JPH11233605A - Electrostatic chuck stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck stage capable of mounting and removing a wafer steadily and having small residual attractive force and good withstand-voltage characteristics. SOLUTION: An electrode is constituted of a disk-shaped inner electrode 16 and a ring-shaped outer electrode 17. An insulating film 20 is formed on a side between these electrodes 16 and 17. There is a gap 18 between these electrodes 16 and 17, and a lift pin 14 is passed through the gap 18. Since the electrode includes the inner electrode 16 and the outer electrode 17, the insulating film 20 is formed easily with reliability at the side thereof. By making the resistivity of an dielectric film 19 on the surface of the electrode to be made from 10<11> to 10<12> Ωcm, or 10<17> Ωcm or more, the residual attractive force is made small. In addition, when the lift pin 14 is positioned adequately, defective one-side lifting or leap of the wafer on the chuck stage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck stage for adsorbing and fixing a semiconductor wafer by static electricity in the manufacture of a semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor manufacturing apparatus such as an etching apparatus or a CVD apparatus, a process using plasma is performed to increase the degree of integration of a semiconductor device. A semiconductor wafer such as silicon (hereinafter, referred to as a wafer) to be processed by these manufacturing apparatuses is heated by energy received from plasma, cooled to a desired temperature, and fixed and held while maintaining temperature uniformity. As a method, an electrostatic chuck is used instead of the mechanical clamp conventionally used. The mechanical clamp is a method of mechanically pressing the outer periphery of a wafer mounted on a stage with a clamp ring or a nail. On the other hand, an electrostatic chuck is a metal electrode with a dielectric film on the surface. A wafer is placed on the dielectric film and an electrostatic force is generated by applying a voltage between the wafer and the electrode plate. Can be adsorbed and fixed on the stage. Various ceramic and polymer films are used as the dielectric film of the electrostatic chuck. The electrostatic chuck can be attracted to the entire surface of the wafer, and is particularly used as a method for holding a large-diameter wafer. Further, since there is no portion that makes physical contact with the wafer processing surface unlike the mechanical clamp, dust generation in the manufacturing apparatus chamber can be reduced.

FIG. 15 shows, for example, Japanese Patent Application Laid-Open No. 4-253356.
FIG. 1 is a cross-sectional view of a conventional electrostatic chuck disclosed in
In the drawing, reference numeral 1 denotes an electrostatic chuck, 2 denotes a wafer attracted to the electrostatic chuck 1, 3 denotes a lift pin for detaching the wafer 2 from the electrostatic chuck 1, and 4 denotes a motor for driving the lift pin 3. When the attracted wafer 2 is removed, after the voltage applied to the electrostatic chuck 1 is released, the electric charge remaining on the wafer 2 is released by the lift pins 3 set to the ground potential, the residual attracting force is reduced, and the wafer 2 is pushed up by the lift pins 3. .

FIG. 16 shows, for example, JP-A-6-338559.
FIG. 1 is a cross-sectional view of a conventional electrostatic chuck disclosed in
Even after the applied voltage is released, the electrostatic chuck 1
The wafer 2 adsorbed on the surface of the electrostatic chuck 1 is sequentially pushed up from one side by the lift pins 3 so as to be separated from the surface of the electrostatic chuck 1.

FIG. 17 shows, for example, Japanese Patent Application Laid-Open No. Hei 5-3123.
FIG. 9 is a cross-sectional view of a conventional electrostatic chuck shown in Japanese Patent Application Publication No. 9-205, in which 5 is a metal electrode, 6 is a lift pin hole formed in the electrode 5, and 7 is a dielectric pin attached to the surface of the electrode 5. The body film 8 is a cylindrical insulating member fitted into the lift pin hole 6. As shown in FIGS. 15 and 16, when removing the attracted wafer 2, the wafer 2 is pushed up by the lift pins 3. To pass the lift pins 3, holes 6 for lift pins are formed in the electrode 5, and the surface of the holes is covered with an insulating member 8 to provide insulation.

[0006]

In the conventional electrostatic chuck, depending on the type, even if the voltage applied to attract the wafer is released, the attracting force does not immediately decrease or disappear, but remains. The attraction force may prevent the wafer from separating from the stage. If the residual suction force is large, various problems may occur, such as a shift in the position of the wafer when the wafer is detached, a failure to reliably remove the wafer from the chamber, and this may be one of the causes of a decrease in the processing capability of the semiconductor manufacturing apparatus. there were. Also, if the surface of the electrostatic chuck has undulations or irregularities, the attraction force is partially weakened, and the amount of heat transfer promoting gas introduced to the back surface of the wafer for cooling may leak from the periphery of the wafer. It is known that as the number of wafers increases, the temperature uniformity of the wafer cannot be maintained.

