JPS5938307B2 - Method of forming metal compound film - Google Patents

Description

Detailed Description of the Invention The present invention provides a coating of metal oxide or metal nitride (hereinafter collectively referred to as "metal compound coating") on the surface of a substrate.
The present invention relates to a method for forming a non-stoichiometric metal compound film having an arbitrary composition ratio between a pure metal and a stable metal compound by reactive sputtering.

For example, in the field of semiconductor manufacturing, techniques for forming thin films of metal oxides or metal nitrides such as SiO2, Si3N4, Fe2O3, Cr2O3, etc. on the surface of Si substrates are very important.

Chemical vapor phase (CV) is a method for forming such a metal compound film.
D) method, vacuum evaporation method, and sputtering method, but the sputtering method is the most commonly used because it has the advantages of good adhesion, low thermal distortion and internal stress, and the ability to control the film thickness with high precision. has been done. Formation of a metal compound film by the sputtering method also includes an RF sputtering method and a reactive sputtering method.

The RF sputtering method uses various insulating materials made of metal compounds as sputtering targets, and performs sputtering by applying a high frequency voltage in an inert gas atmosphere such as argon (Ar). It is possible to form a metal compound film of. This is because sputtering is fundamentally different from vacuum evaporation methods, in that molecules ejected from the target are attached to the substrate as they are without decomposition (reduction, etc.). This property is particularly noticeable in the case of stable compounds. In addition, the reactive sputtering method uses a pure metal target and uses an inert gas such as argon (Ar) and active gases (O2, N
Sputtering is performed in an atmosphere mixed with NH4), and if parameters such as active gas partial pressure and applied voltage are at or above predetermined values, a film of a predetermined metal compound will be deposited on the substrate. However, in recent years in the field of semiconductor manufacturing, in order to diversify or improve the electrical properties of semiconductors, so-called non-stoichiometric compounds, which are unstable to some extent compared to ordinary stoichiometrically stable metal compounds, have been developed. Forming a film of a metal compound, that is, a film of a compound (ABx, where O<x<z) located in the unstable region of a stable compound (ABz) of a pure metal prisoner and its substance (B). are increasingly necessary. However, it is very difficult to form such a non-stoichiometric metal compound film by either the RF sputtering method or the reactive sputtering method described above.

That is, in the RF sputtering method, it is necessary to use a non-stoichiometric metal compound of the same quality as the desired coating as a target material, but this is extremely difficult. On the other hand, in the reactive sputtering method, the sputtering rate changes according to changes in parameters such as active gas partial pressure and applied voltage (that is, the composition ratio 6x1 in ABX changes), but the change characteristics are It is almost like a step response. That is, when the parameters change slightly around a certain value, the sputtering rate changes from a rate that forms a film that is almost pure metal (x+O) to a rate that forms a film that is almost a stable metal compound (x+z). Or, it has the characteristic of rapidly changing in a step-like manner to the contrary. Therefore, in order to form a film of a non-stoichiometric metal compound (ABx) with an arbitrary composition located in the intermediate region between a pure metal (4) and a stable metal compound (ABz), it is necessary to control the parameters with high precision. is necessary, but this is extremely difficult in practice. In addition, the reactive sputtering method has
In the DC voltage application type (DC type), a metal compound film is formed on the target surface, resulting in an extremely low sputtering efficiency (
In other words, in the case of dielectric materials, the surface becomes positively charged and is no longer susceptible to spatter. Therefore, an object of the present invention is to provide a method capable of forming a non-stoichiometric metal compound film having an arbitrary composition as described above with high accuracy and simply. In order to achieve the above object, the method of the present invention comprises setting at least two sputtering targets made of the same metal material in a single bell gear in an atmosphere containing an inert gas and an active gas (B). Different voltages are simultaneously applied to each target so that the sputtering rates of the targets are different from each other, and the substrates to be coated are alternately moved to face each target within the bell gear. By performing sputtering, a thin film close to a pure metal (4) and a thin film close to a stable metal compound (ABz) are alternately laminated in multiple layers on the substrate, resulting in an arbitrary layer of pure metal and stable metal compound as a whole. A film of a non-stoichiometric metal compound (ABx, where O<x<z) is formed in the intermediate region. That is, in the method of the present invention, thin films of pure metals and stable metal compounds, which are easy to form and whose sputtering parameters can be easily controlled, are alternately formed on a substrate in a laminated structure, and the resultant film is formed by the diffusion phenomenon between each thin film. A homogeneous non-stoichiometric metal compound coating can be obtained. A of metal compound ABx
(The composition ratio "x" with 5B can be changed arbitrarily by controlling the amount of each thin film attached.The present invention will be described in detail below based on one embodiment with reference to the attached drawings. FIG. 1 is a diagram schematically showing an example of the basic configuration of a sputtering apparatus used for carrying out the method of the present invention.

This apparatus has a target support 1 and a substrate holder 2 in a bell gear (not shown), and the interior of the bell gear is partitioned into two plasma chambers C1 and C2. The spark system in each plasma chamber is a planar magnetic field type (planar magnetron) DC two-pole system. The plasma chambers C1 and C2 are each equipped with a homogeneous pure metal material (S
i, Fe, etc.)
1 and T2 are set.

Furthermore, the atmosphere in the plasma chambers C1 and C2 is a mixture of an inert gas (Ar, etc.) and an active gas (02, N2, NH4, etc.). On the other hand, a large number of substrates 3 (indicated by dotted lines) on which metal compound coatings are to be formed are attached to the lower surface of the substrate holder 2, and by rotating the substrate holder 2 about the rotation shaft 4, each substrate 3 is sequentially transferred to the plasma chamber C1 and C2
, thus passing alternately over the targets T1 and T2. Hereinafter, a specific example will be described in which a film of SiOx (0x<2) having an arbitrary composition ratio between Si (5Si02) is formed on the surface of a Si substrate using the above-mentioned apparatus.

Targets T1 and T2 are made from pure metal Si. The atmosphere in the plasma chamber is a mixed gas of Ar and O2, and the composition and pressure in the plasma chamber are preferably set to arbitrary values in the following ranges (plasma chamber Cl,
C2 are both equal). Under such conditions, each plasma chamber C
When a target voltage is applied to C1 and C2, sputtering is performed in each plasma chamber according to the applied voltage.

Therefore, as shown in FIG. 2, based on the characteristic that the sputtering rate (vertical axis) of the metal compound SiOx changes almost stepwise with respect to the target voltage V (horizontal axis), the target voltage Vl applied to the plasma chambers Cl and C2 is changed. ,V2
are set as shown in Fig. 2, the plasma chamber C
In plasma chamber C2, a thin film close to pure metal Si is formed, while in plasma chamber C2, a thin film close to stable metal compound SiO2 is formed. Therefore, if the substrate holder 2 is rotated, the surface of each substrate 3 will be coated as shown in FIG.
A multilayer laminated structure film 5 of Si-SiO2-Si-SiO2... is formed. In general, the thickness of each thin film is set from several to several +
The substrate holder is operated at a rotation speed of 1 rotation/1 minute for about 60 minutes to form a film of about 120 layers. This coating 5 consists of adjacent Si, thin films and SiO.
Due to the diffusion phenomenon between the two thin films, a non-stoichiometric metal compound S whose composition substantially depends on the overall Si and O ratio is formed.
It becomes iOx. The composition ratio 6x'' is Si thin film and SiO
By appropriately changing the ratio of the adhesion amount of two thin films, O<X
It is possible to arbitrarily change the opening area ratio within the range of 2. For this purpose, for example, a method of providing an aperture (not shown) between the targets Tl, T2 and the substrate holder 2 and controlling the aperture area ratio is possible. It's simple.

In the above embodiment, different target voltages were applied to the respective plasma chambers to form the Si thin film and the SiO2 thin film, but the partial pressure of the active gas (02) in each plasma chamber was changed to Similar results can be obtained by applying pressure. As is clear from the above explanation, according to the method of the present invention, pure metal (4)
and the stable metal compound (ABz) (
x) with an unstable non-stoichiometric metal compound (ABx
) can be formed very easily and reliably,
Its technical and economic effects are significant.

Note that the method of the present invention is not limited to the field of semiconductor manufacturing as exemplified.
It is also widely applicable to many other fields.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an example of the basic configuration of a sputtering apparatus used to carry out the method of the present invention, FIG. 2 is a diagram showing the characteristics of SiOx sputtering rate with respect to target voltage V, and FIG. FIG. 2 is a cross-sectional view of a multi-metal structure film (Si-SiO2-Si-SiO2-...) formed on a substrate. In the figure, 1 is a target support, 2 is a substrate holder, 3 is a substrate, and 5 is a multilayer structure coating.

Claims (1)

[Claims] 1 At least two sputtering targets made of the same metal material (A) are injected into an inert gas and an active gas (B).
is set in a single bell gear with an atmosphere mixed with By performing sputtering while repeatedly moving the target to face each target, a thin film close to pure metal (A) and a stable metal compound (AB) are deposited on the substrate.
A non-stoichiometric metal compound (ABx, where 0<x<z) with an arbitrary composition ratio between the pure metal and the stable metal compound, by forming thin films close to z) alternately and in multiple layers. A method for forming a metal compound film, the method comprising forming a film of.