CN102722090B - Illumination uniformity compensation device - Google Patents

Abstract

An illumination uniformity compensation device, comprising first and second compensation components arranged along a direction perpendicular to the optical axis of the system, each compensation component is composed of a plurality of compensation units, and the number of compensation units of the first and second compensation components is are equal, the corresponding compensation units form a compensation unit pair. Each compensation unit can move in and out of the illumination field of view along the scanning direction of the illumination field of view, blocking part of the illumination light, so as to achieve the purpose of adjusting the integral energy uniformity of the scanning field of view. The compensation unit of the uniformity compensation device is a strip-shaped thin plate, and one end inserted into the illumination field of view is polygonal or arc-shaped; the compensation units are arranged in two layers, covering the gap formed between the two compensation units in the other layer. The invention effectively increases the number of divided equal parts of the illumination field of view, reduces the width of each equal part, thereby improving the compensation accuracy of the compensation device, and at the same time does not increase the number of compensation units, and does not increase the mechanical design and control system design. Difficulty, easy to achieve.

Description

A lighting uniformity compensation device

technical field

The invention relates to a uniformity compensation device, in particular to an illumination uniformity compensation device in a lithography illumination system.

Background technique

Providing uniform illumination for the mask surface is the main function of the lithography illumination system. Good illumination uniformity reduces the lithography process factor and improves the resolution of the entire lithography system; on the contrary, the uneven distribution of illumination will make the silicon wafer surface The thickness of the exposed lines is uneven, which seriously affects the quality of photolithography.

With the continuous shortening of lithography wavelength and the continuous reduction of feature size, lithography has higher and higher requirements for the uniformity of the illumination system. It is difficult or difficult to achieve uniformity only by using traditional light uniformity devices and light uniformity principles. Require. In addition, the components in the lighting system will wear out over time, reducing their uniformity performance and introducing new non-uniformities. Therefore, in order to meet the requirements of lithography illumination uniformity and compensate the non-uniformity introduced by different factors in the system, it is necessary to add an illumination uniformity compensation device in the system.

U.S. Patent No. 7,173,688 provides a uniformity compensation device in the form of double-sided insertion. The compensator device of this structure is arranged with multiple compensation units on both sides of the illumination field of view. Each compensation unit is a rectangular flat structure, which can be The scanning direction of the field of view is inserted into the field of view of the illumination, and part of the illumination light is blocked to achieve the purpose of adjusting the uniformity of the integral energy distribution of the field of view of the illumination. In this patent, all the compensation units are placed side by side on the same plane, so that there is a gap between adjacent compensation units, resulting in light leakage and new inhomogeneity. In addition, placing them side by side makes the compensation device divide the illumination field of view into equal parts with the width equal to the width of the compensation unit, that is, the adjustment space period for uniformity is equal to the width of the compensation unit, so this type of compensation device can only compensate for a space period greater than the width of the compensation unit unevenness, the adjustment accuracy is low.

In the Chinese patent CN101221373A, a uniformity compensation device with overlapping compensation units is proposed. The compensation unit of this compensation device is also a rectangular flat plate structure, which is placed in two layers alternately, covering the other layer between two adjacent compensation units. gap, which effectively solves the problem of light leakage in US Patent No. 7,173,688. In addition, the overlapping placement form also makes the equal width of the illumination field of view divided by the compensation device smaller than the width of the compensation unit, that is, the adjustment space period for uniformity is smaller than the width of the compensation unit, which improves the compensation accuracy of the compensation device to a certain extent. However, the increase in compensation accuracy is based on the increase in the number of compensation units. The greater the number of compensation units in the same space, the more difficult it is for the mechanical design and control system. Therefore, this patent increases the compensation accuracy while increasing the Difficulty in mechanical design and control. With the development of science and technology, the requirements for illumination uniformity of lithography illumination system are getting higher and higher. Due to the limitation of machinery and control level, the compensation accuracy of uniformity compensation device can be improved by increasing the number of compensation units and reducing the size of compensation units. Pathways are increasingly difficult to achieve.

Contents of the invention

In order to overcome the defects of the prior art, the object of the present invention is to provide a lighting uniformity compensation device, which does not need to reduce the width of the compensation unit or increase the number of compensation units, and increase the mechanical design and control difficulty while increasing The number of divisions of the lighting field of view by the compensation device is reduced to reduce the width of the divisions, thereby improving the compensation accuracy of the compensation device.

In order to achieve said object, the technical scheme proposed by the present invention is:

An illumination uniformity compensation device, which is placed near the field of view plane or its conjugate plane of the illumination system, includes first and second compensation components arranged along a direction perpendicular to the optical axis of the system, and each compensation component consists of a plurality of compensation units Composition, and the number of compensation units of the first and second compensation components is equal, and the corresponding compensation units form a compensation unit pair. Each compensation unit can move in and out of the illumination field of view along the scanning direction of the illumination field of view, blocking part of the illumination light, and achieving the purpose of adjusting the integral energy uniformity of the scanning field of view.

Wherein, the compensation unit of the illumination uniformity compensation device is a thin plate inserted into the end of the illumination field of view to form a polygonal or arc-shaped structure, arranged in two layers, covering the gap formed between the two compensation units on the other layer, such The structural form and arrangement method can effectively increase the number of divisions of the illumination field of view and reduce the width of each division, thereby improving the compensation accuracy of the compensator.

The polygonal insertion end of the compensation unit, each side accounts for 1/2 or 1/3, 1/4 of the entire width of the compensation unit; the inclination angle of each side is 30°, 45°, 60°, etc. Angle between 0~90°.

The compensation unit is a strip-shaped thin plate, and one end inserted into the illumination field of view is in the shape of a corner-cut rectangle.

Each corner of the corner-cutting rectangular compensation unit accounts for 1/2 or 1/3, 1/4 of the width of the entire compensation unit; the inclination angle of each corner is 30°, 45°, 60° ° is an angle between 0° and 90°.

The compensation unit is a strip-shaped thin plate, and one end inserted into the illumination field of view is in the shape of an arc, and the arc is determined according to actual needs.

In the first and second compensation components, all the compensation units are arranged in two layers on the compensation plane, and the upper layer compensation unit covers the gap formed between the two adjacent compensation units of the lower layer. Similarly, the lower layer compensation unit also At the same time, the gap formed between two adjacent compensation units on the upper layer is covered.

The first and second compensation components are completely symmetrical and distributed on both sides of the illumination field of view. The corresponding compensation units on the first and second compensation components form a pair of compensation units. Consistent, the insertion amount is equal and the direction is opposite.

The material used by the compensation unit and the transmittance distribution of the material are exactly the same, and can be made of opaque materials or materials with a certain transmittance. At this time, the transmittance obeys a certain direction along the insertion direction of the compensation unit. Function distribution, but its transmittance cannot be 1, that is, completely transparent materials cannot be used.

Compared with the prior art, the present invention has the following advantages:

(1) Since one end of each compensation unit inserted into the illumination field of view is a polygonal shape, when inserting the illumination field of view, the occlusion area of each side to the illumination field of view is different, so the illumination field of view area affected by a compensation unit is divided into areas wider than itself Several smaller areas can get better compensation effect under the same conditions.

(2) The compensation units of the present invention are arranged in layers and staggered. This arrangement combined with the polygonal shape of the insertion end can further divide the same illumination field of view into more and smaller division areas, improving the uniformity The compensation accuracy of the compensation device.

(3) While improving the uniformity compensation accuracy, the present invention does not increase the number of compensation units, and does not introduce additional driving components, which makes the control difficult. Under the same conditions, better compensation effects can be obtained, and the cost is low and easy to implement.

Description of drawings

FIG. 1 is a schematic diagram of the application of the uniformity compensation device of the present invention to the optical path structure of the projection exposure system of a lithography machine;

Fig. 2 shows the structural representation of the uniformity compensation device of the present invention;

Figure 3 is a schematic diagram of the division of the illumination field of view by the uniformity compensation device arranged in a single layer of rectangular structure;

Figure 4 is a schematic diagram of the division of the illumination field of view by the uniformity compensation device with a rectangular structure and double-layer staggered arrangement;

Fig. 5 is a schematic diagram of the division of the lighting field of view by the uniformity compensation device with double-layer staggered arrangement of a rectangular structure with cut corners according to the present invention;

Figure 6 shows a comparison diagram of the field of view division of the uniformity compensation device with a rectangular single layer, a rectangular double layer and a corner-cut rectangular double layer;

FIG. 7 is a schematic structural diagram of a compensation unit in various embodiments of the present invention.

Detailed ways

The specific implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific examples.

FIG. 1 is a schematic diagram of the optical path structure of the illumination uniformity compensation device of the present invention applied to a projection exposure optical system of a lithography machine. A typical lithography projection exposure optical system includes a system light source 101 , an illumination system 102 , a mask plate 104 , a projection objective lens 105 and a silicon wafer 106 . The laser light emitted by the light source 101 is incident into the illumination system 102. The illumination system 102 includes components such as beam expansion, collimation, beam stabilization, illumination mode conversion, illumination field of view formation, knife edge, illumination objective lens, etc., which generate collimation and expansion of the incident light respectively. Beam, stability, specific pupil formation, specific illumination field of view formation, and uniform illumination light, etc., make the incident light pass through the illumination system 102 and obtain a uniform illumination field of view with a specific illumination field of view shape and a specific exit pupil shape on the mask 104 field. The outgoing light of the mask plate 104 illuminated by the illumination system is projected onto the silicon wafer 106 through the projection objective lens 105, and a clear image of the mask plate 104 is obtained on the silicon wafer 106, so that the photoresist on the silicon wafer 106 can be processed Exposure, the above process completes the exposure process of photolithography, that is, transfers the projection of the pattern on the mask plate 104 to the silicon wafer 106 .

The illumination light field of the projection exposure system of the lithography machine requires high uniformity. Any non-uniform illumination on the mask plate 104 will be projected on the silicon wafer 106 through the projection objective lens 105, resulting in a discrepancy between the obtained actual pattern and the ideal pattern. Deviate. In the actual lithography manufacturing process, the manufacturing error of each component of the illumination system and the loss of each component during use will introduce inhomogeneity to the outgoing light of the illumination system incident on the mask plate 104 . With the continuous reduction of lithographic feature size, the illumination uniformity of the outgoing light of the illumination system is getting higher and higher. It is more and more difficult to achieve the required illumination uniformity only for the components in the illumination system. Through the illumination system 102 Using the uniformity compensation device 103 between the mask plate 104 can adjust the energy distribution of the outgoing light of the illumination system 102, so that the illumination light incident on the mask plate 104 is more uniform, so as to achieve the purpose of compensating the uniformity of the pattern on the silicon wafer 106 Purpose.

FIG. 2 is a schematic structural diagram of the uniformity compensation device of the present invention. The uniformity compensation device 103 is composed of two sets of compensation components 202 and 203, which are arranged in the xy plane perpendicular to the optical axis z of the system near the mask surface of the lithography system or its conjugate surface, and arranged in the rectangular illumination along the non-scanning direction x On both sides of the field 201, each group of compensation components includes a plurality of compensation units 202a-202n, 203a-203n. Each compensation unit can independently move in and out of the lighting field along the scanning direction y of the lighting field. The two groups move in opposite directions, one group moves along the positive direction of the y-axis, and the other group moves along the negative direction of the y-axis.

The corresponding compensation units in the two groups of compensation components, such as 202a and 203a form a compensation unit pair, whose movement direction is opposite, the action is consistent, and the insertion amount is the same, so as to maintain the symmetry of the instantaneous field of view and cover the same area of the illumination field of view. area, jointly adjust the lighting energy distribution of this area.

The compensation components 202 and 203, as shown in FIG. 2 , have a long thin plate structure with a thickness of millimeters or microns, and the front end (the end inserted into the lighting field) is a rectangular shape with cut corners. The two cut corners can be symmetrically distributed, or can be made into an asymmetric shape according to the distribution of illumination light energy in actual use. Each cut corner occupies half of the width of the entire compensation unit (ie 1/2), or according to actual needs. 1/3, 1/4 and other ratios. In addition, according to the different slopes of the energy distribution of the actual lighting light field, the inclination angles of the two cutting angles need to correspond to them. Generally, 30°, 45°, 60°, etc. are taken as angles between 0° and 90°.

The materials used in the compensation components 202 and 203 and the transmittance distribution of the materials are exactly the same, and can be made of opaque materials or materials with a certain transmittance. The direction obeys a certain function distribution, but its transmittance cannot be 1, that is, completely transparent materials cannot be used.

The compensation components 202 and 203 are arranged in two layers on the compensation plane, and the compensation unit of the upper layer covers the gap formed between the two adjacent compensation units of the lower layer. Similarly, the compensation unit of the lower layer also covers the two adjacent compensation units of the upper layer. The gap formed between the units avoids light leakage at the gap and avoids new uneven distribution on the illumination field of view.

The uniformity compensation device 103 is composed of a plurality of compensation units, and each compensation unit moves independently to affect the illumination intensity of a certain area in the illumination field of view, so it divides the illumination field of view into several parts, and each part The size along the non-scanning direction (x direction) determines the compensation accuracy of the uniformity compensation device, that is, the smaller the size of each divided part, the higher the compensation accuracy. Therefore, the compensation accuracy of the uniformity compensation device 103 depends on the size (width) of the compensation unit along the x direction, and the arrangement and movement of the compensation units.

In the present invention, the polygonal structure of the compensation unit inserted into the end of the illumination field of view, and the layered and staggered arrangement of the compensation units make it possible to divide the same illumination field of view into more and smaller division areas compared with the prior art , with higher illumination uniformity compensation accuracy.

Figure 3 is a schematic diagram of the division of the illumination field of view by the uniformity compensation device arranged in a single layer of a rectangular structure, Figure 4 is a schematic diagram of the division of the illumination field of view by the uniformity compensation device of a rectangular structure with a double-layer arrangement of compensation units, and Figure 5 is the basic One of the specific embodiments of the invention, that is, the schematic diagram of the division of the illumination field of view by the uniformity compensation device arranged in two layers with a rectangular structure with cut corners as the compensation unit. By comparing the above three figures, we can see the compensation capabilities of various forms of uniformity compensation devices. In Figure 3, since the compensation units 302a~302n are arranged side by side in a single layer, the compensation device will illuminate the field of view It is divided into several equal parts whose number is equal to the number of compensation units, and the width of each part is equal to the width of a single compensation unit. As shown in Figure 3, four compensation units divide the illumination field of view 201 into four equal parts 3011~3014 . For the uneven illumination energy distribution with a space period greater than the width of the equal division, this rectangular structure single-layer arrangement can be used to compensate, and for the uneven energy distribution with a space period smaller than the width of the division, for example, there are n in the division 3011 This kind of uniformity compensation device is powerless to deal with the uneven distribution of periods, that is, the compensation precision of the uniformity compensation device arranged in a single layer of rectangular structure is equal to the width of the compensation unit.

As shown in FIG. 4 , the uniformity compensation device arranged in two layers with a rectangular structure can double the ability of the compensation device to divide the illumination field of view. This kind of compensation device superimposes a layer of compensation units on the compensation units arranged in a single layer as shown in Figure 3. As shown by the dotted line in the figure, the two layers of compensation units are placed alternately, covering each other and forming a gap between the two compensation units of the other layer. gap. Such an arrangement makes the illumination field of view 201 divided into eight equal parts 4011-4018, twice the original, and the width of each equal part is equal to half of the width of a single compensation unit. Since the compensation accuracy of the compensation device is equal to the width of the division of the illumination field of view, the compensation accuracy of this compensation device is twice as high as that of the compensation device arranged in a single layer. However, the number of compensation units is double that of the compensation device arranged in a single layer, which will add great difficulty to the mechanical design and control system design.

Fig. 5 is a schematic diagram of the division of the illumination field of view by the uniformity compensation device arranged in two layers of staggered rectangles with cut corners in one of the specific embodiments of the present invention. On the basis of the uniformity compensation device arranged in two layers in a rectangular structure, the compensation unit is made into a rectangular structure with cut corners. Compared with the part without cut corners, the compensation amount for the illumination field of view is different. The affected lighting field of view area is divided into smaller parts, so that the lighting field of view 201 is further divided into 16 equal parts from 5011 to 5026, and the accuracy is doubled compared with the uniformity compensation device arranged in a rectangular structure. And it does not increase the number of compensating units of the compensator, and does not increase the difficulty of mechanical design and control system design.

Figure 6 is a comparison diagram of the compensation effects of the three types of uniformity compensation devices in Figure 3, Figure 4, and Figure 5. Compensation effect curves of three kinds of compensating devices arranged in two layers of rectangular structure with cut corners and shown in Fig. 5. Since the field of view is divided into the fewest equal parts and the equal part width is the largest, the compensation effect curve 601 of the compensation device arranged in a single layer of rectangular structure is the roughest, showing a stepped curve. However, the angle-cut rectangular structure double-layer arrangement compensation device of the present invention has the most equal divisions of the field of view, the smallest width, and the smoothest compensation effect curve 603, and the division curves corresponding to the cut corners of each compensation unit have a certain degree. Slope, which adds to the smoothing effect of the curve. The compensation effect curve 602 of the rectangular structure double-layer arrangement compensation device is between the two, which is a stepped curve like the curve 601, but the step width is smaller, which is closer to the compensation target curve.

The main idea of the present invention is to make the insertion end of the compensation unit into a certain shape, and when different parts of the shape are inserted into the illumination field of view, the blocking area of the illumination light is different, so that the illumination field of view corresponding to the width of one compensation unit is divided into multiple parts. The two parts with different compensation amounts, combined with the arrangement and movement of the compensation unit, can reduce the width of the division of the illumination field of view by the compensation device, thereby improving the compensation accuracy of the compensation device.

According to this idea, as shown in Figure 7, the front end of the compensation unit of the uniformity compensation device of the present invention (the end inserted into the illumination field of view) can be made into a shape of a corner-cut rectangle (as shown by 701 in Figure 7 ). , can also be made into other polygons, such as the structure shown by 702 in Figure 7, to divide the illumination field of view corresponding to a compensation unit into smaller and more divided parts. The polygons can be distributed symmetrically, or according to In actual use, the illumination light energy distribution is made into an asymmetric shape, and each side accounts for 1/3, 1/4, etc. of the width of the entire compensation unit; in addition, according to the different slopes of the actual illumination light field energy distribution, each side of the polygon The inclination angle needs to correspond to it, generally take 30°, 45°, 60° and other angles between 0° and 90°. The front end of the compensation unit can be made into an arc, as shown by 703 in Figure 7, that is, a compensation unit is divided into countless infinitely small areas, and of course it can also be a parabolic structure, or other irregular shapes, such as a cone or triangle etc.

The present invention does not elaborate on some of the known techniques that belong to those skilled in the art.

Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention, rather than as a limitation to the present invention, as long as within the scope of the spirit of the present invention, changes to the above embodiments , Modifications will fall within the scope of the claims of the present invention.

Claims (10)

1. an illumination uniformity compensating, comprises first, second compensation assembly along arranging perpendicular to systematic optical axis direction, each compensation assembly forms by multiple compensating unit, and first, the compensating unit number of the second compensation assembly is equal, corresponding compensating unit forms compensating unit pair, each compensating unit all can move along illumination field of view direction of scanning turnover illumination field of view, block partial illumination light, reach the object of adjustment scanning field of view integral energy homogeneity, it is characterized in that: described compensating unit is insert the thin plate that polygon or arcuate structure are made in one end of illumination field of view, it does not need the compensating unit number reducing compensating unit width or increase, while not increasing Machine Design and control difficulty, increase compensation system to numbers such as the divisions of illumination field of view, reduce the width dividing equal portions, thus improve the compensation precision of uniformity compensating.

2. illumination uniformity compensating according to claim 1, is characterized in that: described compensating unit is the thin plate of strip, and the one end of inserting illumination field of view is polygonal shape.

3. illumination uniformity compensating according to claim 2, is characterized in that: the polygon insertion end of described compensating unit, and often accounting for whole compensating unit width is of a size of 1/2,1/3 or 1/4 ratio; The pitch angle on every one side is between 0 ~ 90 °.

4. illumination uniformity compensating according to claim 1, is characterized in that: described compensating unit is strip thin plate, and the one end of inserting illumination field of view is the shape of corner cut rectangle.

5. illumination uniformity compensating according to claim 4, is characterized in that: each corner cut of described corner cut rectangle compensating unit accounts for that whole compensating unit width is of a size of 1/2 or 1/3,1/4 ratio; The pitch angle of each corner cut is between 0 ~ 90 °.

6. illumination uniformity compensating according to claim 1, is characterized in that: described compensating unit is strip thin plate, and the one end of inserting illumination field of view is the shape of arc.

7. according to the illumination uniformity compensating one of claim 1 to 6 Suo Shu, it is characterized in that: in first, second compensation assembly described, its all compensating unit is two-layer arrangement in compensation plane, upper strata compensating unit hides the gap formed between adjacent two compensating units of lower floor, and lower floor's compensating unit also hides the gap formed between adjacent two compensating units in upper strata simultaneously.

8. according to the illumination uniformity compensating one of claim 1 to 6 Suo Shu, it is characterized in that, described first and second compensation assembly full symmetrics, be distributed in illumination field of view both sides, compensating unit corresponding on first, second compensation assembly forms a compensating unit pair, its mode of motion full symmetric, namely inserts illumination field of view time consistency, insertion is equal, and direction is contrary.

9. illumination uniformity compensating according to claim 7, it is characterized in that, described first and second compensation assembly full symmetrics, be distributed in illumination field of view both sides, compensating unit corresponding on first, second compensation assembly forms a compensating unit pair, its mode of motion full symmetric, namely inserts illumination field of view time consistency, insertion is equal, and direction is contrary.

10. according to the illumination uniformity compensating one of claim 1 to 6 Suo Shu, it is characterized in that, the transmitance distribution of the material that described compensating unit uses and material is identical, can by opaque material, also can be made by the material with certain transmitance, now transmitance obeys certain function distribution along the direction of insertion of compensating unit, but its transmitance can not be 1, namely can not adopt the material of complete printing opacity.