JPH04106949A - Apparatus for inspecting thin film - Google Patents

Abstract

PURPOSE:To make it possible to sense thin films such as a residual resist surely and in a short time, by providing a beam projecting means, an excitation beam projecting means, and sensing means. CONSTITUTION:A laser oscillator 3 in the character of a beam projecting means, which projects the beams of respectively different wavelengths on a semiconductor wafer 1 as an object to be inspected, and a picture processing device 10 in the character of a sensing means are provided. Also, an excitation beam source 20 in the character of an excitation beam projecting means, which projects the excitation beams of respectively different wavelengths on the wafer 1, and a picture processing device 30 in the character of a sensing means are provided. From the oscillator 3, the beams of respectively different wavelengths are projected on the wafer 1, and from the differences between the respective brightnesses on the wafer 1, predetermined thin films on the wafer 1 are sensed. Also, from the beam source 20, the excitation beams of respectively different wavelengths are projected on the wafer 1, and from the differences between the respective fluorescent intensities emitted from the wafer 1, predetermined thin films on the wafer 1 are sensed. Thereby, the thin films such as a residual resist can be sensed surely and in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thin film inspection device for detecting residual resist on a semiconductor wafer during inspection after a development step in a semiconductor manufacturing process, for example.

(Prior Art) After a development process in a semiconductor manufacturing process, a semiconductor wafer is inspected. After this development process, a base pattern appears on the semiconductor wafer and a normal resist is formed. However, if the process conditions change even slightly in each step, the resist that should be removed in the development step may remain as an extremely thin film, that is, it may become a residual resist.

Therefore, the residual resist is inspected, and this inspection is carried out by a worker who magnifies the semiconductor urchin/\\ with a microscope. For this reason, it is difficult to save labor when inspecting the residual resist, and there is a high risk of dust generation.

Additionally, residual resist is detected by using computer image processing to compare the pattern of a normal semiconductor wafer with the pattern of a semiconductor wafer to be inspected, but this technology detects the entire semiconductor wafer. The amount of processing required for inspection becomes large and the processing time becomes extremely long.

(Problems to be Solved by the Invention) As described above, inspection by a worker is difficult to save labor and has a high risk of dust generation, and computer image processing requires a very long processing time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thin film inspection device that can detect thin films such as residual resist reliably and in a short time.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a light irradiation means for irradiating an object to be inspected with light of different wavelengths, and a light irradiation means for irradiating light of each wavelength with the light irradiation means. The present invention is a thin film inspection apparatus that attempts to achieve the above object by including a detection means for detecting a predetermined thin film on an object to be inspected based on differences in brightness on the object to be inspected.

The present invention also provides excitation light irradiation means for irradiating an object to be inspected with excitation light of different wavelengths, and each fluorescent light emitted onto the object when the excitation light irradiation means irradiates excitation light of each wavelength. This thin film inspection apparatus attempts to achieve the above object by being equipped with a detection means for detecting a predetermined thin film on an object to be inspected based on a difference in light intensity.

(Function) By providing such a means, the light irradiation means irradiates the object to be inspected with light of different wavelengths, and when these lights are irradiated, the detection means detects each brightness on the object to be inspected. A predetermined thin film on the object to be inspected is detected based on the difference.

Further, by providing the above means, the excitation light irradiation means irradiates the object to be inspected with excitation light of different wavelengths, and when the excitation light of these wavelengths is irradiated, the detection means emits the excitation light onto the object to be inspected. A predetermined thin film on the object to be inspected is detected based on the difference in intensity of each fluorescent light.

(Example) Hereinafter, a first example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a thin film inspection apparatus. semiconductor wafer 1
is placed on the XY child table.

A laser oscillator 3 is arranged above this XY child table. This laser oscillator 3 is wavelength tunable, and is variably set to different wavelengths λ1 and λ2, for example. The laser beam output from this laser oscillator 3 is transmitted to a mirror 4 placed above the XY child table and a beam expander 5.
The optical lens 6 irradiates the semiconductor wafer 1 with parallel light whose beam diameter is expanded. In this case, the positions of the mirror 4, beam expander 5, and optical lens 6 are set so that the laser beam is approximately perpendicularly incident on the surface of the semiconductor wafer 1.

Further, an industrial television camera (ITV camera) 7 is arranged above the XY child table.

This ITV camera 7 images the semiconductor wafer 1 and outputs the image signal. The output terminal of this ITV camera 7 is connected to an image processing device 10.

This image processing device 10 receives an image signal from the ITV camera 7 and irradiates the semiconductor wafer 1 with laser beams of wavelengths λ1 and λ2. It has a function to detect residual resist. The specific configuration is as follows. An image memory 12, a difference image memory 13, and an output section 14 are connected to the main control section 11, and an image difference processing section 15 and a determination section 16 are operated by instructions from the main control section 11. The image difference processing unit 15 has a function of obtaining difference image data indicating the difference in gray level between each image data obtained when irradiating the laser beams of wavelengths λ1 and λ2 stored in the image memory 2. . Further, the determining section 16 has a function of detecting residual resist from the difference image data obtained by the image difference processing section 15. Note that the image memory 12
An A/D converter 17 is connected to the ITV camera 5 so that the image signal from the ITV camera 5 is digitally converted and stored in the image memory 12. Further, a drive device 18 is connected to the output section 14.

Next, the operation of the apparatus configured as described above will be explained.

The laser oscillator 3 outputs a laser beam with a wavelength λ. This laser beam is reflected by a mirror 4, and the beam diameter is expanded by a beam expander 5 and an optical system 6, and the semiconductor wafer 1 is
is irradiated. In this state, the ITV camera 7 images the semiconductor wafer 1 and outputs the image signal. This image signal is converted into a digital image signal by the A/D converter 17 and stored in the image memory 12 as image data.

Next, the oscillation wavelength of the laser oscillator 3 is changed to λ2. The second laser oscillator 3 outputs a laser beam of wavelength λ2,
This laser beam is reflected by a mirror 4, the beam diameter is expanded by a beam expander 5 and an optical system 6, and the beam is irradiated onto the semiconductor wafer. Then, the ITV camera 7 images the semiconductor wafer 1 and outputs the image signal, which is stored as image data in the image memory 12 in the same manner as described above.

By the way, when the semiconductor Ueno\1 is irradiated with a laser beam, the laser beam hits the resist 1-1-a as shown in FIG.
and the lower surface of the resist 1a, and the reflected laser beams from both surfaces cause interference. Here, since the normal resist 1a shown in FIG. 5A and the residual resist IC shown in FIG.

3 to 5 show the interference intensity in normal resist, no resist, and residual resist on a semiconductor wafer, respectively. In these figures, two wavelength regions A (λ1
) and B (including λ2), the third
In the normal resist shown in the figure, the average value of the wavelength intensity peaks is the interference intensity, so the interference intensity is the same in each wavelength region A and B.

Also, even without resist shown in Fig. 4, each wavelength region A
, B have the same interference strength. However, in the residual resist shown in FIG. 5, the interference intensity is different in each wavelength region A and B. -Here, FIG. 6 shows image data when a laser beam with a wavelength λ is irradiated, and FIG. 7 shows image data when a laser beam with a wavelength λ2 is irradiated.

In this case, in the image data of wavelength λ1, the interference intensity in normal resist is α, the interference intensity without resist is β, and the interference intensity in residual resist is 71, and in the image data of wavelength λ2, the interference intensity in normal resist is α, The interference intensity without is β, and the interference intensity with residual resist is 72.

Image difference processing unit] 5 determines the difference in gray level between each image data of wavelength λ1 and wavelength λ2. FIG. 8 shows difference image data showing a difference in density level, and only residual resist remains. In other words, the interference intensity of the normal resist and the parts without resist are at the same level. Thus, the determination unit 1
Step 6 determines the presence of residual resist.

In this way, in the first embodiment, the semiconductor urchin
The residual resist is detected from the difference in interference intensity on the semiconductor wafer 1 when irradiated with laser beams of different wavelengths.
Residual resist can be detected reliably and in a short time. Moreover, it is possible to save labor and there is no risk of dust generation. Furthermore, there is no need to align each image data. Note that in the first embodiment, the wavelength of the emitted light is limited, but the wavelength may be limited using a filter or the like during camera input.

Next, a second embodiment of the present invention will be described.

FIG. 9 is a configuration diagram of the thin film inspection apparatus. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

An excitation light source 20 is arranged above the XY child table. This excitation light source 20 is wavelength tunable, and is variably set to different wavelengths λ3 and λ4, for example.

Further, an output terminal of the ITV camera 7 is connected to an image processing device 30.

This image processing device 30 receives an image signal from the ITV camera 7 and irradiates the semiconductor wafer 1 with excitation light of wavelengths λ9 and λ4. It has a function to detect residual resist on the surface. The specific configuration is as follows. An image memory 32, a difference image memory 33, and an output section 34 are connected to the main control section 31, and an image difference processing section 35 and a determination section 36 are operated by instructions from the main control section 31. The image difference processing unit 35 has a function of obtaining difference image data indicating the difference in gray level between each image data to be inspected obtained when the excitation light of each wavelength λ3 and λ4 stored in the image memory 32 is irradiated. There is. Further, the determining section 36 has a function of detecting residual resist from the difference image data obtained by the image difference processing section 35. Note that an A/D converter 37 is connected to the image memory 32 and the ITV camera 7 is connected to the image memory 32.
The image signal from is digitally converted and stored in the image memory 32.
is stored in the memory. Further, the drive device 18 is connected to the output section 34.

Next, the operation of the apparatus configured as described above will be explained.

