JP4491289B2 - Thin film forming apparatus and method - Google Patents

Description

  The present invention relates to an apparatus for forming a thin film on the surface of a plastic or glass material, and in particular, it can form a thin film with a constant optical property with good reproducibility, for example, when forming an antireflection film on a spectacle lens. It relates to what is preferably used.

  When forming a thin film on a lens made of plastic, glass, etc., it is necessary to produce the product with stable quality. Furthermore, in order to increase production efficiency, the thin film is formed (automatically) without human intervention. Film).

In order to realize this, when the vapor deposition material is evaporated by an electron gun and an antireflection film is deposited on the lens held on the coat dome, the reflected light amount value measured every moment by the optical film thickness meter is a predetermined value. A device that controls the power supplied to the electron gun so as to approximate or equal to the reference light amount value is known (for example, Patent Document 1).
JP 2001-115260 A

  By the way, when performing vapor deposition on materials such as plastic and glass, productivity increases as the thin film formation rate increases, but depending on the type of deposition material and the physical properties of the thin film to be formed, the thin film formation rate can be extremely slow. There are cases where it is unavoidable.

  In the above conventional example, as the thickness of the thin film grows, the reflected light amount value periodically fluctuates between two peaks, a minimum value and a maximum value, but the amount of change in the reflected light amount value decreases near each peak. Since it is difficult to control the electron gun by feedback control, feedback control based on the reflected light amount value is performed only in a predetermined reflected light amount value range excluding the vicinity of each peak.

  For this reason, when the thin film formation speed is high, in other words, when the power supplied to the electron gun is high, the feedback control is terminated at a predetermined reflected light amount value near the peak, and the power at this point is maintained. For example, if vaporization of the vapor deposition material is maintained and the peak of the reflected light amount value is passed and it returns to the predetermined reflected light amount value range, the feedback control can be resumed.

  However, when the formation speed of the thin film is extremely low, the power supplied to the electron gun is small. Therefore, when the feedback control is terminated at a predetermined reflected light amount value near the peak and the power at this time is maintained, the liquefied evaporation The evaporation may stop because the raw material is solidified and the evaporation stops, or the evaporation raw material does not hit the evaporation raw material just by slightly charging (charging) the evaporation raw material. For this reason, it is not possible to return to the feedback control, and the formation of the thin film is temporarily interrupted, so that the thin film cannot be formed. In other words, when the thin film formation rate is extremely low, the power supplied to the electron gun is set to the minimum power required to vaporize the deposition material, so the deposition material changes (liquid phase to solid phase). When this occurred, the progress of film formation sometimes stopped.

  For this reason, when the conventional apparatus is used and the thin film formation speed is extremely low, the thin film is formed under the supervision of an administrator or the like. Therefore, there is a problem that the power supplied to the vehicle needs to be adjusted, the production process cannot be automated, and the manufacturing cost increases.

  Further, in the above-described manual monitoring, it is difficult to keep the thin film formation rate constant in the vicinity of the peak after the end of feedback control. For example, when evaporation stops as described above, it takes time to restart evaporation. When this is applied, the performance of the formed thin film may be deteriorated because the formation speed of the thin film becomes non-uniform.

  Therefore, the present invention has been made in view of the above problems, and accurately performs the power of the electron gun in the vicinity of the peak of the light amount value, so that the deposition can be performed accurately and automatically even when the thin film formation speed is extremely slow. The purpose is to ensure product quality and improve productivity.

The present invention includes a heating unit that heats a film forming material in a chamber and causes the film forming material to fly and deposit on the surface of the film formation target, and to the film formation target on which the thin film is formed. In a thin film forming apparatus, comprising: an optical film thickness meter that measures a transmitted or reflected light amount value when the light is irradiated; and a control unit that controls a flying amount of the film forming material based on the light amount value ,
The control means includes a feedback control unit that controls the output of the heating unit by feedback so that the measured light amount value and a preset reference light amount value are approximate or equal, and an open loop that controls the heating unit by an open loop. A loop control unit, a threshold setting unit that presets a threshold value for switching from feedback control to open loop control in the vicinity of the maximum value and minimum value of the light amount value, and the light amount value reaches the threshold value. And switching from feedback control to open loop control when the predetermined condition is established in the open loop control unit, and a control switching unit to switch from open loop control to feedback control,
The open loop control unit maintains a peak detection unit for detecting a maximum value or a minimum value based on the light amount value, and an output at the end of feedback control for a first time, and when the first time has elapsed when the not detect the maximum or minimum value has an output correction unit that controls the rate of formation of a thin film deposited on the deposition target surface to increase the output.

  In addition, the first time predicts a time at which the maximum value or the minimum value will be detected from the feedback control end time based on the output at the feedback control end time.

