JP2005072072A - Method of regenerating releasable wafer and regenerated wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of regenerating a releasable wafer by which the regenerating cost of the releasable wafer can be reduced by shortening the regenerating time of the wafer at the time of regenerating the wafer and, at the same time, the number of regenerating times of the wafer can be increased by reducing the margin required in regenerating the wafer. <P>SOLUTION: After an ion-implanted region 13b is formed in a semiconductor wafer 13 throughout the wafer 13 by implanting ions into the wafer 13, a laminate 16 is formed by superimposing the wafer 13 upon a supporting wafer 14 and a thick releasable wafer 12 obtained by separating the semiconductor wafer 13 from a thin film 17 in the ion-implanted region 13b by heat-treating the laminate 16 at a prescribed temperature is regenerated. After the releasable wafer 12 is obtained by separating the wafer 13 from the thin film 17 on the whole surface of the ion-implanted region 13b so that no step may be formed in the periphery of the wafer 12, a regenerated wafer 32 is obtained by polishing the separation surface 12a of the wafer 12. The semiconductor wafer 13 is formed to have an outside diameter D<SB>1</SB>smaller than that D<SB>2</SB>of the supporting wafer 14 by ≤4.0 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a semiconductor wafer into which ions have been implanted is superposed on a support wafer to form a laminated body, and the laminated body is heat-treated to regenerate a thick release wafer separated from the thin film of the semiconductor wafer in the ion-implanted region. And a wafer regenerated by this method. More specifically, the present invention relates to a method for reclaiming a separation wafer to be duplicated in a so-called ion implantation separation method for manufacturing a bonded wafer such as an SOI (Silicon On Insulator) wafer and the regenerated wafer.
[0002]
[Prior art]
Conventionally, as a method for manufacturing an SOI wafer, ions are implanted into a main surface of a semiconductor wafer to form an ion implantation region inside the semiconductor wafer, and the main surface of the semiconductor wafer is overlaid on the main surface of a support wafer and stacked. There is known a method of manufacturing an SOI wafer by forming a body, further heat-treating the laminated body at a predetermined temperature, and peeling the ion-implanted wafer after bonding. The semiconductor wafer and the support wafer used in this method have the same outer diameter, and the semiconductor wafer is peeled into a thin film using the ion implantation region implanted into the main surface of the semiconductor wafer as a cleavage plane. This is a technique for strengthening the bonding by heat-treating and forming an SOI wafer. In this method, an SOI wafer having a good mirror surface and a high uniformity in the thickness of the SOI layer can be obtained relatively easily.
[0003]
On the other hand, when a bonded wafer such as an SOI wafer is manufactured by such an ion implantation separation method, one separation wafer is inevitably produced as a by-product. In this ion implantation separation method, by regenerating the by-product separation wafer, a plurality of SOI wafers can be obtained using substantially one semiconductor wafer, so that the cost can be greatly reduced. I can do it.
However, the wafer is generally chamfered, and even if the wafers with the same outer diameter are stacked, the entire periphery does not come into contact with each other. There was a problem that the periphery remained without being peeled, and a step was generated around the peeled wafer produced as a by-product. Further, a damage layer due to ion implantation exists on the separation surface of the separation wafer, and the surface roughness is large, and the separation wafer cannot be used as it is. Therefore, in order to regenerate this exfoliated wafer, it is necessary to remove those steps and damaged layers, improve the surface roughness and regenerate, and the generation of particles due to the ion implantation layer remaining on the steps is reduced. It was also necessary to prevent.
[0004]
Conventionally, as a method for reclaiming a peeled wafer of this type, a peeled wafer that polishes the main surface of the peeled wafer after removing the ion implantation layer remaining on the step around the separation surface of the peeled wafer by chamfering or etching. A reproduction processing method is known (see, for example, Patent Document 1). In this regeneration processing method, since the ion implantation layer is removed by chamfering or the like, the surface roughened by the chamfering or the like is then subjected to so-called mirror polishing (mirror chamfering). In this separation wafer reclaim processing method, by removing the ion implantation layer, the generation of particles due to the presence of the ion implantation layer is prevented, and the damage layer on the surface of the separation wafer is removed. Roughness can be improved.
[0005]
[Patent Document 1]
JP 2001-155978 A (Claim 1, paragraph number 0032, paragraph number 0052)
[0006]
[Problems to be solved by the invention]
However, in the conventional method for reclaiming a peeled wafer shown in Patent Document 1, mirror polishing is performed after the ion-implanted layer is removed by chamfering or etching, so that the surface roughness of the peeled wafer can be reduced. As a result, the time required to regenerate the peeled wafer is increased, and the machining allowance for grinding is relatively increased, resulting in a decrease in the number of times the reprocessing can be performed.
