JPH04239721A - Method and apparatus for photoresist coating - Google Patents

Abstract

PURPOSE:To prevent an asymmetric thickness in photoresist coating at a step portion on a wafer when an excess photoresist remaining at an outer portion of the wafer is removed with a solvent after a surface of the wafer is processed by photoresist spin coating. CONSTITUTION:A photoresist coating apparatus 1 is constituted of a loader 3 for storing a plurality of wafers 2, a coating process unit 4 for coating a surface of the wafer 2 with a photoresist, a first baking unit 5 for baking the photoresist, an edge-portion removing unit 6 for removing an excess photoresist remaining at an outer portion of the wafers 2, a secondary baking unit 7 for baking the photoresist, and an unloader 8 for storing the wafers 2 being completed through a series of these processes.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a photoresist coating technique, and is particularly applicable to a process of removing excess photoresist remaining around the wafer after coating the surface of a semiconductor wafer with photoresist. Concerning effective techniques.

0002

[Prior Art] In the resist process for semiconductor integrated circuit devices, a photoresist is applied to the surface of a semiconductor wafer on which a thin film such as an oxide film, nitride film, or metal film has been deposited, and exposure light such as light or an electron beam is used. A mask pattern is transferred to the photoresist.

A spin coating device (spinner) is used to apply photoresist to the surface of a wafer. In the photoresist coating process using a spin coating device, the most important issue is to coat the wafer surface with a uniform thickness of photoresist. This is because variations in the film thickness of the photoresist cause a decrease in the alignment accuracy of the exposure apparatus, which in turn causes variations in the dimensions of the integrated circuit pattern formed on the wafer.

To apply photoresist to the surface of a wafer using a spin coating device, the wafer is held horizontally on a spin chuck of a coating cup, and while rotating the spin chuck horizontally at a predetermined speed, Photoresist is discharged onto the center of the wafer from the tip of a nozzle placed above the spin chuck. As a result, the photoresist deposited on the surface of the wafer flows toward the periphery of the wafer due to centrifugal force, and spreads uniformly over the entire surface of the wafer.

At this time, the excess photoresist that has reached the periphery of the wafer is separated from the wafer by centrifugal force.
Although it is removed, some of it remains on the periphery of the wafer, and if this becomes foreign matter after drying and re-attaches to the wafer surface, it can cause exposure defects.

For these reasons, in the conventional photoresist coating process using a spin coating device, after coating the photoresist on the surface of the wafer, a nozzle sprays a photoresist solvent onto the periphery of the rotating wafer. However, a so-called edging operation was performed to separate and remove excess photoresist that had accumulated around the periphery along with a solvent.

[0007] Regarding the photoresist coating technique using a spin coating device, Kogyo Kenkyukai, 1986
This is described in the "Electronic Materials Special Volume, VLSI Manufacturing and Testing Equipment Guidebook" published on February 10th.

[0008]

However, when the edging operation is performed, the photoresist, which has been uniformly adhered to the surface of the wafer, flows toward the periphery of the wafer due to the centrifugal force of the rotating wafer. The inventor's studies have revealed that in the stepped portions of patterns and alignment patterns, the thickness of the photoresist becomes asymmetric between the center and the periphery of the wafer, causing a problem in which the alignment accuracy of the exposure device decreases. It became. It is thought that such problems will become more prominent as the diameter of the wafer becomes larger.

The present invention has been made in view of the above-mentioned problems, and its purpose is to remove the excess photoresist that has accumulated around the periphery of the wafer when performing an edging operation using a solvent. An object of the present invention is to provide a technique that can prevent the film thickness of a photoresist from becoming asymmetrical at a stepped portion.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0011]

[Means for solving the problem] (1). One invention of the present application applies a photoresist to the surface of the wafer while rotating the wafer, and then bakes the photoresist.
Excess photoresist accumulated around the wafer is removed by spouting a photoresist solvent around the wafer while rotating the wafer.

(2). One invention of the present application is to apply a photoresist to the surface of the wafer while rotating the wafer, bake the photoresist, irradiate the periphery of the wafer with exposure light, and then apply a developer to the periphery of the wafer. By applying this coating, excess photoresist that has accumulated around the periphery of the wafer is removed.

