JP3491336B2 - Exposure method and exposure apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing semiconductor elements and liquid crystal plates, and more particularly to a projection type exposure apparatus and a projection exposure method.

[0002]

2. Description of the Related Art In a conventional exposure method, all desired patterns to be exposed are arranged on the same reticle and printed on a substrate by one exposure. At that time, a latent image reaction concentration ξ corresponding to the exposure intensity I is generated in the resist applied on the substrate. In the case of using a positive type resist which is generally used at present, it can be expressed as ξ = exp (−CD) and D = I · t (1). Here, I is the exposure intensity, t is the exposure time, and C is a constant determined by the photosensitive material.

In such a method, the exposure intensity distribution I
The spectrum i of (x) is i (ν) = i ₀ , where i ₀ is the object spectrum and f is the optical transfer function (OTF) of the optical system, assuming completely incoherent imaging for simplicity. ν) · f (ν) (2) ν: given in spatial frequency. By the way, the spatial frequency ν ₀ at which the OTF, that is, f is insignificant in the process, is ν ₀ = 0.5NA / (K ₁₎ where λ is the exposure wavelength and NA is the numerical aperture of the projection optical system on the photosensitive material side. Λ) K ₁ : given by the process constant (3). Further, the resolution limit of the optical system is determined in principle by the numerical aperture NA, in which case K ₁ = 0.25, and the cut-off frequency νc of the optical system is νc = 2NA / λ (4). Therefore, in order to obtain a high resolution, the wavelength must be shortened or the numerical aperture NA must be increased.

[0004]

In the conventional exposure method as described above, the numerical aperture NA must be increased or the wavelength λ must be decreased in order to obtain a high resolution. However, the depth of focus Fd of the projection optical system is proportional to the wavelength λ and inversely proportional to the square of NA, as shown in the following equation, and Fd = K ₂ · λ / NA ² (5) K ₂ : Process constant Therefore, in either case, the depth of focus becomes shallow. Also, the optical system becomes larger and specialized, making it impractical. Further, the final resolution limit on the photosensitive material could not exceed the resolution limit determined by the projection optical system.

The present invention has been made in view of the above problems, and forms a high-resolution pattern exceeding the resolution limit of the projection optical system without changing the conventional exposure wavelength and optical system. An object of the present invention is to provide an exposure method and an exposure apparatus capable of performing the exposure.

[0006]

An exposure method according to the present invention is a projection exposure method in which a pattern of a projection original plate is projected onto a predetermined photosensitive material by a projection optical system. A transparent film having a non-linear characteristic with respect to strength is provided, and the pattern formed on the projection original plate
Another projected original plate with a different pattern from the pattern
Or using the projected original plate and the photosensitive material
To move a specified amount in the direction perpendicular to the optical axis
Allows multiple exposures with different light intensity distributions on the transparent film.
By using light, it is possible to form a high resolution pattern that exceeds the resolution limit of the projection optical system.

The transmission film of the present invention is not limited to the case where the transmitted light intensity changes in accordance with the n-th power of the incident light intensity and has a nonlinear characteristic of n> 1, but the transmitted light intensity is It is also possible to have a nonlinear characteristic in which n <1 changes and n <1. An exposure apparatus according to the present invention is a projection exposure apparatus that projects a predetermined pattern of a projection original onto a predetermined photosensitive material by a projection optical system, wherein the transmitted light intensity on the photosensitive material is non-linear with respect to the incident light intensity. With a transparent film, and the photosensitive material coated with the transparent film at each exposure and the projection original plate are placed in a direction relatively perpendicular to the optical axis.
The exposure is repeated a plurality of times by moving by a fixed amount .

Further, the exposure apparatus of the present invention is a projection exposure apparatus for projecting a pattern of an original plate to be projected onto a predetermined photosensitive material by a projection optical system, wherein the transmitted light intensity on the photosensitive material is relative to the incident light intensity. A transparent film having a non-linear characteristic is applied, and a first projection original plate having a first pattern as the projection original plate and a second projection original plate having a second pattern different from the first pattern are provided. Against the photosensitive material
After the first exposure by the first projection original plate, the second projection
The second exposure is performed by the projection original plate.

[0009]

[0010]

[Function] The incident light intensity I
In this case, a transmission film having a characteristic that the emission light intensity is I ⁿ (n ≠ 1) is applied. As a result, the distribution of light intensity incident on the resist is changed. When exposure light is transmitted through the above-mentioned transparent film, the latent image reaction concentration ξ generated in the resist can be expressed by the following formula instead of the formula (1).

Ξ = exp (−CD), D = H · t = I ⁿ · t (6) where I is the exposure intensity, t is the exposure time, and C is a constant determined by the photosensitive material. n is an index representing linearity, and n =
It is said to be linear when 1 and non-linear when n ≠ 1. In the present invention, as described below, n ≠ 1 by changing the effective exposure intensity I to the resist.
Can be As shown in the above equation, for easy understanding, I ⁿ is replaced with H, and H is called effective exposure intensity.

If the transmissivity of the transmissive film is invariable (constant), the transmitted light intensity is proportional to the incident light intensity. That is, n = 1. Next, the transmitted light intensity is n of the incident light intensity.
The principle that a pattern exceeding the resolution limit of the projection optical system can be formed when a transmissive film having a non-linear characteristic that is formed so as to be emphasized corresponding to the power (n> 1) is used is described. This will be described below.

In the conventional exposure method, the light intensity distribution I on the image plane after passing through the entire system in incoherent illumination is used.
(X) is I (x) = I ₀ (x) * F (x) (7) where I ₀ (x) is the light intensity distribution of the object and F (x) is the point image intensity distribution of the optical system. Given. Here, x is a position coordinate on the photosensitive material, and * means convolution. From this, the spectrum i of the light intensity on the image plane is i (ν) = i ₀ (ν) · f (ν) (8) from the convolution theorem of the Fourier transform. Here, ν is the spatial frequency, i ₀ is the spectrum of the light intensity of the object, f corresponds to the so-called OTF of the optical system, and the spectrum of the exposure intensity (light intensity on the image plane) of the optical system is Those that exceed the cutoff frequency (2NA / λ) are not formed.

However, when a transparent film having such a characteristic that the transmitted light intensity is emphasized corresponding to the nth power (n> 1) of the incident light intensity is provided on the photosensitive material, the following will be shown. Thus, a fine pattern is formed. As an example, a case where n = 2, that is, a case where the effective exposure intensity distribution H (x) is formed according to the square of the transmitted light intensity distribution I (x) is shown. In incoherent illumination, I
_{Assuming that 0} (x) and the point image intensity distribution of the optical system are F (x), H (x) = I (x) ² = {I ₀ (x) * F (x)} ² (9). From this, the spectrum h of the effective exposure intensity distribution
Similarly, from the convolution theorem of Fourier transform, h (ν) = {i ₀ (ν) · f (ν)} * {i ₀ (ν) · f (ν)} (10) When n = 2, since the effective exposure intensity distribution is given according to the equation (9), the effective exposure intensity distribution becomes steeper than that of the conventional equation (7). This is specifically illustrated in FIGS. 9A and 9B when the exposure intensity distribution is sinusoidal.

FIG. 9A shows a light intensity distribution in normal exposure, which has the same sine wave shape as the exposure intensity distribution. Figure 9
B represents the effective exposure intensity distribution when n = 2. Figure 9A
9B is compared with FIG. 9B, the contrast is high, but the pitch of the formed pattern is the same in FIG. 9A and FIG. 9B. The pitch cannot be finer than the pitch of the image produced by the optical system and cannot exceed the resolution limit of the optical system. From the equation (10), there is a frequency component that exceeds the resolution limit of the optical system in the effective exposure intensity distribution, but the pitch of the formed pattern does not exceed the resolution limit of the optical system until it gets tired. .

As described above, it is impossible to form a fine pattern exceeding the resolution limit determined by the optical system only by using the transmissive film whose transmitted light intensity is emphasized in accordance with the incident light intensity. . However, in the present invention, a transmissive film whose transmitted light intensity is emphasized in accordance with the incident light intensity is used, and the exposure is performed in plural times to form a fine pattern exceeding the resolution limit by the optical system. Is possible.

In order to explain the basic idea of the present invention, let us consider the formation of a point image by the optical system in the case of n = 2 as in the above. In this case, the point image intensity distribution point image transmitted through the transmission film becomes steep. Furthermore, in this case, the point image intensity distribution F (x) by the optical system may be considered regardless of the illumination state, and the desired object light intensity distribution I ₀ (x) is formed by superimposing point images, If the effective exposure intensity distribution H (x) is formed by this, the light intensities created by the image formation of the respective point images are superposed, so that H (x) = I ₀ (x) * {F It is basically expressed as (x)} ² (11). The effective exposure intensity distribution of the point image is {F
Since it is represented by (x)} ² , the distribution becomes sharper than the point image intensity distribution F (x) by the optical system, resulting in high resolution. By performing the Fourier transform of the equation (11), h (ν) = i ₀ (ν) · {f (ν) * f (ν)} (12) is obtained. Therefore, f * f is interpreted as the OTF of the optical system for obtaining the effective exposure intensity distribution in this method. This is compared with the conventional OTF expressed by Eq. (8), that is, the cutoff frequency (2NA / λ) of f and the cutoff frequency (4
NA / λ), and twice the resolving power can be obtained.

FIG. 10 schematically shows this comparison. Figure 10
A represents OTF in the conventional method, and FIG. 10B represents OTF in the case where an isolated pattern is exposed on a resist using a transmissive film of n = 2. From this, if a transparent film of n = 2 is used and a plurality of exposures are performed based on an isolated pattern to form a latent image, a fine pattern exceeding the resolution limit of the optical system can be formed. In this way, by combining multiple exposures with an isolated pattern and a transmission film having a non-linear characteristic, it is possible to form a pattern that exceeds the resolution limit of the optical system.

Furthermore, when a plurality of exposures are performed using a pattern that is not completely isolated but is considered to be substantially isolated,
As in the case of an isolated pattern, it is possible to form a pattern that exceeds the resolution limit of the optical system. In this case, the spectrum h of the effective exposure intensity distribution is as follows: h (ν) = Σi _0j (ν) · {f (ν) * f (ν)} = i ′ (ν) · {f (ν) * f (ν )} (13) i ′ (ν) = Σi _0j (ν). Here, i _0j is considered to be an object spectrum of patterns that are substantially isolated from each other, and i ′ is considered to be an object spectrum of a virtual pattern configured by superimposing isolated patterns. The spectrum of the conventional effective exposure intensity distribution is, as shown in equation (8), the cutoff frequency of f (2
However, according to the present invention, the spectrum up to the cut-off frequency (4NA / λ) of {f (ν) * f (ν)} is effective according to the present invention. It is formed as an exposure intensity distribution.

As described above, in the present invention, the pitch of the pattern formed does not exceed the resolution limit of the optical system when only the transmissive film having the non-linear characteristic is used by the conventional exposure method. Further, by repeating exposure a plurality of times with different effective exposure intensity distributions on the photosensitive material, if i'is properly given, a density distribution of a pattern having a pitch exceeding the resolution limit of the optical system is formed in the resist. be able to.

In the above, the effective exposure intensity H is the exposure intensity I.
Although the case where it is formed in proportion to the square of is described, the present invention is not limited to this,
It is sufficient that the effective exposure intensity H is a transmissive film having a non-linear characteristic formed according to the nth power (n> 1) of the exposure intensity I. In this case, the effective exposure intensity distribution is represented by the nth power of the point image light intensity distribution F (x), and is a sharper distribution than the point image light intensity distribution F (x). Represented by.

H (x) = I ₀ (x) * {F (x)} ⁿ (14) Then, the illumination state is not limited to incoherent illumination, and oblique illumination and various modified illuminations are also extremely fine. It is possible to form a pattern. Of course, a self-luminous object is also possible. It can be seen from the Fourier transform convolution theorem that the equation (14) is transformed into a pattern (effective exposure intensity distribution) having a frequency n times the cutoff frequency of the optical system. It is possible that a finer pattern can be formed by exposing a pattern that is not completely isolated several times in each exposure.

In the above description, the case where the multiplier n is larger than 1 (n> 1) in the equation (14), that is, the effective exposure intensity H is emphasized more than the light intensity I, is explained. Even when is less than 1 (n <1), it was found as a result of simulation that a fine pattern substantially exceeding the resolution limit of the projection optical system can be formed. The transmission characteristic is also effective when the multiplier n in the equation (14) is not constant but depends on the light intensity I.

