JPH04206927A - Etching apparatus - Google Patents

Abstract

PURPOSE:To detect the end point of etching of a film formed on the surface of an Si wafer easily by locating a detector which detects infrared rays of the specified wave length at the rear surface side of the Si wafer for detecting the end point of etching of the wafer. CONSTITUTION:A detector 7 which detects infrared rays having the wave length of 1000nm or above at the rear surface side of an Si wafer 2 to detect the end point of etching of the said wafer. Before an aluminum film 13 of the wafer 2 is etched, light in a plasma is reflected on the aluminum film 13 and so the light is not detected by the detector 7. After the etching of the aluminum film 13 is finished, however, the light in a plasma passes the wafer 2 through an opening 14a of a mask 14 to be detected by the detector 7. The infrared detector 7 being connected to the rear surface of the Si wafer 2 through an optical fiber 6, the light in a plasma is cut off by the wafer before etching but it passes through the wafer after etching. Therefore, the end point of etching of the aluminum film 13 of the wafer 2 can be found accurately and easily.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an etching device, and in particular, to investigating the etching end point of a film such as a conductive abrasive or resist formed on the main surface of a Si wafer. The present invention relates to an etching device with functions.

(Prior Art) As is well known, in a reactive dry etching apparatus, for example, plasma is emitted when etching an Ag film on a wafer surface. Therefore, in such an etching apparatus, the end point of etching is detected by detecting a change in the amount of light emitted at a specific wavelength in the plasma.

However, in the conventional etching apparatus, the mode of plasma emission changes depending on the type of etching gas, the abrasive material to be etched, and the like. Therefore, there is a problem in that it is necessary to examine the characteristics of each mode and to provide a corresponding detector.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and aims to provide an etching apparatus that can easily detect the end point of etching of a film formed on the surface of a St wafer. do.

[Means for Solving the Problems] The present invention provides an etching apparatus for etching a film formed on a Si wafer, in which a detector for detecting infrared rays with a wavelength of 11,000 nm or more is disposed on the back side of the Si wafer, and This is an etching apparatus characterized by detecting the end point of etching a wafer.

In the present invention, the coating on the surface of the Si wafer is 8Ω
Alternatively, a film made of a wiring material such as Si-containing Aρ, a resist film, etc. may be used.

In the present invention, the reason why the wavelength of the detector is set to 11,000 nm or more is that if the wavelength is less than ], OOOn m, the infrared rays will not pass through the Si wafer and the end point of etching of the film cannot be detected.

In the present invention, the means for detecting the end point of etching the film on the surface of the Sl wafer includes, for example: (1) If the etching apparatus uses plasma, a detector for detecting light emitted from the plasma is placed, for example, on the back side of the wafer; ■ Place the emitter on the front side of the wafer and place the detector on the back side of the wafer, and find the end point based on the degree of transmission of the light emitted from the emitter through the wafer.■ Place the emitter and detector on the back side of the wafer. For example, the end point may be determined by the degree of reflection η·j of the light from the back surface of the wafer.

(Function) In the present invention, an infrared light detector is provided on the back side of the 81 wafer, and a projector is provided on the front or back side of the wafer as necessary, so that the infrared light is transmitted through the wafer and reflected. The intensity of light is detected by a detector using
This makes it possible to find the time when the intensity of light changes significantly, and to detect the end point of etching more easily and reliably than in the past.

(Example) An etching apparatus according to an example of the present invention will be described below.

FIG. 1 is an explanatory diagram of a dry etching apparatus according to the present invention. 1 in the figure indicates a vacuum container.

Inside this vacuum container 1, an S1 wafer 2 is placed on a mounting table 3 which also serves as an electrode. The wafer 2 is placed on a silicon plate 1j with a thickness of 1000 as shown in FIG.
A thermal oxide film 12 of about A is formed, and an AΩ film (aluminum film) containing St with a thickness of about 8000 A is formed on this thermal oxide film 12.
13 is formed, and a mask 14 made of positive resist and having a thickness of 1.2 μm is further formed on this aluminum film 13. Here, the light transmittance of the aluminum film 13 is 10
% or less.

