JP2660044B2 - Manufacturing method of evaporated thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) Use relating to all electronic devices using a single crystal thin film.

(Prior Art) Many attempts have been made to convert a polycrystalline thin film into a single crystal thin film. In the case of silicon, ZMR Zone Melting Recrystaization using a laser beam, an electron beam, or a graphite heater, or a lateral solid phase epitaxy (L-SPE Lateral Solid)
Phase Epitaxy), and many other attempts are currently being made.

However, a method of performing heat treatment at a high temperature is not suitable for manufacturing a three-dimensional IC. This is because the high-temperature heat treatment changes the characteristics of the MOS transistor already formed.

In addition, the crystallization speed is extremely slow in low-temperature processing such as L-SPE. For example, at 600 ° C., about 10 ⁻⁸ cm / sec,
It cannot be put to practical use.

In order to increase the speed of single crystallization, irradiation with high-energy ions has also been attempted to increase the density of vacancies contributing to crystallization, but the growth rate has not been significantly improved at low temperatures. For example, the growth rate when irradiated with 0.6 megaelectron volt neon ions at 400 ° C. is 20
0 angstrom / 10 ¹⁶ ions / cm ² .

As other L-SPE improvement measures, addition of impurities has been attempted, but only about an order of magnitude improvement has been achieved. Also,
The quality of the resulting single crystal is not very good, and the density of lattice defects is large.

(Problems to be Solved by the Invention) In order to make a three-dimensional IC, the orientation of the thin film single crystal must be freely controllable regardless of the properties of the substrate. The single crystal must be grown at a low temperature so as not to affect the characteristics of the underlying MOS transistor already formed. These requirements are necessary not only when creating an active matrix for a display panel but also for a three-dimensional IC.

(Means and actions to solve the problem) Due to the requirement of low temperature, it is optimal to make a single crystal thin film by vapor deposition, but only a polycrystalline thin film with a fine grain size that cannot be used by a normal method. I can't get it. Therefore, it is an object of the present invention to irradiate a deposition surface with an electrically neutral atomic beam having low activity when depositing a thin film, and to use the effect of the irradiation on the crystal structure to enlarge single crystal grains. It is.

When the same substance as the single crystal is deposited on the single crystal, the single crystal grows epitaxially thereon as long as the surface is cleaned, the degree of vacuum is improved, and the substrate temperature is maintained at a certain level or more.

On the other hand, when vapor deposition is performed on an amorphous substrate, no matter how the surface is cleaned, the degree of vacuum is improved, and even if the substrate temperature is increased, a single crystal does not grow and many granular particles are initially formed. Crystal nuclei are formed on the substrate surface, and crystals grow from the crystal nuclei.

Since the crystal orientation of this crystal nucleus is determined by the atomic arrangement on the substrate surface, the crystal orientation of the crystal nucleus becomes disordered on an amorphous substrate where the atomic arrangement is disordered, and the grown film becomes polycrystalline.

In order to make this film a single crystal, of crystal nuclei having disordered crystal orientation, only crystal nuclei having a desired crystal orientation are further grown by vapor deposition, and the growth of other crystal nuclei is suppressed. good.

Generally, when the deposition surface during deposition is irradiated with inert gas ions or neutral atoms of inert gas, the plane perpendicular to the irradiation direction becomes the densest crystal plane, which is known as Bravais' law. . However, it generally does not become a single crystal,
It is a set of microcrystals rotated by an arbitrary angle in the densest crystal plane.

Using this rule, a relatively large single crystal grain can be obtained by irradiating with a neutral atom beam of a low-energy inert gas from a direction perpendicular to a plurality of independent densest crystal planes of a single crystal having a desired crystal orientation. I can do things. In general, it is said that the energy of the deposited atoms or molecules is preferably about 10 electron volts in order to grow a crystal having few distortions and lattice defects.

However, the energy of the evaporant evaporating from the crucible is less than several electron volts, and the energy is insufficient. Also, particles sputtered from the cathode have an appropriate energy, but contain a high-energy positive and negative recoil ion flow, so that the deposited film has many lattice defects and high-quality crystals cannot be obtained. Further, in the ordinary sputtering method, since the electron charge on the substrate surface is used to extract the ion flow from the plasma, there is a restriction that the ion flow must be perpendicular to the substrate surface.

