JPH0368759A - Thin film forming device - Google Patents

Abstract

PURPOSE:To improve the yields of optical parts, etc., by opposing a substrate to be vapor-deposited and a dished heater having a recess in a vacuum vessel and arranging an intermediate plate having plural holes in the recess of the heater away from its bottom. CONSTITUTION:The substrate 6 to be vapor-deposited is set in the vacuum vessel 10 through a strut 4 and a substrate support 5. The dished heater 2 (vaporizing dish) having a recess is opposed to the substrate 6 in the vessel 10. The intermediate plate 16 is provided in the recess of the heater 2 away from its bottom, and the plate 16 is pierced with many holes 15. A vapor- deposition material 1 is heated and vaporized. The film thickness is easily controlled with high precision by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thin film forming apparatus for forming so-called thin films such as antireflection films or partially transmitting films in optical products. The object of the present invention is to provide a thin film forming apparatus that can stabilize the evaporation rate of substances.

Conventional Structure and Problems Conventionally, a vacuum evaporation method has been used to form this type of thin film, and the vacuum evaporation method generally uses a structure as shown in FIG. In FIG. 1, the deposit 1 is placed in an evaporation boat (
The boat 2 is evaporated by directly heating the boat 2 with an electric current, etc., and the film thickness is controlled by opening and closing the shutter plate 3. When the shutter plate 3 is opened, the substrate support 6 fixed to the support column 4
The thin film is deposited on the substrate 6 supported by the evaporator to obtain a thin film depending on the purpose. At this time, consideration is given to keeping the evaporation rate of the deposit 1 constant by monitoring the thickness of the deposited film on the crystal oscillator 7 with a film thickness monitor 8 and feeding it back to the power supply 9 of the boat 2.

10 is a vacuum container installed on the pace 11, 12 is an exhaust hole formed in the pace 11, and the boat 2 is connected from the pace 11 to the electrode column 14 by an insulator 13. Yes, it is connected to power supply 9.

By the way, the conventional boat 2 is shown in Figures 2 (a) and (b).
As shown in the figure, it is formed into a dish shape, and the vapor deposit 1 is placed inside the dish. It has become.

When PbF2 powder is placed as the deposit 1 in such a boat 2 and a thin film is formed using the apparatus shown in FIG. 1, even if there is feedback from the film thickness monitor 8,
As shown in FIG. 3, it was difficult to keep the evaporation rate constant. FIG. 3 is a diagram showing the evaporation rate and the transmittance of the substrate to be evaporated with respect to the evaporation time. As can be seen from the figure, the evaporation rate is dependent on the elapsed time of the evaporation after the shutter is opened (time 0 minutes). It fluctuates over a wide range of ±3.5 people/sea and is extremely unstable. Therefore, the transmittance of the substrate to be evaporated is not stable, and the thickness of the thin film is also not stable, making it very difficult to control the film thickness.

Such instability in the evaporation rate was particularly noticeable when the deposit was a substance exhibiting sinterability, such as PbF2 powder. This connects the deposit 1 to the port 2 shown in Figure 2a, b.
If the deposit 1 is placed directly in the boat 2, the deposit 1 will be directly heated.As the deposition time progresses, evaporation and sintering (volume shrinkage) will occur from the contact area between the deposit 1 and the boat 2, and this will cause the deposit 1 to heat up directly. This is thought to be because the shape of the evaporated material 1 collapses and this is repeated, and the contact area between the vapor deposited material 1 and the boat 2 becomes larger or smaller and changes drastically.

Purpose of the Invention The present invention is directed to a thin film forming apparatus that improves the drawbacks of the conventional methods, has a stable evaporation rate of deposits, is easy to use, has high reproducibility, and can improve the yield of optical components, etc. The purpose is to provide the following.

Structure of the Invention In order to achieve the above object, the present invention provides a dish-shaped evaporation heating element having a recess, and a middle plate with a plurality of holes for indirect heating placed in the recess at a certain distance from the bottom surface. This is a thin film forming apparatus in which the evaporation substrate is placed opposite to the evaporation substrate.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 4(a) and 4(b) are a plan view and a sectional view showing an embodiment of a heating body used in the thin film forming apparatus of the present invention. In FIGS. 4(a) and 4(b), the heating body consists of a concave box-shaped boat 2 and a middle plate 16 having a number of holes 16 installed therein at a predetermined distance from the bottom surface. The deposit 1 is placed on the intermediate plate 16. Since the middle plate 16 is made to be about 10 mm smaller than the internal dimensions of the box-shaped boat 2, a gap 17 is created between the middle plate 16 with the hole 16 and the box-shaped boat 2.

In this state, it is installed in a vacuum apparatus 10 as shown in FIG. 1 in the conventional manner, and after evacuation, electricity is gradually applied to the nine box-shaped ports 2. The deposit 1 undergoes volumetric contraction (
sintering). By further increasing the current and raising the temperature of the box boat 2, the deposit 1 gradually begins to evaporate from the surrounding area including the bottom, and the box boat current is adjusted to maintain a constant evaporation rate. .

