TW201908502A - Method and apparatus for controlling film thickness of reactive sputtering capable of accurately controlling film formation without being influenced by the initial state of a target - Google Patents

Abstract

The present invention provides a method and an apparatus for controlling the film thickness of reactive sputtering, which can accurately control film formation without being influenced by the initial state of a target. The method comprises a first step and a second step. In the first step, with regard to a target used for reactive sputtering, it acquires in advance a relationship between a discharge voltage and a film formation rate at the time of film formation by constant power discharge. In the second step, the thickness of the film that has been formed is calculated according to the film formation rate corresponding to the measured value of the discharge voltage for at least a part of the period in the film formation by reactive sputtering using the target.

Description

Film thickness control method and device for reactive sputtering

The present invention relates to a film thickness control method and apparatus for reactive sputtering.

In a manufacturing process of an optical element, an electronic device, a semiconductor device, or the like, a reactive sputtering device is widely used as a method of forming a compound thin film. The reaction sputtering apparatus is configured to include a device that supplies a reactive gas into a reaction tank in which a conductive target is disposed, and deposits a compound generated by a reaction between a sputter particle that transmits the conductive target and a reactive gas. On the substrate.

In the mass production process, a carousel type sputtering apparatus as disclosed in Patent Document 1 is often used from the viewpoint of improving productivity. In the rotary-type sputtering apparatus, a plurality of substrates to be film-formed are mounted on a rotating drum in which a sputtering target is disposed, and a film is formed by sputtering while rotating the drum. Therefore, a plurality of substrates can be simultaneously processed. In most sputtering apparatuses, the film thickness control is performed only by the management of the film formation time calculated based on the film formation rate measured in advance. [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent No. 3064301

In the reactive sputtering apparatus, when a compound is formed on the surface of the conductive target by the reactive gas, the film formation rate is lowered, and the film thickness cannot be controlled with high precision. For example, when an oxide film is formed by a disk-type sputtering apparatus (see Patent Document 1) in which a plurality of materials can be laminated using a plurality of types of metal targets, plasma is introduced into the processing tank to form plasma. During the period of a certain material, the surface of the target of other materials may oxidize. Shortly after the start of film formation, the surface of the target has been oxidized, and the sputtering rate is much lower than that of the metal monomer in the state after oxidation. Therefore, the film formation rate is slow, and only the film formation time is transmitted. Management is difficult to control film thickness. Further, when the substrate to be coated is a resin, the resin absorbs moisture, which is discharged from the substrate in the form of a gas during the film formation and decomposed in the plasma, which also causes oxidation of the surface of the target. In the past, the film thickness accuracy was not so required, but an antireflection film such as an optical lens gradually required high film thickness precision, and a slight deviation would affect the characteristics of the final product.

In order to improve the film thickness precision, it is also considered to provide a gate between the target and the substrate so that film formation cannot be performed until the discharge state is stabilized. However, the target and the substrate are close to each other, and due to problems such as space, the gate and the mechanism for making it work are often difficult to set. In addition, since the gate itself has an influence on the discharge state, it is preferable not to set it if it is not possible. Further, depending on the reaction sputtering apparatus, there is a type in which a structure such as a shutter mechanism cannot be provided, and in the case of such a structure, it cannot be handled.

An object of the present invention is to solve the above problems and to provide a film thickness control method and apparatus capable of controlling reactive film formation with high precision without being affected by an initial state of a target.

A first aspect of the present invention provides a film thickness control method for reactive sputtering, comprising: a first step and a second step; and in the first step, the target used in the reactive sputtering is preliminarily obtained The relationship between the discharge voltage at the time of film formation by constant power discharge and the film formation rate; in the second step, at least a part of the film formation by reactive sputtering using the target, according to the discharge voltage The measured film thickness corresponding to the measured value is calculated by calculation to determine the film thickness of the film formed.