The excitation light source 20 emits excitation light with a wavelength λ3.

This excitation light is irradiated onto the semiconductor wafer 1. In this state, the ITV camera 7 images the semiconductor wafer 1 and outputs the image signal. This image signal is converted into a digital image signal by the A/D converter 37 and stored in the image memory 32 as image data.

Next, the oscillation wavelength of the excitation light source 20 is changed to λ4.

The second excitation light source 20 emits excitation light having a wavelength λ4, and the semiconductor wafer 1 is irradiated with the second excitation light. Then, the ITV camera 7 images the semiconductor wafer 1 and outputs the image signal, which is stored as image data in the image memory 32 in the same manner as described above.

By the way, when the semiconductor wafer 1 is irradiated with excitation light, fluorescent light is emitted from the normal resist and residual resist portions on the semiconductor wafer 1. Note that no fluorescence is generated in areas without resist. FIG. 10 shows the wavelength characteristics C and D of fluorescence generated in the normal resist and the residual resist. As can be seen from the figure, the light intensity of the wavelength characteristic C of the normal resist is higher than that of the residual resist. This is because the normal resist is thicker than the residual resist.

Here, image data when the excitation light of wavelength λ3 is irradiated is shown in FIG. 11, and image data when the excitation light of wavelength λ4 is irradiated is shown in FIG.

In this case, in the image data of wavelength λ3, the fluorescence intensity in the normal resist is set as Pl, and the fluorescence intensity in the residual resist is set as Ql, and in the image data of wavelength λ4, the fluorescence intensity in the normal resist is set as P2, and the fluorescence intensity in the residual resist is set as P1. Let be Q2.

The image difference processing unit 35 calculates the difference in gray level between each image data of wavelength λ3 and wavelength λ4. FIG. 13 is difference image data showing the difference in gray level. In this difference image data, there is a fluorescence intensity difference G in the normal resist portion.

G 3 ''' P 2 P + is determined, and the fluorescence intensity difference G4 G4-02~Q1 is determined in the residual resist portion. Therefore, the fluorescence intensity difference G3 is a negative value, and the fluorescence intensity difference G4 is a positive value. The value is .

However, the portion where the positive value is present is the portion where residual resist exists. The determination unit 36 determines the presence of residual resist.

In this way, in the second embodiment, the semiconductor wafer 1
Excitation light of different wavelengths is irradiated to the semiconductor wafer 1, and residual resist is detected from the difference in the intensity of the fluorescent light emitted to the semiconductor wafer 1 when the excitation light of these wavelengths is irradiated, so that the same effect as in the first embodiment is achieved. I can play it.

Note that the present invention is not limited to the above embodiments, and may be modified without departing from the spirit thereof. For example, the present invention is applicable not only to detecting residual resist on the semiconductor wafer 1 but also to inspecting a glass panel of a liquid crystal display.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a thin film inspection device that can reliably detect thin films such as residual resist in a short time.

[Brief explanation of the drawing]

1 to 8 show a first diagram of a thin film inspection apparatus according to the present invention.
FIG. 1 is a diagram for explaining an embodiment, and FIG. 1 is a configuration diagram;
Figures 2 to 5 are diagrams for explaining interference intensity, and Figure 6 is a diagram for explaining interference intensity.
8 to 8 are diagrams for explaining the residual resist detection function, and FIGS. 9 to 13 are diagrams for explaining the second actual failure of the thin film inspection apparatus according to the present invention. FIG. 9 is a block diagram, FIG. 10 is a diagram showing fluorescence intensity characteristics, and FIGS. 11 to 13 are diagrams for explaining the residual lens detection function. 1. Semiconductor wafer, 2 XY child table 3. Laser oscillator, 4. Mirror, 5. Beam expander, 6
Optical lens, 7-I TV camera, 10°30...
Image processing device, 11.31... Main control unit, 12.32
...Image memory, 13.33...Difference image memory, 14.
34... Output unit, 15. 35... Image difference processing unit, 16.
36... Judgment unit, 17.37... A/D converter, 18
. . . Drive device, 20. . . Excitation light source. Applicant's agent Patent attorney Takehiko Suzue Figure 6 @ Figure 7 Figure 8 D Kishi

Claims (2)

[Claims] (1) A light irradiation means that irradiates the object to be inspected with light of different wavelengths, and when the light irradiation means irradiates the object with light of each wavelength, the difference in brightness on the object is detected. 1. A thin film inspection device comprising: a detection means for detecting a predetermined thin film on an object to be inspected. (2) An excitation light irradiation means for irradiating the object to be inspected with excitation light of different wavelengths, and each fluorescent light emitted onto the object to be inspected when the excitation light irradiation means irradiates the excitation light of each wavelength. 1. A thin film inspection apparatus comprising a detection means for detecting a predetermined thin film on the object to be inspected based on a difference in intensity.