JPS6273632A - Plasma processing equipment - Google Patents

Abstract

PURPOSE:To contrive the utmost reduction of heat generation by improving heat conduction between a substrate to be treated and an electrode by attracting the substrate to be treated by the electrode by utilizing an electrostatic force due to a self-bias voltage generated in the substrate to be treated and covering the uncovered electrode part with an insulator. CONSTITUTION:A thin insulating film layer 12 is arranged in the opposite position to a substrate 8 to be treated present on a plane electrode 2, a surface of the plane electrode 2 of the part which is not covered with said insulating film layer 12 is covered with a cover plate 9 and an insulating supporting member 10. When a high-frequency electric power is supplied to the plane electrode 2 from a high-frequency power source 4, discharge is generated through a path along the plane electrode 2, insulating film layer 12, substrate to be treated 8, and a plane electrode 3 and a gas introduced between the electrodes is made plasma. At that time, a self-bias voltage is generated between the plane electrode 2 and the substrate to be treated 8 and this voltage causes the plane electrode 2 to attract the substrate 8. Consequently, the heat conduction between the substrate 8 and the plane electrode 2 becomes good and the increase in temperature of the substrate 8 can be restrained, for instance by water-cooling the plane electrode 2.

Description

[Detailed Description of the Invention] [Summary] A plasma processing apparatus that plasma-processes a substrate to be processed includes a grounding potential holding means for holding a DC potential of an electrode at a ground potential, and an insulator provided between the electrode and the substrate to be processed. a membrane layer;
By supplying high-frequency power between the electrodes, a self-bias voltage is generated between the substrate to be processed and the electrode, and this generation The electrostatic force generated by the applied self-bias voltage is used to attract the substrate to be processed to the electrode, thereby improving heat conduction and minimizing heat generation.

[Industrial application field]

The present invention uses electrostatic force due to a self-bias voltage generated between the substrate to be processed and the electrode to adsorb the substrate to the electrode to improve heat conduction, and also covers the electrode using an insulator. The present invention relates to a plasma processing apparatus configured to reduce heat generation as much as possible.

[Conventional technology]

Conventionally, dry etching equipment, which introduces a reactive gas such as halogenated hydrocarbon between electrodes in a vacuum container and generates plasma by high-frequency discharge, etches a substrate placed on the electrodes, has been used in semiconductor manufacturing. It is widely used as a pre-processing device. When using these plasma processing devices to etch a substrate placed on an electrode, the substrate is exposed to the impact of charged particles consisting of ions and electrons, heat radiation from the plasma, and heat generated by etching reactions. It is heated by etc. In extreme cases, the photoresist on the substrate being processed may suffer thermal damage.

For this reason, attempts have been made to cool the electrodes using a coolant such as water to suppress the rise in temperature of the substrate to be processed as much as possible. However, since the substrate to be processed is generally light in weight, such as a Si wafer, heat transfer between the substrate to be processed and the electrode is performed mainly by radiation heat transfer in a vacuum.
If the amount of heat incident on the substrate to be processed increases, the temperature of the substrate to be processed will rise significantly no matter how much the electrode is cooled. Therefore, if an attempt is made to increase the etching rate by increasing the high frequency power applied between the electrodes, thermal damage to the substrate to be processed will increase. One possible solution to this problem is to adsorb (adhere to) the substrate to be processed on the electrode using some method to improve heat conduction between the substrate to be processed and the electrode. Adsorption methods that can be used in a vacuum include mechanically pressing the substrate to be processed against an electrode, cooling the substrate using gas, and using electrostatic force by applying a DC voltage to the substrate. A method has been devised in which the particles are adsorbed onto the electrode.

[Problem that the invention seeks to solve]

However, in the conventional method of mechanically pressing the substrate to be processed onto the electrode, the substrate to be processed must be pushed into the electrode using a clamp, etc., and a large amount of dust is generated from the contact area between the clamp and the substrate to be processed. There was a problem. In addition, with the method of cooling the substrate to be processed using gas, if the seal between the substrate and the electrode is not completely sealed, the cooling gas will mix into the process gas and have a negative effect on the etching characteristics. There was a problem. Furthermore, in the method of using electrostatic force by applying a DC voltage to the substrate to be processed, an electrostatic electrode for electrostatic adsorption is provided inside the electrode to which high frequency power is applied, and a high DC voltage is applied to this electrostatic electrode. There are problems in that the structure becomes complicated and expensive, as a DC high-voltage power supply is required to apply the voltage.

[Means for solving problems]

In order to solve the above problems, the present invention provides 119 layers of insulation between the substrate to be processed and the electrode, and uses electrostatic force due to the self-bias voltage generated in the substrate to be processed to connect the substrate to the electrode. At the same time, by adopting a structure in which the part of the electrode that is not covered by the insulating film layer is covered with an insulator, the heat conduction between the substrate to be processed and the electrode is improved, and the generation of heat is reduced. I try to minimize it as much as possible.

