CN103293865B - Workpiece platform position error measurement and pre-compensation method - Google Patents

Abstract

The invention discloses a workpiece platform position error measurement and pre-compensation method comprising the following steps of: measuring at multiple positions, calculating the influence on the height and the incline of the workpiece platform caused by fluctuation of a support platform according to the measuring results, calculating the influence on the angle of inclination of the workpiece platform caused by the shape of a reflecting surface at the side face of the workpiece platform, and compensating the workpiece platform with the obtained error data according to the position of the workpiece.

Description

The method of work stage measured position error and pre-compensation

Technical field

The present invention relates to field of lithography, particularly relate to and work stage site error measured and the method for pre-compensation.

Background technology

Litho machine exposes the silicon chip be put in work stage, requires the distance that silicon chip upper surface and projection lens keep fixing, to ensure that silicon chip upper surface is positioned at the optimal focal plane of camera lens all the time in exposure process.For this reason, as US Patent No. 6,172,757 B1 describe, generally be designed with focusing and leveling sensor in litho machine, this sensor and projection lens position are fixed, and utilize the height of the detection method Real-Time Monitoring silicon chip of optical reflection on silicon chip, by closed-loop control, thus ensure the unilateral not out of focus of exposed silicon.

Due to the defect of measurement function, be positioned at the situations such as silicon chip edge in measuring position under, due to can reflective surface area too little, the measurement of focusing and leveling sensor can produce comparatively big error.In addition, focusing and leveling sensor needs cost certain hour for measuring position of silicon wafer, therefore will affect the processing speed in exposure process above by measuring silicon chip height in real time and carrying out closed-loop control, thus affect the production efficiency of litho machine.Making great efforts the processing time of compression production technology links with under the prerequisite improving machine formation efficiency, if the height error at this place can be known before work stage moves to certain in advance, the height of silicon chip being transferred to suitable position, then can solving this contradiction.

US Patent No. 5,790,253 methods proposing a kind of side of measurement mirror surface-shaped, can measure the pattern of minute surface on-the-spotly, thus compensate horizontal direction measurement result, as shown in Figure 1.The method can based on the laser interferometer side of the carrying out mirror surface-shaped measurement each direction having diaxon measuring beam.For the measuring system each direction having three axle laser interferometer, it can the simultaneously horizontal level of measuring workpieces platform, rotation and inclination, as shown in Figure 4.For this system, except the square mirror surface-shaped that two light-beam position places, top measured by needs, also need the square mirror surface-shaped impact of measuring the 3rd axle place, below in advance.

Summary of the invention

The present invention proposes a kind of method that site error to work stage carries out pre-compensation, comprise the steps:

Step one, the vertical position of work stage to be remained unchanged, work stage is set to measuring position in the horizontal direction;

Step 2, measurement record the horizontal level of work stage in described measuring position and angle of inclination, work stage moves to next measuring position;

Step 3, judge whether that all measuring positions are all measured complete, if so, then enter step 4, otherwise return step one;

Step 4, rise and fall according to brace table impact on work stage angle of inclination, and the matching platform that is supported rises and falls the coefficient of the height error introduced, and calculates and to be risen and fallen the angle of inclination error of the work stage introduced and height error by brace table;

The angle of inclination error of step 5, the work stage introduced that to rise and fall based on the angle of inclination of the work stage measured and brace table, the angle of inclination error of the work stage that the side's of calculating mirror surface-shaped is introduced;

The error information of step 6, preservation gained;

Step 7, position according to work stage, utilize the error information obtained to compensate the vertical position of work stage and angle of inclination.

Wherein, described measuring position is equidistantly uniformly distributed on brace table, at brace table surface forming array.

Wherein, when work stage moves to described measuring position place, directly pre-compensation is carried out according to error information.

Wherein, when work stage moves between described measuring position, utilize linear interpolation to ask for every error amount, then carry out pre-compensation according to these error amounts.

According to method of the present invention, can a DATA REASONING be passed through, obtain the site error of two aspects of work stage: the vertical height error of the work stage that marble height relief causes and angle of inclination error; The work stage droop error that the square mirror surface-shaped at the 3rd laser interferometer optical axis place causes.