  Therefore, according to the present invention, the feedback control is terminated in the vicinity of the maximum value or the minimum value of the light amount value, the heating unit is controlled by the open loop control, and the feedback control end point is reached until the first time elapses. If the light intensity value does not reach the maximum value or the minimum value at the time when the output is maintained and the first time has elapsed, the deposition material is vaporized near the maximum value or the minimum value by performing correction to increase the output. Thus, it is possible to improve the productivity by automating the thin film formation while ensuring the quality of the thin film by surely forming the film.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a configuration of a thin film forming apparatus according to an embodiment of the present invention. Hereinafter, an embodiment will be described with reference to FIG. This embodiment shows an example in which the present invention is applied to the case where an antireflection film is formed as a thin film on a plastic spectacle lens that is a film formation target.

  In FIG. 1, in a vacuum chamber 1 serving as a film forming chamber, a coat dome 2 that holds a plurality of lenses 2a at the top and a monitor glass 2b for detecting a thin film formation state at a predetermined position is provided. Installed. Below the vacuum chamber 1, a crucible 4 that houses evaporation raw materials (film forming materials) 4 a and 4 b, an electron gun 3 that applies an electron beam to the vapor deposition raw materials 4 a and 4 b of the crucible 4 and vaporizes them, and selectively an electron beam A shutter 5 that shuts off the ion, an ion gun 14 that performs ion beam irradiation to improve the strength and film quality (denseness, etc.) of the deposited thin film, and gas in the vacuum chamber 1 to improve the strength and film quality of the deposited thin film. A gas generator 15 to be filled is provided. The shutter 5 is provided with an actuator and is controlled by a control device 12 described later. Further, the vapor deposition materials 4a and 4b are different kinds of materials, for example, the vapor deposition material 4a is an inorganic material, and the vapor deposition material 4b is an organic material.

  In the vicinity of the upper coat dome 2, a substrate thermometer 6 for measuring the temperature of the lens 2 a as a film formation object held by the coat dome 2 is provided, and the degree of vacuum in the vacuum chamber 1 is further increased. A vacuum gauge 7 for measurement and an exhaust unit 8 for exhausting the inside of the vacuum chamber 1 are provided. Further, a heater 9 for heating the lens 2 a held on the coat dome 2 is provided. The heater 9 is composed of a halogen heater or the like.

  Further, an optical film thickness meter 10 for measuring the reflectance of the monitor glass 2 b set at a predetermined position of the coat dome 2 is provided above the vacuum chamber 1. The optical film thickness meter 10 is connected to the control device 12 via the film thickness monitor 11, and the optical film thickness meter 10 receives reflected light with respect to the amount of irradiation light as light amount data (light amount value) as will be described later. The light intensity ratio is output. The configurations of the optical film thickness meter 10 and the film thickness monitor 11 are the same as the configurations of JP 2001-115260 A and JP 2003-202404 A.

  The control device 12 includes a calculation unit including a CPU, a memory, and the like, and a reference light amount value data storage unit 13 for performing feedback control of power supplied to the electron gun. Further, the control unit 12 is connected to an input unit 12a configured by a keyboard, a mouse, and the like, and includes the above-described electron gun 3, shutter 5, vacuum device 8, heater 9, ion gun 14, gas generator 15, and the like. A control target and sensors such as a substrate thermometer 6, a vacuum gauge 7, and an optical film thickness meter 10 (film thickness monitor 11) are connected, and the control device 12 controls the above based on inputs from each sensor. Control the subject.

  That is, the control device 12 controls the vacuum device 8 on the basis of information from the vacuum gauge 7 so that the inside of the vacuum chamber 1 has a predetermined degree of vacuum. Further, the control device 12 controls the heater 9 based on the information of the substrate thermometer 6 to bring the lens 2a that is the film formation body to a predetermined temperature. Then, the control device 12 has a reference light quantity value data storage means that the light quantity value every moment depending on the optical film thickness every moment of the thin film formed on the monitor glass 2 b measured by the optical film thickness meter 10. The power (current and / or voltage) applied to the electron gun 3 is controlled so as to be equal to the value stored in. In addition, depending on the type of thin film to be formed and the type of vapor deposition materials 4a and 4b to be vaporized, ion beam irradiation by the ion gun 14 and gas filling by the gas generator 15 are performed.

  Here, the coat dome 2 is a holding means for holding the lens 2a so that an antireflection film or the like is deposited on the lens 2a. And it is circular so that the several lens 2a can be vapor-deposited simultaneously, and the coat dome 2 has a predetermined curvature so that all the lenses may become the antireflection film of the same quality.

