KR20100073025A - Method for dechucking a substrate in plasma processing apparatus - Google Patents

Abstract

PURPOSE: A substrate de-chucking method in a plasma processing device is provided to improve de-chucking capability and prevent sticking by effectively removing a remaining charge on a substrate surface according to the control of a de-chucking voltage. CONSTITUTION: A plasma generation is interrupted after completing a plasma processing about a substrate which is maintained on an electro-static chuck with the chucking voltage of electro-static voltage. A first reverse voltage is applied to the electrostatic chuck. A middle turn-off step which stops the first reverse voltage apply in the electrostatic chuck is executed. After the middle turn-off step, a second reverse voltage which is smaller than the first reverse voltage is applied to the electrostatic chuck. The second reverse voltage apply is interrupted in the electrostatic chuck and the substrate is grounded.

Description

METHODE FOR DECHUCKING A SUBSTRATE IN PLASMA PROCESSING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of dechucking a substrate in a plasma processing apparatus (eg, a plasma etching apparatus, a plasma deposition apparatus, etc.) for the manufacture of a semiconductor device, in particular during dechucking by controlling a dechucking voltage applied to a lift pin. The present invention relates to a dechucking method capable of efficiently removing remaining static power between a substrate and an electrostatic chuck, thereby improving dechucking reliability and preventing occurrence of dechucking defects.

In order to manufacture a semiconductor device, a process of depositing a material film on a wafer, a process of patterning the deposited material film into a required form, a cleaning process of removing unnecessary residues on the wafer, and a thin film deposited on the wafer to form a fine pattern It goes through a number of unit processes such as the etching process to etch. Of these, the etching process is one of the most essential processes.

The etching process for the semiconductor wafer is performed by forming a photoresist or hard mask on the wafer (substrate) on which the thin film is deposited, and then removing the thin film formed on the wafer along the photoresist or hard mask pattern. Recently, the etching process is a dry etching apparatus using plasma, which has high step ratio or aspect ratio (AR), fine control of line width, and environmentally friendly and anisotropic etching compared to wet etching according to the increase in the degree of integration of semiconductor devices. Mainly made by. Plasma etching process (plasma etching process) is a process of applying a high-frequency power in the vacuum chamber to flow the etching gas supplied in the chamber in a plasma state and etching and removing the thin film by the high-energy electrons or radicals formed at this time. Say. In order to successfully perform such a plasma etching process, the process of chucking and dechucking a semiconductor substrate in a chamber is essential as an important process. A stable substrate chucking / dechucking process is required in a plasma deposition process as well as a plasma deposition process.

Generally, the holding of a substrate in a process chamber for manufacturing a semiconductor device includes a mechanical clamp method, a vacuum chuck method, and an electrostatic chuck method, but recently, uniformity of particles and processes is achieved. The use of electrostatic chucks (ESCs) with excellent uniformity is increasing rapidly. In particular, the use of an electrostatic chuck as equipment for high-density plasma etching and plasma deposition has become common. However, in the case of using the electrostatic chuck, a problem such as sticking occurs during the separation of the substrate from the electrostatic chuck after the plasma treatment, so that the substrate is broken in the reaction chamber or when the substrate is unloaded from the chamber. The substrate may be misplaced. This is because dechucking and substrate separation are performed in a state where the adsorption force (electrostatic force) due to the charge remaining on the surface of the substrate is not completely removed after completion of a dry etching process. Many methods for removing surface charge have been studied.

1 is a view showing a schematic configuration of a conventional plasma dry etching apparatus. Referring to FIG. 1, the plasma etching apparatus 100 includes a chamber 10 in which an etching space portion 101 is formed, an electrostatic chuck 91 in which a wafer is seated and fixed in the etching space portion 101, and A cathode 21 coupled to the electrostatic chuck and a coil member 30 disposed on an upper surface of the chamber 10 to form a plasma are provided. One end of the coil member 30 is grounded and the other end is connected to a high frequency power supply unit 50 for applying high frequency power. In addition, the cathode 21 is also connected to the high frequency power supply 51. Matching network for impedance matching and transmitting the high frequency power to the coil member 30 and the cathode 21 between the high frequency power supply 50 and the coil member 30 and between the high frequency power supply 51 and the cathode 21, respectively. 60 and 61 are electrically connected. Inside the electrostatic chuck 91 is a lift pin 90 for elevating the substrate 18. In addition, there is an electrostatic chuck power supply unit 70 connected to the lower portion of the electrostatic chuck 91 to supply a constant voltage or a reverse voltage to the electrostatic chuck from the outside of the chamber 10. In the substrate 80 positioned on the electrostatic chuck 91, the opposite polarity charge is induced on the lower surface of the substrate 80 by a constant voltage applied to the electrostatic chuck 91. Induced electromagnetic force or electrostatic force is generated by the induced charges to fix the substrate 80 to the electrostatic chuck 91. The dielectric ceramic coating layer 20 is coated on the top surface of the electrostatic chuck 91.

