JP2003282685A - Cooling plate - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide both heat dissipation for keeping the temperature of a wafer constant to prevent thermal distortion and high rigidity and low thermal expansion for realizing high processing accuracy during exposure processing or the like. To provide a ceramic cooling plate. SOLUTION: The cooling plate of the present invention is a cooling plate for holding a vacuum chuck for fixing a wafer, and has a thermal conductivity of 10 W / K · m or more and a thermal expansion coefficient between 0 ° C. and 50 ° C. 7 × 10 ^-6 / ℃ or less, Young's modulus is 200G
It is characterized by comprising a ceramic base material of Pa or more, and having a vacuum suction path and a cooling medium path disposed therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling plate used in a semiconductor manufacturing apparatus for holding a vacuum chuck for fixing a wafer. In particular, the present invention relates to a ceramic cooling plate having all of high thermal conductivity, low thermal expansion and high rigidity.

[0002]

2. Description of the Related Art With the high integration of LSIs and the like, the miniaturization of circuits has been promoted, and the line width of semiconductors is 0.1.
Attempting to reach a level below micron. In the case of manufacturing a semiconductor, for example, in a semiconductor lithography process, a pattern is transferred and formed on a wafer through a mask by an exposure device, but in order to form a highly accurate pattern in response to ultra-miniaturization of a circuit. For example,
A vacuum chuck for mounting a wafer is disclosed in Japanese Patent Laid-Open No. 11-2.
As disclosed in Japanese Patent Application Laid-Open No. 09171 and Japanese Patent Laid-Open No. 11-343168, the coefficient of thermal expansion at 0 to 40 ° C. is 1 ×.
By using a low thermal expansion ceramics base material having a temperature of 10 ⁻⁶ / ° C. or less, thermal expansion of the vacuum chuck during processing can be eliminated as much as possible, and highly precise fine processing can be realized.

Further, by using silicon carbide, which is a highly rigid and highly heat-conductive material, for the vacuum chuck, the heat of the wafer generated during processing can be quickly released to the vacuum chuck, and the thermal expansion of the wafer can be achieved. Can be reduced,
Highly precise microfabrication is possible.

For the member (cooling plate) for fixing and holding these vacuum chucks, a metal material such as cast iron is used to release heat from the vacuum chuck to the cooling plate in view of good heat conductivity and cost merit. As a result, the temperatures of the vacuum chuck and the wafer are made uniform.

[0005]

However, since the metal cooling plate has a very high coefficient of thermal expansion, even if a temperature difference of several degrees Celsius occurs, the generated distortion of the cooling plate cannot be ignored, and the cooling plate on the cooling plate cannot be ignored. The accuracy of the vacuum chuck and the Si wafer deteriorates.

Further, when the vacuum chuck and the cooling plate are fixed by bolts, only the fixed portion comes into contact with each other and floating occurs in the non-fixed portion, so that the precision of the vacuum chuck and the Si wafer on the cooling plate is lowered.

Further, since the vacuum chuck has a higher hardness than the cooling plate, when the vacuum chuck on the cooling plate is attached / detached, the cooling plate is worn and the accuracy is lowered, and the accuracy of the vacuum chuck and the Si wafer is also lowered.

An object of the present invention is to provide a ceramic cooling which has both a heat exhausting property for keeping a temperature of a wafer during processing constant to prevent thermal distortion and a high rigidity and a low thermal expansion property for realizing a high processing accuracy. To provide the plate.

