JPH098003A - Method of detecting end point in dry etching - Google Patents

Abstract

PURPOSE: To manufacture semiconductor devices reliably and stably by preventing false detection of the end point of dry etching. CONSTITUTION: In the dry etching of a work substrate 11, the angle of elevation of an optical fiber 17 is determined so that the extension of the optical axis of the optical fiber 17 meets and ECR point 15. Light emission generated in an etching device is detected using the optical fiber 17 and the end point of the etching is detected by the detection output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an end point in dry etching, and in particular, in a dry etching process used in a semiconductor device manufacturing process, etching is performed by observing emission intensity using an optical fiber. The present invention relates to a method of detecting an end point.

[0002]

2. Description of the Related Art Conventionally, as the degree of integration of semiconductor devices has improved, dry etching has been used instead of wet etching as means for forming a wiring pattern. In the above, the end point of etching was detected by detecting the intensity of light emission or the like accompanying the etching reaction.

For example, when etching a metal wiring material such as Al for patterning, an increase or decrease in the intensity of the emission spectrum of the reaction product due to the etching reaction is detected through a spectroscope, and the increase is turned to the decrease. The point settled down to a certain low level is detected as the etching end point, and
A moderate amount of additional etching was performed to remove the etching residue.

This situation will be described with reference to FIG. Referring to FIG. 5, first, an Al layer to be a wiring layer is deposited via an interlayer insulating film, and a substrate 11 to be processed made of a silicon substrate on which a photoresist having a predetermined pattern is provided is placed on an ECR (electron cyclotron resonance) type plasma. The sample is placed on the sample table 12 arranged inside the reaction chamber 2 of the etching apparatus.

On the other hand, an etching gas 3 made of CCl ₄ is introduced into the plasma chamber 1 of the ECR type plasma etching apparatus through a gas supply port 4, and the frequency is higher than that of an RF power source (13.56 MHz) connected to the sample stage 12. Electric power is supplied to generate plasma 14, and an electromagnet is used to generate 875
The Gauss magnetic field is applied to rotate the electrons in the plasma 14 at the cyclotron frequency of 2.45 GHz.

At the same time, by supplying a microwave 5 of 2.45 GHz which resonates with the cyclotron frequency from the microwave waveguide 6 through the quartz window 7, the electrons are accelerated to accelerate the plasma reaction and the plasma generated. 14
Is introduced into the reaction chamber 2 and the Al layer is patterned to form an Al wiring pattern. In the figure, reference numerals 9 and 10 respectively represent exhaust gas and exhaust port containing reaction products.

In this etching, 261.6n
Since a light emission having a peak at m occurs, this light emission is detected by the optical fiber 17 installed horizontally through the observation window 19, and the detection output is dispersed by the spectroscope 18 to 261.
The etching end point was judged by taking out only the output of 6 nm and monitoring the increase and decrease of this output.

[0008]

SUMMARY OF THE INVENTION However, ECR
Type inner wall of the reaction chamber 2 of the plasma etching apparatus, in particular,
When reaction products or the like adhere to the surface of the peep window 19,
Alternatively, when the amount of etching is small, the observed emission intensity decreases, so when the emission is detected with the optical fiber 17 installed in parallel, the determination of the etching end point becomes inaccurate and excessive. Etching often occurred.

Due to this excessive etching, residues due to under-etching and thinning of the wiring pattern due to over-etching were generated, and in extreme cases, wire breakage was also caused, so that there was a problem in reproducibility and manufacturing yield. .

Therefore, it is an object of the present invention to eliminate a detection abnormality in detecting an etching end point and to manufacture a reliable and stable semiconductor device.

[0011]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and means for solving the problems in the present invention will be described with reference to FIG. See FIG. 1 (1) In the present invention, in the end point detection method when dry-etching the substrate 11, the extension line of the optical axis of the optical fiber 17 is included in the ECR point (electron cyclotron resonance point) 15. Elevation angle θ of optical fiber 17
Is set and the light emission generated in the etching apparatus is detected by the optical fiber 17.

(2) Further, the present invention is characterized in that, in the above (1), the elevation angle θ of the optical fiber 17 is an angle at which the detected intensity of the light emission generated in the etching apparatus becomes maximum.

(3) Further, the present invention is characterized in that in the above (1), the optical fiber 17 is installed through the detection window 16 provided in the etching apparatus.

(4) Further, the present invention is characterized in that, in the above (1), the optical fiber 17 is installed inside the etching apparatus.

