JP3101614B2 - Exposure method and exposure apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure method and an exposure apparatus, and more particularly to an exposure method and an exposure apparatus for exposing a photosensitive substrate with a fine circuit pattern. The exposure method and exposure apparatus of the present invention are used for manufacturing various devices such as semiconductor chips such as ICs and LSIs, display elements such as liquid crystal panels, detection elements such as magnetic heads, and imaging elements such as CCDs.

[0002]

2. Description of the Related Art Conventionally, when manufacturing devices such as ICs, LSIs, and liquid crystal panels using photolithography technology, a photomask or a reticle (hereinafter, referred to as a “mask”) is used.
It is written. The circuit pattern is projected onto a photosensitive substrate such as a silicon wafer or a glass plate (hereinafter, referred to as a "wafer") coated with a photoresist or the like by a projection optical system, and the circuit pattern is transferred thereto. A projection exposure method (exposure with a circuit pattern) and a projection exposure apparatus are used.

In response to the high integration of the above devices, it is required to miniaturize the pattern transferred to the chip area of the wafer, that is, to increase the resolution, and to increase the area of one chip area in the wafer. Also in the projection exposure method and the projection exposure apparatus, which form the center of the fine processing technology for
At present, resolution and exposure area are being improved in order to form an image having a dimension (line width) of 0.5 μm or less over a wide range.

FIG. 1 shows a schematic view of a conventional projection exposure apparatus. In FIG. 1, reference numeral 191 denotes an excimer laser as a light source for exposure to far ultraviolet rays, 192 denotes an illumination optical system, 193 denotes illumination light, 194 denotes a mask, and 195 denotes an object side exposure which exits from the mask 194 and enters the optical system 196. Light, 196 is a reduction projection optical system, 197 is an image side exposure light exiting from the optical system 196 and incident on a wafer 198 which is a photosensitive substrate, 1
Reference numeral 99 denotes a substrate stage for holding a photosensitive substrate.

The laser light emitted from the excimer laser 191 is guided to an illumination optical system 192 by a drawing optical system, and the illumination optical system 192 determines a predetermined light intensity distribution, light distribution, and opening angle (numerical aperture NA). ) And illumination light 193
The illumination light 193 illuminates the mask 194. A fine pattern to be formed on the wafer 198 is projected on the mask 194 by a projection optical system 196.
Is formed on the quartz substrate by chrome or the like, and the illumination light 193 is diffracted by the fine pattern when transmitted through the mask 194. 195 becomes the object side exposure light 195. The projection optical system 196 converts the object-side exposure light 195 to the fine pattern of the mask 194 at the above-described projection magnification and with a sufficiently small aberration.
The light is converted into image-side exposure light 197 which forms an image on the upper side. Image side exposure light 197
Is a predetermined numerical aperture as shown in the enlarged view at the bottom of FIG.
The light converges on the wafer 198 at NA (= sin θ) to form an image of a fine pattern on the wafer 198. Substrate stage 199 is wafer 1
The wafer 198 is moved stepwise along the image plane of the projection optical system in order to sequentially form fine patterns in a plurality of different areas 98 (shot areas: areas forming one or more chips). The position with respect to the projection optical system 196 is changed.

However, it is difficult for a projection exposure apparatus using the above-described excimer laser as a light source to form a pattern of 0.15 μm or less.

The projection optical system 196 has a wavelength of exposure light (hereinafter,
It is described as "exposure wavelength". ) Is dependent on the trade-off between the optical resolution and the depth of focus. The resolution R and depth of focus DOF of the projection exposure apparatus are as follows:
It is represented by a Rayleigh equation such as equations (1) and (2).

R = k ₁ (λ / NA) (1) DOF = k ₂ (λ / NA ² ) (2) where λ is the exposure wavelength, and NA is the image side of the projection optical system 196. It is a numerical aperture, and the values of k ₁ and k ₂ are usually about 0.5 to 0.7.
From the equations (1) and (2), there is a `` high NA '' in which the numerical aperture NA is increased in order to increase the resolution R to reduce the resolution R, but
In actual exposure, the depth of focus DOF of the projection optical system 196 needs to be set to a certain value or more, so it is impossible to increase the NA higher than a certain value. It is understood that "short wavelength" for reducing the size is required.

However, as the wavelength becomes shorter, a serious problem arises. This problem is that the glass material of the lens of the projection optical system 196 runs out. The transmittance of most glass materials is close to 0 in the deep ultraviolet region, and synthetic quartz is currently available as a glass material manufactured for exposure equipment (exposure wavelength: about 248 nm) using a special manufacturing method. Also decreases sharply for exposure wavelengths below 193 nm,
Exposure wavelength 150nm corresponding to fine pattern of 0.15μm or less
It is considered very difficult to develop a practical glass material having sufficiently high transmittance in the following regions. Glass materials used in the deep ultraviolet region have durability, uniformity of refractive index,
It is necessary to satisfy certain conditions from a plurality of viewpoints such as optical distortion and workability, and this also threatens the existence of a practical glass material in an exposure wavelength region of 150 nm or less.

As described above, in the conventional projection exposure method and projection exposure apparatus, in order to form a pattern of 0.15 μm or less on the wafer 198, it is necessary to shorten the exposure wavelength to about 150 nm or less. Since there is no practical glass material in this wavelength region, a pattern of 0.15 μm or less cannot be formed on the wafer 198.

US Pat. No. 5,415,835 discloses a technique for forming a fine pattern by exposure using interference fringes formed by causing two coherent light beams to interfere with each other (hereinafter, referred to as “two-beam interference exposure”). According to the two-beam interference exposure, a pattern of 0.15 μm or less can be formed on the wafer.

The principle of two-beam interference exposure will be described with reference to FIG. In the two-beam interference exposure, a laser beam having coherence and a parallel beam from the laser 151 is
52 divides the two light beams into two light beams, respectively.
The two laser beams (coherent parallel light beams) intersect at an angle greater than 0 and less than 90 degrees by being reflected by 53 to form an interference fringe at the intersection, and this interference fringe ( By exposing and exposing the wafer 154 according to the light intensity distribution, a fine periodic pattern (periodic exposure amount distribution) corresponding to the light intensity distribution of the interference fringes is formed on the wafer, and the wafer is developed. , So that a fine periodic resist mask / for etching can be obtained on a wafer.

In FIG. 2, when two light beams intersect on a wafer surface in a state where the two light beams are inclined at the same angle in opposite directions with respect to perpendiculars formed on the wafer surface, the resolution R in the two light beam interference exposure is expressed by the following (3). ) Expression.

[0014] Here, R is the line width of each of the bright portion and the dark portion of the interference fringes, that is, the line width of each of the lines and spaces constituting the periodic pattern, and θ is the incident angle (absolute value) of the two light beams with respect to each image plane. Represents Since sin θ corresponds to the image-side numerical aperture of the optical system in projection exposure, it is expressed as sin θ = NA.

Expression for resolution in normal projection exposure
Equation (1) and equation for resolution in two-beam interference exposure (3)
Comparing with the equation, the resolution R of the two-beam interference exposure is (1)
Since this corresponds to the case where k ₁ = 0.25 in the equation, it is possible to obtain a resolution twice or more as high as that of a normal projection exposure in which k ₁ = 0.5 to 0.7 in two-beam interference exposure.
Although not disclosed in the above U.S. patent, for example, λ = 0.24
When NA = 0.6 at 8 nm (KrF excimer), R = 0.10μ
m is obtained.

[0016]

However, in the two-beam interference exposure, a simple periodic pattern (exposure amount distribution) basically corresponding to the light intensity distribution of interference fringes can be obtained. Cannot be formed.

In the above-mentioned US Pat. No. 5,415,835, a simple periodic exposure dose distribution is given to a resist on a wafer by interference fringes by a two-beam interference exposure apparatus, and then the image is taken from an image of a mask opening by another exposure apparatus. By exposing a portion corresponding to the bright part of the interference fringes of the resist and adding a certain amount of exposure to this location, the exposure amount of only a specific line part of the multiple bright parts of the interference fringe is made uniform. It has been proposed to obtain an isolated line (resist pattern) after development by increasing the threshold value of the resist so as to exceed the threshold value.

However, the double exposure method disclosed in the above-mentioned US Pat. No. 5,415,835 only obtains a circuit pattern having a simple shape composed of a part of a stripe pattern formed by two-beam interference exposure. A circuit pattern having a more complicated shape, such as a circuit pattern which is a set of a plurality of patterns having a line width and a directionality, cannot be obtained.

Japanese Patent Application Laid-Open No. 7-253649 discloses a double exposure method capable of obtaining a fine isolated pattern similar to that of US Pat. No. 5,415,835.
The double exposure method of 253649 is a two-beam interference exposure using a phase shift pattern using a normal projection exposure apparatus,
Conventionally, exposure using an image of a fine aperture pattern, which could not be resolved by this exposure apparatus, is performed on the same region of the resist on the wafer, and the exposure wavelength of each exposure differs by 50 nm or more.

In the double exposure method disclosed in JP-A-7-253649, a two-beam interference exposure and a normal exposure are performed with one mask (pattern) by forming a pattern with a material having wavelength selectivity on the mask. The pattern (of the mask) in the normal exposure is one or more isolated patterns, and the circuit pattern (exposure amount distribution or unevenness distribution after development) obtained as a result of the double exposure is only one or more isolated patterns. is there.

Therefore, the double exposure method disclosed in Japanese Patent Application Laid-Open No. 7-253649 cannot obtain a circuit pattern having a more complicated shape as in US Pat. No. 5,415,835.

An object of the present invention is to provide an exposure method and an exposure apparatus capable of obtaining a circuit pattern having a more complicated shape than the conventional one by multiple exposure. The process referred to as "multiple exposure" in the present application is to perform a plurality of exposures to the same place on the resist without developing between exposures, and this exposure is not limited to double exposure but includes triple exposure or more. It is.

[0023]

According to a first aspect of the present invention, there is provided an exposure method for exposing a resist to a pattern , comprising: a first step of providing a first exposure amount distribution by two-beam interference exposure ; Pattern formed
Exposure amount is not 0 but small by exposure using mask
And a second step of providing a second exposure amount distribution having a portion with partial exposure amount is large, the first exposure amount distribution one
The exposure amount of the portion and the second exposure amount distribution is not 0
Overlapping small parts of the pattern
Exposure is performed, and the other portion of the first exposure amount distribution
A portion where the exposure amount is large in the second exposure amount distribution overlapping with
The exposure for the other part of the pattern is performed in minutes . According to a second aspect of the invention, used in an exposure method for exposing a pattern in the resist, the first mask having an array of phase shifters and / or light shielding part 2
The exposure amount of the resist is increased by the light beam interference exposure.
A first step of providing a first exposure amount distribution is the value or less, before
Although the exposure amount is not 0 by the exposure using the second mask in which a pattern similar to the above-described pattern is formed,
And the exposure amount is above the exposure threshold
A second step of providing a second exposure distribution having: a part of the first exposure distribution and the second exposure
The exposure amount of the distribution is not 0 but is equal to or less than the exposure threshold value
By overlapping the parts, the exposure of a part of the pattern
Light is applied and overlaps with other portions of the first exposure dose distribution.
A portion of the second exposure distribution that is equal to or greater than the exposure threshold
And the other portion of the pattern is exposed . The invention according to claim 3 is that the resist is put on the pattern.
In an exposure method for performing exposure related to a pattern, a periodic pattern
A first step of providing a first exposure dose distribution by means of
Using a mask with a pattern similar to the above
Exposure is not 0 but small part due to exposure and exposure
Giving a second exposure dose distribution having a portion where
And a part of the first exposure dose distribution and the second
Part where the exposure amount is not zero but small in the exposure amount distribution of No. 2
Exposure on a part of the pattern
Wherein the overlap with the other part of the first exposure dose distribution
In a portion where the exposure amount is large in the second exposure amount distribution, the pattern
The exposure is performed on other portions of the pattern . The invention according to claim 4 relates to a pattern on a resist.
In an exposure method for performing exposure, a phase shifter and / or
Periodic pattern exposure using a first mask in which light shielding portions are arranged
The light exposure is below the exposure threshold of the resist.
A first step of providing a first exposure dose distribution;
Using a second mask on which a pattern similar to
The exposure amount is not 0 due to light, but is less than the exposure threshold value.
Having a portion and a portion where the exposure amount is equal to or greater than the exposure threshold value.
Providing a second exposure dose distribution; and
A part of the exposure distribution of
The light amount is not 0, but the part below the exposure threshold is overlapped.
Exposure of a part of the pattern
The second exposure overlapping with the other part of the first exposure dose distribution.
The pattern in a portion of the exposure amount distribution of
The exposure is performed on other portions of the pattern . According to a fifth aspect of the present invention, there is provided any one of the first to fourth aspects.
3. The exposure method according to claim 1, wherein the first step is followed by the second step.
Performing two steps, or after the second step,
Performing one step, or the first step and the second step
The feature is that floors are held simultaneously . The invention according to claim 6 is directed to the exposure method according to any one of claims 1 to 4.
Wherein the portion of the pattern has a minimum line width
Minutes . The invention of claim 7 is the claim
5. The exposure method according to any one of 1 to 4, wherein
The pattern is a circuit pattern. The invention according to claim 8 is directed to the exposure apparatus according to any one of claims 1 to 7.
To form the first exposure dose distribution in the optical method
This is the mask to be used. The invention of claim 9 is the invention of claims 1 to 7
The second exposure in the exposure method according to any one of
This is a mask used for forming a light quantity distribution. According to a tenth aspect of the present invention, there is provided an exposure apparatus according to any one of the first to seventh aspects.
An exposure apparatus capable of performing the light method. The invention according to claim 11 includes a step of exposing and developing a resist.
The first exposure by two-beam interference exposure
A first step of providing a quantity distribution, and a pattern similar to the pattern.
The exposure amount is reduced to 0 by the exposure using the mask on which the pattern is formed.
But has a small part and a large exposure amount
Providing a second exposure dose distribution; and
A part where the exposure amount is not 0 but small in the exposure amount distribution of
The pattern based on a part of the overlapping first exposure distribution.
Another part of the first exposure distribution forming a part of the turn.
The exposure amount of the second exposure distribution overlapping the portion is large
It characterized the this <br/> to form other portions of the pattern based on have parts. According to the twelfth aspect of the present invention, the resist is exposed.
The method of forming a pattern, including the steps of
A first mass on which a phase shifter and / or a light shielding portion are arranged.
Exposure by the two-beam interference exposure using a resist
That gives a first exposure dose distribution that is less than or equal to the exposure threshold
One step and a pattern similar to the above pattern was formed
If the exposure amount is 0 due to normal exposure using the second mask,
But the exposure amount is less than the exposure threshold
Giving a second exposure distribution having a portion above the threshold
The exposure of the second exposure distribution.
The amount is not 0, but overlaps the part below the exposure threshold
The pattern based on a portion of the first exposure dose distribution
And a portion of the first exposure dose distribution
Not less than the exposure threshold value of the overlapping second exposure amount distribution
Another part of the pattern is formed based on the part . The invention of claim 13 exposes the resist.
The method of forming a pattern, including the steps of
To give a first exposure dose distribution by periodic pattern exposure
A first step, wherein a pattern similar to said pattern is formed
Exposure amount is not 0 but small
Second exposure amount having a portion having a large exposure amount and a portion having a large exposure amount.
A second step of providing a cloth.
The first exposure in which the exposure amount is not 0 but overlaps a small portion
Part of the pattern based on a part of the exposure distribution of
Before overlapping the other portion of the first exposure dose distribution.
The second exposure amount distribution is based on the portion where the exposure amount is large.
Forming another part of the pattern by
You. According to a fourteenth aspect of the present invention, the resist is exposed and developed.
In a method for forming a pattern, the method includes the steps of:
And / or a period using the first mask in which the light shielding portions are arranged
The exposure amount of the resist is increased by the pattern exposure.
A first step of providing a first exposure distribution that is less than or equal to
Mask on which a pattern similar to the above-described pattern is formed
Exposure amount is not 0 by normal exposure using
The portion below the light threshold and the exposure amount are above the exposure threshold
A second step of providing a second exposure distribution having a portion of
And the exposure amount of the second exposure amount distribution is not 0.
The first exposure overlapping with the portion below the exposure threshold.
Form part of the pattern based on part of the light distribution
Forming the first exposure amount distribution and overlapping the other portion of the first exposure amount distribution.
2 based on the portion of the exposure dose distribution above the exposure threshold
Forming another part of the pattern by
You. According to a fifteenth aspect of the present invention, there is provided the
In the turn forming method, the second step is performed after the first step.
Performing a step or, after the second step, the first
Performing a step, or said first step and said second step
Are performed simultaneously. The invention of claim 16
Is the pattern forming method according to claim 11.
The part of the pattern is the part having the smallest line width
There is a feature. The invention of claim 17 is based on claim 1
15. The pattern forming method according to any one of 1 to 14, wherein
The characteristic is a circuit pattern. Claim 1
The invention according to claim 8 is the invention according to any one of claims 11 to 17.
Specializes in manufacturing devices using pattern formation methods.
This is a device manufacturing method.

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[0072]

In the present invention, the exposure wavelength is not limited, but the present invention is, for example, 400 nm or less, especially
It is suitable to be applied when exposing at an exposure wavelength of 50 nm or less. In order to obtain light having an exposure wavelength of 250 nm or less, a KrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 nm) is used.
nm) as the light source.

The present invention provides, for example, a projection optical system for projecting a mask pattern onto a wafer, a partial coherent illumination having a relatively large σ (sigma) (large σ),
And a mask illumination optical system capable of performing both partial coherent illumination and coherent illumination. For example, two-beam interference exposure is performed by projecting and exposing the mask pattern (circuit pattern) by the above-mentioned large σ partial coherent illumination and illuminating the phase shift type mask by the coherent illumination or small σ partial coherent illumination. Exposure of a high contrast image by interference fringes.

“Partial coherent illumination” is illumination in which the value of σ (= numerical aperture on the mask side of the illumination optical system / numerical aperture on the mask side of the projection optical system) is greater than zero and less than 1.
The term “coherent illumination” means that the value of σ is zero or a value close thereto, and is considerably smaller than σ of partially coherent illumination. The large σ is σ of 0.6 or more,
The small σ means that σ is 0.3 or less.

In this exposure apparatus, an optical system capable of switching between partially coherent illumination and partially coherent illumination having a smaller σ relative to coherent illumination may be employed as a mask illumination optical system.

The present invention provides, for example, a two-beam interference exposure apparatus as shown in FIG. 2, a projection exposure apparatus as shown in FIG. 1, a moving stage for holding a wafer which is a photosensitive substrate shared by both apparatuses, Can be implemented by an exposure system having The exposure wavelength of various exposure apparatuses for carrying out the present invention is 400 nm or less, particularly 250 nm or less as described above. 250nm
A KrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 nm) is used to obtain light having the following exposure wavelengths.

[0078]

FIG. 3 is a flowchart showing one embodiment of the exposure method of the present invention. FIG. 1 shows a periodic pattern exposure step of exposing a resist with a high-contrast image (high-contrast image) constituting the exposure method of the present embodiment. Each block and the flow of a normal exposure step of exposing the resist with an image of a mask having the resist and a development step of developing the resist subjected to double exposure by these two steps are shown. The order of the normal exposure step and the normal exposure step may be the reverse of FIG. 1 or may be simultaneous. If one of the exposure steps is a triple or more exposure including a plurality of exposure steps, each of the synchronous pattern exposure and the normal exposure is performed. The steps can be performed alternately. In addition, there is a step of performing precise alignment between each exposure step, but is not shown here. or,
The periodic pattern exposure step and the normal exposure step are performed by, for example, a step & repeat type or step & scan type projection exposure apparatus.

The mask in the normal exposure step is
The above circuit pattern, which has a plurality of patterns having different line widths and directions and should improve the exposure distribution in the resist by multiple exposure, has a minimum contrast of the image having the minimum line width among the plurality of patterns. It is a fine pattern.

In the case of performing multiple exposure according to the flow of FIG. 3, first, the resist on the wafer of the photosensitive substrate is exposed with a periodic pattern image as shown in FIG. The numbers in FIG. 4A represent the exposure amounts, and FIG.
(A) shows an image of a periodic pattern of a mask, in which white portions are portions where the resist is not exposed (ie, shadows), and hatched portions are portions where the resist is exposed (ie, light). Generally, the white part is set to 0, and the shaded part is set to 1. still,
FIG. 4A can be regarded as a pattern of the mask itself.

If the resist is exposed only with this periodic pattern image and is not subjected to multiple exposure but is subsequently developed,
Usually, the relationship between the exposure amount of the periodic pattern image and the exposure threshold of the resist is determined by the exposure threshold Eth of the resist on the wafer.
(Boundary value at which the thickness of the resist after development becomes 0) is shown in FIG.
The exposure amount is set to be between 0 and 1 as shown in the lower graph of (B). Note that the upper part of FIG.
FIG. 4 shows a plan view of a lithography pattern (concavo-convex pattern) that finally obtains a resist exposed with the image of FIG. In the figure, after development of the gray part and the white part, one is a peak of unevenness and the other is a valley of unevenness.

In FIGS. 53 (A) and (B), regarding the resist on the wafer in FIG. 4, a positive resist (hereinafter, referred to as “positive”) and a negative resist (hereinafter, “negative”) are described. 3) shows the dependence of the thickness of the resist after development on the exposure dose and the exposure threshold value when each of the above is used. In the case of the negative type, when the exposure amount is equal to or less than the exposure threshold value, the resist film thickness after development becomes zero.

FIG. 6 shows the result of such exposure.
Lithography through exposure & development and etching process
Negative type (top left of the figure) showing how the pattern is formed
FIG. 4 is a schematic diagram showing the case of the positive type (the upper right side of the figure).

In the double exposure method according to the present embodiment, unlike the ordinary exposure sensitivity setting shown in FIGS.
As shown in FIG. 4A and FIG. 8, a periodic pattern (ferst in FIG.
Assuming that the maximum exposure amount in step (step) is 1, the exposure threshold value Eth of the resist of the wafer as the photosensitive substrate is set to be larger than 1 (see the lower part of FIG. 8). At this time, when the exposure pattern (exposure amount distribution) of the resist which has been exposed only by the periodic pattern image shown in FIG. 7 is developed, the exposure amount is insufficient. , The portion where the film thickness becomes 0 by development does not occur,
A so-called lithography pattern with irregularities is not formed on the wafer by etching. This can be regarded as the disappearance of the periodic pattern recorded on the resist by the latent image. In the following, a case will be described in which a pattern (convex pattern) is formed on the resist by using a pattern resist, but a similar pattern can be formed using a positive resist. At this time, in the case of a positive resist, it is assumed that, for example, each of two reticles used for double exposure has a light transmitting portion and a light shielding portion reversed with respect to the reticle in the case of a negative resist. Alternatively, a punched pattern (concave pattern) can be formed in the resist using each of the positive and negative resists. In FIG. 8, the upper part shows a plan view of a lithography pattern obtained as a result of exposing only the periodic pattern image (a plurality of fine lines are drawn, but nothing can actually be done). The relationship of Eth is shown.

The feature of this embodiment is that the exposure pattern (E1) based on a periodic pattern image including a fine high-contrast image, which at first glance disappears only by the periodic pattern exposure as the first step in FIG. Sec
By combining with an exposure pattern (E2) of a circuit pattern image of an arbitrary shape including a dimensional pattern smaller than the resolution of the exposure apparatus by an ordinary exposure which is an on-step, a desired area of the resist is selectively formed. Only the exposure amount (E1 + E2) equal to or more than the exposure threshold value Eth is exposed, and finally, a lithography pattern corresponding to a desired circuit pattern having an arbitrary shape can be formed. The point of this fusion is the pattern with the smallest line width of the circuit pattern, and a high-contrast image can be successfully superimposed on the position of the pattern image where the exposure distribution of the desired contrast cannot be obtained by exposure alone. is there.

FIG. 9A shows the exposure pattern of the resist by the above-described normal exposure, which is the pattern having the smallest line width among the circuit patterns projected on the wafer and having a resolution smaller than the resolution of the projection exposure apparatus. This is an exposure dose distribution of the resist by a pattern image which is not resolved because it is a fine pattern. Clearly, this exposure distribution is blurred and wide.

The pattern having the minimum line width on the mask for forming the exposure pattern shown in FIG. 9A has a line width which is about half the resolvable line width (a desired contrast is obtained) of the projection exposure apparatus. Have a fine pattern. On the mask, in addition to this fine pattern, patterns having various resolvable line widths are included.

The normal exposure of the circuit pattern for forming the blurred exposure pattern shown in FIG. 9A is performed after (or before or simultaneously with) the periodic pattern exposure for forming a fine exposure pattern without blur as shown in FIG. Assuming that the resist is overlapped on the same region (same position) of the same resist, the total exposure distribution of this resist in this region is as shown in the lower graph of FIG. 9B. Here, the ratio of the exposure amount E ₂ of the blurred image by the exposure amount E ₁ and the normal exposure of high-contrast images by periodic pattern exposure is 1: 1, the exposure threshold E _th of the resist, periodic pattern exposure of an exposure amount E _{9 is set between 1} (= 1) and the sum E1 + E2 (= 2) of the exposure amount E ₂ (= 1) of the normal exposure. The lithography pattern shown in the upper part of (B) is formed. At that time, the center of the blurred exposure pattern of the normal exposure is made to coincide with the peak of the non-blurred exposure pattern of the periodic pattern exposure. The plan view of the lithography pattern in the upper part of FIG. 9B is an isolated line pattern in which the resolution, that is, the line width is the same as that of the lithography pattern by periodic pattern exposure, and can be realized by single exposure using a normal projection exposure apparatus. This means that a pattern with a fine line width higher than the resolution is obtained by double exposure. On the other hand, among the patterns exposed by the normal exposure, a pattern having a relatively large line width within the resolution of the apparatus other than the minimum line width at which the exposure amount distribution contrast is improved by the double exposure has a good image contrast. The exposure amount distribution exceeds the exposure threshold value Eth of the resist in the image alone.

Here, suppose that the normal exposure (FIG. 7) shown in FIG.
Projection exposure that can form an exposure distribution equal to or larger than the exposure threshold Eth with a line width twice as large as the exposure pattern (having an exposure twice as large as the threshold here), and which can resolve with high contrast) If, after the periodic pattern exposure of FIG. 7, without performing the developing step, the same pattern is overlapped on the same region (the same position) of the same resist, the center of the exposure pattern by the normal exposure will be The symmetry of the synthesized image and the synthesized exposure pattern obtained by superimposing the peak and the synthesized pattern is good, and a good synthesized image and the synthesized exposure pattern can be obtained. The composite exposure pattern, that is, the total exposure distribution is as shown in the lower graph of FIG.
After development, the exposure pattern of the periodic pattern exposure disappears,
Finally, only the lithography pattern by the normal exposure shown in the upper part of FIG.

Although not shown, a circuit pattern such as the one shown in FIG. 11A, which produces an exposure pattern having a line width three times as large as that of the exposure pattern shown in FIG. In the case of a circuit pattern in which an exposure pattern having a line width four times or more the exposure pattern of FIG.
As in the case of 0, even if double exposure is performed, after development, only a lithography pattern by normal exposure is formed (FIG. 1).
0 (B)). Accordingly, even in the double exposure of the normal exposure and the periodic pattern exposure using a mask having a plurality of patterns having different line widths such that the exposure pattern of FIG. 7 and the exposure patterns of FIGS. The lithography pattern can be correctly defined in a form corresponding to the circuit pattern of the mask including its line width. For example, various lithography patterns that can be realized by projection exposure can be formed by the double exposure method of the present embodiment. .

The exposure amount distribution (absolute value and distribution) by the periodic pattern exposure composed of the high-contrast image described above and the normal exposure including the low-contrast image corresponding to the pattern of the minimum line width, and the exposure of the resist on the photosensitive substrate. Threshold E
8 and 9 (B) by adjusting th.
It is composed of a combination of various patterns as shown in FIGS. 10 (B) and 11 (B), and has the same minimum line width (resolution) as that of a simple periodic pattern exposure (the pattern of FIG. 9 (B)). ) Can be formed on the wafer.

The features of the double exposure according to the present embodiment are summarized as follows. The exposure pattern by the periodic pattern exposure, in which the maximum exposure amount in the area where normal exposure is not performed, is equal to or less than the exposure threshold value Eth of the resist, disappears by development. 2. An exposure pattern area (exposure area) for normal exposure in which an exposure amount equal to or less than the exposure threshold value Eth of the resist is supplied to the resist.
With respect to the exposure pattern, an exposure pattern having the same resolution as the exposure pattern of the periodic pattern exposure determined by the combination of the respective exposure patterns of the normal exposure and the periodic pattern exposure is formed. 3. The exposure pattern area (exposure area) of the normal exposure in which an exposure amount equal to or more than the exposure threshold value Eth of the resist is supplied to the resist is determined by a combination of each exposure pattern of the normal exposure and the periodic pattern exposure. An exposure pattern having the same resolution as the exposure pattern is formed.
It turns out that.

Further, as an advantage of the double exposure method of this embodiment, if the periodic pattern exposure requiring the highest resolution is performed by two-beam interference exposure using a phase shift reticle or the like, the periodic pattern exposure by the normal projection exposure In this case, a much larger depth of focus can be obtained as compared with the case of imaging.

In the above description, the order of the periodic pattern exposure and the normal exposure is the order of the periodic pattern exposure, but may be reversed or simultaneous.

Next, a specific example of the exposure method of the present invention will be described as a second embodiment.

The present embodiment is directed to a so-called gate pattern shown in FIG. 12 as a circuit pattern (lithography pattern) obtained by exposure. Therefore, a circuit pattern similar to the pattern of FIG. 12 is drawn on the mask used for normal exposure.

In the gate pattern of FIG. 12, the minimum line width in the horizontal direction, that is, in the AA 'direction in the figure is 0.1 μm, whereas in the vertical direction, the line width is within the range of the resolving power by the normal exposure of the apparatus. Within 0.2 μm. According to the present invention, the two-dimensional pattern having the minimum line width pattern S for which high resolution is required only in the one-dimensional direction only in the horizontal direction is subjected to periodic pattern exposure by, for example, two-beam interference exposure. Perform only in the one-dimensional direction that requires high resolution. B in the drawing indicates a pattern having a relatively large line width.

Referring to FIG. 13, the state of double exposure at the same exposure wavelength, consisting of one-dimensional periodic pattern exposure and normal exposure using a gate pattern that cannot be resolved by normal exposure alone, in the second embodiment will be described. explain.

FIG. 13A is a plan view showing a periodic exposure pattern by two-beam interference exposure in which a repetitive pattern occurs only in one-dimensional direction. The cycle of this exposure pattern is 0.2 μm, and this exposure pattern corresponds to a line and space pattern in which the line width of each line and space is 0.1 μm. Numerical values in the lower part of FIG. 13 represent exposure amounts in the resist.

As an exposure apparatus for realizing such a periodic pattern exposure by two-beam interference, as shown in FIG.
FIG. 1 is a diagram showing an apparatus including an interferometer type demultiplexing / multiplexing optical system including a laser 151, a half mirror 152, and a plane mirror 153;
In a projection exposure apparatus partially shown in the schematic view of FIG. 16, there is an apparatus in which a mask and illumination light are configured as shown in FIG. 17 or FIG.
Of course, the exposure apparatus shown in FIGS. 16 to 18 can be used for normal exposure.

First, the exposure apparatus shown in FIG. 2 will be described.

In the exposure apparatus shown in FIG. 2, as described above, each of the two multiplexed light beams is obliquely incident on the wafer 154 at an incident angle θ, and an interference fringe (image) can be formed on the resist on the wafer 154. The line width of the interference fringes that can be formed on the wafer 154 is expressed by the above equation (3). The relationship between the angle θ and the NA on the image plane side of the demultiplexing / multiplexing optical system is NA = sin θ. Angle θ is a pair of plane mirrors -153
Can be arbitrarily adjusted by changing the respective angles of the interference fringes. If the value of the pair of plane mirror angles θ is set to be large, the line width of each of the interference fringe patterns becomes small. For example, when the wavelength of two light beams (exposure wavelength) is 248 nm (KrF excimer laser), interference fringes having a line width of about 0.1 μm can be formed even at θ = 38 degrees. In this case, NA = sin θ = 0.62. If the angle θ is set to be larger than 38 degrees, it is needless to say that a higher resolution can be obtained because an interference fringe having a finer line width can be formed.

Next, the exposure apparatus shown in FIGS. 16 to 18 will be described.

The exposure apparatus shown in FIG. 16 is a step-and-repeat type or step-and-scan type projection exposure apparatus using a reduction projection optical system (comprising a large number of lenses) for reducing and projecting a reticle circuit pattern onto a wafer. At present, there is an image with an NA of 0.6 or more on the image side for an exposure wavelength of 248 nm.

In FIG. 16, reference numeral 161 denotes a mask (reticle);
Is an object-side exposure light that emerges from the mask 161 and enters the optical system 163, 163 is a projection optical system, 164 is an aperture stop, 165 is an image-side exposure light that emerges from the projection optical system 163 and enters the wafer 166, and 166 is photosensitive. 167 is an explanatory diagram showing the position of two light beams on the pupil plane corresponding to the circular opening of the stop 164 by a pair of black dots. FIG. 16 is a schematic diagram of a state of a light beam when two-beam interference exposure is performed by setting the exposure mode of the exposure apparatus to periodic pattern exposure, and both the object-side exposure light 162 and the image-side exposure light 165 Unlike the normal projection exposure shown in FIG. 1, there is no light beam parallel to the optical axis, and it consists of only two parallel light beams.

In order to perform two-beam interference exposure in a normal projection exposure apparatus as shown in FIG. 16, a mask and its illumination method may be set as shown in FIG. 17 or FIG. Figure 1 below
An example of a combination of the three mask-illumination methods shown in FIGS. 7 and 18 will be described.

The mask shown in FIG. 17A is a Levenson-type phase shift mask, and this mask is illuminated from a vertical direction as shown in the left diagram of FIG. In this mask, for example, the pitch P _O of the light-shielding portion 171 made of chromium is expressed by equation (4), and the pitch P _{OS of the} phase shifter 172 made of quartz is
Is a mask represented by the equation (5).

[0108]

[Outside 1] Here, M is the projection magnification of the projection optical system 163, λ is the exposure wavelength,
NA indicates the numerical aperture on the image side of the projection optical system 163.

On the other hand, the mask shown in FIG. 17B is a shifter-edge type phase shift mask made of chrome without a light-shielding portion, and this mask is also illuminated from a vertical direction as shown in the left diagram of FIG. I do. This mask is a phase shifter 181 made of quartz, similar to the Levenson-type phase shift mask.
Is configured so as to satisfy the above expression (5). In both masks (A) and (B), the substrate is quartz.

In order to perform two-beam interference exposure using the phase shift masks of FIGS. 17A and 17B, so-called coherent illumination of σ = 0 (a value close to 0) is applied to these masks. And partial coherent illumination with small σ of σ ≦ 0.3. Specifically, the circular aperture stop of the illumination optical system that illuminates the mask is changed from a stop for a general mask (for partial coherent illumination with a large σ of σ ≧ 0.6 to a small σ for these phase shift masks). And irradiates the mask with illumination light in a direction perpendicular to the mask surface (a direction parallel to the optical axis of the projection optical system 163).

When the phase shift mask is illuminated, the 0th-order transmitted diffracted light emitted from the mask in the above-described vertical direction is canceled out by the phase shifter because the phase difference between adjacent transmitted lights becomes π. Although no longer present, two parallel light beams composed of ± 1st-order transmitted diffracted light are generated symmetrically with respect to the optical axis of the projection optical system 163 from the mask.
And interference fringes (images) are formed on the wafer 166 as the two object-side exposure lights 165. Further, second-order or higher-order diffracted light does not enter the aperture of the aperture stop 164 of the projection optical system 163, and therefore does not contribute to image formation.

In the mask shown in FIG. 18, the pitch PO of the light-shielding portion made of chrome is, for example, the same as that of the equation (4) (6).
The angle θ with respect to the optical axis of the projection optical system 163 is expressed by a mask represented by the following expression. Illuminated from a tilted direction.

[0113]

[Outside 2] Here, M is the projection magnification of the projection optical system 163, λ is the exposure wavelength,
NA indicates the numerical aperture on the image side of the projection optical system 163.

On a mask having no phase shifter as shown in FIG. 18, two light beams for forming interference fringes are generated by illuminating one or two parallel light beams in oblique directions. In this case, the incident angle θ ₀ of the illumination light to the mask
Is set to satisfy, for example, equation (7). An ideal case is a case where the mask is illuminated by a pair of parallel light beams inclined by θ0 in opposite directions so as to be symmetric with respect to a symmetry plane including the optical axis.

Sin θ ₀ = M · NA (7) Here, M is the projection magnification of the projection optical system 163, and NA is the image-side numerical aperture of the projection optical system 163.

When oblique incidence illumination is performed on a mask having no phase shifter shown in FIG. 18 with a parallel light beam satisfying the above equation (7), an angle θ from the mask with respect to the optical axis is obtained.
_0- order transmitted diffracted light that travels straight at 0, and travels along an optical path that is symmetrical with respect to the optical path of the 0-order transmitted diffracted light and the optical axis of the projection optical system (travels at an angle -θ ₀ with respect to the optical axis) —first-order transmission 2 with diffracted light
A luminous flux is generated as two object-side exposure lights 162 in FIG.
These two light beams enter the opening of the aperture stop 164 of the projection optical system 163, and form an image of a repetitive pattern of chrome. The image at this time is also an interference fringe.

In the present application, such oblique incidence illumination using a parallel light beam is also treated as “coherent illumination”.

The technique for performing two-beam interference exposure using a projection exposure apparatus has been described above, and a periodic exposure pattern shown in FIG. 13A can be obtained using this technique. Since the illumination optical system 192 of the projection exposure apparatus as shown in FIG. 1 is configured to perform partial coherent illumination at about σ = 0.6, the illumination optical system 192 shown in FIG. By switching the optical system, for example, by replacing the aperture stop of about 0.6 with an aperture stop for small σ corresponding to σ ≦ 0.3, a partial coherent illumination of small σ and substantially It is configured to perform coherent illumination.

Returning to the description of the second embodiment shown in FIGS.

In the present embodiment, normal exposure by mask projection is performed next to or before the periodic pattern exposure by the two-beam interference exposure (for example, σ =
Exposure of the gate pattern shown in FIG. 13 (B) as a white portion is performed by using a partially coherent illumination of about 0.6. In the upper part of FIG. 13B, the relative positional relationship between the gate pattern (image) when performing double exposure and the periodic pattern (image) by two-beam interference exposure, and exposure of the gate pattern to be projected and exposed by using a mask The lower part of FIG. 13 shows the exposure amount of the gate pattern image by the normal exposure to the resist of the wafer, which is mapped at a resolution of 0.1 μm in vertical and horizontal directions.

The portion of the minimum line width (pattern image) of the image of the gate pattern due to the projection exposure is not resolved but spreads, the contrast is low, and the value of the exposure amount at each point in this portion is low. The exposure amount by the image is defined as a,
b, and the portion between the pattern images where the blur images come from both sides is C, the exposure amount is 1 <a <2.
When 0 <b <10 and 0 <C <1, the central portion of the pattern image is large and both sides are small, and an exposure amount distribution having a different exposure amount for each region of the gate pattern image is generated. In the case of double exposure using a mask having such a gate pattern formed thereon, the exposure amount ratio in each exposure is, for example, periodic pattern exposure: normal exposure =
1: 2.

The manner in which the gate pattern, which is the fine circuit pattern shown in FIG. 12, is formed by a combination of the periodic pattern exposure and the normal exposure will be described in detail. In the present embodiment, there is no development process between the two exposures, the periodic pattern exposure by the two-beam interference exposure and the normal exposure by the projection exposure. Therefore, the exposure amount of each point in the region where the exposure pattern of each exposure overlaps is added, and a new exposure pattern (exposure amount distribution) is generated after the addition. Development is performed on this new exposure pattern. Becomes In the new exposure pattern, the double exposure improves the contrast of the exposure distribution of the gate pattern having the smallest line width, and the exposure exceeds the exposure threshold of the resist as described later.

The upper part of FIG. 13 (C) shows the exposure pattern of FIG. 13 (A) by the double exposure of this embodiment and FIG.
9B shows an exposure pattern (exposure amount distribution) resulting from addition of the exposure pattern of FIG. 9B and an exposure amount of a region indicated by e is 1 + a, which is larger than 2 and smaller than 3. FIG.
The lower part of (C) shows the concavo-convex pattern obtained by developing the exposure pattern shown in the upper part of FIG. 13 (C) in white and gray. In the present embodiment, a resist having an exposure threshold of greater than 1 and less than 2 is used as the resist on the wafer. Therefore, only a portion having an exposure amount of greater than 1 appears as an uneven pattern due to development. FIG.
The shape and size of the pattern shown in gray at the bottom of FIG. 3 (C) match the shape and size of the gate pattern shown in FIG. 12, and the fineness of 0.1 μm is obtained by the exposure method of this embodiment. A gate pattern, which is a circuit pattern including a plurality of patterns B and C having different line widths having different line widths, is, for example, the same exposure light (the same exposure wavelength).
Performing the above-described double exposure using a projection exposure apparatus having an illumination optical system capable of switching between types of masks and switching between large coherent illumination and partial coherent illumination with large σ and coherent illumination or partial coherence with small σ. As a result, it can be formed.

FIGS. 14 and 15 show a second embodiment of the second embodiment using a stepper (projection exposure apparatus) using a KrF excimer laser emitting a laser beam having a wavelength λ = 248 nm as a light source.
FIG. 9 is a diagram showing a specific example when a double exposure is performed.
A word obtained by exposing a resist on a wafer with an image of a gate pattern having a minimum line width of 0.12 μm as shown in FIG. 14. A Levenson type phase shift mask is superimposed on a resist pattern image exposure position of the resist without development. Thus, a high-contrast interference fringe image is exposed so that the bright portion of the interference fringe overlaps with the image of the pattern having the minimum line width in the gate pattern. The exposure conditions of this specific example are shown below.

The projection lens has an NA of 0.3, and the illumination system has vertical illumination of σ of 0.3 in periodic pattern exposure using a Levenson type phase shift mask, and ring illumination in normal exposure using a mask having a gate pattern. From an annular secondary light source (light source at or near the exit surface of the optical integrator) that can provide annular illumination with σ at the outer diameter of 0.8 and σ at the inner diameter of the ring of 0.6. It was decided to illuminate obliquely with light. Preferably, the outer diameter of the ring is at least 0.8 and the width of the ring is at least 0.2, each value being determined according to the minimum line width and other line widths. The exposure was set such that the exposure during normal exposure was twice as large as the exposure during periodic pattern exposure.

In FIG. 15, the top line uses the contour lines to show the exposure amount distribution of the resist on the wafer due to the interference fringes (image) at the time of the periodic pattern exposure, and the second line shows the exposure of the resist by the gate pattern image during the normal exposure. In the third stage, the exposure amount distribution in the double exposure of the periodic pattern and the projection exposure
The lower row shows a concavo-convex pattern (resist pattern) on the wafer by the developed resist.

In each stage, the focus position of the projection optical system on the wafer is 0.0 μm and the defocus amount from this focus position is:
The exposure amount distribution and the concavo-convex pattern are drawn for three cases of 0.02 μm and 0.4 μm.

As shown in the second row of FIG.
Although the pattern image of the fine gate having high contrast is not obtained by only one projection exposure, the high contrast image of the periodic pattern of the first stage in FIG. 15 is overlapped with the exposure position of the projection exposure of the resist. As shown in the third row of FIG. 15, the fine portion of the gate pattern image (the image of the pattern S having the minimum line width) is also resolved and improved in resolution, and actually, as shown in the fourth row of FIG. A concavo-convex pattern corresponding to a desired gate pattern could be created.

FIG. 19 is a schematic diagram showing an example of an exposure apparatus for two-beam interference exposure capable of performing periodic pattern exposure in the multiple exposure method of the present invention. In FIG. The multiplexing optical system has the same basic configuration as the optical system shown in FIG. Reference numeral 202 denotes a KrF excimer laser (wavelength: about 248 nm) or ArF excimer laser (wavelength: about 193 nm); 203, a half mirror; 204, a plane mirror; Off-axis type alignment optical system that can be detected as length), and alignment mark 2 on wafer 206 for auto alignment.
09 is observed and its position is detected. 207 is an optical system 2
XYZ stage movable freely along the X-Y plane orthogonal to the optical axis 208 of the optical axis 01 and in the optical axis direction (Z direction) using a laser interferometer or the like (not shown) in two X and Y directions. Is precisely controlled. Since the configurations and functions of the devices 205 and 207 are well known, a detailed description is omitted.

FIG. 20 is a schematic diagram showing a high-resolution exposure system which can carry out the multiple exposure method of the present invention and comprises a two-beam interference exposure apparatus for performing periodic pattern exposure and a projection exposure apparatus for performing normal exposure. .

In FIG. 20, reference numeral 212 denotes a two-beam interference exposure apparatus having the optical systems 201 and 205 shown in FIG.
Reference numeral 13 denotes an illumination optical system (not shown) and a reticle alignment optical system 214, an off-axis alignment optical system 217 for aligning the wafer, and a circuit pattern such as that shown in FIG. This is a normal projection exposure apparatus including a projection optical system 216 for projecting. The illumination optical system (not shown) of the apparatus 213 can perform large σ illumination similarly to the projection exposure apparatus used in the second embodiment. A system capable of performing annular illumination with σ = 0.8.

The reticle positioning optical system 214 observes the positioning mark 220 on the mask 215 and detects its position for automatic alignment. The wafer alignment optical system 217 observes the alignment mark 209 for projection exposure or dual light beam interference on the wafer 206 and detects the position for automatic alignment. Since the configurations and functions of the optical systems 214, 216, and 217 are well known, a specific description will be omitted.

Reference numeral 219 in FIG. 20 denotes a two-beam interference exposure apparatus 2
12 is one XYZ stage shared by the projection exposure apparatus 213, and this stage 219
The optical axis can be freely moved in a plane orthogonal to each of the optical axes 208 and 221 in the optical axis direction, and its position in the XY directions is accurately controlled using a laser interferometer or the like.

Stage 219 holding wafer 218
20, the position of the wafer 218 is accurately measured by being sent to the position (1) in FIG. 20, and based on the measurement result, the wafer 218 is sent to the exposure position of the device 212 indicated by the position (2) and Light beam interference exposure (periodic pattern exposure)
Thereafter, the wafer 218 is sent to the position (3) to accurately measure the position of the wafer 218, and is sent to the exposure position of the apparatus 213 shown at the position (4) to perform projection exposure (normal exposure) on the wafer 218. It is.

In the apparatus 213, instead of the off-axis positioning optical system 217, a positioning mark on the wafer 218 is observed via a projection optical system 216, and the TTL positioning (not shown) for detecting the position is detected. It is also possible to use an optical system or a TTR alignment optical system (not shown) for observing an alignment mark on the wafer 218 via the projection optical system 216 and the mask 215 and detecting the position.

FIG. 21 shows that the exposure method of the present invention can be implemented.
FIG. 2 is a schematic diagram showing a high-resolution exposure apparatus capable of performing both periodic pattern exposure (high-contrast projection exposure) and normal projection exposure (low-contrast image or low- and high-contrast image mixed projection exposure).

In FIG. 21, reference numeral 221 denotes a KrF excimer laser (wavelength: about 248 nm) or ArF excimer laser (wavelength: about 193 nm); 222, an illumination optical system; 223, a mask; 224, a mask stage;
A projection optical system 225 for reducing and projecting the circuit pattern No. 3 onto the wafer 228 is a mask (reticle) changer. The stage 224 includes a mask on which a circuit pattern as shown in FIG. It is provided for selectively supplying one of a periodic pattern reticle on which a circuit pattern is not drawn, such as a phase shift mask, an edge shifter type mask, or a periodic pattern mask having no phase shifter. The periodic pattern reticle may have a certain circuit pattern drawn at a location different from the periodic pattern.

Reference numeral 229 in FIG. 21 denotes one XYZ stage shared by the periodic pattern exposure by the two-beam interference exposure and the normal exposure by the projection exposure.
The optical system 227 can be freely moved along a plane perpendicular to the optical axis and in the optical axis direction, and its position in the X and Y directions is accurately controlled using a laser interferometer (not shown) or the like.

The apparatus shown in FIG. 21 includes a reticle positioning optical system (not shown) and an off-axis positioning optical system 217 (FIG. 20).
A TL alignment optical system and a TTR alignment optical system are also provided, and alignment between the mask 223 and each shot area of the wafer 228 is performed using these alignment optical systems.

The illumination optical system 222 of the apparatus shown in FIG. 21 is configured to be able to switch between partially coherent illumination of large σ and partially coherent illumination of small σ or coherent illumination. The illumination light of (1a) or (1b) described above with reference to FIGS. 17 and 18 is used as the illumination light of (1c) in the block 230 in the case of partial coherent illumination of small σ. To one of the aforementioned Levenson-type phase shift masks or edge shifter-type masks or periodic chrome pattern masks without a phase shifter, illustrated in block 230 for large σ partial coherent illumination ( The illumination light of 2) is supplied to a mask on which a desired circuit pattern is drawn. Switching from large σ partial coherent illumination to small σ partial coherent illumination is performed by the illumination optics 222
A stop with a large aperture usually placed immediately after the fly-eye lens can be replaced with a coherent illumination stop with a sufficiently small aperture compared to this stop. Note that large σ is σ ≧
0.6 and small σ are σ ≦ 0.3. Block 230
Instead of the illumination light of (2), the annular illumination light described above can be used.

Various devices such as semiconductor chips such as ICs and LSIs, display elements such as liquid crystal panels, detection elements such as magnetic heads, and image pickup elements such as CCDs can be manufactured using the above-described exposure method and exposure apparatus. .

The present invention is not limited to the embodiment described above, and can be variously modified without departing from the gist of the present invention. In particular, the number of exposures and the number of exposure steps in the periodic pattern exposure such as the two-beam interference exposure and the normal exposure can be appropriately selected, and the overlay of the exposure patterns is also adjusted as appropriate, such as performing a slight shift on purpose. It is possible. By doing so, the number of variations in the circuit pattern that can be formed increases.

FIGS. 22 to 26 show a third example of the exposure method according to the present invention.
It is explanatory drawing of embodiment. FIG. 22 is a flowchart illustrating an exposure method according to the third embodiment. FIG. 22 shows the blocks of the high-contrast image exposure step, the normal exposure step (performed by, for example, projection exposure), and the development step, which constitute the exposure method of the present invention, and the flow thereof. The order of high-contrast image exposure and normal exposure in FIG.
Actually, it can be reversed or simultaneous, and if either one of the exposures is more than 2 multiple exposures including multiple exposure steps, each exposure step of high contrast image exposure and normal exposure can be performed alternately It is. Also, between each exposure. Although there is a step of performing precise alignment, the illustration is omitted here. When high-contrast image exposure is performed using a phase-type mask having no light-shielding portion and exposure is performed according to the flow of FIG. 22, first, exposure is performed using a mask M as shown in FIG. I do. 1 is a substrate made of quartz, and 2 is a phase shift portion made of quartz.

FIG. 23A shows a phase type mask M which gives a phase difference to a light beam passing between two adjacent regions without passing through a light shielding portion.
Where the phase of light passing therethrough is 180 degrees more than that of light passing through other surrounding areas as a mask pattern.
The phase shifter 2 having a thickness that changes by ± 30 ° is used. FIG. 23B shows an exposure amount distribution when the resist is exposed by projecting the pattern 2 of the phase mask M of FIG. 23A onto a wafer by the projection exposure apparatus of FIG. 21, for example. Considering that the phase shift unit 2 is overlapped with the exposure amount distribution on the wafer in FIG. 23B in consideration of the reduction magnification of the projection optical system, the exposure amount distribution has a local maximum value at the center of the shift unit 2. And has a local minimum value at a position corresponding to the edge of the shift unit 2. Assuming that the line width L2 of the shift unit 2 is near the resolution limit determined by the NA of the projection optical system, the exposure amount distribution of the central portion having the maximum value is close to a sine wave distribution as shown in FIG. Become. Note that a slight drop corresponding to the intensity distribution of the next cycle occurs on both sides of the entire exposure amount distribution.

When the resist is developed after exposing only the pattern of the phase shift portion 2 as described above, if the threshold value Eth of the resist on the wafer is set as shown in FIG. Using “positive type”), a resist pattern having two lines of convex portions as shown in FIG. 23C is formed, and using a negative type resist (hereinafter, “negative type”) is used. As shown in FIG. 23D, a resist pattern having two lines of concave portions is formed.

In the present embodiment, unlike the exposure sensitivity setting (exposure threshold Eth) shown in FIG.
As shown in FIG. 23E, when the central exposure amount in the high-contrast image exposure is set to 1, the exposure threshold value Eth of the resist of the wafer to be exposed is set to be larger than 1. In this case, an exposure pattern (exposure amount distribution) obtained by performing only exposure of the pattern of the phase shift unit 2 shown in FIG.
Since the amount of exposure is insufficient, when development is performed, there is some variation in the film thickness, but there is no portion where the film thickness becomes zero, and no lithography pattern (uneven pattern) is formed on the wafer by etching. This can be regarded as the disappearance of the pattern.

At this time, the result of development using the positive type is shown in FIG. 23 (F), and the result of development using the negative type is shown in FIG. 2 (G).

The feature of this embodiment is that, in relation to the exposure threshold value Eth of the resist, a high-resolution and high-contrast exposure pattern which disappears only by exposure of the pattern (image) is equal to or lower than the resolution of a normal projection exposure apparatus. The exposure of the resist by performing a double exposure to fuse with an exposure pattern of an arbitrary shape having a plurality of patterns having different line widths including a low-contrast pattern (which cannot be resolved by the exposure alone) having a size of Exposure is performed with an exposure amount equal to or more than the exposure threshold value Eth of the resist only in a desired region.
A lithography pattern corresponding to the exposure pattern (mask pattern) having the arbitrary shape can be formed.

A method of exposing a pattern (image) of an isolated line will be described with reference to FIG. FIG. 24 (A) is the same as FIG.
24, the mask pattern of the phase type mask M described in FIG.
(B) shows the exposure distribution on the resist of the wafer on which the projection exposure of the phase mask M has been performed as the high contrast image exposure step of FIG.

FIG. 24C shows a mask Ma on which a circuit pattern for performing projection exposure corresponding to the normal exposure step of FIG. 22 is formed. The circuit pattern of the mask Ma is a fine pattern having a resolution equal to or less than the resolution of the projection exposure apparatus. Therefore, the pattern cannot be resolved with the line width LX, and the intensity distribution of the pattern image on the wafer is blurred and wide as shown in FIG. 24D, and the contrast is low. In the exposure using such a low-contrast image, the exposure amount distribution of the resist is also shown in FIG.
(D), and even if the exposure threshold value Eth is lower than the exposure amount E2, a fine convex or concave resist pattern having a line width corresponding to the line width LX of the opening of the mask Ma cannot be formed.

In the present embodiment, the line width LX of the fine pattern of the mask Ma is set to a line width that is about half the line width (resolution) that can be resolved by the projection exposure apparatus.

The fine pattern line width of the mask Ma may be 1/2 to 1/4 of the resolution of the projection exposure apparatus.

The normal exposure for exposing the resist with the fine opening pattern of the mask Ma shown in FIG.
After exposure of a high-contrast image using the phase mask M, without performing a developing step, using another mask at the same exposure wavelength and using the same mask and overlapping the same region of the same resist, The total exposure distribution of the resist becomes a distribution as shown in FIG. 24E obtained by adding the distribution of FIG. 24D to the distribution of FIG. Here, the ratio of the exposure amount E ₂ of the normal exposure of the opening pattern of the exposure amount E ₁ and the mask Ma high contrast image exposure by the phase shifting unit 2 of the mask M is l: 1, the resist exposure threshold Eth is It is set between the exposure amount E ₁ (= 1) and the sum (= 2) of the exposure amounts E ₁ and E ₂ .

For this reason, if a positive resist is used, a lithography pattern as shown in FIG. 24F is obtained after development, and if a negative resist is used, the lithography pattern shown in FIG.
A lithography pattern as shown in (G) is obtained. At this time, the phase mask M shown in FIG.
24C and the mask Ma in FIG.
Extreme position (peak) of the exposure pattern by the pattern of
It is preferable to perform double exposure so that

The lithographic patterns of the isolated lines obtained by the double exposure according to the present embodiment shown in FIGS. 24F and 24G are those exposed by the phase type mask M, and unnecessary patterns are also included. Absent. Therefore, a circuit pattern having a higher resolution than that which can be realized by a normal projection exposure apparatus is obtained.

In the following, when a high-contrast image (high-contrast exposure pattern) is formed using a phase-type mask M without a light-shielding film, some configurations of a phase shift portion and an exposure dose distribution on a wafer (resist) corresponding to each configuration are described. Are arranged and shown in FIG. In FIG. 25 as well, the hatched portion is the phase shift unit 2.

FIG. 25A shows a cross-sectional structure of a mask in the case of only a single edge, and has a light exposure distribution as shown in FIG. 25B on a wafer. This corresponds to a pattern of one black stripe. FIG. 25C shows a cross-sectional structure of the mask M in the case of the above-mentioned isolated pattern, and an exposure amount distribution corresponding to a pattern of two black stripes and one white stripe therebetween as shown in FIG. Is formed on the resist of the wafer. FIG.
(E) shows a cross-sectional structure of a mask M having a phase shift portion for forming an exposure amount distribution corresponding to a pattern of three black stripes and two white stripes therebetween.
An exposure distribution as shown in FIG. FIG. 25G shows a cross-sectional structure of a mask M that forms an exposure amount distribution corresponding to a pattern of four black stripes and three white stripes therebetween when the number is further increased, and FIG. Is the exposure dose distribution on the wafer at that time.

In the present embodiment, a high γ resist is used for the wafer, and after exposing the resist of the wafer with a high contrast image by the pattern of the phase shift portion of the phase mask M, a fine line width (for example, L & S) that cannot be resolved is obtained. The same exposure position as that of the high-contrast image of the resist is usually exposed at the same exposure wavelength with a single mask pattern having a plurality of patterns having different line widths including the above-mentioned pattern. To form a circuit pattern including a fine line width pattern corresponding to the mask pattern. Incidentally, the maximum exposure amount in the exposure amount distribution shown in FIGS. 24B and 24D does not exceed the exposure threshold value.

The principle of the double exposure method of the present embodiment is summarized as follows. Exposure patterns by high-contrast image exposure, in which the maximum exposure amount is equal to or less than the exposure threshold value Eth of the resist, in an area where normal exposure is not performed, disappear by development. 2. An exposure pattern area (exposure area) for normal exposure in which an exposure amount equal to or less than the exposure threshold value Eth of the resist is supplied to the resist is determined by a combination of each exposure pattern for normal exposure and high-contrast image exposure. Then, an exposure pattern having the same resolution as the exposure pattern of the high contrast image exposure is formed. 3. The exposure pattern area (exposure area) of the normal exposure in which an exposure amount equal to or more than the exposure threshold value Eth of the resist is supplied to the resist is determined by a combination of each exposure pattern of the normal exposure and the periodic pattern exposure. An exposure pattern having the same resolution as the exposure pattern is formed. It turns out that. Further, an advantage of the double exposure is that a much larger depth of focus can be obtained for an exposure pattern having the highest resolution as compared with normal exposure.

The order of the high-contrast image exposure and the normal exposure with the mask pattern image including the low-contrast image and the high-contrast image is the high-contrast image exposure, but may be reversed or simultaneous.

Next, an embodiment in which a two-dimensional isolated pattern such as a contact hole is formed on a wafer will be described. FIG. 26 is an explanatory diagram showing the situation of creating a two-dimensional isolated pattern.

FIG. 26A is a plan view of a phase type mask M for forming a high-contrast image serving as a base when viewed from above, and shows a distribution of the exposure amount of the resist on the wafer. FIG.
The phase shifter 2 changes the phase of light passing through a portion 2 indicated by oblique lines in FIG. 1A by 180 ° as compared with the light passing through other regions. The amount of exposure decreases near the edge of the phase shift unit 2 where the phase is changing. The reduced exposure area outside the edge portion is indicated by a halftone dot, and the reduced exposure area inside the edge portion is indicated by a solid square line superimposed on the mask M.

A phase type mask M for forming a high contrast image
With respect to a partial cross section and exposure dose distribution of a mask Ma having a circuit pattern including a plurality of patterns having different line widths where a low contrast image and a high contrast image are generated,
The X-axis direction is shown on the left side of FIG. 26, and the Y-axis direction is shown on the right side of FIG. FIG. 26B is a cross-sectional view of the mask M in the X direction and the Y direction, and FIG. 26C shows the exposure dose distribution of each cross section in the X and Y directions of the resist when a high contrast image is exposed by the mask M. Shown in Since the width of the phase shift portion 2 (pattern) of the mask M in the Y-axis direction is larger than the width in the X-axis direction, the exposure amount distribution in the Y-direction section is the exposure amount distribution in the X-axis section. Is stretched as it is.

FIG. 26D shows a cross section in the X-axis and Y-axis directions of the opening of the mask Ma projected during normal exposure.
The dimensions LX and LY of the openings are shown. Since the values LX and LY are lower than the resolution of the exposure apparatus, the mask Ma
Cannot be resolved only by ordinary exposure. Therefore, the image of the opening pattern Ma is blurred, and the exposure dose distribution in the resist is widened in the cross sections in both the X-axis and the Y-axis as shown in FIG. FIG. 26 shows a total exposure amount distribution obtained by adding the exposure amount distributions in each exposure using the two masks M and Ma.
FIG. 2 in which the distribution of FIG. 26C and the distribution of FIG.
6 (F). If the exposure threshold value Eth is set as shown in FIG. 26 (F), the resist pattern after development when using a positive type resist becomes as shown in FIG. 26 (G). The subsequent resist pattern is as shown in FIG. 26H, and a fine isolated pattern that cannot be obtained by ordinary projection exposure can be formed. still,
The maximum exposure in the exposure distribution shown in FIGS. 26C and 26E does not exceed the exposure threshold Eth.

Next, another embodiment of the present invention will be described. This embodiment is directed to a gate pattern shown in FIG. 12 as a circuit pattern (lithography pattern) obtained by exposure.

To explain again, the gate pattern of FIG. 12 has a minimum line width of 0.1 μm in the horizontal direction, that is, the AA ′ direction in the figure, while the minimum line width in the vertical direction is 0.2 μm. It is. According to the present embodiment, such an A
For a two-dimensional pattern in which high resolution is required only in one direction -A ', exposure of a high-contrast image may be performed by focusing on one direction requiring high resolution.

The double exposure for superposing and exposing a high-contrast image to an opening (opening in the figure) of a gate pattern will be described with reference to FIGS.

First, a high-contrast image is used as a base.
The case where the resist is exposed by projecting it onto a resist as an exposure pattern that gives a large exposure amount to the exposure pattern of the gate pattern will be described.

FIG. 27 shows (A), (B) and (C) on the left for exposure with a high-contrast image, and (D), (E) and (F) on the right for exposure with a gate pattern. Show.

FIG. 27A shows a plan view of a phase type mask M for forming a high contrast image and a distribution of an exposure amount when the resist is exposed with the phase type mask M. A portion 2 indicated by oblique lines is a phase shift portion in which the phase of the transmitted light is changed by 180 ° as compared with the transmitted light in other regions. The amount of exposure decreases near the edge where the phase is changing. The reduced exposure area outside the edge portion is indicated by a halftone dot, and the reduced exposure area inside the edge portion is indicated by a square solid line superimposed on the mask M. FIG. 27B is a cross-sectional view of the phase type mask M, and FIG. 27C shows an exposure amount distribution when the resist is exposed to a high contrast image using the mask M.

FIG. 27D shows a mask Ma having a gate pattern used at the time of normal exposure.
FIG. 27E is a sectional view taken along the line A- '. Since the width LX of the two openings of the mask Ma in FIG. 27E is not resolved by only one projection exposure and the two opening images are blurred, the exposure amount distribution of the resist by the projection exposure of the mask Ma is shown in FIG. It spreads like F).

However, the total exposure distribution of the respective exposure distributions of the mask M and the mask Ma as a result of the double exposure is as shown in FIG. If the exposure threshold value Eth of the resist is set as shown in FIG. 28A, the resist pattern after development when using a positive resist is as shown in FIG.
8 (B). 27 (C), (E)
The maximum exposure amount of the exposure amount distribution indicated by
Not exceed.

FIG. 28C shows a resist pattern after development when a negative resist is used.

The situation of double exposure has been described by focusing on the pattern having the minimum line width at the center of the gate pattern. Hereinafter, the situation of double exposure of the entire gate pattern will be described with reference to FIG.
It is explained based on.

In FIG. 29, FIG.
3 shows an exposure pattern (exposure amount distribution) generated by high-contrast image exposure by projection exposure of FIG. The period of this exposure pattern is 0.2 μm, and this exposure pattern has a line width of 0.1 μm.
Equivalent to mL & S pattern. Numerical values in the lower part of FIG. 32 represent exposure amounts on the resist.

In this embodiment, the normal exposure (for example, the apparatus shown in FIG. 21 performs partial coherent illumination of large σ on the mask) following the above-described high-contrast image exposure makes the outline of FIG. The projection exposure of the gate pattern shown by. The mask M is shown in the upper part of FIG.
FIG. 29B shows the relative positional relationship between the exposure pattern by the gate pattern and the exposure pattern by the mask M and the exposure amount on the mask at the time of projection exposure of the gate pattern. The lower part of FIG. The exposure amount of the resist on the wafer is mapped with a vertical and horizontal resolution of 0.1 μm.

Since the portion (pattern image) having the minimum line width of the image of the gate pattern of the mask Ma is not resolved and spreads, resulting in a low contrast, the value of the exposure amount at each point in this portion decreases. This low contrast pattern image exposure amount is defined by a,
b, where C is the portion between the pattern images where the blur images from both sides overlap, and 1 <a <20 <b
When <10 <C <1, the center is large and both sides are small. When the masks M and Ma are used, the ratio of the amount of exposure to the resist in exposure by each mask is as follows: exposure of a high contrast image by the mask M: gate pattern image exposure of the mask Ma =
1: 2.

FIG. 1 shows a double exposure of a high-contrast image exposure and a normal exposure of a gate pattern having a pattern that cannot be resolved because of a low contrast due to exposure alone.
The manner in which two fine gate patterns are formed will be described. In this embodiment, there is no development process between the high-contrast image exposure and the normal exposure with the gate pattern image,
The exposure wavelength of each exposure is the same. Therefore, the exposure amount in the region where the exposure pattern of each exposure overlaps is added, and a new exposure pattern (exposure amount distribution) is generated by the added exposure amount.

The upper part of FIG. 29C is the same as FIG.
29A and 29B show an exposure pattern (exposure amount distribution) obtained as a result of adding the exposure pattern of FIG. 29A and the exposure pattern of FIG. 29B.
Larger and less than 3. The lower part of FIG. 29 (C) shows the lithography pattern obtained by developing this exposure pattern in gray. In the present embodiment, the resist of the wafer has an exposure threshold value Eth of more than 1 and less than 2, and therefore, only a portion where the exposure amount is more than 1 appears as a pattern by development.

The shape and size of the pattern shown in gray at the bottom of FIG. 29C match the shape and size of the gate pattern shown in FIG. 12, and are reduced to 0.1 μm by the exposure method of this embodiment. A circuit pattern having a fine line width can be formed using a projection exposure apparatus.

In the next embodiment, referring to FIGS. 30 to 32, a high-contrast image as a base is projected onto a resist so as to form an exposure pattern that gives a small amount of exposure to a black exposure pattern of a gate pattern. Is shown.

FIG. 30 shows (A), (B) and (C) on the left for exposure with a high contrast image, and (D), (E) and (F) on the right for exposure with a gate pattern. Show.

FIG. 30A shows a plan view of a phase type mask M for producing a high contrast image and a distribution of the exposure amount when the resist is exposed with the phase type mask M. The hatched portion is the phase shift unit 2 in which the phase of the transmitted light is changed by 180 ° compared to the transmitted light in other areas. The amount of exposure decreases near the edge where the phase is changing. The reduced exposure area outside the edge portion is indicated by a halftone dot, and the reduced exposure area inside the edge portion is indicated by a square solid line superimposed on the mask M. FIG. 30B is a cross-sectional view of the phase type mask M, and FIG. 30C shows an exposure amount distribution when the resist is exposed with the mask M.

FIG. 30D shows a mask Ma having a gate pattern used at the time of normal exposure.
FIG. 30E is a sectional view taken along the line A ′. Since the pattern of the two fine lines in the center of the mask Ma is not resolved by one projection exposure, the image is blurred and has low contrast, and the exposure dose distribution of the resist by the image is spread as shown in FIG. It will be.

FIG. 31A shows the total exposure amount distribution of the resist obtained by performing double exposure of high-contrast image exposure by projection of the phase shift portion of the mask M and normal exposure by projection of the mask Ma gate pattern image. become that way. By setting the exposure threshold value Eth of the resist as shown in FIG. 31A, a resist pattern after development when a positive resist is used is obtained as shown in FIG. 31B. The resist pattern after development when using a negative resist is shown in FIG.
(C).

Focusing on the central part of the gate pattern,
The situation of the exposure has been described. Hereinafter, the situation of the double exposure of the entire gate pattern will be described with reference to FIGS.

The period of the high-contrast image of this embodiment or the exposure pattern formed by the high-contrast image is 0.2 μm, and this image or exposure pattern corresponds to a line width of 0.1 μmL & S pattern. Numerical values in the lower part of FIGS. 32A to 32C represent exposure amounts on the resist.

In this embodiment, projection exposure of a high-contrast image of the mask M (for example, the mask
The projection exposure of the gate pattern image of the mask Ma (which may be performed at the same time and subsequent), which is performed by performing partial coherent illumination on the mask Ma (for example, using the apparatus of FIG. 21)
32B is performed by performing a partial coherent illumination with a large σ and performing projection. The upper part of FIG. 32B shows the relative positional relationship between the high-contrast image pattern of the mask M and the gate pattern image of the mask Ma, and the lower part of FIG. 32B shows a single projection exposure of the gate pattern image of the mask Ma. Is a mapping of the exposure amount of the wafer to the resist with a resolution of 0.1 μm pitch in the vertical and horizontal directions.

The portion having the minimum line width of the exposure pattern formed by the projection exposure of the gate pattern image is not resolved but is widened, and the value of each point of the exposure amount is lowered to lower the contrast. The exposure amount of each region of the exposure pattern is roughly small at the center of the pattern and large on both sides. Here, assuming that the exposure amounts at the center and both sides are represented by f and g, respectively, and the exposure amount at the center where the blurred images on both sides overlap is represented by h, 0 <f <11 <g
<21 <h <2. An exposure pattern based on a gate pattern image having a line width that cannot be resolved as described above causes a multi-level exposure distribution in which the exposure differs for each region.

When the masks M and Ma are used, the exposure ratio in each exposure is as follows: exposure of a high-contrast image of the mask M: exposure of the gate pattern image of the mask Ma = 1: 2 on the resist of the wafer.

The manner in which the fine circuit pattern shown in FIG. 14 is formed by the double exposure of the high contrast image projection exposure and the gate pattern image projection exposure described above will be described. In this embodiment, there is no development process between the high contrast image exposure and the gate pattern image exposure. Therefore, the exposure amount in the region where the exposure pattern of each exposure overlaps is added, and a new exposure pattern (exposure amount distribution) is generated by the added exposure amount.

The upper part of FIG. 32C is the same as that of FIG.
32A shows an exposure pattern (exposure amount distribution) obtained by adding the exposure pattern of FIG. 32B and the exposure pattern of FIG. 32B, and the exposure amount of an area indicated by i and j is 1 + i, 1+
j is greater than 2 and less than 3.

The lower part of FIG. 32C shows a pattern obtained by developing this exposure pattern in gray. In the present embodiment, the resist on the wafer has an exposure threshold value greater than 1 and less than 2, so that only a portion where the exposure amount is less than 2 appears as a pattern due to development. The shape and size of the pattern shown in gray at the bottom of FIG. 32C match the shape and size of the gate pattern shown in FIG. 14, and a fine line such as 0.1 μm is obtained by the exposure method of this embodiment. A circuit pattern having a width can be formed using a projection exposure apparatus.

Next, an embodiment in which the present invention is applied to a circuit pattern having another shape will be described. The shape of the circuit pattern of this embodiment is shown in FIG. 33 (B), where the minimum line width is 0.1 μm and the wide portion has a width of 0.2 μm which is twice the minimum line width. Are arranged at intervals of 0.1 μm.

In the present embodiment, referring to FIGS.
A case where a large amount of exposure is given to an exposure pattern based on a circuit pattern image including a portion where a low contrast image is formed by an exposure pattern based on a high contrast image will be described.

FIG. 33A shows a pattern shape when a phase type mask M for creating a high contrast image used for double exposure according to the present embodiment is viewed from above. FIG. 33B shows a pattern shape when a mask pattern Ma for creating a circuit pattern image (including a low contrast image) used for double exposure according to the present embodiment is viewed from above.

FIG. 37 shows the state of projection exposure by each of the masks M and Ma. The case where a high-contrast image is formed using the mask M and exposure is performed is shown on the left side of each of FIGS.
(C) shows a case where exposure is performed using a pattern image in which high and low contrast images of the mask Ma coexist.
(E) and (F) show.

FIG. 34A is a plan view of a phase type mask M for producing a high-contrast image. The phase of the light passing therethrough indicated by oblique lines is one time smaller than the phase of light passing through other regions.
This is the part that has been changed by 80 °. FIG. 3 is a sectional view of the mask M.
FIG. 34C shows an exposure amount distribution on the resist when the pattern image of the mask M is projected, as shown in FIG.

FIG. 34D is a plan view of a mask Ma for creating a circuit pattern image, and schematically shows an exposure amount distribution in consideration of blur at the time of projection exposure. In FIG. 34D, a white portion is a portion where the exposure amount is large, and a hatched portion is a portion where the amount of light is reduced due to widening with blur. FIG. 34 is a sectional view of the center of the mask Ma.
(E). Since the circuit pattern image is not resolved by the projection exposure using the mask Ma, the image is blurred and has low contrast. The exposure distribution of the resist by this exposure is shown in FIG.
4 (F).

FIG. 35 shows the total exposure distribution of the resist after the double exposure by the projection exposure of the high contrast image by the mask M and the projection exposure of the circuit pattern image of the mask Ma.
It is schematically represented as in (A). FIG. 35B shows the exposure distribution at the center. Exposure threshold Et
If h is set as shown in FIG. 35 (B), the resist pattern after development when using a positive resist is as shown in FIG. 35 (C).
It is obtained as follows. Further, the resist pattern after development when using a negative resist is as shown in FIG.

FIG. 35 is a plan view of this resist pattern.
As shown in (E), a desired circuit pattern is obtained.
The double exposure according to the embodiment described above can be performed by the exposure apparatus shown in FIGS. At this time, the exposure wavelength is
It is the same between each exposure. The following description is also for the case where the exposure wavelength is the same.

Next, the light amount ratio between the exposure of the high-contrast image (to be referred to as a periodic pattern hereinafter) and the exposure of the circuit pattern image in the above-described double exposure and the contrast of the exposure pattern formed by the double exposure will be described in detail. I do.

FIG. 36 shows an exposure pattern consisting of a periodic pattern formed by two-beam interference exposure in black and an exposure pattern consisting of a circuit pattern formed by one projection exposure in a gray portion. The positional relationship is shown. The exposure pattern in the gray part is a high-contrast part due to exposure of a high-contrast image, and the exposure pattern in the black part is a low-contrast part due to a low-contrast image (circuit pattern image). The circuit pattern here is composed of a bar pattern. FIG. 36 (A) shows one bar, and FIGS.
Is a pattern of two bars, and FIG. 36 (C) is a pattern of three bars.

FIG. 37 (A) shows an exposure distribution on the X section which is given to the resist by the image of the three-bar pattern of FIG. 36 (C). The contrast A of the exposure distribution (image) in FIG.

[0205]

[Outside 3] When b <c, the contrast is minus (FIG. 4).
8), the contrast is zero if b = c (see FIG. 47).

The three-bar pattern, which is a low-contrast, unresolvable pattern shown in FIG. 37A, has been described repeatedly in each of the embodiments described above. FIG. 37 (B)
By performing double exposure with the periodic pattern of forming a high-contrast exposure distribution (image) shown in FIG. 37, an exposure distribution that becomes a pattern that can be resolved with high contrast as shown in FIG. 37C is obtained.

Now, assuming that the exposure ratio between the exposure using the three-bar pattern (circuit pattern) and the exposure using the periodic pattern (high contrast image) is 1: k,

[0208]

[Outside 4] It is.

At this time, the contrast A ′ of the exposure amount distribution due to the double exposure is

[0210]

[Outside 5] Becomes

Here, the light amount ratio k can be determined from the resolvable contrast value (contrast threshold value) of the resist. For example, if the contrast threshold of the resist used is Ic

[0212]

[Outside 6] What is necessary is just to determine the light quantity ratio k that satisfies. In the same mask pattern of the same projection optical system, the values of b and c are determined by the illumination conditions when illuminating the mask, and the values of I ₀ and I ₁ are determined by the periodic pattern forming method.

The contrast A 'of the exposure amount distribution after the double exposure is the contrast A of the single exposure of the ordinary circuit pattern.
A'-A has changed. The amount of change is (1)
From equation and equation (2)

[0214]

[Outside 7] Becomes here

[0215]

[Outside 8] And in equation (3)

[0216]

[Outside 9] Is the contrast of the periodic pattern image due to the two-beam interference exposure and the exposure amount distribution thereby. Also, in equation (3)

[0219]

[Outside 10] Is the contrast of the circuit pattern image and the exposure dose distribution due to the same as in (1). In the area where the dimension smaller than the limit resolution is fine, the contrast of the two-beam interference exposure is higher than that of the exposure by the circuit pattern image. Because it ’s big

[0218]

[Outside 11] It is.

That is, A'-A> 0, and it is clear that the contrast of the exposure distribution is increased by the double exposure.

Here, in the case of the double exposure shown in FIG. 36C, the light amount ratio k will be obtained.

At present, the most high-performance resist can be resolved with a 40% contrast (that is, the contrast threshold is 40%). View. In a normal mask pattern, the transmittance of the pattern portion is 1 and the transmittance of the background is 0 (the transmittance of the pattern portion is 0, and the transmittance of the background is 2).
There is also a mask pattern). The transmittance of the background is not necessarily zero, and may be a so-called halftone in which the phase is inverted by 180 ° to have a transmittance of several% (often 10% or less). Such a halftone mask will be described later.

The numerical aperture (NA) of the projection optical system on the wafer side is 0.60, the exposure wavelength is λ = 248 nm of a KrF excimer laser beam, and the width of the three-bar pattern on the mask surface and the periodic pattern Are equal in width, 0.12 μm
And the image of the periodic pattern as shown in FIG.
It is formed by illuminating and projecting a Levenson-type phase shift mask with an illumination condition of σ = 0.2. The exposure dose distribution of the resist by this periodic pattern image is

[0223]

[Outside 12] (See FIG. 37B). The image of the three-bar pattern as shown in FIG.
It is formed by illuminating and projecting the mask with annular illumination having illuminance in the range of σ = 0.53 and illuminance of σ = 0.53 or less and zero. The exposure distribution of the resist by the three bar pattern image is

[0224]

[Outside 13] (See FIG. 37A))). With only the projection exposure of the three-bar pattern, the contrast A becomes 12 as shown below.
%

[0225]

[Outside 14] It cannot be resolved.

In order for the contrast A 'after double exposure of the periodic pattern image and the three-bar pattern image to be 40% or more,

[0227]

[Outside 15] It is necessary to satisfy the following condition. In this conditional expression, I ₀ ,
When k is obtained by substituting the values of I ₁ , b, and c, k = 1.67. In order to increase the contrast A ′ after the double exposure to 40% or more, the light amount ratio k is set to 1.67. That would be good.

Assuming that k = 1.67, FIG.
In the cases (A) and (B), the pattern image calculates the contrast of the exposure amount distribution. In the case of double exposure of a single bar pattern in FIG. 36A, the minimum intensity value c is an intensity value at a position separated by the line width from the position X at which the maximum intensity value b is obtained. .

[0229]

[Outside 16] The double exposure increases the contrast from 37% at the time of projection exposure of a single bar pattern to 60%.

The calculation result in the case of double exposure of the double bar pattern shown in FIG.

[0231]

[Outside 17] The double exposure increases the contrast from 9% at the time of projection exposure of the double bar pattern to 41%.

As described above, the contrast is increased to 40% or more by double exposure for any pattern from isolated to periodic such as one bar, two bars, and three bars.
Resolution became possible with 40% resist.

As described above, by the double exposure of the projection exposure of the normal circuit pattern image and the projection exposure of the periodic pattern image supplying a high contrast image, the exposure amount distribution by a fine pattern image smaller than the limit resolution which cannot be normally resolved. Can be improved. At this time, by appropriately setting the illumination condition for the circuit pattern and the illumination condition for the periodic pattern and setting an appropriate light amount ratio k, the exposure distribution (double exposure) that reaches a contrast level resolvable by the resist used. ) Can be obtained. This result is shown in FIG.
8 is shown. The projection optical system has NA = 0.60 and the light source is Kr.
The exposure wavelength is λ = 248 nm using an F excimer laser.
And

In FIGS. 38A to 38C, the intensity distribution of the periodic pattern image (exposure amount distribution) is shown in the upper part, the intensity distribution of the bar pattern image (exposure amount distribution) is shown in the middle part, and the composite after double exposure is shown in the lower part. 3 shows an image intensity distribution (exposure amount distribution). The bar pattern is a single bar of a line pattern having a line width of 0.12 μm,
There are two bars and three bars. The portions indicated by rectangles in the respective intensity distributions in the figure are the intensity distributions of the bar patterns on the mask. The intensity distribution after the double exposure in the lower row has improved contrast, a higher intensity peak, and the pitch of the pattern at the center of the mask pattern is higher than that of the bar pattern in the middle row. Is equal to

FIG. 39 shows an intensity distribution (exposure amount) of a pattern image when exposed once using a Levenson-type phase shift mask in which adjacent bars have the same pattern as the bar pattern of FIG. Distribution). The case where the illumination condition is σ = 0.2 and σ = 0.5 is shown.
In the case of the isolated single bar shown in FIG. 39A, there is no adjacent pattern whose phase is inverted, so that it is exactly the same as the single bar pattern of the normal mask.

In the case of two or three bars in FIGS. 39 (B) and 39 (C), a high contrast is obtained because the phases of adjacent patterns are inverted, and a smaller σ than in the case of σ = 0.5 is obtained. The effect of improving the contrast is greater with coherent illumination than when σ = 0.2. However, at both ends of the pattern, there is no adjacent pattern whose phase is inverted, so that the image intensity is different from that of the central portion. Particularly, when σ = 0.2, the difference between the intensity peaks at the central portion and both ends is large. When σ is large, σ = 0.5, the contrast slightly decreases, but the intensity peak difference from both ends disappears. In any case, since the image is blurred at both ends, the bottom of the intensity distribution is widened, the position of the intensity peak is shifted from the center of the mask pattern, and the pitch of the pattern is not equal to the pitch of the mask pattern.

Next, the defocus characteristic of the contrast of the exposure distribution obtained by the double exposure will be described. FIGS. 40 and 41 show changes in contrast with respect to defocus for the single exposure of the phase shift mask and the double exposure method. As the circuit patterns, three types of one, two, and three bar patterns having a line width of 0.12 μm were used. FIG.
In 0 & 41, the solid line shows the contrast at the center of the bar, and the dotted line shows the contrast at the end, that is, the contrast obtained from the intensity at the position separated from the intensity peak of the end bar by the line width (the place without the bar).

FIG. 40 shows a change in contrast with respect to defocus in the exposure amount distribution when exposure is performed once with a phase shift mask, and the illumination condition is σ = 0.5.

FIG. 41 shows a change in contrast with respect to defocusing of the exposure amount distribution due to double exposure. The illumination condition is such that when the projection exposure of a bar pattern produces a low-contrast image, σ = 0.8 to 0.53. Σ = 0.
The illuminance inside 53 was set to zero, and in the projection exposure of a periodic pattern for forming a high-contrast image, partial coherent illumination with small σ of σ = 0.2 was used, and the light amount ratio of each exposure was set to 1.5. The NA of the projection optical system is 0.6, and the exposure wavelength is 248 nm.
It is.

The contrast at the center of the bar indicated by the solid line in FIG. 40 becomes higher in the best focus as the periodicity of the three bars, the two bars, and the one bar is lost, but the ratio of the decrease becomes larger as the defocus is made. That is, when the periodicity is lost, the depth of focus is reduced. The difference between the contrast at the center of the bar indicated by the solid line and the contrast at the edge at the end indicated by the dotted line is large. The depth of focus at which the contrast of 40% and 30% is obtained is the smaller of the depth of focus at the center and at the end of the bar. The depth of focus of the 40% contrast is 1.2 μm for three bars and 1.1 μm for two bars. In this bar, the depth of focus of 0.6 μm 30% is 3 μm for 3 bars, 1.4 μm for 2 bars, and 0.7 μm for 1.3 μm 1 bar.

On the other hand, in FIG. 41, the contrast value at the center of the bar is relatively low, but the difference between the three-bar, two-bar, and one-bar contrast peaks is small. The rate of decline is small. The difference between the contrast at the center of the bar indicated by the solid line and the contrast at the edge at the end indicated by the dotted line is small.

The 40% contrast depth of focus is 0.6 μm for 3 bars, 0.9 μm for 2 bars, 1.6 μm or more for 1 bar, and the 30% contrast depth of focus is 1.6 μm or more for 3 bars. With this bar, it is 1.6 μm or more. With one bar, it is 1.6 μm or more.
The same result as that of the single exposure was obtained, but when the contrast ratio was reduced to 35% or 30%, the double exposure method provided a larger depth. Further, since the contrast changes depending on the ratio of the light amount ratio, it can be set to be equal to or higher than the contrast threshold value of the resist.

The case where the bar pattern has one line width has been discussed. Next, the line width linearity will be described in the case where the line width of the periodic pattern is one and bar patterns having various line widths are mixed. The projection optical system and exposure wavelength are the same as before,
The illumination conditions for the periodic pattern projection exposure and the bar pattern projection exposure were the same as before. The line width of the periodic pattern was fixed at 0.12 μm as before, and the line width of the bar pattern was from 0.1 μm to 0.16 μm, with five bars, two bars, and one bar.

For each pattern, when the line width is sufficiently large (in this case, 0.36 μm), the exposure dose slice level is determined so that the mask and the wafer line width are equal, and the same slice level is used on the wafer side. It was examined how much each line width corresponding to 0.1 μm to 0.16 μm has an error from the line width on the mask. For comparison, the line width linearity error of only one exposure of the normal bar pattern exposure under the same illumination conditions was also examined.

FIGS. 42 and 43 show that 0.1 μm to 0.16 μm.
m is the line width linearity error. The line width linearity error is shown when the defocus is 0 and when the defocus is ± 0.2 and ± 0.3 μm. FIG. 42 shows the line width linearity error of the normal exposure, and the illumination condition is σ = 0.53-
The illuminance inside σ = 0.53 in the annular illumination of 0.8 was set to zero.

FIG. 43 shows the line width linearity error of the double exposure method. The illumination condition is σ = 0.
In the annular illumination of 53 to 0.8, the illuminance inside σ = 0.53 is set to zero, and in the exposure of the periodic pattern, the small σ of σ = 0.2
Was partially coherent illumination. These line widths are below the limit resolution, and the contrast is low. Here, even if the contrast is equal to or less than the resolvable contrast, the line width is obtained if the exposure amount reaches the slice level.

In FIG. 42, the portion where the line is broken in the middle is not present as a pattern and is in a uniformly blurred state. As described above, the case where the line has been written does not reach the resolvable contrast. There is also.

In FIG. 43, in each pattern, the critical resolution as the reproducibility of the line width is increased at each defocus. In addition, the numerical value of the line width error is also low.

In the double exposure method, a line width larger than these is excellent in reproducibility of a line width three times the periodic pattern.
This is because both edges of the bar pattern coincide with the periodic pattern as shown in FIG. A line width twice as large as the periodic pattern has poor reproducibility.

When the line width of the bar pattern includes a minimum line width and a line width twice as large as the minimum line width, it is effective to partially change the pitch of the periodic pattern as shown in FIG. The line width linearity error of the double exposure method is shown in FIG.
In the above, the line width of the periodic pattern was fixed to 0.12 μm and the line width of the bar pattern was changed. However, the pitch of the periodic pattern was doubled or doubled as shown in FIG. Obviously, the method of partially varying the value to be close to double will result in less linewidth linearity error.

In the method of performing one exposure using a Levenson-type phase shift mask in which adjacent bars of the same pattern as the bar pattern are inverted from each other, the line width linearity error at the center of the periodic pattern is reduced by the above-described method. The line width of the bar pattern of double exposure and the pitch of the periodic pattern are set to 2 times the line width.
Although the line width linearity error becomes almost equal to the method of making it equal to twice, the edge width of the periodic pattern and the isolated pattern become almost equal to the result of the line width linearity error of the normal exposure as shown in FIG. Also has the advantage of double exposure.

FIG. 46 is a two-dimensional image of the result of single exposure and the result of double exposure in which the isolated line is projected. The table shows the relationship between the line width change with respect to defocus when resolving with the exposure amount when the line width of the best focus is equal to the result of the mask line width in FIG. 46, and the length in the longitudinal direction as the line width of the mask. It is expressed as a ratio. 10 when equal to mask line width
0%.

The result of the double exposure is that the length in the longitudinal direction approaches the mask line width even at the best focus, the line width change with respect to defocus is small, and the depth of focus is smaller than the result of the single exposure of the bar pattern projection exposure. Is improving.

FIGS. 49 to 52 show another embodiment of the present invention.
This will be described with reference to FIG. In the present embodiment, a modified example of a mask (reticle) that forms a pattern that cannot be resolved by one exposure will be described.

In the double exposure method, in a single exposure using a normal exposure apparatus, double exposure was performed when a normal Cr film pattern shown in FIG. 49 was used for projection exposure using a pattern image that could not be resolved. It is conceivable that the exposure amount of the portion becomes excessive. In this case, the resist pattern is reduced in film thickness, or the contrast of the mask pattern image is insufficient at the time of defocusing, so that it is difficult to obtain a depth of focus. However, the following three types of patterns (1) to (3) are formed. When a mask (reticle) is used, a mask pattern image having a higher contrast than the Cr film pattern in FIG. 49 can be obtained.
The depth of focus also improves.

The halftone phase shift pattern (FIG. 5)
0) Transmittance: 2 to 10% Shifter material: Mo-based, Cr-based, other metal oxides, nitrides Dimensions: L1 to 5 are appropriately determined Phase: Phase difference between light passing through a halftone portion and other portions Is 180 °

Rim-type phase shift pattern (FIG. 51) dimension: L1 to 9 are appropriately determined Phase: The phase difference between light passing through the rim portion and other portions is 1
80 °

Chromium-less shifter light-shielding phase shift pattern (FIG. 52) This type is particularly effective for patterns having a finer line width than the above two types. In this type, in a pattern having a small line width, a phase shift effect generated at both edges of the phase shift pattern is combined to form a resist image as one line pattern. Dimensions: L1 to 5 are appropriately determined. Phase difference of light passing through other parts is 180 °

Various devices such as semiconductor chips such as ICs and LSIs, display elements such as liquid crystal panels, detection elements such as magnetic heads, and image pickup elements such as CCDs can be manufactured using the above-described exposure method and exposure apparatus.

The present invention is not limited to the embodiments described above, but can be variously modified without departing from the gist of the present invention. The number of exposures and the number of exposure steps in the exposure with the high-contrast image and the exposure with the circuit pattern image can be appropriately selected as described above. It is possible to By performing such an adjustment, variations in circuit patterns that can be formed increase.

By the double exposure method described above, the contrast of a fine pattern having a low contrast which cannot be resolved by the conventional exposure alone is improved, and the resolution can be achieved. In addition, the double exposure method is superior in line width reproducibility as compared with the single exposure of the pattern of the Levenson-type phase shift mask. In particular, the single exposure of the pattern of the Levenson-type phase shift mask is not effective for a pattern having no periodicity, and the pattern arrangement for phase inversion is limited.
It is possible to form a pattern having no periodicity or a pattern having a more complicated shape. This double exposure method is disclosed in U.S. Pat. No. 5,415,835 and JP-A-7-253649.
It is possible to form a pattern having a more complicated shape as compared with the double exposure method shown in the publication.

[0262]

As described above, according to the present invention, a more complicated pattern can be formed by the double exposure method.

[Brief description of the drawings]

FIG. 1 is a view showing a conventional projection exposure apparatus.

FIG. 2 is a view showing an example of a two-beam interference exposure apparatus for performing periodic pattern exposure.

FIG. 3 is a flowchart of the exposure method of the present invention.

FIG. 4 is an explanatory view showing a periodic pattern (exposure pattern) obtained by two-beam interference exposure.

FIG. 5 is an explanatory diagram showing exposure sensitivity characteristics of a resist.