Preferably, in the first step, the discharge voltage and the film formation speed at the time of film formation are changed by the surface state of the target, and the discharge voltage at a constant power discharge is correlated with the film formation speed. In addition, the amount of introduction of the reactive gas introduced into the reaction vessel in which the reactive sputtering is performed is changed, and the film thickness is formed for a longer period of time than the actual film formation condition in a state where the discharge voltage is constant, and the film thickness is measured and changed. The measurement was repeated for the value of the discharge voltage. In the first step, in addition to the introduction of the reactive gas, water H ₂ O in an amount corresponding to the material to be formed can be introduced.

Preferably, in the second step, the film formation time is extended or shortened to compensate for the film thickness of the film formed during at least a part of the film formation determined in the second process and at least a part of the film formation period The difference in film thickness formed. In the period from the start of the discharge of the reactive sputtering to the stabilization of the discharge voltage, the film thickness of the film formation can be calculated by calculation, and the film formation time can be extended or shortened to compensate the film thickness and the obtained film thickness. The difference in film thickness to be formed during the period of stabilization.

It is also possible to reduce the amount of introduction of the reactive gas to a value less than that which should be introduced after the discharge voltage is stabilized, before the discharge voltage at the initial stage of film formation is stabilized. Further, it is also possible to set feedback control of the amount of introduction of the reactive gas before the discharge voltage at the time of film formation becomes a predetermined value.

Preferably, the first step is performed on the target used in the sputtering region of the reactive sputtering apparatus, and the second step is performed when the target is used for film formation, wherein the reactive sputtering apparatus has a film formation The substrate of the object is mounted on a rotating drum and sequentially passes through the sputtering region and the plasma region. In this case, it is possible to have a plurality of sputtering regions in which different materials are laminated and formed in the reactive sputtering apparatus, and to perform at least one of the targets of the different materials used in the plurality of sputtering regions. In the first step, when the film is formed using the target that has been subjected to the first step, the second step is performed.

As the substrate to be coated, a resin substrate can be used.

A second aspect of the present invention is a film thickness control device for reactive sputtering, which is provided in a control device for controlling the operation of the reactive sputtering device, and controls a thickness of a film formed by the reaction sputtering device. The film thickness control device for reactive sputtering includes a storage unit, an input unit, and a calculation unit. The storage unit stores a film that is used in the reactive sputtering device and stores a film that is previously obtained by transmission of a constant power discharge. The relationship between the discharge voltage and the film formation rate; the input portion inputs the measured value of the discharge voltage at the time of film formation; and the calculation portion inputs the film during at least a part of the film formation by reactive sputtering using the target. The measured value of the discharge voltage input from the unit is accessed to the storage unit, and the film thickness of the formed film is obtained by calculation based on the corresponding film formation rate. (invention effect)

According to the present invention, it is possible to control the film formation with high precision without being affected by the initial state of the target at the time of film formation by the reactive sputtering device.

Fig. 1 is a perspective view showing an example of a device for simplifying a film thickness control method for performing reactive sputtering according to the present invention, and Fig. 2 is a view of the device as viewed from above. Here, the case where the present invention is carried out by the rotary-type reactive sputtering apparatus shown in Patent Document 1 is shown as an example.

The reaction sputtering apparatus (sputtering system) 10 has a cage drum 14 in a reaction tank (housing) 11, and a substrate 15 for film formation is attached to the drum 14. A substrate heating mechanism (not shown) that heats the substrate 15 may be provided. The drum 14 is provided to be rotatable about the rotation shaft 16. Sputtering regions (sputtering stations) 26 and 27 and plasma regions (reaction stations) 28 are disposed in the reaction vessel 11 along the outer peripheral surface of the drum 14. Sputtering electrodes are respectively disposed in the sputtering regions 26, 27, a reactive gas is introduced into the plasma region 28, and another plasma for generating a plasma different from the sputtering plasma and the film on the substrate 15 is provided. The plasma source of the reaction. In the embodiment, the coil antenna is connected to a high-frequency power source to generate an inductively coupled plasma, but other methods such as microwave plasma or direct current discharge plasma may be used. The illustration of the gas introduction mechanism for generating plasma is omitted.