(5) Further, the present invention is characterized in that in any one of the above (1) to (4), the elevation angle θ of the optical fiber 17 is automatically set.

(6) Further, according to the present invention, in any one of the above (1) to (5), a plurality of emission wavelengths of the emitted light generated in the etching apparatus are detected, and the detection output of each emission wavelength is detected. The feature is that the etching end point is detected by the change.

[0017]

Since the emission intensity in the ECR type plasma etching apparatus becomes maximum near the ECR point 15 inside the plasma chamber 1, the extension line of the optical axis of the optical fiber 17 is ECR.
The elevation angle θ of the optical fiber 17 is included in the point 15.
By setting, it is possible to obtain a sufficient detection output even when the emission intensity is low, whereby the etching end point can be detected with high accuracy.

Further, by setting the elevation angle θ of the optical fiber 17 to an angle at which the detection intensity of the light emission generated in the etching apparatus is maximized, the etching end point can be detected with the highest detection accuracy.

Further, the optical fiber 17 is installed through the detection window 16 made of glass thinner than the glass used for the peep window provided in the etching apparatus, so that the etching end point can be detected with high accuracy. be able to.

By installing the optical fiber 17 inside the etching apparatus, it is possible to improve the heating efficiency as compared with the case where the optical fiber 17 is installed through the detection window 16, and the optical fiber 17 is used for the detection window 16. Since synthetic quartz having a higher density than that of the window glass is used, the reaction products are less attached and the detection output is less deteriorated.

By automatically setting the elevation angle θ of the optical fiber 17, the throughput of the dry etching process can be greatly improved.

Further, by detecting a plurality of emission wavelengths of the emitted light generated in the etching apparatus and detecting the etching end point by the change of the ratio or difference of the detection output of each emission wavelength, it is possible to use a single wavelength. Can also improve the detection accuracy.

[0023]

FIG. 2 is an explanatory diagram of an embodiment of the present invention. An embodiment of the present invention will be described with reference to FIG. The ECR type plasma etching apparatus used for carrying out the present invention is substantially the same as the conventional ECR type plasma etching apparatus, except that a detection window 16 is provided at a position facing an ECR point 15 described later, and The thickness of the quartz glass for windows is about 5 mm, which is thinner than the thickness (12 mm) of the quartz glass used for the peep windows provided in other portions.

The ECR type plasma etching apparatus is roughly divided into an inner diameter R ₁ = 200 mm and a height h.
₁ = 200 mm cylindrical plasma chamber 1 and inner diameter R ₂ = 4
It is composed of a cylindrical reaction chamber 2 having a height of 30 mm and a height of h ₂ = 450 mm.

First, an AlCuTi layer containing Al as a main component, which will be a wiring layer, is deposited through an interlayer insulating film such as a SiO ₂ film, and a silicon substrate on which a photoresist having a predetermined pattern is provided is processed. The substrate 11 is placed on the sample table 12 arranged inside the reaction chamber 2 of the ECR type plasma etching apparatus.

On the other hand, in the plasma chamber 1 of the ECR type plasma etching apparatus, 50 to 150 are provided through the gas supply port 4.
sccm, preferably 87 sccm of Cl ₂ and 30-10
0 sccm, preferably 58 sccm of etching gas 3 made of BCl ₃ was introduced to adjust the pressure in the plasma chamber 1 to 3.0 × 10 ^{−3 to} 6.0 × 10 ⁻³ Torr, preferably 4.
5 × 10 ⁻³ Torr and set the temperature of the sample table 12 to 2
The sample stage 12 under the condition of 0 to 50 ° C., preferably 35 ° C.
7 if the RF power source connected to is 13.56MHz
0 to 130 W, preferably 100 W, and 400 kHz
In the case of, the high-frequency power of 25 to 45 W, preferably 35 W is supplied to generate the plasma 14, and a magnetic field of 875 Gauss is applied by the electromagnet to rotate the electrons in the plasma 14 at the cyclotron frequency of 2.45 GHz. Let

At the same time, 700 to 1 at a frequency of 2.45 GHz which resonates with the cyclotron frequency through the quartz window 7.
By supplying microwave 5 of 300 W, preferably 1000 W from the microwave waveguide 6, the plasma 14
The electrons inside are accelerated to accelerate the plasma reaction, the generated plasma 14 is introduced into the reaction chamber 2, and the AlCuTi layer is patterned at an etching rate of 700 nm / min to form an AlCuTi wiring pattern. The exhaust gas 9 composed of reaction products and unreacted etching gas is exhausted from the reaction chamber 2 through an exhaust port 10 provided in the reaction chamber 2.

