JPH10163179A - Method of dry-etching platinum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of residue after etching and side wall deposit, by using gas containing at least chlorine, and CO gas or CO2 gas, as etching gas. SOLUTION: An mixed gas of Cl2 gas and CO gas is used as etching gas. The Cl2 gas is introduced in a vacuum chamber at a flow rate of 30sccm, and the CO gas is introduced in the vacuum chamber at a flow rate of 20sccm. The pressure of the vacuum chamber is set to be 0.26Pa. Source power of 500W is supplied to an antenna, and substrate bias power of 100W is supplied to a substrate holder. Under the above condition, a Pt film 16 and a TiN film 14 are etched in a batch. After that, a resist mask 18 is eliminated by ashing. As a result, etching residue is not left on the Pt film 16, and deposit films are not observed on pattern side walls of the Pt film 16 and the TiN film 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of dry-etching platinum (Pt) using plasma, and more particularly to a method of etching a platinum wiring film of a semiconductor device into a predetermined pattern.

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated, the cell area becomes smaller, and accordingly, it is necessary to make the capacitance insulating film of the element thinner, and a film having a low dielectric constant is not formed on the electrode surface. Is needed. Then, in recent years, examples of using platinum for wiring of semiconductor devices have appeared.

In order to form a platinum wiring on a semiconductor device such as a DRAM, it is necessary to process a platinum film into a predetermined pattern. For this processing, dry etching is used. When this dry etching is used, the anisotropy of the etching can be ensured, the difference in dimensional conversion of the etching is reduced, and a fine pattern of half a micron or less can be etched with high accuracy.

As a method of dry-etching a platinum film, a method of performing etching by physical sputtering using Ar gas as disclosed in Japanese Patent Application Laid-Open No. 6-112169, and a method disclosed in “42nd Applied Physics Joint Lecture Meeting (Spring 1995) Preliminary Proceedings 645 pages 30a-ZA-
2 and 767-77 of Jpn.J.Appl.Phys.Vol.34 (1995)
0 page "and" 52nd Annual Meeting of the Japan Society of Applied Physics (19
(Autumn 1991) Cl (chlorine), F (fluorine) and B
There is a method of etching using a reactive gas containing r (bromine).

[0005]

However, in the etching by physical sputtering using Ar gas, the adhesion of platinum to the pattern side wall cannot be avoided. Also, Cl
Etching using a halogen-based reactive gas such as ₂ causes a problem caused by a halogen compound of platinum. That is, since the halogen compound of platinum is unstable or has a low vapor pressure, even if dry etching can be performed, an etching residue or wet etching occurs unless the substrate is heated to a high temperature of 300 ° C. or higher. There is a problem that an etching product which is difficult to remove in the post-processing adheres to the pattern side wall again.

FIG. 5A is a cross-sectional view showing a shape after dry etching of platinum using only Cl ₂ gas. SiO ₂ film 12 on Si substrate 10
And a TiN film 14 and a Pt film 16 are formed, and a resist mask 18 is formed thereon. The Pt film 16 and the TiN film 14 are collectively etched using the resist mask 18 as a mask. A sidewall attachment film 20 is formed on the sidewall of the etching pattern.

FIG. 5B is a sectional view of the state shown in FIG. 5A in which the resist mask 18 has been removed by ashing. Even if the resist mask 18 is removed, the side wall adhesion film 20 remains. Further, a residue 22 remains on the Pt film 16. The same phenomenon occurs even when another material such as SiO ₂ is used as the material of the mask. The residue and the film attached to the side wall are a compound of Pt and Cl or a compound of Pt, Cl and C.