[0009]

A cooling plate according to the present invention is a cooling plate for holding a vacuum chuck for fixing a wafer, having a thermal conductivity of 10 W / Km or more,
Characterized by a ceramic base material having a coefficient of thermal expansion of 7 × 10 ⁻⁶ / ° C. or less between 0 ° C. and 50 ° C. and a Young's modulus of 200 GPa or more, and a vacuum suction path and a cooling medium path are provided therein. And

The cooling plate is formed by laminating a plurality of ceramic base materials including a groove-processed ceramic base material, and the base materials are bonded to each other through a metal-based bonding material layer or an inorganic-based bonding material layer. Therefore, it is preferable that the vacuum suction path or the cooling medium path is provided on the joint surface with the grooved ceramic substrate. Further, the ceramic base material contains any one of alumina, silicon carbide, silicon nitride and aluminum nitride as a main component, and the content of the main component is preferably 80% by mass or more.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION (Cooling Plate) The cooling plate of the present invention has a thermal conductivity of 10 W / K · m or more and 0 ° C. to 50 ° C.
Coefficient of thermal expansion between ℃ is less than 7 × 10 ^-6 / ℃, Young's modulus is 2
It is characterized by being made of a ceramic base material of 00 GPa or more and having a vacuum suction path and a cooling medium path provided therein. By specifying the characteristics and structure of the cooling plate material, the thermal expansion of the cooling plate is suppressed even if the temperature rises during processing in semiconductor manufacturing equipment, the wafer temperature is kept constant, and circuit miniaturization is addressed. Is possible.

As shown in FIG. 1, the cooling plate 1 of the present invention is bonded to a vacuum chuck 2 for fixing a wafer 3 and holds the vacuum chuck 2. Inside the cooling plate 1,
A vacuum suction path 12 and a cooling medium path 11 are provided. The cooling medium flows in the cooling medium path 11 as shown by the arrow in FIG. In the example shown in FIG. 1, a large number of protrusions 13 are provided on the upper surface of the cooling plate 1, hold the vacuum chuck 2, and vacuum-suck through the vacuum suction path 12 to fix the vacuum chuck 2.

FIG. 2A shows a plan view of the cooling plate. In this example, a large number of protrusions 2 are provided on the upper surface of the cooling plate.
3 is provided, the vacuum suction path 22 may have a substantially concentric shape, as shown in FIG. 2B. The cooling plate of the present invention is not limited to these aspects. The cooling plate of the present invention has a vacuum suction path 22 inside, and a vacuum chuck mounted on the cooling plate is sucked and fixed via a vacuum suction port 26. When tightened with bolts as is done conventionally,
Since only the fastening part comes into contact, floating occurs in the non-fastening part,
Exposure accuracy decreases. In the present invention, since the vacuum chuck is fixed by vacuum suction, floating does not easily occur on the bonding surface,
The mounting accuracy of the cooling plate is improved, and the exposure accuracy is improved accordingly. 1 and 2, the mode in which the vacuum chuck is suction-held at the central portion of the cooling plate is illustrated, but the present invention is not limited to this mode.

In FIG. 1, the cooling plate and the vacuum chuck have substantially the same outer diameter. However, in order to improve the fixing accuracy of the vacuum chuck, the outer diameter of the cooling plate is increased and steps are provided. The shape of the vacuum chuck may be set in this step, or the opposite shape may be used.

FIG. 3 shows a plan view of the ceramic base material (base side) to be laminated on the lower side in the case of manufacturing a cooling plate in which two ceramic base materials are laminated. The cooling medium enters through the cooling medium inlet 37, passes through the cooling medium passage 31 and is discharged through the cooling medium outlet 38. Since the cooling plate of the present invention has the cooling medium path 31 inside,
Heat can be efficiently exhausted during the exposure process, the temperature of the wafer can be kept constant, and thermal distortion can be suppressed. Therefore, miniaturization of the circuit can be dealt with. In the example of FIG. 3, the cooling medium path 31 has a substantially concentric shape, but other modes are also possible. 1 and 3 illustrate a mode in which the cooling medium is injected from the central part of the cooling plate and discharged from the peripheral part of the cooling plate, but the cooling plate of the present invention is not limited to these modes. Not something.

The cooling plate of the present invention has a thermal conductivity of 10%.
W / K · m or more, thermal expansion coefficient between 0 ° C and 50 ° C is 7 × 1
It is made of a ceramic base material having a Young's modulus of not less than 0 ^-6 / ° C and 200 GPa or more. The cooling plate made of a ceramic base material having such characteristics has a heat exhausting property for keeping the temperature of the wafer constant during the exposure process to prevent thermal distortion, a high rigidity for realizing high processing accuracy, and a low thermal expansion property. Combined with all, it is excellent overall.

