JP2019023335A - Control method and device of film thickness of reactive sputtering - Google Patents

Abstract

To provide a control method and a device of a film thickness of reactive sputtering which can accurately control film formation without influence of an initial condition of a target.SOLUTION: A method includes a first process in which, regarding a target used in reactive sputtering, a relation between a discharge voltage and a film formation speed in forming a film with a constant electric power discharge is preliminarily acquired, and a second process in which, regarding at least a part of a period of forming a film by means of reactive sputtering using the target, a film thickness of a formed film is calculated from the film formation speed corresponding to the discharge voltage measured value.SELECTED DRAWING: Figure 7

Description

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

  A reactive sputtering apparatus is widely used as a method for forming a compound thin film in a manufacturing process of an optical component, an electronic component, a semiconductor device, or the like. The reactive sputtering apparatus includes means for supplying a reactive gas into a reaction vessel in which a conductive target is disposed, and deposits a compound generated by the reaction between the sputtered particles of the conductive target and the reactive gas on the substrate. Configured.

  In the mass production process, a carousel type sputtering apparatus as disclosed in Patent Document 1 is often employed from the viewpoint of improving productivity. In the carousel type sputtering apparatus, a plurality of substrates to be deposited are mounted on a rotating drum having a sputtering target arranged around it, and sputtering deposition is performed while rotating the drum. Therefore, a plurality of substrates can be processed at a time. it can. In many sputtering apparatuses, the film thickness is controlled only by managing the film formation time calculated based on the film formation speed measured in advance.

Patent No. 3064301

  In a reactive sputtering apparatus, when a compound is formed on the surface of a conductive target by a reactive gas, the film formation rate decreases and the film thickness may not be accurately controlled. For example, when forming an oxide film using a carousel-type sputtering apparatus (see Patent Document 1) that can stack a plurality of types of materials using a plurality of types of metal targets, oxygen gas is introduced into the treatment tank. Since plasma is generated, the surface of the target of another material is oxidized while a certain material is being formed. Immediately after the start of film formation, the sputtering rate is often lower when the target surface is oxidized and the oxidized state is lower than the state of a single metal. It becomes difficult to control the film thickness. In the case where the substrate to be deposited is a resin, the resin absorbs moisture, and the moisture is released from the substrate as a gas during the deposition and dissociates in the plasma, which also causes oxidation of the target surface. In the past, film thickness accuracy was not so required, but high film thickness accuracy was required for anti-reflection coatings for optical lenses, for example, and slight deviations would affect the characteristics of the final product. ing.

  In order to increase the film thickness accuracy, a shutter may be installed between the target and the substrate so that the film cannot be formed until the discharge state is stabilized. However, the target and the substrate are close to each other, and it is often difficult to install a shutter and a mechanism for moving the shutter due to problems such as space. Further, since the shutter itself affects the discharge state, it is better if it is not necessary. Furthermore, some reactive sputtering apparatuses have a structure in which a shutter mechanism cannot be installed, and such a structure cannot be used.

  An object of the present invention is to solve such a problem and to provide a reactive sputtering film thickness control method and apparatus capable of accurately controlling film formation without being affected by the initial state of a target.

  The first aspect of the present invention is a method for controlling the film thickness of reactive sputtering, and the relationship between the discharge voltage and the film formation rate during film formation by constant power discharge is acquired in advance for the target used for reactive sputtering. A first step and a second step of calculating the formed film thickness from the film forming speed corresponding to the measured value of the discharge voltage for at least a part of the film during the reactive sputtering using the target. These steps are included.

In the first step, reactive sputtering is performed by utilizing the fact that the discharge voltage and deposition rate during film formation vary depending on the surface state of the target, and the discharge voltage and deposition rate in constant power discharge are correlated. The amount of reactive gas introduced into the reaction vessel was changed, and the film thickness was measured over a longer period of time than the actual film formation conditions with the discharge voltage at a constant value. It is desirable to repeat while changing the value of. In the first step, in addition to the reactive gas, an amount of water H ₂ O corresponding to the material to be deposited can be introduced.

