JP2004228471A - Semiconductor wafer holding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holding device effective for uniformizing the temperature of the heating surface of a semiconductor wafer in a holding section, in addition to the prevention of discharges at a conductive terminal section and corrosion of the conductive terminal section by a process gas and the shortening of the device lifetime and in addition to being quickly changeable the temperature of the heating surface of the holding section. <P>SOLUTION: The semiconductor wafer holding device 20A has the semiconductor-wafer holding section 1, a cylindrical support member 9 jointed with the rear of the holding section 1 in an airtight manner, cooling members 4 for cooling the holding section 1 and a gas supply means 6 for controlling the quantity of a heat dissipated from the holding section 1, by supplying heat-transfer spaces 12 formed among the holding section 1 and the members 4 with a gas A. The discharge of the gas fed into the spaces 12 is prevented by a discharge preventive means 5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer holding device.
[0002]
2. Description of the Related Art In semiconductor manufacturing processes such as etching, PVD, CVD, and ion implantation, more advanced characteristics are required with changes in device design rules. In order to improve the characteristics of the semiconductor manufacturing process and to stably produce the semiconductor, it is important to control the temperature of the wafer to be etched, formed and ion-implanted with high accuracy. However, it is not easy to control the temperature of the wafer because the temperature is increased by the heat generated by the collision of the plasma generated during the process or the film-forming / injecting substance. Patent Literature 1 and Patent Literature 2 disclose an apparatus for releasing a heat input by bonding or joining a wafer holding device of a low-temperature process to a cooling member with a resin or a low melting point metal. Patent Literature 3 describes a holding member having a cooling function for improving a cooling rate of a semiconductor wafer. This apparatus includes a susceptor capable of heating up to 1200 ° C. and a cooling member installed on the back side of the susceptor. The cooling member is, for example, a gas supply device that injects a cooling gas to a rear surface of the susceptor.
[Patent Document 1]
JP-A-3-3249 [Patent Document 2]
JP-A-4-287344 [Patent Document 3]
Japanese Patent Application Laid-Open No. 7-21606 [0003]
However, it has been difficult to realize a wafer holding device capable of controlling the wafer temperature with high precision while releasing heat input from the process in a high-temperature process. The reason is that when the wafer holding device and the cooling member are bonded with a resin, they cannot be used at, for example, 200 ° C. or higher due to the heat resistance of the bonding resin. Further, when the wafer holding device and the cooling member are joined by a low melting point metal, there is a problem that if the temperature of the wafer holding device is raised to a high temperature, the wafer holding device may be damaged due to a difference in thermal expansion between the wafer holding device and the cooling member. Was. Further, in a susceptor for a semiconductor wafer, when the temperature of the heating surface is set to a set temperature, it is required to highly reduce the temperature difference of the heating surface. The semiconductor wafer holding device described in Patent Document 3 is excellent in that the temperature of the heating surface of the holding member can be rapidly lowered from a high temperature to a low temperature region. However, no consideration has been given to making the temperature of the semiconductor wafer heating surface of the susceptor uniform. Further, in the case of a structure having a resistance heating element, a terminal extracted from an electrostatic chuck electrode or a high frequency generation electrode on the back surface of the holding member, for example, when an inert gas is introduced for cooling the holding member, discharge occurs at the terminal portion. However, there is a problem that the electrodes cannot be used due to short-circuit. Further, there has been a problem that the terminal portion is corroded by being exposed to the process gas and the life of the device is shortened.
An object of the present invention is to provide a holding device which is effective in that the temperature of the heating surface of the semiconductor wafer holding portion can be changed quickly and that the temperature of the heating surface of the semiconductor wafer of the holding portion is made uniform. It is to be.
[0005]
SUMMARY OF THE INVENTION The present invention provides a semiconductor wafer holding portion, a cylindrical support member hermetically joined to the wafer holding portion, a cooling member for cooling the semiconductor wafer holding portion, and a semiconductor wafer holding device. Gas supply means for controlling the amount of heat radiated from the semiconductor wafer holder by supplying gas to the heat transfer space provided between the heat transfer space and the cooling member, and discharge for preventing gas discharge from the heat transfer space The present invention relates to a semiconductor wafer holding device including a prevention means.
