JPH1055998A - Processing of silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of processing a silicon wafer, which does not cause the deterioration of silicon in the peripheries of the processing parts of the surface of the wafer and readhesion of the silicon, can process the wafer by a simple device, and is superior also in the mass productivity of the wafer. SOLUTION: This is a method of performing a removal processing on a silicon wafer 1, and the method is executed in such a way that it is provided with a process for forming a pattern, which masks the parts other than scheduled processing parts A of the surface of the wafer 1, a process for performing the removal processing by a way, wherein etching gas is fed to the parts 4 with exposed silicon and the etching gas is chemically reacted with the silicon to remove the silicon in the above parts 4 by a volatilization, and a process for removing the above pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a silicon wafer, in which the surface of the silicon wafer is subjected to removal processing such as drilling and groove processing.

[0002]

2. Description of the Related Art Conventionally, in order to form a semiconductor device such as a large-scale integrated circuit (LSI) or a solar cell, a surface of a silicon wafer has been subjected to a removal process such as a fine drilling process or a groove process. I have. In particular, recently, a through-hole type solar cell used by forming a large number of through-holes in a silicon wafer has been devised and its practical use has been studied. As a method of forming a hole or a groove on the surface of a silicon wafer, a method using a solid laser, a gas laser, an electron beam, or the like is generally known. That is, a laser beam or an electron beam is applied to the surface of the silicon wafer, and the surface of the silicon wafer is melted and evaporated by the heat, thereby performing a removing process such as drilling.

[0003]

However, in the processing using the laser, the electron beam, or the like, the silicon around the processed portion is deteriorated due to rapid heating, or
Since the molten silicon scatters around the processing portion and reattaches, and contaminates the surface of the silicon wafer, there is a problem in that device formation after processing is likely to be hindered. Also, in the drilling process using the laser, the electron beam, or the like, 1
The processing time required for drilling individual holes is relatively short. However, since this is an individual process in which a beam is irradiated to a predetermined location and drilling is performed one by one, a large number of holes (for a through-hole type solar cell, for example, 100 mm × 100 mm Need more than 1000 holes in silicon wafer)
There is a problem that processing time is extremely long, mass productivity is low, and the cost is high. In addition, if a groove or the like of a complicated pattern is to be processed by using the laser or the electron beam, the irradiation position of the beam must be moved along the processing pattern, which requires a large and complicated device. However, there is a problem that the processing time is long.

The present invention has been made in view of such circumstances, and a silicon wafer processing method which does not cause deterioration or reattachment of silicon around a processing portion, can be processed with a simple apparatus, and has excellent mass productivity. The purpose is to provide.

[0005]

In order to achieve the above object, a method for processing a silicon wafer according to the present invention is a method for performing a removing process on a silicon wafer. A step of forming a pattern for masking a portion, and supplying an etching gas to the portion to be processed where silicon is exposed, and performing a chemical reaction between the etching gas and silicon to volatilize and remove the silicon in the portion to be processed. It is a first gist that the method includes a step of performing and a step of removing the pattern.

Further, a method of processing a silicon wafer according to the present invention is a method of removing a silicon wafer, comprising the steps of forming an oxide film on the surface of the silicon wafer, and forming an oxide film on the surface of the silicon wafer. Forming an oxide film pattern for masking a portion other than the portion to be processed by removing the oxide film in the portion to be processed; and etching gas to the portion to be processed in which the oxide film is removed and silicon is exposed. And a step of removing the silicon oxide by volatilizing and removing silicon in the portion to be processed by chemically reacting the etching gas with the silicon, and a step of removing the pattern of the oxide film. And

[0007]

Next, an embodiment of the present invention will be described.

The silicon wafer to which the present invention is applied may be any silicon wafer that has been used in the manufacture of semiconductor devices and solar cells. For example, a single crystal ingot or a polycrystal ingot may be sliced into a disk or a square plate having a predetermined thickness and mirror-finished.