[0008] In order to remove such a residue and a film deposited on the side wall, a chemical post-treatment such as wet etching may be used, or “The 52nd Annual Meeting of the Japan Society of Applied Physics (Autumn 1991) Proceedings 516” As described in page 9p-ZF-17, it was necessary to use a physical post-treatment such as a jet scrubber method. However, even if these removal methods are used, it is not always possible to completely remove the residue and the side wall-adhered film, and the cost for this post-processing step is also a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to carry out a chemical or physical post-treatment without heating a substrate to a high temperature. It is an object of the present invention to provide a method for dry-etching platinum, which does not generate an etching residue or a film deposited on a side wall even if it is not provided.

[0010]

The present invention is characterized by an etching gas for dry-etching platinum.
That is, it is characterized in that at least a gas containing chlorine and a CO gas or a CO ₂ gas are used. When platinum is etched using such an etching gas, a compound containing Pt, CO and Cl as a reaction product, for example, Pt (CO) Cl ₂ , Pt (CO) ₂ Cl ₂ , Pt ₂
(CO) ₂ Cl _{4 and the} like are generated. These compounds include platinum chlorides such as PtCl ₂ , PtCl ₃ , PtCl _{4, and the} like.
Since the boiling point is lower and the saturated vapor pressure is higher than the above, residues and deposits on the side walls are less likely to occur. Therefore, for example, as compared with the conventional method using only Cl ₂ gas (in which chloride of platinum is generated), residues and deposits on side walls are less likely to occur.

Table 1 below shows numerical data of the melting point and the boiling point of the compound containing Pt, CO and Cl and the chloride of platinum under atmospheric pressure. As can be seen from Table 1,
The melting points of the compounds containing Pt, CO and Cl are as follows:
Significantly lower than platinum chloride. By analogy with the melting point data, it can be understood that the compound containing Pt, CO and Cl has a lower boiling point and a higher saturated vapor pressure than the chloride of platinum. Also, it has been experimentally confirmed that the compound containing Pt, CO, and Cl has higher volatility (higher saturated vapor pressure) than chloride of platinum.

[0012]

Table 1 Compound name Melting point (° C.) Boiling point (° C.) Pt (CO) Cl ₂ 195 300 (decomposition) Pt (CO) ₂ Cl ₂ 142 -CO.250 Pt ₂ (CO) ₂ Cl ₄ 130 250 (decomposition) _{PtCl 2 581 --- PtCl 3 435 ---} PtCl 4 370 ---

The "chlorine-containing gas" used in the present invention is not particularly limited.
Gases such as l ₂ , SiCl ₄ , BCl ₃ , S ₂ Cl ₂ and CCl ₂ F ₂ can be used.

Gas containing chlorine and CO gas or CO gas
_{The two} gases are essential, but besides this, a gas that does not participate in the reaction, such as Ar gas, may be added to increase the gas flow rate. In this manner, in an etching apparatus having a relatively high etching pressure, the residence time of the gas can be shortened by increasing the gas flow rate, and the side wall adhering film and residue can be reduced as much as possible.

Various methods can be used as a dry etching apparatus for carrying out the dry etching method of the present invention. For example, various etching apparatuses such as an etching apparatus having a helicon wave plasma source, a magnetron RIE (reactive ion etching) apparatus, an ECR (electron cyclotron resonance) etching apparatus, and an ICP (inductively coupled plasma) etching apparatus are used. be able to.

[0016]

FIG. 1 is a front sectional view showing an example of an etching apparatus for carrying out the present invention. This etching apparatus includes a helicon wave plasma source. That is, the antenna 26 is provided around the bell jar 24 made of quartz.
The antenna 26 is connected to a high-frequency power supply 28 for generating plasma. An electromagnet 30 for generating an external magnetic field is arranged outside the antenna 26.

The vacuum chamber is composed of the bell jar 24 and the diffusion chamber 3.
The lower end of the bell jar 24 is connected to the diffusion chamber 32. A substrate holder 34 is arranged inside the diffusion chamber 32. Inside the diffusion chamber 32, there is a substrate holder 34, on which a wafer 36 to be processed is placed. Substrate holder 34
The electrode 40 is connected to a high-frequency power source 38 for bias and to a DC power source 42 via a frequency filter 44.
The temperature of the substrate holder 34 is controlled by a temperature controller (not shown), and the potential of the electrode 40 is controlled by a DC power supply 42 to electrostatically attract the wafer 36 to be processed, thereby controlling the temperature of the wafer 36 to be processed. You can do it.