Method of the present invention, by the interferometer measuring system of measuring workpieces platform position, measures the error that the height relief of Dali Shitai County and square mirror surface-shaped are introduced the attitude of work stage off-line.Utilize the error information of demarcating in advance, feedforward compensation can be carried out to work stage position fast and effectively in litho machine normally works.Based on height error coefficient, can in the hope of the height error of optional position in work stage range of movement, angle of inclination error.When work stage moves to certain position, by the height of corresponding position and inclination being compensated, the error that the fluctuating due to marble surface is introduced effectively can be eliminated.When work stage moves to certain position of horizontal direction, according to the dip plane shape of this position prescription mirror, can correct the reading of interferometer, the side's of removal mirror surface-shaped is on the impact of interferometer measurement result.The measuring system of litho machine itself is adopted to carry out owing to measuring, thus without the need to additionally using extraneous measuring system; And be directly the attitude of work stage is measured, compare and adopt third party's measuring system, measure acquired results more true, simple, efficient; The error separate that the influence factors such as square mirror pattern, marble fluctuating cause is opened by algorithm dexterously that simultaneously adopt in test, and make to measure object single, the error term surveyed is separated; In addition, the height of work stage and droop error are demarcated in advance, in normal work, carry out feedforward compensation in real time, effectively can improve the positioning precision of work stage, improve the exposure efficiency of litho machine simultaneously.

Accompanying drawing explanation

Can be further understood by following detailed Description Of The Invention and institute's accompanying drawings about the advantages and spirit of the present invention.

Figure 1 shows that the schematic diagram of prior art measuring method;

Figure 2 shows that the structural representation of typical litho machine;

Figure 3 shows that the height error schematic diagram of work stage;

Figure 4 shows that the interferometer measuring system structural representation of measuring workpieces platform position;

Figure 5 shows that the mirror out-of-flatness of work stage side affects schematic diagram to angle of bank measurement result;

Figure 6 shows that the distribution schematic diagram of the measuring position of work stage in work stage stroke range.

Figure 7 shows that the method flow diagram of site error pre-compensation of the present invention.

Embodiment

Specific embodiments of the invention are described in detail below in conjunction with accompanying drawing.

Figure 2 shows that the structural representation of typical litho machine.Litho machine generally includes mask platform 101, camera lens 102, work stage 103 and focusing and leveling sensor 104, usual employing Dali Shitai County is as the brace table of work stage and mask platform, in this case, surface due to Dali Shitai County is difficult to accomplish definitely smoothly, when work stage and mask platform move above, height may change, and then introduces error.Figure 3 shows that the height error schematic diagram of work stage.Suppose that the work stage 103 in litho machine is moved on marble, the fluctuating of marble surface will affect height and the inclination of work stage.Simultaneously because work stage is supported by multiple gas foot, the height change reflection of work stage be not the height change of marble a single point, but multiple gas foot acts on the impact on the whole height of work stage after on marble.

The present invention utilizes the laser interferometer of measuring workpieces platform attitude to carry out.Figure 4 shows that the interferometer position measurement mode schematic diagram of work stage, from the measuring beam of the laser interferometer outgoing of measuring workpieces platform attitude according to the Fang Jing to work stage side, obtain the attitude of work stage by the change of measuring beam.Because when marble has height relief, the lateral attitude of work stage can be caused to change.By the attitude of measuring workpieces platform, the height error introduced when work stage is moved on marble effectively can be measured.X to Y-direction 6 laser interferometer measurement light beams altogether, they constitute a measuring system, and 6 light beams work simultaneously, can measure the attitude of work stage.Have fluctuating owing to supporting the marble of work stage, when therefore work stage is moved on marble, its attitude can be subject to marble impact, the error of work stage attitude that marble causes that Here it is; On the other hand, as shown in Figure 5, Fang Jing exists not at ordinary times, and interferometer can be made to produce error to the position measurements of work stage.Above two errors are measurement target of the present invention, finally will compensate it.

In test, the height of work stage and inclination are not additionally arranged, allow the upper surface of work stage be parallel to the marble surface of gas foot.As shown in Figure 6, successively work stage is set to multiple position, these positions are equidistant in the stroke range of work stage to be uniformly distributed.When work stage is positioned at these positions, by the attitude of laser interferometer measurement work stage, comprise horizontal level x, y and angle of inclination Rx _meas, Ry _meas.

In above-mentioned situation, the work stage angle of inclination Rx that laser interferometer records _meas, Ry _measbe made up of following three parts

Rx _meas＝Rx _stone+Rx _mirror

Ry _meas＝Ry _stone+Ry _mirror

Wherein, Rx _meas, Ry _measrepresent the angle of inclination of the work stage that laser interferometer records, Rx _stone, Ry _stonethe angle of inclination of the work stage that representative is introduced due to marmorean height error, Rx _mirror, Ry _mirrorrepresent the angle of inclination caused by the injustice of square mirror surface-shaped.

Due to marmorean processing technology, and the smoothing effect of work stage gas foot, determine it and close to arc surface, and should can not produce sudden change to the impact that work stage height produces.Therefore the equation with two unknowns of low order can be adopted to describe height error:

$z(x,y)=\underset{n=0}{\overset{N}{\mathrm{\Σ}}}\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{x}^n{y}^m$

Wherein, a ₀b ₀the item at place is constant, will not describe in detail here, a _nb _mrepresent x in this polynomial expression ⁿy ^mthis coefficient, z is the height change that marmorean fluctuating causes, x and y is respectively the horizontal position coordinate of work stage.A ₁b ₀and a ₀b ₁what the item at place described is marmorean single order angle of inclination, and these two amounts all can correct in focal plane corrects, and therefore also do not consider this in the present invention.The present invention only tests the error term higher than second order in height error and compensates.

According to the coordinate system meeting the right-hand rule, angle of inclination Rx _stone, Ry _stonewith height z exist as shown in the formula relation:

$\mathrm{Rx}=\frac{\∂z}{\∂y}=\underset{n=0}{\overset{N}{\mathrm{\Σ}}}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{\mathrm{mx}}^n{y}^{m-1}$

$\mathrm{Ry}=-\frac{\∂z}{\∂x}=-\underset{n=1}{\overset{N}{\mathrm{\Σ}}}\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{\mathrm{nx}}^{n-1}{y}^m$

Therefore accordingly, the angle of inclination Rx that height error causes if can record _stone, Ry _stone, then height error can be obtained by integral and calculating.

The work stage angle of inclination that laser interferometer records comprises two components.Need the angle of inclination Rx isolating the work stage introduced by marmorean height error _stone, Ry _stone.The error Rx of laser interferometer itself _mirror, Ry _mirrorsquare mirror surface-shaped primarily of interferometer measuring system causes, and the feature of this amount is exactly when the x coordinate of work stage is constant, and angle of inclination Rx error is constant, and when the y coordinate of work stage is constant, angle of inclination Ry error is constant.

Therefore, the variable quantity at the angle of inclination be shown below can the side's of elimination mirror surface-shaped introduce the impact of error, by carrying out matching to this variable quantity, obtain the coefficient a of height error _nb _m.

${\mathrm{\ΔR}}_x(x,y)={\mathrm{Rx}}_{\mathrm{meas}}(x,y+\mathrm{dy})-{\mathrm{Rx}}_{\mathrm{meas}}(x,y)=\underset{n=0}{\overset{N}{\mathrm{\Σ}}}\underset{m=2}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{\mathrm{mx}}^n({(y+\mathrm{dy})}^{m-1}-y^{m-1})$

${\mathrm{\ΔR}}_y(x,y)={\mathrm{Ry}}_{\mathrm{meas}}(x+\mathrm{dx},y)-{\mathrm{Ry}}_{\mathrm{meas}}(x,y)=\underset{n=2}{\overset{N}{\mathrm{\Σ}}}\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_{m}n(x^{n-1}-{(x+\mathrm{dx})}^{n-1})y^m$

Based on required height error coefficient, can in the hope of the height error of optional position in work stage range of movement, angle of inclination Rx _stone, Ry _stoneerror.When work stage moves to certain position, by the height of corresponding position and inclination being compensated, the error that the fluctuating due to marble surface is introduced effectively can be eliminated.

