JP2724649B2 - Low pressure CVD equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pressure CVD apparatus for manufacturing a semiconductor substrate having a polycrystalline Si film or the like formed on a surface of a semiconductor wafer made of Si single crystal (hereinafter, referred to as a wafer).

[0002]

2. Description of the Related Art In a process of manufacturing a semiconductor device (hereinafter, referred to as a device), a wafer is subjected to various heat treatments. In each heat treatment process, carbon or metal impurities present in the wafer, or during a process of manufacturing a device. Metal impurities contaminating the wafer surface precipitate in the wafer and cause various crystal defects. These crystal defects also occur on the surface of the wafer and in the vicinity thereof, increasing the leak current and reducing the lifetime of the wafer, and adversely affect the characteristics and yield of devices manufactured using the wafer.

On the other hand, strains and microcrystalline defects formed on the back surface or inside of the wafer have the effect of capturing and fixing impurities that adversely affect device characteristics, or removing point defects or the like involved in defect generation. Have. This effect is called gettering, the former being extrinsic gettering (EG) and the latter being intrinsic gettering (I).
G).

As one of the semiconductor substrates provided with the EG effect, a polycrystalline Si film is formed on the back surface of a wafer, and a strain field generated at a grain boundary of the polycrystalline Si film and a strain field due to lattice mismatch are gettered. Known ring sources are known (see, for example, JP-A-52-120777 and JP-A-55-1).
Nos. 3318 and 57-136331. The wafer used here is usually a wafer obtained by etching a disk sliced from a Si single crystal rod after polishing.

In order to form a polycrystalline Si film on a wafer surface, a low pressure CVD apparatus is usually used. This low-pressure CVD apparatus heats a wafer set in a reaction chamber whose pressure has been reduced and, while heating a wafer such as SiH ₄ into the reaction chamber.
This is an apparatus for supplying a reaction gas containing i and forming a polycrystalline Si film on a wafer surface by a thermal decomposition reaction.

[0006]

The properties and thickness of the polycrystalline Si film formed in such a low-pressure CVD apparatus depend on the heating temperature, reaction gas concentration and reaction time of each of the wafers loaded in the apparatus. Therefore, if at least the heating temperature and the reaction gas concentration are made uniform in the reaction chamber, the non-uniformity of the properties and the thickness of the polycrystalline Si film caused by the non-uniformity of the heating gas and the reaction gas concentration are eliminated. In addition, it is possible to significantly suppress the warpage of the semiconductor substrate.

However, in the conventional temperature control using a single heater, when processing a small number of wafers in a small-sized reaction chamber, there is not much trouble in uniforming the temperature in the same chamber. It has been found that in a large-scale mass-production apparatus for simultaneously processing several hundred wafers, even if the single-type heater appears to be stable at first glance, its temperature distribution is not necessarily uniform. Reasons for this are irregular heating of the reaction chamber, the influence of the flow of the raw material gas in the reaction chamber, and, when the heater is long, defects in the heater itself or defects due to heater deterioration. It is presumed that.

Particularly, in the case of a resistance heating type heater, it is well known that the unevenness in the temperature of the heater immediately causes a change in the heater resistance, which further increases the unevenness in the temperature.

[0009] In addition, there is a lack of effective means for keeping the reaction gas concentration in the reaction chamber uniform.

The present invention has been made in view of the above circumstances, and an object thereof is to form a film having a predetermined thickness uniformly on each wafer when a large number of wafers are processed at the same time. It is an object of the present invention to provide a low-pressure CVD apparatus capable of eliminating variations in quality of the substrate and simultaneously suppressing and improving the occurrence of warpage of the substrate.

[0011]

In order to achieve the above object, the present invention provides an inner tube and an outer tube having a double inner / outer structure, a heater surrounding the inner tube and the outer tube, and a reduced pressure reaction chamber in the inner tube. In a low-pressure CVD apparatus that supplies a reaction gas into the reaction chamber and forms a film on the surface of the wafer while heating the wafer set in the reaction chamber with the heater, the heater is divided into a plurality of parts, and the temperature distribution in the reaction chamber is uniform. By controlling the power of each heater segment by measuring the temperature in the vicinity of each heater segment so that the inner tube and the outer tube communicate with each other, the reaction gas is introduced into the reaction chamber from a plurality of locations in the height direction thereof. And a plurality of exhaust ports that open at the same angular pitch in the circumferential direction in the same plane in the space between the inner tube and the outer tube Characterized by being configured for exhausting et reaction gas.

