JPS58161993A - Production of thin film - Google Patents

Abstract

PURPOSE:To produce multielement thin films having desired compsn. destributions in a thickness direction by using a specific target electrode material, and moving the position of a substrate in the direction where the compsns. of the electrode material change within the plane parallel with the surface of the target electrode. CONSTITUTION:A target electrode 2 for sputtering wherein materials 4 of different compsns. are arrayed and combined successively by means of adhesive agents 3 on a flat plate and a substrate 5 which is supported with a holder 6 mounted with a heater 7 are provided in parallel in a vacuum vessel 1 which is provided with an introducing port 9 for an inert gas on the top surface and an evacuating port 10 on the side surface in the lower part. An inert gas is introduced into the vessel 1 through the port 9, and is controlled to a specified gaseous pressure. Voltage is then applied to the electrode 2 and the substrate 5 is moved by a moving mechanism 8 in the direction where the comspns. of the materials of the electrode 2 change within the plane parallel with the surface of the target electrode, whereby the multielement thin films having desired compsns. in the depth direction are formed.

Description

Detailed Description of the Invention The present invention uses a sputtering method that is easy to use industrially to realize an arbitrary composition distribution in the depth direction inside a thin film, and artificially controls the epitaxy mechanism of crystal growth of the thin film. Regarding how to.

The sphuttering method is a method in which atoms of a target material are blown out with activated inert gas atoms and deposited on a substrate to form a film, and is carried out in the following steps. First, 10""-1OTo of an inert gas such as
Under an atmosphere of RR, a desired material is used as a target electrode, and a high frequency (13.56 MHz) or DC voltage is applied to the target electrode. Here, the ionized and positively charged inert gas atoms collide with the target electrode surface, and the impact causes the electrode material atoms to fly out. This is deposited on a substrate opposite the target electrode to form a thin film of the desired material.

When forming a thin film of an alloy or compound using Sunotatsuta ring, it is common to use an alloy or compound with the same composition as the film to be formed as a target electrode, and even if the target electrode material is uniform, For example, the composition of the formed thin film is
It has properties that are almost independent of the number of times the thin film is formed or the conditions during sputtering. The uniformity of the composition in the Suffu tuttering method can be improved by electron beam evaporation method or Mol@cular method.
This is an industrial feature that is difficult to obtain with other methods such as the beam epitaxy method.

However, when it is desired to change the component ratio in the depth direction of the thin film to form a compositional distribution and control the epitaxy of the crystal growth of the thin film, the above-mentioned properties of the sputtering method become disadvantageous.

For example, in a thin film of a binary alloy of A and B atoms,
The film composition directly above the substrate is AxBl-x (0≦X≦l), and the surface portion of the film is Ax'B1-x'(0:ii;x'≦
1), it is necessary to form a constant composition in the depth direction of the film, but in order to do this with the normal sputtering method, for example, a target electrode consisting of M atoms and a structure of B atoms must be formed. In this method, two target electrodes are placed opposite to the substrate, and a co-spooling method is adopted in which the deposition rate of negative atoms from each target electrode is temporally controlled.

However, this method requires two sets of target electrode mechanisms and power supplies, and therefore requires modification or new design of the sputtering apparatus. Furthermore, in order to realize a compositional distribution in the arbitrary q depth direction in a film composed of m-hard elements, the co-sputtering method requires a 2-m-strong target electrode mechanism and a 2-meter-hard power source. , not economical.

The present invention provides a method for forming a thin film that solves these problems, and uses a composite material made by sequentially arranging materials with different compositions as a target electrode material for sputtering. By moving in the direction of compositional change of the target electrode material in a plane parallel to the target electrode surface, it is possible to fabricate a multi-element thin film having a desired composition distribution in the depth direction of the gland. It is something.

The present invention will be explained in detail below. FIG. 1 shows the basic configuration of an apparatus according to the method of the present invention. First, a water-cooled target electrode 2 and a substrate 5 are provided inside a vacuum chamber l. An inert gas inlet 9 is provided on the upper surface of the vacuum chamber l, and an exhaust port 10 is provided on the lower side surface. The target electrode 2 is made by bonding strip-shaped target materials 4 of different compositions onto a flat plate of Cu or the like using a high melting point solder or an organic adhesive 3. Therefore, the shape of the target electrode 2 is preferably rectangular (planar) rather than circular.

