to claim 1, wherein the flattening processing of the semiconductor wafer is any one of lapping, double-side grinding, and double-side polishing.
[0015]
[Action]
According to the present invention, the protective film is formed on the outermost peripheral surface of the semiconductor wafer. Thereby, even in the case where the outermost peripheral portion of the semiconductor wafer comes into contact with the inner peripheral wall of the wafer holding hole in the flattening process of the semiconductor wafer, the contact becomes the protective film. As a result, the outermost peripheral portion of the wafer is unlikely to be damaged by rubbing.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flow sheet showing a method for manufacturing a semiconductor wafer according to a first embodiment of the present invention. FIG. 2 is an enlarged sectional view of a main part of the lapping device in the method for manufacturing a semiconductor wafer according to the first embodiment of the present invention.
As shown in FIG. 1, in the first embodiment, the surface is mirror-finished through the steps of slicing, chamfering, wax application, wrapping, wax removal, etching, PCR, primary polishing, finish polishing, and cleaning. A finished silicon wafer is produced. Hereinafter, each step will be described in detail.
The silicon ingot pulled up by the CZ method is sliced into an 8-inch silicon wafer having a thickness of about 860 μm in a slicing step (S101).
Next, in the chamfering step (S102), the outer periphery of the sliced wafer is chamfered into a predetermined shape by using a # 600 metal chamfering grindstone. Thereby, the outer peripheral portion of the silicon wafer is formed into a predetermined rounded shape (for example, a MOS type chamfered shape).
[0017]
Subsequently, wax is applied to the entire exposed surface of the chamfered silicon wafer (S103). Specifically, a silicon wafer is immersed in liquid wax stored in a wax bath. After being pulled up, it is loaded into a predetermined drying device for a predetermined time and dried. As a result, a wax protective film of 5 to 10 μm is formed on the entire exposed surface of the silicon wafer. The wax to be used is, for example, “AC-05429” or “MA” manufactured by Nikka Seiko Co., Ltd. The thickness to be applied and the immersion time vary depending on the type of the wax.
Thereafter, the silicon wafer coated with the wax is wrapped (S104).
FIG. 2 shows the wrapping device 10. The lapping apparatus 10 holds a silicon wafer W in a plurality of wafer holding holes 12 formed in a carrier plate (wafer holding plate) 11 and simultaneously laps both sides of the wafer while supplying a predetermined lapping liquid from above. Configuration.
That is, a carrier plate 11 having an outer gear 13 on an outer peripheral portion is rotatably and revolvably provided between a sun gear 20 and an internal gear 21 which are rotatably provided, and a silicon wafer W held by the carrier plate 11 is provided. While supplying a lapping liquid which is a mixture of alumina abrasive grains, a dispersant, and water from above the upper and lower sides (upper and lower sides), the upper lap surface plate 16 having lattice-shaped lap grooves on both lap action surfaces and the lower side. The silicon wafer W is wrapped by being pressed and slid in contact with the lap surface plate 17.
[0018]
During the lap, there is a concern that the chamfered surface of the silicon wafer W comes into contact with the inner peripheral wall of the wafer holding hole 12 of the carrier plate 11 and causes rubbing, thereby damaging the outermost peripheral portion of the silicon wafer W. However, a protective film Wa made of wax is formed on the entire exposed surface of the silicon wafer W. Therefore, even when the outermost peripheral portion of the silicon wafer W contacts the inner peripheral wall of the wafer holding hole 12 during the wafer flattening process (lap), the protective film Wa actually comes into contact. During this processing, the protective film Wa is shaved, but not to the silicon wafer. Thereby, the outermost peripheral portion of the silicon wafer W is less likely to be damaged by rubbing. The portions of the protective film Wa formed on both the front and back surfaces of the wafer are removed during the lapping.
[0019]
Next, after this wrapping, the protective film Wa remaining on the outer peripheral surface of the wafer or the like is removed (S105). More specifically, the wrapped silicon wafer W is removed with a wax-removing detergent, a mixed solution of alkali (NaOH, KOH, NH ₄ OH) and hydrogen peroxide, or high-concentration ozone water. A mixed solution of sulfuric acid and an oxidizing agent (hydrogen peroxide solution, ozone water) can also be used. Thereby, the protective film Wa remaining on the exposed surface of the silicon wafer W after the lap is melted and removed.
Next, the wrapped silicon wafer W from which the protective film Wa has been removed is etched (S106). Specifically, the silicon wafer W is immersed for a predetermined time in a mixed acid solution (normal temperature to 50 ° C.) in which hydrofluoric acid and nitric acid are mixed. Thereby, the damage in each of the steps of chamfering and wrapping the silicon wafer W is removed.
[0020]
Next, the outer peripheral portion of the etched silicon wafer W is subjected to PCR processing (S107). Here, a known PCR processing device is used. That is, an apparatus for rotating a cylindrical polishing cloth by a motor is employed. The polishing cloth is rotated by a motor, and the outer peripheral surface of the silicon wafer W is brought into contact with the outer peripheral surface of the rotating polishing cloth under the supply of the abrasive. Thereby, the outer peripheral surface of the wafer is mirror-finished. At this time, only one surface of the silicon wafer W is sucked and held by the holding plate. The suction source is a negative pressure generator connected to the holding plate via a hose or the like. In addition, by performing this PCR processing, damage due to rubbing remaining on the outermost peripheral portion of the wafer is removed.
[0021]
