JP3397467B2 - Substrate processing 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 substrate processing apparatus used for forming a thin film on the surface of a semiconductor wafer by vapor phase epitaxy.

[0002]

As is well known, there are several methods for forming a thin film on the surface of a substrate such as a semiconductor wafer. The vapor phase growth method is one of them. The vapor phase growth method uses a chemical reaction of a raw material gas at a high temperature, and has various advantages such as obtaining various kinds of films with strong adhesion strength and relatively easy film thickness control. . As a substrate processing apparatus for actually forming a thin film on the surface of a substrate, a batch type apparatus for simultaneously forming a film on the surfaces of a plurality of substrates is widely used.

However, in recent years, the diameter of semiconductor wafers, which are substrates, has increased, and it has become difficult to ensure uniformity of film formation within a wafer surface or between wafers in a batch type apparatus. For this reason, in the semiconductor element manufacturing field, there is a tendency to use a single-wafer type apparatus for forming a film on a semiconductor wafer one by one.

By the way, in the single-wafer type substrate processing apparatus, usually, a substrate holder which is driven to rotate is provided in a processing container, a rectifying plate is provided so as to face the substrate holder, and the rectifying plate is used to hold the substrate holder. The processing gas is supplied to the existing substrate and the substrate temperature is controlled.

However, the conventional substrate processing apparatus thus configured has the following problems.

That is, the processing cost when using the single wafer type substrate processing apparatus is inevitably higher than that of the batch type. Therefore, how to reduce the processing cost is an important issue. However, in the conventional single-wafer type substrate processing apparatus, the gas flowing out from the peripheral portion of the flow straightening plate is not used for processing and is wasted, which causes an increase in processing cost. Further, when the processing gas is a film forming gas, particles and the like generated in the processing container adhere to the inner wall of the processing container, causing contamination in the processing container.

Further, if the pressure during substrate processing is increased,
Although the partial pressure of the processing gas increases and the processing speed increases, vortices easily occur in the gas flow in the processing container due to the effect of thermal expansion of the gas and the rotation of the substrate as the pressure increases, and There is also a problem that the processing characteristics are adversely affected.

If the pressure during substrate processing is increased,
There is also a problem that the volumetric flow rate of the gas becomes small, the gas is not smoothly switched in the processing container at the start and the end of the processing, and the processing efficiency of the substrate deteriorates.

[0009]

As described above, in the conventional substrate processing apparatus, the use efficiency of the processing gas is poor, the processing cost is high, and the pressure during processing is increased in order to increase the processing speed. However, there is a problem in that the processing characteristics are deteriorated when the value is increased.

Therefore, the present invention can improve the utilization efficiency of the processing gas, and can exhibit good processing characteristics even when the processing conditions are changed, thereby contributing to the reduction of the processing cost. An object is to provide a substrate processing apparatus.

[0011]

To achieve the above object, the present invention provides a substrate processing apparatus for supplying a gas to a substrate held by a substrate holder in a processing container to perform a predetermined process, It is provided to face the substrate holder,
The rectifying plate in contact with the inner wall of the processing container, the processing gas supply means for flowing the processing gas toward the substrate through the central part of the rectifying plate, and the purge gas for flowing the purging gas through the peripheral part of the rectifying plate. It is characterized by comprising a supply means.

It is preferable that the portion of the flow straightening plate through which the processing gas flows is set to be substantially equal to or larger than the area of the substrate.

In the processing gas supply means and the purge gas supply means, the flow rate of the processing gas flowing out through the straightening plate and the flow rate of the purge gas are made substantially equal to each other, or the flow rate of the purge gas is set large. It is preferable that

Further, the distance between the straightening plate and the substrate is in the range of approximately 5 mm to 50 mm under the condition that the glasshoff number with respect to the substrate or the substrate holder is 1708 or more.
It is preferably set.

