JP2000357679A - Method of detecting etching end point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid influences due to contamination with reaction products, in plasma etching of an Al alloy layer, TiN layer or a laminate of these layers, etc. SOLUTION: In plasma etching of a laminate of TiN layer 44a, AlCu alloy layer 44b and a TiN layer 44c are laminated in this order, using chloric gas, the light emission of an activated species at a wavelength longer than 396.2 mm is monitored to detect the etching end point, based on change in its light intensity. Lights having long wavelengths of 703 nm, 836 nm, 837.6 nm, etc., have high transmittances with respect to reaction products in plasma etching, as compared with short wavelengths of 396.2 nm, etc., and hence, even if reaction products deposit on the end point detecting window of an etching reaction chamber, the end point can be detected stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an Al alloy layer, T
The present invention relates to a method for detecting an etching end point suitable for plasma etching of an iN layer or a lamination of these layers, in particular, monitoring the emission of an active species having a wavelength longer than 396.2 nm and detecting the etching end point from a change in the emission intensity. This makes it possible to detect an end point which is less susceptible to contamination by reaction products.

[0002]

2. Description of the Related Art Generally, in order to perform etching automatically and accurately, it is necessary to determine or detect the end point of etching (the point at which a film to be etched is removed from the substrate surface). Conventionally, etching end point detection methods include (1) a method of detecting from a change in the concentration of a reactive gas species,
(2) a method of detecting from a change in the concentration of an etching reaction product; (3) a method of detecting from a change in the thickness of a film to be etched; Detection method from (5)
Emission spectroscopy, (6) mass spectrometry, (7) laser interferometry, etc. are known (for example, monthly Semiconductor World
October, 1985, pp. 155-159). Among these methods, the emission analysis method is most frequently used in a commercially available plasma etching apparatus. The emission analysis method monitors the emission of active species generated or consumed by the etching reaction, and detects the end point of etching from a change (increase or decrease) in the emission intensity.

[0003]

Conventionally, in plasma etching of an Al alloy layer, AlCl (wavelength 261.
4 nm) or Al (wavelength 394.4 nm or 39)
An emission analysis method of monitoring the emission of (6.2 nm) and detecting the etching end point is generally used. However, light of these wavelengths has a low transmittance to reaction products generated when etching an Al alloy or the like with a plasma of a chlorine-based gas (for example, a chlorine-containing gas such as Cl ₂ / BCl ₃ ), so that the etching reaction is performed. When the thickness of the reaction product attached to the end point detection window of the chamber increases, the intensity of light incident on the emission analysis system decreases, and it becomes difficult to detect the etching end point.

[0004] When it becomes difficult to detect the end point of the etching, the plasma etching apparatus is temporarily stopped, and wet cleaning is performed to remove a reaction product attached to the inner wall of the etching reaction chamber. Thereafter, the plasma etching apparatus is operated again. Therefore, according to the conventional method, there is a problem that the frequency of wet cleaning is high and the downtime of the plasma etching apparatus becomes long.

An object of the present invention is to provide a novel etching end point detecting method which is hardly affected by contamination by a reaction product.

[0006]

SUMMARY OF THE INVENTION An etching end point detecting method according to the present invention provides a method for detecting the emission of active species when performing plasma etching of an Al-based metal layer, a TiN-based conductive layer, or a laminate of these layers using a chlorine-based gas. And monitoring the etching end point based on the change in the light emission intensity, wherein light having a wavelength longer than 396.2 nm is monitored as the light emission of the active species.

According to the study of the inventor, Al alloy layer and Ti
As for a reaction product generated when the stack with the N layer is etched by the plasma of the chlorine-based gas, it has been found that light having a longer wavelength has higher transmittance than light having a shorter wavelength.
Therefore, if the emission of the long wavelength light is monitored and the etching end point is detected from the change in the emission intensity, the etching end point can be detected stably without being significantly affected by the contamination of the end point detection window by the reaction product.

In the etching end point detecting method according to the present invention, the emission of chlorine as an active species is monitored during plasma etching of the Al-based metal layer, or when the TiN-based conductive layer is plasma-etched or when the Al-based metal layer and Ti are etched.
At the time of plasma etching of the stack with the N-type conductive layer, at least one of chlorine and nitrogen may be monitored as the emission of active species. By doing so, it is possible to select an appropriate monitor light from light having a large number of wavelengths described later.

[0009]

FIG. 1 shows an inductively coupled plasma etching apparatus 10 and an emission analysis system 26 used in the embodiment of the present invention.

