JPH11333359A - Formation of coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent such defective coating as nonuniform coating by controlling the suspension of a coating soln. so that the soln. surface is stopped above the tip face of a nozzle so that the coating soln. to be applied on a substrate to be treated is not isolated and left in the tip of the nozzle. SOLUTION: A resist soln. is dripped, and then the tip face of the resist soln. in a nozzle 21 is stopped at a first position A 0.5-1.0 mm above the tip opening of the nozzle 21 by closing a pneumatic valve at a specified speed to prevent dripping. Subsequently, a suck-back valve is gradually opened in 1-2 sec to stop the tip face of the resist soln. in the nozzle 21 at a second position B about 3 mm above the tip opening of the nozzle 21, and the drying of the soln. surface is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a coating film for forming a resist film or the like on the surface of a substrate to be processed.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a resist liquid is applied to a semiconductor wafer (hereinafter, referred to as a wafer) as a substrate to be processed, the resist film is exposed using a photomask, and developed. Accordingly, a photolithography technique for producing a resist mask having a desired pattern on a wafer has been used. At that time, a spin coating method is generally used as a method of applying a resist liquid. As shown in FIG. 8, a resist solution is dropped from a nozzle 102 disposed above a wafer W while the wafer W is rotated by a motor M while being vacuum-sucked on a spin chuck 101 as shown in FIG. This is performed by uniformly spreading the resist solution on the surface of the wafer W by force. After the resist solution is dropped, the resist solution in the nozzle 102 stops at a position where the liquid level coincides with the tip surface of the nozzle 102, and is left in that state until it is dropped on the next wafer W.

[0003]

However, if the resist liquid is left in a state where the liquid level of the resist liquid coincides with the tip end face of the nozzle 102, dripping may occur, as described above.
This may cause uneven coating. In addition, the resist liquid in the vicinity of the tip of the nozzle dries before the next dropping, and coating unevenness may occur when the resist liquid is dropped on the next wafer W.

Therefore, the stop position of the resist liquid in the nozzle 102, that is, the liquid surface position, is determined by the closing speed of an opening / closing valve provided in a resist liquid flow path between the nozzle 12 and a resist liquid supply source (not shown). For this reason, it is conceivable to increase the closing speed of the valve so that the liquid level is raised above the tip end surface of the nozzle 102. However, when the liquid level is rapidly raised, a part of the resist liquid is torn. The nozzle 102 may remain near the tip of the nozzle 102, resulting in poor coating.

The present invention has been made under such circumstances, and an object of the present invention is to make it possible for a coating liquid to be applied on a substrate to be processed to remain at the nozzle tip without being isolated and remaining in the nozzle tip. An object of the present invention is to provide a method for controlling a supply stop of a coating liquid so as to stop at a position higher than a surface, thereby forming a coating film on a substrate to be processed without causing coating defects such as coating unevenness.

[0006]

According to the present invention, there is provided a method for forming a coating film, comprising the steps of: positioning a nozzle provided at the tip of a flow path of a coating liquid above a substrate; and opening a valve provided in the flow path. To discharge the coating liquid from the nozzle and supply it to the substrate surface.
Forming a coating film on the substrate surface, and then closing the valve so that the tip surface of the coating solution stops at a first position above the tip opening of the nozzle; A step of sucking the application liquid by a suction means provided on the downstream side of the above and drawing the leading end surface of the application liquid to a second position above the first position.

In the present invention, the first position is a position which is, for example, 0.5 mm to 1.0 mm above the tip opening of the nozzle, and the second position is a position which is higher than the tip opening of the nozzle. For example, it is a position on the upper side by 3.0 mm to 4.0 mm. As the suction means, for example, a suck-back valve that enlarges the volume of the flow path by expanding a part of the wall of the flow path to the outside can be used.

According to the present invention, after the coating liquid is discharged from the nozzle, the valve is closed at a certain speed, and then the coating liquid is sucked by the suction means, and the leading end surface of the coating liquid is pulled up in two stages. Therefore, when the valve is closed, the front end surface is rapidly raised. However, in this step, the coating liquid may be raised slightly so as not to cause dripping, so that the application liquid moves between the front end opening of the nozzle and the stop position (first position). There is no danger of remaining between. Then, in the next step, the tip surface is pulled up by the suction means, so that even if it is pulled up to a position sufficient to prevent drying of the liquid, it can be pulled up gently. There is no adverse effect on the ejection of.

