阅读说明：本技术 一种射频电源的调谐方法 (Tuning method of radio frequency power supply ) 是由 邱文杰 刘洋 于 2021-09-01 设计创作，主要内容包括：本发明公开了一种射频电源的调谐方法,其中射频电源包括频率控制模块、闭环控制器,通过改变射频电源频率,在复数平面中建立相应的曲线；以复数平面中任意一点作为起点,以复数平面的原点或原点附近的一点为终点,并以起点和终点作参考矢量；判断曲线是否为目标曲线,若不是目标曲线,则通过曲线变换得到修正曲线；所述参考矢量将目标曲线或修正曲线分成左右区域；根据目标曲线或修正曲线上的复数值处于左右区域的位置调节射频电源的频率。本发明所提供的射频电源调谐方法计算方式简单高效、并且本方法能够克服现有技术无法对非目标曲线进行频率调节的缺陷,具有更强的适应性。(The invention discloses a tuning method of a radio frequency power supply, wherein the radio frequency power supply comprises a frequency control module and a closed-loop controller, and corresponding curves are established in a plurality of planes by changing the frequency of the radio frequency power supply; taking any point in the complex plane as a starting point, taking an original point of the complex plane or a point near the original point as an end point, and taking the starting point and the end point as reference vectors; judging whether the curve is a target curve or not, and if not, obtaining a correction curve through curve transformation; the reference vector divides the target curve or the correction curve into a left area and a right area; and adjusting the frequency of the radio frequency power supply according to the positions of the complex values on the target curve or the correction curve in the left and right areas. The radio frequency power supply tuning method provided by the invention is simple and efficient in calculation mode, can overcome the defect that the prior art cannot adjust the frequency of a non-target curve, and has stronger adaptability.)

1. A tuning method of a radio frequency power supply, wherein the radio frequency power supply comprises a frequency control module and a closed-loop controller,

changing the frequency of the radio frequency power supply, and establishing a corresponding curve in a complex plane;

taking any point in the complex plane as a starting point, taking an original point of the complex plane or a point near the original point as an end point, and taking the starting point and the end point as reference vectors;

judging whether the curve is a target curve or not, and if not, obtaining a correction curve through curve transformation;

the reference vector divides the target curve or the correction curve into a left area and a right area;

and adjusting the frequency of the radio frequency power supply according to the positions of the complex values on the target curve or the correction curve in the left and right areas.

2. The method of claim 1, wherein the curve transformation divides the non-target curve into two segments based on the reference vector, and the two segments of the curve are transformed to the left and right by function transformation to obtain correction curves at two sides of the reference vector; or a section of curve is transformed to the left or the right through functional transformation to obtain correction curves positioned at two sides of the reference vector.

3. The method of claim 2, wherein the increasing or decreasing the frequency of the rf power source when the complex value on the target curve or the modified curve is in the left region of the reference vector is opposite to the adjusting when the complex value on the target curve or the modified curve is in the right region of the reference vector.

4. The method of claim 1, wherein the starting point is located on an end-to-end line of the target curve or the correction curve, or on an extension of the end-to-end line, or on one side of the end-to-end line or the extension thereof.

5. The method of claim 1, wherein the point near the origin is a point in a region where a reflection coefficient mode value is 0.5 or less or a transmission efficiency of the rf power source is 75% or more.

6. The method of claim 3, wherein the functional transformation is a matrix or a transposed matrix, the impedance is Z, and the correction curve is ZThe transpose matrix isSaidWherein, in the step (A),to change the angle.

7. The method of claim 6, wherein the target curve or the correction curve is any of a plurality of points V_m：Reference vectorComprises the following steps:use ofAndconstructing a determinant:

wherein the content of the first and second substances,is a plurality of pointsThe abscissa of the (c) axis of the (c),a plurality of dotsThe ordinate of (a);as reference vectorsThe abscissa of the (c) axis of the (c),as reference vectorsThe ordinate of (a);

when T is larger than 0, increasing the frequency of the radio frequency power supply through the frequency control module; and when T is less than 0, reducing the frequency of the radio frequency power supply through the frequency control module.

8. The method of claim 7, wherein the frequency of the RF power source is adjusted by a closed-loop controller and a frequency control module.

9. A method of tuning a radio frequency power supply as claimed in claim 1, wherein said curve comprises an impedance curve or an admittance curve, or a reflection coefficient curve.

Technical Field

The invention relates to the technical field of radio frequency power supply tuning, in particular to a tuning method of a radio frequency power supply.

