DE102011082775A1 - Method for simultaneous optimization of different layer properties by controlling vacuum separation process, involves forming mathematical links from spectral lines and generating intensity linkage by multiplying mathematical links - Google Patents

Abstract

The method involves coating substrate in vacuum chamber using material extracted from target connected with magnetron under application of voltage between target and counter electrode by controlled voltage source. The process gas is introduced into vacuum chamber using an optical emission spectrum. The optical emission spectrum is received by spectral lines during coating process. The layer parameters are controlled based on optical emission spectrum. The mathematical links are formed from spectral lines and an intensity linkage is generated by multiplying the mathematical links.

Description

The invention relates to a method for the simultaneous optimization of different layer properties by controlling a vacuum deposition process in which a substrate in a vacuum chamber by means of a material dissolved out of a magnetron associated with a target voltage provided by a regulated voltage source voltage between the target and a counter electrode and under Initiation of a process gas is coated in the vacuum chamber in a process space, wherein an optical emission spectrum is recorded and from it process-significant data of the vacuum deposition process for further processing in measurement or control processes are determined.

Intensity is understood below to mean the value of the intensity of a spectral line of a material. If several intensities of a material are mentioned, this means that several spectral lines are defined from a spectrogram, in whose height, that is, the value of the intensity of the respective spectral line is determined and further processed as intensity.

A process gas, as referred to below, serves, among other things, to adjust the pressure in the vacuum space. It can consist of a working gas, which is inert, ie does not chemically influence the process, such as argon, krypton or xenon. However, for reactive processes, the process gas can also consist of a reactive gas, for example oxygen, in order to trigger chemical reactions during the layer deposition, for example from oxygen for oxidation. The process gas may also consist of a mixture of working gas and reactive gas.

The process gas, in particular the working gas and the reactive gas are materials involved in the coating process, in short also referred to as process materials in the context of the invention.

Another process material is the target material that makes up a target of a magnetron, such as aluminum or zinc. Likewise, newly developed materials are process materials in a reactive process.

In order to ensure the deposition of a layer having constant layer properties, it is necessary to keep the working point of the coating process constant for a long time during which the target material consumes. In particular, homogeneity with respect to the layer thickness, the layer composition (doping) and other properties, such as sheet resistance, must be maintained for a long time. The successive consumption of the target material counteracts this. First and foremost, geometric relationships between target surface, magnetic field and gas inflow change geometrically as a result of consumption.

With a first optimization (so-called trimming) gas pressure distributions of working and reactive gases can be made.

In the ongoing process, the flows of the gases and the target voltage, which are also referred to as process parameters, are readjusted. Another process parameter is the rotation speed with rotating targets.

The process parameters also automatically readjust for a short time is necessary because of the passing substrate. A solution in which the quotient of two intensities is used for control has already been described in the DE 10 2009 053 903 B2 described.

The verification of the long-term stability is based on optical emission spectroscopy (OES) of at least two lines from the plasma, which is established in a vacuum above the target surface when the target voltage is applied. Intensity lines at discrete wavelengths provide information about states of materials involved in the coating process, process materials, as named above.

The plasma is observed, and process parameters are tracked to ensure constant layer parameters, in particular a constant sheet resistance of the growing layer.

Conventional (inexpensive) spectrometers and their arrangement near the process have disadvantages with respect to the measured intensities or their absolute values (accuracy, deposits, fluctuations). The z. T. fuzzy resolution over the wavelength has the consequence that compromises must be made with respect to perfectly identifiable (control technically usable) intensity lines. The lines are sometimes very close to each other.

In the DE 103 41 513 B4 "Method for controlling the reactive gas flow in reactive plasma-assisted vacuum coating processes" has already been described an observation of two lines of the OES signal and discloses a solution for controlling the reactive gas flow in reactive plasma-assisted vacuum deposition processes, in which a controlled variable, which is determined by a plasma of the vacuum coating process out the vacuum chamber is detected as a controlled system by means of optical spectroscopy in a measuring element and set the amount of reactive gas fed to the vacuum coating process as a manipulated variable becomes. In this case, the controlled variable is used as a calculated value from a measured value of the intensity of a spectral line of the process-involved coating material and a measured value of the intensity of a spectral line of the reactive gas or as a calculated value from a value to be determined of the corresponding intensities. In the arrangement also disclosed therein, the measuring element includes an acousto-optic spectrometer with a control input connected to a controller output.