[0009]

FIG. 1 and FIG. 2 show an example of a coating film forming apparatus used for carrying out a coating film forming method according to the present invention. This coating film forming apparatus includes a spin chuck 12 rotatably and vertically movable supported by a motor M and an elevating means 11, and a spin chuck 12.
A nozzle 21 that can be arranged above the wafer W vacuum-adsorbed by the nozzle and a connection between the nozzle 21 and a coating liquid supply source, for example, a resist tank 38, are connected to supply a coating liquid, for example, a resist liquid. A pipe 31 and a pump 39, an opening / closing means 32, and a suction means 36, which are provided in the middle of the supply pipe 31 in order from the upstream side (the lower side in FIG. 1), are provided.

The opening / closing means 32 is made of, for example, an air-operated valve as shown in FIG. The pneumatic valve is configured such that the valve element is opened by an elastic return force of a spring, and the valve element is closed by air pressure against the restoring force of the spring. By adjusting the opening of the needle valve in the air supply path, the closing speed of the valve is adjusted. The liquid level position (first position A) of the resist solution in the nozzle 21 when the supply of the resist solution is stopped by closing the air-operated valve is determined by the closing speed of the air-operated valve. The liquid level (first position A) is preferably 0.5 mm to 1.0 mm above the tip opening of the nozzle 21 (see FIG. 4B). Is adjusted. This is because if the tip surface of the resist liquid comes out below the tip surface of the nozzle 21, there is a possibility that dripping may occur. To avoid this, the first position A is moved from the tip opening of the nozzle 21. If the distance is set farther, the speed at which the resist solution is pulled back when the air-operated valve is closed becomes too fast, and a portion of the resist solution is torn off at the tip of the nozzle 21 and remains, thereby causing poor coating. So to prevent it.

The suction means 36 is made of, for example, a suck back valve as shown in FIG. The suck-back valve has a suction chamber formed by a bellows communicating with a flow path on the outlet side of the air-operated valve (opening / closing means 32). After the air-operated valve is closed, the bellows extends to the open position. As a result, a negative pressure is generated to draw in the tip end surface of the resist solution. When the resist liquid is discharged, the bellows returns to the original position (reference position).
Then, by changing the volume of the suck-back valve with the needle 37, the liquid surface position (second position B) in the nozzle 21 after drawing the tip end surface of the resist liquid can be adjusted. In this example, the liquid surface position (second position B) in the nozzle 21 is preferably 3.
0 mm to 4.0 mm above (see FIG. 4C)
Thus, the volume of the suckback valve is adjusted. This is because if the second position B is too far from the tip opening of the nozzle 21, the next time the resist solution is discharged, the tip surface of the resist solution passes through the tip opening of the nozzle 21 at a high speed, so that the momentum is increased. This is to prevent bubbles from being trapped.

The extension speed of the bellows is adjustable. By adjusting the extension speed, it is possible to adjust the speed at which the tip end surface of the resist solution is drawn in after the air-operated valve is closed. The elongation speed of the bellows is adjusted so that the tip surface of the resist solution can be pulled up, for example, over a distance of 2.5 mm between AB over 1 to 2 seconds, for example. This is to prevent the resist liquid from being drawn in too fast, a part of the resist liquid is left isolated at the tip of the nozzle 21, thereby causing poor coating. Although not particularly limited, in this example, the air operated valve and the suck back valve are integrated.

As the pump 39, for example, a bellows pump as a pressurizing means is used. The pump chamber is depressurized to suck the resist liquid from the resist tank 38, and then the pump chamber is pressurized to supply the resist liquid to an air-operated valve ( Opening / closing means 3
2) and discharge to the nozzle 21 side via the suck back valve (suction means 36).

The nozzle 21 is attached to a support piece 24 at the tip of a support arm 23 extending horizontally from the upper end of a vertically extending support column 22 as shown in FIGS. One direction (Y direction in FIG. 2) is provided on the bottom plate 13 of the coating film forming apparatus.
Guide rails 14 are laid along the
Are horizontally movable along a guide rail 14 by a drive mechanism (not shown). That is, the nozzle 21 is Y
It is supported so that it can move horizontally in the direction. The support arm 23 is driven by a driving mechanism (not shown) to move the X-axis perpendicular to the Y-direction.
The nozzles 21 having various diameters and the like which are waiting in the nozzle standby unit 15 can be selected and mounted on the support piece 24. A rinse nozzle support column 43 is provided on the guide rail 14 so as to be movable in the Y direction.
Is provided with a rinse nozzle 41 via a rinse nozzle support arm 42 extending horizontally.

In this coating film forming apparatus, as shown in FIG. 1 and FIG. 2, extra resist scattered from the periphery of the wafer W around the periphery of the wafer W adsorbed by the spin chuck 12 during spin coating of the resist solution is provided. A cup 16 for receiving the liquid is provided. Further, a window 17 for loading and unloading the wafer W is opened in the coating film forming apparatus, and the wafer W is loaded and unloaded by the wafer transfer arm 51 through the window 17.