In each exposure of a plurality of exposures, if a high-resolution and high-contrast pattern is formed by using a phase shift mask or a modified illumination method, the effective exposure intensity exceeding the resolution limit of the optical system. The distribution can be formed with higher contrast. As described above, using a transmissive film having a non-linear transmission characteristic with respect to the effective exposure intensity,
By performing exposure a plurality of times with different light intensity distributions on the transmission film, it is possible to obtain a semiconductor element having a high resolution pattern exceeding the resolution limit of the projection optical system.

[0025]

EXAMPLES The present invention will be described below based on examples. FIG. 1 shows a sectional view of a reticle pattern as a projection original plate according to the present invention. 1st exposure is performed by the pattern shown in FIG. 1A, and 2nd exposure is performed by the pattern of FIG. 1B. In the first pattern of FIG. 1A, the light shielding film 2a provided on the substrate 1a forms the opening 4a. Then, the phase film 3a is provided on one of the adjacent openings 4a, and constitutes a so-called phase shift mask. Similarly, in the second pattern of FIG. 1B, the light-shielding film 2b and the phase film 3b are provided on the substrate 1b, and the phase shift mask is similarly configured. The opening 4a of the first pattern overlaps the position of the light-shielding film 1b of the second pattern, and the opening 4b of the second pattern is arranged so as to overlap the position of the light-shielding film 1a of the first pattern to provide a transparent film. The photosensitive material is exposed separately.

The light amount distribution on the transparent film obtained by the exposure with the first and second patterns is shown in FIGS. 2A and 2B. Here, in this embodiment, the coherent illumination ±
As shown in FIGS. 2A and 2B, sinusoidal light intensities Ia and Ib are created in each exposure by only the first-order diffracted light. In these two exposures, the peak positions of the light intensity distribution on the transmissive film are out of phase by a half cycle.

Considering the case of high resolution, it is assumed that a light intensity distribution having a frequency at the resolution limit of the optical system is created in each exposure. That is, if the numerical aperture is used sufficiently effectively so that the ± 1st-order diffracted light passes through the peripheral portion of the aperture of the optical system, the pitch created in each exposure is the resolution limit λ / 2NA, and the incident light intensity distribution Is expressed as Ia (x) = 1 + cos (2π · 2NA · x / λ) (15) Ib (x) = 1 + cos (2π · 2NA · x / λ + π) (16). When the effective exposure intensity transmitted by the characteristics of the film coated on the resist is given by the square of the light intensity, the effective exposure intensity distributions are as shown in FIGS. 3A and 3B: Ha (x) = Ia (x ) ² = 3/2 + 2 cos (2π · 2NA · x / λ) + cos (4π · 2NA · x / λ) / 2 (17) Hb (x) = Ib (x) ² = 3/2 + 2 cos (2π · 2) 2NA · x / λ + π) + cos (4π · 2NA · x / λ) / 2 (18). The effective exposure intensity distribution finally obtained by multiple exposures is the sum of (17) and (18), and H (x) = Ha (x) + Hb (x) = 3 + cos (4π · 2NA · x / λ) (19). From the equation (19), the effective exposure intensity H in this embodiment is
(X) has a periodic structure with a pitch (λ / 4NA), which is twice as fine as the limiting resolution (λ / 2NA) of the optical system. This effective exposure intensity H (x) is shown in FIG. A fine resist pattern is formed by performing development after the exposure of a plurality of times (here, twice).

As can be seen from the equation (12) and FIG. 10B, if a latent image is formed by superimposing complete isolated patterns (point objects), a latent image with a pitch (λ / 4NA) is formed. However, in this case, since the contrast is not so high, in the above embodiment, the phase shift mask is coherently illuminated to form a high contrast effective exposure intensity distribution.

If a transmissive film having a non-linear characteristic and a constant transmissivity is used, exposure is performed by the simple sum of the above equations (15) and (16), that is, the simple sum of FIGS. 2A and 2B. Therefore, no pattern is formed. In the above embodiment, the effective exposure intensity is obtained by the square of the light intensity (n = 2), but the cube, the fourth power or more (n =) of the light intensity is obtained.
When an effective exposure intensity is obtained with the non-linear characteristics (3, 4, ...), a higher resolution can be expected. For example, the effective exposure intensity distribution shown in FIG. 5 is obtained when the effective exposure intensity distribution is obtained by the cube of the light intensity distribution (n = 3), and the pattern of the projection original plate shown in FIG. 1A is (1/3) pitch. That is (λ / 6
It was obtained by exposing three times with each shift of (NA).
Here, as shown in the figure, the periodic structure has a pitch (λ / 6NA), which is three times as fine as the resolution limit (λ / 2NA) of the optical system.

It is also possible to use a transmissive film which can obtain an effective exposure intensity by the 1.5th power of light intensity (n = 1.5). FIG. 6 is an effective exposure intensity distribution obtained by separately exposing the reticles shown in FIGS. 1A and 1B with n = 1.5, and the effective exposure intensity distribution is twice as fine as the resolution limit of the optical system. The exposure intensity distribution is obtained. Also in this case,
By coherently illuminating the phase shift mask,
The contrast can be increased.

Next, another embodiment of the present invention will be described. In the embodiment shown in FIG. 1, the light intensity distribution is formed by coherent imaging using the so-called phase shift method, but this embodiment uses a normal reticle to perform partial coherent imaging. The conditions of the optical system were such that the used wavelength λ = 0.365 μm, the numerical aperture NA = 0.5, and the coherence degree σ = 0.6. FIG. 8A shows the case where n = 2,
Exposure is performed by shifting an isolated line having a width of 0.25 μm three times and
It is an effective exposure intensity distribution when three 5 μm isolated lines are formed. FIG. 8B shows the distribution when n = 2 and when three main lines having a width of 0.25 μm are collectively exposed. FIG. 8C is an exposure intensity distribution of three lines with a width of 0.25 μm by the conventional method.

By comparing these FIG. 8A, FIG. 8B, and FIG. 8C, the effective exposure intensity distribution chart 8A obtained by the method of the present invention is effective in forming a fine pattern that is far superior to other methods. It is clear that there is. Generally, a resist pattern after development is formed almost in proportion to the latent image reaction density, but if it is further emphasized in the development process, a resist pattern of higher contrast can be formed.

Further, an embodiment in which the multiplier n is smaller than 1 (n <1) will be described. As an example, a case of using a permeable membrane with n = 0.5 will be described. The effective exposure intensity when a transmissive film of n = 0.5 is used is made according to the 0.5th power of the light intensity. That is, H (x) = I (x) ^0.5 (20) is given. Here, x is a coordinate. A case where a line and space is printed by using the reticle with a phase shifter shown in FIG. 1 under coherent illumination will be shown. The period of this reticle is the resolution limit λ / 2 of the projection optical system.
It is NA. FIG. 11 is a diagram of an incident light intensity distribution formed on the transmission film. The incident light intensity distribution I (x) is thus sinusoidally distributed. That is, I (x) = 1 + COS (2π · 2NA · x / λ) (21). On the other hand, FIG. 12A shows the effective exposure intensity distribution H (x) obtained from the equation (21).

H (x) = (1 + COS (2π · 2NA · x / λ)) ^0.5 (22) Thus, as shown in FIG. 12A, the effective exposure intensity distribution H (x) is the light intensity distribution I (x ) Is more gentle near the bright part, but in the dark part has a feature that the width becomes extremely dark and extremely narrow. However, since the nonlinear exposure intensity distribution H (x) is obviously formed with the same period as the light intensity distribution I (x), in this state, a pattern exceeding the limit resolution of the projection optical system cannot be formed.

On the other hand, if the effective exposure intensity distributions H (x) (FIG. 12B) formed by shifting the pattern of FIG. 12A by 1/2 cycle are overlapped, a finer structure is formed on the image plane as shown in FIG. 12C. Therefore, this pattern has a periodic structure twice that of the limit resolution. On the other hand, when a transmissive film with n = 1, that is, a film whose transmittance is constant with respect to the exposure intensity is used, the effective exposure intensity distribution H (x)
Completely agrees with the light intensity distribution I (x) of FIG.
Even if these are overlapped as in the case of FIG. 11D, H (x) = 1 + COS (2π · 2NA · x / λ) + 1−COS (2π · 2NA · x / λ) = 2 (23) The obtained effective exposure intensity distribution H (x) becomes flat and is useless at all (FIG. 13).

As described above, even when a transmissive film having n <1 is used, it is possible to form a latent image reaction concentration distribution ξ (x) which is finer than the limit resolution of the projection optical system. In the present invention, needless to say, the resist may be either a positive type or a negative type. However, especially when n <1, it is considered to be advantageous for the positive type, and in the example shown in FIG. 12, an extremely thin leaving line can be formed.

FIG. 7 shows a schematic structure of an exposure apparatus for performing a plurality of exposures having different light intensity distributions on the photosensitive material provided with the above-mentioned transparent film. The illumination light flux from the light source 11 is condensed by the elliptical mirror 12, guided to the collimator lens 14 by the mirror 13, becomes a substantially parallel light flux, and enters the fly-eye integrator 15. The light flux emitted from the fly-eye integrator 15 is guided to the main condenser 17 by the mirror 16 and the reticle 1 as the projection original plate.
Illuminate 8a uniformly. A predetermined pattern on the projection original plate 18a is projected and exposed by the projection optical system 19 onto the wafer 20 coated with a photosensitive material. Where the reticle 18
After exposure, a is replaced with a reticle 18b having a different pattern by the reticle loader 21, and a second exposure is performed.

Instead of exchanging different patterns by the reticle loader 21, the reticle 18a is moved to the optical axis Ax of the projection optical system 19 after the first exposure by the reticle 18a.
Alternatively, the second exposure may be performed by moving in the vertical direction by a predetermined amount. When the effective exposure intensity is proportional to the square of the light intensity when the above-described pattern of FIG. 1A is used, the predetermined amount is converted into coordinates on the wafer (λ / 4NA). Is. Further, when the effective exposure intensity is proportional to the cube of the light intensity, it is effective to convert it into coordinates on the wafer and set it to (λ / 6NA).

Needless to say, when the same reticle pattern is exposed a plurality of times, instead of moving the reticle, the wafer itself may be moved for every plurality of exposures. Also, before the wafer is placed at a predetermined position for performing a predetermined first exposure, a coater 22 is used to apply a resist 32 as a photosensitive material and a transparent film having a non-linear characteristic on a wafer substrate 31 as shown in FIG. 33 and 33 are applied. First, a resist 32 which is a photosensitive material is applied on the wafer substrate 31. At this time, the center of rotation of the wafer is connected to the rotation axis of the motor of the applicator, and the resist 32 is thinly and uniformly extended on the wafer substrate 31 by the rotation of the motor of the applicator 22. Next, the transmission film 33 having a non-linear characteristic is thinly and uniformly extended on the resist 32 by the same method as in the previous step. In addition, as a method of applying the transmission film 33 having a non-linear characteristic on the resist 32,
It is also possible to use vapor deposition.

For the alignment between a plurality of exposures, the so-called latent image alignment for observing and aligning the latent image is effective. By the way, in the present invention, it is effective to use a phase shift pattern to form a high resolution pattern as in the embodiment shown in FIG. It is also effective to use the annular illumination proposed in JP-A-61-191662 and the so-called SHRINC illumination proposed in JP-A-4-225358.

At present, as a transparent film used in the present invention, the transmitted light intensity of which changes in accordance with the incident light intensity, silver halide used in sunglasses or the like is considered when n <1. Also contemplated are dimmers such as spiroxagine, spiropyran, flugimide, chromel. On the other hand, as the transmission film used in the present invention, in which the transmitted light intensity changes according to the incident light intensity, when n> 1, copper fine particles, cadmium sulfide (CdS), cadmium selenide (CdSe), phthalocyanine-based Dye,
Substances that cause saturable absorption such as porphine-based dyes and substances that cause two-photon absorption such as polysilicon and quinizarin are considered. Further, a substance that causes three-photon absorption is also considered.

[0042]

As described above, according to the present invention, a fine pattern exceeding the resolution limit of a projection optical system is formed by exposing different patterns a plurality of times using a transmission film having a non-linear transmission characteristic. Is possible. Moreover, it is possible to form a high-resolution pattern without changing the conventional exposure wavelength and optical system.

According to the exposure method of the present invention,
This makes it possible to manufacture a semiconductor element having an extremely fine circuit pattern, which cannot be realized by the conventional projection type exposure apparatus, and has a great effect that the degree of integration of the integrated circuit can be remarkably increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing patterns of a first projection original plate and a second projection original plate used in the present invention.

FIG. 2 is a light intensity distribution chart on the transmission film according to the pattern shown in FIG.

FIG. 3 is an effective exposure intensity distribution chart of the pattern shown in FIG.

FIG. 4 is a composite effective exposure intensity distribution chart in the example of the present invention.

FIG. 5 is a composite effective exposure intensity distribution map obtained by three times of exposure.

