JPH0714779A - Semiconductor production equipment - Google Patents

Abstract

PURPOSE:To keep the uniformity of film thickness by preventing the film thickness on the periphery of an orientation flat from increasing significantly as compared with the central part of a wafer. CONSTITUTION:A wafer supporting board 4 supports a plurality of wafers 3 vertically to the axial direction of a vertical reaction furnace through a predetermined interval while shifting the orientation of the orientation flat 15 of each wafer 3 sequentially by a predetermined angle with respect to the axis of the vertical reaction furnace. This constitution decreases the difference of gas concentration per unit area in the vertical reaction furnace thus preventing the film thickness from increasing on the periphery of orientation flat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing apparatus,
In particular, it relates to a semiconductor manufacturing apparatus having a vertical reactor.

[0002]

2. Description of the Related Art A conventional semiconductor manufacturing apparatus uses a polycrystalline silicon film, a silicon dioxide (SiO ₂ ) film, or a silicon nitride (S) film on the surface of a semiconductor substrate (hereinafter referred to as a wafer).
It is used in a CVD (chemical vapor deposition) process for forming an insulating film such as an i ₃ N ₄ ) film. FIG. 5 is a structural diagram showing an outline of a conventional vertical decompression CVD apparatus generally used, which includes a reaction vessel having an outer furnace core tube 1 and an inner furnace core tube 2,
The wafer holding boat 24 for holding the wafer 3, a vertical movement mechanism unit 11 for vertically moving the boat, a wafer transfer machine 10 for transferring the wafer 3 between the wafer holding boat 24 and the wafer storage box 9, and the like. Has been done.

In order to form, for example, a polycrystalline silicon film on the wafer 3 by using this type of apparatus, first, the wafer transfer machine 10 is capable of rotating the wafer 3 back and forth, up and down, and from the wafer storage box 9. The wafer holding boat 24 is mounted on the wafer holding boat 24. Next, the wafer holding boat 24 is introduced into the inner furnace core tube 2 by using the vertical movement mechanism unit 11, and silane (SiH ₄ ) is supplied from the raw material gas supply port 6 into the inner furnace core tube 2. A thermal decomposition chemical reaction of silane occurs on the surface of the wafer 3 heated by the heating source 5 to form the above-mentioned thin film.
The product gas generated by the reaction and the unreacted silane gas pass between the inner furnace core tube 2 and the outer furnace core tube 1, and are exhausted to the outside from the reaction gas exhaust port 7 by the vacuum pump 8.

FIG. 6 illustrates the details of the wafer holding boat 24 generally used in the above-mentioned CVD apparatus. FIG. 6A is a top view and FIG. 6B is a side view. The wafer holding boat 24 is a quartz rod 23 having a diameter of about 16 mm.
Four rods A, 23B, 23C, and 23D are arranged on a semicircle whose axis has a diameter substantially equal to the circumscribed circle of the wafer 3,
The distance between the quartz rods 23A and 23D is substantially equal to the diameter of the wafer 3, and the upper and lower ends of each of the four quartz rods are the quartz plate 16A,
The skeleton is formed by firmly bonding with 16B. Each of the four quartz rods has grooves 13 slightly wider than the thickness of the wafer 3 and equally spaced. The wafer 3 is held in such a manner that four positions of the outer peripheral edge of the arc portion excluding the orientation flat 15 are fitted into the groove 13.

As another example of the prior art, a chemical vapor deposition apparatus having a structure shown in the sectional view of the essential part of FIG. 7 has also been proposed (JP-A-2-291115). The features of this device are shown in FIG.
And a wafer holding boat having the structure shown in the sectional view of FIG. 9. That is, in the lidded boat 27 including the boat main body 26A having the wafer holding portion 25 and the lid portion 26B, a part of the side surface of the lid portion 26B is formed to be parallel to the orientation flat 15 of the wafer 3. . With this structure, the distance between the inner surface of the boat 27 with a lid and the outer periphery of the wafer 3 can be made substantially uniform around the wafer 3.

[0006]

However, in the conventional vertical decompression CVD apparatus shown in FIG. 5, a silicon dioxide (SiO ₂ ) film is formed by using, for example, silane and nitrous oxide (N ₂ O). When the film thickness within the wafer surface is measured on the straight line X direction on the wafer surface as shown in FIG. 11, the film thickness distribution shown by the broken line in FIG. 10 is obtained. That is, there is a problem that the film thickness around the outer periphery of the wafer 3, particularly the film around the orientation flat 15 is much thicker than the film thickness at the center of the wafer 3.

This is because the reaction system for forming a silicon dioxide film by silane and nitrous oxide has a rate-determining supply that largely depends on the amount of raw material gas supplied to the wafer 3. The reason is shown in FIG. It demonstrates using. 12
6A and 6B are a horizontal cross-sectional view and a vertical cross-sectional view for explaining the positional relationship between the wafer holding boat 24 and the inner furnace core tube 2 of the conventional technique described in FIG.

In FIG. 1A, the wafer holding boat 2
Quartz rods 23A, 23B, 23C, and 23D, which are the skeleton of 4
It is difficult to reduce the diameter to 12 mm or less in terms of strength,
Therefore, the radius of the circumscribed circle 28 of the wafer holding boat 24 is about 6 mm larger than the radius of the wafer 3. Further, in order to improve the reliability of the transfer of the wafer holding boat 24, the radius of the inner furnace core tube 2 is also 10 mm with respect to the radius of the circumscribed circle 28.
It is necessary to increase the size. Therefore, the distance A between the circumferential end of the wafer 3 and the inner furnace core tube 2 is about 16 mm,
Further, the distance C from the orientation flat 15 to the inner furnace core tube 2 has a positional relationship of opening about 30 mm. On the other hand, as shown in FIG. 3B, the distance B between the wafers 3 is determined by the distance between the grooves of the wafer holding boat 24.
Generally, the distance is 4.76 mm, which is the same as the distance between the wafers 3 in the wafer storage box 9 (FIG. 5).

Due to the above-mentioned positional relationship, the distance A between the wafer circumference and the inner furnace core tube 2 is larger than the distance B between the wafers 3, and the distance C between the orientation flat 15 and the inner furnace core tube 2 is the largest. ing. Since the raw material gas flows a lot in a portion having a wide interval in the inner furnace core tube 2, that is, a portion having a small conductance, comparing the gas densities in a space of a unit volume in a unit time, the space 29 of the C portion having the largest interval is The gas density is largest, and then the gas density decreases in the order of the space 30 and the space 31. Therefore, when the reaction system is rate-controlled, the vapor phase growth reaction becomes active in the vicinity of the orientation flat 15 where the gas density is high, and the film thickness is thicker than the central portion of the wafer 3 and the circumferential portion of the wafer 3. Such a non-uniform film thickness distribution on the wafer surface has a problem that the manufacturing yield and reliability of semiconductor devices are significantly reduced.

It has been confirmed that the nonuniformity of the film thickness distribution shown by the broken line in FIG. 10 can be improved by installing the wafer 3 in the boat with a lid 27 shown in FIG. No. 291115). That is, by making the side shape of the boat with lid 27 similar to the outer peripheral shape of the wafer 3 and making the cross-sectional area of the source gas flow passage around the wafer 3 uniform, the film thickness distribution can be made uniform. However, when the lidded boat 27 of FIG. 8 is used, the work of mounting the lid portion 26B on the boat body 26A is difficult with the wafer transfer machine 10 described in FIG.
Transfer of B is common. There is a high probability of manual operation error, and dust generated due to damage to the wafer 3 or friction with the boat body 26A when the lid 26B is transferred adheres to the wafer 3, reducing the manufacturing yield of semiconductor devices. There is a problem.

[0011]

A semiconductor manufacturing apparatus according to the present invention holds a plurality of wafers in a direction perpendicular to a central axis direction of a vertical reactor at predetermined intervals and in parallel with each other. The wafer holding boat is arranged so that the orientation of the orientation flat is sequentially shifted by a predetermined angle with respect to the central axis of the vertical reactor.

[0012]

The present invention will be described below with reference to the drawings. FIG. 1 is a structural diagram showing an embodiment of the present invention.

The semiconductor manufacturing apparatus of this embodiment uses a vertical reactor having a double furnace core tube structure of an outer furnace core tube 1 and an inner furnace core tube 2 as a reaction container, and holds a wafer 3 for holding a wafer 3. A boat 4, a heating source 5 for heating the wafer 3, a source gas supply port 6 for supplying a source gas into the inner furnace core tube 2, a reaction gas discharge port 7, a vacuum pump 8 for an exhaust system, and a wafer storage box 9. A wafer transfer machine 10 for carrying wafers to and from the wafer holding boat 4, and a vertical movement mechanism unit 11 and a rotation mechanism unit 12 of the wafer holding boat 4 are main constituent elements.

