JPH11238727A - Plasma cvd system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the rate of operation, and reduce the man-hours required for maintenance work by providing a section for reinforcing the field of high frequency voltage discharge action on the surface of an electrode substrate for mounting a substrate to be processed contiguously on the outer fringe thereof. SOLUTION: This plasma CVD system comprises an electrode substrate (susceptor) for mounting a substrate to be processed, while serving as one electrode for generating plasma through capacity coupling. A disc-like susceptor 30 is provided with a central fixing hole 21. A plurality of small hole groups, each comprising a set of three small holes 23a, 23b and 23c, are provided on the periphery of the susceptor 30 in the region 22 for mounting a semiconductor wafer, for example. A section for enhancing the field of high frequency voltage discharge action, e.g. a groove 31 in the surface of the susceptor 30, is provided in a region which is contiguous to the outer fringe of the mounting region 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD apparatus, and more particularly, to a plasma CVD apparatus having a structure of an electrode substrate on which a substrate to be processed is mounted and which is one electrode for generating plasma in a capacitive coupling type. Related to the device.

[0002]

2. Description of the Related Art In recent years, as a film forming apparatus for forming a conductor film, an insulating film, a polysilicon film, etc. in a semiconductor device manufacturing process,
A plasma CVD apparatus is frequently used. This plasma C
The VD apparatus has a capacitively coupled plasma CV due to a difference in power supply method for generating a plasma of a reaction gas.
There are D equipment, inductively coupled plasma CVD equipment, microwave plasma CVD equipment, ECR plasma CVD equipment, etc., and plasma CVD aimed at improving film quality and film thickness uniformity, film formation speed, etc. on the surface of a semiconductor wafer. The device is being studied.

Here, a conventional capacitively coupled plasma CV
An example of a parallel plate type plasma CVD apparatus which is one of apparatuses D will be described with reference to FIGS. First, as shown in FIG. 5, a parallel plate type plasma CVD apparatus 1 includes a reaction chamber 2 which is a processing container, a wafer substrate (susceptor) 3 on which a semiconductor wafer 10 in the reaction chamber 2 is mounted, and a reaction chamber 2. Is disposed facing the susceptor 3 in the
An upper electrode 4 to which a high-frequency electrode 5 for converting the reaction gas into plasma is connected, a gas pipe 6 for feeding the reaction gas into the reaction chamber 2, an exhaust pipe 7 for exhausting the reaction gas and the like in the reaction chamber 2, and the like. It is schematically configured.

The susceptor 3 has a disk shape. A plurality of semiconductor wafers 10 are mounted on a peripheral portion of the disk shape, and the susceptor 3 is rotated by a rotating shaft 8 connected to a driving unit such as a motor. It has become. The susceptor 3 is grounded and serves as a lower electrode corresponding to the upper electrode 4. A heater 9 for heating the semiconductor wafer 10 by radiant heat is provided inside the upper electrode 4.
On the side wall of the gas pipe 6 in the reaction chamber 2, a plurality of small holes 6 a for ejecting the reaction gas into the reaction chamber 2 are provided, and the reaction gas is ejected toward the center of the susceptor 3 in parallel with the susceptor 3. It is supposed to.

Next, the detailed structure of the disc-shaped susceptor 3 will be described.
This will be described with reference to FIGS. Here, FIG.
FIG. 6A is a schematic plan view of the susceptor 3, and FIG.
FIG. 7A is a schematic cross-sectional view of the AA part, and FIG. 7 is an enlarged view of the P part of FIG. 6B, in which the semiconductor wafer 10 is mounted on the susceptor 3. As shown in FIG. 6, the susceptor 3 has a disk shape, and a hole 21 for attaching the susceptor 3 to the rotating shaft 8 is formed in the center of the disk-shaped susceptor 3.
Is provided around the susceptor 3, and a plurality of small hole groups provided as a set of three small holes 23 a, 23 b, and 23 c provided in the mounting area 22 on which the plurality of semiconductor wafers 10 are mounted. Is provided.

The above-described set of small holes 23a, 23b, 23
c, when placing the semiconductor wafer 10 on the susceptor 3,
These are small holes into which push-up pins (not shown) of the semiconductor wafer 10 arranged below the susceptor 3 shown in FIG. 5 are inserted. When the semiconductor wafer 10 is sent to the susceptor 3 by a wafer handler or the like, the push-up pins receive the semiconductor wafer 10 at the tips of the push-up pins projecting upward from the surface of the susceptor 3, and the push-up pins descend in that state. The semiconductor wafer 10 is placed at a predetermined position on the susceptor 3, or the semiconductor wafer 10 is lifted above the surface of the susceptor 3 after the film forming process is completed, and the semiconductor wafer 10 is transferred to a wafer handler. The mounting area 22 of the semiconductor wafer 10 described above is an area determined by the position of the semiconductor wafer 10 transferred above the push-up pins by the wafer handler.

[0007] By operations such as movement of the wafer handler, the push-up pins, and the susceptor 3 in the rotational direction, the semiconductor wafer 10 is successively formed in a plurality of mounting areas 22 on the surface of the susceptor 3 in which the small holes 23a, 23b, and 23c are set. Is placed.
FIG. 7 is an enlarged view of a portion P in FIG. 6B in a state where the semiconductor wafer 10 is mounted on the mounting area 22 on the susceptor 3.

Next, the above-mentioned parallel plate type plasma CVD
An operation of forming an insulating film or the like using the apparatus 1 will be described.
First, a plurality of semiconductor wafers 10 are mounted on the mounting area 22 around the susceptor 3, and then the inside of the reaction chamber 2 is evacuated by an exhaust system connected to the exhaust pipe 7. Thereafter, while the susceptor 3 is rotated by the driving unit, the upper electrode 4
The semiconductor wafer 10 is heated to a predetermined temperature by the heater 9 described above. Thereafter, a reaction gas for forming an insulating film and the like in the reaction chamber 2 from the gas pipe 6, for example, when the insulating film to be formed is an SiN film, a mixed gas of SiH ₄ gas and NH ₃ gas is reacted. After being introduced into the chamber 2 and setting the pressure of the reaction gas in the reaction chamber 2 to a predetermined pressure, the power of the high-frequency power supply is turned on to generate plasma in the reaction chamber 2 and the SiN film on the semiconductor wafer 10. Is deposited. When the thickness of the SiN film reaches a predetermined thickness, the power of the high-frequency power supply is turned off to extinguish the plasma, the introduction of the reaction gas is stopped, and the reaction gas in the reaction chamber 2 is exhausted. Thereafter, N ₂ gas or the like is introduced into the reaction chamber 2, the pressure in the reaction chamber 2 is set to the atmospheric pressure, and then the semiconductor wafer 10 on the susceptor 3 is taken out.

The above-mentioned parallel plate type plasma CVD apparatus 1
As a result, the SiN film deposited on the semiconductor wafer 10 initially has a substantially uniform thickness within the surface of the semiconductor wafer 10. However, if the above-described plasma CVD operation of the SiN film is repeatedly performed, The uniformity of the film thickness of the SiN film becomes worse, and as shown in FIG.
From the center toward the periphery. If the film thickness distribution of the SiN film becomes non-uniform in this way, there is a possibility that the characteristics of a semiconductor device manufactured using this SiN film will vary greatly. Therefore, before the non-uniformity of the film thickness becomes large, the plasma C
Stop the repetitive operation of VD, and place the mounting area 2 on the susceptor 3.
Thick Si accumulated by repeated deposition outside
The maintenance work of the susceptor 3 for removing the N film by mechanical cleaning is performed. The frequency of this maintenance work is high, for example, it is necessary to perform it about once every eight plasma CVD operations, which causes a problem that the operation rate of the parallel plate type plasma CVD apparatus 1 is reduced and the number of operation steps is increased. .

[0010]

In the conventional parallel plate type plasma CVD apparatus described above, the uniformity of the thickness of the SiN film deposited on the semiconductor wafer within the semiconductor wafer surface is deteriorated as the number of plasma CVD operations is increased. There is a problem,
In order to avoid this problem, it is necessary to frequently perform a maintenance work on the susceptor, which is to mechanically clean and remove a thick SiN film accumulated by being repeatedly deposited outside the mounting area on the susceptor. CVD
There has been a problem that the operation rate of the device is reduced and the number of man-hours is increased. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma CVD apparatus having a high operation rate and a small number of maintenance work steps.

[0011]

Means for Solving the Problems Plasma CVD of the present invention
The apparatus is proposed in order to solve the above-mentioned problem, and has a plasma C having an electrode substrate on which a substrate to be processed is mounted and which is also one electrode for generating plasma in a capacitive coupling type.
In the VD apparatus, the mounting surface of the substrate to be processed of the electrode substrate is
An electric field enhancing portion is provided adjacent to the outer edge of the mounting area of the substrate to be processed, for enhancing the electric field of the discharging action by the high frequency voltage.

According to the present invention, the groove or the protrusion for enhancing the electric field of the discharge action by the high-frequency voltage is provided on the mounting surface of the electrode substrate on which the substrate is to be processed, adjacent to the outer edge of the mounting area of the substrate to be processed. Since the electric field above the electric field enhancement part is strengthened and the discharge action is increased by providing the electric field enhancement part by this, this effect is increased due to an increase in the number of film forming operations, which is accumulated outside the mounting area of the substrate to be processed. The deposited film serves to compensate for the decrease in the discharge effect due to the decrease in the electric field outside the mounting area of the substrate to be processed, and to improve the uniformity of the film thickness within the surface of the substrate to be processed even after a large number of film forming operations. Can last. Therefore, in order to maintain the film thickness uniformity of the film formed on the surface of the substrate to be processed, the maintenance work of the electrode substrate for removing the thick deposited film accumulated on the electrode substrate by mechanical cleaning is performed as frequently as the conventional one. This eliminates the need, improves the operation rate of the plasma CVD apparatus, and can significantly reduce the number of maintenance work steps.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. The same components as those in FIGS. 5 to 7 referred to in the description of the related art are denoted by the same reference numerals.

Embodiment 1 This embodiment is an example in which the present invention is applied to a parallel plate type plasma CVD apparatus which is one of capacitively coupled plasma CVD apparatuses, and this is used in the description of the prior art. This will be described with reference to FIG. 5, FIG. 1 and FIG. First, the basic configuration of the plasma CVD apparatus of the present invention is the same as that of the conventional plasma CVD apparatus 1 shown in FIG. And an electrode substrate (susceptor) which also serves as one electrode for generating plasma in a capacitive coupling type will be described in detail.

The structure of the susceptor 30 is shown, for example, in FIG.
1 is a schematic plan view of the susceptor 30 shown in FIG.
As shown in FIG. 1B, which is a schematic cross-sectional view of a portion B, the susceptor 30 has a disk shape. In the peripheral portion of the susceptor 30, three small holes 23a provided in a mounting area 22 for mounting a plurality of substrates to be processed, for example, the semiconductor wafer 10,
A plurality of small hole groups each including 23b and 23c are provided. In a region adjacent to the outer edge of the mounting region 22, an electric field enhancing portion for enhancing an electric field of a discharge action by a high frequency voltage, for example, a groove 31 formed on the surface of the susceptor 30 is provided.

Next, the groove 31 and the semiconductor wafer 1
The positional relationship with 0 will be described with reference to FIG. here,
FIG. 2 is an enlarged view of a portion Q in FIG. 1B in a state where the semiconductor wafer 10 is mounted on the susceptor 30. The semiconductor wafer 10 is mounted on the mounting area 22 on the surface of the susceptor 30 by the operation of the wafer handler and the push-up pins provided corresponding to the three small holes 23a, 23b, 23c, as in the conventional example. You. A groove 31 is provided along the outer edge of the mounting area 22 of the semiconductor wafer 10. The groove 31 in the case of a circular substrate to be processed such as the semiconductor wafer 10 has a circular structure located outside the mounting region 22 of the circular semiconductor wafer 10 as shown in FIG. Becomes

As shown in FIG. 2, for example, when the size of the semiconductor wafer 10 is 5 inches in diameter, the width W of the groove 31 is about 10 mm and the depth D of the groove 31 is about 5 mm. The diameter of the circular groove 31 viewed from the upper surface is a diameter at which the distance L between the circular outer edge of the 5-inch diameter semiconductor wafer 10 and the inner side wall of the groove 31 is about 1 mm.

Next, the operation of the plasma CVD apparatus using the susceptor 30 will be described. First, in the same manner as in the conventional example, a plurality of semiconductor wafers 10 are mounted on the mounting area 22 of the plurality of semiconductor wafers 10 of the susceptor 30, and then the reaction chamber 2 is connected to the exhaust pipe 7 by an exhaust system.
Vacuum the inside. Thereafter, the semiconductor wafer 10 is heated to a predetermined temperature by the heater 9 of the upper electrode 4 while rotating the susceptor 30 by the driving unit. Then, the gas piping 6
A reaction gas for forming an insulating film or the like in the reaction chamber 2, for example, when the insulating film to be formed is an SiN film, S
Reaction gas mixture of iH ₄ gas and NH ₃ gas
After the pressure of the reaction gas in the reaction chamber 2 is set to a predetermined pressure, the power of the high-frequency power supply is turned on to generate plasma in the reaction chamber 2 and the semiconductor wafer 1.
The deposition of the SiN film on the substrate 0 is started. When the thickness of the SiN film reaches a predetermined thickness, the power of the high frequency power supply is turned off.
To extinguish the plasma, stop introducing the reaction gas,
The reaction gas in the reaction chamber 2 is exhausted. Thereafter, an N ₂ gas or the like is introduced into the reaction chamber 2 to set the pressure in the reaction chamber 2 to atmospheric pressure, and then the semiconductor wafer 10 on the susceptor 30 is taken out.

The above-described susceptor 30, that is, the mounting area 22
In the plasma CVD apparatus using the susceptor 30 provided with the groove 31 adjacent to the outer edge, a voltage is applied from a high frequency power supply to a mixed gas of a reaction gas, ie, a SiH ₄ gas and an NH ₃ gas, in the reaction chamber 2. To generate a plasma between the upper electrode 4 and the susceptor 30,
When the SiN film is deposited on the semiconductor wafer 10, a portion having a high plasma density is generated as shown in FIG. 3, that is, above the groove 31 provided outside the semiconductor wafer 10.
This is because the electric field in the corners 31a and 31b above the groove 31 is increased by providing the groove 31 on the surface of the flat susceptor 30, and the discharge action in this portion is increased.

By generating a high-density plasma above the groove 31 outside the semiconductor wafer 10, even if the plasma CVD operation of the SiN film is repeated, the film thickness distribution of the conventional SiN film shown in FIG. That is, a film thickness distribution in which the film thickness decreases from the center to the periphery of the semiconductor wafer 10 is less likely to occur. The reason for this is that when the operation of depositing the SiN film by the plasma CVD apparatus is repeated, the semiconductor wafer 1
0 on the surface of the susceptor 30 outside the mounting area where the
By repeating the operation of depositing the iN film, the insulating film Si
The N film is deposited thickly, and in the conventional susceptor 30, the thick SiN film weakens the electric field in this region, reduces the discharge action, and reduces the plasma density. Thus, the electric field for compensating the above-mentioned plasma density decreasing effect is generated by the corners 31 a above the groove 31,
It is inferred that this is caused by the occurrence in the portion 31b.

The plasma C using the susceptor 30 described above
The VD apparatus performs a film forming operation of a SiN film while maintaining flatness,
Since it can be repeated many times as compared with the related art, the frequency of the maintenance work of the susceptor 30 can be reduced, and the operation rate of the plasma CVD apparatus can be improved and the number of maintenance work can be significantly reduced.

Embodiment 2 This embodiment is an example in which the present invention is applied to a parallel plate type plasma CVD apparatus which is one of the capacitively coupled plasma CVD apparatuses, and is used in the description of the prior art. This will be described with reference to FIGS. Since the basic structure of the plasma CVD apparatus of the present invention is the same as that of the conventional plasma CVD apparatus 1 shown in FIG. 5, the description of the same parts will be omitted, and the structure of the susceptor which is a feature of the present invention will be described in detail.

The susceptor 40 of the present invention is a susceptor in which the shape of the electric field enhancing portion is different from that of the first embodiment, and mounts the semiconductor wafer 10 corresponding to the Q portion in FIG. 1B of the first embodiment. The vicinity of the mounting area is as shown in the schematic sectional view of FIG. That is, on the surface of the susceptor 40 outside the outer edge of the mounting area where the semiconductor wafer 10 is mounted, the electric field enhancer for enhancing the electric field of the discharge action by the high frequency voltage, for example, passes through the center of the mounting area of the semiconductor wafer 10. A projection 41 having a circular cross section in a plane is provided.

The structure of the above-described projection 41 is, for example, when the size of the semiconductor wafer 10 is 5 inches in diameter, as shown in FIG.
As shown in the figure, an arc having a radius R of about 6 mm protrudes about 3 mm from the surface of the flat susceptor 40, and the diameter of the circular protrusion 41 seen from the upper surface is set to 5 inches. The distance L between the circular outer edge of the wafer 10 and the inner end of the projection 41 is set to a diameter of about 1 mm.

In the above-described plasma CVD apparatus using the susceptor 40, that is, the susceptor 40 provided with the projection 41 as the electric field enhancing portion, the reaction gas in the reaction chamber 2 is made of the SiH ₄ gas and the NH ₃ gas. When a plasma is generated between the upper electrode 4 and the susceptor 40 by applying power from a high frequency power supply to the mixed gas to deposit a SiN film on the semiconductor wafer 10, the same as that shown in FIG. A portion having a high plasma density is generated above the plasma density distribution, that is, above the protrusion 41 provided outside the semiconductor wafer 10. This is because when the above-described protrusion 41 is provided on the flat susceptor 40 surface, the electric field above the protrusion 41 increases, and the discharge action in this portion increases.

Projection 41 outside semiconductor wafer 10
By generating a high-density plasma on the upper side, even if the plasma CVD operation of the SiN film is repeated as in the first embodiment, the film thickness distribution of the conventional example shown in FIG. A film thickness distribution such that the film thickness decreases toward the periphery hardly occurs.

Therefore, the plasma CVD apparatus using the susceptor 40 can repeat the operation of forming the SiN film while maintaining the flatness many times more than in the prior art, as in the first embodiment. It is possible to reduce the frequency of the maintenance work of 40, improve the operation rate of the plasma CVD apparatus, and significantly reduce the number of maintenance work steps.

Although the present invention has been described with reference to the two embodiments, the present invention is not limited to these embodiments. For example, in the embodiments of the present invention, the present invention has been described with a so-called batch-type parallel plate type plasma CVD apparatus in which films are formed on a large number of semiconductor wafers at the same time. The present invention may be applied to a so-called single-wafer parallel plate type plasma CVD apparatus. In the embodiment of the present invention, the capacitively coupled plasma CVD apparatus is described as a parallel plate plasma CVD apparatus. However, the present invention is applied to a multipolar quartz tube plasma CVD apparatus, a coaxial cylindrical plasma CVD apparatus, and the like. Is also good.

