JPH02229577A - Coater - Google Patents

Abstract

PURPOSE:To eliminate the fluctuation in the film thickness of a coating liquid by measuring the film coating of the coating liquid or the physical quantity correlating therewith and controlling the rotation stop time of the object to be coated. CONSTITUTION:Measuring means 10, 11 which measure either of the film thickness of the coating liquid 2 on the object 1 to be coated or the physical quantity correlating with this film thickness during application of the coating liquid 2 on the object 1 and a control means 12 which controls the rotation stop time of the object 1 in accordance with the measured value of the measuring means 10, 11 are provided. The film thickness of the coating liquid 2 is always uniform if the rotation of the object 1 is so controlled as to be stopped when the intensity of the light reflected form, for example, the coated film attains a prescribed value.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid coating device, and more specifically, to a coating device called a subin coater that spins and coats resist onto the surface of a semiconductor wafer, for example.

[Prior art] Conventionally, this fence coating device was manufactured by Kogyo Kenkyukai Co., Ltd.
As shown in "Electronic Materials J, December 1988 Special Issue, pages 78-83, it is used to form a thin film with a uniform thickness on a 1Ijl coated body such as a wafer. Figure 4 shows the conventional method. A general coating device (hereinafter referred to as conventional example 1) is shown in which the object to be coated (1) is placed on a chuck (4) and fixed by a method such as vacuum suction.Coating liquid (2)
The coating liquid (2) is dripped from the nozzle (3) onto the coating material (1), and the motor (5) rotates the chuck (4) and the coating material (1) at high speed for a certain period of time. )
to form a thin film.

The rotation speed and rotation time of the motor (5) are determined in advance by determining conditions based on the viscosity of the coating liquid used and the desired film thickness.

Conventional coating equipment as described above is operated uniformly under predetermined conditions, so it is usually difficult to make the film thickness of many resists uniform, and it is difficult to prevent variations in film thickness. There was a drawback to this.

As a means to eliminate such drawbacks, Japanese Patent Application Laid-Open No. 63-
There is an invention disclosed in Japanese Patent No. 51976 (hereinafter this invention will be referred to as Conventional Example 2), which is shown in FIG. In the figure, (104) is a film thickness measurement section, (105) is a film thickness control section, (
tOa) is a motor control unit, and (100) is a laser beam.

In the conventional example 2, the film thickness measuring section (104) measures the film thickness of the coating liquid (2) on the rotating object (1) by observing interference fringes with a laser beam (100); Based on the measured value in the measurement section, the film thickness control section (
106), the rotational speed of the object to be coated that is being rotated is controlled to obtain a predetermined film thickness. Here, the rotational speed of the motor is dynamically controlled during coating by comparing the time-film thickness relationship stored in advance with the film thickness measurement value during rotation.

In this way, in Conventional Example 2, the problem of film thickness variation is solved by incorporating the idea of feedback control into the coating device, which was conventionally operated uniformly under predetermined conditions as in Conventional Example 1. This is what I was trying to solve.

[Problems to be Solved by the Invention] However, the time required for the spin coating process is usually several tens of seconds at most, and in order to dynamically control the spin coating during this time, it is necessary to rapidly increase the film thickness. It is not easy to construct such a control system, as it must be measured, a control policy must be determined at high speed, and control must be executed at high speed. Furthermore, in equipment that applies photoresist solution to semiconductor wafers, for example, the baking process after applying the resist solution takes a longer time, and the time required for the spin coating process can be changed simply by changing the waiting time of the baking process. Yes, it does not affect the overall duration of the process and therefore
There is no point in deliberately keeping the rotational coating time constant.

This invention was made in order to solve the above-mentioned problems, and it is possible to easily control the rotation of the object to be coated and eliminate variations in film thickness due to fluctuations in supply liquid temperature and atmospheric conditions. The purpose is to obtain a coating device.

[Means for Solving Problem i, /(] The coating device according to the present invention measures other physical quantities correlated with the film thickness during rotational coating, and stops the rotation of the mt cloth based on the measured values. It is designed to determine the time.

[°Function] In the present invention, for example, when the intensity of reflected light from the coating film reaches a predetermined value, the rotation of the VT coating body is stopped.

[Embodiment] FIG. 1 shows an embodiment of the present invention. Here, when applying the coating liquid (2) to the object to be coated (1), first the object to be coated (1) is placed on the chuck (4). ) and fix it by vacuum suction. Thereafter, the coating liquid (2) is dropped onto the object to be coated (1) from the nozzle '<3).

Further, the motor (5) rotates the workpiece (1) and the chuck (4) at high speed for a certain period of time, and the workpiece (1)
Spread the upper coating liquid (2) by centrifugal force to form coating liquid (2).
Forms a film of During coating, the object to be coated (
1) Irradiate light onto the top and measure the intensity of the reflected light on the light receiving element (l1
) to detect. During coating, the film thickness of coating liquid (2) decreases,
Therefore, the intensity of reflected light increases. This situation is shown in FIG. The figure (a) shows the relationship between the time 7 and the film thickness Q, and the figure (b) shows the relationship between the time t and the reflected light intensity I. In the figure,
Q, indicates the desired film thickness, and 2, indicates the reflected light intensity when the desired film thickness is Qt. It is determined in advance through experiments and the like, and is stored in the motor rotation stop control section (12). As shown in FIG. 3, the motor rotation stop control unit (l2) receives the electrical signal from the light receiving element (11), calculates the reflected light intensity I from the signal strength, and determines that the value is I. At this point, the rotation of the motor (5) is stopped.

Although one embodiment of the present invention has been specifically described above, the present invention does not limit the film thickness measurement method, the types of physical quantities correlated with the film thickness, and the measurement methods thereof. In the above embodiment, the optical absorption method was used for measurement, but other means such as optical interference method or polarization method may be used.

[Effects of the Invention] As described above, according to the present invention, the thickness of the coating liquid film can be controlled by measuring the coating liquid film thickness or a physical quantity correlated thereto and controlling the rotation stop time of the object to be coated. Since it can be kept constant, it has the effect of reducing variations in film thickness, which greatly contributes to improving the quality and yield of semiconductor products, for example.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of an embodiment of the present invention, Fig. 2 is an operating characteristic diagram of the one shown in Fig. 1, Fig. 3 is a flowchart showing a control method of the one shown in Fig. FIG. 5 is a schematic side view of a conventional coating device. l... coating body, 2... coating liquid, 3... nozzle, 5...
Motor, 10...Light source, 1l...Light receiving element, 12...Motor rotation stop control unit. In each figure, the same reference numerals indicate the same or equivalent parts. Figure 1: Exposure time (t') in subject body 2 Figure Figure 6 Procedural amendment 6. Contents of amendment June 1, 1990 Specification, page 3, line 13

Claims (1)

[Claims] In a coating device that drops a coating liquid onto an object to be coated, rotates the object to spread the coating liquid by centrifugal force, and forms a thin film of the coating liquid on the object to be coated. A measuring means for measuring either the film thickness of the coating liquid on the coating body during coating or a physical quantity having a correlation with this film thickness, and a rotation stop time of the coating body based on the measured value by this measuring means. A coating device comprising: a control means for controlling.