CN103199048A - Wafer prealignment control method - Google Patents

Abstract

A wafer prealignment control method comprises the following steps: a first step of providing a negative pressure absorption rotating device for pumping air between a tray and a wafer to form a vacuum state and driving the wafer to rotate, and a second step of providing a sensor used for collecting edge data of the wafer and recording rotating speed information of the rotating device. The wafer prealignment control method further comprises wafer positioning and wafer notch positioning, wherein the wafer positioning comprises the following steps: a first step of data acquisition, a second step of data preprocessing, and a third step of circle fitting to find the circle center position of the wafer. The wafer notch positioning comprises the following steps: a first step of notch coarse positioning, a second step of notch fitting, a third step of an iteration termination, a fourth step of finding a coordinate of the center according to the notch edge center, and the position and the angle of the wafer are adjusted.

Description

Wafer prealignment control method

Technical field

The present invention relates to a kind of computer control field, refer to that especially a kind of IC makes field wafer prealignment control method.

Background technology

The control of wafer prealignment is one of link important in the IC manufacturing process.Specifically, the process of wafer prealignment control is exactly by certain method, makes the center of circle of wafer within certain scope, and notched wafer rests on the angle of appointment simultaneously, namely comprises location, the center of circle and two main processes of breach detection.

In existing technology, patent name is Silicon Wafer prealignment control method, publication number is CN100355055C, adopted the line array CCD transducer to the crystal round fringes data sampling, find out the approximate location of breach, in the certain limit at breach place the gap edge data are carried out secondary and carefully sample, utilize least square method that the data fitting of gathering is obtained the central coordinate of circle of breach, the breach center of circle and wafer circle center line connecting can obtain the edge center coordinate of notched wafer.This kind method has influenced the operating efficiency of clean robot greatly owing to need carry out rescan to the gap edge data.Name of document is the wafer prealignment method based on the high accuracy micrometer, nanometer technology and precision engineering 7 (3): 249-253, existing method is improved, equally the crystal round fringes data are carried out double sampling, after determining the marginal date of breach, utilize non-linear least square method to solve the central coordinate of circle of breach, the breach center of circle and wafer circle center line connecting can obtain the centre coordinate of notched wafer.Adopt the advantage of nonlinear least square method to be that justifying match for the less like this data volume sampled point of breach can obtain higher precision.The Rule of judgment that the geometric distance in the breach center of circle that the shortcoming of the method calculates before and after being to adopt when the match iteration stops as iteration, because breach center of circle radius may be very big or breach is irregular, cause iterations so too much or can not find the result who satisfies Rule of judgment, and be to carry out double sampling to crystal round fringes, efficient is not high.

Summary of the invention

In view of above content, be necessary to provide a kind of wafer prealignment control method rapidly and efficiently.

A kind of wafer prealignment control method may further comprise the steps: a negative-pressure adsorption whirligig is provided, has formed vacuum state in order to the air between pallet and the wafer is extracted out, and drive the wafer rotation; Transducer; One in order to gathering the crystal round fringes data, and the rotary speed information of record whirligig; This method also includes wafer location and notched wafer location,

Described wafer positioning method may further comprise the steps:

Data sampling: described negative-pressure adsorption whirligig drives the rotation of described wafer, and described transducer is gathered rotate a circle marginal date in the process of described wafer, and records the rotary speed information of described whirligig simultaneously;

Data preliminary treatment: remove the bigger value of fluctuation, invalid sampled data and the notched wafer scope of sensor measurement scope;

Data transaction: the data that described transducer collects are handled, and converted to the coordinate figure of crystal round fringes sampled point;

Circle match: adopt the match of linear least-squares circle algorithm to try to achieve radius and the central coordinate of circle of described wafer;

Described notched wafer localization method may further comprise the steps:

Breach coarse positioning: according to wafer one all sampled datas, note the notched wafer range data;

Breach match: adopt the Levenberg-Marquardt nonlinear least square method that the breach data are justified match, seek the breach central coordinate of circle by the method for iteration;

Iteration stops: calculate breach central coordinate of circle and the angle value of the wafer center of circle for trunnion axis that each iteration is come out, with the rate of change of this angle value condition as the iteration termination, and the breach home position information that will satisfy end condition is noted;

The gap edge center: with the wafer center of circle and breach circle center line connecting, the positional information of the point that intersects with gap edge is exactly the coordinate figure at gap edge center;

Adjust wafer: according to angle and the position of crystal circle center's coordinate and gap edge center point coordinate adjustment wafer.

