JPS6258653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for uniformly applying a photoresist liquid (hereinafter referred to as resist liquid) to both sides of a semiconductor wafer.

[Conventional technology]

Conventionally, equipment for applying resist solution to wafers was generally structured to apply resist solution to one side at a time, so with regard to the uniformity of the applied resist film, only efforts were made to improve the uniformity within one side; No efforts were made to make the resist coatings on both sides uniform.

[Problem that the invention seeks to solve]

The present inventors have researched and developed a method and device for forming a resist film by simultaneously spraying resist liquid onto both sides of a wafer while rotating it. It is necessary not only to make each resist film uniform in thickness, but also to make both resist film thicknesses equal.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coating device that can simultaneously coat both sides of a wafer with a resist solution, and can also make the resist film thickness uniform and uniform on both sides.

In order to achieve the above objective, the present inventors experimentally discovered and confirmed that in order to equalize the resist film thickness on both sides of the wafer, the air flow condition in contact with both sides of the wafer must be made the same. In addition, as a result of detailed research on the influence of various factors on the air flow conditions, we focused on the difference in air flow conditions on the upper and lower surfaces of the wafer as a major factor causing non-uniform resist film thickness.

In other words, vortices are generated on both sides of the wafer gripped by the chuck mechanism due to the "entanglement" of air, but if one side of the wafer faces a stationary member and the other faces a rotating member, , the above eddy current state is different. This is one of the major causes of uneven film thickness.

In order to reduce the influence of opposing members on each side of the wafer, the simplest method is to widen the distance between the opposing members.

Therefore, in the present invention, as a result of experiments with variously changing the above-mentioned interval dimensions, the interval dimensions were determined to be wafer diameter/5.
We discovered and confirmed that the degree of influence differs markedly across the boundaries.

[Means for solving problems]

The present invention has been made based on the above-mentioned principle, and has a structure in which one side of the wafer held by a chuck mechanism faces a rotating member, and the other side of the wafer faces a stationary member and is rotated. Applied to a resist coating device, the diameter of the wafer is D, the distance between the wafer and the rotating member facing each other in parallel, and the distance between the wafer and the stationary member facing each other in parallel are each D/5 or more, and It is characterized in that resist spraying nozzles are provided toward the center of the upper surface and the center of the lower surface of the wafer, respectively.

[Effect]

According to the above configuration, the state of air flow relative to the wafer is the same on both the upper and lower surfaces of the wafer, so that a uniform coating film thickness can be obtained on both surfaces.

Furthermore, since nozzles are provided toward the center of the top surface of the wafer and toward the center of the bottom surface of the wafer, it is possible to simultaneously spray the top and bottom surfaces of the wafer.
High work efficiency.

Moreover, since the resist is sprayed onto the center of the wafer, it is immediately spread over the entire surface of the wafer by centrifugal force, and this, combined with the uniformity of the airflow conditions described above, forms a uniform film thickness.

〔Example〕

1A and 1B are a plan view and a side view of a wafer 1 to which a resist is to be applied. The wafer 1 used in this example has a thin disk shape with a diameter of 75 mm and has a notch 1a formed therein.

FIG. 2 is a partially sectional front view showing an example of a resist coating apparatus configured to perform double-sided coating.

Reference numeral 3 denotes a chuck mechanism having three claws 9 (only two are shown) for gripping the wafer 1, and this chuck mechanism 3 is fixed to the lower end of the cylindrical rotating section 6. The rotating section 6 described above is rotationally driven by a DC motor (not shown) via a pulley 4 and a timing belt 5.

An upper nozzle 10 for spraying resist liquid onto the upper surface of the wafer 1, which is held by chuck claws 9 and rotating together with the rotating section 6, is inserted through the center hole of the rotating section 6. In addition, a lower nozzle 11 that sprays resist liquid onto the lower surface of the wafer 1 is connected to the cup 1.
Penetrate and fix to the center of the bottom of 2.

The above-mentioned cup 12 is a member for covering the periphery of the resist liquid scattered by the centrifugal force from the rotating wafer 1, and has a structure that can be moved up and down by the cylinder 8. 7 is a guide member for vertical movement.

