KR101233757B1 - Method for De-chucking Substrate from ESC - Google Patents

Abstract

The present invention relates to a method for de-chucking a substrate in an electrostatic chuck (ESC), the electrostatic chuck, a power supply for supplying power to the electrostatic chuck, and a cooling gas supply source for supplying cooling gas to the electrostatic chuck And a cooling gas supply line connecting the electrostatic chuck and the cooling gas supply source, and a cooling gas discharge line connected to the cooling gas supply line to discharge the cooling gas on the cooling gas supply line to the outside. A method of chucking, comprising: (A) disconnecting power applied to an electrostatic chuck from a power supply; (B) shutting off the cooling gas supply from the cooling gas source; (C) opening the valve of the cooling gas discharge line to discharge the cooling gas remaining in the cooling gas supply line to the outside; (D) stopping the discharge of the cooling gas by closing a valve of the cooling gas discharge line according to whether a set condition is satisfied; (E) measuring a residual coolant gas pressure change on the cooling gas supply line to determine a dechucking state.

Description

Substrate Dechucking Method {Method for De-chucking Substrate from ESC}

The present invention relates to a method of de-chucking a substrate in an electrostatic chuck (ESC), and more particularly, to fix the substrate on an electrostatic chuck (ESC) that fixes the substrate by an electrostatic force. And a substrate dechucking method for safely separating the substrate from the electrostatic chuck after the process is completed.

Flat panel display devices such as semiconductor devices or LCDs are processed through numerous processes such as depositing a material film on a substrate such as a wafer, patterning the deposited material film into a required form, and cleaning to remove unnecessary residues on the substrate. Becomes In order to proceed with these processes, the substrate is loaded on the substrate support in the chamber to perform a predetermined process and then unloaded to the outside.

In order to successfully perform such a substrate processing process, it is very important to chuck and fix the substrate in the chamber, and to dechuck and separate the substrate so as not to damage the substrate after the substrate processing process is completed.

The method of fixing the substrate to the substrate support in the process chamber in the substrate loading step is to fix using a hardware structure such as a clamp (clamp), and to fix the substrate by adsorbing the back side of the wafer using a vacuum (vacuum) chuck), a method of fixing to a wafer support in a natural state using gravity, and a method of fixing using an electric piezoelectric effect.

Among these methods, a method of fixing by using an electric piezoelectric effect has been widely used recently. In this method, an electrostatic chuck (ESC) is used to fix a substrate.

Typically, a chucking process of fixing a substrate using an electrostatic chuck and a de-chucking process of separating a substrate from the electrostatic chuck after the process is completed are performed as follows.

First, in the chucking process, when the substrate transfer device places the substrate on the lift pin which is raised to the upper side of the electrostatic chuck, the substrate is placed on the upper surface of the electrostatic chuck while the lift pin is lowered. Subsequently, a high DC voltage is applied to the electrostatic chuck to generate a strong electrostatic force between the substrate and the electrostatic chuck, thereby allowing the substrate to be fixed to the electrostatic chuck. Thereafter, the cooling gas (eg, helium gas) is supplied through the cooling gas pipe of the electrostatic chuck to control the temperature rise of the substrate, and the process is performed while supplying RF (RF) power and processing gas.

When the process is complete, the dechucking process is performed. First, the RF power and the process gas are cut off and the plasma is removed (in contrast, the dechucking process may be performed while the plasma is generated by applying the RF power), and then the cooling gas supply is cut off. After that, the supply of DC high voltage is cut off to release the constant power. After the electrostatic force is released, the lift pin is raised to completely separate the substrate from the electrostatic chuck, and the substrate is transferred to the outside using the substrate transfer device.

However, when performing the dechucking process after the completion of the process as described above, when the substrate is lifted using the lift pin while the electrostatic force is not released to the dechucking state, between the electrostatic force to fix the substrate and the lifting force Due to the repulsive force of the substrate, the substrate is excessively bent, which causes the substrate to break or damage the circuit board.

In order to solve the problem of the dechucking process, a pressure sensor is mounted on the lift pin lift cylinder. When the lift pin is recognized as a pressure that cannot be raised, the pressure is lowered again to remove the static power and then dechuck again. It became. However, in this case, installation costs are expensive, and pressure sensing is difficult.

