JP5952475B1 - Diffusion wafer and manufacturing method thereof - Google Patents

Abstract

Disclosed is a diffusion wafer that obtains a desired impurity concentration distribution regardless of an increase in diameter or partial removal of a diffusion layer, and a method for manufacturing the diffusion wafer. Along the concentration attenuating layer portion 21 formed so as to have an impurity concentration equivalent to that of the diffusion layer of the conventional small-diameter diffusion wafer while having a larger diameter than the conventional small-diameter diffusion wafer, By forming the uniform concentration layer portion 22 in which the impurity concentration is substantially the same as the maximum impurity concentration in the concentration attenuation layer portion 21, the thickness is larger than that of a conventional diffusion wafer having a small diameter. For this reason, even if it is handled in a subsequent process for manufacturing a semiconductor element or a semiconductor device, it does not break, and even if the concentration uniform layer portion 22 is finally scraped off, the diffusion layer of the conventional small-diameter diffusion wafer It is possible to ensure the same impurity concentration distribution. Thereby, the freedom degree at the time of shaving off a part of diffusion layer 2 becomes high. [Selection] Figure 1

Description

  The present invention relates to a diffusion wafer having a non-diffusion layer and a diffusion layer, and a manufacturing method for producing the diffusion wafer, which are used in manufacturing processes of semiconductor elements and semiconductor devices.

Conventionally, the manufacturing process of this type of semiconductor element is roughly divided into a wafer preparation process for forming a semiconductor wafer from a rod-shaped semiconductor single crystal and an element formation process for forming a semiconductor element on the main surface portion of the semiconductor wafer. . In the wafer preparation process, first, a silicon wafer sliced from a rod-like silicon single crystal is subjected to diffusion treatment, diffusion layers are formed on both main surfaces thereof, and then the intermediate portion of the silicon wafer after diffusion treatment is sliced. Semiconductor is obtained by cutting and separating by processing, and then performing mirror polishing on each cut surface so that the thickness other than the diffusion layer becomes the target thickness, thereby obtaining two semiconductor wafer pieces having substantially the same thickness There is a method for manufacturing an element (see, for example, Patent Document 1).
Finally, a p-type layer and an n-type layer are formed on a part of the non-diffusion layer of the semiconductor wafer piece, which is cut and separated into pellets, thereby completing the element formation step.

Japanese Patent Laid-Open No. 54-041665

Incidentally, the wafer creation process and the element formation process are generally performed at different places. For example, a semiconductor wafer (diffusion wafer) created at a first factory that performs the wafer creation process is shipped to a second factory, and the element formation process is performed at the second factory, so that various types of semiconductor elements are obtained. Is efficiently manufactured.
In addition, by increasing the diameter of a silicon wafer, it becomes possible to make more semiconductor devices from one wafer, and the productivity is greatly increased.
Similarly, in the diffusion wafer, it has been studied to improve productivity by switching from the conventional small diameter size to the large diameter size.
However, since the diffusion wafer is a single crystal plate, it is very easy to chip. When the diameter of the diffusion wafer is increased while maintaining the same size as the conventional small diameter size, the mechanical strength further decreases. Therefore, there is a problem that it is broken by handling in the subsequent element formation process.
Therefore, in order to solve such problems, a non-diffusion having the same thickness as the conventional small-diameter size is performed by performing a diffusion process on the silicon wafer that is thicker and larger than the conventional small-diameter size in the wafer preparation process. It is conceivable to produce a diffusion wafer having a layer and a diffusion layer thicker than the conventional diffusion layer. If the diffusion wafer has a large diameter and is thick, it will not break even if it is handled in the subsequent element formation step, and finally, an excess portion of the diffusion layer may be scraped off to a target thickness. As a result, even for a diffusion wafer having a large diameter, the mechanical strength is improved and cracking in the element forming process can be prevented, and a semiconductor element can be formed in the same manner as a conventional small diameter size. It is possible to prevent a decrease in sex.
However, in this case, since the additional thickness of the diffusion layer thickened by increasing the mechanical strength is scraped off, the impurity concentration distribution in the diffusion layer of this large-diameter diffusion wafer is the diffusion of the conventional small-diameter diffusion wafer. This is different from the impurity concentration distribution in the layer.
Specifically, the impurity concentration distribution at the time of performing the diffusion process in the wafer preparation process is the same for the diffusion layer of the thick and large-diameter diffusion wafer and the diffusion layer of the conventional small-diameter diffusion wafer. Although there is a large-diameter diffusion wafer, a portion having a high impurity concentration distribution is subsequently scraped off from the diffusion surface of the diffusion layer.
Compared to the conventional small-diameter diffusion wafer, the large-diameter diffusion wafer whose impurity concentration distribution differs due to scraping is different from the existing small-diameter diffusion wafer, which is an existing product, in product specifications. However, there is a problem that it cannot be used as a substitute for the conventional small-diameter diffusion wafer.

