KR101198356B1 - Process for producing diffusion wafer and diffusion wafer - Google Patents

Abstract

And a spin etching step of removing part 23 of the non-diffusion layer 21 in the diffusion wafer 20 having the non-diffusion layer 21 and the diffusion layer 22 by a single wafer. This spin etching is performed by using a spin etching apparatus which is movable in the in-plane direction D2 of the diffusion wafer 20 and has a liquid supply port for supplying the etching liquid to the non-diffusion layer 21 of the diffusion wafer 20. The liquid supply port of the apparatus is positioned at the in-plane peripheral portion 20c and the in-plane direction central portion 20d of the diffusion wafer 20, respectively, and the etching liquid is supplied to the non-diffusion layer 21 from the liquid supply port, thereby The wafer in-plane distribution of the etching removal amount of the non-diffusion layer 21 during spin etching is controlled based on the shape in the thickness direction.

Description

Method for manufacturing diffusion wafer and diffusion wafer {PROCESS FOR PRODUCING DIFFUSION WAFER AND DIFFUSION WAFER}

The present invention relates to a method of manufacturing a diffusion wafer having a non-diffusion layer and a diffusion layer, and a diffusion wafer.

In order to manufacture power devices for discrete (single-function) applications such as large output transistors, diodes, rectifiers, and the like, a diffusion wafer having two layers of a diffusion layer and a non-diffusion layer is used. The diffusion layer is a low resistivity layer in which a high concentration dopant is diffused. The non-diffusion layer is a high resistivity layer with little or no diffusion of dopant.

The thickness of the non-diffusion layer in the diffusion wafer affects the properties of the semiconductor device. Therefore, the non-diffusion layer is required to be formed with high precision so that the thickness of the non-diffusion layer does not vary between the wafers and also in the in-plane direction of the wafer (the direction orthogonal to the thickness direction of the wafer). For example, since the drain-source breakdown voltage (VDSS) characteristics and the thickness of the non-diffusion layer are highly correlated, in order to obtain a semiconductor device having VDSS characteristics uniform in the in-plane direction, the non-diffusion layer having a uniform thickness in the in-plane direction is provided. Diffusion wafers are needed.

By the way, the non-diffusion layer of the diffusion wafer is etched by, for example, sheet-fed spin etching (see, for example, Japanese Patent Laid-Open No. 2007-103857).

An example of the manufacturing method of the conventional diffusion wafer is demonstrated with reference to FIG. 11 and FIG. 11 is a flowchart showing an example of a conventional method for manufacturing a diffusion wafer. 12 (a) and 12 (b) are cross-sectional views showing a procedure of obtaining two diffusion wafers from one silicon wafer.

As shown in FIG. 11, an example of the conventional manufacturing method of a diffused wafer is provided with the following process (S1-S10).

(S1) slice process

The silicon ingot is sliced to obtain a silicon wafer (hereinafter also referred to as "wafer").

(S2) chamfering process

The chamfering process (beveling) is performed to the wafer which passed through the slicing process S1. In detail, a grinding wheel is applied to the side edge of the wafer to round the edge. As a result, cracking or cracking of the wafer can be prevented.

(S3) Lapping Process

The wafer which has undergone the chamfering process (S2) is set in the lapping apparatus and lapping is performed on the wafer surface. As a result, damages such as scratches and irregularities on the surface of the wafer caused by the slices are removed, and the wafer is flattened.

(S4) alkali etching process

The wafer flattened through the lapping step (S3) is immersed in the alkaline etching solution to perform alkali etching. As a result, the processing strained layer on the wafer surface is removed.

(S5) diffusion process

The wafer having undergone the alkali etching step (S4) is loaded into a heat treatment boat, and is exposed to an atmosphere (diffusion furnace, etc.) where a high temperature dopant is present for a predetermined time (diffusion processing). As a result, as shown in FIG. 12A, the diffusion layer 122 is formed on the surface of both surfaces of the wafer 110 with the non-diffusion layer 121 interposed therebetween.

(S6) two-division process

As shown in FIGS. 12A and 12B, the wafer 110 that has undergone the diffusion step S5 is wired along a centerline (one dashed line in FIG. 12A) in the thickness direction D1. The wafer 110 is divided into two in the thickness direction D1 by cutting with a wire saw or the like. As a result, two diffusion wafers 120 can be obtained from one wafer 110. The diffusion wafer 120 has a non-diffusion layer 121 and a diffusion layer 122, respectively.

(S7) plane grinding process

The diffusion wafer 120 formed by the two-segmentation step S6 is set in the planar grinding machine, and the grinding wheel is pressed on the non-diffusion layer 121 surface 121a of the diffusion wafer 120 to planar grinding the diffusion wafer 120. Perform the processing. As a result, the non-diffusion layer 121 surface 121a of the diffusion wafer 120 is planarized.

