JPS62190728A - Method and apparatus for monitoring etching end point - Google Patents

Abstract

PURPOSE:To eliminate the influence of contamination of a substance to be etched by introducing an infrared light of a predetermined wavelength to the surface of a semiconductor substrate of the side not formed with a thin metal film of the surface of the substrate, measuring the intensity of the light reflected on the thin film through the substrate of the infrared light, and obtaining the etching end point by the intensity of the reflected light to readily position a detector, thereby improving S/N ratio. CONSTITUTION:The infrared light of 1.3mum of wavelength modulated by a sinusoidal wave of 1kHz from an infrared light emitting unit 5 is passed through a half mirror 4 to an optical fiber 1, and emitted to a silicon substrate 10 formed with the thin metal film as parallel beam via a rod lens 3. Part of the infrared light of 1.3mum of wavelength is reflected on the back surface of the substrate 10, but is passed through the Si, reflected on the metal film surface, again through the lens 3, and returned to the optical fiber 1. The returned infrared light is reflected on the half mirror 4, and detected by an infrared light detector 6. When the metal film is etched and removed by the plasma, the reflected light is erased from the metal film, thereby notifying the etching end point.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for monitoring the etching end point during the etching process of metal thin films, which is essential in the manufacturing process of various devices.

[Conventional technology]

Accurately knowing the end point of metal thin film etching during etching, which is essential in the manufacturing process of various devices, is
It is extremely important to obtain fine patterns with high precision.
Several proposals have been made so far. Among them, practical methods and means are shown in Table 1.

Table 1 Etching end point detection methods and means Optical methods include a method that relies on human senses by observing with the human eye through the window of the vacuum chamber during etching, and a method that relies on the human senses by observing the end point of the vacuum chamber during etching, and a method that uses laser light to etch through the window of the vacuum chamber. There is a method in which a surface is irradiated with light and a change in reflected light is detected, or a method in which an ellipsometer is used to detect a change in refractive index.

The method using laser light enters the light from outside the window of the vacuum chamber and detects from outside the window, but it has the disadvantage that the detection ability decreases due to the etched material adhering to the window. Was.

Furthermore, since the detection is performed at a position far from the sample, there remain problems with the alignment of the detection unit and the signal-to-noise ratio.

The spectroscopic analysis method and the gas analysis method are both methods in which an etched gaseous substance is detected by spectroscopy or gas analysis, and the end point of etching is defined as the point in time when the etched substance is no longer detected.

Similar to the above-mentioned optical method, detection is performed from outside the window of the vacuum chamber, so the detection ability is degraded due to deposits on the window, and even after etching is completed, the etched material remains Since it remains in the vacuum chamber for a while, it has the disadvantage that it is detected later than the actual end point of etching.

[Problem that the invention seeks to solve]

Therefore, the purpose of the present invention is to solve the following problems: the detection ability deteriorates due to contamination of the vacuum chamber window with etching deposits, it is difficult to align the detection part due to detection at a position far from the sample, and a good signal-to-noise ratio is achieved. An object of the present invention is to provide a method and device for monitoring the etching end point, which solves the drawbacks of not being able to remove the etching end point.

[Means for solving problems]

In order to achieve such an object, in the present invention, an optical fiber is introduced into a vacuum chamber, and installed in an electrode plate to which a high voltage for generating plasma is applied, so that the metal thin film to be etched is Si from the back side of the Si substrate being formed
Infrared light of 1.2 μm or more is irradiated, and the end point of etching is monitored using reflection from the metal thin film surface or the ratio of transmitted light to reflected light.

That is, in the first embodiment of the present invention, when monitoring the etching end point when etching a metal thin film formed on a semiconductor substrate surface, the semiconductor substrate surface on the side of the semiconductor substrate surface where the metal thin film is not formed is monitored. To, wavelength 1.
Infrared light of 2 μm or more and 2 μm or less is incident, the intensity of the infrared light that is transmitted through the semiconductor substrate and reflected on the metal thin film surface is measured, and the etching end point is determined from the intensity of the reflected light. shall be.

In a second embodiment of the present invention, when monitoring the etching end point when etching a metal thin film formed on the surface of a semiconductor substrate, a method for monitoring the end point of etching when etching a metal thin film formed on the surface of a semiconductor substrate is provided. Infrared light with a wavelength of 1.2 μm or more and 2 μm or less is incident, and the intensity of the light that has passed through the semiconductor substrate and reflected on the metal thin film surface and the light that has passed through the metal thin film is measured. It is characterized by comparing the intensity of light reflected from the substrate and the intensity of light transmitted through the semiconductor substrate.