  The electron gun 3 evaporates the vapor deposition raw materials (substances) 4a and 4b accommodated in the crucible 4 by heating to the melting temperature of the vapor deposition raw materials 4a and 4b, and deposits the vapor deposition raw materials (substances) on the lens 2a and the monitor glass 2b. Is deposited and deposited to form a thin film.

  The crucible 4 is a known container used to hold the vapor deposition materials 4a and 4b. The crucible 4 is cooled or a material having high thermal conductivity is preferable so that the vapor deposition material does not bump due to the heating of the vapor deposition material by the electron gun 3.

  The shutter 5 is controlled so as to open when the deposition is started or closed when the deposition is completed, and facilitates control of the thin film. The heater 9 is a heating unit that heats the lens 2a to an appropriate temperature in order to obtain physical properties such as adhesion of a thin film deposited on the lens 2a.

  The optical film thickness meter 10 utilizes a phenomenon in which when a transparent substrate having a transparent thin film formed thereon is irradiated with light, the reflected light from the surface of the thin film and the reflected light from the surface of the transparent substrate interfere with each other due to the phase difference between the two. It is a thing. That is, the phase difference changes depending on the refractive index and optical thickness of the thin film, the state of interference changes, and the amount of reflected light changes depending on the refractive index and optical thickness of the thin film. If the reflected light changes, the transmitted light also inevitably changes. Therefore, the same can be done by measuring the amount of the transmitted light, but the case where the reflected light is used will be described below.

  The optical film thickness meter 10 irradiates the monitor glass 2b held at the center of the coat dome 2 with light of a predetermined wavelength and measures the reflected light. Since it can be considered that the thin film formed on the monitor glass 2b depends on the thin film formed on each lens 2a, it is possible to obtain information that can guess (reproduce) the thin film formed on each lens 2a. it can.

  FIG. 2 is a diagram showing a change in the amount of reflected light when a thin film is formed by performing vapor deposition on the surface of the monitor glass 2. In the figure, the vertical axis represents the light amount value (relative value: unit;%), and the horizontal axis represents the deposition time. When the physical film thickness of the thin film to be deposited is thick, the light amount value is periodically increased and decreased as the physical film thickness increases under the condition that the refractive index of the thin film is constant. By utilizing the change in the amount of light that uniquely corresponds to the refractive index of the thin film and the physical film thickness of the thin film, the thin film can be uniquely measured or controlled. In this case, the difference between the maximum value and the minimum value in each period Pk1 to Pk5 is referred to as an elongation amount. In general, the elongation amounts L1, L2, L3,...

  Here, the light amount value is obtained by the equation (1) of the above-mentioned JP-A-2003-202404, and the light amount value Qt at a certain time t is

である。
ただし、Ｑ０：初期設定光量
Ｐ(λ,t)＝Ｒmonitor(ｄ1,ｄ2,……,ｄk(t), ｎ0(λ),ｎ1(λ), ｎ2(λ),……,ｎk(λ))・Ｔ(λ)・Ｘ(λ)
Ｐ：光量の絶対値
Ｔ(λ)：光学式膜厚計１０内のフィルターの透過率
Ｘ(λ)：光学式膜厚計１０内の投光ランプの強度関数（Ｓ(λ)）や反射鏡の反射率（Ｒmirror（λ））等の膜厚計１０を構成する光学部品による関数で、一般に装置定数として扱うことができる
λ：光の波長
である。

It is.
However, Q0: Initial setting light quantity P (λ, t) = Rmonitor (d1, d2,..., Dk (t), n0 (λ), n1 (λ), n2 (λ),..., Nk (λ) ) ・ T (λ) ・ X (λ)
P: Absolute value of light quantity T (λ): Transmittance of the filter in the optical film thickness meter 10 X (λ): Intensity function (S (λ)) and reflection of the projection lamp in the optical film thickness meter 10 A function of the optical component constituting the film thickness meter 10 such as a mirror reflectivity (Rmirror (λ)), which can be generally treated as a device constant. Λ: wavelength of light.

  FIG. 2 shows an example in which power supply to the electron gun 3 is started from time 0 and vapor deposition is performed. The light amount value increases as the thin film grows, and the peak Pk1 that is the first maximum value is first shown. Then, the light amount value decreases due to the above-described interference of light, and reaches the peak Pk2, which is the first minimum value. Thereafter, the film thickness increases while periodically repeating the maximum value and the minimum value. When the film thickness reaches a predetermined value, the supply of electric power to the electron gun 3 is stopped and the shutter 5 is closed to deposit the evaporation material. Evaporation of 4a and 4b is stopped and vapor deposition is completed.

  FIG. 3 is a graph showing an outline of the control that is the main part of the present invention, and shows the relationship between the light amount value and time as in FIG.