It is benchmark match one rectangular coordinate system when not rotating with described whirligig in one embodiment.

In one embodiment, the rotary speed information of described crystal round fringes sample point coordinate value by described whirligig when not rotating be the angle value of benchmark conversion and described crystal round fringes point extremely the distance at described whirligig center calculate.

In one embodiment,

Described crystal circle center coordinate figure calculation procedure is as follows:

Marginal date [(x for all collections ₁, y ₁), (x ₂, y ₂) ..., (x _N, y _N)] to the circle center (a, geometric distance sum of errors b) is:

$d=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{(\sqrt{{(x_i-a)}^2+{(y_i-b)}^2}-R_0)}^2$

R in the formula ₀Be the radius of wafer, linear least square can get apart from the replacement geometric distance with algebraically:

$d\≈\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{({(x_i-a)}^2+{(y_i-b)}^2-{R_0}^2)}^2=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{((x_i^2+y_i^2)+{\mathrm{Bx}}_i+C{y}_i+{\mathrm{Cy}}_i+D)}^2$

In the formula, B=-2a, C=-2b, D=a ²+ b ²+ c ², x _i ²+ y _i ²=z _i

To B, C, D asks extreme value to set up equation group and finds the solution and obtain by B, C, and the D value can be tried to achieve coordinate figure and the radius value in the wafer center of circle thus.

In one embodiment, breach central coordinate of circle value calculation procedure is as follows:

The breach target function is:

$f\left(x\right)=\frac{1}{2}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{\θ}}_i^2\left(x\right)$

Wherein,

Center of circle iterative formula based on the Levenberg-Marquardt algorithm is:

x _i+1＝x _i-(H(x)+λ _LM) ^-1·J(x)

In the formula: J (x) is the Jacobi matrix of θ (x), and H (x) is the Hesse matrix of θ (x).Damping coefficient is:

λ _LM＝λdiag[H(x)] λ＞0

Iteration convergence judgement formula is:

$0<|{\left|\right|\mathrm{\&theta;}\left(x_i\right)\left|\right|}_2^2-{\left|\right|\mathrm{\&theta;}\left(x_{i+1}\right)\left|\right|}_2^2|<\mathrm{\&epsiv;}$

Wherein, ε is a very little number, calculates breach centre coordinate value thus.

In one embodiment, find the breach scope by edge rate.

Compared with prior art, in the above-mentioned wafer prealignment control method, obtain wafer central coordinate of circle and notched wafer edge center coordinate by once gathering the crystal round fringes data, adjust the center that described wafer position and angle simply and efficiently calculate wafer by wafer central coordinate of circle and breach centre coordinate.

Description of drawings

Fig. 1 is a schematic diagram of wafer prealignment control appliance example structure of the present invention.

Fig. 2 is a flow chart of wafer prealignment control method of the present invention.

The main element symbol description

Transducer	1
		Wafer	2
Footstock	3
		The negative-pressure adsorption whirligig	4
Control cubicle	5

Following embodiment will further specify the present invention in conjunction with above-mentioned accompanying drawing.

Embodiment

See also Fig. 1, in a preferred embodiments of the present invention, crystal circle center's prealignment equipment comprises a control cubicle 5, in order to control prealignment wafer 4; One footstock 3 is in order to support described wafer 4 before prealignment wafer 4; One is located at the negative-pressure adsorption whirligig 4 on the described control cubicle 5, holds up described wafer 2 in order to rise and extracts the air between pallet and the wafer 2 out the formation vacuum state, drives described wafer 2 simultaneously and rotates; One is located at the transducer 1 on the described control cubicle 5, is used for gathering wafer 4 marginal date and the rotary speed information that obtains corresponding negative-pressure adsorption whirligig 4.In one embodiment, described transducer is a single ccd sensor, in order to gather the data at wafer 2 edges.

Described negative-pressure adsorption whirligig 4 has a pivot.The maximum range of described transducer 1 is L, and its maximum range is S to the distance of described negative-pressure adsorption whirligig 4, and then described transducer 1 is L+S to the distance of the pivot of described negative-pressure adsorption whirligig 4.

Please refer to Fig. 2, described wafer prealignment control method includes wafer 2 location and notched wafer location.

Described wafer 2 location may further comprise the steps:

S11, data sampling: described negative-pressure adsorption whirligig 4 drives described wafer 2 and rotates a circle, and described transducer 1 is gathered rotate a circle marginal date in the process of described wafer 2, and obtains the rotary speed information of corresponding negative-pressure adsorption whirligig 4 simultaneously.Wherein, suitably regulate sample frequency according to wafer 2 sizes.

S12, data preliminary treatment: for the data that sampling among the S11 obtains, can not directly justify match.On the one hand and since transducer 1 measuring range limited, so will reject data (the bigger value that fluctuates, the invalid sampled data of sensor measurement scope) beyond the sensor measurement scope; Be the processing to breach on the other hand, because the circle match does not comprise the breach data, so the breach data also will be rejected.The boundary point that earlier described transducer 1 sampled data is converted to wafer 2 is l apart from the physical length data of the pivot of negative-pressure adsorption whirligig 4 _i(i ∈ (1,2,3...N)), N are total sampling number, and then described wafer 2 edges to the distance of described pivot is S+L-l _i, (i ∈ (1,2,3...N)); Be datum mark when described negative-pressure adsorption whirligig 4 is not rotated, it is θ that the rotating speed data that sampling is obtained is converted to angle-data _i(i ∈ (1,2,3...N)) calculates the coordinate figure [(x of each sampled point under coordinate system xo ' y according to angle-data ₁, y ₁), (x ₂, y ₂) ... (x _N, y _N)] be: ((S+L-l _i) cos θ _i, (S+L-l _i) sin θ _i) (i ∈ (1,2,3...N), so just finish that sampled data is converted to the rectangular coordinate data.Can find the point on the notched wafer (3 adjacent sampled points to be calculated angle be edge rate by edge transition rate method.Because the distribution of crystal round fringes sampled point basically relatively evenly, so adjacent 3 corner dimension is similar on the circumference, the some angle then has bigger variation on the breach);

S13, the circle match: adopt the linearisation least square fitting method, calculate wafer central coordinate of circle (a, b) and wafer radius R ₀Marginal date [(x to all collections ₁, y ₁), (x ₂, y ₂) ... (x _N, y _N)] to the center of circle (a, geometric distance sum of errors b) is:

Linear least square can get apart from the replacement geometric distance with algebraically:

$d\&ap;\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{({(x_i-a)}^2+{(y_i-b)}^2-{R_0}^2)}^2=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{((x_i^2+y_i^2)+{\mathrm{Bx}}_i+C{y}_i+{\mathrm{Cy}}_i+D)}^2;$

B=-2a wherein, C=-2b, D=a ²+ b ²-R ₀ ², x _i ²+ y _i ²=z _i

By the rule of asking extreme value as can be known, if the d minimum then must be had:

$\frac{\&PartialD;d}{\&PartialD;B}=2\underset{i}{\overset{N}{\mathrm{\&Sigma;}}}((x_i^2+y_i^2)+{\mathrm{Bx}}_i+{\mathrm{Cy}}_i+D)x_i=0;---\left(1\right)$

$\frac{\&PartialD;d}{\&PartialD;C}=2\underset{i}{\overset{N}{\mathrm{\&Sigma;}}}((x_i^2+y_i^2)+{\mathrm{Bx}}_i+{\mathrm{Cy}}_i+D)y_i=0;---\left(2\right)$

$\frac{\&PartialD;d}{\&PartialD;D}=2\underset{i}{\overset{N}{\mathrm{\&Sigma;}}}((x_i^2+y_i^2)+{\mathrm{Bx}}_i+{\mathrm{Cy}}_i+D)=0;---\left(3\right)$

