JPH052260A - Exposing method, photomask used for the same, and manufacture of semiconductor integrated circuit device using the same - Google Patents

Abstract

PURPOSE:To facilitate the designing of a pattern by superposing a diffracted projection image due to the phase difference of light transmitted through the light transmission area of a 1st photomask and a projection image of light of a 2nd photomask on a sample, one over the other. CONSTITUTION:The light L emitted by a light source 2 is expanded by a beam expander 4 and refracted by a mirror 5, and then split by a half-mirror 9 into two light beams L1 and L2. One light beam L1 travels straight as it is and is made incident on the 1st photomask M1 and the other light beam L2 is refracted by a mirror 6 and then made incident on the 2nd photomask M2. The light L1 passed through the 1st photomask M1 is passed through a lens 10, refracted by a mirror 7, and made incident on the surface of the sample 3 through an objective 12. The light L2, on the other hand, is passed through a lens 11 and then refracted by a mirror 8, and further made into a spot light beam through an objective 13; and the light beam is made incident on the surface of the sample 3 where the light L1 is made incident and their projection images are put on one over the other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure technique, for example, a technique effectively applied to transfer of an integrated circuit pattern using a photomask in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art As the miniaturization of semiconductor integrated circuits progresses and the design rules of circuit elements and wiring are on the order of submicrons, light such as i-line (wavelength 365 nm) is used to form integrated circuit patterns on a photomask. In the photolithography process of transferring onto a semiconductor wafer, the reduction of pattern accuracy becomes a serious problem.

That is, when a pattern consisting of a pair of light transmitting regions P _{1 and} P ₂ and a light shielding region N on a photomask (M) as shown in FIG. 37 is transferred onto a wafer, the light emitted from a light source is emitted. 38 are in phase with each other, the phases of the two lights immediately after passing through the light transmitting regions P _{1 and} P ₂ are in phase with each other, as shown in FIG.

Therefore, as shown in FIG. 39, these two lights interfere with each other to strengthen each other at a portion which originally becomes a light-shielded area on the wafer, and as shown in FIG. 40, a projected image of the above pattern on the wafer is formed. As a result of a decrease in contrast and a decrease in the depth of focus, when the pattern size is on the order of submicrons, which is approximately equal to the wavelength of the light source, the transfer accuracy will be significantly reduced.

As a means for improving such a problem, attention has been paid to a phase shift technique for preventing the deterioration of the contrast of a projected image by reversing the phase of light passing through a photomask.

For example, in Japanese Examined Patent Publication No. 62-59296, a transparent film (phase shifter) is formed on one of a pair of light transmitting regions sandwiching a light shielding region on a photomask, and a transparent film (phase shifter) is transmitted through the pair of light transmitting regions. A phase shift technique has been disclosed in which the intensities of interference lights of two lights are weakened in a portion that originally serves as a light shielding region on a wafer by making the phases of two lights opposite to each other.

In the above phase shift technique, a pair of light transmitting regions P on the photomask (M) as shown in FIG.
_When a pattern composed of _1, P ₂ and a light shielding area N is transferred onto the wafer, a phase shifter 15 composed of a transparent film having a predetermined refractive index is formed on either _{one of the} light transmitting areas P _{1 and} P ₂ to The film thickness of the phase shifter 15 is adjusted so that the phases of the two lights immediately after passing through the transmission regions P _{1 and} P ₂ are opposite to each other (see FIG. 42).

By doing so, the two lights interfere with each other in the light shielding region N and weaken on the wafer (see FIG. 43), so that the contrast of the projected image of the pattern is improved (see FIG. 44). As a result of improving the resolution and the depth of focus, the transfer accuracy of a fine pattern is improved.

Further, in Japanese Patent Laid-Open No. 62-67514, a second minute light transmitting area is provided around a first light transmitting area on a photomask, and either one of these light transmitting areas is provided. A phase shifter that prevents the amplitude of the light transmitted through the first light transmission region from spreading in the lateral direction by forming a phase shifter on the two and making the phases of the light transmitted through the two light transmission regions opposite to each other. The technology is disclosed.

Further, in Japanese Patent Laid-Open No. 2-140743, a phase shifter is formed in a part of a light transmitting region, and the phases of two lights transmitted through a portion having the phase shifter and a portion not having the phase shifter are opposite to each other. There is disclosed a phase shift technique for emphasizing the boundary portion of the phase shifter by setting the phase.

[0011]

However, in an actual photomask, various integrated circuit patterns are arranged in a complicated manner. Therefore, when the above-mentioned phase shift technique is applied to the actual photomask, the phase shifter is changed. There is a problem in that it is extremely difficult to select a place to arrange the pattern, and it takes a lot of time and labor to design the pattern of the photomask.

Therefore, an object of the present invention is to provide a phase shift technique capable of easily designing a photomask pattern.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0014]

[Means for Solving the Problems]

(1) The exposure method of the present invention, when the predetermined pattern formed on the photomask is transferred to the sample, the pattern is superposed on the first photomask provided with a phase shifter in a part of the light transmission region. Of the second photomask separately formed, the diffraction projection image by the phase difference of the light transmitted through the light transmission region of the first photomask and the projection image of the light transmitted through the light transmission region of the second photomask And are superposed on the sample.

(2) In the exposure method of the present invention, when the predetermined pattern formed on the photomask is transferred to the sample, the pattern is formed into a first pattern region in which a phase shifter is provided in a part of the light transmission region. Formed separately for the second pattern area for superposition, and the diffraction projection image due to the phase difference of the light transmitted through the light transmission area of the first pattern area and the light transmitted through the light transmission area of the second pattern area. And the projected image of is superimposed on the sample.

