JPH05275377A - Plasma treatment method and apparatus thereof - Google Patents

Abstract

PURPOSE:To improve the cooling efficiency of the temperature of a sample substrate by increasing the efficiency of heat transfer from a cooling gas for the sample substrate without increasing the size of an electrode in the plasma treatment for applying a plasma bean to the sample substrate mounted on the electrode within a vacuum container and performing etching and the like with the sample substrate being cooled from the electrode side. CONSTITUTION:This is constituted in such an arrangement that a gas channel groove 2a is provided in the upper surface of an electrode 2 arranged within a vacuum treatment chamber 1 and at the same time interconnected with a liquefied gas bomb for inactive gas 6 and an exhaust pump 8 arranged outside the vacuums treatment chamber 1 through a gas introduction and exhaust hole 2b, 2c and a gas introduction and exhaust pipe 7, 9. A low-temperature inactive gas is introduced between a sample substrate W, the circumferential part of which is pushed against the upper surface of the electrode 2 to adhere close thereto with the presser hook 3a of a sample presser 3 and the gas channel groove 2a, thereby cooling the sample substrate W by direct contact and heat exchange with the inactive gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus, and more particularly to a plasma processing method and apparatus applied to dry etching or CVD processing of a sample substrate such as a silicon wafer in the semiconductor manufacturing field. Is.

[0002]

2. Description of the Related Art As a plasma processing method, methods such as dry etching, sputtering, and CVD are known. In these plasma processing, the temperature of the sample substrate depends on the energy of ions, electrons and radicals in the plasma to be irradiated. To rise. On the other hand, since the processing speed and the side reaction speed in dry etching and CVD processing are both a function of the plasma parameter and a function of the sample substrate temperature, a plasma processing apparatus that performs these processes uses a sample substrate such as a silicon wafer. A method of suppressing the temperature rise of the sample substrate due to the irradiation of the plasma beam is provided by providing a cooling means on the electrode on which the substrate is mounted and transferring heat from the cooled electrode to the sample substrate. Further, in these plasma devices, in order to sufficiently transfer heat from the electrodes to the sample substrate and perform reliable temperature control, a mechanism for closely holding the sample substrate to be processed in contact with the electrode surface is required, An electrostatic chucking mechanism utilizing electrostatic force or a mechanical chucking mechanism using mechanical means is adopted.

In recent years, from the viewpoint of improving the processing speed and accuracy, the sample substrate temperature in these plasma processes has been controlled to a low temperature below room temperature, or even an extremely low temperature. A refrigerant liquid tank is provided in the tank, and liquefied nitrogen can be introduced into the tank to control the temperature to a lower temperature. In addition, since the electrostatic chucking mechanism uses a ceramic-based chuck sheet, its thermal conductivity is low, and its insulating properties decrease at temperatures below 0 ° C, so plasma treatment that requires treatment under these low-temperature conditions is required. The device generally employs a mechanical chucking mechanism. An example of a conventional plasma processing apparatus having such a configuration is shown in a schematic explanatory view of FIG.

In the conventional plasma processing apparatus shown in FIG. 4, an electrode (42) connected to a high frequency power source (46) is provided inside and below a vacuum processing chamber (41) whose inside is degassable. While arranging it, a wafer retainer (43) is provided so that it can move up and down, and the electrode (42)
The outer peripheral edge portion of the wafer W placed on the wafer W is held (43)
By pressing it against the upper surface of the electrode (42) with the holding claw (43a) of
A configuration is adopted in which the wafer W is held in close contact with the upper surface of the electrode (42). Further, the electrode (42) includes a heater (44) connected to the power supply means (47) and a liquefied nitrogen tank (45) connected to the liquefied nitrogen supply source (48) and the gas discharge means (49). The temperature of the wafer W can be controlled by being provided inside, and under this configuration, the temperature of the wafer W that is in close contact with and held on the upper surface thereof is controlled to a predetermined low temperature.

