JPH02172150A - Appearance inspection apparatus - Google Patents

Abstract

PURPOSE:To carry out highly precise inspection after development of resists by detecting secondary electrons generated from a sample when an electron beam is radiated to the sample, making an image, and at the same time making a fluorescent image based on the fluorescence radiating in the time of radiation of excited light to the sample. CONSTITUTION:At first a sample 3 is set in the position of the solid line on a sample stand 12 and an electron beam is radiated from an electrooptical mirror cylinder 1 to and at the same time brought into scanning by a scan signal from a scan signal generator 4. Secondary electrons generated from the sample 3 are detected by a secondary electron detector 5 and made into an image on an image display part 7. Then, the sample stand 12 is moved so as to move the sample to the dotted line and a light source lamp 12 is turned on. An excited light with a desired wavelength is radiated to the sample 3 and fluorescent image generated from the sample 3 is photographed by a color camera 17 and at the same time appearance inspection is carried out by an observer with the naked eye using a focusing lens 8. By this, highly precise inspection to investigate whether resist remains or not on the surface after resist development on semiconductor sample, etc., can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a visual inspection technique, and in particular to a technique that is effective when applied to the evaluation of the presence or absence of resist residue on the surface of a semiconductor sample or the like after resist development.

[Conventional technology]

For example, there are various methods for visually inspecting deep hole patterns such as contact holes and through holes in semiconductors from the surface.
A scanning electron microscope (SEM) as described in "Examples of Semiconductor Evaluation Technology" May 1986, written by Akira Usami, pages 20-21.
Microscopy).

This scans the surface of a sample such as a semiconductor material or semiconductor device with an electron beam focused into a small beam, and displays the intensity distribution of secondary electrons or reflected electrons from the sample as an image while further synchronizing with the beam. The shape of the surface of the sample is evaluated from the observation of the image.

[Problem to be solved by the invention]

However, in the conventional technology as described above, the amount of information is insufficient because the amount of secondary electrons generated from the bottom of the hole pattern with a large aspect ratio reaching the secondary electron detector is small.
It was not possible to obtain a good quality SEM image, and it was extremely difficult to determine the presence of resist residue on the bottom.

An object of the present invention is to provide a visual inspection technique that enables clear determination of organic matter residue at the bottom of a hole pattern.

The above-mentioned objects and novel features of the present invention will become clear from the description of this specification and the accompanying drawings. [Means for Solving the Problems] Outline of representative inventions among the inventions disclosed in this application A brief explanation is as follows.

That is, a first observation means detects and images secondary electrons generated from the sample when the sample is irradiated with an electron beam; and second observation means for forming an image.

[Effect]

According to the above-described means, the shape of the hole pattern of the sample is inspected by secondary electrons generated by an electron beam irradiated onto the surface of the sample. Then, excitation light is irradiated to the bottom of the deep hole in the resist where a small amount of secondary electrons reach the secondary electron detector, and the presence or absence of fluorescence generated at that time or the presence or absence of resist remaining in the fluorescent light layer is detected. In this way, by combining the observation means using electron beam scanning and the observation means using excitation light irradiation and performing an appearance inspection using the advantages of each, it is possible to perform an appearance inspection of a resist deep hole pattern with high precision.

〔Example〕

The figure is an explanatory view showing the main parts of a visual inspection device that is an embodiment of the present invention.

The electron optical system lens barrel 1 is disposed above the sample 3, and an electron beam travels toward the sample 3 through its center. An electron beam deflection coil 2 for deflecting an electron beam is disposed at the bottom of the electron optical system barrel 1. A scanning signal generator 4 for generating a scanning signal is connected to the electron beam deflection coil 2 . A secondary electron detector 5 is connected to an electron beam deflection coil 2 to detect secondary electrons generated from the sample 3 when the sample 3 is irradiated with an electron beam from the electron optical system barrel 1.
An amplifier 6 is connected to amplify the detected output. Scanning signal generator 4 and amplifier 6
An image display section 7 is connected to the image display section 7 so that a secondary electron image from the sample 3 can be displayed based on the output signal of the amplifier 6 and the scanning signal.

The sample 3 is placed on a sample stand 12 in the sample chamber 11 for evaluation and measurement, and the sample stand 12 is arranged so that the sample 3 can be moved from the solid line position to the broken line position in the figure. This sample stage 12 is controlled by a sample stage control section 9. An opening window is opened in the ceiling of the sample chamber 11 above the broken line position to allow light to pass through, a half mirror 13 is disposed above the opening window, and an excitation light absorption filter 14 is placed above the half mirror 13. An optical path switching mirror 15, an imaging lens 16, and a color camera 17 are sequentially arranged on the same optical axis. Further, an imaging lens 18 is disposed on the branching optical axis of the optical path switching mirror 15, and the operator's eyes are positioned at the imaging portion of the imaging lens 18. Further, on the branching optical axis of the half mirror 13, an ND filter 19 for attenuation, an excitation light wavelength selection filter 20, and a light source lamp 21 are sequentially arranged, and a light source is supplied to the sample 3 at the position of the broken line. Although the light source lamp 21 emits visible light, it may also emit ultraviolet light.

