JPS63273321A - Removal of resist - Google Patents

Abstract

PURPOSE:To remove the resist remnants by injecting hydrogen into the resist to be removed, thereby oxidatively decomposing the resist. CONSTITUTION:With a resist mask 12, a reactive ion etching is performed on a silicon oxide film 11 on a silicon substrate 13 using a CHF3 gas. Then, by injecting hydrogen into a surface contaminated layer 16 of the mask 12, a reaction of the impurity in the contaminated layer 16 with the hydrogen atoms is caused. Thus, when the resist is made to react with oxygen in the subsequent process, C, H constituting the resist become volatile materials such as CO, OH, and As and C, F constituting fluorocarbons simultaneously become volatile materials such as AsH3, HF to be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for removing resist used in electronic device manufacturing processes and the like.

[Prior Art] Conventionally, a typical method used for resist removal is an oxygen plasma ashing method. The oxygen plasma ashing method is a method in which a discharge is performed in an oxygen atmosphere to generate oxygen plasma, and compounds constituting the resist are oxidized and burned by active oxygen excited species in the plasma. this[
! As an alternative to the 2m plasma ashing method, an ashing method using ozone that does not involve the generation of charged particles is also being considered.

In this method, ozone is generated by ultraviolet irradiation or silent discharge, this ozone is introduced into a reaction vessel, and organic compounds constituting the resist are oxidized and decomposed by the oxidizing power of ozone.

[Problems to be Solved by the Invention] However, as device structures have become more complex, the requirements for resists used as masks for dry etching and ion implantation have also become stricter. In cases where resistance as a mask is required, such as reactive ion etching or high-concentration ion implantation (A1), the resist may be hardened or altered by irradiating the resist mask with ultraviolet rays or plasma treatment in advance. Attempts have been made to improve heat resistance and ion bombardment resistance. When removing a resist that has been hardened or altered in quality, or a resist that has had impurities introduced through ion implantation, a residue that cannot be removed by conventional oxygen plasma ashing or ozone resist removal methods is generated. A new problem has arisen.

Figures 3 (a) and (b) show arsenic (As) ionized at 1 x 1015 ions/150 keV acceleration energy, respectively.
- A plan view of the sample in which the resist mask 2 is formed on the silicon oxide film 1 after implantation, and the resist residue 4 after the resist is removed by the oxygen plasma ashing method.
FIG. 4 is a plan view of a sample having
) are A- in FIGS. 3(a) and (b), respectively.
5(a) and (b) show a silicon oxide film (5i02) 11 on a silicon (Si) W plate 13 by CHF.
3 is a plan view of a sample with a resist mask 12 after forming an anisotropic pattern by reactive ion etching using three gases, and a plan view of a sample having a resist residue 14 after removing the resist by oxygen plasma ashing. FIGS. 6(a) and 6(b) are cross-sectional views taken along lines c-c' and DD'' in FIGS. 5(a), i; and (b>, respectively).

In either case, similar resist residues were left after the resist was removed.

FIGS. 7(a) to (C) are plan views of a sample showing the process of forming resist residue 4 in the case of the former As ion implantation, and FIGS. It is a sectional view taken along the line AA- corresponding to the plan view. As shown in FIG. 8 (a>), a surface contamination layer 6 is formed on the resist mask 2 after ion implantation by AS injection.These contamination layers 6 are removed by oxygen plasma as shown in FIG. 7 (b>). During ashing, the resist residue 4 exists on the surface without reacting with oxygen to create volatile substances, and as shown in FIG. This is the same when reactive ion etching is performed, and a surface contamination layer due to fluorocarbon is formed on the resist mask after reactive ion etching, and eventually a resist residue 14 mainly composed of fluorocarbon is formed. remain.

An object of the present invention is to provide a resist removal method that does not generate such resist residue.

[Means for Solving the Problems] The present invention provides a resist removal method comprising a step of injecting hydrogen into the resist to be removed, and a step of oxidizing and decomposing the resist after this step. be.

[Operation] By injecting hydrogen into the surface contamination layer of the resist mask after ion implantation or reactive dry etching,
This causes a reaction between impurities in the surface contamination layer and hydrogen atoms.