[0012]

According to the present invention, the temperature distribution in the reaction chamber is improved by measuring the temperature in the vicinity of a plurality of divided heater segments and controlling the power of each divided segment. Reaction gas is supplied from a plurality of locations in the chamber in the height direction, and the reaction gas flows out of the reaction chamber into a space between the inner tube and the outer tube, and is discharged out of the device from an exhaust port opened at a plurality of locations in the space. Therefore, the reaction gas concentration distribution in the height direction in the reaction chamber is kept substantially uniform, and a large number of wafers set in a layered manner in the height direction in the reaction chamber are supplied with a reaction gas having a uniform concentration. At the same time, a film having a predetermined thickness is uniformly formed on each wafer, and at the same time, the occurrence of warpage of the semiconductor substrate is made uniform, reduced, and improved.

[0013]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing a schematic configuration of a low pressure CVD apparatus according to the present invention, and FIG. 2 is a sectional view taken along line AA of FIG.

A low-pressure CVD apparatus 1 shown in FIG. 1 has an inner tube 2 and an outer tube 3 made of transparent quartz and having a dual inner / outer structure, and these are covered by a heater 4.

The lower portions of the inner tube 2 and the outer tube 3 are sealed by a stainless steel cap 5, and a reaction chamber R formed in the inner tube 2 is formed.
Inside, a vertical support shaft 6 penetrating through the cap 5 faces from below. A stainless steel turntable 7 is supported on the upper end of the support shaft 6, and a transparent quartz susceptor 8 is supported on the turntable 7. The susceptor 8 has a large number of holders 9 arranged in layers vertically at appropriate intervals, and a plurality of wafers (not shown) are set in each holder 9. The wafer set on the holder 9 is
A disk sliced from a Si single crystal rod is etched after polishing.

On the other hand, a bevel gear 10 is connected to the lower end of the support shaft 6, and a bevel gear 11 connected to the output shaft of the drive motor M meshes with the bevel gear 10.

An opening 12 is formed at the top of the inner tube 2, and a space S formed between the inner tube 2 and the outer tube 3 and the reaction chamber R are formed through the opening 12. Communicating with each other. In the space S, a quartz protection tube 13 which is long in the height direction is vertically installed, and three thermocouples T are provided in the protection tube 13.
1, T2 and T3 are inserted at predetermined intervals in the height direction. The heater 4 has three divided pieces 4 in the height direction.
A, 4B, and 4C, and these divided pieces 4
The temperatures near A, 4B, and 4C depend on the thermocouples T1, T2, and T, respectively.
3 so that the temperature distribution in the height direction inside the reaction chamber R becomes substantially uniform.
The amount of current supplied to C is controlled.

Further, three gas supply pipes 14, 15, 16 are provided in the reaction chamber R, and these are opened at predetermined intervals in the height direction. That is, the pipe 14 is open at the top in the reaction chamber R, and the pipe 15
Is opened at an intermediate position, and the pipe 16 is opened at the lowest position. These pipes 14, 15, 16 are connected to a reaction gas supply source (not shown).

On the other hand, as shown in FIG. 2, two exhaust ports 17 are opened opposite to each other (ie, at a pitch of 180 °) in the same plane below the space S. 1
An exhaust pipe 18 is connected to 7, and these two exhaust pipes 18 join one large-diameter exhaust pipe 19 and are connected to a vacuum pump (not shown).

Next, the operation of the low pressure CVD apparatus 1 will be described.

As shown in FIG. 1, a plurality of wafers are accommodated in a reaction chamber R in a state set in a susceptor 8, and the drive motor M is driven to rotate the wafers via bevel gears 11 and 10. Transmitted to the support shaft 6,
The turntable 7 and the susceptor 8 supported on the susceptor 8 are rotationally driven. As a result, a plurality of wafers set on the susceptor 8 are rotated at a predetermined speed in the reaction chamber R. At the same time, the heater 4 is driven to keep the inside of the reaction chamber R uniform at a predetermined temperature, and a vacuum pump (not shown) is driven to drive the reaction chamber R.
The inside is evacuated and the reaction chamber R is set to less than 1 Torr to 0.0
It is kept under a reduced pressure of 1 Torr.

When the above conditions are satisfied, a reaction gas obtained by mixing SiH ₄ and another inert gas at an appropriate ratio becomes
The gas is supplied from the gas supply pipes 14, 15, 16 into the reaction chamber R. In this case, as described above, since the gas supply pipes 14, 15, and 16 are opened at predetermined intervals in the height direction in the reaction chamber R, the reaction gas is
It is supplied simultaneously from the middle and lower stages, and causes a thermal decomposition reaction with the wafer in the reaction chamber R to form a polycrystalline Si film on the entire surface of the wafer. Then, the reaction gas supplied to the raw film of each wafer is drawn by the negative pressure of the exhaust system and flows into the space S from the reaction chamber R through the opening 12 as shown by an arrow in FIG. The air is exhausted from the apparatus 1 through two exhaust ports 17 opening at the lower part of the space S via exhaust pipes 18 and 19.

