JP2008221124A - Rotary coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary coating method capable of forming a point symmetric wet region in a planar shape without leaving an air accumulation and as a result, obtaining a coating film having uniform thickness on the whole surface of a substrate by subsequent high speed rotation, when a low viscosity coating liquid is supplied on the surface of the substrate. <P>SOLUTION: The rotary coating method is carried out by dispersing the coating liquid 12 on the surface of the substrate by rotating the substrate W on the surface of which the coating liquid 12 is supplied and includes a step for forming a first wet region 101a by supplying the coating liquid 12 on the center position of the substrate and a step for forming a second wet region 101b being in contact with the first wet region 101a and surrounding the first wet region 101a by supplying the coating liquid 12 on the outside position of the outer peripheral edge of the first wet region 101a while slowly rotating the substrate W at a second speed of rotation N2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a spin coating method in which a coating solution supplied onto a substrate surface is dispersed and coated on the substrate surface by rotating the substrate, and more particularly to a spin coating method for coating a low viscosity coating solution.

  In order to obtain a coating film with a more uniform thickness when a coating solution is supplied to the substrate surface using a spin coater and the supplied coating solution is spin-coated with a centrifugal force of high-speed rotation, It is important how to form a wet region having a point-symmetric plane shape on the substrate surface during supply.

  In particular, with a coating solution having a low viscosity and a small surface tension (cohesive force), it has been difficult to form a stable planar wet region in a wide range on the substrate surface.

  As an example of a conventional spin coating method, FIGS. 4 and 5 show a spin coating method of a liquid coating diffusion source that forms a coating film on the surface of a semiconductor substrate using a spin coater and thermally diffuses impurities contained therein.

  FIG. 4 is a side sectional view, and FIG. 5 is a plan view showing the planar shape and nozzle position of the wet region on the semiconductor substrate.

  4 and 5, 1 is a spin coater, 2 is a spin chuck, 3 is a speed change mechanism, 4 is a rotation motor, 5 is a cup, 6 is a nozzle, 7 is a nozzle moving motor, 8 is a nozzle moving guide, and 9 is A coating solution storage unit, 10 is a control unit, 11 is a discharge port, 12 is a coating solution (liquid coating diffusion source), 12a and 12b are wet regions on the substrate surface, S is a scribe pattern groove, and W is a semiconductor substrate.

In such a spin coating method using the spin coater 1, first, the nozzle 6 is disposed above the center of the semiconductor substrate W in a stationary state, and an amount of a coating solution 12 that can sufficiently cover the substrate surface is dropped on the substrate surface. Thereafter, the semiconductor substrate W is rotated at a high speed, and the coating liquid 12 is dispersed over the entire substrate surface by the centrifugal force to form a thin coating film. (For example, see Patent Document 1)
JP-A-5-347265 JP-A-2005-230552

  However, when the coating liquid 12 in an amount sufficient to cover the substrate surface is supplied dropwise from the nozzle 6 to the center of the substrate, the surface tension (aggregation) of the coating liquid 12 is maintained while the area of wetting and spreading on the substrate surface is small. Force), but when the wet spreading area gradually increases, the influence of slight warpage and inclination of the entire substrate becomes greater than the surface tension (cohesive force) of the coating liquid 12, and the As a result, a distorted planar shape (asymmetrical asymmetry) was formed as shown in FIG. 5A.

  FIG. 5A shows the case where the substantially circular wet region 12a is formed. However, the present invention is not limited to this. As shown in FIG. 5B, the scribe pattern grooves formed in a lattice shape are used. Depending on the capillary phenomenon due to S or the like, wetting and spreading may be formed to form a substantially rectangular wet region 12b.

  Further, even when the coating liquid 12 in the distorted planar wet regions 12a and 12b is rotated at a high speed and dispersed over the entire substrate surface by centrifugal force, a coating film having a uniform thickness cannot be obtained. .

  In addition, the occurrence of the distortion of the planar shape of the wet region is more remarkable in the low-viscosity coating solution 12 having a small surface tension (cohesive force).

  Moreover, when the height position of the nozzle 6 for dropping the coating liquid 12 was high, air was easily trapped in the dropped coating liquid 12, which caused coating unevenness.

  In Patent Document 2, as a method of supplying a high-viscosity coating solution such as a photoresist, the nozzle is moved intermittently in the radial direction of the substrate sequentially from the center of the substrate and intermittent coating solution supply is repeated. Although a method for forming a region is disclosed, in this method, adjacent ring-shaped wet regions are separated and independent, and it is difficult to stably maintain the planar shape of each wet region. In addition, there is a possibility that air pockets remain after dispersion.

  The main problem of the present invention is that when supplying a low-viscosity coating liquid onto the substrate surface, a wet region having a point-symmetric plane shape can be formed without leaving an air pocket, resulting in subsequent high-speed rotation. Thus, it is an object to provide a spin coating method in which a coating film having a uniform thickness is obtained on the entire substrate surface.

