JPS60143625A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To unify film thickness of thin films to be grown on semiconductor substrates by unifying distribution of plasma by a method wherein low-frequency electric power is applied to a coil on the side near the exhaust tube of a reaction tube, and high-frequency electric power is applied to a coil on the side near a gas feed tube. CONSTITUTION:A coil 7 to be applied with low-frequency electric power is provided on the side near an exhaust tube 3, and moreover, a coil 8 to be applied with high-frequency electric power is provided on the side near a gas feed tube 2 respectively. Accordingly, even when batch processing is performed arranging wafers of a large number in a reaction tube, film thickness of the wafers arranged at any place in the reaction tube excluding the part being especially close to the exhaust tube are nearly unified, and moreover, in-plane distribution of film thickness is not generated at the respective wafers.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device suitable for making the thickness of a thin film uniform over the entire surface when a thin film is formed on a semiconductor substrate.

Conventional Techniques and Problems In recent years, a high-frequency coil is wound around a reaction tube, a semiconductor substrate is placed inside the coil, a reaction gas is supplied, and the reaction is performed using an electromagnetic field generated by passing a high-frequency current through the high-frequency coil. 2. Description of the Related Art A thin film is formed by exciting a reactive gas in a tube to cause a glow discharge, and using plasma generated thereby to cause a direct reaction between the reactive gas and a semiconductor substrate.

FIG. 1 is an explanatory view of the main parts of a conventional example of a growth apparatus for carrying out the plasma direct growth method.

In the figure, 1 is a reaction tube made of, for example, quartz, 2 is a gas supply pipe, 3 is an exhaust pipe, 4 is a cap that covers an opening for inserting and removing a wafer or susceptor (not shown), etc.; 6 indicates a high frequency coil, and 6 indicates a wafer.

In this device, when plasma is generated in the reaction tube, the reaction tube may
Since the degree of vacuum is not uniform within the interior, the distribution of the plasma is also not uniform, and strong plasma is generated near the exhaust pipe 3, where gas excitation is active and thin film growth is prevented. is promoted.

Therefore, when batch processing is performed, not only film thickness non-uniformity occurs between each wafer, but also in-plane non-uniformity occurs within a single wafer.

In the conventional technology, in order to alleviate the above-mentioned drawbacks as much as possible, a long reaction tube is used and a similarly long high-frequency coil is installed so that the part where the plasma distribution and heat distribution are uniform becomes long. ing.

However, it is clear that there are problems in terms of economy and handling when relying on the prior art as described above.

Purpose of the Invention The present invention makes it possible to make the plasma distribution in the reaction tube uniform without requiring a long reaction tube or a high-frequency coil, and to maintain a uniform thickness of a thin film grown on a semiconductor substrate. .

Structure of the Invention In the method for manufacturing a semiconductor device of the present invention, a semiconductor wafer is disposed in a reaction tube having a plurality of divided coils, a reaction gas is supplied, and a side of the reaction tube near an exhaust pipe is provided. A low frequency power is applied to the coil on the side of the reaction tube near the gas supply pipe, and a high frequency power is applied to the coil on the side of the reaction tube near the gas supply tube to generate a uniform plasma over substantially the entire length of the reaction tube. Since it contains about 1 to grow a thin film on the wafer, even if the wafers are subjected to hatch processing, the thickness of the thin film grown on each wafer can be made fairly uniform.
Moreover, the thickness distribution of the thin film within the wafer surface can also be eliminated.

Embodiment of the Invention FIG. 2 is for explaining an embodiment of the present invention.
(a) is an explanatory diagram of main parts showing an example of a growth apparatus applied when carrying out the present invention, and the same parts as those explained in connection with FIG. Diagram (a)
FIG. 3 is a diagram showing the average in-plane film thickness of each wafer when a thin film is grown using the growth apparatus shown in FIG.

In FIG. 2(a), 7 and 8 are coils, where the coil 7 is a low frequency coil (LFC) and the coil 8 is a high frequency coil (HFC).

In this example, the coil 7, which is LFC, has a temperature of 4°O(
Kllz), 13.56 (
Each high frequency power of M Ilz ) was applied.

In order to carry out the experiment in which 400 (KHz) was applied to the coil 7, which is an LFC, it was necessary to inductively heat the carbon susceptor holding the wafer 6 and use that heat. If such a thing is unnecessary, 13. 56
It is of course possible to apply high frequency power of CMllz) and apply high frequency power of a higher frequency to the coil 8 which is HF C. Incidentally, as the frequency becomes higher, the reaction gas can be efficiently turned into plasma, so less power is required, and the efficiency of induction heating for the carbon susceptor is reduced, so the temperature rise of the susceptor is reduced. This is well known.

