JPH10189697A - Electrostatic chuck device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irregular attraction from occurring in an electrostatic chuck device when a polarity difference is present in a dielectric layer by a method wherein voltages applied to a first chucking electrode and a second chucking electrode built in an electrostatic chuck are so controlled as to make currents which flow through the first and second electrode nearly equal to each other. SOLUTION: A work 10 is placed on the holding surface 5 of a dipole electrostatic chuck 1, and a positive voltage and a negative voltage are applied to a first chucking electrode 4a and a second chucking electrode 4b through high-voltage power supplies 8a and 8b respectively. At this point, a first part of the work 10 confronting the first chucking electrode 4a is charged with negative electricity, and a second part of the work 10 confronting the second chucking electrode 4b is charged with positive electricity, so that a potential difference is induced to generate attraction. At this point, currents following through the chucking electrodes 4a and 4b are measured with ammeters 7a and 7b, and the high power supplies 8a and 8b are adjusted through an arithmetic processing unit 9 from the above measured values so as to make the absolute values of currents which flow through the chucking electrodes 4a and 4b nearly equal to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first electrode for applying a positive voltage, which is used for holding an object to be adsorbed such as a semiconductor wafer or a liquid crystal glass substrate in a semiconductor manufacturing apparatus or a liquid crystal manufacturing apparatus. The present invention relates to an electrostatic chuck device including a second electrode for application.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing process, in a film forming apparatus for forming a thin film on a semiconductor wafer or a dry etching apparatus for performing fine processing on a wafer, an electrostatic chuck is used to hold the wafer. It is used.

[0003] This type of electrostatic chuck includes a monopolar type in which a voltage is applied between a suction electrode built in the electrostatic chuck and a wafer mounted on a holding surface to suction and hold the wafer. The electrostatic chuck is provided with a first suction electrode for applying a positive voltage and a second suction electrode for applying a negative voltage, and a voltage is applied between these electrodes to hold the wafer on the holding surface. There is a bipolar type for holding, and among them, the bipolar type electrostatic chuck has an advantage that there is little adverse effect on the wafer because there is no need to directly energize the wafer unlike the monopolar type.

The structure of the bipolar electrostatic chuck is as follows.
A first attracting electrode for applying a positive voltage to the upper surface of the insulating base and a second attracting electrode for applying a negative voltage are respectively provided on the upper surface of the insulating base so as to cover these electrodes. In some cases, a dielectric layer is integrally coated and the upper surface is used as a holding surface.

Further, in recent years, the characteristics required for an electrostatic chuck have been increased with an increase in the degree of integration of semiconductor elements, and an electrostatic chuck in which a dielectric layer including a holding surface is formed of ceramics has been used. And those formed of alumina ceramics containing titanium or aluminum nitride ceramics have been proposed (see JP-A-62-264638 and JP-A-6-151332).

When the wafer is held by the bipolar electrostatic chuck, after the wafer is placed on the holding surface,
A positive voltage is applied to the first suction electrode built in the electrostatic chuck,
By applying a negative voltage to the second suction electrode so that the absolute values of the respective voltages become substantially equal, the wafer is suction-held on the holding surface.

[0007]

However, by using a bipolar electrostatic chuck in which the dielectric layer is made of ceramics in a high-temperature atmosphere, the dielectric layer has a volume resistivity of 10 ¹³ Ω · cm. When it is reduced to less than 1, the positive and negative charge amounts are different, and there is a problem that the wafer placed on the holding surface cannot be uniformly sucked.

This is because if the volume resistivity of the dielectric layer during use is less than 10 ¹³ Ω · cm, ceramics have properties equivalent to those of a semiconductor element such as a silicon semiconductor. When the layer is formed of aluminum nitride ceramics, properties similar to those of a PN-bonded semiconductor element appear, with the properties of an N-type semiconductor near the adsorption electrode and the properties of a P-type semiconductor near the holding surface. become. Therefore, the wafer side facing the second attracting electrode to which the negative potential is applied has a positive potential, and a forward bias circuit is formed for the PN-coupled semiconductor element, so that electric charges are not generated. While the wafer moves smoothly to obtain a strong suction force, the wafer side facing the first suction electrode to which the positive potential is applied has a negative potential, and a reverse bias circuit is provided for the PN-coupled semiconductor element. As a result, the electric charge did not move smoothly, and the adsorption force was weak, so that the adsorption unevenness occurred.

When the polarity difference occurs in the dielectric layer, the wafer cannot be held with a uniform suction force, and when the wafer is heated, it cannot be heated uniformly.

In addition, since the polarity difference of the dielectric layer is not always the same, it is difficult to optimize even if the area and voltage distribution of the adsorption electrode are determined in advance in consideration of the polarity difference. there were.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a first attracting electrode for applying a positive voltage and a negative voltage applied to the lower surface of a dielectric layer having a holding surface. An electrostatic chuck provided with a second attraction electrode for detecting a current value flowing through the first attraction electrode and the second attraction electrode, respectively; From the control means for adjusting the voltage value applied to both the first and second attraction electrodes based on the signal value of the first and second attraction electrodes so that the absolute values of the currents flowing through the first and second attraction electrodes become substantially equal. This constitutes a chuck device.

That is, the inventor of the present invention has repeatedly conducted research to eliminate uneven adsorption in the case where there is a difference in polarity between the dielectric layers, and found that the first and second adsorption electrodes have the same size. It has been found that the current value flowing through the first suction electrode differs from the current value flowing through the second suction electrode when the above voltage is applied. Further, the volume resistivity of the dielectric layer is 10 ¹³
If it is less than Ω · cm, the attraction force is related to the value of the current flowing through the dielectric layer, so that the absolute value of the current value flowing through the first attraction electrode and the second attraction electrode is made substantially equal. Thus, the present inventors have found that a uniform adsorption force can be obtained, and have reached the present invention.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic view showing an electrostatic chuck device according to the present invention, in which a first attracting electrode 4a for applying a positive voltage and a negative electrode for applying a negative voltage are formed on the upper surface of a ceramic substrate 2. And a ceramic dielectric layer 3 on the upper surface of the ceramic base 2 so as to cover the electrodes 4a and 4b, and the upper surface of the ceramic dielectric layer 3 is held as a holding surface. 5, a bipolar electrostatic chuck 1 and two suction electrodes 4 built in the electrostatic chuck 1.
The ammeters 7a and 7b capable of measuring a minute current value as detection means for measuring the current value flowing through the a and 4b, and the first suction based on the signal values measured by the ammeters 7a and 7b. The arithmetic processing unit 9 is configured as control means for adjusting a voltage value applied to both of the attraction electrodes 4a and 4b so that the absolute values of current values flowing through the attraction electrode 4a and the second attraction electrode 4b become substantially equal. It is.

The pattern of the suction electrodes 4a and 4b incorporated in the electrostatic chuck 1 is shown in FIG.
2 (b), a comb-like shape as shown in FIG. 2 (b), or a ring-shaped first suction electrode 4a as shown in FIG. 2 (c). The second suction electrode 4b is formed concentrically, or the fan-shaped first suction electrode 4a and the second suction electrode 4b are alternately formed radially as shown in FIG. 2D. Objects having various pattern shapes such as objects can be used.
The first and second suction electrodes 4a and 4b preferably have the same area, but any one of them may be large as long as it is small.

Power supply terminals 6a and 6b are connected to the suction electrodes 4a and 4b built in the electrostatic chuck 1, and a high voltage power supply 8a for applying a DC voltage between the power supply terminals 6a and 6b. , 8b.

Although not shown in FIG. 1, the power supply to the suction electrodes 4a and 4b is turned off before the holding surface 5
In order to enhance the desorption response of the substance 10 adsorbed on the
By forming a concave groove in a portion of the holding surface 5 where the suction electrodes 4a and 4b are not formed to reduce the contact area of the object 10 to be sucked, the detachment responsiveness can be improved. further,
By supplying a gas such as He into the concave groove, the heat transfer characteristic to the object 10 when the electrostatic chuck 1 is heated can also be improved.

The ceramic dielectric layer 3 constituting such an electrostatic chuck 1 may be formed of a ceramic mainly composed of alumina, aluminum nitride, yttrium-aluminum-garnet, yttria, silicon nitride, silicon carbide and the like. When the electrostatic chuck 1 is used under plasma generation such as a film forming apparatus or an etching apparatus, the content of alumina which is particularly excellent in plasma resistance among the above ceramics is 99% by weight or more, and silica is used as a sintering aid. Alumina ceramics containing a small amount of magnesia and aluminum nitride ceramics containing 99% by weight or more of aluminum nitride are preferable.