FIG. 6 is a composite effective exposure intensity distribution chart in another example.

FIG. 7 is a schematic configuration diagram of an exposure apparatus suitable for the present invention.

FIG. 8 is a composite effective exposure intensity distribution chart according to another embodiment.

FIG. 9 is a light intensity distribution diagram and an effective exposure intensity distribution diagram on the transmission film according to the present invention.

FIG. 10 is a characteristic diagram of OTF.

11 is a light intensity distribution chart based on the pattern shown in FIG.

FIG. 12 is a composite effective exposure intensity distribution chart according to another embodiment.

FIG. 13 is a composite effective exposure intensity distribution chart when a transmission film having a linear characteristic is used.

FIG. 14 is a configuration diagram of a transparent film, a resist, and a wafer substrate.

[Explanation of symbols]

1a, 1b ... Substrate of projection original plate 2a, 2b ... oblique film 3a, 3b ... Phase shifter 4a, 4b ... Opening 51, 52, 53, 54 ... Light transmitting portion 52s, 54s ... Phase shifter

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Oki 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation (56) Reference JP-A-7-181668 (JP, A) JP-A-5- 90149 (JP, A) JP 64-13544 (JP, A) JP 63-272030 (JP, A) JP 4-206813 (JP, A) JP 5-62872 (JP, A) JP-A-6-310391 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521

Claims (8)

(57) [Claims] 1. A projection exposure method for projecting a pattern of an original plate to be projected onto a predetermined photosensitive material by a projection optical system,
A light-transmitting film having a non-linear characteristic of transmitted light intensity with respect to incident light intensity is provided on the photosensitive material, and is formed on the projection original plate.
Pattern that is different from the
The use of a shadow original plate, or the projected original plate and the photosensitive material
Moves the material relative to the optical axis in a direction perpendicular to the optical axis by a predetermined amount.
The light intensity distribution on the transmissive film
An exposure method characterized by performing exposure several times. 2. A transparent film having a non-linear characteristic such that the transmitted light intensity changes corresponding to the nth power (n ≠ 1) of the incident light intensity is used. Exposure method. 3. The exposure method according to claim 2, wherein the transmission film has a non-linear characteristic in which the transmitted light intensity changes corresponding to the n-th power of the incident light intensity and n> 1. . 4. The exposure method according to claim 2, wherein the transmission film has a non-linear characteristic in which the transmitted light intensity changes corresponding to the n-th power of the incident light intensity and n <1. . 5. A projection exposure apparatus for projecting a predetermined pattern of a projection original onto a predetermined photosensitive material by a projection optical system, wherein the transmitted light intensity has a non-linear characteristic with respect to the incident light intensity on the photosensitive material. Multiple exposures by applying a transparent film and moving the photosensitive material coated with the transparent film and the projection original plate at a predetermined amount in each direction relative to each other in a direction perpendicular to the optical axis.
A projection exposure apparatus characterized by repeating the above. 6. A projection exposure apparatus for projecting a predetermined pattern of a projection original onto a predetermined photosensitive material by a projection optical system, wherein the transmitted light intensity has a non-linear characteristic with respect to the incident light intensity on the photosensitive material. Apply a transparent film and transmit the light after each exposure.
A predetermined amount of the photosensitive material coated with a film in the direction perpendicular to the optical axis.
The projection exposure apparatus is characterized in that it only moves and repeats multiple exposures. 7. A projection exposure apparatus for projecting a predetermined pattern of a projection original onto a predetermined photosensitive material by a projection optical system, wherein the transmitted light intensity has a non-linear characteristic with respect to the incident light intensity on the photosensitive material. Apply a transparent film, and apply the above-mentioned coating after each exposure.
Move the projection master by a specified amount in the direction perpendicular to the optical axis
A projection exposure apparatus characterized by repeating exposure once . 8. A projection exposure apparatus for projecting a pattern of a projection original onto a predetermined photosensitive material by a projection optical system,
The transmitted light intensity on the photosensitive material coated with a permeable membrane having a non-linear characteristic with respect to incident light intensity, first projected original and the first pattern having a first pattern as the object to be projected original
A second projection original plate having a second pattern different from that of the first projection original plate for the photosensitive material.
After the first exposure, the second exposure is performed by the second projection original plate.
Projection exposure apparatus, characterized in that.