At the time of this etching, the plasma chamber 1
In the inside, an ECR point 15 with strong emission intensity is formed, and in the case of etching the AlCuTi layer, Al atoms separated by the etching are excited in the plasma chamber 1 and a strong emission peak due to Al at 396 nm is seen. The optical fiber 17 is set through the detection window 16 so as to face the ECR point 15, and the time when the detection output is lowered and stabilized is detected as the etching end point. In addition, "to face the ECR point 15" means the optical fiber 1
The extension of the optical axis 7 is included in the ECR point 15.

The detection output of the optical fiber 17 is used as the spectroscope 1
FIG. 3 shows the result of measuring the intensity for each wavelength by 8 and in this measurement, when the frequency of the RF power supply is set to 400 kHz, the time when the emission intensity of 396 nm becomes maximum, that is, the AlCuTi layer. When the thickness is 700 nm, the elevation angle θ of the optical fiber 17 is 0.0 °, 12.8 °, 27.8 ° 50 to 60 seconds after the start of etching.
The setting was performed at 30.0 °, 34.5 °, and 44.4 °.

See FIG. 3. As is apparent from FIG. 3, at the wavelength of 396 nm, A
The emission peak due to 1 is observed, and in other wavelength regions, the emission wavelength peak due to other components Cu and Ti constituting the wiring layer, the emission wavelength peak due to the excited etching gas component, and The emission wavelength peaks caused by the reaction products of the constituent elements of the wiring layer and the etching gas are observed, and the intensity of these emission peaks has the same tendency of elevation angle dependence.

In this case, the emission peak at 396 nm due to Al is not so high in intensity as the other emission peaks, but the emission peak is relatively isolated, so that it is suitable as a wavelength used for measurement. is there.

FIG. 4 shows the elevation angle dependence of the optical fiber 17 of the intensity of the emission peak at 396 nm.
FIG. 4A shows the elevation angle dependence of the relative intensity when the RF power source is set to 13.56 MHz, and FIG.
4 shows the elevation angle dependence of relative intensity when 0 kHz (corresponding to FIG. 3).

See FIG. 4A. When the RF power supply is set to 13.56 MHz, the elevation angle θ =
The maximum intensity is obtained at 23.6 °, and θ = 0 °, and the detection output of 23.5 times that of the conventional example in which the optical fiber 17 is installed horizontally is obtained.

When the elevation angle θ becomes larger than 23.5 °, the detection output sharply drops and becomes smaller at θ = 30 ° than the detection output at θ = 0 °. The shape and structure of the plasma etching apparatus, in particular, the position of the detection window 16, also has an influence, that is, if the elevation angle θ of the optical fiber 17 becomes too large, the reaction chamber 2
Is blocked by each wall between the plasma chamber 1 and the optical fiber 17
Will not reach the ECR point 15.

See FIG. 4B. When the RF power source is set to 400 kHz, the elevation angle θ
= 30.0 ° gives the maximum intensity, and θ = 0 ° gives 3
A 7.5 times higher detection output is obtained. In this case, the emission intensity is about 4 when the RF power source is 13.56 MHz.
0%.

Also in this case, the elevation angle θ is 30.0 °.
When it becomes larger, the detection output sharply drops, and θ = 34.
At 5 °, the detection output is about θ = 0 °, but this is also due to the influence of the shape and structure of the ECR type plasma etching apparatus used.

Therefore, by setting the elevation angle θ of the optical fiber 17 to an angle at which the maximum intensity can be obtained, a detection output approximately 20 to 40 times higher than that in the case where it is horizontally set as in the conventional case can be obtained. The detection accuracy in detecting the end point is improved, and the detection abnormality can be significantly reduced.

The elevation angle θ is optimally the angle at which the maximum intensity is obtained, but it is not necessarily the angle at which the maximum intensity is obtained, as long as it is an angle at which 50% to 100% of the maximum intensity is obtained. good. Further, since the elevation angle θ at which the maximum intensity is obtained depends on the shape / structure of the ECR type plasma etching apparatus used and the installation position of the optical fiber 17, the numerical value in the embodiment has no absolute meaning.

Further, by reducing the thickness of the quartz glass of the detection window 16, the attenuation due to the absorption of light when passing through the quartz glass is reduced and the detection accuracy is improved. Incidentally, when light emission was detected through a general observation window having a quartz glass thickness of 12 mm, no significant improvement in detection intensity was observed even if the elevation angle of the optical fiber 17 was changed.

Although the optical fiber 17 is installed outside the ECR type plasma etching apparatus in this embodiment, it may be installed inside the reaction chamber 2 using a metal member. Since the detection window 16 is not required, the heating efficiency of the inside of the reaction chamber 2 is improved, and since the optical fiber 17 is made of synthetic quartz having a higher density than that of the window member, it reacts with the optical fiber 17. The sex product does not adhere and become dirty. However, since the metal member used to install the optical fiber 17 may disturb the plasma 14, it is necessary to pay attention to the installation place.

Although the elevation angle θ is manually set in the above embodiment, it may be set automatically to improve the throughput. In this case, the emission intensity is measured while automatically changing the elevation angle θ of the optical fiber 17 by using the motor, and the emission intensity is at least 1.5 times or more that in the case of θ = 0 °, and the measurement is performed. The point where the intensity changes from the increasing tendency to the decreasing tendency is detected, and the optical fiber 17 is set to the point where the measured intensity changes from the increasing tendency to the decreasing tendency or the elevation angle θ near the point.

Further, in the above-mentioned embodiment, the end point is detected by utilizing only the light emission of Al separated by the etching reaction, but the detection method is not limited to such a detection method, and the light emission due to the etching reaction is performed. Peak (eg,
In the etching of Si ₃ N ₄ by CF ₄ , the emission peak due to N is 749 nm), and the emission peak due to the etching gas itself (also, in the etching of Si ₃ N ₄ by CF ₄ is 686 nm due to F), etc. Alternatively, the end point may be detected by measuring a plurality of emission peaks.

In this case, the intensity of the emission peak due to the etching reaction decreases as the etching approaches the end point, and the intensity of the emission peak due to the etching gas itself sharply increases. By monitoring the ratio or the difference between the two, the detection accuracy is higher than when only one emission peak is monitored.

Further, in the above embodiment, a downstream type (flare type) ECR type plasma etching apparatus is used as the ECR type plasma etching apparatus, but the present invention is a magnetic field microwave type (plasma inside) E.
It also applies to a CR type plasma etching apparatus.

Further, the present invention is not limited to the dry etching process of AlCuTi using Cl ₂ and BCl ₃ and can be applied to the patterning process of other wiring materials or insulating films. In that case, it is desirable to select a relatively isolated emission peak with high emission intensity as the detection wavelength.

[0046]

According to the present invention, when the etching end point in the dry etching step is detected, the optical fiber is used and the elevation angle θ of the optical fiber is set to an angle at which the strength of a predetermined value or more can be obtained. Since the detection output of a certain value or more can be secured, the end point detection abnormality can be eliminated, whereby the semiconductor device can be manufactured with high reproducibility and high throughput.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is an explanatory diagram of an example of the present invention.

FIG. 3 is an explanatory diagram of optical fiber elevation angle dependence of intensity of each emission wavelength.

FIG. 4 is an explanatory diagram of optical fiber elevation angle dependence of emission intensity in the present invention.

FIG. 5 is an explanatory diagram of a conventional end point detection method in dry etching.

[Explanation of symbols]

 1 plasma chamber 2 reaction chamber 3 etching gas 4 gas supply port 5 microwave 6 microwave waveguide 7 quartz window 8 electromagnet 9 exhaust gas 10 exhaust port 11 processed substrate 12 sample stage 13 RF power supply 14 plasma 15 ECR point 16 for detection Window 17 optical fiber 18 spectroscope 19 peep window

Claims (6)

[Claims] 1. An elevation angle of the optical fiber is set so that an extension line of an optical axis of the optical fiber is included in an electron cyclotron resonance point, and light emission generated in an etching apparatus is detected by the optical fiber. End point detection method in dry etching. 2. The method for detecting an end point in dry etching according to claim 1, wherein the elevation angle of the optical fiber is an angle at which the detected intensity of light emission generated in the etching apparatus is maximized. 3. The method for detecting an end point in dry etching according to claim 1, wherein the optical fiber is installed through a detection window provided in the etching apparatus. 4. The method for detecting an end point in dry etching according to claim 1, wherein the optical fiber is installed inside the etching apparatus. 5. The end point detection method in dry etching according to claim 1, wherein the elevation angle of the optical fiber is automatically set. 6. The etching end point is detected by detecting a plurality of emission wavelengths of emitted light generated in the etching apparatus and detecting an etching end point based on a change in detection output of each emission wavelength. The method for detecting an end point in dry etching according to any one of items.