Can be obtained by (3): $D=-\stackrel{\&OverBar;}{z}-B\stackrel{\&OverBar;}{x}-C\stackrel{\&OverBar;}{y};---\left(4\right)$

Bring (4) formula into (1), (2) respectively, B, C are found the solution obtain:

$B=(A_{\mathrm{zx}}{A}_{\mathrm{yy}}-A_{\mathrm{xy}}{A}_{\mathrm{zy}})/(A_{\mathrm{xy}}^2-A_{\mathrm{xx}}{A}_{\mathrm{yy}})$

$C=(A_{\mathrm{zy}}{A}_{\mathrm{xx}}-A_{\mathrm{xy}}{A}_{\mathrm{zx}})/(A_{\mathrm{xy}}^2-A_{\mathrm{xx}}{A}_{\mathrm{yy}})$

In the formula, $A_{\mathrm{xx}}=\stackrel{\&OverBar;}{x^2}-{\stackrel{\&OverBar;}{x}}^2,$ $A_{\mathrm{yy}}=\stackrel{\&OverBar;}{{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA0000128929240000011.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}-{\stackrel{\&OverBar;}{y}}^2,$ $A_{\mathrm{zx}}=\stackrel{\&OverBar;}{\mathrm{zx}}-\stackrel{\&OverBar;}{z}\stackrel{\&OverBar;}{x},$ $A_{\mathrm{zy}}=\stackrel{\&OverBar;}{\mathrm{zy}}-\stackrel{\&OverBar;}{z}\stackrel{\&OverBar;}{y},$ $A_{\mathrm{xy}}=\stackrel{\&OverBar;}{\mathrm{xy}}-\stackrel{\&OverBar;}{x}\stackrel{\&OverBar;}{y}.$ By B, C, the D value can be tried to achieve coordinate figure and the radius value in the wafer center of circle.

Described notched wafer location may further comprise the steps:

S14, breach coarse positioning: according to wafer one all sampled datas, adopt the edge rate method to detect the notched wafer scope, and the data in this scope are noted separately;

S15, breach match: the home position that simulates breach according to the Levenberg-Marquardt iterative algorithm.The target function of breach match is:

$f\left(x\right)=\frac{1}{2}\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&theta;}}_i^2\left(x\right),$ Wherein, ${\mathrm{\&theta;}}_i\left(x\right)=\arctan \frac{y_i-b}{x_i-a}-{\mathrm{\&theta;}}_0.$

Center of circle iterative formula based on the Levenberg-Marquardt algorithm is:

x _i+1＝x _i-(H(x)+λ _LM) ^-1·J(x)

In the formula: J (x) is the Jacobi matrix of θ (x), and H (x) is the Hesse matrix of θ (x).Damping coefficient is:

λ _LM＝λdiag[H(x)] λ＞0

Iteration convergence judgement formula is:

$0<|{\left|\right|\mathrm{\&theta;}\left(x_i\right)\left|\right|}_2^2-{\left|\right|\mathrm{\&theta;}\left(x_{i+1}\right)\left|\right|}_2^2|<\mathrm{\&epsiv;}$

Wherein, ε is a very little number.

S16, iteration stops: calculate breach central coordinate of circle and the angle value of the wafer center of circle for trunnion axis that each iteration is come out, with the rate of change of this angle value condition as the iteration termination, and the breach home position information that will satisfy end condition is noted;

S17, the gap edge center: with wafer 2 centers of circle and breach circle center line connecting, the positional information of the point that intersects with gap edge is exactly the coordinate figure at gap edge center;

S18 is according to angle and the position of wafer 2 centre coordinates and gap edge center point coordinate adjustment wafer 2.

Compared with prior art, in the wafer prealignment control method of the present invention, obtain wafer central coordinate of circle and notched wafer edge center coordinate by once gathering the crystal round fringes data, adjust the center that described wafer position and angle simply and efficiently calculate wafer by wafer central coordinate of circle and breach centre coordinate.