A gas introduction pipe 4 having a large number of gas introduction ports is arranged above the wafer 2 . A gas exhaust port 5 is attached to the side wall of the vacuum container 1. Said Ueno\2
An infrared detector 7 is connected to the back surface of the infrared detector 7 via an optical fiber 6 (see FIG. 4). An RF power source 9 is connected to the mounting table 3 via a matching box 8.

In addition, water for cooling is circulated through the mounting table 3.

In such an etching apparatus, before etching the aluminum film 13 of the wafer 2, the state is shown in FIG. 2, and in this state, the light in the plasma is reflected by the aluminum film 13 and is not detected by the detector 7. However, aluminum film 1
When etching 3 is completed (as shown in Figure 3), mask 1 is removed.
Light in the plasma passes through the wafer 2 through the opening 14 a of the wafer 4 and is detected by the detector 7 . FIG. 5 is a characteristic diagram showing the relationship between the intensity of light in plasma and time. From the figure, it can be seen that the light does not pass through the wafer until near time T, so the light intensity is 0, and at time T, the aluminum film is etched and the light intensity suddenly increases.

As described above, according to the etching apparatus according to the above embodiment, the infrared detector 7 is connected to the back surface of the Si wafer 2 via the optical fiber 6, and the light in the plasma is blocked by the wafer before etching. Since the latter part is configured to be transparent, the end point of etching of the aluminum film 13 of the wafer 2 can be accurately and easily determined.

In the above embodiment, the end point of etching is detected based on whether the light in the plasma passes through the wafer or not, but the present invention is not limited to this.

For example, as shown in FIG.
1, a detector 7 may be provided on the back side of the wafer 2, and the light from the light projector 21 may be detected by the detector 7. Alternatively, as shown in FIG. 7, a light projector 2I and a detector may be provided on the back side of the wafer 2, and a configuration may be used in which light from the light projector 21 is reflected on the back surface of the wafer.

In the latter case, the relationship between the intensity of the reflected light from the back surface of the wafer and time is as shown in the characteristic diagram shown in FIG. From the same figure,
Before etching the aluminum film, the light from the projector 21 does not pass through the wafer, so the intensity of the light is high (11). However, it can be seen that when the aluminum film is etched at time T, most of the light from the light projector 21 passes through the wafer 2, so that the intensity of the light decreases (I2). Therefore,
The end point of etching can be confirmed when the difference in light intensity is greatest.

In the above embodiment, a case was described in which the end point of etching of a Si-containing aluminum film formed on a wafer surface was determined, but the present invention is not limited to this. For example, the present invention can be similarly applied to finding the end point of etching a film made of other metal abrasives or a film such as resist.

In the above embodiment, a case has been described in which the detector detects one point on the back surface of the wafer, but the present invention is not limited to this, and the case may be such that the detector detects several points. By doing so, a more accurate end point within the wafer plane can be detected.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a highly reliable etching apparatus that can easily and reliably detect the end point of etching of a film formed on the surface of an St wafer.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a dry etching apparatus according to an embodiment of the present invention, and FIG. 2 is an illustration of Si before etching used in the same apparatus.
3 is a cross-sectional view of the Si wafer after etching, FIG. 4 is a partially enlarged explanatory view of FIG. 1, and FIG. FIGS. 6 and 7 are explanatory diagrams of etching apparatuses according to other embodiments of the present invention, and FIG.
FIG. 3 is a characteristic diagram showing the relationship between the intensity of light reflected from a wafer and time by the apparatus shown in the figure. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... Si wafer, 3... Mounting table, 4... Gas introduction pipe, 5... Gas exhaust port, 6...
- Optical fiber, 7... Infrared photodetector, 11... Silicon substrate, 13... Aluminum film, 14... Mask, 2
1... Floodlight. Applicant's agent Patent attorney Takehiko Suzue No. 6 Fig. 7

Claims (1)

[Claims] In an etching apparatus that etches a film formed on a Si wafer, a wavelength of 10 nm is etched on the back side of the Si wafer.
An etching apparatus characterized in that a detector for detecting infrared rays of 00 nm or more is arranged to detect the end point of etching of the wafer.