JPH1030171A - Electron beam vacuum depositing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam vacuum depositing device using dielectrics as an evaporating source. SOLUTION: The quantity of light radiated from an evaporating source 5 is measured by a photosensor 7 arranged on the outside of a vacuum depositing chamber. The quantity of light and the evaporating velocity lies in a proportional relation. A telescope 9, a glass pane 10 and a mask 11 are arranged between the photosensor 7 and the evaporating source 5 to check reduction in the light receiving sensitivity of the photosensor 7. As for the output of the photosensor, emission current is controlled via an electron beam controller 14 so as to maintain the photoelectric current standard value treated and set by a center control circuit 15. The relational formula between the photoelectric current standard value of the photosensor and the evaporating velocity or the like are previously inputted into the center control circuit 15. On reference to the information on the evaporating velocity from a crystal sensor, the standard value of photocurrent is corrected. Since the control of the evaporating velocity at a high speed with high precision is made possible and there is no need of exchanging the expensive crystal sensor, continuous vacuum deposition is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electron beam vacuum evaporation apparatus using a dielectric as an evaporation source. A photoelectric conversion element (hereinafter referred to as an optical sensor) is employed for controlling the evaporation rate of the evaporation source.

[0002]

2. Description of the Related Art When a deposited film of SiO2 or TiO2 is formed, these dielectrics are used as an evaporation source, and a lower oxide (SiO or Ti2 O3) or a metal thereof is used as an evaporation source and oxygen is introduced into a vacuum chamber. There is a case where SiO2 or TiO2 is finally deposited by causing an oxidation reaction. It is placed in an electron beam vacuum evaporation apparatus, and starts and ends evaporation by opening and closing a shutter above the evaporation source. A quartz crystal oscillator (hereinafter, referred to as a quartz sensor) arranged near the substrate to be deposited monitors a deposition rate and a deposition amount, controls emission current of an electron gun, and opens and closes a shutter. Since the dielectric does not have electric conductivity, an electrostatic potential barrier is generated around the evaporation source when the electron beam is irradiated. Since the electron beam is reflected by this barrier, the evaporation process is more complicated than that of metal.

[0003]

Unless deposition starts on the surface of the quartz sensor 2, the evaporation rate cannot be measured. At the stage of preheating in which the shutter is closed, the evaporation rate is an estimated value. The evaporation rate when the shutter is actually opened may be significantly different from the desired value. Especially sublimable SiO2
In such a case, the evaporation rate does not become constant even if the emission current is kept constant. As a countermeasure, a method of monitoring the evaporation source with a quartz sensor to monitor the evaporation rate even when the shutter is closed is being studied. However, in this method, a considerably large amount of evaporating substance adheres to the quartz sensor, so that the saturation frequency is reached immediately, which is not suitable for long-time deposition. After the shutter is opened, feedback control of the emission current by the quartz sensor is performed.
It takes time to stabilize as shown by the dotted curve in FIG.
Point C of the same curve indicates when the shutter is opened, and point D indicates when control by the quartz sensor is started. Thus, if the evaporation rate is significantly different from the desired value immediately after the shutter opens,
It has a significant effect on the physical properties and thickness of the film.

In the method using the quartz sensor, when the amount of the evaporated substance increases, the film once attached to the quartz sensor 2 is peeled off, or oscillation failure occurs in the quartz sensor itself. At this time, a method of stopping the automatic vapor deposition process or thereafter continuing the vapor deposition while keeping the emission current of the electron gun constant is adopted. For this reason, although expensive, the quartz sensor is frequently replaced. In calculating the evaporation rate of the quartz sensor 2, a difference of the oscillation frequency that changes according to the amount of adhesion is obtained at certain time intervals, and a time lag of about 0.5 seconds is generated in order to calculate the evaporation rate from the frequency difference. I do. It is said to be unsuitable for high-speed control.

