JPH07147274A - Control of low-temperature processing device - Google Patents

Abstract

PURPOSE:To treat a material to be treated at a desired temperature by a method wherein heat transfer gas is fed to the contact surface of the material to be treated with an electrostatic chuck means and after an elapse of a prescribed time, process gas introduced in a treating chamber is brought into a plasma state. CONSTITUTION:A semiconductor wafer W is housed in a treating chamber 36 by a transfer arm and is placed on an electrostatic chuck sheet 4 provided on the placement surface of a susceptor 6. Then, with a DC voltage applied from a high-voltage DC source 92 to the sheet 4, He gas 11 is introduced in the chamber 36 and plasma is applied to the sheet 4 by a short time to make sufficient an adsorption to the semiconductor wafer W. In that state, back clean gas is fed from a gas source 13 to the rear of the wafer W via a pipeline 15. Thereby, an low-temperature etching, which is superior in anisotropic etching characteristics from the first of a treatment, can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a method of controlling a low temperature processing apparatus for processing an object in a low temperature atmosphere.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a plasma etching apparatus using a reactive plasma is used for processing a processing surface of an object to be processed such as a semiconductor wafer. In particular, recently, the development of an etching method capable of performing ultrafine processing corresponding to the half-micron era and even the quarter-micron era has been under development, and among them, it is possible to achieve good anisotropic etching. Attention has been paid to possible low temperature etching methods.

In this low temperature etching method, for example, a cooling jacket such as a liquid nitrogen is supplied to a cooling jacket provided on a susceptor in a processing chamber to transfer cold heat to an object to be processed such as a semiconductor wafer placed on the susceptor. It is heated, the processed surface is cooled to a desired temperature, for example, an ultralow temperature region of −100 ° C., and an etching process is performed by reactive plasma.

In this type of etching apparatus, an electrostatic chuck is installed on the upper surface of the susceptor to attract and hold the object to be processed on the susceptor during processing, and the object to be processed is held on the upper surface of the susceptor by electrostatic force. The structure is adopted. Then, in order that the cold heat from the susceptor is satisfactorily transferred to the semiconductor wafer via the electrostatic chuck, helium gas or the like is transferred to a minute gap formed between the back surface of the object to be processed and the suction surface of the electrostatic chuck. Hot gas (back cooling gas) is supplied.

[0005]

By the way, as shown in FIG. 6, an adsorption circuit using a monopolar electrostatic chuck as shown in FIG. 5 is not closed circuit due to the presence of conductive plasma. Since the heat transfer gas is supplied to the back surface of the object to be processed at a stage where sufficient attraction force is not yet generated, the object to be processed is placed on the susceptor due to the supply pressure of the heat transfer gas. There was a case where it was out of the position, which was a problem.

Therefore, after the object to be processed is placed on the attracting surface of the electrostatic chuck, a high DC voltage is applied to the electrostatic chuck, plasma is generated, and the attracting circuit of the electrostatic chuck is sufficiently closed. A control method has been proposed which employs a control sequence in which the heat transfer gas is supplied between the back surface of the object to be processed and the suction surface of the electrostatic chuck after the suction force is obtained.

However, when such a control sequence is used, after the plasma is generated, the cold heat is transferred to the semiconductor wafer through the heat transfer gas and the desired temperature is maintained until the semiconductor wafer reaches the desired temperature. Etching is performed at a temperature higher than the temperature of. This tendency becomes more serious as the processing temperature is lowered in order to improve the shape characteristics of etching or the etching time is shortened.

Further, in the case of the bipolar electrostatic chuck as schematically shown in FIG. 7, a sufficient attraction force can be obtained without generating plasma unlike the monopolar electrostatic chuck. When the semiconductor wafer is attracted to the electrostatic chuck and the heat transfer gas is supplied, and then the plasma is immediately ignited, as in the control sequence of, the time until the semiconductor wafer is cooled to the predetermined temperature is the predetermined time. Since the etching is carried out at a temperature higher than the above temperature, there has been a problem in performing ultra-fine processing.

