JPH01134202A - Laser end point detecting device - Google Patents

Abstract

PURPOSE:To obtain a device which accurately detects an etching end point without using any complex, expensive control system for an optical system by providing a beam expander which expands the diameter of a laser beam to size larger than the spread of one chip. CONSTITUTION:The beam expander 29 is installed between a laser light source 27 and a wafer 11, the diameter size of the laser beam 21 for detection is expanded to the size larger than the spread of one chip 14 on the wafer 11, and the expanded beam 30 is projected on the chip 14. Further, a beam splitter 28 for classifying reflected light from the wafer 11 is installed between the beam expander 29 and laser light source 27. Then light from the beam splitter 28 is made incident on a photodetecting element 31 and connected to a recording analysis unit.

Description

[Detailed Description of the Invention] [Important] By enlarging the beam diameter of the laser beam to at least the same size as the chip, it is possible to detect the end point of etching without being placed in the etching range on the chip. To provide a laser end point detecting device which can accurately detect the end point of etching without using a complicated and expensive fine movement control system for an optical system. In a device that uses a laser beam to detect the end point of a process performed on a wafer, the laser beam emitted from a laser light source is A beam expander that expands into an expanded beam is placed on the laser light source side of the wafer, and a beam splitter that passes the laser beam through the beam expander and inputs the reflected expanded beam to a photodetector. The configuration includes a laser end point detection device, which is disposed between the two and the light receiving element is connected to a recording analysis unit.

[Industrial application field]

The present invention is a simple and low-cost method that enables the end point of etching to be detected without being located in the etching range on the chip by enlarging the beam diameter of the laser beam to be equal to or larger than the chip dimensions. The present invention relates to a laser end point detection device.

[Conventional technology]

Conventionally, in order to detect the end point of etching using a laser beam, the laser beam system has been narrowed down to, for example, 0.7 mm, 1 mm or less. There are various methods of detecting the end point of etching using such a laser beam.
1st order is a method of detecting and analyzing 0th order reflected light that is reflected perpendicularly from the same surface.

2nd, 3rd 61. There are also methods to detect and analyze the scattered light. In the method of looking only at the zero-order reflected light, a laser beam is irradiated onto the groove pattern that is being etched, and changes in the reflected light are observed as the reflected light strengthens or weakens each other due to the optical path difference of the reflected light.

[Problem that the invention seeks to solve]

In the conventional end point detection method, as mentioned above, the laser beam diameter is narrowed down to 1 mm or less, so it is necessary to apply the beam to the part where etching is actually performed.
Positioning each wafer becomes important. Referring to FIG. 4, when etching the groove 13 on the wafer 11 using the resist mask 12, the beam 21a of 1 mm or less as described above is used.

21b and detects the end point. In the example shown, it is detectable at the position of beam 21a, but
At the position, detection is impossible because only the flat surface of the resist mask 12 is irradiated, so the beam 21
b must be moved to the position of beam 21a.

The apparatus for this purpose is as shown in FIG. 5, in which a laser beam 21 is irradiated from an optical system 24 through a window 23 provided in a partition wall 22 between the wafer 11 and the processing chamber, and the laser beam 21 is moved as described above. In order to do this, the optical system 24 is finely adjusted in the direction of the white arrow using the fine movement control system 25. Although this fine movement control system has a complicated structure and is expensive, it is necessary because the beam diameter of the laser beam is narrowed down to 1 mm or less. As an alternative to the above method, there is a method in which the optical system is fixed and a stage is used to control fine movement of the wafer, but this also requires an expensive stage.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser end point detection device that can accurately detect the end point of etching without using a complicated and expensive fine-movement feed control system for the optical system.

[Means for solving problems]

The above problem is that in a device that uses a laser beam to detect the end point of processing performed on a wafer, the laser beam emitted from the laser light source is A beam expander is placed on the laser light source side of the wafer, and a beam splitter that passes the laser beam through the beam expander and inputs the reflected expanded beam to the photodetector connects the laser light source and the beam expander. The problem is solved by a laser end point detection device disposed between the two and a light receiving element connected to a recording analysis unit.

[Effect]

In the present invention, by making the beam diameter larger than the chip size, the detection signal is not affected by the position where the beam is applied, and positioning becomes unnecessary. Furthermore, since the beam diameter can be irradiated within a certain range, information on surface irregularities can be obtained over a wide range, and it can be used, for example, to detect the end point of a process such as flattening treatment.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to illustrated embodiments.

The principle of the invention is illustrated in FIG. In the present invention,
By making the diameters of the laser beams 21c and 21d sufficiently larger than the dimensions of the chips 14 formed on the wafer 11, it is possible to cover and detect the etching range of approximately the same area at both the laser beam 21c and 21d positions. Do as you like. That is, each of the laser beams 21c and 21d covers approximately 50% of the etched area and approximately 50% of the non-etched area.

For this purpose, a beam expander shown in FIG. 2 is used. In the same figure, a laser beam 21 emitted from a laser light source 27 passes through a beam splitter 28 and enters a beam expander 29, where one chip is separated. The wafer 11 to be processed is irradiated with an expanded beam 30 whose spread is sufficiently larger than that of the window 23.
, passes through the beam expander 29, and beam splitter 2
8 and sent to the light receiving element 31, and then the fifth
The reflected light is input to the recording analysis unit 26 shown in the figure, and the reflected light is recorded and analyzed.

FIG. 3 is a perspective view of an embodiment of the present invention, in which the optical system 24 is connected to the partition wall 22.
is fixed. That is, in the present invention, the first
As explained with reference to the figures, the necessary information can be completely obtained no matter where on the wafer the laser beam is irradiated, so there is no need to move the optical system 24. In actual operations, the record analysis unit is connected to an etching device, etc., and instructions for changing etching conditions and other instructions are given based on the analyzed information.

〔Effect of the invention〕

As described above, according to the present invention, when the apparatus shown in FIGS. 2 and 3 is incorporated into a process apparatus, a mechanism and a control system for scanning the wafer are not required, so the apparatus can be made compact and can be easily modified. It was simple and could reduce costs.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of the present invention, Fig. 2 is a diagram of an embodiment of the invention, Fig. 3 is a perspective view of an embodiment of the invention, Fig. 4 is a diagram illustrating problems of the conventional example, and Fig. 5 The figure is a perspective view of a conventional example. In the figure, 11 is a wafer, 12 is a resist mask, 13 is a groove, 14 is a chip, 21, 21a, 21b, 21c, and 21d are laser beams, 22 is a partition, 23 is a window, 24 is an optical system, and 25 is a fine movement feed. 26 is a recording analysis unit; 27 is a laser light source; 28 is a beam splinter; 29 is a beam expander; 30 is an expanded beam; and 31 is a light receiving element. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney Akimoto Kukimoto 4F - M1 map of the country showing Ming Dynasty, heather, hammer 5g, moon laughing, l chili's mouth 2nd figure, Oshino Rizuki laughing example 43 Jr Agent 1 country Figure 3

Claims (1)

[Claims] In a device that uses a laser beam (21) to detect the end point of a process performed on a wafer (11), the laser beam (21) emitted from a laser light source (27) is
A beam expander (29) that expands into an expanded beam (30) with a size larger than the spread of one chip (14) formed on the wafer (11) is arranged on the laser light source 27 side of the wafer (11), The laser beam (21) is passed through the beam expander (29), and the reflected expanded beam (30) is passed through the light receiving element (31).
) is placed between the laser light source (27) and the beam expander (29), and the light receiving element (31) is connected to the recording and analysis unit (26). Characteristic laser end point detection device.