When the plasma etching process is completed, a reverse voltage having a polarity opposite to the constant voltage supplied to the electrostatic chuck 91 is applied to cancel the induced electromagnetic force acting on the substrate 80. At this time, if the lift pin 90 lifts the substrate 80 on the electrostatic chuck 91 without completely removing the surface charge induced on the substrate 80, the substrate may be caused by the electrostatic charge remaining on the surface of the substrate 80. The 80 is not properly separated from the electrostatic chuck 91, and a sticking phenomenon occurs. This phenomenon can change the alignment state of the substrate 80 and damage the substrate 80, so that the lift pin 90 is grounded even after the reverse voltage is applied to the electrostatic chuck during dechucking. The 90 is raised to separate the substrate 80 from the electrostatic chuck 91.

However, even if the substrate chucking / dechucking apparatus and method thereof of the plasma etching apparatus are subjected to a series of dechucking procedures, the capacitance of the electrostatic chuck 91 increases as the usage amount of the electrostatic chuck 91 increases, As the capacitance increases continuously, the surface charge of the substrate increases. Accordingly, since the dechucking is performed by applying a constant reverse voltage or by simply grounding, the dechucking reliability is lowered and the dechucking defect is increased, resulting in damage of the substrate or poor substrate transfer.

The present invention has been made to solve the above-described problems, the plasma that can effectively remove the residual charge on the surface of the substrate during dechucking by the control of the dechucking voltage to enhance the dechucking ability and prevent the occurrence of dechucking failure It is an object of the present invention to provide a substrate dechucking method in a processing apparatus.

The substrate dechucking method in the plasma processing apparatus according to the present invention,

Stopping plasma generation after completion of plasma processing on the substrate held on the electrostatic chuck by the chucking voltage of the constant voltage, and applying a first reverse voltage to the electrostatic chuck;

An intermediate turn off step of stopping application of the first reverse voltage to the electrostatic chuck;

Applying a second reverse voltage of a magnitude less than the first reverse voltage to the electrostatic chuck after the intermediate turn off step; And

And a grounding step of stopping application of the second reverse voltage to the electrostatic chuck and grounding the substrate.

According to an embodiment of the present invention, the first and second reverse voltages may be applied to a lift pin inserted into the electrostatic chuck. In the grounding step, the substrate may be grounded through a lift pin contacting the substrate while grounded to a ground terminal. The lift pins contacting the substrate may be in contact with the substrate by forming a contact portion in contact with the substrate with Cu, Ag, Pt or Al having high electrical conductivity.

According to an embodiment of the present invention, the first and second reverse voltages may be applied to one or more first lift pins inserted into the electrostatic chuck. In addition, in the grounding step, the substrate may be in contact with the substrate in a state of being grounded to the ground terminal and grounded through a second lift pin dedicated to ground different from the first lift pin. Also, in the grounding step, the substrate may be grounded through the second lift pin and the first lift pin. In this case, the first and second lift pins may be connected in parallel with each other.

According to the present invention, by controlling the dechucking voltage, it is possible to reliably remove residual charges on the surface of the substrate during dechucking to enhance the dechucking ability and effectively prevent dechucking defects caused by sticking or the like.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Shapes and sizes of the elements in the drawings may be exaggerated for clearer explanation, elements represented by the same reference numerals in the drawings are the same elements. Before describing the dechucking method according to the present embodiment, a substrate chucking for plasma processing is briefly described with reference to the timing diagram of FIG. 2.

2 is a timing diagram showing an example of a chucking voltage applied to an electrostatic chuck when the substrate is fixed to the electrostatic chuck for plasma processing. The chucking voltage may be applied to the substrate 80 using the electrostatic chuck 91 and the electrostatic chuck voltage supply unit 70 of the plasma processing apparatus as shown in FIG. 1. By disposing the substrate 80 on the electrostatic chuck 91 and then applying a constant voltage to the electrostatic chuck 91, the substrate is fixed to the electrostatic chuck by the electrostatic attraction between the substrate 80 and the electrostatic chuck 91. As shown in FIG. 2, the chucking voltage may be stepped up to a constant voltage in the off state just before the initial ti. When a constant constant voltage is reached, the constant voltage is continuously applied during plasma processing (plasma etching or plasma deposition) to keep the substrate 80 firmly on the electrostatic chuck. When the plasma processing is completed, the chucking voltage can be reduced stepwise to be turned off at the end of chucking (tf). This chucking voltage may be applied to the lift pins in the electrostatic chuck 91.