Further, when used in extreme temperature conditions, for example, in a high-temperature atmosphere of 200 ° C. or more, depending on the type of dielectric film on the surface of the electrostatic chuck, the electrostatic chuck itself cannot withstand heat or the electrode itself cannot withstand heat. In some cases, a defect such as cracking or peeling may occur due to the difference in the coefficient of linear expansion from the base material. Further, when lift pins are used as means for pushing up the wafer from the electrostatic chuck surface and detaching the wafer, it is necessary to provide a hole for penetrating the lift pins in the electrostatic chuck. However, when the dielectric film is formed by the ceramic spraying method, if the diameter of the hole is small, the sprayed film is not completely formed in the hole, the electrode base material of the electrostatic chuck is exposed, and a voltage is applied. Abnormal discharge may occur.

For example, in the electrostatic chuck shown in FIG. 15 in which the wafer is easily grounded by setting the wafer to the ground potential, even if the wafer is set to the ground potential, the dipole which remains polarized in the dielectric film instantaneously returns to its original state. Or the electric charge remains in the electrostatic chuck, so that the residual suction force does not instantaneously decrease or disappear. Further, when the lift pins are pushed up while the residual suction force is large, the wafer is pushed up while a part of the wafer is sucked, and the wafer is in an oblique state. Here, such a state is referred to as one-sided movement, and FIG.
Shown in In such a state, the wafer is displaced or falls off the stage, making it impossible to collect the wafer from the chamber. In addition, when the wafer falls off the stage, it may be destroyed. In such a case, it is necessary to open the chamber and collect the wafer inside or to take out the damaged wafer. Is one of the causes of lower productivity.

Further, in the wafer detaching method shown in FIG. 16, when the outer peripheral portion of the wafer is pushed up, even if it is pushed up from one side, if the residual suction force is large, the wafer warps and does not detach so as to come off. Further, in this method, since the outer peripheral portion of the wafer is pushed up, if the residual suction force is large, the wafer is deformed into a concave shape. This state is shown in FIG. At this time, the elastic energy due to the deformation is stored in the wafer, and when the wafer is further pushed up, the elastic energy stored at the moment when the pushing force exceeds the residual suction force and the wafer is separated is released, and the wafer jumps up. At this time, the wafer is displaced or falls off the stage, which is one of the causes of lowering the productivity of the apparatus as in the case described above.

[0010] In the case where the withstand voltage in the lift pin hole is improved by using an insulating member as shown in FIG. 17, the following problem occurs. In an apparatus using a process for generating plasma, such as an etching apparatus, heat is applied to the electrostatic chuck via a wafer by generating plasma. Even if the electrostatic chuck is provided with a cooling mechanism, heat history is added to the electrostatic chuck for each process. The insulating member and the electrode base material or the dielectric film have different coefficients of linear expansion, so repeated stress is applied due to the thermal history, and cracks occur at the interface of each material or the sprayed dielectric film. This causes the electrode substrate to be exposed, thereby deteriorating the withstand voltage characteristics of the electrostatic chuck, causing a decrease in the attraction force and destruction of the device due to the overcurrent penetrating the wafer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides an electrostatic chuck stage having a small residual attraction force to a wafer and an electrostatic chuck stage capable of stably removing a wafer. The purpose is to: It is another object of the present invention to provide an electrostatic chuck stage having good withstand voltage characteristics, a large suction force, and capable of maintaining uniform wafer temperature.

[0012]

According to the electrostatic chuck stage of the present invention, the resistivity of the electrostatic film on the electrode surface is reduced to 10 ^11.
To 10 ¹² Ωcm or 10 ¹⁷ Ωcm or more. Also, the radius of the circle in which the n lift pins are arranged is
The ratio to the radius of the wafer is set to the following value. When n = 3, 90% to 100% When n = 4, 75% to 95% When n ≧ 5, 67% to 87% Also, the ratio of the radius of the lift ring to the radius of the wafer is defined as It is 58% to 78%. Further, the electrodes comprise a disk-shaped inner electrode and a ring-shaped outer electrode, and the outer peripheral side surface of the inner electrode and the inner peripheral side surface of the outer electrode are covered with an insulating film, and lift pins are arranged between the inner and outer electrodes.

