JP2005150573A - Impurity diffusion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impurity diffusion device which enables a uniform impurity diffusion layer to be formed in a semiconductor wafer by a simple method without involving the deterioration of productivity and a great increase of an installation cost. <P>SOLUTION: The device has an exhaust port side gas shielding plate 4 with a cut-out portion 4a in an outer circumferential end part arranged almost vertically to a longitudinal direction of a process tube 1 between a gas exhaust port 1b and a semiconductor wafer 2, and an introduction port side gas shielding plate 5 with a cut-out portion 5a in an outer circumferential end part arranged almost vertically to a longitudinal direction of the process tube 1 between a gas introduction port 1a and the semiconductor wafer 2. A downstream side resistance current plate 6 (first resistance current plate) and an upstream side resistance current plate 7 (second resistance current plate) are provided between a boat 3 whereon the semiconductor wafer 2 is mounted and an inner wall of the process tube 1, and both thereof have a plate-like shape with a plurality of holes, and are arranged in a longitudinal direction of the process tube 1 to hold the boat 3 from both sides. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an impurity diffusion device in a manufacturing process of a semiconductor element including a solar cell.

  A typical example of a conventional semiconductor wafer impurity diffusion apparatus is shown in FIG.

  The horizontal process tube 1 has a gas inlet 1a at one end and a gas exhaust 1b at the other end, and is heated from the outside by a heater (not shown) or the like. A boat 3 loaded with semiconductor wafers 2 such as single crystal silicon and polycrystalline silicon is accommodated in the process tube 1, and a semiconductor wafer is introduced by introducing a gas containing impurities such as phosphorus and boron from the gas inlet 1a. An impurity diffusion layer is formed on the surface 2 (see, for example, Patent Document 1).

  As shown in FIG. 7, the semiconductor wafer 2 may be placed in parallel to the gas flow in the process tube 1 (see, for example, Patent Document 1) or placed perpendicular to the gas flow. In some cases (for example, see Patent Document 2).

  In the conventional impurity diffusion apparatus described above, since the semiconductor wafers 2 loaded on the boat 3 are exposed to the gas atmosphere in order from the side closer to the gas inlet 1a, the impurity diffusion is performed. There is a difference in the time at which the impurity diffusion is started on the side of the mouth 1a and the gas exhaust port 1b. As a result, the thickness of the film formed on the surface of the semiconductor wafer 2 and the depth of the impurity diffusion layer formed on the inner surface layer become non-uniform, and when the semiconductor element is used as it is, the performance and yield of the semiconductor element are reduced. There was a problem that led to a decline.

  In order to avoid this problem, for example, Patent Document 3 proposes providing a plurality of gas introduction nozzles having a large number of gas ejection holes in the process tube 1. According to this method, since the gas containing impurities reaches the semiconductor wafer 2 almost simultaneously, the thickness of the film formed on the surface of the semiconductor wafer 2 and the depth of the impurity diffusion layer formed on the inner surface layer are not uniform. The problem that occurs is solved to some extent. However, in this method, the semiconductor wafer 2 has a different distance from the gas introduction nozzle, so that there remains a problem in the in-plane uniformity of the semiconductor wafer 2.

Therefore, the applicant has proposed a method of providing a plurality of gas introduction nozzles as described in Patent Document 4 and further providing a gas flow rate control device for each gas introduction nozzle. According to this method, since the gas containing impurities reaches the semiconductor wafer 2 almost simultaneously, the thickness of the film formed on the surface of the semiconductor wafer 2 and the depth of the impurity diffusion layer formed on the internal surface layer are reached. The problem of non-uniformity is solved and the concentration of impurities contained in the gas can be adjusted for each nozzle, and the time for starting and stopping the gas flow can be adjusted. In-plane uniformity can also be ensured.
JP 2001-185502 A JP 2001-185501 A JP-A-7-58045 Japanese Patent No. 3359474

  However, in the method of providing a plurality of gas introduction nozzles having a large number of gas ejection holes in the conventional process tube 1 shown in Patent Document 3 and Patent Document 4, the gas introduction nozzle is used in the high-temperature process tube 1. Therefore, the problem that the nozzle bends or breaks may occur. In addition, the apparatus is expensive and the gas setting is complicated.