Instead of performing the dividing process (S6), instead, the wafer 110 may be subjected to a planar grinding with a planar grinding machine, thereby obtaining a diffused wafer having a flat surface 121a of the non-diffusion layer 121.

(S8) Chamfering Process

The chamfering process (beveling) is performed to the diffused wafer 120 which passed through the planar grinding process S7. In detail, a grinding wheel is applied to the side end edge of the diffusion wafer 120 to round the edge. As a result, cracking or dust generation of the diffusion wafer 120 can be prevented.

(S9) spin etching process

Etching liquid is supplied to each part of the non-diffusion layer 121 surface 121a of the diffusion wafer 120 which passed through the chamfering process S8, and spin etching is performed one by one with respect to the diffusion wafer 120. As a result, a portion of the non-diffusion layer 121 of the diffusion wafer 120 is removed.

(S10) cleaning process

The diffusion wafer 120 which has undergone the spin etching step S9 is cleaned. The diffusion wafer 120 which passed through the cleaning process S10 is sent to the next process, and the next process is performed.

By the way, in the diffusion wafer 120, as mentioned above, it is required that the thickness of the non-diffusion layer 121 is uniform in the in-plane direction (direction perpendicular to the thickness direction of the wafer) D2.

However, in the conventional method for manufacturing a diffusion wafer described above, it is difficult to make the thickness of the non-diffusion layer 121 uniform in the in-plane direction D2. 13A and 13B are cross-sectional views showing a procedure for obtaining two diffusion wafers from one silicon wafer having different shapes of diffusion layers.

In detail, as shown in FIG. 13A, the diffusion layer 122 of the wafer 110 is formed thinner in the center portion of the in-plane direction D2 than in the peripheral portion of the in-plane direction D2. This phenomenon occurs mainly due to the in-plane tendency of the temperature of the wafer 110 in the diffusion process S5 or the in-plane uniformity of the dopant gas.

Therefore, as shown in FIG. 13B, the diffusion layer 122 in the diffusion wafer 120 obtained by cutting the wafer 110 along the center line in the thickness direction D1 (a dashed-dotted line in FIG. 13A). ) Is formed thinner in the in-plane direction center portion 120d than in-plane peripheral portion 120c. On the other hand, the surface 121a of the non-diffusion layer 121 is flat in the in-plane direction D2. As a result, the non-diffusion layer 121 is formed to be thicker in the in-plane direction central portion 120d than the in-plane peripheral portion 120c as opposed to the diffusion layer 122. As such, the thickness of the non-diffusion layer 121 is not uniform in the in-plane direction D2.

In addition, by uniformizing the thickness of the diffusion layer 122 (prevention of thickness variation), the thickness of the non-diffusion layer 121 can also be achieved. However, the formation of the diffusion layer 122 on the wafer 110 is formed by diffusion treatment for a long time in a diffusion furnace at a very high temperature. Therefore, it is difficult to achieve uniform thickness of the diffusion layer 122 by further improving the accuracy of the diffusion treatment under industrial conditions.

Accordingly, the present invention provides a method for manufacturing a diffusion wafer capable of almost uniformly thicknessing the non-diffusion layer by performing spin etching on the diffusion wafer having a non-diffusion layer and a diffusion layer having a non-uniform thickness, and removing a portion of the non-diffusion layer, and An object of the present invention is to provide a diffusion wafer obtained by a manufacturing method.

In addition, although not related to the diffusion wafer, Japanese Patent Application Laid-open No. Hei 5-283397 discloses a technique for manufacturing a semiconductor device (semiconductor device). A method of manufacturing a semiconductor device in which, after forming an epitaxial layer, the epitaxial layer is etched to a predetermined thickness using a predetermined etching solution at a reaction rate, wherein the spin etching apparatus is used to etch the epitaxial layer. And a method of manufacturing a semiconductor device, wherein the diffusion of the etchant is increased at the periphery of the wafer rather than the center of the wafer while the wafer is brought into contact with the etchant while rotating the wafer.

However, while the present invention is a technique of removing a portion of the non-diffusion layer of the diffusion wafer by spin etching, the technique described in Japanese Patent Application Laid-open No. 5-283397 discloses a part of the epitaxial layer formed on the semiconductor substrate for spin etching. By technology. As a result, the technique described in Patent Literature 2 differs from the layer (epitaxial layer / non-diffusion layer) or the like removed by spin etching.

Further, the technique described in Japanese Patent Application Laid-Open No. 5-283397 differs greatly from the size (thickness) of the removal portion removed by spin etching. That is, while the technique described in Japanese Patent Application Laid-Open No. 5-283397 is a technique of removing a size of 1 μm or less from the epitaxial layer, the present invention removes a size of 10 μm or more from the non-diffusion layer, as described below. With the technique, the size (thickness) of the removal part differs by two orders of magnitude in the μm order.

