JPH02186312A - auto focus illumination device - Google Patents

Abstract

PURPOSE:To allow the exact illumination of a surface to be detected by constituting the device in such a manner that the 1st driving means focuses a coupling optical system in accordance with the detection signal of a position detecting means, a moving quantity detecting means detects the moving quantity of the 1st driving means to measure the thickness of the object to be detected and the 2nd driving means focuses a transmission of the moving quantity detecting means. CONSTITUTION:This device consists of the imagery optical system 1 having the position detecting means for detecting the position of the object 200 to be detected and the transmission illuminating optical system 2 for illuminating this object 200. The imagery optical system 1 is provided with the 1st driving means 15 for focusing the coupling optical system 1 in accordance with the detection signal of the position detecting means 14 and the moving quantity detecting means 16 for detecting the thickness of the object 200 by detecting the moving quantity by the 1st driving means 15. The transmission illuminating optical system 2 is provided with the 2nd driving means 23 for focusing the transmission illuminating optical system 2 in accordance with the detection signal of the moving quantity detecting means 16. The inspection of a semiconductor mask 200 is exactly and efficiently executed in this way under the optimum conditions without deviating the illuminating position.

Description

Detailed Description of the Invention: "Industrial Application Field" The present invention relates to an illumination device used in an inspection device for semiconductor masks, etc., and in particular, the present invention relates to an illumination device used in an inspection device for semiconductor masks, etc. The present invention relates to an automatic focusing illumination device that can automatically focus a transmitted illumination optical system according to the conditions.

"Conventional technology" In the illumination devices installed in conventional inspection equipment for semiconductor masks, etc., the imaging optical system used for inspection and inspection has an automatic focusing function that can automatically adjust the focus. Ta. However, automatic focusing fll#t has not been adopted in the transmitted illumination optical system for illuminating the test object. Therefore, before inspecting a semiconductor mask, etc., the imaging optical system is first focused on the object to be inspected, and the YG over-illumination optical system is adjusted by giving parameters such as the thickness and refractive index of the object. This was done by moving the transmitted illumination system to a position corresponding to this parameter. That is, instead of performing a focusing operation for each individual object, adjustment is performed by moving the transmitted illumination optical system to a predetermined focusing position obtained from various parameters.

"Problems to be Solved by the Invention") - However, the illumination used in the above-mentioned secondary type semiconductor mask force inspection device is
Although we were able to achieve a sufficiently uniform transmitted illumination for practical use even at the transmitted illumination position under the set conditions, when inspecting a relatively large object, the object would bend due to its own weight.
The problem is that uniform transillumination cannot be achieved at a predetermined transillumination position. Especially when inspecting a relatively large reticle, etc., the reticle, etc. will bend by several hundred μm due to its own weight, so the illumination position of a Koehler-type transmitted illumination system, for example, must be set based only on the thickness of the reticle, etc. Then, there was a serious moment where the focus position deviated from the best position for illumination.

Although it is conceivable to equip the second diagonal transmission illumination optical system with a separate automatic focusing device, the first position detection means must be provided separately from the coupling optical system.

There were problems in that the device became complicated, the cost increased, and the overall size of the device could not be reduced.

"Means for Solving the Problems" The present invention covers all of the above! *It consists of an imaging optical system with a position detection means for detecting the position of the specimen, and a transmitted illumination optical system for illuminating the specimen. The optical system includes a first drive means for focusing the coupling optical system based on the detection signal of the position detection means, and detects the amount of movement by the first drive means to determine the thickness of the object. It is equipped with a movement amount detection means for detection.

The transmitted illumination optical system is characterized in that it is equipped with a second driving means for focusing the transmitted illumination optical system based on the detection signal of the FJ recorded movement amount detection means.

Crf! In the present invention, the first driving means focuses the coupling optical system based on the detection signal of the position detection means.

Then, the movement amount detection means detects the movement amount of the first drive means and Jl! Measure the thickness of the specimen. Further, a second driving means focuses the transmitted illumination system based on a detection signal from the movement amount detecting means.

“First Practical Example” An example of the present invention will be described based on the drawings. Figure 1 shows the configuration of the automatic focusing device of this embodiment.Automatic focusing!
The apparatus has two optical systems: an imaging optical system 1 and a transmitted illumination system 2. The coupling optical system 1 is.

It consists of a light emitting section 11, reflecting members 121 to 124, a light receiving section 1), a three-position detecting means 14, a first drive [15], and a movement amount detecting section 16. 5! The light section 11 is for emitting infrared rays or laser beams, and employs an infrared LED, a semiconductor laser, or the like. The light rays emitted from this light emitting section 11 are as follows.

The light is reflected by the first reflecting member 121 and the second reflecting member 122, and is irradiated obliquely onto the test surface of the test object 200. Subject?
The light beam reflected by the test surface of v200 is.

Third reflective member 123. The light is reflected by the fourth reflecting member 124 and is made incident on the light receiving section 1). This optical path constitutes an optical lever. The light receiving section 1) measures the position of the surface to be measured of the object 200 based on the incident light, and in this embodiment, a semiconductor device detector (PSD) is employed.

The second semiconductor device detector (PSD) is for outputting the center of brightness of the light spot on the surface of the semiconductor device detection 1.

At the knee, the structure of the semiconductor device detector (PSD) 1) is
This will be explained based on the diagram. A semiconductor device detector 1) has a uniform resistance N1)1 formed on one or both sides of a high-resistance semiconductor surface, and a pair of IE electrodes for signal collection at both ends of this resistance layer 1)1. The 9 surface layers provided with 1)2.1)3 form a PN junction and are configured to generate a photocurrent due to the light t, *.

Calculate the distance between the PSD's t-poles A1)2 and t5B1)3, and calculate [
Let the resistance be RL, the distance in height from the incident position be X, and the resistance of that part be R.

The photogenerated charge generated at the light incident position is converted into light Wla (T o) proportional to the incident light energy in the resistive layer 1) 1
reach. And the optical IE current is connected to each electrode 1)
2.1) Divided in inverse proportion to the resistance value up to 3.

Therefore, t[xA1)2 and t! The current IA E* that can be collected from 1ft81)3 is calculated as follows.

! , 4 -111 2X, and the resistance layer 1) 1 is uniform, and the length and resistance value! Assuming that it is imaginary proportional.

1m=To　・□ ・　・　・(4) It can be expressed as. And let the position signal be P.

■ Calculate the sum and difference of and l, and divide them (i'.

Therefore, the light receiving position can be calculated.

In this example, two detectors equipped with two detectors based on these principles are used.
Although dimensional PSD is adopted, one-dimensional PSD is adopted,
-It is also possible to measure the position in the dimension.

Next, the position detection section 14 will be explained based on FIG.

Location detection #! 14 is the completion test from the output signal of the light receiving section 1)?
9 This position detection unit 14 calculates the position of the test surface 1200, and includes a preamplifier 141 and an addition calculator 14.
2, a subtraction arithmetic unit 143, and a division arithmetic unit 144. The preamplifier 141 is for amplifying the output signal of the PSD1). First prefix #IIi device 1
411Jl: The second preamplifier 1412 amplifies the output signal for detecting the position in the Y-axis direction, and the third preamplifier 14
1) and a fourth amplifier 1414 are configured to amplify the output signal for detecting the position in the X-axis direction. The first addition arithmetic unit 1421 performs addition of Y, , Y, which are output signals for Y-axis direction detection.

Furthermore, the first subtraction calculator 1431 subtracts Y, .

The first division arithmetic unit 1441 is the first subtraction arithmetic unit 1
431 is divided by the output signal of the first addition arithmetic unit 1421. The output of the first division calculator 1441 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 1422, the second subtraction arithmetic unit 1432, and the second division arithmetic unit 442, a position signal in the X-axis direction can be obtained.

The first drive unit 15 is for focusing the coupling optical system 1 on the test surface of the test object 2QO. This focusing is achieved when the light beam emitted from one light beam fljll is reflected on the test surface of the test object 200, and this reflected light enters the light receiving section 1), but the position of the incident light that enters the light receiving section 1) It is possible to utilize the fact that the distance changes depending on the distance from the test subject 200. That is, it is possible to measure the distance to the *lateral surface 200 based on the output signal of the position detection unit l11. Therefore, the first drive unit 15 can move the optical system according to the distance to the test surface of the five test objects 200 and focus the imaging optical system l. Further, the movement amount detection section 16 measures the movement distance of the optical system due to the focusing operation of the first drive section 15.
The movement detection unit 16 may use a linear scale or the like, or may measure by installing an encoder or the like in the driving means, that is, it may measure the amount of movement of the moving means of the optical system due to the focusing operation. That's enough.

Next, the transmission optical system 2 will be explained. Y! 1 optical system 2 is
It is composed of a light source section 21, an electric light means 22, and a second driving section 23. The light source section 21 is a light source for illuminating the test object 200, and an appropriate lamp or the like is used. 11
．． The light means 22 focuses the light beam from the light source section 21 on the surface to be examined of the object 200 to illuminate the surface to be examined. The second driving means 23 performs rIR adjustment on the electric light means 22 based on the detection signal of the movement amount detecting section 16 of the coupling optical system 1 to focus the transmitted illumination optical system 2 on the test surface of the test object 200. It is something.

The computer 3 includes a position detection section 14 and a movement amount detection section 16.
The first drive section 15 and the second drive section 2
This is for controlling and driving 3.

In this embodiment configured as described above, a semiconductor mask (test object 200) on which a mask pattern is formed is first placed on the reference table 4, and then a light beam is emitted from the light emitting section 11, and the semiconductor mask 200 is irradiate it.

