JPH0992594A - Forming method of coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a pattern formed of coating film to be uniform in dimensions by a method wherein liquid is applied onto the surface of a substrate, and another liquid is fed to the applied former liquid. SOLUTION: A wafer substrate 51 is rotated in the direction of an arrow. Thereafter, coating liquid 61 is fed to nearly the center of the wafer 51 and spread over the wafer 51 in a radial direction (direction of arrow a) by a centrifugal force generated by the rotation of the wafer 51. Then, liquid 7 such as water, water and alcohol, or aqueous alcohol solution is fed to the coating liquid 61 applied onto the surface of the wafer 51. The liquid 7 is applied onto nearly the center of the wafer 51. The liquid 71 is spread over the coating liquid 61 spread over the surface of the wafer 51 in a radial direction (direction of arrow b).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film such as a resist film or an SOG (Spin on glass) film used in a semiconductor device.

[0002]

2. Description of the Related Art In recent years, with the high integration of LSIs,
A highly accurate pattern forming technique is required. The accuracy is generally within ± 10% of the design rule. For example, ± 0.0 for a VLSI with a design rule of 0.35 μm
Uniformity of the pattern size of 35 μm is required.

The following items can be cited as causes of the deterioration of the accuracy. (1) Variation of resist film thickness, (2) Standing wave effect, (3) Variation of resist dissolution rate, (4) Variation of various resist material properties, (5) Exposure equipment optical and mechanical Variation, (6) reticle pattern dimension variation, (7) etching variation, (8) substrate light reflectance variation (or film thickness variation of coating film formed on substrate surface), (9) substrate Step due to pattern, influence of acid / alkali in (10) atmosphere (especially in case of chemically amplified resist). Among the above, (1) to (4) and (10) are factors of variation of the pattern dimension in the photolithography process. The problem to be solved by the present invention is
Regarding (1) and (2), it is the variation of the pattern dimension due to the local variation of resist film thickness caused by the step.

Considering the above-mentioned factors of variation in the pattern size, in a VLSI having a design rule of 0.35 μm, for example, a so-called bare wafer is required to have a film thickness uniformity of 5 nm or less.

Here, the relationship between the dimensions of the resist pattern and the resist film thickness will be described. When the resist film thickness changes, the dimensions of the resist pattern after development also change. This relationship is shown in FIG. In FIG. 10, the vertical axis represents the resist pattern size, and the horizontal axis represents the resist film thickness.

As shown in FIG. 10, in general, the size of the resist pattern has a certain amplitude and a period [2λ / n (λ: exposure wavelength, due to interference between exposure light and light reflected from the underlayer).
n: refractive index of resist)]. The state is shown by the curve a. This is called the standing wave effect. Since this amplitude becomes larger as the reflected light from the underlayer becomes stronger, the controllability of the dimensions of the resist pattern becomes worse. Therefore, it is necessary to prevent reflection on a base having a high reflectance such as an aluminum film. Examples of the material of the antireflection film include amorphous silicon (a-Si), titanium oxynitride (TiON), and organic high absorption materials. The standing wave effect is reduced by reversing the phase and causing the light to interfere in the direction of canceling the standing wave by using the film as described above.

Then, the dimension change of the resist pattern when the antireflection is completely applied becomes almost linear as shown by the straight line b, and the phenomenon that the dimension of the resist pattern becomes thicker as the resist film thickness becomes larger remains. . This is called the bulk effect.

The required uniformity of film thickness can be realized when the film is formed on a flat substrate surface. However, a step is usually formed on an actual substrate, and the step causes a film thickness variation more than an allowable value. In general, the resist film thickness is a region where the film thickness variation due to the standing wave is small, that is, the peak of the standing wave (p in FIG. 10).
Point). That is, the position near the point p has the largest allowable range for the film thickness variation.
However, since the local variation of the resist film thickness is large in the vicinity of the step, it was unclear at which point of the standing wave the film thickness is in the vicinity of the step.

Therefore, there is a demand for a method of forming a coating film that can reduce the area where the coating film thickness varies in the step portion to reduce the dimensional variation due to the bulk effect.

[0010]

However, the film thickness uniformity required for the resist film must be at least 5 nm or less when the film is formed on a so-called bare wafer. Normally, even if it is possible to realize when a film is formed on a flat substrate surface, since a step is formed on an actual substrate, the step causes a film thickness variation more than an allowable value. Along with this, the area in which the dimensions of the pattern formed on the step varies also becomes large.

An object of the present invention is to provide a method for forming a coating film in which the dimensional variation of the pattern formed by the coating film is small.

[0012]

The present invention is a method for forming a coating film, which has been made to achieve the above object. That is, in a method of forming a coating film by applying a coating liquid to a surface of a substrate having a step by spin coating, a liquid different from this coating liquid is supplied onto the coating liquid supplied to the surface of the substrate. It is a method of forming a coating film. The liquid is, for example, water, water and alcohol, or an aqueous alcohol solution. After supplying the liquid, it is preferable to further rotate the substrate to remove the liquid on the coating liquid.

In the method for forming a coating film, on the coating liquid supplied to the surface of the substrate, as a liquid different from this coating liquid,
For example, since water, water and alcohol, or an aqueous alcohol solution is supplied, the interfacial tension of the coating liquid is adjusted by the liquid. On the other hand, in order to reduce the dimensional variation of the pattern formed by the coating film, it is necessary to apply a coating liquid having a surface tension suitable for the width of the underlying step. This surface tension is the energy at the interface with the saturated vapor. Therefore, since the interfacial tension of the coating liquid is adjusted by the liquid supplied onto the coating liquid, a coating film having a film thickness distribution that reduces the dimensional variation of the pattern is formed.

By using water and alcohol or an aqueous alcohol solution as the liquid, the ratio of water and alcohol can be changed. Therefore, by appropriately selecting the magnitude of the interfacial tension of the liquid according to the ratio of water and alcohol, the interfacial tension of the coating liquid can be adjusted freely. For example, in a liquid obtained by mixing water and alcohol, the interfacial tension changes depending on the mixing ratio. For example, the interfacial tension between methyl ethyl ketone and a mixed liquid of water and ethyl alcohol is 11. when the ethyl alcohol concentration is 0.348 mol%.
87mN / m, ethyl alcohol concentration is 11.0
It becomes 2.32 mN / m at 39 mol%.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A first example of an embodiment according to the present invention will be described with reference to the explanatory view of the embodiment shown in FIG.

As shown in (1) of FIG. 1, the wafer 51 as a base is rotated, for example, in the direction of arrow A. A step (not shown) is formed on the surface of the wafer 51, for example. After that, the coating liquid 61 is supplied onto almost the center of the wafer 51. As a result, the coating liquid 61 is applied to the surface of the wafer 51 by the centrifugal force generated by the rotation of the wafer 51.
1 spreads in the outer peripheral direction (direction of arrow a).

Then, as shown in FIG. 1 (2), the coating liquid 6 is used to spread the surface of the wafer 51 in the direction of arrow c.
As the liquid 71, for example, water, water and alcohol, or an aqueous alcohol solution is supplied onto the liquid 1. The liquid 71 is supplied almost on the center of the wafer 51. As a result, liquid 7
1 is the wafer 5 due to the centrifugal force generated by the rotation of the wafer 51.
The coating liquid 61 spread on the surface of No. 1 spreads in the outer peripheral direction of the wafer 51 (direction of arrow D). At this time, the wafer 5
1 continues to rotate in the direction of arrow A. The liquid 71 may be supplied in the form of, for example, a mist, a shower, a liquid droplet, or a state of continuous flow, but it is preferable that the liquid 71 be supplied in the form of a mist. That is, since the supply pressure of the liquid 71 to the coating liquid 61 can be relieved by supplying the liquid in the form of mist, it is possible to prevent the flatness of the surface of the coating liquid 61 in the region where the liquid 71 is supplied from being deteriorated. .

Further, the wafer 51 continues to rotate in the direction of the arrow A and continues to supply the liquid 71, and when the predetermined time elapses, the supply of the liquid 71 is stopped as shown in (3) of FIG. The figure shows a state in which the supply of the liquid 71 is stopped.

Then, as shown in FIG. 1D, the wafer 51 continues to rotate in the direction of arrow A. Then, the centrifugal force generated by the rotation of the wafer 51 causes 2
The liquid 71 shown by the dashed line is removed by shaking it in the direction of arrow E.

Next, an example of the spin coating apparatus 1 for realizing the above coating method will be described with reference to the schematic diagram of FIG.

As shown in FIG. 2, this spin coater 1 is constructed as follows. That is, the motor 11 for rotating the wafer 51 is provided. A wafer chuck 13 is provided at one end of a rotary shaft 12 of the motor 11. A coating liquid supply nozzle 14 and a liquid supply nozzle 15 are provided above the wafer chuck 13. Further, a control unit 16 is provided for controlling the rotation of the motor 11, the supply timing and the supply amount of the coating liquid 61 from the coating liquid supply nozzle 14, and the supply timing and the supply amount of the liquid 71 from the liquid supply nozzle 15. There is. The control of the supply timing and the supply amount is performed, for example, by opening and closing the adjusting valves 17 and 18 provided in the coating liquid supply nozzle 14 and the liquid supply nozzle 15, respectively. Furthermore, the coating liquid supply nozzle 14 is provided with a coating liquid storage tank (not shown), and the liquid supply nozzle 15 is provided with a liquid storage tank (not shown).

Next, an example of the operation of the spin coating apparatus 1 will be described below with reference to FIG. The same components as those described in FIG. 2 are designated by the same reference numerals.

First, as shown in FIG. 3A, the wafer 51 is mounted and fixed on the wafer chuck 13. Then, the motor 11 is driven to rotate the wafer chuck 13 in the arrow A direction, for example, to rotate the wafer 51.

Next, as shown in FIG. 3B, the coating liquid 6 is applied from the coating liquid supply nozzle 14 to approximately the center of the wafer 51.
Supply 1 At this time, since the wafer 51 is rotating in the arrow A direction, the coating liquid 61 spreads on the surface of the wafer 51 in the outer peripheral direction of the wafer 51 by the centrifugal force generated by the rotation of the wafer 51.

Subsequently, as shown in FIG. 3 (3), the coating liquid 61 which spreads the surface of the wafer 51 in the outer peripheral direction.
The liquid 71 (e.g., water,
Water and alcohol, or an aqueous alcohol solution) are supplied. The liquid 71 is supplied almost on the center of the wafer 51. At this time, since the wafer 51 is rotating in the direction of the arrow A, the coating liquid 61 spreads over the entire surface of the wafer 51 due to the centrifugal force generated by the rotation of the wafer 51, and the liquid 71 is placed on the coating liquid 61 so as to chase it. Spread to. The liquid 71 may be supplied in the form of, for example, a mist, a shower, a liquid droplet, or a state of continuous flow, but it is preferable that the liquid 71 be supplied in the form of a mist. That is, the liquid 71 with respect to the coating liquid 61 is supplied in the form of mist.
Since it becomes possible to relieve the supply pressure of the liquid 71
It is possible to prevent deterioration of the flatness of the surface of the coating liquid 61 in the region where the liquid is supplied.

Then, as shown in (4) of FIG. 3, the motor 11 is continuously driven to continuously rotate the wafer 51 in the direction of arrow A and the liquid 71 is continuously supplied so that the liquid 71 is applied to the entire surface of the coating liquid 61. When the liquid 71 is spread and a predetermined time has elapsed, the supply of the liquid 71 is stopped. In this figure, the state where the supply of the liquid 71 is stopped is shown.

Further, as shown in (5) of FIG. 3, the motor 11 is continuously driven to continuously rotate the wafer 51 in the arrow A direction, and the coating liquid 6 is generated by the centrifugal force generated by the rotation of the wafer 51.
The liquid 71 indicated by the two-dot chain line above 1 is removed by shaking it in the direction of arrow E.

In this way, as shown in FIG. 3 (6), a coating film 62 made of the coating liquid (61) coated on the wafer 51 is formed.

Next, a specific method for forming a coating film will be described below as an example.

In the first embodiment, an example of forming a resist film by applying a resist using cyclohexane as a solvent on a wafer will be described. In the following description, components having the same components as those of the spin coating device described with reference to FIG.

A step width of 15 is formed on the surface of the wafer 51.
A concave step 52 having a height of 0 μm and a height of 1 μm is formed. Such a wafer 51 is placed and fixed on the wafer chuck 13. Then, the motor 11 is driven to rotate the wafer 51 together with the wafer chuck 13 at, for example, 800 rpm.

Next, the wafer 5 is discharged from the coating liquid supply nozzle 14.
The coating liquid 61 is supplied onto the substantially central portion of 1. As the coating liquid 61, a resist using cyclohexane as a solvent was used. At this time, since the wafer 51 is rotating, the coating liquid 61 spreads on the surface of the wafer 51.

Subsequently, from the liquid supply nozzle 15 to the wafer 51.
The liquid 71 is supplied onto the coating liquid 61 which is spread on the surface of the. Water was used as the liquid 71. At this time, since the wafer 51 is rotating, the coating liquid 61 spreads over the entire surface of the wafer 51, and the liquid 71 spreads over the coating liquid so as to follow the spreading coating liquid 61. The interfacial tension between the cyclohexane and water is 51.01 mN / m.
It is.

Then, the liquid 71 is continuously supplied while keeping the rotation of the motor 11 at 3000 revolutions, the liquid 71 is spread over the entire surface of the spread coating liquid 61, and the supply of the liquid 71 is stopped when a predetermined time elapses. To do.

Then, the rotation of the motor 11 is further continued, and the liquid 71 on the coating liquid 61 is shaken off and removed.

In this way, the coating film 62 made of the coating liquid (61) coated on the wafer 51 is formed.

Using the coating film (resist film) treated according to the first embodiment, the pattern was formed by exposure and development, and as a result, the dimensional variation of the pattern was 0.
It became 014 μm. On the other hand, as a comparative example, at the time of applying a resist, a resist film is formed by applying a method that does not supply water on the resist, and the resist film is exposed and developed,
As a result of forming the pattern, the dimensional variation of the pattern was 0.025 μm. Therefore, the resist film (coating film 6) formed by the method described in the first embodiment is used.
In 2), when the pattern was formed, the dimensional variation of the pattern was significantly reduced.

Next, a step 5 is obtained by simulation.
The relationship between the position 2 and the dimensional variation of the pattern was obtained.
The simulation was performed as follows. That is, the film thickness distribution of the coating film was obtained, and further the dimensional variation of the pattern was obtained.

Here, as shown in FIG. 4, a step 52 (for example, width =
A case will be described in which the coating film 62 is formed on the surface of the wafer 51 having a w, height = δ concave portion. Further, from the center direction of the wafer 51 toward the outer peripheral direction, the upper part of the step is Sui, the bottom part of the step is Sb, and the upper part of the step is Suo.

First, a coating film 62 is formed on the surface of the wafer 51 rotating at a set angular velocity by the spin coating method. The film thickness of the coating film 62 is expressed by the equation (1).

[0041]

H = aexp (-λx) + bexp (λx / 2) cos (√3λx / 2) + cexp (λx / 2) sin (√3λx / 2) (1) [wherein (1) ^{λ = (3Ω 2) 1/3 =} {3 (ρω 2 w 3
_{r 0) / (γhf)}} 1/3, x = ( represents the _{r-r 0) / w,} ρ: density of the coating liquid, omega: wafer of the angular velocity, w: a wafer step width, r: a wafer center , R ₀ : distance between wafer center and step center, γ: surface tension of coating liquid, h
f: represents the coating film thickness at a flat position on the wafer away from the step]

From the above equation (1), the step upper part Sui
The film thickness H ₁ of the upper coating film 62 is expressed by the equation (2).

[0043]

H ₁ = b ₁ exp (λx / 2) cos (√3λx / 2) + c ₁ exp (λx / 2) sin (√3λx / 2) +1 (2)

Further, the film thickness H ₂ of the coating film 62 on the step bottom Sb is expressed by the equation (3).

[0045]

H ₂ = a ₂ exp (−λx) + b ₂ exp (λx / 2) cos (√3λx / 2) + c ₂ exp (λx / 2) sin (√3λx / 2) +1 (3) )

Further, the film thickness H ₃ of the coating film 62 on the step upper portion Suo is expressed by the equation (4).

[0047]

## EQU00004 ## H ₃ = a ₃ exp (-λx) +1 (4)

Here, ex in the above equations (2) to (4)
p (-λx), exp (λx / 2) cos (√3λx /
2) and exp (λx / 2) sin (√3λx / 2) are represented by ψ ₁ , ψ ₂ , ψ as shown in formulas (5) to (7).
Replace with ₃ .

[0049]

[Expression 5] exp (-λx) = ψ ₁ (5)

[0050]

(6) exp (λx / 2) cos (√3λx / 2) = ψ ₂ (6)

[0051]

(7) exp (λx / 2) sin (√3λx / 2) = ψ ₃ (7)

Therefore, the above equations (2) to (4) are
Expressions (8) to (10) are expressed.

[0053]

[Equation 8] H ₁ = b ₁ ψ ₂ + c ₁ ψ ₃ +1 (8)

[0054]

H ₂ = a ₂ ψ ₁ + b ₂ ψ ₂ + c ₂ ψ ₃ +1 (9)

[0055]

[Equation 10] H ₃ = a ₃ ψ ₁ +1 (10)

Then, the continuous condition at the step 52 is
Equations (8) to (10), equations (8) to (10) that have been differentiated once, and equations (8) to (10) that have been differentiated twice are defined as continuous conditions at the step 52. Obtained by solving as a simultaneous equation. That is, equations (8) to (1
The expression obtained by differentiating the expression (0) once is expressed as the expressions (11) to (13).

[0057]

H ₁ '(x) = b ₁ ψ' ₂ + c ₁ ψ ' ₃ (11)

[0058]

H ₂ '= a ₂ ψ ₁ ' + b ₂ ψ ₂ '+ c ₂ ψ ₃ ' (12)

[0059]

[Equation 13] H ₃ '= a ₃ ψ ₁ ' (13)

The expressions obtained by differentiating the expressions (8) to (10) twice are expressed as the expressions (14) to (16).

[0061]

[Equation 14] H ₁ "(x) = b ₁ ψ" ₂ + c ₁ ψ " ₃ (14)

[0062]

[Equation 15] H ₂ "= a ₂ ψ ₁ " + b ₂ ψ ₂ "+ c ₂ ψ ₃ " (15)

[0063]

[Equation 16] H ₃ '= a ₃ ψ ₁ "... (16)

Therefore, the step top Sui and the step bottom Sb
Considering the step, the continuous condition at the step with
Expressions (7) to (19) are obtained. Also, s = δ
/ Hf, which represents a step difference standardized by the thickness of the resist film.

[0065]

B ₁ ψ ₂ + c ₁ ψ ₃ + s = a ₂ ψ ₁ + b ₂ ψ ₂ + c ₂ ψ ₃ (17)

[0066]

B ₁ ψ ′ ₂ + c ₁ ψ ′ ₃ = a ₂ ψ ₁ ′ + b ₂ ψ ₂ ′ + c ₂ ψ ₃ ′ (18)

[0067]

## EQU19 ## b ₁ ψ " ₂ + c ₁ ψ" ₃ = a ₂ ψ ₁ "+ b ₂ ψ ₂ " + c ₂ ψ ₃ "(19)

Further, the continuous condition for the step difference between the step bottom Sb and the step upper part Suo is as follows (20) in consideration of the step.
Expressions to (22) are obtained.

[0069]

## EQU20 ## a ₂ ψ ₁ + b ₂ ψ ₂ + c ₂ ψ ₃ = a ₃ ψ ₁ + s (20)

[0070]

[Expression 21] a ₂ ψ ₁ ′ + b ₂ ψ ₂ ′ + c ₂ ψ ₃ ′ = a ₃ ψ ₁ ′ (21)

[0071]

[Equation 22] a ₂ ψ ₁ "+ b ₂ ψ ₂ " + c ₂ ψ ₃ "= a ₃ ψ ₁ " (22)

For example, the above equations (17) to (22) are set to 6
When the continuous condition at x = ± _1/2 is calculated as the simultaneous equations, a ₂ , a ₃ , b ₂ , b ₁ , c ₁ , c ₂ are given by the following equations (23) to (28). become.

[0073]

A ₂ = s / 3exp (λ / 2) (23)

[0074]

A ₃ = s / 3exp (λ / 2) −s / 3exp (−λ / 2) (24)

[0075]

B ₂ = 2s · cos (√3λ / 4) / 3exp (λ / 4) (25)

[0076]

B ₁ = 2s [cos (√3λ / 4) / 3exp (λ / 4) -cos (-√3λ / 4) / 3exp (-λ / 4)] (26)

[0077]

C ₁ = 2s [sin (√3λ / 4) / 3exp (λ / 4) -sin (-√3λ / 4) / 3exp (-λ / 4)] (27)

[0078]

C ₂ = 2s · sin (√3λ / 4) / 3exp (λ / 4) (28)

As a result, the above a ₂ , a ₃ , b ₂ , b ₁ ,
By substituting c ₁ and c ₂ into the equations (2) to (4), H ₁ representing the film thickness distribution of each coating film 62 on the step top on Sui, the step bottom on Sb, and the step top on Suo. , H ₂ and H ₃ are obtained.

Then, the dimension y of the pattern which fluctuates due to the film thickness distribution of the coating film 62 and the standing wave effect is given by (29)
Calculate by formula.

[0081]

[Mathematical formula-see original document] y = (aχ + b) sin (4nπχ / λ _c + c) + dχ + e (29) [wherein (29), χ: coating thickness, n: refractive index of coating film,
λ _c : exposure wavelength, a, b, _C , d, e: standing wave regression constant]

That is, the film thickness at a predetermined position of the coating film thickness distribution represented by the above H ₁ , H ₂ , and H ₃ is defined by the above (29).
By substituting for χ in the equation, the dimension y of the pattern at the predetermined position, for example, the line width of the line pattern is obtained.

Next, the dimensional variation is obtained from the value of the pattern dimension y obtained above. The dimensional variation is
For example, it is simply _calculated as the difference between the maximum value y _max of the pattern dimension y and the minimum value y _min of the pattern dimension y. Usually, when the standard dimension value is y _s , y _max ≧ y _s ≧ y _min . Alternatively, it may be a difference from the average value of the pattern dimensions of a plurality of calculation points, and the variation of the pattern dimensions may be defined by other criteria.

Using the simulation method described above, the dimension of the pattern patterned by using the resist film formed by applying resist using cyclohexane as a solvent by the method described in the first embodiment corresponds to the position of the step. I asked for it. In the above simulation,
By supplying water on the resist, the interfacial tension at the resist interface changes. That is, calculation was performed in consideration of changes in the surface tension of the resist.

As a result, the pattern size distribution corresponding to the step position x becomes as shown in (1) of FIG. 5, and the pattern size variation in the lower part Sb of the step is 0.014 μm.
Became. On the other hand, when resist is applied without supplying water to form a resist film and a pattern is formed using the resist film, the pattern size distribution corresponding to the step position is shown in (2) of FIG. And the lower part of the step Sb
The dimensional variation of the pattern was 0.025 μm. Therefore, also from the simulation, it can be said that a pattern with small dimensional variation can be formed by using the resist film formed by applying the resist by the method of the first embodiment. Note that FIG.
In (1) and (2), the vertical axis represents the dimension of the resist pattern, and the horizontal axis represents the step position x. The discontinuity of the pattern size at the step portion is that the resist film thickness changes discontinuously at the boundary between the step upper portions Sui, Suo and the step lower portion Sb, that is, at the position of x = ± 1/2. This is because.

Next, as a second embodiment, an example of forming a resist film by applying a resist using cyclohexanol as a solvent on a wafer will be described. In the following description, the same components as those of the spin coater described with reference to FIG. The wafer 51 has the same surface shape as the wafer used in the first embodiment. Then, a coating solution (a resist using cyclohexanol as a solvent) 61 was supplied onto the wafer 51 and water was supplied as a liquid 71 onto the coating solution 61 by the same method as described in the first embodiment. , Coating film 6
Formed 2.

Thereafter, the coating film 62 is exposed and developed to form a pattern. As a result, a region (hereinafter referred to as a prohibited region) in which the dimensional variation of the pattern is larger than an allowable value (for example, 0.005 μm) is , 15 μm. On the other hand, as a comparative example, a resist film is formed by applying a method in which water is not supplied onto the resist when applying the resist,
The resist film was exposed and developed to form a pattern, and as a result, the above-mentioned prohibited area became 30 μm. Therefore, in the resist film applied by the method of the present invention, the forbidden region was significantly reduced when the pattern was formed.

Using the above-described simulation method, a resist using cyclohexanol was applied to a solvent to form a resist film by the method described in the second embodiment, and the resist film was exposed, developed and patterned. The dimension of the obtained pattern was determined in correspondence with the position of the step. In the above simulation, the surface tension of the resist interface is changed by supplying water onto the resist. That is, calculation was performed in consideration of changes in the surface tension of the resist.

As a result, the dimensional distribution of the pattern corresponding to the step position x having the step width of 150 μm is as shown in FIG. 6A, and the size of the prohibited region near the step is 15 μm.
Became. On the other hand, when a resist film is formed by coating without supplying water and a pattern is formed using the resist film, the pattern size distribution corresponding to the step position x is as shown in (2) of FIG. Became. That is, the size of the prohibited area near the step was 30 μm. Therefore, from the simulation as well, it can be said that the prohibited area can be reduced according to the coating method of the second embodiment. In addition,
In (1) and (2) of FIG. 6, the vertical axis represents the dimensions of the resist pattern, and the horizontal axis represents the step position x. Further, the discontinuity of the pattern size at the step portion is due to the step upper portion Su.
The boundary between i, Suo and the lower part of the step Sb, that is, x = ± 1 /
This is because the resist film thickness changes discontinuously at the position 2.

Next, as a third embodiment, an example of forming an SOG film by applying SOG (Spin on glass) using cyclohexane as a solvent on a wafer will be described. In the following description, the same components as those of the spin coater described with reference to FIG. The wafer 51 has the same surface shape as the wafer used in the first embodiment. Then, a coating liquid (SOG using cyclohexane as a solvent) 61 is supplied onto the wafer 51 by the same method as described in the first embodiment, and water is supplied as the liquid 71 onto the coating liquid 61 to apply the liquid. A film (SOG film) 62 was formed.

After that, the flatness of the surface of the coating film (SOG film) was examined. As a result, the flatness became 95%.
The flatness referred to here is (d−δ) as a difference δd between the film thickness d of the coating film 61 on the flat portion and the surface height of the coating film 61.
It is represented by d) / d × 100%. Hereafter, flatness is defined in this way. On the other hand, as a comparative example, when applying SOG, the SO
The flatness of the surface of the SOG film formed by applying the method on G without applying water was examined. As a result, the flatness was 80%. Therefore, the surface flatness of the SOG film applied by the method of the third embodiment was significantly improved.

Using the above-mentioned simulation method, the film thickness distribution of the SOG film formed by applying SOG using cyclohexane to the solvent was obtained by the method described in the third embodiment, corresponding to the position of the step. It was That is,
(23) becomes to (28) _{a 2, a 3, b 2} ,
Equation (2) representing the film thickness distribution using b ₁ , c ₁ , and c ₂
H ₁ , H ₂ and H ₃ of the equation (4) are calculated. In addition, in the above simulation, by supplying water onto the SOG, the interfacial tension at the SOG interface changes. Ie SOG
It was calculated in consideration of the change of the surface tension of.

As a result, as shown in (1) of FIG. 7, the film thickness distribution corresponding to the step position x = ± 1/2 is obtained, and the flatness of the surface of the SOG film near the step becomes 95%. It was On the other hand, as shown in (2) of FIG. 7, the step position x = ± 1 of the SOG film formed by applying SOG without supplying water.
A film thickness distribution corresponding to / 2 was obtained, and the flatness of the surface of the SOG film corresponding to the step position x was 80%. Therefore,
From the simulation, it was verified that the flatness of the SOG film could be improved by the coating method of the third embodiment.
In addition, in (1) and (2) of FIG. 7, the vertical axis represents the SOG film thickness, and the horizontal axis represents the step position x.

Next, as a fourth embodiment, an example of forming a resist film by coating a resist using methyl ethyl ketone as a solvent on a wafer and supplying an 11 mol% ethanol aqueous solution as a liquid will be described. In addition,
The same components as those of the spin coater described with reference to FIG. 2 are designated by the same reference numerals in the following description. The wafer 51 has the same surface shape as the wafer used in the first embodiment. And 11 mol% in liquid
A coating solution (a resist using methyl ethyl ketone as a solvent) 61 is applied on the wafer 51 by the same method as described in the first embodiment except that the ethanol aqueous solution is used. ) 62 was formed.

Thereafter, the coating film 62 is exposed and developed to form a pattern, and as a result, the dimensional variation of the pattern is 1 in the prohibited area where the size variation is larger than 0.005 μm.
It became 5 μm. On the other hand, as a comparative example, as a result of exposing and developing a resist film applied by a method in which water was not supplied onto the resist at the time of applying the resist to form a pattern, the above-mentioned prohibited area was 30 μm. Therefore, in the resist film applied according to the fourth example, the forbidden region was significantly reduced when the pattern was formed.

Next, a fifth embodiment in which a resist film is formed using the spin coater described with reference to FIG. 8 will be described.
First, the spin coating apparatus will be described with reference to the schematic configuration diagram of FIG. In this figure, the same components as those described in FIG. 2 are designated by the same reference numerals.

As shown in FIG. 8, in this spin coating apparatus 2, the motor 11, the wafer chuck 13, which is provided at one end of the rotary shaft 12 of the motor 11, the coating liquid supply nozzle 14 and the liquid supply nozzle 15, are the same as those shown in FIG. It has the same configuration as that of the spin coating apparatus (1) described above. The coating liquid supply nozzle 14 is provided with a coating liquid storage tank (not shown). On the other hand, a water storage tank 21 and an alcohol storage tank 2
2 are provided, and the pipes 23 and 24 are connected to the concentration controller 25 from the water storage tank 21 and the alcohol storage tank 22. A pipe 26 is connected to the liquid supply nozzle 15 from the concentration controller 25. Further, the rotation of the motor 11 and the coating liquid 6 from the coating liquid supply nozzle 14
A control unit 16 is provided for controlling the supply timing and the supply amount of the liquid No. 1 and the supply timing and the supply amount of the liquid 71 from the liquid supply nozzle 15. The control of the supply timing and the supply amount is performed, for example, by opening and closing the adjusting valves 17 and 18 provided in the coating liquid supply nozzle 14 and the liquid supply nozzle 15, respectively.

Then, a resist using methyl ethyl ketone as a solvent is applied onto the wafer using the spin coater 2 described with reference to FIG.
A 5 mol% ethanol aqueous solution is supplied to form a resist film. Pure water is stored in the water storage tank 21, and ethyl alcohol is stored in the alcohol storage tank 22. The ethanol aqueous solution is
Pure water in the water storage tank 21 and ethyl alcohol in the alcohol storage tank 22 are supplied to the concentration controller 25 through the pipes 23 and 24, and are adjusted so that the desired alcohol concentration is obtained. Then, from the concentration controller 25, an aqueous ethanol solution having a desired concentration is supplied to the liquid supply nozzle 15 through the pipe 26.

The wafer 51 has the same surface shape as the wafer used in the first embodiment. Then, a coating liquid (a resist using methyl ethyl ketone as a solvent) 61 is applied on the wafer 51 by the same method as described in the first embodiment except that a 0.35 mol% ethanol aqueous solution is used as the liquid 71. Then, a coating film (resist film) 62 was formed.