An object of the present invention is to reduce a processing time when regenerating a peeled wafer and reduce a regenerating cost, and reduce a machining allowance at the time of regenerating and increase a number of times of reclaimed wafer, and a regenerated processing method for the regenerated wafer. Is to provide a new wafer.
[0007]
[Means for Solving the Problems]
In the invention according to claim 1, as shown in FIGS. 1 and 2, ions are implanted into the main surface of the semiconductor wafer 13 to form an ion implantation region 13 b inside the semiconductor wafer 13, and the main surface of the semiconductor wafer 13 is formed. Are stacked on the main surface of the support wafer 14 to form a stacked body 16, and the stacked body 16 is heat-treated at a predetermined temperature to separate the semiconductor wafer 13 from the thin film 17 at the ion implantation region 13 b. This is an improvement of the method for reprocessing the peeled wafer 12.
The characteristic configuration is that the separation wafer 12 is obtained by separating the semiconductor wafer 13 from the thin film 17 over the entire surface of the ion implantation region 13b so as not to cause a step in the periphery.
[0008]
In the separation wafer regeneration processing method according to the first aspect, since the semiconductor wafer 13 is separated from the thin film 17 over the entire surface of the ion implantation region 13b, no step is generated around the separation surface 12a of the separation wafer 12. . For this reason, the chamfering process or etching conventionally performed in order to remove the ion implantation layer remaining in the step can be omitted. Therefore, in the invention according to the first aspect, the processing time for regenerating the peeled wafer is shortened compared to the conventional method, and the regenerating cost can be reduced, and the machining allowance 12c at the time of regenerating can be decreased to increase the number of times of regenerating. it can.
[0009]
The invention according to claim 2 is the invention according to claim 1, characterized in that the outer diameter D ₁ of the semiconductor wafer 13 is smaller than the outer diameter D ₂ of the support wafer 14.
In the method for reclaiming a peeled wafer according to claim 2, the outer diameter D ₁ of the semiconductor wafer 13 is overlapped with the semiconductor wafer 13 to form the stacked body 16 and the outer diameter D ₂ of the support wafer 14. By making the diameter small, the entire overlapping surface of the semiconductor wafer 13 comes into contact with the support wafer 14, so that the semiconductor wafer 13 can be relatively easily separated from the thin film 17 over the entire surface of the ion implantation region 13 b.
[0010]
The invention according to claim 3 is the invention according to claim 2, when the width of the chamfered portion of the support wafer 14 and w ', the outer diameter D ₂ of the outer diameter D ₁ and the supporting wafer 14 of semiconductor wafer 13 The difference is {(w ′ × 2) +0.2 mm} or more and 4.0 mm or less.
In the method for reclaiming a peeled wafer according to claim 3, the semiconductor wafer 13 is compared from the thin film 17 over the entire surface of the ion implantation region 13 b by bringing all of the superimposed main surfaces of the semiconductor wafer 13 into contact with the support wafer 14. Thus, it is possible to obtain an SOI wafer in which an oxide film is formed in a predetermined range while being easily separated. Here, the outer diameter _{D 1} and the difference between the outer diameter _{D 2} of the support wafer 14 is a semiconductor wafer 13 {(w '× 2) + 0.2mm} around the layer transferred wafer 12 is less than there is a problem that a step is formed If the difference exceeds 4.0 mm, it is difficult to obtain an SOI wafer in which an oxide film is formed in a predetermined range.
[0011]
The invention according to claim 4 is the invention according to any one of claims 1 to 3, characterized in that the width w of the chamfered portion around the overlapping surface of the semiconductor wafer 13 is 20 μm or less.
In the method for reclaiming a peeled wafer according to the fourth aspect, by making the width w of the chamfered portion 13c as small as 20 μm or less, the chamfered portion 13c breaks in the middle of the chamfered portion 13c to separate the separation surface 12a of the peeled wafer 12. Can be effectively prevented from occurring, and the semiconductor wafer 13 can be reliably separated from the thin film 17 over the entire surface of the ion implantation region 13b. Here, when the width w of the chamfered portion exceeds 20 μm, there is a problem that a step is generated around the separation surface 12a of the separation wafer 12.