  In FIG. 3, when the minimum light amount value is 20% and the maximum is 70% and the elongation amount is 50%, for example, in the region of 5% before the peak, the peak control described later is used to determine the light amount value. However, thin film formation is controlled using feedback control (or rate control) in other areas.

  That is, in this case, on the maximum value (70%) side, when the light amount value reaches the predetermined threshold B2 (65%) due to the increase in the film thickness of the thin film, the feedback control is switched to the peak control. The switching from the peak control to the feedback control is switched to the feedback control after detecting the peak Pki (where i is a natural number). As an example of detection of the peak Pki, the sign of the amount of change in the light amount value changes when the light amount value is not less than a predetermined value on the maximum side (for example, 68%) or not more than a predetermined value on the minimum side (for example, 18%). It is determined as a peak.

  In the region where feedback control is performed, the control device 12, from time to time, from the thin film formed on the monitor glass 2 b measured by the optical film thickness meter 10, as in the conventional Japanese Patent Application Laid-Open No. 2001-115260. The electric power (current or voltage or duty ratio) applied to the electron gun 3 is controlled so that the light quantity value becomes equal to the light quantity value stored in the reference light quantity value data storage unit 13.

  On the other hand, in the region where peak control is performed, the peak detection prediction time tx that will reach the peak Pki is determined based on the output (supply power) of the electron gun 3 at the end of feedback control (for example, the light amount value = B2). And is calculated from preset reference light quantity value data. Then, until the peak detection prediction time tx elapses, the power at the time point B2 when the feedback control is completed is maintained and supplied to the electron gun 3.

  When the peak Pki is detected within the peak detection predicted time tx, the power at this time is maintained and supplied to the electron gun 3, and the feedback control is switched from the detection time of the peak Pki to the next peak Pki + 1. Head.

  If the peak Pki is not detected even after the peak detection predicted time tx has elapsed, the power supplied to the electron gun 3 is added and corrected by a predetermined value ΔPw. At this time, counting of the predetermined time ty is started from the time when the predetermined time ty is set and the peak detection predicted time tx is flowered.

  Then, by adding and correcting the power supplied to the electron gun 3 by ΔPw, the evaporation of the vapor deposition materials 4a and 4b is promoted, and when the peak Pki is detected, the control is switched to the feedback control from the detection time of the peak Pki.

  On the other hand, when the predetermined time ty has elapsed despite the addition of the power supplied to the electron gun 3 by ΔPw, the power supplied to the electron gun is corrected again by the predetermined value ΔPw, and again after the predetermined time ty. Count the progress and detect the peak.

  The addition correction of ΔPw and the peak detection within the predetermined time ty are repeated a plurality of times (for example, four times).

  As described above, when the light amount value is equal to or greater than the threshold value B2 (for example, 65%) or less than B1 (for example, 25%) before the peak Pki, the feedback control is switched to the peak control. If the peak Pki is not detected within the time tx, the power supplied to the electron gun 3 is added and corrected step by step by a predetermined value ΔPw. And if the peak Pki is detected, it will switch to feedback control from the detection time, and will go to the next peak.

  Next, an example of vapor deposition control when forming the antireflection film performed by the control device 12 will be described in detail below.

  First, standard film formation is performed on the lens 2a and the monitor glass 2b.

  The lens 2a and the monitor glass 2b are set in advance on the coat dome 2, the vapor deposition raw materials 4a and 4b are set in the crucible 4, the vacuum device 8 is started, the inside of the vacuum chamber 1 is set to a predetermined degree of vacuum, and the heater 9 Is operated to bring the lens 2a and the monitor glass 2b to a predetermined temperature. Thereafter, control of electric power applied to the electron gun 3 is started to start vapor deposition.

  The deposition film is formed only after the shutter 5 is opened. Therefore, the time when the shutter 5 is opened is set to 0, and the elapsed time thereafter is set to t (seconds). Generally, when the shutter 5 is opened, the light quantity of the optical film thickness meter 10 starts to change. However, in reality, sometimes the start of the change in the amount of light is delayed. In such a case, the control can be started by forcibly applying a predetermined power to the electron gun 3 after a predetermined time elapses.

  First, various conditions such as the output of the electron gun 3 are set to conditions that allow the best film formation, and the standard film formation is performed. The film formation of this standard is a film formation in which a desired antireflection film is formed as a result. Therefore, when the various conditions of the apparatus are favorable, it may be necessary to keep the applied power to the electron gun constant. In some cases, film formation may be started while controlling various conditions according to the experience and skill of the skilled worker.