The present invention has been made in view of the problems of the control sequence of the low temperature processing apparatus as described above, and an object of the present invention is to provide a backing for processing an object to be processed at a desired temperature. It is an object of the present invention to provide a new and improved low-temperature processing apparatus control method relating to a cooling gas supply sequence.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 performs a predetermined process on an object to be processed, which is cooled by being held by electrostatic chuck means on an susceptor in a processing chamber. In controlling the low temperature processing apparatus for plasma processing by the reactive plasma of gas, the object to be processed is placed on the adsorption surface of the electrostatic chuck means, and the heat transfer gas is applied to the contact surface between the object and the electrostatic chuck means. Is supplied, and after a lapse of a predetermined time, for example, 20 seconds, the processing gas introduced into the processing chamber is turned into plasma to perform plasma processing.

In the invention according to claim 2, in executing the control sequence according to claim 1, when the electrostatic chuck means is a monopolar electrostatic chuck, the object to be processed and the electrostatic chuck are Before supplying the heat transfer gas to the contact surface with the means, at a low power, for example, 100 W or less, preferably 50 W or less, for a short time, for example, 1 to 2 seconds, so that the inert gas is not etched on the object to be processed. It is characterized in that a step of converting to plasma is performed.

[0012]

According to the first aspect of the present invention, the object to be processed is placed on the adsorption surface of the electrostatic chuck, the back cooling gas is supplied, and then the cold heat of the electrostatic chuck is transferred to the object to be processed. , The processing gas after the object to be processed reaches the desired temperature,
For example, since plasma processing is performed using HF gas, low-temperature etching having excellent anisotropic etching characteristics can be performed from the beginning of the processing, and ultrafine processing required in the half-micron era can be precisely performed.

According to the second aspect of the present invention, even when the electrostatic chuck means is of the unipolar type as schematically shown in FIG. 5, low power, for example 100 W or less, which does not cause etching. An inert gas that does not affect etching is converted to plasma by electric power, and a sufficient suction force is obtained by closing the suction circuit of the electrostatic chuck, and then, between the back surface of the object to be processed and the suction surface of the electrostatic chuck. The heat transfer gas is supplied, and after waiting for the temperature of the object to be processed to reach the desired temperature, the processing gas is converted into plasma and processed, so that the object is sufficiently absorbed by the electrostatic chuck and is sufficiently cooled. The plasma treatment can be performed in this state.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a method for controlling a low temperature processing apparatus constructed according to the present invention is applied to a low temperature plasma etching apparatus will be described in detail below with reference to the accompanying drawings.

As shown in the figure, the plasma etching apparatus 30 includes a processing chamber 36 composed of an inner frame 32 and an outer frame 34 made of a material such as aluminum.
The inner frame 32 includes a cylindrical wall portion 32A and the cylindrical wall portion 32.
It is composed of a bottom portion 32B provided at a slight distance above the lower end of A and an outer flange portion 32C provided on the outer periphery of the lower end of the cylindrical wall portion 32A. On the other hand, the outer frame 34 includes the cylindrical wall portion 34A and the ceiling portion 34B.
And is placed on the outer flange portion 32C so as to cover the inner frame 32 in an airtight manner.

Above the cylindrical wall portion 34A of the outer frame 34, a processing gas from the processing gas source 10 such as HF gas and an inert gas from the inert gas source 11 such as H.
A gas supply conduit 38 is provided through which the e gas can be introduced into the processing chamber 36 via the mass flow controller 12. Further, a gas exhaust pipe line 40 is provided below the other side of the cylindrical wall portion 34A so that a vacuum pump (not shown) can evacuate the gas.

Above the ceiling portion 34B of the outer frame 34, a magnetic field generator for forming a horizontal magnetic field on the surface of an object to be processed, for example, a semiconductor wafer W, for example, a permanent magnet 42 is rotatably provided. The magnetron discharge is configured to be generated by forming a horizontal magnetic field by the magnet and an electric field orthogonal to the horizontal magnetic field.

A susceptor assembly 44 for mounting and fixing an object to be processed, for example, the semiconductor wafer W is arranged in the processing chamber 36. This susceptor assembly 4
4 is mounted on the bottom portion 32B of the inner frame 32 via a plurality of insulating members 46, and at the same time, insulation is provided between the side surface of the susceptor assembly 44 and the cylindrical wall portion 32 of the inner frame 32. Since, for example, an O-ring 48 is inserted as a seal member, the susceptor assembly 44 is
It is configured to be held in an insulated state from the inner frame 32 and the outer frame 34 that are grounded externally.