[0012]
The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the separation surface 12 a of the separation wafer 12 is further polished to further include a recycled wafer 32, and the separation surface 12 a of the separation wafer 12 is The machining allowance 12c at the time of polishing is 0.2 μm or more and 1.0 μm or less.
In the method for reclaiming a peeled wafer according to claim 5, the processing time for regenerating the peeled wafer 12 is shortened by setting the machining allowance 12c at the time of polishing shown in FIG. Thus, the reproduction cost can be reduced and the number of reproductions can be sufficiently increased. Here, if the machining allowance 12c is less than 0.2 μm, there is a problem that damage on the separation surface 12a is not removed.
[0013]
The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the recycled wafer 32 is used as the semiconductor wafer 13 or the support wafer 14.
In the method for reclaiming a peeled wafer described in claim 6, the reclaimed wafer 32 can be reused twice or more by making the first semiconductor wafer 13 relatively thick, and the SOI wafer can be reused. The manufacturing cost can be further reduced.
The invention according to claim 7 is the regenerated wafer 32 regenerated by the method according to any one of claims 1 to 5.
In the reclaimed wafer 32 described in claim 7, the separation surface 12a of the separation wafer 12 from which the semiconductor wafer 13 is separated from the thin film 17 is polished on the entire surface of the ion implantation region 13b so that no step is generated in the periphery. Both main surfaces are uniform and have high flatness.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, when the SOI wafer 11 is manufactured, a separation wafer 12 is generated as a secondary. In order to manufacture the SOI wafer 11, a semiconductor wafer 13 as a bond wafer and a support wafer 14 as a base wafer are prepared. In this embodiment, these wafers 13 and 14 are each manufactured by the Czochralski method and have the same thickness. These wafers 13 and 14 are RCA cleaned wafers after being polished on both sides.
[0015]
First, by thermally oxidizing the semiconductor wafer 13, an oxide film 13 a (SiO ₂ film) as an insulating film is formed on the first main surface that is the overlapping surface of the wafer 13, and then hydrogen is applied to the first main surface of the wafer 13. Hydrogen ions (H +) which are gas ions are ion-implanted with a dose amount of 3.0 × 10 ¹⁶ / cm ² or more or hydrogen molecular ions (H ²⁺ ) of 1.5 × 10 ¹⁶ / cm ² or more (FIG. 1 ( a)). Here, reference numeral 13b in FIG. 1 (a) denotes an ion implantation region formed inside the semiconductor wafer 13 by implantation of hydrogen gas ions or hydrogen molecular ions, and this ion implantation region 13b is parallel to the oxide film 13a. That is, it is formed parallel to the surface of the semiconductor wafer 13. Further, in the case of hydrogen gas ions (H ⁺ ), an implantation amount approximately twice that of hydrogen molecular ions (H ²⁺ ) is required. Instead of hydrogen gas ions and hydrogen molecular ions, helium ions (He +) may be implanted together with hydrogen gas ions or hydrogen molecular ions. In this case, the dose of helium ions is preferably 0.5 × 10 ¹⁶ / cm ² or more.
[0016]
Next, a laminated body 16 is formed by superimposing the first main surface of the semiconductor wafer 13 on the main surface of the support wafer 14 shown in FIG. 1B through the oxide film 13a at room temperature (FIG. 1C). . The laminated body 16 is heated to a temperature of 500 to 800 ° C. in a nitrogen (N ₂ ) atmosphere, and kept in this temperature range for 5 to 30 minutes to perform a thin film separation heat treatment. As a result, the semiconductor wafer 13 is broken at the ion implantation region 13b and separated into an upper thick release wafer 12 and a lower thin film 17 (FIG. 1D).
[0017]
Here, the characteristic point of the present invention is that the separation wafer 12 is obtained by separating the semiconductor wafer 13 from the thin film 17 over the entire surface of the ion implantation region 13b so as not to cause a step in the periphery. For this purpose, the outer diameter D ₁ of the semiconductor wafer 13 is formed smaller than the outer diameter D ₂ of the support wafer 14. Further, in order to separate the semiconductor wafer 13 from the thin film 17 over the entire surface of the ion implantation region 13b, the width w of the chamfered portion 13c around the overlapping surface of the semiconductor wafer 13 is 20 μm as shown in the enlarged view of FIG. The semiconductor wafer 13 is manufactured as follows. On the other hand, the width of the chamfered portion of the support wafer 14 'when the outer diameter _{D 1} and the difference between the outer diameter _{D 2} of the support wafer 14 of semiconductor wafer 13 {(w' w × 2 ) + 0.2mm} or 4 The semiconductor wafer 13 is produced so that it may become 0.0 mm or less.
