JPH03232959A - Production of thin film - Google Patents

Abstract

PURPOSE:To produce a thin film excellent in heat resistance and secondary emission ratio by subjecting a target consisting of (LaBa)B6 containing specific amounts of Ba to high frequency magnetron sputtering at specific discharge input voltage in a specific discharge gas atmosphere. CONSTITUTION:A thin film is produced on a substrate by using a high frequency magnetron sputtering method. In the method for manufacturing the above thin film, Ar having 6X10<-4>-2X10<-2>Torr pressure and >=about 99.9% purity is used as the discharge gas atmosphere at the time of sputtering. Further, as a material for sputtering target, an (LaBa)B6 sintered compact containing 0.01-30mole% Ba is used. Moreover, discharge input to the target at the time of sputtering is regulated to 1-4W/cm<2> energy density. By this method, the thin film excellent in electric properties and mechanical properties can be obtained. This thin film can be formed into a cathode material for electric discharge excellent in heat resistance and ion bombardment resistance and having high secondary emission ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a thin film of a cathode material for discharge, which requires a high secondary electron emission rate with excellent heat resistance and ion bombardment resistance.

[Prior art] As an example of conventionally using L a B e as a thin film electrode, J, J, Appl, Phys, 2B(10)p, 1
722-p, 1726 ('87), when a thin film is formed by electron beam evaporation, the electrical resistance is 5X1.
0'Ω・Cm (film thickness ≧ 600 nm), the weight ratio of La at that time is 69.9% (equivalent to LaB5.5), and the discharge characteristics are also better than the normal cathode (Ni) as shown in Figure 2. It has also been reported that it has quite excellent characteristics, allowing a large current to be extracted at low voltage. In addition, the secondary electron emission rate of L a B e differs depending on the crystal structure, and the thin film formed by electron beam evaporation has the highest secondary electron emission rate [
100] crystal orientation (work function: 2.4-3.9 eV). L a B e inherently has excellent electronic properties as described above, and is also known to have excellent chemical resistance and heat resistance (melting point: 2700°C).

In addition, when a sintered L a B e is used as a target and a L a B e thin film is formed by sputtering vapor deposition, it is in principle a high energy (electron temperature) vapor deposition method using ions, so it was formed by electron beam vapor deposition. It is generally known that thin films with superior adhesion can be obtained.

Next, the action of the conventionally formed L a B e thin film will be explained.

Electrode materials generally generate Joule heat based on the material's inherent resistance when energized, so first they must have low resistance to reduce heat loss in the electrode, and second, they must be heat resistant to ensure long life against heat generation. be excellent at;
Materials that have strong adhesion to the substrate to avoid disconnection due to peeling from the substrate, and materials that have excellent chemical resistance to withstand various processes have been considered optimal. In addition, as a discharge electrode material, it must act in such a way that secondary electrons are multiplied like an avalanche by ions formed by discharge based on initial electrons, and therefore it must have even higher ion resistance than the conditions of general electrode materials. There are additional requirements for materials with high impact resistance and secondary electron emission rate. La
Be is an ideal material that satisfies all of these conditions.

In order to use L a B e, which originally has a number of characteristics as described above, as an electrode, it is necessary to print it directly on a metal conductor pattern with a thickness that corresponds to the current density on the substrate, or on the substrate using a direct printing method or vapor deposition method. A method of patterning is generally used. By energizing the electrode pattern formed in this way, it acts as a simple electrode, and when the electrode is in the discharge space, it acts as a cathode that efficiently releases secondary electrons as the ions approach. act. Figure 2 (a) shows the Xe discharge gas pressure p and the cathode-anode distance d between the cathode and Ni anode, which were formed on a Ni pattern with a film thickness of 600 nm or more by heating the substrate to 300°C by electron beam evaporation. Figure 2 shows the results of discharging under conditions such that the product of ITorr-cm
b) showed similar characteristics with only Ni without LaB6 deposited, but it has been reported that the electrode with LaBe deposited has much better characteristics (J, J.

Appl, Phys, 2B(10)P, 1722-17
28 ('87)).

It has also been reported that when a thin film is formed by the above-mentioned vapor deposition method, a considerable proportion of the crystal orientation [100] is formed, so that the work function is further reduced, making it preferable as a discharge electrode.

Also, JP-A-64-81143 and JP-A-64-
No. 89242 discloses that a predetermined amount of Ba is added to L a B e.
It is disclosed that chemically stable properties can be obtained by forming the film by sputtering vapor deposition with the addition of .

[Problems to be Solved by the Invention] However, when forming L a B 6 using the conventional printing method, a small amount of glass frit is added to the L a B e powder to maintain adhesion to the substrate. A baking process is required at the melting temperature of the glass frit. In the case of this method, there was a problem in that the printed surface was difficult to become flat and the surface had to be polished to the depth of escape of secondary electrons (several tens of people). In addition, depending on the firing conditions, L a B e
There was also the problem that it was quite difficult to handle, such as the resistance of the membrane increasing.

On the other hand, when forming by electron beam evaporation, there are problems in that it is difficult to mass-produce and to form a homogeneous large-area thin film due to the convergence nature of the beam. Furthermore, when forming with this method, binary system vapor deposition (preparing and simultaneously vapor depositing each material of La and B) is required to control the stoichiometric composition, and the material itself must be vaporized. There were also problems in film formation, such as chemical stability (La is highly reactive with water vapor and oxygen) and poor uniformity of the film over the entire deposition surface.

Furthermore, it has been reported that when this problem is ignored and electron beam evaporation is performed using a single evaporation source (directly using LaB6), the stoichiometric composition ratio is not sufficiently controlled.

Furthermore, in order to solve these problems,
When a sputtering vapor deposition method is used to form a film as disclosed in JP-A-4-81143 and JP-A-6489242, mass production and formation of a large-area thin film are possible, and the stoichiometric Although it is possible to control the chemical composition ratio, there is still a problem in that it has not reached a sufficient level from the viewpoint of the secondary electron emission rate inherent to the material.

This invention was made in order to solve all of the above problems, and the target has even better secondary electron emission characteristics (L a B a ) without impairing the above physical properties.
) We developed a manufacturing method that uses a B+3 target and forms a film using the sputtering method to form an electrode that is superior to conventional electrodes in all respects, including heat resistance, secondary electron emission rate, and adhesion to the substrate. The purpose is to provide.

[Means for Solving the Problems] A method for producing a (LaBa)Be thin film according to the present invention includes the steps of a radio frequency (RF) magnetron sputtering method.
Ba is 0.01 to 30m.

Using a (L a B a) Be target doped in a range of 1%, a discharge power of 1 to 4 W/cm2 was set in an Ar gas atmosphere with a purity of 99.9% or higher, and the Ar pressure at that time was set to 6X10= or 2×10 −2 Torr.

[Function] The method for producing the (L a B a) Be thin film in this invention is similar to other forming methods by depositing in an Ar gas atmosphere at a discharge power of 1 to 4 W/am2 using the RF magnetron sputtering method. In addition, a film with a more homogeneous and uniform thickness is formed, and by controlling the Ar atmosphere during vapor deposition 4 in the range of 6×10 to 2×10, the atomic ratio B/
(LaBa) is controlled to be near 6, and as shown as the shaded area in FIG. 2(c), B in (LaBa)Be
The amount of a added is o.

By limiting the content to a range of 1 to 30 mol %, it becomes possible to form a high current density thin film cathode with an extremely high secondary electron emission rate.

[Example 1] Hereinafter, an example of the present invention will be described based on the drawings. 1st
In the figure, the horizontal axis indicates the composition of the thin film in case 1 when the discharge Ar gas pressure is set in the range of 10 to 10-4 during vapor deposition by RF magnetron sputtering using a (L a B a) Be target. It is a diagram in which the ratio B/(LaBa) is selected as the vertical axis and measurement points are shown.