As mentioned above, the work stage angle of inclination that interferometer measurement obtains, except comprising marmorean fluctuating pattern error, further comprises the square mirror surface-shaped information at the 3rd light beam place for measuring workpieces platform angle of inclination.According to the affecting laws of square mirror surface-shaped to angle of inclination, namely for identical x coordinate, the angle of inclination error Rx of Fang Jing is constant, and for identical y coordinate, the angle of inclination error Ry of Fang Jing is constant.Therefore the angle of inclination error that square mirror surface-shaped causes can by being averaging calculating to the angle of inclination of same position.Based on the angle of bank measurement result Rx at each measuring position place _meas(x _i, y _j), Ry _meas(x _i, y _j) and marmorean angle of inclination error Rx _stone(x _i, y _j), Ry _stone(x _i, y _j), the angle of inclination error of square mirror surface-shaped can be calculated to obtain:

${\mathrm{Rx}}_{\mathrm{mirror}}\left(x_i\right)=\frac{1}{N_y}\underset{j=1}{\overset{N_y}{\mathrm{\Σ}}}({\mathrm{Rx}}_{\mathrm{meas}}(x_i,y_j)-{\mathrm{Rx}}_{\mathrm{stone}}(x_i,y_j))$

${\mathrm{Ry}}_{\mathrm{mirror}}\left(y_j\right)=\frac{1}{N_x}\underset{i=1}{\overset{N_x}{\mathrm{\Σ}}}({\mathrm{Ry}}_{\mathrm{meas}}(x_i,y_j)-{\mathrm{Ry}}_{\mathrm{stone}}(x_i,x_j))$

After having recorded the error that Dali Shitai County height relief and the position of square mirror surface-shaped to work stage cause, these errors are preserved.When work stage moves to certain position of horizontal direction, go out the height in this Dali, position Shitai County according to coefficient calculations and tilt to adjust the attitude of work stage, the impact of marble on work stage attitude can be removed.When work stage moves to certain position of horizontal direction, according to the dip plane shape of this position prescription mirror, thus the reading of interferometer is corrected, can the side's of removal mirror surface-shaped on the impact of interferometer measurement result.Because the marble fluctuating pattern of trying to achieve in said process and square mirror dip plane shape only just have value in specific location, for the value of compartment betwixt, the result based on contiguous measurement point is needed to carry out interpolation.If the X of certain x position is to dip plane shape, it is as follows that the face shape based on its adjacent position carries out linear interpolation formula

Rx _mirror(x)＝α·Rx _mirror(x _i)+(1-α)·Rx _mirror(x _i+1)

Wherein, x is positioned at x _iand x _i+1between a position, wherein

In sum, shown in Figure 7, according to typical method work stage being carried out to pre-compensation of the present invention, comprise the following steps:

Step one, the vertical control gear of work stage is arranged to 0, the vertical position of work stage is remained unchanged, work stage is set in the horizontal direction the measuring position of specifying, these measuring positions are equidistantly uniformly distributed on brace table (as Dali Shitai County), at surface, Dali Shitai County forming array;

Step 2, when work stage is positioned at each measuring position, measures and record the horizontal level of work stage in described measuring position and angle of inclination, work stage is moved to next measuring position;

Step 3, judge whether that all measuring positions are all measured complete, if so, then enter step 4, otherwise return step one;

Step 4, according to the fluctuating of Dali Shitai County on the impact at work stage angle of inclination, the following formula of matching, obtains the coefficient a in formula _nb _m:

${\mathrm{\ΔR}}_x(x,y)={\mathrm{Rx}}_{\mathrm{meas}}(x,y+\mathrm{dy})-{\mathrm{Rx}}_{\mathrm{meas}}(x,y)=\underset{n=0}{\overset{N}{\mathrm{\Σ}}}\underset{m=2}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{\mathrm{mx}}^n({(y+\mathrm{dy})}^{m-1}-y^{m-1})$

${\mathrm{\ΔR}}_y(x,y)={\mathrm{Ry}}_{\mathrm{meas}}(x+\mathrm{dx},y)-{\mathrm{Ry}}_{\mathrm{meas}}(x,y)=\underset{n=2}{\overset{N}{\mathrm{\Σ}}}\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_{m}n(x^{n-1}-{(x+\mathrm{dx})}^{n-1})y^m$

By matching gained coefficient, can calculate work stage when being positioned at any level position, the fluctuating pattern of Dali Shitai County is to the error of the angle of inclination of work stage and highly introducing:

$\mathrm{Rx}=\frac{\∂z}{\∂y}=\underset{n=0}{\overset{N}{\mathrm{\Σ}}}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{\mathrm{mx}}^n{y}^{m-1}$

$\mathrm{Ry}=-\frac{\∂z}{\∂x}=-\underset{n=1}{\overset{N}{\mathrm{\Σ}}}\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{\mathrm{nx}}^{n-1}{y}^m$

$z(x,y)=\underset{n=0}{\overset{N}{\mathrm{\Σ}}}\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{a}_n{b}_m{x}^n{y}^m;$

The angle of inclination error of step 5, the work stage introduced that to rise and fall based on the angle of inclination of the above-mentioned work stage recorded and Dali Shitai County, the angle of inclination error of the work stage that the side's of calculating mirror surface-shaped is introduced:

${\mathrm{Rx}}_{\mathrm{mirror}}\left(x_i\right)=\frac{1}{N_y}\underset{j=1}{\overset{N_y}{\mathrm{\Σ}}}({\mathrm{Rx}}_{\mathrm{meas}}(x_i,y_j)-{\mathrm{Rx}}_{\mathrm{stone}}(x_i,y_j))$

${\mathrm{Ry}}_{\mathrm{mirror}}\left(y_j\right)=\frac{1}{N_x}\underset{i=1}{\overset{N_x}{\mathrm{\Σ}}}({\mathrm{Ry}}_{\mathrm{meas}}(x_i,y_j)-{\mathrm{Ry}}_{\mathrm{stone}}(x_i,x_j));$

The error information of step 6, preservation gained;

Step 7, judge the position of work stage, when work stage is in measuring position place, directly to carry out pre-compensation according to error information; When work stage is between measuring position, utilizes linear interpolation to ask for every error amount, then carry out pre-compensation according to these error amounts.

Just preferred embodiment of the present invention described in this instructions, above embodiment is only in order to illustrate technical scheme of the present invention but not limitation of the present invention.All those skilled in the art, all should be within the scope of the present invention under this invention's idea by the available technical scheme of logical analysis, reasoning, or a limited experiment.

Claims (4)

1. the site error of work stage is carried out to a method for pre-compensation, comprise the steps:

Step one, the vertical position of work stage to be remained unchanged, work stage is set to measuring position in the horizontal direction;

Step 2, measurement record the horizontal level of work stage in described measuring position and angle of inclination, work stage moves to next measuring position;

Step 3, judge whether that all measuring positions are all measured complete, if so, then enter step 4, otherwise return step one;

Step 4, rise and fall according to brace table impact on work stage angle of inclination, according to fitting formula:

The coefficient of the height error that the platform that is supported fluctuating is introduced wherein be respectively work stage X to the variable quantity with Y-direction angle of inclination, be respectively work stage X to Y-direction angle of inclination, for X to Y-direction position;

Then the coefficient of the height error of trying to achieve is utilized according to formula: with

Calculate angle of inclination error and the height error of the work stage introduced by brace table fluctuating, wherein represent respectively by brace table rise and fall introduce work stage X to Y-direction angle of inclination error, the height error that Z (x, y) is work stage, for X to Y-direction position;

The angle of inclination error of step 5, the work stage introduced that to rise and fall based on the angle of inclination of the work stage measured and brace table, according to formula: with

The angle of inclination error of the work stage that the side's of calculating mirror surface-shaped is introduced, wherein the X of the work stage that the side of being respectively mirror surface-shaped is introduced to Y-direction angle of inclination error, be respectively by brace table rise and fall introduce work stage X to Y-direction angle of inclination error;

The error information of step 6, preservation gained;

Step 7, position according to work stage, utilize the error information obtained to compensate the vertical position of work stage and angle of inclination.

2. method according to claim 1, wherein, described measuring position is equidistantly uniformly distributed on brace table, at brace table surface forming array.

3. method according to claim 1, wherein, when work stage moves to described measuring position place, directly carries out pre-compensation according to error information.

4. method according to claim 1, wherein, when work stage moves between described measuring position, utilizes linear interpolation to ask for every error amount, then carries out pre-compensation according to these error amounts.