(1) The manufacturing method of the diffusion wafer which concerns on this invention is a manufacturing method of the diffusion wafer provided with the spin-etching process which removes a part of said non-diffusion layer of the diffusion wafer which has a non-diffusion layer and a diffusion layer by a single wafer by spin etching. The liquid in the spin etching apparatus using the spin etching apparatus in the spin etching process, the spin etching apparatus being movable in an in-plane direction of the diffusion wafer and having a liquid supply port for supplying etching liquid to the non-diffusion layer of the diffusion wafer. The supply port is positioned in the in-plane peripheral portion and the in-plane direction center of the diffusion wafer, respectively, and the etching liquid is supplied from the liquid supply port to the non-diffusion layer, so that the spin diffusion may be performed on the basis of the shape of the non-diffusion layer in the thickness direction. The wafer in-plane distribution of the etching removal amount of the non-diffusion layer is controlled.

According to the invention of (1), the thickness of the non-diffusion layer can be made almost uniform by performing spin etching on the diffusion wafer having the non-diffusion layer and the diffusion layer having a non-uniform thickness.

(2) In the invention of (1), the diffusion layer has a concave shape in which the non-diffusion layer side is recessed toward the center in the in-plane direction from the in-plane peripheral portion of the diffusion wafer, and is removed from the diffusion wafer. Part of the layer preferably has a convex shape in which the diffusion layer side is bulged toward the center in the in-plane direction from the in-plane peripheral portion of the diffusion wafer.

According to the invention of (2), in the case where the non-diffusion layer side in the diffusion layer has a concave shape which is recessed from the in-plane peripheral portion of the diffusion wafer toward the in-plane direction center (generally, the diffusion layer has such concave shape) from the diffusion wafer A portion of the non-diffusion layer to be removed (ie the removal portion) has a convex shape that bulges out from the in-plane peripheral portion of the diffusion wafer toward the in-plane direction center portion. Therefore, the shape of the non-diffusion layer in the thickness direction after the spin etching is in the form of air (bowl). Therefore, the thickness of the non-diffusion layer tends to be almost uniform.

(3) In the invention of (1) or (2), the non-diffusion layer thickness measuring step of measuring the thickness of the non-diffusion layer of the diffusion wafer by the FT-IR method before the spin etching step, wherein the spin etching step The wafer in-plane distribution of the etching removal amount of the non-diffusion layer is preferably performed based on the thickness distribution of the non-diffusion layer measured by the non-diffusion layer thickness measuring step.

According to the invention of (3), the spin etching step controls the in-plane distribution of the etching removal amount of the non-diffusion layer at the time of spin etching based on the thickness distribution of the non-diffusion layer measured by the non-diffusion layer thickness measurement process. Therefore, the thickness uniformity of the non-diffusion layer after spin etching improves further.

(4) The diffusion wafer of the present invention is also manufactured by the method for manufacturing the diffusion wafer, characterized in that the difference between the maximum thickness and the minimum thickness of the non-diffusion layer is within 3 μm.

According to the present invention, a method of manufacturing a diffusion wafer capable of substantially uniformly thicknessing a non-diffusion layer by spin-etching a diffusion wafer having a non-diffusion layer and a diffusion layer having a non-uniform thickness and removing a portion of the non-diffusion layer, and The diffusion wafer obtained by the manufacturing method can be provided.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of the manufacturing method of the diffused wafer of this invention is described, referring drawings. 1 is a flowchart showing an embodiment of a method of manufacturing a diffusion wafer of the present invention. 2 (a) and 2 (b) are cross-sectional views showing a procedure of obtaining two diffusion wafers from one silicon wafer. 3A and 3B are cross-sectional views showing a procedure of removing a part of the non-diffusion layer in the diffusion wafer.

As shown in FIG. 1, the manufacturing method of the diffused wafer of this embodiment is provided with the following process (S1-S8, S11, S12, and S10). The following steps (S1 to S8 and S10) are almost the same as the steps (S1 to S8 and S10) of the conventional method for manufacturing a diffusion wafer, but will be described again.

(S1) slice process

The silicon ingot is sliced to obtain a silicon wafer (hereinafter also referred to as "wafer").

(S2) chamfering process

The chamfering process (beveling) is performed to the wafer which passed through the slicing process S1. In detail, a grinding wheel is applied to the side edge of the wafer to round the edge. As a result, cracking or cracking of the wafer can be prevented.

(S3) Lapping Process

The wafer which has undergone the chamfering process (S2) is set in the lapping apparatus and lapping is performed on the wafer surface. As a result, damages such as scratches and irregularities on the surface of the wafer caused by the slices are removed, and the wafer is flattened.

(S4) alkali etching process

The wafer flattened through the lapping step S3 is immersed in an alkaline etching solution and alkali etching is performed. As a result, the processing strained layer on the wafer surface is removed.