[0005]

However, like the above-mentioned conventional plasma processing apparatus, liquefied nitrogen is introduced as a refrigerant into the electrode, and the sample substrate is indirectly cooled by heat transfer from the cooled electrode. Then, there is a problem that the cooling efficiency of the sample substrate temperature is poor and the responsiveness to the processing speed is poor, and in addition, the electrode becomes large.

This is because the amount of heat transferred from the electrodes to the sample substrate depends on the contact area between them, whereas in the mechanical chucking mechanism, the outer peripheral edge of the sample substrate is affected by the plasma beam irradiation. The entire surface of the sample substrate must be brought into close contact with the electrode surface by pressing the part toward the electrode surface. Moreover, since the sample substrate such as a silicon wafer is thin and weak, it is necessary to increase the pressing force too much. Cannot be done (60g / cm ² is the limit), and because of this,
This is because it is substantially difficult to surely adhere the entire surface of the sample substrate to the electrode surface, and as a result, heat cannot be efficiently transferred from the coolant to the sample substrate. Further, although the electrostatic chucking mechanism can bring the sample substrates into contact with each other relatively evenly, it is difficult to apply the electrostatic chucking mechanism for the above reason. on the other hand,
When liquefied nitrogen is used as a refrigerant, cryogenic temperature can be obtained relatively economically, but latent heat of vaporization is used to obtain the cooling effect, so it is necessary to provide a vaporization space in the liquefied nitrogen tank inside the electrode. Moreover, since nitrogen gas is usually active for dry etching and CVD processing, it is necessary to reliably prevent leakage into the vacuum processing chamber, which makes the electrode complicated and large.

The present invention has been made to solve the above-mentioned problems of the prior art, and enhances the heat transfer coefficient from the refrigerant gas to the sample substrate without increasing the size of the electrode on which the sample substrate is placed. Thus, it is an object of the present invention to provide a plasma processing method and apparatus capable of improving the cooling efficiency of the sample substrate temperature.

[0008]

In order to achieve the above object, the present invention has the following constitution. That is, the plasma processing method according to the present invention irradiates the sample substrate placed in close contact with the upper surface of the electrode in the vacuum container provided with the exhaust means with the plasma beam, and cools the sample substrate from the electrode side to produce the beam. In a plasma processing method in which a plasma processing such as etching is performed while suppressing a temperature rise due to irradiation, a low temperature inert gas is introduced and flowed between a concave portion provided on the upper surface of the electrode and the sample substrate. The feature is that the sample substrate is cooled by direct contact and heat exchange.

Further, the plasma processing apparatus according to the present invention is
A vacuum container provided with an evacuation unit, an electrode provided in the vacuum container for mounting a sample substrate on an upper surface thereof, and a chucking mechanism for holding the sample substrate in close contact with the electrode surface. In a plasma processing apparatus that irradiates a plasma beam onto a sample substrate that is in close contact with and is held on the upper surface, and cools this sample substrate from the electrode side to perform plasma processing such as etching while suppressing the temperature rise due to beam irradiation, Has a recess for allowing gas to flow therethrough on the upper surface excluding the outer peripheral edge thereof, and has a gas introduction hole and a discharge hole for communicating the recess with the outside of the vacuum container, and the gas introduction hole of the electrode and The discharge hole is connected to an inert gas supply and discharge means arranged outside the vacuum container.

[0010]

In the method of the present invention, the electrode is internally cooled as in the prior art, and the sample substrate is cooled by the contact with the cooled electrode, rather than the indirect cooling. A low temperature inert gas is introduced between the substrate and the substrate, and the sample substrate is cooled by direct contact and heat exchange with this inert gas. The resistance can be reduced to increase the heat transfer coefficient, which can improve the cooling efficiency of the sample substrate temperature. Moreover, since an inert gas is used as the refrigerant gas,
Even if some of these gas leaks between the electrode and the sample substrate and flows into the vacuum container, the gas can be discharged to the outside of the system by the exhaust means provided in the vacuum container without affecting plasma processing such as etching. it can.