[0015]

The flow rate of the processing gas can be reduced as compared with the conventional case by flowing the processing gas from the central portion of the straightening plate and the purge gas from the peripheral portion, which can contribute to the reduction of the processing cost. At this time, if the flow rates of the processing gas and the purge gas are made substantially the same, the flow of the gas in the processing container is not disturbed, so that the in-plane uniformity of the substrate processing can be ensured. When the substrate is rotating and the number of rotations of the substrate is high, an imbalance occurs between the amount of gas discharged and the amount of gas supplied by the centrifugal pump action accompanying the rotation of the substrate. However, by increasing the flow rate of the purge gas, the imbalance can be compensated and the processing uniformity can be maintained.

When the processing pressure is increased, the effect of gas thermal convection becomes a problem. That is, where ρ is the gas density, g is the gravitational acceleration, α is the coefficient of thermal expansion of the gas, ΔT is the temperature difference between the gas at the inlet and the substrate surface, r is the radius of the substrate or substrate holder, and η is the gas viscosity. , Gr = ρ ² · g · α · ΔT · r ³ / η ^{2 If the} Grashof number is 1708 or more, heat convection easily occurs (edited by Chemical Society of Japan, Chemical Engineering Handbook, p. 130, Published by Maruzen Co., Ltd. on March 18, 1988).

However, even in such a case, by setting the distance between the current plate and the substrate to be about 5 mm to 50 mm,
A force in the direction opposite to the direction in which thermal convection is generated is generated by the inertial force of the gas flowing out of the straightening plate in the direction perpendicular to the substrate and the inertial force of the gas sucked by the substrate by the centrifugal pump action. It is possible to prevent the generation of vortices in the processing container. The effect of preventing the generation of vortices by bringing the straightening plate closer to the substrate is also present in the case where an imbalance occurs between the discharge flow rate due to the rotation of the substrate and the gas amount supplied to the processing container.

When the processing pressure becomes large, the gas switching becomes poor at the time of switching the processing gas, but the volume upstream of the straightening plate is V ₁ , the volume between the straightening plate and the substrate is V ₂ , and the gas When the volumetric flow rate is Q, setting V ₁ / Q and V ₂ / Q to 5 seconds or less makes it possible to handle a processing time of several tens of seconds to several minutes.

[0019]

Embodiments will be described below with reference to the drawings.

FIG. 1 is a schematic vertical sectional view of a substrate processing apparatus according to an embodiment of the present invention, which is an example applied to a single wafer type vapor phase growth apparatus.

Reference numeral 1 in the drawing denotes a processing container. Although the processing container 1 is actually composed of a combination of several parts, it is shown here to be integrally formed for simplification of the drawing.

A processing chamber 2 is formed above the inside of the processing container 1, and a housing space 3 for housing a magnetic bearing 34 and a motor 35 as a rotary drive mechanism, which will be described later, is formed below the processing chamber 2.

The upper wall 11 of the processing chamber 2 is formed of a transparent member such as a quartz plate. Then, a radiation thermometer or the like (not shown) is arranged above the upper wall 11. Upper wall 11 in processing chamber 2
A rectifying plate 12 formed of a heat-resistant transparent member such as quartz is arranged at a position facing to.

An annular partition plate 13 is arranged on the peripheral portion of the upper surface of the flow regulating plate 12, and the partition plate 13 divides the flow regulating plate 12 into a source gas supply chamber 14 and a purge gas supply chamber 15. The source gas supply chamber 14 is selectively connected to a source gas supply source (not shown) via a source gas introduction port 16, and the purge gas supply chamber 15 is selectively connected to a purge gas source (not shown) via a purge gas introduction port 17. Connected to.

At the upper position on the side wall of the processing chamber 2, there is provided a carry-in port 18 for taking in and out a substrate S to be processed which will be described later. The carry-in port 18 is closed by a valve (not shown) except during the period when the substrate S to be processed is taken in and out. Further, exhaust ports 19 for discharging the raw material gas and the purge gas that have passed through the inside of the processing chamber 2 are formed at a lower position on the side wall of the processing chamber 2 at a plurality of positions in the circumferential direction. These exhaust ports 19 are connected to an exhaust system (not shown).