[0005]

Means for Solving the Problems The amount of light emitted from the surface of the evaporation source heated by beam irradiation is detected by an optical sensor,
The emission current of the electron gun is controlled so that this output information maintains a preset reference value, and the reference value is changed with reference to the evaporation rate value from the quartz sensor. From the knowledge that "the evaporation rate and the amount of light emitted from the evaporation source are proportional," the present invention monitors the evaporation rate with an optical sensor and controls the emission current in real time. The evaporation rate can be maintained at a desired value even during preheating with the shutter closed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A substrate rotating dome 16 on which a number of substrates to be deposited are mounted is disposed in an upper portion of a vacuum deposition chamber 1, and an electron beam main body 3 is disposed in a lower portion. This electron beam body 3
An evaporation source 5 is placed on the upper surface of the substrate, and the surface is irradiated with an electron beam whose magnetic field is controlled. The evaporant reaches the substrate rotating dome 16 only when the shutter 4 is open. A telescope 8, a neutral density filter 9, and a rotatable glass plate 1 are provided between an optical sensor 7 composed of a photodiode and an evaporation source 5.
0 and the mask 11 are sequentially arranged. Since the optical sensor 7 and the like are provided outside the vacuum chamber, these members can be replaced without interfering with the vapor deposition process. The output of the optical sensor 7 is transmitted to the central control circuit 15 via the amplifier 6. The central control circuit 15 controls the electron beam power supply 13 and the beam controller 14 and controls the electron beam power supply 13 and the beam controller 14 to process an evaporation rate signal from the quartz sensor 2.
It is also connected to. The relational expression (reference value group) between the photocurrent value from the optical sensor 7 and the evaporation rate of the evaporation source 5 is input to the central control circuit 15 in advance. When a reference value of a photocurrent corresponding to a target evaporation rate is externally set in the central control circuit 15, the circuit 15 always controls the emission current of the electron gun by feedback control to keep the photocurrent at the reference value. In the actual vapor deposition process, it is necessary to finely correct this reference value each time. In this case, first, the central control circuit 15 controls the emission current based on the evaporation rate information from the quartz sensor 2 to maintain a desired evaporation rate. The photocurrent value of the optical sensor 7 at this time is adopted as a new reference value.
The quartz sensor 2 is normally protected by a shutter (not shown). The shutter is opened only when a new reference value is changed, and the evaporation rate information is sent to the central control circuit 15. Sign 1
Reference numeral 8 denotes a light projector, reference numeral 17 denotes an optical film thickness meter that receives light from the light projector and measures the film thickness of the substrate to be deposited, reference numeral 20 denotes a halogen heater, and reference numeral 23 denotes a vacuum flange window.

[0007]

FIG. 2 shows that the evaporation source 5 is made of SiO which is a sublimable substance.
2 is a graph showing a change in the emission current of the electron beam, a change in the photocurrent of the optical sensor 7, and a change in the evaporation rate signal of the quartz sensor 2 when 2 is adopted. Telescope 8 in FIG.
Has been removed. The photocurrent value responds to the emission current value almost in real time. The response of the quartz sensor evaporation rate signal is much slower than this photocurrent. The photocurrent is about 300 milliseconds faster than the quartz sensor and the delay to the emission current is only within 100 milliseconds. FIG. 3 is a graph showing each change when TiO2 which is a melting substance is used as the evaporation source 5. Each change curve exhibits substantially the same characteristics as in FIG. The photocurrent responds about 500 milliseconds faster than the quartz sensor.