  Further, the difference in the impurity diffusion start time with respect to the semiconductor wafer 2 can be alleviated by providing a wide interval between the semiconductor wafers 2 loaded on the boat 3, but in this case, it corresponds to an increase in the interval between the semiconductor wafers 2. It is necessary to reduce the number of treatments to be performed or to increase the diameter of the process tube 1, and there is a problem that the productivity is reduced or the equipment installation area and the equipment investment cost are greatly increased due to the increase in equipment size. It was.

  The present invention has been made in view of such problems of the prior art, and a uniform impurity diffusion layer can be formed on a semiconductor wafer by a simple method without a decrease in productivity and a significant increase in equipment cost. An object is to provide an impurity diffusion device that can be formed.

  In order to achieve the above object, an impurity diffusing apparatus according to claim 1 of the present invention includes a semiconductor wafer placed in a high temperature heated horizontal process tube having a gas inlet at one end and a gas outlet at the other end. An impurity diffusing device that accommodates a loaded boat and introduces a gas containing impurities from the gas inlet to diffuse the impurities into the semiconductor wafer, wherein the exhaust outlet is provided between the gas outlet and the semiconductor wafer. A side gas shielding plate is provided. Normally, the gas containing impurities introduced from the gas inlet into the process tube has a higher flow velocity as it approaches the gas outlet, but according to the configuration of the present invention, the exhaust speed can be reduced. A difference in time during which the semiconductor wafer is exposed to the gas in the process tube can be suppressed.

  The impurity diffusion device according to claim 2 of the present invention is the impurity diffusion device according to claim 1, wherein an introduction side gas shielding plate is provided between the gas introduction port and the semiconductor wafer. The gas containing impurities introduced from the gas inlet into the process tube does not directly hit the semiconductor wafer and spreads into the process tube after hitting the gas shielding plate, eliminating the influence of the distance from the gas inlet. be able to.

  The impurity diffusing device according to claim 3 of the present invention is the impurity diffusing device according to claim 1 or 2, wherein the exhaust-side gas shielding plate has an outer peripheral edge that is not in contact with an inner wall of the process tube. Since they are arranged, the gas that has passed through the region of the semiconductor wafer does not concentrate in one direction, but goes out from any direction on the wall surface side of the process tube and goes downstream.

  The impurity diffusing device according to claim 4 of the present invention is the impurity diffusing device according to claim 2 or 3, wherein the inlet-side gas shielding plate has its outer peripheral edge not in contact with the inner wall of the process tube. Since they are arranged, a gas containing impurities is directed to the semiconductor wafer from all directions on the wall surface side of the process tube.

  The impurity diffusing device according to claim 5 of the present invention is the impurity diffusing device according to claim 1 or 2, wherein the exhaust-side gas shielding plate and the inlet-side gas shielding plate are notched at outer peripheral edges thereof. Since the gas is contained in the gas shielding plate, it can be guided through this notch, without being affected by the distance between the gas inlet and the gas outlet. The flow of gas can be controlled freely.

  The impurity diffusion device according to claim 6 of the present invention is the impurity diffusion device according to claim 5, wherein the exhaust-side gas shielding plate and the inlet-side gas shielding plate are arranged in the longitudinal direction of the process tube. Since the projection shape is arranged so that there is no gap when superposed and projected, the gas containing impurities is sufficiently diffused in the region sandwiched between these gas shielding plates. It becomes like this.