Accordingly, in the present invention, the amount of heat transfer from the wafer holding portion to the cooling member can be controlled by controlling the gas introduction amount, and thereby the wafer temperature can be controlled with high accuracy. Further, the uniformity of the heating surface of the wafer holding unit can be improved. In particular, by providing an emission preventing means for preventing gas emission from the heat transfer space, and by sealing the gas in the heat transfer space, the pressure in the heat transfer space is adjusted, and the degree of heat transfer in the heat transfer space can be easily and easily increased. Accurate control can improve the uniformity of the temperature of the heating surface. For example, in the invention described in Patent Literature 3, the gas supplied to the heat transfer space is discharged as it is, and thus is suitable for rapidly cooling the susceptor. However, since pressure adjustment in the heat transfer space is not taken into consideration, the temperature of the heating surface cannot be made uniform by controlling heat transfer in the heat transfer space.
Further, a gas can be introduced into the heat transfer space by airtightly joining the cylindrical support portion to the wafer holding portion. In this embodiment, the amount of heat transfer from the wafer holding unit can be controlled without causing discharge of the conductive terminal unit or corrosion due to the process gas.
[0008]
FIG. 1 is a sectional view schematically showing a holding device 20A according to one embodiment of the present invention. The holding device 20A includes a substantially flat ceramic susceptor 1, a support member 9 joined to the back surface 2b of the susceptor 1, and a cooling member 4 installed on the back surface 2b side.
The holding portion 1 includes a substantially flat base 2, a functional member 3 embedded in the base 2, and a terminal 15 connected to the member 3. The base 2 of the susceptor includes a flat heating surface 2a, a back surface 2b opposite to the heating surface 2a, and a side surface 2c. The support member 9 has a substantially cylindrical shape. One end 9 a of the support member 9 is joined to the back surface 2 b of the base 2, and the other end 9 b is joined to the chamber 10. As a result, the opening 10 a of the chamber 10 communicates with the inner space 17 of the support member 9, and the inner space 17 of the support member 9 is hermetically sealed in the chamber 10. For example, a rod-shaped power supply unit 11 is connected to the terminal 15.
A cooling member 4 is provided on the back surface 2b side of the base 2. In this example, the cooling member 4 has a substantially ring shape when viewed in plan, and is provided so as to surround the support member 9. The cooling member 4 is sealed to the back surface 2b of the base 2 by the discharge prevention means 5, and a heat transfer space 12 is formed between the cooling member 4 and the back surface 2b.
In operation, the temperature distribution of the semiconductor wafer on the heating surface 2a and the heating surface 2 is observed by the observation device 8. Then, this observation result is transmitted to the control device 7, and the control device 7 controls the operation state of the gas supply device 6. Gas is supplied from the gas supply device 6 into the heat transfer space 12 as shown by an arrow A.
Hereinafter, the function and effect of the present invention will be further described. Since the inside of the chamber 10 is under reduced pressure, the gap between the back surface 2b of the base 2 and the cooling member 4 is also under reduced pressure. Under a reduced pressure state or a vacuum state, there is almost no heat transfer by convection between the substrate 2 and the cooling member 4 and only purely heat transfer by radiation, so that there is a high heat insulating effect. Here, when the heat transfer space 12 is provided between the cooling member 4 and the back surface 2b and gas is supplied into the heat transfer space 12, heat transfer by convection between the cooling member 4 and the back surface 2b of the base 2 is performed. Be done. As a result, it is possible to control the movement of the amount of heat from the base 2 to the cooling member 4 so that the temperature distribution on the heating surface is minimized. At this time, by preventing the discharge of the gas from the heat transfer space by the discharge prevention means 5, the pressure in the heat transfer space can be accurately adjusted, whereby the movement of the amount of heat from the base 2 to the cooling member 4 can be prevented by heating. It can be controlled to minimize the temperature distribution on the surface.
The gas is preferably an inert gas. In particular, in applications for heating a semiconductor wafer, an inert gas is particularly preferable from the viewpoint of preventing a reaction between a gas and ceramics. As the inert gas, argon, helium, and nitrogen are preferable. The temperature at the time of gas introduction may be room temperature, may be heated, and may be cooled below room temperature. Further, a gas introduced to the back surface of the wafer may be simultaneously introduced into the heat transfer space 12 for cooling the wafer, improving the uniformity of the wafer, and the like.
The pressure in the heat transfer space 12 is not particularly limited. This is because, if it is desired to prioritize the heat insulation effect, the pressure must be reduced to, for example, 10 ⁻² Torr or less, or gas need not be introduced, and if it is desired to promote heat transfer, it is necessary to increase the pressure. .
Since the holding device 20B of FIG. 2 is substantially the same as the device 20A of FIG. 1, the same components are denoted by the same reference numerals and description thereof will be omitted. In the holding device 20 </ b> B of FIG. 2, the heat transfer auxiliary plate 13 is accommodated in the heat transfer space 12. In this example, the plate 13 is provided on the cooling member 4.