Many hydrides of atoms are volatile, such as As, which is a hydride of arsenic (As) and fluorine (F).
t13, HF is also a gas at normal temperature and normal pressure. Therefore, when the resist is reacted with oxygen in the next step, the C1H that makes up the resist becomes volatile substances such as CD and DH.
Further, since C and F constituting AS fluorocarbon are simultaneously removed as volatile substances such as AsH3 and HF, no resist residue is generated by the process shown in FIG.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.-0 Fig. 1 is a process diagram showing an example of the present invention.

Using a resist mask 12 as shown in FIG. 1(a),
CH
Reactive ion etching was performed using F3 gas. FIG. 1(b) shows the cross-sectional shape of the sample after reactive ion etching. At this time, a surface contamination layer 16 made of fluorocarbon is formed on the resist mask. FIG. 1(C) shows the hydrogen injection process into the resist, and in this example, the CtlF3 gas pressure was 80 mTorr.
After reactive ion etching of the silicon oxide film with RF power of 200%, the gas was exchanged from CHF3 to CHF112 in the same etching chamber, and the hydrogen pressure was 100%.
Discharge was performed for 30 minutes under the conditions of mTorr and RF power of 150-. After this step, the resist was removed by the usual oxygen plasma ashing method. At that time, no resist residue was observed. In this embodiment, a parallel plate type etching device used for reactive ion etching was used as a method for implanting hydrogen into the resist, but it is also possible to implant hydrogen ions into the resist using an ion implantation device. When an ion implantation device is used, the penetration depth of hydrogen ions into the resist can be adjusted by adjusting the ion acceleration energy. Further, in this example, an oxygen plasma ashing method was used in the step after hydrogen injection, but a method using ozone could also have the same effect.

FIG. 2 is a process diagram showing an example of preventing hydrogen from being implanted into parts other than the resist mask in the hydrogen implantation process. After forming a 5i02 pattern by reactive ion etching as shown in FIG. 2(a), a second layer of resist 10 of 1 m is formed as shown in FIG. 2(b).

The second layer of resist is removed by oxygen plasma ashing until the top of the -1st resist mask 2 is exposed (Fig. 2(C)), and then hydrogen is implanted (Fig. 2(d)). . By going through such a step, hydrogen is prevented from being injected into the base substrate other than the resist mask, and device deterioration due to hydrogen permeation into the base silicon substrate can be prevented.

[Effects of the Invention] As described above, according to the present invention, by injecting hydrogen before oxidizing and decomposing the resist components, the resist can be removed satisfactorily without leaving any resist residue. In addition, the exposed portion of the substrate other than the resist mask is
By covering the substrate with a resist, hydrogen can be prevented from being injected into the base substrate, so that it is possible to perform good resist removal while preventing device deterioration.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing one embodiment of the present invention, Fig. 2 is a process diagram showing another embodiment of the invention, and Fig. 3 (a) is a plan view of a sample before resist removal according to a conventional example. , FIG. 3(b) is a plan view of the sample after resist removal, FIG. 4(a) and (
b) are A- in FIGS. 3(a) and (b), respectively.
5(a) is a plan view of a sample before removing the resist according to another conventional example; FIG. 5(b) is a plan view of the sample after removing the resist. , Fig. 6 (a>
and (b) are cross-sectional views taken along lines CC- and D-D' in FIGS. 5(a) and (b), respectively, and FIG. 7 is a plan view of a sample showing a conventional resist removal process. 8th
The figures are cross-sectional views taken along the line A-A'' in FIG. 7. 1.11...Silicon oxide film 2.12...Resist mask 3.13...Silicon substrate 4.14... ...Resist residue 5...Arsenic ion implantation layer 6.16...Surface contamination layer 10...Resist agent Chieko Tateno, patent attorney, c.
(b) Figure 3

Claims (2)

[Claims] (1) Injecting hydrogen into the resist to be removed;
A resist removal method comprising the step of oxidizing and decomposing the resist after this step. (2) The method according to claim 1, wherein the step of injecting hydrogen into the resist is performed with the exposed portion of the substrate covered with the second resist.