Also shown in Fig. 1 are voltage sources 34, 35, 33 for supplying electric power for discharge to the sputtering regions 26, 27 and the plasma region 28, and voltmeters 34, 35 for controlling the output voltage values of the power sources 31, 32, and control. Control unit 36 for these components.

Here, a case where the substrate 15 is a resin lens and an antireflection film composed of a multilayer film of titanium dioxide TiO ₂ and cerium oxide SiO ₂ is formed on the resin lens will be described as an example. In this case, titanium Ti and 矽Si are respectively sputtered as targets in the sputtering regions 26 and 27, and oxidation by oxygen plasma is performed in the plasma region 28. That is, with the rotation of the drum 14, Ti is deposited on the substrate 15 facing the sputtering region 26, and the deposited Ti is oxidized in the plasma region 28. At this time, no processing is performed in the sputtering region 27. Next, the processing in the sputtering region 26 is stopped, Si is deposited on the substrate 15 facing the sputtering region 27, and the deposited Si is oxidized in the plasma region 28. A multilayer film of TiO ₂ and SiO ₂ is formed on the substrate 15 by repeating the above operation. In the embodiment, oxygen O ₂ is introduced into the plasma region 28 as a reactive gas, but ozone O ₃ or water H ₂ O or carbon dioxide CO ₂ may be introduced.

Here, there is a problem in that, by alternately operating the sputtering regions 26 and 27, the surface of the target reacts with a reactive gas or other molecules at a sputtering station that is stopped to form a compound thin film. For example, in the step of forming a thin film of SiO ₂ on the substrate 15, the oxygen or the generated oxygen plasma introduced into the plasma region 28 reaches the sputtering region 26 in the process of stopping the processing, and the surface of the Ti target is oxidized. Further, the resin of the substrate 15 absorbs moisture, which is discharged as a gas during the film formation, and oxidizes the surface of the target. The change in the surface state of such a target affects the film thickness control at the time of film formation.

Fig. 3 is a view showing an example of a change in discharge voltage with time when a film is formed by constant power discharge using a Ti target. As can be seen from the figure, the discharge state is unstable about 50 seconds after the start of discharge. This is caused by a change in the surface state of the target (oxidation).

Fig. 4 is a view showing an example of a change in discharge voltage with time when a TiO ₂ film is formed on a resin substrate containing a large amount of water. It is understood that the oxide film on the surface of the target is removed shortly after the start of film formation, and the discharge voltage is lowered. However, after 20 seconds, the target material is oxidized under the influence of water discharged from the resin substrate, and the discharge voltage is increased. Once the surface of the target is oxidized, the film formation speed becomes slow. In general, the control of the film thickness is carried out by controlling the film formation time. Therefore, when the film formation rate is changed due to the oxidation state, the film thickness can not be controlled with high precision only by the management of the film formation time.

As a method of controlling the film thickness with high precision, it is also considered to measure the film thickness at the time of film formation, and it is generally used in a vapor deposition apparatus. That is, in the case of the vapor deposition device, the film thickness sensor can be disposed at the center (rotation center) of the dome of the mounting substrate, and the film thickness can be measured during the film formation. On the other hand, in the reactive sputtering apparatus, it is necessary to move between the sputtering region and the plasma region, and it is difficult to perform measurement by the film thickness sensor. Therefore, the film thickness control in reactive sputtering is carried out through the management of the film formation time.

In order to compensate for the change in the film formation speed due to the surface state of the target, the following method is carried out here. In other words, in the target material used for reactive sputtering, the relationship between the discharge voltage and the film formation rate at the time of film formation by constant power discharge is obtained in advance (first step). Then, at least a part of the film formation by reactive sputtering using the target (not limited to the same target and including the target of the same specification) is formed according to the measured value of the discharge voltage. The film thickness of the film formed was determined by calculation (second step).

Fig. 5 is a flow chart for explaining a method (first step) for obtaining a relationship between a discharge voltage and a film formation speed. Here, the Ti target attached to the sputtering region 26 will be described as an example using oxygen O ₂ as a reactive gas.