3A and 3B are timings for explaining the dechucking voltage application according to the prior art (Fig. 3 (a)) and the dechucking voltage application according to the embodiment of the present invention (Fig. 3 (b)). It is also. After completion of the plasma treatment, the electrostatic chuck 91 has a reverse voltage having the opposite polarity of the constant voltage to turn off the constant voltage applied to the electrostatic chuck and cancel the induced electromagnetic force (electrostatic attraction) between the substrate 80 and the electrostatic chuck 91. ) Is applied.

Referring to FIG. 3A, a dechucking voltage of a reverse voltage is applied for a time t1 to t2, and then the dechucking voltage of a reverse voltage is turned off. When the dechucking voltage is turned off, the substrate 80 is grounded through the lift pin 90 connected to the ground terminal, and the charge remaining on the surface of the substrate 80 is removed to the ground terminal even after the reverse voltage is applied. However, it takes a considerable time for the charge remaining on the surface of the substrate 80 to reliably escape to the ground terminal, and the surface of the electrostatic chuck 91 deteriorates as the chucking / dechucking operation is repeated. As the capacitance increases, the amount of residual charge on the surface of the substrate 80 increases. Therefore, if the lift pin 90 is raised while the residual charge on the surface of the substrate 80 remains large, dechucking defects such as substrate damage and misplacement of the substrate due to the sticking of the substrate 80 may be caused. Will occur.

In contrast, in the present embodiment, two levels of reverse voltage are applied as shown in FIG. 3 (b), but dechucking with an intermediate turn-off time (t2 to t3) between the two levels of reverse voltage. Use voltage.

Specifically, the plasma generation is stopped when plasma processing such as plasma etching or plasma deposition is completed. Then, the dechucking voltage of the first reverse voltage is applied during the time t1 to t2 so as to turn off the constant voltage applied to the electrostatic chuck 91 and cancel the induced electromagnetic force between the substrate 80 and the electrostatic chuck 91. 1 reverse voltage application step). Then, after temporarily turning off the dechucking voltage of the first reverse voltage (intermediate turn-off step) for a time t2 to t3, the dechucking voltage of the reverse voltage is applied again, but this time, 2 Reverse voltage is applied (second reverse voltage application step). By setting the second reverse voltage to a size smaller than the first reverse voltage, the electrostatic chuck 91 and other internal elements in the chamber are prevented from being overwhelmed, and in particular, spark generation in the substrate transfer robot arm is prevented. The above-described dechucking voltages of the first and second reverse voltages may be applied to the lift pins inserted into the electrostatic chuck 91. Thereafter, the application of the second reverse voltage to the electrostatic chuck 91 is stopped and the substrate 80 is grounded. The substrate 80 may be grounded through a lift pin 90 connected to the ground end and in contact with the substrate 80.

The above-described series of dechucking voltage application processes (FIG. 3 (b)) result in a short reverse flux of the substrate surface charge and more reliably remove the electrostatic attraction between the substrate and the electrostatic chuck and the surface charge remaining on the substrate. do. In particular, by additionally providing an intermediate turn-off step (t2 to t3) and a second reverse voltage applying step (t3 to t4), the time required in the grounding step is reduced even though the dechucking ability to remove the electrostatic attraction is enhanced. When chucking, there is little waste in overall time. As a result, the dechucking reliability is increased and the dechucking failure due to sticking or the like can be effectively prevented.

The dechucking voltage described above with reference to FIG. 3B may be applied to a lift pin disposed in the electrostatic chuck 91. Typically, the lift pin serves to lift up the wafer for conveyance of the wafer substrate, as well as to ground the substrate by contacting the substrate back side while being connected to the ground terminal during dechucking. In order to increase the grounding performance when grounding the board through the lift pin, the contact pin of the lift pin (the contact point on the top of the lift pin in contact with the board) may be made of Cu, which has excellent electrical conductivity, so that the lift pin may contact the board. The contact portion of the lift pin can be formed of Ag, Pt or Al having high electrical conductivity in addition to Cu.

Increasing the number of lift pins 90 may help dechucking, but due to the nature of the device constituting the electrostatic chuck, the electrode part is the most complex, making it difficult to construct the entire electrostatic chuck 91 including the lift pin 90. There is this. In addition, since high current RF is used for the cathode 21 coupled to the electrostatic chuck 91, the lift pin 90 can serve as a source of RF power loss. A simple increase in the number of lift pins 90 can lead to an increase in the source of RF power loss and thus is not the best way to improve dechucking capability. To solve this problem and increase grounding capability, shorter lift pins dedicated to ground voltage can be used.

