JPS639583B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical field) The present invention provides the following techniques when forming a multi-element alloy thin film:
This invention relates to a magnetron sputtering electrode that facilitates control of film composition and makes the composition uniform within the plane of a substrate. (Background Art) Conventionally, when manufacturing a multi-element alloy thin film using a magnetron sputtering electrode, there are two methods: using multiple sputtering electrodes, and attaching targets with different compositions to one cathode. There is. In the former method using a plurality of sputtering electrodes, raw materials sputtered from targets with different compositions with independently controlled sputtering amounts are alloyed onto a substrate. Conventional magnetron sputtering electrodes have a magnetic generation source built into the electrode, so they are larger than general sputtering electrodes. On the other hand, in order to make the composition uniform within the substrate plane, it is necessary to make the distance between each target as short as possible. However, since the conventional magnetron sputtering apparatus is large-sized, it has the disadvantage that it cannot satisfy the condition of shortening the distance between each target as much as possible. In the latter method, which combines targets with different compositions on one cathode, the only way to achieve compositional uniformity within the plane of the substrate is to rotate the substrate, and to further control the composition, it is necessary to change the substrate position. I needed to move it. Therefore, in this type of method, it is difficult to determine the position of the substrate to obtain the desired alloy composition, and in reality, it is difficult to precisely control the composition by mechanically moving the substrate. (Objective) The object of the present invention is to provide a magnetron sputtering electrode that solves these problems, allows easy control of film composition, and makes the composition uniform within the substrate plane. be. (Structure of the Invention) In order to achieve the above object, the present invention has the following features:
A plurality of targets whose amount of sputtering can be independently controlled are incorporated into one magnetic field generation source. According to this, the distance between each target can be shortened and an integrated electrode structure can be used to form the same plasma region. (Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the basic structure of a magnetron sputtering electrode having two coaxial magnetron targets as an embodiment of the magnetron sputtering electrode of the present invention, taken in a cross section parallel to the lines of magnetic force. Here, 11 and 12 are plate targets, and 13 is an electron reflecting plate. 14 is a grounded anode. 15 is an insulator. 16 and 17
are plate-shaped magnetic bodies for forming lines of magnetic force parallel to the target surfaces of targets 11 and 12, respectively, and their lower surfaces are connected to the N and S poles of the permanent magnets, respectively. Here, it is assumed that the position of the substrate on which the multi-element alloy thin film is formed is above the plane of the paper of FIG. Furthermore, V ₁₁ and V ₁₂ are
A DC power supply for adjusting the amount of sputtering is arranged between the target 11 and the anode 14 and between the target 12 and the anode 14 so that the voltage value can be independently controlled for each target. FIG. 2 is a perspective view showing the structure of the target section shown in FIG. In operating such a magnetron sputtering electrode, the magnetron sputtering electrode is placed in an inert gas atmosphere, and a gap is placed between the anode 14 and each of the targets 11 and 12 as shown in FIG. DC voltage to power supply V ₁₁ and
Apply independently from V ₁₂ . This voltage application causes a discharge to occur around each of the targets 11 and 12, and a plasma loop is formed with each target 11 and 12 as an axis. The formation of such a plasma loop is shown in FIG. 3 in a cross section perpendicular to the lines of magnetic force in the target section. Applying a negative voltage to each of targets 11 and 12 forms an independent plasma loop 31 and 32 around each of targets 11 and 12, respectively. The electrons in these plasma loops 31 and 32 move within a magnetic field parallel to the target plane and an electric field induced perpendicular to the target plane by an applied voltage according to the following equations of motion. d〓/dt=e/m(〓+〓×〓) Here, 〓: Velocity vector of electron e: Amount of charge of electron m: Mass of electron The electron according to this equation follows the trajectory 33 and Performs a trochoidal motion as shown in 34. In this example, the gap between the targets 11 and 12 was varied from 5 mm to 50 mm, but in this case, the in-plane composition of the substrate 35 was uniform, and the plasma loop 31 and 32 are independent, and the gap between the targets that can maximize the overlap of plasma loops is 20
It turned out to be mm. According to the present invention, since the gap between the targets can be made as close as 20 mm, it is clear that even if a plurality of targets are arranged, the magnetron sputtering electrode can be constructed in one piece. Furthermore, the substrates 35 of targets 11 and 12
We varied the opening angle θ from 180° to 90°, and found that in order to increase the overlap of the plasma loops as much as possible and increase the deposition rate,
= 120° was optimal. By being able to integrally construct a magnetron sputtering electrode having a plurality of targets in this way, the price per target can be reduced. Further, since the electrode structure can be made compact in this way, it becomes easy to design the composition to make the composition uniform within the plane of the substrate. Furthermore, since the plasma loops formed on each target are independent, it is clear that the amount of sputtering on each target can be controlled independently. Furthermore, it is expected that the plasma density will increase in areas where each plasma overlaps. Using the magnetron sputtering electrode of the present invention having the structure described above, according to the manufacturing conditions shown in Table 1.
Nb-Si alloy thin films were formed and the in-plane composition distribution and crystal phase determined by substrate temperature and Si concentration were investigated.

[Table] DC voltage for each target 11 and 12 -
200V was applied and the discharge current was 0.4A. Board 3
A Nb-Si alloy thin film with a thickness of 3000 Å was formed on 5.
The in-plane Si concentration (at.%) was evaluated using Auger electron spectroscopy. The substrate 35, each side of which is 25 mm, was divided into 10 equal parts, and the center of each division was used as the measurement point for the in-plane distance of the substrate, and the results are shown in FIG. Here, Si in the substrate plane
The concentration distribution is suppressed to within 1at.%, with a
22.5at.%Si and 17at.%Si on the target side
It was 22 at.%, 28 at.%, and 23 at.% on the Si target side. In the magnetron sputtering electrode of the present invention,
Plasma loops 31 and 32 formed around each target 11 and 12 are connected to the target 11.
Since the plasmas are overlapped in the space between the targets 11 and 12 and the substrate 35, even if there is a difference in plasma density between the targets 11 and 12, the plasma density will be uniform in the area where the plasmas are overlapped. become. For this purpose, Nb and Si coming from each target 11 and 12 are
elements are uniformly mixed in a space where the plasma overlaps. It is thought that this effect suppressed the Si concentration distribution within the substrate plane to within 1 at.%. FIG. 5 shows the identification of crystal phases by X-ray diffraction of various films fabricated using substrate temperature and Si concentration as parameters. Here, the film composition is determined by the sputtering amount of each target. Therefore, the amount of sputtering is proportional to the input power to each target (discharge voltage x discharge current: Vs·Is). Is
is determined by Vs, which in the case of magnetron sputtering is Is∝V ⁿ . Here, n is a parameter that depends on Ar gas pressure, and at 100 mTorr, it is approximately
It was 10. Therefore, the amount of sputtering is V ⁿ⁺¹
Since the film composition can be controlled by changing the value of the voltage applied to each target. In Fig. 5, below 21 at.% Si, an A15 single-phase film is formed, as shown by the white circle. In the 21 to 22 at.% Si region, as shown by the mixed white and black circles, it is a two-phase mixed film of A15 phase and Tetragonal phase with Ti ₃ P structure. At 22at.%Si or higher, as shown by the black circle,
It is a film of Tetragonal phase. When the substrate temperature decreases again, the film becomes amorphous, as shown by the double circle with a black circle on the inside. According to the magnetron sputtering electrode of the present invention, the gap between each target is narrowed, and the plasma formed around each target is overlapped in the space between the target and the substrate, so that the plasma in that area is Plasma density increases. Therefore, when the magnetron sputtering electrode of the present invention is used, a large amount of ion particles will flow into the substrate. does not exist in the equilibrium phase diagram
Synthesizing Nb ₃ Si films with the A15 structure is difficult, and when using a conventional sputter electrode, which is one of the non-equilibrium phase synthesis methods, the A15 phase cannot be obtained at 20 at.% Si or more. By using the magnetron sputtering electrode of the present invention, an A15 single-phase film up to 21 at.%Si can be obtained, and
A15 phase can be obtained up to 22at.%Si. The reason why the A15 phase was obtained at such a high concentration of Si is thought to be that a large amount of ion particles flowed into the substrate, which promoted the nucleation of the non-equilibrium A15 phase. FIG. 6 shows another embodiment of the magnetron sputtering electrode of the present invention, in which three targets are provided within the same magnetic field. In FIG. 6, the composition of target 51 located in the center is Nb ₃₈ Si ₁₇ , and the composition of targets 52 and 53 located on both sides thereof is Nb ₇₂ Si ₂₈ . The manufacturing conditions for the membrane were as shown in Table 1. A DC voltage of -200V and a discharge current of 0.4A were supplied to the target 51, and a DC voltage of -195V and a discharge current of 0.2A were supplied to the targets 52 and 53. A film with a thickness of 3000 Å is deposited on the substrate 35.