[0018]
In order to manufacture the semiconductor wafer 13 having a predetermined outer diameter D ₁ smaller than the outer diameter D ₂ of the support wafer 14, after slicing the ingot stage or the ingot, the peripheral surface of the ingot or the sliced wafer is etched. . By this etching, the processing damage on the peripheral surface is removed and the diameter of the ingot or sliced wafer can be reduced. When the outer diameter is reduced in the ingot state, the peripheral surface of the wafer obtained by subsequent slicing is further etched. By etching the peripheral surface of the wafer in this way, the width w of the chamfered portion 13 c generated around the main surface is reduced, and the width w of the chamfered portion 13 c around the overlapping surface of the semiconductor wafer 13 can be reduced to 20 μm or less. it can.
[0019]
Next, the temperature of the laminated body 16 in which the semiconductor wafer 13 is broken in the ion implantation region 13b is lowered, and the separation wafer 12 is separated from the support wafer 14 (hereinafter simply referred to as the support wafer 14) on which the thin film 17 is laminated via the oxide film 13a. Remove. The support wafer 14 is heated to 900 to 1200 ° C. in an oxygen (O ₂ ) or nitrogen (N ₂ ) atmosphere, and heat treatment is performed for 30 to 120 minutes in this temperature range (FIG. 1E). This heat treatment is a heat treatment for strengthening the bonding of the thin film 17 to the support wafer 14. Further, the separation surface of the support wafer 14 is annealed or polished (touch polishing) to be smoothed (FIG. 1 (g)). As a result, the support wafer 14 becomes the SOI wafer 11.
[0020]
On the other hand, since the semiconductor wafer 13 is separated from the thin film 17 over the entire surface of the ion implantation region 13b, no step is generated around the separation wafer 12. Then, the separation wafer 12 is regenerated by polishing the separation surface 12a. As shown in FIG. 2A, when the oxide film 12d formed by heat treatment or the like remains on the second main surface opposite to the separation surface 12a of the separation wafer 12, the separation wafer 12 is polished. Before this, the oxide film 12d may be removed as shown in FIG. 2B by immersing the peeled wafer 12 in hydrofluoric acid.
[0021]
Next, the release wafer 12 is polished. This polishing is performed in a general polishing apparatus (not shown). Specifically, the peeling wafer 12 is mounted and fixed on a holding table of a polishing apparatus (not shown), the polishing liquid is supplied from the polishing liquid supply means, and the polishing cloth is impregnated with the polishing cloth. In this state, the holding table is rotated together with the peeling wafer 12 and the polishing cloth holder is rotated together with the polishing cloth. Then, the polishing cloth is pressed against the separation surface 12a of the peeling wafer 12 by pressure contact / rotation means to polish the peeling wafer 12. To do. At this time, since grinding using a grindstone performed when a level difference is generated is not performed, there is no damage due to grinding, and a machining allowance 12c at the separation surface 12a of the separation wafer 12 shown in FIG. 2C is 1 μm. It can be as follows. Further, the surface of the release wafer 12 is finish-polished and then subjected to finish cleaning. For finish polishing, use a suede type finish polishing cloth in which urethane resin is foamed on a non-woven fabric base fabric, and a finishing abrasive with an organic polymer added as a haze inhibitor in addition to abrasive grains. Is done. In this way, the peeled wafer 12 is reclaimed to obtain a reclaimed wafer 32 shown in FIG.
[0022]
As described above, in the separation wafer reclaim processing method of the present invention, the semiconductor wafer 13 is separated from the thin film 17 over the entire surface of the ion implantation region 13b so as not to cause a step in the periphery, so that the separation wafer 12 is obtained. A chamfering process or etching which has been conventionally performed in order to remove the ion implantation layer remaining on the step generated around the surface can be omitted. Accordingly, the reclaimed wafer 32 can be obtained by a relatively simple operation of only polishing the separation surface 12a of the release wafer 12, and the obtained reclaimed wafer 32 is not damaged and has a very small polishing allowance 12d during polishing. The number of times that the semiconductor wafer 13 or the support wafer 14 can be reused increases, and the manufacturing cost of the SOI wafer 11 can be reduced.
