KR100690136B1 - Apparatus for removing residual charge of electrostatic chuck and method thereof - Google Patents

Abstract

An apparatus for removing residual charges of an electrostatic chuck and a removing method of the same are provided to neutralize residual charges from a wafer by using a dechucking module. A chamber(10) has predetermined volume and an exhaust hole formed at the bottom. An electrostatic chuck(20) includes a lamination structure of an upper insulating layer, an upper electrode for receiving a DC voltage, a lower insulating layer, and a lower electrode for receiving bias power. A coil part(30) is installed at an upper part of the chamber. A helium gas supply and exhaust unit improves thermal conductivity between the electrostatic chuck and the wafer and supplies an ionized gas to a rear surface of a wafer. A DC voltage module(60) is connected with the electrostatic chuck. A dechucking module(70) is connected with the electrostatic chuck in order to change alternately a positive voltage and a negative voltage.

Description

Apparatus for removing residual charge of electrostatic chuck and method

1 is a configuration diagram of a process chamber of a conventional plasma etching apparatus having a unipolar electrostatic chuck;

Figure 2a is a block diagram of a process chamber of the plasma etching apparatus according to an embodiment of the present invention,

Figure 2b is a waveform diagram showing the waveform of the voltage applied to the electrostatic chuck by the dechucking module of the present invention,

3A is a schematic diagram showing a charged state of a charged wafer and an electrostatic chuck in a chucking state,

3B is a schematic diagram showing the charged state of the initially charged state of the wafer and the electrostatic chuck during the dechucking step;

3C is a schematic diagram showing a charged state of an intermediate state of a charged wafer and an electrostatic chuck during the dechucking step;

Figure 3d is a schematic diagram showing a state in which the residual charge of the wafer and the electrostatic chuck of the end state is removed during the dechucking step,

4 is a graph showing comparative data of the frequency of dechucking error before and after application of the dechucking module according to the present invention;

5 is a graph for explaining a method of removing residual charge of an electrostatic chuck according to an embodiment of the present invention;

6A is a waveform diagram of a voltage biased in the plus direction according to a monitored DC bias value;

6B is a waveform diagram of a voltage biased in the negative direction according to the monitored DC bias value;

7 is a block diagram of a helium gas supply unit of the method for removing residual charge of an electrostatic chuck according to an embodiment of the present invention;

8 is a graph illustrating a method of removing residual charge of an electrostatic chuck according to another embodiment of the present invention;

9 is a graph illustrating a method of removing residual charge of an electrostatic chuck according to another embodiment of the present invention.

* Explanation of symbols for main parts of drawings *

10 chamber 20 electrostatic chuck

21: upper insulating layer 22: upper electrode

23: lower insulating layer 24: lower electrode

25: lift pin

30: coil part 40: source power

41: source high frequency oscillator 42: source matcher

50: bias power 51: bias high frequency oscillator

52: bias matcher 60: DC voltage module

70: dechucking module 80: wafer

90: helium gas supply and discharge 91: helium supply module

92: helium supply line 93: helium valve

94: dump line 95: dump valve

96: List 97: Pumping Line

The present invention relates to an apparatus and a method for removing residual charge of an electrostatic chuck of a semiconductor manufacturing equipment for manufacturing a semiconductor, and more particularly, to remove residual charge of an electrostatic chuck for fixing a wafer in a process chamber in which an etching process is performed using plasma. A device and a method of removal are provided.

In general, semiconductor devices are made by depositing a thin film on a wafer, applying a photosensitive agent to pattern the deposited thin film into a desired shape, and then performing a photolithography process and an etching process to perform a complicated process of removing unnecessary thin films. . Each of these processes is performed in a chamber, which is a closed container, and a chuck is installed inside the chamber as a means for fixing a wafer.

There are various types of chucks, such as mechanical chucks, vacuum chucks, and electrostatic chucks, depending on how the wafer is held. Among them, the electrostatic chuck is formed between the wafer and the electrode installed inside the chuck. It refers to a chuck that fixes a wafer by an electrostatic attraction applied to it, and has been increasing in recent years because it is superior in terms of particle reduction and process uniformity compared to other types of chucks.

In particular, the use of an electrostatic chuck is common in etching equipment using high density plasma, and a bipolar type or a unipolar type is commonly used.

Hereinafter, a configuration of a process chamber using an electrostatic chuck and a method of removing residual charge between a conventional electrostatic chuck and a wafer using the electrostatic chuck will be described with reference to the accompanying drawings.