Next, a basic procedure for implementing the dry etching method of the present invention using this etching apparatus will be described. The wafer 36 to be processed is suction-held on the substrate holder 34 and controlled to a desired temperature. An etching gas is introduced from the side of the diffusion chamber 32, the exhaust speed is adjusted using an orifice of an exhaust system, and the pressure in the vacuum chamber is maintained at a predetermined value. Source power is supplied from a high frequency power supply for plasma generation 28 to the antenna 26 to generate plasma inside the bell jar 24. On the other hand, the substrate bias power is supplied from the bias high frequency power supply 38 to the substrate holder 34 to control the substrate bias voltage. Bell jar 24
Plasma is generated inside the wafer, and the activated species generated here diffuse into the diffusion chamber 32, and P
The t film and the TiN film are collectively etched.

[0019]

Embodiment 1 A first embodiment will be described. FIG. 2A is a sectional view of a wafer to be processed used in the first embodiment. The method of manufacturing the wafer to be processed will be briefly described. An SiO ₂ film 12 is formed on a Si substrate 10 by a CVD method, a TiN film 14 is formed on the SiO ₂ film 12 by a CVD method, and a sputtering method is further formed thereon. A Pt film 16 is formed by a method. This Pt film 1
A photoresist is applied on the substrate 6 and exposed and developed by a known method to form a resist mask 18 having a predetermined pattern. The Pt film 16 and T
The iN film 14 was collectively etched. The etching conditions are as follows. Cl ₂ gas and CO as etching gas
Using a gas mixture, Cl ₂ gas was introduced into the vacuum chamber at a flow rate of 30 sccm, and CO gas was introduced at a flow rate of 20 sccm. The pressure in the vacuum chamber was 0.26 Pa. Antenna 26
To the substrate holder 3
4 was supplied with a substrate bias power of 100 W. When the Pt film 16 and the TiN film 14 were collectively etched under these conditions, a cross-sectional shape as shown in FIG. 2B was obtained. That is, the Pt film 16 is formed at the opening of the resist mask 18.
And the TiN film 14 were etched. When this was ashed to remove the resist mask 18, the cross-sectional shape became as shown in FIG. As is apparent from FIG.
No etching residue remains on the t film 16 and
No adhesion film was found on the pattern side walls of the Pt film 16 or the TiN film 14.

Next, a second embodiment will be described. FIG. 3 (A)
FIG. 7 is a sectional view of a wafer to be processed used in the second embodiment. This wafer to be processed is the same as the wafer to be processed used in the first embodiment up to the Si substrate 10, the SiO ₂ film 12, the TiN film 14, and the Pt film 16. The difference is that an SiO ₂ mask 44 is used instead of the resist mask. The Pt film 16 and Ti
The N film 14 was collectively etched. The etching conditions are as follows. Using a mixed gas of Cl ₂ gas and CO ₂ gas as the etching gas, Cl ₂ gas at a flow rate of 40 sccm, was introduced into the vacuum chamber of CO ₂ gas at 10sccm flow rate. The pressure in the vacuum chamber was 0.52 Pa. Antenna 26
To the substrate holder 3
4 was supplied with a substrate bias power of 80 W. When the Pt film 16 and the TiN film 14 were collectively etched under these conditions, the cross-sectional shape became as shown in FIG. That is, the Pt film 16 is formed at the opening of the SiO ₂ mask 44.
And the TiN film 14 were etched. When this was removed by chemical dry etching to remove the SiO ₂ mask 44, a cross-sectional shape as shown in FIG. 3C was obtained. As in the case of the first embodiment, no etching residue was left on the Pt film 16, and no adhesion film was found on the pattern side walls of the Pt film 16 and the TiN film 14.

