JPH01122124A - Dry etching method - Google Patents

Abstract

PURPOSE:To form a taper, and to improve its dimensional accuracy by performing an isotropic etching by an intermittent etching, and then anisotropically etching by continuous etching. CONSTITUTION:High frequency power is intermittently applied from the start of etching to an article 12 to be etched to etch the article 12 to its midway, and then the power is applied continuously to the article 12 to etch the article 12 to a finishing base 13. That is, it is isotropically etched in a first step to form a taper, and a resist mask is then anisotropically etched in a second step. In the first step, when the application of the high frequency power is stopped, the isotropic etching is proceeded with remaining activated neutral reaction gas. Since the etching conditions except the presence or absence of the application of the high frequency power may be all constant through the first and second steps, a loss time of switching the steps is eliminated. Further, since all are dry etched, an accurate working without contamination can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to dry etching used in the manufacturing process of electronic components such as semiconductors, and in particular to taper etching. The spacing between interconnects and the diameter of contact holes are also becoming smaller. Therefore, due to the problem of step coverage during film formation, etching technology for forming tapers in interconnects and contact holes has become indispensable.

Conventional taper etching methods include a method that combines wet x etching and dry etching, and a method that uses resist regression by dry etching.

FIG. 4 is a process diagram of a method combining wet etching and dry etching. In the first step, the object to be etched 42 is etched through a resist mask 41 by wet etching, and an undercut is created directly under the resist as shown in 43. to occur. As a second step, the object to be etched 42 is anisotropically etched perpendicularly to the resist mask 41 by dry etching. For anisotropic dry etching, a method based on reactive ion etching (hereinafter referred to as R, I, E) is usually used.

By this method, a taper is formed at the edge of the object to be etched after the resist is removed.

FIG. 6 is a process diagram of a method using resist regression by dry etching. When performing dry etching, the etching speed of the resist mask 61 is higher than that of the object to be etched 52.
Select etching conditions that are equivalent to or faster than the etching speed of The dry etching method is R.
,1,E are often used. When etching is performed under the above conditions, the resist recedes as the etching progresses, and a taper is formed in the object 62 to be etched.

Problems to be Solved by the Invention However, in the above-mentioned method that combines wet etching and dry etching, there are problems such as foreign matter adhering to the undercut portion and becoming a source of contamination, and the resist mask expanding and making it impossible to process with good dimensional accuracy. It has points. Further, the method using resist regression by dry etching has a problem in that it is difficult to obtain dimensional accuracy because the taper shape changes depending on the difference in resist film thickness.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a dry etching method that can easily form a taper and has good dimensional accuracy.

Means for Solving the Problems In order to achieve the above object, the dry etching method of the present invention is a dry etching method in which a high frequency power is applied to parallel plate electrodes to turn a reactive gas into plasma to etch the object to be etched. There is a first step in which the high-frequency power is applied intermittently from the start of etching to etch the object to be etched halfway, and a second step in which the high-frequency power is continuously applied thereafter to etch the object to be etched to the end point. It is characterized by consisting of the following steps.

Function The present invention uses the above-described structure to perform isotropic etching to form a taper in the first step, and perform anisotropic etching on the resist mask in the second step. In the first step, when the application of high frequency power is stopped, etching proceeds isotropically due to the remaining activated neutral reaction gas. Since all the etching conditions except whether or not high frequency power is applied may be kept constant throughout the first step and the second step, there is no lost time due to process switching. In addition, since all processes are performed by dry etching, highly accurate processing without contamination is possible.

EXAMPLE Hereinafter, a dry etching method according to an embodiment of the present invention will be explained with reference to the drawings.

FIG. 2 shows a block diagram of a dry etching apparatus used in an embodiment of the present invention. Reference numeral 21 indicates a substrate electrode, and 22 indicates a counter electrode. An object to be etched 23 is placed on the substrate electrode 21, and high frequency power is applied from a high frequency power source 24. Reference numeral 26 denotes a magnet having a rotating means installed to generate a leakage magnetic field on the side of the substrate electrode 21, and is configured as a magnetic field type reactive ion etching apparatus.

FIG. 3 shows the etched cross-sectional shape of a dry etching method in a comparative example of the present invention. Using the dry etching apparatus with the above configuration, the pressure was set at 1 mTorr.

