JP3149468B2 - 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 film forming technique in semiconductor manufacturing, and more particularly to a CVD apparatus for obtaining a uniform film thickness distribution between a large number of wafers and a desired film quality.

[0002]

2. Description of the Related Art Polycrystalline silicon (polysilicon) films are:
It is widely used as a semiconductor element material such as a gate wiring of a semiconductor. Usually, this film is used by doping phosphorus, boron or the like in order to reduce the electric resistance. When semiconductor elements are miniaturized and the film thickness is reduced to submicron,
The conventional doping technique cannot be used, and a method of doping these impurities simultaneously with the formation of the polysilicon film has been used. Conventionally, SiH ₄ (monosilane) has been used as a source gas, but in recent years, Si ₂ H ₆ (disilane) has been used instead. PH ₃ (phosphine) is used as the doping gas. The reason for using disilane is that a film can be formed at a lower temperature than monosilane, and that the film formation rate does not decrease even in the presence of phosphine. However, at a low temperature, the low-pressure CVD device can
When a doped silicon film is formed, there is a problem that the uniformity of the doping amount between the wafers in the flow direction is deteriorated. As a method for performing such doping with good uniformity,
Japanese Patent Application Laid-Open No. 61-269307 discloses a method in which a raw material is heated in advance and introduced using a nozzle.

In the production of compound semiconductors, phosphine is used as a raw material for InP, and it is well known that phosphine is not easily decomposed. One solution to this problem is the Journal of Crystal Grouse, 55
(1981) p. 64-73 (J. Cryst. Gr)
owth, 55 (1981) 64-73), a method is proposed in which only phosphine is thermally decomposed before being introduced into a reactor.

[0004]

In the above prior art, the raw material is simply heated, and there is a problem in controllability for doping uniformly on a large number of wafers. SUMMARY OF THE INVENTION It is an object of the present invention to improve the above disadvantages and to provide an apparatus for obtaining a uniform film thickness and composition between wafers.

[0005]

The object of the present invention is to provide a reaction means for forming a thin film on a substrate, a gas supply means for supplying a reactive gas to the reaction means, and a preheating for preheating a part of the reactive gas. Means, the gas supply means is constituted by two supply means, one of which is a means for supplying a reactive gas to the upstream side of the preheating means, and the other is a means for supplying the reactive gas to the upstream side of the preheating means. This is achieved by means of supplying a reactive gas on the way.

[0006]

A plurality of source gases are supplied by gas supply means, and a thin film is formed from the source gas or an intermediate produced from the source gas. At that time, if the raw materials are simultaneously supplied to the reactor, the lifetime of the intermediate varies depending on each raw material gas, so that there is a problem that a uniform film thickness and film quality cannot be obtained on a large number of wafers.

For example, in a polycrystalline silicon film to be doped, two kinds of source gases are used. Phosphine, a source gas for the doping, has a lower intermediate gas generation rate in the gas phase than monosilane or disilane. Also, the reaction rate of the intermediate on the wafer surface is low. Therefore,
The phosphine introduced into the reactor is gradually decomposed to produce an intermediate, but the intermediate accumulates in the gas phase because the rate of attachment of the intermediate to the film is low. This leads to a higher intermediate concentration downstream of the apparatus. Since the film formation is proportional to the concentration in the gas phase, a non-uniform doping amount appears between the wafers. Thereafter, the concentration of the phosphine intermediate increases as the phosphine is decomposed, but becomes constant without further increase because the phosphine itself decreases. Further downstream, the concentration of the intermediate decreases as the intermediate is gradually incorporated into the membrane.

On the other hand, disilane forms a film at a substantially constant rate in the reaction tube, so that the above-mentioned phenomenon does not occur in the film thickness distribution.

As described above, when gases having different reactivities are used, if the raw materials are simultaneously supplied to the reaction tube, the composition cannot be controlled because the respective film forming mechanisms are different. At this time, if the introduction of phosphine into the reaction furnace is delayed and the phosphine is introduced into the reaction furnace such that the intermediate concentration becomes constant, the film formation rate and the doping amount can be kept constant.

