TWI485277B - Multi-sputtering cathodes stabilized process control method for reactive-sputtering deposition - Google Patents

Description

Multi-target reactive sputtering process stability control method

The present invention relates to a multi-target reactive sputtering process, in particular to a multi-target reactivity which can be used for plating a hard film such as aluminum nitride titanium or a mixed film of optoelectronics such as a tungsten trioxide-bismuth pentoxide mixed film. Sputtering process stability control method.

In recent years, due to advances in materials science and thin film process technology, composite films made of two or more compounds have been increasingly used. For example, a titanium aluminum nitride (TiAlN) film, an aluminum nitride chromium (AlCrN) film, or the like, which can be used to improve the performance and life of a tool, or a tungsten trioxide-pentaoxide bismuth (WO ₃ -Nb) which can be used for an optical product. ₂ O ₅ ) a mixed film, a tantalum pentoxide-titania (Ta ₂ O ₅ -TiO ₂ ) mixed film, or the like. On the other hand, although these composite film films may be manufactured in more than one way, with the rise of environmental awareness, the low-pollution reactive sputtering process has received increasing attention and widespread adoption.

However, since many reactive sputtering products are insulated, so-called target poisoning may occur, the sputtering rate may be greatly slowed down, or the arcing phenomenon may occur in the system, resulting in poor coating quality, even equipment. damage. Therefore, generally, when performing a reactive sputtering process, a radio frequency (RF) power source or a pulsed DC power source is used as a working power source for the sputtering gun; in addition, in order to make the process stable, it is generally first Find the hysteresis curve of the individual material targets for the reaction gas used, and set the control conditions in the middle of the transition zone of the hysteresis curve to avoid slight changes in the system state, which will cause the process parameters to leave the transition zone and cause process interruption. These methods, while addressing the process stability issues of a single target during reactive sputtering processes. However, when reactive sputtering is performed simultaneously with two or more targets in the same sputtering equipment system, the reaction rates and working conditions of different target materials for the same reaction gas are different. Therefore, when reactive sputtering is performed simultaneously with two or more targets in the same sputtering apparatus system, the sputtering guns containing the two or more targets are respectively connected to the reaction gas through the targets to be mounted. Reactions interact with each other, making process control more difficult. Therefore, how to improve this problem has become the primary goal of the relevant industry to actively invest in seeking solutions.

In view of this, the present invention is directed to the absence of the prior art, and its main object is to provide a multi-target reactive sputtering process stability control method, which is used in multi-target reactive sputtering equipment to find the hysteresis of each target. After the curve and the transition zone of the hysteresis curves, the set point of each process parameter, the control range of the reaction gas flow controller and the control parameters of the PID controller are determined, and then the PID controller is used to control the process stability. According to the implementation of the present invention, it is possible to solve the problem that when two or more targets are simultaneously subjected to reactive sputtering in a sputtering apparatus system, the sputtering guns containing the two or more targets may affect each other, and the process is not easily stabilized. Control problem.

To achieve the above object, the present invention provides a multi-target reactive sputtering process stability control method, which is implemented in a reactive sputtering apparatus, the reactive sputtering apparatus comprising a vacuum chamber and at least one process parameter sensor. The vacuum chamber is provided with a substrate and at least two sputtering guns, the sputtering guns respectively are provided with targets of different materials, and the sputtering guns are respectively configured with reaction gases Flow controller and Proportional-Integral-Derivative Controller (PID Controller), the method is to first use the sputtering guns to sputter the substrate, and synchronously adjust the reaction gas flow controllers. To separately supply and control the gas flow rate of the reaction gas to each of the sputtering guns, and simultaneously read at least one process parameter of each target by the process parameter sensor, and corresponding to the gas flow rate change process parameter of each target The generated change is made into a hysteresis curve, and the transition zone of each hysteresis curve is found. Then, according to the hysteresis curve corresponding to each target, the set point of the process parameters for controlling each target and the flow rate of each reaction gas flow controller are determined. The control range and various control parameters of each PID controller, and the control range of each reaction gas flow controller is between the upper limit and the lower limit of the gas flow in the transition region of the hysteresis curve corresponding to each target, and finally, the The PID controller controls the stability of the sputtering process according to the control parameters, and respectively receives the readings from the process parameter sensors. Process parameters of the material, and controls the respective reaction gas flow controller in accordance with various process parameters, so that the process parameters of each target value is maintained at Jieke each corresponding to the set point.