FIG. 4 shows each output intensity graph when the emission current is controlled so that the photocurrent value maintains the reference value. FIG. 4A shows the case where the evaporation source 5 is SiO2, and FIG. 4B shows the case where the evaporation source 5 is TiO2. Point A indicates emission current ON, point B indicates start of photocurrent control, and point C indicates when shutter 4 is opened. When a shutter (not shown) is disposed on the quartz sensor 2, the shutter 4 is opened at the same time as the shutter 4 is opened. The evaporation rate signal from the quartz sensor 2 is also shown as a dotted curve in the figure for confirmation. By maintaining the photocurrent at the set reference value, the evaporation rate of the evaporation source 5 was maintained at a desired value. It has been proved that the light amount detection method of the evaporation source of the present invention is an excellent evaporation rate control system if the reference value is set correctly. What is particularly noteworthy is that even in the preheating state before the point C when the shutter 4 opens, the evaporation rate can be controlled by the feedback control.
In the emission current control method using the conventional quartz sensor 2, the preheating before the shutter 4 is opened is a statistical process based on empirical data. In the case of SiO2 which is a sublimable substance, since the electron beam reflects on the electrostatic barrier formed around the evaporation source, the preheating is not stable as shown by the photocurrent curve in FIG. In the present invention, the photocurrent between the points B and C is extremely stable (FIG. 4).

FIG. 5 is a photocurrent output diagram when emission current control is performed by photocurrent using the telescope 8. FIG. 5 (a) shows a case where TiO2 is used for the evaporation source 5. FIG. Since the amount of light can be measured more accurately by preventing stray light from the surroundings, the feedback control accuracy of the emission current is improved. The photocurrent waveform in the figure is almost a straight line. (The photocurrent waveforms in FIGS. 3 and 4 are drawn as straight lines for the sake of simplicity, but are actually a series of minute jagged edges). A magnified image of the evaporation source 5 is given to the optical sensor 7 using the telescope 8, and the optical sensor 7 can efficiently take in only the light radiated from the surface of the evaporation source 5; Does not cause a decrease in the sensitivity of the optical sensor 7 even when the distance is far or when there is another illuminant such as a halogen lamp in the surroundings. By using the mask 11, stray light to the optical sensor 7 can be reduced in the same manner.

FIG. 5B shows an embodiment in which SiO 2 is used as the evaporation source 5. During preheating (points B to C) until the shutter 4 opens, the emission current is feedback-controlled with the target of the preset photocurrent reference value, and when the shutter 4 opens (point C), The reference value corresponding to the desired evaporation rate is changed based on the evaporation rate information from the sensor 2 (point D). Thereafter, the emission current is controlled based on the corrected reference value. After this resetting, the information from the crystal sensor 2 becomes unnecessary. During the long-time deposition process, the evaporant gradually adheres to the window glass plate between the optical sensor 7 and the evaporation source 5, and the amount of light to the optical sensor 7 changes slightly. Since the refractive index of SiO2 is close to that of glass, there is no significant change in the amount of light, but the refractive index of TiO2 is high and cannot be ignored. Therefore, the photocurrent reference value of the optical sensor 7 is reset every approximately ten minutes. Each time,
The shutter (not shown) arranged in front of the quartz sensor 2 is opened for about 2 seconds and reset.

A rotatable glass plate 10 and a mask 11 are arranged in a flange 21 in front of the optical sensor 7 (seventh embodiment).
Figure). The glass plate 10 on which the evaporant is adhered is rotated via the knob 22 in combination with the mask 11, and the light amount to the optical sensor 7 is made constant. A method in which the glass plate 10 is slidably replaced as appropriate may be used. FIG. 8 shows an embodiment in which the optical sensor 7 is disposed in the vacuum evaporation chamber 1. A hermetic flange 24 is arranged at the rear of the telescope 8 and the optical sensor 7 to guide a signal line from the optical sensor 7 to the outside.

[0012]

In short, according to the present invention, the optical sensor 7 for measuring the light quantity of the evaporation source 5 irradiated with the electron beam is disposed outside the vacuum evaporation chamber, and the measured value is stored in the central control circuit 15 as desired. Since the emission current is controlled so as to maintain the value corresponding to the evaporation rate (reference value), the desired evaporation rate can be maintained at higher speed and with higher precision than the conventional quartz sensor system. Then, since the reference value of the photocurrent is appropriately corrected based on the evaporation rate information from the quartz sensor 2, the high accuracy of the evaporation rate is maintained even during the long-time deposition process. Since the expensive quartz sensor 2 is usually protected by a shutter, there is no need to replace it.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an electron beam vacuum evaporation apparatus.