A substrate holder 20 for holding the substrate S to be processed is arranged at a position above the center of the processing chamber 2. The substrate holder 20 is made of a carbon-based material that withstands a high temperature atmosphere and a corrosive atmosphere and generates little gas. In this example, the substrate holder 2
Reference numeral 0 denotes a substrate holder main body 21, a shaft portion 22 extending downward from a central portion of a lower surface of the main body 21 in a tubular shape by a predetermined length,
A flange portion 23 formed integrally with the lower end of the shaft portion 22
It is formed by. Then, the flange portion 23 is screw 2
It is connected to the upper end portion of the rotary shaft 25 via 4.

Here, the relationship between the current plate 12 and the substrate holder 20, the relationship between the source gas supply source and the purge gas supply source, the volume of the source gas supply chamber 14, that is, the volume of the gas space in the source gas supply chamber 14, and The relationship between the volume and the exhaust system between the current plate 12 and the substrate S to be processed will be described.

As described above, the presence of the partition plate 13 causes the raw material gas A to flow from the so-called central portion of the straightening plate 12.
Is introduced into the reaction chamber 2, and the purge gas B is introduced into the reaction chamber 2 from the peripheral portion. The central portion of the rectifying plate 12 faces the substrate holder body 21, and the diameter L thereof is set to be substantially equal to or slightly larger than the diameter of the substrate S to be processed held by the substrate holder body 21. . Further, the distance between the rectifying plate 12 and the substrate holder main body 21 is 5 mm when the distance between the rectifying plate 12 and the substrate S to be processed is 5 mm in a state where the target substrate S is held by the substrate holder main body 21. It is set to be 50 mm. In this example, it is set to 10 mm. In addition, the source gas supply source and the purge gas supply source make the flow velocity of the source gas A flowing out through the central portion of the flow straightening plate 12 and the flow velocity of the purge gas B flowing out through the peripheral portion of the flow straightening plate 12 substantially equal to each other, or The supply amounts of both gases can be adjusted so that the flow velocity of B is slightly increased. Further, the raw material gas supply chamber 1
4, the volume of the gas space in the raw material gas supply chamber 14 is V ₁ , and the volume between the current plate 12 and the substrate S to be processed is V ₁ .
_{2. When} the volumetric flow rate of the gas under the influence of the exhaust system is Q, the relationship between the above respective parts is set so that V ₁ / Q and V ₂ / Q are 5 seconds or less.

The rotary shaft 25 is formed of stainless steel or the like, and is actually composed of a combination of several parts, but here it is integrally formed for the sake of simplification of the drawing. As shown. Rotating shaft 25
Is hollow, and a hollow large-diameter portion 26 is formed in a connecting portion with the flange portion 23. The lower end of the rotary shaft 25 is inserted into the accommodation space 3.

A heat shield cylinder 27 is arranged around the substrate holder 20, and the heat shield cylinder 27 is fixed to the side wall of the processing chamber 2 via a support member 28. An electric heater 29 serving as a heating source is arranged below the substrate holder 20 in close proximity to the substrate holder 20. This electric heater 2
9 is fixed to the side wall of the processing chamber 2 by a support member 30 which also serves as a power feeding path, and the power feeding line is guided outside the processing chamber 2 in an insulated state. Further, a heat shield plate 31 is arranged between the electric heater 29 and the flange portion 23. Further, around the hollow large diameter portion 26 formed on the rotating shaft 25, a minute gap is provided between the hollow large diameter portion 26 and the hollow large diameter portion 26 so that the cooling liquid flow path 32 is provided.
Are opposed to each other. Cooling water is introduced into the cooling liquid flow path 32 through an unillustrated inlet and is discharged through an outlet 33.

On the other hand, in the housing space 3, a rotational force is applied to the rotary shaft 25 in a non-contact manner with respect to the magnetic bearing 34 which realizes a non-contact bearing of the rotary shaft 25 with the elements provided on the rotary shaft 25. The motor 35 is arranged. The magnetic bearing 34 is
The radial bearings 36 and 37 and the thrust bearing 38 are of a 5-axis control type and are controlled by a known method.