Means for solving the problems will be explained using the configuration of one embodiment of the present invention shown in FIG.

In FIG. 1, the plate electrodes 2.3 are disk-shaped electrodes arranged in parallel. A thin insulating film layer 12 is provided on the flat electrode 2 at a position facing the substrate 8 to be processed, as shown in the figure. The surface of the flat electrode 2 that is not covered by the insulating film layer 12 is covered by a cover plate 9 and an insulating support 10. Furthermore, since the flat plate electrode 2 is grounded via the high frequency choke coil 13, it is always held at a DC ground potential.

High frequency power is supplied from a high frequency power source 4 to the flat plate electrode 2 via a blocking capacitor 5.

[Effect]

When the configuration explained using FIG. 1 is adopted and high frequency power is supplied from the high frequency power source 4 to the flat plate electrode 2 via the blocking capacitor 5, the flat plate electrode 2
ii12, a discharge occurs through the path between the substrate to be processed 8 and the flat electrode 3, and the gas introduced between the two electrodes is turned into plasma. At this time, a voltage (this is called a self-bias voltage) is generated between the electrode 2 and the substrate 8 to be processed. Due to this self-bias voltage, the substrate 8 to be processed is attracted (closely attached) to the flat electrode 2 . For this reason, the substrate to be processed 8
The heat conduction between the plate electrode 2 and the plate electrode 2 is improved, and the plate electrode 2
By cooling the substrate 8 with water or the like, the temperature rise of the substrate 8 to be processed can be suppressed. Further, the top of the flat electrode 2 other than the area where the insulating film layer 12 is provided is covered with a cover plate 9 and an insulating support 10 which are insulators. As a result, heat generation due to plasma processing does not occur in parts other than the substrate 8 to be processed, and the temperature rise of the substrate 8 to be processed can be suppressed to a minimum.

〔Example〕

Fig. 1 is a side sectional view of one embodiment of the present invention, and Fig. 2 shows a relationship curve between dielectric breakdown voltage and alumite film thickness. is a high frequency power supply, 5 is a blocking capacitor, 6 is an exhaust pipe, 7 is a gas introduction pipe, 8 is a substrate to be processed, 9 is a cover plate, 1
0 is an insulating support, 11 is a shield, 12 is an insulating film layer, 1
3 represents a high frequency choke coil, and 14 represents a valve.

The embodiment shown in FIG. 1 is an example in which the present invention is applied to a batch type parallel plate type reactive ion etching apparatus. Inside the vacuum container 1, two flat plate electrodes 2 and 3 are arranged. The flat plate electrode 2 located at the bottom is supplied with high frequency power from a high frequency power source 4 through a blocking capacitor 5. After evacuating the vacuum container 1 to vacuum using a vacuum pump (not shown) connected to the exhaust pipe 6, a desired reactive gas is introduced into the vacuum container 1 from the gas introduction pipe 7, and a predetermined amount of Valve 14 is controlled to maintain pressure. In this state, when high frequency power is supplied between the flat plate electrode 2 and the flat plate electrode 3, plasma is generated between the two electrodes.

At this time, since a thin insulating film Jm12 is provided between the substrate to be processed 8 to be subjected to plasma processing and the flat plate electrode 2 at the bottom, the distance between the substrate to be processed 8 and the flat plate electrode 2 is approximately several hundred ports. A self-bias voltage of Similarly, a voltage of about several hundred volts is generated on the surface of the cover plate 9. Since a self-bias voltage is applied between the substrate 8 to be processed and the flat electrode 2 with the plate electrode 2 sandwiching the installed 119 layer 12 via the high-frequency choke coil 13 in a direct current manner, the substrate 8 to be processed is A force acts in the direction in which the substrate 8 and the flat electrode 2 are attracted to each other, and heat conduction between the substrate 8 to be processed and the flat electrode 2 can be improved. Therefore, if a structure is adopted in which the flat electrode 2 can be cooled from the outside with water or the like, the substrate 8 to be processed during plasma processing can be efficiently cooled and the temperature rise can be kept to a minimum. .

The adsorption force F acting between the substrate 8 to be processed and the flat plate 2 is expressed by the following formula.

F=KV/d”・・・・・・・・・・・・(1)
Here, K is a constant, ■ is the voltage generated between the substrate 8 to be processed and the flat electrode 2 located on both sides of the insulating film layer 12, and d is the thickness of the insulating film layer 12. As is clear from this equation (1), in order to increase the attraction force F, it is necessary to increase the voltage (2) and/or decrease the thickness d of the insulating film layer 12. In the present invention, the approximate value of voltage (2) is determined depending on the conditions for generating plasma. Therefore, in order to obtain a large adsorption force F, it is necessary to make the thickness d of the insulating film layer 12 as small as possible. As the thickness d decreases, the electric field strength in the insulating film layer 12 increases and eventually dielectric breakdown occurs, the value of the self-bias voltage between the substrate 8 to be processed and the flat electrode 2 decreases, and the voltage between the two increases. Electrostatic adsorption force no longer works. When the electrostatic adsorption force ceases to work, heat conduction between the substrate 8 to be processed and the flat electrode 2 becomes poor, the temperature of the substrate 8 to be processed rises by 2'', and when dielectric breakdown occurs, plasma The potential difference between the substrate 8 and the substrate 8 to be processed changes, making it impossible to perform etching with good reproducibility. For this reason, the breakdown voltage of the insulating film layer 12 must be greater than the self-bias voltage.