Further, molybdenum is used for the electrode, a ceramic sprayed film of a mixture of alumina and titania is used for the dielectric film, and a ceramic sintered body mainly containing alumina is used for the insulating base. Further, the flatness of the electrode side surface of the insulating base is set to 10 μm or less, the electrode is mounted on the insulating base through a through hole of the insulating base using a mounting screw, and a voltage is applied to the electrode via the mounting screw. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1 and 2 are cross-sectional views of an electrostatic chuck stage according to a first embodiment of the present invention, and FIG. 3 is a plan view of the same. FIGS. 1 and 2 are respectively a line II and a line II-II in FIG. 2 shows a section along the line. Numeral 11 denotes an electrostatic chuck stage, 12 denotes an electrostatic chuck for adsorbing and fixing a wafer, 13 denotes a ceramic base as an insulating base for fixing the electrostatic chuck 12, and 15 denotes a detached wafer 2 from the electrostatic chuck 12. The lift member is composed of four lift pins 14. The electrostatic chuck stage 11 includes an electrostatic chuck 12, a ceramic base 13, a lift member 15, and the like.

Reference numeral 16 denotes a disk-shaped inner electrode, and 17 denotes an inner electrode 16.
The outer electrodes are provided on the outer peripheral side thereof with a gap 18 therebetween, and molybdenum is used as a material for both electrodes 16 and 17. Reference numeral 19 denotes a dielectric film that covers the upper surfaces of the electrodes 16 and 17 and is made of a ceramic sprayed film in which alumina and titania are mixed. Reference numeral 20 denotes an insulator film that covers both sides of the gap 18, that is, the outer peripheral side of the inner electrode 16 and the inner peripheral side of the outer electrode 17, and sprays alumina ceramic to form both electrodes 16,
17 base materials are not exposed. As described above, the electrostatic chuck 12 includes the electrodes 16 and 17, the dielectric film 19 covering these electrodes, and the insulator film 20. Reference numeral 23 denotes a mounting screw for attaching the electrodes 16 and 17 to the ceramic base 13, and reference numeral 21 denotes a quartz cover provided on an outer peripheral end of the outer electrode 17, covering a portion not covered by the wafer 2 so as not to be exposed to plasma. I have.

The ceramic base 13 has a lift pin 14
Four through-holes 22 are formed to allow the lift pins 14 to pass therethrough.
Are provided at equal intervals on the circumference formed by the
Through the gap 18 and protrudes to the upper surface of the electrostatic chuck 12. The lift pins 14 are arranged on a circumference having a radius of 85% of the radius of the wafer 2. 2
Reference numeral 4 denotes a cylinder for driving the lift pins 14, 25 denotes four lift pins 1 connecting the lift pins 14 and the cylinder 24.
A coupling 26 for raising and lowering 4 at the same time is a bellows 26 which covers the lift pin 14 and keeps the penetrating portion airtight. The flow path of the refrigerant flowing to control the temperature of the electrostatic chuck 12 is indicated by an arrow in FIG. 27 is a refrigerant passage formed in the inner electrode 16 and the outer electrode 17, and 28 is a refrigerant passage 27 of the outer electrode 17
, A refrigerant outlet from the refrigerant passage 27 of the inner electrode 16, and a refrigerant passage 27 of both electrodes 16, 17.
A bridging flow path 31 for connecting between the ceramic base 13 and the electrostatic chuck 12 is formed to penetrate the ceramic base 13 and the electrostatic chuck 12 for flowing He gas into a gap between the front surface of the electrostatic chuck 12 and the back surface of the wafer 2.
e Gas inlet.

FIG. 4 is a sectional view of an etching apparatus provided with the electrostatic chuck stage shown in FIGS.
In the drawing, reference numeral 32 denotes a chamber for performing an etching process, reference numeral 33 denotes a transfer arm for carrying the wafer 2 into and out of the chamber 32, reference numeral 41 denotes a wafer receiver provided on the transfer arm 33, reference numeral 34 denotes a gate shutter, and reference numeral 35 denotes a gate shutter. Is a processing gas inlet for introducing a gas for etching the wafer 2, 36 is a valve, 37 is a vacuum pump for evacuating the chamber 32, 38 is a pressure regulating valve, 39
Is a vacuum gauge, 40 is a He gas pressure adjusting valve, 42 is a ground electrode, 43 is a power supply A for electrostatic chuck, 44 is a power supply B for electrostatic chuck, 45 is a power supply A43 for electrostatic chuck, and the inner electrode 16 and the outer electrode A changeover switch for switching to a circuit for supplying voltage to both 17, 46 is an RF power supply for generating plasma, 47 is a matching box for efficiently introducing the power of the RF power supply 46 to the chamber 32 side, 48 is This is a filter for preventing power from entering the electrostatic chuck power supply A33 from the RF power supply 46.