That is, uniformity of the film thickness and film quality can be achieved simultaneously by controlling the residence time, temperature, pressure, flow rate and the like of the raw material gas.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

FIG. 1 shows a first embodiment of the present invention, and is a configuration diagram of an entire CVD apparatus. As shown in FIG. 1, a CVD apparatus for forming a doped polysilicon film includes:
Source gas cylinders (phosphine 1, disilane 2), flow rate control devices 3, 4, 5 for the respective source gases, pipes 6 and 7 for introducing the source gases 1, 2 into the mixing pipe 23, source gas 2
8, a reactor 9 for forming a film, and a wafer table 1 on which a plurality of wafers 10 are arranged at regular intervals.
1, a heater 12 for keeping the inside of the reaction furnace 9 at a constant temperature, and a vacuum exhaust device 13 for keeping the inside of the reaction tube furnace at a low pressure. Here, the heater 12 is maintained at about 500 ° C. The raw materials are mixed in the mixing tube 23, and the residence time is controlled. The cross-sectional shape of the mixing tube is not limited to a circle, but may be another shape. At the same time, it is heated by the heater 21 and is introduced into the reaction tube by the nozzle 25.

Here, the operation of this embodiment will be described.

When the raw material gas a reacts in the gas phase to form an intermediate b and the intermediate becomes a film, the gas flow velocity is u, the radius of the reaction tube is r, the gas heat velocity is Vt, and the raw material gas is Assuming that the body concentration is Ca, Cb, the first-order reaction rate constant in the gas phase is k, and the adhesion probability on the surface is Sc, the concentration distribution in the reaction tube can be obtained by solving the following mass balance equation.

[0015]

(Equation 1)

[0016]

(Equation 2)

The solution is

[0018]

(Equation 3)

[0019]

(Equation 4)

## EQU1 ## Therefore, the concentrations of the source gas and the intermediate change as shown in FIG. The concentration of the intermediate increases when the gas phase reaction starts, but becomes constant when the amount of the intermediate produced from the raw material gas is equal to the amount taken in as a film, and thereafter decreases as the raw material is consumed. . This concentration change is represented by a function of the reaction rate constant and the flow rate. When the adhesion probability is small and the flow rate is large as compared with the gas phase reaction rate constant, the region having a uniform concentration is expanded. Since the film is formed according to the concentration of the intermediate, uniformity of the film is achieved in the region where the concentration is uniform.

In this case, it can be seen that the doping amount can be made uniform by setting the mixing tube to 4 [m] and introducing gas into the reaction furnace. Further, if the radius of the mixing tube 23 is doubled, the flow velocity becomes 1/4, so the length may be 1 [m]. In addition, it can be shortened by increasing the temperature. As described above, by providing the mixer outside the reactor, the mixing position can be freely controlled. Further, it is easy to remove the film attached to the inner wall of the mixer.

In the embodiment of the present invention, the thermal decomposition of only the phosphine gas is considered. However, when another gas (for example, disilane gas) accelerates the thermal decomposition of the phosphine gas, the gas is converted into the phosphine gas by the pipe 7. The gas amount may be controlled and added.

FIG. 2 shows another embodiment of the present invention. In addition,
In the following description, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the mixing tube 23 is provided in the reactor. Thus, the distance between the mixer and the wafer can be set freely. Further, by providing the mixer in the apparatus, safety such as gas leakage is high. The mixing position can be freely controlled by changing the length of the inlet pipe into the mixer.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the mixing tube 23 is heated by heaters 31, 32, and 33 so that the temperature of the raw material gas can be freely set. As a result, it is possible to prevent the generation of powder due to a sharp rise in temperature when the mixer is introduced.