  The impurity diffusion device according to claim 7 of the present invention is the impurity diffusion device according to any one of claims 1 to 6, wherein a plurality of holes are provided between the boat loaded with the semiconductor wafers and the inner wall of the process tube. A plate-like first resistance rectifying plate having a shape and a second resistance rectifying plate having substantially the same shape are arranged in the same direction as the longitudinal direction of the process tube so as to sandwich the boat from both sides. Since it was made to do so, the ratio which the gas containing the impurity directed through this resistance rectifier plate passes a semiconductor wafer can be raised.

  An impurity diffusion device according to an eighth aspect of the present invention is the impurity diffusion device according to the fifth or sixth aspect, wherein a plate having a plurality of holes between a boat loaded with the semiconductor wafers and an inner wall of the process tube. A first resistance rectifying plate having a shape and a second resistance rectifying plate having substantially the same shape are arranged in the same direction as the longitudinal direction of the process tube so as to sandwich the boat from both sides, and the exhaust port The side gas shielding plate is arranged with its notch corresponding to the first resistance rectifying plate, and the inlet side gas shielding plate is arranged with its notch corresponding to the second resistance rectifying plate. Therefore, after the gas containing impurities is once retained by the gas shielding plate, it can be led to the inlet or the outlet of the resistance rectifying plate through this notch.

  The impurity diffusion device according to claim 9 of the present invention is the impurity diffusion device according to claim 7 or 8, wherein the first resistance rectifying plate and the second resistance rectifying plate are both loaded on the boat. Since the semiconductor wafer is installed so as to be substantially perpendicular to the semiconductor wafer, the gas containing impurities flows uniformly between the semiconductor wafers installed between the resistance rectifying plates.

  As described above in detail, according to the impurity diffusion device of the first aspect of the present invention, the gas containing impurities, which is normally introduced from the gas inlet into the process tube, has a flow velocity as it approaches the gas outlet. However, according to the configuration of the present invention, since the exhaust speed can be reduced, the difference in the time during which the semiconductor wafer is exposed to the gas in the process tube can be suppressed, and the diffusion of the semiconductor wafer can be suppressed. The uniformity can be improved by a simple method.

  Even when the exhaust means is natural exhaust instead of forced exhaust, the gas containing impurities flowing between the semiconductor wafers from the gas inlet is pushed back against the gas shielding plate, so that the diffusion start time Slow semiconductor wafers on the gas exhaust side will be exposed to the gas containing impurities again. Therefore, the uniformity of diffusion of the semiconductor wafer can be improved by a simple method.

  According to the impurity diffusing apparatus according to claim 2 of the present invention, the gas containing the impurity introduced into the process tube from the gas inlet does not directly hit the semiconductor wafer, and hits the gas shielding plate before the process. Since it spreads in the tube, the influence of the distance from the gas inlet can be eliminated. Therefore, the problem that the diffusion of only the portion near the gas inlet of the semiconductor wafer rapidly proceeds can be solved by a simple method.

  Furthermore, according to the impurity diffusing apparatus according to claim 3 of the present invention, the gas that has passed through the region of the semiconductor wafer does not concentrate in one direction, and escapes from any direction on the wall surface side of the process tube to the downstream side. And come to go. According to the impurity diffusing apparatus according to claim 4 of the present invention, the gas containing impurities is directed to the semiconductor wafer from all directions on the wall surface side of the process tube. Therefore, according to these impurity diffusion apparatuses, the in-plane uniformity of the diffusion of the semiconductor wafer can be appropriately ensured.

  According to the impurity diffusing device according to claim 5 of the present invention, the gas containing impurities can once be retained by the gas shielding plate and then guided through the notch, and the distance between the gas inlet and the gas outlet. The flow of gas can be controlled freely without being affected by the above.

  Further, according to the impurity diffusion device of the sixth aspect of the present invention, the gas containing impurities is sufficiently diffused in the region sandwiched between these gas shielding plates, so that the impurity diffusion device is formed on the semiconductor wafer. This improves the uniformity of the diffusion layer.

  According to the impurity diffusion device of the seventh aspect of the present invention, since the gas containing impurities directed through the resistance rectifying plate can increase the rate of passing through the semiconductor wafer, Use efficiency improves.

  Further, according to the impurity diffusing device according to the eighth aspect of the present invention, the gas containing impurities can be once retained by the gas shielding plate and then led to the inlet or the outlet of the resistance rectifying plate through the notch. . Thus, impurity diffusion can be started almost simultaneously for all the semiconductor wafers without being affected by the distance between the gas inlet and the gas outlet, so that a uniform diffusion layer can be formed on the semiconductor wafer. Moreover, the utilization efficiency of gas can be raised.

  According to the impurity diffusion device of claim 9 of the present invention, the gas containing impurities flows uniformly between the semiconductor wafers installed between the resistance rectifying plates, so that a uniform diffusion layer is formed on the semiconductor wafer. Can be formed.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of an impurity diffusion apparatus according to the present invention. (A) is a perspective view, (b) is a cross-sectional structure diagram viewed from the XX direction of (a), and (c) is a cross-sectional structure diagram viewed from the Y-Y direction of (a).

  In the figure, 1 is a process tube, 1a is a gas introduction port, 1b is a gas exhaust port, 3 is a boat, 4 is an exhaust side gas shielding plate, 5 is an introduction side gas shielding plate, and 6 is a first resistance rectifying plate. A certain downstream resistance rectifying plate 7 is an upstream resistance rectifying plate which is a second resistance rectifying plate.

  The horizontal process tube 1 has a gas inlet 1a at one end and a gas outlet 1b at the other end, and is heated to a high temperature by a heater (not shown). Then, by introducing a gas containing impurities from the gas introduction port 1a, the impurities can be diffused into the semiconductor wafers 2 loaded on the boat 3 accommodated inside the process tube 1.

  The impurity diffusing apparatus of the present invention includes an exhaust port side gas shielding plate 4, a gas inlet port 1a, and a semiconductor wafer, which are disposed substantially perpendicularly to the longitudinal direction of the process tube 1 between the gas exhaust port 1b and the semiconductor wafer 2. 2, the inlet side gas shielding plate 5 is disposed substantially perpendicular to the longitudinal direction of the process tube 1. Each of the exhaust port side gas shielding plate 4 and the introduction port side gas shielding plate 5 is provided with a cutout portion 4a and a cutout portion 5a at the outer peripheral ends.

  A downstream resistance rectifying plate 6 (first resistance rectifying plate) and an upstream resistance rectifying plate 7 (second resistance rectifying plate) are provided between the boat 3 loaded with the semiconductor wafers 2 and the inner wall of the process tube 1. Is provided. Each of these resistance rectifying plates has a plate shape having a plurality of holes, and is arranged in the longitudinal direction of the process tube 1 so as to sandwich the boat 3 from both sides. At this time, as shown in FIGS. 1 (b) and 1 (c), the exhaust-side gas shielding plate 4 is arranged with the notch 4a at the outer peripheral end thereof corresponding to the downstream resistance rectifying plate 6, The inlet side gas shielding plate 5 is arranged with the notch 5 a at the outer peripheral end thereof corresponding to the upstream resistance rectifying plate 7.

  Next, FIG. 2 shows a flowchart when gas is introduced into the impurity diffusion device according to the present invention.

Nitrogen and oxygen are usually used as a carrier gas for carrying impurities into the process tube 1. For example, when phosphorus is diffused into the semiconductor wafer 2, liquid POCl ₃ is bubbled with nitrogen gas to vaporize POCl ₃ and introduced into the process tube 1 together with nitrogen gas and oxygen gas. When boron is diffused, nitrogen gas is flowed over the liquid BBr ₃ and introduced into the process tube 1 together with nitrogen gas and oxygen gas.

