JPH02187604A - Light receiving position detection device - Google Patents

Abstract

PURPOSE:To perform high precision measurement even of an object to be detected like a semiconductor wafer whose surface to be detected has not a uniform reflection factor by providing a light receiving optical system with a correcting means which corrects the light from the object to reduce the change of the light in accordance with the intensity of light. CONSTITUTION:The surface to be detected of an object 200 is obliquely irradiated with infrared rays by a flood lighting optical system consisting of an infrared LED 2 and reflection members 31 and 32. The reflected light from the object 200 is led to a semiconductor position detector (PSD) 6 through the light receiving optical system consisting of reflection members 33 and 34 and a condenser lens 4, and the luminance centroid of the light spot on the surface of the semiconductor position detector is obtained. In this case, the transmittance of the reflected light from the object 200 is corrected by a transmittance automatic varying filter 5 provided in the light receiving optical system so that the change of light is reduced when the reflected light is transmitted through the filter 5. Consequently, the light reception position is detected without being affected by a partial difference of the reflection factor on the object 200.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a light receiving position detection device that detects the receiving position of reflected light from an object to be measured. By detecting it with a light receiving element,
"Conventional technology" that relates to a light receiving position detection device that can perform highly accurate measurements. There were measurement devices that used image sensors and mechanical scanning such as mirrors and reticles.

However, these scanning methods have the problem that the detection speed is determined by the scanning speed. A device was developed. Then, a light receiving position detecting device that can detect the position by irradiating light onto the surface to be inspected and receiving the second reflected light with a semiconductor device detector has been realized.The second light receiving position detecting device is , f? In IIL, there was an optical lever method as shown in FIG. 7(a) and an astigmatism method as shown in FIG. 7(b).The optical lever method shown in FIG. 7(a) is Laser light, infrared light, etc. are emitted from a light-emitting element such as a laser diode or a helium-neon laser/LED, and this laser beam is reflected by an appropriate reflective member and is emitted diagonally to the surface of the object to be measured. Irradiate 9 The reflected light reflected from this test surface is reflected by an appropriate reflecting member, and after being converted into a parallel light beam by a condenser lens etc., it is sent to a semiconductor device detector (PSD).
) etc. 5 This semiconductor device detector (PSD) detects the position of the reflected light and can measure the position of the surface to be inspected.

Furthermore, the astigmatism method shown in Fig. 7(b) irradiates laser light etc. emitted from a light emitting element vertically onto the surface of the object to be measured via a transmissive reflective surface and a condenser lens. let The reflected light reflected by this test surface is reflected by a transmissive reflective surface, and is configured to be guided to a semiconductor device detector having a four-divided light-receiving element.

``Problems to be Solved by the Invention'' However, the conventional light-receiving position detection device described above requires that the surface to be detected have a uniform reflectance or a certain pattern. I'm here.

There was a problem that accurate measurements could not be made at interfaces with different reflectances.9 For example, when the test object is a semiconductor wafer made of various materials, it is difficult to measure with high precision. There was a serious problem when expectations were not met.In other words, in semiconductor wafers, aluminum is mainly used for internal conductive wires, and gold is used for external connection wires.

Furthermore, since the semiconductors on the wafer are also made of multiple types of materials, the reflectance on the wafer differs locally, and there was a problem in that it was not possible to measure with high precision, especially at the interface. Means for Solving the Problems The present invention has been devised in view of the above-mentioned problems, and is a measuring device for measuring objects to be measured that have partially different light transmission or reflectance. a light emitting optical section that emits light toward the object to be measured; a light receiving optical system that guides the light from the object to be measured onto the light receiving surface; In a light-receiving position detection device comprising a light-receiving element for outputting a signal indicating the position of an object, the light-receiving optical system is corrected to reduce corresponding changes depending on the intensity of light from the object to be measured. The present embodiment configured as described above is characterized in that the light receiving position is detected by the output signal of the light receiving element. Light is irradiated toward the object to be measured, the light receiving optical system guides the light from the object to the light receiving surface, and the light receiving element determines the position of the surface to be measured according to the receiving position of the light guided by the light receiving optical system. 7 At this time, a correction means provided in the light receiving optical system,
Corrects to reduce changes in light depending on the intensity of light from the object to be measured. As a result, the light receiving position can be detected without being affected by local differences in light transmission or reflectance of the object to be measured.

Embodiment In this embodiment, an embodiment of the present invention will be explained based on the drawings, taking an optical lever type light receiving position detection device 1 as an example. FIG. 1 is a diagram showing the configuration of a light receiving position detecting device 1. The light receiving position detecting device 1 includes an infrared LED 2, a reflecting member 3, a condenser lens 4, an automatically variable transmittance filter 5, and a semiconductor device detecting device. 2 corresponds to a light emitting element, and is composed of an infrared light emitting device (PSD) 6, a preamplifier 7, an arithmetic unit 8, an arithmetic unit 9, and an arithmetic unit 100. The first reflecting member 31 and the second reflecting member 32 are capable of emitting infrared rays from the infrared LED 2 to the test surface of the test object 200. Reflection member 31 and second reflection member 32
This corresponds to a light projection optical system.9 This light projection optical system allows infrared rays to be irradiated obliquely onto the surface to be inspected of the object 200 to be inspected. The condenser lens 4 is
00 to make the force reflected light into a parallel light beam. The automatically variable transmittance filter 5 automatically changes the light transmittance according to the light intensity of incident light, and reduces the width of change in the transmitted light intensity. This transmittance automatic variable filter 5 is
It is composed of automatically variable transmittance glass, and has the characteristic transmittance characteristics shown in Figure 3.2 In other words, as the intensity of incident light increases, the transmittance decreases, and the intensity of transmitted light changes. 7 This automatically variable transmittance glass is doped with an element that emits photoelectrons when stimulated by near ultraviolet rays or short wavelength visible light, and is made of high-purity glass made under strong reducing conditions. 9 This automatically variable transmittance filter 5 is made of silicate glass or the like.
This corresponds to correction means. Note that this correction means is not limited to the automatically variable transmittance filter 5, but can also employ a liquid crystal element such as a TN liquid crystal cell, and use a material that performs a similar function, such as a means for controlling the transmittance of this liquid crystal cell. The third reflecting member 33 and the fourth reflecting member 34 are connected to the test object 200.
The reflected light is reflected and guided to the semiconductor device detector 6. Here, the 9 semiconductor device detector (PSD) 6, in which the third reflecting member 33, the condenser lens 4, and the fourth reflecting member 34 constitute a light receiving optical system, corresponds to a light receiving element.

The structure of the semiconductor device detector (Psi') 6 will be explained based on FIG. 4. The semiconductor device detector 6 has a uniform resistance @61 formed on one or both sides of a high-resistance semiconductor surface, and a pair of electrodes 62 and 63 for signal extraction are provided at both ends of this resistance layer 61. The 7th surface layer is P
The distance between the electrode A62 and the electric current of the PSD, which form an N junction and generate a photocurrent by the photoelectric effect, is the distance between the electrode A62 and the electric current 863, the resistance is R1-, and the incident position of light from the electrode A62 is Let the distance to the point be X, and the resistance of that part be R\.

The photogenerated charge generated at the light incident position reaches the resistive layer 61 as a photocurrent (Io) that is proportional to the incident light energy, and the photocurrent is inversely proportional to the resistance value up to each electrode 62, 63. It is divided as follows. Therefore, electric f
iA 62 & Biden [! Current IA that can be collected from B63
IP is calculated as follows: 5LRX ■A −I[l 2X If we assume that the resistance layer 61 is uniform and the length and resistance are proportional, then A Io ・ ・ ・ ・ (3) u Io ・・(4) It can be expressed as: Then, let the position signal be P, calculate the sum and difference of 1 and 18, and divide these to become 2. The light receiving position can be calculated. In this example, two detectors based on these principles are used. Although the equipped two-dimensional PSD is used, a one-dimensional PSD can also be used to measure the -dimensional position.

The preamplifier 7 is for amplifying the output signal of the PSD 6.9 The first preamplifier 71 and the second preamplifier 72 amplify the output signal for detecting the position in the Y-axis direction. , the third amplifier 73 and the fourth amplifier 74 are configured to amplify the output signal for detecting the position in the X-axis direction. Further, the first subtraction arithmetic unit 91 is used to add the output signals Yll and Y2.Furthermore, the first subtraction arithmetic unit 91 is used to subtract the output signals Yl and ¥2 for Y-axis direction detection.

The first division arithmetic unit 101 is the first subtraction arithmetic unit 91
is divided by the output signal of the first addition arithmetic unit 81. The output of the first division calculator 101 is equivalent to the result of calculating the above equation (5), and a position signal in the Y-axis direction can be obtained. Similarly, by connecting the second addition arithmetic unit 82, the second subtraction arithmetic unit 92, and the second division arithmetic unit 102, a position signal in the X-axis direction can be obtained.

Next, a case of measurement using the test object 200 shown in FIG. 5 will be described. This test object 200 is made of materials with different reflectances, and the black part is a material with a low reflectance, and the white part is a material with a high reflectance. The external light rays are reflected by the first and second reflecting members 31 and 32, and are obliquely irradiated onto the test surface of the test object 200. This infrared ray is reflected by the surface to be inspected,
Figure 2 (a) shows the reflectance distribution of the test object 200 at location (3).
The reflected lights 9 and 1 shown in are reflected by the third reflecting member 33. FIG. 2(b) shows the reflected light distribution at the position marked (■). This reflected light intensity shows the same tendency as the reflectance distribution of the test object 200, and the reflected light in areas with high reflectance has a high light intensity.9 Furthermore, if the difference in the reflectance is large, The difference in light intensity is also large.7 Then, the reflected light that is made into a parallel beam by the condenser lens 4 is reflected by the fourth reflection member 34 and enters the automatically variable transmittance filter 5. Since the filter 5 has the transmittance characteristics shown in Fig. 3, the intensity of light at the position (2) that does not pass through the automatically variable transmittance filter 5 varies depending on the strength of the light intensity as shown in Fig. 2 (C). 9 The reflected light that has passed through this automatically variable transmittance filter is detected by the semiconductor device detector 6.
incident on . The output signal of this semiconductor device detector (PSD) 6 is amplified by a preamplifier 7, and an analog arithmetic unit 8.
In step 9,100, the above equation (5) is calculated, and position signals corresponding to the light receiving positions on the X, l and Y axes are generated. Since the automatic variable filter 5 is inserted, the light distribution of the reflected light is made uniform, and this uniform reflected light is projected onto the semiconductor device detector 6, so that the reflectance of the surface to be inspected is This has the advantage that even when the values are not uniform, measurements can be carried out with high accuracy.

In particular, the pattern of Ste-Sober's mask and the like has a large influence, and is therefore suitable for application to this embodiment.

Note that at least one embodiment is a lever-type light receiving position detection device 1 shown in FIG. 6(a), but it may also be applied to an astigmatism-type light receiving position detection device 91 shown in FIG. 6(b). ``Effects'' In the present invention configured as described above, the projecting light unit emits light toward the object to be measured, the light receiving optical system guides the light from the object to the light receiving surface, and the light receiving element outputs a signal indicating the position of the surface to be inspected in accordance with the light receiving position of the light guided by the light receiving optical system.

At this time, the correction means provided in the light receiving optical system corrects the change in light according to the intensity of the light from the object to be measured, so that the part of the light transmission or reflectance of the object to be measured is corrected. This has the outstanding effect of being able to detect the light receiving position without being affected by optical differences.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention. Fig. 1 is a diagram explaining the configuration of this embodiment, Fig. 2(a) is a diagram showing the reflectance distribution, and Fig. 2(b) is a diagram showing the reflectance distribution. Diagram showing reflected light distribution, 2nd
Figure (C) is a diagram showing the distribution of light after passing through the filter.
The figure shows the characteristics of the transmittance automatic variable filter, Figure 4 shows the configuration of the semiconductor device detector, Figure 5 shows the surface of the non-tested object, and Figure 6 <a > is a diagram for explaining the configuration of the optical lever system, FIG. 6(b) is a diagram for explaining the configuration of the astigmatism system, and FIG. 7 is a diagram for explaining the prior art. 9 1... Light receiving position detection device 2... Infrared LED 3... Reflection member 4... Condenser lens 5 . . . Transmittance automatic variable filter 6 . . Semiconductor device Detector (PSD) ・Test object

Claims (1)

[Claims] (1) A measuring device for measuring an object to be measured with partially different light transmission or reflectance, which includes a projection optical section that irradiates light toward the object to be measured, and a light emitting optical section that emits light toward the object to be measured; Light-receiving position detection consists of a light-receiving optical system for guiding light onto a light-receiving surface and a light-receiving element for outputting a signal indicating the position of the object according to the receiving position of the light guided by the light-receiving optical system. In the apparatus, the light-receiving optical system is equipped with a correction means for correcting to reduce changes in the light according to the strength of the light from the object to be measured, and the light-receiving optical system is equipped with a correction means for reducing changes in the light from the object to be measured, and the light-receiving optical system is A light receiving position detection device characterized in that a position is detected.