Next, the operation will be described. FIG.
FIG. 3 is an operation sequence diagram of the etching apparatus shown in FIG. 1, and a wafer process (wiring etching) using the etching apparatus will be described as an example. First, the gate shutter 34 is opened, the wafer 2 placed on the transfer arm 33 is transferred to a position directly above the electrostatic chuck 12 mounted in the chamber 32, and the lift pins 16 are pushed up to receive the wafer 2 from the transfer arm 33. Then, the transfer arm 33 is moved out of the chamber 32, the lift pins 14 are lowered to the original positions, and the wafer 2 is put on the electrostatic chuck 12. Next, the gate shutter 34 is closed, the pressure adjusting valve 38 is opened, and the inside of the chamber 32 is evacuated by the vacuum pump 37 to a pressure of about 10 ^-5 Torr.

Thereafter, a mixed gas of chlorine and boron trichloride is introduced at a rate of 100 cc / min as a gas for etching processing from the processing gas inlet 35 at a gas pressure of about 100 mTorr using the pressure regulating valve 38. To maintain. With the changeover switch 45 connected to the 45a side, a voltage of −400 V is applied to the inner electrode 16 by the power supply A43 for electrostatic chuck, and a voltage of +400 V is applied to the outer electrode 17 by the power supply B44 for electrostatic chuck. To adsorb the wafer 2, and beforehand, He gas is introduced into the gap between the back surface of the wafer 2 and the surface of the electrostatic chuck 12.
The gas is introduced from the e gas inlet 31 and the pressure is adjusted to 10 Torr by the He gas pressure adjusting valve 40. Subsequently, the changeover switch 45 is switched to the 45b side, and the inner electrode 16 and the outer electrode 1 of the electrostatic chuck 12 are switched by the electrostatic chuck power supply A43.
7, a voltage of -400 V is supplied to the electrostatic chuck 12 at the same time, and then an RF power supply 46 supplies 500 W of RF power to the electrostatic chuck 12 on which the wafer 2 is mounted via a matching box 47, and the electrostatic chuck 12 and the ground electrode 42 A plasma is generated during.

Then, an electric circuit is formed via the plasma, and the wafer 2 is attracted to the electrostatic chuck 12. In order to prevent an excessive rise in temperature of the wafer 2 due to heat input from the plasma, 10 Torr
Since He gas is introduced at a pressure of, the temperature of the wafer 2 can be kept constant. The ions and radicals generated in the chlorine-based gas introduced by the plasma etch the wafer 2, and after a predetermined time, when the processing is completed, the RF voltage applied to the electrostatic chuck 12 is released. To stop the plasma, stop the etching processing gas, exhaust the remaining processing gas, close the He gas pressure adjusting valve 40 to stop the He gas introduced to the back surface of the wafer 2, and detach the wafer 2 to the electrostatic chuck 12. (Herein, referred to as a detachment sequence).

The detachment sequence is as follows.
After applying a voltage of -600 V to the outer electrode 17 for 26 seconds, the voltage of each electrode is switched to the opposite polarity.
That is, −600 V is applied to the inner electrode 16 and +60 V is applied to the outer electrode 17.
That is, 0 V is applied. Experiments have shown that by applying the voltage in this manner, the residual attraction force can be effectively reduced even if an oxide film is attached to the back surface of the wafer 2. After applying the detachment sequence, the lift pins 14 are pushed up to detach the wafer 2. The gate shutter 34 is opened, the transfer arm 33 is moved right above the electrostatic chuck 12, the lift pins 14 are lowered to the original position, and the wafer 2 is placed on the transfer arm 33 and transferred out of the chamber 32.

The electrostatic chuck 12 configured as described above
In the above, the dielectric film 19 is formed by forming a mixture of alumina (Al ₂ O ₃ ) and titania (TiO ₂ ) by a ceramic plasma spraying method, changing the mixing ratio of alumina and titania, and using the operating temperature of the electrostatic chuck 12. By adjusting the resistivity so as to be 10 ¹² Ωcm or less or 10 ¹⁷ Ωcm or more, the residual suction force when the wafer 2 is detached can be reduced. FIG. 6 shows an experimental result of the relationship between the resistivity of the dielectric film 19 and the relative residual attraction force. Here, the relative residual attraction force indicates the ratio of the residual attraction force after the voltage is released to the attraction force generated at the electrostatic chuck 12 during the application of the voltage, and in FIG. From such an experimental evaluation, the relative residual attraction force increases because the resistivity of the dielectric film 19 is 10 ¹² to 1.
0 ¹⁷ Ωcm was found. Also, the dielectric film 19
Is too small, the current flowing from the dielectric film 19 through the wafer 2 becomes large, and there is a possibility that devices formed on the wafer 2 may be destroyed. The allowable value of this current varies depending on the process.
Assuming A / cm ² , the dielectric must be at least 10 ¹¹ Ωcm. In addition, in the case of ordinary ceramic spray material,
The resistivity changes depending on the intended use temperature. Therefore, at the stage temperature at the time of use, that is, the process temperature, the dielectric film of the electrostatic chuck 12 has a resistance of 10 ¹¹ to 10 ¹² Ωc.
m or 10 ¹⁷ Ωcm or more.

