JPS6231123A - Dry etching method - Google Patents

Abstract

PURPOSE:To allow miniature patterning by a method wherein, following a reactive ion beam etching process, the irradiation of an ion beam is stopped by stopping the application of a voltage to a drawer electrode, and etching is performed with plasma excitation gas. CONSTITUTION:SF6 gas is introduced into a plasma generation section 2 from an etching gas introduction pipe 5, and a vacuum chamber 1 is depressed to about 5X10<-4>Torr by discharging air from a discharge opening 7. In this state, microwave of 2.45GHz is introduced from the wave conduction pipe 6 so as to generate plasma by applying electric field of 875 gaus. A specified voltage is applied to an ion drawer electrode 4, and ions are drawn out from the generated plasma, and the ions are accelerated to irradiate it onto a wafer 9 as an reactive beam, thereby etching the poly-Si film on the wafer 9. Then, a plasma is generated in a plasma generation section 2 to etch the poly-Si film of about 100s Angstrom remaining on the wafer 9.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention utilizes a reactive ion beam etching method that uses a reactive gas to irradiate the surface of a semiconductor wafer, etc. with an accelerated and focused reactive ion beam, and plasma etching. The present invention relates to a dry etching method using both plasma excitation gas etching methods using activated excitation gas.

[Background of the Invention 1] With the increasing density of integrated circuits, submicron-order dry etching technology is required in the semiconductor manufacturing process.

A reactive ion beam etching method has been developed as such a dry etching means. The conventional reactive ion beam etching method uses a reactive gas (CF4.02 F8, etc.) as the etching gas, converts it into plasma, and generates plasma reactive ions (CF
3”, CF2”, CF”.

These reactive ions are accelerated to a predetermined energy to form an ion beam, and the wafer is irradiated with the ion beam to perform etching through physical and chemical effects.

On the other hand, a plasma-excited gas etching method has been used in which an etching gas is activated by plasma and the wafer surface is etched by the chemical action of the plasma-excited gas.

By the way, in the conventional reactive ion beam etching method, due to the physical etching effect of the ion beam, the anisotropy is thicker (and relatively fine patterns with less undercuts) than in the case of chemical etching alone. On the other hand, it was not possible to change the etching speed depending on the material of the material to be etched due to low selectivity.

Therefore, for example, pony − based on 5iO2yA
When etching 8ill, after etching the Po1y-8i film, the 8102 film is etched in the same way, resulting in a problem that the underlying layer is severely damaged. In addition, since the energy of the ion beam is large (usually 5
ooev or higher) There was also the problem of damage to the base due to ion bombardment.

In addition, in the conventional plasma-excited gas etching method, etching is performed by the chemical action of the excited gas, so while the selectivity is good, the etching is isotropic, resulting in the problem of undercuts.

[Object of the Invention] The present invention was devised in view of the drawbacks of the conventional etching methods described above, and an object of the present invention is to provide a dry etching method that causes less undercuts, allows fine processing, and has high selectivity. do.

[Structure of the Invention] In the dry etching method according to the present invention, the etching gas is introduced into an etching apparatus having a plasma generation section and an etching processing section via an ion extraction electrode in a vacuum chamber to which an etching gas introduction pipe is connected. A first etching step in which a reactive gas is introduced through an introduction tube to generate plasma, a voltage is applied to the ion extraction electrode to extract an ion beam, and etching is performed by irradiation with the ion beam; A second etching step is continuously performed in which the voltage application is stopped, the ion beam irradiation is stopped, only the plasma excitation gas is introduced into the etching processing section, and etching is performed using the plasma excitation gas.

[Example] FIG. 1 shows the configuration of an apparatus used in the dry etching method according to the present invention. The vacuum chamber 1 consists of an upper plasma generating section 2 and a lower etching processing section 3. An ion extraction electrode 4 is provided between the plasma generation section 2 and the etching processing section 3 for extracting ions from the generated plasma and accelerating them. An etching gas introduction pipe 5 and a microwave introduction waveguide 6 are connected to the plasma generation section 2. The etching processing section 3 is provided with an exhaust port 1 and connected to a vacuum pump (not shown). A wafer 9 mounted on a holder 8 is disposed within the etching processing section 3 .

The method of the present invention using the apparatus having such a configuration will be described below. This example concerns the case where a Po1y-8i film is etched using, for example, SFe gas as the reactive gas.