This method utilizes a case where the discharge voltage and the film formation speed at the time of film formation fluctuate due to the oxidation state of the surface of the target, and the discharge voltage under constant power discharge is correlated with the film formation speed (interrelated). The situation. First, the control device 36 performs control for sputtering Ti on the substrate 15 in the sputtering region 26 while the discharge voltage is constant, and oxidizing Ti in the plasma region 28 (step S11). . This treatment is carried out for a longer period of time than the actual film formation conditions. The obtained film thickness was measured, and the film formation speed was obtained from the measured value and the film formation time (step S12). The above operation is repeated under different discharge voltage conditions (step S13). The relationship between the obtained discharge voltage and the film formation speed is recorded in the form of a table and stored in the control device 36 (step S14). The data that is recorded and saved is preferably a non-measured value, but is approximated by a polynomial to remove the influence of noise. An example of the relationship between the film formation speed and the discharge voltage is shown in Fig. 6.

The oxygen O ₂ as the reactive gas introduced into the reaction vessel 11 is used in the plasma region 28, but actually diffuses into the reaction vessel 11 to oxidize the surface of the Ti target in the sputtering region 26. By adjusting the amount of O ₂ introduced, the oxidation condition of the surface of the target in the sputtering region 26 changes. In this case, although the discharge voltage is unstable at the start of film formation, the film is formed for a long period of time, and the discharge voltage becomes a constant value corresponding to the amount of introduction of O ₂ , so that the influence of the rate fluctuation shortly after the film formation starts can be obtained. Control is within the error range. Further, by changing the amount of introduction of O ₂ , the discharge voltage can be set to another constant value.

In addition, when a substrate in which water is discharged as a substrate 15 is used as the substrate 15, in addition to introducing O ₂ into the reaction vessel, H ₂ O is introduced as a basis. The reason for introducing H ₂ O is to consider the effect of oxidation on the target in the case of oxygen and water. When the type of product (especially resin) changes, the amount of water discharged also changes greatly. Therefore, regarding the introduction amount of H ₂ O, the most appropriate fixed value is selected in consideration of the material according to the type of product. In a state where the selected fixed value of H ₂ O is introduced, the O ₂ introduction amount is changed and the discharge voltage is controlled to obtain data. For example, it is set as: Product A: H ₂ O: 10 [sccm], change O ₂ introduction amount control voltage, and obtain data product B: H ₂ O: 20 [sccm], the same product C: H ₂ O: 30 [sccm ], ibid.

By obtaining the above data in advance, it is possible to improve the film thickness control accuracy at the time of actual film formation. Further, since the amount of water discharged depends on the substrate temperature, the fixed value of the H ₂ O introduction amount can be adjusted according to the set temperature of the substrate heating mechanism. After selecting the product type and the temperature in the reaction tank, the most appropriate H ₂ O introduction amount can be selected and the data can be obtained. For example, when the substrate is actively heated by the substrate heating mechanism for the purpose of discharging water from the resin substrate, H ₂ O based on the set temperature of the substrate heating mechanism is introduced in the first step, thereby being highly accurate. The correlation data between the discharge voltage and the film formation rate in the H ₂ O atmosphere was obtained.

Fig. 7 is a flow chart for explaining a film forming process performed by the reactive sputtering device 10 shown in Fig. 1, showing the flow of control performed by the control device 36. This film formation process is a process performed after the table which has been prepared for the relationship between the film formation speed and the discharge voltage and which has been stored in the control device 36 in the form of a table.

The control device 36 first inputs a recipe (process step) (step S21), and sets each layer in accordance with the recipe (the number of layers of the recipe is n, and each layer is represented by an ith layer (1 ≤ i ≤ n). The final target film thickness di and the time required for film formation ti, and the film formation process is performed. First, let i = 1 (step S22), set the final target film thickness d _{i of} the i-th (i = 1) layer (step S23), and set the time t _i required for film formation in the timer (step S24). . Next, each part of the reactive sputtering apparatus 10 is controlled to start film formation (step S25). At this time, the second step described above is carried out.

