JPS62171127A - Method of detecting end point of etching - Google Patents

Abstract

PURPOSE:To detect the end point of etching with high sensitivity and accuracy, by utilizing a phenomenon that an amount of regulator reflection of unidirectional light applied onto the surface of a substance to be etched is varied by the height of a step of the surface of the substance to be etched. CONSTITUTION:Plasma is generated in an etching apparatus 3 and thereby a board to be processed is etched. In parallel with etching, a laser beam 5 of 633(nm) is applied to a desired region of a surface to be etched in the board to be processed, and regular reflection light 7 and plasma light are led into an optical filter 9 by a condenser 8. By this filter, only the desired regular reflection light 7 obtained from the laser beam 5 is separated, and a variation in the intensity thereof is detected by a light intensity detecting device 11. A light S reflected in the direction other than the direction of a desired reflection angle theta by the surface of a step (h) formed between a pattern 15 exposed on the surface by etching and a film 16 is not contained in the regulator reflection light 7, and the mount of light in the direction of the desired angle thetadecreases dependently on the step (h). Since the intensity of the regular reflection light detected from the point of time at which etchback is ended lowers sharply, the end of the etchback can be detected distinctly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an end point detection method used in an etching method.

[Background of the invention]

In etching used in the manufacturing process of semiconductor devices, try-
In etching, a method is widely used in which a change in the intensity of an etching product contained in plasma light generated during etching is used to detect the intensity of the plasma light. However, in this method, the plasma light contains light of various wavelengths, and it is difficult to perform complete spectroscopy.

When the area of the etching region is small, there is a problem that the detection sensitivity of the end point is not sufficient due to the small intensity change, and the detection value becomes uncertain due to the instability of the plasma. Similar problems arise in end point detection methods using mass spectrum analysis of etching waste gas.

In addition, there is an increasing need for flattening technology (hereinafter referred to as etch-back) for the surface of semiconductor devices, such as multilayer wiring technology, but there is also the problem that it is difficult to detect the end point of this etch-back using the above methods. .

This etchback end point detection method includes a method of detecting the difference in scattering intensity of incident light between a film such as an insulating material applied to the entire surface of the semiconductor device and a pattern film such as metal exposed from the film by etching. However, this method has a problem in that the materials that can be used for the coating and pattern are limited. There is also a method of detection based on changes in the intensity of diffracted light due to a pattern, but this method has the drawback that it requires a diffraction grating pattern of equal thickness and width to be present on the surface of the semiconductor device.

[Purpose of the invention]

In view of the above problems of the conventional method, the present invention provides a method and apparatus for detecting the end point of etching, which can detect the end point of etching with high sensitivity and accuracy, regardless of the type of object to be etched or the pattern of the pattern. The goal is to provide the following.

[Summary of the invention]

In the present invention, etching is performed while irradiating the surface of the object to be etched with unidirectional light, and among the light that is specularly reflected in the direction of a desired reflection angle equal to the incident angle of the dazzling light with respect to the plane of the object to be etched, the etching process is performed. The decrease in light reflected from the stepped surface on the etched surface in a direction other than the desired angle is:
This is a method and apparatus for detecting the end point of etching using the dependence on the step height.

[Embodiments of the invention]

Hereinafter, the present invention will be described in a manufacturing process of a multilayer wiring semiconductor device, etc., in which an aluminum layer (Afl
) using dry etching method,
The first example describes an example in which an electrode made of A2 is formed, an insulating film such as a resist material is applied to the entire surface of the device, and this is etched back to form a desired semiconductor device layer. A schematic diagram of the manufacturing apparatus in one embodiment shown in the figure, a partial partial view and a schematic diagram of a light reflecting surface of a semiconductor device to be etched (hereinafter referred to as a target plate) shown in FIG. 2, and a schematic diagram of a light reflecting surface shown in FIG. A specularly reflected light intensity profile at a desired reflection angle in one embodiment will be described in detail with reference to the drawings.

For example, the plasma etching apparatus used in the method of the present invention is a parallel plate type plasma etching apparatus 3 having a lower electrode 1 and an upper electrode 2 facing each other, as shown in FIG.
, helium for irradiating the target plate 4 placed on the lower electrode 1 with a laser beam 5 which is a high quality unidirectional light.
The neon (He-Ne) laser 6 is specularly reflected at an angle equal to the incident angle O with respect to the desired plane of the plate 4 to be processed. A condenser 8 that collects specularly reflected light 7 from the laser beam 5 and a part of the plasma light generated during etching at a desired angle θ.
, an optical filter for separating only the regularly reflected light 7 of the laser beam from the light introduced by the condenser 8, a photodiode 10 for converting the separated light 7 into an electrical signal, and measuring the intensity of the electrical signal. It has a photodetecting device 11 that performs

In FIG. 1, 12 represents a radio frequency (RF) power source, 13 represents a gas introduction pipe, and 14 represents an exhaust pipe.

