JP4637034B2 - Manufacturing method of cleaned silicon wafer - Google Patents

Description

  The present invention relates to a method of manufacturing a cleaned silicon wafer by slicing a silicon ingot using a slurry to produce a silicon wafer, and cleaning and drying the silicon wafer using a cleaning liquid. This cleaned silicon wafer can be used for manufacturing solar cells.

  A conventional method of slicing a silicon ingot to produce a silicon wafer, cleaning the silicon wafer, and drying the silicon wafer will be described (for example, see Patent Document 1).

First, a silicon wafer is manufactured by slicing a silicon ingot while being bonded to the base block. At this time, the silicon wafer is bonded to the base block.
Next, the silicon wafer bonded to the base block is accommodated in the basket. A brush is attached to the inner side of the basket. This brush maintains a gap between adjacent silicon wafers so that the silicon wafers do not adhere to each other.
Next, the silicon wafer is cleaned by spraying a cleaning liquid onto the silicon wafer accommodated in the basket.
Next, a peeling solution is sprayed on the silicon wafer to peel the silicon wafer from the base block. In the peeling process, the upper surface of the silicon wafer is held down by using pressing means composed of parallel bars so that the gap between the silicon wafers is maintained after peeling. Accordingly, the silicon wafer is held in the basket without changing its position after peeling.
Next, the silicon wafer is transferred to the drying chamber together with the basket and dried.
JP 11-111162 A

  However, in the above method, it is necessary to attach a brush to the basket, and in order to maintain a gap between the silicon wafers, a pressing means for pressing the upper surface of the silicon wafer is required. In particular, the process of pressing the upper surface of the silicon wafer before peeling the silicon wafer is troublesome.

  The present invention has been made in view of such circumstances, and provides a method for manufacturing a cleaned silicon wafer that can clean and dry the silicon wafer by a simple method.

Means for Solving the Problems and Effects of the Invention

  In the method for producing a cleaned silicon wafer according to the present invention, a silicon ingot bonded to a support member is sliced using a slurry in which abrasive grains are dispersed in a water-soluble coolant, and the silicon wafer bonded to the support member is obtained. The manufactured silicon wafer is cleaned, then the silicon wafer is peeled off from the supporting member, and the peeled silicon wafer is dried in a stacked state.

  In the case where a silicon wafer is prepared by slicing a silicon ingot using a slurry in which abrasive grains are dispersed in a water-soluble coolant, the present inventors can dry the silicon wafer even if the silicon wafer is stacked. As a result, it was found that no problem occurred, and the present invention was completed. Here, “stacked state” means a state in which a plurality of silicon wafers are substantially in contact with each other (for example, in a state where the gap between the wafers is 0.2 mm or less) and overlapped, It does not include a state in which the gap between the silicon wafers is maintained by a conventional brush or a wafer cassette for storing silicon wafers one by one at intervals.

  Conventionally, it has been thought that it is very important to clean and dry with a sufficient gap between silicon wafers. For this reason, a gap is provided between silicon wafers using the physical means as described above, and cleaning and drying are performed in that state. Unlike the conventional common sense, the present invention makes it possible to clean and dry a silicon wafer very easily by performing cleaning and drying without providing means for maintaining a gap between the silicon wafers.

  The method of the present invention is particularly effective as compared with the conventional method in which a silicon wafer is housed in a wafer cassette and precision cleaning and drying are performed manually. In the conventional method, an operator moves silicon wafers one by one to a wafer cassette. At that time, a wafer crack of about several percent occurs (specifically, the wafer thickness is 155 square by 200 μm thick, A 1-year-old expert had cracks of about 1%.) Further, when the wafer was taken out from the wafer cassette in the subsequent inspection process, a wafer crack of about several percent occurred (specifically, the wafer thickness was 155 square 200 μm thick, and it was about 2% by a skilled worker for one year). Cracks have occurred.) Since the wafer cassette is not used in the method of the present invention, wafer cracking does not occur in the above process, and as a result, the yield can be improved. Also, since there is no manual process, labor costs can be saved. The superiority of the present invention becomes more remarkable as the silicon wafer is made thinner.