Specifically, the process parameters of each target are the voltage, current, power, plasma emission spectral intensity or reactive gas partial pressure of the working power source of the sputtering gun corresponding to each target. The transition zone of the hysteresis curve corresponding to each target refers to a section between when the reaction gas is introduced into the sputtering process so that the process parameters are changed until the targets are completely poisoned so that the process parameters stop changing. Each of the set points is a transition zone selected from the hysteresis curves corresponding to the respective targets, and within the overlapping sections of the control gas flow controllers for the control range of the gas flow rate.

With the implementation of the present invention, at least the following advancements can be achieved:

(1) The sputtering apparatus can stably perform reactive sputtering while using targets of a plurality of different materials.

(2) A high-quality and stable composite film product obtained by mixing a plurality of materials and a reaction product obtained by reacting a reaction gas with each other can be obtained.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

1‧‧‧Reactive Sputtering Equipment

10‧‧‧First Sputter Gun

11‧‧‧First power supply

12‧‧‧First power supply voltage and current sensor

13‧‧‧Tungsten target

14‧‧‧First Reaction Gas Flow Controller

15‧‧‧First PID Controller

20‧‧‧Second Sputter Gun

21‧‧‧Second power supply

22‧‧‧Second supply voltage and current sensor

23‧‧‧ Target

24‧‧‧Second reactant gas flow controller

25‧‧‧Second PID controller

26‧‧‧Substrate

27‧‧‧Substrate holder

50‧‧‧vacuum chamber

Fig. 1 is a system configuration diagram of a reactive sputtering apparatus used in an embodiment of the present invention.

2 is a flow chart showing the steps of a multi-target reactive sputtering process stability control method according to an embodiment of the present invention.

Fig. 3 is a graph showing the hysteresis curve of the surface voltage of the tungsten target in the tungsten monoxide-bismuth pentoxide mixed film sputtering process according to the embodiment of the present invention.

4 is a graph showing the hysteresis curve of the target surface voltage of the tantalum trioxide-bismuth pentoxide mixed film sputtering process according to an embodiment of the present invention.

Figure 5 is a graph showing the relationship between the PID value and the target surface voltage according to an embodiment of the present invention.

FIG. 6 is a graph showing monitoring results of tungsten target surface voltage and oxygen flow in a tungsten monoxide-bismuth pentoxide mixed film sputtering process according to an embodiment of the present invention.

FIG. 7 is a graph showing monitoring results of target surface voltage and oxygen flow rate of a tantalum trioxide-bismuth pentoxide mixed film sputtering process according to an embodiment of the present invention.

Embodiments of the present invention provide a multi-target reactive sputtering process stability control method applicable to a reactive sputtering apparatus configured with a plurality of targets. Please refer to FIG. 1 , which is a system configuration diagram of a reactive sputtering apparatus used in an embodiment of the present invention.

The reactive sputtering apparatus 1 used in this embodiment comprises a vacuum chamber 50 and at least one process parameter sensor (described in detail later). The vacuum chamber 50 is provided with a substrate 26 and different materials are respectively installed. A plurality of sputtering guns of the target, in this embodiment, a first sputtering gun 10 equipped with a tungsten target 13 and a second sputtering gun 20 equipped with a target 23 are provided. Moreover, each of the sputtering guns is respectively provided with a reactive gas flow controller, a Proportional-Integral-Derivative (PID) controller; and in the embodiment, the first sputtering gun 10 is configured with a first A reactive gas flow controller 14 and a first PID controller 15; the second sputtering gun 20 is configured with a second reactive gas flow controller 24 and a second PID controller 25. Wherein, the first reactive gas flow controller 14 is responsible for supplying oxygen to the first sputtering gun 10 and controlling its gas flow rate, and the second reactive gas flow controller 24 is responsible for supplying oxygen to the second sputtering gun 20 and controlling the gas thereof. The flow rate, the first PID controller 15 is electrically connected to the first reactive gas flow controller 14 and controls its operation, and the second PID controller 25 is electrically connected to the second reactive gas flow controller 24 and controls the same. action.

The substrate 26 to be plated is fixedly placed on the substrate holder 27 which can be rotated rapidly. Since the substrate holder 27 can be rotated rapidly, the substrate 26 to be plated can be rapidly alternately moved to the first sputtering gun 10 containing the tungsten target 13 and the second sputtering gun 20 containing the target 23. In the plating zone, the tungsten atoms deposited on the surface of the substrate 26 (or the oxidation in the oxidation reactive sputtering process) may be passed each time through the sputtering zone of the first sputtering gun 10 or the second sputtering gun 20 The amount of the tungsten molecule or the germanium atom (or the antimony pentoxide molecule in the oxidation reactive sputtering process) is insufficient to completely cover the surface of the substrate 26, so that the surface of the substrate 26 can be plated to obtain tungsten-germanium (or oxidation reaction). A mixed film of tungsten trioxide-bismuth pentoxide in a sputter process.

The process parameter sensor used on the reactive sputtering apparatus 1 may be a power supply voltage or a power supply current sensor. Therefore, the process parameters monitored are the voltage, current, or power of the operating power of each sputtering gun. (ie, the product of the voltage and current values). In this embodiment, the process parameter sensor includes a first power voltage and current sensor 12 and a second power source. Pressure and current sensor 22. The first power voltage and current sensor 12 is built in a first power supply 11 electrically connected to the first sputtering gun 10 and responsible for supplying the working power of the first sputtering gun 10, and the second power voltage and The current sensor 22 is a second power supply 21 built in electrical connection with the second sputtering gun 20 and responsible for supplying the working power of the second sputtering gun 20.

The first power voltage and current sensor 12 and the second power voltage and current sensor 22 are respectively electrically connected to the first PID controller 15 and the second PID controller 25 to respectively send the signals to the first A PID controller 15 and a second PID controller 25 serve as a reference for control by the first PID controller 15 and the second PID controller 25.

In addition to the supply voltage or supply current sensor, the process parameter sensor used on the reactive sputtering apparatus 1 can also be a Plasma Emission Monitor (PEM). When the process parameter sensor installed and used on the reactive sputtering apparatus 1 is a plasma emission spectrum monitor, it monitors the change of the intensity of the radiation spectrum emitted by the reaction gas when it is ionized into plasma. .

In addition, in the reactive sputtering process, in addition to the working gas required to pass all the sputtering processes, the reaction gas must be introduced, so the process parameter sensing installed and used on the reactive sputtering apparatus 1 is sensed. The device can also be a reactive gas partial pressure sensor. At this time, it is monitored by the change in the partial pressure of the gas which the reaction gas occupies in the vacuum chamber 50 of the reactive sputtering apparatus 1.

Next, please refer to FIG. 2, which shows a flow chart of the steps of the multi-target reactive sputtering process stability control method according to the embodiment of the present invention. The method is performed in the reactive sputtering apparatus 1 by performing the following steps: as shown in step S1, finding the hysteresis curve of each target and the transition zone of the hysteresis curves. Sputter all the sputtering guns simultaneously. In this embodiment, the first power supply 11 and the second power supply 21 are simultaneously fixed to the first sputtering gun 10 and the second sputtering gun. The power, voltage or current of 20 is sputtered using both the first sputtering gun 10 equipped with the tungsten target 13 and the second sputtering gun 20 equipped with the target 23 . At the beginning, the reaction gas is not introduced first, that is, the oxygen is not introduced first.