In this second embodiment, SiO ₂ is used as the material of the mask, and CO ₂ gas is used as the CO-based etching gas. This combination will be described. It is considered that the CO ₂ gas has a higher etching rate of the resist mask than the CO gas. When the etching rate of the resist mask is high, the etching products of the resist also increase. As a result, there is a concern that the etching product of the resist containing a large amount of C, together with the etching product of Pt, further increases the thickness of the side wall adhesion film. Therefore, when a CO ₂ gas is used, an SiO ₂ mask is used instead of a resist mask.

Next, a third embodiment will be described. In this embodiment, a magnetron RIE (reactive ion etching) apparatus was used as an etching apparatus. In this etching apparatus, the same wafer to be processed (having the sectional structure of FIG. 2A) as in the first embodiment was used. The Pt film 16 and the TiN film 14 were collectively etched on the wafer to be processed. The etching conditions are as follows.
A mixed gas of Cl ₂ gas, CO gas, and Ar gas is used as an etching gas, and a Cl ₂ gas is supplied at a flow rate of 30 sccm, a CO gas is supplied at a flow rate of 30 sccm, and
It was introduced into the vacuum chamber at a flow rate of 0 sccm. The pressure in the vacuum chamber was 10 Pa. A power of 600 W is supplied to this etching apparatus to generate plasma, and the Pt film 16 and TiN
When the film 14 was collectively etched, the cross-sectional shape became as shown in FIG. When the resist mask 18 was removed by ashing, a cross-sectional shape as shown in FIG. 4B was obtained. Also in this embodiment, no etching residue remains on the Pt film 16 and the Pt film 16 and the TiN film 14
No adhesion film was found on the pattern side wall.

In the third embodiment, a magnetron RIE apparatus is used, and an Ar gas is added to the etching gas. This combination will be described. The magnetron RIE has a higher etching pressure than the helicon wave plasma source. When the etching pressure is high, the residence time of the gas becomes longer when the gas flow rate is the same. Then, the re-adhesion of the etching product to the substrate increases, and the side wall-adhered film and the residue tend to increase. Therefore,
A large amount of Ar gas is added to shorten the residence time of the gas.

[0024]

According to the present invention, platinum is dry-etched using at least a gas containing chlorine and a CO gas or a CO ₂ gas as an etching gas. Deposits are less likely to occur. Therefore, it is effective for etching a platinum wiring film of a semiconductor device into a predetermined pattern.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an example of an etching apparatus for carrying out the present invention.

FIG. 2 is a sectional view of a wafer to be processed before and after etching in a first embodiment.

FIG. 3 is a cross-sectional view of a wafer to be processed before and after etching in a second embodiment.

FIG. 4 is a cross-sectional view of a processed wafer after etching in a third embodiment.

FIG. 5 is a cross-sectional view of a processed wafer after etching in a conventional etching method.

[Explanation of symbols]

10 Si substrate 12 SiO ₂ film 14 TiN film 16 Pt film 18 resist mask 24 bell jar 26 antenna 28 high frequency power supply 30 electromagnet 32 diffusion chamber 34 the substrate holder 36 to be processed wafers 38 a high frequency bias power supply for plasma generation

Claims (3)

[Claims] 1. A dry etching method for etching a platinum film into a predetermined pattern by introducing an etching gas into a vacuum chamber to generate plasma, wherein the etching gas includes at least a gas containing chlorine; A dry etching method for platinum, characterized by using a gas. 2. A dry etching method for etching a platinum film into a predetermined pattern by introducing an etching gas into a vacuum chamber to generate plasma, wherein the etching gas includes at least a gas containing chlorine, A dry etching method for platinum, characterized by using _two gases. 3. The dry etching method for platinum according to claim 1, wherein the platinum wiring film of the semiconductor device is etched.