[0016]

[Action]

(1) According to the means described above, one pattern is divided into two photomasks, and the phase shifter is arranged on one of the photomasks. Therefore, it becomes easy to select the place where the phase shifter is arranged, and the phase shift photomask can be selected. It is possible to significantly reduce the time and labor required for the mask pattern design.

(2) According to the above means, one pattern is divided into two pattern areas of the same photomask,
Since the phase shifter is arranged in one of the pattern regions, the place where the phase shifter is arranged can be easily selected, and the time and labor required for pattern design of the phase shift photomask can be significantly reduced.

[0018]

Embodiment 1 FIG. 1 shows an optical system of an exposure apparatus 1 used in this embodiment. On the optical path connecting the light source 2 and the sample 3, the beam expander 4, the mirrors 5, 6, 7, and 8, the half mirror (or beam splitter) 9, the lens 1
0, 11 and objective lenses 12, 13 are arranged, and the alignment system includes a pair of photomasks M ₁ , M ₂
Is positioned.

The light source 2 is, for example, i-line (wavelength 365 nm)
Is a high-pressure mercury lamp that emits light L such as
Is a semiconductor wafer made of, for example, a silicon single crystal. A photoresist that is sensitive to the light L is spin-coated on the surface of this wafer.

The pair of photomasks M ₁ and M ₂ are reticles on which a predetermined integrated circuit pattern is transferred onto a wafer, for example, an original image of the integrated circuit pattern having a size five times the actual size is formed. The integrated circuit pattern is formed is divided into two photomask M _1, M _2, by superposing the respective patterns of the photomask M _1, M _2,
The original pattern is transferred onto the wafer.

Light L emitted from the light source 2 of the exposure apparatus 1
Is expanded by the beam expander 4 and the mirror 5
After being refracted by the half mirror 9, it is split into two lights L _{1 and} L ₂ by the half mirror 9. After that, one of the two lights L _{1 and} L ₂ (L ₁ ) goes straight on and goes straight to the first photomask M.
_The light enters the first photomask ₁ , and the other (L ₂ ) enters the _second photomask M ₂ after being refracted by the mirror 6.

In order to prevent the interference of the two lights L _{1 and} L _2, an incoherent converter (not shown) may be inserted on the optical axis of the light L ₂ . Further, transparent glass may be inserted so that the optical path difference between the two lights L _{1 and} L ₂ is equal to or longer than the coherence length.

The light L ₁ that has passed through the first of a photo-mask M ₁
After passing through the lens 10, the light is refracted by the mirror 7 and further becomes a spot light beam by the objective lens 12 and is incident on the surface of the sample 3 positioned on the XY table 14. Further, the light L ₂ transmitted through the second photomask M ₂ is transmitted through the lens 11 and then refracted by the mirror 8, and further becomes a spot light beam by the objective lens 13, so that the light L _{1 on} the surface of the sample 3 is changed. It is incident on the incident point.

As described above, the exposure apparatus 1 of this embodiment splits the light L emitted from the light source 2 into two lights L _{1 and} L ₂ ,
After one light L ₁ is incident on the first photomask M ₁ and the other light L ₂ is incident on the _second photomask M ₂ , two transmitted lights L _{1 and} L ₂ are incident on the sample 3. It is incident on the same place simultaneously.

Instead of the above means, it is also possible to perform exposure with the photomask M ₁ using a conventional exposure apparatus, and then perform overexposure with another photomask M ₂ . However, in this case, since it takes time to replace the photomasks M ₁ and M ₂ , the throughput of the exposure process is reduced.

FIG. 2 is a sectional view of the main part of the _first photomask M ₁ , and FIG. 3 is a plan view of the same. The main surface of the photomask M ₁ for example in which the refractive index is from about 1.47 transparent synthetic quartz glass, is surrounded by the light blocking regions N _1, for example, a rectangular light transmission region P ₁ is formed . The light shielding area N ₁ is made of a metal thin film such as Cr.

In order to form the light-transmitting region P ₁ and the light-shielding region N ₁ , an electron beam resist is spin-coated on the main surface of a glass substrate (mask blanks) on which a Cr thin film is deposited by sputtering, for example. Then, the glass substrate is irradiated with an electron beam by using an electron beam drawing apparatus.

The electron beam drawing apparatus scans an electron beam by computer control based on pattern data such as graphic information and position coordinates of an integrated circuit pattern. After that, the exposed portion of the electron beam resist is removed with a developing solution,
After etching the exposed Cr film, the remaining electron beam resist is removed to complete the photomask M ₁ .

A part of the light transmitting region P ₁ of the first photomask M ₁ is, for example, spin on glass.
A phase shifter 15 made of a transparent thin film such as ss) is provided. The phase shifter 15, the area occupied in the interior of the light transmission region P ₁ is set to be approximately half of the area of the entire light transmission region P _1. Accordingly, the light L ₁ which passes through the light transmission region P ₁ is the amount of light transmitted through the free portion of light quantity and the phase shifter 15 that transmits the portion having the phase shifter 15 is substantially equal.

In order to invert the phases of the two lights transmitted through the part with the phase shifter 15 and the part without the phase shifter 15, the wavelength of the light is λ, the refractive index of the phase shifter 15 is n, and the film thickness of the phase shifter 15 is set. (D) may be set so as to satisfy the relationship of an integral multiple of d = λ / 2 (n-1). For example, assuming that the wavelength of light is 365 nm (i-line) and the refractive index of the spin-on glass that constitutes the phase shifter 15 is 1.5, the phase shifter 1
The film thickness of 5 may be 365 nm or an integral multiple thereof.

In order to form the phase shifter 15 in a part of the light transmitting region P ₁ , spin-on glass is spin-coated on the entire surface of the photomask M ₁ and baked, and then only a necessary portion is formed by using a lithography technique. You can leave it.

FIG. 4 is a sectional view of an essential part of the _second photomask M ₂ , and FIG. 5 is a plan view of the same. The photomask M ₂ is made from a first photomask M ₁ and the same material, in its main surface, the light shielding region N ₂ is formed which is surrounded by the light transmission region P _2. The light shielding region N ₂ has substantially the same shape and size as the light transmitting region P _{1 of} the first photomask M ₁ .

As shown in FIG. 6, the light L ₁ immediately after passing through the light transmitting region P ₁ of the first photomask M ₁ and the phase of the light transmitted through the portion where the phase shifter 15 exists and the phase shifter 15 The phases of the light transmitted through the non-existing portions are opposite to each other.

Therefore, on the sample 3, the two lights interfere with each other at their boundaries and weaken each other, and a diffraction projection image (D) having a pattern as shown in FIG. 7 is obtained. This diffraction projection image (D) becomes an image of an extremely fine line with good contrast when the phases of the light L emitted from the light source 2 are aligned.

On the other hand, the light L ₂ immediately after passing through the periphery of the light shielding region N ₂ the second photomask M _2, since the amplitude as shown in FIG. 8, on the sample 3, FIG. 9 A projected image of the pattern as shown is obtained.

Therefore, when the diffraction projection image (D) of the first photomask M ₁ and the central portion of the projection image of the second photomask are overlapped with each other, as shown in FIG. A projected image of an extremely fine line as shown is formed. That is, according to the exposure method of the present embodiment, an extremely fine pattern can be transferred onto the sample 3, so that the integrated circuit pattern can be remarkably miniaturized.

Moreover, according to the exposure method of this embodiment, when a predetermined pattern is transferred to the sample, the pattern is formed by dividing it into _two photomasks M ₁ and M ₂ , and one photomask M ₁ is formed. Since the phase shifter 15 is arranged only, the place where the phase shifter 15 is arranged is easier to select as compared with the conventional phase shift technique of forming the phase shifter on one photomask, and the time required for the pattern design of the photomask is increased. And labor can be significantly reduced.

In the first photomask M ₁ , a phase shifter 15 is formed by depositing a transparent thin film such as spin-on glass on a part of the light transmission region P ₁ as shown in FIG. Alternatively, a part of the light transmitting region P ₁ may be processed by etching to form a groove, which can be used as the phase shifter 15. In this case, the refractive index of the synthetic quartz glass constituting the photomask M ₁ is n and the wavelength of light is λ,
The depth of the groove may be λ / 2 (n-1) or an integral multiple thereof.

[0039]

[Embodiment 2] Next, another embodiment of the photomask used in the exposure method of the present invention will be described with reference to FIGS.

FIG. 12 is a sectional view of the main part of the _first photomask M ₁ , and FIG. 13 is a plan view of the same. On the main surface of the photomask M _1, is surrounded by the light blocking regions N _1, for example, a rectangular light transmission region P ₁ is formed, in a part of the light transmission region P ₁ is, for example, spin-on A phase shifter 15 made of glass is provided.

In the first photomask M ₁ , the area ratio of the phase shifter 15 occupying the inside of the light transmitting region P ₁ is smaller than that of the photomask M ₁ of the above embodiment,
Therefore, the amount of light transmitted through the portion where the phase shifter 15 is present is
It is less than the amount of light that passes through a portion where the phase shifter 15 is absent.

FIG. 14 is a sectional view of the main part of the _second photomask M ₂ , and FIG. 15 is a plan view of the same. _On the main surface of the second photomask M ₂ , a light shielding region N ₂ surrounded by light transmitting regions P _{2 on} three sides is formed.

The light L ₁ immediately after passing through the light transmission region P ₁ of the first photomask M _1, as shown in FIG. 16,
Since the phase of the light transmitted through the portion with the phase shifter 15 and the phase of the light transmitted through the portion without the phase shifter 15 are opposite to each other, the two lights on the sample 3 are separated from each other at their boundaries. Interfering with each other and weakening each other, a diffraction projection image (D) having a pattern as shown in FIG. 17 is obtained. This diffraction projection image (D) becomes an image of an extremely fine line with good contrast when the phases of the light L emitted from the light source 2 are aligned, as in the case of the above-described embodiment.

On the other hand, the light L ₂ immediately after passing through the periphery of the light shielding region N ₂ the second photomask M _2, since the amplitude as shown in FIG. 18, on the sample 3, FIG. 19 A projected image of the pattern as shown is obtained.

Therefore, when the diffraction projection image (D) of the first photomask M ₁ and the end portion of the projection image of the _second photomask M ₂ are superposed, the figure 3 As shown in 20, a projected image with improved contrast at the end of the light shielding region N ₂ of the second photomask M ₂ is formed.

As described above, according to the exposure method of this embodiment, it is possible to improve the contrast of the end portion of the pattern transferred onto the sample 3.

[0047]

[Embodiment 3] In the exposure method of the present invention, when transferring a U-shaped pattern in which two parallel lines are connected at one end thereof onto a sample 3 as shown in FIG. The first photomask M ₁ shown in FIG. 22 and the second photomask M ₂ shown in FIG. 23 are separately formed.

That is, in the first photomask M ₁ ,
Two light transmitting areas P ₁ and P surrounded by a light shielding area N _1.
1 is formed, and the phase shifter 15 made of, for example, spin-on glass is formed in one of the light transmission regions P ₁ . The pair of light transmitting regions P ₁ and P ₁ correspond to the two parallel lines shown in FIG.

[0049] On the other hand, the second photomask M _2, to form a light transmission region P ₂ ambient is surrounded by the light shielding area N _2.
The light transmitting area P ₂ corresponds to the connecting portion of the two parallel lines shown in FIG.

[0050] As shown in FIGS. 24 and 25, the light L ₁ immediately after passing through the light transmission region P ₁ of the first photomask M ₁ is transmitted through the light transmission region P ₁ having the phase shifter 15 Light transmission area P ₁ without light phase and phase shifter 15
Since the phase of the light transmitted through is opposite to each other,
In the above, the two lights interfere with each other at their boundaries and weaken each other, so that a projected image having a pattern as shown in FIG. 26 is obtained.

On the other hand, the second photomask M shown in FIG.
Light L ₂ immediately after transmitting a _second light transmissive area P ₂ is 28
Since the amplitude is as shown in, a projected image of the pattern as shown in FIG. 29 is obtained on the sample 3.

Therefore, when the projected image of the _first photomask M _{1 and} the projected image of the second photomask M ₂ are superposed on each other, as shown in FIG. A projected image is formed in which the contrast of the connection portion of the parallel lines of the book is improved.

As described above, according to the exposure method of this embodiment, it is possible to improve the contrast of the connecting portion of two parallel lines.

When the photomasks M ₁ and M ₂ used in the exposure method of the present invention are prepared, as shown in FIG.
The light-shielding region N can also be formed by a pattern in which the transparent films forming the phase shifter 15 are repeatedly arranged at minute intervals. In this case, spin-on glass may be applied to the main surface of a transparent glass substrate and the spin-on glass may be patterned using an electron beam drawing device.

According to the method of manufacturing the photomasks M ₁ and M ₂ as described above, since the light transmitting region P, the light shielding region N and the phase shifter 15 can be formed at the same time, the photomasks M ₁ and M ₂ are manufactured. The time and labor required for can be significantly reduced.

[0056]

Fourth Embodiment Next, another embodiment of the photomask used in the exposure method of the present invention will be described with reference to FIGS.

As shown in FIG. 32, for example, the refractive index is 1.4.
Photomask M made of transparent synthetic quartz glass of about 7
A _first pattern area A ₁ and a second pattern area A ₂ surrounded by a light shielding area N are provided adjacent to each other on the main surface of the.

The light-shielding region N is made of a metal thin film such as Cr and has a width of 0.5 to 0.5, for example.
It is about 10 mm. Further, outside the light-shielding region N, alignment marks B ₁ and B _{2 also} made of a metal thin film such as Cr are provided.

FIG. 33 is a plan view of an essential part of the first pattern area A ₁ . Inside the pattern area A _1, is surrounded by the light blocking regions N _1, for example, a rectangular light transmission region P ₁ is formed. The light shielding area N ₁
Is composed of a metal thin film such as Cr.

[0060] phase shifter 1 a part of the light transmission region P ₁ is, for example composed of a transparent thin film such as a spin-on-glass
5 are provided. The phase shifter 15, the area occupied in the interior of the light transmission region P ₁ is set to be approximately half of the area of the entire light transmission region P _1. Therefore,
The light L ₁ transmitted through the light transmission region P ₁ is transmitted by the phase shifter 1
The amount of light passing through the portion where 5 is present and the amount of light passing through where there is no phase shifter 15 are substantially equal.

FIG. 34 is a plan view of an essential part of the second pattern area A ₂ . Inside the pattern area B ₂ , a light shielding area N surrounded by a light transmitting area P ₂ is provided.
₂ is formed. The light shielding area N ₂ has substantially the same shape as the light transmitting area P _{1 of} the first pattern area A ₁ .
Have dimensions.

Thus, the first pattern area A ₁
The pattern formed on the first photomask M ₁ of Example 1 has the same structure as that of the first photomask M ₁ , and the pattern formed on the second pattern region A ₂ is the same as that of the pattern formed on the _first photomask M _1. It has the same structure as the pattern formed on the second photomask M ₂ of Example 1.

That is, in the first embodiment, the predetermined pattern to be transferred onto the sample 3 is divided into _two photomasks M ₁ and M ₂ , and the phase shifter 15 is formed on one of the photomasks M _1.
On the other hand, in the present embodiment, a predetermined pattern to be transferred onto the sample 3 has the same photomask M.
Are formed separately in the two pattern areas A ₁ and A ₂ of
The phase shifter 15 is arranged in _one pattern area A ₁ .

FIG. 35 shows an optical system of the exposure apparatus 1 used in this embodiment. Mirrors 5 and 6, a shutter 16, an aperture 17, a shortcut filter 18, a mask blind 19, a condenser lens 20, and a reduction projection lens 21 are arranged on the optical path connecting the light source 2 and the sample 3, and the alignment system includes The photomask M is positioned. The photomask M can be moved in the horizontal direction by the mask moving table 22.

The light source 2 is a high pressure mercury lamp that emits light L such as i-line, and the sample 3 is a semiconductor wafer made of, for example, a silicon single crystal. A photoresist that is sensitive to the light L is spin-coated on the surface of this wafer. The wafer is placed on the wafer suction table 23, and can be moved vertically and horizontally by the Z-axis moving table 24, the X-axis moving table 25, and the Y-axis moving table 26.

The photomask M is a reticle on which a predetermined integrated circuit pattern is transferred onto a wafer, for example, an original image of the integrated circuit pattern having a size five times the actual size is formed. This integrated circuit pattern is formed by being divided into a first pattern area A ₁ and a second pattern area A ₂ of the photomask M, and by overlapping the patterns of the respective pattern areas A ₁ and A ₂ . , The original pattern is transferred onto the wafer.

To transfer a predetermined integrated circuit pattern onto a wafer using the exposure apparatus 1 and the photomask M of this embodiment, first, the light L emitted from the light source 2 is incident on the photomask M. At this time, the mask blind 19 is adjusted so that the light L is incident only on the first pattern region A ₁ of the photomask M.

Light L transmitted through the first pattern area A ₁
Becomes a spot light beam through the reduction projection lens 21 and is incident on the surface of the wafer positioned on the wafer suction table 23.

As shown in FIG. 36, the surface of the wafer which is the sample 3 is divided into a large number of exposure areas E ₁ , E ₂ , E ₃ ... And transmitted through the first pattern area A ₁ . The light L first enters the first exposure area E ₁ . Then, the X-axis moving table 25 and the Y-axis moving table 26 are driven to move the wafer in the horizontal direction, and the light L transmitted through the first pattern area A ₁ is incident on the second exposure area E ₂ .

Thereafter, by repeating such an operation, the light L transmitted through the first pattern area A ₁ is made incident on all the exposure areas on the wafer surface, whereby the integration formed in the first pattern area A ₁ is performed. Transfer the circuit pattern to the wafer.

Next, the mask blind 19 is adjusted so that the light L emitted from the light source 2 is incident only on the second pattern area A ₂ of the photomask M. Second pattern area A ₂
The light L that has passed through is a spot light beam via the reduction projection lens 21 and becomes the first exposure area E _{1 on} the surface of the wafer.
Incident on.

Thereafter, by repeating such an operation, the light L transmitted through the second pattern area A ₂ is made incident on all the exposure areas on the wafer surface, whereby the integration formed in the second pattern area A ₂ is performed. Transfer the circuit pattern to the wafer.

As described above, according to the exposure method of this embodiment, the predetermined pattern to be transferred to the sample 3 is divided into two pattern areas A ₁ and A ₂ of the same photomask M, and the first pattern area is formed. After the pattern formed on A ₁ is exposed on the wafer, the pattern formed on the second pattern area A ₂ is overlaid on the same position on the wafer.

The light L ₁ immediately after passing through the light transmission area P ₁ of the first pattern area A ₁ is the phase of the light transmitted through the portion having the phase shifter 15 and the phase shifter as shown in FIG. The phases of the light transmitted through the portion without 15 are opposite to each other.

Therefore, on the sample 3, the above two lights interfere with each other at their boundaries and weaken each other.
A diffraction projection image (D) having a pattern as shown in FIG.
This diffraction projection image (D) becomes an image of an extremely fine line with good contrast when the phases of the light L emitted from the light source 2 are aligned.

[0076] On the other hand, the second light L ₂ immediately after passing through the periphery of the light shielding region N ₂ pattern area A _2, since the amplitude as shown in FIG. 8, on the sample 3, FIG. A projected image of a pattern as shown in 9 is obtained.

Therefore, when the diffraction projection image (D) of the first pattern area A ₁ and the central portion of the projection image of the second pattern area A ₂ are overlapped, Figure 1
A projected image of an extremely fine line as shown by 0 is formed.
That is, according to the exposure method of the present embodiment, an extremely fine pattern can be transferred onto the sample 3, so that the integrated circuit pattern can be remarkably miniaturized.

Moreover, according to the exposure method of the present embodiment, when a predetermined pattern is transferred to the sample, the pattern is divided into two pattern areas A ₁ and A ₂ of the same photomask M, and one of them is formed. Phase shifter 1 only in pattern area A ₁ of
5 is arranged, it becomes easier to select the place where the phase shifter 15 is arranged, as compared with the conventional phase shift technique, and the time and labor required for the pattern design of the photomask can be significantly reduced.

Further, according to the exposure method of this embodiment, since the pattern to be transferred to the sample is formed separately in the two pattern areas A ₁ and A ₂ of the same photomask M, it is not necessary to replace the photomask. Therefore, the throughput of the exposure process does not decrease.

The pattern formed in the first pattern area A ₁ has the same structure as the pattern formed in the _first photomask M ₁ of the second embodiment, and is formed in the second pattern area A ₂ . The formed pattern may have the same structure as the pattern formed on the _second photomask M ₂ of the second embodiment.

In this case, the diffraction projection image of the first pattern area A ₁ and the end portion of the second pattern area A ₂ are overlapped with each other so that the light-shielding area of the second pattern area A ₂ is formed on the sample 3. It is possible to form a projected image with improved contrast at the end of N ₂ .

The pattern formed in the first pattern area A ₁ has the same structure as the pattern formed in the _first photomask M ₁ of the third embodiment, and is formed in the second pattern area A ₂ . The formed pattern may have the same structure as the pattern formed on the _second photomask M ₂ of the third embodiment.

In this case, by superimposing the projected image of the first pattern area A _{1 and} the projected image of the second pattern area A ₂ , the contrast of the connecting portion of the two parallel lines on the sample 3 is increased. It is possible to form a projected image with improved image quality.

The phase shifter 15 formed in a part of the light transmitting area P ₁ of the first pattern area A ₁ has the structure shown in FIG.
As shown in FIG. 5, a part of the light transmitting region P ₁ may be formed by a groove formed by etching.

Further, as shown in FIG. 31, the light shielding region N may be formed by a pattern in which the transparent films forming the phase shifter 15 are repeatedly arranged at minute intervals.

Next, an example of a method for manufacturing a semiconductor integrated circuit device using the photomask M of this embodiment will be described with reference to FIGS.
Will be explained.

37 to 39, M is a negative type photomask, A ₁ and A ₂ are first and second pattern regions, 21 is a reduction projection lens of the exposure apparatus 1, 3 is a wafer,
741 is a silicon oxide film formed on the main surface, 742 is a polycrystalline silicon film deposited on the entire surface by the CVD method, and 754 is spin-coated on it to a thickness of 0.6 μm.
It is a negative type photoresist film of a certain degree.

In FIG. 38, 754a is a patterned photoresist film, and in FIG.
2a is a polycrystalline silicon film patterned by using the photoresist film 754a as a mask.

41 to 47 are sectional views showing the manufacturing process flow of a CMOS-static RAM (SRAM) by the twin well system, and FIG. 48 is a layout diagram on the chip. Hereinafter, they will be sequentially described.

FIG. 41 shows an n-well and p-well formation process by the twin well process. In the figure, 3 is a wafer (substrate) made of n ⁻ -type silicon single crystal, 760 n is an n-type well region, and 760 p is a p-type well region.

FIG. 42 shows the subsequent gate forming process and the process of forming the source and drain of each MOSFET by self-aligned ion implantation using the formed gate as a mask. In the figure, 761a
~ 761c are field oxides, 762n and 762
p is a gate oxide film, 763n and 763p are polycrystalline silicon gate electrodes, and 764n and 764p are n-type and p-type high-concentration source / drain regions, respectively.

FIG. 43 shows an interlayer insulating film forming process, a second layer polycrystalline silicon wiring and a high resistance forming process. In the figure, 765 is an interlayer insulating film, 766 is a polycrystalline silicon wiring, and 766r is a polycrystalline silicon high resistance which serves as a load resistance of the SRAM memory cell.

FIG. 44 shows a flattening process and a contact hole (or through hole) forming process by spin-on-glass. In the figure, 767 is a spin-on-glass film, 768a, 768b, 768d, 76.
8e is a contact hole with a silicon substrate, 768c
Is a through hole between the polycrystalline silicon wiring 766 and the upper layer.

FIG. 45 shows a first layer Al wiring forming process. In the figure, 769a to 769e are the first layer Al
Wiring.

FIG. 46 shows an interlayer insulating film forming process on the first layer Al wiring and a second layer Al wiring forming process. In the figure, 770 is an interlayer insulating film on the first-layer Al wiring, and 771a and 771b are second-layer Al wirings connected to the first-layer Al wiring via through holes.

FIG. 47 shows the final passivation film forming process on the second layer Al wiring. In the figure, 772 is a final passivation film.

FIG. 48 is a plan view showing a layout of the SRAM in chip units. In the figure, 721
Is a semiconductor chip, 722 is a memory cell mat, 723
Is a peripheral circuit including an I / O circuit, an address decoder, a read / write circuit, and the like.

FIG. 40 is an exposure process flow chart showing a photolithography process of the SRAM manufacturing process, that is, an exposure process extracted and made into a flow. In the figure, n-well photo process 7
P1 is a step of forming a photoresist pattern on the silicon nitride film (on the substrate) so as to cover a portion other than an n-well portion, and field photo step 7P2 is a step of n.
In order to pattern the silicon nitride film so as to cover the active regions of the channel and p-channel, a step of depositing and patterning a photoresist film thereon is performed.

The p-well photo step 7P3 is a step of patterning a photoresist film covering the n-well to form a channel stopper region of the p-well, and the gate photo step 7P4 is a gate electrode 763.
This is a step of patterning a photoresist film on the polycrystalline silicon layer deposited on the entire surface for patterning n, 763p.

In the n-channel photo step 7P6, a step of patterning a photoresist film on the p-channel side in order to ion-implant an n-type impurity using the gate electrode 763n as a mask on the n-channel side, p-channel photo step 7P6 Is a step of patterning a photoresist film on the n-channel side in order to ion-implant p-type impurities using the gate electrode 763p as a mask on the p-channel side.

The polycrystalline silicon photo step 7P7 is performed by using the polycrystalline silicon wiring 766 or the polycrystalline silicon high resistance 7
The step of patterning a photoresist film on the polycrystalline silicon layer deposited on the entire surface for patterning the second layer polycrystalline silicon film to be 66r (FIG. 43), the R / photo step 7P8, is a step of increasing the polycrystalline silicon film. This is a step of patterning the photoresist film serving as a mask for injecting impurity ions into other portions with the photoresist film covering the resistor 766r (FIG. 43) by a negative process.

The contact / photo step 7P9 is for the substrate,
Source / drain regions, first-layer polycrystalline silicon layer, second-layer polycrystalline silicon layer, etc. and first-layer Al wiring (Al-I)
Contact hole 768 for making contact with
a, 768b, 768d, 768e (FIG. 44) is formed by depositing and patterning a photoresist pattern by a positive process, Al-I photo step 7P10 (FIG. 45) is the first layer Al wiring. Is a photoresist patterning process for patterning.

The through hole photo step 7P11 is a step of forming a photoresist pattern for opening a through hole for connecting the first layer Al wiring and the second layer Al wiring, Al-II photo. Process 7P12 (Fig. 4
6) is a photoresist patterning process for patterning the second layer Al wiring, and the bonding pad photo process 7P13 is a pad for forming an opening of about 100 μm square corresponding to the bonding pad in the final passivation film 772. Finals other than
This is a step of depositing a photoresist film on the passivation film.

Of these exposure processes, n-well
Photo process 7P1, n-channel photo process 7P5, p
Since the channel photo step 7P6 and the bonding pad photo step 7P13 have relatively large minimum dimensions, it is generally unnecessary to use the phase shift method, but in other photo steps, the phase shift method using the exposure method of the present invention is used. To use.

