KR100631425B1 - Method for dechucking substrate from esc - Google Patents

Abstract

A substrate dechucking method is provided to prevent the damage of a substrate by checking exactly an electrostatic force release point and to reduce a processing time by releasing completely an electrostatic force in a short time. A DC(Direct Current) power source supplied to a predetermined electrode of an electrostatic chuck is stopped(S120). The pressure of cooling gas between the electrostatic chuck and a substrate is set to a first pressure value. The cooling gas is continuously supplied to keep the first pressure value and the flow rate of the cooling gas is measured(S130). When the flow rate of the cooling gas reaches a critical flow rate, the pressure of the cooling gas is reset from the first pressure value to a second pressure value. The cooling gas is continuously supplied to keep the second pressure value and the flow rate of the cooling gas is measured(S140). The substrate is unloaded from the electrostatic chuck when the flow rate of the cooling gas is below the critical flow rate.

Description

Substrate Dechucking Method {METHOD FOR DECHUCKING SUBSTRATE FROM ESC}

1 is a cross-sectional view schematically showing the structure of a general electrostatic chuck.

2 is a process diagram of a conventional substrate dechucking method.

3 is a process diagram of the substrate dechucking method according to the first embodiment of the present invention.

4 illustrates a change in flow rate with time during the dechucking process according to the embodiment shown in FIG. 3.

5 is a process diagram of the substrate dechucking method according to the second embodiment of the present invention.

The present invention relates to a dechucking method for detaching a substrate fixed to an electrostatic chuck, and more particularly, to accurately determine a time point for releasing electrostatic power, and to reduce the process time by releasing electrostatic power completely within a short time. The present invention provides a chucking method.

In recent years, with the rapid spread of information media such as computers, semiconductors and LCDs are rapidly developing. In the semiconductor and LCD manufacturing process, as the amount of information processed increases rapidly, technology is being developed to improve integration and reliability.

However, in order to improve the integration and reliability, the precision of the unit process must be increased, and to increase the precision of the unit process, it is required to more accurately fix the semiconductor wafer and the LCD substrate during the unit process. Generally, a device for fixing a semiconductor wafer and an LCD substrate includes a vacuum chuck for fixing a wafer using mechanical properties and an electrostatic chuck (ESC) for fixing a wafer using electrical properties. This is widely used.

The vacuum chuck has a limitation in use because no pressure difference is generated between the vacuum chuck and the external vacuum when the unit processes are performed under vacuum conditions. In addition, since the wafer or substrate is fixed by the local suction action, there is a drawback in that precise fixing is impossible.

Electrostatic chucks, on the other hand, use the principles of dielectric polarization and electrostatic forces generated by potential differences to fix adsorbates such as substrates. This allows the electrostatic chuck to be subjected to microfabrication of a semiconductor or LCD substrate without being affected by pressure.

As an example of an electrostatic chuck, US Pat. No. 6,134,096 discloses an electrostatic chuck consisting of an insulating layer, an electrode layer, and a dielectric layer for adsorbing a substrate using electrostatic energy. In addition, US Pat. No. 6,141,203 discloses an electrostatic chuck for forming a capacitor plate having a plurality of structures to adsorb a substrate with electrostatic energy.

A general electrostatic chuck may have a certain degree of variation in the arrangement and configuration of internal components depending on the purpose. However, since the electrostatic chuck is common in terms of its purpose and function, the electrostatic chuck embedded in a plasma processing chamber for processing a substrate through plasma will be described below. The chuck is described as an example.

1 is a cross-sectional view showing the structure of a general electrostatic chuck (1), which is a cooling plate 20 and the electrostatic chuck electrode (30) is mounted in the body 10, respectively, helium channel (top) Further comprising 40, this electrostatic chuck 1 is coupled to bellows which are installed to be able to rise and lower through the bottom of the chamber. The substrate S is mounted on the upper surface of the helium channel panel 40.

At this time, the electrostatic chuck electrode 30 is connected to a DC voltage rod 31 for applying a DC voltage from the outside to form an electric field to hold the substrate more tightly, the cooling plate installed inside the electrostatic chuck body 10 ( 20 is a cooling solvent path having a size corresponding to that of the substrate S seated on the upper surface of the helium flow channel panel 40, respectively, and a cooling solvent inflow pipe 21 for introducing the cooling solvent from the outside; In addition, a cooling solvent outlet pipe 22 for discharging the cooling solvent circulated in the cooling plate 20 is connected to control the temperature of the substrate by storing and circulating the cooling solvent therein.

The helium channel panel 40 coupled to the upper end of the electrostatic chuck body 10 assists the temperature control of the substrate by circulating helium gas at the interface with the substrate S seated on the upper surface thereof. On the upper surface of the helium flow channel panel 40, a helium flow path (not shown), that is, a groove pattern through which helium gas can be circulated, is formed, and in each of the groove patterns, helium inflows into which helium gas is introduced are introduced. The pipe 41 is connected.