Thereafter, the surface of the silicon wafer W after the PCR processing is primarily polished by a single-side polishing apparatus (S108). Specifically, a silicon wafer W is attached to the lower surface of the carrier held by the polishing head with wax, and while supplying a slurry containing free abrasive grains, the nonwoven fabric is pressed against a polishing cloth impregnated with a urethane resin and hardened to polish the polishing. I do.
Next, the surface of the silicon wafer W is subjected to finish polishing (S109). A known finish polishing device is used. At this time, a nonwoven fabric for finish polishing is used. The polishing amount is about 0.1 to 2 μm.
Next, finish cleaning of the silicon wafer W is performed (S110). This cleaning is RCA cleaning based on two types of cleaning liquids, SC-1 liquid and SC-2 liquid.
[0022]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a flow sheet of a method for manufacturing a semiconductor wafer according to a second embodiment of the present invention.
The second embodiment is an example in which a silicon oxide film is used as the protective film Wa of the silicon wafer W instead of the wax used in the first embodiment.
As shown in FIG. 3, in the second embodiment, slice (S301), chamfering (S302), oxide film formation (S303), lap (S304), oxide film removal (S305), etching (S306), PCR (S307) Through the respective steps of primary polishing (S308), finish polishing (S309), and cleaning (S310), a silicon wafer W having a mirror-finished surface is manufactured.
[0023]
In the oxide film forming step, a protection film Wa made of a silicon oxide film is formed on the entire exposed surface of the silicon wafer W after the chamfering. Specifically, the silicon wafer W is inserted into a thermal oxidation furnace, and an oxidizing heat treatment is performed at 1100 ° C. for a predetermined time in an oxygen gas atmosphere.
On the other hand, in the step of removing the protective film Wa, the wrapped silicon wafer W is immersed in the HF cleaning liquid (23 to 50 ° C.) for a predetermined time to remove the protective film Wa remaining on the exposed surface of the wrapped silicon wafer W. .
Other configurations, operations, and effects are the same as those of the first embodiment, and a description thereof will not be repeated.
[0024]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flow sheet of a method for manufacturing a semiconductor wafer according to a third embodiment of the present invention.
The third embodiment is an example in which the outermost peripheral surface of the wafer is prevented from being damaged not in the lapping process but in the double-side grinding process after the chamfering.
As shown in FIG. 4, in the third embodiment, slicing (S401), chamfering (S402), wax application (403), double-side grinding (S404), lap (S405), wax removal (S406), and etching ( S407), PCR (S408), primary polishing (S409), finish polishing (S410), and cleaning (S411) are performed to produce a silicon wafer W having a mirror-finished surface.
[0025]
In the double-side grinding step, for example, both the front and back surfaces of the silicon wafer W are simultaneously ground using two # 400 resinoid grinding wheels arranged vertically.
In a pre-process of the double-side grinding, a protective film Wa made of wax is formed on the exposed surface of the wafer W after the chamfering, and after the double-side grinding and lapping, the remaining portion of the protective film Wa is removed with a wax removing liquid. Also in the lapping process, the chamfered surface of the wafer is protected by the wax.
Other configurations, operations, and effects are the same as those of the first embodiment, and a description thereof will not be repeated.
[0026]
【The invention's effect】
According to the present invention, since the protective film is formed on the outermost peripheral surface of the wafer, even if the outermost peripheral portion of the semiconductor wafer contacts the inner peripheral wall of the wafer holding hole during the planarization of the semiconductor wafer, the outermost peripheral portion of the wafer (Or chamfer) is less likely to be damaged by rubbing.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing a method for manufacturing a semiconductor wafer according to a first embodiment of the present invention.
FIG. 2 is an enlarged sectional view of a main part of the lapping device in the method of manufacturing a semiconductor wafer according to the first embodiment of the present invention.
FIG. 3 is a flow sheet of a method for manufacturing a semiconductor wafer according to a second embodiment of the present invention.
FIG. 4 is a flow sheet of a method for manufacturing a semiconductor wafer according to a third embodiment of the present invention.
FIG. 5 is a flow sheet showing a method for manufacturing a semiconductor wafer according to a conventional means.
FIG. 6 is a schematic plan view of a wrapping device used in a method of manufacturing a semiconductor wafer according to a conventional means.
FIG. 7 is an enlarged sectional view taken along line S7-S7 of FIG. 6;
[Explanation of symbols]
10 wrapping device,
11 Carrier plate (wafer holding plate),
12 wafer holding holes,
W silicon wafer (semiconductor wafer),
Wa protective film.

Claims (3)

A protective film forming step of forming a protective film on at least the outermost peripheral surface of the chamfered semiconductor wafer,
A wafer flattening step of holding a semiconductor wafer having this protective film in a wafer holding hole formed in a wafer holding plate and flattening the semiconductor wafer,
A protective film removing step of removing the protective film from the planarized semiconductor wafer. 2. The method for manufacturing a semiconductor wafer according to claim 1, wherein the material of the protective film is any one of wax, resin, silicon dioxide, and silicon nitride. The method for manufacturing a semiconductor wafer according to claim 1, wherein the flattening processing of the semiconductor wafer is any one of lapping, double-side grinding, and double-side polishing.

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