JPH0513372A - Plasma treatment device - Google Patents

Abstract

PURPOSE:To restrain the damage thereby enhancing the reliability upon the title plasma treatment device by a method wherein a microwave transmission window is formed of translucent alumina in the plasma treatment device which is exciting gas by irradiating the gas fed to a plasma production chamber with the microwaves through a microwave transmission window. CONSTITUTION:Within a dry etching device, a translucent alumina in diameter of 160mm and thickness of 12mm is used as a microwave transmission window 6. At this time, a substrate 10 to be processed is composed of a substrate formed of an SiO2 film 1mum thich and coated with a resist for making multiple viaholes in diameter of 1mum by photolithography to be aligned on a susceptor 11 later. As for the plasma production gas 1, a mixed gas of CF4 and O2 is used to be fed to a plasma production chamber 3 through a gas leading-in pipe 2 so as to keep the title plasma treatment device containing the substrate treatment chamber 9 in the vacuum state of 1Torr. Next, the transmission window 6 is irradiated with the microwaves in 1.5 kW from a magnetron to produce the plasma for etching the substrate 10 to be treated.

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 having improved reliability. Since it is necessary to process a large amount of information at high speed, the semiconductor devices that make up the main body of information processing devices are becoming more integrated and LSIs and VLSIs are being put to practical use.

Here, the integration is performed not by increasing the size of a semiconductor chip that constitutes a semiconductor device but by reducing the size of a unit element. Therefore, wiring such as electrodes and conductor lines forming the unit element is performed. The minimum line width of the pattern extends to sub-micron, and there is a tendency for further miniaturization.

For example, the minimum line width of the 64 Mbit D-RAM currently under development is expected to be 0.4 μm. Here, thin film formation technology and photo-etching technology are used for pattern formation.
(Photolithography or electron beam lithography) is used, and various types of processing equipment are used.However, as the pattern becomes finer, processing efficiency is higher and high precision is required. Is often used.

[0004]

2. Description of the Related Art As a thin film forming technique, a thin film is formed on a substrate to be processed by a physical method such as a vacuum vapor deposition method or a sputtering method, or a chemical method such as a vapor phase growth method (Chemical Vapor Deposition: CVD method). It is a technology.

Here, the CVD method is a method of supplying a component gas to a substrate to be processed while the substrate to be processed is placed on a susceptor and heated to decompose or react on the substrate to be processed. Although it is a method of forming a thin film by the method, an insulator or a semiconductor is widely used because a thin film can be formed.

Particularly, the plasma CVD method can be used at a low temperature and has high reaction efficiency, so that it is increasingly used. In the photo-etching technique, a resist thin film is formed on the substrate to be processed on which a thin film has been formed by using a spin coating method or the like, and then projection exposure of ultraviolet rays or scanning of an electron beam is performed to select a fine pattern. When exposed and the resist is a positive type, the exposed part is decomposed and easily dissolved in the developing solution, and in the case of a negative type, it is difficult to dissolve due to cross-linking polymerization etc. This is a method of forming a fine pattern by etching the substrate to be processed using this as a mask.

Here, as a method of etching the substrate to be processed using the resist pattern formed on the substrate to be processed as a mask, a wet etching method using a chemical agent and a dry etching method using a reactive gas such as reactive ion etching are used. However, the latter is suitable for forming a fine pattern, and plasma etching using a plasma of a gas having excellent reactivity is often used.

Thus, a thin film is formed on the substrate to be processed,
Plasma is used to form a fine pattern by selective etching of this, and this plasma is generated by using a microwave oscillator such as a magnetron to generate microwaves and guiding the plasma to a plasma processing device. The gas introduced into the apparatus is irradiated through the microwave transmission window, and the gas is made into plasma to generate radicals of gas constituent molecules, and the radicals are applied to the substrate to be processed and reacted.

Here, there are ion radicals and neutral radicals as radicals, both of which are very active, and vapor phase growth and dry etching can be effectively progressed by these radicals of halogen-based gas. When used, the corrosiveness was excellent, so that the microwave transmission window for guiding the microwave to the plasma generation chamber was etched, and frequent replacement was necessary.

FIG. 1 shows the construction of a down-flow type dry etching apparatus used to selectively etch a substrate to be processed using a halogen-based gas. That is, the plasma forming gas 1 is supplied from the gas introducing pipe 2 to the plasma generating chamber 3
Is supplied to.

Microwaves for generating plasma are oscillated by a microwave oscillator 4, propagate through the waveguide 5 into the apparatus, and irradiate the plasma generation chamber 3 through the microwave transmission window 6. It is configured as follows.

A gas diffusion plate 7 is provided below the plasma generation chamber 3, and the plasma is confined in the plasma generation chamber 3 by adjusting the length of a diffusion plate support rod 8 so that electrons and ions are generated. Except for the above, plasma downflow is supplied to the substrate processing chamber 9 therebelow.

Next, the substrate 10 to be processed is placed on the susceptor 11 whose height can be adjusted in the substrate processing chamber 9. Further, there is an exhaust port 12 on the lower side of the device, which is connected to an exhaust system (not shown).

Using such a dry etching apparatus,
From the gas introduction pipe 1, for example, a plasma forming gas in which oxygen (O ₂ ) and carbon tetrafluoride (CF ₄ ) are mixed is supplied to the plasma generation chamber 3, and the exhaust system is operated to exhaust from the exhaust port 11. With the vacuum degree of the plasma generation chamber 3 adjusted to a constant value, microwaves are radiated through the microwave transmission window 6 to generate plasma to generate radicals, and the substrate 10 to be processed is dry-etched by this downflow. There is.