The susceptor assembly 44 is made of, for example, aluminum and has a three-layer structure in the illustrated example. The susceptor 6 and the susceptor support base 20 for supporting the susceptor 6 are provided below the susceptor 6. It is composed of a jacket housing 50. And this susceptor 6
The electrostatic chuck sheet 4 is adhered to the mounting surface of the upper surface of the above with an adhesive or the like to form the electrostatic chuck 52. Then, the semiconductor wafer W as the object to be processed is suction-held on the electrostatic chuck sheet 4.

The susceptor support 20 is provided with a temperature adjusting device, such as a heater 54, for adjusting the temperature of the semiconductor wafer W. The heater 54 is connected to a heater controller (not shown), and is configured to perform temperature control according to a signal from a temperature sensor (not shown) that monitors the temperature of the susceptor 6.

The susceptor 6 is the susceptor support base 2
It is removably fixed to 0 by using a connecting member such as a bolt 56. With this configuration, the high frequency power source 58
Separately from the susceptor support 20 connected to
It becomes possible to replace only the above 6 parts of the susceptor,
Maintenance of the device becomes easy.

Further, as described above, since the O-ring 48 is interposed between the side wall of the susceptor 6 and the inner surface of the cylindrical wall portion 32A of the inner frame 32, the processing gas introduced into the processing chamber does not flow. It does not reach below the susceptor support 20, and contamination of these parts is prevented.

Inside the cooling jacket accommodating table 50, a cooling jacket 62 for accumulating a coolant 60 such as liquid nitrogen is installed. The cooling jacket 62 is connected to a liquid nitrogen source 68 by a pipe 64 via a valve 66. A liquid level monitor (not shown) is arranged in the cooling jacket 62, and by opening and closing the valve 66 in response to a signal from the liquid level monitor, the refrigerant 60 in the cooling jacket 62, for example, the liquid. It is configured to control the supply amount of nitrogen. Further, the bottom surface of the inner wall of the cooling jacket 62 is formed, for example, in a porous form so that nucleate boiling can be caused.
For example, it can be maintained at -196 ° C.

The susceptor assembly 44 thus constructed is electrically insulated from the inner frame 32 and the outer frame 34 forming the processing chamber 36 by the insulating member 46 and the O-ring 48, and is electrically the same. The high frequency power supply 58 is connected to the susceptor support 20 via a matching device 69, which constitutes a polar cathode coupling. Thus, the susceptor assembly 8
The counter electrode is constituted by the ceiling portion 34B of the outer frame 34 that is grounded, and by applying high-frequency power, it is possible to generate plasma discharge between the electrodes, that is, in the processing chamber 36.

Furthermore, between the susceptor 6 in the upper layer of the susceptor assembly 8 according to the present embodiment and the susceptor support 20 in the middle layer provided with the heater 54, and between the susceptor support 20 and the lower cooling jacket receiving portion 50. Gaps 70 and 72 are formed between
These gaps are formed by the sealing member 7 such as an O-ring.
4 and 76 are airtightly constructed,
Through the gas supply line 78, a predetermined pressure, for example, 10 To
An inert gas of about rr, such as helium or argon, can be supplied from the gas source 13 via the flow rate controller 14.

The gaps 70 and 72 are 1 to 100 μm.
m, and preferably about 50 μm. By the action of the inert gas which is the heat transfer medium sealed in these gaps 70 and 72, the cooling heat from the cooling jacket 62 can be transferred to the object to be processed with a minimum heat loss.

On the other hand, the electrostatic chuck 52 according to the present invention.
As shown in FIG. 2, is composed of an electrostatic chuck sheet 4 made of, for example, polyimide having an insulating property and a cylindrical susceptor 6 made of, for example, aluminum. The electrostatic chuck sheet 4 is formed by laminating a pair of polyimide resin films 4A and 4B, and a thin conductive film 8 such as a copper foil is enclosed in an insulating state in the electrostatic chuck sheet 4. A DC voltage of, for example, 2.0 KV can be applied to the conductive film 8 from the high voltage DC power supply 92. In the embodiment shown in FIG. 1, a monopolar electrostatic chuck as schematically shown in FIG. 5 is used, but the present invention is not limited to this, and as shown schematically in FIG. It is also possible to apply to a bipolar electrostatic chuck.

The electrostatic chuck sheet 4 is firmly bonded to the mounting surface of the susceptor with, for example, an epoxy adhesive. In addition, between the adsorption surface of the electrostatic chuck sheet 4 and the object W to be processed, an inert gas of about 10 Torr from the gas source 13 via the conduit 15 and the flow rate controller 14,
For example, helium gas can be introduced, and due to the action of this heat transfer gas, the cold heat from the cooling jacket 50 can be satisfactorily transferred from the electrostatic chuck sheet 4 to the object to be processed.

The pressure of the heat transfer gas supplied is 10T.
It is preferable to set it to about orr. That is, as can be seen from FIG. 8 showing the transient response of the wafer temperature, when the supply gas pressure is 10 Torr or less, the gas flow state on the back surface of the wafer becomes a molecular flow, so that the time constant of the wafer temperature depends on the gas pressure. However, at 10 Torr or more, the gas flow state on the back surface of the wafer becomes an intermediate flow, so that the time constant of the wafer temperature does not depend on the pressure and the time constant becomes a constant value in about 20 seconds.

Further, the plasma etching apparatus is provided with a controller 15, which includes a high frequency power source 58, a high voltage DC source 92 for electrostatic chuck, a liquid nitrogen source 68, a back cooling gas flow rate controller 14, and a processing gas. Flow controller 12
It is possible to execute a desired processing sequence by sending an appropriate control signal.

As described above, the low temperature plasma processing apparatus to which the control method of the low temperature processing apparatus constructed according to the present invention can be applied is constructed.

Next, an embodiment in which a control sequence constructed according to the present invention is applied to the above-mentioned low temperature plasma processing apparatus mounted with a monopolar electrostatic chuck sheet will be described with reference to the flow chart shown in FIG. explain. First, the semiconductor wafer W is housed in the processing chamber 36 by a transfer arm (not shown) via a gate valve (not shown), and the electrostatic chuck sheet 4 is provided on the mounting surface of the susceptor 6 in S1.
Place on top. Next, in S2, a DC voltage is applied to the electrostatic chuck sheet 4 from the high-voltage DC source 92, and the semiconductor wafer W is adsorbed on the electrostatic chuck sheet 4. However, at this stage, the adsorbing force is insufficient and back cooling is performed. When the gas is supplied to the back surface of the semiconductor wafer W via the conduit 15, the semiconductor wafer W may come off the susceptor 6.

Therefore, according to the method of the present invention, in order to make the adsorption force of the electrostatic chuck sheet 4 sufficient, an inert gas such as helium is introduced from the gas source 11 into the processing chamber 36 in S3, The plasma is kept at a low power, for example, 100 W or less, preferably 50 W or less, for a short time, preferably 1 to
By raising for 2 seconds, the adsorption circuit of the electrostatic chuck is closed. As a result, a sufficient adsorption amount is secured for the object W to be processed, so that it is possible to supply the back cooling gas from the gas source 13 to the back surface of the object W at a predetermined pressure, for example, 10 Torr in S4. is there.

However, as shown in the table of FIG. 4, it takes about 20 seconds or more from the time when the back cooling gas is supplied until the processing surface of the object W is cooled to a desired low temperature. According to the invention, the back cooling gas is supplied before the etching process is started, and a predetermined time is waited in S3, preferably 10 seconds or longer, more preferably 20 seconds or longer. Since the processing surface of the object W is cooled to a desired temperature by this step, a predetermined processing gas, for example, HF gas is introduced from the processing gas source 10 into the processing chamber 36 in S6, and this processing gas is plasma-processed. Desired etching can be carried out.

As described above, according to the present invention, even when the monopolar electrostatic chuck sheet is used, the adsorption is sufficiently performed by the low power plasma which does not cause the etching. Since the back cooling gas is supplied from the above, it is possible to avoid an unexpected situation in which the object W to be processed comes off. Further, after supplying the back cooling gas, after waiting for a predetermined time, plasma of the processing gas is generated, so that the object W to be processed can be etched at a desired low temperature,
Good anisotropic etching can be realized.

