JPS6039175A - Dry etching method - Google Patents

Abstract

PURPOSE:To judge well the end of the etching of a material capable of forming a Y compound having a high vapor pressure when the material is etched with Y dissociated from gaseous XnYm, by monitoring the emission spectrum of Xl (each of X and Y is an atom or a molecule, and each of l, m and n is a positive integer). CONSTITUTION:For example, when W is etched with SF6, the end of the etching is judged from a change in the intensity of the emission spectrum of S2. It is possible to consider that numbers of dissociated molecules such as F, SFn(n= 0-6) and S2 or molecules produced by the recombination of such dissociated molecules are present in plasma by the etching reaction. When emission spectra during the etching of W are examined, it is apparent that the emission spectrum of S2 appears intensely. The emission spectrum of S2 also appears when W is not present in SF6 plasma, yet the intensity is considerably lower than that of the emission spectrum of S2 during the etching of W. Accordingly, the end of the etching of W can be judged in a high S/N ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a dry etching method, and particularly to a method in which a change in the intensity of the emission spectrum of a reaction product during etching is used as a monitor for determining the completion of etching.

[Background of the invention]

Methods for determining the etching end point in dry etching include (1) emission spectroscopy, (2) laser interferometry, and (3) gas pressure monitoring, among which emission spectroscopy is often used as a simple monitoring method. ing.

For example, when etching Si in the plasma of SFs, the Si combines with the 7-wires and becomes volatile fluoride. Si fluoride is generated. When the Si to be etched is completely gone, no Si fluoride is generated, and the remaining Si fluoride is also removed by the exhaust system, so the Si fluoride in the plasma is removed.
decreases rapidly. Therefore, if the emission spectrum of this Si fluoride is monitored with a spectrometer, S
The start and end points of the etch leg of i can be determined.

Actually, when etching Si with SF6 plasma, S
By monitoring the iF emission spectrum (wavelength: 443 nm), the end point of etching can be accurately determined.

In recent years, W+, which has a lower resistivity than the conventionally used Po1y- and Si, has been used as a gate electrode material for MO8LSI.
Mo or these Si compounds are attracting attention, and research into dry etching methods for these materials is actively underway, but we performed dry etching of W by a reactive sputtering method using SF6. As an etching end point determination method in the W dry etching method, the above-mentioned si
By analogy with the case described above, an attempt was made to monitor the emission spectrum of W fluoride using a spectrometer. However, the emission spectrum of W fluoride could not be detected and could not be used as a monitoring method.

[Purpose of the invention]

The object of the present invention is to eliminate the drawbacks of the above-mentioned etching end point determination method and to etch Si, W in SF6 plasma.

It is an object of the present invention to provide a good method for determining the end point of etching when etching materials that can form fluorides with high vapor pressure, such as Mo and 'l'a.

[Summary of the invention]

In developing a dry etching method for W, we used SFg as an etching gas and obtained good results. In SF6 plasma, W is WF with high vapor pressure,
It is thought that it becomes etched. therefore,
As a W etching end point monitoring method, by analogy with the method using the emission spectrum of SiF described above, WF6 or its dissociated molecules, WP, WF2, WFs, W
F4.

We devised a method to monitor the emission spectrum of WF5, etc.

Therefore, in order to investigate these emission spectra, WF
6 was tried to generate plasma, but the luminous efficiency of W fluoride was low and its luminous spectrum was almost undetectable.

Now, if we reconsider the etching reaction of W in the SF6 plasma, it is thought that the following reaction occurs: 6SFa-→68Fs +6FW+6F-WWF6, and in the plasma, F, SFn (""0~6), St Kawaaki et al.'s SF
It is thought that there are many dissociated molecules from 6 or these recombined molecules. When we examine the emission spectrum during etching of W in detail from this perspective, we find that S
It was found that the emission spectrum of No. 2 appears strongly.

Furthermore, this s2 emission spectrum appears even when W is not present in the SF6 plasma, but its intensity is sufficiently small compared to that during W etching, so the end point of W etching can be determined using a high 8/N ratio. I can do it.

[Embodiments of the invention]

An embodiment of the present invention will now be described with reference to FIGS. 1 and 2.

Example 1 FIG. 1 is a schematic diagram of a reactive sputtering device and a spectroscopic analyzer used in the present invention. Plasma light is collected through a window 2 made of a quartz plate provided on the side wall of the etching chamber 1, and the emission spectrum is monitored by a spectrometer 3 installed just in front of the window 2. The sample 4 was placed on the lower electrode 5 in the etching chamber, and the height of this sample was made almost the same as the height of the window 2 and the light window of the spectroscopic analyzer 3. The sample is one in which W is deposited on a Si wafer, and SF is applied from the center of the upper electrode 6.
s was introduced to generate plasma, and W was etched. FIG. 2 shows an example of monitoring the emission spectrum of 82 during W etching.

Although any wavelength may be used as long as the emission peak of N2 is present, 2892 people with relatively high emission intensity were used here. The monitor curve starts to rise with the start of discharge and reaches 30-60118O.
After that, it becomes a constant value. After the etching is completed, the monitor curve begins to fall again and settles at the emission intensity of 82 when no W is present in the SFg plasma. This monitor curve shows gas pressure and power.

Since it sensitively reflects the etching conditions such as the type of gas and the influence of adsorbed gas in the etching chamber, it is useful not only for determining the end point of etching but also for determining whether the etching condition is good or bad. In addition to the etching of W described here, the etching of Si) MO, Ta, etc., which can combine with fluorine dissociated from SF6 in SF6 plasma to form fluoride with a high vapor pressure, Also, the end point of etching can be determined satisfactorily by monitoring the emission spectrum of N2.

Example 2 NFa was used as an etching gas for W.

In this case, the intensity of the N% or N2 emission spectrum increased during W etching and decreased when etching was completed. Therefore, these emission spectra could be used as etching completion monitoring signals.

〔Effect of the invention〕

According to the present invention, a material that can combine with fluorine to form a fluoride with a high vapor pressure in an XFn-based plasma ( Si, W, Mo.

This method has the advantage of being able to provide a method for determining the end point of etching (Ta, etc.). In particular, an etching method using fluorine dissociated from XFr1 as an etchant does not limit the material to be etched, and is therefore considered to have a wide range of applications.

Furthermore, the present invention can also be applied to the dry etching of materials etched by Ct in an XCtn plasma based on the same principle.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a reactive sputtering apparatus and a spectroscopic analyzer for monitoring the emission spectrum, and FIG.
It is a graph showing the luminescence peak o = curve fm. 1... Etching chamber, 2... Window, 3... Spectroscopic analyzer, 4 Figure 1 Figure 2 Figure 1 Time

Claims (1)

[Claims] A material that is etched by Y dissociated from XnYm is dry etched using an etching gas whose molecular formula is represented by XnYl,l, where i, x, and y are atoms or molecules, and n9m is a positive integer. 1. A dry etching method characterized in that intensity changes in the emission spectrum of Xt, where t is a positive integer, are used as a monitor for determining the completion of etching. 2. In the dry etching method according to claim 1, X constituting the etching gas XnYm is S, N
, C, B, P, Si, XelH, and Y is an atom or molecule containing at least one of halogen and H. 3.% The dry etching method according to claim 1, characterized in that SF6 is used as the etching gas and the material is etched with fluorine atoms. 4. The dry etching method according to claim 3, wherein the material etched by the fluorine atoms is Si, W, Mo, Ta, or a compound thereof. 5. A dry etching method according to claim 1, characterized in that a spectroscopic analyzer for monitoring the emission spectrum of Xt is provided and used.