FIG. 2 shows the relationship between the thickness (microns) of a normal anodized alumite layer and the dielectric strength voltage (V). As shown in Figure 2, in order to maintain a dielectric strength higher than the self-bias voltage of, for example, 600V obtained by reactive ion etching of a silicon oxide film, an alumite layer with a thickness of about 15 microns or more is required. Considering part 2
It is necessary to form an alumite layer that is more than twice as large. However, a normal alumite treated layer has low durability against dry etching. For this reason, in the portion of the insulating film layer 12 that protrudes from the substrate 8 to be processed, the alumite treated layer may disappear if the etching process is performed for a long time. On the other hand, if the alumite layer is made too thick, cracks will form in the alumite layer itself, reducing the dielectric strength.

In order to eliminate this inconvenience, this embodiment uses an insulating film layer 12 in which the alumite treatment layer is impregnated with an organic polymer such as Teflon. In this case, an insulating film layer 12 that satisfactorily satisfies dry etching resistance and insulation resistance even with a thickness of about 30 microns was obtained. Furthermore, if the insulating film layer 12 is an alumite layer that has been subjected to alumite treatment in an oxalic acid treatment bath, it is possible to obtain excellent suction power because cranking does not occur even if the thickness is large. On the other hand, a film made of polyimide, polyethylene terephthalate, etc. coated with a pressure-sensitive adhesive on the back side is used as the insulating film layer 12.
A similar effect can be obtained when used as

Furthermore, in this embodiment, the high frequency choke coil 13 is used as a means for grounding the flat plate electrode 2 in a DC manner.
It is not necessarily necessary to use a high frequency choke coil. This is because direct current hardly flows in a steady state, so the means for grounding in a direct current manner may be cooling water for cooling the flat plate electrode 2, which is a high resistance body. Flat electrode 2
If cooling water is used to cool the system, there is no need to provide new elements such as the high frequency choke coil 13, and the configuration can be simplified and made inexpensive.

〔Effect of the invention〕

As explained above, according to the present invention, a thin insulating film layer is provided between the substrate to be processed and the electrode, and the electrostatic force due to the self-bias voltage generated in the substrate to be processed is used to move the substrate to the electrode. At the same time, since the electric bridge portion not covered by this insulating film layer is covered with an insulator, the track passage between the substrate to be processed JN and the electrode can be prevented by self-lifting.
This makes it possible for Gosumiy to reduce heat generation as much as possible. Therefore, using a simple configuration, the substrate to be processed 8 can be cooled by adsorption to the flat electrode, and the temperature rise of the substrate to be processed 8 can be suppressed to the minimum.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view of one embodiment of the present invention, and FIG. 2 shows a relationship curve between dielectric breakdown voltage and alumite film thickness. In the figure, 1 is a vacuum container, 2.3 is a flat plate electrode, 4 is a high frequency power supply, 5 is a blocking capacitor, 6 is an exhaust pipe, 7 is a gas introduction pipe, 8 is a substrate to be processed, 9 is a cover plate, 1
0 is an insulating support, 11 is a shield, 12 is an insulating film layer, 1
3 represents a high frequency choke coil, and 14 represents a valve.

Claims (2)

[Claims] (1) The electrodes are installed in a vacuum container configured to be evacuated to a vacuum, and high frequency power is supplied between the electrodes,
In a plasma processing apparatus that places a substrate to be processed on this electrode and processes the substrate using plasma generated by introducing a reactive gas, the DC potential of the electrode is maintained at ground potential. an insulating film layer provided between the electrode and the substrate to be processed placed on the electrode and having a dielectric strength higher than the self-bias voltage generated in the substrate to be processed; and an insulator that covers the electrode portions not covered by the insulating film layer, and generates a self-bias voltage between the substrate to be processed and the electrode by supplying high-frequency power between the electrodes, and generates a self-bias voltage between the substrate to be processed and the electrode. A plasma processing apparatus characterized in that the substrate to be processed is attracted to an electrode using electrostatic force generated by a voltage to improve heat conduction and to reduce heat generation as much as possible. (2) The insulating film layer is either an alumite-treated layer impregnated with Teflon or other organic polymer, an alumite-treated layer treated with oxalic acid, or an organic polymer film coated with a pressure-sensitive adhesive. A plasma processing apparatus according to claim (1).