In addition, the Republic of Korea Patent Publication No. 10-0631425 (registered September 27, 2006) is a step of shutting off the DC power applied to the electrostatic chuck electrode, and setting the pressure of the cooling gas between the electrostatic chuck and the substrate as a first pressure value And continuously supplying the cooling gas to maintain the first pressure value, and measuring the flow rate thereof. When the measured cooling gas flow rate reaches a critical flow rate, the pressure of the cooling gas is lower than the first pressure value. Resetting to a value, measuring the flow rate while continuously supplying the cooling gas to maintain the second pressure value, if the flow rate of the cooling gas does not rise above the critical flow rate by lifting the substrate located in the electrostatic chuck Disclosed is a substrate dechucking method comprising evacuating a furnace.

The substrate dechucking method of the registered patent can prevent damage to the substrate by accurately identifying the timing of releasing the electrostatic power through measuring the flow rate of the cooling gas, and the electrostatic power is completely released within a short time to shorten the process time. To provide.

On the other hand, since the substrate dechucking method of the registered patent needs to continuously supply the cooling gas during the dechucking process, when the cooling gas is excessively supplied, there is a problem that the position of the substrate may be displaced or the substrate may be damaged.

The present invention is to solve the above problems, an object of the present invention is to accurately determine the release time of the electrostatic chuck of the electrostatic chuck without supplying a cooling gas during the dechucking process, through which safe and accurate substrate dechucking To provide a substrate dechucking method that can be made.

According to an aspect of the present invention for achieving the above object, an electrostatic chuck, a power supply for supplying power to the electrostatic chuck, a cooling gas supply source for supplying cooling gas to the electrostatic chuck, the electrostatic chuck and the cooling gas supply source A method of dechucking a substrate in a substrate processing apparatus having a cooling gas supply line to be connected and a cooling gas discharge line connected to the cooling gas supply line and discharging the cooling gas on the cooling gas supply line to the outside; Cutting off power applied to the electrostatic chuck from the power supply; (B) shutting off the cooling gas supply from the cooling gas source; (C) opening the valve of the cooling gas discharge line to discharge the cooling gas remaining in the cooling gas supply line to the outside; (D) stopping the discharge of the cooling gas by closing a valve of the cooling gas discharge line according to whether a set condition is satisfied; (E) A substrate dechucking method is provided, comprising determining a dechuckable state by measuring a change in the residual coolant gas pressure on the cooling gas supply line.

Here, the setting condition in the step (D) is a predetermined time from the condition that the cooling gas pressure on the cooling gas supply line reaches a preset pressure value (P1), or when the cooling gas discharge on the cooling gas supply line is made. This can be a passing condition.

According to the present invention, when the dechucking process is performed after the process on the substrate on the electrostatic chuck, the pressure change of the remaining cooling gas in the state of stopping the supply of the cooling gas is measured to clearly determine the timing of releasing the electrostatic chuck. can do.

Therefore, it is possible to lift the substrate from the electrostatic chuck by using a lift pin without distorting or damaging the substrate during the dechucking process.

BRIEF DESCRIPTION OF THE DRAWINGS It is the block diagram which showed an example of the structure of the substrate processing apparatus provided with the electrostatic chuck which the substrate dechucking method which concerns on this invention is implemented.
2 is a flowchart illustrating a substrate dechucking method according to an embodiment of the present invention.
3 is a graph showing a change in the cooling gas pressure measured on the cooling gas supply line in the process of performing the substrate dechucking method according to the present invention.
4 is a flow chart illustrating a substrate dechucking method according to another embodiment of the present invention.