  An object of the present invention is to cope with such a problem, and an object thereof is to obtain a desired impurity concentration distribution regardless of enlargement of the diameter or partial removal of the diffusion layer. It is.

In order to achieve such an object, a diffusion wafer according to the present invention includes a non-diffusion layer in which a semiconductor element is formed in the wafer, and a diffusion layer in which impurities are diffused from the entire surface of the wafer , The diffusion layer is adjacent to the non-diffusion layer and has a concentration attenuation layer portion formed so that the concentration of the impurity attenuates toward the non-diffusion layer, and along the exposed diffusion surface of the diffusion layer. A concentration uniform layer portion formed, wherein the concentration uniform layer portion has a concentration of the impurity from the diffusion surface to a boundary surface between the concentration attenuation layer portion and the impurity concentration in the concentration attenuation layer portion. maximum concentration Ri substantially equal der, characterized Rukoto that having a site scraping to the diffusion layer to a target thickness.

A method for manufacturing a diffusion wafer according to the present invention is a method for manufacturing a diffusion wafer having a non-diffusion layer on which a semiconductor element is formed on a wafer and a diffusion layer in which impurities are diffused from the entire surface of the wafer. A deposition step for adhering and infiltrating the impurities on the surface of the wafer; a removal step for removing a compound layer formed on the surface of the wafer during the deposition step; and the impurities inside the wafer. And a drive-in step of forming a concentration attenuation layer part in which the concentration of the impurity attenuates toward the non-diffusion layer as the diffusion layer, and the deposition step and the removal step are performed a plurality of times. By repeating the drive-in process after repeating, the concentration of the impurities along the exposed diffusion surface of the diffusion layer is reduced in the concentration attenuation layer portion. That Ri substantially Do the same as the maximum concentration of the impurity, and forming the diffusion layer concentration equivalent layer portion that is part of the site scraped to target thickness of.

The diffusion wafer according to the present invention having the above-described features is formed so as to have an impurity concentration equivalent to that of the diffusion layer of the conventional small-diameter diffusion wafer while having a larger diameter than the conventional small-diameter diffusion wafer. By forming the concentration uniform layer portion having the impurity concentration substantially the same as the maximum impurity concentration in the concentration attenuation layer portion along the concentration attenuation layer portion, the thickness becomes thicker than the conventional diffusion wafer having a small diameter. For this reason, even if it is handled in a subsequent process for manufacturing a semiconductor element or a semiconductor device, it does not break, and even if the concentration equalization layer part is finally scraped off, it is the same as the diffusion layer of the conventional small-diameter diffusion wafer. It is possible to ensure the impurity concentration distribution. Thereby, the freedom degree at the time of shaving off a part of diffusion layer becomes high.
Therefore, a desired impurity concentration distribution can be obtained regardless of the increase in the diameter and the partial removal of the diffusion layer.
As a result, a large-diameter diffusion wafer can be used as an alternative to a conventional small-diameter diffusion wafer that is an existing product.
For this reason, it is possible to prevent cracking due to a decrease in mechanical strength accompanying the increase in diameter, and it is possible to significantly increase productivity and improve economic rationality by increasing the diameter.
Further, since the impurity concentration in the deep layer portion near the non-diffusion layer in the diffusion layer can be precisely adjusted, it is also possible to improve the electrical conductivity immediately under the region of the semiconductor device.
Therefore, a semiconductor device with little power loss can be manufactured.

