JPH0625848A - Method for controlling film thickness in vacuum deposition - Google Patents

Abstract

(57) [Abstract] [Purpose] To control the film thickness in vacuum deposition constant. [Structure] A metal or alloy contained in a crucible is melted by an electron beam of a constant power, and a metal film evaporated from the molten metal or alloy is vapor-deposited on the substrate film while supplying the substrate film. the thickness t of the metal intermittently or continuously measured, error Delta] t = calculates t-t _0, and negative feedback that value in feedback rate of 50% or less as compared with its value set thickness t ₀ It is characterized in that the vapor deposition film thickness is regulated within a target range by controlling the supply rate of the base film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal vapor deposition, and more particularly to automatic control of vapor deposition film thickness.

[0002]

2. Description of the Related Art In a vacuum chamber, an electron beam is generated from an electron gun, which is made into a spot by squeezing it by a lens and made to collide with a metal to be vaporized contained in a crucible and melted. A method of evaporating a metal vapor from a temperature metal to deposit it on a substrate is used. Such technology is disclosed in Japanese Examined Patent Publication No. 3-41897, Japanese Examined Patent Publication 3-3.
8340, JP-A-59-178626, JP-A-3-1.
No. 26823 and the like.

In a vacuum vapor deposition apparatus using such an electron gun, a high-energy electron beam emitted from the electron gun is advanced straight toward a crucible. The crucible is usually in the shape of a rectangle elongated in the width direction of the substrate, and the electron beam is scanned in the length direction of the crucible under the action of a deflecting magnetic field or electric field in order to heat the metal surface of the crucible almost uniformly. For example, in the case of manufacturing an obliquely oriented vapor-deposited metal magnetic recording medium, C
O or Co alloy metal is housed in a crucible (boat) made of high-purity magnesia (MgO), and maximum 30kV from electron gun
With an accelerating voltage of a certain degree, the electron beam is directed straight toward the crucible and collides with the metal. At that time, the electron beam is scanned in the length direction of the crucible (and also in the width direction in some cases) to uniformly heat the metal (Japanese Patent Publication No. 3-38340).

In the above conventional vapor deposition method, sufficient adhesion strength of the vapor deposited metal to the substrate cannot be ensured, and a vapor deposited film having sufficient durability cannot be provided. The cause is that the electron beam power is about 120 to 150 kW (about 4 to 5 A at 30 kV).
In the above case, the electrons that fly out from the surface of the molten metal together with the metal vapor and the electrons from the electron gun repel each other, and the electrons cannot be converged, and the effective power cannot be increased to about 100 kW or more, and the vapor velocity is sufficiently improved. Because I couldn't. Here, the effective power is a power in a range in which the evaporation rate changes depending on the power of the electron gun (for example, 100 to 100).
If the evaporation rate does not change even after adding 150 kW, the maximum effective power is 100 kW). is there.

The effective power of the electron gun is determined by arranging the axis of the electron beam emitted by the electron gun such that the center of the rectangular crucible and the axis connecting the centers of the openings intersect at a substantially right angle, and the electron beam is generated by a magnetic field. It has been found that a substantial increase can be obtained by deflecting the light at a substantially right angle to form an image in the crucible.

More specifically, such an apparatus is provided opposite to the elongated rectangular crucible containing the metal to be vaporized, the electron gun for generating an electron beam directed in the crucible, and the crucible. Rotating drum, feeding and winding means for feeding a plastic substrate along the surface of the rotating drum, a mask provided along the surface of the rotating drum and having an opening partly facing the crucible, and the mask It can be realized in a vacuum vapor deposition apparatus including a shutter member for opening and closing. Such a vapor deposition apparatus can be used, for example, to obliquely vapor deposit Co or Co alloy on polyester (PET or the like) to manufacture a magnetic recording medium having diagonal anisotropy. At that time, a gas such as oxygen, carbon dioxide, nitrogen, ammonia, styrene or the like, particularly oxygen is introduced during vapor deposition for the purpose of adjusting magnetic properties (Japanese Patent Publication No. Sho 41-41897). That is, the gas is discharged from a supply nozzle having a slit-shaped outlet. A pressure equalizing tank may be used between the gas supply source and the nozzle in order to keep the flow rate distribution of the discharged gas constant.