The material of the suction electrodes 4a and 4b is similar to the coefficient of thermal expansion of the ceramic base 2 and the ceramic dielectric layer 3 constituting the electrostatic chuck 1, and
High heat resistance is good, molybdenum, copper
Metal such as metal or tungsten may be used.

Further, inside the ceramic substrate 2,
A heater electrode or a plasma generation electrode can be built in, and the suction electrodes 4a and 4b can also have a function as a plasma generation electrode.

When the electrostatic chuck 1 is manufactured, green sheets forming the ceramic dielectric layer 3 and the ceramic substrate 2 are prepared from the above-mentioned ceramic raw material, and the green sheets forming the ceramic substrate 2 are formed on the green sheets. Via holes for fixing the attracting electrodes 4a and 4b and the power supply terminals 6a and 6b are formed, and a green sheet forming the ceramic dielectric layer 3 is laminated so as to cover the attracting electrodes 4a and 4b. Can be obtained.

Alternatively, only the ceramic dielectric layer 3 can be formed by a film forming method.
A ceramic substrate 2 having via holes for fixing the a and 6b is manufactured by using the above-described green sheet laminating method, and a first voltage for applying a positive voltage is provided so as to be electrically connected to the via hole exposed on the upper surface. Are formed, and a second suction electrode 4b for applying a negative voltage is formed. The electrodes 4a and 4b may be formed by a method such as brazing a metal foil, forming a film such as a CVD method, or printing and printing a conductive paste. Thereafter, the two electrodes 4a, 4
The dielectric layer 3 made of a ceramic film may be formed by a film forming method such as a PVD method or a CVD method so as to cover b, and the holding surface 5 may be formed on the dielectric layer 3.

Next, a method of adsorbing an object to be adsorbed by the electrostatic chuck device of the present invention will be described with reference to FIG.

First, the holding surface 5 of the bipolar electrostatic chuck 1
An object to be adsorbed 10 such as a semiconductor wafer is placed on the substrate. Then, a positive voltage is applied to the first suction electrode 4a by the high voltage power supplies 8a and 8b, and the second suction electrode 4b
Is applied with a negative voltage. At this time, the first adsorption electrode 4
The object 10 facing the a is negatively charged, and the object 10 facing the second adsorption electrode 4b is positively charged. Therefore, a potential difference is generated between the first electrode for adsorption 4a and the object 10 and between the second electrode for adsorption 4b and the object 10, and an attraction force is exerted.

On the other hand, the volume resistivity of the ceramic dielectric layer 3 constituting the electrostatic chuck 1 is 10 ¹³ when used.
When the resistance is equal to or less than Ω · cm, a polarity difference occurs inside the ceramic dielectric layer 3. For example, the ceramic dielectric layer 3 has a property equivalent to a PN junction semiconductor,
When the property of the N-type semiconductor is generated near the suction electrodes 4a and 4b and the property of the P-type semiconductor is generated near the holding surface 5, the side of the second suction electrode 4b to which the negative voltage is applied has a forward bias. A circuit is formed, and the electric charge moves smoothly, so that a strong adsorption force is obtained. On the other hand, the first adsorption electrode 4a to which the positive voltage is applied forms a reverse bias circuit, so that the electric charge is smoothed. However, it is difficult to uniformly adsorb the object to be adsorbed 10.
b is measured by the ammeters 7a and 7b, and based on the signal values, the high-voltage power supply 8a is operated by the arithmetic processing unit 9 so that the absolute values of the current values flowing through the suction electrodes 4a and 4b become substantially equal. , 8b are adjusted.

Therefore, the first suction electrode 4a side and the second
Since a substantially uniform suction force is obtained on the suction electrode 4b side, the object 10 can be suction-held with high accuracy.

The processing by the arithmetic processing unit 9 is as follows.
The current value flowing through the first attracting electrode 4a to which the positive voltage is applied is I ₁ , the current value flowing through the second attracting electrode 4b to which the negative voltage is applied is I _2, and the total sum of the absolute values of the applied positive and negative voltages If V is V, it is sufficient to perform the arithmetic processing by Equation 1.

