JPH0828329B2 - Thin film forming equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin film forming apparatus for forming a thin film by depositing a metal vapor on a substrate, and a thin film forming apparatus characterized by a controller for controlling a vapor deposition rate. Is.

[Prior Art] FIG. 3 is a schematic block diagram showing a conventional example of a thin film forming apparatus of this type. In the figure, 13 is a vacuum chamber, 19 is a power supply device, 20 is a vapor deposition rate measuring instrument, and 30 is an operation panel.

Inside the vacuum chamber 13, as shown below. A deposition source and a deposition target are incorporated. Reference numeral 1 is a crucible which also contains a metal 2 to be vapor-deposited and which also serves as a container for evaporating the metal. 3 is a small hole of the crucible 1 provided in an opening for taking in and out the metal 2. 4 is a metal ejected from the small hole 3. Steam, 5 is a bombarding filament used for generating electrons for bombarding (shock heating) of the crucible 1, 6 is an ionizing filament for generating electrons used for ionizing the metal vapor 4, and 7 is a grid (high potential) , 8 is an ion accelerating electrode (ground potential), 9 is a substrate holder, 10 is a substrate as a vapor deposition target, 11 is a vapor-deposited thin film, and 12 is a vapor deposition rate sensor. In addition, among the above-mentioned members, except the metal vapor 4, 1
The functional assembly of ~ 8 parts is the deposition source. And
The vacuum chamber 18 is evacuated by an exhaust device (not shown) so that it is kept at a high vacuum while the device is in operation.

In the power supply device 14, 14 is a bombard filament power supply for supplying a current to the bombarding filament 5, 15 is an ionizing filament power supply for supplying a current to the ionizing filament 6, and 16 is a bombardment emitted from the bombarding filament 5. Bombard power supply for supplying a voltage for energizing (accelerating) the electrons for use, 17 is an ionization power supply for energizing (accelerating) the electrons for ionization, and 18 is a metal vapor ion ionized by the ionized electrons in the metal vapor 4 ( (Not shown) is an ion acceleration power source for urging the substrate 10 toward the substrate 10.

Then, the voltage setting value or current setting value of each power supply in the power supply device 19 is configured to be output from the operation panel 30.

Next, the operation will be described. The bombarding filament 5 is heated by the bombarding filament power supply 14 and emits thermoelectrons. The thermoelectrons are accelerated by the voltage given by the bombard power source 16, and the accelerated electrons bombard the outer wall of the crucible 1 as bombarding activating electrons to heat the crucible 1 to a temperature higher than the melting point of the metal 2. To do. The metal 2 in the heated crucible 1 is melted, evaporated, and ejected from the small holes 3.

The temperature of the crucible 1 is increased by increasing the electron current of the above-mentioned bombarding energizing electrons, increasing the energizing energy (eV), or increasing both of them, and as a result, the gas is ejected. The evaporation amount of metal 2 increases. That is, the evaporation amount of the metal 2 is equal to that of the heated crucible 1.
Depends on the power applied to (P _B ).

Then, the metal vapor 4 ejected in the state shown by the dotted line in the figure is deposited on the substrate 10 with the thermal energy at the time of ejection, but a part thereof is released from the ionization filament 6 and is energized by the voltage of the ionization power supply 17. The ionization electrons collide with each other (not shown, but the electrons are accelerated to a predetermined energy eV higher than the ionization voltage of the atom of the metal 2) and ionized. The thermoelectrons emitted from the ionization filament 6 heated by the ionization filament power supply 15 are energized by the voltage of the ionization power supply 17, and the ionization electrons pass through the grid 7 to enter the space (ionization region). In the central region), the metal vapor 4 collides with atoms or polyatomic particles forming the traveling metal vapor 4, and the metal vapor 4 is ionized.

The ionized metal vapor ions (not shown) are accelerated by the high voltage of the acceleration power supply 18 applied between the grid 7 and the acceleration electrode 8 and collide with (reaches) the substrate 10 in the state of energized ions. Deposit and form a thin film 11 on the surface of the substrate 10.

At this time, metal vapor ions (including the metal vapor 4 described above)
The rate at which the metal is vapor-deposited on the substrate 10 is measured and displayed by the vapor deposition rate sensor 12 and the vapor deposition rate measuring device 20.