Since in the present embodiment, the process parameter sensor used in the reactive sputtering apparatus 1 is the first power supply voltage and current sensor 12 built in the first power supply 11 and the second power supply 21 And the second power voltage and current sensor 22, therefore, in this embodiment, the first power supply 11 and the second power supply 21 are selected to be set in a constant power mode, and the current time is monitored and recorded. a voltage value read by the power voltage and current sensor 12 and the second power voltage and current sensor 22 (that is, a target voltage value of the tungsten target and the target) or a current value; of course, the first A power supply 11 and a second power supply 21 are set in a constant voltage mode, and record the current or power value at this time; or the first power supply 11 and the second power supply 21 are set. In the current mode, record the power or voltage at this time.

In addition, since the process parameter sensor installed and used in the reactive sputtering apparatus 1 can also be a plasma emission spectrum monitor or a reactive gas partial pressure sensor, the process parameters recorded at this time can also be It is the intensity of the plasma emission spectrum or the partial pressure of the reaction gas.

Then, the reaction gas is introduced, and the flow rate of the reaction gas supplied to each of the sputtering guns is synchronously adjusted, that is, the first reaction gas flow controller 14 and the second reaction gas flow controller 24 are synchronously controlled to adjust the supply to the loading. The oxygen flow rate of the first sputtering gun 10 of the tungsten target and the second sputtering gun 20 equipped with the target, and recording the voltage, current, power, plasma emission spectrum intensity or reactive gas partial pressure of the working power source The hysteresis curve of the reactive sputtering of each target and the reaction gas used can be obtained by the change of the parameter with the change of the flow rate of the reaction gas. The hysteresis curve begins when the reactive gas is introduced into the reactive sputtering process so that the monitored process parameters change until the target is completely poisoned so that the monitored process parameters stop changing, that is, The transition zone of a hysteresis curve.

Referring to FIG. 3, in the constant power supply mode, the tungsten target 13 and the target 23 are sputtered by a reactive sputtering process to obtain tungsten oxide (WO ₃ ) and tantalum pentoxide (Nb ₂ O _{5 ).} For example, the mixed film of the first sputtering gun 10 with the tungsten target 13 in the process has a hysteresis curve of the change of the operating power voltage (ie, the target voltage) with respect to the flow rate of the reaction gas (ie, oxygen). As can be seen from Fig. 3, the transition region of the hysteresis curve of tungsten is between about 375 volts to 660 volts of the power supply voltage.

Please also refer to FIG. 4, which is the change of the operating power supply voltage (ie, Target Voltage) of the second sputtering gun 20 equipped with the target 23 in the same process relative to the flow rate of the reaction gas (ie, oxygen). Hysteresis curve. As can be seen from Fig. 4, the transition region of the hysteresis hysteresis curve is between about 370 volts to 610 volts.

Since the process parameter sensor installed and used in the reactive sputtering apparatus 1 can also be a plasma emission spectrum monitor or a reactive gas partial pressure sensor, when the process parameter sensor is installed and used, In the case of a plasma emission spectrum monitor, the hysteresis curve obtained is the hysteresis curve of the intensity of the radiation spectrum of tungsten or tantalum relative to the flow rate of the reaction gas; and when the process parameter sensor is installed and used, In the case of a reaction gas partial pressure sensor, the hysteresis curve obtained is a hysteresis curve formed by the change of the partial pressure of the reaction gas supplied to the tungsten target or the target with respect to the flow rate of the reaction gas.

Next, as shown in step S2, the set point of the process parameters for controlling each target, the control range of each reaction gas flow controller for the gas flow rate, and the control parameters of each PID controller are determined. This is based on the hysteresis curve corresponding to each target obtained in step S1. In this embodiment, the first sputtering gun 10 with the tungsten target 13 and the second target 23 are mounted. In the process of sputtering the gun 20 and performing reactive sputtering by using oxygen as a reactive gas to form a tungsten trioxide-bismuth pentoxide mixed film, the first sputtering gun 10 containing the tungsten target 13 and the target 23 are equipped. The hysteresis caused by the change of the power supply voltage (target surface voltage) of the second sputtering gun 20 with respect to the change of the oxygen flow rate Lines, and according to the hysteresis curves, the target values of the respective process parameters are determined for the first sputtering gun 10 equipped with the tungsten target 13 and the second sputtering gun 20 equipped with the target 23, respectively. In this embodiment, the target value of the power supply voltage of the first sputtering gun 10 containing the tungsten target 13 and the second sputtering gun 20 equipped with the target 23 is set, and the target values of the processing parameters are set to The set point of the process parameter sensor signal reading, that is, the set point of the first power voltage and current sensor 12 and the second power voltage and current sensor 22 readings. In order to balance the requirements of film properties, sputtering rate and process stability, each set point is usually selected from the transition zone of the hysteresis curve corresponding to each target, and is the control range of the gas flow rate of all reactive gas flow controllers (eg Inside the overlapping section of the description). For example, in the present embodiment, the selected first supply voltage and current sensor 12 read set point is 625 volts, and the second supply voltage and current sensor 22 read set point is 587.5 volts.

The control range of the gas flow rate of the first reaction gas flow controller 14 is such that the first sputtering gun 10 equipped with the tungsten target 13 can be stably operated between the upper limit and the lower limit of the oxygen gas flow rate in the transition region of the hysteresis curve of tungsten. According to the results shown in Fig. 3, this embodiment is set in the range of 0 to 6 sccm (standard number of milliliters per unit time).

The control range of the gas flow rate of the second reaction gas flow controller 24 is such that the second sputtering gun 20 equipped with the target 23 can be stably operated between the upper limit and the lower limit of the oxygen gas flow rate in the transition region of the hysteresis curve of the crucible. According to the results shown in Fig. 4, this embodiment is set in the range of 0 to 5 sccm.

Please also refer to Figure 5, the control parameters of the PID controller, namely P parameters, I parameters and D parameters. In the present embodiment, the P parameter changes the vibration frequency of the hysteresis curve, the I parameter changes the rate of rise of the hysteresis curve, and the D parameter affects the small amount of error caused by the disturbance to the hysteresis curve. For a reactive sputtering system, the value of the PID parameter also has different representative meanings. The P parameter can be used to represent the reaction state of the target surface voltage, the I parameter represents the rate of change of the target surface when changing the oxygen flow rate, and the D parameter is Indicates the target surface voltage disturbance state. It can be known that there is a good PID parameter, which will greatly help the stability of the process. Here, you can use the concept of critical damping, using Laplace transform, to find a PID three-valued equilibrium equation, as follows:

When δ is equal to 1 in equation (1), there will be a stable PID parameter, so that it can be known how to adjust to the initial PID parameter.

By the above method, the values of the control parameters required by the first PID controller 15 and the second PID controller 25 can be respectively obtained through the hysteresis curves of tungsten and germanium.

Finally, as shown in step S3, the PID controller is used to control the process stability. Step S3 is to input the control parameter values required by the first PID controller 15 and the second PID controller 25 obtained in step S2 to the first PID controller 15 and the second PID controller 25, respectively. A PID controller 15 controls the first reactive gas flow controller 14 based on the received first power supply voltage and current sensor 12 signal reading changes, and causes the second PID controller 25 to receive the second The supply voltage and current sensor 22 signal reading changes to control the second reactive gas flow controller 24 to read signals from the first supply voltage and current sensor 12 and the second supply voltage and current sensor 22 The values can be maintained at respective set points, that is, the signal reading of the first power voltage and current sensor 12 is maintained at about 625 volts, and the signal reading of the second power voltage and current sensor 22 is about It is 587.5 volts.

Referring to FIG. 6, after the control is performed by using the method provided in this embodiment, the signal reading of the first power voltage and current sensor 12 is approximately the same as the oxygen flow rate of the first reactive gas flow controller 14 over time. The change, and the two curves in the figure sequentially indicate the target surface voltage of the tungsten target 13 and the oxygen flow rate of the tungsten target 13 from top to bottom; and, referring to FIG. 7, after controlling by using the method provided by the embodiment The signal reading of the second power voltage and current sensor 22 and the oxygen flow rate of the second reactive gas flow controller 24 change with time, and the two curves in the figure are The target surface voltage of the target 23 and the oxygen flow rate of the target 23 are sequentially shown from top to bottom. From the results shown in FIGS. 6 and 7, it can be seen that the first sputtering gun 10 equipped with the tungsten target 13 can be used simultaneously in the reactive sputtering apparatus 1 by the control method provided in this embodiment. In the process of plating the tungsten trioxide-pentaoxide mixed film with the second sputtering gun 20 of the target 23, the oxygen flow supplied by the first reaction gas flow controller 14 and the second reaction gas flow controller 24 is effectively controlled. Therefore, the entire process can be maintained stable.

From the above description, according to the multi-target reactive sputtering process stability control method provided by the present invention, the control parameter value of the PID controller can be surely found, and the signal reading value from the process parameter sensor for the process parameter can be made. Maintaining the selected set point, thereby effectively controlling the gas flow rate of the reaction gas supplied by each reaction gas flow controller, thereby maintaining the stability of the entire reactive sputtering process and achieving stable use of a plurality of different materials. Simultaneous reactive sputtering, as well as the ability to obtain a high quality and stable composite film product obtained by mixing a plurality of materials with a reaction gas, respectively.

The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, any changes or modifications of the features and spirits of the present invention should be included in the scope of the present invention.

Claims (5)

A multi-target reactive sputtering process stability control method is implemented in a reactive sputtering apparatus, the reactive sputtering apparatus comprising a vacuum chamber and at least one process parameter sensor, the vacuum chamber being provided with a substrate And at least two sputtering guns, each of which is provided with one of different materials, and the sputtering guns are respectively configured with a reaction gas flow controller and a proportional-integral-derivative controller (Proportional-Integral) -Derivative Controller (PID Controller), the method comprises the steps of: sputtering the substrate by using the sputtering guns, and simultaneously adjusting the reaction gas flow controllers to respectively supply and control a reaction to each of the sputtering guns a gas flow rate of the gas, and simultaneously reading at least one process parameter of each of the targets by the process parameter sensor, and forming a hysteresis curve corresponding to the change of the gas flow rate by the process parameter of each target And finding a transition zone of each of the hysteresis curves; determining, according to the hysteresis curve corresponding to each target, a set point of each of the process parameters for controlling each target, each a reaction gas flow controller controls a range of the gas flow rate and a plurality of control parameters of each of the PID controllers, and the control range of each of the reaction gas flow controllers is the transition of the hysteresis curve corresponding to each of the targets Between the upper and lower limits of the gas flow rate in the zone; and controlling the stability of the sputtering process according to the control parameters by the PID controllers, and respectively receiving the respective readings from the process parameter sensor The process parameters of the target are controlled, and each of the reaction gas flow controllers is controlled according to each of the process parameters, so that the process parameters of each target can be maintained at corresponding respective set points. The multi-target reactive sputtering process stability control method according to claim 1, wherein the target of each of the targets The process parameter is the voltage, current, power, plasma emission spectrum intensity or reaction gas partial pressure of the working power source of the sputtering gun corresponding to each target. The multi-target reactive sputtering process stability control method according to claim 1, wherein the transition zone of the hysteresis curve corresponding to each of the targets is subjected to the sputtering process after the reaction gas is introduced to cause the process parameter to be generated. The change is until the section between each of the targets is completely poisoned such that the process parameters stop changing. The multi-target reactive sputtering process stability control method according to claim 1, wherein the control parameters of each of the PID controllers are P parameters, I parameters, and D parameters, and the P parameters are vibrations of the hysteresis curves. Frequency, the I parameter is the rate of rise of each of the hysteresis curves, and the D parameter is a small amount of error caused by each of the hysteresis curves. The multi-target reactive sputtering process stability control method according to claim 1, wherein each of the set points is selected from the transition region of the hysteresis curve corresponding to each of the targets, and the reaction gas flow controller is Within the overlapping sections of the control ranges of the gas flows.