JPH04107816A - Thin film forming apparatus - Google Patents

Abstract

PURPOSE:To improve heating efficiency at the central part of a susceptor or the like and to heat a large diameter wafer uniformly by providing a protrusion approximately in the center of the outer face of a supporting table at the opposite side to the non-supporting face of the supporting table. CONSTITUTION:A susceptor protrusion 10 made of graphite is provided approximately in the center of the outer face of a supporting table at the opposite side to the supporting table, i.e., a spot facing 8 of a susceptor 6, and coupled through a silicon section with a rotary shaft 5 comprising a stainless steel section. Heat is blocked by the silicon section and airtightness is established between the rotary shaft 5 and a reaction furnace 1 through a magnetic shield unit at the stainless steel section. Furthermore, inner face of the water-cooled reaction furnace 1 is mirror finished thus minimizing heat loss through radiation. According to the constitution, a high quality thin film having no slip and reduced number of particle can be obtained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin film forming apparatus suitable for epitaxial single crystal growth in the manufacturing process of semiconductor wafers (hereinafter simply referred to as wafers).

[Conventional technology] In recent years, with the increasing integration and miniaturization of semiconductor integrated circuits,
For example, an epitaxial single crystal film is formed on a wafer. This epitaxial film is becoming thinner as the diameter of the wafer becomes larger, and demands for ensuring uniformity of film thickness distribution and resistivity distribution and for achieving higher quality thin films are becoming more severe.

Conventionally, three types of epitaxial growth furnaces have been used: horizontal furnaces, vertical furnaces, and cylinder furnaces called barrel furnaces. Horizontal furnaces have been used as the primary equipment since the early days. However, horizontal furnaces have problems in terms of quality and mass production, such as film thickness, resistivity uniformity, and crystal defects.

Currently, vertical furnaces and barrel furnaces are mainly used.

When the epitaxial growth method using a vertical furnace employs a high-frequency heating method, the wafer is heated by a single-sided heating method by heat conduction from a base that supports the wafer 1, that is, a susceptor. For this reason, the wafer is likely to warp, resulting in temperature non-uniformity within the wafer surface, and slips are likely to occur in the epitaxially grown film. Furthermore, since the wafer is placed horizontally, there is a problem in that foreign matter from the gas phase tends to accumulate.

On the other hand, in a barrel furnace, the mounting surface of the susceptor is almost vertical. For this reason, the accumulation of foreign matter from the gas phase is suppressed, but the thin film growth conditions differ between upstream and downstream of the gas flow, leading to the problem of uneven film thickness and resistivity distribution between the sea urchins. Ada.

JP-A-63-36519 discloses an epitaxial growth apparatus that combines only the advantages of a vertical furnace and a barrel furnace. FIG. 2 is an explanatory diagram of essential parts showing an example of this epitaxial growth apparatus. 1 in the figure is a reactor. The reactor 1 is also provided with an inlet 2 . Inlet 2
In this figure, the raw material gas 3 and other gases to be used are introduced into the reactor 1. Further, the reactor 1 is provided with an outlet through which the raw material gas 3 and other gases to be used flow out of the reactor 1. The reactor 1 is provided with a disc-shaped graphite susceptor 6 attached to a rotating shaft 5. In other words, the structure is such that the susceptor 6 can be rotated substantially vertically by rotating the rotating shaft 5 from the outside. Wafers to be processed are loaded into a plurality of circular grooves 98 formed on opposing surfaces of a pair of susceptors 6.

In other words, the circular notch 98 is used to support the wafer 7. The wafer 7 is heated through the susceptor 6 by applying high frequency current to a high frequency heating coil 9 provided near the mounting surface of the rotating shaft 5 of the susceptor 6. In general, the surface of the susceptor 6 including the circular counterbore 8 is coated with a thin film of SiC or the like.

In the epitaxial growth method using the conventional apparatus configured as described above, first, the wafer 7 is loaded into the circular counterbore 8 . Then, the raw material gas 3 and the carrier gas are introduced into the reactor 1 from the inlet 2 and are discharged from the outlet 4 while the susceptor 6 is rotated. Raw material gas 3 and carrier gas are
For example, in the case of Si epitaxial growth, 5iH2CJ
2, and H2 gas is used. Next, the high-frequency heating coil 9 is operated and set at a predetermined growth temperature, thereby forming an epitaxially grown film on the wafer 7 by the CVD method. In this case, temperature adjustment is performed by increasing (heating) and decreasing (cooling) the temperature according to a predetermined schedule.

[Problems to be Solved by the Invention] However, when epitaxial growth is performed using such a conventional thin film growth apparatus, it is possible to obtain a thin film with uniform film quality within slip. The center of the susceptor was heated and the surface temperature tended to be lower than the surrounding area.For this reason, it was necessary to place the wafer off the center of the susceptor, and There was a problem in that it was difficult to realize a compact reactor of sheet type (one sheet on each side).

The present invention has been made in view of these points, and provides a thin film forming apparatus that can increase the heating efficiency of the central portion of a susceptor and the like, and can evenly heat a large diameter wafer.

