JP2819592B2 - Positioning device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an alignment device, and more particularly, to a method of manufacturing a semiconductor device such as an IC or an LSI, in which an electronic circuit pattern formed on a reticle surface is reduced in size. The present invention relates to a positioning apparatus suitable for performing relative positioning (alignment) between a reticle and a wafer when projecting onto a wafer surface by a projection optical system.

(Prior Art) In recent years, an exposure apparatus for manufacturing a semiconductor element has been required to further miniaturize an electronic circuit pattern formed on a wafer surface with an increase in the density of an integrated circuit.

There is a so-called reduction projection type exposure apparatus as an exposure apparatus that can relatively easily achieve miniaturization of an electronic circuit pattern. In this device, m is smaller than the size requiring an electronic circuit pattern.
A reticle formed at a magnification of 2 × is projected as a subject on a wafer surface by a projection optical system at a magnification of 1 / m and reduced. At this time, the area that can be projected and exposed on the wafer surface at one time is smaller than the wafer size because the effective screen of the projection optical system is smaller than the size of the wafer. It employs a so-called step-and-repeat method that is performed repeatedly and sequentially.

The alignment between the reticle and the wafer is performed, for example, using an alignment mark on the wafer surface and an alignment mark on the reticle surface by an observation optical system.

(Problems to be Solved by the Invention) When performing alignment between a reticle and a wafer, an alignment system using light having a different wavelength from exposure light (printing light) when projecting and exposing a pattern on the reticle surface onto the wafer surface. There is a method using a fiducial mark provided in the inside, and this method is frequently used because relatively accurate alignment is possible. In this method, instead of directly measuring the relative position between the wafer and the reticle using printing light, the relative position between the wafer and the reference mark is measured using light of a wavelength other than the printing light, and the relative position between the known reticle and the reference mark is measured. Is used to align the reticle and the wafer with light other than printing light.

There are various known methods for measuring the relative position between the reticle and the reference mark, for example, a method of actually performing printing (exposure) or a method of directly measuring a reference mark on a wafer stage with printing light.

This method is performed for each carrier or for each wafer so as not to deteriorate the throughput. For this reason, for example, during the measurement, the reticle or fiducial mark moves due to instability of mechanical holding, and if the relative position fluctuates, the fluctuation amount becomes an alignment error between the reticle and the wafer. There was a problem.

The present invention uses a reference mark plate in which a dedicated or common reference mark for a reticle and a wafer is provided on the same substrate surface as a reference mark in an alignment system, so that the reticle and the reference mark change with time. Another object of the present invention is to provide a positioning apparatus which can prevent alignment errors from occurring and can always perform highly accurate alignment.

(Means for Solving the Problems) According to the present invention, when a pattern on a reticle surface is projected onto a wafer surface by a projection optical system, a reference reticle mark for the reticle and a reference wafer for the wafer are placed on the same substrate surface. A reference mark plate having a mark is arranged in an optical path between the projection optical system and the reticle, and a relative positional relationship between the reference reticle mark and a reticle alignment mark on the reticle surface is detected. The relative positional relationship between the reticle and the wafer is obtained by detecting a relative positional relationship between the reference wafer mark and a wafer alignment mark on the wafer surface via the projection optical system. And

(Embodiment) FIG. 1 (A) is a schematic view of an optical system according to a first embodiment of the present invention. FIG. 1 (B) is a view as viewed from A in FIG. 1 (A), and FIG. 1 (C). FIG. 3 is a view as viewed from B in FIG.

In FIG. 1, reference numeral 5 denotes a reticle on which an electronic circuit pattern is formed, and reference numeral 3 denotes a wafer chucked and fixed by a wafer chuck 2 placed on a movable wafer stage 1. 4
Denotes a projection optical system for projecting (printing) an electronic circuit pattern on the reticle 5 surface onto the wafer 3 surface at a predetermined reduced magnification.
doing.

Reference numeral 21 denotes an alignment system for a wafer, which measures a relative positional shift between the wafer 3 and the reference mark plate 6 in the alignment system 21.

On the surface of the reference mark plate 6, a reference reticle mark 6A for the reticle 5 and a reference wafer mark 6B for the wafer 3 are provided. Reference numeral 8 denotes a light source which emits light having a wavelength different from the wavelength of printing light such as a He-Ne laser. The reference mark plate 6 is arranged at a position where the image is projected and imaged by the projection optical system 4 of the wafer 3 when the wavelength emitted from the He-Ne laser is used.

In the alignment system 21, the light beam from the light source 8 is condensed by the illumination lens 14, passes through the beam splitter 15, and then passes through the lens system 12, the reference mark plate 6, the mirror 16, and the projection optical system 4, and Upper wafer alignment mark 3a
Lighting. The wafer alignment mark 3a on the wafer 3 is imaged on the reference wafer mark 6B of the reference mark plate 6 via the mirror 16 by the projection optical system 4.

At this time, the reference wafer mark 6B and the wafer alignment mark 3a are separated by the objective lens 12 and the erector lens 13.
An enlarged image is formed on the CCD7 surface. The wafer 3 and the reference mark plate 6 are obtained from the image information of both marks obtained from the CCD 7.
And the relative positional relationship with is detected.

Reference numeral 22 denotes an alignment system for the reticle.
And the relative displacement between the reference mark plate 6 in the alignment system 22 and the reference mark plate 6 is measured.

In the figure, a light beam from an exposure light source (not shown) is guided by a fiber 9, and the reference reticle mark 6A is illuminated by an illumination lens 14a. The reference reticle mark 6A is imaged on the reticle alignment mark 5a on the reticle 5 by the lens system 11 via the mirror 17. At this time, both the reference reticle mark 6A and the reticle alignment mark 5a are enlarged and imaged on the surface of the CCD 7a by the objective lens 12a and the erector 13a. The relative positional relationship between the reticle 5 and the reference mark plate 6 is detected from the image information of both marks obtained from the CCD 7a.

Since the alignment system 22 in this embodiment does not pass through the projection optical system 4, there is no particular limitation on the wavelength, and light of a wide range of wavelengths can be used.

In addition, the optical system after the objective range 12a and the erector 13a is movable, and a so-called optical system through the projection optical system using the exposure wavelength.
When the function of directly observing the reticle and the wafer is provided by the TTL method, it is preferable to make the correction wavelength of the alignment system coincide with the wavelength of the exposure light.

As described above, in the present embodiment, the relative positional relationship between the wafer and the reference wafer mark and the reticle and the reference reticle mark using the reference mark plate 6 having the reference reticle mark and the reference wafer mark on the same substrate surface are detected. By doing so, the amount of positional deviation between the wafer and the reticle is obtained, and alignment is performed from this.

In this embodiment, the relative positional relationship between the fiducial mark plate and the reticle can be always recognized. Therefore, due to the instability during mechanical holding, even if these elements fluctuate, the alignment between the reticle and the wafer may be difficult. It has features such as not having any effect.

FIG. 2 is a schematic view of a main part of an optical system according to a second embodiment of the present invention.

In this embodiment, the configuration for projecting and exposing the electronic circuit pattern on the reticle 5 surface onto the wafer 3 is the same as that of the first embodiment shown in FIG.

In FIG. 2, reference numeral 46 denotes a light source, which emits light having a wavelength of 400 to 700 nm, such as a xenon lamp. The light beam from the light source 46 is condensed by a lens 47 and illuminates a reference mark plate 49 via a filter 48. The reference mark plate 49 is provided with a common reference mark 49a for the reticle 5 and the wafer 3. The filter 48 is provided with a dichroic film that allows light having a wavelength of 500 to 700 nm to pass. The light beam from the reference mark plate 49 is reflected by the polarization beam splitter 50, guided to the main optical path of the alignment system, passed through the λ / 4 plate 51, and then enters the lens system 12b.

The lens system 12b includes a reference mark plate 49 including the projection optical system 4.
And the wafer 3 are corrected for aberrations in the wavelength range of 520 to 700 nm, and the reference mark plate 49 and the reticle 5 are corrected for aberrations in the wavelength range of 500 to 520 nm as described later.

Wavelength 5 out of the luminous flux of 500-700 nm from lens system 12b
The reticle 5 reflects a light beam having a wavelength of 00 to 520 nm on the dichroic surface 18a of the prism type mirror 18 on which the dichroic film is applied.
Light is guided on the surface.

Thus, the reference mark 49a is imaged on the reticle alignment mark 5a on the reticle 5.

The reference mark 49a and the reticle alignment mark 5a are imaged on the CCD 7a surface by the optical system 12a and the erector lens 13a. The relative positional relationship between the reticle 5 and the reference mark plate 49 is detected from the image information of both the reference mark 49a and the reticle alignment mark 5a formed on the surface of the CCD 7a.

On the other hand, a light beam having a wavelength of 520 to 700 nm passes through the dichroic surface 18a of the prism type mirror 18, is reflected by the reflecting surface 18b, passes through the projection optical system 4, and is guided to the wafer 3. Thus, the reference mark 49a is imaged on the wafer alignment mark 3a.

Multi-layer resists generally used for semiconductor device fabrication,
Since the absorption characteristics of the absorbent resist and the like are about 520 nm, a light beam within a wavelength range of 520 to 700 nm is suitable as a wavelength range for observing the wafer.

Both the wafer alignment mark 3a and the reference mark 49a on the surface of the wafer 3 return the optical path, that is, sequentially pass through the projection optical system 4, the prism type mirror 18, and the lens system 12b, and
The polarization direction is changed by four plates, and the light passes through the polarization beam splitter 50. Then, both marks are imaged on the CCD 7 surface by the erector lens 13.

Thus, the relative positional relationship between the wafer 3 and the reference mark plate 49 is detected from the image information of both the reference mark 49a and the wafer alignment mark 3a formed on the CCD 7 surface.

As described above, the relative positional relationship between the reference mark 49a and the reticle 5 and the relative position between the reference mark 49a and the wafer 3 are detected in the same manner as in the first embodiment of FIG. Alignment is being performed.

In the present embodiment, various conditions regarding the holding stability are relaxed by using the prism type mirror 18, so that the configuration can be made with a very loose tolerance.

FIG. 3 is an explanatory view showing an optical path passing through the prism type mirror 18 at this time. It is now assumed that the prism type mirror 18 is displaced to a dotted line position by moving in the Z direction by ΔZ due to unstable holding or the like in FIG. Then, since the optical axis shift of the alignment system 21 is shifted by ΔZ for both the wafer system and the reticle system, no alignment error occurs between the wafer and the reticle. The same is true for displacement in the Y direction and rotation about X, Y, and Z.

In this embodiment, instead of using the light transmitted through the reticle 5, the light reflected by the reticle 5 may be used to return to the lens system 12b and be guided on the CCD 7 surface.

In the embodiment shown in FIGS.
As shown in the figure, two alignment marks are arranged on the reticle 5 and extend in the radial direction with respect to the projection optical system 4.
Similar effects can be obtained by performing alignment using 51A and 51B.

At this time, the alignment mark 51A measures the shift amount in the Y direction, and the alignment mark 51B measures the shift amount in the X direction. With this configuration, it is very advantageous for the allowable value of the attitude error in assembling the prism type mirror 18.

In the first embodiment shown in FIG. 1, the mirrors 16 and 17 may be integrally formed as shown in FIG. This is preferable because the holding accuracy can be reduced to the same level as the prism type mirror 18 in FIG.

(Effects of the Invention) According to the present invention, by using a reference mark plate having a reference reticle mark and a reference wafer mark on the same reference plane and performing alignment of the reticle and the wafer via the reference mark plate, This makes it possible to achieve a highly accurate alignment device that can perform high-precision alignment that is not affected by the alignment between the reticle and the wafer even if the reference mark plate, the reticle, or the like moves for some reason due to holding instability.

[Brief description of the drawings]

FIGS. 1 and 2 are schematic views of the main parts of an optical system according to the first and second embodiments of the present invention, respectively, and FIG. 3 is a prism type mirror 18 shown in FIG.
FIG. 4 is an explanatory view of an embodiment when the mirrors 16 and 17 of FIG. 1 are integrated, and FIG. 5 is an explanatory view of an alignment mark on a reticle surface according to the present invention. In the figure, 3 is a wafer, 3a is a wafer alignment mark, 4 is a projection optical system, 5 is a reticle, 5a is a reticle alignment mark, 6 and 49 are reference mark plates, 6a is a reference reticle mark, 6b is a reference wafer mark, 7 and 7a, 7b are CCD, 8, 46
Is a light source, 9 is a fiber, 11 is an imaging lens, 12 and 12a are lens systems, 13 and 13a are erector lenses, 14 is an illumination lens, 15 is a beam splitter, 16 and 17 are mirrors, 18 is a prism type mirror, 21 is an alignment system for wafers, 22
Is an alignment system for a reticle, 51A and 51B are alignment marks, 48 is a filter, and 51 is a λ / 4 plate.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027 G03F 7/20 521

Claims (2)

(57) [Claims] When a pattern on a reticle surface is projected onto a wafer surface by a projection optical system, a reference mark plate having a reference reticle mark for the reticle and a reference wafer mark for the wafer on the same substrate surface. It is disposed in the optical path between the projection optical system and the reticle, detects the relative positional relationship between the reference reticle mark and a reticle alignment mark on the reticle surface, and detects the reference wafer mark and the projection optical system. A relative positional relationship between the reticle and the wafer by detecting a relative positional relationship with a wafer alignment mark on the wafer surface via a system. 2. The alignment apparatus according to claim 1, wherein said reference reticle mark and said reference wafer mark are constituted by a common mark.