In addition, the method for manufacturing a diffusion wafer according to the present invention having the above-described features includes a deposition process for infiltrating impurities into the wafer surface, and a removal process for removing a compound layer generated on the wafer surface during the deposition process. Then, a drive-in process for diffusing impurities permeated in the deposition process into the wafer is performed. For this reason, a concentration attenuation layer portion for attenuating the impurity concentration toward the non-diffusion layer is formed as a diffusion layer by the drive-in process. At the same time, by repeating the deposition step and the removing step a plurality of times, the impurity concentration from the diffusion surface to the boundary surface of the diffusion layer is the same as the maximum impurity concentration in the concentration attenuation layer portion regardless of the depth. Thus, the uniform concentration layer portion can be easily created in a short time.
Therefore, a desired impurity concentration distribution can be obtained by a short heat treatment.
As a result, the desired impurity concentration distribution can be obtained more easily in a short time regardless of the increase in the diameter or partial removal of the diffusion layer.

It is explanatory drawing which shows the whole structure of the diffusion wafer which concerns on embodiment of this invention, (a) is a concentration distribution graph of an impurity, (b) is a vertical front view. It is explanatory drawing which shows the manufacturing method of the diffusion wafer which concerns on embodiment of this invention, (a)-(e) is the vertical front view which showed the manufacturing process in process order.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The diffusion wafer A according to the embodiment of the present invention performs diffusion treatment on a wafer sliced from a rod-shaped single crystal (ingot) used in the manufacturing process of semiconductor elements, semiconductor devices, etc., so that impurities such as phosphorus ( (Dopant) is diffused.
More specifically, as shown in FIGS. 1A and 1B, the diffusion wafer A according to the embodiment of the present invention mainly includes a non-diffusion layer 1 and a diffusion layer 2 in which the impurity is diffused. As an element.
Although not shown, it is possible to add another layer in addition to the non-diffusion layer 1 and the diffusion layer 2.

The diffusion layer 2 includes a concentration attenuation layer portion 21 that attenuates as the concentration of the impurity moves toward the non-diffusion layer 1 side, and a concentration equalization layer portion 22 formed along the exposed diffusion surface 2a. .
The concentration attenuation layer portion 21 has a depth (hereinafter referred to as “depth”) from the diffusion surface 2 a side opposite to the non-diffusion layer 1 to the adjacent surface 2 b adjacent to the non-diffusion layer 1 in the diffusion layer 2. Accordingly, the impurity concentration is gradually reduced.
The concentration uniform layer portion 22 does not attenuate the concentration of the impurity from the diffusion surface 2a to the boundary surface 2c between the concentration attenuation layer portion 21 and the concentration attenuation layer portion 21 regardless of the depth. This is a portion formed so as to be substantially the same as the maximum concentration of the impurity in the portion 21.
Here, “substantially the same” is not limited to the fact that the concentration of the impurity from the diffusion surface 2 a to the boundary surface 2 c is exactly the same (same) as the maximum concentration of the impurity in the concentration attenuation layer portion 21. In addition, the impurity concentration from the boundary surface 2c toward the diffusion surface 2a is slightly increased by the maximum concentration of the impurity in the concentration attenuation layer portion 21.
Further, the concentration uniform layer portion 22 can be used to scrape the diffusion layer 2 to a target thickness in a subsequent process.
The post-process refers to an element formation process for making a semiconductor element for the non-diffusion layer 1, a device formation process for making a semiconductor device, and the like.

