JP2007100172A - Film-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit the formation of particles by inhibiting a material gas from causing a reaction in a gas supply zone in a CVD apparatus. <P>SOLUTION: The CVD apparatus 10 has double-structured gas supply pipes 26 and 27 for supplying the material gas to the gas supply zone 51. The material gas passing through the gas supply pipes 26 and 27 passes through minute orifices 28 and 29 placed in its tip, then arrives at a film-forming zone 52 and forms a thin film on wafers 41 and 42. The material gas keeps its predetermined high pressure until arriving at the orifices 28 and 29 of the gas supply pipes 26 and 27, and is cooled down to a reaction temperature or lower due to adiabatic expansion in the gas supply zone 51. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film forming apparatus, and more particularly to a film forming apparatus capable of controlling a supply temperature of a material gas.

  A film forming apparatus, for example, a CVD (Chemical Vapor Deposition) apparatus is an apparatus for supplying a material gas to grow a thin film on a semiconductor wafer. In such a film forming apparatus, the film is formed at a high temperature in order to decompose and react the material gas. Therefore, there has been a problem that the temperature of the reaction vessel is increased and a reaction product is generated when various material gases are mixed in the supply zone, and particles of the reaction product inhibit film formation.

  In the conventional apparatus, since the supply gas pressure is made constant at the supply source, the temperature is increased by the internal temperature (1500 to 2000 ° C.) until the gas reaches the supply zone, and the gas heated in the supply zone reacts. Therefore, the generation of particles is inevitable in principle.

  In recent years, it has been proposed to deal with this problem by flowing a refrigerant (cooling liquid) around the gas flow path (see Patent Document 1). With reference to FIG.3 and FIG.4, the low pressure CVD apparatus 70 which added the gas cooler proposed is demonstrated. FIG. 4 is an enlarged view of the main part of FIG.

  The reduced-pressure CVD apparatus 70 includes a reduced-pressure reaction vessel. The reaction vessel is opposed to a disk-shaped wafer heating unit 71 disposed in the lower portion thereof, and two gases are provided in the central portion. Supply pipes 72 and 73 are arranged side by side, and wafer holding units 75 and 76 that support the wafer and rotate the wafer are arranged around the supply pipes 72 and 73. The semiconductor wafers 91 and 92 held by the wafer holding units 75 and 76 are reacted with the material gas in the film formation zone 95 facing the wafer heating unit 71 to form a thin film on the wafers 91 and 92. The wafer heating unit 71 and the wafer holding units 75 and 76 are rotatable as shown by the arrow r in FIG.

  The material gas is supplied from two gas supply pipes 72 and 73. A gas cooler 80 is provided around the gas supply pipes 72 and 73, and the gas cooler 80 is filled with a liquid 81 which is a refrigerant. The refrigerant 81 is introduced from a refrigerant inlet (not shown) and discharged from a refrigerant outlet (not shown). When the material gas is introduced from the end outlets of the gas supply pipes 72 and 73, the gas supply pipes 72 and 73 are cooled by the gas cooler 80 so as not to react even if the material gas is mixed.

However, the low pressure CVD apparatus to which a gas cooler is added has the following problems.
(1) Since the periphery of the high temperature part is liquid-cooled, airtightness is required and the structure becomes complicated.
(2) It is difficult to cool to the supply port and it is difficult to enhance the gas cooling effect.
(3) When the liquid leaks into the high-temperature apparatus, the liquid is instantly vaporized and the internal pressure of the apparatus increases rapidly, which may damage the apparatus.
Therefore, with such a system, it has been difficult to make a system with high productivity.

  Conventionally, a thin-film forming apparatus is provided with a double-structure gas introduction pipe and flows with the concentration of the raw material gas in the inner pipe lower than that of the outer pipe (see Patent Document 2), and the process temperature is kept low. For this purpose, those using adiabatic expansion (see Patent Document 3) are known.

JP 2004-507898 A JP 2004-292255 A JP-A-1-206629

  An object of this invention is to provide the apparatus which can reduce gas temperature with the supply port of a gas supply pipe by simple structure in view of said problem.