In FIG. 2(b), the circle mark indicates the average in-plane film thickness of each wafer in accordance with one embodiment of the present invention, and the cross mark indicates the average in-plane film thickness in the case where only low frequency power is applied. It will be appreciated that in one embodiment, the thickness of the grown thin film is uniform no matter where the wafer is placed throughout the entire length of the reaction tube 1. However, although it is non-uniform in the vicinity of the exhaust pipe 3, it can still be seen that it is better compared to the case where only low frequency power is applied.

According to the present invention, it is preferable to arrange the coil for applying low frequency power on the side closer to the exhaust pipe, and the coil for applying high frequency power on the side closer to the gas supply pipe. However, this can be confirmed by the following experiment.

FIG. 3 is for explaining an experiment to confirm that the configuration of the present invention is the best. ) is a diagram showing the average in-plane film thickness of each wafer when a thin film is grown using the growth apparatus shown in FIG. In FIG. 3, the same parts as those explained with reference to FIG. 2 are indicated by the same symbols.

In the growth apparatus shown in FIG. 3(a), the LFC coil 7 and the HFC coil 8 are installed so as to overlap concentrically.

Comparing the characteristic line shown in Figure 3 (b) with the characteristic line in the case of only the low frequency coil in Figure 2 (, b), the range in which the inter-wafer film thickness distribution is constant is narrower. , and it can be seen that the film thickness increases rapidly as it approaches the end of the coil or the exhaust pipe.

All of these are caused by the fact that the coils 7 and 8 overlap. That is, because such a configuration is adopted, strong plasma due to high frequency is generated in the central portion of the reaction tube 1 and near the exhaust pipe 3, thereby narrowing the range of uniform distribution.

As can be seen from the explanation regarding FIGS. 2 and 3, HF
By providing the coil 8, which is C, adjacent to the coil 7, which is 1, FC, on the side away from the exhaust pipe 3, it is possible to achieve a wide uniform film thickness distribution between wafers. . Moreover, as for the position, it is preferable to install the high frequency coil in the vicinity of a position where almost no film thickness can be obtained when only the low frequency coil is used.

Effects of the Invention In the method for manufacturing a semiconductor device of the present invention, a semiconductor wafer is placed in a reaction tube having a plurality of divided coils, and a reaction gas is supplied to the coil on the side of the reaction tube near the exhaust pipe. applies low-frequency power and high-frequency power to the coil on the side of the reaction tube near the gas supply tube to generate a uniform plasma over substantially the entire length of the reaction tube to form a thin film on the semiconductor wafer. Even if a large number of wafers are placed in the reaction tube for batch processing, the film thickness of the wafers placed anywhere in the reaction tube, except for the parts particularly close to the exhaust pipe, will be reduced. approximately average,
Moreover, no in-plane distribution of film thickness occurs on each wafer.

In addition to the above-mentioned effects, the growth apparatus used to carry out the semiconductor device manufacturing method of the present invention is economical because there is no need to make the reaction tube or coil long to make the plasma distribution uniform. Moreover, it has the effect of being extremely easy to implement in terms of carrying and handling.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the main parts of a growth apparatus implementing the conventional technique, and Fig. 2 is for explaining one embodiment of the present invention. (a) is an explanatory diagram of the main parts of the growth apparatus, and (b) is a Figure 3 is a diagram showing the average in-plane film thickness of each wafer corresponding to the device, and is for explaining an experiment to determine the best coil arrangement in the present invention. Explanatory diagram of the main parts of the growth device, (b)
1 and 2 respectively represent diagrams showing the average in-plane film thickness of each wafer corresponding to the growth apparatus. In the figure, 1 is a reaction tube, 2 is a gas supply tube, 3 is an exhaust tube, 4 is a cap, 6 is a wafer, and 7 is a low frequency coil (L
FC), and 8 indicates a radio frequency coil (RFC). Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A semiconductor wafer is placed in a reaction tube having a plurality of divided coils, and a reaction gas is supplied thereto.Low frequency power is applied to the coil on the side of the reaction tube closer to the exhaust tube, and the gas in the reaction tube is The method includes the step of growing a thin film on the semiconductor wafer by applying high-frequency power to the coil near the supply tube to generate uniform plasma over substantially the entire length of the reaction tube. A method for manufacturing a semiconductor device.