In the figure, the atomic ratio B (L a B a) of the thin film is 6.
The closer the atomic ratio is to 6, the better the properties are in heat resistance, ion bombardment resistance, and secondary electron emission characteristics.The further the atomic ratio is from 6, the more excess atoms form oxides and precipitate at grain boundaries, increasing the electrical resistance. However, the performance as a cathode deteriorates. It can be seen that this tendency is more pronounced in the region where the atomic ratio is smaller than 6. Looking at Figure 1 from this perspective, there is a practical range in which the atomic ratio B/(LaBa) is in the range of 5.8 to 6.5, and the Ar gas pressure used in the RF magnetron sputtering deposition method at that time exists. is 6X10
' to 2×10 −2 Torr.

Next, a specific example will be shown. The pressure of Ar, which is the vapor deposition atmosphere, is 1
The physical properties of the (LaBa)B thin film deposited at a discharge energy density of 1 to 4 W/cm2 to the target in the range of 0-3 to 10' Torr are that the composition of the thin film is almost uniform and the electrical resistivity is stable even in the atmosphere. shows a minimum value (on the order of 10'), and the composition of the thin film is B/(
LaBa)-6, and a thin film with excellent properties as an electrode material could be obtained.

A similar demonstration was carried out using Ar pressure of 6X10 for sputtering deposition.
-'~2X10-. As a result of conducting experiments while changing the pressure within a range of 2 Torr, it was confirmed that the same tendency could be obtained within a practical range without excess metal being oxidized in the atmosphere.

In this example, we have described the deposition atmosphere, the electrical resistance and composition ratio of the thin film, but the thin film deposited within the range of the above example has maximum adhesion to the substrate, and the internal stress of the thin film is also reduced. and exhibits many excellent physical properties.

Furthermore, as shown in FIG. 2(C), in the RF sputtering vapor deposition method, the Ar gas pressure is limited to the range of 6×4 10 to 2×10 −2 Torr, and (
When experiments were conducted by changing the amount of Ba added in the L a B a ) B e target, the amount of secondary electron emission increased as the amount of Ba increased, resulting in the characteristics shown in Figure 2 (c).
If the amount of Ba added is less than 1 mol% of Q, no addition effect will be observed, and if it exceeds 30 mol%, the adhesion as a film will decrease and the stability against oxidation in the atmosphere will decrease. Addition amount is 0.01~30m
It was found that ol% was within the appropriate range.

In this example, the thin film electrode material has been described. The thin film containing Ba has a golden color and is superior in chemical resistance, heat resistance, conductivity, etc. It has some advantages as a material, and can be applied to these fields.

[Effects of the Invention] As described above, according to the present invention, in the sputtering vapor deposition method, the amount of Ba added as a target is 0.01
~30 mol% (L a B a
) Using Be sintered body, Ar pressure was set to 6X10~2
By introducing in the range of X10-2 Torr, it is possible to obtain a thin film with excellent electrical and mechanical properties.

[Brief explanation of drawings]

1 Figure 1 shows the relationship between the Ar pressure during RF sputtering deposition and the atomic ratio B/(La
Figure 2, which shows the relationship between Ba), is an explanatory diagram of physical property evaluation. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a thin film manufacturing method for forming a thin film on a substrate using high frequency magnetron sputtering method, the discharge gas atmosphere during sputtering is 6×10^-^4 to 2×
Using Ar with a pressure of 10^-^2 Torr, 0.01% Ba was used as the sputtering target material.
A method for manufacturing a thin film, characterized in that (LaBa)_9_4B_6 (atomic ratio) containing 30 mol% to 30 mol% is used, and the discharge input voltage to the target during sputtering is 1 to 4 W/cm^2.