High frequency electric crab 350W, reaction gas: CR2/BCR3=
80/20 SCCM' + Magnetic flux density on substrate electrode 21: About 20 Gauss. Etching was performed only in the first step of the present invention. This is a study of the shape. The object to be etched 23 has a 5lO3 film on its surface 6
Film thickness 111m sputtered on inch SL substrate
Etching was performed using an A4-1% Si-0, 5% Cu film 31 through a resist mask 32.

FIG. 3a shows the etched cross-sectional shape when high frequency power is continuously applied. When high frequency power is continuously applied, the etched cross-sectional shape becomes anisotropic as shown in the figure. At this time, the time required for etching was 65 seconds. In Figure 3, high frequency power was applied and stopped at intervals of 5 seconds, and the etching time was 80 seconds.
The etching time was 9 seconds, and the etching time was 15 seconds.
0 seconds.

It was 103 seconds.

The etched cross-sectional shape becomes isotropic as the taper angle becomes gentler as the interval between application and stop of high-frequency power becomes longer. Comparing intermittent etching and continuous etching in terms of etching time, in intermittent etching the time during which high-frequency power is applied is tso% of the etching time, so it is clear that etching is progressing even when high-frequency power is stopped. Recognize. Therefore, from the etching cross-sectional shape, it is considered that etching proceeds isotropically due to the activated neutral reaction gas remaining when the high frequency power is stopped.

As described above, it can be seen that isotropic etching is possible even under normal anisotropic etching conditions by intermittently applying high frequency power.

However, dimensional accuracy cannot be obtained with the above-mentioned intermittent pre-etching. Therefore, dimensional accuracy can be ensured by using the intermittent etching as the first step and performing anisotropic etching by continuous etching using the resist as a second step.

Figure 1 shows Ajl-1%5t-0 in an example of the present invention.
, s% A process diagram of a dry etching method for a Cu film is shown. In FIG. 1, 11 is a resist mask;
2 = 11 st-o, s% Cu film (film thickness 1 μm
), 13 is the underlying 5i02 film, and 14 is the Si substrate.

Figure 1A shows the cross-sectional shape before etching, Figure 1C shows the etched cross-sectional shape after performing the first step (intermittent etching) for 40 seconds, in which high-frequency power is applied and stopped at 10-second intervals, and Figure C shows the etched cross-sectional shape. A second device that continuously applies high frequency power.
This is the etched cross-sectional shape after the process. Etching was carried out under the same etching conditions as in the comparative example. Figure d shows the resist mask 11 removed after etching, and a taper is formed at the edge, so that good step coverage can be obtained during subsequent sputtering film formation.

In this way, by performing isotropic etching with intermittent etching and then performing anisotropic etching with continuous etching, a taper can be formed and processing with good dimensional accuracy can be achieved. In this method, a cycle of applying and stopping high-frequency power is simply introduced into the normal process, so that the process is easy and there is no risk of contamination unlike wet etching.

In addition, in this example, Afl-1% Si-
Although the etching of a 0.5% Cu film was shown, a film that is isotropically etched with an activated neutral reaction gas (S1
Similar effects can be obtained with 3N4 films, PoIJSi films, etc.). Furthermore, in this example, the interval between application and stop of high-frequency power was set to 10 seconds in the first step, but as described in the comparative example of the present invention, the taper shape can be changed by changing this interval. It is.

Effects of the Invention As described above, the present invention provides a first method that applies high frequency power intermittently.
By performing a dry etching method having a second step in which the step and the application of high-frequency power are performed in succession, taper etching of the object to be etched can be performed with high dimensional accuracy.

[Brief explanation of the drawing]

Fig. 1 is a process diagram of a dry etching method in an embodiment of the present invention, Fig. 2 is a block diagram of a dry etching apparatus used in an embodiment of the present invention and a comparative example, and Fig. 3 is a diagram of a dry etching method in a comparative example of the present invention. Etching cross section of method,
4 and 6 are process diagrams of a conventional dry etching method. 21...Substrate electrode, 22...Counter electrode, 23...Object to be etched, 24...
High frequency power supply. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure I Resist figure 4
The 9th school of the 5th school

Claims (3)

[Claims] (1) In a dry etching method in which a high-frequency power is applied to a parallel plate type electrode and a reactive gas is turned into plasma to etch the object to be etched, the high-frequency power is intermittently applied from the start of etching to partially remove the object to be etched. A dry etching method comprising a first step of etching, and a second step of etching the object to be etched to the end point by continuously applying the high frequency power. (2) The dry etching method according to claim 1, characterized in that a magnetic field is superimposed within the parallel plate electrodes. (3) The dry etching method according to claim 1, wherein the object to be etched is an Al alloy.