Background

The radio frequency power supply can be widely applied to the fields of film coating, semiconductor preparation and the like, for example, semiconductor plasma etching. However, during plasma etching, the rf power output, gas composition, gas flow rate, etc. are typically varied due to variations in process requirements. As these parameters change, the load impedance will also change dynamically, requiring the rf power supply to achieve a fast response and maximize power transfer throughout the process.

In general, frequency tuning is usually performed by a gradient method. The absolute value of the reflection power or the reflection coefficient is used as a reference value, the frequency tuning direction is uncertain due to the scalar, the modulation is usually targeted to the minimum reflection power or the minimum reflection coefficient, and the time for frequency tuning is measured in milliseconds, so that the requirement of rapid frequency tuning control cannot be met.

There is a prior art that is directed to finding a method and apparatus capable of fast tuning, such as chinese patent application No. 2017800311002, which discloses generating an impedance curve and a reference vector in a complex reflection coefficient plane, calculating a frequency adjustment step size by scaling the measurement angle by a predetermined multiple according to the measurement angle between the reference vector and an actually measured impedance value, and adjusting the frequency of an exciter according to the frequency step size. In addition, the method only considers the frequency adjustment of an ideal impedance trajectory curve (target curve), as shown in fig. 1, if an actually formed impedance curve is a closed curve in a non-target curve, at this time, the same measurement angle may correspond to two impedance points n1 and n2 on the curve, and the occurrence of the two impedance points will cause the problem of frequency tuning direction disorder, and according to the adjustment method described in the application, both the frequency point n1 and the frequency point n2 will move in the direction of decreasing frequency; at this time, the frequency point n2 will move to the minimum frequency point in the adjusting processAnd cannot be tuned to the frequency tuning optimum.

Disclosure of Invention

The invention aims to solve the problem that the frequency adjustment of an ideal impedance track curve is only considered in the prior art, and when the impedance curve is a non-target curve, the same measurement angle corresponds to two impedance points, so that the optimal point of the frequency cannot be adjusted.

In order to achieve the above purpose, the invention provides the following technical scheme:

a tuning method of a radio frequency power supply, wherein the radio frequency power supply comprises a frequency control module and a closed-loop controller, and comprises the following steps:

changing the frequency of the radio frequency power supply, and establishing a corresponding curve in a complex plane;

taking any point in the complex plane as a starting point, taking an original point of the complex plane or a point near the original point as an end point, and taking the starting point and the end point as reference vectors;

judging whether the curve is a target curve or not, and if not, obtaining a correction curve through curve transformation;

the reference vector divides the target curve or the correction curve into a left area and a right area;

and adjusting the frequency of the radio frequency power supply according to the positions of the complex values on the target curve or the correction curve in the left and right areas.

The curve is a target curve, and otherwise, the curve is a non-target curve.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, the curve transformation includes: dividing the non-target curve into two sections based on the reference vector, and respectively converting the two sections of curves to the left and the right through function conversion to obtain correction curves positioned at two sides of the reference vector; or a section of curve is transformed to the left or the right through functional transformation to obtain correction curves positioned at two sides of the reference vector.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, when the complex value on the target curve or the correction curve is in the left area of the reference vector, the frequency of the radio frequency power supply is increased or decreased, and when the complex value on the target curve or the correction curve is in the right area of the reference vector, the adjustment is opposite to that in the left area.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, the starting point is located on an end-to-end connection line of the target curve or the correction curve, or on an extension line of the end-to-end connection line, or on one side of the end-to-end connection line or the extension line thereof.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, the point near the origin is a point in an area where a reflection coefficient mode value is less than or equal to 0.5 or a transmission efficiency of the radio frequency power supply is greater than or equal to 75%.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, the function transformation adopts a matrix or a transposed matrix, the impedance is Z, and the correction curve isThe transpose matrix isSaidWherein, in the step (A),to change the angle.

The size of the transformation angle can determine the distance between the correction curve and the reference vector, and the larger the angle is, the larger the opening is, and the size can be set according to the size of the opening of the non-target curve to be transformed.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, the target curve or the correction curve takes any number of points，Reference vectorComprises the following steps:use ofAndconstructing a determinant:

wherein the content of the first and second substances,is a plurality of pointsThe abscissa of the (c) axis of the (c),a plurality of dotsThe ordinate of (a);as reference vectorsThe abscissa of the (c) axis of the (c),as reference vectorsThe ordinate of (a);

when T is larger than 0, increasing the frequency of the radio frequency power supply through the frequency control module; and when T is less than 0, reducing the frequency of the radio frequency power supply through the frequency control module.