  The gas introduced from the gas introduction port 1a flows in the direction of arrow A, is shielded by the introduction port side gas shielding plate 5, and once stays. Thereafter, the gas flows into the upper portion of the upstream resistance rectifying plate 7 as shown by an arrow B via the notch 5 a and is shielded by the exhaust port side gas shielding plate 4. If it stays in the upper space of the upstream resistance rectifying plate 7 and reaches a certain pressure, it flows uniformly from the top toward the semiconductor wafer 2 in the direction of arrow C through the opening formed in the upstream resistance rectifying plate 7. Further, the gas flowing through the gap between the semiconductor wafers 2 passes through the downstream resistance rectifying plate 6 and reaches the lower part thereof. Here, since the gas inlet 1a side of the process tube 1 is shielded by the inlet-side gas shielding plate 5, the gas flows in the direction of arrow D, and passes through the notch 4a provided in the exhaust-side gas shielding plate 4. Via, it is discharged from the gas exhaust port 1b to the outside.

  Therefore, regardless of the distance between the gas introduction port 1a and the gas exhaust port 1b, all the gas flows through the gap at the same time with respect to the semiconductor wafers 2 loaded on the boat 3, and all the semiconductor wafers 2 are simultaneously doped with impurities. Diffusion is started and a uniform diffusion layer can be formed on the semiconductor wafer.

  Here, the downstream resistance rectifying plate 6 and the upstream resistance rectifying plate 7 are perforated plates in which a plurality of through holes are formed in a staggered pattern or a lattice shape. These thicknesses and aperture ratios are designed according to the number of rows of semiconductor wafers 2 loaded on the boat 3, but are usually 5 to 20 mm in thickness and about 40 to 60% aperture ratio.

  The upstream resistance rectifying plate 7 is preferably arranged as close as possible to the inner wall of the process tube 1 so as to cover the entire upper surface of the semiconductor wafer 2, and the downstream resistance rectifying plate 6 covers the entire lower surface of the boat 3. It is desirable to dispose as close as possible to the inner wall of the tube 1. Furthermore, it is desirable that the upstream side resistance rectifying plate 7 and the downstream side resistance rectifying plate 6 be installed so that the gap between each end face and the inlet side gas shielding plate 5 and the exhaust side gas shielding plate 4 is minimized. .

  Further, it is desirable that the inlet side gas shielding plate 5 and the exhaust port side gas shielding plate 4 have shapes similar to the inner cross-sectional shape of the process tube 1. Further, when the notches 4a and 5a are provided, it is desirable to arrange them as close as possible to the inner wall of the process tube 1 in order to promote gas inflow and outflow from these notches.

  FIG. 3 illustrates a combination in the case where notches 4a and 5a are provided in the exhaust port side gas shielding plate 4 and the inlet port side gas shielding plate 5, respectively. The figure shows the projection shape 8 when these shielding plates 4 and 5 are projected in the longitudinal direction of the process tube 1 from the longitudinal direction of the process tube 1. Fig.3 (a) shows the example of FIG. 1 and FIG. 3 (b) and 3 (c) show the case where the inlet side gas shielding plate 5 is the same as that shown in FIG. 3 (a) and the exhaust side gas shielding plate 4 is rotated.

  3 (a) and 3 (b) show a case where there is no gap in the projected shape 8 of the exhaust port side gas shielding plate 4 and the inlet port side gas shielding plate 5, and at this time, the notch 4a and Since the gas flows between the notches 5a, the gas containing impurities is sufficiently diffused in the region sandwiched between the shielding plates 4 and 5 to form a uniform diffusion layer on the semiconductor wafer. become able to. In particular, as shown in FIG. 3 (a), when the notches 4a and 5a of the shielding plates 4 and 5 are arranged at substantially symmetrical positions with respect to the central axis of the process tube 1, the above-described gas diffusion is performed. This is more preferable because the effect of the above is most prominent.