(S5) diffusion process

The wafer having undergone the alkali etching step (S4) is loaded into a heat treatment boat, and is exposed to an atmosphere (diffusion furnace, etc.) where a high temperature dopant is present for a predetermined time (diffusion processing). As a result, as shown in FIG. 2A, a diffusion layer 22 is formed on each of both surface sides of the wafer 10 with the non-diffusion layer 21 interposed therebetween.

(S6) two-division process

As shown in (a) and (b) of FIG. 2, the wafer 10 having undergone the diffusion step (S5) is wired along the centerline (one dashed line in FIG. 2 (a)) in the thickness direction D1 thereof. The wafer 10 is divided into two parts in the thickness direction D1 by cutting into small pieces or the like. As a result, two diffusion wafers 20 can be obtained from one wafer 10. The diffusion wafer 20 has a non-diffusion layer 21 and a diffusion layer 22, respectively.

The surface 21a side of the non-diffusion layer 21 of the diffusion wafer 20 is referred to as the surface 20a of the diffusion wafer 20. The surface 22a side of the diffusion layer 22 of the diffusion wafer 20 is the back surface 20b of the diffusion wafer 20.

In the non-diffusion layer 21, the diffusion layer 22 side has a central portion 20d of the in-plane direction D2 from the peripheral portion 20c of the in-plane direction D2 of the diffusion wafer 20. As it faces, it has a bulging convex shape from the non-diffusion layer 21 toward the diffusion layer 22.

On the other hand, the diffusion layer 22 is formed from the non-diffusion layer 21 from the non-diffusion layer 21 as the non-diffusion layer 21 side faces the in-plane direction center portion 20d from the in-plane peripheral portion 20c of the diffusion wafer 20. It has a concave shape that is recessed toward the surface.

(S7) plane grinding process

The diffusion wafer 20 formed by the two-segmentation step S6 is set in a planar grinding machine, and the grinding wheel is pressed by pushing the grinding wheel on the surface 20a (the surface 21a of the non-diffusion layer 21) of the diffusion wafer 20. The wafer 20 is subjected to surface grinding. As a result, the surface 21a of the non-diffusion layer 21 of the diffusion wafer 20 is planarized.

(S8) Chamfering Process

The chamfering process (beveling) is performed to the diffused wafer 20 which passed through the planar grinding process S7. In detail, a grinding wheel is applied to the side edge of the diffusion wafer 20 to round the edge. Thereby, cracking, dust generation, etc. of the diffusion wafer 20 can be prevented.

(S11) Non-Diffusion Layer Thickness Measurement Process

Using the FT-IR (Fourier Transform Infrared Spectroscopy) 31 (see FIG. 4), the thickness of the non-diffusion layer 21 of the diffused wafer 20 which has undergone the chamfering step S8 is measured by the FT-IR method. The spin etching system 30 including the FT-IR device 31 will be described later.

(S12) Spin Etching Process

Etching liquid is supplied to the surface 20a of the diffusion wafer 20 which passed through the non-diffusion layer thickness measuring process S11, and spin etching is performed one by one with respect to the diffusion wafer 20. As a result, as shown in FIGS. 3A and 3B, a part 23 of the non-diffusion layer 21 of the diffusion wafer 20 is removed. Hereinafter, the part 23 removed from the non-diffusion layer 21 is also called "removing part."

The detail of the spin etching apparatus 40 which implements a spin etching process S12 is mentioned later. The spin etching system 30 is composed of an FT-IR device 31, a spin etching device 40, and the like.

(S10) cleaning process

The diffusion wafer 20 that has undergone the spin etching step S12 is cleaned. The diffused wafer 20 which passed through the cleaning process S10 is sent to the next process, and the next process is performed.

Next, the spin etching system 30 will be described. 4 is a functional block diagram showing a spin etching system including an FT-IR device and a spin etching device. 5 is a perspective view schematically illustrating the spin etching apparatus. 6 is a plan view schematically showing the spin etching apparatus, (a) is a view showing a state where the liquid supply port is located in the periphery of the diffusion wafer, and (b) is a liquid supply port of the diffusion wafer. It is a figure which shows the state located in the center of in-plane direction.

As shown in FIG. 4, the spin etching system 30 includes an FT-IR device 31 and a spin etching device 40.

The FT-IR apparatus 31 can measure the thickness of the non-diffusion layer 21 of the diffusion wafer 20 by the FT-IR method.

As shown in FIG. 4 and FIG. 5, the spin etching apparatus 40 includes a spin chuck 41, a liquid supply port 42, a rotation arm 43, a CPU 44, and a memory 45. Equipped.

As shown in FIG. 5, the spin chuck 41 can hold and rotate the diffusion wafer 20 so that the non-diffusion layer 21 faces upward (opposite the upper surface of the spin chuck 41). The rotational speed (angular velocity) of the spin chuck 41, that is, the rotational speed of the diffusion wafer 20 held by the spin chuck 41 can be appropriately set according to etching conditions or the like. The rotational speed of the spin chuck 41 is not particularly limited, but may be set to, for example, 500 to 900 rpm.