A method of irradiating a deposition surface with a low-energy ion stream to improve the film quality of a deposited thin film has been reported for a long time. However, all the examples reported so far are deposition from one direction or irradiation with an ion beam, and the crystal of the formed film is still polycrystalline even if the direction of the crystal is uniform. In addition, when the energy is low, the flow of ions diverges due to the electrical repulsion of ions, and it is impossible to create a parallel flow, and the limit is about 200 electron volts. Further, when an attempt is made to form a vapor-deposited thin film on an insulating substrate by this method, electric charges are accumulated on the insulating substrate and ion particles do not reach.

However, irradiating the deposition surface with a neutral atomic flow of an inert gas can eliminate all of these disadvantages. To create a neutral atom stream of inert gas, create an ion stream of an inert gas with an appropriate energy value, for example, 600 electron volts, and apply this ion stream to a target made of a vapor-deposited substance and make it bounce. At the same time as neutralizing, the momentum, and hence the energy, greatly decreases according to the law of perfect elastic collision. In order to remove the remaining positive and negative high energy particles, an electric field which decelerates these particles may be provided in the path of the recoil beam.

A plurality of neutral atom flows of the inert gas are created by the above-described means, and these flows are arranged so as to be perpendicular to the densest crystal plane of the single crystal having a desired crystal orientation, and irradiate the deposition surface. The problem-solving method of the present invention is to increase the size of the crystal grains.

Example 1 FIG. 1 is a diagram showing an example of a thin film forming method using the present invention.

(11) is a silicon single crystal substrate having a thickness of 0.5 mm, which is provided on a surface of a silicon oxide film (12) having a thickness of 5000 Å by thermal oxidation. (15) is a cage-type ion source, into which argon gas is introduced from a conduit (14), ionized plasma is generated therein by an electron beam, and only argon ions are extracted by an extraction electrode to form an ion beam.

The diameter of this cage type ion source (15) is 10cm,
Argon ions can be accelerated to 200-600 volts, and their current density is 1-9 milliamps / cm ² . The target (17) is irradiated at an incident angle of 45 degrees by this argon ion beam. This target is a silicon single crystal plate having a diameter of 15 cm, and the crystal plane of the target is (1,1,1). The silicon sputtered from this target and the recoiled argon atoms are aligned, and pass through a filter (16) for removing undesired high-energy charged particles. Reach the plane. (13) is a heater for heating the substrate, which can raise the substrate temperature to 600 ° C.

The filter (16) is formed of a normal (wave) type molybdenum plate, and has a whole shape as shown in FIG. 2 (a). FIG. 2 (b) shows a method of forming a molybdenum plate having a normal (wave) shape and an incident direction of an ion beam. FIG. 2C shows a cross section of a normal (wave) type molybdenum plate in which silicon (42) is vapor-deposited on both surfaces of the molybdenum plate (41) so that the molybdenum is not exposed. .

Fig. 2 (a) shows a stack of 20 of these molybdenum plates. Fig. 2 (a) shows a flow of an inert gas between the molybdenum plates, the direction of the gas flow is aligned, and the potential of this filter is set to a silicon target ( In the same way as in 17), high-energy charged particles are removed or neutralized.

The area of the filter is 10 × ¹⁰ cm ² , the length is 15 cm, and the height of the normal (wave) shape is 0.5 cm.

The flow of the particles passing through these filters is applied to the deposition surface of the substrate at an angle of 35.5 degrees with the normal to the substrate surface. Generally, sputtered silicon has a distribution peak at 3 electron volts, with an energy distribution having an average energy of 10 electron volts. The energy of the recoiled argon ions is 3% of the energy of the incident argon ions, and the variance is small.

The energy of argon ions hitting the deposition surface of the substrate is 25
Above electron volts, the deposited silicon is sputtered in reverse. Also, it is said that if it exceeds 12.9 electron volts, the ion bombardment deteriorates the periodicity of the crystal lattice. At less than 12.9 electron volts, dense crystals grow.

When the acceleration voltage of the ion source is set to 400 volts and the silicon target is sputtered, the sputter yield becomes
At about 0.3, the energy of recoil argon ions is 12 electron volts. In the arrangement shown in FIG. 1, when the deposition is performed while maintaining the temperature of the substrate at 400 ° C. under such conditions, the growth rate of the film becomes 50 Å / min, which is a relatively large value of tens to hundreds of microns. Large crystal grains could be obtained.

