JPH06324472A - Exposure master plate and projection exposure apparatus using the same - Google Patents

Abstract

PURPOSE:To obtain a projection pattern having high resolution by forming a pattern for exposure constituted of a phase member and another pattern constituted of a material reflecting or scattering a luminous flux having a specified wavelength on a transparent substrate. CONSTITUTION:The pattern 3 for exposure formed of the transparent phase member and a reticle alignment mark 4 are provided on a reticle 2, and the pattern 3 for exposure is projected and transferred on the surface of a wafer 6 on which resist is applied by a reduction type projecting lens 9. A reference mark 20 o a reference plate 19 arranged proximately to the lower part of the alignment mark 4 is constituted of a light shielding pattern made of Cr, and transmissively illuminated by the luminous flux having the same wavelength as the luminous flux exposure from a fiber 18 with the alignment mark 4 through a collimator lens 21. Thus, an edge can be clearly observed in the case of observing the alignment mark 4, positional deviation between the alignment mark 4 and the reference mark 20 is detected based on the deviation of the images of the detected alignment mark 4 and the reference mark 20 on an image-pickup surface 25, so that the reticle 2 can be aligned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure master plate and a projection exposure apparatus using the same, and more particularly to an electronic circuit pattern (exposure pattern) formed on a reticle surface (mask surface) by applying a so-called phase shift method. Is suitable for manufacturing a semiconductor device by projecting and exposing the wafer on a wafer surface via a projection lens or directly transferring and exposing the wafer on the wafer surface.

[0002]

2. Description of the Related Art Conventionally, in a so-called stepper of an exposure apparatus for manufacturing semiconductor devices, a reticle (photomask) on which an electronic circuit pattern is formed is illuminated by an illumination system, and the reticle is projected onto a wafer surface by a projection lens for exposure. is doing.

With the recent higher integration of semiconductor elements, this exposure apparatus is required to have a deep depth of focus as well as a finer pattern image (higher resolution) capable of being projected and transferred.

A method using a so-called phase shift method as one method for making the projected pattern image finer and improving the depth of focus of the projection lens is disclosed in, for example, Japanese Patent Publication No. 62-50811.
IEEE, Trans.on Electric Device, vol ED-29, No.12 (198
2), P1282, etc.

In this phase shift method, a phase shift film capable of imparting a constant phase difference (for example, 180 degrees) to a passing light beam is provided on a part of a transparent portion of a transparent portion and an opaque portion forming an electronic circuit pattern. The applied phase shift mask is used to improve the resolution and contrast of the pattern image.

In addition, as a phase shift mask, there is a "non-attenuation type" phase shift mask which forms a pattern image only with a phase film pattern without providing a light shielding pattern such as Cr.

This non-attenuation type phase shift mask has an advantage that the light shielding pattern and the phase film pattern need not be aligned with each other.

In general, the use of a phase shift mask is characterized in that the resolution of a periodic pattern image can be improved and the depth of focus can be increased even if the numerical aperture (NA) and exposure wavelength of the projection optical system are constant. is there.

[0009]

In a projection exposure apparatus for manufacturing a semiconductor device, relative position detection (alignment) between a reticle and a wafer is performed.

The alignment at this time is performed by observing the alignment mark on the reticle surface with an alignment system (observation system).

However, when the alignment mark composed of the non-attenuating type phase shift mask without the light-shielding pattern is used as the reticle, the alignment mark cannot be observed by the conventional alignment system.

In addition, in many cases, in the projection exposure apparatus, as a method for detecting the best focus position of the projection optical system,
A so-called TTL (Through the lens) Auto Focus (hereinafter referred to as "TTL, AF") function of detecting a focus position by using a light beam that has passed through a projection optical system is provided.

According to this method, for example, a slit image is projected on a wafer surface through a projection lens, received by a light amount detector through the slit, and the best focus position is determined from the characteristic of the received light amount.

TT is applied to the portion other than the circuit pattern of the reticle.
With the L autofocus mark (autofocus mark) formed and the reticle mounted on the stage,
Light having the same wavelength as the exposure light from the illumination means is directed to the TTL autofocus mark of the reticle, the light passing through the reticle is directed onto the wafer stage via the projection optical system, and the light amount detector is passed through the slit. To receive light.

By moving the wafer stage up and down in the direction of the optical axis of the projection optical system to change the position of the light amount detector, and by detecting the light receiving surface indicating the center of gravity of the output signal from the light receiving element at this time, this position is detected. Is detected as the optimum focus position (best image plane position) of the projection optical system.

Even when such a TTL or AF method is adopted, when the mark composed of the non-attenuation type phase shift mask is used, there is no light-shielding pattern, so that the focus position cannot be detected.

Further, as with TTL and AF, it becomes impossible to correct the baseline of reticle alignment and wafer alignment.

According to the present invention, when an alignment signal is detected through a reticle alignment mark using a non-attenuating type phase shift film, the alignment system (observation system) is appropriately configured so that the phase shift on the reticle surface can be controlled. Effectively distinguishing the area with and without the phase film, the relative positioning of the reticle and the wafer is performed with high accuracy, and the exposure master plate and the exposure master plate that can obtain a high-resolution projection pattern are used. The purpose of the present invention is to provide a projection exposure apparatus.

[0019]

The exposure original plate of the present invention comprises: (1-1) an exposure pattern made of a phase member on a transparent substrate and another pattern made of a material that reflects or scatters a light beam of a predetermined wavelength. Is formed.

In particular, the different pattern is an alignment pattern or a focus pattern, and the different pattern is made of a Cr material.

(1-2) When the pattern of the exposure original plate on which the exposure pattern is formed on the transparent substrate by the phase member is transferred onto the object to be exposed through the photographing system, the photographing system of the photographing system is formed on the transparent substrate. It is characterized in that a focus pattern having a pitch below the resolution limit is provided.

Further, the projection exposure apparatus of the present invention is (1-3) illuminating an exposure original plate having a pattern formed on a transparent substrate by a phase member with a light beam from an illumination system, and projecting the exposure original plate into a projection optical system. It is characterized in that an observation system is provided for observing the pattern of the exposure original plate with a transmitted light flux when performing projection exposure on the exposed object surface coated with the photosensitizer.

[0023]

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

In the figure, a reticle 2 as an exposure original plate is illuminated by an exposure light flux emitted from an exposure illumination system 1. The reticle 2 is provided with an exposure pattern (electronic circuit pattern) 3 formed of a transparent phase member and a reticle alignment mark 4 formed of a transparent phase member.

Then, the exposure pattern 3 on the surface of the reticle 2 is projected and transferred onto the surface of the wafer 6 coated with the resist by the reduction type projection lens 5.

The wafer 6 is adsorbed and fixed to the wafer chuck 7, and the wafer chuck 7 is placed on the XY stage 8.
Further, the XY stage 8 is placed on the surface plate 9.

The XY stage 8 is two-dimensionally movable in a plane perpendicular to the optical axis of the projection lens 5. The amount of movement at this time is such that the beam from the laser length measuring instrument 11 is incident on the mirror 10 provided on the XY stage 8 and
The beam reflected by is detected by the laser length measuring device 11 for monitoring.

Reference numeral 12 is a reference surface provided on the surface of the XY stage 8.

A stage reference mark 13 is provided on the reference surface 12.
Are provided and illuminate through the mirror 15 and the collimator lens 16 with the light flux of the same wavelength as the exposure light flux guided by the fiber 14.

The alignment of the wafer 6 is performed by the off-axis alignment scope 17.

Reference numeral 101 denotes an observation system, which forms the alignment mark 4 on the surface of the reticle 2 and the reference mark 20 provided on the reference plate 19 on the image pickup surface 25a of the image pickup device 25 for observation. The observation system 101 has a mirror 22, an objective lens 23, and a relay lens 24.

The reference plate 19 has the alignment mark 4
The reference mark 20 is fixed to the stepper main body below and is arranged close to the alignment mark 4 so that the reference mark 20 is within the depth of focus of the observation system 101.

The reference mark 20 of the reference plate 19 is Cr
And a light beam of the same wavelength as the exposure light beam guided by the fiber 18, and the collimator lens 2
It is transmitted and illuminated together with the alignment mark 4 via 1.

Fiber 18, collimator lens 21
Constitutes one element of the illumination system 102. The reference mark 20 and the alignment mark 4 which are transmitted and illuminated are observed by the observation system 10.
The image is formed on the image pickup surface 25a of the image pickup device 25 by the image pickup device 1.

In this embodiment, the exposure pattern 3 composed of the phase member (phase shift film) is formed on the surface of the wafer 6 with the film thickness, the refractive index and the like being optimized with respect to the wavelength of the exposure light beam. Has become. Therefore, the alignment mark 4 produced by the same process as this is also imaged on the imaging surface 25a by the transmission illumination in the same manner as the exposure pattern 3.

In this embodiment, when observing the alignment mark 4, a light beam having the same wavelength as the exposure light beam is used. As a result, the alignment mark 4 composed of the phase member
The edge of is clearly visible.

Therefore, the reference mark 2 of the reference plate 19
The transmission part of 0 has a shape capable of catching the edge of the phase member.

In the present embodiment, the reticle 2 is aligned by detecting the positional deviation between the alignment mark 4 and the reference mark 20 detected as described above based on the amount of deviation between the images on the imaging surface 25. .

In this embodiment, the objective lens 23 and the relay lens 24 of the observation system 101 are afocal coupled.

That is, the pattern surface (alignment mark 4) of the reticle 2 is located at the focal position of the objective lens 23,
The image pickup surface 2 of the image pickup device 25 is located at the focal position of the relay lens 24.
5a is located. The objective lens 23 and the mirror 22 are integrally configured to be movable in a plane parallel to the reticle 2 so that the pattern surface of the reticle 2 and the imaging surface 25a maintain the imaging relationship. It should be noted that a plurality of the above-mentioned elements 4, 18 to 25 are provided symmetrically with respect to the optical axis of the projection lens 5.

Next, in this embodiment, a vector b, a so-called baseline, from the optical axis of the projection lens 5 to the optical axis of the off-axis alignment scope 17, which is indispensable when the wafer is aligned by the off-axis alignment scope 17, is set. A measuring method will be described.

First, the XY stage 8 is moved so that the stage reference mark 13 on the reference surface 12 passes through the projection lens 5 and the alignment mark 4 located at a position of the vector α from the reticle center different from the reticle alignment mark 4.
It comes to a position that can be detected by the observation system 101 together with a. Then, the amount of deviation from the alignment mark 4a with respect to the stage reference mark 13 is detected as a vector β.

Also in this case, the edge of the reticle alignment mark 4 composed of the phase member is clearly observed due to the transmitted illumination. Therefore, the shape of the stage reference mark 13 is also determined to illuminate the edge portion used for alignment of the alignment mark on the surface of the reticle 2.

Next, the XY stage 8 is moved again to bring the stage reference mark 13 to a position where it can be detected by the off-axis alignment scope 17. Then, the shift amount (vector) γ from the reference position in the off-axis alignment scope 17 is detected. The movement amount (vector) δ of the XY stage during this period is accurately measured by the laser length measuring device 11. From each of the above vector amounts, the vector b, that is, the baseline is calculated by b = −α / M−β−γ + δ where M is the reduction ratio of the projection lens 5.

FIG. 2 is a schematic view of the main part in the vicinity of the observation system 101 according to the second embodiment of the present invention.

In this embodiment, a ring aperture stop 26 is provided in a part of the illumination system 102 and a phase plate 27 (for example, λ / 4 plate) is provided in a part of the observation system 101 as compared with the first embodiment in FIG. And has the function of a phase contrast microscope. This is different in that the pattern image formed on the image pickup surface 25a of the image pickup device 25 is made clearer, and the other configurations are the same.

FIG. 3 is a schematic view of the ring aperture stop 26 shown in FIG. 2 as viewed from the optical axis direction.

In addition, in the present invention, as the third embodiment, the illumination system 102 and the observation system 101 may have the same structure as the dark field microscope.

According to this, even in the pattern made of the transparent phase member, the pattern image can be captured by the image pickup device 25 by detecting the scattered light at the edge.

In the above two configurations of the second and third embodiments, the alignment mark 4 does not necessarily have to be the transillumination as in the first embodiment, and epi-illumination may be used. Therefore, there is no restriction on the structure, the number of optical elements is reduced, and the entire apparatus is simplified.

In each of the above embodiments, σ of the illumination system must be increased due to the relation of the amount of light, and thus the edge image of the phase film becomes unclear and desired alignment detection is not possible, or necessary. If you cannot obtain accurate accuracy,
In addition to the exposure pattern 3 made of the transparent phase member of the reticle 2, an alignment mark 28 patterned with a light-shielding member such as Cr may be provided for alignment by a conventional method as shown in FIG.

Since the relative alignment between the position of the alignment mark 28 and the exposure pattern 3 can be offset, it does not necessarily require precision in terms of hardware, and thus the alignment between the phase pattern and the light shielding pattern is unnecessary. The advantage of the non-attenuation type phase shift mask is not impaired. However, it is necessary to accurately measure the relative positional relationship that is an offset.

Further, in this method, the TTL and AF described above are used.
Marks for can also be formed.

When it is desired to perform TTL and AF without a Cr pattern, the pattern is set to be below the resolution limit of the projection lens 5. That is, the pattern size is set such that the flying angle of the diffracted light generated by the pattern is equal to or larger than the NA (numerical aperture) of the projection lens 5. If this condition is expressed by an equation, d <λ · NA (d: pattern pitch, λ: wavelength, NA: projection lens numerical aperture). With the pattern having such a size, the diffracted light cannot be captured by the projection lens 5, so that the light amount is reduced, and the same effect as the arrangement of the light shielding pattern is obtained.

[0055]

As described above, according to the present invention, when the alignment signal is detected through the reticle alignment mark using the non-attenuation type phase shift film, the alignment system (observation system) is appropriately configured. The effective alignment of the phase shift film on the reticle surface with and without the phase film makes it possible to perform relative alignment between the reticle and the wafer with high accuracy and to obtain a high resolution projection pattern. The obtained exposure master plate and the projection exposure apparatus using the same can be achieved.

[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 a schematic view of a main part of a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a part of FIG.

FIG. 4 is an explanatory diagram of a reticle pattern according to the present invention.

[Explanation of symbols]

 2 Reticle 3 Exposure pattern 4 Alignment mark 5 Projection lens 6 Wafer 13 Reference mark 17 Off-axis alignment scope 26 Ring aperture stop 27 Phase plate 101 Observation system 102 Illumination system

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/027

Claims (6)

[Claims] 1. An exposure master plate, which comprises an exposure pattern made of a phase member and another pattern made of a material that reflects or scatters a light flux having a predetermined wavelength on a transparent substrate. 2. The original plate for exposure according to claim 1, wherein the different pattern is an alignment pattern or a focus pattern. 3. The exposure master plate according to claim 1, wherein the different pattern is made of a Cr material. 4. When the exposure pattern of an exposure master plate on which an exposure pattern is formed on a transparent substrate by a phase member is transferred to an object to be exposed through a photographing system, the photographing system of the photographing system is transferred onto the transparent substrate. An exposure original plate, which is provided with a focus pattern having a pitch equal to or less than the resolution limit. 5. An exposure original plate having a pattern formed on a transparent substrate with a phase member is illuminated with a light beam from an illumination system, and the exposure original plate is placed on an exposed object surface coated with a photosensitizer by a projection optical system. A projection exposure apparatus comprising an observation system for observing a pattern of the exposure original plate with a transmitted light flux during projection exposure. 6. The projection exposure apparatus according to claim 5, wherein the observation system has a phase contrast microscope or a dark field microscope.