The liquid supply port 42 can supply the etching liquid to the non-diffusion layer 21 of the diffusion wafer 20 rotated by the spin chuck 41. The form of supplying the etching liquid to the diffusion wafer 20 is not particularly limited, and may be, for example, dropping, spraying, or dropping. The rate (mL / s) of supplying the etching liquid to the diffusion wafer 20 can be appropriately set according to the etching conditions and the like.

Since the liquid supply port 42 is connected to the rotational arm 43 as described later, the liquid supply port 42 can move in the in-plane direction D2 of the diffusion wafer 20.

Etching liquid can use what has a suitable viscosity (surface diffusivity) according to etching conditions, etc., and is not specifically limited. As the etching solution, for example, a mixed acid of phosphoric acid (H ₃ PO ₄ ? HNO ₃ ? H ₂ SO ₄ ? HF) is used.

The diffusion rate of the etching solution (the rate at which the etching solution spreads over the surface 20a of the diffusion wafer 20) is appropriately set according to the etching conditions and the like. The diffusion speed of the etching liquid can be changed by changing the viscosity of the etching liquid, the supply speed of the etching liquid, the rotation speed of the spin chuck 41, and the like.

One end of the rotation arm 43 is connected to the liquid supply port 42. Moreover, the rotation arm 43 is comprised so that rotation of the other end as a support point is possible. According to the rotational arm 43, the liquid supply port 42 is rotated by the spin chuck 41, for example, as shown in FIG. 6A, and the in-plane peripheral portion 20c of the diffusion wafer 20 is rotated. ) Can be positioned for a predetermined time. Alternatively, according to the rotational arm 43, the liquid supply port 42 is rotated by the spin chuck 41 as shown in FIG. 6B, and the in-plane direction center portion 20d of the diffusion wafer 20 is rotated. Can be placed at a predetermined time.

Or according to the rotational arm 43, the liquid supply port 42 is shown to FIG. 6 (b) from the in-plane direction peripheral part 20c of the diffusion wafer 20 shown to FIG. 6 (a), for example. The in-plane direction center portion 20d of the diffusion wafer 20 can be moved. Alternatively, according to the rotational arm 43, the liquid supply port 42 is diffused from the in-plane direction center portion 20d of the diffusion wafer 20 shown in FIG. 6B, as shown in FIG. 6A. It can move to the in-plane peripheral part 20c of the wafer 20.

The liquid supply port 42 can move in the substantially radial direction of the spin chuck 41 (that is, the substantially radial direction of the diffusion wafer 20) in accordance with the rotation of the rotation arm 43. The moving speed of the liquid supply port 42 along the radial direction of the spin chuck 41 is appropriately set according to etching conditions and the like, and can be set to 0 to 20 (mm / s), for example.

In addition, the liquid supply port 42 can supply the etching liquid E to the diffusion wafer 20 while moving along the radial direction of the spin chuck 41.

The CPU 44 controls the entire spin etching system 30. In particular, the CPU 44 performs predetermined control on the spin chuck 41, the liquid supply port 42, the rotation arm 43, and the like. For example, the CPU 44 rotates the spin chuck 41 based on the shape of the thickness direction D1 of the diffusion layer 22 and the thickness of the non-diffusion layer 21 measured by the FT-IR device 31. Speed, supply speed of the etching liquid E from the liquid supply port 42, rotation speed of the rotation arm 43 (moving speed of the liquid supply port 42 along the radial direction of the spin chuck 41), rotation arm The stop position of 43 is controlled.

Predetermined data is stored in the memory 45. For example, the memory 45 stores various functional programs for executing the spin etching system 30, the etching conditions DB 45a, and the like. The etching condition DB 45a is a database in which etching conditions according to the thickness of the non-diffusion layer 21 measured by the FT-IR apparatus 31 and the like are stored.

Next, the spin etching step (S12) will be described in detail.

In the spin etching step S12, the in-plane distribution of the etching removal amount of the non-diffusion layer 21 during spin etching is controlled by using the spin etching system 30. In detail, in the spin etching step (S12), the liquid supply port 42 is positioned at the in-plane peripheral portion 20c and the in-plane direction central portion 20d of the diffusion wafer 20, respectively, from the liquid supply port 42. The etching solution E is supplied to the non-diffusion layer 21.

In detail, the liquid supply port 42 is positioned in the in-plane peripheral portion 20c of the diffusion wafer 20 for a predetermined time so that the etching liquid E is transferred from the liquid supply port 42 to the surface 21a of the non-diffusion layer 21. Supplies).