The thermal conductivity is 10 W / K · m or more, and 1
It is preferably 5 W / K · m or more, more preferably 20 W / K · m or more. When the thermal conductivity is less than 10 W / K · m,
Exhaust heat during exposure processing becomes insufficient, the temperature of the wafer cannot be kept constant, and it becomes difficult to suppress thermal distortion.

The coefficient of thermal expansion between 0 ° C. and 50 ° C. is 7 × 10 ^-6
/ ° C or less, preferably 6.5 × 10 ^-6 / ° C or less,
It is more preferably 6 × 10 ⁻⁶ / ° C. or less. When the coefficient of thermal expansion between 0 ° C. and 50 ° C. is larger than 7 × 10 ⁻⁶ / ° C., it is not possible to sufficiently deal with the production of a fine circuit that requires high precision during the exposure process.

Young's modulus is not less than 200 GPa and is 25
0 GPa or more is preferable, and 300 GPa or more is more preferable. For example, a vacuum chuck used in an exposure apparatus
Placed on a stage that can be stepped in the XY directions,
The exposure process is performed while moving in the XY directions. Therefore, when the Young's modulus of the ceramic base material forming the cooling plate is less than 200 GPa, vibration during movement is not attenuated, and exposure failure is likely to occur. Further, since the cooling plate in the present invention has a structure in which the cooling medium is passed inside, if the Young's modulus of the ceramic base material is less than 200 GPa, it is not possible to suppress the vibration generated by the passage of the medium and exposure failure occurs. It tends to occur.

The porosity of the ceramic base material may be in the range that does not hinder the leakage of the cooling medium, for example, 1%.
The following are preferred.

As the ceramic substrate having such characteristics, any one of alumina, silicon carbide, silicon nitride and aluminum nitride is a main component, and the content of the main component is 80% by mass or more. Is preferred.
By setting the content of these components to 80% by mass or more, it is possible to easily obtain a cooling plate having appropriate characteristics with respect to thermal conductivity, Young's modulus, and thermal expansion coefficient.

On the other hand, for example, zirconia and quartz are not preferable because they have a thermal conductivity of less than 10 W / K · m and emit a small amount of heat. Further, for example, ceramics such as zirconia and forsterite, and metals such as cast iron, aluminum, and SUS have a coefficient of thermal expansion between 0 ° C and 50 ° C of more than 7 × 10 ^-6 / ° C. This is not preferable because the accuracy deteriorates. Further, for example, quartz is used for ceramics and aluminum is used for metals because the Young's modulus is less than 200 GPa and exposure accuracy is deteriorated due to insufficient rigidity, which is not preferable.

The cooling plate of the present invention can be formed by laminating a plurality of ceramic base materials, but even if the ceramic base materials to be laminated are of the same type,
Also, different types may be used. For example, the material of the surface that should be the surface for sucking the vacuum chuck may have a high thermal conductivity, and the material of the surface that is not related to vacuum suction may have a high Young's modulus. Further, a material having a different thermal expansion coefficient may be used. Further, a material having a different volume resistivity or the like may be used.

(Manufacturing Method of Cooling Plate) For example, when alumina is the main component, the purity is 99 to 99.99.
%, Alumina powder having a particle size of 0.1 to 2 μm is mixed with 0 to 20% by mass of a sintering aid, for example, MgO powder or SiO ₂ powder having a particle size of 1 μm or less. An organic binder is added to the blended raw materials, water is added, and then slurried by a ball mill and granulated (granulated) by a spray dryer.
The obtained granules are molded by a metal mold or CIP (cold isotropic pressure press molding), cut if necessary, and sintered at a temperature of 1300 to 1700 ° C. in an air atmosphere to obtain a sintered body. To get

Further, for example, when aluminum nitride is the main component, Y ₂ O ₃ powder and CaO powder are added to aluminum nitride powder having a purity of 99 to 99.9% and an average particle size of 0.4 to ₂ μm. , 0 to 4% and 0 to 3%, respectively. An organic binder is added to the blended raw materials, ethanol is added, a slurry is formed by a ball mill, and granulated (granulated) by a spray dryer. The obtained granules are molded by a metal mold or CIP (cold isotropic pressure press molding), and if necessary, subjected to cutting processing, and 400 to 700 in an air atmosphere.
After heat treatment of the binder removal at a temperature of ℃,
Sintering is performed at a temperature of 1900 ° C. to obtain a sintered body.

