JPH02156523A - Upright wafer boat - Google Patents

Abstract

PURPOSE:To make it possible to form wafers having a uniform film thickness and a uniform resistivity within wafer surfaces into a filmy form by a method wherein wafer mounting parts are respectively formed into a disc or an annular susceptor having a diameter larger than those of the wafers and the number of props for supporting the susceptors is reduced into two or one. CONSTITUTION:For example, a boat is constituted of two 10mm-phi long support pillars 3 and rings, on which wafers 1 are mounted, and this boat is used is various film-forming devices provided with a reaction tube erected upright. Moreover, as the number of the boat props is decreased into one, the diameter of the support prop is made fine and the props and the wafer growth surfaces can be separated from each other, a region to be had an effect due to the turbulence of a reaction gas flow, which is generated by the boat props within the wafer growth surfaces, can be remarkedly made small. Thereby, the film thickness of the wafers and the distribution of the resistivity of the wafers can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wafer boat, and particularly to a vertical wafer boat used in a vapor phase growth apparatus in which a reaction vessel is vertically erected.

[Conventional technology]

Conventionally, this type of vertical wafer boat is shown in Fig. 2(a).
As shown in (b), a plurality of (three or more) vertically erected columns 5 were provided with grooves at approximately equal intervals. Film formation is carried out by mounting a wafer 11 between the grooves of each support column 5 of this wafer boat, as shown in FIGS. This was done by flowing a reactive gas through the

[Problem to be solved by the invention]

Conventionally, in the vapor phase growth method in which a vertical wafer boat is used to flow a reactive gas almost parallel to the wafer growth surface, the support of the wafer boat obstructs the supply of the reactive gas onto the wafer growth surface. There were drawbacks of poor film thickness uniformity and resistivity uniformity in the vicinity. Figure 4 shows the reaction gas flow near the conventional vertical wafer boat. It can be seen that there is a region near the boat support 5 in the wafer growth surface where the amount of reactant gas supplied is extremely small. I understand. The reaction gas flow near the pillar 5 changes from a laminar flow to a turbulent flow due to the influence of the pillar 5, and the area actually affected by the pillar 5 is quite large, with the occurrence of thin flow especially near the pillar 5. It's getting wider. For this reason, the film thickness uniformity and resistivity uniformity in the vicinity of the pillars 5 are deteriorated. The magnitude of the negative influence caused by this boat support varies depending on the diameter of the support 5, the positional relationship between the support 5 and the wafer growth surface, the number of support supports 5, and the like. That is, the smaller the number of pillars, the smaller the diameter, and the farther the pillars are from the wafer growth surface, the smaller the influence on the film thickness uniformity and resistivity uniformity of the port pillars. However, in the conventional wafer boat, the wafers 4 are mounted so as to be sandwiched between grooves provided in the support pillars 5, so that the wafer growth surface and the support pillars cannot be separated. Also, the wafer cannot be held unless there are three or more supports. Furthermore, there were other problems, such as the inability to reduce the diameter of the props due to problems with the strength of the boat.

[Means to solve the problem]

The vertical wafer boat of the present invention holds and rotates a plurality of substrates (wafers) to be subjected to vapor phase growth in a horizontally stacked manner, and performs vapor phase deposition by flowing a reaction gas almost parallel to the wafer growth surface. It is used in a growth apparatus and is characterized in that the wafer mounting part is composed of a disk or ring-shaped susceptor with a diameter larger than the wafer outer circumference, and there are two or one pillars supporting the susceptor.

Therefore, by increasing the diameter of the disk or ring-shaped wafer susceptor, it is possible to increase the distance between the boat support and the wafer growth surface. Furthermore, since the susceptor is fixed to the boat support, wafers can be mounted even with two or one support. Furthermore, since the susceptor itself serves as a boat reinforcement material, there are advantages such as the ability to reduce the diameter of the boat support. Therefore, by using the wafer boat of the present invention, it is possible to form a wafer with uniform film thickness and resistivity within the wafer surface.

Note that it is preferable to use quartz, poly-Si, or SiC as the material for the vertical wafer boat.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) and 1(b) show a vertical wafer boat according to an embodiment of the present invention. This boat is 10m
It consists of two mφ pillars 3 and a ring on which the wafer is mounted. This boat is used in various film forming apparatuses in which reaction tubes are vertically erected, but here we will discuss a Si epitaxial growth apparatus.

Figure 3 shows a vertical S using the wafer boat of the present invention.
FIG. 3 is a vertical cross-sectional view of the i-epitaxial growth apparatus. This device supplies a pedestal 8 for supporting the device, a reaction tube with a double tube structure consisting of an outer tube 6 and an inner tube 7, a wafer boat 9 of the present invention for loading Si wafers, a resistance heating furnace 11, and a reaction gas. It consists of four nozzle pipes 12.