Further, the voltage or current value of each power source described above is set by the operation panel 30. That is, the operator changes the voltage command value or the current command value of the bombard power source 16 by looking at the display of the vapor deposition rate measuring device 20 (vapor deposition rate, that is, the thin film forming rate) to obtain a desired vapor deposition rate. There is.

[Problems to be Solved by the Invention] Although the conventional thin film forming apparatus as described above is generally widely used, its vapor deposition rate is affected by the ejection amount of metal vapor ejected from the crucible. Yes, and the ejection amount of this metal vapor depends on the heating temperature of the crucible. Therefore, the deposition rate changes depending on the condition around the crucible or the amount of metal in the crucible. For this reason, the deposition rate is not stable, so that not only the deposition time is not fixed, but also the quality of the deposition is affected. This invention was made to solve the above-mentioned problems. The purpose is to obtain a thin film forming apparatus with good quality.

[Means for Solving the Problems] A thin film forming apparatus according to the present invention melts a metal in a crucible placed in a vacuum at a high temperature by bombarding electrons into the crucible with energizing electrons, and from a small hole in the crucible. The deposition rate Rate at the bombarded power P _B of the thin film forming apparatus that ionizes the ejected vapor of metal and deposits it on the substrate is
It is expressed by a relational expression of αP _B ^β (where α is a coefficient that changes depending on the state of the apparatus). Using this relational expression, the vapor deposition rate feedback value with respect to the optimum vapor deposition rate setting value is compared, and this comparison value is set to the optimum vapor deposition rate setting value. When the value is out of the allowable range, the coefficient α is calculated, and from this result, the optimum deposition rate Ra
A control device is provided for calculating the bombarded power P _B in this state so as to obtain te, and outputting to the power supply device a current or voltage command value for obtaining the bombarded power corresponding to the change in the state of the device.

[Operation] In the present invention, when the feedback value of the vapor deposition rate obtained from the actual measurement of the vapor deposition rate measuring device changes with respect to the vapor deposition rate set value, based on the comparison result between the set value and the feedback value, An appropriate bombardment power for heating the crucible is calculated, and a current or voltage command value is output to the power supply device of the thin film forming apparatus based on the calculation result, and the temperature of the crucible is controlled so that the vapor deposition rate becomes constant. Therefore, a stable vapor-deposited thin film can be obtained.

[Embodiment] FIG. 1 is a schematic block diagram showing an embodiment of the present invention. In the figure, the same reference numerals as those of the conventional apparatus in FIG.

In the figure, 44 is a vapor deposition rate control device, 41 in this device is a comparator of the measured vapor deposition rate obtained from the vapor deposition rate measuring device 20 and the vapor deposition rate set value from the vapor deposition rate setting device 50, 42 is a comparator An arithmetic unit for the bombarded power calculated based on the output of 41, and 43 is an output device for the current or voltage command value to the bombarded power supply 16 obtained based on the calculation result of the arithmetic unit 42.

In the thin film forming apparatus shown in FIG. 1, the process and the operation until the metal vapor 4 is ejected from the small holes 3 of the crucible 1 and vapor-deposited on the substrate 10 to form the thin film 11 are shown in FIG. It is exactly the same as that explained in.

The feature of the present invention resides in the vapor deposition rate control device 44 and its control operation. Therefore, this control means will be described in detail below.

First, the current vapor deposition rate obtained by the vapor deposition rate measuring device 20 is one input of the comparator 41, and the set value from the vapor deposition rate setting device 50 is the other input. The comparator 41 compares the values of the two inputs described above, and outputs a calculation command if there is a difference.
The calculator 42 calculates the bombarded power based on this difference in the following procedure. The operation state will be described with reference to the schematic diagram of FIG.

(A) In this example, the relationship between the vapor deposition rate (Rate) and the bombard power (P _B ) of the target thin film forming apparatus is Rate.
= ΑP _B ^β (where α is a coefficient that changes depending on the state of the apparatus), and the vapor deposition rate (Rate) is proportional to the β power of the bombarded power (P _B ). Here, β is an experimentally determined constant when standard α is used. And
This coefficient α is calculated from the feedback rate of the control system.