In the plasma etching apparatus 10, a bottom electrode 14 for holding a wafer 12 to be processed is provided at the bottom of the etching reaction chamber 10A. Reaction chamber 10A
Is closed by a dielectric plate 16,
An induction coil 18 is provided near the dielectric plate 16. The induction coil 18 includes a first high-frequency power supply 2
High frequency power for plasma formation of 0 to 13.56 MHz is supplied, and high frequency power for bias of 13.56 MHz is supplied to the bottom electrode 14 from the second high frequency power supply 22. A plasma 24 can be generated above the wafer 12 to be processed by supplying a predetermined amount of high-frequency power from the high-frequency power supply 20 to the induction coil 18 while flowing an etching gas into the reaction chamber 10A by a gas circulation system (not shown). .

An end point detection window 10a is provided in the reaction chamber 10A beside the position where the plasma 24 is formed.
The end point detection window 10a is provided for extracting light emission of active species from the plasma 24.

In the emission analysis system 26, light from the end point detection window 10a enters a spectroscope 30 via a lens. The spectroscope 30 extracts light having a predetermined wavelength or a plurality of wavelengths from the incident light.
It is converted into an electric signal by the photoelectric converter 32. The electric signal transmitted from the photoelectric converter 32 is amplified by the amplifier 34 and recorded by the recorder 36 as illustrated in FIG.

FIGS. 2 to 4 show a wiring forming process as one application example of the present invention.

In the step of FIG. 2, a wiring material layer 44 is formed on an insulating film 42 made of silicon oxide (SiO ₂ ) covering a semiconductor substrate 40 made of silicon. As the wiring material layer 44, a TiN layer (barrier layer) 44
a, AlCu alloy layer 44b and TiN layer (anti-reflection layer)
44c is formed by a sputtering method or the like.

Next, in the step of FIG. 3, a resist layer 46 is formed on the wiring material layer 44 according to a predetermined wiring pattern by a known photolithography process.

Next, in the step shown in FIG. 4, the wiring material layer 44 is selectively etched by using the apparatus 10 of FIG.
Then, a wiring layer 44A including the remaining portion of No. 4 is formed. After this,
The resist layer 46 is removed by ashing or the like.

In the plasma etching in the step of FIG. 4, the substrate 40 of FIG.
And inserted on the bottom electrode 14. As an example, plasma etching is performed in the order of (a) breakthrough etching, (b) main etching, (c) TiN layer (barrier layer) etching, (d) overetching, and each of the steps (a) to (d). Were set as follows.

The conditions for the breakthrough etching are as follows: pressure: 10 mTorr Power supply of the power supply 20: 350 W Power supply of the power supply 22: 150 W Gas flow rate: Cl ₂ / BCl ₃ / Ar = 40/60/40
sccm Etching time: 20 seconds (fixed).

The conditions of the main etching were as follows: pressure: 10 mTorr Power supply of the power supply 20: 800 W Power supply of the power supply 22: 130 W Gas flow rate: Cl ₂ / BCl ₃ / CHF ₃ = 120/60
/ 5 sccm.

The conditions for etching the TiN layer (barrier layer) are as follows: pressure: 10 mTorr Supply power of power supply 20: 350 W Supply power of power supply 22: 150 W Gas flow rate: Cl ₂ / BCl ₃ / CHF ₃ = 30/50 /
5 sccm was set.

The conditions of over-etching are as follows: pressure: 10 mTorr Supply power of power supply 20: 300 W Supply power of power supply 22: 100 W Gas flow rate: Cl ₂ / BCl ₃ / CHF ₃ = 50/50 /
5 sccm was set.

In the above main etching, as shown in FIG. 5, light emission at a wavelength of 703 nm is monitored by the light emission analysis system 26, and the end point of the etching of the AlCu layer 44b is detected from the increase of the light emission intensity. The process moved to the TiN layer (barrier layer) etching described above. In the above-described etching of the TiN layer (barrier layer), the emission at a wavelength of 837.6 nm is monitored by the emission analysis system 26 as shown in FIG. 5, and the end point of the etching of the TiN layer 44a is detected from the increase in the emission intensity. In response to the detection of the end point, the process shifted to the above-described overetching.

In order to enable such an etching end point detection, prior to the above wiring forming process, a number of samples having the same configuration as that shown in FIG. 3 were subjected to plasma etching under the same conditions as described above. Was performed and the monitor wavelength was changed by the emission analysis system 26, and a waveform showing a change in emission intensity as illustrated in FIG. 5 was recorded. Then, based on the recording waveform for each monitor wavelength,
The emission intensity change near the etching end point of the Cu alloy layer 44b and the emission intensity change near the etching end point of the TiN layer 44a were obtained. The results are shown in Table 1 below.

