KR20010001105A - Apparatus for measuring the alignment status of a semiconductor wafer - Google Patents

Abstract

PURPOSE: An apparatus for measuring wafer arrangement is provided to promptly and easily check the wafer arrangement state by comparing the marks of vertical and horizontal direction with preliminarily set pattern. CONSTITUTION: An apparatus for measuring wafer arrangement state having cross-grating arrangement marks includes a light source(110); a light path providing part providing a straight path of a light generated from the light source to be radiated to arrangement marks on the semiconductor wafer and providing a path of a diffraction reflected light diffracted at the arrangement marks and having image of the reflected arrangement marks in the backward direction; a first beam splitter(120) transmitting the diffraction reflected light after separating as a first path and a second path; a first space filtering part(160) separating an optical signal corresponding to the horizontal line of the arrangement marks from the diffraction reflected light separated as the first path for imaging; a first image sensor(170) imaging the light imaged by the first space filtering part; a second space filtering part(180) separating an optical signal corresponding to the vertical line of the arrangement marks from the diffraction reflected light separated as the second path for imaging; and a second image sensor(190) imaging the light imaged by the second space filtering part.

Description

Wafer alignment measuring device {APPARATUS FOR MEASURING THE ALIGNMENT STATUS OF A SEMICONDUCTOR WAFER}

The present invention relates to a semiconductor wafer alignment system, and more particularly, to a semiconductor wafer alignment system capable of measuring in real time the alignment state of the semiconductor wafer in the horizontal and vertical direction.

Photographic processes in the semiconductor manufacturing process can be classified into three types, for example, a photo resist coating process, an alignment / exposure process, and a developing process. Here, the alignment process determines whether the semiconductor wafer mounted on the X-Y table is aligned at a desired position, and recently, alignment by a field image alignment (FIA) method has been used.

The FIA method detects the position of a mark by taking an alignment mark as an image signal on a wafer and computing its waveform, and uses light of a non-interfering nature with a broadband by a halogen lamp for alignment.

In general, an alignment method using a laser uses an alignment mark of a diffraction grating, so that it is highly distinguishable from other patterns, and also excellent in recognition of a low step mark. However, due to the high coherence, there are cases where there is a coating error or asymmetry of the mark shape, such as scaling error, random error in a rough aluminum wafer, etc. The precision decreases. On the other hand, in the FIA system, by using broadband light with low coherence, scaling errors in the aluminum wafer are small and random errors are reduced by averaging image processing. Such a FIA method generally performs alignment with respect to the horizontal axis direction of the wafer and alignment with respect to the vertical axis direction of the wafer.

1 is a schematic diagram of an apparatus for wafer alignment by a conventional FIA method, in which the wafer 10 is moved down and aligned under the FIA apparatus 20, 30. In this case, the FIA device 20 is for performing alignment with respect to the horizontal axis (X-axis) direction of the wafer 10, and the FIA device 30 is aligned with respect to the vertical axis (Y-axis) direction of the wafer 10. To do this. That is, according to the wafer alignment by the FIA method, after the wafer 10 is moved below the FIA device 20, the light output from the FIA device 20 is precisely irradiated onto the horizontal axis wafer mark formed on the wafer 10. To check the horizontal alignment. Thereafter, the wafer 10 is moved under the FIA device 30, and then the light output from the FIA device 30 is irradiated to the vertical axis mark formed on the wafer 10 to check the vertical axis alignment state of the wafer. .

As such, the wafer alignment by the conventional FIA method requires the alignment of the wafer to the horizontal axis and the vertical axis again after the alignment with the horizontal axis direction. In addition, the wafer alignment time is relatively long because the wafer must be moved to the horizontal and vertical axis, respectively. There was a problem.

Accordingly, an object of the present invention is to provide a semiconductor wafer alignment apparatus capable of reducing wafer alignment time by simultaneously checking wafer alignment in the horizontal and vertical axis directions of the wafer.

The semiconductor wafer alignment measuring apparatus according to the present invention for achieving the above object comprises a light source for measuring the alignment state of the semiconductor wafer having a cross-grating alignment mark of a series of regular lines intersected; Providing a straight path of the light such that the light generated from the light source is irradiated to the alignment mark on the wafer, and reverses a path of diffracted reflected light having an image of the alignment mark diffracted at and reflected from the alignment mark on the wafer Optical path providing means for providing in a direction; A first beam splitter which separates and transmits the diffracted reflection light into a first path and a second path; First spatial filtering means for separating and imaging an optical signal corresponding to a line in a horizontal direction of the alignment mark from the diffracted reflection light separated by the first path; A first image pickup device for picking up the imaged image by the first spatial filtering means; Second spatial filtering means for separating and imaging an optical signal corresponding to a vertical line of the alignment mark from the diffracted reflection light separated by the second path; And a second imaging device for imaging the light imaged by the second spatial filtering means.

1 is a view for explaining a wafer alignment process by a conventional FIA method,

2 is a view showing a wafer alignment measuring apparatus according to an embodiment of the present invention;

3A and 3B show detailed constructions of the spatial filter unit illustrated in FIG. 2, respectively.

4A and 4B illustrate another embodiment of the spatial filter illustrated in FIGS. 3A and 3B, respectively.

<Description of the code | symbol about the principal part of drawing>

100: wafer 105: alignment mark

110: light source 120, 150: beam splitter

130: reflection mirror 140: projection lens

160, 180: space filter unit 170, 190: imaging device

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 shows a semiconductor wafer alignment apparatus in accordance with an embodiment of the present invention. The semiconductor wafer alignment apparatus of the present invention includes a light source 110, a first beam splitter 120, a first reflecting mirror 130, a projection lens 140, a second beam splitter 150, and a first and second spatial filter. The unit 160, 180, and the first and second imaging devices 170 and 190 are included.

The light beam generated by the light source 110 is provided on the semiconductor wafer 100 via the first beam split 120, the reflection mirror 130, and the projection lens 140. The first beam split 120, the reflection mirror 130, and the projection lens 140 provide a straight path of light so that the light beam generated from the light source 110 is irradiated onto the semiconductor wafer 100, and the wafer 100 is provided. ) Provides a reverse path of the light so that the light reflected from the light beam is transmitted toward the first and second imaging elements 170 and 190. More specifically, the light beam generated from the light source 110 is provided and transmitted to the beam splitter 120 as non-photosensitive broadband light for a resist, then reflected by the reflecting mirror 130 and the projection lens 140 Irradiated onto the wafer 100 through.

On the wafer 100 seated on an unillustrated wafer stage, cross-grating alignment marks 105 are formed in which a series of regular lines intersect, as shown in FIG. The light beam irradiated by the mirror 130 and the projection lens 140 is reflected from the wafer 100 and directed back to the projection lens 140. At this time, the light beam reflected from the wafer 100 is generated as diffracted light at the cross lattice alignment mark on the wafer 100.

Thereafter, the reflected diffracted light beam is reflected back to the first beam splitter 120 at the reflection mirror 130, and the first beam splitter 120 directs the reflected diffracted light to the second beam splitter 150. The second beam splitter 150 transmits the incident diffracted reflection light in one direction to the first spatial filter unit 160 and reflects it in the other direction to provide it to the second spatial filter unit 180.

The first and second spatial filter units 160 and 180 perform spatial transformation to separate and image incident diffracted reflected light in X and Y (horizontal and vertical) directions, respectively. The first imaging device 150 and the second imaging device 160 may be, for example, configured as a charge coupled device (CCD), and may be formed from the first and second spatial filter units 160 and 180. The provided spatially converted light beam is imaged.

As shown in detail in FIGS. 3A and 3B, the spatial filter units 160 and 180 may include a first lens 162 and 182 which may include a converging lens or an objective lens and a second lens 166 that inverts a light beam. 186, and a spatial filter 164 disposed in the transform plane between the first lens 162, 182 and the second lens 166, 186. In FIG. 3A, the spatial filter 164 is formed with a vertical slit dot that matches the shape of the vertical line of the cross-lattice alignment mark 105, and the spatial filter 184 in FIG. 3B. ) Is a dot in the form of a horizontal slit (vertical slit) to match the shape of the horizontal line of the cross-lattice alignment mark. The spatial filters 164 and 184 respectively filter spatial frequency components in the vertical and horizontal directions for incident diffracted reflection light, that is, diffractive reflection light having the shape of a cross-lattice alignment mark. The filtering function of passing the light beam component in the vertical direction is performed. In this case, diffraction images generated on the conversion plane according to the periodicity in the horizontal and vertical directions also have periodic characteristics. 4A and 4B illustrate different forms of spatial filters 164 and 184, in which ring-shaped annular apertures are formed in the vertical and horizontal directions, respectively.

The spatial filter unit 160 will be described in more detail with reference to FIG. 3A as follows. First, the diffracted reflecting light incident from the second beam splitter 150 is first transformed by the first lens 162 and then incident on the spatial filter 164 disposed on the conversion plane. The spatial filter 164 having the vertical slot removes the spatial frequency component of the alignment mark 105 image with respect to the primary converted light beam, and transmits the light beam corresponding to the horizontal line of the alignment mark 105. Provided by two lenses 166. The second lens 166 transforms the light beam of the filtered horizontal spatial frequency component passing through the spatial filter 164 in the focal plane thereof and inverts it to form an image. The image shaped by the second lens 166 is captured by the imaging device 170, and the captured image has a shape corresponding to the horizontal line of the alignment mark 105.

Similarly, in the spatial filter unit 180 illustrated in FIG. 3B, the horizontal component of the alignment mark 105 is removed by the spatial filter 184 so that an image captured by the image pickup device 190 is vertically aligned with the alignment mark 105. Except that formed in the form corresponding to the line is substantially the same as described with reference to Figure 3a, detailed description thereof will be omitted.

Subsequently, marks in the vertical and vertical directions of the semiconductor wafers captured by the first imaging device 150 and the second imaging device 160 may be compared with a preset pattern to confirm and measure the alignment state of the semiconductor wafer.

Therefore, as described above, the present invention allows the light beams reflected from the wafer to be separated into optical components in horizontal and vertical directions and imaged so that the horizontal and vertical alignment of the wafer can be checked simultaneously. It is faster and easier to check wafer alignment.

Claims (6)

In a semiconductor wafer alignment measuring apparatus for measuring the alignment state of a semiconductor wafer having a cross-grating alignment mark in which a series of regular lines are crossed: Light source; Providing a straight path of the light such that the light generated from the light source is irradiated to the alignment mark on the wafer, and reverses a path of diffracted reflected light having an image of the alignment mark diffracted at and reflected from the alignment mark on the wafer Optical path providing means for providing in a direction; A first beam splitter which separates and transmits the diffracted reflection light into a first path and a second path; First spatial filtering means for separating and imaging an optical signal corresponding to a line in a horizontal direction of the alignment mark from the diffracted reflection light separated by the first path; A first image pickup device for picking up the imaged image by the first spatial filtering means; Second spatial filtering means for separating and imaging an optical signal corresponding to a vertical line of the alignment mark from the diffracted reflection light separated by the second path; And a second imaging device for imaging the light imaged by the second spatial filtering means. The method of claim 1, Each of the first and second spatial filtering means is: A primary lens converting the diffracted reflected light into a first plane and providing the converted plane; A spatial frequency component disposed on the conversion plane and filtering the spatial signal corresponding to the vertical or horizontal line of the alignment mark with the optical signal primarily converted by the primary lens, and filtering the spatial or horizontal component of the filtered horizontal or vertical spatial frequency component. A spatial filter for transmitting an optical signal; And a secondary lens for converting an optical signal of a horizontal or vertical spatial frequency component filtered by the spatial filter into the image and providing the secondary lens to the image pickup device. The method of claim 2, The spatial filter is: Dots in the form of vertical or horizontal slits for blocking optical signals corresponding to the vertical or horizontal lines of the alignment marks of the cross-lattice alignment marks are formed, and the vertical or horizontal slits form the vertical of the alignment marks. Or conform to the shape of the horizontal line. The method of claim 2, The spatial filter is: Ring-shaped annular apertures are formed in a slit shape in the vertical and horizontal directions to block optical signals corresponding to the vertical or horizontal lines of the alignment marks of the cross-lattice alignment marks. Wafer alignment measuring device, characterized in that the vertical or horizontal slit shape coincides with the shape of the vertical or horizontal line of the alignment mark. The method of claim 2, The optical path providing means is: A second beam splitter for transmitting the light beam generated from the light source toward the wafer and reflecting the diffracted reflection light generated at the alignment mark on the wafer to the first beam splitter; A reflection mirror which reflects the light beam through the second beam splitter toward the wafer and provides the diffracted reflection light to the second beam splitter; And a projection lens for irradiating the light beam reflected by the reflection mirror to the wafer and providing the diffracted reflection light to the reflection mirror. The method of claim 2, And the first and second imaging devices are charge coupled devices (CCDs).