In particular, by using the exposure method of the present invention in the gate photo step 7P4, it is possible to realize fine gate processing with less variation in gate dimensions.

Although the invention made by the present inventor has been concretely described above based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

In the above embodiment, the phase shifter is formed only on one of the two photomasks (or the two pattern regions), but the phase shifter may be formed on both of them.

The number of photomasks (or pattern regions) used in the exposure method of the present invention may be three or more. That is, the pattern to be transferred to the sample is formed by dividing it into three or more photomasks,
It may be formed by dividing into three or more pattern regions of one photomask.

[0109]

The effects obtained by the typical ones of the inventions disclosed by the present application will be briefly described as follows.
It is as follows.

(1) The pattern to be transferred to the sample is formed separately for the first photomask in which a phase shifter is provided in a part of the light transmitting region and the second photomask, and the first photomask is formed. According to the exposure method of the present invention, the diffraction projection image due to the phase difference of the light transmitted through the light transmission region of the mask and the projection image of the light transmitted through the light transmission region of the second photomask are superimposed on the sample. As a result, it becomes easy to select the place where the phase shifter is arranged, and the time and labor required for the pattern design of the phase shift photomask can be significantly reduced.

(2) The pattern to be transferred to the sample is separately formed into a first pattern area in which a phase shifter is provided in a part of the light transmitting area and a second pattern area, and the first pattern is formed. According to the exposure method of the present invention, the diffraction projection image due to the phase difference of the light transmitted through the light transmission region of the region and the projection image of the light transmitted through the light transmission region of the second pattern region are superimposed on the sample. The same effect as the above (1) can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an exposure apparatus used in an exposure method that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts of a first photomask used in this embodiment.

FIG. 3 is a plan view of a main part of a first photomask used in this embodiment.

FIG. 4 is a cross-sectional view of essential parts of a second photomask used in this embodiment.

FIG. 5 is a plan view of an essential part of a second photomask used in this embodiment.

FIG. 6 is a diagram showing the amplitude of light immediately after passing through a first photomask.

FIG. 7 is a diagram showing the intensity of this light on a sample.

FIG. 8 is a diagram showing the amplitude of light immediately after passing through a second photomask.

FIG. 9 is a diagram showing the intensity of this light on a sample.

FIG. 10 is a diagram showing the intensity of combined light on a sample.

FIG. 11 is a main-portion cross-sectional view showing another example of the first photomask.

FIG. 12 is a cross-sectional view of essential parts of a first photomask used in another embodiment of the present invention.

FIG. 13 is a plan view of an essential part of the same first photomask.

FIG. 14 is a cross-sectional view of essential parts of a second photomask used in this example.

FIG. 15 is a plan view of an essential part of the second photomask.

FIG. 16 is a diagram showing the amplitude of light immediately after passing through a first photomask.

FIG. 17 is a diagram showing the intensity of this light on a sample.

FIG. 18 is a diagram showing the amplitude of light immediately after passing through a second photomask.

FIG. 19 is a diagram showing the intensity of this light on a sample.

FIG. 20 is a diagram showing the intensity of combined light on a sample.

FIG. 21 is a plan view showing an example of a pattern transferred to a sample.

FIG. 22 is a plan view of an essential part of a first photomask used in another embodiment of the present invention.

FIG. 23 is a main-portion plan view of a second photomask used in this embodiment.

FIG. 24 is a cross-sectional view of essential parts of a first photomask.

FIG. 25 is a diagram showing the amplitude of light immediately after being transmitted through the first photomask.

FIG. 26 is a diagram showing the intensity of this light on a sample.

FIG. 27 is a cross-sectional view of essential parts of a second photomask.

FIG. 28 is a diagram showing the amplitude of light immediately after passing through a second photomask.

FIG. 29 is a diagram showing the intensity of this light on a sample.

FIG. 30 is a diagram showing the intensity of combined light on a sample.

FIG. 31 is a main-portion cross-sectional view showing another example of the first photomask.

FIG. 32 is a plan view of an essential part of a photomask used in another embodiment of the present invention.

FIG. 33 is a main-portion plan view of the first pattern region of the photomask used in this embodiment.

FIG. 34 is a main-portion plan view of the second pattern region of the photomask used in this embodiment.

FIG. 35 is a schematic view of an exposure apparatus used in an exposure method that is another embodiment of the present invention.

FIG. 36 is a plan view of a semiconductor wafer.

FIG. 37 is a CMOS-SRA using the exposure method of the present invention.
FIG. 6 is a cross-sectional view of the essential parts of the wafer, for showing the method for manufacturing M.

FIG. 38 is a cross-sectional view of essential parts of a wafer, showing a method for manufacturing this CMOS-SRAM.

FIG. 39 is a fragmentary cross-sectional view of the wafer, showing the method of manufacturing the CMOS-SRAM.

FIG. 40 is an exposure process flow chart showing the exposure process of the manufacturing process of the CMOS-SRAM, which is extracted and made into a flow.

FIG. 41 is a cross-sectional view of essential parts of a wafer, showing a method for manufacturing this CMOS-SRAM.

FIG. 42 is a cross-sectional view of essential parts of a wafer, showing a method for manufacturing this CMOS-SRAM.

FIG. 43 is a cross-sectional view of essential parts of a wafer, showing a method for manufacturing this CMOS-SRAM.

FIG. 44 is a fragmentary cross-sectional view of the wafer, showing the method of manufacturing the CMOS-SRAM.

FIG. 45 is a fragmentary cross-sectional view of the wafer, showing the method of manufacturing the CMOS-SRAM.

