JP2011241451A - Film deposition method and sputtering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film deposition method which forms a high-quality film in a low-temperature process and which can freely control a nature of the film in a sputtering method and a sputtering apparatus.SOLUTION: In the film deposition method performed by a vacuum film deposition system using a sputtering method, sputtering plasma is used to decompose a target material, and ions are irradiated onto a deposition surface being deposited using a controllable surface modification plasma separately from the sputtering plasma.

Description

  The present invention relates to a method for forming a thin film using vacuum and plasma and a sputtering apparatus used for the film formation.

  A film formation apparatus using a vacuum can reduce impurities in the film and can form a high-quality film. In particular, the sputtering method is used in various industrial fields such as optical materials, semiconductors, flat panel displays and the like because of its simple system and high productivity.

  However, in order to obtain a high-quality film by a normal sputtering method, it is necessary to heat the substrate and promote migration on the surface of the substrate, and the film quality is limited by the heat-resistant temperature of the substrate used. In particular, when plastic is used for the substrate, the film quality cannot be significantly reduced.

  In order to solve this problem, film formation is promoted by accelerating the diffusion of plasma formed near the target surface to the vicinity of the substrate and promoting the action of the plasma on the thin film formed on the substrate by the so-called plasma assist effect. There is known unbalanced magnetron sputtering that lowers the temperature and increases the hardness of a hard film (Non-Patent Document 1).

  The unbalanced magnetron sputtering is characterized in that magnetic lines of force extending from the target toward the substrate are formed. As a result, ions formed in the vicinity of the target surface diffuse toward the substrate along the lines of magnetic force, but due to the non-uniformity of the lines of magnetic force, in-plane non-uniformity occurs in the irradiation of ions to the substrate, As a result, there arises a problem that the film quality becomes inhomogeneous. In order to solve this, a device such as making the vertical magnetic field distribution in the substrate plane uniform (Patent Document 1) has been devised.

JP 2000-282235 A

J. et al. Vac. Sci. Technol. A4 (2), pp 186-202, 1986

  In the unbalanced magnetron sputtering, since a part of ions formed near the target surface is irradiated to the substrate, it is difficult to adjust the ion amount as an essential problem. In other words, if the input power to the sputtering plasma for hitting the target is increased, the amount of ions increases, and if it is decreased, the amount of ions only decreases. Depending on the desired membrane conditions, it was not possible to introduce the optimum amount of ions.

  In addition, there is basically a problem of the vertical magnetic field distribution in the substrate surface, and although various devices have been devised to make it homogeneous, there is a need for labor to design the equipment, and in recent years industrialization has progressed. Insufficient to apply to size substrates.

  That is, in unbalanced magnetron sputtering, the amount of plasma ions irradiated onto the substrate is controlled by a magnetic field. Since the increase / decrease in the amount of ions irradiated on the substrate depends on the amount of ions generated at the target, it is difficult to control the optimum amount of ions on the substrate, and the distribution of ions irradiated can be controlled uniformly. It was difficult.

  In order to solve the above problems, the present invention provides a film forming method using a vacuum film forming apparatus using a sputtering method, wherein sputtering plasma is used to decompose a target material and is controlled separately from the sputtering plasma. A film forming method characterized by irradiating ions on the film formation surface during film formation using possible surface modification plasma was used.

  Here, it is desirable to use high-frequency plasma as the surface modification plasma.

  Further, it is desirable that the power source for generating the surface modification plasma is capable of precisely controlling the amount of ions and electrons irradiated on the substrate, such as the strength of the input power and on / off.

  In addition, in order to control the film quality of the material to be deposited, the power source that generates the plasma for sputtering is equipped with a mechanism that can precisely control the amount of material that is blown from the target to the substrate, such as the strength of the input power and on / off desirable.

  Furthermore, it is desirable to use a magnetron cathode for the sputtering plasma in order to increase the deposition rate.

  By using the film forming method according to the present invention, the sputtered particles that have reached the substrate and once adsorbed on the surface of the substrate can be given appropriate energy by the surface modification plasma and guided to a stable site, so that the quality is very good. A film can be formed, and the film quality can be controlled. In addition, since the surface modification plasma is formed so as to face the entire surface of the substrate on which the film is formed, a highly uniform film can be formed.

It is a schematic cross section which shows the sputtering device by this invention. It is a schematic cross section which shows the conventional sputtering device. It is the surface SEM image of Ti film | membrane formed into a film by the conventional sputtering method. It is the surface SEM image of Ti film | membrane formed into a film by the sputtering method of this invention. It is the surface SEM image of Ti film | membrane formed into a film by the sputtering method of this invention.

  Embodiments of the present invention will be described with reference to the following drawings. FIG. 1 is a schematic sectional view showing a sputtering apparatus according to the present invention. Here, first, the substrate 4 is placed on the substrate holding cathode 3 a in the vacuum chamber 1. Subsequently, after evacuating the inside of the vacuum chamber 1, an inert gas such as Ar gas is introduced, and direct current power is applied to the target material 2 by the direct current power source 22 to generate a sputtering plasma 32. In FIG. 1, the DC power source 22 is used to generate the sputtering plasma 32. However, the DC power source 22 is not necessarily required, and other power sources such as a microwave power source may be used as long as the power source can form plasma. .