Further, in the apparatus of the present invention, the electrode has a concave portion for allowing gas to flow therethrough except the outer peripheral edge portion thereof, and has a gas introduction hole and a discharge hole for communicating the concave portion with the outside of the vacuum container. Since the gas introduction hole and discharge hole are connected to the inert gas supply and discharge means arranged outside the vacuum container, the sample substrate is placed on this electrode and the chucking mechanism is used to While holding the substrate in close contact with the electrode surface, a low temperature inert gas is introduced and flowed between the recess on the upper surface of the electrode and the sample substrate, and direct contact and heat exchange with this inert gas are performed. The sample substrate can be cooled efficiently. In addition, the structure of the electrode can be remarkably simpler than that of the prior art in which a liquefied nitrogen tank or the like is provided inside.

The inert gas in the present invention is a gas of a zero group element and includes helium (He) and argon (A).
r) and gases such as xenon (Xe).

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a plasma processing apparatus according to one embodiment of the present invention, in which (a) is a front sectional view and (b) is A- of FIG. FIG.

In FIG. 1, (1) is a vacuum processing chamber, and the inside of this vacuum processing chamber (1) can be evacuated by deaeration means (not shown), and is also not shown. The microwave from the microwave generating means is introduced from above to generate plasma inside.

Reference numeral (2) is an electrode, and this electrode (2) is erected in the vacuum processing chamber (1) via a heat insulating member (4), and a high frequency power source for applying a negative high frequency voltage. It is connected to (5). The upper surface of the electrode (2) is provided with a double spiral gas passage groove (2a) continuous at the center, as shown in FIG. In addition, a gas introduction hole (2b) and a gas discharge hole (2c) penetrating downward and communicating with the outside of the vacuum processing chamber (1) are provided at the start end and the end of the gas flow channel (2a). ing.

The gas introduction hole (2b) of this electrode (2) is
Gas supply pipe (7) with a valve (7a) having a flow rate adjustment function
Via a liquefied gas cylinder outside the vacuum processing chamber (1)
On the other hand, the gas discharge hole (2c) is connected to (6), and the gas discharge hole (2c) is connected to the exhaust pump (8) outside the vacuum processing chamber (1) via the gas discharge pipe (9) equipped with the valve (9a). ). The liquefied gas cylinder (6) is equipped with a pressure reducing valve (6a) and
An inert gas such as He gas is liquefied and filled, while the exhaust pump (8) is connected to a gas recovery means (not shown).

(3) is a sample holder.
(3) is composed of three columnar legs (3c) surrounding the electrode (2) at an equal circumferential pitch, and a support ring (3b) connected to the upper ends of these legs (3c). The support ring (3b) is provided with an annular plate-shaped pressing claw (3a) having an inner diameter smaller than the outer diameter of the electrode (2).

The lower ends of the legs (3c) of the sample holder (3) penetrate the bottom of the vacuum processing chamber (1), and the lower ends of the disks are arranged below the vacuum processing chamber (1). Shaped Support Plate (10)
Is linked to. The support plate (10) is an insulating member (11).
It is connected to the cylinder (12) via the sample holder (3)
Is moved up and down by the operation of this cylinder (12). The lower end of the leg (3c) of the sample holder (3) is
While penetrating the bottom of (1) in a non-contact state, between the lower surface of the vacuum processing chamber (1) and the support plate (10) at the penetrating part, bellows joints (13) that surround and flex each leg (3c) are provided. ), And is intended to maintain airtightness at the penetrating portions of these legs (3c).

In FIG. 1 (a), W is a sample substrate such as a silicon wafer, which is placed on the electrode (2) and its outer peripheral edge is held by the sample holder (3). Nail (3
In a), the state of being pressed against the upper surface of the electrode (2) and closely contacted and held is shown.

In the plasma processing apparatus of this embodiment having the above structure, plasma is generated in the vacuum processing chamber (1) whose pressure is reduced, and a negative high frequency voltage is applied to the electrode (2),
While irradiating the sample substrate W placed on the electrode (2) with the generated plasma, the sample substrate W is cooled according to the procedure described below to suppress the temperature rise due to the irradiation of the plasma beam while performing etching or the like. Plasma treatment is performed.