In this known solution, although the intensities of two lines were set in relation and used as a controlled variable, but the reactive gas flow was used as a control variable, which does not sufficiently ensure a consistency of the layer parameters in continuous target erosion, such as a constant sheet resistance, the growing layer ,

In the EP 1 553 206 A1 describes a magnetron sputtering process with an operating point control. The quotient of two intensities of spectral lines in the coating process of participating materials is used as the control variable for the control. In this control, the target voltage is effective as a manipulated variable. The invention has shown that the effect of such operating point control can be improved.

Disadvantage of the above-mentioned method is that only a layer property, hereinafter referred to as layer parameters, can be controlled with an operating point control of the method using mathematical combinations of intensities of spectral lines in the coating process of participating materials, thus only on the basis of measurable process properties.

It is therefore an object of the invention to provide a coating method with which simultaneously different layer parameters can be optimized and which is reliable and safe long-term stable.

This object is achieved by means of a method according to independent claim 1. The subject matter of dependent claims 2 to 15 relates to particular embodiments.

In the method according to the invention, it is provided that spectral lines from the optical emission spectrum are determined for controlling a first layer parameter a of at least three process materials,
at least two intensities are determined and a relative intensity is formed by a first mathematical link f ₁ (I _i , I _j ), i ≠ j (with more than two intensities the relative intensities R ₁ , R ₂ , ... are formed in pairs) .
in the case of more than one relative intensity with a second mathematical linkage f ₂ (R _i ), a first intensity linkage IV_1 is calculated as the first process-significant datum for controlling the first slice parameter a,
that spectral lines from the optical emission spectrum are determined for controlling a second layer parameter b of at least one process material,
in each case two relative intensities of at least two intensities are formed by the first mathematical link f ₁ (I _i , I _j ), i ≠ j,
in that from the relative intensities with a second mathematical linkage f ₂ (R _i ), a second intensity linkage IV_2 is calculated as a second process-significant datum for controlling the second slice parameter b.

In the process, the substrate temperature should be kept constant. Also suitably such spectral lines are used for the determination of intensity, which are sufficiently significant.

In a preferred embodiment of the method is provided
in that spectral lines from the optical emission spectrum are determined for controlling a first layer parameter a of at least three process materials,
that at least four intensities I ₁ ,... I _{4 are} determined from a first process material and from at least three of the four intensities R ₁ , R ₂ , R ₃ by a first mathematical link f ₁ (I _i , I _j ) , _{i ≠ j are} formed,
that at least one intensity I _{5 is} determined from a second process material and at least one intensity I _{6 is} determined from a third process material and a relative intensity R _{4 is formed} by the first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} ,
that from the relative intensities R ₁ , R ₂ , R ₃ and R ₄ with a second mathematical linkage f ₂ (R _i ) a first intensity linkage IV_1 is calculated as the first process-significant datum for controlling the first slice parameter a,
that spectral lines from the optical emission spectrum are determined for controlling a second layer parameter b of at least two process materials,
at least six intensities I ₇ ,... I _{12 are} determined from the first process material, and at least three relative intensities R ₅ , R ₆ , R _{7 are} determined by the first mathematical link f ₁ (I _i , I _j ) from two of the six intensities. , _{i ≠ j are} formed,
that at least one intensity I _{13 is} determined from a fourth process material and at least one further intensity I _{14 is} determined from the first process material and a relative intensity R _{8 is formed} by the first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} ,
a second intensity connection IV_2 is calculated from the relative intensities R ₅ , R ₆ , R ₇ and R ₈ with a second mathematical linkage f ₂ (R _i ) as a second process-significant datum for controlling the second slice parameter b.

In a preferred embodiment of the method, it is provided that the first mathematical combination is a quotient which is formed from two intensities.

Furthermore, it is possible for the second mathematical combination to be a product of at least two such quotients, which represent relative intensities.

In one embodiment, it is provided that the first intensity linkage IV_1 is used as a controlled variable in the control process in such a way that the setpoint of the generator voltage is controlled as a manipulated variable of the control in such a way that the intensity linkage IV_1 is used as the controlled variable of the closed-loop control, setpoint value IV_1 _S set as the reference variable the intensity link IV_1 is kept constant.

In one embodiment, it is provided that the intensity linkage IV_2 is used as a control variable in the control process such that the pressure of the process gas, in particular the pressure of the working gas, via a position on a mass flow controller and / or the power for a control device for controlling the Oxygen flow is performed as a control variable of the control such that the intensity linkage IV_2 is kept constant as a control variable of the control, set to a setpoint as the reference value IV_2 _{S of} the intensity link IV_2.

In one embodiment, it is provided that the desired value IV_1 _S for a value a _{i of} a first slice parameter a _{s to be achieved is determined} from a function IV_1 = f (a).

In one embodiment, it is provided that the target value to be reached IV_1 _S for a value a _i of a layer parameter a _s from a function IV _S = f (a _s) is determined and that the function IV _S = f (a _s) during a Kalibrierbeschichtungsprozesses is detected by values a _{i of} the layer parameter are measured, if a current value a _{n of} the values a _{i is} not matched, the generator voltage is changed until a later value a _{n + x} corresponds to the value of the intended layer parameter a _s and thereby determining intensity link IV_1 used as setpoint IV_1 _S and set as a reference variable.

In one embodiment, it is provided that the target value IV_1 _S for a value a _i a to-reach layer parameter a is determined by measuring during a coating process values a _i of the layer properties a, in case of non-conformity of a current value a of the values _n a _i is the target voltage and / or the speed of the relative movement between the magnet system and the target is changed until a later value a _{n + x} corresponds to the value of the intended layer property a and the intensity linkage IV to be determined is used as the desired value IV _S and set as the reference variable.

In one embodiment, it is provided that the desired value IV_2 _S for a value b _{i of} the second process parameter b _{s to be achieved is determined} from a function IV_2 = f (b).

In one embodiment, it is provided that the desired value IV_2 _S for a value b _{i of} a slice parameter b to be achieved is determined from a function IV _S = f (b _s ) and that the function IV detects _S = f (b _s ) during a calibration coating process is measured by measuring values b _{i of} the layer parameter, if a current value b _{n of} the values b _i does not match the pressure on the mass flow controller and / or the power for the control device for regulating the oxygen flow is changed until a later value b _{n + x} corresponds to the value of the intended layer parameter b and the intensity linkage IV_2 to be determined is used as the desired value IV_2 _S and set as the reference variable.

In one embodiment, it is provided that the control of the first slice parameter a and the control of the second slice parameter b occur simultaneously independently of each other without subsequent control of the respective other parameter.

In one embodiment, it is provided that the control of the generator voltage by means of a proportional-integral-differential controller takes place.

In one embodiment, it is provided that the control of the pressure of the working gas at the mass flow controller and / or the power at the control device for controlling the oxygen flow by means of a proportional-integral controller takes place.

It is an effort to use spectral lines that are as significant as possible in order to increase the accuracy of the method according to the invention. For this purpose, the spectral lines of different materials were given above. Furthermore, the significance can be increased by virtue of the fact that at least one of the spectral lines as the emission line, which is not the neutral material state, but the excited state Material State, for example, an ionized line, assign is selected.

The invention can now be directed in particular to a long-term stabilization of the layer quality in deposition processes and in particular to the development of a long-term stable reactive process for the deposition of ZnO: Al as TCO, wherein in one embodiment a reactive gas with argon as the first process material and oxygen as the second process material , is provided.

Thus, in one embodiment of the method, it is provided that the third process material is Zn + and the fourth process material is aluminum.

In this case, a substrate is coated by means of a material released from the target connected to the magnetron by applying a target voltage provided by a regulated voltage source between the target and a counterelectrode, and introducing a process gas into the vacuum chamber in a process space, the power via an oxygen flow is regulated.

In one embodiment, it is provided that the resistivity of the layer is controlled as the first layer parameter a, and the dynamic deposition rate is controlled, preferably optimally controlled, as the second layer parameter.

Starting point of the method according to the invention is that a clear assignment of layer properties, voltage of the target voltage, speed of the relative target movement and the intensity of spectral lines is observed. It should also be noted that disturbing influences on this unambiguous assignment can be eliminated by the formation of an intensity combination of two intensities.

The invention will be described in more detail with reference to an embodiment. In the accompanying drawings shows

1 the control circuit with the generator voltage as manipulated variable and

2 the control loop with the oxygen flow as a control variable,

In this exemplary embodiment, which relates to a reactive process for the deposition of ZnO: Al, the sheet resistance ρ, which is to have a specific value and is intended to be constant and homogeneous over the substrate length, becomes representative of all other possible combinations of layer properties a and b , as well as the dynamic rate of precipitation ddr considered. Two independent control loops are used at the same time, one for regulating sheet resistance and one for controlling the dynamic deposition rate.

As in 1 are shown by means of one or more optical emission spectrometer as a measuring element 4 the intensities I ₁ to I ₆ measured. From each two of these spectral lines, a first mathematical link f ₁ (I _i , I _j ) is formed. The quotient of a Zn + line and an oxygen line, as well as three quotients of argon lines is formed. From the four quotients, a second mathematical link f ₂ () is formed, which is the product of four first mathematical links and, as a result, the first intensity link IV_1.

From a previous calibration coating process, the value pairs {IV_1 _i , ρ _i } for a value a _{i of} an i-th measurement of a layer property a, for example with ρ _i as the sheet resistance determined here, are now present.

If a specific surface resistance ρ is now to be set, the corresponding IV_1 value is taken from the corresponding value pair and used as the desired value IV_1 _S. The control deviation ΔIV_1 is then calculated from the actual value IV_1 and the desired value IV_1 _S and a controller 5 fed. The regulator 5 and the calculation presented here is in a process computer 6 realized. This also determines the corresponding value of a control voltage U _st , the voltage-controlled generator 7 is supplied as an actuator, resulting in this an output voltage sets as a target voltage U _T , which is applied to the target in the vacuum chamber 8th , which can be regarded as a controlled system, is created.

As in 12 are shown by means of one or more optical emission spectrometer as a measuring element 4 the intensities I ₇ to I ₁₄ measured. From each two spectral lines, a first mathematical link f ₁ (I _i , I _j ) is formed. It is the quotient of an aluminum line and an argon line, which here is ionized argon I ₁₄ , and three quotients of argon lines formed. From the four quotients, a second mathematical link f ₂ () is formed, which is the product of four first mathematical links and, as a result, the second intensity link IV_ 2.

From a previous calibration coating process, the value pairs {IV_2 _i , ddr _i } are now present for a value b _{i of} an ith measurement of a layer property b, for example with ddr _i as the dynamic deposition rate determined thereby.

If a specific dynamic deposition rate ddr is to be set, the corresponding IV_2 value is taken from the corresponding value pair and used as the desired value IV_2 _S. From the actual value IV_2 and the desired value IV_2 _S , the control deviation ΔIV_2 is then calculated and a controller 5 fed. The regulator 5 and the calculation presented here is in a process computer 6 realized. This also determines the corresponding value of a control power U _st , the power-controlled reactive gas controller 9 is supplied as an actuator, resulting in this adjusts an oxygen flow in the vacuum chamber 8th , which can be regarded as a controlled system, is generated or introduced into this.

With the invention is thus achieved that such mathematical operations, in particular those quotients are found that show a definite dependence of ddr and ρ for each control.

LIST OF REFERENCE NUMBERS

4

measuring element

5

regulator

6

process computer

7

generator

8th

vacuum chamber

9

Reactive gas controller

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009053903 B2 [0009]
• DE 10341513 B4 [0013]
• EP 1553206 A1 [0015]

Claims (15)