ここで、Ｎｄは、拡散ウエハ内の拡散による不純物の濃度（拡散によってウエハ内に追加された不純物の濃度）、ｔは、拡散ウエハの拡散時間、ｘは、拡散ウエハ内における深度、Ｄは、拡散係数である。
数式１を満たすｘとｔの関数をＦ（ｘ，ｔ）、拡散ウエハの露出した拡散面における拡散による不純物の濃度（拡散によってウエハ内に追加された不純物の表面濃度）をＮｓとすると、数式２に示すようになる。

さらに、拡散ウエハ内における不純物の最小濃度（拡散前からウエハ内に存在する不純物の濃度）をＮｂとすると、拡散ウエハの全体における全不純物の濃度Ｎの分布は、数式３に示すように表せる。

On the other hand, the diffusion wafer A according to the embodiment of the present invention is a large-diameter diffusion wafer that can be used as an alternative to the conventional small-diameter diffusion wafer B that is an existing product.
In the case of the example shown in FIGS. 1A and 1B, the conventional small-diameter diffusion wafer B that is an existing product is obtained by changing the concentration uniform layer portion 22 from the large-diameter diffusion wafer A according to the embodiment of the present invention. The removed boundary surface 2c corresponds to a structure exposed as a diffusion surface.
By the way, the distribution of the impurity concentration in the conventional small-diameter diffusion wafer B that is an existing product and the distribution of the impurity concentration in the large-diameter diffusion wafer A are in accordance with the basic law of diffusion phenomenon (Fick's law). It is expressed by the diffusion equation shown below.

Here, Nd is the concentration of impurities by diffusion in the diffusion wafer (concentration of impurities added in the wafer by diffusion), t is the diffusion time of the diffusion wafer, x is the depth in the diffusion wafer, and D is Diffusion coefficient.
Assuming that the function of x and t satisfying Equation 1 is F (x, t), and the concentration of impurities due to diffusion on the exposed diffusion surface of the diffusion wafer (surface concentration of impurities added in the wafer by diffusion) is Ns. As shown in 2.

Furthermore, if the minimum impurity concentration in the diffusion wafer (concentration of impurities existing in the wafer before diffusion) is Nb, the distribution of the concentration N of all impurities in the entire diffusion wafer can be expressed as shown in Equation 3.

ここで、ｘｍは、図１（ａ）（ｂ）に示されるように、拡散層２の拡散面２ａから任意の深度である。

Thus, when the distribution of the concentration of all impurities in the conventional small-diameter diffusion wafer B that is an existing product has the diffusion profile expressed by Equation 3, it can be used as an alternative to the conventional small-diameter diffusion wafer B. The distribution of the concentration N of all impurities in the large-diameter diffusion wafer A has a diffusion profile approximately expressed by Equations 4 and 5.

Here, xm is an arbitrary depth from the diffusion surface 2a of the diffusion layer 2, as shown in FIGS.

ここで、ｘｊは、図１（ａ）（ｂ）に示されるように、拡散層２の拡散面２ａから非拡散層１と隣り合う隣接面２ｂまでの深度である。
数式６から、従前の小口径な拡散ウエハＢの代替品として使用可能な大口径な拡散ウエハＡの全不純物の濃度Ｎの分布を、近似的に数式７に示される拡散プロファイルを有するように変更することも可能である。

数式４及び数式５又は数式７により、拡散層２において拡散面２ａから任意の深度ｘｍまでの箇所には、その全不純物の濃度Ｎの分布が、その深度に関係なく濃度減衰層部２１へ向かって減衰せず、濃度減衰層部２１における不純物の最大濃度と略同じ又は同一になる、濃度均等層部２２が形成される。
すなわち、この実施形態に係る拡散ウエハＡにおいても、前述した実施形態に係る拡散ウエハＡと同様になる。 In particular, as specific examples of Equation 3, “a constant where the diffusion coefficient D does not depend on x and t”, “the total amount of impurities used for diffusion is constant”, and “all diffusion at the start of diffusion (t = 0)” When all of the “impurities used are concentrated on the diffusion surface (x = 0)” are satisfied, the distribution of the concentration N of all impurities in the entire diffusion wafer can be expressed as shown in Equation 6.

