JPS5966115A - Inspecting device for defect of thin film - Google Patents

Abstract

PURPOSE:To enable even the inspection of a very minute defect such as a very small change in a film thickness, by detecting an interference ray generated by the application of a light onto a thin film and by measuring the change in the intensity of the interference ray. CONSTITUTION:When a light 4 having a wave surface (ab) is applied onto a resist film 2 as a thin film and reflected thereby, a surface reflection light 13 passing through (b), being reflected at (d) and entering a prescribed point and a back-surface reflection light 14 being refracted at (a), falling into the resist film 2, being reflected at (c) and refracted again at (d) and entering the same light-receiving point are different in a time required for reaching the light-receiving point. Accordingly, when the light 4 in the same phase at (ab) is received by a spectroscope after being reflected by the resist film 2, a difference is caused in the phase and the back-surface reflection light 14 passing through (a), (c) and (d) is delayed when it is superposed on the light 13. As the result, an interference occurs. When the thickness of the resist film 2 changes, the degree of the difference in the phase also changes with said change, and thus the optical component of an intensified color changes as well. By measuring the optical component of this intensified color, the very small change in the thickness of the resist film 2 can be inspected.

Description

[Detailed description of the invention] The present invention relates to a thin film defect inspection device.

Generally, in the manufacturing process of semiconductor devices, a photoresist film is applied extremely thinly to the surface of a silicon wafer, and a circuit pattern is exposed to light on the resist film.

If this resist film has defects such as uneven thickness, ridges, scratches, adhesion of foreign matter (dust, oil film, water film, etc.), the exposure accuracy of the circuit pattern will be impaired.

The present invention has been made in view of the above circumstances, and its purpose is to provide a thin film defect inspection device that can inspect defects such as uneven thickness of thin films such as resist films. It is in.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of a thin film defect inspection apparatus according to the present invention, and FIGS. 2 and 3 are explanatory diagrams showing the principle of occurrence of interference.

In this example, a resist film 2 is applied extremely thinly to the surface of the sea urchin/Sl, and the light 4 from the light source 3 is applied to the resist film 2 through the nauf mirror 5 and the objective lens d.
is configured to be irradiated through the Specularly reflected light (not diffusely reflected light but regularly reflected light) 7 from the resist film 2 is configured to be detected by an interference light measuring device 8 via a nof mirror 5. This measuring device 8 includes a spectroscope 9 that receives interference light (described later) constituting specularly reflected light and separates it into a red light component R1, a green light component G, and a blue light component B; Three comparators 10R, 110G and 10B are connected to the three output terminals of 9 and compare the output value of each component with the set value, respectively, and are respectively connected to the other input terminals of these comparators and compare the set value with the output value of each component. A determiner 12 is connected to the setting devices 11R, 11G, and 11B to set the respective settings, and the output end of each comparator, and compares the output signals to identify the color of the interference light currently being detected, and determines the presence or absence of a defect. It is equipped with

Next, the effect will be explained.

As shown in FIG. 2, the light 4 irradiated onto the resist film 2 on the front surface of the wafer 1 is divided into two types: surface reflected light 13 that is reflected from the surface of the resist film 2, and light 4 that enters the resist film 2 and enters the back surface (the wafer 1).
The back surface reflected light 14 is reflected by the surface of In FIG. 2, when light 4 whose wavefront is ab is irradiated onto the resist film 2 as a thin film and reflected, it is reflected from b through d and reaches a predetermined point (in this example, the light receiving point of the spectrometer 9). ) and the back surface reflected light 14 which is refracted at a, enters the resist film 2, reflected at C, refracted at d, and enters the same light receiving point. Time is different.

Therefore, when the light 4, which had the same phase in AB, is reflected by the resist film 2 and then received by the spectroscope 9, there is a phase shift and the back reflected light 14 that has passed through the ACD overlaps with a delay.

Interference occurs.

Since the degree of phase shift differs depending on the wavelength of the light, the interference wave includes light components of colors that are strengthened due to the wavelength, or color difference K, as shown in Figure 3 (Fig. 3).
As shown in B), a light component of a color is weakened.

Furthermore, the degree of phase shift varies depending on the thickness of the resist film 2. Therefore, if the thickness of the resist film 2 changes, the degree of phase shift changes along with the swirl pattern variation, and therefore the light component of the color that is strengthened (and the light component of the color that is weakened) changes. ') Furthermore, by measuring variations in the light component of this enhanced color, extremely minute variations in the thickness of the υ resist film 2 can be inspected.

In this way, the specularly reflected light 7, which has become an interference light due to the pair of lights 13 and 14 shown in FIG. 2, becomes as shown in FIG.
The light is received by the spectrometer 9. The spectrometer 9 separates this interference light 7 into a red light component R, a green light component G, and a blue light component B, and applies these to each comparator 11R, 111G, and 11B, respectively.

As mentioned above, since the interference light includes color light components that are strengthened and color light components that are weakened, the R, which is separated by the spectrometer 9,
There will be a difference in strength between G and B. Each comparator compares the intensity value of each color light component inputted from the spectrometer with the reference intensity setting value inputted from each setting device at the same time, and for example, if the former is stronger than the latter. In this case, a predetermined output signal is applied to the determiner 12.

For example, due to interference in the resist film 2, the red light component R
When the signal is strengthened, only the comparator 10H applies a signal to the determiner 12 when the crab comes out, and the other comparator 10G applies the signal to the determiner 12.

10B does not apply an output signal. And resist film 2
When there is unevenness in the thickness of the film 2 and the colored light, which is strengthened by interference in the film 2, shifts from the red light component R to the blue light component B,
Only the comparator 10B applies an output signal to the determiner 12, and the red light component comparator 10R no longer applies an output signal.

The determiner 12 determines the presence or absence of a defect in the resist film 2 by comparing the applied signals from each of the comparators 10R, LOG, and IOB.

For example, as in the specific example above, the red light component comparator 10R
When the applied signal shifts to the applied signal of the blue light component comparator 10B, it is determined that the resist film 2 has an uneven thickness.

According to this embodiment, variations in film thickness are inspected by measuring changes in the intensity of color components of interference light, so extremely minute variations in film thickness can be inspected.

It should be noted that not only irregularities in the thickness of the resist film but also scratches on the resist film, adhesion of foreign matter, etc. can be inspected as defects because the color of the film surface changes.

Further, the present invention is applicable to defect inspection of not only resist films but also thin films in general.

As explained above, according to the present invention, even extremely minute defects such as extremely minute variations in the thickness of a thin film can be inspected.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. Figure 2 is an explanatory diagram showing the principle of interference generation, Figure 3 (B)
) are each waveform diagram. 1... Wafer, 2... Resist film, 3... Light source,
4...Irradiation light, 7...Specular reflection light (interference light), 8...
・Interference light identifier, 9... Spectrometer, IOR, 10G, 1
0B... Comparator, 11R, 11G, 11B... Setter, 12... Determiner.

Claims (1)

[Claims] 1. A thin film defect inspection device characterized by irradiating a thin film with light, detecting interference light generated by the light, and measuring changes in the intensity of the interference light to inspect defects.