As for the orientation of the crystal grains, it was confirmed by X-ray diffraction that the plane perpendicular to the flow of the particles incident on the substrate was the (1,1,1) plane.

By the method described above, a thin film of relatively large crystal grains can be formed not only on a silicon crystal substrate but also on another insulating substrate, and at a low temperature, the material and structure of the substrate are relatively unrestricted. In addition, since the crystal orientation can be controlled, it is effective for a three-dimensional LSI manufacturing process.

Embodiment 2 FIG. 3 is an explanatory view showing a second embodiment of the present invention.

(21) is a silicon single crystal substrate having a heat of 0.5 mm, which is provided on the surface of a 5000 mm silicon oxide film (22) by thermal oxidation. (25) is a cage type ion source, conduit (24)
, A nitrogen gas is introduced therein, and ionized plasma is generated therein by an electron beam, and only nitrogen ions are extracted by an extraction electrode to form an ion beam. The target (27) is irradiated with the ion beam at an incident angle of 45 degrees.
This target is made of boron metal, and the boron and nitrogen atoms sputtered from this target pass through a filter (26) for aligning the same direction as in Example 1, and unnecessary charged particles are removed. Reach the substrate surface.

Unlike Example 1, the surface of this filter is covered with a boron film. The dimensions are the same as those of the filter (16) of Example 1, but the material is as shown in FIG. 4, and both sides of a normal (wave) type molybdenum plate (52) are covered with boron (53). It is not exposed.

The energy of the ions created by the ion source (27) is
300 electron volts, current density 5 mA /
It is cm ^2. When reflected by the target, the energy of the nitrogen ions drops to about 4%, and the target sputter yield of boron is about 0.3. Further, Example-1
The difference is that the substrate is incident at an angle of 55 degrees with respect to the substrate normal, and the deposition surface is oriented at (1,1,1).

Also, in the figure, (29) is a crucible for electron beam evaporation of boron, (30) is molten boron, (31) is a hot cathode for electron beam generation, and these were used to increase the film forming speed. .

Under these conditions, when the substrate temperature is set to 400 ° C. and evaporation is performed in combination with an electron beam evaporation apparatus, an evaporation rate of 100 Å / min is obtained, and a cubic having a size of tens to hundreds of microns is obtained. Crystalline boron nitride crystal grains were obtained.

According to x-ray diffraction, almost no wurtzite-type and hexagonal crystals were observed.

(Effect of the Invention) By using the present invention as described above, a single crystal thin film can be easily formed at a low temperature. At present, it is difficult to obtain a high-quality single-crystal thin film for manufacturing active elements such as a three-dimensional LSI, a 1: 1 sensor, and a liquid crystal (LCD) panel. It can be expected to make a significant contribution in these fields.

[Brief description of the drawings]

FIG. 1 is a diagram of a thin film forming apparatus showing a first embodiment of the present invention. FIG. 2 is a diagram showing a structure of a filter for equalizing the flow of the reflective particles. FIG. 3 is a diagram of a thin film forming apparatus showing Embodiment 2 of the present invention. FIG. 4 is a diagram showing a structure of a filter for equalizing the flow of the reflective particles. (Explanation of symbols) 11, 21: Silicon substrate 12, 22: Quartz film 13, 23: Heater for substrate heating 18, 28: Shutter 15, 25: Cage ion source 14, 24: Argon gas Conduit 17 Silicon target 27 Boron target 16 Silicon, argon, beam filter 26 Boron, argon beam filter 29 Boron crucible for electron beam evaporation 30 Boron 31 Hot cathode for electron beam 41 , 52 ... Molybdenum plate 42 ... Silicon coating 53 ... Boron coating

Claims (2)

(57) [Claims] In a method of manufacturing a vapor-deposited thin film on a substrate, a desired crystal orientation can be obtained by irradiating a neutral atom beam of a relatively low energy inert gas while vapor-depositing a thin film material on the substrate surface. A method for producing a vapor-deposited thin film, comprising irradiating at least two or more different close-packed crystal planes of a crystal having a desired orientation from a direction perpendicular to the crystal plane to obtain relatively large crystal grains. . 2. The method for producing a vapor-deposited thin film on a substrate according to claim 1, wherein the thin film material is a compound and the component element is a relatively inert gas. A method for producing a vapor-deposited thin film, characterized by using a neutral atom beam of this component element instead of an atom beam.