For example, when the processing is being performed in the sputtering region 26, the control device 36 inputs the output voltage value of the power source 31 measured by the voltmeter 34 (step S26), and confirms whether or not the voltage value is stable at a predetermined value, that is, confirms the discharge. Whether the voltage is stable (step S27). When the voltage value is unstable (NO in step S27), referring to the table obtained in the first step, the film thickness estimated to be deposited is calculated based on the film formation speed corresponding to the voltage value (step S28). Further, the cumulative film thickness d is calculated based on the calculated film thickness (step S29). When the cumulative film thickness d does not reach the target value d(t) of the film thickness at the timing value (NO in step S30), the film formation is continued based on the insufficient film thickness, and the compensation is performed. The timer is corrected so that the difference between the film thickness and the film thickness to be formed is stable (step S31), and the film formation time is prolonged. Specifically, the cumulative film thickness d is compared with the target value d(t) of the film thickness at the timing value, and the timing time of the film formation portion of the film thickness is prolonged. The timer can also be temporarily stopped before the cumulative film thickness d reaches the target value of the film thickness at the timing value.

When the cumulative film thickness d calculated in step S29 reaches the target value d(t) of the film thickness at the timing value (YES in step S30), it is determined whether or not the cumulative film thickness d has reached the level set in step S23. The final target film thickness di of the i layer (step S32). When the cumulative film thickness d reaches di (YES in step S32), the film formation of the i-th layer is ended (step S33), and the process proceeds to step S35. When the cumulative film thickness d has not reached di (NO in step S32), the process returns to step S26, and the film formation process is continued as it is.

When the voltage value is stabilized at the predetermined value in step S26, that is, when the discharge voltage is stable, the film formation is continued until the timer expires (step S34). The processes of steps S23 to S34 are repeated until the film formation of all the layers designated by the recipe input in step S21 is completed, that is, until the process of incrementing i and i=n is completed (step S35, S36).

In the above flow, it is set to correct the timing time only when the cumulative film thickness d is smaller than the target value d(t), but it can also be set to be shortened in the case where the cumulative film thickness d is larger than the target value d(t). Timing time to adjust the excess film thickness to this process. In other words, the flow may be set such that when the step S30 is YES and the step S32 is NO, the timer is corrected for the time corresponding to d-d(t).

In the flowchart of Fig. 7, the second process is performed on all the layers of the lamination, that is, the processes of steps S26 to S31 are performed. However, in the case of using a target which does not cause a change in film formation rate due to oxidation, it is not necessary to obtain a relationship between the discharge voltage and the film formation speed in advance (first step), and it is not necessary to perform calculation based on the relationship. The film thickness of the film formation was determined (second step). In this case, step S34 can be directly executed from step S25. In addition, in the flowchart of FIG. 7, when the discharge voltage is stabilized in step S27, the film formation transition is performed to the transmission time control (step S34), but step S34 may be omitted, and the measurement and accumulation of the discharge voltage may be repeated. The calculation of the film thickness d reaches the final target film thickness di set in step S23 (the repeated processing of steps S26 to S33).

Fig. 8 is a graph showing an example of measurement of antireflection characteristics when a multilayer antireflection film of TiO ₂ and SiO ₂ is formed on a resin lens. (A) is a measurement example when time-correction is not performed in forming a film of TiO2 film, and (B) is a measurement example at the time of time-correction. Both are the result of 10 batches of continuous processing. The horizontal axis of the coordinate graph is the wavelength, and the vertical axis is the reflectance [%]. In (A) of FIG. 8 , spectral characteristics are caused by oxidation of the target material, increase in substrate temperature, and discharge of gas from the substrate and other portions, and gas introduction from the storage chamber (omitted in FIGS. 1 and 2). Poor reproducibility. On the other hand, in the case of performing time correction at the time of film formation, as shown in FIG. 8(B), it is understood that reproducibility is excellent even in continuous batch processing, and desired optical characteristics can be obtained. Compared with the film formation of SiO ₂ using the Si target, the film formation of TiO ₂ using the Ti target is significantly larger due to the variation in the film formation rate due to the oxidation of the surface of the target, and therefore, the TiO ₂ is transmitted. The present invention is carried out at the time of film formation, and in particular, a large effect can be obtained.

Fig. 9 is a flow chart showing a modification of the film forming process shown in Fig. 7. In this modification, the oxygen introduction amount is set to be less than a predetermined amount required for film formation before the film formation starts (step S25) (step S41). Then, when the power supply output voltage value becomes a predetermined value, the oxygen gas introduction amount is set to a predetermined amount (step S42). Here, for ease of explanation, when the oxygen introduction amount is set to a predetermined amount, the discharge voltage is stabilized. Actually, since a sufficient amount of oxygen is required in a state where the discharge voltage is stable, it is preferable to introduce the amount of oxygen introduction into a predetermined amount at a slightly earlier stage. For example, it is preferable to make the oxygen introduction amount a predetermined amount after a predetermined time which is set in advance independently of the loop of the input voltage value. By reducing the amount of introduction of oxygen in the initial stage of film formation, it is possible to quickly discharge the discharge voltage without introducing more oxygen than necessary into the reaction tank before the discharge voltage is stabilized. In addition, there is a possibility that the film obtained in a state where the discharge voltage is unstable is different from the film obtained in a state where the discharge voltage is stable, but the uniformity of the obtained film can be improved by rapidly stabilizing the discharge voltage. .

Fig. 10 is a flow chart showing a further modification of the film forming process shown in Fig. 9. In this modification, when the power supply output voltage value becomes a predetermined value (NO in step S27), that is, when the discharge voltage at the initial stage of film formation is unstable, the oxygen introduction amount is performed based on the power supply output voltage value. Feedback control (step S51). The moisture discharged from the resin of the substrate 15 changes under the conditions in the reaction tank, and gradually increases with the passage of time due to the heat after the start of film formation. This effect can also be removed by performing feedback control.

In the film formation process shown in Fig. 9, in the case of using a film-forming layer, in the case of using a target which is less likely to change in film formation rate due to oxidation, steps S41, S42 are not necessarily required. Further, also in the film formation process shown in Fig. 10, step S42 and step S51 are not necessarily required depending on the layer to be formed.

Fig. 11 is a flow chart showing a modification of the film forming process shown in Fig. 7. This modification does not perform correction of the timer every time the power supply output voltage is input, but performs correction of the timer after the voltage value is stabilized at a predetermined value, which is different from the film forming process shown in FIG. In other words, until the discharge voltage is stabilized (step S65, corresponding to step S27 of FIG. 7 and until YES), the input voltage value of the power source 31 is repeatedly input (step S61, corresponding to FIG. 7). Step S26), calculation of the deposited film thickness of the table obtained in the first step (step S62, corresponding to step S28 of FIG. 7), and calculation of the cumulative film thickness d (step S63, corresponding to step S29 of FIG. 7) . In this iterative process, when the cumulative film thickness d reaches the final target film thickness di (step S64, corresponding to step S32 of FIG. 7 and YES), the film formation of the i-th layer is completed (step S68, equivalent) Step S33) of Fig. 7 . When the discharge voltage is stabilized (YES in step S65), the cumulative film thickness d is compared with the target value of the film thickness at the timing value, and the timer is corrected to compensate for the insufficient film thickness (step S66, which corresponds to FIG. 7). Step S31), the time is extended, and film formation is continued until the timer expires (step S67). In step S66, when the cumulative film thickness d is larger than the target value of the film thickness at the timing value, the timing time is shortened to adjust the excess film thickness. The above process is repeated until the film formation of all the layers is completed (steps S35, S36).

Fig. 12 is a block diagram showing an example of a control device 36 shown in Fig. 1, showing an example of a configuration using a computer system.