[0015] However, in the plasma generation chamber O ₂ and CF ₄ is in an excited state other than the O radical by plasma CF _4,
CF ₃ radicals and F ⁻ _, CF ₃ ⁻ and F radicals, CF ₃ ⁺ and F radicals and electrons (e ⁻ ), etc. are generated, and among these, ion radicals are extremely active. 3, the microwave transmitting window 6 is etched and thinned, and the reaction product becomes dust and pollutes the surrounding environment.

Here, although quartz (SiO ₂ ) or alumina (Al ₂ O ₃ ) is used as the material of the microwave transmitting window 6, SiO ₂ easily invades halogen radicals, especially fluorine radicals. As a result, dust is liable to be generated, and alumina is liable to be damaged, which deteriorates the reliability of the plasma processing apparatus.

[0017]

Since plasma is generated by irradiating a reactive gas with microwaves and radicals of the reactive gas are used, a chemical reaction proceeds at a low temperature. Therefore, a plasma processing apparatus is a dry etching apparatus or a CVD apparatus. It has been applied to the equipment and has been put to practical use as a plasma etching equipment and a plasma CVD equipment.

However, since the radicals of the reaction gas are extremely active, particularly in the dry etching apparatus, the microwave transmission window for introducing microwaves into the plasma generation chamber is corroded and damaged or becomes a source of dust generation. Is a problem, and this solution is a problem.

[0019]

[Means for Solving the Problems] The above problem is that the gas supplied to the plasma generation chamber is irradiated with microwaves through a microwave transmission window to excite the gas and generate plasma to generate radicals of the gas. This can be solved by forming the microwave transmission window using translucent alumina in a device that supplies this radical to the substrate to be processed and causes a chemical reaction.

[0020]

The function of the microwave transparent window forming material is that the dielectric loss is small. That is, it is necessary that the amount of energy lost as heat when microwaves are applied to the microwave transmission window is small, and from this point of view, quartz (SiO ₂ ) with a low complex dielectric constant loss factor (tan δ) and Alumina (Al ₂ O ₃ ) has been used.

The reaction gas used in the plasma CVD apparatus is silane (SiH ₄ ), ammonia (NH ₃ ), nitrogen (N
₂ ) is a gas with low corrosiveness, but the reaction gas used in plasma etching equipment is fluorine-based gas such as CF ₄ and CHF ₃ , chlorine-based gas such as CCl ₄ and CCl ₂ F ₂ . Since it is a mixed gas, SiO ₂ is not used because it is easily attacked by fluorine gas.

Therefore, an alumina substrate having excellent chemical resistance has been used as the microwave transmitting window of the dry etching apparatus. However, there is a problem that when a microwave transmitting window made of alumina is irradiated with a high power micro, it is easily broken.

The inventor has found that the cause of the cracking is that the alumina substrate is a sintered body and contains many fine pores, in which moisture and gas are adsorbed, and when this is irradiated with microwaves, moisture and gas are absorbed. It was presumed that swelled and increased internal stress, causing destruction.

Therefore, high-density alumina was investigated, and attention was paid to translucent alumina used in the arc tube for sodium (Na) lamp, and good results were obtained when this was used. Here, the conventional alumina plate is made by the sintering method, which is white and has a density of 3.70 to 3.80 g / cm ³ , while the translucent alumina is made by the hot pressing method. , Density is 3.
High as 90~3.98g / cm ^3, not more than 0.01% water absorption, even those of water absorption 0.0% is commercially available, the dielectric loss 1 × 10
^-6 and so few. (For example, product name TPA-10, Toshiba Ceramics) The present invention is such a high density, does not include fine pores, has a low dielectric loss, and has excellent chemical resistance. By forming the window, the conventional problems are solved.

[0025]

EXAMPLE In the conventional dry etching apparatus shown in FIG. 1, a transparent alumina (TPA-10, Toshiba Ceramics) having a diameter of 160 mm and a thickness of 12 mm was used as the microwave transmitting window 6.

Then, as a substrate 10 to be processed, a resist is coated on the SiO ₂ film by a spin coating method for forming a via hole of a Si substrate having a SiO ₂ film formed to a thickness of 1 μm, and then a photograph is taken. It was positioned on the susceptor 11 using an etching technique in which a large number of holes having a diameter of 1 μm were formed.

Next, CF ₄ is used as a plasma forming gas.
A mixed gas of O ₂ is supplied to the plasma generation chamber 3 through the gas introduction pipe 2 and the exhaust system is operated to maintain the degree of vacuum in the apparatus including the substrate processing chamber 9 at 1 torr, while 1.5 KW from the magnetron. The microwave transmission window 6 was irradiated with the microwave of (1) through the waveguide 5 to generate plasma in the plasma generation chamber 3, and the substrate 10 to be processed was down-flow etched.

As a result, a large number of via holes could be accurately formed. Further, even if this process is continuously performed, damage is not generated unlike the conventional case, and stable dry etching can be performed.

[0029]

EFFECTS OF THE INVENTION By using high-density translucent alumina instead of conventional alumina as the material for the microwave transmitting window, the microwave output could be increased up to about 500 W in the past, but 1.5 It has become possible to increase it to over KW, and since damage can be suppressed, a great improvement in processing capacity has been achieved.

[Brief description of drawings]

FIG. 1 is a sectional view of a dry etching apparatus.

[Explanation of symbols]

 2 gas introduction tube 3 plasma generation chamber 4 microwave oscillator 6 microwave transmission window 9 substrate processing chamber 10 substrate to be processed

Claims (1)

Claim: What is claimed is: 1. A gas supplied to a plasma generation chamber is irradiated with microwaves through a microwave transmission window to excite the gas, and plasma is generated to generate radicals of the gas. An apparatus for supplying radicals to a substrate to be processed to cause a chemical reaction, wherein the microwave transmission window is formed by using translucent alumina.