Claims (6)

1. a wafer prealignment control method may further comprise the steps: a negative-pressure adsorption whirligig is provided, forms vacuum state in order to the air between pallet and the wafer is extracted out, and drive the wafer rotation; Transducer; In order to gathering the crystal round fringes data, and the rotary speed information of record whirligig; This method also includes wafer location and notched wafer location, it is characterized in that:

Described wafer positioning method may further comprise the steps:

Data sampling: described negative-pressure adsorption whirligig drives the rotation of described wafer, and described transducer is gathered rotate a circle marginal date in the process of described wafer, and records the rotary speed information of described whirligig simultaneously;

Data preliminary treatment: remove the bigger value of fluctuation, invalid sampled data and the notched wafer scope of sensor measurement scope;

Data transaction: the data that described transducer collects are handled, and converted to the coordinate figure of crystal round fringes sampled point;

Circle match: adopt the match of linear least-squares circle algorithm to try to achieve radius and the central coordinate of circle of described wafer;

Described notched wafer localization method may further comprise the steps:

Breach coarse positioning: according to wafer one all sampled datas, note the notched wafer range data;

Breach match: adopt the Levenberg-Marquardt nonlinear least square method that described breach range data is justified match, seek the breach central coordinate of circle by the method for iteration;

Iteration stops: calculate breach central coordinate of circle and the angle value of the wafer center of circle for trunnion axis that each iteration is come out, with the rate of change of this angle value condition as the iteration termination, and the breach home position information that will satisfy end condition is noted;

The gap edge center: with the wafer center of circle and breach circle center line connecting, the positional information of the point that intersects with gap edge is exactly the coordinate figure at gap edge center;

Adjust wafer: according to angle and the position of crystal circle center's coordinate and gap edge center point coordinate adjustment wafer.

2. wafer prealignment control method as claimed in claim 1 is characterized in that: be benchmark match one rectangular coordinate system when not rotating with described whirligig.

3. wafer prealignment control method as claimed in claim 2 is characterized in that: the rotary speed information of described crystal round fringes sample point coordinate value by described whirligig when not rotating be the angle value of benchmark conversion and described crystal round fringes point extremely the distance at described whirligig center calculate.

4. wafer prealignment control method as claimed in claim 3, it is characterized in that: described crystal circle center coordinate figure calculation procedure is as follows:

Marginal date [(x for all collections ₁, y ₁), (x ₂, y ₂) ..., (x _N, y _N)] to the circle center (a, geometric distance sum of errors b) is:

$d=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{(\sqrt{{(x_i-a)}^2+{(y_i-b)}^2}-R_0)}^2$

R in the formula ₀Be the radius of wafer, linear least square can get apart from the replacement geometric distance with algebraically:

$d\&ap;\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{({(x_i-a)}^2+{(y_i-b)}^2-{R_0}^2)}^2=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{((x_i^2+y_i^2)+{\mathrm{Bx}}_i+C{y}_i+{\mathrm{Cy}}_i+D)}^2$

In the formula, B=-2a, C=-2b, D=a ²+ b ²+ c ², x _i ²+ y _i ²=z _i

To B, C, D asks extreme value to set up equation group and finds the solution and obtain by B, C, and the D value can be tried to achieve coordinate figure and the radius value in the wafer center of circle thus.

5. wafer prealignment control method as claimed in claim 1, it is characterized in that: breach central coordinate of circle value calculation procedure is as follows:

The breach target function is:

$f\left(x\right)=\frac{1}{2}\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&theta;}}_i^2\left(x\right)$

Wherein,

Center of circle iterative formula based on the Levenberg-Marquardt algorithm is:

x _i+1＝x _i-(H(x)+λ _LM) ^-1·J(x)

In the formula: J (x) is the Jacobi matrix of θ (x), and H (x) is the Hesse matrix of θ (x).Damping coefficient is:

λ _LM＝λdiag[H(x)] λ＞0

Iteration convergence judgement formula is:

$0<|{\left|\right|\mathrm{\&theta;}\left(x_i\right)\left|\right|}_2^2-{\left|\right|\mathrm{\&theta;}\left(x_{i+1}\right)\left|\right|}_2^2|<\mathrm{\&epsiv;}$

Wherein, ε is a very little number, calculates breach centre coordinate value thus.

6. wafer prealignment control method as claimed in claim 5 is characterized in that: find the breach scope by edge rate.

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