FIG. 4 shows another embodiment of the present invention. This embodiment shows a case where the mixing tube is set in the reaction furnace. The mixing tube includes an outer tube 23, a middle tube 41, and an inner tube 42, and a heater 43 is installed inside the inner tube 42. The source gas 1 is introduced between the middle tube 41 and the inner tube 42, and the source gas 2 is introduced between the outer tube 23 and the middle tube 41. Middle tube 41
And a small hole is formed in the outer tube 23,
The mixture is supplied to the reactor at 4. This makes it possible to efficiently use energy and prevent waste of raw materials due to overheating of the heater and mixing of foreign substances.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the mixing pipe 23 is extended to the inside of the reaction furnace by the pipe 51 so that the raw material is evenly distributed to the wafers 10. Further, the raw material 2 is similarly distributed by the pipe 52. As a result, an intermediate having a short life can be uniformly supplied to many wafers.

FIG. 6 shows another embodiment of the present invention. In this embodiment, a flexible tube 61 is used in the mixing section, and a driving device 62 for controlling the length of the flexible tube 61 is provided.

In this embodiment, when controlling the doping amount or performing a film forming process with a different doping amount, the residence time is controlled and the temperature is controlled by changing the pipe length of the mixing section by the driving device 62. Thus, an appropriate gas composition in the reaction furnace can be obtained. Further, by attaching the flexible pipe so as to intersect the flow path, the cross-sectional area of the flow path can be controlled.

FIG. 7 shows another embodiment of the present invention. In this embodiment, the raw material 1 is heated by a heater 72 before being introduced into the mixing tube 23. The pressure of the mixing tube is adjusted by a valve 75 to a pressure different from that of the reaction furnace. Since the pressure and the flow velocity are inversely proportional at a constant flow rate, the length of the mixing tube 23 can be reduced to 1/10 by setting the pressure to 10 times. In this way, the residence time and gas composition can be controlled with a small container. Further, the amount of film formed in the mixer is small because the surface area is small.

FIG. 8 shows another embodiment of the present invention. In this example, the raw materials 1 and 2 consist of three mixing tubes 81, 82 and 8
3 and mixed. In addition, each mixing tube has a heater.
Heated to different temperatures by 84, 85, and 86, the residence time and composition can be controlled. As described above, by using the mixing tubes having different cross-sectional areas, it is possible to control the reaction amount in the mixing tube and to control the film forming speed.

FIG. 9 shows another embodiment of the present invention. In this embodiment, the raw materials 1 and 2 are each supplied with a flow controller 91,
Mixing tubes 84, 8 by 92, 93, 94, 95, 96
5, 86. This makes it possible to control the flow rate and control the consumption of the raw material due to film formation in the mixer.

FIG. 10 shows another embodiment of the present invention. In this embodiment, the temperature, flow rate and pressure in FIGS. 8 and 9 are controlled simultaneously. This allows precise control of the gas composition.

FIG. 11 shows another embodiment of the present invention. In this embodiment, the pipe 7 is distributed to the pipes 111, 112 and 113 and connected to different positions of the mixing pipe 23. Also, the flow control devices 114, 115, 116 control the mixing amount.

FIG. 12 shows another embodiment of the present invention. In this embodiment, mixing is performed at different positions by using a multi-tube as the mixing tube 121. At this time, by controlling the flow path in the mixing tube, the mixing position can be controlled using a small mixing tube. Further, by the pressure control device 123,
The pressure is adjusted. As a result, the space can be effectively used. Further, since the cross-sectional area of the flow channel is small, precise control of the mixing position is possible.

FIG. 13 shows another embodiment of the present invention. In this embodiment, the water coolers 134 and 138 and the water cool tube examples 133 and 137 are provided at the mixing position and the position where the mixture is introduced into the reaction tube.
Is provided. Thereby, mixing of the gas at a high temperature can be avoided, and generation of foreign matter can be prevented.

FIG. 14 shows another embodiment of the present invention. In this embodiment, the residence time is controlled by using a heater of the reactor. At this time, the residence time may be controlled by winding the introduction tube around the outer wall of the reactor. As a result, there is no need to provide a heater for preheating, and energy can be saved.
Can be used effectively.