The reflected light from the semiconductor mask 200 is made incident on the light receiving section 1). The light receiving section 1) outputs a current corresponding to the incident position of one reflected light, and the position detecting means 14 performs arithmetic processing and outputs a position signal to the computer 3. The computer 3 calculates the distance to the semiconductor mask 200 based on the position signal from the 1-position detection means 14.

The coupling optical system 1 then drives the first drive unit 15 in order to focus on the test surface of the semiconductor mask 200. As a result, the imaging optical system 1 automatically focuses. Further, the movement amount detection section 16 detects the amount of movement of the coupling optical system 1 by the first drive section 15 . That is, by measuring the distance from the position of the reference stand 4 to the in-focus position of the semiconductor mask 200, the thickness of the semiconductor mask 200 can be measured. The computer 3 calculates the focal position of the transmitted illumination optical system 2 in consideration of the thickness of the semiconductor mask 200. Then, the computer 3 drives the second drive unit 23, so that the transmission irradiation optical system 2 can focus on the surface to be inspected of the semiconductor mask 200 and illuminate it accurately.

Next, an example in which this embodiment is applied to a semiconductor mask inspection apparatus will be described with reference to FIG. This semiconductor mask inspection device inspects the pattern of a semiconductor mask, and includes an objective lens 5 and a half mirror 6.

CCD 7, drive circuit 8, A, /D converter 9 and 1
A determination unit 100, regular pattern data fI1110,
It consists of a computer 120, an external storage device 1) 0, a TV camera 140, and a monitor 150.

The above-mentioned automatic focusing device allows the imaging optical system 1 and the transmitted illumination system 2 to be
After both are in focus, the semiconductor mask inspection apparatus of the second embodiment is operated. The objective lens 5 transmits the image of the semiconductor mask 200, which is the object to be inspected, through the half-8 rays and displays it on the CCD.
(Charge-coupled device) Image on 7. The CCD 7 sends an electric signal corresponding to the imaged semiconductor mask to the drive circuit 8. In the drive circuit 8, the output signal of the CCD 7 is increased II.
After processing, it is output to the A/D converter 9. The A-'D converter 9 performs AD conversion of the image signal of the drive circuit 8 at high speed. Then, the judgment section 100 uses the image data stored in the regular pattern data section J10 and the CCD.
The image captured in step 5 is checked to see if the data matches, and then the computer 120 performs processing to determine whether there are any damaged parts such as scratches on the semiconductor mask 200. 1) The judgment results are stored in a floppy disk, which is an external storage device 1). At this time, the iI image can be displayed on the monitor 150 without being captured by C0D7.4. In addition, here is the image of the light beam reflected by the half mirror 6.
Ti*L can be displayed on the monitor 150 on the camera 140. With this configuration, the computer 120
You can check whether the input image data is appropriate.

In this embodiment configured in the above-described manner, the semiconductor mask 200
Since the focusing of the imaging optical system 1 and the transmitted illumination optical system 2 is performed taking into account the thickness of the lens, the illumination position does not go out of order! & The semiconductor mask 200 can be inspected under suitable conditions.

Further, since automatic focusing can be performed in real time, there is an effect that semiconductor masks can be inspected accurately and efficiently.

"Effects" In the present invention configured as described above, the first driving means focuses the coupling optical system based on the detection signal of the position detecting means, and the movement amount detecting means focuses the coupling optical system based on the detection signal of the position detecting means. The second driving means detects the amount of movement of the object and measures the thickness of the object to be inspected, and the second driving means is driven so as to focus the transmitted illumination system. Therefore, the transmitted illumination optical system can be focused using the 1-position detection means and the movement amount detection means.The transmitted illumination optical system also takes into account the thickness of the object to be inspected and deflection due to its own weight, so it can accurately focus the transmitted illumination optical system. This has the effect of being able to illuminate a surface.In particular, since the automatic focusing device of the present invention only needs to be installed in the imaging optical system, the Wi-Fi structure is not complicated, the cost is low, and the overall device size is reduced. It has the outstanding effect of being able to be miniaturized.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. FIG. 1 is a diagram explaining the configuration of this embodiment, FIG. 2 is a diagram showing an example in which this embodiment is applied to a semiconductor mask inspection device, and FIG. Figure 3 is PSD
FIG. 4 is a diagram showing the structure of a position detection section. 2 ・ ・ 23 ・ 3 ・ 4 ・ ・ Transmitted illumination optical system 2nd driving unit Computer reference stand 1... Imaging optical system 14... Position detection unit 15... 1st driving unit 16... Movement amount Detection unit

Claims (1)

[Claims] (1) Consisting of an imaging optical system having a position detection means for detecting the position of the object to be inspected, and a transmitted illumination optical system for illuminating the object, the imaging optical system includes a A first driving means for focusing the coupling optical system based on the detection signal of the detection means, and a movement amount detection for detecting the amount of movement by the first driving means and detecting the thickness of the object to be examined. and the transmitted illumination optical system is provided with a second driving means for focusing the transmitted illumination optical system based on the detection signal of the movement amount detection means. An automatic focusing illumination device featuring: