JPH06204121A - Illuminator and projection aligner using the same - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor element capable of projection alignment of high resolution, by selecting the optimum illumination system through the direction, the line width, etc., of a pattern form. CONSTITUTION:The light flux from a light source 1 is subjected to amplitude division into a plurality of incoherent light fluxes by an optical means. A plurality of secondary light sources are formed by applying a plurality of the light fluxes to an optical integrator 10. The light fluxes from a plurality of the secondary light sources are converged by a condenser lens, and illuminate a pattern on a surface to be irradiated. The pattern is subjected to projection exposure on the substrate surface by a projection optical system 13. The optical means has an adjusting member which independently adjusts the respective relative light quantities of a plurality of the light fluxes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device and a projection exposure apparatus using the same, and more specifically, a so-called stepper, which is a semiconductor device manufacturing apparatus, appropriately illuminates a pattern on a reticle surface and has a high resolution. The present invention relates to an illumination device which can be easily obtained and a projection exposure apparatus using the same.

[0002]

2. Description of the Related Art The recent progress in manufacturing technology of semiconductor devices is remarkable, and accompanying it, the progress of fine processing technology is remarkable.
In particular, the optical processing technology has reached the level of fine processing technology having submicron resolution at the border of the production of semiconductor elements of 1M DRAM. In many cases, the exposure wavelength has been fixed and the NA (numerical aperture) of the optical system has been fixed as a means for improving the resolution.
Was used. However, recently, various attempts have been made to change the exposure wavelength from g-line to i-line and improve the resolution by an exposure method using an ultra-high pressure mercury lamp.

Along with the development of the method of using g-line or i-line as the exposure wavelength, the resist process has also developed. The combination of this optical system and the process has led to a rapid advance in optical lithography.

It is generally known that the depth of focus of a stepper is inversely proportional to the square of NA. Therefore, when trying to obtain submicron resolution, a problem arises that the depth of focus becomes shallower with it.

On the other hand, various methods have been proposed for improving the resolution by using light having a shorter wavelength, which is represented by an excimer laser. It is known that the effect of using light having a short wavelength generally has an effect that is inversely proportional to the wavelength, and the depth of focus becomes deeper as the wavelength becomes shorter.

In addition to the use of light with a short wavelength, various methods using a phase shift mask (phase shift method) have been proposed as methods for improving resolution. This method is intended to improve the resolution by forming a thin film that gives a 180-degree phase difference with respect to the passing light on one part of the conventional mask and the other part. According to Levenson et al. Of IBM (USA) Proposed. Resolving power RP is wavelength λ, parameter k
₁ , where NA is the numerical aperture, it is generally expressed by the equation RP = k ₁ λ / NA. It is known that the parameter k ₁ , which is usually in the practical range of 0.7 to 0.8, can be greatly improved to about 0.35 by the phase shift method.

Various types of phase shift methods are known, for example, Nikkei Microdevice 1990 7
It is described in detail in the papers by Fukuda et al.

However, many problems still remain in order to actually improve the resolution by using a spatial frequency modulation type phase shift mask. For example, there are the following as problems at present. (I). The technology for forming the phase shift film has not been established. (B). The development of the optimum CAD for the phase shift film has not been established. (C). The existence of a pattern that cannot have a phase shift film. (D). There is no choice but to use a negative resist in relation to (c). (E). Inspection and correction techniques have not been established.

Therefore, actually, there are various obstacles in manufacturing a semiconductor device using this phase shift mask.
At present it is very difficult.

On the other hand, the applicant of the present invention has proposed an exposure method and an exposure apparatus using the same with a higher resolution.
Proposed in Japanese Patent No. 8631 (filed on February 22, 1991).

Therein, the illumination light (effective light source) is divided into four parts to form a quadrupole illumination light for high-resolution projection.

FIG. 9 is a schematic view of a main part of a high resolution projection exposure apparatus previously proposed by the present applicant.

In the figure, after the light beam emitted from the excimer laser 101 is beam-shaped by a beam shaping optical system (not shown), it is amplitude-divided into a plurality of incoherent light beams by the light splitting means 109a and is emitted to the optical beam. It is incident on the integrator 110.