  In the film formation of the above standard, the light quantity value L (%) of the optical film thickness meter 10 with respect to the time t (second) in the film formation process is recorded in a memory or the like at any time according to a predetermined sampling interval Tsmp (second). Then, the light amount value data in which the time and the light amount are paired is created. The above light quantity value data is set as reference light quantity value data and stored in the reference light quantity value data storage unit 13.

  When the above standard film formation process is completed, vapor deposition control is performed based on the flowchart shown in FIG.

  This flowchart is executed when there is a start command from the input unit 12a or the like. The vacuum device 8 and the heater 9 are operated in advance.

  First, in step S1, the power supplied to the electron gun 3 (hereinafter, an example of controlling the current) is set to a preset initial value, and the supply of power is started. At the same time, the shutter 5 is opened. Further, when ion beam irradiation or gas filling is used together based on the set film type, that is, the type of vapor deposition raw materials 4a and 4b, vapor deposition conditions, and the like, the ion gun 14 and the gas generator 15 are operated. .

  In step S2, it is determined whether or not a feedback control start condition is satisfied when the film is formed toward the first peak Pk. As the feedback control start condition, for example, a light amount value is detected after a predetermined time has elapsed, and if the light amount value reaches a predetermined value (for example, B1), it is determined that the start condition is satisfied. That is, it may be determined whether or not vaporization of the vapor deposition raw materials 4a and 4b proceeds smoothly.

  If the feedback control start condition is satisfied, the number i indicating the position of each 1 / 4λ layer is set to i = 1 since it is the first time, and the process proceeds to step S3 to form the i-th 1 / 4λ layer. I do. For example, in FIG. 2, the quarter λ layer is the first quarter λ layer from the start of film formation (time = 0) to the peak Pk1, and the second quarter λ layer is from the peak Pk1 to Pk2. Thereafter, the number i increases as the film thickness increases. The number i indicates the i-th control count of the feedback control, and the initial value is 1.

  Next, in step S4, the current value of the electron gun 3 is controlled by feedback as follows.

  First, the light amount at time ti-1 (actual time) after the shutter 5 is opened is Li-1 (actual value = actual light amount), and a reference light amount value Ls (= Li-1) equal to Li-1 is set. The reference light quantity value data stored in the reference light quantity value data storage unit 13 is searched. If there is no identical value, an approximate value is calculated. Then, a time ts (reference time) corresponding to the light quantity value Ls is calculated from the reference light quantity value data.

Next, the light amount value (actual value = actual light amount) corresponding to the time ti after the control interval Δt (seconds) from the actual time ti−1 is set to Li. Further, the reference light amount Ls ′ corresponding to the reference time ts ′ (= ts + Δt) is obtained from the reference data. At this time,
ΔLi≡Li-Li-1
ΔLsi≡Ls'-Ls
And where
Ri≡L−ΔLi / ΔLsi
Or
Ri≡ (Ls′-Li) / (Ls′-Ls)
And FIG. 5 and FIG. 6 show the change of the actual light amount and the change of the reference light amount with respect to time, respectively.

  The following conversion is further performed on the Ri.

Qi≡kRi | Ri |
Here, k is an arbitrary constant. PID control (proportional, integral, derivative control) is performed on the light quantity value Qi, and the electron gun power value Pi is determined as needed. The PID control equation for determining the electron gun power value Pi is shown below.

Pi≡Pi−1 + Kp · Qi + Ki · ΣQi + Kd · detQi
Here, Kp, Ki, and Kd are arbitrary constants.

  Also,

ｄｅｔＱｉ≡Ｑｉ−Ｑi-1である。以上の制御を制御間隔Δｔi（秒）毎に行う。

detQi≡Qi-Qi-1. The above control is performed every control interval Δti (seconds).

However, the control interval Δti (seconds) is changed according to the coincidence rate (Ri). In general, the control interval Δti is increased as the coincidence rate is higher (Ri is closer to 0). Note that it is possible to perform PID control (proportional, integral, derivative control) on Ri and determine the electron gun power value Pi at any time.
Qi≡kRi | Ri |
When the values of ΔLsi and ΔLi are approximated, an appropriate current value of the electron gun 3 can be set.

  As described above, the power of the electron gun 3 is adjusted so that the actual light amount matches or approximates the reference light amount value data by performing feedback control by PID control immediately after the light amount value is detected or in the range of the threshold value B1 or more and B2 or less. To control.

  Next, in step S5, it is determined whether or not the preset film forming conditions are completed. The determination of the film forming condition is based on whether or not a predetermined film thickness has been reached, and whether or not the number i indicating the number of feedback control (that is, the number of 1 / 4λ layer formation) has reached a predetermined value. It is done by judging. If the film formation conditions are not completed, the process proceeds to step S6 to form the next 1 / 4λ layer. If the film formation conditions are satisfied, the process proceeds to an end process in step S19.