As the etching gas used for processing the silicon wafer, a gas having a property of reacting with silicon to generate a volatile substance is optimal, and a chlorine-based gas or a fluorine-based gas is preferably used. Examples of such gas include ClF ₃ , NF ₃ , CCl ₂ F ₂ , C
F ₄ , C ₂ F ₆ , C ₃ F ₈ , CHF ₃ , CCl ₄ , SF
₆ , CCl ₃ F, HCl, CBrF _{3 and the} like, and can be used alone or as a mixed gas of two or more kinds. Among these, C is particularly preferred from the viewpoint that silicon is easily etched only by a thermal decomposition reaction without using plasma, in addition to excellent etching properties and excellent mass productivity.
lF ₃ is preferably used.

First, a method of processing a silicon wafer according to a first embodiment of the present invention will be described.

The processing method according to the first embodiment includes a step of forming a pattern for masking a portion other than a portion to be processed on the surface of a silicon wafer, and supplying an etching gas to the portion to be processed where silicon is exposed. Then, a step of removing the silicon by volatilizing and removing silicon in the portion to be processed by chemically reacting the etching gas with the silicon, and a step of removing the pattern are provided.

More specifically, first, a silicon wafer is prepared, and a pattern for masking a portion of the surface of the silicon wafer other than a portion to be processed is formed. Hereinafter, this processing is referred to as masking processing.

The masking process is performed, for example, by photolithography. That is, first, as shown in FIG. 1, a resist film 3 is formed on a silicon wafer 1 by spin coating or the like. At this time,
The resist film 3 is also formed on the side surface of the silicon wafer 1. Next, the resist film 3 is exposed to ultraviolet light or far ultraviolet light through a glass mask (not shown) or the like to be developed, and as shown in FIG.
A pattern of the resist film 3 in which the other portions are covered with the resist film 3 is formed. The resist film 3 has a negative shape,
Any positive type is acceptable. Thereby, the silicon is exposed only in the portion 4 to be processed. In the masking process by the photolithography, the pattern of the resist film 3 can be arbitrarily set by setting an exposure pattern through a glass mask.
The number and the like can be set arbitrarily.

The resist for forming the resist film 3 is not particularly limited. For example, a dichromic acid obtained by using a dichromate as a photosensitive material in a polymer such as glue, casein, shellac, polyvinyl alcohol, or the like Water-soluble photoresist, water-soluble synthetic resin and 4,4 '
Non-bichromic acid-based compounds, such as mixtures of sodium diazidostilbene-2,2'-disulfonate, polyvinyl alcohol and vinyl acetate emulsions with diazo resins, and water-soluble photopolymers in which stilbazolium groups have been introduced into polyvinyl alcohol Water-soluble photoresist, rubber-based resist with cyclized rubber and azide compound dissolved in xylene, poly (vinyl p-azidobenzoate), poly (vinyl cinnamate), methacryloyloxychalcone-glycidyl methacrylate copolymer, photosensitive polyimide, acrylic Various types are used, such as a photopolymer oil-soluble photoresist such as a urethane polymer and an acrylic copolymer, and a positive photoresist in which a sulfonic acid ester of a naphthoquinone diad compound and a novolak resin are dissolved in a cellosolve-based solvent.

Next, an etching gas is supplied to the portion to be processed 4 where the silicon is exposed, and a chemical reaction is performed between the etching gas and the silicon to volatilize and remove the silicon in the portion to be processed 4 to perform a removing process.

That is, as shown in FIG. 3, the silicon wafer 1 subjected to the masking process is loaded into the processing chamber 6,
The inside of the processing chamber 6 is evacuated to about 10 ⁻³ Torr or less. Next, an etching gas such as ClF ₃ is introduced into the processing chamber 6 and the etching gas is supplied to the portion 4 to be processed where the silicon is exposed. Then, a chemical reaction is caused between the etching gas and silicon, and for example, silicon is volatilized and removed by a reaction represented by the following formula (1), and a hole 19 is formed. In FIG. 3, reference numeral 7 denotes an exhaust pipe for evacuating the inside of the processing chamber 6, and reference numeral 8 denotes an etching gas introduction pipe.

