JPS6225747B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vapor phase growth method, and more specifically, the present invention relates to a vapor phase growth method using a source gas replenishment method that can uniformly form a thin film layer on a substrate in large quantities by vapor phase chemical reaction. Concerning vapor phase growth methods.

Conventionally, vapor phase growth using a raw material gas replenishment method (hereinafter abbreviated as replenishment method) has been performed in a horizontal furnace and a vertical (rotary disk) furnace.

In a horizontal furnace, the vapor phase growth rate is high on the upstream side of the gas flow, which causes attenuation of the raw material concentration and makes the thickness of the film grown on the substrate non-uniform. That is, as shown in FIG. 1, a heating table 3 is placed in a reaction furnace 1 heated by a heating coil 2, a substrate 4 is placed on it, and a raw material gas inlet 5 is connected to one end. In addition, an exhaust gas discharge pipe 6 is provided at the other end, and a supplementary gas introduction pipe 11 is inserted into the reactor 1 separately from the raw material gas introduction port 5.
A method has been adopted in which additional raw material gas is added midway through the gas flow inside the furnace. This extracts a part of the reaction gas through a sampling tube 7 and sends it to an analyzer 8, where the concentration of the raw material gas and by-products is measured.The values are input into a microcomputer 9 and a supplementary gas flow rate controller 10. The purpose is to feed back the required replenishment gas flow rate into the furnace from the replenishment gas nozzle 11, and to grow a thin film layer with a uniform growth thickness distribution on the substrate 4 in a vapor phase.

However, even if the raw material gas and by-products in the furnace are extracted and their concentrations are measured, the concentrations are not necessarily accurate.
It was found that the rate did not correspond to the vapor phase growth rate in some areas within the furnace.

Furthermore, in a horizontal furnace, as the number of sheets to be processed increases, the furnace becomes larger, and a new problem arises: non-uniformity in film thickness in the direction perpendicular to the gas flow direction. This non-uniformity has poor regularity and reproducibility, so by simply arranging the supplementary gas in a direction perpendicular to the gas flow direction,
It is not possible to easily make the grown film thickness uniform just by adjusting the replenishment flow rate.

The unevenness of the film thickness distribution correction effect that occurs when the replenishment method is applied to a horizontal furnace can be solved to some extent by applying the replenishment method to a vertical (rotary disk) type furnace, as shown in FIG. That is, the substrates 14 are arranged on the heating table 13 in the bell gear 18, and while the heating table 13 is rotated, the substrates 14 are heated to 1150° C. by the heating coil 2. The film thickness distribution is corrected by supplying the raw material gas horizontally from the main nozzle 12 and supplementary supplying the raw material gas vertically from the supplementary gas nozzle 17. Note that 15 is an exhaust gas discharge pipe, and 16 is a base.

Since the heating table 13 is rotated in the vertical furnace, the film thickness distribution is uniform on the concentric circles of the heating table.
Similarly, the effect of the distribution modification by supplementary gas is uniform in the concentric direction of the heating table. When using the replenishment method in a vertical furnace to make the film thickness distribution uniform, the heating table 13
It is only necessary to consider the distribution in the radial direction. However, when using the replenishment method, the replenishment gas conditions, the position of the replenishment gas nozzle, the replenishment gas concentration, the replenishment gas flow rate, etc. have been determined empirically. Therefore, it took time and skill to determine replenishment conditions. Furthermore, if the distribution becomes non-uniform for some reason after repeating the vapor phase growth when the distribution becomes uniform, it is not easy to correct the replenishment conditions.

An object of the present invention is to provide a vapor phase growth method that is systematic in operation and that easily makes the film thickness distribution uniform when a replenishment method is used for the vapor phase growth reaction.

The feature of the present invention is that the area on which the substrate is placed on the heating table is divided into a plurality of areas, a plurality of replenishment gas nozzles are arranged corresponding to each divided area, and each replenishment gas nozzle is assigned to each area. Therefore, the relationship between the replenishment gas concentration and the replenishment effect determined in advance,
The purpose is to make the film thickness distribution uniform by supplying source gas at a concentration determined for each region based on the actually measured film thickness distribution. That is, the present invention supplies raw material gases in different directions, concentrations, and distributions from each of the main nozzle and two or more supplementary gas nozzles, so that after the heating table has rotated at least once, the source gas is supplied onto each substrate. This allows a uniform vapor phase growth film thickness to be obtained.

Hereinafter, the present invention will be explained with reference to the drawings showing one embodiment.

FIG. 3 shows a schematic diagram of a vapor phase growth apparatus used in the present invention. a is a schematic diagram of the device, and b is the A- of a.
FIG. 3 is a cross-sectional view taken along section line A. Components that are the same or equivalent to those shown in FIG. 2 are given the same reference numerals, and 19 is a drive device, and 20 is a raw material gas supply device.

The equipment is a vertical (rotary disc) type furnace. The diameter of the heating table 13 is 600 mm. The main nozzle 12 uses a side blowing type. The diameter of the outlet is 3mm.
There are 3 rows vertically, and a total of 9 in 3 directions, spaced 120 degrees apart in the circumferential direction. The effective distance in the radial direction on the heating table 13 is 240 mm. A Si wafer is placed on the heating table 13. Three supplementary gas nozzles 17 are used.
The struts of each nozzle 17 are arranged circumferentially at intervals of 120 degrees, and are passed between the heating table 13 and the bell gear 18 into the furnace. The refill gas nozzle 17 has a cylindrical outlet with a diameter of 30 mm and a height of 50 mm. The supplementary gas nozzle can be driven vertically and rotationally by a drive device 19. Replenishment gas nozzle 2 by rotational movement
The radial position of No. 5 on the heating table 13 changes.
As a result, the position at which the film thickness increases due to the replenishment gas also changes in the radial direction. The height of the replenishment gas nozzle 17 from the heating table 13 changes due to the vertical drive, and the type of film thickness increase distribution due to the replenishment gas changes. Each replenishment gas nozzle 17 is made to correspond to each region of the heating table 13 by vertically and rotationally driving the replenishment gas nozzle 17 . Corresponding areas [1] to [3] are divided by dashed lines in FIG. 3b. Silicon tetrachloride is used as a raw material gas. Hydrogen is flowed from the main nozzle 12 as a carrier gas at a rate of 50 per minute. The raw material gas concentration is 1.5 mol%. Hydrogen flows from each supplementary gas nozzle 17 three times per minute. Replenishment gas concentration is typically 2-6 mol per nozzle
Vary within a range of %.

A control method using this device will be explained below. After each replenishment gas nozzle 17 is made to correspond to each region of the heating table 13, only the replenishment gas concentration is changed to control the film thickness distribution.

FIG. 4 shows the growth rate distribution using only the main raw material gas without supplying supplementary gas. The growth rate is determined by measuring the film thickness after growth using a Fourier transform infrared spectrometer and then dividing it by the growth time. The horizontal axis represents the distance x in the radial direction, and the vertical axis represents the growth rate G. Variation in radial growth rate (film thickness) distribution is ±8
%. Variations in growth rate in the circumferential direction are negligible.

FIG. 5 shows the film thickness distribution when supplementary gas is added using each supplementary gas nozzle one by one. The growth rate distribution is obtained when a is the outer replenishment gas nozzle, b is the middle one, and c is the inner replenishment gas nozzle. Each figure shows three changes in the replenishment gas concentration. heating table 1
The radial distance of 3 is the three replenishment gas nozzles 17
It is divided into three regions corresponding to each other and is shown by dotted lines. The three areas of the heating jig are from the outside [1] ~
It is numbered [3]. Even if the same concentration of replenishment gas is supplied, the area becomes larger toward the outside, so the increase in the growth rate due to the replenishment gas is smaller toward the outside.

FIG. 6 is a graphical representation of the replenishment effect in FIG. That is, the horizontal axis shows the replenishment gas concentration C _a , and the vertical axis shows the average growth rate increase ΔG in each region when the replenishment gas is supplied to each region. The slope of straight line A is smaller than that of straight line C.
This corresponds to the fact that the area of region [1] on the heating table 13 is larger than that of region [3]. Straight line A~
If the slope of C is K(n) (n=1, 2, 3), then each straight line is ΔG=K(n)C _a (n=1, 2,
3).

FIG. 7 shows the required growth rate G ₀ on the heating table 13. When obtaining a uniform film thickness distribution, the required growth rate distribution is a straight line of G=k. The value of k can be chosen arbitrarily. Each region of growth rate without supplementary gas [1] ~
The average value in [3] is G ₀ (n) (n=1,
2, 3), the required growth rate increase is ΔG ₀ (n)=k−G ₀ (n) (1). The concentration of the supplementary gas supplied to each region is C _a (n)=k-G ₀ (n)/K(n) (2). FIG. 8 shows the growth rate distribution obtained when gas was replenished from each nozzle 17 at the replenishment gas concentration determined from the second equation. The gas replenished in each area [1] to [3] will affect other areas, so
The distribution obtained in the figure appears slightly above the distribution of G=k. The average growth rate of each region [1] to [3] in FIG. 8 is assumed to be G ₁ (n) (n=1, 2, 3). In the next growth, the supplementary gas concentration is corrected using the relational expression ΔC _a (n)=k-G ₁ (n)/K(n) (3). The growth rate distribution thus obtained is shown in FIG. Thereafter, a uniform growth rate distribution can be obtained by repeating the same operation. Using this control method, the variation in the radial film thickness distribution is ±1.5 after two corrections of the replenishment gas concentration.
%was gotten.

The configuration, operation, and effects of the present invention will be explained below using specific numerical values.

The diameter of the heating table 13 is 600 mm, and the effective distance in the radial direction is 240 mm. The main nozzle 12 is a side blowing type,
The diameter of the air outlet is 3 mm, and the number of air outlets is 3 vertically, and 9 air outlets are provided in 3 directions at 120° intervals in the circumferential direction. Three supplementary gas nozzles 17 were used, and they were installed on the outer periphery of the heating table 13 above the heating table 13 by means of struts at intervals of 120° in the circumferential direction. The column also serves as an introduction pipe for supplementary gas, and the column passes through the base 16 via an O-ring, and can be manually operated and rotated by a gear, and can be moved up and down by a worm gear. The outlet of each supplementary gas nozzle 17 is cylindrical with a diameter of 30 mm and a height of 50 mm, and the distance from the heating table 13 to the outlet is 50 mm for all three, and the outlet of the supplementary gas nozzle 17 for the corresponding area [1] is The heating table 13 was arranged so that its center was 260 mm away from the radial position of the heating table 13. Similarly, the other two replenishment gas nozzles 17 were installed at locations of 180 mm for the corresponding area [2] and 100 mm for the corresponding area [3].

The heating table 13 is rotated at 15 rpm, hydrogen carrier gas is supplied from the main nozzle 12 at 50/min, the silicon tetrachloride raw material gas concentration is 1.5 mol%, and when no other supplementary gas is added, the The film thickness distribution of the Si thin film grown on the Si wafer was ±9%.

Therefore, while keeping the position of each replenishment gas nozzle fixed, the gas flow rates of the replenishment gas nozzles in corresponding areas [1] to [3] were adjusted to 2.0/min, 1.5/min, and 1.0/min, or the raw material gas concentration was set to 2.1mol%, 6.2mol%. %,
5.7 mol% was flowed. Here, the gas flow rate refers to the sum of the carrier gas and source gas. With this first correction, the film thickness distribution of the Si thin film grown on the Si wafer on the heating table 13 was ±4.6%. A second correction was made to further improve the film thickness distribution. In the second modification, only the raw material gas concentration was changed without changing the position of the supplementary gas nozzle or the gas flow rate. That is, the raw material gas concentrations of each supplementary gas nozzle in corresponding areas [1] to [3] were set to 1.8 mol%, 6.0 mol%, and 5.3 mol%.

As a result, the thickness distribution of the Si thin film after the second correction was ±1.5%.

Although the above embodiment describes an example in which a Si thin film is grown on a Si wafer, the substrate is not limited to Si, and the thin film is not limited to Si.

A modification of this control method is shown in FIG. If the growth rate distribution is uniform in one part and smaller in other parts and the growth rate is to be adjusted to the maximum value, it is only necessary to divide only the region where the growth rate is low and share it with the replenishment gas nozzle. At this time, the required growth rate is 1
I end up deciding.

When this control method is used in a horizontal furnace, the heating table is divided into several regions in the gas flow direction. The supplementary gas nozzles may be arranged slightly upstream of each region of the heating table in the gas flow direction at intervals corresponding to the width of each region of the heating table.

Calculations in this control method may be performed using a microcomputer. Control can also be automated by combining it with an automatic film thickness distribution measurement device.

As described above, according to the present invention, when a supplementary gas method is used for the vapor phase growth reaction, the film thickness distribution can be easily made uniform and can be automated.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional horizontal furnace, Fig. 2 is a schematic diagram of a conventional vertical furnace, Fig. 3 a is a schematic diagram of a vapor phase growth apparatus used in the present invention, and b is an A-A section of a. 4 is a diagram showing the growth rate distribution in the apparatus shown in FIG. 3 without supplementary gas, and FIGS. Figure 6 is a diagram showing the replenishment effect of each replenishment gas nozzle, Figure 7 is a diagram showing the required growth rate distribution, and Figure 8 is a diagram showing the growth rate distribution when using three replenishment gas nozzles. FIG. 9 is a diagram showing a growth rate distribution made uniform using three supplementary gases, and FIG. 10 is a diagram showing a growth rate distribution according to a modification of the present invention. It is. 2... Heating coil, 12... Main nozzle, 13...
... heating table, 15 ... exhaust gas discharge pipe, 17 ... supplementary gas nozzle, 18 ... bell gear, 19 ... drive device, 20 ... raw material gas supply device.

Claims (1)

[Claims] 1. A plurality of substrates are placed on a heating table rotatably provided in a reaction furnace, and a main nozzle provided at the rotation center position of the heating table is directed toward the radial direction of the heating table. In addition to supplying raw material gas horizontally, the heating table on which each substrate is placed is divided into at least two regions, and enough replenishment gas nozzles are provided to correspond to each region, and the specified raw material gas is replenished from each replenishment gas nozzle. A vapor phase growth method characterized by supplying gas vertically from above a heating table to form a uniform thin film on each substrate, and guiding exhaust gas from around the heating table to the outside of the reactor. 2. The vapor phase growth method according to claim 1, wherein the reactor is vertical and the heating table is rotated.