  Furthermore, the present inventors have found that cleaning and drying by a simple method such as the present invention can be performed for the first time by employing a water-soluble coolant. Cleaning by a simple method is considered possible because the viscosity of the water-soluble coolant is low and the cleaning liquid easily enters the gaps between the stacked wafers. In addition, drying by a simple method is considered possible because the boiling point of water-soluble coolant is low.

  In the method for producing a cleaned silicon wafer according to the present invention, a silicon ingot bonded to a support member is sliced using a slurry in which abrasive grains are dispersed in a water-soluble coolant, and the silicon wafer bonded to the support member is obtained. The manufactured silicon wafer is cleaned, then the silicon wafer is peeled off from the supporting member, and the peeled silicon wafer is dried in a stacked state.

1. Silicon wafer manufacturing process In this process, a silicon ingot bonded to a support member is sliced using a slurry in which abrasive grains are dispersed in a water-soluble coolant to manufacture a silicon wafer bonded to the support member.

  The support member is a member for supporting the silicon ingot, and is usually a support plate such as a steel plate or an aluminum plate bonded with a discard plate such as a glass plate or a carbon plate. In this case, the silicon ingot is adhered to the discard plate, and the silicon ingot is sliced until the discard plate is reached. The support member may be any member that can support the silicon ingot, and a carbon plate or the like may be used as it is as a support member in addition to a member obtained by bonding two plates.

  The adhesive used for bonding is not particularly limited as long as it can bond the silicon ingot or the wafer to the support member with sufficient strength and can peel the silicon wafer from the support member in a subsequent peeling step. The adhesive is, for example, an epoxy adhesive. The shape of the silicon ingot is not limited, and may be cylindrical or prismatic.

  The silicon ingot can be sliced using a general multi-wire saw or the like. The slurry used for slicing is obtained by dispersing abrasive grains in a water-soluble coolant. The abrasive grains are made of SiC, diamond, CBN, alumina, or the like. The water-soluble coolant means a water-soluble coolant, for example, a coolant made of a mixture of a water-soluble base material and water. “Solubility in water” means that the solubility in water is 5 wt% or more (preferably 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt% or 95 wt%). It means that. Examples of the base material include glycol materials such as ethylene glycol, propylene glycol, and polyethylene glycol. The viscosity of the water-soluble coolant is preferably 100 CP or less. In this case, it is because water and cleaning liquid enter between the wafers relatively easily in the cleaning process. The boiling point of the water-soluble coolant is preferably 250 ° C. or lower. In this case, it can be evaporated relatively easily in the drying step.

  Here, for reference, an example of a silicon wafer bonded to a support member is shown in FIG. In FIG. 1, the support member is obtained by bonding a discard plate 3 to a support plate 1. The silicon ingot is sliced in a state of being bonded to the discard plate 3, and a plurality of silicon wafers 5 bonded to the discard plate 3 are produced.

2. Cleaning step In this step, the silicon wafer manufactured in the above step is cleaned. The cleaning of a silicon wafer usually includes a plurality of processes, for example, a water shower cleaning process, a cleaning liquid cleaning process, and a pure water cleaning process. Each process may be performed a plurality of times. Each cleaning step can be performed by the following method. (1) It is performed by spraying water or a cleaning liquid on the silicon wafer (shower cleaning). (2) Water or a cleaning solution is contained in a container, and a silicon wafer is immersed in the water or the cleaning solution to generate ultrasonic waves in the water or the cleaning solution (ultrasonic cleaning). (3) Water or a cleaning solution is contained in a container, a silicon wafer is immersed in water or a cleaning solution, and the silicon wafer is moved in that state. (4) It is performed by putting a silicon wafer into and out of water or a cleaning solution. In (3) or (4), the direction in which the silicon wafer is moved is preferably parallel to the main surface of the silicon wafer. This is because water or cleaning liquid easily enters between adjacent silicon wafers.

The type of the cleaning liquid is not limited, and any of nonionic, anionic, and cationic surfactants may be used. As the cleaning liquid, for example, a nonionic surfactant diluted with water can be used. When such a cleaning liquid is used, the cleaning liquid preferably does not contain an alkaline component such as NaOH or KOH. Further, the temperature of the cleaning liquid is preferably set to a temperature at which fogging does not occur on the wafer surface (specifically, 50 ° C. or lower, preferably 45 ° C., 40 ° C. or 35 ° C. or lower). According to the experiments by the present inventors, it is confirmed that when the cleaning liquid contains an alkaline component and the temperature of the cleaning liquid is high, the wafer surface is fogged, and when the clouding occurs, the texture structure is not easily formed properly. It was because it was done.
Including an alkaline component in the cleaning liquid generally improves its cleaning power. Accordingly, an alkaline component is included in the cleaning liquid, and the temperature of the cleaning liquid may be set to a temperature at which fogging does not occur on the wafer surface (specifically, 50 ° C. or lower, preferably 40 ° C., 30 ° C. or 25 ° C. or lower). .
As the cleaning liquid, an anionic or cationic surfactant added to water may be used. When the nonionic surfactant is used and the residue remains on the wafer depending on the conditions, the inventors of the present invention use a nonionic surfactant in a texture structure forming process using an alkaline aqueous solution, which is a subsequent process. The aqueous solution and silicon react to form a film in the form of water glass, and the texture may not be formed well. However, when an anionic or cationic surfactant is used, this problem does not occur. It was.

The nonionic surfactant is preferably fatty acid diethanolamide, polyoxyethylene alkyl ether (AE), polyoxyethylene alkyl phenyl ether, or the like. The anionic surfactant is preferably a fatty acid, higher fatty acid salt, alphasulfo fatty acid methyl ester salt (α-SF), linear alkylbenzene linear alkylbenzene sulfonate (LAS), higher alcohol, Alkyl sulfate ester (AS), alkyl ether sulfate ester salt (AES), monoalkyl phosphate ester salt (MAP), alpha olefin type, alpha olefin sulfonate (AOS), normal paraffin type, alkane sulfonate (SAS). The cationic surfactant is preferably an amino acid alkylamino fatty acid salt, a betaine alkylbetaine, an amine oxide alkylamine oxide, or the like.

3. Stripping step In this step, the silicon wafer is stripped from the support member. This step is performed so that the peeled silicon wafer is in a stacked state. For this reason, it is preferable that the support member and the silicon wafer bonded to the support member are set in a wafer container that can accommodate the peeled silicon wafer. An example of the wafer container is shown in FIG. The wafer container 10 in FIG. 2 includes a bottom wall (not visible in FIG. 2) with which the lower part of the silicon wafer abuts, a side wall 11 for preventing the silicon wafer from falling off, and a partition plate for preventing the silicon wafer from falling over. 13 and a support plate holding part 15 for holding the support plate. FIG. 3 shows a state in which the silicon wafer bonded to the support plate via the discard plate shown in FIG. 1 is set in the wafer container shown in FIG. In FIG. 3, the end portion of the support plate 1 is placed on the support plate holding portion 15 of the wafer container 10. The wafer container shown in FIG. 2 can also be used in the above-described cleaning process.

  The silicon wafer can be peeled by immersing an adhesive for bonding the silicon wafer and the support member in a stripping solution and dissolving it. If possible, the silicon wafer may be peeled off by softening or melting the adhesive by heating or the like.

  It is preferable to further include a step of washing the silicon wafer with water (preferably pure water) after the peeling step. The cleaning step here may be performed by any of the methods described in the section “Cleaning step”. However, when cleaning is performed by moving a wafer container containing a peeled silicon wafer in water, the silicon wafer may be damaged by collision or friction between the silicon wafers. Therefore, the cleaning here is preferably performed by storing water in a container, immersing a wafer container in which a silicon wafer is stored in pure water, and generating ultrasonic waves in the water.

4). Drying step In this step, the silicon wafer peeled off from the support member is dried in a stacked state. Specifically, for example, in a state where the silicon wafer is accommodated in the wafer container (at this time, the silicon wafer is in a stacked state), the silicon wafer and the wafer container are moved into a dryer and dried. Dry the silicon wafer in the machine.

  The stacked silicon wafers are preferably arranged so that the angle between the main surface and the horizontal plane (see θ in FIG. 7) is preferably 45 degrees or more, more preferably substantially vertical. This is because the larger the angle between the main surface of the silicon wafer and the horizontal plane, the more the silicon wafer stands and the more easily the silicon wafer is dried.

  The silicon wafer can be dried by vacuum drying or electromagnetic wave drying. The process up to here completes the production of the cleaned silicon wafer.

5. Texture structure forming step When the manufactured cleaned silicon wafer is used for manufacturing a solar cell, a texture structure is then formed on the surface of the cleaned silicon wafer. The texture structure can be formed by spraying an alkaline aqueous solution (for example, NaOH aqueous solution) on the surface of the cleaned silicon wafer and leaving it in that state.

Embodiment 1 of the present invention will be described below with reference to FIGS. 4 (a) to 4 (d) and FIGS. 5 (e) to 5 (h).

1. Silicon wafer manufacturing process (FIG. 4A)
First, a single crystal silicon ingot bonded to an aluminum plate support plate 1 via a glass plate discard plate 3 is sliced using a slurry in which abrasive grains are dispersed in a water-soluble coolant, and then discarded. A single crystal silicon wafer 5 bonded to the support plate 1 via 3 was produced (see also FIG. 1).

  The support plate 1 and the discard plate 3 and the discard plate 3 and the silicon ingot were bonded with an epoxy adhesive, respectively.

  Slicing was performed using a multi-wire saw for solar cells. This multi-wire saw can process four silicon ingots (155W × 155D × 400L) at a time and process about 3,500 silicon wafers (155W × 155D × 0.2L) in one slice. Is. The support plate 1 has a screw hole, and is fastened with a multi-wire saw holding jig to attach the support plate 1 to the multi-wire saw.

  The slurry tank for storing the slurry to be supplied to the multi-wire saw was about 200 L in size. The slurry was a mixture of SiC abrasive grains (# 800, specific gravity: 3.21) and a water-soluble coolant (specific gravity: 1) at a mass ratio of 1: 1. As the water-soluble coolant, a mixture of propylene glycol and water at a mass ratio of 80:20 was used. A viscosity modifier was added to the water-soluble coolant. The viscosity of the water-soluble coolant after adjustment was about 100 CP.

2. Cleaning Step Next, the silicon wafer manufactured in the above step was cleaned. Cleaning was performed in the following steps.

2-1. City water shower cleaning process (Figure 4 (b))
The sliced support plate 1, discard plate 3 and silicon wafer 5 (hereinafter referred to as “silicon wafer 5 etc.”) are set in the wafer container 10 (see also FIG. 3), and the silicon wafer 5 is shower cleaned. It was. The shower cleaning was performed in the shower cleaning tank 21. In the shower washing tank 21, two nozzles 23 are attached, and a shower of 20 L / min city water is discharged from each nozzle.

  Each nozzle 23 emitted a shower in a direction perpendicular to the paper surface, and showered the silicon wafer 5 from a direction parallel to the main surface of the silicon wafer 5. The nozzle 23 was moved laterally (in the direction of arrow A in FIG. 4B) at a speed of 5 mm / s during shower discharge. During that time, the wafer container 10 was moved in the vertical direction (the direction of arrow B in FIG. 4B) at a speed of 5 mm / s. The shower was washed for 20 minutes. After 20 minutes, it was confirmed that the drainage became translucent, and the next process was started.

2-2. First cleaning liquid cleaning step (FIG. 4C)
Next, the silicon wafer 5 was set in the wafer container 10 and the silicon wafer 5 was cleaned with the first cleaning liquid. The first cleaning liquid cleaning was performed in the first cleaning liquid cleaning tank 27 in which the cleaning liquid 25 was accommodated. As the cleaning liquid 25, a nonionic surfactant (product name: Poryl AL7, manufacturer: Kusunoki Chemical Co., Ltd.) diluted with water so as to have a concentration of 2 wt% was used. The cleaning solution temperature was controlled at 35 +/- 1 ° C. An ultrasonic generator was not used. Instead, the wafer container 10 was moved up and down. The vertical movement speed was 10 mm / s. In this up-and-down movement, the entire wafer container 10 comes out of the cleaning liquid 25 and is stopped for 10 seconds outside the cleaning liquid 25 in a cycle of 1 minute. This process was repeated for 80 minutes.

2-3. Second cleaning liquid cleaning step (FIG. 4D)
Next, the silicon wafer 5 and the like were set in the wafer container 10 and the silicon wafer 5 was subjected to the second cleaning liquid cleaning. The second cleaning liquid cleaning was performed in the second cleaning liquid cleaning tank 31 in which the cleaning liquid 29 was accommodated. The cleaning liquid 29 for the second cleaning liquid cleaning was the same as the first cleaning liquid cleaning. The second cleaning liquid cleaning was performed by immersing the silicon wafer 5 in the cleaning liquid 29 for 80 minutes without moving the wafer container 10. The cleaning solution temperature was controlled at 28 +/- 1 ° C. An ultrasonic generator was not used.

2-4. Pure water cleaning process (Figure 5 (e))
Next, pure water cleaning of the silicon wafer 5 was performed with the silicon wafer 5 and the like set in the wafer container 10. The pure water cleaning was performed in a pure water cleaning tank 35 in which pure water 33 was accommodated. The pure water temperature was controlled at 35 +/- 1 ° C. An ultrasonic generator was not used. Instead, the wafer container 10 was moved up and down. The vertical movement speed was 10 mm / s. In this up-and-down movement, the entire wafer container 10 comes out of the pure water 33 in a cycle of 1 minute, stopped for 10 seconds outside the pure water 33, and drained. This process was repeated for 80 minutes. In addition, as the pure water 33, the overflow water in the pure water washing | cleaning process after a peeling process was used.

3. Peeling process (Fig. 5 (f))
Next, the silicon wafer 5 was peeled from the discard plate 3 with the silicon wafer 5 and the like set in the wafer container 10. The silicon wafer 5 was peeled in a peeling tank 39 in which a peeling liquid 37 was accommodated. As the stripping solution 37, a solution obtained by diluting lactic acid in water so as to have a concentration of 20 wt% was used. The temperature of the stripping solution 37 was controlled at 70 +/- 1 ° C. The silicon wafer 5 was peeled by immersing the silicon wafer 5 in the stripping solution 37 for 80 minutes without moving the wafer container 10.

4). Pure water cleaning process (Fig. 5 (g))
Next, pure water cleaning of the silicon wafer 5 was performed in a state where the silicon wafer 5 peeled from the discard plate 3 was accommodated in the wafer container 10. The pure water cleaning was performed in a pure water cleaning tank 43 in which pure water 41 was accommodated. The pure water temperature was controlled at 35 +/- 1 ° C. The wafer container 10 was not moved, and the ultrasonic generator 44 was used to generate ultrasonic waves in pure water for cleaning.

5. Drying process (Fig. 5 (h))
Next, the silicon wafer 5 was vacuum-dried in a state where the silicon wafer 5 was accommodated in the wafer container 10. At this time, the angle (θ in FIG. 7) between the main surface of the silicon wafer 5 and the horizontal plane was 75 degrees or more. This adjustment of the angle was performed by adjusting the position of the partition plate 13 of the wafer container 10.
Vacuum drying was performed in a vacuum drying tank 45. In vacuum drying, first, the inside of the vacuum drying tank 45 was sealed, purged with nitrogen at normal pressure, the temperature of nitrogen was set to 80 ° C., and the surface temperature of the silicon wafer 5 was heated to 70 ° C. or higher. Thereafter, the pressure in the vacuum drying tank 45 was reduced to 1 Torr or less and left for 10 minutes. Thereby, the water | moisture content between the adjacent silicon wafers 5 evaporated, and the silicon wafer 5 dried.

  In another example, high-frequency drying (2.4 GHz, 15 KW) was performed instead of vacuum drying. In this case, the silicon wafer 5 was dried in 20 minutes.

6). Texture Structure Formation Step Next, the silicon wafer 5 was taken out from the vacuum drying tank 45, and a texture structure for solar cells was formed on the silicon wafer 5. A texture structure for solar cells was formed on the silicon wafer 5. The formation of the texture structure was performed by leaving the silicon wafer 5 in a 2 wt%, 60 ° C. NaOH aqueous solution for 40 minutes.

  In Example 2, as the cleaning liquid 25 used in the first and second cleaning liquid cleaning steps of Example 1, the concentration of the nonionic surfactant (the same as in Example 1) is 2 wt%, and the concentration of NaOH is 1 wt%. As described above, those diluted with water were used. Further, in the first and second cleaning liquid steps, the cleaning liquid temperature was controlled at 60 +/- 1 ° C. Except for this, the same steps as in Example 1 were performed under the same conditions as in Example 1.

(Comparison between Examples 1 and 2-results of appearance inspection of single crystal silicon wafer)
SEM photographs of the main surface of the silicon wafer 5 on which the texture structure was formed in Examples 1 and 2 were taken at a magnification of 1000 times, and the appearance of the texture structure was inspected.
FIGS. 6A and 6B show examples of SEM photographs of texture structures with good and bad appearance, respectively. In FIG. 6 (a), most pyramid sizes (length of one side on the photograph) of the texture structure are 10 μm or more, whereas in FIG. 6 (b), the pyramid size is more than 10 μm. There are many quite small ones, and the texture structure is not properly formed.

First, for the texture structures formed in Examples 1 and 2, the number of pyramids having a size of 10 μm or more per unit area was examined. The relative values of the average values are shown in Table 1.

  From Table 1, it can be seen that in Example 1, a larger number of pyramids (10 μm or more) having a sufficiently larger size than in Example 2 were formed.

Next, the quality of the appearance of the texture structure formed in Examples 1 and 2 was determined based on the criteria of FIGS. 6A and 6B as good and bad, respectively, and the yield was obtained. The relative values are shown in Table 2.

  From Table 2, it can be seen that the yield of Example 1 was better than that of Example 2.

From the above, it can be seen that in both Table 1 and Table 2, the results of Example 1 were better than those of Example 2. The reason why such a result was obtained is not necessarily clear, but (1) the cleaning liquid used in Example 1 does not contain an alkaline component such as NaOH or KOH; (2) Example The reason is that the temperature of the cleaning liquid used in 1 is lower than the temperature of the cleaning liquid used in Example 2. The action is considered as follows. As in the second embodiment, when the cleaning liquid contains an alkaline component, the wafer surface after cleaning with the cleaning liquid may become cloudy when the temperature of the cleaning liquid increases. This haze may remain after the pure water washing and drying process. When the texture structure forming step is performed with the cloudiness remaining, the cloudy component (which is considered to be mainly composed of nonionic surfactant and silicon) reacts with the aqueous alkali solution for forming the texture structure to form water. A glassy film is formed. This coating hinders contact between the aqueous alkali solution and the wafer surface, inhibits the formation of a texture structure on the wafer surface, and deteriorates the yield and the like.
Therefore, it is preferable that the cleaning liquid does not contain an alkaline component, and it is preferable that the cleaning liquid has a temperature that does not cause fogging on the wafer surface even if it contains an alkaline component. The temperature at which cloudiness does not occur is considered to depend on the content of alkaline components contained in the cleaning liquid and the concentration of the cleaning liquid, and can be easily determined experimentally.

In the present embodiment, the silicon wafer 5 was dried by changing the angle θ (hereinafter referred to as “wafer angle”; see FIG. 7) between the main surface of the silicon wafer 5 and the horizontal plane. The drying was vacuum drying, the heating temperature was 120 degrees, and the time until the ultimate vacuum reached 0.1 Torr or less was compared. A stack of 200 silicon wafers 5 was made. 1000 silicon wafers 5 were dried at once. Other points are the same as in the first embodiment. The results are shown in Table 3.

  A wafer angle of 90 degrees indicates that the silicon wafer 5 is completely upright, and a wafer angle of 0 degrees indicates that the silicon wafer 5 is completely lying down. As is apparent from Table 3, when the wafer angle is 0 to 45 degrees, the drying time becomes shorter as the wafer angle becomes larger. When the wafer angle is 45 to 90 degrees, the drying time does not depend on the wafer angle. I understand that. This is because when the wafer angle is smaller than 45 degrees, the weight of the wafer itself hinders the escape of vapor generated by the evaporation of moisture between the wafers, but when the wafer angle exceeds 45 degrees, This is probably because such a phenomenon does not occur.

In Example 4, instead of a single crystal silicon ingot, a polycrystalline silicon ingot was sliced to produce a polycrystalline silicon wafer, and this wafer was cleaned and dried. In addition, the surface damage layer was removed from the wafer instead of forming the texture structure. Other points are the same as in the first embodiment. For reference, flowcharts of the first embodiment and the fourth embodiment are shown in FIGS. 8A and 8B, respectively.
The first and second cleaning liquid cleaning steps of Example 4 were performed under the same method and conditions as in Example 1.
The removal of the surface damage layer was performed by immersing the wafer in a 10 wt% NAOH aqueous solution at 70 ° C. for 20 minutes. As a result, the surface layer was removed by about 20 μm on each side.

The first and second cleaning liquid cleaning steps of Example 5 were performed under the same method and conditions as in Example 2.
Except for this, the same steps as in Example 4 were performed under the same conditions as in Example 4.

(Comparison of Examples 4 to 5-Results of appearance inspection of polycrystalline silicon wafer)
A visual inspection of the polycrystalline silicon wafer from which the damaged layer was removed in Examples 4 to 5 was performed. Yield was determined by determining that the surface had no color unevenness and that there was a defect. The relative values are shown in Table 4.

  From Table 4, it can be seen that the yield of Example 4 was better. This is because (1) the cleaning liquid used in Example 4 does not contain an alkaline component such as NaOH or KOH, and (2) the temperature of the cleaning liquid used in Example 4 is the same as that used in Example 5. It is assumed that this is because the temperature is lower than the temperature of the cleaning liquid.

  In Example 6, an anionic surfactant was used in place of the nonionic surfactant in the first and second cleaning liquid cleaning steps of Example 2. Other points are the same as in the second embodiment.

  In Example 7, a cationic surfactant was used in place of the nonionic surfactant in the first and second cleaning liquid cleaning steps of Example 2. Other points are the same as in the second embodiment.

(Comparison between Examples 2, 6, and 7-results of appearance inspection of single crystal silicon wafer)
SEM photographs of the main surface of the silicon wafer 5 on which the texture structure was formed in Examples 2, 6, and 7 were taken at a magnification of 1000 times, and the appearance of the texture structure was inspected.

First, for the texture structures formed in Examples 2, 6, and 7, the number of pyramids having a size of 10 μm or more per unit area was examined. Table 5 shows the relative values of the average values.

  From Table 5, it was found that a sufficiently large pyramid (10 μm or more) is less likely to be formed when a nonionic surfactant is used than when an anionic or cationic surfactant is used. .

Next, the quality of the appearance of the texture structure formed in Examples 2, 6 and 7 was judged based on the criteria of FIGS. 6A and 6B as good and bad, respectively, and the yield was obtained. The relative values are shown in Table 6.

  Table 6 shows that the yield is much worse when the nonionic surfactant is used than when the anionic and cationic surfactants are used.

This result is thought to be due to the difference in the surfactant used in the cleaning process. The surfactant used in the cleaning process may remain as a residue until just before the formation of the texture structure. The residue of anionic and cationic surfactants does not adversely affect the formation of the texture structure. Since the drugs are prone to adverse effects, the results may have been different. The reason why the influence of the residue of the surfactant is different is not necessarily clear, but it is considered that the nonionic surfactant reacts with the NaOH aqueous solution and easily generates an object on the water glass on the silicon wafer 5. .

  In Example 8, an anionic surfactant was used instead of the nonionic surfactant. Other points are the same as in the fifth embodiment.

  In Example 9, a cationic surfactant was used in place of the nonionic surfactant. Other points are the same as in the fifth embodiment.

(Comparison between Examples 5, 8, and 9-results of appearance inspection of polycrystalline silicon wafer)
A visual inspection of the polycrystalline silicon wafer from which the damaged layer was removed in Examples 5, 8, and 9 was performed. Yield was determined by determining that the surface had no color unevenness and that there was a defect. The relative values are shown in Table 7.

  Table 7 shows that even in the case of a polycrystalline silicon wafer, the yield is very poor when a nonionic surfactant is used compared to when an anionic or cationic surfactant is used.

It is a perspective view which shows the silicon wafer adhere | attached on the support plate through the discard board based on this invention. It is a perspective view which shows the wafer container based on this invention. It is a perspective view which shows the state which the silicon wafer adhere | attached on the support plate through the discard board based on this invention was set to the wafer container. (A)-(d) is sectional drawing which shows the manufacturing process of the cleaned silicon wafer which concerns on Example 1 of this invention. (E)-(h) is sectional drawing which shows the manufacturing process of the cleaned silicon wafer which concerns on Example 1 of this invention. (A), (b) is a SEM photograph showing a texture structure formed on a silicon wafer in Examples 1 and 2 of the present invention, and (a), (b) are good appearance and bad, respectively. An example is shown. It is sectional drawing which shows the angle between the main surface of a silicon wafer and a horizontal surface based on this invention. (A), (b) shows the flowchart of Example 1 and 4 of this invention, (a) respond | corresponds to Example 1, and (b) corresponds to Example 4. FIG.

Explanation of symbols

1: Support plate 3: Discard plate 5: Silicon wafer 10: Wafer container 11: Side wall 13: Partition plate 15: Support plate holder 21: Shower cleaning tank 25, 29: Cleaning liquid 27: First cleaning liquid cleaning tank 31: No. 2 Cleaning liquid cleaning tank 33: Pure water 35: Pure water cleaning tank 37: Stripping liquid 39: Stripping tank 41: Pure water 43: Pure water cleaning tank 44: Ultrasonic generator 45: Vacuum drying tank

Claims (7)

Bonding silicon ingot to the support member, and sliced using a slurry prepared by dispersing abrasive grains in a water-soluble coolant, to produce a plurality of silicon wafers bonded to the support member, a plurality of silicon wafers produced were washed and cleaned plurality of silicon wafers were peeled off from the support member, comprising the step of drying the plurality of silicon wafers peeled,
The step of peeling a plurality of silicon wafers from the support member is performed in a state where the support member and the plurality of silicon wafers bonded thereto are set in a wafer container,
The wafer container can accommodate a plurality of peeled silicon wafers,
The method for producing a cleaned silicon wafer is characterized in that the step of drying the plurality of silicon wafers is performed in a state where the plurality of silicon wafers are accommodated in the wafer container in a stacked state . The method according to claim 1, wherein the step of cleaning the plurality of silicon wafers is performed using a cleaning liquid that does not contain an alkali component . The step of cleaning the plurality of silicon wafers is performed using a cleaning liquid containing an alkali component,
2. The method according to claim 1, wherein the cleaning liquid has a temperature at which fogging does not occur on the surfaces of the plurality of silicon wafers after cleaning and a concentration of an alkali component. The method according to any one of claims 1 to 3 , wherein the step of drying the plurality of silicon wafers is performed by vacuum drying or electromagnetic wave drying. The wafer container includes a bottom wall with which the lower portions of the plurality of separated silicon wafers abut, and a plurality of partition plates for preventing the plurality of separated silicon wafers from falling over,
The method according to claim 1, wherein the plurality of peeled silicon wafers are accommodated between two adjacent partition plates. 6. The method according to claim 5, wherein the plurality of silicon wafers accommodated between the two adjacent partition plates are accommodated in a stacked state and at an angle of 45 degrees or more and 90 degrees or less with respect to the bottom wall. . The water-soluble coolant is a mixture of a glycol-based material and water and has a viscosity of 100 cP or less.
The method according to claim 1, wherein the glycol-based material is ethylene glycol, propylene glycol, or polyethylene glycol.

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