[0007]

When the film thickness of the vapor-deposited film changes, such as magnetic films of Co and Co alloys, the magnetic properties and the like of the films change greatly. Therefore, it is necessary to control the thickness of the vapor deposition film once set so as not to change. As a method for controlling the thickness of the vapor deposition film to be constant, adjustment of the feed rate of the base film, adjustment of the opening degree of the shutter, and adjustment of the evaporation rate of the molten metal can be considered. However, adjusting the shutter is inconvenient in that the magnetic properties change due to the change in the minimum incident angle. Further, if the evaporation rate is adjusted by the electric power of the electron beam, it takes a long time to control although there is an advantage that the film running is stabilized. The method of controlling the feeding rate of the base film is immediate and preferable.

Feedback is generally used for such control. That is, the film thickness is measured in real time and compared with a reference value, and the error obtained is fed back to adjust the driving energy of the electron beam. However, since such feedback has inertia in control, overcorrection occurs (overshoot), the vapor deposition film thickness oscillates, and the film thickness cannot be quickly adjusted to a set value within the target range.

It is known that the vapor deposition film thickness is controlled by changing the feed rate of the substrate film (Japanese Patent Laid-Open No. 41918/1993). However, it is not disclosed that the once set film thickness is controlled to be constant. Therefore, an object of the present invention is to provide a film thickness control method for providing a deposited film with a small variation in the deposited thickness.

[0010]

According to the present invention, a metal or an alloy contained in a crucible is melted by an electron beam of a constant power, and is vaporized from the melted metal or alloy into a substrate film supplied at a constant speed. Metal vapor is vapor-deposited on the substrate film, the thickness t of the obtained vapor-deposited metal is measured intermittently or continuously, and the value is compared with a set thickness t ₀ to obtain an error signal Δt = t−t ₀ . It is characterized in that it is calculated and negatively fed back at a feedback rate of 50% or less to control the vapor deposition film thickness within a target range. This introduces an appropriate damping resistor to allow quick adjustment to the setpoint and solve the problem of overshoot. However, when the feedback rate is 20% or less, the damping resistance is too large and it takes too long to correct the setting value. 50 feedback rate
When it exceeds%, overshoot occurs and adjustment to the target value becomes slow.

Alternatively, negative feedback is applied when the calculated error Δt is out of the target range of 30 to 70%. This eliminates the risk that the film thickness will deviate from the target range.
If negative feedback is applied in a range narrower than 30 to 70%, overshoot occurs. If negative feedback is applied in a range wider than 30 to 70%, the film thickness may deviate from the target range.

As a further alternative, negative feedback of the calculated error Δt is performed at intervals of 10 to 30 seconds. According to this method, the fluctuation of the film thickness becomes gentle, and at the same time, the necessary control can be achieved relatively quickly. If the distance is narrower than this, overshoe occurs. If the interval is wider than this, the control becomes slow. In addition,
The above three methods can also be used in combination with each other.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a vapor deposition apparatus 1 of the present invention. However, the illustrated portion is housed in a vacuum chamber (not shown) and has a predetermined exhaust device. 3 is a rotating drum that rotates in the direction of the arrow (or the opposite direction),
A base film 5 made of polyester or the like that constitutes the vapor-deposited base is passed around it, and wound around a winding roll 7 from a pay-out roll 9 through the peripheral surface of the rotary drum 3. A mask 11 is provided in the vicinity of the rotating drum 3 and a part of which is opened so that the vapor-deposited metal is not vapor-deposited on the film 5 except at a predetermined angle. A shutter 13 is provided along the outer surface (or inner surface) of the mask 11, and it is slid in the direction of the arrow at the beginning and the end of the deposition to block the opening of the mask 11 to prevent unnecessary deposition. Mask 11
The size of the opening is selected so that a predetermined vapor deposition width can be obtained on the film 5 in the axial direction of the rotary drum 3 and a predetermined vapor deposition angle θ can be obtained on the film in the circumferential direction of the rotary drum. . A gas supply nozzle 25 is arranged between the shutter 13 and the mask 11 to introduce a gas such as oxygen.