  The spin coating method of the present invention is a spin coating method in which the coating liquid supplied on the surface of the substrate is applied by being dispersed on the surface by rotating the substrate, and the coating liquid is supplied to the center position of the substrate. Then, the step of forming the first wetting region, and while rotating the substrate at the second rotation speed, the coating liquid is supplied to the outside position of the outer peripheral edge of the first wetting region, and the first wetting region Forming a second wetted region surrounding and in contact with the substrate.

  According to the spin coating method of the present invention, when supplying a low-viscosity coating liquid onto the substrate surface, a wet region having a point-symmetric plane shape can be formed without leaving an air pocket, and as a result, By high-speed rotation, a coating film having a uniform thickness is obtained on the entire substrate surface.

  When supplying a low-viscosity coating liquid onto a substrate surface, the present invention can form a wet region having a point-symmetric plane shape without leaving an air pocket. As a result, the substrate surface is rotated by high-speed rotation thereafter. For the purpose of obtaining a coating film having a uniform thickness on the whole, a step of supplying a coating liquid to the central position of the substrate to form the first wetting region, and while rotating the substrate at the second rotational speed, This is realized by including a step of supplying a coating liquid to a position outside the outer peripheral edge of the first wetting region to form a second wetting region that is in contact with and surrounds the first wetting region.

  As an example of the spin coating method of the present invention, a spin coating method of a liquid coating diffusion source that forms a coating film on the surface of a semiconductor substrate using a spin coater and thermally diffuses impurities contained therein is shown in FIGS. The same parts as those in FIGS.

  1 is a side sectional view, FIG. 2 is a plan view showing a substantially circular wetting region and nozzle position on a semiconductor substrate, and FIG. 3 shows a substantially rectangular wetting region and nozzle position on the semiconductor substrate. It is a top view.

  In FIG. 1, 1 is a spin coater, 2 is a spin chuck, 3 is a speed change mechanism, 4 is a rotary motor, 5 is a cup, 6 is a nozzle, 7 is a nozzle moving motor, 8 is a nozzle moving guide, and 9 is a coating solution storage. , 10 is a control unit, 11 is a discharge port, 12 is a coating liquid (liquid coating diffusion source), 101a is a first wetting region, 101b is a second wetting region, and N1 is a semiconductor substrate W in the first supply process. The first rotation speed, N2 is the second rotation speed of the semiconductor substrate W in the second supply step, and W is the semiconductor substrate.

  Here, the nozzle 6 height H is set to such a height that the coating liquid 12 becomes a continuous body between the tip of the nozzle 6 and the substrate surface.

  When the nozzle height H is set to such a value, the coating liquid 12 is smoothly supplied onto the substrate surface, and air is not caught in the dropped coating liquid 12, which can prevent uneven coating.

  First, as shown in FIGS. 1 (a), 2 (a), and 3 (a), as a first supply process, a nozzle 6 is disposed above the center of the substrate, and a predetermined amount of coating solution is applied. 12 is supplied onto the substrate surface to form a first wetting region 101a. FIG. 2A shows a case where the first wet region 101a has a substantially circular shape, and FIG. 3A shows a case where the first wet region 101a has a substantially rectangular shape.

  Here, the supply amount of the coating liquid 12 is approximately equal to the coating liquid 12 on the substrate surface in consideration of the viscosity (for example, 10 to 130 cp) of the coating liquid 12 and the warp, inclination, and formation pattern of the substrate W. The first wet region 101a having a planar shape that is wet spread and point-symmetric (for example, in the case of a circular shape; radius = 10 to 20 mm, in the case of a rectangular shape; one side length = 20 to 40 mm) is set to a supply amount that can be maintained.

  In addition, the first supply process is performed while rotating the substrate W at a first rotation speed N1 at a low speed (for example, N1 = 10 to 50 rpm).

  When the coating liquid 12 is supplied while rotating the semiconductor substrate W at a low speed in this way, the coating liquid 12 supplied onto the substrate surface is preferably spread evenly in the circumferential direction of the substrate by an appropriate centrifugal force f.

  Next, the supply of the coating liquid 12 is once stopped.

  Next, the nozzle 6 is moved from the center position of the substrate to a position outside the outer peripheral edge of the first wetting region 101a.

  The supply position after the movement is such a supply position that the coating liquid 12 supplied onto the substrate surface spreads out and comes into contact with the first application region gradually and sequentially by rotation. The nozzle 6 is set to a nozzle height H.

  Here, the reason for setting the supply position to be outside the outer peripheral edge of the first wet region 101a is that if the supply position is in the first wet region 101a or on the outer peripheral edge, the first wet region 101a is over the first wet region 101a. This is because the coating liquid 12 is directly supplied from the nozzle 6 and deformation of the wet region occurs due to the impact.

  In addition, it is preferable that the supply position is outside the outer peripheral edge of the first wetting area 101a because a wider area can be formed.

  Then, as shown in FIGS. 1B, 2B, and 3B, as the second supply step, the semiconductor substrate W is rotated at a low speed (for example, the rotational speed N2 = The second wetting region 101b that surrounds the first wetting region 101a is formed by supplying the coating liquid 12 while the pressure is 5 to 40 rpm.