Next, an example of a method for forming a coating film according to the present invention will be described with reference to FIGS. First, the wafer W is loaded into the coating film forming apparatus through the loading / unloading window 17 by the wafer transfer arm 51, and is vacuum-sucked to the raised spin chuck 12. At this time, the nozzle 21 has escaped to a predetermined initial position that does not interfere. Thereafter, the spin chuck 12 is lowered, the wafer W is rotated together with the spin chuck 12, and the nozzle 21 is moved to the center of the rotation.

In this state, the drive of the pump 39 is started at time t1 shown in FIG. 5, the air operated valve (opening / closing means 32) is shifted from the closed state to the open state, and the suck back valve (suction means 36) is turned on. ) Shifts from the open position to the reference position, whereby the resist liquid is sent from the resist tank 38 to the nozzle 21. Thereby, the resist solution flows out from the tip of the nozzle 21 and is dropped (FIG. 4).
(A)). The dropped resist liquid is thinly spread on the surface of the wafer W by centrifugal force due to rotation.

After the resist solution is dropped, at time t2 (FIG. 5)
), The drive of the pump 39 is stopped, and the air-operated valve starts to be closed at a predetermined speed, thereby completing the discharge process. As a result, the tip surface of the resist solution in the nozzle 21 is 0.5 mm or more wider than the tip opening of the nozzle 21.
Stop at the first position A on the upper side by 1.0 mm (FIG. 4
(B)). Since the first position A is slightly above the nozzle tip surface, even if the tip surface of the resist solution is suddenly pulled up to the first position A, a part of the resist solution is caused by the surface tension of the resist solution. It will not be torn and isolated. The suck back valve (suction means 36) is still at the reference position.

When the air-operated valve is completely closed at time t3 (see FIG. 5), the suck-back valve is gradually opened immediately, for example, over a period of one second to two seconds. As a result, the tip surface of the resist solution in the nozzle 21 is pulled up from the first position A and stops at the second position B, for example, about 3.0 mm above the tip opening of the nozzle 21 (FIG. 4). (C)). At this time, the tip surface of the resist solution is gently pulled up, so that a portion of the resist solution does not remain isolated at the tip portion in the nozzle 21.

Thereafter, the rotation of the wafer W is stopped, the nozzle 12 returns to the initial position, and the spin chuck 12 is raised. Then, the wafer W is moved by the wafer transfer arm 51.
Is carried out of the apparatus. Subsequently, when the next wafer W is loaded, the above-described processing is repeated. At that time, when the discharge of the resist liquid is started, the opening speed of the air-operated valve is adjusted so that air bubbles are not trapped. In other words, at the time of resuming discharge, if the rising speed of the pump that sends out the resist solution is set to be slow and the discharge speed is slowed down, if the opening of the air-operated valve is fast, the tip surface of the resist solution is drawn up and pulled back. At this time, bubbles are trapped. If air bubbles are trapped, application unevenness will occur. To prevent this, the opening speed of the air-operated valve is adjusted so that the tip surface is sent out without returning.

According to the above-described embodiment, after the resist solution is dropped, the air-operated valve is closed at a predetermined speed so that the tip surface of the resist solution in the nozzle 21 is located above the tip opening of the nozzle 21. Since the operation is stopped at the first position A, dripping can be prevented. Further, since the first position A is slightly higher than the opening of the tip of the nozzle 21, it is possible to prevent a part of the resist solution from remaining at the tip of the nozzle 21.

Further, according to the above-described embodiment, after the air-operated valve is closed, the suck-back valve is gradually opened so that the tip end surface of the resist solution in the nozzle 21 is removed.
Since the stop is performed at the second position B above the first position A, it is possible to prevent the tip of the resist solution from drying. Further, since the speed at which the resist liquid is pulled up is low, it is possible to prevent a part of the resist liquid from remaining at the tip in the nozzle 21. Therefore, according to the above-described embodiment, a resist film can be formed on the wafer W without causing coating defects such as coating unevenness.

Next, an outline of an example of a coating and developing apparatus incorporating a coating film forming apparatus used for carrying out the coating film forming method according to the present invention will be described with reference to FIGS. 6 and 7. FIG. Reference numeral 6 in FIG. 6 denotes a cassette loading / unloading stage for loading / unloading a wafer cassette, and a cassette C containing, for example, 25 sheets is placed by, for example, an automatic transfer robot. On the back side of the loading / unloading stage 6, for example, when viewed from the loading / unloading stage 6, for example, a coating / developing system unit is disposed on the left side, and a heating / cooling unit is disposed on the right side.