  On the other hand, when the gap 8a is present in the projection shape 8 shown in FIG. 3C, the gas containing impurities passes through the notches 4a and 5a provided in the shielding plates 4 and 5, respectively. Because it tries to flow straight, gas diffusion is not promoted.

  Further, when the gas shielding plate is used in combination with the resistance rectifying plate, it is as described above that the notch portions are arranged corresponding to the position of the resistance rectifying plate, but at this time, FIG. As shown in FIG. 1 (c), the gas flowing in from the gas inlet 1 a flows through the notch 5 a of the inlet-side gas shielding plate 5 and is guided to the inlet side of the upstream resistance rectifying plate 7. Further, it is desirable that the gas flowing out from the outlet side of the downstream resistance rectifying plate 6 flows out from the gas exhaust port 1b through the cutout portion 4a of the exhaust port side gas shielding plate 4. This is because the gas can be efficiently used without waste by arranging in this way.

  In the example shown in FIGS. 1 and 2, the cutout portion 5a of the inlet port side gas shielding plate 5 is the upper side, and the cutout portion 4a of the exhaust port side gas shield plate 4 is disposed on the lower side. However, this arrangement is desirable for the following reasons.

As described above, nitrogen and oxygen are usually used as the carrier gas for transporting impurities into the process tube 1. Phosphorus and boron carried by these carrier gases are liquid POCl ₃ and BBr ₃ vapors. And since specific gravity is large, it becomes easy to accumulate on the lower side of the process tube 1. As a result, there is a problem that non-uniform diffusion occurs in the surface of the semiconductor wafer 2. Therefore, as shown in FIG. 1, if the notch 5a of the inlet side gas shielding plate 5 is provided on the upper side and the notch 4a of the exhaust port side gas shielding plate 4 is provided on the lower side, the gas is introduced from the gas inlet 1a. As shown in FIG. 5, the gas containing impurities flows from the upper portion of the downstream resistance rectifying plate 6 toward the semiconductor wafer 2 and passes through the lower upstream resistance rectifying plate 7 to the process tube 1 from the gas exhaust port 1b. This is preferable because a flow of exhausting to the outside can be formed naturally.

  FIG. 4 shows another embodiment of the impurity diffusion device of the present invention. 4A is the same as FIG. 1A except that the upstream side resistance rectifying plate 7, the downstream side resistance rectifying plate 6, and the inlet port side gas shielding plate 5 are not provided, and FIG. 4B is the inlet port. Except for not providing the side gas shielding plate 5, it is the same as FIG.

  In the case of the conventional impurity diffusion device shown in FIG. 7, the flow rate of the gas containing impurities increases as it approaches the gas exhaust port 1b. However, by providing the exhaust port side gas shielding plate 4 as shown in FIG. 4 (a), the exhaust speed can be reduced, so that the time difference during which the semiconductor wafer 2 is exposed to the gas can be suppressed. The uniformity of diffusion of the semiconductor wafer 2 can be improved by a simple method. 4B, by adding the upstream resistance rectifying plate 7 and the downstream resistance rectifying plate 6 to FIG. 4A, the semiconductor wafer 2 loaded on the boat 3 can be The gas flows through the gaps more uniformly, and a uniform diffusion layer can be formed by the semiconductor wafer 2.

  Even when the exhaust means is natural exhaust instead of forced exhaust, the gas containing impurities flowing between the semiconductor wafer 2 from the gas introduction port 1a hits the exhaust port side gas shielding plate 4 and is pushed back. The semiconductor wafer 2 on the gas exhaust port 1b side, whose diffusion start time is slow, is again exposed to the gas containing impurities. Therefore, the uniformity of diffusion of the semiconductor wafer 2 can be improved by a simple method.

  FIG. 5 shows still another embodiment of the impurity diffusion apparatus according to the present invention, and shows a case where the gas shielding plate is not provided with a notch. FIG. 5A is a perspective view showing an example in which the exhaust port side gas shielding plate 4 is provided, and FIG. 5B shows a gas flow in the case of FIG.