  In the second step, the film thickness obtained in the second step and formed in at least a part of the film formation period and the film thickness planned in the at least part of the film formation period It is desirable to extend or shorten the film formation time so as to compensate for the difference. During the period from the start of reactive sputtering discharge until the discharge voltage stabilizes, the film thickness was determined by calculation, and the film thickness was planned to continue with the calculated film thickness while continuing the film formation. The film formation time can be extended or shortened to compensate for the difference from the film thickness.

  The amount of reactive gas introduced can be reduced from the amount to be introduced after the discharge voltage is stabilized until the discharge voltage at the beginning of film formation is stabilized. Also, the reactive gas introduction amount can be feedback controlled until the discharge voltage at the time of film formation reaches a predetermined value.

  The first step is performed on a target used in a sputtering region of a reactive sputtering apparatus having a structure in which a substrate to be deposited is mounted on a rotating drum and sequentially passes through the sputtering region and the plasma region. It is desirable to execute the second step at the time of film formation using. In this case, the reactive sputtering apparatus includes a plurality of sputtering regions for stacking different materials, and the first is used for at least one target among the different materials used in the plurality of sputtering regions. The second step can be executed at the time of film formation using the target that has executed the first step and performed the first step.

  As the substrate for film formation, a resin substrate can be used.

  A second aspect of the present invention is a film thickness control apparatus that is provided in a control apparatus that controls the operation of a reactive sputtering apparatus and controls the film thickness of a film formed by the reactive sputtering apparatus. With respect to the target used in the apparatus, a means for storing the relationship between the discharge voltage during film formation by constant power discharge obtained in advance and the film formation speed, a means for capturing a measured value of the discharge voltage during film formation, and a target For at least a part of the period during film formation by reactive sputtering used, access is made to the means for storing based on the measured value of the discharge voltage taken in by the means for taking in, and the film thickness formed from the corresponding film formation speed And calculating means for calculating by calculation.

  According to the present invention, the film formation can be accurately controlled without being affected by the initial state of the target during the film formation by the reactive sputtering apparatus.

It is a perspective view which simplifies and shows an example of the apparatus which implements the film thickness control method of the reactive sputtering of this invention. It is the figure which looked at a part of apparatus shown in FIG. 1 from the top. It is a figure which shows an example of the time change of the discharge voltage at the time of the film-forming by the constant power discharge using Ti target. When forming a TiO ₂ on a resin substrate containing a large amount of moisture is a diagram showing an example of a time variation of the discharge voltage. It is a flowchart explaining the method (1st process) which acquires the relationship between a discharge voltage and the film-forming speed | rate. It is a figure which shows an example of the relationship between the film-forming speed | rate and discharge voltage. It is a flowchart explaining the film-forming process by the reactive sputtering apparatus shown in FIG. Is a diagram showing an example of measurement of the anti-reflection characteristics when forming the multilayer antireflection film of TiO ₂ and SiO ₂ in a resin lens, (A), when not subjected to time correction at the time of forming the TiO ₂ film (B) is a measurement example when time correction is performed. It is a flowchart which shows the modification of the film-forming process shown in FIG. It is a flowchart which shows the further modification of the film-forming process shown in FIG. It is a flowchart which shows the modification of the film-forming process shown in FIG. It is a block block diagram which shows an example of the control apparatus shown in FIG.

  FIG. 1 is a perspective view showing a simplified example of an apparatus for carrying out the reactive sputtering film thickness control method of the present invention, and FIG. 2 is a view of the apparatus as viewed from above. Here, the case where this invention is implemented with the carousel type reactive sputtering apparatus shown by patent document 1 is shown as an example.

  The reactive sputtering apparatus (sputtering system) 10 has a cage-type drum 14 in a reaction tank (housing) 11, and a substrate 15 to be deposited is attached to the drum 14. A substrate heating mechanism (not shown) for heating the substrate 15 may be provided. The drum 14 is rotatably installed around the shaft 16. In the reaction tank 11, sputtering regions (sputtering stations) 26 and 27 and a plasma region (reaction station) 28 are arranged along the outer peripheral surface of the drum 14. Sputtering electrodes 26 and 27 are each provided with a sputtering electrode, and a reactive gas is introduced into the plasma region 28 to generate a plasma different from the sputtering plasma to react with the film on the substrate 15. Is provided. In the embodiment, the coil antenna is connected to a high frequency power source to generate inductively coupled plasma, but other means such as microwave plasma or DC discharge plasma may be used. A gas introduction mechanism for generating plasma is not shown.

  Also shown in FIG. 1 are power supplies 31, 32, 33 that supply power for discharge to sputtering regions 26, 27 and plasma region 28, and voltmeters 34, 35 that measure the output voltage values of power supplies 31, 32, respectively. And a control device 36 for controlling them.

Here, a case where the substrate 15 is a resin lens and an antireflection film made of a multilayer film of titanium dioxide TiO ₂ and silicon dioxide SiO ₂ is formed on the resin lens will be described as an example. In this case, sputtering is performed in the sputtering regions 26 and 27 using titanium Ti and silicon Si as targets, respectively, and in the plasma region 28, oxidation by oxygen plasma is performed. That is, as the drum 14 rotates, 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, nothing is done in the sputtering region 27. Next, the process 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. By repeating this, a multilayer film of TiO ₂ and SiO ₂ is formed on the substrate 15. In the embodiment, oxygen O ₂ is introduced into the plasma region 28 as a reactive gas, but ozone O ₃ , water H ₂ O, and carbon dioxide CO ₂ may be introduced.

The problem here is that since the sputtering regions 26 and 27 are operated alternately, the surface of the target reacts with the reactive gas and other molecules to form a compound film at the stationary station. It is. For example, in the process of forming the SiO ₂ film on the substrate 15, oxygen introduced in the plasma region 28 or generated oxygen plasma reaches the sputtering region 26 where the process is stopped, and oxidizes the surface of the Ti target. Further, the resin of the substrate 15 absorbs moisture, and the moisture is released as a gas during film formation, which oxidizes the target surface. Such a change in the surface state of the target affects the film thickness control during film formation.

  FIG. 3 is a diagram illustrating an example of a temporal change in discharge voltage during film formation by constant power discharge using a Ti target. This figure shows that the discharge state is not stable for about 50 seconds after the start of discharge. This is because the surface state of the target is changed (oxidized).

FIG. 4 is a diagram showing an example of a change over time in the discharge voltage when TiO ₂ is formed on a resin substrate containing a large amount of moisture. Immediately after the start of film formation, the oxide film on the target surface is removed and the discharge voltage decreases, but after 20 seconds, the target is oxidized and the discharge voltage increases due to the influence of water released from the resin substrate. I understand. If the target surface is oxidized, the film formation rate becomes slow. Normally, the film thickness is controlled by managing the film formation time. Therefore, if the film formation rate changes depending on the oxidation state, the film thickness cannot be accurately controlled only by managing the film formation time.

  As a method for accurately controlling the film thickness, it is conceivable to measure the film thickness at the time of film formation, which is commonly used in a vapor deposition apparatus. That is, in the case of a vapor deposition apparatus, a film thickness sensor can be arrange | positioned in the center (rotation center) of the dome with which a board | substrate is mounted | worn, and a film thickness can be measured during film-forming. On the other hand, in the reactive sputtering apparatus, it is necessary to move between the sputtering region and the plasma region, and measurement with a film thickness sensor is difficult. For this reason, the film thickness control in the reactive sputtering is performed by managing the film formation time.

  In order to compensate for the change in the deposition rate due to the surface state of the target, the following method is performed here. That is, regarding the target used for reactive sputtering, the relationship between the discharge voltage during film formation by constant power discharge and the film formation speed is acquired in advance (first step). Then, from at least a part of the period during film formation by reactive sputtering using the target (not limited to the same target but including the target of the same specification), from the film formation rate corresponding to the measured value of the discharge voltage. Then, the formed film thickness is obtained by calculation (second step).

FIG. 5 is a flowchart for explaining a method (first step) for acquiring the relationship between the discharge voltage and the deposition rate. Here, a Ti target mounted on the sputtering region 26 is taken as an example, and a description will be given assuming that O ₂ is used as a reactive gas.

  This method utilizes the fact that the discharge voltage and film formation rate during film formation vary depending on the oxidation state of the surface of the target, and the discharge voltage and film formation rate in constant power discharge are correlated. First, the controller 36 sputter deposits Ti on the substrate 15 in a state where the discharge voltage becomes a constant value in the sputtering region 26, and oxidizes Ti in the plasma region 28 (step S11). This is performed over a longer time than the actual film formation conditions. The obtained film thickness is measured, and the film forming speed is obtained from the measured value and the film forming time (step S12). This is repeated under conditions that result in different discharge voltages (S13). The relationship between the obtained discharge voltage and the film formation rate is recorded and stored as a table in the control device 36 (S14). The data to be recorded / stored is preferably approximated by a polynomial in order to remove the influence of noise, not actual measurement values. An example of the relationship between the deposition rate and the discharge voltage is shown in FIG.