[0023]
【The invention's effect】
As described above, according to the present invention, the separation wafer is obtained by separating the semiconductor wafer from the thin film over the entire surface of the ion implantation region so that no step is generated around the periphery. A chamfering process or etching which has been conventionally performed to remove the remaining ion implantation layer can be omitted. Therefore, the processing time for reclaiming the peeled wafer by reclaiming the separated wafer immediately by polishing the separation surface of the peeled wafer is remarkably shortened compared to the conventional method, the reclaiming cost is reduced, and the allowance for reclaiming is also reduced. To increase the number of playbacks.
[0024]
In addition, if the outer diameter of the semiconductor wafer is made smaller than the outer diameter of the support wafer, all of the superimposed main surfaces of the semiconductor wafer come into contact with the support wafer, so the semiconductor wafer is compared from the thin film over the entire ion implantation area. If the difference in the outer diameter is within a predetermined range of 4.0 mm or less, the separation is facilitated and an SOI wafer having an oxide film formed in the predetermined range is obtained. Can do. If the width of the chamfered portion around the overlapping surface of the semiconductor wafer is set to a small value of 0.1 μm or less, the chamfered portion is prevented from being broken in the middle of the chamfered portion, and a step is generated on the entire surface of the ion implantation region. The semiconductor wafer can be reliably separated from the thin film.
[0025]
In addition, if the removal allowance at the time of polishing on the separation surface of the peeled wafer is 1 μm or less, the processing time for reclaiming the peeled wafer will be further shortened to reduce the regeneration cost and increase the number of times of regeneration sufficiently. Can do. By using this recycled wafer as a support wafer or a semiconductor wafer, the recycled wafer can be reused twice or more, and the manufacturing cost of the SOI wafer can be further reduced.
Furthermore, since the reclaimed wafer regenerated in the present invention is polished on the entire surface of the ion implantation region so as not to cause a step in the periphery, the separation surface of the separation wafer from which the semiconductor wafer is separated from the thin film is polished. Each has uniform and high flatness.
[Brief description of the drawings]
FIG. 1 is a view showing a manufacturing method of an SOI wafer including a separation wafer according to an embodiment of the present invention in the order of steps.
FIGS. 2A and 2B are diagrams sequentially illustrating a process of obtaining a reclaimed wafer by polishing a separation surface of the peeled wafer.
[Explanation of symbols]
12 Wafer 12a Separation surface 12c Removal allowance 13 Semiconductor wafer 13b Ion implantation area 14 Support wafer 16 Laminate 17 Thin film 32 Recycled wafer D1 Outer diameter of semiconductor wafer D2 Outer diameter of support wafer w Width of chamfered portion of semiconductor wafer Support Wafer chamfer width

Claims (7)

Ions are implanted into the main surface of the semiconductor wafer (13) to form an ion implantation region (13b) inside the semiconductor wafer (13), and the main surface of the semiconductor wafer (13) is used as the main surface of the support wafer (14). A laminated body (16) is formed on the surface, and the laminated body (16) is further heat-treated at a predetermined temperature to separate the semiconductor wafer (13) from the thin film (17) in the ion implantation region (13b). In the method of reprocessing the thick exfoliated wafer (12) obtained by
Separating the semiconductor wafer (13) from the thin film (17) over the entire surface of the ion-implanted region (13b) so as not to cause a step in the periphery, thereby obtaining a peeled wafer (12). Method. The method for reclaiming a peeled wafer according to claim 1, wherein the outer diameter (D ₁ ) of the semiconductor wafer (13) is smaller than the outer diameter (D ₂ ) of the support wafer (14). The width of the chamfered portion of the support wafer (14) w 'when a difference in outer diameter _{(D 2)} of the outer diameter of the semiconductor wafer (13) _{(D 1)} and the support wafer (14) {(w' The method for reclaiming a peeled wafer according to claim 2, which is × 2) +0.2 mm} or more and 4.0 mm or less. The method for reclaiming a peeled wafer according to any one of claims 1 to 3, wherein the width (w) of the chamfered portion around the overlapping surface of the semiconductor wafer (13) is 20 µm or less. The method further includes the step of polishing the separation surface (12a) of the release wafer (12) to obtain a reclaimed wafer (32), and the removal allowance (12c) during polishing of the separation surface (12a) of the release wafer (12) is 0. The method for reclaiming a peeled wafer according to any one of claims 1 to 4, wherein the thickness is 2 µm or more and 1.0 µm or less. The method for reclaiming a peeled wafer according to any one of claims 1 to 5, wherein the reclaimed wafer (32) is used as a semiconductor wafer (13) or a support wafer (14). A wafer reclaimed by the method according to claim 1.

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