  In order to solve the above problems, a film forming apparatus according to the present invention is different from the substrate holding unit (2) and the substrate heating unit (3) in the reaction vessel (1) as described in claim 1. A plurality of gas supply pipes (21, 22) arranged in multiples for supplying each gas, and the supply port of the gas supply pipe comprises an opening for holding the gas at a predetermined pressure up to the supply port; The gas is cooled by adiabatic expansion when the gas is supplied from the opening.

  Thus, the present invention pays attention to the supplied material gas pressure and utilizes the cooling effect by adiabatic expansion when the material gas is supplied to the reaction vessel, and has a simple configuration in which a predetermined opening is provided. The gas temperature can be lowered, the generation of particles can be suppressed, and the material gas can be stably supplied to the film formation zone. Moreover, since it is not what cools using a coolant, there is no worry of the failure by coolant leakage.

  As described in claim 2, the opening can be provided on the side wall of the end of the gas supply pipe. According to this, the gas can be supplied to the film formation zone at a short distance.

  As described in claim 3, the opening may be constituted by a small orifice, or as described in claim 4, the opening may be configured to have a valve structure having a variable opening area. When the opening is configured with a small orifice, the gas temperature can be controlled with a simple configuration. When the opening is configured with a valve having a variable opening area, the opening area can be easily adjusted.

  Furthermore, as described in claim 5, if a gas with higher heat resistance is passed through the outermost supply pipe of the multiple pipe, the heat rise of the gas passing through the inside can be further prevented, and the cooling effect can be further improved. Can be increased.

  Further, when the present invention is applied to a film forming apparatus in which the substrate holding part (21, 22) and the substrate heating part (3) are arranged to face each other as described in claim 6, the cooling of the present invention. The effect becomes remarkable.

  As described in claim 7, when the substrates held by the substrate rotating means of the substrate holder (21, 22) are rotated, a more stable film formation is performed without uneven film thickness. be able to.

  As described in claim 8, when the substrate heating unit is rotated by the heating unit rotating means of the substrate heating unit (3), the substrate can be heated more uniformly.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a schematic view showing a cross section of a low pressure CVD apparatus 10 according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part thereof.

In the present embodiment, the low pressure CVD apparatus 10 is used for vapor-phase growth of SiC on a Si substrate. The material gas is propane gas (C ₃ H ₈ ) and silane gas (SiH ₄ ), and the carrier gas is hydrogen H ₂ .

  The low-pressure CVD apparatus 10 includes a reaction vessel 1 that is airtightly constituted by a main body 11 and an upper lid 13. A wafer heating unit 3 is provided below the reaction vessel 1. Two gas supply pipes, a gas supply pipe 26 and a gas supply pipe 27 formed on the outer periphery of the gas supply pipe 26, are arranged at the center of the upper portion. The gas supply pipe 26 and the gas supply pipe 27 are double pipes sharing the central axis. In addition, wafer holding units 21 and 22 that hold the wafers 41 and 42 are disposed around the two gas supply pipes 26 and 27. In addition, the wafer heating unit 3 can be arranged at the upper part, and the wafer holding units 21 and 22 can be arranged at the lower part.

  In the present embodiment, the two gas supply pipes 26 and 27 and the wafer holding units 21 and 22 are integrally assembled by the upper support 2 as a member facing the wafer heating unit 3. The space formed between the upper gas supply pipes 26 and 27, the wafer holding units 21 and 22, and the lower wafer heating unit 3 is provided with the supply ports of the gas supply pipes 26 and 27 at the center. This is a gas supply zone 51, and a peripheral portion is a film formation zone 52 where the wafers 41 and 42 and the wafer heating unit 3 face each other. A material gas, also called a reaction gas, supplied to the gas supply zone rides on the carrier gas and reaches the film formation zone, and grows an SiC film on the wafers 41 and 42.

  The wafer holding units 21 and 22 have wafer rotation or turning means for rotating or turning the held wafer. The wafer holding units 21 and 22 have a holding portion for holding the wafers 41 and 42 and a rotatable support shaft, and the wafers 41 and 42 held by the wafer holding units 21 and 22 are arranged in a horizontal plane around the central axis of the wafer. Can be rotated. This is because there is a difference in gas concentration between the upstream side (center side) and the downstream side (peripheral side) of the gas supplied from the gas supply zone 51, so that the gas concentration is substantially uniform by swirling the wafer. Thus, there is no difference in film thickness. Although not shown in the figure, the upper support 2 is provided with another wafer holding unit so that a total of three wafers can be processed in the reaction vessel 1 at a time. .

  The lower wafer heating unit 3 includes a heating plate made of disc-shaped carbon, and a high-frequency induction coil (not shown) is disposed in a toroidal shape on the lower side of the heating plate to inductively heat the heating plate. . The opposing wafers 41 and 42 are heated by the radiant heat from the heated heating plate. Further, the wafer heating unit 3 has a rotatable support shaft and is configured to be rotatable in a horizontal plane. Even when the heating plate is not heated uniformly, the wafers 41 and 42 are heated uniformly. It is configured to be able to.

  The distal ends of the gas supply pipes 51 and 52 formed of concentric cylinders in the reaction vessel 1 are closed, and a plurality of minute openings, that is, orifices 28 and 29 are formed as gas supply ports on the side wall near the closed distal end. Has been. The inner gas supply pipe 26 protrudes from the outer supply pipe 27, and an orifice 28 is provided on the inner wall of the protruding portion.

  The small orifices 27 and 29 introduce the material gas into the reaction vessel and maintain the pressure of the material gas at a predetermined high pressure from the material gas supply tank (not shown) to the supply ports of the supply pipes 26 and 27. Work. Incidentally, in response to the supply pipe 51 protruding from the supply pipe 52. A recess is formed at the center of the wafer heating unit 3 in order to prevent the gas supply pipe 51 from being overheated by taking a distance from the wafer heating unit 3.

The operation of the low pressure CVD apparatus 10 having such a configuration is as follows.
First, the upper lid 13 of the reaction vessel 1 is opened, and a wafer, which is a substrate on which a thin film is to be formed, is set in the wafer holding units 21, 22 and the like.

  Next, the upper lid 13 is closed to keep the reaction vessel 1 airtight, and the pressure is reduced to 20 Torr using an exhaust means (not shown).

  Thereafter, an electric current is passed through a high-frequency coil (not shown) disposed under the heating unit 3 to heat the heating plate of the heating unit 3 and the wafers 41 and 42 are heated by radiant heat. Here, since the heating unit 3 rotates horizontally around the central axis, uniform wafer heating is performed.

  It is detected that a predetermined high temperature has been reached, and a material gas (propane, silane) is supplied through a supply pipe together with a carrier gas (hydrogen) while maintaining a predetermined pressure, for example, 0.2 MPa. In this embodiment, silane gas is passed through the inner gas supply pipe 26, and propane gas and hydrogen H 2 that is a carrier gas are passed through the outer gas supply pipe 27. This is because propane gas and hydrogen have higher heat resistance compared to silane gas, and even if the temperature of propane gas or hydrogen gas rises due to the heat from wafer heating unit 3, the influence thereof is relatively small. It is.

  Using a triple pipe instead of the double pipe, the most heat-resistant hydrogen gas is introduced into the outermost periphery, propane gas is introduced inside, and the supply pipe arranged on the innermost side is introduced. If the silane gas is passed, the influence of heat from the wafer heating unit can be further reduced.

  The material gas or the like flowing through the gas supply pipes 26 and 27 is jetted to the supply zone 51 from the orifices 28 and 29 which are supply ports provided around the tip of the supply pipe, and then the material gas (propane, Silane) is transported to hydrogen gas as a carrier and supplied to the film formation zone 52.

  The gas supplied to the supply port at a predetermined pressure of 0.2 MPa is injected from the orifices 28 and 29 into the supply zone 51 having a pressure of 26.6 kPa and adiabatically expands, whereby the temperature of the gas decreases. Therefore, even if the gas temperature rises to the reaction temperature inside the gas supply pipe in the reaction vessel that reaches 1500 to 2000 ° C., it is ejected from the orifices 28 and 29 that are the supply ports of the gas supply pipes 26 and 27. Since the gas is adiabatically expanded and cooled, the temperature of the gas itself can be lowered to a reaction temperature and a decomposition temperature, for example, 500 ° C. or lower. Therefore, in the gas supply zone 51, propane and silane supplied through the gas supply pipes 26 and 27 are mixed, but the gas temperature is kept below the reaction temperature and the decomposition temperature, so that the reaction or decomposition occurs. In addition, the generation of particles that cause film formation defects can be suppressed.

