JP3293912B2 - Method of forming oxide thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a thin film of a compound such as an oxide mainly by using reactive sputtering.

[0002]

2. Description of the Related Art A conventional reactive sputtering apparatus used for forming an oxide crystal thin film has, for example, a structure as shown in FIG. A vacuum chamber 41 is evacuated to a vacuum through an exhaust hole 42. An electric field is introduced from the DC or high-frequency power supply 43 to the electrode / raw material target holder 44, and an electric field is applied between the substrate holder and the electrode 45 capable of heating the substrate to generate plasma. Reference numeral 46 denotes a gas inlet, and when forming an oxide thin film, a sputtering gas such as Ar or a reactive gas for oxidation such as O ₂ is introduced. These gases are decomposed into plasma, and ions in the plasma are made to collide with the target 47 at an accelerated rate, and are deposited and formed on the substrate 48 by so-called sputter deposition. At this time, when the sputtered active particles reach the substrate, they contact and react with reactive particles such as active oxygen ions and oxygen radicals in the plasma and oxidize on the substrate almost reflecting the composition of the constituent elements of the target. An object thin film is formed.

[0003]

However, in a method using such a conventional reactive sputtering apparatus, when an oxidation reaction is insufficient and a high-quality oxide thin film is to be obtained,
It was necessary to extremely reduce the deposition rate and keep the substrate temperature relatively high. For this reason, for example, there are various restrictions such as difficulty in combination with a semiconductor device and inability to form a device on a low-melting substrate, and there are many restrictions in device design and in the manufacturing process. At present, there is a high demand for formation at lower temperatures.

In the conventional continuous deposition method, sputtered particles and ionic charged particles consequently directed toward the substrate continue to receive the impact of colliding with the film formation surface. And formation of a lattice were hindered, and it was difficult to form a sufficient compound particularly in ideal crystal growth and low-temperature formation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film forming method and apparatus capable of forming a high quality oxide thin film at a low temperature in order to solve the above-mentioned conventional problems.

[0006]

In order to achieve the above object, a method of forming an oxide thin film according to the present invention comprises, as a first step, a method of forming an oxide thin film by sputtering a target as a raw material of the thin film. A reactive sputtering deposition step involving a chemical reaction with a gas containing a thin film raw material element or its discharge plasma, and as a second step, a deposition step is not included, or the deposition rate is extremely low compared to the first step and Used for oxidation in a gas atmosphere containing a gas that reacts with at least the thin film raw material element
Electric field that can decompose gas causes substantial sputtering
And a reaction step of causing the decomposition and excitation of the reactive gas by the plasma not to be generated on the deposition surface or in the vicinity of the surface, a plurality of times alternately, and the second step includes the step of forming the oxide formed in the first step. It is characterized in that oxygen deficiency in the thin film is compensated by oxygen atoms.

In the above structure, in the first step, a mixed gas of a gas involved in a chemical reaction during deposition and an inert gas not involved in the reaction but involved only in sputtering is supplied. , It is preferable to supply a gas containing a reactive element.

In the above structure, in the step of alternately performing the first step and the second step a plurality of times, in both steps, the gas involved in the reaction during the deposition is not involved in the reaction but only the sputtering. It is preferable to supply a mixed gas of an inert gas.

Next, in the thin film forming apparatus of the present invention,
In a thin film deposition apparatus by sputtering of a target as a raw material of a thin film, a reactive sputtering deposition means involving a chemical reaction with a gas containing a thin film raw material element or a discharge plasma thereof, and a deposition step is not included, or the first step A reaction means for causing decomposition and excitation of a reactive gas by plasma on a deposition surface or near a surface in a gas atmosphere containing a gas that reacts with at least the thin film raw material element at an extremely low deposition rate, and wherein the deposition and the reaction are performed. It is characterized by comprising means for alternately performing a plurality of times.

In the above configuration, the electric field introduction port such as a plasma generating electrode or a waveguide is installed in the same container as the target electrode for generating the sputtering deposition, or the substrate is kept under reduced pressure conditions. It is preferable to provide a means for moving between a container or region for performing sputtering and a container or region for performing plasma processing.

[0011] In the above structure, the moving means between the container or region for performing sputtering and the container or region for performing a process in which a reaction on the deposition surface or near the surface is mainly performed by plasma decomposition is provided with a substrate for supporting the substrate. Preferably, it is means for rotating the holder.

Further, in the above configuration, it is preferable to use a direct current as a plasma generation source. In the above configuration, the plasma generation source is 100 kHz to 100 MHz.
It is preferable to use a high frequency of z.

Further, in the above configuration, it is preferable to use a microwave of 1 GHz to 10 GHz as a plasma generation source.