  As shown in FIG. 5A, when the gas shielding plate is not provided with a notch, it is desirable that the outer peripheral edge of the gas shielding plate is not in contact with the inner wall of the process tube 1. In this way, as shown in FIG. 5 (b), the gas that has passed through the region of the semiconductor wafer 2 does not concentrate in one direction, and escapes from all directions on the wall surface side of the process tube 1 to the downstream side. This is because the in-plane uniformity of diffusion of the semiconductor wafer 2 can be appropriately ensured.

  It should be noted that the embodiment of the present invention is not limited to the above-described example, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  For example, in the above description, the gas shielding plate has been described as an example in which the gas shielding plate is disposed substantially perpendicular to the longitudinal direction of the process tube 1. However, the present invention is not limited to this and may be disposed obliquely. FIG. 6 is a perspective view of still another embodiment according to the impurity diffusion device of the present invention in which the gas shielding plate is disposed obliquely. In this example, the exhaust port side gas shielding plate 4 and the inlet port side gas shielding plate 5 are not provided with cutouts, but each is disposed obliquely. A gap can be provided between the inner wall and the inner wall, and this gap has the same effect as the notch in FIG. 1 and can achieve the above-described effects of the present invention. In addition, it arrange | positions so that a clearance gap may not be formed in the projection shape when these gas shielding plates are projected in the longitudinal direction of the process tube 1, and also has the effect described in claim 6 of the present invention. It has a configuration.

  For example, in the example shown in FIG. 1, the notch 5 a of the inlet side gas shielding plate 5 is the upper side, and the notch 4 a of the exhaust side gas shielding plate 4 is arranged on the lower side. May be reversed.

  Further, it is desirable that all horizontal lines drawn in the longitudinal direction of the process tube 1 from all the semiconductor wafers 2 mounted on the boat 3 hit the exhaust port side gas shielding plate 4. By doing so, the influence of the turbulence of the gas flow near the gas exhaust port 1 b is not given to the semiconductor wafer 2, and the gas reflected by the exhaust port side gas shielding plate 4 is reliably directed to the semiconductor wafer 2. Can be returned.

  Further, it is desirable that a straight line connecting all the semiconductor wafers 2 mounted on the boat 3 to the gas introduction port 1 a hits the introduction side gas shielding plate 5. By doing so, it becomes possible to prevent the gas introduced from the gas inlet 1a from directly hitting the semiconductor wafer 2, and the gas containing impurities once once introduces the gas shielding plate 5 on the inlet side. Since it is possible to prevent the semiconductor wafer 2 from being hit immediately after hitting, the gas containing impurities can be more effectively diffused into the process tube 1. Therefore, the uniformity of diffusion of the semiconductor wafer 2 can be improved by a simple method.

  Moreover, in the figure shown in the above-mentioned embodiment, although the exhaust port side gas shielding plate 4 and the inlet port side gas shielding plate 5 are described in a complete plane, the present invention is not limited to this, and the gas flow rate and Depending on the size of the apparatus, a gas shielding plate having a plurality of holes such as a punching plate may be used. For example, when a large apparatus having a large length in the longitudinal direction of the horizontal process tube 1 is used, the gas flow rate is usually increased so that the gas also reaches the downstream side in the apparatus. At this time, for example, if the inlet-side gas shielding plate 5 has a perfect surface structure, the pressure applied to the gas shielding plate is increased, causing cracks. In such a case, if a gas shielding plate having a plurality of holes is used, the uniformity of diffusion in the apparatus can be improved while maintaining the gas shielding effect.