[Means for Solving the Problems] The present invention provides a reactor having an inlet and an outlet for a reaction fluid, and a reactor which is rotatably installed substantially parallel to the reactor with a predetermined facing interval, A thin film forming apparatus comprising a pair of support stands having supporting parts for the object to be processed on opposing surfaces thereof, and a high-frequency coil provided in the reactor so as to surround the support stands. This thin film forming apparatus is characterized in that a convex portion is provided at approximately the center of the outer surface of the support base on the opposite side to the support surface of the object to be processed.

Here, the convex portion should be sharpened toward its tip to have a diameter that is approximately the same as the rotation axis of the support base, and the tip should be located on a line perpendicular to the outer surface of the support base and at the minimum height of the high-frequency coil. It is preferable to position it closer to the inner wall surface of the reactor than the inner diameter portion.

Moreover, it is preferable to plate the high frequency coil with gold.

[Function] According to the thin film forming apparatus according to the present invention, since the convex portion is provided from the center of the susceptor toward the high-frequency coil side,
The convex portion of the graphite susceptor that approaches the high-frequency coil receives induction heating, and due to conductive heat transfer from the convex portion, the surface of the central portion of the susceptor is heated to the same extent as the surrounding area.

[Example] Example 1 An example will be described below using the thin film forming apparatus shown in FIG. 1. Note that the same parts as in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. In the thin film forming apparatus of this embodiment, a susceptor convex portion 10 made of graphite is provided approximately at the center of the outer surface of the susceptor 6, which is a support base, on the side opposite to the circular counterbore 8. If the susceptor convex portion 10 is made of a stainless steel portion, it is connected to the rotating shaft 5 via a quartz portion. The quartz part blocks heat, and the stainless steel part maintains airtightness between the rotating shaft 5 and the reactor 1 by means of a magnetic shield (not shown). In addition, this thin film forming bag is
The inner surface of the water-cooled reactor 1 is mirror-finished to minimize heat loss due to radiation.

When we investigated the relationship between the position on the susceptor 6 and the temperature distribution when using the thin film forming apparatus configured as described above, we found that as shown by characteristic line I in FIG. It was confirmed that the temperature was set at approximately 1150°C throughout the entire area. On the other hand, in the case of the conventional thin film forming apparatus shown in FIG. 3, as shown by the characteristic line ■ in FIG. It was confirmed that a temperature drop was occurring.

Example 2 The shape of the susceptor convex portion 10 is sharpened from the portion corresponding to the minimum inner diameter of the high-frequency coil 9 toward the high-frequency coil 9 side until the tip thereof has approximately the same diameter as the rotating shaft 5. A thin film forming apparatus was constructed in the same manner as in Example 1.

Regarding this thin film forming apparatus, as in Example 1, the susceptor 6
When the relationship between the upper position and the temperature distribution was investigated, the results shown by characteristic line H in FIG. 2 were obtained. As is clear from the characteristic line (3), it was confirmed that in this thin film forming apparatus, the temperature of the susceptor 6 was kept constant within a range of ±10° C. from the center of the susceptor 6 to the outer peripheral edge. As a result, it was also confirmed that epitaxial growth could be performed on the wafer 7 placed on the rotating shaft 5, which was impossible with the conventional thin film forming apparatus shown in FIG.

Example 3 Example 1 except that the high frequency coil 9 was plated with gold.
A thin film forming apparatus was constructed in the same manner as described above.

Regarding this thin film forming apparatus, as in Example 1, the susceptor 6
When we investigated the relationship between the upper position and the temperature distribution, we obtained the results shown by the characteristic line ■ in FIG. As is clear from the characteristic line (2), it was confirmed that this thin film forming apparatus provided even better temperature characteristics than the thin film forming apparatus of Example 1.

[Effects of the Invention] As explained above, according to the thin film forming apparatus according to the present invention, it is possible to easily obtain a high quality thin film with no slip and few particles.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the main parts of a thin film forming apparatus according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between the position on the susceptor and temperature distribution, and Fig. 3 is a conventional improvement. FIG. 2 is an explanatory diagram of a barrel furnace thin film forming apparatus. 1019 reactor, 2... inlet, 3... raw material gas,
4... Discharge port, 5... Rotating shaft, 6... Susceptor,
7... Ueno 1.8... Circular counterbore, 9... High frequency heating coil, 10... Susceptor convex portion.

Claims (3)

[Claims] (1) A reactor having an inlet and an outlet for a reaction fluid;
A pair of support stands which are rotatably installed in the reactor in substantially parallel relation to each other with a predetermined facing interval, each having a support portion for the object to be processed on opposing surfaces thereof; and a high-frequency coil provided in the reactor, characterized in that a convex portion is provided at approximately the center of the outer surface of the support base on the opposite side to the surface of the support base that supports the object to be processed. Thin film forming equipment. (2) The convex portion becomes sharp toward its tip to a size that is approximately the same diameter as the rotation axis of the support, and the tip is located on a line perpendicular to the outer surface of the support and is connected to a high-frequency coil. 2. The thin film forming apparatus according to claim 1, wherein the thin film forming apparatus is located closer to the inner wall surface of the reactor than the smallest inner diameter part of the reactor. (3) The thin film forming apparatus according to claim 1, wherein the high frequency coil is plated with gold.