  The rotation speed N2 of the semiconductor substrate W at this time is preferably set so that the rotation speed N2 <the rotation speed N1 so that the coating liquid 12 in the first wet region 101a does not spread due to centrifugal force.

  As described above, when the second wetting region 101b is formed so as to be in contact with the first wetting region 101a, there is no fear that an air pocket remains between them.

  Further, since the second wet region 101b is formed while being in contact with the first wet region 101a, the first wet region 101a is applied to the coating liquid 12 in the second wet region 101b being formed. The tensile force t due to the surface tension (cohesive force) acts to suppress the second wetting region 101b from spreading rapidly and a stable planar shape can be obtained.

  That is, in the second supply step, the tensile force t from the first wetting region 101a acts on the coating liquid 12 applied on the substrate surface, and on the other hand, due to the low speed rotation (rotation speed N2). A centrifugal force f (opposite to the tensile force t) acts.

  For this reason, the point-symmetric second wetting region 101b is stably formed by controlling the balance of these forces (f, t) with the rotational speed N2 or the like.

  Next, when the formation of the first and second wet regions 101a and 101b is completed, the semiconductor substrate W is rotated at a high speed (for example, 1000 rpm or more) to apply the coating liquid 12 for the first and second wet regions 101a and 101b. Is dispersed over the entire surface of the semiconductor substrate W using centrifugal force.

  In this way, the coating liquid 12 is evenly dispersed over the entire substrate surface from the point-symmetric plane-shaped first and second wet regions 101a and 101b, and a coating film having a uniform thickness is obtained.

  In the above example, the first supply process has been described by supplying the coating liquid 12 while rotating the semiconductor substrate W at the first rotation speed N1 at a low speed. However, the present invention is not limited to this. The coating liquid 12 may be supplied to the stationary semiconductor substrate W, or after the coating liquid 12 is supplied to the stationary semiconductor substrate W, the semiconductor substrate W is rotated at the first rotation speed N1. You may go.

  In the above example, the coating liquid 12 has been described as being divided into two parts for the first and second supply processes. However, the present invention is not particularly limited to this, and it is more extensive on the substrate surface. If it is desired to secure a wet area that spans, as a third supply process, a step of forming a third wet area surrounding and in contact with the second wet area 101b may be added. Needless to say, a wetted region surrounding the wetted region may be formed.

  When supplying a low-viscosity coating liquid onto a substrate surface, the present invention can form a wet region having a point-symmetric plane shape without leaving an air pocket. As a result, the substrate surface is rotated by high-speed rotation thereafter. The present invention can be applied to a spin coating method in which a coating film having a uniform thickness can be obtained as a whole.

Side sectional view explaining an example of the spin coating method of the present invention The top view explaining an example of the spin coating method of this invention The top view explaining an example of the spin coating method of this invention Side sectional view explaining an example of a conventional spin coating method Plan view for explaining an example of a conventional spin coating method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spin coater 2 Spin chuck 3 Transmission mechanism 4 Rotating motor 5 Cup 6 Nozzle
7 Nozzle movement motor 8 Nozzle movement guide 9 Coating liquid storage section 10 Control section 11 Discharge port 12 Coating liquid (liquid coating diffusion source)
12a, 12b Wetting region 101a First wetting region 101b Second wetting region N1 Number of rotations of semiconductor substrate W in first supply step N2 Number of rotations of semiconductor substrate W in second supplying step S Scribe pattern groove W Semiconductor substrate

Claims (8)

A spin coating method in which the coating liquid supplied on the surface of the substrate is dispersed and coated on the surface by rotating the substrate,
Supplying the coating liquid to a central position of the substrate to form a first wetting region;
While rotating the substrate at a second rotational speed, the coating liquid is supplied to an outer peripheral position of the first wetting region to surround a second wetting region that is in contact with and surrounds the first wetting region. A spin coating method including a forming step.   The first wet region is formed by supplying a coating solution to a stationary substrate, or by supplying the coating solution to a stationary substrate and then rotating the substrate at a first rotation speed. Alternatively, the spin coating method according to claim 1, wherein the coating liquid is supplied while rotating the substrate at the first rotation speed.   The spin coating method according to claim 2, wherein the second rotation speed is a lower rotation speed than the first rotation speed.   4. The spin coating method according to claim 1, further comprising a step of forming a wetted region surrounding and contacting the outermost wetted region sequentially on the outer side after forming the second wetted region. 5.   A step of rotating the substrate at a rotational speed faster than a rotational speed at the time of forming the wetted area after the formation of the predetermined wetted area is completed, and further dispersing the coating liquid in the wetted area over the entire substrate surface; The spin coating method according to any one of claims 1 to 4.   The spin coating method according to any one of claims 1 to 5, wherein a height position of the nozzle for supplying the coating liquid is a height position at which the coating liquid becomes a continuous body between the nozzle tip and the substrate surface.   The spin coating method according to any one of claims 1 to 6, wherein the coating liquid is a liquid coating diffusion source that is coated on the surface of a semiconductor substrate and thermally diffuses impurities contained therein.   The spin coating method according to claim 1, wherein the coating solution has a viscosity of 10 cp to 130 cp.

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