The allowable value of the residual suction force is the lift pin 14
It depends on the number. The residual suction force allowable value is a limit value of the residual suction force that does not cause wafer lifting or wafer jumping. Here, the wafer uplift refers to FIG.
As shown in (2), if the lift pins 14 are to be separated from the wafer 2 when the suction force remains above the allowable value,
This means that the wafer 2 tilts obliquely while a certain portion of the wafer outer periphery is attracted to the electrostatic chuck 12. Also, as shown in FIG. 8, when the residual suction force is large and the vicinity of the outer periphery of the wafer 2 is pushed up by the lift pins 14 as shown in FIG. 8, the central portion of the wafer 2 is attracted to the electrostatic chuck 12. As it is, it is greatly deformed into a concave shape,
Further, when the lift pins 14 are used to push up, the elastic energy accumulated by the deformation is released at a stretch, and the wafer jumps up, which means that the wafer is displaced or falls off from the electrostatic chuck stage.

[0024] These tolerances were calculated as follows. The offset distance is considered here in order to obtain a residual suction force that prevents the wafer from rising. The offset distance refers to the shortest distance between a side of a figure formed by connecting adjacent lift pins with a straight line and the center of the electrostatic chuck, and is represented by X. The lift pin radius here refers to the radius of the circumference where the lift pins are arranged with the center of the electrostatic chuck as the center, and is represented by r. If the lift pins are arranged near the center and the electrostatic chuck has a residual suction force, the wafer may be lifted.
FIG. 9 is an explanatory diagram thereof. Here, with respect to a fulcrum at a position separated by the offset distance X from the center of the electrostatic chuck, the direction in which the wafer is lifted is referred to as a Wu portion, and the direction in which the wafer is attracted to the stage is referred to as a Wd portion.

One-sided lifting occurs when the moment at the Wd portion is larger than the moment at the Wu portion around the fulcrum. Therefore, the weight of the Wu part is Mu, the distance from the fulcrum to the center of gravity of the Wu part is Xmu, the weight of the Wd part is Md,
Let Xmd be the distance from the fulcrum to the center of gravity of the Wd section. Further, the magnitude of the residual suction force acting on the wafer per unit area is denoted by f, the area of the portion where the wafer remains sucked is Sf, and the distance to the center of gravity is Xsf. Not all the Wd portions are attracted to the electrostatic chuck, and the lift pins move away from the surface of the electrostatic chuck so as to be peeled to some extent when the lift pins are lifted, and there are few actually attracted portions. Therefore, the ratio of the area of the part adsorbed to the electrostatic chuck to the area of the Wd part was set to 0.25. This is a numerical value estimated from the experience that the wafer did not crack when the lift pins were raised under the condition that a certain amount of the residual suction force was present, in consideration of the relationship between the residual suction force and the stress generated in the wafer.

The condition that the moments are balanced even when the residual suction force is present, that is, the condition of the limit of the residual suction force that does not cause the wafer to lift up, is to satisfy the following expression (1). Mu · Xmu = Md · Xmd + f · Sf · Xsf (1) This relationship does not depend on the thickness of the wafer. The offset distance X used in deriving the above equation is determined by the lift pin radius and the number of lift pins. Assuming that n lift pins are evenly arranged with a lift pin radius r, the following relationship holds between r and n. r = x / cos (π / n) (2) In consideration of these, the allowable value of the residual adsorption force is derived as shown in FIG.
Get a result of 0. The horizontal axis indicates the position of the lift pin radius with respect to the wafer radius, and the vertical axis indicates the allowable value of the residual suction force. “Circular” in the drawing means a case where a circular lift ring as described in a second embodiment described later is used. In view of this, it seems that the larger the lift pin radius, the larger the allowable value of the residual suction force. However, in the electrostatic chuck in which lift pins are actually arranged on the outer periphery of the wafer, if the residual suction force is large, the wafer jumps up instead of the wafer piece as described below. FIG. 11 is a diagram for explaining this.

A residual suction force that does not cause the wafer to jump is determined. First, for simplicity, it is assumed that the wafer is not lifted at several points, such as lift pins, but simultaneously lifts the circumference drawn by the lift pin radius. Further, the portion where the wafer is attracted to the stage by the residual attracting force is also circular, and its radius is rf. At this time, the ratio between rf and r used was 0.25. This is obtained by using the same method as when the ratio between the Wd portion and the portion where the wafer is sucked is obtained. The maximum deflection ωmax when the lift pin is pushed up by the load P is expressed by the following equation, assuming that the wafer is fixed at the portion where the wafer is attracted. Here the maximum deflection ωm
ax refers to the height from the surface of the electrostatic chuck to the position where the lift pin is pushed up. ωmax = α (r ² / Et ³ ) P (3) where α is a constant determined from r and rf, t is the thickness of the wafer, and t = 0.72 mm is used as a general thickness. Was. E is the longitudinal elastic modulus of the wafer. If r and rf are determined, this equation becomes a first-order equation, which is in agreement with the equation of spring strain and force, and the spring coefficient k can be determined. That is, the energy when the spring having the spring coefficient k is displaced by ωmax is ・ · k (ωmax) ² (4). On the other hand, if the wafer is flipped up by the height h, the energy required for it is expressed by mgh (5). Here, m is the weight of the wafer, and g is the gravitational acceleration.

Here, the height at which the robot can be flipped up is 1 m.
m, and the residual adsorption force at that time can be calculated. FIG. 12 shows the result. From this, it can be seen that the smaller the lift pin radius, the larger the residual suction force of the jump. The jump height of the wafer is set to 1 mm for the following reason. For example, in FIG. 4, a step slightly higher than the lower surface of the wafer (about 0.5 to 1 mm) is formed on the outer peripheral side of the wafer by the wafer receiving claw 41 of the transfer arm 33 so that the wafer does not shift during the wafer transfer. I have. When a wafer is received from the electrostatic chuck stage, if the wafer is misaligned, the wafer will ride on this stage, resulting in a wafer transfer error. The play of receiving the wafer is set to about 2 mm. If the wafer jumps in the direction of 45 ° from the vertical with respect to the surface of the electrostatic chuck when the wafer jumps, the largest deviation occurs. Assuming that the initial velocity at this time is all used to jump in the vertical direction of the wafer, the jump height is about 1 mm.

Considering the allowable residual attraction force when the wafer is lifted and when the wafer is jumped together, FIG.
Becomes The point at which the curve of the upward movement of the wafer and the curve of the upward movement of the wafer intersect is the point at which the allowable value of the residual suction force becomes the largest. The value varies depending on the number or shape of the lift pins. When the number of lift pins is the smallest, three, the outermost peripheral portion of the wafer, and when the number is four, the radius of the wafer is 85.
% Position, 5 positions are 77% of the wafer radius, and 5 positions are 68% of the wafer radius when the lift ring described in the second embodiment is used. A slight deviation from these optimal positions is practically acceptable, but a large deviation degrades the allowable value.
%. Also, even when n ≧ 6, the value is not so different from n = 5, so that n = 5 may be used.

When a lift pin is attached to a conventional electrostatic chuck, a lift pin hole 6 is provided in the electrostatic chuck itself to penetrate the lift pin as shown in FIGS. In particular, when the electrode body drills a hole 6 for a lift pin in a conductive electrostatic chuck, the inside of the hole is insulated by an insulating member 8 such as a ceramic bush, and the dielectric film 7 is sprayed thereon. However, in this method, the insulating member 8 and the dielectric film 7 are peeled off due to factors such as heat history, and the base of the electrode 5 is exposed, causing abnormal discharge. In this embodiment, the inner electrode 16 and the outer electrode 17
In this case, the insulator film 20 (for example, alumina) can be easily formed by thermal spraying on the inner electrode 16 and the outer peripheral side surface and the inner peripheral side surface of the outer electrode 17, and a ceramic bush or the like is not used. Film peeling is unlikely to occur, and abnormal discharge due to exposure of the electrode substrate does not occur.

As described above, the dielectric film 19 is a mixture of alumina and titania. This is because it is easy to adjust the desired resistivity by changing the mixing ratio of these two materials. In order to reduce the difference in linear expansion coefficient between the dielectric film 19 and the inner and outer electrodes 16 and 17, molybdenum is used as a base material for each of the electrodes. The linear expansion coefficient of the dielectric film 19 is 7.9 × 10 ⁻⁶ (1 / ° C.)
That of each electrode is 5.3 × 10 ⁻⁶ (1 / ° C.). This makes it difficult for the film to peel off from the electrode due to the heat history. Also, the electrostatic chuck 1
By using the ceramic base 13 for attaching the ceramic chuck 2, the difference in the coefficient of linear expansion between molybdenum, which is the base material of the electrostatic chuck 12, and the ceramic is small. In a case where the ceramic base 13 is used in a high temperature environment, the thermal stress generated by the difference between the thermal strains is small, and the ceramic base 13 is not damaged or distorted.

Even if the front and back surfaces of the electrode member of the electrostatic chuck 12 are processed with high precision, when the ceramic film is sprayed on the electrode member, the electrode member is distorted by the heat of the spraying. At this time, if the flatness of the electrode side surface of the ceramic base 13, that is, the flatness of the electrostatic chuck mounting surface is accurately processed, even the electrostatic chuck 12 slightly distorted by thermal spraying can be made to follow the ceramic base 13. By mounting, the distortion can be corrected, and thus the flatness of the surface of the electrostatic chuck 12 can be improved. When the relationship between the undulation of the surface of the electrostatic chuck 12 and the attraction force is experimentally examined, the undulation is 9.8 μm at a measured length of 50 mm.
m, the adsorbing force obtained was about 72 gf / cm ² , whereas when the swell was 15 μm, about 39 gf / cm 2
Reduced to ² . Therefore, in order to obtain a sufficiently large suction force, it is necessary to suppress the undulation on the surface of the electrostatic chuck 12 to about 10 μm. The flatness of the surface of the electrostatic chuck 12 is 1
In order to keep the thickness within 0 μm, the processing accuracy of the mounting surface of the ceramic base 13 needs to be 10 μm or less in flatness. In order to increase the strength of the ceramic base 13, the thickness is preferably set to 10 mm or more.

Since the material is selected so that the difference in linear expansion coefficient is reduced by using an alumina sintered body for the ceramic base 13, a through hole for the mounting screw 23 of the electrostatic chuck 12 is formed in the ceramic base 13. Even when the opening 22 is opened, no crack or the like is generated by the thermal stress from the through hole 22, the electrostatic chuck 12 can be easily attached, and a voltage is applied to the electrostatic chuck 12 through the attachment screw 23. By supplying, the structure of the mounting portion of the electrostatic chuck 12 can be simplified.

Embodiment 2 FIG. 14 is a cross-sectional view of an electrostatic chuck stage according to a second embodiment of the present invention. A lift member 15 for detaching the attracted wafer 2 from the electrostatic chuck 12 includes a lift pin 14 and a circular lift ring 5.
Consists of one. The lift pins 14 are the same as those in the first embodiment, except that the lift ring 51 comes into contact with the wafer 2 and the lift pins 14 push up the lift ring 51. The center of the lift ring 51 is the electrostatic chuck 12
And its radius (average radius) is 68% of the radius of the wafer 2. It is the first embodiment shown in FIG.
This is because it is an optimal value as described using. The other parts are the same as those in the first embodiment, and a description thereof will be omitted.

The electrostatic chuck stage according to the present invention is of a type other than the above-mentioned parallel plate type (capacitive coupling type), for example, an ECR (Electron Cyclotron Resonance) type or dielectric coupling type etching apparatus, or a CVD or the like. It goes without saying that it can be used in an apparatus of another process. In addition, a method other than the two-electrode voltage application method described above, for example, an electrostatic chuck using a single-pole voltage application method can be used.

[0036]

According to the electrostatic chuck stage of the present invention, the resistivity of the electrostatic film on the surface of the electrode is increased from 10 ¹¹ to 10
By setting the resistance to ¹² Ωcm or 10 ¹⁷ Ωcm or more, the residual suction force can be reduced, and the wafer can be easily separated. The ratio of the radius of the n lift pin arrangement circles or the radius of the lift ring to the radius of the wafer is: 90% to 100% when n = 3, 75% to 95% when n = 4, and n ≧ 5. In the case of a lift ring of 67% to 87%, by setting the ratio to 58% to 78%, it is possible to prevent the wafer from lifting and the wafer from jumping, thereby improving the productivity of the process. Furthermore, the electrode is composed of an inner electrode and an outer electrode, the outer peripheral side surface of the inner electrode and the inner peripheral side surface of the outer electrode are covered with an insulator film, and a lift pin is arranged between the inner and outer electrodes, thereby providing an insulating structure that is resistant to heat history. And withstand voltage characteristics are improved.

Also, by using molybdenum, a mixed ceramic sprayed film of alumina and titania, and a ceramic sintered body for the electrode, the dielectric film, and the insulating base, respectively, the difference in linear expansion coefficient of each member is reduced, and the heat history is reduced. The possibility of generation of cracks and the like is reduced, and the withstand voltage characteristics are improved. Further, the flatness of the insulating base is reduced to 10 μm or less, the electrodes are mounted on the insulating base with mounting screws, and a voltage is applied through the mounting screws, thereby increasing the attraction force and maintaining uniformity of the wafer temperature. Yes, the structure can be simplified.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electrostatic chuck stage according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electrostatic chuck stage according to the first embodiment of the present invention.

FIG. 3 is a plan view of the electrostatic chuck stage according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of an etching apparatus provided with the electrostatic chuck stage of FIG.

5 is an operation sequence diagram of the etching apparatus of FIG.

FIG. 6 is a graph showing a resistivity of a dielectric substance versus a residual suction force in the electrostatic chuck stage of FIG. 1;

FIG. 7 is an explanatory view showing the upward movement of a wafer.

FIG. 8 is an explanatory diagram showing a jump of a wafer.

FIG. 9 is an explanatory diagram for obtaining a wafer lifting condition.

FIG. 10 is a graph showing a radius of a lift pin arrangement circle versus an allowable value of a residual suction force with respect to a wafer lift;

FIG. 11 is an explanatory diagram for obtaining a wafer jump condition.

FIG. 12 is a graph showing a radius of a lift pin arrangement circle versus an allowable value of a residual suction force with respect to a jump of a wafer.

FIG. 13: One-sided and bouncing wafers are considered.
It is a graph which shows the lift pin arrangement | positioning circle radius versus the residual suction force allowable value.

FIG. 14 is a sectional view of an electrostatic chuck stage according to a second embodiment of the present invention.

FIG. 15 is a sectional view showing a conventional electrostatic chuck.

FIG. 16 is a sectional view showing another conventional electrostatic chuck.

FIG. 17 is a sectional view showing still another conventional electrostatic chuck.

[Explanation of symbols]

11 electrostatic chuck stage, 12 electrostatic chuck, 1
3 ceramic base, 14 lift pins, 15 lift members, 16 inner electrodes, 17 outer electrodes, 18 voids, 1
9 dielectric film, 20 insulator film, 22 through hole, 23
Mounting screw, 51 lift ring.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Minoru Hanasaki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (6)

[Claims] 1. An electrostatic chuck stage comprising a metal electrode covered with an electrostatic film and provided with an electrostatic chuck for attracting a wafer by electrostatic force, wherein the resistance of the dielectric film at the operating temperature is controlled. Rate from 10 ¹¹ to 10 ¹² Ωcm or 1
An electrostatic chuck stage having a resistance of 0 ¹⁷ Ωcm or more. 2. The wafer comprising an electrostatic chuck configured to cover a surface of a metal electrode with a dielectric material and adsorbing a wafer by electrostatic force, and n lift pins arranged at equal intervals on a circumference. Wherein the ratio of the radius of the circle on which the lift pins are arranged to the radius of the wafer is set to the following value. Chuck stage. 90% to 100% when n = 3, 75% to 95% when n = 4, 67% to 87% when n ≧ 5 3. A wafer comprising: an electrostatic chuck configured to cover a surface of a metal electrode with a dielectric material; adsorbing a wafer by electrostatic force; a lift ring in contact with the wafer; and lift pins pressing the lift ring. Wherein the ratio of the radius of the lift ring to the radius of the wafer is 58% to 78%. stage. 4. An electrode comprising: a disk-shaped inner electrode; and a ring-shaped outer electrode arranged with a gap on the outer peripheral side of the inner electrode, wherein an outer peripheral side surface of the inner electrode and an inner peripheral side surface of the outer electrode are provided. The electrostatic chuck stage according to claim 2 or 3, wherein the substrate is covered with an insulator film, and a lift pin is disposed between the inner electrode and the outer electrode. 5. An electrostatic chuck stage comprising a metal electrode covered with a dielectric film and comprising an electrostatic chuck for attracting a wafer by electrostatic force and an insulating base for fixing the electrode. While using molybdenum as a material for the electrode, a ceramic sprayed film obtained by mixing alumina and titania was used as a material for the dielectric film, and a ceramic sintered body mainly containing alumina was used as a material for the insulating base. An electrostatic chuck stage characterized in that: 6. The flatness of the surface of the insulating base on the electrode side is 1
A thickness of 0 μm or less, a through hole is provided in the insulating base, an electrode is mounted on the insulating base through the through hole using a mounting screw, and a voltage is applied to the electrode via the mounting screw. The electrostatic chuck stage according to claim 5, wherein