Accordingly, helium gas introduced through the helium inlet pipe 41 assists in temperature control by improving heat conduction with the substrate while circulating the groove pattern. At the end of the process, helium gas is removed by the pump by opening the pump valve (42). At this time, the helium pressure between the helium flow channel panel 40 and the substrate (S) is measured, and this pressure is always maintained at a constant pressure so that the temperature control of the substrate is accurately performed.

The chucking process of fixing the substrate to the electrostatic chuck and the dechucking process of detaching the fixed substrate will be described.

First, in the chucking process, a substrate is placed on the helium channel panel. Generally, the lift pin is used to place the substrate on the upper surface of the helium flow channel panel. Then, by applying a DC power supply to the electrostatic chuck electrode, the electrostatic chuck is generated between the electrostatic chuck and the substrate. In this way, when the substrate is fixed to the electrostatic chuck, a sealed space is formed between the substrate and the helium flow channel panel. Then, helium is introduced into the sealed space through the helium inlet tube so that the temperature of the substrate is kept constant. Then, the RF power is applied to the RF electrode, and the process is performed while supplying the process gas.

When the process is completed, the dechucking process is performed in the reverse order of the above chucking process. That is, in the state in which the plasma is removed by cutting off the RF power and the process gas (S10), after blocking the helium gas (S20), the DC power applied to the electrostatic chuck electrode is cut off (S30) to release the static power. After the electrostatic force is released, the substrate S is lifted up using the lift pins and then transported out of the plasma processing apparatus (S40). However, when the substrate is taken out in a state where electrostatic power is not completely removed, the substrate may be excessively bent in the process of lifting the substrate, resulting in damage such as damage to the circuit pattern formed on the substrate or breaking of the substrate itself. Dechucking should be done with the electrostatic chucks between the electrostatic chucks completely removed.

However, as described above, in the case of dechucking the substrate, a long time is taken to discharge the charge from the substrate, and a lot of time is consumed in the dechucking. There is a problem that cannot be correctly identified. In this case, when the substrate is taken out without knowing exactly whether it is dechucking, serious problems may occur such that damage to the circuit pattern formed on the substrate or damage to the substrate itself occurs due to excessive bending of the substrate during the lifting of the substrate. .

In particular, in recent years, as the substrate of the LCD, such as a large area takes more time to discharge the charge, the above-mentioned problem is more serious.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a substrate dechucking method capable of preventing the damage of the substrate by accurately grasping the timing of releasing the electrostatic force.

In order to solve the above problems, a method for dechucking a substrate mounted on an electrostatic chuck in a plasma processing apparatus according to the present invention, the method comprising: 1) blocking a DC power applied to the electrostatic chuck electrode; 2) setting the pressure of the cooling gas to the first pressure value between the electrostatic chuck and the substrate; 3) measuring the flow rate while continuously supplying the cooling gas to maintain the first pressure value; 4) resetting the pressure of the cooling gas to a second pressure value lower than the first pressure value when the measured flow rate reaches a critical flow rate; 5) measuring the flow rate while continuously supplying the cooling gas to maintain the second pressure value; And 6) repeating steps 2) to 5), if the flow rate of the cooling gas does not increase above a critical flow rate, lifting and discharging the substrate located in the electrostatic chuck to the outside.

The first pressure value may be lower than or equal to the process pressure of the cooling gas in the plasma treatment process.

In addition, the dechucking method may be performed in a state in which plasma is removed after plasma processing is completed, or in a state in which plasma is maintained.

In particular, when the plasma is maintained in a state of maintaining plasma, the RF power and the process pressure are lower than the RF power and the process pressure during the plasma treatment process, and the process gas is preferably reset to argon (Ar).

Hereinafter, with reference to the accompanying drawings will be described in detail specific embodiments of the present invention.

<Example 1>

First, a first embodiment of the present invention will be described with reference to FIGS. 3 and 4. In the substrate dechucking method according to the present embodiment, first, a step (S110) of cutting off the RF power and the process gas applied inside the plasma processing apparatus is performed. In this step, after the substrate processing is completed, the substrate is prepared for dechucking, and the RF power and the process gas used during the processing are cut off. When the RF power and the process gas are cut off, the plasma generated inside the plasma processing apparatus is removed. However, the cooling gas supplied between the substrate and the electrostatic chuck is continuously supplied.

Next, a step (S120) of cutting off the DC power applied to the electrostatic chuck electrode is performed. When the DC power is cut off in this way, the charge concentrated between the substrate and the electrostatic chuck begins to escape.

Here, steps S110 and S120 may be performed by reversing the order.

Next, a first pressure value is set for the pressure of the cooling gas continuously supplied between the electrostatic chuck and the substrate, and the flow rate is measured while supplying the cooling gas so that the first pressure value is maintained (S130). In order to maintain the first pressure value, more cooling gas must be supplied. This is because the release of the electrostatic force between the substrate and the electrostatic chuck proceeds. Therefore, although the pressure in the t ₂ section at t ₁ (the time point at which the plasma treatment is completed) of FIG. 4 is constant at the first pressure value p ₁ , the flow rate is at f ₁ . It can be seen that the increase to f ₂ .

