JPH02237678A - Coating device - Google Patents

Abstract

PURPOSE:To supply only a conforming article to the treating stage after the coating stage and to efficiently reduce the working cost and material cost by detecting a film thickness in the radial direction as well as in the peripheral direction during the rotational coating. CONSTITUTION:A body 1 to be coated is placed on a chuck 4 and fixed by vacuum suction. A coating soln. 2 is dripped from a nozzle 3. The chuck 4 is rotated at high speed for a specified time by a motor 5 to expand the coating soln. 2 by centrifugal force, and the film of the coating soln. 2 is formed. When the body 1 is irradiated by the laser beams from He-Ne lasers 50 and 51 during coating, the beams are reflected by the interface between the body 1 and the film of the coating soln. 2 and by the interface between the film of the coating soln. 2 and the atmosphere, and the beams interfere with each other. The interference beams are received by photodetectors 52 and 53 and transduced into electric signals, which are sent to a detection part 200, amplified by amplifiers 54 and 55, and passed through low-pass filters 58 and 59. As a result, an electric signal proportional to the intensity of the reflected light is obtained. The signal is processed by the arithmetic part 81 of a discrimination part 24, and the quality of the film thickness distribution is discriminated by a radial film thickness distribution discrimination part 82.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid coating device, such as a spin coater that spins and coats a photoresist onto the surface of a semiconductor wafer.

[Prior art] Regarding spin coating, as shown in [Electronic Materials J, December 1988 issue, special edition, pages 78 to 83, published by Kogyo Research Association Co., Ltd., a thin film with a uniform thickness is coated on a silicon wafer, etc. It is used for forming on the target material. Figure 3 shows a conventional general applicator of this type, with a limb applicator (
1) is placed on the chuck (4) and fixed by a method such as vacuum suction. By dropping the coating liquid (2) onto the object to be coated (1) through the nozzle (3), and rotating the object to be coated (1) at high speed for a certain period of time by the motor (5) via the chuck (4). , the coating liquid (2) is spread by centrifugal force to form a thin film.

Before or during rotation, uneven solvent evaporation of the coating liquid (2), dust or droplets of the coating liquid (2) may adhere to the surface of the object to be coated (1), or scratches on the surface of the object to be coated may cause coating problems. The liquid film is disturbed, resulting in uneven film thickness.

Figures 4 to 6 show a workpiece on which a coating liquid film with a uniform thickness distribution was formed (hereinafter referred to as a good product) and a workpiece on which a coating liquid film with an uneven thickness distribution was formed. A schematic diagram of a top surface and a cross section of a body (hereinafter referred to as a defective product) is shown. The defective products shown in Figure 4 include striations (l5) and dust (
Coating failure (17) due to 16) occurred, and the coating film thickness became non-uniform. The defective product shown in FIG. 5 has non-uniform film thickness distribution in the radial direction due to non-uniform evaporation of the solvent contained in the coating liquid within the surface.

The product shown in FIG. 6 is a good product, with no coating defects and a uniform coating thickness. If patterning in the exposure and development steps is performed in the conditions shown in FIGS. 4 and 5, the pattern line width may become uneven or the pattern may not be drawn.
At that location, the product will be defective and the yield will be poor.

The conventional coating apparatus described above does not detect the film thickness distribution, and cannot discover non-uniformity in the film thickness distribution of the coating liquid film formed on the object to be coated.

For this reason, there is a problem in that the limb-applied body proceeds to the processing steps after the coating step without distinguishing between good and defective products, and defects are discovered in the further processed state.

In order to solve this problem, the present inventors invented what is shown in FIG. This prior invention detects the circumferential film thickness of the coating liquid (2) or other physical quantities correlated with the film thickness at a point other than the rotation center of the coated object (1) during coating using an optical method. a detection unit (14) that determines whether the coating film is good or bad based on the detection result, a cleaning liquid supply device (6) that performs processing based on the determination result, and a cleaning liquid nozzle (7). ). The detection unit (100) includes a light receiving element (11) that receives reflected laser light from the laser (10), an amplifier (12), and a high-pass filter (I3).

With the above configuration, first, the object to be coated (1) is placed on the chuck (4) and fixed by vacuum suction. Thereafter, the coating liquid (2) is dripped onto the object to be coated (1) from the nozzle (3). Furthermore, the object to be coated (1) is
Then, the chuck (4) is rotated at high speed for a certain period of time to spread the coating liquid (2) on the object to be coated (1) by centrifugal force, thereby forming a film of the coating liquid (2). During coating, a tie-Ne laser (10) irradiates the object to be coated (1) with laser light.