[0024]

[Table 1] Table 1 shows the active species of the monitor wavelengths whose active species are known. Further, the films to be etched from which the end point of the etching can be determined based on the change in the light emission intensity are shown as “Al alloy” and “TiN”.

On the other hand, the light having a wavelength of 703 nm is used for detecting the etching end point of the AlCu alloy layer and the wavelength is 837.6.
nm light for the detection of the etching end point of the TiN layer, the conventional technique of using the light of the wavelength of 261.4 nm for the detection of the etching end point of the AlCu alloy layer and the TiN layer, and the light of the wavelength of 394 nm for the AlCu alloy. Layer and Ti
In order to compare the wet etching cycle with another conventional technique used for detecting the etching end point of the N layer, FIG.
In addition, plasma etching was performed on a number of samples having the same configuration as that described above under the same conditions as described above, and a waveform indicating a change in emission intensity was recorded by the emission analysis system 26. Here, the term "wet etching cycle" refers to the number of processed wafers in which it is necessary to perform wet etching on the etching reaction chamber 10A, and the comparison results are shown in Table 2 below.

[0026]

[Table 2] The reason why the wet cleaning is performed on the 6,500 wafers in the case of the present invention is to deal with a problem other than the detection of the etching end point. According to the present invention, it can be seen that the wet cleaning cycle is two to three times that of the prior art.

Table 3 shows the wavelengths of light that can be used as monitor light for detecting an etching end point together with active species when an Al-based metal layer such as an Al alloy layer is etched by plasma of a chlorine-based gas. is there.

[0028]

[Table 3] Used as a monitor light for etching end point detection when etching a TiN-based conductive layer such as a TiN layer with a chlorine-based gas plasma or when etching a stack of an Al-based metal layer and a TiN-based conductive layer with a chlorine-based gas plasma Table 4 below shows possible light wavelengths together with active species.

[0029]

[Table 4] The present invention is not limited to the above embodiment, but can be implemented in various modified forms. For example,
The following changes are possible:

(1) Although the AlCu alloy layer is shown as the Al alloy layer, an AlSiCu alloy layer or the like can be used. Further, the Al-based metal layer is not limited to the Al alloy layer, and an Al layer can also be used.

(2) The TiN-based conductive layer is not limited to the TiN layer, and a TiON layer can be used.

[0032]

As described above, according to the present invention, Al
When etching a metal-based layer, a TiN-based conductive layer, or a stack of these layers with a chlorine-based gas plasma, the wavelength is 396.
Since the emission of the active species longer than 2 nm is monitored and the end point of the etching is detected based on the change in the emission intensity, it is possible to detect the end point which is hardly affected by the contamination by the reaction product. Therefore, the frequency of wet cleaning performed in the etching reaction chamber is reduced, and an effect that downtime of the plasma etching apparatus can be reduced is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a plasma etching apparatus and an emission analysis system used for carrying out the present invention.

FIG. 2 is a cross-sectional view of a substrate showing a wiring material layer forming step in a wiring forming process according to a first embodiment of the present invention;

FIG. 3 is a substrate cross-sectional view showing a resist layer forming step following the step of FIG. 2;

FIG. 4 is a cross-sectional view of a substrate showing a plasma etching step following the step of FIG. 3;

FIG. 5 is a waveform chart showing a change in luminescence intensity recorded by the luminescence analysis system.

[Explanation of symbols]

10: plasma etching apparatus, 26: emission analysis system, 44a, 44c: TiN layer, 44b: AlCu alloy layer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G043 AA03 BA01 BA03 CA07 DA01 EA08 GA08 GB21 HA01 JA01 KA05 LA01 4K057 DA14 DB05 DD01 DE04 DE20 DG13 DG15 DJ02 5F004 CA02 CA03 CB02 CB15 DA04 DA11 DA16 DA25 DB08 DB09 DB12 EB02

Claims (3)

[Claims] 1. The method according to claim 1, wherein when the Al-based metal layer, the TiN-based conductive layer, or a stack of these layers is plasma-etched using a chlorine-based gas, the emission of active species is monitored, and the etching end point is determined based on a change in the emission intensity. A method of detecting an etching end point, wherein light having a wavelength longer than 396.2 nm is monitored as emission of the active species. 2. The method of detecting an etching end point according to claim 1, wherein, when plasma-etching the Al-based metal layer, emission of chlorine as the emission of the active species is monitored. 3. The etching according to claim 1, wherein at least one of chlorine and nitrogen is monitored as the emission of the active species when the TiN-based conductive layer or the stack is subjected to plasma etching. Endpoint detection method.