1 is a block diagram of a conventional plasma etching apparatus having a unipolar electrostatic chuck.

Etching apparatus using a plasma is basically a chamber 10 having a predetermined volume and having an exhaust port at the bottom, an electrostatic chuck 20 installed at a lower portion of the chamber, to which a DC voltage and a bias power are applied, and installed at an upper portion of the chamber. Coil unit 30 to which source power is applied, helium gas supply and discharge unit (not shown), process gas injection unit (not shown), and pumping line (not shown) to improve thermal conductivity between the electrostatic chuck and the wafer. Not).

The electrostatic chuck 20 includes an upper insulating layer 21 on which the wafer 80 is placed, an upper electrode 22 to which a direct current voltage is applied, a lower insulating layer 23, and a lower electrode 24 to which a bias power is applied. 1) is a laminated structure as shown in FIG. 1, and is composed of a plurality of lift pins 25 for safely placing the wafer 80 on the upper insulating layer 21.

The upper insulating layer 21 insulates the wafer 80 and the upper electrode 22, and the lower insulating layer 23 insulates the upper electrode 22 and the lower electrode 24, respectively. The source power supply 40 is composed of a source high frequency oscillator 41 and a source matcher 42, and the bias power supply 50 is composed of a bias high frequency oscillator 51 and a bias matcher 52, which are necessary for generating and maintaining plasma. It serves to supply power.

When the wafer 80 is placed on the upper insulating layer 21 of the electrostatic chuck to perform the etching process, a process gas is injected from the gas injection unit into the chamber, the source power 40 is applied to the coil unit 30, and the electrostatic Plasma is generated inside the chamber 10 by applying the DC voltage module 60 and the bias power supply 50 to the upper and lower electrodes 22 and 24 of the chuck, respectively.

In this case, when a positive charge (or negative charge) is charged by a DC voltage applied to the upper electrode 22 to form an electrostatic field, a negative charge (or positive charge) is induced in the lower portion of the wafer 80 by the electrostatic field, and the wafer 80 The wafer 80 is fixed by the electrostatic attraction between the wafer 80 and the electrostatic chuck 20 formed as the positive charge (or negative charge) is induced on the upper portion of the.

Meanwhile, since the surface of the wafer is continuously heated by the plasma during the process, the helium gas, which is a gas having excellent thermal conductivity, is maintained between the wafer and the electrostatic chuck at a predetermined pressure in order to maintain the temperature of the wafer.

When the wafer 80 is fixed to the upper surface of the upper insulating layer 21 of the electrostatic chuck 20 by the electrostatic attraction, the etching process by the plasma is performed in this state. After the etching process is completed, the power supply 40, 50 supplied to the coil unit 30 and the lower electrode 24 is cut off, and at the same time, the DC voltage applied to the upper electrode 22 is cut off, so that the upper electrode of the electrostatic chuck ( 22) and the electrostatic attraction is removed as no charge is charged to the wafer 80.

The reactive chemical species (radical) is supplied with the energy of the cation incident on the surface of the wafer 80 during the above-described etching process to form a volatile reaction product by reacting with the etching target to form an anisotropic etch.

Positive charges accumulate inside the wafer etched by these cations, and when the etching process is completed, the positive charges charged on the wafer are discharged through the ground connected to the lift pin 25, thereby remaining charges existing between the electrostatic chuck and the substrate. Will be removed.

In general, however, an insulating layer (for example, a silicon oxide film) is present on the back surface of the wafer which has undergone various processes, and thus, when the positive charge cannot escape through the ground connected to the lift pin 25, the residual positive charge is induced and As the electrostatic attraction between the negative charges of the upper electrode 22 remains, a sticking phenomenon occurs in which the charged wafer 80 does not fall well when the wafer and the electrostatic chuck 20 are separated (dechucked). Therefore, since the wafer 80 is to be separated by applying a mechanical force to overcome this problem, a sliding phenomenon or a popping phenomenon occurs and the wafer 80 is broken.

Various methods have been tried to overcome these disadvantages in the wafer dechucking, and one of the commercialized methods is to cut off the DC voltage applied to the electrostatic chuck 20 after completion of the etching process and to deactivate the reactive gas atmosphere inside the chamber. The residual charge on the wafer 21 is reduced by the ionized gas formed by replacing the gas and lowering the source power source 40 and the bias power source 50.