In the coating / developing system unit, for example, two developing units 71 are provided in an upper stage, and two coating units 72 are provided in a lower stage. In the heating / cooling system unit, as shown in FIG. 7, a heating unit 61, a cooling unit 62, and the like are vertically arranged. Actually, heating
The cooling system unit includes a hydrophobizing unit, but is not illustrated for convenience of illustration.

A wafer transfer arm 51 is provided between the coating / developing system unit and the heating / cooling system unit. The wafer transfer arm 51 is configured to be movable up and down, movable left and right, back and forth, and rotatable about a vertical axis, for example, a coating / developing system unit, a heating / cooling system unit, a loading / unloading stage 6 and an interface unit 64 described later. The transfer of the wafer W is performed. When the above-described portion including the coating / developing system unit and the heating / cooling system unit is referred to as a clean track, the interface unit 64 is interposed between the clean track and the exposure device 65, and is transported by a transport system (not shown). Delivery of wafers between the apparatuses is performed.

The wafer flow of this apparatus will be described. First, a wafer cassette C containing a wafer W is loaded into the loading / unloading stage 6 from the outside, and the wafer W is taken out of the cassette C by a transfer arm which cannot be seen in the drawing. Then, it is transported to the delivery unit 60. Subsequently, the wafer W is transferred by the transfer arm 51 to the heating / cooling unit described above, and subjected to a hydrophobizing treatment. Then, a resist liquid is applied by the coating unit 72 to form a resist film. The wafer coated with the resist film is heated by a heating unit 61.
After being heated by the above, the wafer is sent to the exposure device 65 via the interface unit 64, where exposure is performed via a mask corresponding to the pattern. Thereafter, the wafer W is heated by the heating unit 61, then cooled by the cooling unit 62, and then sent to the developing unit 71 to be developed,
A resist mask is formed. Thereafter, the wafer W is returned to the cassette C on the loading / unloading stage 6.

In the above, according to the present invention, the opening / closing means 32 and the suction means 36 are not limited to the air operated valve and the suck back valve, respectively. The substrate to be processed is not limited to a wafer, but may be a glass substrate for a liquid crystal display. Further, the present invention can be applied to, for example, a case where a solution that is a precursor of a silicon oxide film is applied to a substrate surface.

[0028]

As described above, according to the present invention, a coating film can be formed on a substrate to be processed without causing coating defects such as coating unevenness.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an example of a coating film forming apparatus used for carrying out a coating film forming method according to the present invention.

FIG. 2 is a plan sectional view of the coating film forming apparatus.

FIG. 3 is a schematic configuration diagram of an example of a valve used in the coating film forming apparatus.

FIG. 4 is an operation explanatory view showing how the liquid level of the coating liquid changes.

FIG. 5 is a timing chart showing drive timings of a pump, a pneumatic valve, and a suck-back valve.

FIG. 6 is a schematic perspective view showing a coating / developing apparatus to which the coating film forming apparatus is applied.

FIG. 7 is a schematic view of the coating / developing apparatus as viewed from the side.

FIG. 8 is a schematic diagram for explaining a general spin coating method.

[Explanation of symbols]

 W Wafer (substrate) 21 Nozzle 31 Supply pipe (flow path) 32 Air-operated valve (opening / closing means) 36 Suck back valve (suction means) 38 Resist tank 39 Pump

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[Procedure amendment]

[Submission date] July 13, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

FIG. 4

FIG. 5

FIG. 6

FIG. 7

FIG. 8

Claims (4)

[Claims] A step of positioning a nozzle provided at an end of a flow path of the coating liquid above the substrate; opening a valve provided in the flow path to discharge the coating liquid from the nozzle to supply the coating liquid to the surface of the substrate Forming a coating film on the surface of the substrate; closing the valve so that the tip surface of the coating solution stops at a first position above the tip opening of the nozzle; And a step of drawing the coating liquid by a suction means provided on the downstream side of the valve and drawing the tip end surface of the coating liquid to a second position above the first position. Coating film forming method. 2. The coating film forming method according to claim 1, wherein the first position is a position 0.5 mm to 1.0 mm above the tip end opening of the nozzle. 3. The method according to claim 1, wherein the second position is a position that is 3.0 mm to 4.0 mm above the tip opening of the nozzle. 4. The suction device according to claim 1, wherein the suction means is configured to increase a volume of the flow channel by expanding a part of a wall portion of the flow channel outward. The method for forming a coating film according to the above.