FIGS. 15 and 16 show another embodiment of the present invention. In this embodiment, a double circular nozzle 158 made of quartz and having both ends sealed is connected to the introduction pipe 24, and the raw material gas is ejected through the fine holes 164. The pressure in the nozzle 158 can be controlled by the size and number of the pores,
When the pressure is 0 sccm and the temperature is 500 ° C., the pressure can be set to 470 Pa by forming eight 1 mm diameter holes. Since the inner diameter of the double circular tube 158 is equal to or larger than the diameter of the wafer and the wafer can be transported through the inside thereof, it can be easily attached to a conventional apparatus.

FIG. 17 shows another embodiment of the present invention. In this embodiment, the position at which the pipe 8 is blown out of the reactor
5 is installed downstream from the pipe 24, and the front of the reactor is heated by the reactor heater-151. At this time, the position of the lowermost wafer and the ejection position of the nozzle 165 are aligned, and the residence time is controlled by setting the distance between the lowermost portion of the reaction furnace and the wafer. According to this embodiment, it is only necessary to change the wafer board of the conventional apparatus and to change only the installation of the nozzle, and the application of the present invention is easy.

Although only the polycrystalline silicon film has been described in the above embodiments, the present invention is not limited to the silicon nitride film using a silane-based gas (silane, disilane, dichlorosilane, etc.) and ammonia, or an organic-based film. Silica film using gas (such as tetraethoxysilane) and ozone, silica film formation using silane-based gas (such as silane, disilane, dichlorosilane) and nitrogen oxide (such as nitrous oxide and nitric oxide). It can be applied to a thin film produced from the raw material. Not only horizontal CVD equipment but also vertical C
The present invention is applicable to an apparatus for processing a plurality of wafers, such as a VD apparatus.

[0041]

According to the present invention, since various kinds of source gases can be controlled separately, the film forming speed, composition and film quality of many wafers can be controlled simultaneously. Further, in the low pressure CVD apparatus, the doping amount between wafers can be made uniform, and the productivity is improved. Further, according to another embodiment of the present invention, since the mixing tube can be easily attached without improving the conventional CVD apparatus, the application to the conventional apparatus is simple.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a CVD apparatus showing an embodiment of the present invention in which means for setting a residence time and a temperature are provided outside a reactor.

FIG. 2 is a configuration diagram of a CVD apparatus showing another embodiment of the present invention in which means for setting a residence time and a temperature are provided in a reaction furnace.

FIG. 3 is a configuration diagram of an apparatus in which a temperature in a mixing unit is set.

FIG. 4 is a configuration diagram of an apparatus for setting a temperature in a mixing unit.

FIG. 5 is a configuration diagram of an apparatus in which an introduction pipe is extended into a reaction furnace.

FIG. 6 is a configuration diagram of a CVD apparatus provided with an apparatus for changing a control region of a residence time and a temperature.

FIG. 7 is a configuration diagram of an apparatus that controls the pressure of a gas supply unit.

FIG. 8 is a configuration diagram of a device that controls a flow path and a temperature of a gas supply unit.

FIG. 9 is a configuration diagram of an apparatus in which a flow rate of a gas supply unit is set.

FIG. 10 is a configuration diagram of a device that controls a flow path, a temperature, and a pressure of a gas supply unit.

FIG. 11 is a configuration diagram of CVD showing another embodiment of the present invention for controlling a mixing position of raw materials.

FIG. 12 is a configuration diagram of CVD showing another embodiment of the present invention for controlling a mixing position of raw materials.

FIG. 13 is a configuration diagram of CVD showing another embodiment of the present invention in which a mixing position of raw materials and an introduction portion to a reaction furnace are cooled.

FIG. 14 is a configuration diagram of CVD showing another embodiment of the present invention in which the residence time is controlled using a heater of a reaction furnace.

FIG. 15 is a configuration diagram of CVD showing another embodiment of the present invention in which the residence time is controlled using a double circular tube.

FIG. 16 is a detailed explanatory diagram of FIG. 15;

FIG. 17 is a configuration diagram of CVD showing another embodiment of the present invention in which the residence time is controlled by utilizing the space in the reactor.