According to this method, even though the plasma is maintained by not using the etching gas, the etching process does not proceed any more, and since the source power and the bias power are lowered, the DC bias monitored at the lower electrode can be lowered. This is a way to reduce the residual charge.

However, this method also has a disadvantage in that it is not possible to completely remove the residual charge of the charged wafer, thereby causing a problem of damage to the wafer due to the repulsive force during dechucking.

Accordingly, the present invention has been made to solve the above-mentioned problems, and in the electrostatic chuck to fix the wafer of the process chamber for depositing or etching thin films using plasma for semiconductor manufacturing, the charge remaining on the wafer after the process is efficiently It is an object of the present invention to provide a residual charge removal apparatus and a removal method of an electrostatic chuck which can reduce the damage of the wafer during dechucking by removing the residual adsorption force.

The remaining charge removing device of the electrostatic chuck of the present invention for achieving the above object is a chamber having a constant volume for manufacturing a semiconductor and having an exhaust port at the bottom; An electrostatic chuck installed in the chamber and having a wafer on the top surface thereof; A coil unit installed above the chamber; A helium gas supply and discharge portion connected to the electrostatic chuck to improve thermal conductivity between the electrostatic chuck and the wafer; A DC voltage module connected to the electrostatic chuck; And a dechucking module connected to the electrostatic chuck.

Residual charge removal method of the electrostatic chuck of the present invention comprises a chamber having a constant volume for manufacturing a semiconductor and having an exhaust port at the bottom; An electrostatic chuck installed in the chamber and having a wafer on the top surface thereof; A coil unit installed above the chamber; A helium gas supply and discharge portion connected to the electrostatic chuck to improve thermal conductivity between the electrostatic chuck and the wafer; A DC voltage module connected to the electrostatic chuck; And a dechucking module connected to the electrostatic chuck; a first step in which dechucking is started while the inflow of process gas is blocked by using the residual charge removing device of the electrostatic chuck, and the dechucking module is operated to the DC voltage module. In the method of removing residual charge comprising the second step of the voltage is cut off, the third step of the operation of the dechucking module is stopped and the source power is completely cut off, the second step is monitored during the process Compare the DC bias value and the DC bias value monitored when the dechucking power is turned on to apply the voltage of the waveform biased in the positive direction if the former is larger than the latter, and the voltage of the waveform biased in the negative direction if the former is smaller than the latter. It is characterized by.

In addition, the helium gas supply unit is characterized in that for supplying the ionized gas to the back of the wafer.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2A is a schematic diagram of an apparatus for removing a residual charge of an electrostatic chuck according to an embodiment of the present invention, and FIG. 2B is a waveform diagram showing a waveform of a voltage applied to the electrostatic chuck by the dechucking module of the present invention.

Residual charge removing device of the electrostatic chuck according to the present invention is the chamber 10, the electrostatic chuck 20, the coil portion 30, helium gas supply and discharge (not shown), DC voltage module 60, dechucking module It comprises 70, the chamber 10; An electrostatic chuck 20; Coil unit 30; Helium gas supply and discharge (not shown); The configuration of the DC voltage module 60 is the same as in the prior art, and will be described in detail with reference to the operation of newly added constituent members to avoid repetition of the description.

The residual charge removing device of the electrostatic chuck according to the present invention alternates the positive and negative voltages of a magnitude smaller than the DC voltage applied to the upper electrode 23 to the upper electrode 23 at a high speed (switch B, C on /). off decoupling) is provided.

The dechucking module 70 has a size smaller than the DC voltage applied to the upper electrode to the upper electrode 22 in a state in which the DC voltage applied to the upper electrode 22 is switched off after the process is completed. A positive voltage and a negative voltage are alternately applied as shown in FIG. 2B. As a result, the remaining charge present on the wafer 80 is neutralized and removed, thereby preventing the sticking phenomenon.

3A is a schematic diagram showing the charged state of the charged wafer and the electrostatic chuck in the chucking state. As shown in FIG. 3A, the electrostatic chuck 20 is charged with negative charge by a negative voltage applied to the upper electrode 22 of the electrostatic chuck, and a wafer disposed on an upper surface of the charged electrostatic chuck 20 ( 80) a positive charge is induced at the bottom and a negative charge is induced at the top. Therefore, during the etching process, the wafer is chucked by the electrostatic attraction between the negative charge of the electrostatic chuck and the positive charge on the bottom of the wafer.