A crucible 15 made of high-purity magnesia (MgO) or the like is arranged so as to face the opening of the mask 11, and a raw material metal 17 to be vapor-deposited is charged therein. Crucible 1
5 is elongated in the axial direction of the rotary drum 3 by a length sufficient to obtain a required vapor deposition width. The width W of the substrate film moving along the plane of the rotating drum preferably has the above-mentioned relationship to the scanning length l of the electron beam scanning the crucible, whereby the thickness of the deposited film is changed to the substrate width. Can be constant in direction. The crucible 15 is arranged so as to obtain a predetermined vapor deposition angle θ (which slightly varies depending on the position in the opening of the mask). The raw metal 17 charged in the crucible 15 is heated by the electron beam 21 emitted from the electron gun 19. In the present invention, the electron beam 21 of the electron gun 19
The electron beam 21 is emitted in a direction forming an angle of about 90 degrees with respect to a line connecting the crucible 15 and the opening of the mask 11. This electron beam is bent about 90 degrees by the action of a magnetic field 23 by an appropriate condenser lens, a converging lens, and a deflection coil (not shown), and at the same time, it is converged into a small spot and collides with the raw material metal 17. Experiments have shown that a significant increase in power can be achieved compared to the conventional straight-ahead electron gun 19 'arranged at the position of the chain line in FIG.

Although the optimum angle of the minimum incident angle θ min differs depending on the use, especially Co or Co is used as a magnetic recording medium.
-If a Ni film is obliquely vapor-deposited on a base film such as polyester such as polyethylene terephthalate so that the direction of easy magnetization is oblique to the base, the minimum incident angle θmi
n is 10 ° to 60 °, preferably 20 ° to 50 °. Examples of the Co alloy include those described in Japanese Patent Publication No. 3-41897.

A specific operation example of the apparatus shown in FIG. 1 is as follows. The average minimum incident angle θ min is 30 degrees, and the average distance between the liquid surface of the crucible and the vapor deposition surface of the rotating drum 3 is about 300.
mm, the mask opening width is 500 mm, the vacuum chamber is evacuated to 1 × 10 ⁻⁵ Torr, and a polyethylene terephthalate film (PET) having a thickness of 7 μm is 100 to 2
Co-Ni alloy (80: 2) was run at 50 m / min.
The driving power of the electron gun 19 is 40 kV × (3 to 5 A) = 120 to 2 while intermittently supplying the pellet of 0) to the crucible 15.
It melts at 00 kW and vapor deposition is performed. Adjusting the film transport speed while keeping the electron gun power constant, the deposition film thickness is about 18
00 Å. Further, a gas material containing oxygen as a main component, which is introduced into the gas supply nozzle 25 at the time of vapor deposition, is appropriately adjusted to form a film so that equivalent magnetic characteristics can be obtained.

Next, referring to FIG. The thickness of the vapor deposition film is measured by the optical sensor 27 of FIG. 1 using the transmittance of the vapor deposition film. Measured thickness t calculates the error Delta] t = t-t ₀ as compared to the set thickness t _0. Such calculation is performed, for example, every 1 second sampling interval. If the error value is negatively fed back as it is, an overshoot occurs as shown by the curve A, and thus negative feedback is performed at a feedback rate of 50% or less according to the present invention. The negative feedback signal adjusts the current or voltage of the base film supply system by a controller (not shown) to adjust the base film supply speed. In this way, the vapor deposition film thickness can be regulated within the target range. When the feedback rate is 50% or less, overshoot is suppressed and the control shown by the curve B in FIG. 2 is obtained. At a feedback rate of 20% or less, for example, the target range was 1800Å ± 7% under the above specific vapor deposition conditions, and at a feedback rate of 50%, overshoot did not occur.

Referring to FIG. In this example, the error Δt =
t-t ₀ is an error Δ when the target range deviates from 30% to 70%.
By negatively feeding back t, the feed rate of the base film is controlled. According to this method, the possibility of exceeding the target range is substantially eliminated as compared with the previous example. For example, under the specific vapor deposition conditions listed above, the target range is 1800Å ± 7%,
When the negative feedback was applied at the moment when it deviated from 2.1%, the target range could be maintained at all times. Also, at a feedback rate of 50%,
No overshoot occurred.