[0017]

Embedded image 3Si + 4ClF ₃ → 3SiF ₄ (volatile substance) + 2Cl ₂ (gas) (1)

At this time, portions other than the portion 4 to be processed are:
Since it is masked by the resist film 3, it hardly reacts with the etching gas, and only the portion 4 to be processed is volatilized and removed. At this time, the silicon wafer 1
Since it is placed on the base 9, the lower surface of the silicon wafer 1 hardly comes into contact with the etching gas. Then, if necessary, the etching process is further continued until the hole 19 penetrates to the back surface of the silicon wafer 1 to form the through hole 11 as shown in FIG. Of course, depending on the case, it is also possible to form a hole having a constant depth without penetrating the hole 19.

In the above-mentioned etching treatment, the treatment can be carried out satisfactorily even at a normal temperature, but it is preferable to heat it to about 50 to 150 ° C. in order to increase the etching rate. The etching gas concentration is 10 to 10
It is preferably set to 0% by volume. Also in this case, the etching rate can be increased as the etching gas concentration increases. The pressure in the processing chamber 6 is 10 ^{−3 to} 76.
Preferably, it is set to 0 Torr. The etching rate can be arbitrarily changed by changing the processing temperature, the etching gas concentration, and the pressure in the processing chamber 6. By adjusting the etching rate and the etching time, the amount of etching can be controlled, and the amount of processing can be arbitrarily controlled. For example, it is possible to control the groove depth in the groove processing or to control the depth of the hole in the drilling processing. When the processing temperature is increased, a heater is provided on the base 9 to heat the silicon wafer 1 itself, thereby improving the heating efficiency. Also,
A heater may be provided in the processing chamber 6 to heat the processing chamber 6, or an etching gas heated in advance may be introduced into the processing chamber 6.

Then, the unnecessary resist film 3 is stripped by a stripping agent or a plasma asher, etc., and the silicon wafer 1 having the through holes 11 as shown in FIG.
Can be obtained.

As described above, the silicon wafer 1 can be subjected to removal processing such as drilling and groove processing. According to the above-mentioned processing method, silicon is not rapidly heated unlike conventional processing using a laser or the like, so that heat-induced deterioration and re-adhesion of molten silicon do not occur, and the silicon can be directly used in a device forming process. Further, an expensive laser generator or the like is not required, and the apparatus cost is reduced. Furthermore, by arbitrarily setting the pattern of the resist film 3, the shape, location, number, and the like of the processed portion can be arbitrarily set. In addition, even if a complicated pattern is processed, the entire surface of the silicon wafer 1 can be etched and processed at a stretch, so that the processing time can be shortened and mass productivity is excellent.

Next, a method of processing a silicon wafer according to a second embodiment of the present invention will be described.

The processing method according to the second embodiment includes a step of forming an oxide film on the surface of a silicon wafer and a step of removing an oxide film in a portion to be processed of the oxide film formed on the surface of the silicon wafer. Forming an oxide film pattern that masks a portion other than the portion to be processed by the above, and supplying an etching gas to the portion to be processed where the oxide film is removed and the silicon is exposed, thereby causing a chemical reaction between the etching gas and silicon. A step of removing the silicon by volatilizing and removing the silicon in the portion to be processed, and a step of removing the pattern of the oxide film.

More specifically, first, a silicon wafer 1 as shown in FIG. 6 is prepared, and as shown in FIG.
The surface of the silicon wafer 1 to form an oxide film 2 of SiO ₂ or the like.

The method for forming the oxide film 2 is as follows.
For example, a silicon wafer 1 is placed in an O ₂ gas atmosphere at 800
A heat treatment of heating and holding at 1200 ° C. for 60 to 180 minutes is performed. Note that the above heat treatment is not limited to the O ₂ gas atmosphere, and may be performed in a steam atmosphere, an air atmosphere, or the like. Alternatively, a method of immersing the silicon wafer 1 in an HNO ₃ solution to form a SiO ₂ film on the surface may be used. The thickness of the oxide film 2 is preferably 10,000 ° or more, from the viewpoint of obtaining an effective masking effect at the time of an etching process performed later, and is preferably 1000 to 50 °.
00 ° is more preferable.

Next, by removing the oxide film 2 in the portion to be processed of the oxide film 2 formed on the surface of the silicon wafer 1, a pattern of an oxide film for masking a portion other than the portion to be processed is formed. Hereinafter, this processing is referred to as patterning processing.

The patterning process is performed, for example, by photolithography. That is, first, FIG.
As shown in FIG. 3, a resist film 3 is formed on the silicon wafer 1 on which the oxide film 2 is formed by spin coating or the like.
To form At this time, the resist film 3 is also formed on the side surface of the silicon wafer 1. Next, the resist film 3 is exposed to ultraviolet light or far ultraviolet light through a glass mask (not shown) or the like to develop the resist film 3. As shown in FIG. The pattern of the film 3 is formed. The resist film 3 may be either a negative type or a positive type. Next, by immersing the silicon wafer 1 on which the pattern of the resist film 3 is formed in an HF solution or the like, the oxide film 2 of the portion 4 to be processed which is not covered with the resist film 3, as shown in FIG. Dissolve and remove. Thereby, the silicon is exposed only in the portion 4 to be processed. Then, the unnecessary resist film 3 is peeled off by a peeling agent or a plasma asher, and as shown in FIG.
The pattern of the oxide film 2 that masks the other parts is formed. In the patterning process by the photolithography, the pattern of the oxide film 2 can be arbitrarily set by setting the exposure pattern through a glass mask, whereby the shape, location, number, etc. of the processed portion can be arbitrarily set. Can be set to

Next, as shown in FIGS. 12 and 13, an etching gas is supplied to the portion 4 to be processed where the oxide film 2 has been removed and the silicon has been exposed in the same manner as in the first embodiment. Then, a removing process is performed by causing a chemical reaction between the etching gas and silicon to volatilize and remove silicon in the portion 4 to be processed. At this time, since the portions other than the portion to be processed 4 are masked by the oxide film 2, they hardly react with the etching gas, and only the portion to be processed 4 is volatilized and removed.

As described above, the silicon wafer 1 can be subjected to removal processing such as drilling and groove processing. According to the above-described processing method, since the mask is formed by the pattern of the oxide film 2, when a device or the like is formed and used as a wafer, the oxide film 2 is previously formed when manufacturing a device to be used with the oxide film 2 formed on the surface. It is convenient because it is formed. In addition, there is an advantage that a complicated pattern of the oxide film 2 can be easily formed as described above. In addition, since the oxide film is simultaneously formed on the side surface of the silicon wafer, there is an advantage that it is not necessary to newly mask the side surface. Other than that, it is the same as the processing method of the first example, and has the same effect.

In both of the above embodiments, the resist film 3 is exposed to ultraviolet light or the like to form a pattern of the resist film 3 during the masking process and the patterning process. However, the present invention is not limited to this. As shown in FIG. 14, a resist film 3 is formed on the silicon wafer 1 on which the oxide film 2 is formed by screen printing or the like.
The pattern a may be directly printed. According to this method, the patterning process is greatly simplified, so that the cost can be further reduced.

Further, in both of the above-described embodiments, the etching gas is introduced from the etching gas introduction pipe 8 into the processing chamber 6 during the etching process. However, the present invention is not limited to this. Using a micro nozzle extending to the vicinity of the part 4 to be processed 1
An etching gas may be directly blown onto the portion 4 to be processed through the micro nozzle. By doing so, the loss of the etching gas is reduced, and the running cost can be reduced. Further, it is also possible to process only a necessary portion of the surface of the silicon wafer 1.

[0032]

As described above, in the method for processing a silicon wafer according to the present invention, the etching gas is subjected to a chemical reaction, and the silicon to be processed is volatilized and removed by the etching action. As a result, deterioration due to rapid heating of silicon unlike the conventional processing using a laser or the like does not occur. Further, contamination of the silicon wafer surface due to scattering and reattachment of the molten silicon does not occur. Therefore, there is no hindrance to device formation after processing, and the device can be used as it is in the device formation process. Further, an expensive laser generator or the like is not required, and the apparatus cost is reduced. Furthermore, in order to form and process a pattern that masks a portion other than the portion to be processed on the silicon wafer surface, the pattern is arbitrarily set, so that the shape of the processed portion,
The location, number, etc. can be set arbitrarily. In addition, even when processing a large number of holes or complex patterns, the entire surface of the silicon wafer can be etched and processed all at once, so the equipment and processing operations are simple, the processing time is short, and extremely excellent mass productivity is achieved. Processing at a cost becomes possible. In addition, since the processing can be performed only by supplying the etching gas, the operation is simple, and the silicon wafer is not damaged or cracked due to mechanical shock.

Next, an embodiment will be described.

[0034]

Example 1 As Example 1, the processing method of the present invention was applied to the production of a through-hole type solar cell. First, 100m
A silicon wafer having a size of mx 100 mm x a thickness of 0.3 mm is prepared, and a through hole having a hole size of 0.5 mm x 0.5 mm and a hole pitch of 3 mm (the number of holes is 1089).
Was drilled under the following etching conditions. [Masking] resist solution: S1818 (Shupure Far East Co., Ltd.) Exposure time: 12 seconds developer: MF-319 (manufactured by Shupure Far East Co.) resist stripping: acetone Etching Process] etching gas: ClF ₃ (concentration 33%) Processing temperature: 25 ° C Processing chamber pressure: 150 Torr

By performing the etching treatment for 30 minutes, a through-hole penetrating a silicon wafer having a thickness of 0.3 mm could be formed.

Then, a through-hole type solar cell was manufactured using the silicon wafer 1 having a large number of through-holes 11 obtained as described above. That is,
First, the silicon wafer 1 is subjected to an impurity diffusion treatment, and as shown in FIG. 15 and FIG.
The n-layer 12 was formed over the periphery of the opening on the back surface side. Next, a negative electrode 13 is connected to the n-layer 12 in the opening of the through hole 11 on the back surface side of the silicon wafer 1, and a positive electrode 15 is connected to the silicon part (p-type substrate) 14. Was prepared.

On the other hand, FIGS. 17 and 18 show general solar cells. In this case, the through hole 11 is not formed in the silicon wafer 10, and the negative electrode 16 is provided on the surface (light receiving surface) of the silicon wafer 10.
The negative electrode 16 has two slightly wider bus bar electrodes 17.
(2 mm width × 100 mm) and narrow finger electrodes 18 (0.1 mm width × 100 mm) branching from the bus bar electrode 17 at a pitch of 3 mm. The size of the silicon wafer 10 is 10
It is 0 mm × 100 mm × thickness 0.3 mm, which is the same as that of the through-hole type solar cell.

In the above conventional solar cell, the loss of the effective area of the light receiving surface due to the shadow of the negative electrode 16 on the surface reaches about 7.3%. On the other hand, in the through-hole type solar cell, the decrease in the effective area due to the through-hole 11 is about 2.
7% is enough. Thus, through-hole solar cells are:
Short circuit current is improved by reducing the loss of the effective area. In addition, by providing both the positive and negative electrodes 13 and 15 on the back surface side of the silicon wafer 1, a high-density module can be achieved. Further, application to consumer products due to the integrated structure can be achieved, and a solar cell excellent in high performance can be obtained. According to the method for processing a silicon wafer of the present invention, the through-hole solar cell as described above can be manufactured at a low cost, which cannot be obtained by a conventional processing method. Practical application can be promoted.

[0039]

Example 2 As Example 2, the processing method of the present invention was applied to the production of a through-hole type solar cell. First, 100m
A silicon wafer having a size of mx 100 mm x a thickness of 0.3 mm is prepared, and a through hole having a hole size of 0.5 mm x 0.5 mm and a hole pitch of 3 mm (the number of holes is 1089).
Was drilled under the following etching conditions. [Oxide film formation treatment] Heating condition: wetO ₂ atmosphere 1000 ° C x 100
Min SiO ₂ film thickness: 4000４ [patterning treatment] Resist solution: S1818 (manufactured by Supre-Far East) Exposure time: 12 seconds Developing solution: MF-319 (manufactured by Supre-Far East) Resist stripping: acetone [etching treatment] Etching gas: ClF ₃ (concentration 33%) Processing temperature: 25 ° C. Processing chamber pressure: 150 Torr

By performing the etching treatment for 30 minutes, a through-hole penetrating a silicon wafer having a thickness of 0.3 mm could be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a resist film is formed on a silicon wafer in a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state where a resist film pattern is formed on the silicon wafer.

FIG. 3 is an explanatory diagram showing a state of an etching process.

FIG. 4 is an explanatory diagram showing a state of an etching process.

FIG. 5 is a cross-sectional view showing a silicon wafer on which a through hole is formed.

FIG. 6 is a sectional view showing a silicon wafer used in the second embodiment of the present invention.

FIG. 7 is a sectional view showing a state where an oxide film is formed on the silicon wafer.

FIG. 8 is a sectional view showing a state where a resist film is formed on the silicon wafer.

FIG. 9 is a cross-sectional view showing a state where a resist film pattern is formed on the silicon wafer.

FIG. 10 is a cross-sectional view showing a state where an oxide film in a portion of the silicon wafer to be processed is removed.

FIG. 11 is a sectional view showing a state where an oxide film pattern is formed on the silicon wafer.

FIG. 12 is an explanatory diagram showing a state of an etching process.

FIG. 13 is an explanatory diagram showing a state of an etching process.

FIG. 14 is a cross-sectional view showing a processing step of another embodiment.

FIG. 15 is a partially enlarged plan view showing a through-hole type solar cell.

FIG. 16 is a partially enlarged sectional view showing the through-hole type solar cell.

FIG. 17 is a plan view showing a general solar cell.

FIG. 18 is a partially enlarged sectional view showing the general solar cell.

[Explanation of symbols]

 1 Silicon wafer 4 Planned processing part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masato Yamamoto 2-6-6 Chikushinmachi, Sakai City, Osaka Prefecture Daido Hokusan Sakai Plant (72) Inventor Takahiro Mishima 2-6 Chikushinmachi, Sakai City, Osaka Prefecture No. 40 Daido Hokusan Co., Ltd. Sakai Factory (72) Inventor Go Matsuda 2-6-6 Chikako Shinmachi, Sakai City, Osaka Prefecture (72) Inventor Shigeki Ito 2 Chiku Shinmachi 2 in Sakai City, Osaka Prefecture 6-6-40 Daido Hokusan Co., Ltd. Sakai Factory (72) Inventor Koichi Sugibuchi 2-6-40 Chikushinmachi, Sakai City, Osaka Daido Hokusan Co., Ltd. Sakai Factory

Claims (3)

[Claims] 1. A method for performing a removal process on a silicon wafer, comprising: forming a pattern for masking a portion other than a portion to be processed on the surface of the silicon wafer; and etching gas on the portion to be processed where silicon is exposed. A silicon wafer, comprising: a step of performing a removing process by volatilizing and removing silicon in the portion to be processed by chemically reacting the etching gas with the silicon to remove the pattern; and a process of removing the pattern. Method. 2. A method for removing a silicon wafer, comprising: forming an oxide film on a surface of the silicon wafer; and removing an oxide film of a portion to be processed of the oxide film formed on the surface of the silicon wafer. Forming an oxide film pattern that masks portions other than the portion to be processed, and supplying an etching gas to the portion to be processed where the oxide film has been removed and the silicon is exposed, thereby chemically etching the etching gas and silicon. A method for processing a silicon wafer, comprising: a step of performing a removal process by volatilizing and removing silicon in the portion to be processed by reacting; and a step of removing a pattern of the oxide film. 3. The etching gas is ClF._Three, NF_Three,
CCl_TwoF_Two, CF _Four, C_TwoF₆, C_ThreeF₈, CH
F_Three, CCl_Four, SF₆, CCl_ThreeF, HCl, CBr
F_ThreeFrom at least one component selected from the group consisting of
3. The method of processing a silicon wafer according to claim 1 or 2.
Law.