JPH065563A - Ashing method of resist - Google Patents

Abstract

PURPOSE:To peel off and remove resist without damaging a foundation layer by using chlorine gas or bromine gas together with oxygen gas as reactive gas for removing a resist on a substrate by ashing. CONSTITUTION:An Si substrate 11 is coated with a positive resist 13 using SiO2 12 as a foundation, a wafer A wherein ion implantation of phosphorus 14 is performed as impurities is set in a treatment chamber 3 and an inside of the treatment chamber 3 is decompressed. Chlorine gas or bromine gas is introduced at a low pressure to a plasma generation chamber 1 together with oxygen gas. The reactive gas is made into plasma by applying high frequency to the plasma generation chamber 1 and introduced to the treatment chamber 3 wherein the wafer A is set. The resist 13 applied to a surface of the wafer A is removed by ashing by plasma inside the treatment chamber 3. The resist can be completely peeled off and removed without affecting a foundation and without making residue remain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of removing a resist in a semiconductor manufacturing process, and more particularly to a method of removing a resist by ashing.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, there are various processes using a resist as a mask such as pattern formation on a semiconductor substrate and impurity diffusion. Further, after each step is completed, a resist peeling removal step is provided. In this step, the Si substrate and Si
It is required to completely remove the resist without damaging the 0 ₂ film or the like. Conventionally, a so-called plasma ashing method has been widely used in the above resist stripping and removing step, in which a resist is exposed to oxygen plasma to be oxidized and removed at a low temperature. Further, in order to completely remove the residue without leaving a residue, a method using fluorine plasma, hydrogen plasma or the like together with the oxygen plasma, and an ashing method such as RIE (Reactive Ion Etching) with oxygen are used.

[0003]

However, the resist is altered in various ways by various treatments in each step, for example, by ion implantation into the semiconductor substrate, and the resist is not completely stripped and removed even after the above ashing step. Or leave
Or the following problems were seen. First, in the method of using fluorine plasma together with oxygen plasma, although the residue can be reduced, the underlying Si substrate and SiO ₂
The film etc. will also be etched. Next, in the method of using hydrogen plasma together with oxygen plasma, hydrogen having a small atomic radius is injected into the semiconductor substrate, resulting in deterioration of device characteristics. In RIE using oxygen, since the energy of oxygen ions is high, damage such as crystal defects is added to the underlying layer, and the device characteristics also deteriorate. An object of the present invention is to solve the above problems and to provide an ashing method for completely peeling and removing the resist without damaging the Si substrate and the underlying layer such as the SiO ₂ film in the resist removing step.

[0004]

In order to achieve the above object, the present invention provides a method for ashing and removing a resist on a semiconductor substrate by using a reactive gas that has been turned into plasma.
As the reactive gas, chlorine-based gas and / or bromine-based gas is used together with oxygen gas.

[0005]

According to the resist ashing method of the present invention,
Since chlorine-based gas or bromine-based gas is used together with oxygen as the reactive gas, etching of the underlayer and crystal defects due to ashing can be suppressed, and the resist can be stripped without leaving a residue.

[0006]

EXAMPLES Examples of the present invention will be described in detail below. FIG. 1 is a block diagram of a down-flow type plasma ashing apparatus to which the resist ashing method of the present invention is applied.
This apparatus is composed of a plasma generation chamber 1 in which a reactive gas is turned into plasma by a high frequency electromagnetic field, and a processing chamber 3 in which a resist ashing process is performed in a vacuum state. The plasma generation chamber 1 and the processing chamber 3 communicate with each other via a connecting pipe 2,
The connecting pipe 2 is installed above the processing chamber 3. Further, since the exhaust pipe 4 is provided at the bottom of the processing chamber 3 and the inside of the processing chamber 3 is kept in a vacuum state by the vacuum pump, the airflow in the chamber always flows toward the bottom. The wafer A to be ashed is set in the processing chamber 3.

In the ashing by the down-flow type plasma ashing device having the above-mentioned structure, first, the plasma generating chamber 1
The reactive gas introduced into the chamber is turned into plasma by the high-frequency electromagnetic field generated in the room. The reactive gas that has been turned into plasma is processed from the connecting pipe 2 to the processing chamber 3 in a vacuum state.
Will be introduced to. The resist on the surface of the wafer A set in the processing chamber 3 is removed by ashing by the plasma. The residual gas inside the processing chamber 3 is exhausted from the exhaust pipe 4 at the bottom. The reason why the down-flow type device is used is that since ions are hardly present in the generated plasma, damage to the base due to high energy due to the ions can be reduced.

Next, an example of the resist ashing method of the present invention using the above apparatus will be described. As the wafer A to be processed, as shown in FIG. 2A, the positive resist 13 is formed by using the SiO ₂ 12 on the Si substrate 11 as a base.
Was used as the impurity, and phosphorus 14 was ion-implanted as an impurity at an acceleration voltage of 100 keV and a dose of 1 × 10 ¹⁶ cm ^-2 .

First, the wafer A is set in the processing chamber 3 and the inside of the processing chamber 3 is decompressed. Next, a reactive gas, for example, oxygen gas 2000 sccm (Standard cm ³ / m 2) and chlorine gas 1
What added 00 sccm was added to the plasma generating chamber 1 at 1 Torr.
Introduced at low pressure. A high frequency of 1 kW is applied to the plasma generation chamber 1 to turn the reactive gas into plasma, and the plasma is introduced into the processing chamber 3 in which the wafer A is set. Inside the processing chamber 3, the resist 13 coated on the surface of the wafer A is removed by ashing by the plasma. The residual gas inside the processing chamber 3 is exhausted from the exhaust pipe 4.

The results of the above ashing treatment were good. First, a residue was confirmed by ashing using only oxygen plasma, but in the above ashing treatment, the resist 13 coated on the wafer A was completely stripped and removed as shown in FIG. 2B. Was done. This is probably because chlorine was used together with oxygen. Further, neither etching of the underlying Si substrate 11 nor the SiO ₂ film 12 due to ashing was observed. It is considered that this is because the reactivity of chlorine with respect to Si and SiO ₂ is weaker than that of fluorine which has been conventionally used together with oxygen. Regarding device characteristics, no deterioration was observed, which is considered to be due to the fact that chlorine has a large atomic radius and is difficult to be injected into the substrate, and the effect of preventing the generation of ions in plasma by using a downflow type ashing device.

Similar results were obtained when bromine gas was used instead of chlorine gas under the above conditions, and when chlorine gas and bromine gas were added to oxygen gas.

[0012]

As described in detail in the above embodiments,
According to the resist ashing method of the present invention, even a resist that has been altered by various treatments in a semiconductor manufacturing process such as ion implantation does not affect the underlying Si substrate and SiO ₂ film and leaves a residue. It is completely stripped and removed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a downflow type plasma ashing apparatus.

FIG. 2 is a sectional view showing an example of a wafer used for an ashing process.

[Explanation of symbols]

 A wafer (semiconductor substrate) 13 resist film

Claims (1)

[Claims] 1. A method for ashing and removing a resist on a semiconductor substrate with a reactive gas that has been turned into plasma, wherein a chlorine-based gas and / or a bromine-based gas are used together with oxygen gas as the reactive gas. Resist ashing method.