First, the valves (7a) and (9a) of the gas supply pipe (7) and the gas discharge pipe (9) connected to the gas introduction hole (2b) and the gas discharge hole (2c) of the electrode (2), respectively. ) Is closed and in this state,
The inside of the vacuum processing chamber (1) is depressurized to a predetermined vacuum degree (about 10 ^-3 torr).

Next, a sample substrate W such as a silicon wafer is placed on the electrode (2), and the sample substrate W is attached to the electrode (2) by the ring-plate-shaped holding claw (3a) of the sample holder (3). ) Press on the top surface to make it adhere. The pressing force of the pressing claw (3a) at this time is 60 g / cm ² or less. At this time, the lower surface of the outer peripheral edge of the sample substrate W is brought into close contact with the upper surface of the outer peripheral edge of the electrode (2),
The upper opening of the gas flow channel (2a) of the electrode (2) is closed by the sample substrate W.

From this state, while the irradiation of the plasma beam is started, the gas supply pipe (7) and the gas discharge pipe (9)
Open the valves (7a), (9a) and introduce the low temperature inert gas such as He gas from the liquefied gas cylinder (6) into the gas channel groove (2a) on the upper surface of the electrode (2). Then, the sample substrate W is cooled by direct contact and heat exchange with this inert gas. At this time, the inert gas from the liquefied gas cylinder (6) has a predetermined pressure (0.01 to 0.0) by the pressure reducing valve (6a) of the liquefied gas cylinder (6).
After reducing the pressure to 50 kg / cm ² ) and adjusting the flow rate with the valve (7a) of the gas supply pipe (7), through this gas supply pipe (7) the gas flow channel groove ( Supply in 2a). Then, by controlling the supply amount, the amount of heat removed from the sample substrate W is adjusted to control the sample substrate temperature. On the other hand, the gas channel groove of the electrode (2)
The inert gas introduced and flowing into (2a) receives heat from the sample substrate W and its temperature rises, and accordingly the volume expands to increase the internal pressure. The exhaust pump (8) connected to (9) sucks and discharges the gas, so that the gas internal pressure in the gas flow channel (2a) of the electrode (2) is adjusted to stop within the range of 10 torr to 50 torr.

When the predetermined plasma treatment is completed, the valve (7a) of the gas supply pipe (7) is closed to stop the supply of the inert gas, while the exhaust pump (8) continues suction for a while.
When the inert gas in the gas flow channel (2a) of (2) is discharged and the pressure in this gas flow channel (2a) becomes approximately equal to the pressure in the vacuum processing chamber (1), The valve (9a) of the gas discharge pipe (9) is closed, the exhaust pump (8) is stopped, and then the processed sample substrate W is taken out and the next process is performed.

In this way, in the plasma processing apparatus of this embodiment for controlling the temperature of the sample substrate during processing, the contact heat transfer resistance with the inert gas, that is, the refrigerant gas is decreased to increase the heat transfer coefficient, and The cooling efficiency of the sample substrate temperature can be improved. On the other hand, the lower surface of the outer peripheral edge of the sample substrate,
The outer peripheral edge of the electrode (2) and the upper surface of the outer peripheral edge are in close contact with each other by a mechanical pressing force.
Although not necessarily reliable, in the present embodiment, since an inert gas such as He gas is used as the refrigerant gas, these gases leaked somewhat between the electrode and the sample substrate and flowed into the vacuum container. Even in this case, the gas can be discharged to the outside of the system by the exhaust means provided in the vacuum container without affecting the plasma processing such as etching.

Further, the electrode may be provided with a gas passage groove on the upper surface and a gas introduction hole and a discharge hole for communicating the gas passage groove with the outside. Compared with the one provided with a liquefied nitrogen tank or the like, the structure can be remarkably simple, so that the entire apparatus can be made compact.

FIG. 2 is a drawing showing a main part of a plasma processing apparatus according to another embodiment of the present invention, in which (a) is a front sectional view of the main part and (b) is (a). FIG. In addition,
The plasma processing apparatus of the present embodiment is basically the same as that shown in [FIG. 1] except that the configuration of the gas flow path provided in the electrode is different. Here, only the main parts are shown and Equivalent parts will be denoted by the same reference numerals, description thereof will be omitted, and the differences will be summarized.