In one embodiment of the apparatus of the present invention, a plate to be processed is used, in which an electrical insulating material or the like is coated on the surface of a semiconductor device layer on which an AQ pattern is formed as described above. Using a Ha-Ne laser having an oscillation wavelength of nml and an optical output of about 5 [mW],
3 [Use an optical filter that allows only light having a wavelength of nml to pass through.

Then, a gas introduction pipe is provided in the etching apparatus 3 shown in FIG. A high frequency of, for example, 13.56 MHz is applied between the electrodes using an RF power source to generate plasma between the upper electrode 2 and the lower electrode 1, thereby etching the substrate to be processed.

In parallel with the partial etching, a laser beam 5 of 633 [nml] generated by the He-Ne laser 6 is irradiated onto a desired area of the surface to be etched of the plate to be processed, and the incident angle with respect to the plane of the plate to be processed is adjusted. Specularly reflected light with a reflection angle equal to Only the desired specularly reflected light by the beam is separated, the intensity of the specularly reflected light is converted into an electrical signal by, for example, a photodiode, and a change in the intensity is detected by a light intensity detection device.

Then, the desired angle θ of the beam with respect to the surface of the plate to be processed is determined.
As shown in FIG. 2, the light that is specularly reflected includes the light S that is reflected in a direction other than the desired reflection angle θ due to the stepped surface between the pattern 15 and the coating 16 exposed on the surface by etching. As a result, a step appears in the etching. The amount of light in the desired angle θ direction decreases. The amount of decrease depends on the level difference because the angle θ and the width Q of the pattern 15 are constant. Therefore, if the applied film is on the pattern, or if the pattern is on the same plane as the film, the intensity of the specularly reflected light detected is high, and etching progresses further, causing a step difference between the film and the pattern. If this occurs, the intensity of the specularly reflected light detected will be significantly lower than under the above situation. Therefore, as shown in FIG. 3, the intensity of the specularly reflected light detected from the point at which the etch-back is completed rapidly decreases, so that the end of the etch-back can be clearly detected. Furthermore, the end point of film etching can be clearly detected from the point in time when the detected specularly reflected light intensity becomes constant. In addition, in FIG. 3, R is the specular reflection intensity at a desired reflection angle.

S represents the reduction in light intensity at the desired reflection angle due to the step, t represents the etching time, E represents the end point of etch back, and F represents the end point of etching of the film.

〔Effect of the invention〕

Since a He-Na laser or the like used as a unidirectional light source in the present invention has a strong optical output, the specular reflection intensity at a specific wavelength is significantly larger than the intensity of plasma light at that wavelength. Therefore, according to the present invention, etch-back and normal etching end points can be detected with high sensitivity and accuracy without being affected by the intensity of plasma light. Furthermore, since the intensity of the laser beam is extremely stable, the detection accuracy is further improved in this respect as well.

In addition, in the above embodiment, He − is used as a unidirectional light source.
Although a Ne laser is used, other high-power light sources with excellent directivity other than the above may also be used, such as an Ar+ laser or a mercury lamp, or a monochromator or the like can be used to separate specularly reflected light with strong intensity. Furthermore, a spectroscopic device with higher resolution may be used, and other photodetector elements or devices such as a photomultiplier tube may be used to convert the light intensity into an electrical signal.

Furthermore, the method of the present invention can be applied to wet etching in addition to the above-mentioned dry etching.

As explained above, according to the present invention, the end point of etching can be detected with high sensitivity and accuracy.
The manufacturing yield of semiconductor devices can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus structure according to an embodiment of the present invention, FIG. 2 is a partial sectional view of a plate to be processed and a schematic diagram of a light reflecting surface, and FIG. 3 is a schematic diagram of an embodiment of the present invention. FIG. 3 is a profile diagram of specular reflection intensity in FIG. 3... Plasma etching device, 4... Processed plate, 5... Laser beam, 7... Specularly reflected light, 8...
Concentrator, 9... Interference filter, 10... Photodiode, 11... Specular reflection light detection device, 12... RF
Constant power source 15...pattern, 16...coat.

Claims (1)

[Claims] 1. When etching an object to be etched, the surface of the object to be etched is irradiated with unidirectional light, and the amount of specularly reflected light changes depending on the height of the step on the surface of the object to be etched, which is caused by etching. A method for detecting the end point of etching, characterized by the use of the method.