JP2535734B2 - Conductive thin film deposition method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of burying and depositing a conductive thin film in fine recesses of a substrate.

(Prior Art) Embedding and depositing a conductive thin film inside a fine hole groove of a substrate is important for application to a multilayer wiring of an integrated circuit device. It is known that by using bias sputtering, which performs sputtering while applying voltage to the substrate or substrate holder, conductive thin films can be embedded and deposited in contact holes and through holes in the wiring of integrated circuit devices (Most (T.Mogami) In addition, solid-state devices and materials conference (Extended Abstracts of the 16th (1984 Internation
al) Conference on Soild State Devices and Material
s), Kobe, 1984, pp. 43-46).

(Problems to be Solved by the Invention) However, the present inventor has conducted a more detailed study and found that when the aspect ratio (ratio of depth to diameter or plane dimension) of fine holes or grooves becomes about 0.8 or more. It was clarified that the fine holes and grooves were not completely filled, and the cavities 16 remained in the deposited film 12 as shown in FIG. 2 (b). In conventional bias sputtering, the deposition of atoms and molecules sputtered from the target and sputter etching that occurs when sputter gas ions are accelerated by the substrate bias and enter the substrate surface occur simultaneously. There is. Sputtering gas ions are accelerated by the bias electric field on the substrate surface and are incident almost vertically on the substrate surface, but the atoms and molecules sputtered from the target are incident on the substrate surface in various directions, and are incident at an angle. It also has a large ingredient. Therefore, when a film is deposited on a fine hole or groove having a high aspect ratio by bias sputtering, as shown in FIG. 2 (a), as the film deposition progresses, an oblique incident component on the entrance (shoulder) of the fine hole is obtained. As a result, the lateral "overhang" shown in Fig. 14 grows, and the proportion of the deposited atoms and molecules incident in the micropores is increased by this "overhang". Decrease. Then, the "overhang" grows more and more, and the rate of incidence into the micropores further decreases, resulting in a vicious circle, which eventually blocks the micropore inlets and creates cavities in the deposited film as shown in Fig. 2 (b). It is thought to remain.

In addition, when a conductive film is deposited by applying a high bias voltage such that it is embedded in fine holes by bias sputtering, an inert gas ion such as argon, which is a discharge gas, is taken into the deposited film, It has also been found that the resistance of the deposited conductive film increases significantly. The generation of such cavities and the mixing of impurities cause a decrease in yield, a decrease in reliability, and a decrease in electrical characteristics (operating speed, etc.) of the circuit when the deposited film is applied to wiring of an integrated circuit device. Not preferable.

The present invention provides a novel method for depositing a conductive film on a minute recess, which solves the problems of the conventional method.

(Means for Solving Problems) The present invention is to ionize and accelerate a part of atoms and molecules evaporated from a molten conductive material, and to accelerate both the ionized atoms and molecules and non-ionized atoms and molecules. It is incident on a substrate having a minute concave portion with a sufficiently large aspect ratio on the surface from almost vertical direction, and the lateral sputter etching rate of the deposited film at the shoulder portion of the concave portion due to the impact of ionized atoms and molecules on the deposited film This is a method for depositing a conductive thin film, which is characterized in that the ionization rate and the acceleration energy of ions are selected so as to be higher than the lateral growth rate of the deposited film at the shoulder portion.

(Operation) In the method of the present invention, since atoms and molecules are incident from a direction substantially perpendicular to the substrate surface, the growth rate of the lateral “overhang” at the entrance of the micropores is small, and at the entrance of the micropores, The incidence rate is also high. Therefore, by setting the ionization rate and acceleration energy of atoms and molecules above a certain value determined by the material, etc., lateral growth at the micropore entrance is suppressed by the impact of ionized atoms and molecules, and " Can be prevented. Specifically, the ratio of ionized particles to the total number of incident particles that is greater than or equal to the reciprocal of the sputter rate of the deposited film due to ionized particles, or the ratio of ionized particles whose sputter rate due to ionized particles is greater than or equal to the ratio of the ionized particles to all incident particles. By using the acceleration energy, the lateral growth rate toward the center of the hole at the entrance shoulder of the hole can be made almost zero or a negative value. The sputter rate for determining the required ratio of ionized particles and the acceleration energy of ionized particles depends on the type of ion and the material of the deposited film, but the reported value of the acceleration energy dependence of the sputter rate (for example, R. Behris
ch edition 1981 Springer-Verlag issue "Sputtering by
Many results are summarized in a book entitled "Particle Bombardment I") or by using the acceleration energy dependence of the sputter rate obtained by experiments. Therefore, at the shoulders of the fine holes, as shown in FIG. 1, it is possible to form a taper in the direction in which the inlet is widened, so that a thin film can be embedded and deposited in the fine holes. Further, in the method according to the present invention, the conductive material can be evaporated in a high vacuum of about 10 ⁻³ Pa, and the ion bombardment for suppressing the lateral growth at the entrance of the micropores should also be deposited. Since the impurities are mixed into the deposited film very little, the electric resistance of the conductive thin film does not increase due to the problem of mixing impurities when bias sputtering is performed.

(Example) In an example of the present invention, an arc discharge type ionization vapor deposition apparatus having a schematic view shown in Fig. 4 was used. Using molybdenum (Mo) as the conductive material (vapor deposition material 40),
It is heated and melted in the vacuum chamber 45 by the electron gun 42 to be evaporated.
Arc power supply 46 to arc electrode 44 located near the electron gun
By applying a voltage of several tens of V, arc discharge is generated in the vicinity of the arc electrode 44, and a part of the evaporated molybdenum vapor is ionized. The molybdenum atoms 48 and the ions 50 are incident on the substrate 52. At that time, the molybdenum ions 50 are accelerated by the acceleration voltage applied to the substrate holder 54 by the acceleration power source 56 and bombard the substrate 52. Fig. 1 shows the width under the conditions of an accelerating voltage of −1.6 kV, an ion current density on the substrate of 6 mA / cm ² , and a film deposition rate of 15 Å / sec (the ionization rate of molybdenum atoms incident on the substrate is about 40%).
An outline of the cross-sectional shape of a sample in which molybdenum is deposited in a groove portion having a depth of 1.5 μm and a depth of 1.2 μm is shown. It can be seen that the molybdenum is uniformly deposited in the groove as compared with the case where the accelerating voltage shown in FIG. 3 is not applied and the case of the conventional bias sputtering shown in FIG. 2 (b). . The shape shown in Fig. 1 is
It was also possible to achieve acceleration voltages of −0.5 kV, −1 kV, and −3 kV. As described above, the reason why such a shape is obtained is that the lateral growth of the deposited film 12 at the step shoulder is suppressed by the ion bombardment. It is well known that etching by ion bombardment depends on the acceleration voltage and ion current density of ions, so by increasing the ion current density by methods such as increasing the ionization rate, the acceleration voltage is lower than -0.5 kV. Even with a negative bias, it is possible to obtain the cross-sectional shape as shown in FIG. Further, the electric resistance of the molybdenum thin film deposited according to this example was 8 μΩ · cm, which was about half that of the conventional sputtering with a high bias.

In the above embodiments, molybdenum was used as the metal material, but tungsten and aluminum were also effective.

(Effects of the Invention) By using the method of the present invention, it becomes possible to bury and deposit metal in fine recesses having a high aspect ratio on the surface of a substrate.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a sample in which a metal thin film is deposited in fine grooves on the surface of a substrate by the method of the present invention. Figure 2 (a),
(B) is a schematic cross-sectional view of the sample deposited by the conventional bias sputtering method, and FIG. 3 is a schematic cross-sectional view of the sample when the accelerating voltage is zero V in the ionization deposition. FIG. 4 is a schematic diagram of an arc discharge type ionization vapor deposition apparatus used in an example of the method of the present invention. The numbers in the figure indicate the following. 10 …… Substrate, 12 …… Deposited film 42 …… Electron gun, 44 …… Arc electrode 56 …… Acceleration power supply

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-193336 (JP, A) JP-A-50-63883 (JP, A) JP-A-51-31187 (JP, A) JP-A-52-1 103978 (JP, A)

Claims (1)

(57) [Claims] 1. A part of atoms or molecules evaporated from a molten conductive material is ionized and accelerated, and both the ionized atoms and molecules and the non-ionized atoms and molecules are fine on the surface and have a sufficiently large aspect ratio. The film is made to enter the substrate having the concave portion from a substantially vertical direction, and the lateral sputter etching rate of the deposited film at the shoulder portion of the concave portion due to the impact of ionized atoms and molecules on the deposited film is the lateral direction of the deposited film at the shoulder portion of the concave portion. A method for depositing a conductive thin film, characterized in that the ionization rate and ion acceleration energy are selected so as to be higher than the directional growth rate.