A Nb-Si alloy thin film was formed, and the in-plane Si concentration was evaluated using Auger electron spectroscopy. Board 3 with a side of 25mm
Figure 7 shows the results of dividing 5 into 10 equal parts and using the center of each division as the measurement point of the substrate in-plane distance. Here, the distribution of Si concentration within the substrate plane is suppressed to within 0.5 at.%, with 22 at.% Si at the center and 22 at.% Si at both ends.
It was 22.5at.%Si. (Effects) As explained above, according to the present invention, many types of alloy targets with different compositions can be constructed as a single electrode in a relatively compact manner, and the voltage of each target can be controlled independently. In this way, a film having a desired composition can be produced by making the composition distribution uniform within the film plane. In the above-described embodiments of the present invention, a plurality of targets are arranged so that each target surface is substantially parallel to the lines of magnetic force, but the present invention is not limited to these embodiments. A plurality of targets may be placed in the magnetic field so that the plasma loops overlap between the targets and the substrate, even if they are not parallel to each other, thereby making the plasma density uniform.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the magnetron sputtering electrode of the present invention having two targets, FIG. 2 is a perspective view showing the structure of the target portion thereof, and FIG. Figure 4 is a cross- _sectional view conceptually showing the discharge _state taken perpendicular to _the magnetic field of _the substrate. A graph showing the in-plane Si concentration, FIG. 5 is a phase diagram when substrate temperature and Si concentration are used as parameters, and FIG. 6 is a cross-sectional view showing another embodiment of the present invention in which three targets are arranged. FIG. 7 is a graph showing the Si concentration within the substrate plane in the example shown in FIG. 6 in which three targets are arranged. 11...Target, 12...Target, 1
3...Electron reflector, 14...Anode, 15...Insulator, 16...Permanent magnet, 17...Permanent magnet,
V ₁₁ , V ₁₂ ... DC power supply for sputtering amount adjustment,
31, 32...Plasma loop, 33, 34...
Trajectory of electron, 35...Substrate, θ...Target 1
Opening angle between 1 and 12, 51...Target (Nb ₈₃ Si ₁₇ alloy target), 52, 53... Target (Nb ₇₂ Si ₂₈ alloy target).

Claims (1)

[Claims] 1. A method comprising a means for generating a magnetic field, and a plurality of targets arranged within the magnetic field generated by the means, and each of which can independently control the amount of sputtering. Magnetron sputtering electrode. 2. The magnetron sputtering electrode according to claim 1, wherein each target surface of the plurality of targets is substantially parallel to the lines of magnetic force of the magnetic field. 3. In the magnetron sputtering electrode according to claim 1 or 2, the amount of sputtering is controlled by individually controlling the discharge voltage applied to the plurality of targets. A magnetron sputtering electrode characterized by: