JPH10144671A - Spin coating method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the useless consumption of a coating liq. to form an economical coat by dripping the coating liq. on a substrate, and rotating the substrate with a specified initial rotation acceleration. SOLUTION: On a stationary semiconductor wafer 11 a specified amt. of coating liq. 15 according to the coating area of the wafer 11 and required thickness of a protective film is dripped approximately on the center of the wafer 11. Thereafter a drive source 14 is actuated to rotate a chuck 13 at a rotation acceleration of 33rpm/sec or more from the stop state, together with the semiconductor wafer 11 integrated with the chuck 13 to form a coat film of approximately uniform thickness, without discharging much waste liq.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a polyimide liquid, which is a material for forming a protective film, on a semiconductor wafer, for example, to form a protective film covering an IC circuit portion incorporated on a semiconductor wafer. The present invention relates to a suitable spin coating method and apparatus.

[0002]

2. Description of the Related Art A spin coating method is known as a method of forming a coat film such as a protective film covering a semiconductor wafer. According to this, the coating liquid dropped on the central portion of the semiconductor wafer is
Due to the centrifugal force accompanying the rotation of the semiconductor wafer, it is pushed out to the periphery of the semiconductor wafer, and by drying this coating liquid
A coat film covering the semiconductor wafer is formed. Such a spin coating method is also used for forming a protective film of an IC circuit incorporated in a semiconductor wafer.

However, in such a spin coating method, unless the coating liquid is sufficiently supplied to the surface to be coated,
Since the coating liquid is dried while being spread radially on the surface to be coated, it is not possible to obtain a coating film having a uniform thickness over almost the entire surface of the surface to be coated.

[0004]

Therefore, conventionally, it has been attempted to form a uniform coating film by excessively supplying the coating liquid to the surface to be coated. However, in the conventional spin coating method of supplying an excessive coating solution, a large amount of the coating solution exceeding 90% of the supplied coating solution is released from the edge of the coated surface as an excess,
It had been treated as waste liquid. Therefore, there has been a demand for a method capable of economically forming a coat film by eliminating waste of the coating liquid and an apparatus capable of performing the method.

[0005]

The present invention adopts the following constitution in order to solve the above points. <Structure> The spin coating method according to the present invention employs a static pin coating method in which a coating liquid is dropped on a substrate, and the dropped coating liquid is rotated on the substrate by centrifugal force accompanying rotation of the substrate to rotate the substrate. The method is characterized in that the substrate is rotated at a rotational acceleration of 30,000 rpm / sec or more at the start of the rotation of the substrate.

In the spin coating method according to the present invention, a coating liquid is dropped on a stationary substrate, and the coating liquid is supplied in a state of maintaining a circular shape on the substrate by this dropping. The coating liquid supplied while maintaining a circular shape on the substrate is 30,000 rpm /
Strong centrifugal force is applied almost uniformly in the circumferential direction by the integral movement with the substrate that is rotated at a high speed with a sudden rising rotational acceleration of not less than a second, so that it can be spread evenly in the circumferential direction.

Accordingly, it is possible to apply the coating liquid almost uniformly on the substrate to be coated without requiring an excessive supply of the coating liquid as in the prior art, thereby discharging a large amount of waste liquid. Without this, a coat film having a substantially uniform thickness can be formed.

As a specific example of this coating solution, for example, about 1
A polyimide synthetic resin material having a viscosity of 500 cP can be used, whereby a protective film for protecting an IC circuit incorporated therein can be suitably formed on a substrate formed of a semiconductor wafer.

Further, the spin coater according to the present invention comprises:
In order to spread the coating liquid dropped on the substrate onto the substrate by centrifugal force caused by the rotation of the substrate, a spin coating apparatus operated at a rotation acceleration of 30,000 rpm / sec or more at the start of the rotation of the substrate is used. A detection mechanism for detecting that the coating liquid has reached the section, and a control mechanism for controlling the rotation speed of the substrate based on a detection signal from the detection mechanism.

In the spin coating apparatus according to the present invention, the coating liquid supplied while maintaining a circular shape on the substrate is 30,000 rpm /
Intense centrifugal force is applied almost uniformly in the circumferential direction by the integrated movement with the substrate that is rotated at a high speed with a sudden rising rotational acceleration of more than a second. The detection mechanism reliably detects that the coating liquid spread toward the edge reaches the edge of the substrate, and the control mechanism suppresses the rotation speed of the substrate based on the detection signal.

Since the centrifugal force acting on the coating liquid is reduced by suppressing the rotation speed, it is possible to further reduce the amount of the coating liquid discharged as waste liquid beyond the edge of the substrate.

Further, by providing a bank portion in advance at the edge of the substrate to prevent overflow of the coating liquid from the edge of the substrate, it is possible to reliably prevent overflow of the coating liquid from the edge of the substrate. This makes it possible to prevent generation of waste liquid due to release of excessive coating liquid. For example, by forming the bank portion from a quick-drying synthetic resin material, the bank portion can be quickly formed without significantly increasing the operation time.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. <Specific Example> FIG. 1 is a front view schematically showing a specific example of a statics pin coating apparatus for effectively implementing the method of the present invention. In the illustrated example, the statics pin coating apparatus 10 is, for example, a semiconductor wafer 1 in which an IC circuit is incorporated.
1 is used as a substrate to form a protective film mainly for the purpose of preventing moisture from the IC circuit so as to cover the surface thereof.

The spin coater 10 includes a chuck 13 having a rotating shaft 12 and a chuck 13 for driving the chuck 13 at a rotational acceleration of 30,000 rpm / sec or more from a stopped state.
A drive source 14 such as an electric motor connected to the rotating shaft 12
And A well-known holding means (not shown) such as a vacuum suction mechanism is incorporated in the chuck 13, and the semiconductor wafer 11 is held by the chuck 13 by this holding means.

Above the chuck 13, for example, 1500
A coating liquid supply nozzle 16 for dropping a coating liquid 15 made of a polyimide synthetic resin material having a viscosity of cP is provided. As shown by a broken line in FIG. 1, the nozzle 16 is provided on the semiconductor wafer 11 in a stationary state with a predetermined amount of the coating liquid 15 according to the area to be coated on the semiconductor wafer 11 and the thickness of the protective film required. To the semiconductor wafer 1
1 is dropped almost at the center. The coating liquid 15 dropped on the semiconductor wafer 11 is supplied as a substantially hemispherical mass as shown by a broken line due to the surface tension thereof, and is substantially coaxial with the semiconductor wafer 11 at the center on the semiconductor wafer 11. Draw a circle.

When the coating liquid 15 is dropped on the semiconductor wafer 11, the chuck 13 is driven at a rotational acceleration of 30,000 rpm / second or more from the stopped state by the operation of the drive source 14, and is integrally formed with the chuck 13. The semiconductor wafer 11 rotates. This rapid rotational acceleration is maintained until the rotational speed of the chuck 13 exceeds, for example, 4000 rpm.

Due to the strong centrifugal force generated by the rapid rotation of the chuck 13, the coating liquid 15 supplied as a hemispherical lump to the center of the semiconductor wafer 11 does not spread radially locally as in the conventional case. , The outer edge of which is almost evenly spread in the circumferential direction while maintaining a substantially circular shape,
Further, by drying, a protective film is formed. Therefore, without performing the conventional excessive supply of the coating liquid,
By supplying an appropriate amount of the coating liquid 15 according to the thickness of the protective film and the area of the protective film, a protective film having a substantially uniform thickness is formed.

In the example shown in FIG. 1, a detecting mechanism for detecting that the coating liquid 15 has reached the edge of the semiconductor wafer 11 in order to suppress the release of the coating liquid 15 from the edge of the semiconductor wafer 11. A control mechanism 18 for controlling the operation of the drive source 14 based on the detection signal from the detection mechanism 17 is provided.

The detecting mechanism 17 can be constituted by detecting means such as an infrared sensor or a reflection type optical sensor. The detection mechanism 17 detects that the coating liquid 15 is applied to the semiconductor wafer 11 by centrifugal force caused by the rotation of the chuck 13.
, The detection signal is sent to the control mechanism 18.

Upon receiving the detection signal from the detection mechanism 17, the control mechanism 18 sends a control signal to the drive source 14. With this control signal, the drive source 14 reduces the rotation speed of the chuck 13. Due to this reduction in the rotation speed, the coating liquid 1
Since the centrifugal force acting on the semiconductor wafer 11 is also reduced, the amount of the coating liquid 15 supplied onto the semiconductor wafer 11 released as waste liquid from the edge of the semiconductor wafer 11 is reduced.
As a result, the amount of wasted use of the coating liquid 15 can be reduced, and thereby effective use of resources can be achieved.

FIGS. 2 and 3 show another embodiment of the present invention. As shown in FIGS. 2 and 3, a bank portion 19 can be formed at the edge of the semiconductor wafer 11 before the chuck 13 is rotated. As shown in FIG. 3, the bank portion 19 is formed along the edge of the semiconductor wafer 11, and is a band-shaped member made of a quick-drying synthetic resin material having a width W of 3 mm and a height H of 2 mm, for example. Can be formed.

As described with reference to FIG. 1, the coating liquid 15 coaxially supplied to the center position of the semiconductor wafer 11 indicated by the symbol A in FIG.
To ensure that they are not released from the edges of the In addition, the coating liquid 15 is dropped on the ridge portion 19 at an eccentric position shifted from the center position A, as indicated by reference numeral B in FIG. 2, and is applied to the edge of the semiconductor wafer 11 by centrifugal force acting uniformly in the circumferential direction. Even if the arrival time is partially different in the circumferential direction of the semiconductor wafer 11, the portion that has reached the embankment 19 earlier is regarded as the embankment 1
9 surely blocks. Therefore, even if a slight error occurs in the arrangement relationship of the nozzle 16 with respect to the semiconductor wafer 11, the bank liquid 19 causes the coating liquid 1 from the edge of the semiconductor wafer 11.
5 can be reliably prevented. This allows
A predetermined protective film can be formed at a cost of 1/5 to 1/10 or less as compared with the related art.

In the above description, the coating liquid is I
Although the example of the polyimide liquid for forming the protection film of the C circuit has been described, the present invention is applied to other coating liquids such as a resist liquid for a photoresist film of a lithography technique used in a manufacturing process of a semiconductor IC. Can be applied.

[0024]

According to the method of the present invention, as described above, the coating liquid supplied while maintaining a circular shape on the substrate is rotated at a high speed at a rapid rising rotational acceleration of 30,000 rpm / sec or more. By receiving the strong centrifugal force almost uniformly in the circumferential direction by the integral movement with the substrate, the coating liquid can be spread evenly in the circumferential direction. The coating can be applied almost uniformly on the substrate, whereby a coating film having a substantially uniform thickness can be formed without releasing a large amount of waste liquid.

According to the apparatus of the present invention, in addition to the method of the present invention being able to be suitably carried out, the detection mechanism detects that the coating liquid spread toward the edge of the substrate reaches the edge of the substrate. Since the control mechanism suppresses the rotation speed of the substrate based on the detection signal, the centrifugal force acting on the coating liquid when the coating liquid reaches the edge of the substrate can be reduced. Accordingly, it is possible to further reduce the amount of the coating liquid discharged as waste liquid over the edge of the substrate.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing a statics pin coating apparatus for performing a spin coating method according to the present invention.

FIG. 2 is a plan view showing another example of the statics pin coater shown in FIG.

FIG. 3 is a sectional view taken along line III-III shown in FIG. 2;

[Explanation of symbols]

 Reference Signs List 10 spin coater 11 substrate (semiconductor wafer) 15 coating liquid 17 detection mechanism 18 control mechanism 19 bank

Claims (6)

[Claims] 1. A static pin coating method in which a coating solution is dropped on a substrate, and the substrate is rotated so that the dropped coating solution is spread on the substrate by centrifugal force accompanying rotation of the substrate. And spinning the substrate at a rotational acceleration of 30,000 rpm / sec or more at the start of rotation of the substrate. 2. The spin coating method according to claim 1, wherein the coating liquid is a polyimide liquid. 3. The viscosity of the polyimide liquid is about 1500 c.
The spin coating method according to claim 2, wherein P is P. 4. A method for spreading a coating liquid dropped on a substrate onto the substrate by centrifugal force accompanying rotation of the substrate.
The rotational acceleration at the start of rotation of the substrate is 30,000 rpm
A spin coater that operates at a speed of at least about / sec, and controls a rotation speed of the substrate based on a detection signal from the detection mechanism for detecting that the coating liquid has reached an edge of the substrate. And a control mechanism for controlling the spin coating. 5. An edge of the substrate, along the edge,
5. The spin coater according to claim 4, wherein a bank portion for preventing overflow of the spin coat liquid is provided in advance. 6. The spin coater according to claim 5, wherein the bank is formed of a quick-drying synthetic resin material.