  Next, in step S6, it is determined whether or not the actual light quantity value has reached the feedback control end threshold value B1 or B2 shown in FIGS. When the end threshold value B1 or B2 is reached, the process proceeds to step S7 to end the feedback control and shift to the peak control. On the other hand, if the actual light quantity value is immediately after peak detection or within the range of the threshold values B1 and B2, the process returns to step S4 to continue the feedback control. Note that the threshold values B1 and B2 used for this determination are switched according to the value of the previous peak Pki-1. That is, if the previous peak Pki-1 is a maximum value, the threshold value B1 is used, and if the previous peak Pki-1 is a minimum value, the threshold value B2 is used.

  In step S8, peak power control is started while maintaining the power supplied to the electron gun 3 at the end of the feedback control.

  In step S9, a peak detection prediction time tx that reaches the peak Pki with the current power of the electron gun 3 is calculated. The peak detection prediction time tx is calculated from the time Δti corresponding to the change amount ΔLi (see FIG. 5) of the actual light amount value at the time when the feedback control ends.

  Next, in step S10, the peak detection prediction time tx obtained from the above is set in the timer Tm1, and the timer Tm1 starts counting.

  In steps S11 to S12, while waiting for the peak detection prediction time tx to elapse, the peak Pki is detected. As described above, peak detection is performed based on the sign of the amount of change in the actual light amount value. When the peak Pki is detected within the peak detection predicted time tx, the film formation is proceeding normally. Therefore, the process proceeds to step S18, i = i + 1 is set, and the process returns to step S3. From peak control to feedback control. Then, the formation of the next 1 / 4λ layer is started.

  On the other hand, if peak detection cannot be performed even after the peak detection predicted time tx elapses, the process proceeds to step S13, and the power supplied to the electron gun 3 (here, the current value) is increased by a predetermined increment value ΔPw. Correction is made (see FIG. 7).

  In step S14, a predetermined monitoring time ty (for example, 10 seconds) is set in the timer Tm2. Note that the value of the predetermined time ty may be appropriately set according to the magnitude of the current value increment ΔPw for which the increase correction is performed.

  In steps S15 to S16, the above-described peak detection is performed while counting the timer Tm2 and monitoring the elapse of the predetermined time ty. When the peak Pki is detected within the predetermined time ty, the process proceeds to step S18 in the same manner as described above, shifts from peak control to feedback control, and proceeds to formation of the next 1 / 4λ layer.

  On the other hand, if the peak Pki is not detected even after the predetermined time ty has elapsed, the process proceeds to step S17.

  In step S17, it is determined whether or not the number of power increase corrections has reached a predetermined number (for example, 5 times). If the number has not reached the predetermined number, the number of increase corrections is incremented, and the process returns to step S13. Then, the increase in the supplied power is corrected again, and the progress of the predetermined time ty is monitored.

  On the other hand, when the number of power increase corrections reaches a predetermined number, since the progress of film formation is not observed despite the power increase correction up to the predetermined number, the evaporation raw materials 4a, 4b, etc. Since it can be inferred that a problem has occurred, the process proceeds to step S19 to perform a vapor deposition control termination process.

  In step S19, the vapor deposition control is terminated when the film forming conditions are completed. In this end processing, the shutter 5 is closed, the electron gun 3 is stopped, and when the ion gun 14 and the gas generator 15 are operated, these are also stopped.

  After the first feedback control is started by the above control, as shown in FIG. 3, when the light quantity value reaches the threshold value B1 or B2 immediately before the next peak Pki, the control shifts to the peak control. To do.

  In the peak control, the power at the end of the feedback control is maintained, and the peak detection predicted time tx reaching the peak Pki is obtained in a state where this power is maintained, and whether or not the peak Pki is detected within this time tx is determined. judge.

  If the peak Pki is detected after the peak detection predicted time tx has elapsed, the film formation is proceeding normally, and the feedback control is resumed again.

  On the other hand, if the peak Pki is not detected even after the peak detection predicted time tx elapses, power (current value) increase correction is performed step by step. This example will be described with reference to FIG.

  When the light quantity value reaches the maximum threshold B2 at time t0, feedback control is terminated and peak control is started. At the time t1 when the scheduled peak detection time tx has elapsed, since the peak Pki is not detected, a predetermined increment value ΔPw is added to the power at the end of the feedback control, and the power increase correction to the electron gun 3 is performed. After the increase correction, vaporization of the vapor deposition materials 4a and 4b is promoted by an increase in the output of the electron gun 3. Then, the detection of the peak Pki is monitored in the period of the predetermined time ty after the increase correction. When the peak Pki is detected at the time t2 within the predetermined time ty, the control shifts from the peak control to the feedback control.