(B) First, α in the initial state of the apparatus is α ₀ . That is, the coefficient α is determined so that the optimum bombardment power is P _B ^β with respect to the deposition rate setting value Rates.
Let α be α ₀ . This corresponds to the curve of Rate = α ₀ P _B ^β in FIG.

(C) If Ratef is fed back as the current vapor deposition rate when P _B is being output, Rates ≠
Ratef.

(D) Therefore, α that satisfies Ratef = αP _B ^β is set to α ₁ . This becomes the curve of α ₁ in FIG. Where Rate
f and P _B ^β are the current Rate and the current P _B , respectively.

(E) Then, from this curve of α ₁ (FIG. 2), Rates =
ΔP _B that satisfies α ₁ (P _B −ΔP _B ) ^β is obtained.

(F) Next, at the end of this operation (e), the power value (P _B −ΔP _B ) is preset. With this preset, the deposition rate of the set value Rate can be obtained.

(G) Thereafter, returning to the operation (c), the process is repeated to continue. At this time, as shown by the α ₂ curve in FIG. ₂ , Rates = α
₂ (P _B + ΔP _B ) ^β in some cases.

In this way, the comparator 41 and the arithmetic unit 42 constantly obtain the new coefficient α, obtain the ± ΔP _B equivalent to the difference between the set Rate and the feedback Rate, and output it to the output device 43.

Put the output device 43, when outputting a voltage command than _{(± ΔP B) = (±} ΔV B) (I B), while retaining the I _B as fixed data, calculated out a ± [Delta] V _B, a current command If from _{(± ΔP B) = (V} B) (± ΔI B), while maintaining a V _B as fixed data, which Motomede a ± [Delta] I _B. And
V _B ± ΔV _B (voltage command value) or I _B outputs a ± [Delta] I _B (current command value) to the bombardment source 16.

In this way, based on the measured value of the deposition rate, by adding a control device that makes the power supplied to the crucible variable,
By eliminating the temperature change of the crucible with respect to the change of the inside and outside of the crucible, a thin film forming apparatus with a stable deposition rate can be obtained.

Further, by introducing a β value simulating the actual in Rate = αP _B ^β used as the control function, it becomes possible to promptly obtain the optimum bombarded power P _B in feedback to the deposition rate. .

As described above, according to the present invention, the electric power supplied for heating the crucible to a high temperature is calculated based on the result of comparison between the vapor deposition rate set value and the vapor deposition rate feedback value, and the apparatus at that time is calculated. The optimum bombardment electric power is calculated in accordance with the above condition, and the voltage or current command value is output to the power supply device of the thin film forming apparatus based on this calculation result. Even if the temperature changes, the temperature of the crucible is controlled, the vapor deposition rate is stabilized regardless of the conditions inside and outside the crucible, the vapor deposition time is stabilized, and a high quality thin film can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a thin film forming apparatus showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the embodiment apparatus of FIG. 1, and FIG. 3 is a conventional thin film forming apparatus. It is a schematic block diagram showing. In the figure, 1 is a crucible, 2 is a metal, 3 is a small hole, 4 is a metal vapor, 10 is a substrate, 11 is a thin film, 12 is a deposition rate sensor, 13
Is a vacuum chamber, 19 is a power supply device, 41 is a comparator, 42 is a computing unit, 43
Is an output device, and 50 is a vapor deposition rate setting device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A metal in a crucible placed in a vacuum is melted at a high temperature by bombardment of energizing electrons to the crucible,
In the thin film forming equipment that ionizes the vapor of the metal ejected from the small holes of this crucible and deposits it on the substrate, the deposition rate Rate at the bombarding power P _B is Rate = α P _B ^β , where α changes depending on the state of the equipment. It is expressed by a relational expression of a coefficient, and by using this relational expression, the vapor deposition rate feedback value with respect to the optimum vapor deposition rate set value is compared, and when the comparison value is outside the allowable range of the optimum vapor deposition rate set value, the coefficient Calculate α, and calculate the bombarding power P _B in this state so as to obtain the optimum deposition rate Rate from the result. A thin film forming apparatus comprising a control device for outputting a command value for obtaining a bombarded power P _B corresponding to a change in the state of the device to a power supply device. 2. The thin film forming apparatus according to claim 1, wherein the control device outputs a voltage command value to the power supply device. 3. The thin film forming apparatus according to claim 1, wherein the control device outputs a current command value to the power supply device.