JP2000021756A - Pattern forming method and exposure apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove an unnecessary pattern produced in a multiple exposure by performing whole surface etching and surface reforming when a pattern is formed by surface imaging. SOLUTION: A silicon wafer Wa is spin- coated with a resist RE, and for double exposures, the pattern of a reticle A is then transferred to the resist RE and the pattern of a reticle B is then transferred to the same region at the same time. The resist RE is put into contact with a silicon coupling gas over a hot plate at 120 deg.C with a surface reforming apparatus to silylate the surface of the resist. The whole surface of the resist RE is then etched away using a mixed gas of CF4 and O2 under the condition in which the etching rate of a silylated portion is equal to that of a not-silylated portion until an unnecessary portion is etched away. Next, the resist is dry-developed with O2 RIE by using the silylated portion as a mask to obtain an objective pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method and an exposure apparatus, and more particularly, to a method for exposing a photosensitive substrate with a fine circuit pattern to a semiconductor chip such as an IC or LSI.
Display elements such as liquid crystal panels, detection elements such as magnetic heads, C
It is suitable for use in the manufacture of various devices such as an image sensor such as a CD.

[0002]

2. Description of the Related Art Conventionally, when devices such as ICs, LSIs, and liquid crystal panels are manufactured using photolithography technology, circuits formed on the surface of a photomask or reticle (hereinafter, referred to as "mask"). A projection exposure method and projection in which a 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 transferred (exposed) there. An exposure apparatus is used.

In recent years, in response to the higher integration of the above devices, there has been a demand for miniaturization of a pattern to be transferred to a wafer, that is, higher resolution and larger area of one chip on the wafer. Therefore, even in the above-described projection exposure method and projection exposure apparatus that form the center of microfabrication technology for wafers,
In order to form an image (circuit pattern image) having a dimension (line width) of 0.5 / μm or less over a wide range, improvement in resolution and enlargement of an exposure area have been attempted.

FIG. 20 shows a schematic view of a conventional projection exposure apparatus. In FIG. 20, 191 is an excimer laser as a light source for far ultraviolet exposure, 192 is an illumination optical system, 193 is illumination light emitted from the illumination optical system 192, 194 is a mask,
Reference numeral 95 denotes an optical system (projection optical system) 19 which exits from the mask 194.
Reference numeral 196 denotes an object-side exposure light, reference numeral 196 denotes a reduction type projection optical system, reference numeral 197 denotes an image-side exposure light which exits from the projection optical system 196 and enters a substrate 198, reference numeral 198 denotes a wafer which is a photosensitive substrate,
Reference numeral 99 denotes a substrate stage for holding a photosensitive substrate.

[0005] The laser light emitted from the excimer laser 191 is guided to the illumination optical system 192 by the routing optical systems (190a, 190b), and the illumination optical system 192 provides a predetermined light intensity distribution, light distribution, and opening angle (Sekiguchi). The mask 19 is adjusted so as to have the illumination light 193 having several NA) or the like.
Light 4 On the mask 194, a pattern having a size obtained by reciprocally multiplying (for example, 2 times, 4 times, or 5 times) the fine pattern formed on the wafer 198 by a projection magnification of the projection optical system 196 is formed on a quartz substrate by chrome or the like. And illumination light 1
93 is transmitted and diffracted by the fine pattern of the mask 194, and becomes the object side exposure light 195. The projection optical system 196 includes:
The object-side exposure light 195 is converted into image-side exposure light 197 that forms a fine pattern of the mask 194 on the wafer 198 at the above-described projection magnification and with sufficiently small aberration. Image side exposure light 19
Reference numeral 7 converges on the wafer 198 at a predetermined numerical aperture NA (= Sin (θ)) as shown in the enlarged view at the bottom of FIG. 20, and forms an image of a fine pattern on the wafer 198. The substrate stage 199 has a plurality of different areas (shot areas: areas to be one or more chips) of the wafer 198.
When sequentially forming a fine pattern, the wafer 19 is moved stepwise along the image plane of the projection optical system.
8 with respect to the projection optical system 196.

Among the above, Kr, which is currently becoming mainstream,
Although a projection exposure apparatus using an F excimer laser as a light source has a high projection resolution, it is technically difficult to form a pattern image of, for example, 0.15 μm or less.

[0007] The projection optical system 196 has a resolution limit due to a trade-off between the optical resolution due to (exposure) wavelength and the depth of focus. The resolution R of the resolution pattern and the depth of focus DOF by the projection exposure apparatus are expressed by the following Rayleigh formulas (1) and (2).

R = k ₁ × (λ / NA) ‥‥‥ (1) DOF = k ₂ × (λ / NA ² ) ‥‥‥ (2) where λ is an exposure wavelength, and NA is a projection optical system 196. The numerical apertures k ₁ and k ₂ on the image side, which represent the brightness of the image, are constants determined by the development process characteristics of the wafer 198, resist materials, exposure conditions such as super-resolution technology, and are generally about 0.5 to 0.7. Is the value of From the equations (1) and (2), the resolution R
In order to achieve a high resolution in which the value of is reduced, there is “high NA” in which the numerical aperture NA is increased. However, 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 that it is difficult to increase the NA to a certain value or more. It is understood that "short wavelength" for reducing the wavelength λ is required.

However, as the exposure wavelength becomes shorter, a serious problem arises. It is the projection optical system 196
Is that the glass material of the lens that constitutes is lost. The transmittance of most glass materials is close to 0 in the deep ultraviolet region,
Using a special manufacturing method for exposure equipment (exposure wavelength about 248
As a glass material manufactured in (nm), there exist crystals such as fused quartz, calcium fluoride, and magnesium fluoride, and the transmittance of the fused quartz also sharply decreases for an exposure wavelength of 193 nm or less. It is very difficult to develop a practical glass material in a region having an exposure wavelength of 150 nm or less corresponding to a fine pattern having a line width of 0.15 μm or less. In addition, the glass material used in the deep ultraviolet region must satisfy various conditions such as durability, uniformity of refractive index, optical distortion, workability, etc. in addition to transmittance. Existence is at stake.

As described above, in the conventional projection exposure method and projection exposure apparatus, it is necessary to reduce the exposure wavelength to about 150 nm or less in order to form a pattern having a line width of 0.15 μm or less on a wafer. On the other hand, at present, there is no practical glass material in this wavelength region, so that a pattern having a line width of 0.15 μm or less cannot be formed on the wafer.

US Pat. No. 5,415,835 discloses a technique for forming a fine pattern by two-beam interference exposure. According to the two-beam interference exposure, a pattern having a line width of 0.15 μm or less is formed on a wafer. be able to.

The principle of two-beam interference exposure will be described with reference to FIG. In the two-beam interference exposure, a laser beam L151 having coherence from a laser 151 and being a parallel beam is converted into laser beams L151a and L151 by a half mirror 152.
The two laser light beams (coherent parallel light beams) are divided from larger than 0 to 9 by being split into two light beams of ab and reflecting the split two light beams by the plane mirrors 153a and 153b, respectively.
An interference fringe is formed at the intersection by intersecting at an angle of less than 0 degree on the surface of the wafer 154. By exposing and exposing the wafer 154 with (the light intensity distribution of) the interference fringes, a fine periodic pattern corresponding to the light intensity distribution of the interference fringes is formed on the wafer 154.

The two light beams L151a and L151b are
In the case where the wafer intersects with the perpendiculars formed on the 54 surfaces in a state inclined at the same angle in the opposite directions to each other on the wafer surface, the resolution R in the two-beam interference exposure is expressed by the following equation (3).

R = λ / (4 sin θ) = λ / 4NA = 0.25 (λ / NA) (3) where R is the width of each L & S (line and space), ie, interference fringes. The width of each of the light and dark portions is shown. Θ represents the angle of incidence (absolute value) of the two light beams with respect to each image plane, and NA = Sin θ.

Comparing equation (1), which is the equation for resolution in normal projection exposure, and equation (3), which is the equation for resolution in two-beam interference exposure, the resolution R of two-beam interference exposure is expressed by equation (1). Since this corresponds to the case where k ₁ = 0.25, 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 US patent, for example, when λ = 248 nm (KrF excimer) and NA = 0.6
In this case, R = 0.10 μm is obtained.

On the other hand, one of the methods of patterning the pattern of the latent image projected on the resist layer is DESIRE (Diffus Diffus).
There is a so-called silylation process.

[0018]

However, in a pattern forming method using a surface modification step such as a silylation process, a part of the resist surface is modified in addition to an intended pattern, and an unnecessary pattern is generated after development. Turns out there are cases.

The generation of the unnecessary pattern frequently occurs also in the multiple exposure pattern latent image of the aforementioned US Patent.

That is, in the silylation process by multiple exposure, a portion where a pattern is not finally formed in the resist device also has a weakly silylated portion, and an unnecessary pattern is formed. If dry development by O ₂ RIE is performed in this state, the weakly silylated portion becomes an etching mask, and an unnecessary pattern other than the target pattern is formed. In general, the target pattern at this time has a large exposure amount, and the unnecessary pattern has a small exposure amount, so that a difference occurs in the silylated reaction.

The present invention provides a pattern forming method and an exposure apparatus capable of effectively forming only a target pattern by effectively removing unnecessary patterns when forming a pattern by surface imaging by a silylation reaction. With the goal.

In particular, it is an object of the present invention to provide a pattern forming method and an exposure apparatus which can effectively remove unnecessary patterns which are frequently generated in multiple exposure.

[0023]

The pattern forming method of the present invention is characterized in that: (1-1) a pattern forming method for forming a pattern by surface imaging includes a whole surface etching step and a surface modification step.

(1-2) A pattern forming method for performing multiple exposure of the same region of a photosensitive substrate with different patterns to form a pattern by surface imaging includes a whole surface etching step and a surface modification step. Features.

In particular, (1-1-1) the entire surface etching step is performed under the condition of a selectivity of 1.

(1-1-2) The surface modification step is a silylation process.

(1-1-3) The pattern forming method includes a first exposing step, a second exposing step, a silylation step, and a dry developing step. To be included between the development process.

(1-1-4) The pattern forming method comprises the following steps: first exposure step → silylation step → second exposure step → silylation step →
Including a dry development step, the entire surface etching step is included between the second exposure step and the dry development step.
And so on.

The exposure apparatus of the present invention is characterized in that (2-1) the pattern on the mask is transferred to a photosensitive substrate using the pattern forming method of the constitution (1-1).

The method of manufacturing a device according to the present invention is characterized in that the device is manufactured using the pattern forming method of (3-1) Configuration (1-1).

(3-2) After the pattern on the mask surface is exposed on the wafer surface using the exposure apparatus of the configuration (2-1), the wafer is subjected to a developing process to manufacture a device. It is characterized by.

In the present invention, "multiple exposure" refers to "exposing the same area on a photosensitive substrate with different light patterns without passing through a developing process".

[0033]

FIG. 1 is a block diagram showing a main part of a pattern forming method according to the present invention. The present invention is characterized in that a process for forming a pattern by surface layer imaging includes a whole surface etching step and a surface modification step in the process steps.

In this case, a silylation process is used as a surface modification step.
Particularly, the present invention is characterized in that unnecessary patterns, which are frequently generated when a pattern image is formed by multiple exposure, are effectively removed through an entire surface etching process.

Next, the pattern forming method of FIG. 1 will be described. Although FIG. 2 shows the case of double exposure as multiple exposure, single exposure or multiple exposure of double exposure or more may be used.

In FIG. 3A, a pattern of a reticle (first mask) A for performing double exposure after spin-coating a resist RE to a thickness of 1 μm on a silicon wafer Wa is transferred onto the resist RE. Next, the pattern of the reticle (second mask) B is similarly transferred to the same region. At this time, each reticle may be sequentially aligned with an alignment mark formed in advance, or may be aligned with a latent image formed by reticle A.

Next, as shown in FIG. B, the surface of the resist is silylated by contact with a gas of HMDS (hexamethyldisilazane), which is a silicon coupling agent, on a hot plate at 120 ° C. using a surface modification apparatus. . At this time, the depth of the silylation by the silylation reaction in the resist layer differs depending on the exposure amount at the time of the previous exposure. Thereafter, as shown in FIG. (C), using a mixed gas of CF ₄ and 0 _2, under the condition that the etching rate of the portion which is not silylated as the silylated portions are equal, unnecessary silyl The entire surface is etched until there is no oxidized portion. Next, as shown in FIG. 3D, the resist is dry-developed with O ₂ RIE alone using the silylated portion as a mask to obtain a desired pattern.

In this embodiment, the steps of exposure (reticle A) → exposure (reticle B) → silylation → entire etching → dry development (O ₂ RIE) are performed.

In this embodiment, a chemically amplified resist may be used as the resist.

In the pattern forming method of the present invention,
The order of various steps may be performed as follows in addition to the first embodiment.

(A-1) First exposure step → Second exposure step → Overall etching step (O ₂ RIE) → Silylation step → O ₂ R
IE (Dry Development) Step The entire surface etching step may be performed after the silylation step.

(A-2) First Exposure Step → Second Exposure Step → Silylation Step → O ₂ RIE (Dry Development) Step The whole surface etching step is included after the second exposure or after the silylation step.

In the above embodiment, the C / D control is improved by performing time management between each process with high accuracy.

In the present embodiment, the present invention is not limited to the double exposure process, and can be similarly applied to a process of performing surface imaging on the resist layer in one exposure process.

Next, a method for forming a pattern on a photosensitive substrate by surface imaging by multiple exposure according to the present invention will be described.

In the following embodiments, the entire surface etching step and the surface modification step are not particularly described, but are patterned using the above-described steps. Also, the pattern image (by surface imaging) formed on the resist layer shows that the entire layer is patterned for simplicity.

FIGS. 2 to 10 are explanatory views of the first embodiment of the exposure method (multiple exposure) according to the present invention. FIG. 2 is a flowchart showing the exposure method according to the present invention. FIG. 2 shows a periodic pattern exposure step, a projection exposure step (normal pattern exposure step), which constitutes the exposure method according to the present invention,
Each block of the development step and its flow are shown. In the figure, the order of the periodic pattern exposure step and the projection exposure step may be reversed, and when one of the steps includes a plurality of exposure steps, each step may be performed alternately. Also, between each exposure step. Although there is a step of performing precise alignment, the illustration is omitted here.

An exposure method and an exposure apparatus according to the present invention are characterized in that double exposure of periodic pattern exposure and normal exposure is performed on a substrate to be exposed (photosensitive substrate).

Here, the normal pattern exposure is an exposure in which the resolution is lower than that of the periodic pattern exposure, but the exposure can be performed in an arbitrary pattern. As a typical example, the projection optical system shown in FIG. Exposure.

The pattern (normal pattern) exposed by the normal pattern exposure includes a fine pattern having a resolution equal to or less than the resolution, and the periodic pattern exposure forms a periodic pattern having substantially the same line width as the fine pattern. A large pattern having a resolution equal to or larger than the resolution of the normal pattern exposure is not limited to the line width of the periodic pattern exposure, but an integer multiple is effective.

Normally, the pattern exposure has an arbitrary shape and may be directed in various directions. Generally, an IC pattern has two directions, one direction and the direction perpendicular to the other.
In many cases, it is oriented in a direction, and the finest pattern is often limited to only one specific direction.

When performing periodic pattern exposure by double exposure, it is important to match the direction of the periodic pattern with the direction of the finest pattern of the normal pattern.

The exposure is performed such that the center of the peak of the periodic pattern coincides with the center of a fine pattern having a resolution lower than that of the normal pattern.

The double exposure in the present invention means a double exposure of a periodic pattern exposure and a normal pattern exposure. The periodic pattern exposure is repeated several times in parallel with the direction of the finest pattern of the normal pattern exposure. Exposure.

Each of the periodic pattern exposure and the normal pattern exposure of the exposure method and the exposure apparatus according to the present invention comprises one or a plurality of exposure steps. Different exposure dose distributions are given to the photosensitive substrate.

When exposure is performed according to the flow of FIG.
First, the wafer (photosensitive substrate) is exposed in a periodic pattern as shown in FIG. The numbers in FIG. 3 represent the exposure amounts. The hatched portions in FIG. 3A indicate the exposure amount 1 (actually arbitrary) and the white portions indicate the exposure amount 0.

When developing only such a periodic pattern after exposure, usually, the exposure threshold value E of the resist on the photosensitive substrate is used.
th is set between the exposure amounts 0 and 1 as shown in the lower graph of FIG. The upper part of FIG. 3B shows a finally obtained lithography pattern (concavo-convex pattern). Here, the exposure threshold value Eth refers to the minimum exposure amount patterned by the silylation process.
same as below.

FIG. 4 shows the relationship between the exposure amount dependency of the film thickness after development and the exposure threshold value of the resist on the photosensitive substrate in this case and the negative type resist. Each of the resists (hereinafter referred to as “negative type”) is shown. In the case of the silylation process, the exposure threshold value Eth is used in the case of the negative type, which is opposite to the process after the normal development and the process used.
In the above case, in the case of the positive type, the film thickness after development becomes 0 when the exposure threshold value Eth or less. The development here is the dry development in FIG. same as below.

FIG. 5 is a schematic diagram showing a state in which a lithography pattern is formed through the development and etching processes in the case of performing such exposure, for a negative type and a positive type.

In the present embodiment, unlike the normal exposure sensitivity setting, FIG. 6 (same as FIG. 3A) and FIG.
As shown in the figure, when the central exposure amount in the periodic pattern exposure is 1, the exposure threshold value Eth of the resist on the exposed substrate is 1
It is set larger than. When the exposure pattern (exposure amount distribution) obtained by performing only the base pattern exposure shown in FIG. 3 is developed, the exposure amount of the photosensitive substrate becomes insufficient. Does not occur, and no lithography pattern is formed by etching. This can be regarded as the disappearance of the periodic pattern. (Here, the present invention will be described using an example in which a positive type is used, but the present invention can also be implemented in a negative type.) In FIG. 7, the upper part shows a lithography pattern (what The lower graph shows the relationship between the exposure distribution and the exposure threshold. Incidentally, E ₁ according to bottom the exposure amount in the periodic pattern exposure, E ₂ represents an exposure amount in the conventional projection exposure.

The feature of the present embodiment is that a high-resolution exposure pattern that is apparently lost only by periodic pattern exposure is fused with an exposure pattern of an arbitrary shape including a pattern having a size equal to or smaller than the resolution of an exposure apparatus by ordinary projection exposure. And selectively exposing only the desired area to the exposure threshold or more of the resist,
Finally, a desired lithography pattern can be formed.

FIG. 8A shows an exposure pattern by normal projection exposure (normal pattern exposure), which is a fine pattern and cannot be resolved, and the intensity distribution on the object to be exposed is blurred and wide. . In the present embodiment, a fine pattern having a paper width of about half the resolution of normal projection exposure is used.

The projection exposure for forming the exposure pattern of FIG. 8A is performed without the development process after the periodic pattern exposure of FIG.
Assuming that the exposure is performed on the same region of the same resist, the total exposure distribution on the resist surface is as shown in the lower graph of FIG. 8B. Here, 1 is the ratio of the exposure amount E ₂ of the exposure amount E ₁ and the projection exposure of the periodic pattern exposure: 1, the exposure amount exposed threshold Eth is resist E ₁ (= 1) and the exposure amount E ₁ projection since that is set between the sum of the exposure amount E ₂ exposure (= 2), lithography pattern shown in the upper portion shown in FIG. 8 (B) is formed.

At this time, the center of the normal pattern is matched with the peak of the periodic pattern. Also, the direction of the normal pattern and the direction of the periodic pattern are matched.

The isolated line pattern shown in the upper part of FIG. 8B has the resolution of the periodic pattern exposure and has no simple periodic pattern. Therefore, a high-resolution pattern higher than the resolution that can be realized by ordinary projection exposure is obtained.

Here, suppose that the projection exposure for forming the exposure pattern shown in FIG. 9 (projection exposure with a line width twice as large as the exposure pattern in FIG. 6 and an exposure threshold or more (here, an exposure amount twice as large as the threshold)) 6) is superimposed on the same region of the same resist without the development step after the periodic pattern exposure of FIG. At this time, by making the center of the normal pattern coincide with the peak position of the periodic pattern exposure, the symmetry of the superposed pattern is good, and a good pattern image can be obtained.

The total exposure distribution of this resist is shown in FIG.
As shown in (B), the exposure pattern of the two-beam interference exposure (periodic pattern exposure) disappears, and finally only the lithography pattern by the projection exposure is formed.

As shown in FIG. 10, the same principle applies when the exposure is performed with a line width three times the exposure pattern of FIG.
In an exposure pattern having a line width of twice or more, basically, a line width of a finally obtained lithography pattern is obvious from a combination of an exposure pattern having a double line width and an exposure pattern having a triple line width, All lithography patterns that can be realized by projection exposure can be formed in this embodiment as well.

By adjusting the exposure amount distribution (absolute value and distribution) and the threshold value of the resist on the photosensitive substrate by each of the periodic pattern exposure and the projection exposure briefly described above,
The minimum line width is composed of a combination of various patterns as shown in FIG. 7, FIG. 8 (B), FIG. 9 (B), and FIG. A circuit pattern serving as a pattern can be formed.

The principles of the above-described exposure methods can be summarized as follows: (a-1) A pattern area not subjected to projection exposure (normal pattern exposure), that is, a periodic exposure pattern equal to or less than the exposure threshold of a resist disappears by development.

(A-2) Regarding the pattern area of the projection exposure performed with the exposure amount equal to or less than the exposure threshold value of the resist, the exposure pattern having the resolution of the periodic pattern exposure determined by the combination of the projection exposure and the periodic pattern exposure is used. It is formed.

(A-3) In the pattern area of the projection exposure performed with the exposure amount not less than the exposure threshold value, a fine pattern (corresponding to a mask) which is not resolved only by the projection exposure is similarly formed. It turns out that. Further, as an advantage of the exposure method, if the periodic pattern exposure having the highest resolution is performed by two-beam interference exposure, a much larger depth of focus can be obtained as compared with normal exposure.

In the above description, the order of the periodic pattern exposure and the projection exposure is the order of the periodic pattern exposure, but is not limited to this order.

Next, a second embodiment of the present invention will be described.

The present embodiment is directed to a so-called gate type pattern shown in FIG. 11 as a circuit pattern (lithography pattern) obtained by exposure.

The gate pattern in FIG. 11 has a minimum line width of 0.1 μm in the horizontal direction, that is, in the direction of AA ′ in the figure, whereas it has a minimum line width of 0.2 μm or more in the vertical direction. According to the present invention, it is possible to obtain a high resolution only in such a one-dimensional direction.
For two-dimensional patterns, two-beam interference exposure (periodic pattern exposure) may be performed only in one-dimensional directions that require such high resolution.

In this embodiment, an example of a combination of two-beam interference exposure only in one-dimensional direction and ordinary projection exposure will be described with reference to FIG.

FIG. 12A shows a periodic exposure pattern by two-beam interference exposure only in one-dimensional direction. The period of this exposure pattern is 0.2 μm, and this exposure pattern corresponds to a line width of 0.1 μmL & S pattern. Numerical values in the lower part of FIG. 12 represent exposure amounts.

As an exposure apparatus for realizing such two-beam interference exposure, an exposure apparatus having an interferometer-type demultiplexing / multiplexing optical system using a laser 151, a half mirror 152, and a plane mirror 153 as shown in FIG. , As shown in FIG.
There is a projection exposure apparatus in which a mask and an illumination method are configured as shown in FIG. 18 or FIG.

The exposure apparatus shown in FIG. 16 will be described.

In the exposure apparatus shown in FIG. 16, as described above, each of the two light beams to be multiplexed is obliquely incident on the wafer 154 at an angle θ, and the line width of the interference fringe pattern (exposure pattern) formed on the wafer 154 is as described in (3) above. It is expressed by an equation. The relationship between the angle θ and the NA on the image plane side of the demultiplexing / multiplexing optical system is NA = sin θ. The angle θ is a pair of flat mirrors 153 (153a, 15a).
3b) can be arbitrarily adjusted and set by changing each angle. If the value of the angle θ is set to be large with a pair of plane mirrors, the line width of each interference fringe pattern becomes small.
For example, when the wavelength of the two light beams is 248 nm (KrF excimer), an interference fringe pattern 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 goes without saying that higher resolution can be obtained.

Next, the exposure apparatus shown in FIGS. 17 to 19 will be described.

The exposure apparatus shown in FIG. 17 is, for example, a projection exposure apparatus using an ordinary step-and-repeat or step-and-scan type reduction projection optical system (comprising a large number of lenses), and currently has an exposure wavelength of 248 nm. On the other hand, there are those having NA of 0.6 or more.

In FIG. 17, reference numeral 161 denotes a mask; 162, object-side exposure light which emerges from the mask 161 and enters the optical system 163; 163, a projection optical system; 164, an aperture stop; 165, a wafer which emerges from the projection optical system 163; Image-side exposure light 166 incident on the wafer 166 indicates a wafer serving as a photosensitive substrate.
FIG. 9 is an explanatory diagram showing the position of a light beam on the pupil plane corresponding to the circular opening of the stop 164 by a pair of black dots. FIG. 17 is a schematic diagram showing a state in which the two-beam interference exposure is performed. Both the object-side exposure light 162 and the image-side exposure light 165 are different from the normal projection exposure in FIG. Consists only of

In order to perform two-beam interference exposure (periodic pattern exposure) in a normal projection exposure apparatus as shown in FIG. 17, the mask 161 and its illumination method may be set as shown in FIG. 18 or FIG. Hereinafter, these three examples will be described.

FIG. 18A shows a Levenson-type phase shift mask 173, in which a light-shielding portion 17 made of chrome is used.
The pitch PO of 1 is 0 in the equation (4), and the pitch POS of the phase shifter 172 is the mask of the equation (5).

P ₀ = MP = 2MR = Mλ / (2NA) ‥‥‥ (4) P _OS = 2P ₀ = Mλ / (NA) ‥‥‥ (5) where M is the projection magnification of the projection optical system 163. , Λ indicates the exposure wavelength, and NA indicates the numerical aperture of the projection optical system 163 on the image side.

On the other hand, a mask 174 shown in FIG. 18B is a shifter edge type phase shift mask made of chrome without a light-shielding portion, and is similar to the Levenson type.
The pitch POS of No. 5 is configured to satisfy the above equation (5).

In order to perform two-beam interference exposure using the phase shift masks shown in FIGS. 18A and 18B, these masks are subjected to so-called coherent illumination with σ = 0 (or a value close to 0). Specifically, as shown in FIG.
The mask 170 is irradiated with a parallel light beam from a direction perpendicular to the mask (a direction parallel to the optical axis).

Here, σ = numerical aperture of the illumination optical system / numerical aperture of the projection optical system.

When such illumination is performed, the phase difference between adjacent transmitted lights becomes π by the phase shifter 172 (175) with respect to the 0th-order transmitted diffracted light emitted from the mask 170 in the above-described vertical direction, and the 0-order transmitted diffracted lights cancel each other. The two parallel light beams of ± 1st-order transmitted diffraction light are generated symmetrically from the mask 170 with respect to the optical axis of the projection optical system 163, and the two object-side exposures 165 in FIG. I do. Also 2
The higher-order diffracted light of higher order is transmitted through the aperture stop 1 of the projection optical system 163.
Since it does not enter the aperture 64, it does not contribute to imaging.

The mask 180 shown in FIG. 19 is a mask in which the pitch PO of the light shielding portion 181 made of chrome is represented by the following equation (6) similar to the equation (4).

P ₀ = MP = 2MR = Mλ / (2NA) ‥‥‥ (6) where M is the projection magnification of the projection optical system 163, λ is the exposure wavelength, and NA is the aperture on the image side of the projection optical system 163. Indicates a number.

The mask without the phase shifter shown in FIG. 19 is subjected to oblique incidence illumination using one or two parallel light beams. In this case, the incident angle θ of the parallel light beam to the mask 180
₀ is set to satisfy Expression (7). When two parallel light fluxes are used, the mask is illuminated with parallel light fluxes inclined by θ _{0 in} opposite directions with respect to 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 a mask having no phase shifter shown in FIG. 19 is subjected to oblique incidence illumination with a parallel light beam satisfying the above equation (7), the mask 180 outputs an angle θ with respect to the optical axis.
₀ proceeds along symmetrical optical paths with respect to the optical axes of the rectilinear to 0-order transmitted diffracted light and the optical path of the 0-order transmitted diffracted light projection optical system (traveling at an angle - [theta] ₀ with respect to the optical axis) -1 order transmission Two light beams of the diffracted light are generated as two object-side exposure light beams 162 in FIG. 16, and these two light beams enter the opening of the aperture stop 164 of the projection optical system 163 to form an image.

In the present invention, such oblique incidence illumination using one or two parallel light beams is also treated as "coherent illumination".

The technique for performing two-beam interference exposure using an ordinary projection exposure apparatus has been described above. The illumination optical system of the ordinary projection exposure apparatus as shown in FIG. 20 is configured to perform partial coherent illumination. Therefore, the aperture stop (not shown) corresponding to 0 <σ <1 of the illumination optical system in FIG. It can be configured to provide coherent illumination.

Returning to the description of the second embodiment shown in FIGS. In the present embodiment, the normal projection exposure (normal pattern exposure) (for example, the apparatus shown in FIG. 20 that performs partial coherent illumination on a mask) subsequent to the two-beam interference exposure (periodic pattern exposure) described above is used in FIG. Exposure is performed on the gate pattern shown in FIG. The upper part of FIG. 12C shows the relative positional relationship with the exposure pattern by the two-beam interference exposure and the exposure amount in the area of the exposure pattern of the normal projection exposure, and the lower part of FIG. The exposure amount of the resist on the wafer is mapped vertically and horizontally with a resolution of a pitch of a minimum line width.

The exposure amount distribution shown in the lower part of FIG. 12 shows the intensity distribution for exposing the wafer with the light intensity incident from the mask as 1.

The exposure amount distribution by the exposure of the periodic pattern in FIG. 12A should ideally be a rectangular wave of 1 and 0, but uses a line width near the resolution limit of the two-beam interference exposure. Therefore, it is a sine wave formed by only the zero-order light and the first-order light. Io the maximum value of the sin wave, a minimum value represented as I _1. At this time, the values of I ₀ and I ₁ are determined by σ of the illumination condition.

The exposure amount distribution by the normal projection exposure shown in FIG. 12B shows typical values in each part. The portion of the minimum line width of the exposure pattern by this projection exposure is blurred and widened without resolution, and the value of the light intensity at each store decreases. The exposure is
Generally, the center of the pattern is denoted by b, both sides are denoted by d, and the center of the blurred image from both sides is denoted by c. The line width twice as large as the minimum line width is larger than the values of b, c, and d. However, since the line width is near the resolution limit of the projection exposure, the value of a is slightly blurred. These values of a, b, c, d change depending on the lighting conditions.

The exposure distribution shown in FIG. 12C is a result of adding the exposure amounts of the exposure pattern shown in FIG. 12A and the exposure pattern shown in FIG. 12B.

The light amount ratio in each of the two-beam interference exposure and the projection exposure differs depending on the illumination conditions of each exposure. The light amount ratio at each exposure in the addition is the illuminance ratio of the illumination system,
Two-beam interference exposure: projection exposure = 1: k, and the value of k is determined as follows.

The exposure distribution shown in FIG. 12C can be expressed by the following equation using the above-described exposure distribution and light amount ratio.

A ′ = k × a + I ₀ a ″ = k × a + I ₁ b ′ = k × b + I ₀ c ′ = k × c + I ₁ d ′ = k × d + I ₁ desired gate In order to obtain the pattern, a relational expression with the threshold value Ic of exposure of the resist is obtained, for example, when the resist is a negative type,

[0107] _{a '> I C a ">} I C b'> I C c '<I C d'<I C a ', a", b' is it is desirable difference is less, c 'and particularly b' It is desirable to have a difference with By solving these equations, the optimum light amount ratio under each illumination condition can be obtained. Particularly, the following two equations related to the fine pattern are important. When the resist is negative type, k × b + I ₀ > I _C k × c + I ₁ <I _C resist is positive type, k × b + I ₁ <I _C k × c + I ₀ > I _C resist is positive type. Although the magnitude relationship of the amount distribution is inverted and the inequality sign is inverted with respect to the resist threshold value Ic, the optimum light amount ratio is similarly obtained.