Thereafter, the liquid supply port 42 is moved from the in-plane peripheral portion 20c of the diffusion wafer 20 to the in-plane direction central portion 20d. In the meantime, the etching liquid E is supplied from the liquid supply port 42 to the surface 21a of the non-diffusion layer 21. The liquid supply port 42 is positioned in the in-plane direction center portion 20d of the diffusion wafer 20 for a predetermined time to supply the etching liquid E from the liquid supply port 42 to the surface 21a of the non-diffusion layer 21. In this way, based on the shape of the non-diffusion layer 21 in the thickness direction, in-plane distribution of the etching removal amount of the non-diffusion layer 21 at the time of spin etching is controlled.

In the spin etching step S12, the spin etching is performed based on the thickness direction shape of the non-diffusion layer 21 and based on the thickness distribution of the non-diffusion layer 21 measured by the non-diffusion layer thickness measurement step S11. Wafer in-plane distribution of the etching removal amount of the non-diffusion layer 21 at the time is controlled. For example, when the thickness of the non-diffusion layer 21 of the diffusion wafer 20 is measured by the FT-IR apparatus 31, the CPU 44 is connected to the etching condition DB 45a of the memory 45, Etching conditions suitable for the measured thickness of the non-diffusion layer 21 are obtained. According to the etching conditions, predetermined control is performed on the spin chuck 41, the liquid supply port 42, the rotation arm 43, and the like, and predetermined spin etching is performed on the diffusion wafer 20. .

As a result, as shown in FIG. 3, the removal portion 23 of the non-diffusion layer 21 is removed from the diffusion wafer 20 having a flat shape before the spin etching step S12. The removal portion 23 has a bulging convex shape from the non-diffusion layer 21 toward the diffusion layer 22 from the in-plane peripheral portion 20c of the diffusion wafer 20 toward the in-plane direction central portion 20d. .

As described above, according to the manufacturing method of the present embodiment, the diffusion wafer 20 having the non-diffusion layer 21 and the diffusion layer 22 having a non-uniform thickness is subjected to the steps S1 to S8, S11, S12 and S10. ), The thickness of the non-diffusion layer 21 can be made almost uniform by spin-etching and removing a part of the non-diffusion layer 21 (removing portion 23). As a result, for example, the diffusion wafer 20 can be obtained in which the difference between the maximum thickness and the minimum thickness of the non-diffusion layer 21 is within 3 µm.

Hereinafter, various graphs concerning the effects of the present invention will be described.

7 (a) to 7 (c) are graphs showing measured values of the removed portion size when the target value of the removed portion size of the non-diffusion layer is changed. Fig. 7A is a graph showing a case where the removal portion of the flat shape is intended. FIG. 7B is a graph showing a case where the removal portion having a difference in unevenness (unevenness gap) of 1.5 µm is intended. FIG. 7C is a graph showing a case where the removal portion whose difference in unevenness is 2 μm is aimed at.

In FIG.7 (a)-(c), the vertical line of the dashed-dotted line which passes through the center part of the horizontal axis direction of a graph shows the in-plane direction center part of a removal part. The horizontal axis of the graph represents the distance in the in-plane direction from the in-plane direction center of the removal portion. The right end and left end of the graph each represent a position of 75 mm in the in-plane direction from the in-plane direction center. The vertical axis of the graph represents the thickness of the removed portion (μm). In addition, the solid line shows the measured value of the removal part size when the removal part thickness in the in-plane direction center part of a wafer is 11 micrometers. The broken line shows the measured value of the removal portion size when the removal portion thickness at the in-plane direction center of the wafer is 10 탆. The double dashed line indicates the measured value of the removed portion size when the removed portion thickness at the in-plane direction center portion of the wafer is 9 μm.

According to (a) to (c) of FIG. 7, it can be seen that the difference in the unevenness of the removed portion can be different (0 μm = flat shape, 1.5 μm, 2 μm) by changing the spin etching conditions. In addition, by varying the target value of the non-diffusion layer thickness (11 μm, 10 μm, 9 μm), the actual value of the thickness of the non-diffusion layer can be changed, and the overall shape of the removed portion regardless of the target value of the non-diffusion layer thickness. It turns out that this becomes substantially the same shape.

8 is a graph showing the thickness distribution of the non-diffusion layer. The vertical axis of the graph represents the thickness distribution (maximum value-minimum value of thickness) (μm) in the in-plane direction of the non-diffusion layer. The left side of the graph shows the thickness distribution of the non-diffusion layer in the conventional example, and the right side of the graph shows the thickness distribution of the non-diffusion layer in the present invention. Squares represent a 20% distribution over the median. "20% distribution" means a range of distributions in which 20% of the total number of samples is included. The horizontal lines extending up and down the rectangle represent 75% of the median. "75% distribution" means the range of the distribution which contains 75% of the sample.

According to FIG. 8, it can be seen that the present invention has a smaller thickness distribution of the non-diffusion layer, that is, the thickness uniformity of the non-diffusion layer is improved as compared with the conventional example.

