JP2953866B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dry etching method for electronic devices and the like.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices, the processing of A1 as a wiring material has shifted from wet etching to dry etching. A1 etching gas includes CCl ₄ , SiC which can effectively remove a natural oxide film on the surface.
l _4, BCl _3, a reducing gas is used for. When the natural oxide film on the surface is removed, Al reacts spontaneously with Cl atoms and Cl ₂ molecules. Therefore, a sidewall protective film is necessary for performing anisotropic etching. Therefore, the number of cases where CHCl ₃ or CHF ₃ gas is added so as to actively protect the side wall film has been increased. It has been clarified that the resist mask used suppresses side etching by protecting the carbon polymer from the resist, as compared with an oxide film mask or a nitride film (I. Hasegawa).
et al. : Proc. Symp. Dry. p
process, 126 (1985)) A resist mask has become common sense for Al etching.

However, with further miniaturization, importance has been placed on the dimensional shift and reproducibility due to the side wall film. Also,
This sidewall film needs to be removed after etching,
Problems such as dimensional shifts due to the removal process, after-corrosion due to the inability to completely remove, and poor flatness when an interlayer film is formed on the wiring occur. Further, since the resist is positively etched to form the side wall protective film, the etching selectivity of the resist mask to Al becomes low. In recent memory device structures, the capacitance portion is often of a stacked type, and the base of the Al wiring often has a step near 1 μm.
Therefore, when processing the Al wiring, it is necessary to perform over-etching, and if the selection ratio of the mask is low, there arises a problem that the mask cannot withstand.

Further, since the latter half of 1980, a technique of suppressing the etching in the side direction due to radicals by lowering the temperature of the substrate at the time of etching (0 ° C. or lower) has been used in the etching of polysilicon and organic films. It has become. (K. Tsujimoto et al .: Pr.
oc. Symp. Dry. Process, 42
(1988)) On the other hand, in fine wiring, an increase in current density is inevitable, and the problems of electromigration and stress migration have become apparent. In order to improve the reliability of wiring, addition of Si and Cu and use of barrier metal have been made. However, with these processes, many problems occurred before and after the etching step. That is, generation of residues, reduction in the selectivity of the resist, and generation of after-collision.

[0005]

SUMMARY OF THE INVENTION In a dry etching process of a wiring material film, high-precision controllability of pattern dimensions,
It is necessary to improve the mask resistance and the selectivity with the underlying film, to eliminate the residue of the resist and the immediate wall film, and to suppress the after-corrosion and micro-loading effects. An object of the present invention is to provide an etching method for solving the above contents.

[0006]

According to the present invention, an Al alloy laminated film is dry-etched at a substrate temperature equal to or lower than room temperature using a patterned inorganic insulating film as a mask and using a gas containing at least hydrogen bromide. A dry etching method characterized by the following. As the inorganic insulating film to be used, an oxide film usually used in a semiconductor process is preferably used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An Al alloy laminated film 2 is formed on a base oxide film 1 shown in FIG. 1A by a sputtering method or a vapor deposition method. This Al alloy laminated film 2 is made of Ti having a thickness of 0.05 μm.
Film, 0.1 µm TiN film, 0.3 µm Al-Si-
A Cu film and a 0.25 μm TiN film are sequentially formed. On this Al alloy laminated film 2, a 0.2 μm oxide film 3
Is formed by a plasma CDV method. A photoresist is applied on this film, and a resist mask 4 is formed by a normal photoresist process.

Next, as shown in FIG. 1B, using the resist 4 as a mask, the oxide film 3 is dry-etched with a mixed gas of CF ₄ and CHF ₃ . At this time, the dry etching includes RIE (Reactive Ion Et).
Ching) or ECR (Electron C)
(ytrontron Resonance) etching apparatus is used. After the oxide film 2 is etched, the resist is removed by using O ₂ plasma, and only the patterned oxide film 3 is left as a mask as shown in FIG.

Next, a low pressure (10 ⁻⁴ Torr to 10 ⁻³ Torr)
Torr) under, high-density plasma (10 ¹⁰ to ¹¹ / cm
³⁾ using an ECR etching apparatus capable of forming less
Al alloy laminated film 2 using a gas containing HBr
Is etched as shown in FIG. The etching conditions in this case are such that the etching gas pressure is 10 ⁻³ Torr.
r, microwave power is 300 W, RF power is 150
W, the substrate temperature is −30 ° C. to 20 ° C.

After the etching, in order to suppress after-corrosion, the wafer is vacuum-transferred to an ashing reaction chamber, and ashing is performed by adding NH ₃ gas or CH ₃ OH gas to O ₂ gas.

In the above mask formation, a multilayer resist mask may be used, and EB (Electron Beam) is used.
The exposure step according to m) may be used.

[0012]

The dry etching method for a wiring material film according to the present invention has the following effects. 1) High precision control of pattern dimensions. In the side wall protection by the carbon polymer from the resist mask, it is difficult to control the size to several tens nm or less. On the other hand, the method of performing etching at a low temperature using an oxide film mask suppresses the amount of side etching and enables dimensional control of 40 nm or less.
Further, the control of the taper angle can be easily performed by the substrate temperature. 2) Mask resistance. Selectivity with mask (40 ° C), Al
/ Resist: improved from 2 times to Al / plasma oxide film: 5 to 7 times, and further increased by 10 times or more by lowering the temperature (-50 ° C). 3) Improve the selectivity with the underlying film. Selectivity (Al / thermal oxide film)
Is 15 times or more by low-temperature etching using an oxide film mask, compared with 6 to 7 times by a resist mask. 4) Elimination of resist and sidewall film residues. Since the resist is removed after patterning the oxidation mask, no residue of the resist or the sidewall film occurs after Al etching. 5) Suppression of after collision. By using the oxide film mask, the problem of residual chlorine contained in the resist residue is solved, so that corrosion can be suppressed. Also,
Low-temperature (−50 ° C.) etching with an oxide film mask can reduce the number of after-corrosion after water-washing treatment to 30% or less as compared with normal-temperature etching. 6) Suppression of micro-rotating effect. As described in 2), the oxide film mask has high mask resistance, so that the thickness of the mask can be reduced. Therefore, when processing a space of the same size, the aspect ratio of the mask can be reduced. 0.
When processing the 3 μm space with a 1.2 μm thick resist mask, a micro-rotating effect of 50% or more is produced. On the other hand, in the case of an oxide film mask having a thickness of 0.3 μm, it is reduced to 29% (40 ° C.), and further, at -50 ° C., 18%.
Can be reduced to

[Brief description of the drawings]

FIGS. 1A and 1B are sectional views showing a dry etching method of the present invention in the order of steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base oxide film 2 Al alloy laminated film 3 Mask oxide film 4 Resist mask

Claims (4)

(57) [Claims] Claims: 1. Using a patterned inorganic insulating film as a mask and using a gas containing at least hydrogen bromide,
A dry etching method, wherein an Al alloy laminated film is dry-etched at a substrate temperature equal to or lower than room temperature. 2. The dry etching method according to claim 1, wherein the inorganic insulating film is an oxide film. 3. An Al alloy laminated film comprising TiN, Ti and A
Claims: 1. An aluminum alloy film is laminated.
2. The dry etching method according to 1 . 4. The method according to claim 1, wherein the Al alloy laminated film comprises at least Al.
And an alloy film containing Cu and Cu.
4. The dry etching method according to 1 or 3 .