The manner in which the fine circuit pattern shown in FIG. 13 is formed by combining two different illumination methods of the two-beam interference exposure and the ordinary projection exposure described above will be described. In this embodiment, there is no developing process between the two-beam interference exposure and the normal projection exposure. Therefore, the exposure amount in the region where the exposure pattern of each exposure overlaps is added, and a new exposure pattern is generated by the added exposure amount (distribution).

FIG. 13, FIG. 14 and FIG. 15 show K at a wavelength of 248 nm.
This is a specific example using an rF excimer stepper.

As shown in FIG. 13, a gate pattern having a minimum line width of 0.12 μm is usually exposed, and a periodic pattern is overlapped with a Levenson-type phase shift mask so as to overlap the minimum line width.

The NA of the projection lens was 0.6, and the σ of the illumination system was 0.3 for exposure using a Levenson mask. At the time of normal mask exposure, σ = 0.3, 0.6, 0.8 and annular illumination.

In the case of exposing a periodic pattern by two-beam interference such as a phase shift mask, coherent illumination is σ
Is zero or a value close to it, but if it is too small, the amount of exposure per unit time will be small and the time required for exposure will be long, which is not practical.

In the case of periodic pattern exposure, σ is desirably 0.3 or less, and in exposure using a Levenson mask, the maximum σ is set to 0.3.

In normal exposure, partial coherent illumination is generally used. However, when σ is increased, reproducibility of a complicated shape is improved and depth is increased. In so-called annular illumination in which the illuminance distribution is lower on the inside than on the outside, this tendency is remarkable, but there is a disadvantage that the contrast is reduced.

As shown in FIG. 14A, the σ of the normal exposure
Is set to 0.3 which is the same as σ of the periodic pattern exposure, and the double exposure is performed under the same illumination condition, the gate pattern is defocused to 0.
Although the resolution is within the range of ± 0.2 μm, the line pattern portion is undulating, and the narrow portion causes disconnection, which is not preferable.

In the case of normal pattern exposure, σ = 0.6
It is better to do above. As shown in FIG. 14B, when σ of the normal exposure is set to 0.6, the gate pattern is resolved within the range of defocus 0 ± 0.4 μm, and the undulation of the line pattern is eliminated. Set the exposure amount ratio between normal exposure and periodic pattern exposure to normal exposure: periodic pattern exposure =
1.5: 1.

As shown in FIG. 15A, the σ of the normal exposure
When is increased to 0.8, the reproducibility of a complicated shape is slightly improved. The exposure amount ratio between normal exposure and periodic pattern exposure was set to normal pattern exposure: periodic pattern exposure = 2: 1. In the case of normal pattern exposure, the exposure amount is preferably twice or more as compared with the periodical pattern exposure.

In FIG. 15 (B), the normal exposure is the annular illumination, and the illuminance from 0.6 inside the ring to 0.8 outside the ring is 1, and
This is a two-dimensional intensity distribution in the case where the illuminance is set to 0 or less inside 0.6 of the ring. The exposure amount ratio between normal exposure and periodic pattern exposure was set to normal exposure: periodic pattern exposure = 2.5: 1.

In the annular illumination, the reproducibility of a complicated shape is improved and the depth is increased as compared with when σ is 0.8. A good image was obtained with a defocus of ± 0.4 μm or less.

The fine circuit pattern is formed by double exposure with periodic pattern exposure. Normally, the fine pattern of the exposure pattern is not normally resolved because the light intensity is low and the contrast is low. Become imaged.

On the other hand, even a large pattern having a resolution equal to or higher than the resolution of the normal exposure pattern is superimposed on the intensity of the periodic pattern exposure to enhance the contrast. According to the exposure method of the present invention, a circuit pattern having a fine line width of 0.12 μm can be formed by using a projection exposure apparatus having an illumination optical system capable of switching illumination conditions such as changing σ or a light amount ratio of illuminance. And

The optimum value of the light quantity ratio between the periodic pattern exposure and the normal pattern exposure was determined by the above-mentioned formula according to the combination of the illumination conditions.

Illumination condition 1 Periodic pattern exposure is σ = 0.
3. Normal pattern exposure: σ = 0.3 Exposure amount distribution by periodic pattern exposure shown in the lower part of FIG. 12A and exposure amount distribution by normal projection exposure shown in the lower part of FIG. ) Are shown below.

I ₀ = 0.80 I ₁ = 0.23 a = 1.31 b = 0.34 c = 0.61 d = 0.09 k = 1.0 Optimum, a '= 2.11 a "= 1.54 b' = 1.21 c '= 0.89 d' = 0.32. For the later comparison, the maximum value a 'is normalized by 1 as follows.

A '= 1.0 a "= 0.73 b' = 0.57 c '= 0.42
d '= 0.15 I ₀ = 0.38 Illumination condition 2 σ = 0.3 for periodic pattern exposure, σ = 0.6 I ₀ = 0.80 I ₁ = 0.23 a = 1.25 b = 0.44 c = 0.53 d = 0.13 k = 1.5 for normal pattern exposure Is optimal, and a '= 2.68 a "= 2.11 b' = 1.46 c '= 1.03 d' = 0.43. For later comparison, when the maximum value a 'is normalized by 1, the following is obtained. .

A '= 1.0 a "= 0.79 b' = 0.55 c '= 0.38
d '= 0.16 I ₀ = 0.30 Illumination condition 3 σ = 0.3 for periodic pattern exposure, σ = 0.8 for normal pattern exposure I ₀ = 0.80 I ₁ = 0.23 a = 1.20 b = 0.48 c = 0.47 d = 0.16 k = 2.0 is optimal, and a '= 3.20 a "= 2.63 b' = 1.76 c '= 1.17 d' = 0.55. Normalizing the maximum value a 'to 1 gives the following.

A '= 1.0 a "= 0.82 b' = 0.55 c '= 0.37
d '= 0.17 I ₀ = 0.25 Illumination condition 4 Periodic pattern exposure is σ = 0.3, normal pattern exposure is σ = 0.8, annular illumination, inner (inner zone) σ
Illuminance distribution of 0.6 or less was set to zero.

I ₀ = 0.80 I ₁ = 0.23 a = 1.10 b = 0.47 c = 0.36 d = 0.19 k = 2.5 It is optimal when a = 3.55 a ″ = 2.98 b ′ = 1.98 c ′ = 1.13 d ′ = 0.71 and the maximum value a ′ is normalized by 1 as follows.

A '= 1.0 a "= 0.84 b' = 0.56 c '= 0.32
d '= 0.20 I ₀ = 0.23 In the discussion so far, the resist threshold value was 1.5 when the maximum exposure amount was 3, so if normalized with the maximum exposure amount, the resist threshold value would be 0.5. Looking at this normalized exposure distribution, a ', a ", b' are normalized resist threshold values of 0.
It is larger than 5 and c ', d', I ₀ is smaller than the threshold.

Since a portion where the exposure amount is larger than the resist threshold value by the development is exposed, only the exposure amount a ′, a ″, and b ′ remains as a pattern after the development, so that FIG.
The part shown in gray below is the shape after development.

In general, when exposing a normal exposure pattern, an exposure amount that is about twice as large as that for exposing a periodic pattern is appropriate.
There is an optimum exposure amount ratio depending on a combination of illumination conditions when exposing the periodic pattern, and it can be obtained by the above-described formula.

As a result of calculating various combinations of the illumination conditions from the above-mentioned formula, the following was shown. When σ = 0.3 at the time of periodic pattern exposure and the illumination condition σ of the normal pattern exposure is smaller than 0.8, the exposure amount at the time of exposing the normal pattern is set to be twice or less than the exposure amount at the time of exposing the periodic pattern. Good.

In the case of a periodic pattern, when σ = 0.3 and the illumination condition for exposing the normal pattern is ring illumination, when the width of the ring is small, the exposure amount for exposing the normal pattern is equal to the periodic pattern. It is preferable that the exposure amount is twice or more than the exposure amount at the time of exposure.

Illumination condition σ when exposing periodic pattern
Is smaller than 0.3, the exposure amount for exposing the normal pattern should be at least twice the exposure amount for exposing the periodic pattern.

FIG. 21 is a schematic view showing an example of an exposure apparatus for two-beam interference exposure according to the present invention.
Reference numeral 201 denotes an optical system for two-beam interference exposure.
This is the same as the optical system No. 6. 202 is a KrF or ArF excimer laser, 203 is a half mirror, 204 (20
4a, 204b) are plane mirrors, 205 is an optical system 201
Observing the two-beam interference alignment mark on the wafer 206 with an off-axis type alignment optical system in which the positional relationship with the position can be fixed or appropriately detected as a baseline (amount).
The position is detected. 206 is a wafer which is a photosensitive substrate,
Reference numeral 207 denotes a plane orthogonal to the optical axis of the optical system 201 and an XYZ stage movable in the optical axis direction. The position of the XYZ stage is accurately controlled using a laser interferometer or the like. Since the configurations and functions of the device 205 and the XYZ stage 207 are well known, a detailed description is omitted.

FIG. 22 is a schematic view showing a high-resolution exposure apparatus comprising the two-beam interference exposure apparatus of the present invention and a normal projection exposure apparatus.

In FIG. 22, reference numeral 212 denotes a two-beam interference exposure apparatus including the optical system 201 and the apparatus 205 shown in FIG. 20, and 213, an illumination optical system (not shown), a reticle positioning optical system 214, and a wafer positioning optical system. (Off-axis positioning optical system) A projection optical system 216 for reducing and projecting the circuit pattern of the mask 217 and the mask 215 onto the wafer 218.
This is a normal projection exposure apparatus including:

The reticle positioning optical system 214 observes the positioning mark on the mask 215 and detects the position. The wafer alignment optical system 217 observes an alignment mark for projection exposure or dual light beam interference on the wafer 206 and detects its position. Optical systems 214 and 21
6, 217, the configuration and function of which are well-known, and thus a detailed description is omitted.

Reference numeral 219 in FIG. 22 denotes a two-beam interference exposure apparatus 2
12 is one XYZ stage shared by the projection exposure apparatus 213, and this stage 219
A plane orthogonal to each of the optical axes 13 and in the optical axis direction can be moved, and its position in the XY directions can be accurately controlled using a laser interferometer or the like.

Stage 219 holding wafer 218
22 is sent to the position (1) in FIG. 22, the position is accurately measured, and based on the measurement result, the light is sent to the exposure position of the device 212 indicated by the position (2), and the two-beam interference exposure is performed on the wafer 218. The device 213 is then fed into position (3) and its position is accurately measured and indicated by position (4).
And the wafer 218 is subjected to projection exposure.

In the apparatus 213, instead of the off-axis alignment optical system 217, a TTL alignment optical system (not shown) for observing the alignment mark on the wafer 218 via the projection optical system 216 and detecting the position is detected. System and
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 (reticle) 215 and detecting the position can also be used.

FIG. 23 is a schematic view showing a high-resolution exposure apparatus according to the present invention which can perform both two-beam interference exposure and normal projection exposure.

In FIG. 23, 221 is KrF or Ar
F excimer laser, 222 is an illumination optical system, 223 is a mask (reticle), 224 is a mask stage, 227 is a projection optical system for reducing and projecting the circuit pattern of the mask 223 onto the wafer 228, and 225 is a mask (reticle) changer. To selectively supply the stage 224 with a normal reticle and one of the aforementioned Levenson phase shift mask (reticle), edge shifter type mask (reticle), or periodic pattern mask (reticle) having no phase shifter. It is provided.

The mask stage has a function of rotating the mask based on information previously drawn on a bar code or the like in order to make the direction of the fine pattern parallel to the direction of the periodic pattern. .

In FIG. 23, reference numeral 229 denotes one XYZ stage shared by the two-beam interference exposure and the projection exposure. This stage 229 is movable in a plane perpendicular to the optical axis of the optical system 227 and in the optical axis direction. The position in the XY directions is accurately controlled using a laser interferometer or the like.

The apparatus shown in FIG. 23 includes a reticle positioning optical system (not shown) and a wafer positioning optical system (off-axis positioning optical system, TTL positioning optical system, and TTR positioning optical system described with reference to FIG. 22). And

The illumination optical system 222 of the exposure apparatus shown in FIG. 23 is configured so as to be able to switch between partially coherent illumination and coherent illumination. In the case of coherent illumination, the above-mentioned (1a) shown in FIG. (1b)
Is supplied to one of the above-mentioned Levenson-type phase shift reticles or edge shifter-type reticles or one of the periodic pattern reticles having no phase shifter, and in the case of partial coherent illumination, is illustrated in block 230 (2a). ) Is supplied to a desired reticle. Switching from partially coherent lighting to coherent lighting
The aperture stop usually placed immediately after the fly-eye lens of the optical system 222 may be replaced with a coherent illumination stop whose aperture diameter is sufficiently smaller than this stop.

The exposure method and exposure apparatus of the present invention
When the second exposure is a projection exposure, the exposure wavelength of the first exposure and the second exposure in the double exposure is 400 nm or less, and preferably 250 nm or less. 250n
In order to obtain light having an exposure wavelength of less than m, a KJrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 nm) is used.
nm).

In the present invention, “projection exposure” is performed by exposing three or more parallel light beams from an arbitrary pattern formed on a mask to an image plane at various angles different from each other. Things.