FIG. 3 is an enlarged view of the plate 13. The heat transfer auxiliary plate 13 includes a plurality of convex portions 13 and a plurality of concave portions 13b, and the convex portions 13a and the concave portions 13b are provided alternately. Here, the distance a between the convex portion 13a and the rear surface 2b needs to be smaller than the distance b between the concave portion 13b and the rear surface 2b. As a result, in the protrusion 13a, the distance a between the auxiliary heat transfer plate 13 and the back surface 2b is small, and the amount of heat radiation from the base 2 to the cooling member 4 is large. In the recess 13b, the distance b between the auxiliary heat transfer plate 13 and the back surface 2b is relatively large, and the amount of heat radiation from the base 2 to the cooling member 4 is relatively small. Therefore, by changing the number, height, and planar shape of the convex portions 13a and the number, height, and planar shape of the concave portions 13b, a portion having a large amount of heat radiation from the base body 2 to the cooling member 4 in a plan view can be obtained. Small parts can be created. As a result, the amount of heat radiation from the substrate 2 to the cooling member 4 is increased in a hot portion where the temperature of the heating surface of the wafer holding portion 1 is high, and the amount of heat radiation from the substrate 2 to the cooling member 4 is decreased in a cool portion. Thereby, the uniformity of the temperature of the wafer holding unit 1 can be improved.
The width t of the heat transfer space 12 is preferably equal to or less than the mean free path of gas from the viewpoint of promoting heat transfer. The mean free path here is based on the assumption that gas molecules are sealed in the heat transfer space at a pressure P (10 ⁻³ mmHg). At this time, the mean free path L (cm) of the gas is expressed as follows.
L = 8.6 × 10 ³ η / P√ (T / M)
η: Gas viscosity (poise)
T: Absolute temperature M: Molecular weight For example, when helium gas at room temperature is used, the mean free path L becomes about 15 μm.
When the mean free path is equal to or greater than the width t of the heat transfer space, the heat transfer by the gas is dominated by heat exchange between the gas molecules and the object (here, the wafer holder and the cooling member). . Conversely, if the mean free path is much smaller than the width t, the heat transfer is dominated by the heat conduction between the gas molecules. Generally, the former has a larger amount of heat transfer than the latter, so that the amount of heat transfer can be increased by setting the width t equal to or less than the mean free path of the gas. However, if the width t of the heat transfer space 12 is too small, the surface of the cooling member 4 may partially contact the back surface 12a or the amount of heat transfer may be significantly increased locally. From the viewpoint of preventing this, the width t of the heat transfer space 12 is preferably 0.005 mm or more.
The material of the semiconductor wafer holding portion is not particularly limited since it can be selected according to the application. However, ceramics having corrosion resistance to a halogen-based corrosive gas are preferable, aluminum nitride or dense alumina is particularly preferable, and aluminum nitride ceramics and alumina having a relative density of 95% or more are more preferable. Functional components such as a resistance heating element, an electrode for an electrostatic chuck, and an electrode for plasma generation can be embedded in the semiconductor wafer holder. The material of the functional component is not limited, but is preferably a high melting point metal, particularly preferably molybdenum, tungsten, or a molybdenum-tungsten alloy.
The material of the support member is not particularly limited, but ceramics having corrosion resistance to a halogen-based corrosive gas is preferable, and aluminum nitride or dense alumina is particularly preferable. The method of joining the semiconductor wafer holding portion and the support member is not limited, and may be mechanical fastening such as solid-phase joining, solid-liquid joining, brazing, or screwing. The solid-liquid bonding method is a method described in JP-A-10-273370.
The type of the cooling device 4 is not particularly limited. Preferably, it is a type of cooling device that circulates a refrigerant. The refrigerant may be a gas such as air or an inert gas, or a liquid such as water or oil.
In a preferred embodiment, sealing means for sealing between the chamber 10 and the cooling member can be provided, or sealing means for sealing between the tubular support member and the cooling member. Can be provided. The operation and effect of this embodiment will be described with reference to the example of FIG.
In FIG. 4, the size of the cooling device 4A is relatively large. The space between the cooling device 4A and the inner wall surface 10b of the chamber 10 is sealed by a sealing member 21, and the space between the cooling device 4A and the support member 9 is sealed by a sealing member 22.
According to such an example, the heat transfer space 12 can be easily sealed as compared with the embodiment of FIGS. Because, during operation, the susceptor 1 usually has a high temperature, and thus the discharge prevention means 5 needs to have heat resistance. However, there are few and expensive sealing materials having both high heat resistance and airtightness. On the other hand, in the present embodiment, the atmosphere inside the chamber 10 and the outside of the chamber are sealed by the separate sealing members 21 and 22 instead of the discharge prevention means 5. The sealing members 21 and 22 have a relatively low temperature. Therefore, the sealing member between the cooling member, the supporting member, and the chamber may have low heat resistance, and therefore, a sealing member with high airtightness and low cost can be employed. Further, the discharge prevention means 5 needs heat resistance, but does not need to have high sealing performance.
In the example of FIG. 5, the heat transfer auxiliary plate 13 described above is installed in the heat transfer space 12 in the example of FIG.
As the discharge preventing means 5, for example, a C-ring, an O-ring or the like can be used, and a sheet material such as a carbon sheet may be used. The sealing of the heat transfer space does not need to be airtight and may have some gas leaks. For example, when the gas introduced into the back surface of the wafer is simultaneously introduced into the heat transfer space and cooled, a gas leak amount equal to the gas leak amount between the wafer and the wafer holding device can be allowed. Since the sealing members 21 and 22 between the tubular support member and the cooling member need to be airtight, a highly airtight sealing member such as an O-ring is used.
[0028]
EXAMPLE A holding device 20A shown in FIG. 1 was manufactured. However, a Mo-made coil as a resistance heating element and a # 50-mesh mesh-made Mo electrostatic chuck electrode having a diameter of 0.12 mm were buried in the base 2. A cylindrical pointing member made of aluminum nitride was joined to the back surface of the body 2. The cooling member 4 was installed on the back surface 2 b side of the base 2, a heat transfer space 12 was provided between the cooling member 4 and the back surface 2 b, and sealed with a C-ring 5. An O-ring was hermetically sealed between the side surface of the cylindrical support member and the cooling member to isolate the outside air from the chamber and the heat transfer space. The cooling device 4 is a water-cooled flange. The width t of the heat transfer space 12 was 0.1 mm. The average temperature of the heating surface 2a of the base 2 was heated to 300 ° C. Helium was used as the gas A, and the gas was supplied into the heat transfer space 12. The operation was possible without occurrence of discharge or corrosion in the conduction terminal portion, and the amount of heat escape was controlled at about 0.2 W / mm2 by controlling the pressure of the introduced gas and the heat transfer plate.
[0029]
As described above, according to the present invention, the temperature of the heating surface of the semiconductor wafer holding portion can be rapidly changed without causing discharge or corrosion at the conductive terminal portion. It is possible to provide an effective holding device in making the temperature of the semiconductor wafer heating surface of the portion uniform.
[Brief description of the drawings]
FIG. 1 is a sectional view schematically showing a holding device 20A according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing a holding device 20B according to another embodiment of the present invention.
FIG. 3 is an enlarged view showing the auxiliary heat transfer plate 13;
FIG. 4 is a sectional view schematically showing a holding device 20C according to still another embodiment of the present invention.
FIG. 5 is a sectional view schematically showing a holding device 20D according to still another embodiment of the present invention.
[Description of Reference Numerals] 1 semiconductor wafer holding unit 2 base 2a heating surface 2b back surface 2c side surface 3 functional member 4 cooling device 5 discharge prevention member 6 gas supply device 7 gas supply control device 8 heating surface temperature observation device 9 support member DESCRIPTION OF SYMBOLS 10 Chamber 12 Heat transfer space 13 Heat transfer auxiliary plate 13a Convex part of heat transfer auxiliary plate 13b Concave part of heat transfer auxiliary plate 20A, 20B, 20C, 20D Semiconductor wafer holding device 21, 22 Sealing member A gas

Claims (7)

By supplying a gas to a semiconductor wafer holding unit, a cooling member for cooling the semiconductor wafer holding unit, and a heat transfer space provided between the semiconductor wafer holding unit and the cooling member, the semiconductor wafer holding unit A semiconductor wafer holding device, comprising: gas supply means for controlling the amount of heat released from the unit; and discharge prevention means for preventing discharge of the gas from the heat transfer space. The device according to claim 1, further comprising a heat transfer auxiliary plate housed in the heat transfer space. The apparatus according to claim 1, further comprising a sealing unit that seals between the chamber and the cooling member. The apparatus according to any one of claims 1 to 3, further comprising a cylindrical support member hermetically bonded to a back surface of the semiconductor wafer holder. The apparatus according to claim 4, further comprising a sealing means for sealing between the cylindrical support member and the cooling member. The apparatus according to any one of claims 1 to 5, wherein the semiconductor wafer holding device includes a substrate made of sintered ceramics. 7. The apparatus according to claim 6, wherein at least one of a resistance heating element, an electrostatic chuck electrode, and a high-frequency generation electrode is provided on the base.

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