FIG. 18 is a view showing a calculation result of a change in concentration of a raw material and an intermediate in a reactor.

[Explanation of symbols]

1 ... PH ₃ gas cylinder, 2 ... Si ₂ H ₆ gas cylinder,
3, 4, 5 ... flow controller, 6 ... PH ₃ gas piping, 7,
8: Si ₂ H ₆ gas piping, 9: reaction furnace, 10: wafer,
11: Wafer holder, 12: Heater, 13: Vacuum exhaust device, 21: Heater, 22: Heater power supply, 23: Mixing tube,
41: middle pipe, 42: inner pipe, 43: heater, 45: heater power supply, 51, 52: introduction pipe, 61: flexible pipe, 6
2 ... Drive device for flexible pipe, 74 ... Pressure gauge, 75,
76: pressure control device, 84, 85, 86: heater, 8
7, 88, 89 ... heater power supply, 91, 92, 93, 9
4, 95, 96 ... flow rate controller, 101, 102, 103
... pressure control device, 107, 108, 109 ... pressure gauge, 1
14, 115, 116: flow control device, 121: mixing tube, 122: pressure gauge, 123: pressure control device, 133,
137: Cooling pipe, 134, 138: Cooling device, 144: Nozzle, 151, 152, 153: Heater, 154: Internal heat pipe, 155: Outer furnace pipe, 156: Wafer cover, 15
7 reactor tube, 158 nozzle, 159 cap
160: wafer boat, 161: wafer, 162: wafer support rod, 163: heat insulating plate, 164: pore, 165
… Extension nozzle, 166… Wafer boat holding rod

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Maejima 5-2-1, Josuihonmachi, Kodaira-shi, Tokyo Inside the Musashi Plant, Hitachi, Ltd. (72) Inventor Hisayuki Kato 4-6-chome, Kanda Surugadai, Chiyoda-ku, Tokyo Address Hitachi, Ltd. (72) Inventor Tokio Kato 4-6-1 Kanda Surugadai, Chiyoda-ku, Tokyo Tokyo, Japan (72) Inventor Sadao Yoneyama 5-2-1 Kamimizuhoncho, Kodaira-shi, Tokyo (56) References JP-A-63-156316 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 C23C 16/52

Claims (12)

(57) [Claims] 1. A CVD apparatus comprising: a reaction unit for forming a thin film on a substrate; a gas supply unit for supplying a reactive gas to the reaction unit; and a preheating unit for preheating a part of the reactive gas. In the above, the gas supply means is composed of two supply means, one of which is a means for supplying a reactive gas to the upstream side of the preheating means, and the other is one for supplying the reactive gas in the middle of the preheating means. A CVD apparatus. 2. The method according to claim 1, wherein said preheating means is provided in said reaction means.
VD device. 3. The CVD apparatus according to claim 1, wherein said preheating means is provided outside said reaction means. 4. The CVD apparatus according to claim 1, wherein a heater of said reaction means and a heater of said preheating means are also used. 5. The CVD apparatus according to claim 1, wherein a portion to which a reactive gas is supplied is cooled in the preheating means. 6. The CVD apparatus according to claim 1, wherein said preheating means is provided outside said reaction means and has a plurality of heat sources. 7. The CVD according to claim 6, wherein said heat source is provided in said preheating means.
apparatus. 8. A CV according to claim 6, wherein said heat source is provided outside said preheating means.
D device. 9. The CVD apparatus according to claim 1, wherein said preheating means is provided outside said reaction means and has a variable pressure mechanism. 10. A CVD apparatus comprising: a reaction means for forming a thin film on a substrate; a gas supply means for supplying a reactive gas to the reaction means; and a preheating means for preheating a part of the reactive gas. , Wherein said preheating means has a variable mechanism for changing the residence time of said reactive gas in said preheating means. 11. The CVD apparatus according to claim 10, wherein said variable mechanism is a mechanism for varying the length of said preheating means. 12. The CVD apparatus according to claim 10, wherein said variable mechanism is a mechanism for varying a sectional area of said preheating means.