Here, xj is the depth from the diffusion surface 2a of the diffusion layer 2 to the adjacent surface 2b adjacent to the non-diffusion layer 1, as shown in FIGS.
From Equation 6, the distribution of the concentration N of all impurities in the large-diameter diffusion wafer A that can be used as an alternative to the conventional small-diameter diffusion wafer B is changed to have a diffusion profile approximately represented by Equation 7. It is also possible to do.

According to Equation 4, Equation 5, or Equation 7, the distribution of the concentration N of all impurities in the diffusion layer 2 from the diffusion surface 2a to an arbitrary depth xm is directed toward the concentration attenuation layer portion 21 regardless of the depth. Thus, the concentration equalization layer portion 22 is formed which is not attenuated and is substantially the same as or the same as the maximum impurity concentration in the concentration attenuation layer portion 21.
That is, the diffusion wafer A according to this embodiment is the same as the diffusion wafer A according to the above-described embodiment.

Then, the manufacturing method for producing the diffusion wafer A according to the embodiment of the present invention is a method of attaching and infiltrating impurities 20 into the surface 11 of the wafer 10 as shown in FIGS. A position step, a removal step of removing the compound layer 3 formed on the surface 11 of the wafer 10 during the deposition step after the deposition step, and impurities 20 that have penetrated in the deposition step inside the wafer 10 And a drive-in process for diffusion as a main process.
The compound layer 3 generated on the surface 11 of the wafer 10 during the deposition step is made of an oxide such as phosphorus glass or other silicon compounds.
In particular, in the drive-in process shown in FIG. 2 (e), the impurity 20 is diffused into the wafer 10 so that the concentration of the impurity 20 as the diffusion layer 2 attenuates as it goes toward the non-diffusion layer 1 side. The layer part 21 is formed.
Further, by repeating the deposition process shown in FIGS. 2A and 2C and the removal process shown in FIGS. 2B and 2D a plurality of times, the diffusion surface 2a of the diffusion layer 2 is formed. A concentration uniform layer portion 22 in which the concentration of the impurity 20 is substantially the same as the maximum concentration of the impurity 20 in the concentration attenuation layer portion 21 is formed.

As a specific example of the manufacturing method of the large-diameter diffusion wafer A according to the embodiment of the present invention, a conventional silicon wafer ingot having a larger diameter than the conventional small-diameter diffusion wafer B is used. It is preferable that the wafer 10 is sliced more thickly and subjected to a diffusion treatment by a vapor phase diffusion method or the like on the large diameter and thick wafer 10.
More specifically, in a furnace heated to a predetermined temperature, phosphoryl chloride (phosphorus oxychloride) containing phosphorus as an n-type impurity as the impurity 20, nitrogen, argon, helium, or any mixed gas thereof, and oxygen And are deposited at 1200 ° C. or lower.
As a result, the wafer 10 installed in the furnace takes in impurities such as phosphorus, which is an n-type impurity, and is oxidized under the influence of oxygen and heat. Accordingly, a compound layer 3 made of an oxide such as phosphorus glass is generated on the surface 11 of the wafer 10.
Therefore, in the case shown in FIGS. 2A to 2E, the deposition step and the removal step of removing the phosphor glass or the like that becomes the compound layer 3 are repeated twice. Thereafter, phosphorus that has penetrated into the wafer 10 is diffused into the wafer 10 by the drive-in process.
Although not shown in the drawings as other examples, the diffusion method different from the vapor phase diffusion method, the impurity 20 different from phosphorus is used, or the deposition step and the removal step are repeated three times or more. The deposition conditions can be changed each time the deposition process and the removal process are repeated, or these condition settings can be combined.