After that, the coating film (resist film) 62 was exposed and developed to form a pattern. As a result, the forbidden region in which the dimensional variation of the pattern was larger than 0.005 μm was 20 μm. On the other hand, as a comparative example, as a result of exposing and developing a resist film applied by a method in which water was not supplied onto the resist at the time of applying the resist to form a pattern, the above-mentioned prohibited area was 30 μm. Therefore, in the resist film applied according to the fifth example, the forbidden region was significantly reduced when the pattern was formed.

The sixth embodiment uses the spin coater explained in FIG. First, the spin coating apparatus will be described with reference to the schematic configuration diagram of FIG. In FIG. 9, the same components as those described in FIG. 2 are designated by the same reference numerals.

As shown in FIG. 9, this spin coater 3
In the spin coating apparatus 1 described above, the first liquid supply nozzle 15a and the second liquid supply nozzle 15a are used instead of the liquid supply nozzle 15.
A liquid supply nozzle 15b is provided, and other configurations are the same as those of the spin coating apparatus 1. A water storage tank (not shown) is connected to the first liquid supply nozzle 15a, and an alcohol storage tank (not shown) is connected to the second liquid supply nozzle 15b. Further, the rotation of the motor 11 and the coating liquid 6 from the coating liquid supply nozzle 14
A control unit 16 is provided to control the supply timing and supply amount of No. 1 and the supply timing and supply amount of the liquids 71 and 72 from the first and second liquid supply nozzles 15a and 15b.

Then, using the spin coater 3 described with reference to FIG. 9, a resist using methyl ethyl ketone as a solvent is coated on the wafer, and water and ethanol are supplied as liquids to form a resist film. . Water and ethanol have an ethanol concentration of 11 on the wafer 51.
It is adjusted and supplied so that it may be mol%.

The wafer 51 has the same surface shape as the wafer used in the first embodiment. Then, a coating liquid (a resist using methyl ethyl ketone as a solvent) 61 is applied onto the wafer 51 by the same method as described in the first embodiment except that the supply method of the liquid 71 is different, and a coating film ( A resist film) 62 was formed.

After that, the coating film (resist film) 62 was exposed and developed to form a pattern. As a result, the forbidden region in which the dimensional variation of the pattern was larger than 0.005 μm was 15 μm. On the other hand, as a comparative example, a coating finish film was formed by a method in which water was not supplied onto the resist during resist coating, and the resist film was exposed and developed to form a pattern.
It became m. Therefore, in the resist film applied according to the sixth example, the forbidden region was significantly reduced when the pattern was formed.

By using the simulation method described above, the surface tension of the coating liquid can be adjusted by adjusting the interfacial tension with the liquid. Therefore, (a)
Optimal liquid or coating liquid solvent that maximizes the flatness of the coating film, (b) Optimal liquid or coating liquid solvent that minimizes pattern dimensional variations, and (c) Optimal liquid that minimizes prohibited areas. Alternatively, the solvent of the coating liquid or the like can be obtained.

[0107]

As described above, according to the method for forming a coating film of the present invention, on the coating liquid supplied to the surface of the substrate,
Since water, water and alcohol, or an aqueous alcohol solution is supplied as a liquid different from the coating liquid, the interfacial tension of the coating liquid can be adjusted by the liquid.
Therefore, it becomes possible to adjust the interfacial tension of the coating liquid in a state suitable for reducing the pattern dimensional variation, so that it is possible to form a coating film in which the pattern dimensional variation is reduced corresponding to the underlying step. it can. Further, the range of dimensional variation can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a spin coating device.

FIG. 3 is a schematic explanatory view of the operation of the spin coater.

FIG. 4 is an explanatory diagram of a simulation.

FIG. 5 is a pattern size distribution diagram by a simulation of the first embodiment.

FIG. 6 is a size distribution diagram of a pattern by simulation of the second embodiment.

FIG. 7 is an SOG film thickness distribution diagram by a simulation of the third example.

FIG. 8 is a schematic configuration diagram of a spin coating device.

FIG. 9 is a schematic configuration diagram of a spin coating device.

FIG. 10 is a relationship diagram between the dimensions of a resist pattern and the resist film thickness.

[Explanation of symbols]

 51 Wafer (Substrate) 61 Coating Liquid 62 Coating Film 71 Liquid

Claims (4)

[Claims] 1. A method for forming a coating film by applying a coating solution onto the surface of a substrate by spin coating, wherein a liquid different from the coating solution is applied onto the coating solution supplied to the surface of the substrate. A method for forming a coating film, which comprises supplying. 2. The method for forming a coating film according to claim 1, wherein the liquid is water, water and alcohol, or an aqueous alcohol solution. 3. The method for forming a coating film according to claim 1, wherein after the liquid is supplied, the substrate is rotated to remove the liquid on the coating liquid. 4. The method for forming a coating film according to claim 2, wherein after the liquid is supplied, the substrate is rotated to remove the liquid on the coating liquid.