A third embodiment of the present invention includes a means for emitting infrared light, a half mirror for transmitting the emitted infrared light, a vacuum chamber for etching a semiconductor substrate using plasma, and a device disposed in the vacuum chamber. a lower electrode having a through hole and on which a semiconductor substrate is placed; an upper electrode disposed in a vacuum chamber to face the lower electrode; and a half mirror that is fitted into the through hole of the lower electrode. The present invention is characterized by comprising a first optical fiber that guides transmitted light from the semiconductor substrate to the semiconductor substrate, and a light receiving means that receives reflected light from the metal thin film formed on the semiconductor substrate from the optical waveguide means through the half mirror.

A fourth aspect of the present invention provides a means for emitting infrared light, a half mirror for transmitting the emitted infrared light, a vacuum chamber for etching a semiconductor substrate using plasma, and a device disposed in the vacuum chamber. a lower electrode having a through hole and on which a semiconductor substrate is placed; an upper electrode disposed in a vacuum chamber to face the lower electrode and having a through hole facing the through hole of the lower electrode; , is fitted into the through hole of the lower electrode, forming a half mirror.
a first light-receiving means for receiving reflected light from a metal thin film formed on the semiconductor substrate from the first wave-guiding means via a half mirror; a second optical waveguide that is fitted into the through hole and receives the transmitted light from the metal thin film; a second light receiver that receives the light from the second optical waveguide; and a reflected light output from the first light receiver; It is characterized by comprising means for comparing the transmitted light output from the second light receiving means and determining the etching end point from the comparison output.

[For production]

In the present invention, light is incident from a very close position in contact with the back surface of the Si substrate, and the reflected light is detected, so alignment of the detection part is easy, a good signal-to-noise ratio can be obtained, and etching is avoided. Not affected by contamination of substances.

〔Example〕

Embodiments of the present invention will be described in detail and specifically below based on the drawings.

Embodiment 1 FIG. 1 is a diagram illustrating a first embodiment of the present invention,
Here, 1 is an optical fiber, 2 is an optical fiber vacuum introduction terminal, 3 is a rod lens, 4 is a half mirror, 15 is an infrared emitter, 6 is an infrared light detector, 7 is a window of the vacuum chamber, and 8 is an upper part. Electrode, 9 is a vacuum chamber, 10 is a Si substrate, 11 is a lower electrode, 12
is an RF power source for plasma generation. The optical fiber 1 is led from the half mirror 4 through the terminal 2 into the vacuum chamber 9, and further into the through hole formed in the lower electrode 11. A rod lens 3 is inserted into this hole so that when the silicon substrate IO is placed on the lower electrode 11, the tip of the rod lens comes into contact with the lower surface of the substrate.

To operate this device, an infrared emitter 5 to I KHz
Infrared light with a wavelength of 1.3 μm modulated into a sine wave is transmitted through a half mirror 4, introduced into an optical fiber 1, and is irradiated as parallel light by a rod lens 3 onto a silicon substrate 10 on which a metal thin film is formed. .

A part of the infrared light with a wavelength of 1.3 μm is reflected by the back surface of the silicon substrate 1O, but part of it passes through the inside of the Si, is reflected by the metal thin film surface, passes through the rod lens 3 again, and is connected to the optical fiber 1.
Return to The infrared light returning through the optical fiber 1 is reflected by the half mirror 4 and detected by the infrared light detector 6.

When the metal thin film is etched and removed by plasma, the reflected light from the metal thin film disappears, making it possible to know the end point of the etching.

FIG. 2 shows the measurement results using the apparatus of this example. Second
As can be seen from the figure, the end point of etching can be accurately determined by comparing with the results of spectroscopic analysis.

Embodiment 2 FIG. 3 is a diagram illustrating a second embodiment of the present invention,
1 (a) and 1 (b) are optical fibers, 3 (a)
, 3 (b) is a rod lens, 6' (a),
6(b) is an infrared light detector, and 13 is an arithmetic unit. Rod lenses 3(a) and 3(b) are attached to electrodes 10 and 8, respectively, and optical fibers l(a)
and 1(b). The light from optical fibers 1(a) and 1(b) is detected by infrared photodetectors 6(a) and 6(b).
) respectively.

In this example, as in Example 1, infrared light with a wavelength of 1.3 μm is introduced into the vacuum chamber 9 using the optical fiber 1 (a), and irradiated from the back surface of the St substrate 10 on which the metal thin film is formed. Then, the reflected light is detected by an infrared light detector 6(a). Separately, a through hole is provided in the upper electrode 8, a rod lens 3(b) and an optical fiber 1(b) are arranged from below in alignment with the optical axis of the transmitted light, and the metal thin film is removed by etching. The transmitted light generated when the light is transmitted is received and propagated to the detector 6(b). The reflected light output and the transmitted light output detected by the detectors 6(a) and 6(b) as described above are manually inputted to the arithmetic unit 13, where the transmitted light intensity is divided by the reflected light intensity. Find a clear end point of etching.