A method for simultaneously optimizing various layer properties by controlling a vacuum deposition process comprising exposing a substrate in a vacuum chamber by means of a material released from a magnetron-bonded target applying a target voltage provided by a regulated voltage source between the target and a counter electrode and introducing a process gas into the vacuum chamber is coated in a process space, whereby an optical emission spectrum is recorded and determined and used from intensities of spectral lines of the process materials involved in the coating process, process-significant data of the vacuum deposition process for further processing in measuring or control processes, characterized in that for controlling a first Layer parameters a of at least one process material spectral lines are determined from the optical emission spectrum that relative intensities by a first mathematical combination of f ₁ (I _i, I _{j), i ≠ j} are formed, that more than a relative intensity from the relative intensities with a second mathematical combination f ₂ (R _i) a first intensity link IV_1 first process-significant For controlling the first slice parameter a, it is calculated that for controlling a second slice parameter b of at least one process material, spectral lines are determined from the optical emission spectrum such that relative intensities are formed by the first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} in that with more than one relative intensity from the relative intensities R ₅ , R ₆ , R ₇ and R ₈ with a second mathematical link f ₂ (R _i ), a second intensity link IV_2 is calculated as the second process-significant datum for controlling the second slice parameter b. A method according to claim 1, characterized in that for controlling a first layer parameter a of at least three process materials spectral lines are determined from the optical emission spectrum that at least four intensities I ₁ , ... I _{4 are} determined from a first process material and from two of the four Intensities at least three relative intensities R ₁ , R ₂ , R _{3 are formed} by a first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} that at least one intensity I ₅ determined from a second process material and from a third process material at least an intensity I _{6 is} determined and a relative intensity R _{4 is formed} by the first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} , that of the relative intensities R ₁ , R ₂ , R ₃ and R ₄ with a second mathematical link f ₂ (R _i ) a first intensity link IV_1 as the first process-significant date for controlling the first Schichtpara a is calculated that for controlling a second layer parameter b of at least two process materials spectral lines from the optical emission spectrum are determined that from the first process material at least six intensities I ₇ , ... I _{12 are} determined and from two of the six intensities at least three relative intensities R ₅ , R ₆ , R _{7 are formed} by the first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} that determines at least one intensity I ₁₃ from a fourth process material and at least one further from the first process material Intensity I _{14 is} determined and a relative intensity R _{8 is formed} by the first mathematical link f ₁ (I _i , I _j ), _{i ≠ j} that from the relative intensities R ₅ , R ₆ , R ₇ and R ₈ with a second mathematical Link f ₂ (R _i ) a second intensity link IV_2 as a second process-significant date for controlling the second slice parameter b berec hnet is. The method of claim 1 or 2, characterized in that the first intensity linkage IV_1 is used as a controlled variable in the control process such that the setpoint of the generator voltage is performed as a control variable of the control such that the intensity link IV_1 as a control variable of the scheme, one as a reference variable setpoint IV_1 _{S of} the intensity link IV_1 is kept constant. Method according to one of claims 1 to 3, characterized in that the intensity linkage IV_2 is used as a controlled variable in the control process such that the pressure of the process gas, in particular the pressure of the working gas, via a position on a mass flow controller and / or the power is performed for a control device for controlling the flow of oxygen as a control variable of the control such that the intensity link IV_2 is kept constant as a control variable of the control, set to a setpoint as the reference value IV_2 _{S of} the intensity link IV_2. Method according to Claim 3 or 4, characterized in that the desired value IV_1 _S for a value a _{i of} a first slice parameter a _{s to be achieved is determined} from a function IV_1 = f (a). A method according to claim 5, characterized in that the desired value IV_1 _S to reach a for a value a _i layer parameter a _s from a function IV _S = f (a _s) is determined and that the function IV _S = f (a _s) during one Calibration coating process is detected by values a _{i of} the layer parameter are measured, if a current value a _{n of} the values a _i, the generator voltage is changed until a later value a _{n + x} corresponds to the value of the intended layer parameter a _s and the case to be determined intensity link IV_1 used as setpoint IV_1 _S and set as a reference variable. Method according to Claim 5, characterized in that the desired value IV_1 _S for a value a _{i of} a slice parameter a to be achieved is determined by measuring values a _{i of} the slice properties a during a coating process, if a current value a _{n of} the values a _i does not match the target voltage and / or the speed of the relative movement between the magnet system and the target is changed until a later value a _{n + x} corresponds to the value of the intended layer property a and the intensity linkage IV to be determined is used as the desired value IV _S and set as the reference variable , Method according to one of Claims 3 to 7, characterized in that the desired value IV_2 _S for a value b _{i of} the second process parameter to be achieved b _{s is determined} from a function IV_2 = f (b). Method according to claim 8, characterized in that the desired value IV_2 _S for a value b _{i of} a slice parameter b to be achieved is determined from a function IV _S = f (b _s ) and that the function IV _S = f (b _s ) during a Calibration coating process is detected by values b _{i of} the layer parameter are measured, in case of non-compliance of a current value b _{n of} the values b _i the pressure on the mass flow controller and / or the power for the controller to control the oxygen flow is changed until a later Value b _{n + x} corresponds to the value of the intended layer parameter b and the intensity linkage IV_2 to be determined is used as the desired value IV_2 _S and set as the reference variable. Method according to one of Claims 1 to 9, characterized in that the control of the first slice parameter a and the control of the second slice parameter b occur simultaneously independently of each other without subsequent control of the respective other parameter. Method according to one of claims 1 to 10, characterized in that the control of the generator voltage by means of a proportional-integral-differential controller takes place. Method according to one of claims 1 to 11, characterized in that the control of the pressure of the working gas at the mass flow controller and / or the power to the control device for controlling the oxygen flow by means of a proportional-integral controller takes place. Method according to one of claims 1 to 12, characterized in that one or more intensities is obtained from a spectral line of an ionized form of a process material. Method according to one of Claims 1 to 12, characterized in that the first process material is argon, the second process material is oxygen and the third process material is Zn + and the fourth process material is aluminum. Method according to one of Claims 1 to 14, characterized in that the first layer parameter a is the specific resistance of the layer and the second layer parameter b is the dynamic deposition rate.

Images