That is, the control device 36 includes an arithmetic processing unit 41, a read only memory (ROM) 42, a random access memory (RAM) 43, a data storage unit 44, an input interface 45, and an output interface connected to the arithmetic processing unit 41. 46. Here, it is described that each part is directly connected to the arithmetic processing unit 41, but in general, each of the above units is a bus bar connection. The read-only memory 42 stores data such as a program for operating the control device 36 and fixed parameters for executing the program. The random access memory 43 stores temporary data such as data in processing. The data storage unit 44 stores a recipe for the film formation process, process data, data indicating the relationship between the discharge voltage and the film formation speed, and the like. The input interface 45 inputs the output values of the voltmeters 34, 35 and the outputs of the various sensors. The arithmetic processing unit 41 supplies the contents of the read-only memory 42, the random access memory 43, and the data storage unit 44 to the respective parts of the reactive sputtering device 10, such as the vacuum system device, and the power supply in accordance with the input from the input interface 45. The gas introduction device outputs an output control signal.

The control device 36 is a device that controls the operation of the reactive sputtering device 10, and as a part thereof, realizes a film thickness control device that controls the thickness of the film formed by the reaction sputtering device 10. In other words, the data storage unit 44 operates as a storage unit that stores between the discharge voltage and the film formation speed at the time of film formation by the transmission of the constant power discharge obtained in advance in the target used in the reactive sputtering apparatus 10. The input interface 45 operates as a unit for inputting a measured value of the discharge voltage at the time of film formation, and the arithmetic processing unit 41 operates as a calculation unit for performing reactive sputtering using a target. At least a part of the film, the data storage unit 44 is accessed based on the measured value of the discharge voltage input from the input interface 45, and the film thickness of the film formed is obtained by calculation based on the corresponding film formation rate.

In the above description, the case where Ti is used as a target has been described as an example. However, the present invention can be similarly applied when other materials are used as a target. In addition, when Si is used as the target, fluctuations in the discharge voltage at the start of film formation are small, and when the film thickness accuracy is further pursued, or the film formation time is short, the fluctuation of the discharge voltage at the start of film formation cannot be ignored. The present invention can be similarly implemented in the case of the influence or the like. Further, in the case of a film other than the film-forming oxide, that is, when a gas other than oxygen is introduced into the plasma region 28, the present invention can be similarly carried out. For example, when Ti is used as the target and TiN film is formed by using nitrogen as the reactive gas, by monitoring the discharge voltage, it is possible to detect the fluctuation of the deposition rate due to the nitride formed on the surface of the target, thereby achieving high precision. Control the film thickness. Since the sputtering rate of the nitride on the surface of the target is smaller than that of the oxide, the variation in the deposition rate due to the influence of the nitride is large, and the effect of control by the present invention is large. It is not limited to the TiN film, and may be appropriately selected in combination with a target such as a SiNx film, a TiOxNy film, a TaOx film, a TiSiOxNy film, an AlOx film, or a ZrOx film, and a reactive gas. The present invention is effective in any reactive sputtering apparatus for forming a compound film.

10‧‧‧Response sputtering device

34, 35‧‧ voltmeter

11‧‧‧Reaction tank

36‧‧‧Control device

14‧‧‧Roller

41‧‧‧Operation Processing Department

15‧‧‧Substrate

42‧‧‧Read-only memory

16‧‧‧Rotary axis

43‧‧‧ Random access memory

26, 27‧‧‧ Sputtering area

44‧‧‧Data Storage Department

28‧‧‧ Plasma area

45‧‧‧Input interface

31, 32, 33‧‧‧ power supplies

46‧‧‧Output interface

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an example of a device for simplifying a film thickness control method for carrying out reactive sputtering according to the present invention. Figure 2 is a view of a portion of the apparatus shown in Figure 1 as viewed from above. Fig. 3 is a view showing an example of a change in discharge voltage with time when a film is formed by constant power discharge using a Ti target. Fig. 4 is a view showing an example of a change in discharge voltage with time when a TiO ₂ film is formed on a resin substrate containing a large amount of water. Fig. 5 is a flow chart for explaining a method (first step) for obtaining a relationship between a discharge voltage and a film formation speed. Fig. 6 is a view showing an example of the relationship between the film formation speed and the discharge voltage. Fig. 7 is a flow chart for explaining a film forming process carried out by the reactive sputtering apparatus shown in Fig. 1. Fig. 8 is a schematic view showing an example of measurement of antireflection characteristics when a multilayer antireflection film of TiO ₂ and SiO ₂ is formed on a resin lens, wherein (A) is a measurement when time is not corrected when a TiO ₂ film is formed. In the example, (B) is an example of measurement when time correction is performed. Fig. 9 is a flow chart showing a modification of the film forming process shown in Fig. 7. Fig. 10 is a flow chart showing a further modification of the film forming process shown in Fig. 9. Fig. 11 is a flow chart showing a modification of the film forming process shown in Fig. 7. Fig. 12 is a block diagram showing an example of a control device shown in Fig. 1.