[0028]

(Equation 1)

[0029]

EXAMPLE Here, a bipolar electrostatic chuck 1 having suction electrodes 4a and 4b having a comb-like pattern shape as shown in FIG. 2B was prototyped, and as shown in FIG. A high-voltage power supply 8 is connected to the first and second chucking electrodes 4a and 4b of the electrostatic chuck 1 via minute ammeters 7a and 7b.
a and 8b, respectively, and the microammeters 7a and 7b and the high-voltage power supplies 8a and 8b were connected to the arithmetic processing unit 9. The outer diameter of the electrostatic chuck 1 is 200 m.
The ceramic dielectric layer 3 and the ceramic base 2 were made of aluminum nitride ceramics having a purity of 99%.

When the temperature distribution of the holding surface 5 when the electrostatic chuck 1 was heated to 400 ° C. was measured, the temperature distribution was 3 ° C.
There was a slight temperature difference. The volume resistivity of the ceramic dielectric layer 3 when heated to 400 ° C. is 10 ¹⁰ Ω · c.
m and 10 ¹³ Ω · cm or less.

Therefore, a silicon wafer is placed on the holding surface 5 while the electrostatic chuck 1 is heated to 400 ° C., and +500 V is applied to the first suction electrode 4 a and −500 V is applied to the second suction electrode 4 b. Is applied to each of the suction electrodes 4a, 4b when the wafer is suctioned, the current value of each of the currents measured by the ammeter 7a, 7b.
As shown in Table 1, the difference between the current value of the first suction electrode 4a and the current value of the second suction electrode 4b was twice as large as measured in b. Therefore, when the temperature distribution of the wafer was measured, there was a temperature difference of as much as 28 ° C., and a uniform suction force was not obtained.

[0032]

[Table 1]

[0033]

[Table 2]

Therefore, the processing of equation 1 is performed by the arithmetic processing unit 9 on the basis of the current values of the first suction electrode 4a and the second suction electrode 4b, and +666.6 is applied to the first suction electrode 4a.
As a result of applying a voltage of −333.3 V to the second attracting electrode 4b, as shown in Table 2, the current value of the first attracting electrode 4a and the second attracting electrode 4b was The absolute values became equal, and the temperature distribution of the wafer at this time was measured. As a result, heating unevenness was able to be suppressed to 3 ° C., and a uniform suction force was obtained.

Thus, as in the present invention, the first chucking electrode and the second chucking electrode incorporated in the electrostatic chuck are set so that the current values flowing through the first chucking electrode and the second chucking electrode become substantially equal. It can be understood that the object to be sucked can be held with a uniform suction force by controlling the voltage value applied to the suction electrode 2.

[0036]

As described above, according to the present invention, the first attraction electrode for applying a positive voltage and the first attraction electrode for applying a negative voltage are provided on the lower surface of the dielectric layer having the holding surface. An electrostatic chuck comprising two suction electrodes;
Detecting means for measuring a current value flowing through each of the attraction electrode and the second attraction electrode, and the first attraction electrode and the second attraction electrode based on signal values from these detection means. By configuring the electrostatic chuck device from the control means for adjusting the voltage value applied to both the attracting electrodes so that the absolute values of the flowing current values are substantially equal, it is assumed that a polarity difference occurs in the ceramic dielectric layer. Also, the object to be mounted placed on the holding surface can always be held with a uniform suction force. Therefore, if this electrostatic chuck device is used for a film forming device, a thin film having a uniform film thickness can be formed on an object to be adsorbed, and if it is used for an etching device, it can be processed to a predetermined dimensional accuracy. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an electrostatic chuck device according to the present invention.

2 (a) to 2 (d) are plan views showing various pattern shapes of a suction electrode of the electrostatic chuck device according to the present invention.

[Explanation of symbols]

1. Electrostatic chuck 2. Ceramic substrate 3.
··· Ceramic dielectric layer 4a ··· First suction electrode 4b ··· Second suction electrode 5 ··· Holding surface 6a and 6b ··· Power supply terminal 7a and 7b ··· Ammeter 8a and 8b: High-voltage power supply 9: Arithmetic processing unit 1
0 ... object to be adsorbed

Claims (1)

[Claims] 1. A static electrode comprising a first attracting electrode for applying a positive voltage and a second attracting electrode for applying a negative voltage on a lower surface of a dielectric layer having a holding surface. An electric chuck, each detecting means for measuring a current value flowing through each of the first suction electrode and the second suction electrode, and the first suction electrode and the second suction electrode based on signal values from these detection means. An electrostatic chuck device comprising: control means for adjusting a voltage value applied to both of the attraction electrodes so that the absolute values of the currents flowing through the second attraction electrodes become substantially equal.