As described above, in the present embodiment, the reaction gas is supplied from a plurality of locations in the height direction inside the reaction chamber R, and the reaction gas flows out of the reaction chamber R into the space S, and The reaction gas concentration distribution in the height direction inside the reaction chamber R is kept substantially uniform because the exhaust gas is exhausted from the apparatus 1 through the exhaust port 17 opening to the inside, and the reaction gas is set in a layered manner in the height direction inside the reaction chamber R. A reaction gas having a uniform concentration is supplied to a large number of wafers. As a result, a film of a predetermined thickness is uniformly formed on each wafer, and at the same time, the warpage of the semiconductor substrate is made uniform, and Reduced and improved. In addition, variations in the Si film thickness between the substrates are eliminated.

In the above embodiment, the number of reaction gas supply pipes is three and the number of exhaust ports is two. However, the number is not limited, and the number of reaction gas supply pipes is four. Needless to say, the number of exhaust ports may be three or more, and the number of exhaust ports may be three or more. However, in consideration of the smooth flow of the reaction gas, it is desirable to arrange the exhaust ports at equal angular pitches on the circumference.

[0026]

As apparent from the above description, according to the present invention, the inner tube and the outer tube having the inner / outer double structure, the heater surrounding the inner tube and the outer tube, etc., and the depressurized reaction chamber in the inner tube are provided. In a low-pressure CVD apparatus that supplies a reaction gas into the reaction chamber and forms a film on the surface of the wafer while heating the wafer set in the reaction chamber with the heater, the heater is divided into a plurality of parts, and the temperature distribution in the reaction chamber is uniform. By controlling the power of each heater segment by measuring the temperature in the vicinity of each heater segment so that the inner tube and the outer tube communicate with each other, the reaction gas is introduced into the reaction chamber from a plurality of locations in the height direction thereof. And a plurality of exhaust ports opening at the same angular pitch in the circumferential direction in the same plane in the space between the inner tube and the outer tube. Since the reaction gas is exhausted, a film of a predetermined thickness is uniformly formed on each wafer, and at the same time, the occurrence of warpage of the semiconductor substrate is made uniform, reduced, and improved. The effect of eliminating the variation in the above is obtained.

According to the present invention, since the heater is divided into a plurality of divided pieces, when an abnormality is found in any of the divided pieces, only the divided piece in which the abnormality is found is replaced. This also has the effect of being able to cope.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of a low pressure CVD apparatus according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Decompression CVD apparatus 2 Inner tube 3 Outer tube 4 Heater 12 Opening 14, 15, 16 Gas supply pipe 17 Exhaust port 18, 19 Exhaust pipe R Reaction chamber S space

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masatake Katayama 2-13-1, Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Semiconductor Incorporated Semiconductor Isobe Research Laboratory (72) Inventor Naoyuki Takamatsu Nagoyuki Nishigomura, Nishishirakawa-gun, Fukushima Prefecture Odakura Ohira 150, Shin-Etsu Semiconductor Co., Ltd. Semiconductor Shirakawa Plant (72) Inventor Katsunori Koarai Fukushima, Nishishirakawa-gun, Nishigo-mura O-Cha, Odakura Character 150, Shin-Etsu Semiconductor Co., Ltd. Semiconductor Shirakawa Plant (56) References JP 5-144746 (JP, A) JP-A-1-109714 (JP, A) JP-A 4-131933 (JP, U)

Claims (1)

(57) [Claims] An inner tube and an outer tube having an inner / outer dual structure, a heater surrounding the inner tube and an outer tube, and the like. A heater set in a reduced pressure reaction chamber in the inner tube is heated by the heater to perform a reaction. In a low-pressure CVD apparatus that supplies a reaction gas into a chamber and forms a film on a wafer surface, the heater is divided into a plurality of parts, and the temperature near each heater divided part is measured so that the temperature distribution in the reaction chamber becomes uniform. In addition to controlling the power of each heater segment, the inner tube and the outer tube are communicated with each other, and a reaction gas is supplied to the reaction chamber from a plurality of positions in the height direction of the inner tube and the inner tube and the outer tube. The reaction gas is exhausted from a plurality of exhaust ports that open at the same angular pitch in the circumferential direction in the same plane. Reduced pressure CVD apparatus.