  Then, separately from the sputtering plasma 32 for sputtering the target material 2, the surface modifying plasma 31 is formed to face the substrate holding cathode 3 a using the high frequency power source 21. As a result, the surface of the film is irradiated with ions during film formation, and the film quality can be controlled. Since the surface modification plasma 31 is formed on the entire surface facing the substrate holding cathode 3a, the ion irradiation amount is uniform and the film quality does not vary.

  Although not shown, it is desirable to use a shutter between the target material 2 and the substrate 4, and after the plasma is formed, the film formation is started after the shutter is released. If the surface modification plasma 31 is generated while the shutter is closed, a cleaning effect on the surface of the substrate 4 can also be obtained. However, the surface modification plasma 31 does not necessarily have to be generated before the shutter is released.

  In addition, since a small amount of ions are always present in the vacuum chamber 1 due to the presence of the surface modification plasma 31, the sputtering plasma 32 is always smooth even when intermittently generated by turning on / off the sputtering plasma 32 at a low process pressure. The rise of plasma generation is shown, and due to the consumption of the target material 2 or the like, an abnormality such as a time lag or no discharge is unlikely to occur.

  Since the surface modification plasma 31 is controlled independently of the sputtering plasma 32, the amount of ions irradiated on the surface of the substrate 4 can be arbitrarily selected. In addition, since the method of modulating the high frequency can be performed independently, the ratio of negative ions to electrons can be adjusted independently.

  This makes it possible to adjust the amount of ions appropriate for the material to be deposited and to obtain a thin film with a film quality suitable for the purpose. It is particularly effective for the film formation of amorphous semiconductors and superlattice materials because the film is grown at a high density while breaking the rough polycrystalline growth and flattening it.

  As a further advantage, in reactive sputtering in which a reactive gas such as oxygen gas or nitrogen gas is mixed in an inert gas to form a compound, the amount of reactive gas ions irradiated on the surface of the substrate 4 increases. The compound can be formed with a reactive gas partial pressure less than that of normal sputtering. In other words, the discharge becomes more stable because it becomes a condition in which compounding on the surface of the target material 2 is difficult to proceed.

  FIG. 2 is a schematic cross-sectional view showing a conventional sputtering apparatus. Here, since there is no surface modification plasma 31, the film quality on the surface of the substrate 4 greatly depends on the formation conditions of the sputtering plasma 32. Naturally, when the film quality of the film formed under the same sputtering plasma 32 formation conditions is changed, only the method of changing the temperature of the surface of the substrate 4 must be relied upon.

  FIG. 4 is a surface SEM photograph of a titanium (Ti) film formed using the present invention. At the time of film formation, Ti is used as the target material 2, the vacuum chamber 1 is evacuated, 10 sccm of argon gas is introduced into the apparatus, the pressure in the apparatus is set to 1.0 Pa, and 400 W direct current is applied thereto. Electric power was applied to generate sputtering plasma 32. Furthermore, high-frequency power of 13.56 MHz was applied to the substrate holding cathode 3a to generate the surface modification plasma 31.

  FIG. 4 is a surface SEM photograph of Ti formed with the high frequency power for forming the surface modification plasma 31 being 100 W.

  FIG. 5 is a surface SEM photograph of Ti formed with a high frequency power of 200 W for forming the surface modification plasma 31.

   Further, FIG. 3 is a surface SEM photograph of Ti prepared by a conventional sputtering method without using the surface modification plasma 31.

   From the photograph, it can be seen that the Ti crystal can be controlled by the formation conditions of the surface modification plasma 31.

  Further, as a result of measuring the volume resistivity of these films, the Ti film formed by the conventional sputtering method shown in FIG. 3 is 460 μΩ · cm, and the 100 W surface modification plasma 31 according to the present invention shown in FIG. The Ti film used was 158 μΩ · cm, and the Ti film using the 200 W surface modification plasma 31 according to the present invention shown in FIG. 5 was 84 μΩ · cm.

  It was found that the present invention can control not only the surface shape of the film but also the physical properties.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Target material 3a Substrate holding cathode 3b Substrate holding member 4 Substrate 21 High frequency power source 22 DC power source 31 Surface modification plasma 32 Sputtering plasma

Claims (7)

  A film forming method using a vacuum film forming apparatus using a sputtering method, wherein sputtering plasma is used to decompose a target material, and surface modifying plasma that can be controlled separately from the sputtering plasma is used. A film forming method comprising irradiating ions on a film forming surface in a film.   The film forming method according to claim 1, wherein the surface modifying plasma is generated by high frequency.   3. The film forming method according to claim 1, wherein at least one of a voltage and a current that are elements of a power source for generating sputtering plasma is periodically changed.   4. The film forming method according to claim 1, wherein the high frequency output used for forming the surface modification plasma is periodically changed.   A sputtering film forming apparatus using a sputtering method, comprising: a sputtering plasma power source used for decomposing a target material; and a plasma power source for surface modification that can be controlled separately from the plasma. apparatus.   The sputtering apparatus according to claim 5, wherein a magnetron cathode is used to generate the sputtering plasma.   The sputtering apparatus according to claim 5, wherein the plasma power source for sputtering is plural.