FIG. 46 is a fragmentary cross-sectional view of the wafer, showing the method of manufacturing the CMOS-SRAM.

FIG. 47 is a fragmentary cross-sectional view of the wafer, showing the method of manufacturing the CMOS-SRAM.

FIG. 48 is a plan view showing the layout of this CMOS-SRAM in chip units.

FIG. 49 is a cross-sectional view of a main part of a conventional photomask.

FIG. 50 is a diagram showing the amplitude of light immediately after passing through this photomask.

FIG. 51 is a diagram showing the amplitude of this light on the wafer.

FIG. 52 is a diagram showing the intensity of this light on the wafer.

FIG. 53 is a cross-sectional view of essential parts of a conventional phase shift photomask.

FIG. 54 is a diagram showing the amplitude of light immediately after passing through this photomask.

FIG. 55 is a diagram showing the amplitude of this light on the wafer.

FIG. 56 is a diagram showing the intensity of this light on the wafer.

[Explanation of symbols]

1 exposure device 2 light source 3 sample 4 beam expander 5 mirror 6 mirror 7 mirror 8 mirror 9 half mirror (or beam splitter) 10 lens 11 lens 12 objective lens 13 objective lens 14 XY table 15 phase shifter 16 shutter 17 aperture 18 shortcut filter 19 mask blind 20 condenser lens 21 reduction projection lens 22 mask moving table 23 wafer suction table 24 Z-axis moving table 25 X-axis moving table 26 Y-axis moving table 721 semiconductor chip 722 memory cell mat 723 peripheral circuit 741 silicon oxide film 742 multi Crystal silicon film 742a Polycrystalline silicon film 754 Photoresist film 754a Photoresist film 760n n-type well region 760p p-type well region 761a field oxide film 761b field oxide film 761c Field oxide film 762n Gate oxide film 762p Gate oxide film 763n Gate electrode 763p Gate electrode 764n High concentration source / drain region 764p High concentration source / drain region 765 Inter-layer insulating film 766 Polycrystalline silicon wiring 766r Polycrystalline silicon High resistance 768a Contact hole 768b Contact hole 768d Contact hole 768e Contact hole 768c Through hole 769a Al wiring 769b Al wiring 769c Through hole 769d Al wiring 769e Al wiring 770 Interlayer insulating film 771a Al wiring 771b Al wiring 772 Final passivation film A ₁ Pattern area A ₂ Pattern area B ₁ alignment mark B ₂ alignment mark D diffractive projection image E ₁ exposure region E ₂ exposure region E ₃ exposure region L light L ₁ light L ₂ light M follower Mask M ₁ photomask M ₂ photomask N shielding region N ₁ shielding area N ₂ shielding region P light transmission region P ₁ light transmission region P ₂ light transmission region

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 7352-4M H01L 21/30 311 W

Claims (9)

[Claims] 1. When transferring a predetermined pattern formed on a photomask onto a sample, a pair of photomasks are arranged between a light source and the sample, and a phase is formed on a part of a light transmitting region of one photomask. A shifter is formed, and a diffraction projection image due to the phase difference of light transmitted through the light transmission region of the photomask on which the phase shifter is formed and a projection image of light transmitted through the light transmission region of the other photomask are placed on the sample. An exposure method characterized by overlapping with. 2. The center portion of the projected image of the light transmitted through the light transmission region of the other photomask, which is the diffraction projection image due to the phase difference of the light transmitted through the light transmission region of the photomask on which the phase shifter is formed, The exposure method according to claim 1, wherein the exposure is performed on the end portion. 3. The photomask used in the exposure method according to claim 1, comprising the pair of photomasks. 4. When transferring a predetermined pattern formed on a photomask onto a sample, a photomask having a pair of pattern regions is provided between a light source and the sample, and the light transmitting region of one pattern region is arranged. A phase shifter is formed on a part of the pattern shifter, and a diffraction projection image due to the phase difference of the light transmitted through the light transmission area of the pattern area where the phase shifter is formed and the projection of the light transmitted through the light transmission area of the other pattern area An exposure method characterized by superimposing an image on a sample. 5. The exposure method according to claim 4, wherein a mask blind disposed between the light source and the photomask is used to selectively irradiate each pattern area with light. 6. The center portion of the projection image of the light transmitted through the light transmission region of the other pattern region, or the diffraction projection image due to the phase difference of the light transmitted through the light transmission region of the pattern region where the phase shifter is formed, The exposure method according to claim 4 or 5, wherein the exposure method is overlapped on an end portion. 7. The photomask used in the exposure method according to claim 4, wherein the photomask has the pair of pattern regions provided on the same glass substrate. 8. When transferring a circuit pattern formed on a photomask onto a semiconductor wafer, a pair of photomasks are arranged between a light source and the semiconductor wafer, and a part of a light transmitting region of one photomask is arranged. A phase shifter is formed, and a diffraction projection image due to the phase difference of light transmitted through the light transmission region of the photomask on which the phase shifter is formed and a projection image of light transmitted through the light transmission region of the other photomask are semiconductor. A photomask having a pair of pattern regions is arranged between the light source and the semiconductor wafer so as to overlap with each other on the wafer, and a phase shifter is formed in a part of the light transmitting region of one of the pattern regions. A diffraction projection image due to the phase difference of the light transmitted through the light transmission region of the pattern region where the shifter is formed, and a projection image of the light transmitted through the light transmission region of the other pattern region. A method for manufacturing a semiconductor integrated circuit device, which comprises stacking on a semiconductor wafer. 9. The method of manufacturing a semiconductor integrated circuit device according to claim 8, wherein the circuit pattern is a gate electrode pattern of a field effect transistor.