The three claws 9, 9 are rotatably supported by a plate 13 fixed to the rotating part 6. With the above configuration, the resist liquid can be sprayed from the upper and lower nozzles 10 and 11 toward both the upper and lower surfaces of the wafer 1 while horizontally gripping and rotating the wafer 1 with the claws 9, 9.

When held by the claws 9, the upper surface of the wafer 1 faces the plate 13 in parallel, and the lower surface of the wafer 1 faces the bottom surface of the cup 12 in parallel.

Initially, while rotating the chuck mechanism 3 holding the wafer 1 at a relatively low speed (for example, 500 to 1000 rpm), resist liquid is sprayed onto the center of the upper surface and the center of the lower surface from the upper nozzle 10 and the lower nozzle 11, respectively. It easily spreads over the entire surface of the wafer 1. Then increase the rotation speed to a relatively high speed (e.g. 3000
~5000 rpm), the excess resist solution is shaken off by centrifugal force and scattered, and the resist solution film thickness becomes thinner depending on the rotation speed.

Figure 3A is an enlarged view of the vicinity of the chuck mechanism 3;
FIG. B is a view of the wafer 1 held by the claws 9, 9 of the chuck mechanism 3, viewed from below.

A plate 13 faces above the wafer 1 in parallel, and since these two members rotate together, the air sandwiched between them is also rotated in the same direction, and moves toward the outer circumference of the wafer 1 as shown by arrows D and D'. Flows in a vortex. The state of the flow changes as the distance l between the two members changes.

Additionally, a vortex of air is similarly generated between the lower surface of the wafer 1 and the bottom surface E of the cup 12 facing it, and the state of this vortex changes as the distance m between the two members changes. The state of the vortex flow is between the rotating member wafer 1 and the stationary member cup 12.
This is a phenomenon that occurs between the wafer and the bottom surface of the wafer, so it is different from the vortex state described above on the top surface of the wafer. In addition, the influence of the size of the interval l on the vortex flow, and the influence of the interval dimension m
The effect of the size of the vortex on the eddy current is not the same.

Next, the effects of these conditions on air flow and the resulting changes in resist film thickness will be explained with reference to FIGS. 4 to 7.

In these charts, the ◯ marks represent the film thickness on the upper surface of the wafer, and the ● marks represent the film thickness on the lower surface of the wafer.

As shown in FIG. 4A, the measurement points are three points: a point A at the center of the wafer 1, a point C near the periphery, and a point B between the two. The resist liquid used in these experiments had a viscosity of 60 cp.

FIGS. 4B and 4C show the upper surface of the wafer 1 and the constituent members facing it (in this example, the plate 1
3). Figure 4B shows examples of film thickness distribution when the distance l between the
Figure C shows the case where l=30mm.

As can be clearly understood by comparing the two figures, when the l dimension is too small (5 mm), there is a large difference in the film thickness distribution on the upper surface of the wafer between the center and the periphery. If the l dimension is made appropriate, the difference in film thickness between the center part of the wafer and the peripheral part of the wafer will be reduced, and there will be no large difference in film thickness compared to the film thickness on the lower surface of the wafer.

The reason why this phenomenon occurs is that when the l dimension is small, the flow of air sandwiched between the two rotating members (wafer 1 and plate 13) is fast, and therefore the evaporation rate of the solvent of the resist solution is fast, and the resist solution on the top surface of the wafer is It is thought that the resist solution solidifies faster than the resist solution on the lower surface of the wafer 1, resulting in a thicker film, and that this tendency is particularly noticeable in the center of the wafer.

The intermediate state between the case where l = 5 mm (Fig. 4 B) and the case where l = 30 mm (Fig. 4 C) is not shown, but the interval l is 1/5 of the diameter of the wafer 1 (Fig. 4 C). In the example, when the thickness is 15 mm or less, the non-uniformity of the film thickness becomes noticeable, and when it is 1/5 or more, the film thickness becomes uniform to a practically acceptable extent.

5A and 5B show examples of film thickness distributions when the distance m between the lower surface of the wafer 1 and the member facing it (in this example, the bottom surface E of the cup 12) is varied; Figure 5A shows the fifth case when m=10mm.
Figure B shows the case where m=30mm.

As can be clearly understood by comparing both figures, when the m dimension is too small (10 mm), there is a large difference in the film thickness distribution on the lower surface of the wafer between the center and the periphery. When the m dimension reaches an appropriate value, the difference in film thickness between the center part of the lower surface of the wafer and the peripheral part thereof decreases, and there is no large difference in film thickness compared to the film thickness of the upper surface of the wafer.

The reason for this phenomenon is that as the m dimension decreases, the air flow slows down, and therefore the evaporation rate of the solvent in the resist solution is slow, making it difficult for the resist solution to solidify, resulting in a thinner film. It is thought that this phenomenon is particularly noticeable in the center.

The intermediate state between the case where m = 10 mm (Fig. 5 A) and the case where m = 30 mm (Fig. 5 B) is not shown.
When this interval dimension m is less than 1/5 of the diameter of the wafer 1 (15 mm in this example), the non-uniformity of the film thickness becomes noticeable (0.5 μm or more), and when it is more than 1/5, it is practically tolerable. The film thickness becomes uniform (0.5 μm or less).

The above embodiment has been described for the case where the wafer diameter D is 75 mm, but the case where the wafer diameter D is other than 75 mm is as follows.

It is known that when a horizontal disk (wafer) is rotated around the center, the film thickness h of the liquid (resist) on the surface is expressed by the following equation.

ρ: Resist density (g/cm ³ ) η: Resist viscosity (poise) ω: Wafer angular velocity (rad/sec) t: Wafer rotation time (sec) ho: Film thickness when t=0 The above from relationship Therefore, the film thickness is proportional to the radius r of the wafer.

As a result, even if the D dimension changes, l/D, m/
Since it is theoretically predicted that the relationship between D will remain constant, the inventor conducted experiments with various values of D, and found that l/D>1/5, m/D> It was confirmed that by achieving a relationship of 1/5, the film thickness non-uniformity could be kept to 0.5 μm or less.

As explained above, (a) the distance between the top surface of the wafer 1 and the opposing member, which is a rotating member, is equal to the wafer diameter.
If the distance is 1/5 or more, there will be no influence from the opposing member, and (b) if the distance between the bottom surface of the wafer 1 and the opposing member, which is a stationary member, is 1/5 or more of the wafer diameter, the effect of the opposing member will not be affected. I won't receive it. Combining the above (a) and (b), if the upper and lower surfaces of the wafer 1 are separated from the opposing member by at least 1/5 of the wafer diameter so that the influence can be ignored, the film thickness on the upper surface of the wafer 1 and the film thickness on the lower surface of the wafer 1 are approximately equal.

Figure 6 shows the resist film thickness distribution when the rotational speed of the wafer 1 is changed, with the l dimension and m dimension each set to 1/5 or more of the wafer diameter. After performing the spraying and diffusion operation (hereinafter referred to as "spread"),
A case is shown in which the film thickness is adjusted by increasing the rotational speed to 3000 rpm, and FIG. 6B shows a case in which the film thickness is adjusted by increasing the rotational speed to 3000 rpm after spreading at a rotational speed of 1000 rpm. This shows that it is possible to make the film thickness uniform on both the upper and lower surfaces by performing the spreading at a relatively high speed of about 1000 rpm.

FIG. 7 shows the change in film thickness when the spreading time is varied; FIG. 7A shows the case when the spreading time is 3 seconds, and FIG. 7B shows the case when the spreading time is 10 seconds. This shows that better results can be obtained in terms of uniformity of the film thickness distribution if the spreading operation is completed in a relatively short time.

An embodiment of a resist film uniform coating apparatus constructed by utilizing the above experimental results will be described below with reference to FIG. 3A. This applicator has springs 14, 14
A chuck mechanism 3 that clamps the wafer 1 at the lower ends of the claws 9, 9 by the biasing force of the chuck mechanism 3, a means for rotating the chuck mechanism 3 as explained with reference to FIG. It is equipped with an upper nozzle 10 and a lower nozzle 11 for spraying. Then, by applying the present invention, the wafer 1 and the plate 13 are
The distance l is the diameter of wafer 1 (75 mm) = 1/
The distance m between the wafer 1 and the bottom surface E of the cup 12 is 25 mm, which is considerably larger than 1/5 of the diameter of the wafer 1.
Further, it is desirable that the cross-sectional shape of the claws 9, 9 be thin and smooth so as to reduce the possibility that the claws 9, 9 stir the air and disturb the air flow.

Since the device of the present invention is configured as described above,
When the wafer 1 is gripped by the claws 9, 9 of the chuck mechanism 3 and rotated, the resist liquid is sprayed onto both sides of the wafer 1 and immediately after that, the wafer 1 is rotated at high speed (for example, 3000 rpm). Due to the action described with reference to FIG. 5B, the resist film thickness becomes uniform on each of the upper and lower surfaces of the wafer 1, and furthermore, the resist film thickness on the upper surface and the resist film thickness on the lower surface become equal.

When using the resist film uniform coating apparatus according to the present invention, the spreading operation is performed at a relatively high speed (for example, 1000 rpm) and for a relatively short time (for example, 3 (seconds), the uniformity of the resist film thickness by the apparatus of the present invention becomes much better.

〔Effect of the invention〕

As explained above, in a wafer double-sided resist coating apparatus, the present invention is applicable to the upper and lower surfaces of a wafer held by a chuck mechanism, and the constituent members (rotating members and stationary members) of the resist coating apparatus facing thereto. By setting the distance between the wafer and the wafer to at least 1/5 of the diameter of the wafer, the influence of the member facing the wafer on the air flow is reduced, and the air flow in contact with the top surface of the wafer and the wafer are It is possible to apply the resist solution to the upper and lower surfaces of the wafer at the same time by equalizing the flow of air in contact with the lower surface, thereby making it possible to equalize the resist film thickness on both surfaces.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the apparatus for uniformly coating resist on both sides of a wafer according to the present invention, in which FIG. 1A is a plan view of the wafer, FIG. 1B is a side view of the wafer, and FIG.
The figure is an overall front view with a part cut away, Figure 3A
3B is a partially sectional front view of the chuck mechanism, and FIG. 3B is a bottom view thereof. 4 to 7 are diagrams for explaining the working principle of the apparatus of the present invention, in which FIG. 4A shows the resist film thickness measurement points, and FIG. 4B and FIG. Fig. 5A and Fig. 5B show the change in resist film thickness depending on the l dimension shown in Fig. 3A.
shows the change in the resist film depending on the m dimension shown in
6A and 6B show the change in resist film thickness depending on the spread rotation speed, and FIGS. 7A and 7
Figure B shows the change in resist film thickness with spread time. 1...Wafer, 3...Chuck mechanism, 4...Pulley, 5...Timing belt, 6...Rotating part,
7... Guide member, 8... Cylinder, 9... Claw, 1
0... Upper nozzle, 11... Lower nozzle, 12... Cup, 13... Plate, 14... Spring.

Claims (1)

[Scope of Claims] 1 (a) A chuck mechanism having claws for gripping the outer periphery of a wafer, means for supporting and rotating the chuck mechanism, and a method for applying liquid to both surfaces of the wafer gripped by the chuck mechanism. In a wafer double-sided resist coating apparatus, the wafer double-sided resist coating apparatus has a structure in which one side of the wafer held by a chuck mechanism faces a rotating member, and the other side of the wafer is rotated facing a stationary member, (b) The diameter of the wafer is D, and the chuck mechanism, which is a rotating member, has a plane facing parallel to the wafer, and the distance between the chuck mechanism and the wafer is D/5 or more; (c) The wafer The stationary member facing the wafer has a surface parallel to the wafer, and the distance between the wafer and the stationary member is D/5 or more, and (d) the means for spraying liquid resist onto the upper surface of the wafer includes: (e) The means for spraying the liquid resist onto the lower surface of the wafer has a nozzle facing the center of the lower surface of the wafer. , equipment for uniformly coating resist films on both sides of wafers.