Claims (11)

A film thickness control method for reactive sputtering, comprising: a first step and a second step, wherein in the first step, a film that is used for reactive sputtering is previously formed by a constant power discharge. The relationship between the discharge voltage and the film formation rate in the second step; in the second step, at least a part of the film formation by reactive sputtering using the target is performed according to the measured value of the discharge voltage The film formation rate was calculated by calculation to determine the film thickness of the film formed. The film thickness control method according to claim 1, wherein in the first step, a discharge voltage and a film formation speed at the time of film formation due to a surface state of the target are varied and constant In the case where the discharge voltage under the power discharge is correlated with the film formation rate, the amount of introduction of the reactive gas introduced into the reaction vessel subjected to reactive sputtering is changed, and the discharge voltage becomes a constant value. The film condition was formed for a longer period of time, and the film thickness was measured, and the value of the discharge voltage was changed to repeat the measurement. The film thickness control method according to the second aspect of the invention, wherein, in the first step, water H ₂ O is introduced in an amount corresponding to a material to be film-formed, in addition to the introduction of the reactive gas. The film thickness control method according to claim 1 or 3, wherein the film formation time is extended or shortened to compensate for a film formed in at least a part of the film formation obtained in the second step. The difference between the thickness and the film thickness to be formed in at least a part of the film formation. The film thickness control method according to the first or fourth aspect of the invention, wherein, in the second step, the film formed film is obtained by calculation during a period from the start of discharge of the reactive sputtering to the stabilization of the discharge voltage. When the film formation is continued, the film formation time is extended or shortened to compensate for the difference between the film thickness obtained in the second step and the film thickness to be formed in the period until the stabilization. The film thickness control method according to any one of the first to fifth aspects of the present invention, wherein the amount of introduction of the reactive gas is reduced to less than the discharge voltage after the discharge voltage at the initial stage of film formation is stabilized. The amount that should be imported. The film thickness control method according to any one of the first to sixth aspects of the present invention, wherein the reactive gas introduction amount is feedback-controlled before the discharge voltage at the time of film formation becomes a predetermined value. The film thickness control method according to any one of claims 1 to 7, wherein the first step is performed on a target used in a sputtering region of the reactive sputtering device, and the target is used. The second step is performed when the material is formed into a film, wherein the reactive sputtering apparatus has a substrate having a film formation target mounted on a rotating drum and sequentially passing through the sputtering region and the plasma region. The film thickness control method according to claim 8, wherein the reactive sputtering device has a plurality of sputtering regions laminated with different materials, and used for each of the plurality of sputtering regions. The first step is performed by at least one of the targets of the different materials, and the second step is performed when the film is formed using the target on which the first step has been performed. The film thickness control method according to any one of claims 1 to 9, wherein the substrate to be coated is made of a resin. A film thickness control device for reactive sputtering, which is provided in a control device for controlling the operation of the reactive sputtering device, and controls a thickness of a film formed by the reactive sputtering device, the reactive sputtering The film thickness control device includes a storage unit, an input unit, and a calculation unit. The storage unit stores a film that is used in the reactive sputtering device and stores a film that has been previously obtained through a constant power discharge. a relationship between a discharge voltage and a film formation rate; the input unit inputs a measured value of a discharge voltage at the time of film formation; and the calculation unit performs at least a film formation by reactive sputtering using the target material In a part of the period, the storage unit is accessed based on the measured value of the discharge voltage input from the input unit, and the film thickness of the formed film is obtained by calculation based on the corresponding film formation rate.