O ₂ as a reactive gas introduced into the reaction vessel 11 is for use in the plasma region 28, but actually diffuses into the reaction vessel 11, and the Ti target surface in the sputtering region 26 is dispersed. It will oxidize. By adjusting the amount of O ₂ introduced, the oxidation condition of the target surface in the sputtering region 26 changes. At this time, the discharge voltage is not stable at the start of film formation, but by performing film formation for a long time, the discharge voltage becomes a constant value corresponding to the amount of O ₂ introduced, and the influence of rate fluctuations immediately after the start of film formation is affected. Can be within the error range. Further, the discharge voltage can be set to another constant value by changing the O ₂ introduction amount.

Further, when it is assumed that the substrate 15 is made of a material from which water such as resin is released, H ₂ O is introduced into the reaction vessel as a base in addition to O ₂ . The reason for introducing H ₂ O is that oxygen and water are considered to have different effects on target oxidation. If the type of product (especially resin) changes, the amount of water released will also change significantly. Therefore, the optimum amount of H ₂ O to be introduced is selected for each product type in consideration of the material. In a state where the selected fixed value of H ₂ O is introduced, the discharge voltage is controlled by changing the O ₂ introduction amount to acquire data. For example,
Product A: H ₂ O: 10 [sccm], voltage is controlled by changing the amount of O ₂ introduced, and data is acquired Product B: H ₂ O: 20 [sccm] Same as above Product C: H ₂ O: 30 [sccm], Same as above. By acquiring such data in advance, the accuracy of film thickness control during actual film formation can be improved. Further, since the amount of water released depends on the substrate temperature, the fixed value of the H ₂ O introduction amount may be adjusted based on the set temperature of the substrate heating mechanism. Data may be acquired by selecting the optimum H ₂ O introduction amount in consideration of the product type and the temperature in the reaction vessel. For example, when the substrate is actively heated by the substrate heating mechanism for the purpose of releasing water from the resin substrate, H ₂ O atmosphere is introduced by introducing H ₂ O based on the set temperature of the substrate heating mechanism in the first step. The correlation data between the discharge voltage and the film formation rate can be obtained with high accuracy.

  FIG. 7 is a flowchart for explaining a film forming process by the reactive sputtering apparatus 10 shown in FIG. 1, and shows a control flow by the control apparatus 36. This film forming process is performed after a table of the relationship between the film forming speed and the discharge voltage has already been created and stored as a table in the control device 36.

The control device 36 first takes in the recipe (processing procedure) (step S21), and follows each recipe (the number of film layers in the recipe is n, and each layer is indicated by the i-th layer (1 ≦ i ≦ n)). The final target film thickness d _i and the time t _i required for film formation are set, and the film formation process is executed. First, i = 1 is set (step S22), the final target film thickness d _i of the i-th (i = 1) layer is set (step S23), and the time t _i required for film formation is set 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 is performed.

  For example, when processing is performed in the sputtering region 26, the control device 36 takes in the output voltage value of the power source 31 measured by the voltmeter 34 (step S26), and whether the voltage value is stable at a predetermined value, That is, it is confirmed whether or not the discharge voltage is stable (step S27). If the voltage value is not stable (No in step S27), the film thickness estimated to have been deposited is determined by referring to the table obtained in the first step and from the film formation speed corresponding to the voltage value. Is calculated (step S28). Further, the accumulated film thickness d is calculated from the calculated film thickness (step S29). When the accumulated film thickness d does not reach the target value d (t) in the timer value (No in step S30), the film thickness obtained is determined while continuing the film formation according to the insufficient film thickness. The timer is corrected so as to compensate for the difference from the film thickness planned for the period until stabilization (step S31), and the film formation time is extended. Specifically, the cumulative film thickness d is compared with the target value d (t) of the film thickness at the timer value, and the timer time for the insufficient film thickness is extended. The timer timing may be temporarily stopped until the accumulated film thickness d reaches the target value in the timer value.

If the cumulative film thickness d calculated in step S29 has reached the target film thickness value d (t) in the timer value (Yes in step S30), the cumulative film thickness d is set in step S23. It is determined whether or not the final target film thickness value d _i of the i-th layer has been reached (step S32). The cumulative thickness d has reached d _i (in step S32 Yes), terminates the formation of the i-th layer (step S33), the process proceeds to step S35. The cumulative thickness d does not reach the d _i (No in step S32), the process returns to step S26, and continues the intact film forming process.

  If the voltage value is stable at a predetermined value in step S26, that is, if the discharge voltage is stable, the film formation is continued until the end of the timer timing (step S34). The processes from step S23 to step S34 are repeated until the film formation of all the layers specified by the recipe imported in step S21 is completed, that is, until the process of i = n is completed while i is incremented (step S35). , S36).

  In the above flow, the timer time is corrected only when the accumulated film thickness d is smaller than the target value d (t). However, when the accumulated film thickness d is larger than the target value d (t), the excess film thickness is increased. A flow that shortens the timer time so as to adjust can also be used. That is, when the result in step S30 is Yes and step S32 is No, the timer may be corrected for a time corresponding to dd (t).

In the flowchart of FIG. 7, the second process, that is, the processing from step S <b> 26 to step S <b> 31 is performed on all the layers to be stacked. However, when using a target that does not significantly change the film formation rate due to oxidation, the relationship between the discharge voltage and the film formation speed must be acquired in advance (first step). There is no need to obtain the film thickness by calculation (second step). In that case, step S34 can be directly executed from step S25. Further, in the flowchart of FIG. 7, when the discharge voltage is stabilized in step S27, the process shifts to film formation by time control (step S34), but step S34 is omitted and the final target film thickness value d set in step S23. The measurement of the discharge voltage and the calculation of the accumulated film thickness d may be repeated until _i is reached (repetition processing from step S26 to step S33).

FIG. 8 shows 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 when the TiO ₂ film is formed, and (B) is a measurement example when time correction is performed. All are the results when 10 batches are processed continuously. The horizontal axis of the graph is wavelength, and the vertical axis is reflectance [%]. In FIG. 8A, the reproducibility of the spectral characteristics is poor due to factors such as target oxidation, gas release from the substrate and others due to substrate temperature rise, and gas carry-in from the charging chamber (not shown in FIGS. On the other hand, when time correction at the time of film formation is performed, as shown in FIG. 8B, it can be seen that desired optical characteristics can be obtained with good reproducibility even in a continuous batch. Deposition of TiO ₂ using a Ti target, since the width of the film formation rate fluctuations by comparing the target surface oxidation to deposit the SiO ₂ using a Si target is remarkably large, the present invention is carried out during the formation of TiO ₂ By doing so, a particularly great effect can be obtained.

  FIG. 9 is a flowchart showing a modification of the film forming process shown in FIG. In this modification, prior to the start of film formation (step S25), the oxygen introduction amount is set to be smaller than a predetermined amount required for film formation (step S41). When the power supply output voltage value reaches a predetermined value, the oxygen introduction amount is set to a predetermined amount (step S42). Here, in order to simplify the description, the time point at which the oxygen introduction amount is set to a predetermined value is assumed to be when the discharge voltage is stabilized. Actually, since a sufficient amount of oxygen is already required when the discharge voltage is stable, it is desirable to set the oxygen introduction amount to a predetermined amount just before that. For example, it is desirable to set the oxygen introduction amount to a predetermined amount after a predetermined time elapses independently of the voltage value acquisition loop. By reducing the amount of oxygen introduced at the initial stage of film formation, oxygen gas more than necessary is not introduced into the reaction vessel until the discharge voltage is stabilized, and the discharge voltage can be stabilized quickly. In addition, there is a possibility that there is a difference between a film obtained in a state where the discharge voltage is not stable and a film obtained in a state where the discharge voltage is stable, but the uniformity of the film obtained by quickly stabilizing the discharge voltage Can be increased.

  FIG. 10 is a flowchart showing a further modification of the film forming process shown in FIG. In this modification, the oxygen introduction amount is fed back by the power supply output voltage value until the power supply output voltage value reaches a predetermined value (when No in step S27), that is, when the discharge voltage at the beginning of film formation is not stable. Control (step S51). The moisture released from the resin of the substrate 15 varies depending on the conditions in the reaction tank, and gradually increases with time due to heat after the start of film formation. This influence can also be eliminated by feedback control.

  In the film formation process shown in FIG. 9, when using a target that does not significantly change the film formation rate due to oxidation depending on the layer to be formed, steps S41 and S42 are not necessarily required. Similarly, in the film forming 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 flowchart showing a modification of the film forming process shown in FIG. This modification is different from the film forming process shown in FIG. 7 in that the correction of the timer is not performed every time the power supply output voltage is taken in but after the voltage value is stabilized at a predetermined value. That is, until the discharge voltage is stabilized (step S65, corresponding to step S27 in FIG. 7 until Yes), the output voltage value of the power supply 31 is captured (step S61, corresponding to step S26 in FIG. 7), the first The calculation of the deposited film thickness (step S62, corresponding to step S28 in FIG. 7) and the calculation of the accumulated film thickness d (step S63, corresponding to step S29 in FIG. 7) are repeated based on the table obtained in the step. In this repetition, when the accumulated film thickness d reaches the final target film thickness d _i (Yes in step S64, corresponding to step S32 in FIG. 7), the film formation of the i-th layer is finished (step S68, Equivalent to step S33 in FIG. 7). When the discharge voltage is stabilized (Yes in step S65), the accumulated film thickness d is compared with the target film thickness value in the timer value, and the timer is corrected to compensate for the insufficient film thickness (step S66, FIG. 7). Step S31), the time is extended, and the film formation is continued until the timer timing ends (step S67). In step S66, when the accumulated film thickness d is larger than the target value of the film thickness in the timer value, the timer time is shortened so as to adjust the excess film thickness. The above processing is repeated until all layers are formed (steps S35 and S36).

  FIG. 12 is a block diagram showing an example of the control device 36 shown in FIG. 1, and shows an example configured 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 46 connected to the arithmetic processing unit 41. With. Here, it is described that each unit is directly connected to the arithmetic processing unit 41, but in general, these units are bus-connected. The read-only memory 42 stores a program for operating the arithmetic processing unit 36 and data such as a fixed parameter for executing the program. The random access memory 43 stores temporary data such as data being processed. The data storage unit 44 stores film forming process recipes, process data, data indicating the relationship between the discharge voltage and the film forming speed, and the like. The input interface 45 receives output values of the voltmeters 34 and 35 and outputs of various sensors. The arithmetic processing unit 41 is based on the recorded contents of the read-only memory 42, the random access memory 43, and the data storage unit 44. A control signal is output to each part of the apparatus 10.

  The control device 36 controls the operation of the reactive sputtering apparatus 10, and as a part thereof, realizes a film thickness control apparatus that controls the film thickness of the film formed by the reactive sputtering apparatus 10. . That is, the data storage unit 44 operates as means for storing the relationship between the discharge voltage and the film formation rate during film formation by constant power discharge obtained in advance for the target used in the reactive sputtering apparatus 10, and the input interface 45 operates as a means for capturing a measured value of the discharge voltage during film formation, and the arithmetic processing unit 41 captures the input interface 45 for at least a part of the period during film formation by reactive sputtering using a target. The data storage unit 44 is accessed based on the measured value of the discharge voltage, and operates as calculation means for obtaining the film thickness formed by calculation from the corresponding film formation speed.

  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 implemented when another material is used as a target. In addition, when Si is used as a target, the fluctuation of the discharge voltage at the start of film formation is small. However, when further accuracy of the film thickness is required or the film formation time is short, the influence of the fluctuation of the discharge voltage at the start of film formation is affected. In the case where it cannot be ignored, the present invention can be similarly implemented. Furthermore, when a film other than an oxide film is formed, that is, when a gas other than oxygen gas is introduced into the plasma region 28 for processing, the present invention can be similarly implemented. For example, even when a TiN film is formed using Ti as a target and nitrogen gas as a reactive gas, the discharge voltage is monitored to detect fluctuations in the film formation rate due to the nitride formed on the target surface. The film thickness can be accurately controlled. Since the nitride on the target surface has a smaller sputtering rate than the oxide, the film formation rate fluctuates greatly due to the influence of the nitride, and the control effect of the present invention is great. Not only the TiN film but also a combination of a target material and a reactive gas such as a SiNx film, a TiOxNy film, a TaOx film, a TiSiOxNy film, an AlOx film, and a ZrOx film may be appropriately selected. The present invention is effective in any reactive sputtering apparatus for forming a compound thin film.

DESCRIPTION OF SYMBOLS 10 Reactive sputtering apparatus 11 Reaction tank 14 Drum 15 Substrate 16 Shaft 26, 27 Sputtering area 28 Plasma area 31, 32, 33 Power supply 34, 35 Voltmeter 36 Controller 41 Operation processing part 42 Read-only memory 43 Random access memory 44 Data Storage unit 45 Input interface 46 Output interface

Claims (11)

Regarding the target used for reactive sputtering, a first step of acquiring in advance the relationship between the discharge voltage during film formation by constant power discharge and the film formation rate;
A second step of calculating the deposited film thickness by calculation from the deposition rate corresponding to the measured value of the discharge voltage for at least a part of the period during the deposition by reactive sputtering using the target. A reactive sputtering film thickness control method. In the film thickness control method according to claim 1,
In the first step,
Utilizing the fact that the discharge voltage and film formation rate during film formation vary depending on the surface state of the target, and the discharge voltage and film formation rate in constant power discharge are correlated,
Change the amount of reactive gas introduced into the reaction vessel for performing reactive sputtering, measure the film thickness by forming a film over a longer period of time than the actual film formation conditions in a state where the discharge voltage becomes a constant value, A film thickness control method characterized by repeating this measurement while changing the value of the discharge voltage. In the film thickness control method according to claim 2,
In the first step, in addition to the reactive gas, an amount of water H ₂ O corresponding to the material to be deposited is introduced. In the film thickness control method according to claim 1 or 3,
The film thickness formed in at least a part of the film formation time determined in the second step,
A film thickness control method characterized by extending or shortening a film formation time so as to compensate for a difference from a film thickness planned for at least a part of the film formation in the previous period. In the film thickness control method according to claim 1 or 4,
In the second step, during the period from the start of discharge of reactive sputtering until the discharge voltage is stabilized, the film thickness formed is calculated,
While the film formation is continued, the film formation time is extended or shortened so as to compensate for the difference between the film thickness obtained in the second step and the film thickness planned for the period until stabilization. The film thickness control method. In the film thickness control method according to any one of claims 1 to 5,
A film thickness control method characterized in that the amount of reactive gas introduced is reduced from the amount to be introduced after the discharge voltage is stabilized until the discharge voltage at the beginning of film formation is stabilized. In the film thickness control method according to any one of claims 1 to 6,
A film thickness control method characterized by feedback-controlling the amount of reactive gas introduced until the discharge voltage during film formation reaches a predetermined value. In the film thickness control method according to any one of claims 1 to 7,
Performing the first step on a target used in the sputtering region of a reactive sputtering apparatus having a structure in which a substrate to be deposited is mounted on a rotating drum and sequentially passes through the sputtering region and the plasma region; The film thickness control method, wherein the second step is performed during film formation using the target. In the film thickness control method according to claim 8,
The reactive sputtering apparatus includes a plurality of sputtering regions for stacking different materials, and the first step is performed on at least one target of different materials used in each of the plurality of sputtering regions. The film thickness control method is characterized in that the second step is executed at the time of film formation using the target that has executed the first step. In the film thickness control method according to any one of claims 1 to 9,
A method for controlling a film thickness, wherein the substrate to be deposited is made of resin. In a film thickness control apparatus that is provided in a control apparatus that controls the operation of the reactive sputtering apparatus and controls the film thickness of a film formed by the reactive sputtering apparatus,
With respect to the target used in the reactive sputtering apparatus, means for storing the relationship between the discharge voltage and the film formation rate during film formation by constant power discharge obtained in advance;
Means for capturing the measured value of the discharge voltage during film formation;
For at least a part of the period during film formation by reactive sputtering using the target, the storage means is accessed based on the measured value of the discharge voltage captured by the capture means, and from the corresponding film formation speed, A calculation means for obtaining a film thickness by calculation;
A film thickness control apparatus for reactive sputtering, comprising:

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