According to the diffusion wafer A according to the embodiment of the present invention, the impurity concentration is the same as that of the diffusion layer of the conventional small-diameter diffusion wafer B while the diameter is larger than that of the conventional small-diameter diffusion wafer B. By forming the concentration uniform layer portion 22 having the impurity concentration substantially the same as the maximum impurity concentration in the concentration attenuation layer portion 21 along the concentration attenuation layer portion 21 thus formed, the diffusion wafer B having a small diameter as before is formed. It becomes thicker than.
For this reason, even if it is handled in a subsequent process for manufacturing a semiconductor element, a semiconductor device, etc., it will not crack, and even if the concentration uniform layer portion 22 is finally scraped off, the diffusion layer of the conventional small-diameter diffusion wafer B It is possible to ensure the same impurity concentration distribution.
That is, the same impurity concentration distribution as that of the diffusion layer of the conventional small-diameter diffusion wafer B is obtained even after the concentration uniform layer portion 22 is scraped off while reducing the mechanical strength (preventing cracking) as the diameter increases. As a result, the product standard of the conventional small-diameter diffusion wafer B that becomes an existing product can be met.
Thereby, the freedom degree at the time of shaving off a part of diffusion layer 2 becomes high.
Therefore, a desired impurity concentration distribution can be obtained regardless of the increase in the diameter or the partial removal of the diffusion layer 2.
As a result, the large-diameter diffusion wafer A can be used as an alternative to the existing small-diameter diffusion wafer B, which is an existing product.
For this reason, it is possible to prevent cracking due to a decrease in mechanical strength accompanying the increase in diameter, and it is possible to significantly increase productivity and improve economic rationality by increasing the diameter.
In addition, since the impurity concentration in the deep layer portion near the non-diffusion layer 1 in the diffusion layer 2 can be precisely adjusted, it is possible to improve the conductivity immediately below the region of the semiconductor device.
Therefore, a semiconductor device with little power loss can be manufactured.

Particularly, the concentration equalization layer portion 22 is removed from the diffusion surface 2a of the diffusion layer 2 by (multiple times) removal of the compound layer 3 generated on the diffusion surface 2a of the diffusion layer 2 as the impurities 20 penetrate. 21 is preferably formed up to the boundary surface 2c.
In this case, the concentration of the impurity 20 from the diffusion surface 2a to the boundary surface 2c is higher than that obtained by removing the compound layer 3 generated on the diffusion surface 2a of the diffusion layer 2 only once due to the penetration of the impurity 20. The uniform concentration layer portion 22 having the same concentration as the maximum concentration of the impurity 20 in the concentration attenuation layer portion 21 can be easily created in a short time regardless of the depth.
Therefore, a desired impurity concentration distribution can be obtained by a short heat treatment.
As a result, a desired impurity concentration distribution can be obtained more easily in a short time regardless of the increase in the diameter or partial removal of the diffusion layer 2.

Furthermore, according to the manufacturing method of the diffusion wafer A according to the embodiment of the present invention, the deposition process for infiltrating the impurities 20 into the surface 11 of the wafer 10 and the compound layer generated on the surface 11 of the wafer 10 during the deposition process. 3 is repeated a plurality of times, and then a drive-in process for diffusing the impurities 20 permeated in the deposition process into the wafer 10 is performed.
For this reason, the concentration attenuation layer portion 21 that attenuates the concentration of the impurity 20 toward the non-diffusion layer 1 is formed as the diffusion layer 2 by the drive-in process.
At the same time, by repeating the deposition step and the removal step a plurality of times, the concentration of the impurity 20 from the diffusion surface 2a to the boundary surface 2c of the diffusion layer 2 is changed to the impurity in the concentration attenuation layer portion 21 regardless of the depth. The density uniform layer portion 22 having the same density as the maximum density of 20 is easily created in a short time.
Therefore, a desired impurity concentration distribution can be obtained by a short heat treatment.
As a result, a desired impurity concentration distribution can be obtained more easily in a short time regardless of the increase in the diameter or partial removal of the diffusion layer 2.
Further, the number of repetitions of the deposition step and the removal step, the deposition conditions such as the deposition temperature and deposition time in each of the deposition steps, the supply amount of the impurities 20, or the drive-in temperature in the drive-in step It is possible to arbitrarily set an arbitrary depth xm from the diffusion surface 2a of the diffusion layer 2 by adjusting one or both of the drive-in conditions such as the drive-in time and the drive-in time.