  Further, the flow rate of the gas flowing between the inlet side gas shielding plate 5 and the inner wall of the process tube becomes too fast, and impurities are hardly diffused into the semiconductor wafer 2 close to the inlet side gas shielding plate 5. A phenomenon sometimes occurred. Even in such a case, if a gas shielding plate having a plurality of holes is used, the pressure applied to the gas shielding plate can be lowered. It is also possible to form a gas flow.

BRIEF DESCRIPTION OF THE DRAWINGS (a) is a perspective view which shows one Example of the impurity diffusion apparatus concerning this invention, (b) is sectional drawing of the XX direction of (a), (c) is YY of (a). It is a sectional structure figure of a direction. It is a perspective view which shows the gas flow of the impurity diffusion apparatus concerning this invention shown to Fig.1 (a). (A)-(c) is a figure which shows the arrangement | positioning method of the gas shielding board concerning the impurity diffusion apparatus of this invention. (A) And (b) is a perspective view which shows the flow of the gas of the other Example of the impurity diffusion apparatus concerning this invention. (A) is a figure which shows the other Example of the impurity diffusion apparatus concerning this invention, (b) is a perspective view which shows the flow of the gas of (a). It is a perspective view which shows the other Example of the impurity diffusion apparatus concerning this invention. It is a perspective view which shows an example of the conventional impurity diffusion apparatus.

Explanation of symbols

1: Process tube 1a: Gas introduction port 1b: Gas exhaust port 2: Semiconductor wafer 3: Boat 4: Exhaust port side gas shielding plate 4a: Notch portion 5: Inlet port side gas shielding plate 5a: Notch portion 6: Downstream resistance Rectifying plate 7: upstream resistance rectifying plate 8: projected shape 8a: gap

Claims (9)

A boat loaded with semiconductor wafers is housed in a high-temperature heated horizontal process tube having a gas inlet at one end and a gas exhaust at the other end, and a gas containing impurities is introduced from the gas inlet. An impurity diffusing device for diffusing impurities in the semiconductor wafer, comprising an exhaust port side gas shielding plate between the gas exhaust port and the semiconductor wafer. The impurity diffusion apparatus according to claim 1, further comprising an inlet-side gas shielding plate between the gas inlet and the semiconductor wafer. 3. The impurity diffusion device according to claim 1, wherein the gas shielding plate is disposed so that an outer peripheral edge thereof does not contact an inner wall of the process tube. 4. The impurity diffusion device according to claim 2, wherein the inlet-side gas shielding plate is disposed such that an outer peripheral edge thereof does not contact an inner wall of the process tube. 3. The impurity diffusion device according to claim 1, wherein the exhaust port side gas shielding plate and the introduction port side gas shielding plate are provided with a notch at an outer peripheral edge thereof. The exhaust port side gas shielding plate and the introduction port side gas shielding plate are arranged so that there is no gap in the projected shape when they are projected in the longitudinal direction of the process tube. 5. The impurity diffusion device according to 5. Between the boat loaded with the semiconductor wafer and the inner wall of the process tube, a plate-like first resistance rectifying plate having a plurality of holes and a second resistance rectifying plate having substantially the same shape, The impurity diffusion device according to claim 1, wherein the impurity diffusion device is arranged in a longitudinal direction of the process tube so as to sandwich the boat from both sides. Between the boat loaded with the semiconductor wafer and the inner wall of the process tube, a plate-like first resistance rectifying plate having a plurality of holes and a second resistance rectifying plate having substantially the same shape, The exhaust tube side gas shielding plate is disposed in the longitudinal direction of the process tube so as to sandwich the boat from both sides, the cutout portion thereof is disposed corresponding to the first resistance rectifying plate, and the inlet port side gas is disposed. The impurity diffusion device according to claim 5 or 6, wherein the shielding plate has a notch disposed in correspondence with the second resistance rectifying plate. 9. The impurity diffusion device according to claim 7, wherein each of the first resistance rectifying plate and the second resistance rectifying plate is installed so as to be substantially perpendicular to a semiconductor wafer loaded on the boat.

Images