Regarding the method of sintering the base material, for example,
There are a method of hot pressing a raw material having a predetermined composition at a predetermined temperature, a method of performing HIP (high temperature isotropic pressure sintering) to further densify after firing, and the present invention is not limited to these methods. It is not limited.

The amount of auxiliary agent is preferably less than 20% by mass. If the amount of the auxiliary agent is 20% by mass or more, properties such as Young's modulus and thermal conductivity may be insufficient.

After sintering, it is machined to the desired shape before joining. In the mechanical processing, the cooling medium passage portion is formed into a groove shape, for example, or a suction groove is formed on the suction side of the vacuum chuck.

In the cooling plate of the present invention, a plurality of ceramic base materials including a groove-processed ceramic base material are laminated and the base materials are bonded to each other through a metal-based bonding material layer or an inorganic-based bonding material layer. Therefore, it is preferable that the vacuum suction path or the cooling medium path is provided on the joint surface with the grooved ceramic base material.

As a method for forming the vacuum suction path or the cooling medium path, a method of forming two or more holes from the outer circumference of the vacuum chuck so as to intersect inside without performing a method of joining, or a groove is preliminarily processed. There is a method in which a base material and a non-grooved base material are laminated and bonded. The latter joining method is preferable in that the shape and size of the path to be formed can be easily designed.

As a method of forming a vacuum suction path or a cooling medium path by bonding, a method of bonding with a resin bonding material such as epoxy resin, a method of bonding with an inorganic bonding material such as glass, or a metal bonding material Although there are three types of joining methods, the method using a resin joining material is liable to cause a decrease in joining strength, a decrease in rigidity of a joining portion, an increase in thermal resistance, etc. due to deterioration of a resin component over time. The method using a metal bonding material is preferable.

In the method of bonding with an inorganic bonding material, glass is typically used as the inorganic bonding material. Although the base material according to the present invention is diverse, it is necessary to select a glass according to the thermal expansion coefficient of each base material in order to avoid cracks and peeling at the interface due to the difference in thermal expansion between the glass for bonding and the base material. . For example, if the main component of the ceramic base material is alumina, it is desirable to use lead borosilicate glass or the like for bonding. The construction temperature is preferably 600 ° C to 900 ° C. With such a temperature, melting of the glass proceeds, bubbles are eliminated, and leakage of the cooling solvent after joining can be avoided. In addition, the thickness of the glass after bonding is preferably 5 μm to 100 μm, more preferably 5 μm to 50 μm, in order to relax the stress generated at the bonding interface.

When using the metal joining method, the joining material may be a brazing material containing silver as a main component, a brazing material containing titanium as a main component, or an aluminum material, depending on the characteristics of the ceramic base material. it can. The brazing material is
For example, it is preferable to select the bonding strength and the corrosion resistance depending on the cooling solvent used as a reference. Further, since it is necessary to surely prevent leakage of the cooling solvent after joining, it is preferable to use the brazing material in a foil shape having a uniform thickness rather than a granular shape. The thickness of the brazing material is preferably 10 to 50 μm,
It is more preferably 30 μm.

The heat treatment for metal joining is preferably carried out, for example, in an environment where the degree of vacuum in the furnace during the treatment is higher than 10 ^-1 Pa. Further, the treatment temperature is preferably 700 to 950 ° C. for a brazing material containing titanium, for example. When the degree of vacuum is lower than 10 ^-1 Pa, bubbles may not be sufficiently removed at the joint portion, or the joint material may not be melted due to oxidation. Further, if the treatment temperature is lower than 700 ° C., the bonding material does not melt, while if it is higher than 950 ° C., the bonding material may volatilize and bonding may be insufficient.

After joining the ceramic base materials, finishing processing is carried out if necessary, and commercialized. In particular, it is preferable to finish the fastening portion with the vacuum chuck with high precision in order to ensure the precision of the vacuum chuck. Further, the cooling plate of the present invention may be further improved by a known method.

[0036]

[Examples] After sintering, the main material and, if necessary, the auxiliary agents were mixed in the proportions shown in Table 1, and ethanol was used as a solvent, followed by mixing in a ball mill for 24 hours. The obtained mixture was dried and then sintered under the temperature and atmosphere shown in Table 1 to obtain a ceramic substrate. Table 1 shows the physical properties of the obtained ceramic substrate.

[0037]

[Table 1]

As is clear from the results shown in Table 1, the ceramic substrate of the present invention has a thermal conductivity of 10 W / K · m or more,
The coefficient of thermal expansion between 0 ° C. and 50 ° C. was 7 × 10 ⁻⁶ / ° C. or less, and the Young's modulus was 200 GPa or more. Therefore, by using a cooling plate made of such a ceramic base material, sufficient heat exhaustion is exhibited even when the temperature rises during exposure processing, thermal expansion is kept low, and high-precision wafer processing is possible. It was made possible and it was found that the circuit could be miniaturized sufficiently.

After that, as shown in FIGS. 1 to 3, mechanical processing such as grooving was performed, and joining was performed under the conditions shown in Table 2. After joining, finishing processing was performed to obtain a cooling plate. Water of 3 atm was injected into the obtained cooling plate, but no water leakage occurred.

[0040]

[Table 2]

The embodiments and examples disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0042]

According to the present invention, at the time of exposure processing and the like, both of heat exhaustion for keeping the temperature of the wafer constant to prevent thermal distortion and high rigidity and low thermal expansion for realizing high processing accuracy are provided. It is possible to provide a ceramic cooling plate that also has the above-mentioned features. This cooling plate is particularly useful as a cooling plate that holds a vacuum chuck such as a vacuum chuck for an exposure apparatus and a vacuum chuck for a wafer polishing apparatus, and can be used for a semiconductor manufacturing apparatus or a liquid crystal manufacturing apparatus.

[Brief description of drawings]

FIG. 1 shows a cooling plate of the present invention, a vacuum chuck,
It is sectional drawing which shows the state before stacking | stacking a wafer.

2A and 2B are plan views of a cooling plate, FIG. 2A shows an example in which a large number of convex portions are arranged on the upper surface of the cooling plate, and FIG. 2B shows a vacuum suction path which is approximately concentric. Here is an example:

FIG. 3 is a plan view of a ceramic base material to be laminated on the lower side when manufacturing a cooling plate formed by laminating two ceramic base materials.

[Explanation of symbols]

1 cooling plate, 2 vacuum chuck, 3 wafer, 1
1,31 Cooling medium path, 12,22 Vacuum suction path,
13, 23 Convex part, 26 Vacuum suction port, 37 Cooling medium inlet, 38 Cooling medium outlet.

Claims (3)

[Claims] 1. A cooling plate for holding a vacuum chuck for fixing a wafer, which has a thermal conductivity of 10 W / K.
・ The coefficient of thermal expansion between m and 0 ° C to 50 ° C is 7 × 10 ^-6 /
A cooling plate made of a ceramic base material having a Young's modulus of 200 GPa or more at a temperature of ℃ or less, and a vacuum suction path and a cooling medium path are provided inside. 2. A plurality of ceramic base materials including a grooved ceramic base material are laminated, and the base materials are bonded to each other via a metal-based bonding material layer or an inorganic-based bonding material layer. The cooling plate according to claim 1, wherein a vacuum suction path or a cooling medium path is disposed on a joint surface with the grooved ceramic base material. 3. The ceramic base material contains, as a main component, any one of alumina, silicon carbide, silicon nitride and aluminum nitride, and the content of the main component is 80% by mass or more. The cooling plate according to claim 1.