JPS58122541A - Projection exposing device - Google Patents

Abstract

PURPOSE:To make a wafer surface coincide with a surface of a projection image-formation of a mask pattern, by securing the height of plural positions of the wafer surface by disposing a noncontacting displacement meter at the part positioning the wafer surface and controlling so that the approximate plain surface calculated by this data is made to coincide with the desired virtual-plain surface. CONSTITUTION:The height of plural positions on the surface of a wafer 1 placed on a table 13 is measured without contacting by making a reciprocal scanning on a noncontacting displacement meter 21. The table 13 on which the wafer 1 is placed, is provided on 3 layered electrostriction elements 20, and the elements 20 and the displacement meter 21 are interlocked by a controlling circuit of the table consisting of an A/D transducer 28, a computer 29, a D/A transducer 30 and an electrostriction element driver 31, and the degree of balance of the table 13 is adjusted. While, the extent of shift between the wafer surface and the surface of a projection image-formation of a mask pattern is detected optically and is fed back to the meter 21, and further the degree of balance of the table 13 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of an apparatus for performing pattern transfer by projecting and image-forming a mask pattern onto a wafer surface, and in particular, the present invention relates to an improvement in an apparatus that performs pattern transfer by projecting and image-forming a mask pattern onto a wafer surface, and in particular, it is possible to completely separate the projection image-forming plane of the mask pattern and the surface of the wafer. This invention relates to a projection exposure apparatus with improved resolution.

In order to process fine circuit patterns on the surface of semiconductor wafers (hereinafter simply referred to as wafers), a projector/mask alignment device is used to project, image, and transfer one mask pattern onto a wafer whose surface is coated with a photosensitive thin film. be.

In order to project and form a mask pattern onto the wafer surface with high resolution in this equipment, the wafer surface must be accurately positioned within the depth of focus of the imaging plane, and the mask pattern must be projected onto the wafer surface at a high height. Accurate focusing is the most important technical element.

Furthermore, in connection with other technologies from the production side of ICs and LSIs, high processing capacity is also required.

First, in Figure 0, which explains the outline of the projection mask alignment device using Figure 1,
and mask 2 are mounted and held on tables 3 and 4, respectively, in order to match their patterns, and furthermore, these tables 3 and 4 are movable left and right via air bearing guides (not shown). It is mounted on a traveling table 6 mounted on a stone surface plate 5 (the driving part is not shown). Projection optical system 7, alignment optical system 8.
The surface positioning unit 9 also illuminates the mask 2 from the bottom with ultraviolet light emitted from the UV light source 10 provided at the bottom of the stone surface plate 6 mounted on the stone surface plate 5, and the projection optical system The objective lens 11 of the alignment optical system 8, which images the pattern of the mask 2 on the Uni-No.
A 1-7 mirror 12 is provided at the tip of the wafer 1, and the mask and pattern are imaged onto the wafer 1 by passing through the 7-mirror 12.

Therefore, the alignment optical system 8 simultaneously observes the pattern on the wafer l and the mass j pattern projected onto the wafer l, and performs pattern alignment.

Note that when performing this pattern matching, ultraviolet components are removed from the light from the exposure source 10 using a filter or the like.

Conventional wafer positioning was performed as shown in FIG.

That is, the traveling table 6 described above is moved to the left, and the wafer 1 is placed below the wafer surface positioning section 9. The wafer l mounted on the mounting table 13 is fixed by suction by supplying vacuum pressure to the space 16. Further, this mounting table 13 is supported at its lower part by a spherical bearing 14, and has a structure that allows the surface to be parallel to the sea urchin. After the parallelization is completed, vacuum pressure is supplied to the lower space 15 of the spherical bearing 14 to fix it by suction.

On the other hand, the wear 1 surface positioning part 9 installed above the Unino 1 has three pins attached to it.
In the state shown in Fig. 2, the vertical axis 19 installed on the stage 3 is moved by the ball screw feed of the Noculus motor. mechanism(
(not shown) to press the surface of the wafer 1 against three BIN-Fs. Note that the pins 17 are arranged so as to hit three points around the periphery of the Unino 1, so the
Due to the action of the spherical bearing 14 at the bottom of the tower 13,
Coinciding the surface of l with the plane formed by the three pins 1F After adjusting the surface parallelism of Unino l in this way, lower the vertical axis 19 and align the plane formed by the preset virtual plane (mask pattern). The projection image plane) was made to coincide with the wafer surface, and the projection mask's curves were transferred onto the surface of the wafer.

In this way, in the conventional technology, since the virtual plane and the surface of the wafer are aligned so-called indirect focusing, there is a possibility of measurement errors in the position of the mask pattern projection image plane,
It is easy to suffer from problems such as focal plane deviation due to drift of the mounting position of the projection optical system or the wafer surface positioning section 9, and it has the disadvantage that it is difficult to obtain a low resolution. Along with this, there is also a drawback that the yield of the product is poor.

The present invention aims to provide a projection exposure apparatus that solves the above-mentioned conventional drawbacks.

That is, in the present invention, a non-contact displacement meter is provided in the wafer surface positioning section, the heights of a plurality of locations on the surface of the sea urchin are determined using this non-contact displacement meter, and an approximate plane is calculated from this data.

A control circuit that links the mounting table and a non-single-contact displacement meter controls the mounting table on which the wafer is mounted so that the plane obtained in this manner coincides with the desired virtual plane (mask pattern projection imaging plane). Adjust the parallelism to align the wafer with the virtual plane. The wafer thus positioned is moved to the lower part of the half mirror of the alignment optical system by the traveling table, and the amount of deviation between the wafer surface and the projection image plane of the mask pattern is optically detected and calculated. Feedback is sent to the non-contact displacement meter, and the control circuit further adjusts the parallelism of the mounting base to correct direct errors between the wafer surface and the projection image plane of the mask pattern. This is characterized in that the projection image plane of the mask pattern and the projection image plane of the mask pattern are completely aligned.

The details will be explained below based on the embodiment shown in the figures.

First, for a detailed explanation, the projection optical system 7. Alignment optical system 89 stone surface plate 5. The configurations of the traveling table 6, the table 3.4 of the wafer 1 and the mask 2, and the wafer surface positioning section 9 are the same as those explained in FIG. 1, so their explanations are omitted here. - Explain the surface positioning mechanism. In the figure, number 21 is a non-contact displacement meter that measures heights at multiple locations on the surface of wear N1 in a non-contact manner, and as shown in FIG. 24, and the drive unit 25
O13 is a mounting table which reciprocates the range 26 shown in FIG.
It is installed on the table 3 via three laminated electrostrictive elements 20 (only two are shown) which are fixed by suction by the vacuum pressure applied to the periphery and supported at three positions around the periphery. The laminated electrostrictive element 20 and the non-contact displacement meter 21 are connected to a torque changer 28.
Computer 29, D/A converter 30. and an electrostrictive element driver 31, the laminated electrostrictive element 20 is driven based on the output value of the non-contact displacement meter 21, and the parallelism of the mounting table 13 is adjusted. Further, as shown in FIG. 4, the traveling table 6 is guided by an air pad 27 and moves so as to cross the moving direction 26 of the non-contact displacement meter 21 (in a direction perpendicular to the plane of FIG. 4). As shown in FIG. 5, the displacement of the entire surface of the wafer 1 is measured by these two crossing operations. k! , 6 shows an alignment optical system, and the alignment optical system 8 includes a half mirror 12, an objective lens 11 . Mirror 35. Relay lens 36. and a linear image sensor 33, and these components are assembled so that an image on the approximate plane 32 of the wafer is formed on the linear image sensor 33. Note that the mask pattern is imaged by a flat 34-digit projection optical system 7.

It is a flat plane.

The operation of this embodiment configured as above will be explained below.

First, in the wafer surface positioning section 9, as shown in FIG.
Find the height at multiple locations of 1. Based on this data, the approximate plane 32 of the wafer surface is determined by the least squares method, the difference between this and the mask pattern imaging plane determined in advance is calculated, and each laminated electrostrictive element 20 is arranged such that these planes match. Calculate the amount of drive. Computer 29
and the envy converter 30.

After that, the information is input to the electrostrictive element driver 31 to drive each laminated electrostrictive element 20 to match the surface of the wafer 1 with the previously determined mask pattern and plane. After the wafer surface is made to coincide with the previously determined mask pattern imaging plane in this manner, the traveling surface table 6 is moved until the wafer l is located below the half mirror 12 of the 72-ment optical system 8. This state is referred to as Figure 6 (α). Next, the focal position of the alignment optical system 8 is moved so that the approximate plane 32 of the wafer coincides with the surface of the wafer l. This operation is performed using the objective lens 11. Alternatively, the state of 0ζ1c, which can be achieved by moving the relay lens 36 in the optical axis direction, is shown in 6th ψCb).

Next, the wafer 1 and the plane 32 are moved synchronously and the optical system detects whether the mask pattern imaging surface 34 on which the mask pattern is imaged matches the table 1i11 of the wafer 1. As an example of a focusing point discrimination method for detecting the coincidence of these surfaces, a case will be described in which the sample surface η is a linear pattern 37 such as the seventh +(α) quantity. Linear image sensor 3 in this case
The output of 3 is as shown in FIG. 7+(b). Here, plane 32
Alternatively, move the image plane to be detected in the optical axis direction and
Find the point where the phantom wave height value △ peaks. This is called the optimal focusing state.

This operation is performed on the mask pattern imaging surface 34 and the surface pattern of the wafer I, and the focal point of both surfaces is determined in the process shown in FIG. By determining the focal point in this manner, the amount of deviation between the plane 34 and the surface of the wafer 1 is determined, and this is fed back to the mounting stage control circuit that positions the wafer surface to correct the error.

Of course, it is possible to perform this error correction operation every time, but it is also possible to perform only this optical focusing operation periodically.
It is also possible to save time by periodically correcting errors.

Furthermore, since the measurement of the wafer surface only needs to be able to measure multiple locations on the wafer surface, it is not limited to scanning measurement using one element as in this embodiment.
As shown in FIG. 8, a structure in which a plurality of elements are mounted and fixed may be used.

In addition, as for the in-focus point detection pattern, the detection sensitivity of the plurality of parallel line patterns shown in the t-th line cannot be higher than that of a single line.According to the present invention described in detail above, A non-contact displacement needle is provided in the wafer surface positioning section, and the heights of multiple locations on the wafer surface are determined using this non-contact displacement meter. An approximate plane is calculated from this data, and the approximate plane and the mask pattern projection result obtained in advance are calculated. A control circuit adjusts the parallelism of the wafer mounting table so that the image plane is aligned with the image plane, and an alignment optical system optically detects the amount of deviation of the mask pattern from the projection image plane.
Since the error is corrected by feeding back to the control circuit, it is possible to directly match the projection image plane of the mask pattern projected by the projection optical system with the wafer surface, thereby reducing resolution loss. Transfer is now possible and the yield of products can be improved.0 Also, by periodically performing error correction operations, the surface adjustment time of UNINO is shortened, and error correction operations can be performed periodically. This has many advantages in terms of manufacturing, such as allowing the projection image plane of the mask pattern to directly match the wafer surface and enabling high-resolution transfer processing at high speed.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a projection exposure apparatus, FIG. 2 is a sectional view of a conventional surface positioning unit, and FIGS. 3 to 9 are examples of the present invention. FIG. 4 is a cross-sectional view of the positioning unit; FIG. 4 is a vertical cross-sectional view of FIG. 3; FIG. Figure 6 is an optical path diagram of the alignment optical system, Figure 1 is a diagram showing the relationship between the pattern used for focusing and the detection output, and Figure 8 is another implementation in which a large number of non-contact displacement meters are installed in the wafer surface positioning section. For example,
FIG. 9 is a diagram showing another embodiment in which a large number of patterns used for focusing are provided and the relationship between the large number of patterns and the detection output is shown. l...Waste cloth 2...Mask)...Projection optical system 8...Alignment optical system 9...Wafer surface positioning section 13...Wafer mounting stand 21...Non-contact displacement meter 20... - Laminated electrostrictive element 28... A/, converter 29... Computer 3o... Ru converter 31... Electrostrictive element driver. One Patent Attorney Toshiyuki Usuda Figure 4-i5 Mouth O T Figure (ku) v (b) O 8 Figure 21 Fang B Figure (α)

Claims (1)

[Claims] After positioning the wafer placed on the table under the wafer surface positioning unit and positioning the wafer surface, the wafer is moved to the lower part of the half mirror of the alignment optical system by the scanning table, and the wafer is moved to the lower part of the half mirror of the alignment optical system by the projection optical system. ,
In an apparatus that images a mask pattern onto a wafer, aligns the pattern on the wafer with the projected imaged mask pattern using an alignment optical system, and performs projection transfer.
The height direction and parallelism of the table can be electrically adjusted, a non-contact displacement meter is provided in the surface positioning section, and the non-contact displacement meter and an adjustment section that adjusts the height direction and parallelism of the table are controlled. On the other hand, the alignment optical system is connected to the pattern detection optical system that can focus the image on the detection element surface on the sample surface in the optical axis direction K 11 PJ. A projection exposure apparatus characterized by detecting an optimal focusing state, inputting it to a non-contact displacement needle, and causing -tc between the surface directly to the sea urchin and the mask pattern imaging plane projected onto the wafer surface.