According to a specific implementation manner, in the tuning method of the radio frequency power supply, the frequency of the radio frequency power supply is tracked and adjusted by using the closed-loop controller and the frequency control module.

According to a specific embodiment, in the tuning method of the radio frequency power supply, the curve includes an impedance curve or an admittance curve, or a reflection coefficient curve.

Compared with the prior art, the invention has the beneficial effects that:

the radio frequency power supply tuning method provided by the invention comprises the steps of establishing a curve responding to the frequency of a radio frequency power supply in a plurality of planes, judging whether the obtained curve is a target curve or not, and carrying out curve transformation on a non-target curve to obtain a corrected curve; and meanwhile, reference vectors which can be used for dividing the target curve or the correction curve into a left area and a right area are determined, and finally, the frequency adjusting mode can be determined only by positioning the actually measured complex values in the left area and the right area which are divided by the reference vectors, the calculating mode is simple and efficient, and the tracking adjustment of the radio frequency power supply can be performed. The method can overcome the defect that the prior art cannot adjust the frequency of the non-target curve, is suitable for adjusting the frequency of the target curve and the non-target curve, and has stronger adaptability.

Description of the drawings:

FIG. 1 is a non-target curve 1 of an exemplary embodiment of the present invention;

FIG. 2 is a block diagram of an exemplary embodiment of a RF power system;

FIG. 3 is a target curve for an exemplary embodiment of the present invention;

FIG. 4 is a schematic diagram of a non-target curve 2 and its transformation according to an exemplary embodiment of the present invention;

fig. 5 is a graph transformation diagram of the non-target curve 1 according to the exemplary embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to test examples and specific embodiments. It should be understood that the scope of the above-described subject matter is not limited to the following examples, and any techniques implemented based on the disclosure of the present invention are within the scope of the present invention.

Example 1

Fig. 2 shows a radio frequency power supply system of an exemplary embodiment of the present invention, including: radio frequency power supply, coaxial line, matcher, load cavity. The radio frequency power supply output interface is connected with the matcher input interface through a coaxial line, and the matcher output interface is connected with the load cavity. The radio frequency power supply is internally provided with a sensor for detecting an output radio frequency signal, a frequency control module capable of performing frequency tuning, and the frequency control module is also provided with a closed-loop controller (not shown in figure 2). Further, the radio frequency power supply performs frequency tracking adjustment by the following tuning method, including:

A. establishing a corresponding curve in a complex plane by changing the frequency of the radio frequency power supply, wherein the curve comprises: the whole impedance curve or admittance curve or complex reflection coefficient curve seen from the output port of the radio frequency power supply. And the complex points corresponding to the minimum frequency and the maximum frequency on the curve form the head and the tail of the curve.

B. Regarding the acquired curve (the whole impedance curve or the admittance curve or the complex reflection coefficient curve), taking any point in the complex plane as a starting point, taking an original point of the complex plane or a point near the original point as an end point, and taking the starting point and the end point as reference vectors; the reference vector is used to divide the curve that has been acquired into two regions.

Specifically, the starting point is located on a head-to-tail connection line of the target curve or the correction curve (as shown in a point a in fig. 5), or on an extension line of the head-to-tail connection line (as shown in a point a in fig. 4), or on one side of the head-to-tail connection line or the extension line thereof (as shown in a point a in fig. 3); and a point near the origin is: a point in the region where the mode value of the reflection coefficient is 0.5 or less or the transmission efficiency of the rf power source is 75% or more (the dotted line region shown in fig. 3).

C. Judging whether the curve is a target curve or not, and if not, obtaining a correction curve through curve transformation; the reference vector divides the target curve or the correction curve into a left region and a right region (wherein the left region and the right region are determined based on the space left-right relation of points on the curve and the reference vector); and adjusting the frequency of the radio frequency power supply according to the positions of the complex values on the target curve or the correction curve in the left and right areas.

Specifically, when adjusting the frequency, the frequency adjustment direction is determined according to the left-right position relationship between the impedance measured value and the reference vector by receiving the impedance measured value of the sensor (the measured value is a plurality of points located on the curve), wherein the frequency adjustment modes on the left side and the right side are opposite, one is increased, and the other is decreased, thereby realizing the fast tracking adjustment of the radio frequency power supply frequency. In establishing the corresponding curve, the curve formed in response to the frequency of the rf power source may be a target curve or a non-target curve. Fig. 3 shows target curves obtained by an exemplary embodiment of the present invention, and fig. 1 and 4 respectively show two non-target curves formed in response to the frequency of the rf power supply. For a non-target curve, a point on the curve may be located on an extension line of the reference vector (as shown in fig. 1), and a collinear position relationship exists between the point on the curve and the reference vector, so that a left-right position relationship between a complex point on the curve and the reference vector cannot be determined, and therefore, a curve transformation needs to be performed on the target curve to obtain a modified curve.

Further, the curve transformation includes: dividing the non-target curve into two sections based on the end point of the reference vector, and respectively converting the two sections of curves to the left and the right through function conversion to obtain correction curves positioned at the two sides of the reference vector; or a section of curve is transformed to the left or the right through functional transformation to obtain correction curves positioned at two sides of the reference vector. Wherein the functional transformation comprises: and constructing a transformation matrix, and transforming the two curves (shown in figure 5) or one curve (shown in figure 4) to the left or right through the transformation matrix to obtain the correction curves positioned at the two sides of the reference vector.

Fig. 5 shows a graph transformation diagram of a non-target curve 1 based on a matrix transformation according to an exemplary embodiment of the present invention. Specifically, in this embodiment, it is preferable that the midpoint a of the line connecting the beginning and the end of the curve (point B and point C) is a starting point, the origin O is an end point, and the reference vector is obtained(ii) a Wherein, the plural points B are plural points corresponding to the minimum frequency on the integral impedance curve or the admittance curve or the plural reflection coefficient curve; the plurality of points C are the plurality of points corresponding to the maximum frequency on the overall impedance curve or the admittance curve or the complex reflection coefficient curve. Suppose complex point B is equal toPlural points C equal toThen, the reference point a can be calculated by the following equation (1):

（1）

the two parts BO and CO into which the reference vector is divided are affine-transformed, and after processing, as shown by the dotted line in FIG. 4, BO is transformedCO conversion to 。

The transform matrix is derived from an affine transform: （2）

wherein Z is the input impedance (Z can also be derived by replacing admittance or input reflection coefficient);a transposed matrix that is Z;the impedance curve is obtained after affine transformation. When θ is negative, the BO curve is entirely shifted to the left to become(ii) a When θ is positive, the CO curve shifts to the right as a whole toThereby converting the non-target curve BOC into an ideal correction curve。

In a further embodiment of the present invention, which region of the left and right regions of the reference vector the complex value on the target curve or the correction curve is located in is calculated by means of spatial cross multiplication, after the vector cross multiplication, the relative position relationship between the complex point and the reference vector can be determined by a right-hand rule, and the relative position relationship is located in a left region or a right region of the reference vector, which specifically includes:

when the resulting curve BOC is the target curve: let the actual measured impedance point be，V_mIs an arbitrary complex point on the whole impedance curve or admittance curve or complex reflection coefficient curve, namely an arbitrary complex point on the BOC curve, a reference vectorEqual to: ，can be calculated by the formula (1).

Use ofAndand constructing a determinant to obtain a cross multiplication mathematical result T:

（3）

when the curve BOC is a non-target curve, the actually measured impedance value is still a plurality of points V on the original target curve_mHowever, there is a corresponding matrix-mapped point on the correction curve，As an arbitrary complex point on an affine transformed bulk impedance (admittance) curve or complex reflection coefficient curve (i.e. as a function of the measured impedanceAn arbitrary plurality of points of the curve), at this time, byAndthe determinant of the formula (3) can also be determinedRelative position relationship with reference vector.

When T >0, the frequency control module increases the frequency; when T <0, the frequency control module decreases the frequency; and meanwhile, configuring a closed-loop controller in the frequency control module to track and adjust the frequency according to the rule, preferably adopting a PID (proportion integration differentiation) controller in the existing closed-loop controller, and controlling the frequency to change rapidly according to the control principle so as to adjust the frequency of the radio frequency power supply to a frequency point corresponding to T = 0. The error input of the closed-loop controller is T, and the output of the closed-loop controller is frequency adjustment quantity, so that the rapid tracking adjustment of the frequency of the radio frequency power supply is realized.

Similarly, for the non-target curve 2 shown in fig. 4, the extended line point a of the connection line between the head and the tail of the curve (point B and point C) is used as the starting point, the origin O is used as the end point, and the reference vector is used as the reference vector. Since the BO curve is located at the reference vectorOn the left side of the curve, only affine transformation is needed to be carried out on the CO curve, so that the corrected curveLocated in a reference vectorAnd finally, the frequency of the radio frequency power supply is quickly tracked and adjusted.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.