In this embodiment, the deposit 1 is an intermediate plate 1 with holes 16.
6 and the gap 17, the box-shaped boat 2, which is a direct heating element,
The evaporation rate can be easily controlled because the evaporation rate is uniformly heated by radiant heat from the surroundings and conductive heat from the perforated intermediate plate 16.

FIG. 6 is a sectional view showing another embodiment of the heating body according to the present invention, in which the deposit 1 is in a box-shaped boat 2 and the hole 1 is
It is placed on the middle plate 16 with 6 holes.

The middle plate 16 with the hole 15 is installed at a certain distance from the bottom of the box-shaped boat 2 by providing a protruding receiver 18 on the inner bottom of the box-shaped boat 2.

Furthermore, since the middle plate 16 with the holes 16 is made smaller by about 10% than the internal dimensions of the box-shaped boat 2, a gap 17 is created between the middle plate 16 with the holes 16 and the box-shaped boat 2. In this state, it is installed in a vacuum device, and after evacuation, the box-shaped boat 2 is gradually energized. The deposit 1 shrinks in volume as the box-shaped boat 2 is heated. By further increasing the current and raising the temperature of the box-shaped boat 2, the deposit 1 gradually starts to evaporate from the surrounding area including the bottom, and the box-shaped port current is increased so that the evaporation rate becomes constant. Adjust.

In this embodiment, the deposit 1 is directly applied to a box-shaped boat 2 which is a heating element between a middle plate 16 having holes 16 and a gap 17.
Intermediate plate 1 with holes 15 that does not come in contact with radiant heat from the surroundings
Since it is heated uniformly by the conductive heat from 6, it becomes easy to control the evaporation rate.

Next, specific examples of the present invention will be described. In this example, Zn5 was used as the material for preparing the carbon dioxide laser resonator.
A case where PbF2 is formed as an antireflection film on an e (zinc selenide) substrate will be described.

A Zn5e double-sided mirror-finished @layer plate was used as the substrate to be vapor deposited, and Pb F2 powder, which had almost the same conditions as the antireflection film, was used as the vapor deposition material. (Conditions for anti-reflection film: nt = R, nt
x df-λ/4. nf = refractive index of the film.

n8 = refractive index of the substrate, df = geometric thickness of the film, λ =
10.6 μm) Mo was used as a box-shaped evaporation boat, and the middle plate shown in FIG. 4(a) and <b) was installed in the boat using PT. The film was formed at a vacuum degree of about 10 Torτ and a substrate temperature of 1.10°C. FIG. 6 shows the changes in evaporation rate and optical film thickness at that time.

As can be seen from FIG. 6, in this embodiment, the evaporation rate is 8±0.5 A/sea after 1 minute has passed since the shutter was opened (time 0 minutes), compared to the conventional method shown in FIG. It is very stable compared to the evaporation rate of

Therefore, it can be seen that the transmittance of the substrate to be evaporated also shows a stable change with the passage of time, that the thin film is always formed at a constant thickness, and that the film thickness can be controlled very easily.

In this embodiment, PT was used as the intermediate plate 16, but other materials such as W, Ta, Mo, and other common materials used for resistance heating with good thermal conductivity can be used.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, as described in detail, a vapor deposited material is placed on a perforated intermediate plate placed in a recessed portion of a dish-shaped heating element at a distance from the bottom surface, and a vapor deposition substrate is placed opposite thereto. This thin film forming apparatus effectively utilizes the radiant heat from the dish-shaped heating element, and heats by both this and conductive heat from the middle plate, so the time lapse of vapor deposition is shorter than in conventional methods. The contact area with the heating element does not change greatly due to the evaporated material collapsing, but instead changes gradually, so the evaporation rate is kept constant and the film thickness can be controlled with high precision. The yield of optical parts, etc. can be easily improved.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a conventional vacuum evaporation apparatus, and Figure 2 (a
) and (b) are respectively a collapse diagram and a flat collapse diagram showing the evaporation boat used in the conventional thin film forming apparatus, and Figure 3 is a diagram showing the time change of M constant velocity and permeability in the conventional evaporation method. Fourth
Figures (a) and (b) are a plan view and a cross-sectional view, respectively, showing one embodiment of the evaporation boat used in the thin film forming apparatus of the present invention, and Fig. 5 is a cross-section showing another embodiment of the same evaporation boat. 6 are diagrams showing temporal changes in evaporation rate and permeability according to an embodiment of the present invention. 1... Vapor deposit, 2... Evaporation box boat, 3... Shutter, 4... Support column,
5... Substrate supporter, 6... Substrate to be deposited, 7... Crystal resonator, 8... Film thickness monitor, 9...・Power supply, 10... Vacuum container, 12... Exhaust hole, 16... Hole, 16
...Middle plate, 17...Gap, 18...
・・・Protruding receiver.

Claims (1)

[Claims] a vacuum vessel in which a substrate to be deposited is installed; a dish-shaped heating body having a recess disposed in the vacuum vessel facing the deposition substrate; 1. A thin film forming apparatus comprising: a middle plate arranged in a central plate and having a plurality of holes;