[0013]

[Operation] According to the above-described means, the photoresist is baked and hardened prior to the edging process of removing excess photoresist accumulated around the periphery of the wafer. Since it is possible to prevent the photoresist from flowing toward the periphery of the wafer due to centrifugal force, the thickness of the photoresist does not become asymmetrical at the stepped portions of the wafer after edging.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a photoresist coating apparatus 1. This photoresist coating apparatus 1 includes a loader 3 that accommodates a plurality of wafers 2, a coating processing section 4 that coats the surface of the wafer 2 with photoresist, a first baking section 5 that bakes the photoresist, and a wafer 2. Edging part 6 for removing excess photoresist accumulated around the periphery of 2.
and a second baking section 7 for baking the photoresist.
and an unloader 8 that accommodates the wafer 2 that has undergone the series of steps described above. A transport arm 9 for transporting the wafer 2 is provided between the coating processing section 4 and the second baking section 7 .

The photoresist coating process of this embodiment using the photoresist coating apparatus 1 described above will be explained according to the flow shown in FIG. First, the wafer 2 accommodated in the loader 3
are transported to the coating processing section 4 one by one. The coating processing section 4 includes, for example, first and second constant temperature plates. The wafer 2 adsorbed and held by the first constant temperature plate is heated to about 150° C., and moisture adsorbed on its surface is removed. At this time, in order to strengthen the adhesiveness of the surface of the wafer 2, for example, hexamethyldisilazane (HMDS) is used.
Hydrophobization treatment may be performed using.

The wafer 2 that has been dehydrated on the first constant temperature plate is adsorbed and held on the second constant temperature plate. The second constant temperature plate cools the wafer heated by the first constant temperature plate until it reaches the optimum temperature for photoresist coating. This optimum temperature is, for example, about 23°C.

The wafer 2 cooled to the optimum temperature is transferred from the second constant temperature plate to the coating cup 10 shown in FIG. A spin chuck 11 that holds the wafer 2 horizontally is installed in the center of the approximately cylindrical coating cup 10 that is open at the top and bottom.
is located. The spin chuck 11 has a motor 12
It rotates in a horizontal plane at a speed of several hundred to several thousand revolutions per minute. Above the wafer 2 held by the spin chuck 11, on the rotation axis of the spin chuck 11,
A resist supply nozzle 13 for supplying photoresist to the surface of the wafer 2 is arranged. In addition, application cup 10
An inclined portion 14 is provided on the wall surface at a position approximately at the same height as the wafer 2, so that the photoresist scattered from the wafer 2 can easily fall downward.

To coat the surface of the wafer 2 with photoresist, the wafer 2 is placed on the spin chuck 11 by vacuum suction.
Then, the motor 12 is energized to rotate the wafer 2 at a predetermined speed. Subsequently, a predetermined amount of photoresist is discharged from the tip of the resist supply nozzle 13. As a result, the photoresist adhered to the surface of the wafer 2 rotating at high speed flows toward the periphery due to centrifugal force, and the wafer 2
spreads evenly over the entire surface.

The excess photoresist that has reached the periphery of the wafer 2 leaves the wafer 2, scatters toward the coating cup 10, and adheres to the inner wall thereof. Most of the photoresist deposited on the inner wall of the coating cup 1 falls along the slope 14, but a portion bounces back and becomes mist, which is scattered toward the wafer 2. Air flowing from above toward the air exhaust port 15 is supplied to the coating cup 10, and this air prevents the mist from adhering to the wafer 2 again. In this way, wafer 2
Most of the excess photoresist that has reached the periphery of the wafer 2 is separated and removed from the wafer 2 by centrifugal force.
A portion remains on the periphery of the wafer 2.

Wafer 2 on which photoresist coating has been completed
is transported to the baking section 5 by the transport arm 9 and subjected to a primary soft baking process. As shown in FIG. 4, the transfer arm 9 is structured so as not to come into contact with the periphery of the wafer 2, thereby preventing the photoresist accumulated on the periphery of the wafer 2 from adhering to the transfer arm 9. It has become.

