Exposure method, exposure device and semiconductor device...

Details Exposure method, exposure device and semiconductor device... Exposure method, exposure device and semiconductor device...

2000-06-09

2002-09-17

Kim, Robert H. (Department: 2876)

X-ray or gamma ray systems or devices

Specific application

Lithography

C378S205000

Reexamination Certificate

active

06453000

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an exposure method and an exposure device, which is particularly suitable for exposure and transfer operations of a step-and-repeat type and a step-and-scan type in which a photosensitive substrate such as a wafer or a glass substrate coated with a photosensitive material is exposed to a fine electronic circuit pattern formed on a surface of a mask using X-rays such as from synchrotron radiation (SR) or a plasma X-ray radiation source. In an exposure apparatus for manufacturing fine devices, alignment between the mask and the wafer is one of the important factors in terms of improvement of the performance of the devices. Particularly, the alignment in the recent exposure apparatus requires an alignment accuracy of less than a submicron to meet the demand for highly integrated devices (semiconductor element). The many alignment systems, alignment patterns (alignment marks) are provided on the surface of the mask and the surface of the wafer on scribe lines, and using the positional information obtained from the alignment marks, the mask and the wafer are aligned relative to each other (step-and-repeat type), and in such a system, the alignment mark for the alignment of the element pattern is disposed in the scribe line outside the element pattern area, and is exposed and transferred onto the wafer together with the circuit pattern on the mask.
Since the alignment mark does not have a function of an element, it is not needed after the completion of the lithography step. Therefore, the alignment pattern is disposed on the region of cutting between the elements.
The scribe lines are required to permit the wafer to be divided into a plurality of elements, but since they are not used for the element, the width thereof is minimized.
In a light exposure apparatus using exposure beam light such as i-line, an excimer laser beam or the like, a light blocking film is provided on the mask to limit the exposure view angle. If an attempt is made to limit the exposure view angle by an X-ray absorbing material on the mask in the case of the X line exposure device, several % to 40% of the X-rays pass through the absorbing material, depending on the thickness thereof.
In the exposure system using light, the use is made with a fine dot pattern at the peripheral portion of the half-tone reticle in the i-line exposure system, thus preventing the diffracted light from the reticle from entering the projection optical system. In the excimer laser exposure system, the introduction of the diffracted light to the projection optical system is not avoidable even in the finest pattern that can be drawn on the reticle with the result of the exposure of the marginal areas to the beam. The half-tone transmission factor in this case is approx 8%, but the exposure of the marginal area extends into the actual element with the result that a corner is influenced by four shot areas, and that an amount of blurriness due to the illumination system is 200&mgr; on the wafer, which is quite large as compared with the scribe line, and therefore, even if a half-tone reticle is used, the peripheral portion has to be provided with a Cr film to block the light.
In the X-line exposure, there is generally provided a light blocking plate for blocking the X-rays in the exposure apparatus to limit the exposure view angle. In order to provide the exposure apparatus with a function of limiting the exposure view angle, the function of changing the exposure view angle in accordance with the area to be transferred (exposure area) of the mask is performed.
In order to limit the area to be transferred of the mask, it is necessary to move the light blocking plates in the four directions with high precision and to avoid mechanical interference with the mask and the mask supporting member. Therefore, it is unavoidable to dispose the light blocking plates substantially away from the mask. Then, a boundary region occurs on the mask, in which the amount of the projected X-rays gradually decreases due to the shade of the light blocking plate resulting from the size of the light source and positional relation between the light blocking plate and the mask and the influence of the diffraction of the X-ray at the end of the light blocking plate. This is called blurriness due to the penumbra produced by the light blocking plate.
FIG. 9
shows a major part of an exposure apparatus using X-rays. In
FIG. 9
, designated by
1
is an X-ray radiation source,
2
is a light blocking plate for limiting an exposure view angle,
3
is a mask for X-line exposure,
4
is a wafer,
5
is an X-ray absorbing material disposed outside the exposure view angle of the mask
3
,
6
is an alignment mark on the mask
3
, and
7
is an intensity distribution of the exposure X-rays on the wafer
4
.
As shown in the Figure, the penumbra region
3
a
is a region in which the intensity of the X-rays gradually decreases, and therefore, it is not used for the exposure. When the alignment mark
6
is disposed outside the element pattern area, the width of the scribe line is the region for disclosing the alignment
6
plus the penumbra region
3
a
, as shown in the Figure, that is, the width of the scribe line is large. As a result, the wasteful area on the mask is large, and therefore, the exposure efficiency is low when the pattern of the mask is projected and transferred onto the wafer.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the present invention to provide an exposure method and an exposure apparatus wherein a pattern of the mask is projected and transferred onto the wafer using X-rays with high exposure and transfer efficiency without enlarging the width of the scribe line, so that devices are efficiently produced.
According to an aspect of the present invention, there is provided an exposure method using X-rays as exposure radiation, comprising: a step of preparing a light blocking plate, disposed in an optical path, for blocking the exposure radiation; a step of limiting an exposure view angle on a mask by the light blocking plate so that a penumbra region provided on the mask by the light blocking plate covers an alignment mark portion of the mask; wherein the alignment mark portion is disposed at least at one position inside a low light intensity region and outside an element pattern on the mask; and a step of exposing a photosensitive substrate to a pattern within the exposure view angle on the mask to transfer the pattern onto the photosensitive substrate.
Here, the alignment mark portion may be provided at each of outer sides of the element pattern on the mask.
According to another aspect of the present invention, there is provided an exposure method using X-rays as exposure radiation, comprising: a step of preparing a light blocking plate, disposed in an optical path, for blocking the exposure radiation; a step of limiting an exposure view angle on a mask by the light blocking plate so that a penumbra region provided on the mask by the light blocking plate covers an alignment mark portion of the mask; wherein the alignment mark portion is provided at each of positions which are outside of an element pattern on the mask and which are symmetric about a center line Lx of the mask and positions which are outside of an element pattern on the mask and which are symmetric about a center line Ly which is perpendicular to the center line Lx; and a step of exposing a photosensitive substrate to a pattern within the exposure view angle on the mask to transfer the pattern onto the photosensitive substrate.
According to a further aspect of the present invention, there is provided an exposure apparatus, using X-rays as exposure radiation, for exposing a photosensitive substrate to a pattern within an exposure view angle on a mask to transfer the pattern onto the photosensitive substrate, said apparatus comprising: a light blocking plate, disposed in an optical path for the exposure radiation, for limiting the exposure view angle on the mask by blocking the exposure radiation; and

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