[0014]

According to the structure of the method of the present invention, as a first step, a reactive sputtering deposition step involving a chemical reaction with a gas containing a thin film raw material element or its discharge plasma,
In the second step, the deposition step is not included, or the deposition rate is extremely low compared to the first step, and the decomposition and excitation of the reactive gas by plasma are performed in a gas atmosphere containing at least a gas that reacts with the thin film raw material element. A high-quality oxide thin film can be formed at a low temperature by alternately performing a plurality of times with a reaction step to be performed on or near a deposition surface. For example, after a deposition process by reactive sputtering, an electric field for introducing a gas used for oxidation and supplying reactive atoms and molecules to or near the substrate (deposition) surface without exposing the substrate to sputtered particles. And a process involving plasma generation is performed. As a function of this step, the reaction gas near the surface is decomposed and excited by plasma. For example, in the case of oxygen, a large amount of active atomic oxygen is generated, and the oxygen deficiency in the thin film formed in the deposition step is compensated by oxygen atoms. . As a second effect, for example, in the case of an oxide thin film, oxygen-deficient portions in the formed film are oxygenated, and excess oxygen is combined with the oxygen and removed in the form of O _2. It has the effect of getting lost. By repeating these two steps alternately, even if formed at a low temperature, there is little defect as a result, and there is an effect that an oxide thin film having particularly good film quality and denseness can be realized.

Although an oxide thin film has been mainly described here as an example, the present invention is also useful for a nitride thin film and a hydride thin film, for example, and the effects of the invention are exactly the same. Next, according to the configuration of the apparatus of the present invention, an oxide thin film of high quality can be formed at a high rate and reasonably at a low temperature.

[0016]

The present invention will be described more specifically with reference to the following examples. This embodiment is different from the conventional thin film formation only by the continuous reactive sputtering, in which the substrate to be deposited or the surface of the substrate is first used for the deposition step by sputtering of the target used for the thin film deposition and for the oxidation. By generating an amount of plasma that does not cause sputtering in an electric field capable of decomposing gas, a process of alternately repeating oxidation and crystal growth by active oxygen on the surface of the deposition electrode is promoted.

A description will be given below with reference to the drawings. FIG. 1 is a schematic view of a reactive sputtering apparatus capable of performing a plasma oxidation process according to an embodiment of the apparatus used in the present invention. Reference numeral 11 denotes a vacuum chamber, which is evacuated to a vacuum through the exhaust hole 12.
An electric field is introduced from a DC or high-frequency power supply 13 to the electrode / raw material target holder 14, and the electric field is applied to the substrate holder / electrode 15 capable of heating the substrate to generate plasma. Reference numeral 16 denotes a first gas inlet, into which a sputtering gas such as Ar or a reactive gas for oxidation such as O ₂ is introduced when an oxide thin film is formed. These gases are decomposed into plasma, and ions in the plasma are accelerated and collided with the target 17. If the substrate 18 is on the target by so-called sputter deposition, deposition is performed on the substrate. At this time, when the sputtered active particles reach the substrate, they contact and react with reactive particles such as active oxygen ions and oxygen radicals in the plasma and oxidize on the substrate almost reflecting the composition of the constituent elements of the target. An object thin film is formed. Reference numeral 19 denotes excited species on the substrate by plasma discharge decomposition.
An electrode for supplying active species and a plasma processing power source 20
Supplies an electric field to generate plasma. The substrate holder 15 is supported by, for example, a shaft 21, and by rotating the shaft, the substrate 18 can be made to face a target or a plasma processing electrode. Reference numeral 22 denotes a second gas inlet, for example, when an oxide thin film is formed, only a reactive gas for oxidation such as O ₂ is introduced near the substrate.

In the apparatus used in this embodiment, the partition 23 is provided in the area where the target is installed and the area where the plasma processing electrode for plasma processing is installed, so that rotation of the substrate holder is not hindered. In the deposition process, the atmosphere is a mixed gas of Ar, which is a sputtering gas, and O ₂ , which is a reactive gas. On the other hand, in the plasma treatment process, the atmosphere becomes almost the O ₂ gas atmosphere, which is a reactive gas. I have.

As described above, in the first film deposition step, the substrate is placed on the target 17 and deposited on the substrate 18 by so-called sputter deposition. At this time, when the sputtered particles reach the substrate, a part of the sputtered particles come into contact with reactive particles such as active oxygen ions and oxygen radicals in the plasma to form an oxide thin film on the substrate.

In the second oxidation and the step of removing defects in the deposited film, for example, by rotating the substrate holder,
The substrate is moved to a region where the sputtered particles do not reach from the target or the deposition rate is extremely low, and the excited species generated by the plasma processing discharge electrode 17
It is placed in a region where active species can be effectively irradiated, and promotes an oxidation reaction on and near the substrate surface. At this time, in the vicinity of the substrate, a large number of active oxygen atoms are generated due to plasma decomposition of oxidizing gas molecules such as oxygen molecules. Oxidation of defective portions resulting from insufficient oxidation and removal of excess oxygen on the film surface are performed. Since the second step is effective only in a region relatively shallow from the surface of the deposited film, there is an optimal condition for the relationship between the time for performing the first deposition step and the time for the plasma processing step. In any case, by performing at least these steps alternately, a dense and high-quality thin film can be deposited and formed at a relatively low temperature without damaging the substrate.

In this embodiment, the gas atmosphere in the deposition step and the plasma processing step is distinguished by having a structure provided with partitions. However, the degree of the effect is large. The gas may be continuously supplied as a mixed gas of oxygen, or the gas may be alternately switched from the mixed gas to only the oxygen gas or only from oxygen to the mixed gas according to the rotation of the substrate.

Next, a specific embodiment will be described. FIG. 2 shows that the substrate temperature was kept constant at 550 ° C., the sputtering high-frequency power density in the first deposition step was 0.3 W / cm ² , and the high-frequency power source (13.56 M) was used as the plasma source in the second step.
(Hz), the power density is changed from 0 to 0.1 W / cm ² and the relative permittivity of the formed lead titanate thin film when the rotation speed of the substrate holder is 3 rpm is shown.
In this embodiment, the diameter of the target is 6 inches (about 15 cm).
m), the diameter of the plasma processing electrode is 25 cm, and the time for once passing the substrate on the target is about 5 seconds. Under this condition, about 1.5 nm is deposited, and then the plasma processing is performed for about 6 seconds. I have. There is a clear difference between the plasma treatment and the absence of the plasma treatment (when the discharge power of the plasma treatment is 0 W: the rotation is performed). Improvement is seen.

In the range of the rotation speed of about 1 to 10 rpm, the plasma processing is performed and no processing is performed (rotation is performed).
Although there is a clear difference, the change with rotation speed is
Almost never seen.

As is apparent from FIG. 2, by alternately performing deposition and plasma processing in an oxidizing atmosphere, the dielectric characteristics of the oxide dielectric thin film can be improved even when formed at a relatively low substrate temperature. it is obvious.

[0025]

As described above, according to the present invention, the plasma processing electrode is built in the apparatus container or in a different container which can be moved while maintaining the reduced pressure condition, and the plasma processing electrode or the reactive sputtering method is used for a certain period of time. By alternately performing the thin film deposition step and the step of applying the plasma-excited reactive species to the thin film surface that has not been deposited for a certain period of time a plurality of times, a high-quality oxide thin film can be obtained on a low-temperature substrate.

[Brief description of the drawings]

FIG. 1 is a schematic view of a thin film forming apparatus according to an embodiment of the present invention.

FIG. 2 is a view showing a change in the relative dielectric constant of a formed lead titanate thin film when a substrate holder is rotated and plasma processing is performed to show the effect of the present invention.

FIG. 3 is a schematic view of a conventional general reactive sputtering apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Vacuum chamber 12 Exhaust hole 13 DC or high frequency power supply 14 Electrode / target holder 15 Electrode / substrate holder 16 First gas inlet 17 Target 18 Substrate 19 Plasma processing electrode 20 Power supply for plasma processing 21 Support shaft 22 Second gas introduction Mouth 23 partition

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kazuki Komaki 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-248302 (JP, A) JP-B-3-57185 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 14/00-14 / 58 H01L 21/31 H01L 21/316

Claims (3)

(57) [Claims] In a method for forming an oxide thin film by sputtering a target as a raw material of a thin film, a first step is a reactive sputtering deposition step involving a chemical reaction with a gas containing a thin film raw material element or a discharge plasma thereof. In the second step, the deposition step is not included, or the deposition rate is extremely low compared to the first step, and the gas used for oxidation is decomposed in a gas atmosphere containing at least a gas that reacts with the thin film raw material element. In a possible electric field
And a reaction step of causing decomposition and excitation of a reactive gas by plasma that does not substantially generate sputtering on the deposition surface or near the surface, alternately a plurality of times, wherein the second step is the first step A method for forming an oxide thin film, characterized in that an oxygen deficient portion in the oxide thin film formed by the above step is compensated by oxygen atoms. In the first step, a mixed gas of a gas involved in a chemical reaction during deposition and an inert gas not involved in the reaction but only involved in sputtering is supplied. The method for forming an oxide thin film according to claim 1, wherein a gas containing a reactive element is supplied. 3. A process in which the first step and the second step are alternately performed a plurality of times, and a gas involved in a reaction during deposition and an inert gas not involved in the reaction but only involved in sputtering in both steps. The method for forming an oxide thin film according to claim 1, wherein a mixed gas of the following is supplied.