JPS58193407A - Device for measuring distribution of height of body surface - Google Patents

Abstract

PURPOSE:To measure the distribution of the height of the surface of a body in atmospheric air without contact and without destruction, by forming the image of the surface of a sample, placing a pinhole in the image surface, and selectively receiving light from a part having a specified height. CONSTITUTION:A parallel beam from a laser 1 is reflected by a surface 8 of a cube mirror 2, converged by a lens 4, and irradiated on the surface of a sample 5. The reflected light from the surface of the sample 5 is made to be a parallel beam by a lens 4, and reflected by a surface 9 of the mirror 2. The image is formed at the position of a pinhole 11 by a lens 10. The light passed the hole 11 is detected by a light detector 12. In this case, when the height of the surface of the sample 5 is located at the position of the focal point of the lens 4, the image of the laser spot formed on the hole 11 is small. Then the mirror 2 is vibrated and rotated, and the laser beam is scanned on the sample 5. When the laser beam scans the part where the surface height of the sample 5 agrees with the focal point position of the lens 4, a pulse shaped output appears at the output terminal of the detector 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the height distribution on the surface of an object, such as a semiconductor integrated circuit, and more particularly, to a device that can measure the height distribution in the form of a contour map in a non-contact manner in a short time.

Conventionally, the height distribution on the surface of an object can be measured using (1) a probe sweep method, (2) a stereoscopic scanning electron microscope, or (
This was done using a 3-interference microscope. (1) is a method in which the surface of the sample object is touched and swept with a diamond needle, etc.
Destroy part of the sample. (2) Since the surface of the sample is scanned with Fi and electron beams, there is a risk of damage to the sample due to the electron beam, and there are limitations in that the sample must be placed in a vacuum. C) is a method that allows measurement in the atmosphere without contact, but there are problems in that the measurement takes time and that the data and processing are complicated because it is an indirect measurement.

The purpose of the present invention is 1. The height distribution of the object surface in the atmosphere,
It is an object of the present invention to provide a high-level distribution measuring device that measures non-contact and non-destructively and also directly obtains a contour map at the same time as the measurement.

In order to achieve the above object, the present invention scans the sample surface two-dimensionally with a narrowly focused laser beam. Measurement of the height of a sample surface is based on the fact that when a laser beam is scanned across the sample surface, the laser beam spot will be the smallest at a sample position with a specific height, and will be larger at other positions. Make use of it. In other words, by focusing the surface of the sample using a lens system and placing a pinhole on the image plane,
It is characterized by selectively receiving light from a specific height and knowing its position.

An embodiment of the present invention will be described below with reference to FIG. This embodiment mainly includes a laser 1, a cube mirror 2, a lens 4, a sample stage 6, a lens 10, a pinhole 11, a photodetector 12, a signal processing circuit 13, and a contour map display 14.

The parallel beam from the laser 1 is directed to the surface 8 of the cube mirror 2.
It is reflected by the lens 4, focused by the lens 4, and illuminates the surface of the sample 5. The reflected light from the surface of the sample 5 is turned into a parallel beam by the lens 4, reflected by the surface 9 of the cube mirror 2, and focused at the position of the pinhole 11 by the lens IOK. The light passing through the pinhole 11 is detected by a photodetector 12. In this case, if the surface height of the sample 5 irradiated by the laser spot is at the focal point of the lens 4, the laser spot focused on the pinhole 11 will be small, and most of the light passing through the lens 10y&: , passes through the pinhole 11 and is detected by the photodetector 12. However, if the height of the surface of the sample 5 irradiated by the laser spot is not at the focal point of the lens 4, the size of the laser spot focused on the pinhole 11 will be larger than the hole size of the pinhole 11. , a small portion of the light passing through the lens 10 passes through the pinhole 11 and is detected by the photodetector 12.

Therefore, by vibrating and rotating the cube mirror 2 by the drive system 3 and scanning the laser beam on the sample 5, the output end of the photodetector 12 receives the waveform 2 shown in FIG.
As shown at 1, when the laser beam scans a portion where the surface height of the sample 5 coincides with the focal position of the lens 4, a pulse-like output appears.

In this case, due to the effect of the cube mirror 2, the position of the laser spot on the pinhole 11 does not change due to laser beam scanning.

Next, the signal processing circuit 13 identifies and binarizes this waveform by the height of the broken line shown in the waveform 21 in FIG. (for example, an oscilloscope), and the drive signal of the drive system 3 is a horizontal axis scanning signal of the display 14, for example. On the other hand, the sample stage 6 is swept by the sample drive system 7 in a direction perpendicular to the paper surface, and the sweep signal of the drive system 7 is displayed on the display 14.
For example, let it be a scanning signal along the vertical axis.

By such an operation, a contour map corresponding to the height of the focal position of the lens 4 on the surface of the sample 5 is displayed on the display 14. In order to obtain isoline maps corresponding to various heights, the height of the sample stage 6 is changed stepwise by the drive system 15, and the above operation is repeated.

More than ml? As is clear, according to this embodiment, it is possible to measure the height distribution of the surface of an object in the form of a contour diagram without contact and in a short time.

According to the present invention, the height distribution of the object surface is generally equal to i
Direct measurement in the form of an I#l diagram enables efficient, non-contact, non-destructive measurement of the sample object, so it is useful, for example, for 100% inspection of products in the manufacturing process of semiconductor integrated circuits. It also has a vine effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of a photodetector output and a signal processing circuit output in the embodiment of FIG.

Claims (1)

[Claims] 1. In an optical system, a parallel beam from a laser is reflected by a cube mirror, narrowed down by a lens system, irradiated onto the surface of a sample object, and the reflected light from the sample object is imaged by a lens system and a cube mirror. By scanning a laser beam over the surface of the sample object by vibrating and rotating a mirror, and placing a combination of a pinhole and a photodetector on the convergence plane, the photodetector can detect a specific height of the surface of the sample object. A height distribution measuring device on the surface of an object that measures the height distribution on the surface of the object by selectively receiving reflected light from the object.