In the plasma processing apparatus of this embodiment, instead of providing the double spiral gas passage groove on the upper surface of the electrode (22) on which the sample substrate W is placed, a circle over the entire upper surface except the outer peripheral edge portion is formed. A gas channel recess (22a) having a shallow shape (0.1 mm or less) is provided.

Further, the electrode (22) is provided with a gas distribution chamber (24) formed in a flat disk-shaped space in the lower central portion thereof, and the gas distribution chamber (24) and the gas flow path concave portion on the upper surface. (22a)
A plurality of gas introduction holes (22b) are provided to vertically communicate with a portion near the center of the. In addition, the gas distribution chamber (2
4) A gas collecting chamber (25) formed in a flat annular space is provided in the area surrounding the flexible space (4), and this gas collecting chamber (24) and the area near the outer periphery of the upper gas flow passage recess (22a) are moved up and down. A plurality of gas discharge holes (22c) communicating with each other are provided.

Here, the gas introduction hole (22b) of the electrode (22)
As shown in Fig. (B), the gas passage recesses (22a) are opened at equal pitches in the circumferential direction on the same pitch circle in the central portion of the gas flow passage recesses (22a). Channel recess (2
On the same pitch circle of the outer peripheral part of 2a), openings are made at equal pitch in the circumferential direction. In this embodiment, the number of gas discharge holes (22c) is three times the number of gas introduction holes (22b). On the other hand, the gas distribution chamber (24) of the electrode (22) is connected to the gas supply pipe (7), and the gas collection chamber (24) is connected to the gas discharge pipe (9). A low temperature inert gas is introduced between the sample substrate W and the gas flow channel recess (22a), which are adhered and held on the electrode (22) by the sample retainer (3), and the inert gas (b ) As shown by the arrow in the figure, the sample substrate W is cooled by flowing while being dispersed in the radial direction.

In the plasma processing apparatus of the present embodiment having the above-described structure, the gas flow path provided in the electrode is configured to be easily processed, and the contact area between the sample substrate and the inert gas is further increased to enhance the heat transfer coefficient. Therefore, the cooling efficiency of the sample substrate temperature can be further improved.

FIG. 3 is a drawing showing a main part of a plasma processing apparatus according to still another embodiment of the present invention, where (a) is a front sectional view of the main part and (b) is (a). It is an AA sectional view of a figure. The plasma processing apparatus of the present embodiment is largely different in that an electrostatic chuck is used instead of the mechanical sample holder, but other than that, it is basically the same as that shown in FIGS. 1 and 2. It is the same, and here, equivalent parts will be denoted by the same reference numerals, description thereof will be omitted, and the difference will be briefly described.

In the plasma processing apparatus of this embodiment, the electrode (32) on which the sample substrate W is mounted has an electrostatic chuck (33) attached to the upper part thereof. Then, on the upper surface of the electrostatic chuck (33), as in the case of the electrode shown in FIG. 2, a circular shallow gas flow channel recess (33a) is formed over the entire upper surface except the outer peripheral edge. It is provided.

Further, like the electrode shown in FIG. 2, this electrode (32) is provided with a gas distribution chamber (34) in the central portion of the lower part thereof and at the same time as the gas distribution chamber (34) and electrostatic discharge. A plurality of gas introduction holes (33b) communicating with the central portion of the gas channel recess (33a) on the upper surface of the chuck (33) are provided. Further, a gas collecting chamber (35) is provided in a portion surrounding the gas distribution chamber (34) below the gas collecting chamber (35) and the electrostatic chuck (33) and a gas passage recess (33a) on the upper surface of the electrostatic chuck (33). A plurality of gas discharge holes (33c) communicating with a portion near the outer periphery of is provided.

The gas distribution chamber (34) of the electrode (32) is connected to the gas supply pipe (7), and the gas collection chamber (34) is connected to the gas discharge pipe.
(9), and under this structure, the sample substrate W attracted and held by the electrostatic chuck (33) on the upper side and the gas flow channel concave portion (upper surface of the electrostatic chuck (33) ( A low temperature inert gas is introduced between the sample substrate W and 33a), and the sample substrate W is cooled by flowing this inert gas while being dispersed in the radial direction as shown by the arrow in (b).

In the plasma processing apparatus of this embodiment having the above-mentioned structure, the contact area between the sample substrate and the inert gas is widened to increase the heat transfer coefficient, whereby the cooling efficiency of the sample substrate temperature can be improved. In addition, the device configuration can be remarkably simple.

In the above-mentioned three embodiments, the present invention is applied to the ECR type processing apparatus for supplying the magnetic field by the air-core coil, but this is an example, and the present invention is directed to the electrodes in the vacuum container. If a sample substrate is placed on the sample substrate and the sample substrate is irradiated with a plasma beam to perform plasma processing such as dry etching, for example, an ECR type processing device that supplies a magnetic field with magnets arranged opposite to each other, a parallel plate The same effect can be obtained by applying it to other types of plasma processing apparatuses such as a mold processing apparatus and a counter electrode type processing apparatus. Further, in these examples, helium (He) gas was used as the refrigerant gas, but in addition to this, gases of zero-group elements such as argon (Ar) and xenon (Xe) can be used.

[0039]

As described above, according to the plasma processing method and apparatus of the present invention, the heat transfer coefficient from the refrigerant gas to the sample substrate can be increased without increasing the size of the electrode on which the sample substrate is placed. It is possible to improve the cooling efficiency of the sample substrate temperature by increasing the temperature, thereby increasing the processing efficiency to improve the productivity and simplifying the apparatus to reduce the equipment cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a plasma processing apparatus according to an embodiment of the present invention, in which (a) is a front sectional view and (b) is a diagram.
It is an AA sectional view of a figure.

2A and 2B are views showing a main part of a plasma processing apparatus according to another embodiment of the present invention, wherein FIG. 2A is a front sectional view of the main part, and FIG.
It is an AA sectional view of a figure.

3A and 3B are diagrams showing a schematic configuration of a plasma processing apparatus according to still another embodiment of the present invention, wherein FIG. 3A is a front sectional view, and FIG.
The figure is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a schematic explanatory diagram of a conventional plasma processing apparatus.

[Explanation of symbols]

 (1) --Vacuum processing chamber (2) --Electrode (2a) --Gas channel groove (2b) --Gas inlet (2c) --Gas outlet (3) --Sample holder (3a)- -Holder claw (3b)-Support ring (3c)-Leg (5)-High frequency power supply (6)-Liquefied gas cylinder (6a)-Reducing valve (7)-Gas supply pipe (7a)- Valve (8) --Exhaust pump (9) --Gas exhaust pipe (9a) --Valve (12) --Cylinder W --Sample substrate

Claims (2)

[Claims] 1. A sample substrate placed in close contact with the upper surface of an electrode in a vacuum container equipped with an evacuation unit is irradiated with a plasma beam, and the sample substrate is cooled from the electrode side to suppress a temperature rise due to beam irradiation. However, in a plasma processing method that performs plasma processing such as etching, a low-temperature inert gas is introduced and flowed between the concave portion provided on the upper surface of the electrode and the sample substrate to directly contact and heat the inert gas. A plasma processing method characterized in that the sample substrate is cooled by replacement. 2. A vacuum container provided with an evacuation unit, an electrode arranged in the vacuum container and having a sample substrate mounted on an upper surface thereof,
It comprises a chucking mechanism that holds the sample substrate in close contact with the electrode surface and irradiates it with a plasma beam, while cooling the sample substrate from the electrode side. In a plasma processing apparatus that performs plasma processing such as etching while suppressing a temperature rise due to beam irradiation, an electrode has a recess for allowing gas to flow on the upper surface excluding its outer peripheral edge, and this recess communicates with the outside of a vacuum container. The gas introduction hole and the discharge hole of the electrode are connected, and the gas introduction hole and the discharge hole of the electrode are connected to an inert gas supply and discharge means arranged outside the vacuum container. Plasma processing apparatus.