9A and 9B are graphs showing the relationship between the supply position of the etchant and the thickness of the removed portion of the non-diffusion layer. FIG. 9A is a graph showing the case where the etching liquid is supplied to the in-plane peripheral portion and the in-plane direction central portion of the wafer, and the etching liquid is supplied only to the in-plane direction central portion of the wafer. FIG. 9B is a graph showing a case where the supply time of the etching solution is changed when the etching solution is supplied only to the in-plane peripheral portion of the wafer.

9 (a) and 9 (b), the horizontal axis of the graph shows the distance of the in-plane direction D2 from the in-plane direction center of the removal portion. The vertical axis of the graph represents the thickness of the removed portion (μm).

In addition, in FIG. 9A, the solid line shows the case where the etching liquid is supplied to the in-plane direction peripheral part and in-plane direction center part of a wafer. The broken line shows a case where the etching solution is supplied only to the center portion in the in-plane direction of the wafer.

In addition, in FIG. 9B, the solid line, the broken line, and the dashed line indicate the case where the etching solution is supplied only around the in-plane direction of the wafer. Here, a solid line shows the case where the supply time of etching liquid is 1 second. The broken line shows the case where the supply time of the etching solution is 2 seconds. The double-dot chain line indicates the case where the supply time of the etching solution is 3 seconds.

As shown in Fig. 9A, when the etching liquid is supplied only to the in-plane direction center portion of the wafer (broken line), the thickness of the removed portion at the in-plane direction center portion of the wafer becomes too large. Therefore, the difference in thickness of the removal portion becomes excessively large in the in-plane direction center portion and the in-plane direction peripheral portion of the wafer. Therefore, the removal part cannot be made into a desired shape by the shape of the non-diffusion layer side in a diffusion layer.

In addition, as shown in Fig. 9B, when the etching solution is supplied only to the periphery in the in-plane direction of the wafer (solid line, broken line, double-dotted line), there is little thickness of the removed portion at the center of the in-plane direction of the wafer (non-diffusion layer 21). Is hardly removed), and the thickness of the removed portion becomes larger as it faces toward the in-plane peripheral portion of the wafer. In addition, the longer the etching time is, the larger the thickness of the removed portion is.

On the other hand, as shown in Fig. 9A, when the etching liquid is supplied to the in-plane peripheral part and the in-plane direction center of the wafer (solid line), the difference between the thickness of the removal portion between the in-plane direction center and the in-plane direction peripheral part of the wafer is appropriate. And a removal portion is formed (part of the non-diffusion layer is removed).

Thus, as shown in FIG. 9, it turns out that the removal part which has a shape of a desired thickness direction is formed by supplying etching liquid to both the in-plane direction peripheral part and the in-plane direction center part of a wafer.

10 (a) to 10 (d) are graphs showing the thickness of the removed portion when the etching solution is supplied at the in-plane peripheral portion of the wafer when the etching liquid is supplied to the in-plane peripheral portion and the in-plane direction central portion of the wafer. to be.

10 (a) to 10 (d), the horizontal axis of the graph shows the distance in the in-plane direction from the in-plane direction center of the removal portion. The vertical axis of the graph represents the thickness of the removed part (μm).

In the example shown to (a)-(d) of FIG. 10, after etching liquid is supplied to the periphery direction of a wafer for a predetermined time, etching liquid is supplied to an in-plane direction center part for 70 second. In the example shown in Figs. 10A to 10D, the time for supplying the etchant to the in-plane peripheral portion of the wafer is 0 seconds, 1 second, 2 seconds and 3 seconds, respectively.

According to FIG. 10, it can be seen that the longer the etching liquid is supplied to the in-plane peripheral portion of the wafer, the thicker the removal portion thickness of the in-plane peripheral portion of the wafer becomes, and as a result, the difference in the irregularities in the thickness direction of the removal portion is smaller. On the other hand, the shorter the time for supplying the etchant to the in-plane peripheral portion of the wafer, the thinner the thickness of the removed portion in the in-plane peripheral portion of the wafer, and as a result, the difference in irregularities in the shape of the removed portion in the thickness direction increases.

As mentioned above, although one Embodiment and one Embodiment of this invention were described, this invention is not limited to the above-mentioned Embodiment and one embodiment.

For example, in the above embodiment, after the etching solution is supplied to the in-plane peripheral portion 20c of the diffusion wafer 20, the etching solution is supplied to the in-plane direction central portion 20d of the diffusion wafer 20, but the present invention is not limited thereto. . After the etching solution is supplied to the in-plane direction center portion 20d of the diffusion wafer 20, the etching solution may be supplied to the in-plane direction peripheral portion 20c of the diffusion wafer 20.

