JP2001007171A - Equipment and method for wafer appearance inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the production yield of semiconductor ICs by inspecting the resist pattern during the photolithography process in manufacturing of semiconductor ICs. SOLUTION: A wafer 5, on which a resist pattern is formed, is placed on a stage 4. The wafer 5 is irradiated with light emitted by a mercury lamp 1 via a half mirror 2 and an object lens 3. An image sensor 6 receives the light reflected by the wafer 5, and a computer 7 performs image comparison. This wafer appearance inspection equipment has a filter which removes light with wavelengths causing the resist to be exposed in the optical path between the mercury lamp 1 and half mirror 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wafer appearance inspection in a manufacturing process of a semiconductor integrated circuit device, and more particularly to a wafer appearance inspection device and an inspection method in a photolithography process.

[0002]

2. Description of the Related Art In the manufacture of semiconductor ICs, a large number of IC chips are formed on a single wafer through many manufacturing steps. Among these manufacturing processes, the photolithography process, that is, the resist coating process
The exposure step-development step is an important step.
In the manufacture of C, a plurality of photolithography steps are performed. Usually, after this photolithography step, an appearance inspection is performed to see whether or not the resist pattern formed on the wafer surface is accurately formed.

FIG. 2 shows a schematic configuration of a conventional wafer appearance inspection apparatus. The light emitted from the mercury lamp 21 passes through the half mirror 22 and the objective lens 23 and passes through the stage 24
The wafer 25 placed above is irradiated. Wafer 25
Above, a large number of resist patterns for semiconductor IC fabrication are periodically formed by a photolithography process. The reflected light from the wafer 25 is reflected by the half mirror 22 to form a resist pattern image on the image sensor 26. By comparing the adjacent patterns of the resist pattern image by the computer 27, it is detected whether or not the pattern is correctly formed.

Another conventional wafer appearance inspection apparatus is disclosed in Japanese Patent Application Laid-Open No. 4-99346. As shown in FIG. 3, a wafer 37 placed on a stage 38 is irradiated with white light from a white light source 35 via a half mirror 34 and an objective lens 36, and the reflected light is passed through a color separation filter 39. Images are captured by the imaging camera 33. Image processing of the imaging pattern signal from the imaging camera and comparison with the reference image pattern,
Image processor 3 for inspecting patterns on wafers
2 and a computer 31.

[0005] Further, as a wafer appearance inspection apparatus, one described in Japanese Patent Application Laid-Open No. 1-217912 is known. As shown in FIG. 4, light emitted from an excitation light source 45 such as a mercury lamp selects a desired wavelength by an excitation filter 46 to form excitation light 47. This excitation light 4
Reference numeral 7 irradiates the wafer 42 placed on the stage 41 via the dichroic mirror 44 and the objective lens 43. Fluorescence 47 from resist pattern on wafer 42
a passes through the dichroic mirror 44 and forms an image on the camera 49. This image is displayed on the display unit 51 via the image processing unit 50. Thus, the presence or absence of the resist remaining at the bottom of the resist pattern is observed. In addition,
48 is a filter for absorbing the excitation light.

[0006]

In the manufacture of semiconductor ICs, it is strictly required to increase the yield.
In the photolithography process, that is, in the resist coating process-exposure process-development process process, the resist pattern after development process is subjected to a visual inspection to detect defects and is subjected to development processing using the wafer visual inspection apparatus shown in FIG. Inspection of the subsequent resist pattern has conventionally been performed. However, in order to further improve the manufacturing yield, not only the inspection of the resist pattern after the development processing, but also the inspection of the resist pattern before the exposure after the resist coating and before the development processing after the exposure, dust, scratches, dirt, It is conceivable to check for defects. By the way, when manufacturing a semiconductor IC, a plurality of photolithography steps are performed. For example, in the second photolithography step,
The pattern such as wiring previously formed on the wafer appears on the surface of the resist applied in the resist application step. In the present invention, there is a problem that the resist pattern is inspected after the resist application and before the development processing to detect a defect.
However, conventionally, the wafer appearance inspection during such a photolithography process has not been performed for the following reasons.

In the resist exposure step, visible light g-line (436 nm), h-line (405 nm), ultraviolet i-line (365 nm) and the like are used as light sources, and a resist suitable for them is used. . These resists are selected and used depending on the type of the semiconductor IC. As described above, in the wafer appearance inspection device, a mercury lamp is used as an illumination light source, and its emission wavelength is 300 to 600 n.
m. Therefore, the resist coating process
Exposure process-When a wafer inspection is performed during the development process, the wavelength of light used in the wafer inspection and the g of resist exposure
Since the wavelengths of the line, h-line and i-line overlap, the resist is exposed in the wafer inspection, and the exposed resist part is locally eluted in the development processing after the wafer inspection, causing a problem in that an abnormality occurs in the resist pattern. Because.

Further, the above-mentioned conventional Japanese Patent Application Laid-Open No.
The wafer appearance inspection apparatus described in Japanese Patent Publication No. 6 (1999) is intended to obtain a high-contrast image by separating reflected light from the wafer surface into three primary color lights by using a color separation filter. No description is given about a technique for inspecting a resist pattern during the process. Also, Japanese Patent Application Laid-Open No. 1-217912
The appearance inspection apparatus disclosed in Japanese Patent Application Laid-Open Publication No. H11-133873 attempts to detect the resist remaining at the bottom of the resist pattern from the fluorescent image, but does not attempt to detect the resist pattern during the photolithography process.

An object of the present invention is to provide a wafer appearance inspection apparatus and an inspection method capable of inspecting the appearance of a resist pattern even during a photolithography process in order to improve the production yield of a semiconductor IC.

[0010]

According to the present invention, a light emitted from an illumination light source is radiated to a wafer mounted on a stage and having a resist pattern formed thereon via a half mirror and an objective lens. The reflected light is received by the image sensor through the half mirror, and in a wafer appearance inspection device that compares a resist pattern image with a computer, an optical path between the illumination light source and the half mirror has a photosensitive wavelength range of the resist used. A filter that cuts light is installed. The filter includes a plurality of types of filters so that an appropriate filter can be selected according to a resist to be used. As an illumination light source, a mercury lamp or a xenon lamp can be used.

Further, the present invention provides an external appearance of a wafer for irradiating a resist pattern formed on a wafer with light emitted from an illumination light source and receiving reflected light from the wafer surface with an image sensor to inspect a resist pattern image. In the inspection method, the resist pattern formed on the wafer is irradiated with light obtained by cutting the photosensitive wavelength range of the resist to be used from the emission wavelength range of the illumination light source.
In particular, in the present invention, in a photolithography step of forming a resist pattern on a wafer, the appearance of the resist pattern is inspected after resist coating and before development processing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a wafer appearance inspection apparatus according to a first embodiment of the present invention. The light emitted from the mercury lamp 1, which is an illumination light source, passes through the half mirror 2 and the objective lens 3 after the light wavelength range for exposing the resist is cut by the filter 8b, and passes through the wafer 5 placed on the stage 4. Irradiate. On the wafer 5, a resist pattern for forming a large number of semiconductor IC chips is formed. The light reflected from the wafer 5 is laterally reflected by the half mirror 2 and forms an image of the resist pattern on the image sensor 6 to be converted into an electric signal. The resist pattern image captured by the image sensor 6 in this way is subjected to comparison processing by the computer 7, and a defect in the resist pattern is detected.

More specifically, a photolithography step, ie, a resist coating step, is performed on the wafer 5.
A resist pattern is formed through an exposure step and a development step, and the type of the resist is selected according to the type of the semiconductor IC to be manufactured. For example, when a resist pattern is formed using a g-line resist, the resist pattern is formed by exposure to visible light of 436 nm. If the mercury lamp 1 has an emission wavelength of 300 to 600 nm, the resist is exposed in the wafer inspection, and the exposed resist portion is locally eluted in the development processing after the wafer inspection. However, there is a problem that an abnormality occurs in the pattern shape. In the present invention, the emission of the mercury lamp 1 is filtered by the filter 8b.
To cut the wavelength range in which the g-line resist is exposed, and pass the other wavelength portions. When an h-line resist is used, the photosensitive wavelength range of the h-line resist is cut by passing through another type of filter 8a. When an i-line resist is used, it is allowed to pass through another filter 8c.
The photosensitive wavelength range of the i-line resist is cut. As described above, the wafer appearance inspection apparatus of the present invention includes a plurality of types of filters 8 and uses a filter capable of cutting the photosensitive wavelength range in accordance with the resist used. Even if the resist pattern on the wafer is inspected before the processing, the resist is not eluted by the developing processing, and no abnormality occurs in the pattern shape.

On the other hand, the light reflected from the wafer 5 is reflected laterally by the half mirror 2 to connect and capture a pattern image on the image sensor 6. The captured image is captured with black and white light and dark levels. Thereafter, the computer 7 performs an image comparison process according to the pattern cycle to detect a defect. The defect detection by this image comparison processing is to perform image comparison on a cycle-by-cycle basis, utilizing the fact that a large number of semiconductor IC chips are periodically formed on a wafer and are composed of a repetitive pattern of a certain cycle. Made by That is, the level values of black and white light and dark levels are compared between repeated adjacent points, the difference component is calculated, the address of a point outside a certain threshold is recorded, and the first point vs. the second point, the second point vs.
If there is a difference in the same address at the third location, this method automatically identifies the defect by recognizing that the second address has a defect. In other words, the wafer is composed of many chips, but the wiring arrangement in the chip is the same as the wiring arrangement of the adjacent chip. Therefore, comparing the three adjacent chips, if the wiring arrangement is normally patterned, there is no difference in the black and white light and dark level values, whereas if there is a defect, there is a difference in the level values. In addition, by comparing three chips, it is possible to specify which chip has a defect. In the above description, a case where a mercury lamp is used as the illumination light source has been described, but another light source such as a xenon lamp can be used.

Next, in the wafer appearance inspection method of the present invention, a resist pattern formed on a wafer is irradiated with light emitted from an illumination light source, and reflected light from the wafer surface is received by an image sensor to form a resist pattern image. At the time of inspection, the resist pattern formed on the wafer is irradiated with light obtained by cutting the photosensitive wavelength range of the resist used from the emission wavelength range of the illumination light source. Therefore, even if the resist pattern is inspected after the resist is applied and before the developing process, the resist is not exposed, and the resist pattern is not locally eluted in the developing process, so that an abnormality does not occur in the pattern outer shape. Therefore, it is possible to detect defects such as dust, scratches, dirt, and defects in the resist pattern in the middle of the photolithography process.
Can be improved in production yield.

[0016]

As described above in detail, according to the present invention, there is provided a wafer appearance inspection apparatus capable of inspecting a resist pattern formed on a wafer even during a photolithography step in the manufacture of a semiconductor IC. Since the inspection method can be obtained, there is an effect that the manufacturing yield of the semiconductor IC can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a conventional wafer appearance inspection device.

FIG. 3 is a diagram showing a schematic configuration of another conventional wafer appearance inspection apparatus.

FIG. 4 is a diagram showing a schematic configuration of another conventional wafer appearance inspection apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mercury lamp 2 Half mirror 3 Objective lens 4 Stage 5 Wafer 6 Image sensor 7 Computer

Continued on the front page F term (reference) 2F065 AA49 AA61 BB02 BB03 CC19 FF04 GG03 LL22 QQ31 RR02 RR07 2G051 AA51 AB01 AB07 CA04 CB01 CC07 4M106 AA01 BA04 BA07 CA39 DB04 DB07 DB13 DB15 DJ11 DJ14 DJ18

Claims (6)

[Claims] 1. A light beam emitted from an illumination light source is applied to a wafer, which is mounted on a stage and has a resist pattern formed thereon, via a half mirror and an objective lens, and reflected light from the wafer is applied to the wafer via the half mirror. In a wafer appearance inspection device that receives light with an image sensor and compares a resist pattern image with a computer, a filter that cuts light in the photosensitive wavelength range of the resist to be used is installed in an optical path between the illumination light source and the half mirror. Wafer appearance inspection device characterized by the following. 2. The wafer appearance inspection apparatus according to claim 1, wherein the filter comprises a plurality of types of filters so that an appropriate filter can be selected according to a resist to be used. 3. The wafer appearance inspection device according to claim 1, wherein a mercury lamp is used as the illumination light source. 4. The wafer appearance inspection device according to claim 1, wherein a xenon lamp is used as the illumination light source. 5. A wafer appearance inspection method for irradiating a resist pattern formed on a wafer with light emitted from an illumination light source, receiving reflected light from the wafer surface with an image sensor, and inspecting the resist pattern image. A wafer appearance inspection method comprising irradiating a resist pattern formed on a wafer with light obtained by cutting a photosensitive wavelength range of a used resist from an emission wavelength range of an illumination light source. 6. The wafer appearance inspection method according to claim 5, wherein in a photolithography step of forming a resist pattern on the wafer, the appearance of the resist pattern is inspected after resist application and before development processing.