The scanning signal generator 4, sample stage control section 9, and fluorescence wavelength analysis section 10 are controlled by a central control processing section 8 that manages the entire apparatus.

Next, the operation of the embodiment with the above configuration will be explained.

First, the sample 3 is set at the solid line position on the sample stage 12,
In this state, the surface of the sample 3 is irradiated from the electron optical system barrel 1, and a scanning signal is applied from the scanning signal generator 4 to the electron beam deflection coil 2 to scan the electron beam. Secondary electrons are generated from the sample 3 by this scanning, and the secondary electrons are detected by the secondary electron detector 5 and further amplified by the amplifier 6. The signal amplified by the amplifier 6 is processed by the image display unit 7 based on the scanning signal output from the scanning signal generator 4, and the secondary electrons from the sample 3 are displayed as an image.

With the above steps, the measurement by SEM is completed.

Next, the sample stage control unit 9 moves the sample stage 12 so that the sample 3 is at the position shown by the broken line. When the light source lamp 21 is turned on, the excitation light generated by this lighting becomes a desired excitation light wavelength by passing through an excitation light wavelength selection filter 20, and is further adjusted to a desired light intensity by a dimming ND filter 19.

The excitation light emitted from the attenuation ND filter 19 is reflected by the half mirror 13 and then irradiated onto the trial 3. Due to this irradiation, sample 3 emits fluorescence unique to the composition of the resist, which is an organic substance.

This fluorescence passes through a half mirror 13, and further, the excitation light wavelength is removed by an excitation light absorption filter 14, and then branched into two directions by an optical path switching mirror 15. The fluorescent image that has passed straight through the optical path switching mirror 15 is captured by a color camera 17 via an imaging lens 16. On the other hand, the optical path switching mirror 1
The fluorescent image reflected by 5 is formed by an imaging lens 18 at the position of the observer's eyes. This allows the observer to inspect the appearance of the sample 3 with the naked eye.

The image information captured by the color camera 17 is subjected to fluorescence wavelength analysis by the fluorescence wavelength analysis unit IO, detected as a color vector, and the fluorescence color from the sample 3 is recognized.

As described above, in this example, by using an optical observation means in combination with an observation means based on electron beam scanning, the former allows observation of the resist surface area with high resolution, while the latter is not suitable for electron beam scanning. Resist residue at the bottom of a deep resist hole can be detected from the presence or absence of fluorescence or the amount of fluorescence light. Note that even if an inorganic substance such as a silicon oxide film or a nitride film is irradiated with excitation light, no fluorescence is generated, so an observation means using electron beam scanning is used for this observation. As a result of the two observation means functioning to complement each other in this way, the appearance of the resist deep hole pattern can be inspected with high precision.

As above, the invention made by the present invention has been specifically explained based on the examples, but it goes without saying that the present invention is not limited to the above-mentioned examples and can be modified in various ways without departing from the gist thereof. Nor.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical ones are as follows.

That is, a first observation means detects and images secondary electrons generated from the sample when the sample is irradiated with an electron beam; Since a second observation means for forming an image is provided,
The resist hole pattern and the resist residue at the bottom of the water can be inspected with high accuracy and reliability.

[Brief explanation of the drawing]

The figure is an explanatory view showing the main parts of a visual inspection device that is an embodiment of the present invention. l...electron optical system barrel, 2...electron beam deflection coil,
3... Sample, 4... Scanning signal generator, 5... Secondary electron detector, 7... Image display section, 10... Fluorescence wavelength analysis section, 12... Sample stage, 13 .15... Half mirror 14... Excitation light absorption filter, 17... Color camera, 2O... Excitation light wavelength selection filter, 21
...Light source lamp.

Claims (1)

[Scope of Claims] 1. A first observation means for detecting and imaging secondary electrons generated from the sample when the sample is irradiated with an electron beam; and second observation means for forming a fluorescent image based on the fluorescent light. 2. The appearance inspection device according to claim 1, wherein the excitation light is visible light or ultraviolet light. 3. The appearance inspection apparatus according to claim 1, wherein the formation of the fluorescent image is performed by analyzing the fluorescence wavelength of the fluorescent image to convert it into a color vector to recognize the fluorescent color.