On the lower wall of the accommodation space 3, a purge gas inlet 4 for flowing an inert purge gas into the accommodation space 3 so as to push out the process gas which tries to enter the accommodation space 3.
0 is formed.

In FIG. 1, reference numeral 41 is inserted into the rotary shaft 25 and the shaft portion 22 of the substrate holder 20 so as to be inserted in the vicinity of the base end of the shaft portion 22 so as to be in non-contact with them. The thermocouple used for the temperature measurement of the substrate S) is shown 42,
Reference numeral 43 denotes a touchdown bearing that temporarily supports the rotating portion while the magnetic bearing 34 is not operating.

An example of use of the substrate processing apparatus having the above-mentioned structure, in which a semiconductor wafer is used as the substrate S to be processed,
The case of growing a silicon thin film on this semiconductor wafer will be described.

First, the magnetic bearing 34 is operated to support the rotating portion in a completely non-contact manner. Next, the purge gas inlet 40
The purging gas is continuously caused to flow from the housing space 3 to the accommodation space 3, and then the cooling water is continuously caused to flow to the cooling liquid passage 32. Next, the motor 3
5 is driven to rotate the substrate holder 20 (substrate S to be processed) at a predetermined rotation speed, and then the electric heater 29 is energized to control the substrate holder 20 (substrate S to be processed) to a predetermined temperature. The temperature is measured by a thermocouple 41 or a radiation thermometer (not shown). Further, in the case of this example, the substrate S to be processed can be rotated up to 10,000 rpm.

In this state, a raw material gas A in which, for example, silane as a raw material and hydrogen as a carrier gas are mixed from the raw material gas supply chamber 14 through the central portion of the straightening plate 12 so that the pressure in the processing chamber 2 becomes a predetermined value. And the purge gas B consisting of hydrogen is caused to flow out from the purge gas supply chamber 15 through the peripheral portion of the straightening plate 12 to start the film growth.

As described above, since the raw material gas A is made to flow from the central portion of the straightening plate 12 and the purge gas B is made to flow from the peripheral portion thereof, the region where the raw material gas A flows is restricted to the surface region of the substrate S to be processed. Therefore, the utilization efficiency of the raw material gas can be improved. Therefore, the flow rate of the source gas can be reduced as compared with the conventional case, which can contribute to the reduction of the processing cost.

In this embodiment, the diameter of the substrate holder 20 for holding the 8-inch substrate S to be processed is 260 mm, and the inner diameter of the processing chamber 2 is 340 mm. When the source gas A is supplied only to the diameter of the substrate holder, compared with the case where the source gas is supplied over the entire inner diameter of the processing chamber 2, the source gas is supplied to the entire surface with 58% of the source gas. It is possible to obtain the same film forming rate and uniform film thickness.

When the flow rate of the source gas A and the flow rate of the purge gas B are substantially equal to each other, the gas flow in the processing chamber 2 is not disturbed, so that the in-plane uniformity of the substrate processing is not impaired. When the rotation speed of the substrate S to be processed is large, an imbalance may occur between the amount of gas discharged and the amount of gas supplied by the centrifugal pump action accompanying the rotation of the substrate S to be processed. In this case, by increasing the flow rate of the purge gas B, the imbalance can be compensated and the uniformity of the processing can be maintained.
In addition, since the purge gas B flows near the inner wall surface of the processing chamber 2, it is possible to prevent particles and the like generated in the processing chamber 2 from adhering to the inner wall surface, and prevent contamination of the processing chamber 2. it can.

Further, since the distance between the straightening plate 12 and the substrate S to be processed is set to 5 mm to 50 mm, the discharge flow rate supplied by the centrifugal pump action accompanying the rotation of the substrate S to be processed is supplied. Even under severe film forming conditions in which the flow rate of the raw material gas A does not match or film forming conditions with a high pressure that are easily affected by thermal convection, uniformity of film formation can be ensured.

That is, in FIG. 5, when the diameter of the substrate to be processed is 6 inches, the distance between the rectifying plate 12 and the substrate S to be processed is set to 250 mm, and under the conditions shown in the upper right of the drawing. The results of investigating the relationship between the film formation rate when the film is formed and the position on the substrate are shown. As can be seen from this figure, when the distance between the rectifying plate 12 and the substrate S to be processed is set to 250 mm, uniformity of the film forming rate can be obtained under the predetermined film forming condition, but the condition is slightly below the optimum value. If it deviates to, it becomes impossible to maintain the uniformity of the film formation rate.

FIG. 2 shows the relationship between the film forming speed and the position on the substrate when the distance between the straightening plate 12 and the substrate S to be processed is set to 30 mm and the film forming conditions (pressure) are changed greatly. The results of the examination of are shown. As can be seen from this figure, when the distance between the rectifying plate 12 and the substrate S to be processed is set to 30 mm, the film forming rate is uniform even under the film forming conditions, specifically, the condition that the pressure that is susceptible to thermal convection is high. You can maintain sex.

Further, in FIG. 3, the film forming conditions are kept constant, and the distance between the current plate 12 and the substrate S to be processed is 3 mm, 30 mm, 6 mm.
The results of investigating the relationship between the film formation rate and the position on the substrate when set to 0 mm are shown. As you can see from this figure,
When the distance between the straightening plate 12 and the substrate S to be processed is set to 30 mm, the film forming rate is uniform, but when the distance is 3 mm and 60 mm, the film forming rate is not uniform.
This is presumed as follows. That is, when the distance between the straightening vane 12 and the substrate S to be processed is 3 mm, the distance is short, so that the holes (blowout holes) of the straightening vane 12 are greatly affected and the uniformity deteriorates. Be done. In addition, the current plate 12
When the distance between the substrate and the substrate S to be processed is 60 mm, it is considered that it becomes non-uniform due to the influence of imbalance of rotation and thermal convection. When the distance between the rectifying plate 12 and the substrate S to be processed was 5 mm to 50 mm, the film formation result was the same as when the distance was 30 mm.

On the other hand, FIG. 4 is a diagram visually showing a simulation result of thermal convection generated between the current plate 12 and the substrate S to be processed when a certain pressure is atmospheric pressure. The figure (a) shows the case where the distance between the current plate 12 and the substrate S to be processed is 250 mm, and the figure (b) shows the case where it is 10 mm. The Grashof number in the simulation is hydrogen gas at atmospheric pressure, the inlet temperature is 25 ° C,
Since the substrate temperature is 1025 ℃ and the substrate holder diameter is 260mm, it is about 70
00.

As can be seen from this figure, when the distance is 250 mm, a plurality of vortices are generated in the processing container due to the gas supply amount being smaller than the discharge flow rate and the effect of thermal convection. When the distance is 10 mm, no vortex is generated. When the distance is 10 mm, no vortex is generated although the amount of discharge gas flowing out from the substrate S to be processed by the centrifugal pump action is larger than the amount of supply gas. This is because the flow of gas flowing out of the straightening vane is perpendicular to the substrate, so when the distance between the substrate and the straightening vane is short, this flow suppresses the force that tends to generate vortices. This is because Also,
When the substrate is rotating, the gas on the substrate is sucked in the direction of the substrate by the pump effect, and the effect of suppressing the force that thermal convection is about to occur is also produced.

From the above measurement results, if the distance between the rectifying plate 12 and the substrate S to be processed is set to 5 mm to 50 mm, it is possible to obtain a uniform film forming speed even when the film forming conditions are changed. I understand. In particular, even under the condition that the thermal convection is likely to occur when the Grashof number is 1708 or more, by setting the distance between the straightening plate 12 and the substrate S to be processed to 5 mm to 50 mm, the gas is rotated by the inertial force of the gas flowing out from the substrate. It is possible to prevent the generation of vortices due to the imbalance of the substrate, and to suppress the generation of vortices due to thermal convection due to the addition of the gas suction effect due to the rotation of the substrate.

Further, in the apparatus according to this embodiment, the current plate 1
2 between the volume V ₁ on the upstream side, the volume V ₂ between the straightening plate 12 and the substrate, and the volume flow rate Q of the gas, V ₁ / Q and V
_{Since the} ratio ₂ / Q is 5 seconds or less, the time required to switch the source gas can be shortened, and a short processing time of several tens of seconds to several minutes can be dealt with. That is, in the case where the gas switching time takes several tens of seconds for a process in which the actual processing time is several tens of seconds, the throughput of the apparatus is lowered due to the gas switching, The cost increases. However, if the gas switching time is a few seconds, it will hardly affect the actual processing time of the substrate including the temperature raising / lowering of the substrate, the raising / lowering rotation, the transfer of the substrate, etc.
The through top does not decrease. In this embodiment, V ₁ = V ₂
= 1.6 (liter) and Q = 30 (liter / min)
Therefore, when the pressure is atmospheric pressure, V ₁ / Q = V ₂ / Q
= 3.2 seconds. The time required for film formation is about 60 seconds, and the time required for gas switching has little effect on the overall process time. When the pressure is lowered, the volume flow rate is increased, but the partial pressure of the raw material gas is lowered, so that the film forming rate is lowered. If the flow rate is increased too much, the gas utilization efficiency will deteriorate and the processing cost will increase.

The present invention is not limited to the above embodiment. Although the magnetic bearings are used in the above-mentioned embodiments, the present invention is not limited to this.

[0049]

As described above, according to the present invention,
It is possible to improve the utilization efficiency of the processing gas, and moreover, it is possible to exhibit good processing characteristics even when the processing conditions are changed, which contributes to the reduction of the processing cost.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a substrate processing apparatus according to an embodiment of the present invention.

[Figure 2] Set the distance between the current plate and the board to 30 mm,
Diagram showing the relationship between the film forming speed and the position on the substrate when the film forming condition (pressure) is changed

FIG. 3 is a diagram showing the relationship between the film formation rate and the position on the substrate when the distance between the current plate and the substrate is set to 3 mm, 30 mm, and 60 mm while keeping the film formation conditions constant.

FIG. 4 is a diagram visually showing a simulation result of a gas flow in a processing chamber due to a difference in distance between a current plate and a substrate. (A) is a case of 250 mm and (b) is a case of 10 mm.

FIG. 5 is a diagram showing a relationship between a film forming rate and a position on the substrate when the distance between the current plate and the substrate is set to 250 mm and the film forming conditions are changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing container 2 ... Processing chamber 12 ... Straightening plate 13 ... Partition plate 14 ... Raw material gas supply chamber 15 ... Purge gas supply chamber 19 ... Exhaust port 20 ... Substrate holder 34 ... Magnetic bearing A ... Raw material gas B ... Purge gas S ... Processing target substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-132769 (JP, A) JP-A-5-166734 (JP, A) JP-A-5-218002 (JP, A) JP-A-8- 31758 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 C23C 16/455 C30B 25/14 H01L 21/31

Claims (4)

(57) [Claims] 1. A substrate processing apparatus for supplying a gas to a substrate held in a substrate holder in a processing container to perform a predetermined process, the substrate processing device being provided so as to face the substrate holder.
A straightening plate in contact with the inner wall of the processing container, a processing gas supply means for flowing a processing gas toward the substrate through a central portion of the straightening plate, and a purge gas supply for flowing a purging gas through a peripheral portion of the straightening plate. And a substrate processing apparatus. 2. A portion of the flow straightening plate through which the processing gas flows is set to be substantially equal to or larger than the area of the substrate. Substrate processing equipment. 3. The processing gas supply means and the purge gas supply means make the flow rates of the processing gas and the purge gas flowing out through the straightening plate substantially equal to each other, or set the purge gas flow rate to a large value. The substrate processing apparatus according to claim 1, wherein: 4. The distance between the straightening plate and the substrate is set within a range of approximately 5 mm to 50 mm under the condition that the number of Grasshoffs with respect to the substrate or the substrate holder is 1708 or more. The substrate processing apparatus according to claim 1 .