The baking section 5 includes, for example, a proximity (non-contact) type hot plate, and the wafer 2 is heated to a predetermined temperature on this hot plate. The primary soft baking process in the baking section 5 only needs to harden the surface of the photoresist, and does not need to completely harden the photoresist.

[0022] Wafer 2 after the primary soft bake process has been completed
is transported by the transport arm 9 to the edging section 6, where it is subjected to an edging operation to remove photoresist accumulated around the periphery. As shown in FIG. 5, the edging section 6 has a similar structure to the coating cup 10 provided in the coating processing section 4. That is, in the center of the cup 16,
A spin chuck 11 that holds the wafer 2 horizontally is arranged. The spin chuck 11 is rotated in a horizontal plane by driving the motor 12 . Above or below the periphery of the wafer 2 held by the spin chuck 11, a solvent supply nozzle 17 is arranged to supply a photoresist solvent (for example, ethyl cell solve acetate).

To remove the photoresist accumulated around the periphery of the wafer 2, the wafer 2 is held on the spin chuck 11 by vacuum suction, and then the motor 12 is energized to rotate the wafer 2 at a predetermined speed. Subsequently, the solvent is ejected from the tip of the solvent supply nozzle 17 onto the periphery of the wafer 2 . Excess photoresist accumulated around the periphery of the wafer 2 is dissolved by the solvent, separated and removed from the wafer 2 together with the solvent, and then drained through the drain port 18 at the bottom of the cup 16.

The wafer 2 on which the photoresist edging has been completed is transported by the transport arm 9 to the second baking section 7, where it is subjected to a secondary soft baking process. The second baking section 7 includes, for example, a proximity type hot plate like the first baking section, and the wafer 2 is heated to a predetermined temperature on this hot plate. This secondary soft baking process in baking section 7 is as follows:
This is done to harden the photoresist near the periphery of the wafer 2 that was remelted in the edging process.

Wafer 2 after the secondary soft bake process has been completed
is once accommodated in the unloader 8, and after that, the back side is subjected to a cleaning process as required, and then transported to the exposure apparatus.

As described above, in the photoresist coating process of this embodiment, the photoresist is soft-baked to harden its surface prior to the edging operation for removing excess photoresist accumulated around the periphery of the wafer 2. . This prevents the photoresist from flowing toward the periphery of the wafer 2 due to the centrifugal force of the rotating wafer 2 when edging, so that the photoresist does not flow toward the periphery of the wafer 2 at stepped portions such as integrated circuit patterns and alignment patterns formed on the wafer 2. It is possible to prevent the film thickness of the photoresist from becoming asymmetrical.

[0027] This makes it possible to prevent the alignment accuracy of the exposure apparatus from deteriorating, thereby avoiding dimensional variations in the integrated circuit patterns formed on the wafer 2, and improving the manufacturing yield of semiconductor integrated circuit devices.

FIG. 6 shows another embodiment of the photoresist coating apparatus 1. In FIG. This photoresist coating apparatus 1 is comprised of a loader 3, a coating processing section 4, a baking section 5, a developing section 19, an unloader 8, and a transport arm 9.

The photoresist coating process of this embodiment using the photoresist coating apparatus 1 will be explained according to the flow shown in FIG. First, the wafer 2 accommodated in the loader 3
are transported to the coating processing section 4 one by one. The wafer 2 is first subjected to a dehydration treatment on a first constant temperature plate and then to a cooling treatment on a second constant temperature plate, as in the previous embodiment, and then transferred to the coating cup 10 shown in FIG. .

The coating cup 10 is similar to the coating cup 10 of the previous embodiment except that an exposure light supply means 20 made of an optical fiber or the like is provided above the peripheral portion of the wafer 2 held by the spin chuck 11. The structure is as follows. That is, the coating cup 10 also serves as an exposure section that exposes the peripheral portion of the wafer 2 after photoresist coating and soft baking, which will be described later, have been completed.

The method of applying photoresist to the surface of the wafer 2 is the same as that described in the previous embodiment;
The explanation will be omitted. The wafer 2, on which the photoresist has been coated, is transported by the transport arm 9 to the baking section 5, where it is subjected to a soft baking process. The baking section 5 includes, for example, a proximity type hot plate, as in the previous embodiment, and the wafer 2 is heated to a predetermined temperature on this hot plate.

The wafer 2 that has undergone the soft baking process is
The transfer arm 9 returns the photoresist to the coating cup 10 which also serves as an exposure section, and the photoresist in the peripheral area is exposed. To expose the photoresist on the periphery of wafer 2,
The wafer 2 held by the spin chuck 11 is rotated at a predetermined speed, and exposure light such as ultraviolet light is irradiated from the exposure light supply means 20, thereby selectively exposing only the photoresist in the peripheral area of the wafer 2. Alternatively, after coating without soft baking, the periphery of the wafer may be selectively exposed with low speed rotation, and then soft baking may be performed.

The wafer 2 whose peripheral area has been exposed is
It is transported by the transport arm 9 to the developing section 19, where it is subjected to an edging operation to remove the photoresist that has accumulated around the periphery. As shown in FIG. 9, the developing section 19 has a similar structure to the applicator cup 10 described above. That is,
A spin chuck 11 that holds the wafer 2 horizontally is arranged in the center of the cup 16.
is rotated in a horizontal plane by the drive of the motor 12. A developer supply nozzle 21 for supplying a photoresist developer (alkaline aqueous solution such as tetramethylammonium hydroxide) is arranged above the periphery of the wafer 2 held by the spin chuck 11.

To remove the photoresist accumulated around the periphery of the wafer 2, the wafer 2 is held on the spin chuck 11 by vacuum suction, and then the motor 12 is energized to rotate the wafer 2 at a predetermined speed. Subsequently, the developer is ejected from the tip of the developer supply nozzle 21 onto the periphery of the wafer 2 . The developer supply nozzle 21 can move from the periphery of the wafer toward the center. The excess photoresist accumulated around the periphery of the wafer 2 is dissolved by the developer (in this case, the photoresist is a positive type photoresist), and is separated and removed from the wafer 2 together with the developer. The developer is again ejected onto the periphery of the wafer 2 from the tip of the developer supply nozzle 21 through a circulation pipe (not shown) provided at the bottom of the cup 16 . Alternatively, a developing solution may be supplied to the front surface of the wafer to form an edge around the wafer.

The wafer 2 on which the photoresist has been bordered is once stored in the unloader 8, and after that, the back surface is cleaned if necessary, and then transported to the exposure apparatus.

As described above, in the photoresist coating process of this embodiment, prior to the edging operation in which excess photoresist accumulated around the periphery of the wafer 2 is removed by exposure and development, the photoresist is soft-baked to remove the excess photoresist. Harden the surface. This prevents the photoresist from flowing toward the periphery of the wafer 2 due to the centrifugal force of the rotating wafer 2 when edging, so that the same effect as in the embodiment described above can be obtained.

[0037] Above, the invention made by the present inventor has been specifically explained based on examples, but the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Needless to say.

In the first embodiment of the photoresist coating apparatus, the coating processing section and the edging section are constructed separately, but a solvent supply nozzle is provided in the coating cup of the coating processing section to separate the coating processing section and the edging section. may be configured integrally. In this case, although there is a disadvantage that wafer processing efficiency is reduced, the photoresist coating apparatus can be downsized.

In the first embodiment of the photoresist coating apparatus, the first baking section and the second baking section were constructed separately, but the second baking section was abolished and the first baking section was The primary soft bake and the secondary soft bake can also be performed alternately. In this case as well, although there is a disadvantage that the wafer processing efficiency is reduced, the photoresist coating apparatus can be downsized. Additionally, if the photoresist is sufficiently hardened by the primary soft bake, the photoresist near the wafer periphery will hardly be redissolved during the edging process, so in this case, the secondary soft bake process may be omitted. I can do it.

In the second embodiment of the photoresist coating apparatus, the coating processing section and the exposure section are constructed as one unit, but they may be constructed as separate bodies. In this case, although there is a disadvantage that the photoresist coating apparatus becomes larger, the wafer processing efficiency is improved.

The baking section of the photoresist coating apparatus is not limited to a proximity type hot plate, and a hot air oven or the like may also be used.

[0042]

[Effects of the Invention] Among the inventions disclosed in this application, the effects obtained by the typical inventions will be briefly explained as follows.
It is as follows.