  During the peak control period, if the progress of the film formation is delayed, the power increase correction is performed in an open loop step by step. For this reason, the power supplied to the electron gun 3 is often larger than an ideal value. However, when the peak control is completed, the supply power is corrected to decrease toward an ideal value by shifting to the feedback control based on the light amount value, so that the power does not become excessive.

  Also, as shown by the one-dot chain line in FIG. 7, after the first power increase correction, if the peak Pki is not detected even after the predetermined time ty has elapsed, the power increase correction is repeated up to a predetermined number of times. Therefore, as described in the above-mentioned problem, when the thin film formation rate (deposition rate) must be extremely slow (when the amount of flight of the deposition materials 4a and 4b is extremely small), the change in the deposition material Even if a charge-up (charging) of a liquid phase to a solid phase occurs, the power of the electron gun 3 is gradually increased and corrected by open loop control, so even if the deposition rate is extremely slow In addition, it is possible to form a thin film at a low cost because it is possible to perform film formation and does not require manpower as in the prior art.

  In particular, according to the present invention, it is effective when forming a thin film having a very slow deposition rate and a large variation in elongation for each number of depositions.

  A case where the difference in the actual elongation amount becomes greater for each number of times of vapor deposition is when the change in the refractive index of the vapor deposition material becomes larger (unstable). If the change in the refractive index of the vapor deposition material is large, the shape of the thin film changes drastically, and the control accuracy of feedback control decreases. Therefore, in the feedback control range, the elongation amount immediately after the start of vapor deposition or immediately after the peak Pki is detected becomes narrow. Under such conditions, in the case of the conventional example, if the output of the electron gun 3 is extremely low, vaporization of the vapor deposition materials 4a and 4b often stops near the peak where feedback control is not performed.

  Therefore, as in the present invention, the supply power is gradually increased and corrected by the open loop control from the threshold values B1 and B2 immediately before the peak Pki, and the peak Pki is detected, regardless of variations in the amount of elongation. Therefore, accurate film formation can be automated. In addition, since the peak detection prediction time tx is calculated from the power at the end of the feedback control, the peak detection can be accurately predicted even when the difference in the actual elongation amount increases for each number of depositions. It can be done.

  Here, the vapor deposition raw material for which the vapor deposition rate needs to be extremely slow will be described.

  When the thin film formed by vapor deposition is a plastic lens multilayer antireflection film, at least one of the inorganic substances of silicon dioxide, aluminum oxide, zirconium oxide, tantalum oxide, yttrium oxide, and niobium oxide is one layer in the antireflection film. Is a deposition layer 4a, and at least one of an organic silicon compound or a silicon-free organic compound is a deposition layer 4b, the power supplied to the electron gun 3 is divided into two types of deposition materials 4a and 4b. Film formation is performed at an extremely slow speed as the minimum value that can be stably vaporized.

  When such vapor deposition raw materials 4a and 4b are vapor-deposited on the plastic lens 2a, film formation is performed at a very slow vapor deposition rate (usually 2 to 3 times the rate of an antireflection film made of only an inorganic substance) by the above control. . Even if the output of the electron gun 3 is set to the minimum value at which the vapor deposition raw materials 4a and 4b can be vaporized by this control, the output of the electron gun 3 is controlled in an open loop by the peak control after the feedback control is completed. By doing so, the vapor deposition raw materials 4a and 4b can be surely vaporized, and the vapor deposition can be performed automatically without requiring manual operation.

  The hybrid layer composed of the inorganic substance and the organic substance as described above is formed at the lens 2a for the first time with an anti-reflection film excellent in impact resistance, adhesion, and scratch resistance by performing processing at an extremely slow deposition rate. can do.

  In addition, when depositing the deposition materials 4a and 4b as described above, the adhesion and scratch resistance are further improved by performing ion beam irradiation and filling with gas (for example, oxygen gas and argon gas). It becomes possible.

  In the above-described embodiment, the increase correction of the electric power of the electron gun 3 in the peak control is performed in stages, but the electric power is gradually increased by the increment value per unit time, and every time the predetermined time ty elapses, The increment value per unit time may be increased, or, as shown in FIG. 8, in the first increase correction, the power is increased step by step by ΔPw, and even if the predetermined time ty elapses, the peak is reached. When Pki is not detected, the power may be gradually increased by an increment value per unit time.

  In the above embodiment, the current is controlled to control the output of the electron gun 3, but the control may be performed using a voltage or a duty ratio.

  Moreover, in the said embodiment, although the example which vaporizes vapor deposition raw materials 4a and 4b with the electron gun 3 was shown, the heater etc. which heat the vapor deposition raw materials 4a and 4b may be used.

