JPH02309631A - Plasma etching method - Google Patents

Abstract

PURPOSE:To control a taper angle of an etching shape by performing etching by periodically repeatedly producing and interrupting rf discharge. CONSTITUTION:After a semiconductor substrate 4 is placed on a lower electrode 3, mixture gas such as SF6 and CCl4 is introduced into a chamber 1, and then rf power from a rf power supply 7 is applied across the electrodes 2 and 3 and switched on and off periodically. Once the rf power is interrupted after a plasma state formed, residence time of neutral molecules such as SF2, SFCl, SCl2 and the like in the chamber 1 is made longer to be about several times of seconds, while radicals have shorter residence time differing from the neutral molecules but exist at a state where the rf power is interrupted. Accordingly, discharge time can be controlled by the repeated production and interruption of the rf discharge. Hereby, a taper angle of an etching shape can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a plasma etching method for etching a polycrystalline silicon film on a semiconductor device surface using a parallel plate type plasma etching apparatus using a reactive gas. It is.

Conventional Technology Conventionally, when etching a polycrystalline silicon film of a semiconductor device using a parallel plate type plasma etching apparatus using a reactive gas, etching is performed by continuously generating high-frequency discharge between electrodes placed opposite each other. There is.

Problems that the invention aims to solve In such conventional methods, reactive gases.

The etched shape varies by manipulating several etching parameters such as etching pressure and high frequency power. For example, when etching is performed using SFs as a reactive gas, SFs can generate a large number of radicals, so the shape becomes isotropic etching, resulting in a very large undercut. Also, CCe in SFe
When 4 is added, the rate of formation of sidewall protection by CHX SY CQz, which is a reaction product with the etching mask resist, and the rate of radicals reaching the sidewall are balanced, and the etched shape becomes a vertical shape. .

However, it has been difficult to produce shapes other than those described above, and it has been difficult to control the taper angle of the etched shape by only manipulating the etching parameters. The present invention provides a plasma etching method that solves these problems.

Means for Solving the Problems In order to solve this problem, the present invention is a plasma etching method in which etching is carried out while periodically repeatedly generating and stopping high-frequency discharge.

After forming a plasma state by applying high-frequency power using the active reactive gas SFs, CCE4, the residence time changes of radicals and neutral molecules in the etching reaction chamber after the high-frequency power is turned off are as follows: SF2°5FCe, SCf ! 2
The residence time of neutral molecules such as these influences the exhaust capacity, but generally several tens of seconds are required. Unlike neutral molecules, radicals have a short residence time, but they exist even when high-frequency power is turned off. Furthermore, as a matter of course, when the high frequency power is turned off, there are no electrons, ions, etc. that hold charges. Therefore, it is possible to control the taper angle of the etching shape by repeatedly causing and stopping the high-frequency discharge synchronously and by controlling the generation time of the discharge.

Embodiment FIG. 1 is a cross-sectional structural diagram of a parallel plate type plasma etching apparatus for etching a polycrystalline silicon film. Inside the chamber 1, a pair of electrodes 2 and 3 are arranged facing each other.

After the semiconductor substrate 4 is placed on the lower electrode 3, the chamber 1 contains 5Fs80s e cm, CCe 45
A mixed gas of s cm is introduced from the gas inlet 5, and the pressure inside the chamber is maintained at 100 mTorr by the pressure control valve 6. Next, 50 W of high-frequency power is periodically turned on and off from the high-frequency power source 7 at a set pressure between the electrodes 2 and 3 at 5 second intervals, and after etching 50% of the amount to be etched, the remaining amount to be etched is removed. Continuously generate and etch a large amount.

Effects of the Invention As described above, according to the present invention, when etching a polycrystalline silicon film, the etched shape can be easily controlled, and a semiconductor device having a multilayer structure can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional structural diagram of a plasma etching apparatus. 1... Chamber, 2... Upper electrode,
3... Lower electrode, 4... Semiconductor substrate,
5...Gas inlet, 6...Pressure control valve, 7...High frequency power source. Name of agent: Patent attorney Shigetaka Awano and one other person・-Upper Section ta S-11 Lower List 4 ・--Munumia rice, L! , Saka 5--Kuzubu Entrance

Claims (2)

[Claims] (1) Introducing a reactive gas to generate a high frequency discharge between a pair of flat electrodes arranged opposite each other, and plasma etching the polycrystalline silicon film on the surface of the semiconductor device on the one electrode, A plasma etching method characterized in that etching is performed by periodically repeating the generation and termination of the high-frequency discharge. (2) The plasma etching method according to claim 1, wherein the reactive gas is SF_6 or CCl_4.