The light is transmitted to the interface between the limb coating body (1) and the coating liquid (2) film and to the coating. The liquid is reflected on two surfaces, the interface between the film and the atmosphere, causing interference. Figure 8 shows the changes in film thickness and intensity of reflected light over time. ), the intensity changes in one period with the film thickness △σ, and the rate of decrease in film thickness slows down with the passage of time.Furthermore, when the film thickness is about 1 μm, the period of change is usually one cycle. The period is longer than the time required for rotation.When inspecting the non-defective product shown in Figure 6 and the defective product shown in Figure 4 in a circumferential manner (18), the intensity change of the reflected light is as shown in Figure 9. In the case of this defective product, the reflected light intensity changes even during one revolution due to the unevenness of the film thickness distribution.On the other hand, in the case of a good product, such a rapid periodic change will occur. do not have.

The interference light is received by the light receiving element (11), and the light receiving element (11)
converts the received light into an electrical signal and sends the signal to the detection section (100). In the detection section (100), the signal is amplified by an amplifier (12) and then passed through a high-pass filter (13).
), an electrical signal as shown in FIG. 10 can be obtained. Based on the peak and average value of this signal, there is a section (1
Determine according to 4). As a result of the determination, if it is determined to be a good product, the limb application body (1) is directly allowed to proceed to the next step. If it is determined that the product is defective, the cleaning liquid supply device (6) is activated after coating is completed, the cleaning liquid is dripped from the cleaning liquid nozzle (7), the coating liquid (2) is removed from the object to be coated (1), and after drying. , reapply.

[Problem to be solved by the invention 1 The coating device according to the prior invention as described above detects only the film thickness in the circumferential direction or other physical quantities correlated with the film thickness, and does not detect the film thickness in the radial direction. I can't do anything.

Therefore, if non-uniformity of film thickness distribution occurs in the radial direction, this prior invention cannot deal with it.

This invention was made to solve the above problems, and by detecting the film thickness not only in the circumferential direction but also in the radial direction or other physical quantities correlated with the film thickness during spin coating, To obtain a coating device that can detect defects, supply only good products to a treatment process after the coating process, eliminate wasted processing costs and material costs, and reduce the time required for inspection by inspecting during coating. There is a particular thing.

[Means for Solving the Problems] The coating apparatus according to the present invention uses an optical method to measure the film thickness of the coating liquid or other physical quantities correlated with the film thickness at a plurality of different locations in the radial direction of the object to be coated. The present invention includes a detection section that uses the detection section to detect during coating, a judgment section that judges whether the coating film is good or bad based on the detection result, and processing means that performs processing based on the judgment result.

[Function] According to the present invention, for example, it is possible to detect a limb coated body with uneven film thickness distribution not only in the circumferential direction but also in the radial direction, which is caused by dust or scratches, without adding additional inspection time. . In addition, there is no need to send defective products to processing steps after the coating step.

Furthermore, found defective products can be washed and reused.

U Embodiment FIG. 1 shows an embodiment of the present invention, in which two lie-
Ne lasers (so), (51) and light receiving elements (52), (53) corresponding to these lasers are provided, and the output signals of the light receiving elements (52), (53) are sent to the detection unit (200). ) are connected to amplifiers (54) and (55), respectively. The detection section (200) is equipped with a high-pass filter (corresponding to these amplifiers (54), (55)).
56), (57) and low pass filter (58),
(59) is provided. The determination section (24) connected to the detection section (200) is provided with a radial thickness distribution determination section (82) having a calculation section (81) in addition to a circumferential thickness distribution determination section (80). It is being

The same reference numerals as in FIG. 7 indicate the same parts.

With the above configuration, when applying the coating liquid (2) to the object (1), first place the object (1) on the chuck (4).
Place it and fix it by vacuum suction. After that, nozzle (3
) and drop the coating liquid (2) onto the object to be coated (1). Furthermore, the limb applicator (1) and the chuck (4) are rotated at high speed for a certain period of time by the motor (5), and the coating liquid (2) on the object to be coated (1) is spread by centrifugal force. 2) Form the film. During coating, He-Ne laser (50),
At (51), the object to be coated (1) is irradiated with laser light. These lights are reflected at two surfaces: the interface between the object to be coated (1) and the film of the coating liquid (2), and the interface between the film of the coating liquid (2) and the atmosphere, causing interference with each other. When the defective product shown in FIG. 5 is inspected concentrically along circles (1g) and (19), the intensity change of the reflected light is as shown in FIG. 8. The curve (a) in FIG. 8 is the reflected light intensity tested circumferentially around the circle (19), and the curve (opening) is the reflected light intensity tested circumferentially around the circle (18). In the case of the defective product shown in FIG. 5, the reflected light intensity has a temporal phase shift between the curves (a) and (b) in FIG. 8 due to the non-uniformity of the film thickness distribution in the radial direction. The interference light is received by the light receiving elements (52) and (53), and the light receiving element (52)
), (53) convert the received light into an electrical signal and send the signal to the detection section (200). In the detection section (200), the signal is amplified by amplifiers (54), (55) and passed through low-pass filters (58), (59) to generate an electrical signal proportional to the reflected light intensity as shown in Fig. 8(b). I get a signal. By processing this signal in the arithmetic unit (8l) of the determining unit (24), a signal as shown in FIG. 2 is obtained. Figure 2 (a
) is the result of subtracting the output voltage of (a) in Figure 8 by the output voltage of (mouth), and Figure 2 (b) is the result of subtracting the output voltage of (mouth) from the output voltage of (a) in Figure 8. This is the result of subtracting .