Further, in the first embodiment of the present invention, the cross section of the electric field enhancing portion provided outside the semiconductor wafer mounting area of the susceptor is described as a rectangular groove, but the cross section is semicircular or triangular. It may be a groove part which becomes the same. Further, in the second embodiment of the present invention, the cross section of the electric field enhancing portion provided outside the mounting region of the semiconductor wafer of the susceptor has been described as an arc-shaped projection, but the cross section has a triangular shape, a rectangular shape, or the like. It may be a projection.

[0030]

As is apparent from the above description, in the capacitively coupled plasma CVD apparatus of the present invention, an electrode substrate (susceptor) on which a substrate to be processed is placed and which serves as one electrode to which high-frequency power is applied. On the surface, adjacent to the outer edge of the mounting area of the substrate to be processed, to enhance the electric field of the discharge action by the high-frequency voltage, by providing an electric field enhancing portion by a groove or a protrusion,
Since the electric field above the electric field enhancement part is strengthened and the discharge action is increased, this effect is caused by a thick deposited film accumulated outside the mounting area of the target substrate due to an increase in the number of film forming operations. It works so as to compensate for the decrease in the discharge action due to the decrease in the electric field outside the mounting region, and can maintain the uniformity of the film thickness in the surface of the substrate to be processed even after a number of film forming operations. Therefore, in order to maintain the film thickness uniformity of the film formed on the surface of the substrate to be processed, the maintenance work of the electrode substrate for removing the thick deposited film accumulated on the electrode substrate by mechanical cleaning is performed as frequently as the conventional one. This eliminates the need, improves the operation rate of the plasma CVD apparatus, and can significantly reduce the number of maintenance work steps.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a susceptor according to a first embodiment of the present invention, wherein (a) is a schematic plan view and (b) is a schematic sectional view.

FIG. 2 is an enlarged view of a portion Q in a state where a semiconductor wafer is mounted on the portion Q of FIG. 1B.

FIG. 3 is a diagram for explaining a plasma density distribution when plasma is generated in a plasma CVD apparatus using the susceptor according to the first embodiment of the present invention, and is a schematic cross-sectional view near a mounting region of a semiconductor wafer of the susceptor.

FIG. 4 is a schematic sectional view of a susceptor according to a second embodiment of the present invention in the vicinity of a mounting region of a semiconductor wafer;

FIG. 5 is a schematic sectional view of a conventional plasma CVD apparatus.

6A and 6B are schematic views of a susceptor of a conventional plasma CVD apparatus, wherein FIG. 6A is a schematic plan view and FIG. 6B is a schematic sectional view.

FIG. 7 is an enlarged view of the P portion in a state where a semiconductor wafer is mounted on the P portion of FIG. 6B.

FIG. 8 is a diagram illustrating a film thickness distribution of a SiN film deposited on a semiconductor wafer after a plurality of film forming operations performed by a conventional plasma CVD apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Parallel plate type plasma CVD apparatus, 2 ... Reaction chamber, 3, 30, 40 ... Susceptor, 4 ... Upper electrode, 5 ... High frequency power supply, 6 ... Gas piping, 6a, 23a, 23b, 23
c: small hole, 7: exhaust pipe, 8: rotating shaft, 9: heater
10: semiconductor wafer, 21: hole, 22: mounting area, 31
... groove, 41 ... projection

Claims (3)

[Claims] 1. A plasma CVD apparatus having an electrode substrate on which a substrate to be processed is placed and which also serves as one electrode for generating plasma in a capacitive coupling type, wherein: A plasma CVD apparatus, further comprising: an electric field enhancing section provided adjacent to an outer edge of the mounting area of the substrate to be processed, for enhancing an electric field of a discharging action by a high-frequency voltage. 2. The device according to claim 1, wherein the electric field enhancing portion is a groove formed on a flat surface of the electrode substrate.
3. The plasma CVD apparatus according to 1. 3. The plasma CVD apparatus according to claim 1, wherein the electric field enhancing portion is a protrusion formed on a flat surface of the electrode substrate.