The exposure apparatus of the present invention has a projection optical system for projecting a mask pattern onto a wafer, and a mask illumination optical system capable of performing both partial coherent illumination and coherent illumination. By performing normal exposure and performing two-beam interference exposure by coherent illumination, it is characterized by periodic pattern exposure.
“Partial coherent illumination” is illumination in which the value of σ = (numerical aperture of the illumination optical system / numerical aperture of the projection optical system) is greater than zero and less than 1, and “coherent illumination” means that the value of σ is zero. Or a value close thereto, which is considerably smaller than σ of the partially coherent illumination.

In coherent illumination in periodic pattern exposure, σ is set to 0.3 or less. Partial coherent illumination during normal exposure makes σ 0.6 or more. σ = 0.8 is desirable. Furthermore, it is still more effective to use annular illumination in which the illuminance distribution is lower on the inside than on the outside.

The exposure wavelength of this exposure apparatus is 400 nm or less, preferably 250 nm or less. 250n
In order to obtain light having an exposure wavelength of less than m, a KrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 n) is used.
m).

In the embodiments of the present invention, an optical system capable of switching between partially coherent illumination and coherent illumination is disclosed as a mask illumination optical system.

The exposure apparatus of the present invention has a two-beam interference exposure apparatus and a moving stage for holding a substrate to be exposed (photosensitive substrate) which is commonly used by both apparatuses.

The exposure wavelength of this exposure apparatus is also 400 nm or less, preferably 250 nm or less. 250n
In order to obtain light having an exposure wavelength of less than m, a KrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 n) is used.
m).

Using the above-described exposure method and exposure apparatus, 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. .

The present invention is not limited to the embodiments 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 each step of the two-beam interference exposure and the normal exposure can be appropriately selected, and the exposure can be appropriately adjusted such that the exposure is superimposed and shifted. By performing such an adjustment, variations in circuit patterns that can be formed increase.

In the present invention, (a) as the illumination method of the illumination optical system, it is applicable to illuminate the mask pattern with light from a KrF excimer laser, an ArF excimer laser or an F2 excimer laser.

(B) In an exposure apparatus, a refracting system and a reflecting system
It is applicable to project the mask pattern by a projection optical system composed of either a refraction system or a reflection system.

(C) As the exposure apparatus, a step-and-repeat type reduction projection exposure apparatus having the exposure method of the present invention as an exposure mode, a step-and-scan type reduction projection exposure apparatus having the exposure method of the present invention as an exposure mode, and the like are applied. It is possible.

In each of the above embodiments, the present invention is not limited to the periodic pattern, but may be a pattern having no periodicity.

Next, an embodiment of a method for manufacturing a semiconductor device using the above-described projection exposure apparatus will be described.

FIG. 24 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).

In step 1 (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer.

The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like.

In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 25 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface.

In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of the present embodiment, it is possible to easily manufacture a highly integrated semiconductor device which has conventionally been difficult to manufacture.

[0172]

As described above, according to the present invention, it is possible to effectively form only a target pattern by effectively removing unnecessary patterns when forming a pattern by surface imaging by a silylation reaction. A pattern forming method and an exposure apparatus that can be achieved.

(A-2) It is possible to achieve a pattern forming method and an exposure apparatus capable of effectively removing unnecessary patterns that are frequently generated in multiple exposure.

[Brief description of the drawings]

FIG. 1 is a main block diagram of a pattern forming method of the present invention.

FIG. 2 is a flowchart of an exposure method according to the present invention.

FIG. 3 is an explanatory view showing an exposure pattern by two-beam interference exposure.

FIG. 4 is an explanatory diagram showing exposure sensitivity characteristics of a resist.

FIG. 5 is an explanatory view showing pattern formation by development.

FIG. 6 is an explanatory view showing an exposure pattern by ordinary two-beam interference exposure.

FIG. 7 is an explanatory view showing an exposure pattern by two-beam interference exposure in the present invention.

FIG. 8 is an explanatory view showing an example of an exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 9 is an explanatory view showing another example of an exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

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

FIG. 11 is an explanatory view showing a gate pattern according to the second embodiment of the present invention.

FIG. 12 is an explanatory diagram showing Embodiment 2 of the present invention.

FIG. 13 illustrates a gate pattern.

FIG. 14 is an explanatory diagram of a formed gate pattern.

FIG. 15 is an explanatory diagram of a formed gate pattern.

FIG. 16 is a schematic view showing an example of a conventional two-beam interference exposure apparatus.

FIG. 17 is a schematic diagram illustrating an example of a projection exposure apparatus that performs two-beam interference exposure.

18 is an explanatory view showing an example of a mask and an illumination method used in the apparatus shown in FIG.

FIG. 19 is an explanatory view showing another example of a mask and an illumination method used in the apparatus of FIG. 17;

FIG. 20 is a schematic view showing a conventional projection exposure apparatus.

FIG. 21 is a schematic view showing an example of a two-beam interference exposure apparatus according to the present invention.

FIG. 22 is a schematic view showing an example of a high-resolution exposure apparatus of the present invention.

FIG. 23 is a schematic view showing an example of a high-resolution exposure apparatus of the present invention.

FIG. 24 is a flowchart of a device manufacturing method of the present invention.

FIG. 25 is a flowchart of a device manufacturing method of the present invention.

[Explanation of symbols]

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

Claims (9)

[Claims] 1. A pattern forming method for forming a pattern by surface imaging, comprising a whole surface etching step and a surface modification step. 2. A pattern forming method for performing multiple exposure of the same region of a photosensitive substrate with different patterns and forming a pattern by surface layer imaging, comprising a whole surface etching step and a surface modification step. Pattern formation method. 3. The pattern forming method according to claim 1, wherein the entire surface etching step is performed under a condition of a selectivity of 1. 4. The pattern forming method according to claim 1, wherein the surface modification step is a silylation process. 5. The pattern forming method includes a first exposure step, a second exposure step, a silylation step, and a dry development step, wherein the entire surface etching step is performed between the second exposure step and the dry development step. Claim 2, characterized in that
The pattern forming method of 3 or 4. 6. The pattern forming method includes a first exposure step, a silylation step, a second exposure step, a silylation step, and a dry development step, wherein the entire surface etching step includes the second exposure step and the dry development step. The pattern forming method according to claim 2, 3 or 4, wherein the method is included between the steps. 7. An exposure apparatus, wherein a pattern on a mask is transferred to a photosensitive substrate by using the pattern forming method according to claim 1. Description: 8. A device manufacturing method, wherein a device is manufactured using the pattern forming method according to claim 1. 9. A device according to claim 7, wherein after the pattern on the mask surface is exposed on the wafer surface using the exposure apparatus according to claim 7, the wafer is subjected to a developing process to produce a device. Production method.