Hereinafter, exemplary embodiments of the substrate dechucking method according to the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 1 shows an example of the configuration of a substrate processing apparatus in which the substrate dechucking method of the present invention is implemented. The substrate processing apparatus of this embodiment is coupled to an electrostatic chuck 10 and a lower portion of the electrostatic chuck 10. Cooling block 20 for cooling the electrostatic chuck 10 by a cooling medium supplied from the outside, a power supply unit for supplying power to the electrostatic chuck 10, and supplying cooling gas to the electrostatic chuck 10. A cooling gas supply line 40 connected to the cooling gas supply line 50, a cooling gas supply line 50 connecting the electrostatic chuck 10, and a cooling gas supply source, and the cooling gas supply line 50. Cooling gas discharge line 60 for discharging the residual cooling gas to the outside, and is connected to the cooling gas supply line 50 to provide a uniform cooling gas supply to the electrostatic chuck 10 and the remaining of the cooling gas Bypass line 70 for the discharge is made, It includes a plurality of lift pins (not shown) for moving up and down the substrate (S) on the group electrostatic chuck 10 is capable of lifting up and down motion provided on the electrostatic chuck 10.

The power supply unit is a component that functions to generate an electrostatic force between the electrostatic chuck 10 and the substrate S, a power supply source (not shown) for applying a DC high voltage, and is installed in the electrostatic chuck 10 and the An electrode 30 is applied to the DC high voltage from the power supply. Although not shown in the drawings, when the substrate processing apparatus to which the electrostatic chuck 10 is applied is a plasma processing apparatus, the electrostatic chuck 10 is also electrically connected to an RF power source to generate plasma. RF power is applied.

The cooling gas supply source 40 supplies a cooling gas such as helium gas to assist the temperature control of the substrate S on the electrostatic chuck 10. The cooling gas supply source 40 has a main valve 41 for allowing or blocking the supply of cooling gas to the cooling gas supply line 50 and the bypass line 70, and the pressure of the cooling gas in the cooling gas supply line 50. Pressure sensor 42 for measuring the pressure is installed.

The cooling gas supply line 50 includes a plurality of outer lines 51 and inner lines 52 that supply cooling gas to an interface between the electrostatic chuck 10 and the substrate S. FIG. The outer line 51 is connected to the outer region of the electrostatic chuck 10 to supply the cooling gas, and the inner line 52 is connected to the inner central region of the electrostatic chuck 10 to supply the cooling gas. On the cooling gas supply line 50, a supply valve 53 for controlling the supply of cooling gas to the outer line 51 and the inner line 52 is installed.

A discharge valve 61 is installed between the cooling gas supply line 50 and the cooling gas discharge line 60 to control residual cooling gas discharge through the cooling gas discharge line 60. The cooling gas discharge line 60 is connected to the vacuum pump 62.

In addition, the bypass line 70 is provided with a bypass valve 71 for controlling the discharge of the cooling gas through the bypass line 70. The bypass line 70 is formed of a fine tube connected to the cooling gas supply line 50, and discharges a small amount of cooling gas when the cooling gas is supplied to the electrostatic chuck 10 during the processing of the substrate S. While maintaining a constant pressure of the cooling gas on the cooling gas supply line 50.

The chucking process of fixing the substrate on the electrostatic chuck and the dechucking process of separating the substrate on the electrostatic chuck using the substrate processing apparatus configured as described above are as follows.

First, in the chucking process, when the substrate conveying apparatus (not shown) places the substrate S on a lift pin (not shown) that rises to the upper side of the electrostatic chuck 10, the substrate S is lifted while the lift pin is lowered. The upper surface of the electrostatic chuck 10 is seated. Subsequently, direct current power is applied to the electrostatic chuck 10 through the power supply unit so that a strong electrostatic force is generated between the substrate S and the electrostatic chuck 10, whereby the substrate S is fixed to the electrostatic chuck 10. .

Subsequently, the main valve 41, the supply valve 53, and the bypass valve 71 are opened, and a cooling gas (eg, helium gas) is supplied from the cooling gas supply source 40. The cooling gas supplied from the cooling gas supply source 40 is supplied to the boundary portion between the electrostatic chuck 10 and the substrate S through the outer line 51 and the inner line 52 to increase the temperature of the substrate S. To control.

At the same time, RF power is applied to the electrostatic chuck 10 to generate a plasma, and a process is performed while a process gas is supplied.

When the process for the substrate S is completed, the dechucking process is performed in a reverse order to the above-described chucking process. That is, as shown in FIG. 2, the RF power is cut off, the supply of process gas is stopped (step S1), and the DC power applied to the electrostatic chuck 10 is cut off to release the static power ( Step S2).

At the same time, the main valve 41 is closed to stop the supply of the cooling gas from the cooling gas supply source 40 (step S3). Then, the supply valve 53, the bypass valve 71, and the discharge valve 61 are both opened, and the vacuum pump 62 is operated (step S4). By the operation of the vacuum pump 62, the remaining cooling gas in the cooling gas supply line 50 is sucked through the cooling gas discharge line 60, and thus the cooling gas supply line 50 as shown in FIG. The residual cooling gas pressure in the column drops sharply.

When the pressure in the cooling gas supply line 50 drops to the first set value P1 (0.5 torr in this embodiment), the bypass valve 71 and the discharge valve 61 are closed to discharge residual cooling gas. Is stopped (step S5). At this time, as shown in region ① of FIG. 3, the pressure of the cooling gas supply line 50 increases slightly. This can be explained by Bernoulli's theorem. That is, when the residual cooling gas is discharged by the vacuum pump 62, the flow rate of the cooling gas is high, so the pressure is lower than when the same amount of cooling gas does not move, and after reaching the set pressure P1, the discharge valve When the 61 and the bypass valve 71 are closed, the movement of the remaining cooling gas is stopped, so that the total pressure is slightly increased.

On the other hand, the static power between the electrostatic chuck 10 and the substrate (S) is gradually weakened as time passes in the state in which the remaining cooling gas discharge in the cooling gas supply line 50 is stopped as described above, the substrate (S) and Leakage of the cooling gas occurs between the electrostatic chucks 10. Accordingly, as shown in region ② of FIG. 3, the pressure in the cooling gas supply line 50 gradually decreases. When the pressure in the cooling gas supply line 50 reaches the second set value P2, it is determined that the electrostatic force between the electrostatic chuck 10 and the substrate S is released and is determined as a dechucking state (step S6). ). Here, the second set value P2 is a value corresponding to a predetermined level between the rising maximum pressure P0 and the first setting value P1 after closing the discharge valve 61, for example, the rising maximum pressure P0. And a pressure value that is a percentage of the interval between the first set value P1 and the first maximum value P1, or a pressure value that is a percentage of the rising maximum pressure P0, or a rising maximum pressure P0 and Any specified pressure value between the first set values P1, or any designated pressure value equal to or less than the first set value P1 can be set. In addition, if the inclination of the pressure change with time after reaching the rising maximum pressure (P0) is differently within the set range, it is determined that the leakage of the cooling gas due to the weakening of the electrostatic power is sufficiently generated to determine that the dechucking is possible. It may be.

As described above, when the outflow of the cooling gas due to the weakening of the electrostatic force occurs and the pressure in the cooling gas supply line 50 reaches the set value, and it is determined that the dechucking is possible, the lift pin (not shown) is driven (not shown). As a result, the substrate S on the electrostatic chuck 10 is lifted and separated (step S7). At this time, since the electrostatic chuck 10 is sufficiently discharged from the electrostatic chuck 10, the substrate S is not bent or damaged, and the dechucking process of the substrate is stopped while the supply of the cooling gas is stopped. As a result, it is possible to obtain an advantage that a phenomenon such as a dislocation of the substrate does not occur.

On the other hand, when the cooling gas supply line 50 is divided into the outer line 51 and the inner line 52 as in this embodiment, the discharge valve 61 and the bypass valve 71 are closed during the dechucking process. After monitoring the pressure change of the cooling gas supply line 50 to determine the release time of the electrostatic power, the residual cooling gas pressure of the outer line 51 and the residual cooling angle pressure of the inner line 52 are both the second. The time point at which the set value P2 is reached can be determined as a dechucking state. However, unlike this, even if only the residual cooling angle pressure of any one of the outer line 51 and the inner line 52 reaches the second set value P2, this point may be determined as a dechucking state.

In addition, in the above-described embodiment, the RF power is cut off and the dechucking process is performed in the absence of the plasma. However, as shown in another embodiment of FIG. 4, the dechucking process is continued in the state in which the RF power is continuously maintained. After this is done, the RF power may be cut off (step S8) after the lift pin rises. As described above, when the substrate is dechucked while maintaining the plasma, the electrostatic power may be more quickly removed due to the plasma.