Fifty P-type Si wafers 10 with a diameter of 150 mm were loaded on the wafer boat 9 at 10 mm intervals, and the wafer boat 9 was rotated at a rotational speed of 5 revolutions per minute (5 rpm), and the temperature inside the reaction tube was set at 1050°C. H2 from the nozzle pipe 12 at 20ρ/sieve, 5iN2Cuz at 400ml/min,
Flow PH1 at 50 ml/min, pressure 10jo
An N-type Si epitaxial film was grown on the Si wafer 10 for 30 minutes at rr. Figure 6 shows the film thickness distribution and resistivity distribution within the wafer plane at this time.
Conventional wafer boat (16mmφ) listed for reference
Film thickness distribution compared to Figure 5 results when using 4 pillars).

It can be seen that the resistivity distribution has been improved. In particular, the resistivity distribution has been significantly improved, and in the case of a conventional boat, the region with dense equiporistivity lines near the pillars is about 30% of the entire wafer surface.
%, whereas when the boat of the present invention was used, the phenomenon occurred up to 5%.

As a result, good uniformity of the film thickness distribution within the wafer surface, excluding a 5 mm region around the wafer periphery, and the resistivity distribution of ±5% were obtained.

Next, when we prototyped a 10,000-gate bipolar gate array using the wafer boat of the present invention, we found that when using a conventional boat, 30% of the area on the wafer surface with poor resistivity uniformity was covered by the present invention. In the case of boats of

FIG. 1(c) shows a vertical wafer boat according to another embodiment of the present invention. In this embodiment, the boat support 3
was reduced from two to one, and the diameter of the pillar 3 was expanded from 10 mmφ to 14 mmφ. The purpose of this is to reduce the number of regions affected by the pillars on the wafer surface from two to one by reducing the number of pillars. However, due to strength issues, the diameter of the pillars has been increased by 40%.

Film formation was carried out using the same Si epitaxial growth apparatus and growth conditions as in the example. FIG. 7 shows the film thickness distribution and resistivity distribution at that time, and in the case of this example, the number of dense regions in the equal resistivity lines near the pillars was reduced from two to one. However, since the pillars have become thicker, the influence per pillar is slightly broader than in the first embodiment. Therefore, in the case of this example, good film thickness uniformity and resistivity uniformity almost the same as in the case of the first example were obtained.

〔Effect of the invention〕

As explained above, in the present invention, the wafer loading section of a vertical wafer boat is composed of a disk or ring-shaped susceptor with a diameter larger than that on the wafer surface, so the number of boat supports can be reduced to two or one. The diameter of the pillars can be reduced, and the pillars can be separated from the wafer growth surface.
The area affected by the turbulence of the reaction gas flow caused by the boat support within the wafer growth surface can be significantly reduced, resulting in improved film thickness and resistivity distribution.

[Brief explanation of the drawing]

1(a) and 1(b) are views showing a wafer boat according to one embodiment of the present invention, FIG. 1(C) is a view showing a wafer boat according to another embodiment of the present invention, and FIG. (a), (b)
3 is a diagram showing a conventional wafer boat and wafer loading method, FIG. 3 is a diagram showing a vertical vapor phase growth apparatus used in an example of the present invention, and FIG. 4 is a diagram showing a reaction gas flow near the boat support. Figure 5 is a diagram showing the resistivity distribution when a conventional wafer boat is used, and Figure 6 is a diagram showing the resistivity distribution when a wafer boat according to an embodiment of the present invention is used. FIG. 7 is a diagram showing the resistivity distribution when a wafer boat according to another embodiment of the present invention is used. l...Wafer 2...Susceptor, 3
...Boat prop, 4...Wafer 5
...Boat prop, 6... Outer pipe, 7...
...Inner tube, 8... Frame, 9... Wafer boat, 10... Wafer, 11...
...Resistance heating furnace, 12...Nozzle pipe, 13...
...Gas exhaust hole, 14...Exhaust port. Agent Patent Attorney Shinkyo Uchihara■

Claims (1)

[Claims] A vertical type of vapor phase growth apparatus used in vapor phase growth equipment that holds and rotates multiple vapor phase growth substrates (wafers) stacked horizontally, and forms films by flowing reactive gas almost parallel to the wafer growth surface. A vertical wafer boat, characterized in that the wafer mounting part is composed of a disk or ring-shaped susceptor with a diameter larger than the wafer diameter, and the number of supports for supporting the susceptor is two or one. boat