The measurement results of the etching end point obtained in this example were
As shown in the figure. As can be seen from FIG. 4, according to this example, the etching end point output can be clearly obtained.

In addition, in the above-mentioned embodiment, a silicon substrate was taken as an example, but the present invention is not limited to a silicon substrate.
It can be effectively applied to any semiconductor substrate to which a metal thin film is attached. In that case, it goes without saying that the wavelength of the infrared light should be set to a value that allows it to pass through such a semiconductor substrate, for example, 1.2 to 2 μm.

Furthermore, although an optical fiber is used as a means for guiding light on the upper side, the optical waveguide means is not limited to this, and an optical system such as a lens, an optical waveguide, etc. can be used in combination.

〔Effect of the invention〕

As explained above, according to the present invention, an optical fiber is introduced into a vacuum chamber, light is introduced from the back side of the substrate surface on which the metal thin film to be etched is formed, and light is emitted from the reflective surface of the metal thin film. Since it is mainly detected, there are advantages that alignment of the detection part is easy, the signal-to-noise ratio is good, and it is not affected by contamination of the material to be etched.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention, FIG. 2 is a characteristic diagram showing the measurement results in the first example; FIG. 3 is a configuration diagram showing a second embodiment of the present invention, FIG. 4 is a characteristic diagram showing the measurement results of the second example. 1...optical fiber, 2...Optical fiber vacuum introduction terminal, 3...rod lens, 4...half mirror 1 5... Infrared emitter, 6...Infrared detector, 7...vacuum chamber window, 8... Upper electrode, 9...vacuum chamber, 10...St substrate, 11...lower electrode, 12...RF power supply, 13... Arithmetic unit. ” 11 Chestnuts and talent chart Figure 2 The most powerful aspect of the present invention゛It＞＋＊）N diagram Figure 3

Claims (1)

[Claims] 1) In monitoring the etching end point when etching a metal thin film formed on a semiconductor substrate surface, the semiconductor substrate surface on the side of the semiconductor substrate surface where the metal thin film is not formed. To, wavelength 1.2 μm or more 2
Infrared light of μm or less is incident, and the intensity of the light transmitted through the semiconductor substrate and reflected by the metal thin film surface is measured, and the etching end point is determined from the intensity of the reflected light. An etching end point monitoring method featuring: 2) In monitoring the etching end point when etching a metal thin film formed on the surface of a semiconductor substrate, a wavelength of 1.2 μm is applied to the surface of the semiconductor substrate on the side of the semiconductor substrate where the metal thin film is not formed. Above 2
Infrared light of μm or less is incident, and among the infrared light, the intensity of the light transmitted through the semiconductor substrate and reflected on the metal thin film surface and the light transmitted through the metal thin film are measured, and the intensity of the light transmitted through the metal thin film is measured. An etching end point monitoring method characterized by comparing the intensity of light reflected from a substrate and the intensity of light transmitted through the semiconductor substrate. 3) a means for emitting infrared light; a half mirror for transmitting the emitted infrared light; a vacuum chamber for etching a semiconductor substrate using plasma; a lower electrode on which the semiconductor substrate is placed; an upper electrode disposed in the vacuum chamber to face the lower electrode; and a light receiving means for receiving reflected light from a metal thin film formed on the semiconductor substrate from the optical waveguide through the half mirror. Features: Etching end point monitoring device. 4) A means for emitting infrared light; a half mirror for transmitting the emitted infrared light; a vacuum chamber for etching a semiconductor substrate using plasma; a lower electrode on which the semiconductor substrate is placed; an upper electrode disposed in the vacuum chamber to face the lower electrode and having a through hole facing the through hole of the lower electrode; a first optical waveguide that is fitted into a through hole of the lower electrode and guides the transmitted light from the half mirror to the semiconductor substrate; and a first optical waveguide that guides the reflected light from the metal thin film formed on the semiconductor substrate. a first light-receiving means that receives light from the upper electrode through the half mirror; a second optical waveguide that is fitted into the through hole of the upper electrode and receives the light transmitted from the metal thin film; and a second optical waveguide that receives light from the second optical waveguide. and means for comparing the reflected light output from the first light receiving means and the transmitted light output from the second light receiving means and determining the etching end point from the comparative output. An etching end point monitor device featuring: