JPH07105322B2 - Alignment device - Google Patents

Description

The present invention relates to an alignment apparatus for a mask and a wafer in a mask aligner using a proximity exposure transfer system.

[Prior Art] With the miniaturization of semiconductor devices from IC to LSI and VLSI, exposure devices such as mask aligners are also being considered for shortening the wavelength of exposure light source light, and many proposals regarding X-ray exposure technology are being made. Has been done. It is said that the X-ray exposure technique is required to have an alignment accuracy of 0.15 μm or less commensurate with the realization of a line width of 0.5 μm or less. In general, an optical method has been conventionally used as an alignment method in an exposure apparatus. However, since the X-ray exposure method is proximity exposure of a mask and a wafer, optical alignment causes an optical interference. Therefore, it is difficult to obtain a stable detection signal from the alignment mark, and it is difficult to improve the alignment accuracy.

On the other hand, there is a method that uses an electron beam as an alignment method that does not rely on an optical method. However, even an electron beam accelerated to several tens of kV cannot easily pass through a mask substrate with a thickness of several μm, so the alignment mark on the wafer is detected through the mask. However, it cannot be applied to the alignment of the mask and the wafer in a superposition manner like the optical method, and there is a problem in improving the alignment accuracy.

[Problems to be Solved by the Invention] The present invention eliminates the above-mentioned drawbacks of the prior art and provides an alignment apparatus capable of achieving highly accurate and high-speed alignment even when applied to proximity exposure of a mask and a wafer. It is intended to be provided.

[Means for Solving Problems] In order to achieve this object, according to the present invention, a mask and a wafer arranged with a predetermined gap are aligned in an alignment device that aligns them based on alignment marks formed on the wafer. Beam generating means for generating a charged beam, and for deflecting the focused charged beam generated by the beam generating means for scanning in the vicinity of a limited area of the charged beam transparency formed at a predetermined portion of the mask, A beam scanning unit provided between the beam generating unit and the mask, and electrons emitted from a peripheral portion of a limited area of the mask or an alignment mark on the wafer are scanned by scanning the focused charged beam by the beam scanning unit. A detecting means for detecting, provided between the beam generating means and the mask; Obtaining positional information of the mask and the wafer on the basis of the output, and having a means for relative displacement between the mask and the wafer on the basis of this.

The charged beam used in the present invention is not limited to the electron beam,
The same can be done by using a focused ion beam.

In the present invention, the alignment mark on the object is scanned and detected by the focused charged beam through the mask in a state where the mask and the object are superposed, and the position information of the mask is the boundary of the limited area or the vicinity of the limited area by the charged beam. It is only necessary to scan and detect another mark formed on the mask surface, whereby the position of the alignment mark on the object can be detected as position information relative to the mask position.

Further, in the present invention, as a mask, a transfer pattern is drawn on a mask substrate which is impermeable to a charged beam, and a limited region of the charged beam transparency is provided at a predetermined position on the substrate in a predetermined positional relationship with respect to the transferred pattern. The mask provided is used.

The limited area is specifically a through hole formed in the mask substrate, and in some cases, the through hole may be covered with a charge beam transparent film.

The formation position of the limited area is preferably on the scribe line of the transfer pattern, and in another example, on the extension line of the scribe line and outside the transfer pattern.

As a mask for X-ray exposure, the mask substrate is made of a material having good transparency to X-rays having a wavelength of about 1 nm.
The drawing pattern including the scribe line is formed of a material impermeable to the X-ray.

The focused beam generation means includes an electron beam generation source such as an electron gun or an ion beam generation source and focusing lens means thereof.

[Operation] According to this configuration, the peripheral portion of the limited area of the mask is irradiated with the focused charged beam, and the alignment mark formed on the wafer through the limited area is also scanned. Further, since the detection means is provided closer to the beam generation source than the mask, both the electrons emitted from the mask and the electrons emitted from the wafer are detected, and both mask position information and wafer position information can be obtained at the same time. The alignment is performed with higher accuracy. In addition, the use of the charged beam does not limit the alignment accuracy due to light interference,
Alignment accuracy of 0.15 μm or less can be achieved,
Also, the mask itself can be used with a limited area of the charged beam transparency, for example, by providing a through hole at a predetermined position, and an existing mask can be easily applied to the proximity exposure method without much difference from the optical alignment method. The configuration can be adopted.

To further understand the present invention, examples of the present invention will be described below.

[Embodiment] In FIG. 1, a mask 1 is superposed on a wafer 3 held on an XY stage 9 with a minute gap. For example, in the case of an X-ray exposure apparatus, the mask 1 is formed on a mask substrate 2 made of a material that is transparent to X-rays having a wavelength of about 1 nm, and a transfer pattern P and a scribe for partitioning the transfer pattern P with an X-ray impermeable material. The line S is drawn (see FIGS. 2a and 2b), and the gap between the mask 1 and the wafer 3 is set to a minute gap of several μm to several tens of μm, and moreover, the two planes of the mask and the wafer are highly accurate. After aligning with, exposure is performed. As shown in FIG. 2a, in the embodiment, a minute through hole H is provided on the scribe line S of the mask 1 as a limited region of the charge beam transparency. This through hole H is
It may be provided in a portion other than the pattern P on the extension line of the scribe line S as shown in FIG. 2b. Although the through hole H is exaggerated in FIG. 2a, it is smaller than the line width of the scribe line S as shown in FIG. 3a. still,
In FIG. 3a, H'denotes a through-hole portion of the mask substrate portion, and thus the hole H having a smaller diameter than that of the hole H'is, for example, Au or
This is because the scribe line forming film, which is a material opaque to the charged beam such as Ta, makes the rim of the through hole a sharp edge with respect to the focused charged beam. Also, the circle visible in the through hole H in FIG. 3a is an alignment mark formed on the wafer 3, and the vertical cross section of this portion is shown in FIG. FIG. 4 also shows that the electron beam 5 as the focused charged beam is swung for scanning, and that the photoresist layer 15 is formed on the surface of the wafer 3.

The combination of the alignment mark 14 and the through hole H is not limited to the example of FIG. 3a. For example, as shown in FIG. 3b, four rectangular through holes Ha having a shape corresponding to the mark 14a on the wafer are formed. You may.

In any case, the mask 1 is provided with at least one through hole H or Ha having a size that allows the electron beam 5 that is narrower than the line width of the alignment mark 14 or 14a of the wafer 3 to easily pass therethrough.

Returning to FIG. 1, the electron beam generated from the electron gun 4 passes through the lens 6 and becomes a narrow focused electron beam 5, and passes through the deflector 7 and
It is deflected for scanning in the XY directions. By controlling the conditions of the lens 6, the electron beam 5 can be focused on the mask surface in the vicinity of the through hole or on the surface of the wafer 3. Therefore, the edge of the through hole H on the mask surface or the mask surface in the vicinity thereof. Both the mark provided above and the alignment mark 14 on the wafer 3 can be scanned by the electron beam 5 focused in a dot shape. By the scanning of the electron beam 5 by the deflector 7, the detector 8 detects secondary electrons and reflected electrons generated from the edge (or mark) of the through hole of the mask 1 and the alignment mark 14 of the wafer 3, respectively. The deflector 7 receives the scanning signal from the control section 10 via the deflection amplifier 11 and performs the above-mentioned scanning, and the detector 8 gives the detection signal to the control section 10 via the detection amplifier 12 and the control section
In 10, the shift amount of the mark position between the mask 1 and the wafer 3 is accurately obtained from the scanning signal and the detection signal, and the stage drive unit 13 is controlled so that this shift amount becomes the displacement amount of the stage 9 1 and the wafer 3 are aligned.

In this embodiment, since the alignment mark position is set on the scribe line S having a width of several tens of μm of the mask 1, the exposure area of the mask pattern can be stepwise moved while accurately aligning on a wide wafer surface. still,
In this case, if the through-holes H are arranged outside the pattern as shown in FIG. 2b, the position of H is the same as the position of the scribe line on the extension line of the scribe line and at the same distance as the scribe line pitch. The alignment for each step exposure can be realized.

In the present invention, the edge of the through hole H or Ha, that is, the boundary of the limited area may be used as the alignment mark on the mask side. If the position and the shape accuracy are not sufficient, within the charged beam scanning range. Another mark drawn in the vicinity of the through hole may be used. Incidentally, it can be easily understood that if the through hole H or Ha is formed in the drawing pattern film of the scribe line S as shown in FIGS. 3a and 3b, it can itself serve as an alignment mark of the mask.

Further, in detecting the alignment mark between the mask and the wafer by the focused electron beam, the focusing condition of the lens 6 can be changed according to the size of the gap between the mask and the wafer.
Since the focused electron beam has a deep focal depth, both may be scanned with the lens conditions kept constant.

In the above-described embodiment, the mark detection is performed by using the detector 8 to capture the secondary electrons and the reflected electrons, but the absorption current of the electron beam incident on the mask or the wafer may be used for the mark detection signal.

Further, the alignment mark position is not limited to the scribe line or its extension line. For example, in the case of the batch transfer exposure method, the alignment mark position, and thus the position of the limited area can be arbitrarily selected.

INDUSTRIAL APPLICABILITY The present invention is not limited to the X-ray exposure apparatus as long as an electron beam or an ion beam can be used as a charged beam, but can be widely used for alignment of a proximity exposure system using a mask of light, electrons, ions, or the like.

Further, the through hole as the limited area may be covered with a film made of an organic or inorganic material having a thickness sufficient to allow the charged beam to pass therethrough, and the through hole as the mask side alignment mark may be formed as shown in FIG. It may be arranged not on the side but on the beam incident side to facilitate detection of the alignment mark of the mask.

EFFECTS OF THE INVENTION As described above, according to the present invention, the periphery of the limited area of the mask is irradiated with the focused charged beam, and the alignment mark formed on the wafer is also scanned by passing through the limited area. Since the detection means is provided closer to the beam generation source than the mask, both the electron emitted from the mask and the electron emitted from the wafer can be detected at the same time to obtain both the positional information of the mask and the positional information of the wafer at the same time. Therefore, it is possible to perform alignment with higher accuracy.
Further, it is possible to eliminate a defect such as an influence of interference in the alignment method using light.

[Brief description of drawings]

FIG. 1 is a conceptual view showing an embodiment of an alignment apparatus for carrying out the present invention, FIG. 2a is a schematic plan view showing an embodiment of a mask used in the present invention, and FIG. 2b is another view of the mask. FIG. 3a is an enlarged view of a mask through-hole portion, FIG. 3b is an enlarged view of a mask through-hole portion according to another embodiment, and FIG. 4 is an IV-IV of FIG. 3a. FIG. 1: mask, 2: mask substrate, 3: wafer, 4: electron gun, 5: electron beam, 6: lens, 7: deflector, 8: detector, 9: stage, 10: controller, 13: stage drive Part, 14: wafer alignment mark, S: scribe line, H: through hole, P: drawing pattern.

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Claims (4)

[Claims] 1. An alignment apparatus for aligning a mask and a wafer arranged with a predetermined gap based on an alignment mark formed on the wafer, and a beam generating means for generating a focused charged beam, and the beam. It is provided between the beam generating means and the mask for scanning the vicinity of the limited area of the charged beam transparency formed at a predetermined portion of the mask by deflecting the focused charged beam generated by the generating means. Beam scanning means, and the beam generating means and the mask for detecting electrons emitted from a peripheral portion of a limited area of the mask or an alignment mark of the wafer by scanning the focused charged beam by the beam scanning means. And the position information of the mask and the wafer based on the detection by the detection means. An alignment apparatus comprising: a means for obtaining the relative displacement of the mask and the wafer based on the obtained means. 2. The alignment apparatus according to claim 1, wherein the alignment mark position of the wafer is detected by charged beam scanning to obtain position information of the wafer. 3. An alignment apparatus according to claim 1, wherein the position information of the mask is obtained by detecting the boundary of the limited area of the mask by charged beam scanning. 4. The alignment apparatus according to claim 1, wherein a mark formed around the limited area of the mask is detected by charged beam scanning to obtain position information of the mask.