SFe gas is introduced into the plasma generating section 2 through the etching gas introduction pipe 5, and evacuated through the exhaust port 1 (arrow B) to bring the inside of the vacuum chamber 1 to a pressure of about 5 x 10-4 torr. In this state, a microwave of 2.45GH7 is introduced from the waveguide 6 and a magnetic field of 1175Gauss is applied (arrow A) to generate plasma. Ion extraction electrode 4
A predetermined voltage is applied to the wafer 9 to extract ions from the generated plasma, accelerate the ions to an energy of about 500 eV, and irradiate the wafer 9 as a reactive ion beam as shown by arrow C. As a result, the Po1y-8i film on the wafer 9 is etched by the reactive ion beam. When this reactive ion beam etching is performed by a predetermined amount (for example, with several hundred layers of poly-8i film remaining),
The voltage application to the ion extraction electrode 4 is stopped, and the ion beam irradiation is stopped. Whether or not etching has been performed by a predetermined amount is determined based on the ion irradiation time and resistance detection by the etching monitor.

Next, the pressure in the vacuum chamber 1 is raised to about 10-1 to 1 torr, and plasma is generated in the plasma generating section 2 in the same manner. At this time, the ion extraction electrode 4 is at ground potential.

In this state, ions are not extracted from the plasma generating section 2, and only gas chemically excited by the plasma passes through the extraction electrode 4 and flows into the etching processing section 3. Several hundred Po1y-8i particles remained on the wafer 9 due to the chemical action of the plasma-excited gas.
I! I is etched.

FIG. 2 is a partial cross-sectional view of the wafer immediately before the etching process by ion beam irradiation is completed.

A SiO2 film 11 is formed on a Si substrate 10, and Po1y-S i 15112 is coated thereon.
It is covered with a resist pattern 13. Resist pattern 1
The portion of the Po1y-8i film 12 other than the portion covered by 3 is etched by an ion beam (arrow C). Due to the anisotropy of ion beam etching, undercuts hardly occur, and microfabrication that accurately corresponds to the resist pattern 13 is performed.

FIG. 3 is a partial cross-sectional view of the wafer at the end of the etching process using the plasma excitation gas.

In the case of SFe gas, the selectivity with 5102 is Po1y -8
Since i/SiO2 is 30 or more, the underlying S i 02
1111 is Poly-3t with almost no etching
Only gI is etched. This etching by plasma-excited gas is isotropic etching due to chemical action, so the resist pattern 13 (7) lower part (7) P
oly-5t 11a12 is also etched to some extent.

However, such undercuts caused by isotropic etching can be reduced to a negligible effect on the pattern shape by shortening the etching time using the plasma-excited gas.

[Effects of the Invention] As explained above, in the dry etching method according to the present invention, a normal reactive ion beam etching apparatus is used, and following the reactive ion beam etching process, voltage is applied to the extraction electrode. Etching with plasma-excited gas is performed by a simple switching operation of stopping ion beam irradiation and slightly increasing the pressure.

Therefore, not only is it possible to perform fine buttering by anisotropic etching, but the selectivity is also good, and over-etching or major damage to the underlying layer can be prevented. In addition, since the two etching steps are performed continuously using the same device, it does not take much time.
The etching process is performed efficiently and productivity is improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a reactive ion beam etching apparatus used in the method of the present invention, Fig. 2 is a partial cross-sectional view of a wafer during the reactive ion beam etching process, and Fig. 3 is a wafer at the end of the plasma-excited gas etching process. FIG. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 2... Plasma generation part, 3... Etching processing part, 4... Ion extraction 'R pole, 5...
- Etching gas introduction pipe, 9... wafer.

Claims (1)

[Scope of Claims] 1. In an etching apparatus having a plasma generation section and an etching processing section via an ion extraction electrode in a vacuum chamber to which an etching gas introduction tube is connected, (1) a reaction is carried out from the etching gas introduction tube. a first etching step of introducing a reactive gas to generate plasma, applying a voltage to the ion extraction electrode to extract an ion beam, and performing etching by irradiation with the ion beam; (2) etching to the ion extraction electrode; A dry etching method in which the voltage application is stopped, ion beam irradiation is stopped, only plasma excitation gas is introduced into the etching processing section, and a second etching step is performed in which etching is performed using the plasma excitation gas.