Referring to FIG. In this example, the negative feedback of the error Δt is performed every 10 to 30 seconds to control the electron beam energy. For example, if sampling is performed every second and the error is immediately negatively fed back, an overshoot may occur due to a measurement error. Therefore, for example, a predetermined number of sample values are averaged, and the average error between the set value and this average value is calculated. Then, this is negatively fed back and used for control. According to this example, overshoot can be avoided and more stable control can be performed. For example, under the specific vapor deposition conditions listed above, the target range is 1800Å ± 7%, for example, 10
The sample values of the times were averaged, the average error between the set value and the average value was calculated every 10 seconds, and the negative film feedback was applied to adjust the supply rate of the base film, but no overshoot occurred. If ± 2.1% is not exceeded, negative feedback need not be applied. The feedback rate may be 50% or less.

Specific examples of the above are shown in Table 1. In addition, in the judgment items, double circles are those with extremely high stability, circles are those with good stability and no hindrance, triangles are occasionally undesirable because they occur occasionally, and marks x are those with poor stability.

[0021]

[Table 1]

[0022]

As described above, the present invention provides an excellent method for suppressing the fluctuation of the film thickness by finely adjusting the film substrate while keeping the electron beam energy constant.

[Brief description of drawings]

FIG. 1 is a schematic view of a vacuum vapor deposition apparatus to which the method of the present invention is applied.

FIG. 2 is a diagram showing control of a vapor deposition film thickness according to an embodiment of the present invention.

FIG. 3 is a diagram showing control of vapor deposition film thickness of another embodiment according to the present invention.

FIG. 4 is a diagram showing control of vapor deposition film thickness of still another embodiment according to the present invention.

[Explanation of symbols]

 1 Vapor Deposition Device 3 Rotating Drum 5 Base Film 7 Winding Roll 9 Feeding Roll 11 Mask 13 Shutter 15 Crucible 17 Raw Metal 19 Electron Gun 21 Electron Beam 23 Deflection Magnetic Field 27 Thickness Sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Otsuka 1-13-1 Nihonbashi, Chuo-ku, Tokyo Tea Decay Co., Ltd. (72) Masashi Higo 1-13-1 Nihonbashi, Chuo-ku, Tokyo DC Inc.

Claims (6)

[Claims] 1. A metal or alloy contained in a crucible is melted by an electron beam with a constant power, and a metal film evaporated from the metal or alloy is vapor-deposited on the base film while supplying the base film. and the thickness t of the deposited metal intermittently or to measure continuously, calculates an error Delta] t = t-t ₀ in comparison with its value set thickness t _0, negative the value the feedback rate of 50% or less A method for controlling the film thickness in vacuum evaporation, which comprises returning to control the supply speed of the substrate film to regulate the evaporation film thickness within a target range. 2. A metal or alloy contained in a crucible is melted by an electron beam having a constant power, and a metal film evaporated from the metal or alloy is vapor-deposited on the base film while supplying the base film. and the thickness t of the deposited metal intermittently or to measure continuously, calculates an error Delta] t = t-t ₀ by comparing the value set as the thickness t _0,. 30 to calculated error Delta] t is the target range A method for controlling the film thickness in vacuum vapor deposition, which comprises negatively feeding back an error Δt when the value deviates from 70% to control a supply rate of a substrate film. 3. A metal or alloy contained in a crucible is melted by an electron beam of constant power, and a metal film evaporated from the melted metal or alloy is vapor-deposited on the base film while supplying the base film. and the thickness t of the deposited metal intermittently or to measure continuously, calculates an error Delta] t = t-t ₀ by comparing the value set as the thickness t _0, the average value for each 10-30 seconds A film thickness control method in vacuum evaporation, which comprises negatively feeding back to control a supply rate of a substrate film to regulate an evaporation film thickness within a target range. 4. Negative feedback has an error Δt of 30 to 7 within a target range.
The film thickness control method in vacuum deposition according to claim 1 or 3, which is carried out when it is out of 0%. 5. The method for controlling the film thickness in vacuum vapor deposition according to claim 1, wherein negative feedback of the average value of errors is performed every 10 to 30 seconds. 6. The method for controlling the film thickness in vacuum deposition according to claim 2, wherein the negative feedback is performed at a feedback rate of 50% or less.