Further, in the above embodiment, the etching liquid E at the liquid supply port 42 even while the liquid supply port 42 moves between the in-plane peripheral portion 20c and the in-plane direction central portion 20d of the diffusion wafer 20. ), But is not limited thereto. The supply of the etching liquid E may be stopped at the liquid supply port 42 while the liquid supply port 42 is moved between the in-plane direction peripheral portion 20c and the in-plane direction central portion 20d of the wafer 10.

In the above embodiment, the portion 23 (removal portion) on the non-diffusion layer 21 side in the diffusion layer 22 faces the in-plane direction central portion 20d from the in-plane peripheral portion 20c of the diffusion wafer 20. Therefore, the convex shape is bulging toward the diffusion layer 22 from the non-diffusion layer 21, but is not limited thereto. The removal portion may have other shapes.

In the above embodiment, the diffusion wafer 20 is obtained by dividing the wafer 10 having the diffusion layers 22 on both sides in the thickness direction D1 in the thickness direction D1, but is not limited thereto. For example, about half of the thickness direction D1 in one diffusion layer 22 and the non-diffusion layer 21 is ground with respect to the wafer 10 which has the diffusion layer 22 in both sides of the thickness direction D1. It is also possible to obtain the diffusion wafer 20 by removing it.

1 is a flowchart showing an embodiment of a method of manufacturing a diffusion wafer of the present invention.

2 (a) and 2 (b) are cross-sectional views showing a procedure of obtaining two diffusion wafers from one silicon wafer.

3A and 3B are cross-sectional views showing a procedure for removing a part of the non-diffusion layer in the diffusion wafer.

4 is a functional block diagram showing a spin etching system including an FT-IR device and a spin etching device.

5 is a perspective view schematically illustrating the spin etching apparatus.

6 is a plan view schematically showing a spin etching apparatus, (a) is a view showing a state where the liquid supply port is located in the periphery of the in-plane direction of the diffusion wafer, and (b) is a in-plane direction of the diffusion wafer. It is a figure which shows the state located in a center part.

7 (a) to 7 (c) are graphs showing measured values of the removed portion size when the target value of the removed portion size of the non-diffusion layer is changed.

8 is a graph showing the thickness distribution of the non-diffusion layer.

9A and 9B are graphs showing the relationship between the supply position of the etching liquid and the thickness of the removed portion of the non-diffusion layer.

10 (a) to 10 (d) show the thicknesses of the removed portions when the etching solution is supplied in the in-plane peripheral portion of the wafer when the etching liquid is supplied to the in-plane peripheral portion and the in-plane direction central portion of the wafer. It is a graph.

11 is a flowchart showing an example of a conventional method for manufacturing a diffusion wafer.

12 (a) and 12 (b) are cross-sectional views showing a procedure of obtaining two diffusion wafers from one silicon wafer.

13 (a) and 13 (b) are cross-sectional views showing a procedure for obtaining two diffusion wafers from one silicon wafer having different shapes of diffusion layers.

<Description of the symbols for the main parts of the drawings>

20: diffusion wafer 20c: in-plane peripheral portion

20d: in-plane center 21: non-diffusion layer

22: diffusion layer 23: removal portion

D1: thickness direction D2: in-plane direction

Claims (4)

A method of manufacturing a diffusion wafer, comprising a spin etching step of removing a portion of the non-diffusion layer in a diffusion wafer having a non-diffusion layer and a diffusion layer by sheet etching. In the spin etching step, the spin etching apparatus is formed by using a spin etching apparatus which is movable in the in-plane direction of the diffusion wafer and has a single liquid supply port for supplying etching liquid to the non-diffusion layer of the diffusion wafer. The non-diffusion layer is provided by moving the single liquid supply port of the substrate to position the single liquid supply port in the in-plane peripheral portion and the in-plane direction center of the diffusion wafer, respectively, and supply the etching liquid from the liquid supply port to the non-diffusion layer. On the basis of the shape in the thickness direction in the wafer, the in-plane distribution of the etching removal amount of the non-diffusion layer during the spin etching is controlled, The diffusion layer has a concave shape in which the non-diffusion layer side faces in the in-plane direction center from the in-plane peripheral portion of the diffusion wafer, A portion of the non-diffusion layer removed from the diffusion wafer has a bulging convex shape as the diffusion layer side is directed from the in-plane peripheral portion of the diffusion wafer toward the in-plane direction center portion. The method of claim 1, A non-diffusion layer thickness measuring step of measuring the thickness of the non-diffusion layer in the diffusion wafer before the spin etching step by an FT-IR method, The wafer in-plane distribution of the etching removal amount of the non-diffusion layer in the spin etching step is performed based on the thickness distribution of the non-diffusion layer measured by the non-diffusion layer thickness measuring step. . A diffusion wafer manufactured by the method for manufacturing a diffusion wafer according to claim 1, wherein a difference between the maximum thickness and the minimum thickness of the non-diffusion layer is within 3 µm. delete

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