FIG. 6 is an explanatory diagram showing pattern formation by development.

FIG. 7 is an explanatory diagram showing a periodic pattern (exposure pattern) by two-beam interference exposure.

FIG. 8 is an explanatory view showing a periodic pattern (exposure pattern) by two-beam interference exposure in the present invention.

FIG. 9 is an exposure pattern that can be formed in the first embodiment.
FIG. 4 is an explanatory diagram showing an example of a pattern (lithography pattern).

FIG. 10 is an explanatory diagram showing another example of an exposure pattern (lithography pattern) that can be formed in the first embodiment.

FIG. 11 is an explanatory diagram showing another example of an exposure pattern (lithography pattern) that can be formed in the first embodiment.

FIG. 12 is an explanatory diagram showing a gate pattern that can be formed in the second embodiment.

FIG. 13 is an explanatory diagram illustrating an embodiment showing a state of double exposure according to the second embodiment.

FIG. 14 illustrates a gate pattern.

FIG. 15 is a diagram showing a pattern forming process.

FIG. 16 is a schematic diagram illustrating an example of a projection exposure apparatus that performs periodic pattern exposure by two-beam interference.

FIG. 17 is an explanatory view showing one example of a mask and an illumination method used in the projection exposure apparatus of the present invention.

FIG. 18 is an explanatory view showing another example of a mask and an illumination method used in the projection exposure apparatus of the present invention.

FIG. 19 is a schematic view showing an example of a two-beam interference exposure apparatus of the present invention.

FIG. 20 is a schematic view showing an example of a high-resolution exposure apparatus of the present invention.

FIG. 21 is a schematic view showing another example of the high resolution exposure apparatus of the present invention.

FIG. 22 is a flowchart illustrating an exposure method according to a third embodiment of the present invention.

FIG. 23 is an explanatory diagram showing an exposure pattern obtained by pattern exposure.

FIG. 24 is an explanatory diagram showing an example of an exposure pattern (lithography pattern) that can be formed in the embodiment of the present invention.

FIG. 25 is an explanatory diagram of a phase type mask for creating various patterns and its exposure amount distribution on a wafer surface.

FIG. 26 is an explanatory view showing another example of an exposure pattern (lithography pattern) that can be formed in the embodiment of the present invention.

FIG. 27 is a view for explaining a base mask and a normal mask for gate pattern exposure and their exposure distribution on the wafer surface.

FIG. 28 is a view for explaining a double-exposure dose distribution and a resist image obtained when a gate pattern is formed according to the present invention.

FIG. 29 is a diagram for two-dimensionally explaining the embodiment of the present invention;

FIG. 30 is a diagram showing another example of forming a gate pattern on a black base.

FIG. 31 is a view for explaining an exposure dose distribution obtained by double exposure and an obtained resist image.

FIG. 32 is a diagram for two-dimensionally explaining a pattern forming process.

FIG. 33 shows a mask pattern for creating another circuit pattern.

FIG. 34 is a view for explaining an exposure amount distribution for the circuit pattern of FIG. 15;

FIG. 35 is a view showing a process of forming the circuit pattern of FIG. 15;

FIG. 36 is a diagram showing double exposure using a high-contrast periodic pattern and low-contrast one to three bar patterns, respectively.

FIG. 37 is an intensity distribution generated in a resist by exposure using three bar patterns (images), exposure using a periodic pattern (image), and double exposure using three bar patterns (images) and a periodic pattern (image). It is a figure which shows (exposure amount distribution).

FIG. 38 is a diagram showing an intensity distribution at the time of double exposure using each of one to three bar patterns (images) and a periodic pattern (image).

FIG. 39 is a diagram showing an intensity distribution when exposure with each of one to three bar patterns (images) is performed using a phase shift mask while changing the illumination condition (σ) thereto.

FIG. 40 is a graph showing defocus vs. contrast when exposure with one to three bar patterns (images) is performed at σ = 0.5 using a phase shift mask.

FIG. 41 shows double exposure using each of one to three bar patterns (images) and a periodic pattern (image), normal illumination of σ = 0.2 for a periodic turn, and σ = 0.2 for a bar pattern.
9 is a graph showing defocus vs. contrast when performed with 0.8 annular illumination.

FIG. 42 is a graph showing a line width linearity error when exposure using one to three bar patterns (images) is performed with annular illumination of σ = 0.53 to 0.8.

FIG. 43 shows double exposure using each of one to three bar patterns (images) and a periodic pattern (image); normal illumination of σ = 0.2 for a periodic turn, and σ = 0.2 for a bar pattern.
It is a graph which shows a line width linearity error at the time of performing with 0.53-0.8 annular illumination.

FIG. 44 is a diagram showing double exposure using a periodic pattern and three bar patterns having relatively large line widths.

FIG. 45 is a diagram illustrating double exposure using a periodic pattern and a plurality of types of bar patterns having different line widths.

FIG. 46 is a diagram showing two-dimensional images of a single bar pattern in a single case and in a double exposure with a periodic pattern.

FIG. 47 is a diagram showing intensity distributions when exposure is performed using a pattern (image) having zero contrast, exposure using a periodic pattern (image) having a high contrast, and double exposure composed of these exposures.

FIG. 48 is a diagram showing intensity distributions when exposure is performed using a pattern (image) having zero contrast, exposure using a periodic pattern (image) having a high contrast, and double exposure composed of these exposures.

FIG. 49 is a diagram showing a reticle having a normal chrome pattern.

FIG. 50 is a diagram showing a reticle having a halftone phase shift pattern.

FIG. 51 is a diagram showing a reticle having a rim-type phase shift pattern.

FIG. 52 is a diagram showing a reticle having a chromeless shifter light-shielding type phase shift pattern.

[Explanation of symbols]

 221 Excimer laser 222 Illumination optical system 223 Mask (reticle) 224 Mask (reticle) stage 225 2 Light flux interference mask and mask for normal projection exposure 226 Mask (reticle) changer 227 Projection optical system 228 Wafer 229 XYZ stage

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akiyoshi Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Yuichi Iwasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-7-226362 (JP, A) Proceedings of SP IE vol. 3679 page. 396-407 Proceedings of SP IE vol. 3748 page. 278-289 Proceedings of SP IE vol. 3873 page. 66-77 Japan Society of Applied Physics Silicon Technology No. 11 page. 6-11 (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 INSPEC (DIALOG) WPI (DIALOG)

Claims (18)

(57) [Claims] An exposure method for exposing a resist to a pattern , comprising: a first step of providing a first exposure amount distribution by two-beam interference exposure; and a pattern similar to the pattern.
The exposure amount is reduced to 0 by the exposure using the mask on which the pattern is formed.
And a second step of providing a second exposure amount distribution having a free but a small portion and the exposure amount is large portions, the first
A part of the exposure distribution of
Although the light intensity is not 0, the pattern
Exposure is performed on a portion of the first exposure
The second exposure dose distribution overlapping with another portion of the dose distribution.
The portion where the exposure amount is large and related to other portions of the pattern
An exposure method, wherein exposure is performed . 2. An exposure method for exposing a resist to a pattern, wherein the exposure is performed by two-beam interference exposure using a first mask in which a phase shifter and / or a light-shielding portion is arranged.
Exposing a first step the amount gives a first exposure amount distribution is not more than exposure threshold of the resist, the exposure using the second mask pattern of similar to the above pattern is formed
A part where the amount is not 0 but is below the exposure threshold value and the exposure amount
Providing a second exposure dose distribution having a portion equal to or greater than the exposure threshold value , wherein the first exposure dose distribution
And the exposure amount of the second exposure amount distribution is 0
No, but by overlapping parts below the exposure threshold
Exposure is performed on a part of the pattern, and the first
Of the second exposure distribution overlapping with another part of the exposure distribution
The other portion of the pattern at a portion equal to or more than the exposure threshold
An exposure method, wherein the exposure is performed . 3. A resist is exposed to a pattern.
In the exposure method, the first exposure is performed by periodic pattern exposure.
A first step of providing a light quantity distribution, and a pattern similar to the pattern.
Exposure using masks with turns
It has a small part that is not 0 and a part with large exposure
A second step of providing a second exposure dose distribution.
A part of the first exposure distribution and the second exposure distribution;
The exposure is not 0, but by overlapping small parts,
Exposure is performed on a portion of the turn, and the first exposure is performed.
Before the second exposure dose distribution which overlaps with other parts of the light intensity distribution
The portion where the exposure amount is large is related to other portions of the pattern.
An exposure method characterized in that an exposure is performed . 4. A resist is exposed to a pattern.
In the exposure method, a phase shifter and / or a light shielding portion are provided.
Exposure by periodic pattern exposure using the first mask
A first exposure method in which the light amount is equal to or less than the exposure threshold value of the resist;
A first step of providing a light quantity distribution, and a pattern similar to the pattern.
Exposure using the second mask in which the turns are formed
Exposure to a portion where the light amount is not 0 but is below the exposure threshold
A second exposure having an amount equal to or greater than the exposure threshold
Providing a dose distribution, wherein the first exposure dose
A part of the cloth and the exposure amount of the second exposure amount distribution is 0
No, but by overlapping the parts below the exposure threshold,
Exposure is performed on a part of the pattern, and the first
The second exposure distribution overlapping other parts of the exposure distribution
The other portion of the pattern at a portion not less than the exposure threshold
Exposure method characterized in that exposure for minutes is performed
Law. 5. The method according to claim 1 , wherein the second step is performed after the first step.
Or performing the first step after the second step
Or perform the first and second steps simultaneously
The method according to any one of claims 1 to 4, wherein
Exposure method described above. 6. The part of the pattern has a minimum line width.
5. The method according to claim 1, wherein
2. The exposure method according to claim 1. 7. The pattern is a circuit pattern.
Exposure according to any one of claims 1 to 4, characterized in that:
Method. 8. The dew according to any one of claims 1 to 7,
To form the first exposure dose distribution in the optical method
The mask to use. 9. The dew according to any one of claims 1 to 7,
To form the second exposure dose distribution in the optical method
The mask to use. 10. The method according to claim 1, wherein
An exposure apparatus that can perform an exposure method. 11. A method comprising exposing and developing a resist.
In the pattern forming method, two-beam interference exposure is used.
A first step of providing a first exposure dose distribution;
Exposure using a mask with a pattern similar to
Parts where the exposure is not 0 but small and parts where the exposure is large
A second step of providing a second exposure distribution having
Although the exposure amount in the second exposure amount distribution is not 0,
Based on a part of the first exposure distribution overlapping the small part
Forming a part of the pattern based on the first exposure
The second exposure dose distribution overlapping another portion of the dose distribution.
Other parts of the pattern based on the part with a large amount of exposure
Forming a pattern. 12. The method according to claim 11 , further comprising the steps of exposing and developing the resist.
In a method for forming a pattern, a phase shifter and / or
Is a two-beam interference exposure using the first mask with the light-shielding portions arranged.
The light exposure is below the exposure threshold of the resist.
A first step of providing a first exposure dose distribution;
Using a second mask having a pattern similar to
Although the exposure amount is not 0 due to normal exposure, the exposure threshold
The following part and the part where the exposure amount is equal to or more than the exposure threshold
Providing a second exposure dose distribution having
The exposure amount in the second exposure amount distribution is not 0,
Of the first exposure dose distribution overlapping the portion below the light threshold
Forming a portion of the pattern based on the portion;
The second dose overlapping another portion of the first dose distribution;
The pattern based on the portion of the distribution above the exposure threshold.
Pattern characterized by forming the other part of the pattern
Method. 13. A method comprising exposing and developing a resist.
In the pattern formation method, periodic pattern exposure
A first step of providing a first exposure dose distribution;
Exposure using a mask with a pattern similar to
Exposure amount is not 0 but small part and exposure amount are large
Providing a second exposure dose distribution having
The exposure amount of the second exposure amount distribution is not 0
Is part of the first exposure distribution that overlaps with the smaller part
Forming a portion of the pattern based on the first exposure
Before the second exposure dose distribution overlapping other parts of the light intensity distribution
Another part of the pattern based on the part where the exposure amount is large
Forming a pattern. 14. A method comprising exposing and developing a resist.
In a method for forming a pattern, a phase shifter and / or
Is a periodic pattern using a first mask in which light-shielding portions are arranged
When the exposure amount is below the exposure threshold value of the resist by exposure
A first step of providing a certain first exposure light amount distribution, the putter
Using a second mask on which a pattern similar to the
Although the exposure amount is not 0 due to the normal exposure, the exposure threshold
Part below the value and the part where the exposure amount is above the exposure threshold
A second step of providing a second exposure distribution having:
Although the exposure amount in the second exposure amount distribution is not 0,
The first exposure dose distribution overlapping a portion below the exposure threshold
Forming a portion of said pattern based on a portion of
The second exposure overlapping another portion of the first exposure distribution;
Based on a portion of the quantity distribution equal to or higher than the exposure threshold.
A pattern characterized by forming the other part of the turn
Forming method. 15. Performing the second step after the first step.
Or, alternatively, perform the first step after the second step
No, or the first step and the second step are performed simultaneously
15. The method according to claim 11, wherein the step is performed.
The pattern forming method according to the above item. 16. The method according to claim 16, wherein the portion of the pattern has a minimum line width.
15. A portion having:
The pattern forming method according to any one of the above. 17. The method according to claim 17, wherein the pattern is a circuit pattern.
The method according to any one of claims 11 to 14, wherein
Pattern formation method. 18. The method according to claim 11, wherein:
Manufacturing devices using the on-board patterning method
A device manufacturing method characterized by the above-mentioned.