As such, the flow rate increases, and when the flow rate reaches the preset threshold flow rate f ₂ , the pressure of the cooling gas is reset again to the second pressure value p ₂ (S140). Here, the critical flow rate f ₂ is a flow rate such that particles and the like can adversely affect the plasma-treated substrate when the flow rate of the cooling gas is a predetermined level or more. This is an empirical value obtained through a number of experiments. Therefore, when the flow rate of the cooling gas is monitored and the value reaches the preset threshold flow rate f ₂ , the flow rate is reset by resetting the pressure of the cooling gas to the second pressure value p ₂ lower than the first pressure p ₁ . from f ₂ lowered to f ₁ .

If the substrate is not completely dechucked even at this time t ₂ , if the flow rate of the cooling gas is measured while maintaining the second pressure value (S140), the flow rate of the cooling gas will continue to increase. . Therefore, although the pressure in the interval t _{3 to} t ₂ of FIG. 4 is constant to the second pressure value p ₂ , the flow rate is at f ₁ is increased to f ₂ .

Here, when the flow rate of the cooling gas reaches the critical flow rate f ₂ , the pressure value of the cooling gas is reset again to a third pressure value p ₃ lower than the second pressure value p ₂ (p ₁ > p _2). > p ₃ ).

This process is repeated, where if the substrate was completely dechucked at time t ₅ , the flow rate would no longer be increased to maintain the fourth pressure value p ₄ . Therefore it will be that the constant flow rate as shown in the interval t ₅ in Figure 4 of the t _4, no longer will not happen to reach the threshold flow rate (f _2). In this way, the flow rate was measured while lowering the pressure value, and the point at which the measured value no longer reached the critical flow rate (f ₂ ) was regarded as the time point at which the dechucking of the substrate was completed (t ₅ ). It is to discharge to the outside (S150). In this step, the substrate is lifted using the lift pins provided in the plasma processing apparatus while the electrostatic force is completely released, and the substrate is discharged to the outside using a transfer robot entered from the outside to finish the process. .

<Example 2>

A second embodiment of the present invention will be described with reference to FIG.

In this embodiment, the substrate dechucking method is performed while maintaining the plasma inside the plasma processing apparatus. Therefore, the process proceeds while maintaining the RF power and the process gas inside the plasma processing apparatus. However, at this time, the step (S210) of resetting the RF power, the process gas, or the process pressure inside the plasma processing apparatus may be further performed. That is, the substrate dechucking method is performed under conditions different from the process progress conditions. More specifically, the reset process gas supplies argon (Ar) gas, and the RF power and process pressure are set lower than that during the plasma treatment process.

In this case, when the substrate is dechucked while the plasma is maintained, the electrostatic power is weakened faster than the absence of the plasma.

Next, the DC power is cut off (S220), the pressure of the cooling gas is set to the first pressure value / flow rate measurement (S230), the pressure of the cooling gas to the second pressure value / flow rate measurement (S240) proceeds do. As in the first embodiment, steps S230 and S240 are repeated. As the pressure value is lowered, the flow rate is measured, and thus the dechucking of the substrate is completely completed when the measured value no longer reaches the critical flow rate. Looking at the point of view is to lift the substrate is discharged to the outside of the chamber (S250).

According to the present invention, by accurately grasp the time point to release the electrostatic power, there is an effect that can prevent damage to the substrate.

In addition, the electrostatic power is completely released within a short time has the advantage of shortening the process time.

Claims (10)

A method of dechucking a substrate mounted on an electrostatic chuck inside a plasma processing apparatus, 1) cutting off the DC power applied to the electrostatic chuck electrode; 2) setting the pressure of the cooling gas to the first pressure value between the electrostatic chuck and the substrate; 3) measuring the flow rate while continuously supplying the cooling gas to maintain the first pressure value; 4) resetting the pressure of the cooling gas to a second pressure value lower than the first pressure value when the measured flow rate reaches a critical flow rate; 5) measuring the flow rate while continuously supplying the cooling gas to maintain the second pressure value; And 6) repeating steps 2) to 5), if the flow rate of the cooling gas does not increase above a critical flow rate, lifting and discharging the substrate located in the electrostatic chuck to the outside. ) Way. The method of claim 1, And said first pressure value is lower than a process pressure of said cooling gas during a plasma treatment process. The method of claim 1, And said first pressure value is equal to a process pressure of said cooling gas during a plasma treatment process. The method of claim 1, The dechucking method, A substrate dechucking method characterized in that the plasma is removed after the plasma processing is completed. The method of claim 1, The dechucking method, After the plasma processing step is completed, the substrate dechucking method, characterized in that carried out while maintaining the plasma. The method of claim 5, Resetting the RF power, the process gas, the process pressure before step 1); The substrate dechucking method further comprises. The method of claim 6, And the reset RF power is lower than the RF power during the plasma processing process. The method of claim 6, And said reset process gas is argon (Ar). The method of claim 6, And said reset process pressure is lower than a process pressure during a plasma processing process. The method of claim 1, And said cooling gas is helium.

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