FIG. 2 is a graph showing output curves of a photocurrent and a crystal sensor evaporation rate signal with respect to a change in emission current of an electron gun when silicon dioxide is used as an evaporation source.

FIG. 3 is a graph showing an output current of a quartz sensor and a photocurrent with respect to an emission current when titanium dioxide is used as an evaporation source.

FIG. 4 is a graph of each output value of an embodiment in which the emission current is feedback-controlled to maintain the photocurrent at a set reference value.

FIG. 5 (a) is an output graph diagram when an emission current is controlled based on a photocurrent reference value of an embodiment in which an enlarged image of an evaporation source is sent to an optical sensor using a telescope;
(B) is each output graph figure of the Example which corrects the reference value of a photocurrent with the evaporation rate information from a quartz sensor.

FIG. 6 is an output graph of a crystal sensor evaporation rate signal output and a photocurrent as a reference in a conventional crystal sensor output control system using silicon dioxide as an evaporation source.

FIG. 7 is an explanatory diagram illustrating the arrangement of a glass plate and a mask.

FIG. 8 is an explanatory view of an embodiment in which an optical sensor is arranged in a vacuum evaporation chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum vapor deposition chamber 2 Crystal sensor 3 Electron beam 4 Shutter 5 Evaporation source 6 Amplifier 7 Optical sensor 8 Telescope 9 Light reduction filter 10 Glass plate 11 Mask 12 Recorder 13 Electron beam power supply 14 Beam controller 15 Central control circuit 16 Substrate rotating dome 17 Optical film thickness meter 18 Floodlight 19 Evaporation rate controller 23 Vacuum flange window 24 Hermetic flange

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kokichi Suganuma 3-4-7 Honcho, Hadano-shi, Kanagawa Prefecture

Claims (6)

[Claims] An optical sensor for measuring the light amount of an evaporation source irradiated with an electron beam is disposed outside or inside a vacuum evaporation chamber, and the measured value is stored in a central control circuit for a desired evaporation rate. An electron beam vacuum evaporation system that controls the emission current of the electron gun to maintain the value. 2. An optical sensor 7 detects the amount of light radiated from the surface of the evaporation source heated by the beam irradiation, and controls the emission current so that the output information keeps a preset reference value. An electron beam vacuum vapor deposition device that corrects the above reference value with reference to the evaporation rate value from a sensor. 3. An optical sensor 7 for detecting the amount of light radiated from the evaporation source, a central control circuit 15 for maintaining the photocurrent from the optical sensor at a preset reference value, and under the control of the central control circuit. And a beam controller 14 for adjusting the emission current of the electron beam irradiated to the evaporation source. The reference value is set or changed as needed based on the evaporation rate information from the quartz sensor. Evaporation equipment. 4. During preheating before the start of vapor deposition, the emission current of the electron gun is controlled by controlling the emission current of the electron gun so that the photocurrent from the optical sensor 7 maintains a preset reference value.
Is heated, and after starting the vapor deposition, the emission current is controlled based on the evaporation rate information from the quartz sensor 2, the photocurrent value at this time is changed to a new reference value, and thereafter, the photocurrent of the photosensor 7 is changed. 4. The electron beam vacuum vapor deposition apparatus according to claim 2, wherein the control unit controls the emission current so as to maintain the changed reference value. 5. The electron beam vacuum vapor deposition apparatus according to claim 1, wherein the mask 11 or the telescope 8 is arranged in front of the optical sensor 7. 6. A rotatable or slidable glass plate 10 is arranged between an optical sensor 7 and an evaporation source.
The electron beam vacuum vapor deposition apparatus according to claim 1, 2 or 3.