Next, the substrate 5 is placed parallel to the target electrode 2 and supported by a substrate holder 6. A heater 7 is installed on the substrate holder 6 as required. Further, the substrate holder 6 is provided with a moving mechanism 8 for moving the substrate 5 parallel to the target-pole plane along the arrangement direction of the strip-shaped target materials. It is desirable that the substrate moving mechanism 8 be able to move the substrate at any position and at any speed in order to freely change the composition distribution in the depth direction within the film.

Next, a method for imparting a composition distribution in the depth direction within the thin film in the above device configuration will be explained.

First, the case of a binary thin film composed of human element and B element will be explained. The target electrode is formed of N rectangular alloys, and the composition of the n-th alloy 4n from the top is AxnBl.
-:cn(0≦xn≦1.n=1゜2.3...., N
). Let L be the overall longitudinal dimension of the target electrode material 4, and M be the upper width. The width of the nit-th rectangular alloy is M, but the vertical dimensions may be arbitrary. To simplify the explanation here, the vertical dimensions of the rectangular alloy plates are all equal.
Suppose that it is L/N. Further, the substrate 5 can be moved in the vertical direction in FIGS. 1 and 2, that is, in the direction of composition change of the target electrode material 4, on a plane parallel to the target electrode 2 and spaced apart from the target electrode surface by j5D. Transfer of board 5) Straight line 1
8 desirably corresponds to the center line of the target electrode 2, as shown in FIG. Furthermore, as shown in FIG. 3, when the substrate is located at a position corresponding to the boundary between the n-th target alloy 1g and the n+1-th target alloy 11, this position is named n' position 17 of the substrate 5. Here, n' is a continuously changing number.

When an inert gas such as Ar is introduced into the vacuum chamber, the gas pressure is controlled at an appropriate constant level, and a voltage is applied to the target electrode 2, the target electrode material 4 starts to sludge. In a steady state, Mu atoms and B atoms fly out from the n-th alloy at a ratio of xn/(1-xn). However, because the atoms that fly out of the first alloy have a certain divergence angle, they mix with the nine atoms that fly out of the other alloys while in flight.

Therefore, the composition of the film formed on the movement of the substrate 5** is
It will have gradual changes.

Here, when the substrate 5 is kept stationary at the n' position, the composition of the film formed around the circle is x(n')B1-x(d) (0≦x(nr)
≦1, n' is a consecutive number). This value is based on the compositional arrangement format of the target alloy, the target-substrate spacing, and the
The composition X of the film deposited at each point on the substrate movement line must be determined experimentally because it changes depending on the stumbling conditions. Furthermore, in the case of alloys having different compositions, the amount of sputtered atoms generally differs, and the sputtered amount has a distribution within the target plane, so that the film deposition rate r (n') differs from place to place on the substrate movement line. Therefore r(n
') 4 It is necessary to experimentally determine V4V. This incorrect composition X(n') and the deposition rate r(n・) are obtained as a function B7 of n'.By moving the substrate 5, an A, B alloy ohm having a desired composition distribution in the depth direction is obtained. It becomes possible to obtain. Therefore, considering this point further, if the substrate is moved along the movement line at the speed of n' position, the composition of X(n') will change at n' position during time jt. A film of r(n'zΔ) is formed. Therefore, at a location where the thickness is a, the composition is !(n').

δ= f r(n') dt Here, B6 is the substrate position tt at the start of sputtering. That is, if we calculate δ(n) from the experimentally determined r (n') and the moving speed of the substrate T (n'), and eliminate I)-n by the experimentally determined x (n'), we get The compositional distribution x = f @) within the thin film is determined. From the above, in order to achieve the desired composition distribution within the thin film,
The composition distribution within the thin film as r(n') and x(n') may be planned in advance, and the moving speed of the substrate may be specified so as to realize the composition distribution. Let δ be the thickness measured from the substrate surface, and when realizing the composition profile that changes in the thickness direction: y = yψ) (2), the composition y (δ) when the film thickness is - is the thickness of the deposition at this time. Must be equal to the composition of no. That is, y(J) E−x(n')
(31 holds true. From equation (3), the pan head position n' where the substrate exists can be found as n'=f(δ) (4). Also, the deposition rate r at this time (n is the experimental By substituting equation (4) into the equation obtained, r(n')=g(
δ) (5) , can be found.

Also, at 9 o'clock when the film thickness becomes δ+Aδ, the film composition is changed to y
It is necessary to change from (δ) to y(δ) + (dy/dδ)Δa. To do this, move the substrate from n' position to n'+
By moving to position jn', the composition of the deposited layer is changed to x(
n+(dx/dn')Δn', (dy/
dδ) Δδ and (clx/dn') Δn' must be distributed. Therefore, the change in substrate position is. This is it, the board movement wJ speed vertical machining at n' position (n
') B is required. Here, dδ/at=g(δ): deposition rate.

Also, the time t required to form the film thickness δ is calculated as = h(δ), so from equation (7), δ can be expressed as a function of t = δ = h
−I(t) (8) By substituting equation (8) into equation (5) and t6), the substrate position at time t after starting t# is n' = f (h-'(t)).
In (9), the substrate moving speed at that time is given by. By specifically calculating the formula (9), GQ) and moving the substrate, a thin film having a desired composition distribution in the depth direction can be obtained. Actually Id t! ＞l
.

Since Equation 01 is a very complicated function, n' and ma can be specified and controlled using a microprocessor or the like. In addition, the composition profile can only be controlled between the maximum and minimum values of 9r (n') measured experimentally, and when controlling the composition range beyond that, the alloy composition used for the target electrode must be adjusted appropriately. Need to change. In Figure 4, y = y
An example of (δ) is shown below. Ultimately, AES (Auger
eletron 5pec-troscopy)
While etching in the J& depth direction, the formed nine composition profile and the planned profile are compared and corrected.

As explained above, according to the present invention, one thin jI
II! It becomes possible to produce a thin film having a constant composition distribution in the depth direction inside by sputtering.

For this reason, thin film epitaxial growth control such as the MBE method can be easily performed industrially. For example, A1
It is generally believed that superconducting thin films (Nb, Ge, etc.) made of compounds with a high transition temperature Tc structure (Nb, Ge, etc.) are formed using a polycrystalline self-epitaxial growth mechanism to form a high Te layer on top of the film. By changing the target composition with a constant slope in the depth direction, this growth mechanism can be actively utilized. Therefore, it may be possible to use it for the synthesis of A 15 Nb1Si, which is difficult to produce by conventional methods. Furthermore, the method of the present invention can be generally used for changing the magnetic anisotropy depending on the composition of thin films for magnetic devices, and for manufacturing superconducting devices by controlling electronic properties. The ripple effect is huge.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of a vacuum chamber according to the sputtering method of the present invention, Fig. 2 is a partial front view showing the relative position of the target electrode and the substrate, and the third factor is the target electrode and the substrate. FIG. 4 is a graph of the composition distribution in the thickness direction of the thin film produced according to the present invention. In the drawing, l is a vacuum chamber, 2 is a water-cooled target electrode, 3 is a composite target material fixing plate, 4 is a composite target material, 5 is a substrate 6 is a substrate holder, 7 is a heater for heating the substrate, 8 is a substrate moving mechanism, 9 is an inert gas inlet, 10 is an exhaust port, 1 is the nth target alloy, 11 is the n+1th target alloy, 17 is the n' position of the substrate, 18 is the straight line of movement of the substrate, and 1 is the linear composition change , B is a periodic step composition change. Patent applicant Nippon Telegraph and Telephone Public Corporation Patent attorney Shibu Mitsuishi (and 1 other person) Figure 1 Figure 2 Figure yP) Figure 3 Horse Figure 4

Claims (1)

[Claims] #7N! Materials with different compositions are used as sputtering target electrode materials in one direction! Using nine L combinations,
Thin film 01 characterized in that a multi-element thin film having a composition distribution in the depth direction of the film is obtained by sequentially moving the position of the substrate parallel to the target electrode surface in directions with different compositions.
1 method.