If the changes in the two film thicknesses over time are equal, the values shown in FIG. 2(a) will not change. Also, in the case of Fig. 2(b), it is necessary to check whether the output of the two lasers used for inspection and the sensitivity of the light receiving element are the same, or whether the two signals are processed in the calculation unit (8l) after being normalized. For example, (a) in Figure 8
There should be no temporal variation in the difference between the output voltage of and the output voltage of (mouth).

Therefore, based on this signal, the radial film thickness distribution determining section (82) can determine whether the film is good or bad. This accuracy is extremely high because it uses laser optical interference. When the object to be coated (1) is a silicon wafer and the coating liquid (2) is photoresist, a resolution of about 10 people can be easily achieved. As a result of the judgment, if it is determined to be a good product, the limb application body (1)
Proceed directly to the next step. If it is determined that the product is defective, the cleaning liquid supply device (6) is activated after coating is completed, the cleaning liquid is dripped from the cleaning liquid nozzle (7), the coating liquid (2) is removed from the object to be coated (1), and after drying. , you will have to reapply.

Furthermore, although the above description of the operation describes the detection of defects in the film thickness distribution in the radial direction, the detection of defects in the film thickness distribution in the week direction can also be performed in the same manner as described in the prior invention. The device is the high-pass filter (56) in the figure.
, (57) or the circumferential film thickness distribution determining section (80) may be used.

In addition, in the above embodiment, a cleaning device is shown as a processing device after detecting a defect. may be provided. Further, although a laser is shown as a light source, a combination of a white light source and a filter, or a combination of a lens and a white light source may also be used. Further, as for the measurement method, in addition to the method using optical interference described here, it is also possible to use optical absorption in the film.

[Effects of the Invention] As described above, according to the present invention, the film thickness of the coating liquid or other physical quantities correlated with the film thickness can be measured using an optical method at a plurality of different locations in the radial direction of the object to be coated. By being equipped with a detection unit that detects during coating, a determination unit that determines whether the coating film is good or bad based on the detection results, and processing means that performs processing based on the determination results, the following effects can be achieved. play.

(i) Since the film thickness distribution can be inspected not only in the circumferential direction but also in the radial direction, defects can be found more accurately than in the prior invention.

(11) Since only non-defective products can be sent to the post-coating process, they will not become defective after being processed in the post-process, reducing processing costs and material costs.

(i) Defect detection is easier than visual inspection of the pattern line width created by the coating liquid film on the object to be coated (Ueno, etc.), and is automated, so it can be done accurately and quickly. can be done, and the size can be reduced.

(iv) Since the inspection is performed during application, there is no need to set up additional time or space for it.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view of an embodiment of the present invention, and FIG. 2 is a characteristic line diagram of calculation results for the one shown in FIG. Figures 3 to 10 show a conventional coating device, with Figure 3 being a schematic side view and Figure 4 being a plan view (a) in the case of a defective coating liquid film.
, Cross-sectional views (b.), (bt), (b3) on the plane along the 1-1 line, ■1■ line, and I-III line in (a), Figure 5 shows another case of coating film defect. Plan view (a), cross-sectional view (
b), Figure 6 is a plan view (a) and cross-sectional view (b) when the coating liquid film is good, Figure 7 is a schematic side sectional view of the prior invention, and Figure 8 is the film thickness and reflection during coating. Time change characteristics diagram of light intensity,
FIG. 9 is a comparison diagram of time change characteristics of reflected light intensity of defective products and non-defective products, and FIG. 10 is a comparison diagram of output voltage characteristics corresponding to FIG. 9. (1)...Object to be coated, (2)...Coating liquid, (200) In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a coating device that drops a coating liquid onto an object to be coated, rotates the object to be coated, spreads the coating liquid by centrifugal force, and forms a thin film of the coating liquid on the object to be coated. a detection means for detecting either a thin film of the coating liquid or any other physical quantity correlated with the thin film at a plurality of different locations in the radial direction of the body using an optical method; 1. A coating device comprising: a determination section that determines whether a film is good or bad; and processing means that performs processing based on the determination result.