In the substrate dechucking method of the above-described embodiment, the discharge valve 61 and the bypass valve 71 are opened to discharge residual cooling gas in the cooling gas supply line 50, and then the first setting is a preset pressure value. When the value P1 was reached, the discharge valve 61 and the bypass valve 71 were closed and the pressure change was monitored.

However, if it is assumed that the discharge of the cooling gas is substantially constant, unlike the above embodiment, from the time when the discharge valve 61 and the bypass valve 71 are opened without setting the lower limit pressure value P1 in advance. After a certain time, the discharge valve 61 and the bypass valve 71 may be closed and the pressure change may be monitored. Of course, even in this case, the cooling gas pressure in the cooling gas supply line 50 immediately after closing of the discharge valve 61 and the bypass valve 71 is raised slightly as shown in FIG. When it is weakened, it gradually lowers again, and when the pressure reaches the second set value P2, it is determined as a dechucking state.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. In addition, it is apparent that any person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

10: electrostatic chuck 20: cooling block
30 electrode 40 cooling gas supply source
41: main valve 42: pressure sensor
50: cooling gas supply line 51: outer line (outer line)
52: inner line 53: supply valve
60: cooling gas discharge line 61: discharge valve
62: vacuum pump 70: bypass line
71: bypass valve S: substrate
P0: Maximum rising pressure P1: First set value
P2: Second set value

Claims (8)

An electrostatic chuck, a power supply for supplying power to the electrostatic chuck, a cooling gas supply source for supplying cooling gas to the electrostatic chuck, a cooling gas supply line for connecting the electrostatic chuck and a cooling gas supply source, and the cooling gas supply line In the method for dechucking a substrate in a substrate processing apparatus having a cooling gas discharge line for discharging the cooling gas on the cooling gas supply line to the outside,
(A) cutting off the power applied to the electrostatic chuck from the power supply;
(B) shutting off the cooling gas supply from the cooling gas source;
(C) opening the valve of the cooling gas discharge line to discharge the cooling gas remaining in the cooling gas supply line to the outside;
(D) stopping the discharge of the cooling gas by closing a valve of the cooling gas discharge line according to whether a set condition is satisfied;
(E) determining a dechucking state by measuring a change in the residual cooling gas pressure on the cooling gas supply line. The substrate dechucking method according to claim 1, wherein the setting condition in the step (D) is a condition in which the cooling gas pressure on the cooling gas supply line reaches a preset pressure value (P1). The substrate dechucking method of claim 1, wherein the setting condition in the step (D) is a condition in which a predetermined time elapses from a time point at which the cooling gas is discharged on the cooling gas supply line. The method of any one of claims 1 to 3, wherein in the step (E), after gradually increasing to the maximum pressure P0 higher than the pressure value P1 at the valve closing point of the cooling gas discharge line, the temperature gradually decreases again. It determines with the dechucking state when the 2nd set value P2 is reached, The board | substrate dechucking method characterized by the above-mentioned. The method of claim 4, wherein the second set value (P2) is a value corresponding to a predetermined level of the maximum pressure (P0) or the maximum pressure (P0) and the pressure value (P1) at the valve closing time of the cooling gas discharge line A substrate dechucking method, characterized in that the point between. The pressure of the cooling gas supply lines according to any one of claims 1 to 3, wherein when the cooling gas supply line is connected to a plurality of regions of the electrostatic chuck, the pressure of the cooling gas supply lines connected to the respective electrostatic chuck regions in step (E). Measuring the change and determining that the pressures of all the cooling gas supply lines have reached a preset value as a dechucking state. The pressure of the cooling gas supply lines according to any one of claims 1 to 3, wherein when the cooling gas supply line is connected to a plurality of regions of the electrostatic chuck, the pressure of the cooling gas supply lines connected to the respective electrostatic chuck regions in step (E). Measuring the change, and determining when the pressure of the at least one cooling gas supply line reaches a preset value, the substrate dechucking method. The pressure change according to any one of claims 1 to 3, wherein in the step (E), the pressure on the cooling gas supply line reaches a maximum pressure P0 higher than the first set value P1. And measuring the inclination of the substrate to determine when the inclination reaches within a set range as a dechucking state.

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