  Propane gas and silane gas carried from the supply gas zone 51 to the film formation zone by hydrogen gas react in the film formation zone held at a high temperature to grow a SiC film on the Si wafer. Here, as described above, the wafer is horizontally rotated by the wafer holding units 21 and 22 to enable uniform film formation.

  Since the cooling of the gas according to the present invention uses the principle of reducing the temperature by adiabatic expansion of the compressed fluid, the number of orifices or the orifice diameter and the gas supply pressure are changed based on the thermodynamic theory. Thus, the temperature to be lowered can be set arbitrarily. In general, the higher the supply pressure, the lower the temperature of the gas.

  In this way, when the temperature of the supplied gas is lowered below the reaction temperature and the decomposition temperature, the reaction and decomposition of the material gas in the supply zone 51 are suppressed. As a result, the generation of particles that cause film formation defects can be suppressed, the material gas can be stably supplied to the film formation zone 52, and film formation without defects can be achieved.

  In the present embodiment, the gas supply port is configured by an orifice. However, instead of a simple opening, a valve structure such as a needle valve having a variable and adjustable opening area may be employed in order to appropriately change the opening area. When a valve having an adjustable opening area is used, the opening area can be easily changed in setting a temperature to be a cooling target. The number and position of the orifices or valves are not particularly limited as long as they can be maintained at a predetermined pressure. In this embodiment, the orifice is provided on the side wall of the gas supply pipe. However, for example, it may be provided at the closed end of the gas supply pipe. The structure of the opening of these gas supply pipes can be selected and set according to the gas flow and the gas amount.

  When supplying more material gases, a number of multiple tubes corresponding to the number of material gases or carrier gases may be provided to supply each gas.

  Furthermore, the present invention is not limited to the apparatus described in the embodiment, and can be applied to any apparatus as long as the apparatus supplies a gas and forms a film by heating.

It is the schematic which shows the cross section of the low pressure CVD apparatus which is embodiment of this invention. It is a schematic enlarged view which shows the cross section of the principal part of the low pressure CVD apparatus of FIG. It is the schematic which shows the cross section of the low pressure CVD apparatus provided with the conventional gas cooler. It is a schematic enlarged view which shows the cross section of the principal part of the low pressure CVD apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Low pressure CVD apparatus 1 Reaction container 11 Upper lid 13 Main body 2 Upper support body 21 and 22 Wafer holding unit 26 and 27 Gas supply pipe 3 Wafer heating unit 41 and 42 Wafer 51 Gas supply zone 52 Film-forming zone

Claims (8)

A film forming apparatus for forming a film on a substrate by supplying a gas onto the substrate disposed in the reaction container (1), wherein the reaction container (1) includes:
A substrate holder (21, 22) for holding the substrate;
A substrate heating section (3) for heating the substrate;
A plurality of gas supply pipes (26, 27) arranged at least to supply different gases,
The supply ports (28, 29) of the gas supply pipe have openings that hold the gas at a predetermined pressure up to the supply ports, and cool the gas by adiabatic expansion when the gas is supplied from the openings. A film forming apparatus.   The film formation apparatus according to claim 1, wherein the opening is provided on a side wall of a gas supply pipe end.   The film forming apparatus according to claim 1, wherein the opening includes a small orifice.   The film forming apparatus according to claim 1, wherein the opening has a valve structure having a variable opening area.   The film forming apparatus according to any one of claims 1 to 4, wherein a gas having higher heat resistance is allowed to pass through the outermost supply pipes of the plurality of gas supply pipes (26, 27) arranged in multiplex. .   The film forming apparatus according to claim 1, wherein the substrate holding unit (21, 22) and the substrate heating unit (3) are arranged to face each other.   The film forming apparatus according to claim 1, wherein the substrate holding unit (21, 22) includes a substrate rotating unit, and rotates the substrate held by the substrate rotating unit.   The film forming apparatus according to claim 1, wherein the substrate heating unit (3) includes a heating unit rotating unit, and the substrate heating unit is rotated by the heating unit rotating unit.

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