  As described above, according to the present invention, accurate film formation can be performed automatically regardless of the deposition rate, so that the present invention can be applied to a deposition apparatus for forming an antireflection film for a lens.

The block diagram which shows the outline of the thin film forming apparatus which shows embodiment of this invention. The graph which shows the relationship between the output (light quantity value) of an optical film thickness meter according to progress of thin film formation, and time. The graph which shows the relationship between the output (light quantity value) of an optical film thickness meter according to progress of thin film formation, a control range, and time. The flowchart which shows an example of the vapor deposition control performed with a control apparatus. The graph which shows the relationship between an actual light quantity value and time. The graph which shows the relationship between a reference light quantity value and time. The graph which shows the relationship between a light quantity value and an electric current, and the principal part enlarged view of the maximum side. It is a graph which shows the relationship between another light quantity value and an electric current, and is the principal part enlarged view of the maximum side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Coat dome 2a Lens 2b Monitor glass 3 Electron gun 4a, 4b Vapor deposition raw material 5 Shutter 8 Vacuum apparatus 10 Optical film thickness meter 12 Control apparatus

Claims (8)

A thin-film forming unit that includes a heating unit that heats the film-forming material in the chamber and causes the film-forming material to fly and deposit on the surface of the film-forming body;
An optical film thickness meter that measures the amount of light that is transmitted or reflected when a predetermined light is irradiated on a film-formed body on which a thin film is formed;
In a thin film forming apparatus comprising: a control unit that controls a flying amount of the film forming material based on the light amount value.
The control means includes
A feedback control unit for controlling the output of the heating unit by feedback so that the measured light amount value and a preset reference light amount value are approximate or equal;
An open loop control unit for controlling the heating unit by an open loop;
A threshold value setting unit that presets a threshold value for switching from feedback control to open loop control in the vicinity of the maximum value and the minimum value of the light amount value, and
A control switching unit that switches from feedback control to open loop control when the light amount value reaches a threshold value, and switches from open loop control to feedback control when a predetermined condition is satisfied in the open loop control unit, and
The open loop control unit
Based on the light amount value, a peak detection unit for detecting a maximum value or a minimum value;
The output at the end of the feedback control is maintained for the first time, and when the maximum value or the minimum value cannot be detected when the first time has elapsed, the output is increased and deposited on the film formation surface. thin film forming apparatus comprising: the output correction unit that controls the rate of formation of the thin film, the.   The output correction unit includes a peak detection time prediction unit that predicts, as the first time, a time at which a maximum value or a minimum value will be detected from the feedback control end point based on an output at the feedback control end point. The thin film forming apparatus according to claim 1.   When the maximum value or the minimum value cannot be detected after the first time has elapsed, the output correction unit determines the detection of the maximum value or the minimum value within a second predetermined time, and performs a second predetermined time. 2. The thin film forming apparatus according to claim 1, wherein when the maximum value or the minimum value is not detected every time elapses, the output is increased by a predetermined increment value.   The open loop control unit determines that the predetermined condition is satisfied when the detection of the maximum value or the minimum value of the light amount value after the first time has elapsed, and the control switching unit switches from the open loop control to the feedback control. The thin film forming apparatus according to claim 1, wherein the thin film forming apparatus is switched. A thin film forming method for controlling an output of a heating unit that heats a film forming material in a chamber to cause the film forming material to fly and deposit on the surface of the film formation target,
The output of the heating unit is adjusted by feedback control so that the light amount value transmitted or reflected when a predetermined light is applied to the film formation target on which the thin film is formed approximates or becomes equal to the preset reference light amount value. And the steps to
A procedure for terminating feedback control when the light amount value reaches a preset threshold value in the vicinity of the maximum value or the minimum value;
Holding the output at the end of the feedback control for a first time;
A procedure for determining whether or not the light amount value has reached a maximum value or a minimum value within the first time;
A procedure for controlling the formation rate of a thin film to be deposited on the surface of the film-forming body by increasing the output when the light amount value is not the maximum value or the minimum value when the first time has elapsed; The thin film formation method characterized by including these.   6. The time according to claim 5, wherein the first time is a time predicted to detect a maximum value or a minimum value from the feedback control end point based on an output at the feedback control end point. The thin film formation method of description.   The procedure for increasing the output is to determine the detection of the maximum value or the minimum value within a second predetermined time, and when the maximum value or the minimum value is not detected while the second predetermined time elapses, the output is determined to be predetermined. 6. The method of forming a thin film according to claim 5, wherein the increment is increased by increments of.   6. The method of forming a thin film according to claim 5, wherein the control is switched to the feedback control from the time when the detection of the maximum value or the minimum value of the light quantity value is determined.

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