The light intensity distribution on the incident surface 110a of the optical integrator 110 is, for example, as shown in FIG. At this time, the exit surface 110b also has a light intensity distribution corresponding thereto.

Incidentally, FIG. 10 shows a case where the incident light beam is split into four light beams by the light splitting means 109a.

A light flux from the optical integrator 110 is condensed by a condenser lens 111 to illuminate a reticle 112 which is a surface to be illuminated. And reticle 1
The pattern on the 12th surface is projected onto the wafer 1 by the projection optical system 113.
It is projected on 14 planes.

In the figure, the optical integrator 11 is shown.
0 has a light intensity distribution on the exit surface 110b of 0, and the condenser lens 111 is used for exit surface 11b.
0b is focused on the pupil of the projection optical system 113. As a result, high-resolution pattern projection is performed on a specific pattern of the reticle 112.

[0018]

Generally, the pattern image quality (resolution) transferred onto the wafer surface is greatly influenced by the property of the illumination device, for example, the angular distribution (light distribution characteristic) of the irradiation light on the surface to be irradiated. .

In a projection exposure apparatus for manufacturing semiconductor devices, it is very difficult to maintain uniform light distribution characteristics on the reticle surface, which is the surface to be illuminated, due to variations in assembly accuracy and temporal changes in each element. Therefore, the asymmetry of the light distribution characteristic on the illuminated surface may reduce the resolution of the pattern image.

According to the present invention, in the projection exposure apparatus previously filed by the present applicant, it is possible to arbitrarily adjust the illuminance distribution based on a plurality of light fluxes on the incident surface of the optical integrator which constitutes a part of the illumination apparatus. Accordingly, it is an object of the present invention to provide an illumination apparatus suitable for manufacturing a semiconductor element in which a light distribution characteristic on an illuminated surface is arbitrarily adjusted and a pattern image with high resolution can be easily obtained, and a projection exposure apparatus using the same.

[0021]

In the illumination device of the present invention, the light beam from the light source is amplitude-divided into a plurality of incoherent light beams by the optical means, and the plurality of light beams are transmitted through the optical integrator to the plurality of secondary light sources. Is formed, and when the light beams from the plurality of secondary light sources are condensed by a condenser lens to irradiate the surface to be irradiated, the optical means independently adjusts the relative light amount of each of the plurality of light beams. It is characterized by having.

The projection exposure apparatus of the present invention amplitude-divides the light beam from the light source into a plurality of incoherent light beams by the optical means, forms the plurality of secondary light sources through the optical integrator, and When a light beam from a plurality of secondary light sources is condensed by a condenser lens to illuminate a pattern on a surface to be illuminated and the pattern is projected and exposed on a substrate surface by a projection optical system, the optical means is configured to emit a plurality of light beams. It is characterized in that it has an adjusting member for independently adjusting the relative light amount of each.

Besides, in the projection exposure apparatus of the present invention, (a)
The optical means divides an incident light beam into two light beams having a predetermined polarization characteristic, and a first polarization beam splitter and the first polarization beam splitter.
A second and a third polarization beam splitter for splitting the two light fluxes from the polarization beam splitter into two light fluxes, and (b) the adjusting member has the first, second and third polarization beams. (C) The adjusting member has a constant dimming amount in the optical path of one of the two light beams split by the first polarization beam splitter. Or having a variable fixed or removable light reducing member,
(D) The dimming member is composed of an ND filter or a half mirror, and the like.

[0024]

Embodiment 1 FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the present invention.

Reference numeral 1 in the figure denotes a light source, which is composed of, for example, a narrow band excimer laser. The light flux from the excimer laser 1 has a narrow band due to a prism, a grating, or a combination thereof with an etalon or the like, and has a very strong polarization characteristic.

Reference numeral 1a denotes a beam shaping optical system, which beam-shapes the light beam from the light source 1 and emits it. Reference numeral 20 denotes an optical means, which divides the light beam from the beam shaping optical system 1a into a plurality of incoherent light beams by amplitude, and independently adjusts the relative intensity of each of the plurality of light beams by an adjusting member to emit the light beams. 10 incident surfaces 10a
Is incident on. On the incident surface 10a, for example, a plurality of light amount distributions based on a plurality of light fluxes are formed as shown in FIG.

The optical integrator 10 is composed of a plurality of minute lenses arranged two-dimensionally at a predetermined pitch. Exit surface 10 of optical integrator 10
A plurality of two-dimensional light sources are formed in b.

Reference numeral 11 denotes a condenser lens, which collects the light flux from the exit surface 10b of the optical integrator 10 and makes it enter the half mirror 21. A part of the light flux reflected by the half mirror 21 illuminates the reticle 12, which is the illuminated surface.

Each element from the light source 1 to the reticle 12 described above constitutes one element of the illumination device.

A projection optical system 13 projects the pattern on the reticle 12 surface onto the wafer 14 surface in a reduced scale. Two
Reference numeral 2 denotes a pinhole, which is arranged at a position optically equivalent to the reticle 12 via the half mirror 21.

Reference numeral 23 is a photodetector, which is a half mirror 21.
The illuminance on the surface of the reticle 12 is indirectly monitored by detecting the light flux that has passed through the pinhole 22 and transmitted. The photodetector 23 is composed of a two-dimensional CCD, a four-division sensor, or the like, and measures the total amount of light passing through the pinhole 22 and, as will be described later, a plurality of regions (formed on the exit surface 10b of the optical integrator 10 Eg 4
The intensity ratio of the effective light source in one area is monitored. The optical means 2 described later so that the intensity ratios of a plurality of regions on the exit surface 10b of the optical integrator 10 become equal.
The adjustment member within 0 is used for adjustment.

The condenser lens 11 has a plurality of secondary light sources formed in the vicinity of the exit surface 10b of the optical integrator 10 via the half mirror 21 and the projection optical system 1
A secondary light source image is formed on the third pupil 13a.

In this embodiment, the pupil plane 13a of the projection optical system 13 is
A high-resolution circuit pattern is obtained by changing the light intensity distribution of the secondary light source image formed in FIG. 3 and adopting the same illumination method (high-resolution illumination) as proposed in Japanese Patent Application No. 3-28613. Projection exposure.

Next, the structure of the optical means 20 of this embodiment will be described. FIG. 2 shows a first embodiment of the optical means 20 of the present embodiment.
FIG.

The present embodiment shows a case where the incident light beam from the beam shaping optical system 1a is amplitude-divided into four incoherent light beams and emitted (however, the number of light beams to be divided is not limited to four). May be).

A light source 1 emits a light beam having a strong polarization characteristic. In the figure, 2, 5a, 5b, 8a, 8b, 8
Reference numerals c and 8d denote phase plates such as a λ / 2 plate as an adjusting member, which can be rotationally adjusted about the optical axis. 3,6
Reference numerals a and 6b are first, second and third polarization beam splitters, respectively. Reference numerals 4, 7a and 7b are mirrors.

FIG. 3 shows the polarization state and amplitude of the light beam at each point (A to F ₄ ) in FIG. 2 corresponding to each position (A to F ₄ ) in FIG.

The light beam emitted from the light source 1 in the polarization state (0 ° linearly polarized light) as shown in A of FIG. 3 is shown in B of FIG. 3 by appropriately adjusting the λ / 2 plate 2 as an adjusting member. Is converted into a light beam with a different polarization state (45 ° linear polarization),
By passing through the polarization beam splitter 3, it is split into two light beams of equal intensity having mutually orthogonal polarization states (0 ° linearly polarized light and 90 ° linearly polarized light) like C ₁ and C ₂ in FIG.

These luminous fluxes C ₁ and C ₂ are again converted into 45 ° linearly polarized light like the luminous fluxes D ₁ and D ₂ by appropriately adjusted λ / 2 plates 5a and 5b as adjusting members. Then, by passing through the second and third polarization beam splitters 6a and 6b, the light beams are split into four light beams of equal intensity like light beams E ₁ , E ₂ , E ₃ and E ₄ .

Then, as shown in FIG. 4A, the optical integrator 10 is directed to respective predetermined positions on the entrance surface 10a, four distributions G1 to G4 are formed on the surface 10a, and four distributions G1 to G4 are formed near the exit surface 10b. Two secondary light source groups are formed.

Λ / 2 plates 8a, 8b, 8c and 8d in FIG.
Is for arbitrarily changing the polarization direction of each light beam incident on the incident surface 10a of the optical integrator 10, and by adjusting the four light beams, the four light beams shown in FIGS.
Can be set like.

FIG. 5 shows the polarization state at each position when the λ / 2 plate 2 as the adjusting member is rotated with respect to the optical rotation and shifted from the above position in the optical means 20 of FIG. At this time, the polarization state at the position B in FIG. 2 is slightly deviated from the 45 ° linearly polarized light like the light beam B in FIG. 5, and the ratio of the amounts of light passing through the first polarization beam splitter 3 becomes unequal. Based on such a principle, the relative intensity ratio of each light beam incident on the incident surface 10a of the optical integrator 10 is adjusted.

In this embodiment, a linearly polarized laser is used as the light source 1. However, when a light source which emits a circularly polarized light or an elliptically polarized light beam is used, the phase plate 2 is a λ / 4 plate or a λ plate.
The same effect can be achieved by combining the / 4 plate and the λ / 2 plate. Further, when the laser light contains a small amount of non-polarized component, the adjustment range of the light quantity may be slightly reduced, which causes no problem.

Each polarization beam splitter 3, 6a, 6b
It is desirable that the extinction ratio is small such that S-polarized light has a transmittance of 1% or less and P-polarized light has a reflectance of 1% or less. However, in practice, a certain polarized light has a transmittance of 40% or less, and a polarized light orthogonal thereto has a reflectance of 40% or less. It is possible to adjust the amount of light as required as long as it is about% or less.

FIG. 6 is a schematic view of the essential portions of Embodiment 2 of the optical means according to the present invention.

In the figure, switchable ND filter plates 31 and 32 are provided in the optical paths of the two light beams split by the first polarization beam splitter 3 in FIG. ND
The filter plates 31 and 32 are as shown in FIG. 7, and for example, the ND filter 3 that transmits 100% of the luminous flux.
1a and a plurality of ND filters 31a having various transmittances
˜31 h are provided on the substrate in a turret manner.

The ND filter 31a has a transmittance of 100%,
By inserting a desired ND filter in each optical path such that the ND filter 31b has a transmittance of 95%, the light amount costs of the two light beams split by the first polarization beam splitter 3 are adjusted.

The present embodiment is also effective when the light beam from the light source 1 is completely non-polarized. Further, the ND filter plate may be arranged in the optical path of the four light beams divided by the second and third beam splitters 6a and 6b, and the light quantity ratio of the four light beams may be directly adjusted.

FIG. 8 is a schematic view of the essential portions of Embodiment 3 of the optical means according to the present invention.

In the present embodiment, the light source 1 emits a light beam having no polarization or an extremely small degree of polarization.

In the figure, reference numeral 41 denotes a first polarization beam splitter having a small extinction ratio, and when the light beam from the light source 1 passes through the first polarization beam splitter 41, it becomes almost completely two orthogonal linearly polarized light beams. Be divided. 42a,
42b and 42c are fixed λ / 4 plates, respectively.
It is set to convert linearly polarized light that has passed through the polarization beam splitter into circularly polarized light. 42d, 42
Reference numeral e is a λ / 4 plate as an adjustable member for adjusting the setting, and adjusts the splitting ratio (light flux b ₁ : light flux b ₂ and light flux b ₃ : light flux b ₄ ) of the light flux by the second and third beam splitters 6a, 6b. It is for doing.

Reference numerals 43 and 44 denote half mirror members having a plurality of half mirrors whose reflectance can be changed,
It has the same structure as the ND filter plate of FIG.

Now, when the half mirror members 43 and 44 are not adjusted (when the transmittances of the half mirrors on the optical axis in the half mirror members 43 and 44 are both 100%), the light flux b ₁ +
When the light amount of the light beam b ₂ is 100 and the light amount of the light beam b ₃ + the light beam b ₄ is 80, it is assumed that both light amounts are equal. At this time, the half mirror member 43 has a transmittance of 90% and a reflectance of 10%.
When switched to the half mirror, both light amounts become equal.

The principle at this time will be described below. The polarization beam splitter 41 transmits P-polarized light and reflects S-polarized light with respect to the split surface. The light flux from the light source 1 passes through the polarization beam splitter 41,
It is split into 0% transmitted light (P polarized light) and 10% reflected light (S polarized light). 90% of transmitted light (P polarized light) is λ /
It is converted into circularly polarized light by passing through the four plates 42b.

Of this light, 10% of the light flux reflected by the half mirror 43 passes through the λ / 4 plate 42b again and is converted into S-polarized light. This light is reflected by the polarization beam splitter 41, is reflected by the mirror 44 via the λ / 4 plate 42a, and is again reflected by the polarization beam splitter 41.
When it is incident on, it becomes P-polarized light and is directed to the direction of the mirror 4 (toward b ₃ and b ₄ ) without being reflected.

Then, 10% of the light flux passes through the λ / 4 plate 42c and enters the half mirror section 44. As a result, the light quantity of the light flux (b ₁ + b ₂ ) is 90, and the light quantity of the light flux (b ₃ + b ₄ ) is 90, which are the same.

In this embodiment, the light amounts of a plurality of light fluxes are adjusted without loss of light amount based on the above principle.

[0058]

According to the present invention, by setting each element as described above, the illuminance distribution based on a plurality of luminous fluxes on the incident surface of the optical integrator which constitutes a part of the illumination device in the projection exposure apparatus can be arbitrarily set. To adjust the illuminance distribution on the illuminated surface,
An illumination device suitable for manufacturing a semiconductor element in which a pattern image with high resolution can be easily obtained and a projection exposure apparatus using the same are achieved.

In addition, according to the present invention, by changing the polarization state of the light flux from the light source or by using the light reducing means, the light quantity ratio of the split light flux is controlled and the intensity distribution of the effective light source is controlled. It is possible to prevent deterioration of the imaging performance due to the asymmetry of the effective light source, and it is possible to obtain good imaging performance.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a part of FIG.

FIG. 3 is an explanatory diagram of a polarization state of a light beam at each position in FIG.

FIG. 4 is an explanatory diagram of a light flux on an exit surface of the optical integrator of FIG.

5 is an explanatory diagram of a light flux on an exit surface of the optical integrator of FIG.

FIG. 6 is a schematic view of the essential portions of Embodiment 2 of the optical means according to the present invention.

FIG. 7 is an explanatory diagram of a part of FIG.

FIG. 8 is a schematic view of the essential portions of Embodiment 3 of the optical means according to the present invention.

FIG. 9 is a schematic view of a main part of a conventional projection exposure apparatus.

FIG. 10 is an explanatory diagram of a part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 1a beam shaping optical system 2, 5a, 5b adjusting member 3, 6a, 6b polarizing beam splitter 10 optical integrator 12 reticle 13 projection optical system 14 wafer 20 optical means 21 half mirror 22 pinhole 23 photodetector

Claims (6)

[Claims] 1. A light beam from a light source is amplitude-divided into a plurality of incoherent light beams by an optical means, and the plurality of light beams are formed into a plurality of secondary light sources through an optical integrator. The illuminating device characterized in that the optical means has an adjusting member for independently adjusting the relative amount of light of each of the plurality of light fluxes when the light flux of . 2. A light beam from a light source is amplitude-divided into a plurality of incoherent light beams by an optical means, and the plurality of light beams are formed into a plurality of secondary light sources through an optical integrator. When a pattern on the surface to be illuminated is illuminated by the condenser lens to illuminate the pattern and the pattern is projected and exposed on the substrate surface by the projection optical system, the optical means determines the relative light amount of each of the plurality of beams. A projection exposure apparatus having an adjusting member that adjusts independently. 3. The optical means divides an incident light beam into two light beams having a predetermined polarization characteristic, and a second light beam from the first polarization beam splitter and further divides the two light beams into two light beams. The second and third polarization beam splitters are included.
Projection exposure equipment. 4. The projection exposure apparatus according to claim 3, wherein the adjusting member comprises a rotatable phase element arranged in front of the first, second and third polarization beam splitters. 5. The adjusting member has a fixed or removable dimming member having a constant or variable dimming amount in an optical path of one of the two light beams split by the first polarization beam splitter. The projection exposure apparatus according to claim 3, wherein: 6. The projection exposure apparatus according to claim 5, wherein the dimming member comprises an ND filter or a half mirror.