The flow chart shown in FIG. 2 shows an embodiment in which the method of the present invention is applied to a plasma etching apparatus mounted with a monopolar electrostatic chuck sheet, but the present invention is not limited to this. For example, the method of the present invention can be applied to a plasma etching apparatus mounted with a bipolar electrostatic chuck sheet. In this case, as shown in the flow chart of FIG. 3, by applying a DC voltage to the electrostatic chuck in S2, a sufficient adsorption force can be realized, so that a low power plasma of the inert gas in S3 is generated. It is possible to omit steps.

The object W to which the desired low temperature etching has been completed as described above is again carried out to the load lock chamber (not shown) by the carrying arm, further carried out to the cassette chamber (not shown), and stored in the cassette for the next step. It is possible to send.

The preferred embodiment of the method for controlling the low temperature processing apparatus constructed according to the present invention has been described as applied to the plasma etching apparatus, but the present invention is not limited to this embodiment. It is understood that the present invention can be applied to all low temperature processing devices such as an ashing device, a sputtering device, and a CVD device that need to adsorb and hold an object to be processed.

[0039]

As described above, according to the first aspect of the present invention, the object to be processed is placed on the adsorption surface of the electrostatic chuck, the back cooling gas is supplied, and then the heat of the electrostatic chuck is cooled. Heat-transfers to the object to be processed, and after the object reaches a desired temperature, plasma processing is performed with a processing gas, for example, HF gas, so low-temperature etching with excellent anisotropic etching characteristics is performed from the beginning of the processing. Because it is possible
The ultra-fine processing required in the half-micron era can be precisely applied.

Further, particularly when a monopolar type electrostatic chuck is used, the etching is not affected by a low power which does not cause etching, for example, a power of 100 W or less, as in the invention of claim 2. After the inert gas is turned into plasma and a sufficient suction force is obtained by closing the suction circuit of the electrostatic chuck, heat transfer gas is supplied between the back surface of the object to be processed and the suction surface of the electrostatic chuck. Waiting for the object to be processed to reach the desired temperature, plasma is used for the processing gas, and processing is performed, so plasma processing is performed while the object is sufficiently adsorbed by the electrostatic chuck and sufficiently cooled. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a plasma etching apparatus to which a control method of a low temperature processing apparatus configured according to the present invention can be applied.

FIG. 2 is a flow chart showing a control sequence when the method of the present invention is applied to a plasma etching apparatus using a unipolar electrostatic chuck.

FIG. 3 is a flow chart showing a control sequence when the method of the present invention is applied to a plasma etching apparatus using a bipolar electrostatic chuck.

FIG. 4 is a diagram showing a transient response characteristic of a semiconductor wafer temperature.

FIG. 5 is a circuit diagram schematically showing a monopolar electrostatic chuck.

FIG. 6 is a circuit diagram schematically showing an adsorption circuit of a monopolar electrostatic chuck that forms a closed circuit with plasma.

FIG. 7 is a circuit diagram schematically showing a bipolar electrostatic chuck.

FIG. 8 is a graph showing a transient response of wafer temperature.

[Explanation of symbols]

 4 Electrostatic Chuck Sheet 6 Susceptor 8 Conductive Film 14 Controller 30 Plasma Etching Device 36 Processing Chamber 44 Susceptor Assembly 52 Electrostatic Chuck 58 High Frequency Power Supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Takayama 1st 2381 Kitashitajo, Fujii-cho, Nirasaki-shi, Yamanashi Tokyo Electron Yamanashi Co., Ltd.

Claims (2)

[Claims] 1. When controlling a low-temperature processing apparatus for plasma-processing an object to be processed that is adsorbed and held by an electrostatic chuck means and cooled on a susceptor in a processing chamber by reactive plasma of a predetermined processing gas, The processing object is placed on the attraction surface of the electrostatic chuck means, a heat transfer gas is supplied to the contact surface between the object to be processed and the electrostatic chuck means, and after a predetermined time has passed, it is introduced into the processing chamber. A method for controlling a low-temperature processing apparatus, which comprises converting a processing gas into plasma. 2. The electrostatic chuck means is a monopolar electrostatic chuck, and the inert gas is supplied for a short time before heat transfer gas is supplied to the contact surface between the object to be processed and the electrostatic chuck means. The method for controlling a low-temperature processing apparatus according to claim 1, further comprising the step of converting the material into plasma with low power such that etching does not occur in the object to be processed.