Next, an embodiment of the present invention will be described with reference to the drawings.
As this example, a diffusion wafer A having a larger diameter than the conventional small-diameter diffusion wafer B and having a thickness equivalent to the concentration equality layer portion 22 than the thickness of the conventional small-diameter diffusion wafer B was produced. . It was verified whether the concentration distribution of the entire impurity 20 in the previous small-diameter diffusion wafer B would be the same as that obtained by scraping off the concentration uniform layer portion 22 in a later step after the fabrication of the diffusion wafer A according to this example.
That is, it was verified whether or not the large-diameter diffusion wafer A can be used as an alternative to the existing small-diameter diffusion wafer B that is an existing product.

Therefore, as shown in FIGS. 1 (a) and 1 (b), as a conventional small-diameter diffusion wafer B, which is an existing product, the diameter of 125 mm and the penetration of impurities 20 at a temperature of 1200 ° C. or less by the vapor phase diffusion method are used. 10 which is applied by deposition to adhere to and penetrate the surface 11 (hereinafter referred to as “existing product B”), and a large-diameter diffusion wafer A of this embodiment has a diameter of 150 mm and a concentration higher than that of the existing product B Thickness equivalent to the uniform layer portion 22 and a comparison target diffusion wafer having a diameter of 150 mm and thicker than the existing product B by the concentration uniform layer portion 22 (hereinafter referred to as “comparative products C and D”) Prepared).
Further, in order to easily compare these, in the concentration distribution graph of the impurity 20 shown in FIG. 1A, the concentration distribution A1 of all the impurities 20 in the large-diameter diffusion wafer A of the embodiment is shown by a solid line, The concentration distribution B1 of all impurities 20 in the product B is indicated by a thick broken line, the concentration distribution C1 of all impurities 20 in the comparison product C is indicated by a two-dot chain line, and the concentration distribution D1 of all impurities 20 in the comparison product D is indicated by a two-dot chain line. Show.

In the large-diameter diffusion wafer A of this embodiment, as shown in FIGS. 2A to 2E, the impurities on the surface 11 of the wafer 10 at 1200 ° C. or less by the vapor phase diffusion method as in the existing product B. A deposition process for adhering and infiltrating 20 and a process for removing the compound layer 3 such as phosphorous glass (including the impurity 20) generated on the surface 11 of the wafer 10 during the deposition process were repeated twice.
On the other hand, Comparative products C and D were each subjected to the deposition process and the compound layer 3 removal process only once.
Further, the comparative product C has its concentration distribution C1 copied to a part of the concentration distribution B1 of all impurities 20 in the existing product B as shown by a two-dot chain line in FIG. The concentration is diffused so as to be higher than the concentration distribution D1 of all impurities 20.
In the comparative product D, the concentration distribution D1 of the impurity 20 on the diffusion surface 2a (surface concentration of all impurities, Ns + Nb) is exposed from the existing product B as shown by the two-dot chain line in FIG. The diffusion is performed so as to be thinner than the concentration distribution C1 of all impurities 20 in the comparative product C so as to be the same as the concentration of the impurities 20 on the diffusion surface.

Comparing the large-diameter diffusion wafer A of the example and the comparative products C and D, the large-diameter diffusion wafer A of the example has a diffusion layer whose concentration distribution A1 is indicated by a solid line in FIG. In FIG. 2, the diffusion can be easily performed in a short time so as to be substantially in a straight line from the diffusion surface 2 a to an arbitrary depth xm (the boundary surface 2 c between the concentration attenuation layer portion 21 and the concentration equalization layer portion 22).
Further, the concentration distribution A1 of the large-diameter diffusion wafer A according to the embodiment is from the arbitrary depth xm (boundary surface 2c) to the adjacent surface 2b with the non-diffusion layer 1 and the concentration distribution B1 of the impurity 20 in the existing product B. It was able to diffuse easily in a short time so as to be the same.
As a result, the concentration distribution layer B1 of the impurity 20 in the existing product B was obtained by scraping off the uniform concentration layer portion 22, and it was proved that it easily matched the product standard of the existing product B.
As a result, it was found that the large-diameter diffusion wafer A of the example can be used as an alternative to the existing product B.