2A and 2B are views showing a wafer holding boat which is a main part of this embodiment. FIG. 2A is a side view and FIG. 2B is a sectional view taken along the line AA of FIG. The structure for holding each wafer 3 in the wafer holding boat 4 of this embodiment is as follows.
This is similar to the conventional technique described with reference to FIG. That is, it has a structure in which the quartz rods 23A to 23D of FIG. 6 are divided into holding portions for each wafer. Each holding portion has a groove 13 and four quartz rod pieces 14A having a diameter of 16 mm and a length of 5 mm, 1
4B, 14C, 14D, the rod axes of which are arranged on an arc having a radius substantially equal to the circumscribed circle of the wafer 3, and the distance between 14A and 14D is substantially equal to the diameter of the circumscribed circle. The groove 13 is fitted and held in the groove 13 at four positions on the outer peripheral edge of the arc portion excluding the orientation flat 15 of the wafer 3. These quartz rod pieces 14A, 14B, 1
Each of 4C and 14D rod axes is shifted counterclockwise by 4 degrees about the center axis of the circumscribed circle of the wafer 3 at the same time counterclockwise by 8 degrees, and fixedly joined in a stepwise manner in the vertically downward direction to form quartz rod pieces at the top and bottom. The wafer holding boat 4 is formed by firmly bonding the end face of the to the quartz plates 16A and 16B having a thickness of 6 mm.

With the above structure, when the wafer holding boat 4 is loaded in the reaction vessel, the orientation flat 15 of the wafer 3 is located on the central axis of the inner furnace core tube 2 from the top to the bottom of the wafer holding boat 4. It is possible to maintain a positional relationship that is shifted counterclockwise by 8 degrees. FIG. 3 shows the positional relationship among the inner furnace core tube 2, the wafer holding boat 4, and the wafer 3 in the present embodiment. With the wafer holding boat 4 having the above-described structure, the quartz rod piece in the inner furnace core tube 2 is shown. 14
The arrangement of the thin film products such as A, 14B, 14C, 14D and the orientation flat 15 that influence the flow of the raw material gas can be dispersed to reduce the gas density difference in the unit space 30. A silicon dioxide film made of silane and nitrous oxide was formed using the example thus configured. The solid line shown in FIG. 10 shows the film thickness distribution of the produced film according to the present example, and it can be seen that excellent results were obtained as compared with the conventional example.

Even if the wafer holding boat 4 has the above-described structure, the wafer can be easily transferred between the wafer holding boat 4 and the wafer storage box 9 by using the conventional technique. For example, in FIG. 1, in order to transfer the wafer 3 from the wafer storage box 9 to the wafer holding boat 4, the wafer transfer box 10 capable of vertical, forward, backward, and rotation operations described in the related art is used to transfer the wafer 3 into the wafer storage box 9. The back surface of the wafer 3 is taken out in a state where it is placed and held on the fork 17 of the wafer transfer machine 10. The wafer holding boat 4 includes a stepping motor 18 and an encoder 1.
By the rotation mechanism section 12 composed of 9, four quartz rod pieces 14A, 14B on which the wafer 3 is to be mounted,
Rotate 14C and 14D until the rotation position becomes appropriate. That is, the quartz rod pieces 14A and 14D are rotated so that the straight line connecting the rod axes of the quartz rod pieces 14A and 14D is parallel to the orientation flat 15 of the wafer 3. The orientation flats 15 are stored in the wafer storage box 9 in a pre-aligned state. Under the above-mentioned conditions, the wafer 3 is taken out from the wafer storage box 9 with the fork 17, and is advanced toward the groove 13 of the wafer holding boat 4 so that the outer peripheral end portion of the wafer 3 has the groove 13.
Then, the fork 17 is lowered to fit the wafer holding boat 4
Transfer can be achieved by retreating from.

The present invention is not limited to the above-described embodiment, and for example, a thin film of another embodiment having the wafer holding boat 20 having the structure shown in the side views and sectional views of FIGS. 4 (a) and 4 (b). It may be a growth device. That is, in the wafer holding boat 20, the structure of the wafer holding portion is the nail 22 made of quartz.
Wafer 3 on which four pieces A, 22B, 22C and 22D are mounted so as to project inside quartz ring disk 21
Except for the orientation flat 15, the outer peripheral edge of the arc portion is fixedly connected to four positions supporting it. A plurality of the above-mentioned ring-shaped discs 21, a quartz rod 23A,
The wafer holding boat 20 is formed by being fixedly coupled to 23B, 23C, and 23D at regular intervals and shifted counterclockwise by 8 degrees with respect to the central axis of the wafer circumscribing circle.

In the structure of the wafer holding boat 4 of the above-described embodiment, the orientation flat 15 of each wafer 3 is used.
The relative misalignment angle of the quartz rod pieces 14A, 14B, 14
Although it is determined by the diameters of C and 14D, the use of this embodiment has an advantage that the relative displacement angle of the orientation flat 15 can be arbitrarily determined according to the attachment angle of the ring-shaped disc 21 to the quartz rod. Further, in this embodiment, since a gap can be provided between the claws 22A to 22D and the ring-shaped disc 21 immediately above, the fork on which the wafer is placed is moved up and down by using this gap to attach and detach the wafer. You can Therefore, the distance between the claws 22A and 22D does not need to be substantially equal to the diameter of the wafer circumscribing circle, and the four claws may be arranged at substantially equal angles.