(1). After coating the surface of the wafer with photoresist while rotating the wafer, baking the photoresist and then squirting photoresist solvent onto the periphery of the wafer while rotating the wafer removes any excess that has accumulated around the periphery of the wafer. By removing the photoresist, it is possible to prevent the thickness of the photoresist from becoming asymmetrical at the step portion of the wafer when performing the edging operation.

(2). After coating the surface of the wafer with photoresist while rotating the wafer, this photoresist is baked, the periphery of the wafer is irradiated with exposure light, and the wafer is developed by applying a developer to the periphery of the wafer. The same effect as described above can be obtained by removing the excess photoresist accumulated in the peripheral area.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a photoresist coating apparatus that is an embodiment of the present invention.

FIG. 2 is a flow diagram of a photoresist coating method using this photoresist coating apparatus.

FIG. 3 is a sectional view of a main part showing a coating processing section of this photoresist coating apparatus.

FIG. 4 is a cross-sectional view of a main part showing a transport arm of this photoresist coating device.

FIG. 5 is a cross-sectional view of a main part showing a border portion of this photoresist coating device.

FIG. 6 is an overall configuration diagram of a photoresist coating apparatus according to another embodiment of the present invention.

FIG. 7 is a flow diagram of a photoresist coating method using this photoresist coating apparatus.

FIG. 8 is a sectional view of a main part showing a coating processing section of this photoresist coating apparatus.

FIG. 9 is a sectional view of a main part showing a developing section of the photoresist coating apparatus.

[Explanation of symbols]

1 Photoresist coating equipment 2 Semiconductor wafer 3 Loader 4 Coating processing section 5 Baking section 6 Edging part 7 Baking section 8 Unloader 9 Transfer arm 10 Application cup 11 Spin chuck 12 Motor 13 Resist supply nozzle 14　Slope part 15 Air exhaust port 16 cups 17 Solvent supply nozzle 18 Drain port 19 Developing section 20 Exposure light supply means 21 Developing solution supply nozzle

Claims (5)

[Claims] 1. A step of applying a photoresist to the surface of the semiconductor wafer while rotating the semiconductor wafer, a step of baking the photoresist applied to the surface of the semiconductor wafer, and a step of applying a photoresist to the surface of the semiconductor wafer while rotating the semiconductor wafer. A photoresist coating method comprising the step of removing excess photoresist accumulated in the peripheral area by spouting a solvent for the photoresist onto the peripheral area. 2. A step of applying a photoresist to the surface of the semiconductor wafer while rotating the semiconductor wafer, a step of baking the photoresist applied to the surface of the semiconductor wafer, and a step of applying a photoresist to the surface of the semiconductor wafer while rotating the semiconductor wafer. a edging step of removing excess photoresist that has accumulated in the peripheral portion by spouting a solvent for the photoresist onto the surface of the semiconductor wafer; and a step of re-baking the photoresist applied to the surface of the semiconductor wafer. A photoresist coating method characterized by: 3. A step of applying a photoresist to the surface of the semiconductor wafer while rotating the semiconductor wafer, a step of baking the photoresist applied to the surface of the semiconductor wafer, and a step of applying exposure light to the periphery of the semiconductor wafer. A photoresist coating method comprising the steps of: irradiating the semiconductor wafer; and removing excess photoresist accumulated on the periphery of the semiconductor wafer by applying a developer to the periphery of the semiconductor wafer. 4. A coating processing unit that applies photoresist to the surface of the semiconductor wafer while rotating it; a baking unit that bakes the photoresist applied to the surface of the semiconductor wafer; A photoresist coating apparatus, comprising: a rimming section provided with a solvent supply means for supplying a solvent for the photoresist. 5. A coating processing section that coats a photoresist on the surface of the semiconductor wafer while rotating it, a baking section that bakes the photoresist coated on the surface of the semiconductor wafer, and a coating processing section that coats a photoresist on the surface of the semiconductor wafer; A photoresist comprising: an exposure section equipped with an exposure light supply means for irradiating exposure light; and a development section equipped with a developer supply means for supplying a developer to the peripheral area of the semiconductor wafer. Coating device.