On the other hand, the comparison products C and D have the same concentration distributions 1C and D1 as the concentration distribution B1 of the impurity 20 in the existing product B as indicated by a two-dot chain line in FIG. Could not diffuse.
Thereby, even if the diffusion surface 2a side that becomes the concentration uniform layer portion 22 of the large-diameter diffusion wafer A of the embodiment is scraped off, the concentration distribution B1 of the impurity 20 in the existing product B cannot be obtained, and the product of the existing product B It was proved that the standards could not be met.
Further, even if the deposition step and the removal step are performed only once, in principle, the concentration distribution of all impurities 20 from an arbitrary depth xm (boundary surface 2c) to the boundary adjacent surface 2b with the non-diffusing layer 1 It is estimated that the concentration distribution can be made to be the same as the concentration distribution B1 of the impurity 20 in the existing product B.
However, it was necessary to change the diffusion conditions to be completely different from those of the existing product B, such as a higher temperature and longer time for the heat treatment, and it was also found that this could not be realized easily.

  In the above-described embodiment, the case where the concentration uniform layer portion 22 is scraped off in the subsequent process after the diffusion wafer A is formed has been described. However, the present invention is not limited to this. Or may be changed so as to be further scraped off beyond the density uniform layer portion 22.

A Diffusion wafer 1 Non-diffusion layer 2 Diffusion layer 2a Diffusion surface 2b Adjacent surface 2c Interface 20 Impurity 21 Concentration attenuation layer portion 22 Concentration equality layer portion 3 Compound layer

Claims (3)

A non-diffusion layer on which a semiconductor element is formed in the wafer, and a diffusion layer in which impurities are diffused from the entire surface of the wafer ,
The diffusion layer is formed adjacent to the non-diffusion layer so that the concentration of the impurity attenuates as it goes toward the non-diffusion layer.
A concentration uniform layer formed along the exposed diffusion surface of the diffusion layer,
The density uniform layer unit, the concentration of the impurity from the diffusion surface to the boundary surface between the concentration attenuating layer portion is state, and are substantially the same as the maximum concentration of the impurity in the concentration attenuating layer portion, the diffusion layer spreading a wafer, characterized in Rukoto that having a site scraping to target thickness. A diffusion wafer comprising: a non-diffusion layer on which a semiconductor element is formed on the wafer; and a diffusion layer in which impurities are diffused from the entire surface of the wafer.
Ibid up any depth from the exposed diffusion surface of the diffusion layer is a profile showing the density distribution of the number equation 4 of the impurities, and the diffusion layer concentration equivalent layer that contains the site scraped to target thickness of Part
A diffusion wafer characterized in that the concentration distribution of the impurity has a profile approximately represented by Formula 5 at a location from the arbitrary depth to an adjacent surface adjacent to the non-diffusion layer.

Here, x is the depth in the diffusion wafer, xm is an arbitrary depth from the diffusion surface, N is the concentration of all impurities in the entire diffusion wafer, Ns is the concentration of impurities due to diffusion on the diffusion surface, and Nb is The minimum impurity concentration, t, in the diffusion wafer is the diffusion time. A method for producing a diffusion wafer comprising a non-diffusion layer on which a semiconductor element is formed on a wafer and a diffusion layer in which impurities are diffused from the entire surface of the wafer,
A deposition process for adhering and infiltrating the impurities on the surface of the wafer;
A removal step of removing a compound layer generated on the surface of the wafer during the deposition step;
A drive-in step of diffusing the impurities into the wafer to form a concentration attenuation layer portion in which the concentration of the impurities attenuates toward the non-diffusion layer as the diffusion layer, and
By performing the drive-in step after repeating the deposition step and the removal step a plurality of times, the concentration of the impurity along the exposed diffusion surface of the diffusion layer is increased to the maximum of the impurity in the concentration attenuation layer portion. concentration and Ri substantially Do the same as, the manufacturing method of the diffuse wafer and forming the diffusion layer concentration equivalent layer portion that is part of the site scraped to target thickness of.

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