CN108037642A

CN108037642A - The calibration method of excimer lithography lighting system coherence factor

Info

Publication number: CN108037642A
Application number: CN201711443174.5A
Authority: CN
Inventors: 曹益平
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2017-12-27
Filing date: 2017-12-27
Publication date: 2018-05-15

Abstract

The present invention is that etching system is based on CCD imaging coherence factor measuring system devices, and the calibration consistent with lens focal plane of CCD photosurfaces is realized by pin hole, rotating platform, manual X Y displacement platforms.Suitable coordinate system is established on CCD, is then taken on pin hole a bit, by lens imaging on CCD, the barycenter of this point is obtained, obtains first coordinate points A`.90 ° of rotating platform is rotated, second picture is obtained, obtains its barycenter, obtain second coordinate points B`, be rotated further using same method, respectively obtain the 4th point B`` of the 3rd A``.Then correlation is established using this four coordinates, when the distance of A` to A`` and the bigger distance difference of B` to B``, thinking CCD and lens focal plane, there are certain angle, the relation set up by four coordinates obtains angle, then the angle of CCD photosurfaces is adjusted, until reaching arbitrarily small when the distance of A` to A`` and the difference of distance of B` to B``.It is basically identical so as to fulfill CCD photosurfaces and lens focal plane.

Description

The calibration method of excimer lithography lighting system coherence factor

Technical field

The present invention relates to excimer lithography lighting system coherence factor measuring device, this method realizes survey well Measure calibration of the CCD photosurfaces with lens focal plane there are certain angle in device.

Background technology

Using optics-chemical principle and chemistry, physical etchings method in IC manufacturing, mask graph is turned Move on on single-crystal surface, form the technology of effective functional graphic, be known as photoetching technique.Optical exposure photoetching, due to The advantages that cost is low, high resolution, equipment are simple and convenient to operate and obtain tremendous expansion.Optical exposure photoetching include contact, Four kinds of proximity lithography, laser interference and optical projection lithography, wherein Excimer laser Microlithography are optical projection lithography skills One kind of art.

Continuous with semiconductor devices volume reduces, and the making to chip requires also higher and higher.Etched line on chip The offset of the characteristic size of bar becomes one of restrictive factor in ic manufacturing process.In nineteen ninety-five, Y. Borodovsky proposes that the change of coherence factor can cause the change that line width is etched on whole silicon chip face, this viewpoint is subject to afterwards The concern of many people has simultaneously done related demonstration.So in the daily production process of integrated circuit, simple and reliable coherence factor Detection can preferably optimize conditions of exposure with Instructing manufacture person, and then improve the quality of etching lines.In present technical background Under, it is main to use two kinds of typical coherence factor measuring methods, i.e. diamond shape grating image method and Kirk barriers point imaging method.

Fig. 1 is lithographic exposure systems schematic diagram, as requested, it is necessary to detect the coherence factor of light field each point at mask plane, Dotted line frame is the position that coherence factor measuring system is placed.The measuring method of coherence factor at mask plane based on CCD imagings, should Method basic principle is as follows：

The measuring device of coherence factor is specific as shown in Fig. 2, it is made of three parts at mask plane based on CCD imagings, carries Baffle, lens group and the ccd image sensor of pin hole, as shown in dotted line frame in Fig. 2.Coherence factor measuring system and its support are flat Platform is as shown in figure 3, when designing, it is desirable to which the center of B baffle pin holes is with the center of rear lens L and CCD photosurfaces center one On bar straight line, and parallel to lighting system primary optical axis.Whole measuring device is translating in the plane parallel to mask plane, preferable In the case of require measuring device movement where plane it is vertical with lighting system primary optical axis.It is packaged with light-proof material, avoid not The light and ambient light for wishing participation imaging enter CCD.And in this device, the photosurface of CCD must and lens focal plane Same plane is in, under present technical background, the unified method of neither one is burnt to realize the photosurface of CCD and lens Plane is in same plane, the method that every kind of device has oneself independent make CCD photosurfaces as far as possible with lens focal plane In same plane.

The content of the invention

In order to make CCD photosurfaces reach plumbness with optical axis as far as possible, the present invention be using following technical proposals come Realize：

After pin hole ensures that pin hole panel and lens primary optical axis are vertical with lens using autocollimation, it is fixed, CCD It is placed on the focal plane of lens.A point A is taken on pin hole, it images in A ' points on photosurface, then rotates clockwise CCD, rotation angle are 90 °, and B ' points are obtained on CCD photosurfaces, according to same method, continue to rotate CCD, obtain other two A picture point A ' ' and B ' ' so that the length of A ' to A ' ' and the length of B ' to B ' ' are unequal, and there are certain deviation, it is believed that CCD Photosurface and lens primary optical axis out of plumb, when both deviations are sufficiently small, it is believed that CCD and the main primary optical axis of lens Vertically.Then the relative position relation between four points is established, equation calculation is established and obtains CCD photosurfaces and lens primary optical axis Deviation angle, adjusts the angle of CCD photosurfaces, until making the difference of the length of A ' to A ' ' and the length of B ' to B ' ' arbitrarily small, this When CCD photosurfaces reached substantially with lens focal plane it is consistent.

The present invention has the following advantages compared with prior art：

1 present invention can be eliminated since CCD photosurfaces and lens focal plane are there are certain angle and to the measurement of coherence factor The error brought, meets the accuracy requirement of etching system.

2. the present invention is easy to operate, it need to only operate CCD, rotating platform and calibration can be achieved.

3. the principle of the invention is simple.Utilize the geometrical relationship between the picture point of rotating platform, same point on CCD photosurfaces It can realize the calibration of CCD photosurfaces and lens focal plane there are certain angle.

Brief description of the drawings

Fig. 1 lithographic exposure systems schematic diagrames

Fig. 2 coherence factor measuring principle figures

Fig. 3 CCD probe modular structure schematic diagrams

Fig. 4 laser methods calibrate CCD position views

Fig. 5 measuring system equivalent light paths

Fig. 6 CCD photosurfaces and lens axis out of plumb

Fig. 7 CCD imaging surfaces tilt schematic diagram.

Embodiment

Below in conjunction with the accompanying drawings, operation principle and implementation are described in further detail the present invention.

In Fig. 4, after pin hole is fixed with lens group, coordinate system is established on lens,For lens light Direction of principal axis.Coordinate system is established on CCD photosurfaces,In CCD photosurfaces,For its method Line direction, as shown in figure 5, corresponding unit vector.When CCD photosurfaces aroundAxis rotatesAngle, rotates around Ym axis Angle, coordinate systemWithBetween transformation matrix be：

（1）

CCD photosurfaces normal direction relative lens coordinate is after rotation,

（2）

For in Fig. 6, CCD photosurfaces have certain angle with lens focal plane, and correcting method is as follows：

If the optimum radius of pin hole is, then the maximum incident angle of the light of lens object space node is passed throughFor,

（3）

The position and direction for changing speculum in Fig. 4 arrive position 2 so that the parallel rays sent by laser and lens axis institute Angulation is less thanIncide on pin hole, on pin hole a bitConverged at by lens on CCD photosurfacesPoint position.Gather luminous pointAnd according to formula（4）Calculate its center-of-mass coordinate（）.

；（4）

Rotate CCD three times successively, be rotated by 90 ° every time, collection laser spot obtains、、And calculate its center-of-mass coordinate（）,（）,（）, as shown in Figure 7.

When meeting the following conditions,

（5）

CCD photosurfaces and lens axis are there are certain angle, as shown in fig. 7, sine is applied in △ A ' OF,

（6）

, thenAngle is represented by,

（7）

Then aroundThe deflection angle of axisIt can be expressed as,

(8)

Sine is applied in △ B ' OF,

（9）

, thenAngle can be expressed as,

（10）

Then aroundThe deflection angle of axisIt can be expressed as,

（11）

According to formula（8）And formula（11）Adjust the deflection angle of CCD, until opposite 2 points it is any a small amount of for one apart from its difference, i.e.

（12）

To be any a small amount of, CCD positions reach optimal.

Claims

1. the calibration method of excimer lithography lighting system coherence factor, it is characterised in that by pin hole, rotating platform, Manual X-Y displacement platform and CCD realize the calibration consistent with lens focal plane of CCD photosurfaces, are rotated using rotating platform CCD, changes the position of any formed picture point on CCD on pin hole, is then sentenced by accessed several different picture points Whether disconnected CCD photosurfaces and lens focal plane are in same plane, if not continuing with obtained several points in same plane Coordinate establish the angle that functional relation obtains deviation, then adjust the angle of CCD photosurfaces, until both be in it is same flat Face.

2. in accordance with the method for claim 1, it is characterised in that described application rotating platform rotates CCD so that on pin hole Some image point position on CCD change, then obtain several picture points, establish relevant geometrical relationship formula and functional relation Formula.

3. in accordance with the method for claim 1, it is characterised in that judge CCD photosurfaces and saturating using acquired relational expression The angle of deviation is obtained using the functional relation of foundation, is then adjusted whether in same plane, no longer same plane in the focal plane of mirror The angle of CCD photosurfaces is saved, until both are in same plane.