[0019]

As described above, according to the present invention, a plurality of wafers are held parallel to each other in a direction perpendicular to the central axis of the vertical reactor at a predetermined interval and in parallel with each other. By having the wafer holding boat which is arranged with the direction shifted around the central axis of the vertical reactor by a predetermined angle, it is possible to disperse the arrangement of thin film products that affect the amount of raw material gas supplied to the wafer. . Therefore, it is possible to reduce the difference in the source gas density per unit volume in the reaction furnace, the in-plane uniformity of the formed film is significantly improved compared to the conventional technology, and the manufacturing yield and reliability of the semiconductor device are significantly improved. It has the effect that it can be improved.

[Brief description of drawings]

FIG. 1 is a structural diagram of an embodiment of the present invention.

2A and 2B are views showing an example of a wafer holding boat used in the present embodiment, in which FIG. 2A is a side view and FIG.
FIG.

FIG. 3 is an explanatory diagram showing a positional relationship of wafers in the present embodiment.

4A and 4B are views showing another example of the wafer holding boat used in the present embodiment, in which FIG. 4A is a side view and FIG.
FIG.

FIG. 5 is a structural diagram of an example of a conventional semiconductor manufacturing apparatus.

FIG. 6 is a view showing a wafer holding boat used in a conventional example,
The figure (a) is a top view and the figure (b) is a side view.

FIG. 7 is a main-portion cross-sectional view showing another example of a conventional semiconductor manufacturing apparatus.

FIG. 8 is a perspective view of the boat with a lid shown in FIG. 7.

9 is a cross-sectional view of the boat with a lid shown in FIG.

FIG. 10 is a comparison diagram showing a film thickness distribution on a wafer between the present embodiment and the prior art.

FIG. 11 is an explanatory diagram showing a film thickness measurement direction on a wafer.

12A and 12B are explanatory views showing a positional relationship of wafers in a conventional example, FIG. 12A is a horizontal sectional view, and FIG. 12B is a vertical sectional view.

[Explanation of symbols]

 1 Outer Furnace Core Tube 2 Inner Furnace Core Tube 3 Wafer 4, 20, 24 Wafer Holding Boat 5 Heat Source 6 Raw Material Gas Supply Port 7 Reactive Gas Discharge Port 8 Vacuum Pump 9 Wafer Storage Box 10 Wafer Transfer Machine 11 Vertical Movement Mechanism Section 12 Rotation mechanism part 13 Groove 14A, 14B, 14C, 14D Quartz rod piece 15 Orientation flat 16A, 16B Quartz plate 17 Fork 18 Stepping motor 19 Encoder 21 Ring-shaped disc 22A, 22B, 22C, 22D Claw 23A, 23B, 23C, 23D Quartz rod 25 Wafer holding part 26A Boat body 26B Lid part 27 Boat with lid 28 Circumscribing circle 29, 30, 31 Space

Claims (6)

[Claims] 1. A semiconductor manufacturing apparatus in which a semiconductor substrate having an orientation flat is housed in a vertical reactor and a thin film is grown on a surface of the semiconductor substrate by a chemical reaction of a raw material gas. It is held in a direction perpendicular to the central axis direction of the reaction furnace at a predetermined interval and parallel to each other, and the orientation of the orientation flat of each semiconductor substrate is sequentially shifted by a predetermined angle with respect to the central axis of the vertical reaction furnace. A semiconductor manufacturing apparatus, comprising: 2. The holding boat for holding a plurality of semiconductor substrates is divided into holding units for each semiconductor substrate, and each of the divided holding units is sequentially shifted by a predetermined angle with respect to the central axis of the holding boat and stacked. The semiconductor manufacturing apparatus according to claim 1, which is bonded. 3. The semiconductor manufacturing apparatus according to claim 2, wherein each of the divided holding portions is composed of four rod pieces obtained by cutting a rod having a groove for holding a semiconductor substrate. 4. The semiconductor manufacturing apparatus according to claim 2, wherein each of the divided holding portions includes four claw members each having a groove for holding a semiconductor substrate and a ring to which the claw members are attached. 5. The semiconductor manufacturing apparatus according to claim 2 or 3, wherein the holding boat is formed by stacking and joining the rod pieces obtained by cutting the rod material in a stepwise manner in the vertical direction. 6. The semiconductor manufacturing apparatus according to claim 2, wherein the holding boat is formed by laminating and joining the rings in parallel with a rod member.