4 is a diagram schematically illustrating a lift pin configuration that may be used in a dechucking method according to an embodiment of the present invention. As shown in FIG. 4, the total lift pins are divided by their role, so that the lift pin 90a to which the dechucking voltage as shown in FIG. 3 (b) is applied, and the lift pin for simply grounding the substrate ( 90b). In the ground phase (after time t4 in FIG. 3B), the lift pin 90a for the dechucking voltage and the lift pin 90b for the ground voltage may be connected in parallel and grounded to the ground terminal. In this case, the parallel circuit configuration of the lift pins 90a and 90b has a low impedance, which is more effective for substrate grounding. The lift pin 90b dedicated to the ground voltage provides only a contact point when the board is raised and thus does not cause a large chemical issue. The lift pin 90b dedicated to the ground voltage is shorter than the lift pin 90a for the dechucking voltage, so that the lift pin 90b stops rising at a predetermined height when the substrate is separated, and the other lift pin 90a is higher than the lift pin 90a. The substrate 80 may be supported and lifted up by the.

5 is a plan view schematically showing a substrate contact position of lift pins that may be applied to a dechucking method according to an embodiment of the present invention. As shown in FIGS. 5A and 5B, the lift pins 90a and 90b may be disposed in various ways with respect to the substrate 80. For example, as shown in Fig. 5A, a grounding lift pin 90b is disposed at an outer triangle vertex, and a lift pin 90a for dechucking voltage is disposed at an inner triangle vertex. Can be. In addition, as shown in FIG. 5B, the depinking voltage lift pin 90a may be disposed at a vertex of the quadrangle, and a lift pin 90b dedicated to ground voltage may be disposed inside the quadrangle. The upper ends of the lift pins 90a and 90b, which make contact between the substrate 80 and the lift pins 90a and 90b, may be made of a high conductivity material such as Cu, Ag, Pt, or Al to increase the grounding performance at the contacts. have.

The present invention is not limited by the above-described embodiment and the accompanying drawings. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims, .

1 is a view showing a schematic configuration of a conventional plasma etching apparatus having a substrate chucking / dechucking apparatus.

2 is a timing diagram for explaining the application of the chucking voltage.

3 is a timing diagram for explaining the dechucking voltage application (Fig. 3 (a)) according to the prior art and the dechucking voltage application (Fig. 3 (b)) according to the embodiment of the present invention.

4 is a diagram schematically illustrating a lift pin configuration that may be used in a dechucking method according to an embodiment of the present invention.

5 is a plan view schematically showing a substrate contact position of lift pins that may be applied to a dechucking method according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10 chamber 20 dielectric ceramic coating layer

21: cathode 30: coil member

40: ceramic window 50, 51: high frequency power supply

60, 61: matching network 70: electrostatic chuck power supply

80: substrate 90: lift pin

90a: first lift pin 90b: second lift pin dedicated to grounding

91: electrostatic chuck 100: plasma etching apparatus

101: etching space

Claims (8)

Stopping plasma generation after completion of plasma processing on the substrate held on the electrostatic chuck by the chucking voltage of the constant voltage, and applying a first reverse voltage to the electrostatic chuck; An intermediate turn off step of stopping application of the first reverse voltage to the electrostatic chuck; Applying a second reverse voltage of a magnitude less than the first reverse voltage to the electrostatic chuck after the intermediate turn off step; And And a grounding step of stopping application of the second reverse voltage to the electrostatic chuck and grounding the substrate. The method of claim 1, And the first and second reverse voltages are applied to a lift pin inserted into the electrostatic chuck. The method of claim 1, In the grounding step, the substrate, the substrate dechucking method in the plasma processing apparatus, characterized in that the grounded through the lift pin in contact with the substrate in a grounded ground. The method of claim 1, And a lift pin in contact with the substrate is in contact with the substrate by forming a contact portion in contact with the substrate with Cu, Ag, Pt or Al. The method of claim 1, And the first and second reverse voltages are applied to one or more first lift pins inserted into the electrostatic chuck. The method of claim 5, In the grounding step, in the plasma processing apparatus, the substrate is in contact with the substrate in a grounded state at the ground terminal and the substrate is grounded through a second lift pin dedicated to ground different from the first lift pin. Substrate dechucking method. The method of claim 6, And in the grounding step, the substrate is grounded through the second lift pin and the first lift pin. The method of claim 7, wherein And in said grounding step, said first and second lift pins are connected in parallel to each other.

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