The attached FIG. 3B is a schematic diagram showing the charged state of the initially charged state of the wafer and the electrostatic chuck during the dechucking step. As shown in FIG. 3B, when a voltage of opposite polarity having a magnitude smaller than that of the chucking state is applied, a part of the positive charge and the negative charge present in the charged wafer is eliminated.

As shown in FIGS. 3C and 3D, when the positive and negative voltages having a smaller magnitude than the previous DC voltage are repeatedly applied, residual charges are gradually eliminated while the positive and negative charges present in the wafer are gradually dropped. Will be removed.

4 is a graph showing comparative data of the frequency of dechucking error before and after application of the dechucking module according to the present invention.

In FIG. 4, the above graph and data show a frequency of occurrence of dechucking error before the application of the dechucking module 70 according to the present invention. The graph and data below show the dechucking module 70 according to the present invention. Shows the frequency of dechucking errors after

The data is a result of monitoring an error occurring in the equipment for 7 weeks by performing an etch back process of the undoped silica glass in the etching equipment using a high-density plasma. The occurrence frequency of the dechucking error, which is the third item among the experimental data, shows a remarkable difference before and after applying the dechucking module according to the present invention.

5 is a graph illustrating a method of removing residual charge of an electrostatic chuck according to an embodiment of the present invention.

As shown in FIG. 5, the method of removing residual charge of an electrostatic chuck according to the present invention includes a first step, a second step, and a third step.

In the first step, after the etching process is completed, inflow of process gas is blocked and other inert gas is introduced, and dechucking is started. In this step, the source power is weakly applied, and the plasma is continuously maintained. This step is to decrease the voltage applied to.

In the second step, the operation of the dechucking module is started and the voltage by the DC voltage module is completely blocked. In particular, the DC bias value monitored during the process and the DC bias value monitored when the dechucking power is turned on Comparing to the step of applying the voltage of the waveform skewed in the positive direction when the former is larger than the latter, and the voltage of the waveform skewed in the negative direction when the former is smaller than the latter.

The third step is a step in which the operation of the dechucking module is stopped, and the source power is completely blocked so that the plasma disappears. Then, the wafer is separated from the electrostatic chuck by the lift pin installed in the electrostatic chuck.

According to the method of removing residual charge of an electrostatic chuck according to an embodiment of the present invention, when an unstable charging, that is, positive or negative charge, generated in a wafer as the etching process proceeds, Since the breakage or sliding of the wafer occurs during transfer, the dechucking module of the residual charge removing apparatus according to another embodiment of the present invention biases the alternating voltage as a whole according to the charged state of the wafer. To output a value.

For example, the DC bias value (hereinafter referred to as 'A value') that is monitored during the etching process is compared with the DC bias value (hereinafter referred to as 'B value') when the chucking power is turned on. A value is greater than B value. The alternating voltage applied to the electrostatic chuck is outputted in a positive direction (attached FIG. 6A).

On the contrary, when A value is smaller than B value. The alternating voltage applied to the electrostatic chuck is output in a negative direction (attached FIG. 6B).

Therefore, even if an unstable charging phenomenon occurs in the wafer, as described above, dechucking is desired by applying a voltage having a biased waveform according to the state of being charged on the wafer.

Preferably, the helium gas supply unit of the method for removing residual charge of the electrostatic chuck according to another embodiment of the present invention supplies ionized gas to the back surface of the wafer.

Therefore, in the dechucking step of the removal method of the dechucking module of the electrostatic chuck of the electrostatic chuck according to the present invention, by supplying ionized gas to the back surface of the wafer, it is possible to neutralize the charge remaining on the back surface of the wafer and the electrostatic chuck. This will increase the efficiency of dechucking.

In this case, the gas to be supplied uses nitrogen gas, argon gas, helium gas, etc., which do not affect the process, and it is preferable to supply the wafer at a pressure such that the wafer does not shake, for example, using an 8-inch wafer. In the electrostatic chuck, it is preferable to supply gas at a pressure of 6 Torr or less.

The method of supplying the ionized gas as described above includes a dump timing control method and a dump amount control method. FIG. 7 is a configuration diagram of a helium gas supply unit of a method of removing residual charge of an electrostatic chuck according to an embodiment of the present invention, and FIG. 8 is a graph illustrating a method of removing residual charge of an electrostatic chuck according to another embodiment of the present invention. 9 is a graph illustrating a method of removing residual charge of an electrostatic chuck according to another embodiment of the present invention.

As shown in FIG. 7, the helium gas supply unit of the present invention provides a helium supply module 91 for supplying ionized helium gas, one end of which is connected to the helium supply module 91, and the other end of which is connected to the electrostatic chuck 20. Helium supply line 92 is connected, helium valve 93 is installed in the middle of the helium supply line 92, one end is connected to the pumping line 97 and the other end is the helium valve 93 and the electrostatic chuck 20 It consists of a dump line 94 connected to the helium supply line 92 between the), a dump valve 95 installed in the middle of the dump line 94, and a pumping line (97).

As shown in FIG. 8, dechucking is performed by continuously blocking the dump valve while dechucking is performed by the dechucking module without opening the helium dump valve at a time t1 when the conventional dechucking starts. It is possible to neutralize the charge remaining in the electrostatic chuck and the wafer by the helium gas ionized therein. This method is called dump timing control.

As shown in FIG. 7, the helium gas supply unit according to another embodiment of the present invention is a helium supply module 91 for supplying ionized helium gas, one end of which is connected to the helium supply module 91 and the other end of the Helium supply line 92 is connected to the electrostatic chuck 20, helium valve 93 is installed in the middle of the helium supply line 92, one end is connected to the pumping line 97 and the other end is the helium valve 93 ) Dump line 94 connected to the helium supply line 92 between the electrostatic chuck 20, a dump valve 95 installed in the middle of the dump line 94, a pumping line 97, and the dump valve. And a restrictor 96 provided between the 95 and the pumping line 97.

As shown in FIG. 9, even when the helium dump valve is opened at the time t1 at which the conventional dechucking starts, since the helium gas ionized by the restrictor is discharged in a limited manner, the dechucking module uses the dechucking module. It is possible to neutralize the charge remaining in the electrostatic chuck and the wafer by the helium gas gradually decompressed during the process. This method is called dump amount control method.

Although the above-described embodiment of the present invention illustrates the use of helium as an ionized gas, the present invention can use nitrogen gas, argon gas, etc., which is obvious to those skilled in the art. It is.

As described above in detail, according to the present invention, there is provided an apparatus for removing residual charge and a method for removing an electrostatic chuck, which includes a dechucking module to neutralize and remove residual charge charged on a wafer, thereby reducing the adsorption force due to residual charge. It is possible to reduce the damage of the wafer during dechucking, thereby increasing the yield of semiconductor devices and reducing downtime of equipment.

Claims (3)

A chamber having a constant volume and having an exhaust at the bottom for the manufacture of a semiconductor; An electrostatic chuck installed in the chamber and having an upper insulating layer on which a wafer is placed, an upper electrode to which a DC voltage is applied, a lower insulating layer, and a lower electrode to which a bias power is applied; A coil unit installed above the chamber; A helium gas supply and discharge portion connected to the electrostatic chuck to improve thermal conductivity between the electrostatic chuck and the wafer and to supply ionized gas to the back side of the wafer; A DC voltage module connected to the electrostatic chuck; And a dechucking module connected to the electrostatic chuck to alternate a positive voltage and a negative voltage having a smaller magnitude than a DC voltage applied to the upper electrode at a high speed. Removal device. A chamber having a constant volume and having an exhaust at the bottom for the manufacture of a semiconductor; An electrostatic chuck installed in the chamber and having an upper insulating layer on which a wafer is placed, an upper electrode to which a DC voltage is applied, a lower insulating layer, and a lower electrode to which a bias power is applied; A coil unit installed above the chamber; A helium gas supply and discharge portion connected to the electrostatic chuck to improve thermal conductivity between the electrostatic chuck and the wafer and to supply ionized gas to the back side of the wafer; A DC voltage module connected to the electrostatic chuck; And a dechucking module connected to the electrostatic chuck to alternate the positive and negative voltages having a smaller magnitude than the DC voltage applied to the upper electrode at a high speed. A first step in which dechucking is started while the inflow of gas is blocked, the dechucking module is operated, and a second step in which the voltage by the DC voltage module is cut off, the operation of the dechucking module is stopped, and source power is completely cut off. A method for removing residual charge comprising a third step, wherein the second step compares the monitored DC bias value during the process process with the monitored DC bias value when the dechucking power is turned on so that the former is larger than the latter. If the voltage is biased in the positive direction, and the former is smaller than the latter, How to remove residual charges of the electrostatic chuck, characterized in that for applying a voltage waveform of the parent. delete

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