JP2618521B2 - Method for producing ceramic film on semiconductor substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technique for forming a ceramic layer on a semiconductor substrate required for manufacturing a semiconductor element and a method for forming a functional ceramic film on a semiconductor crystal. It relates to a forming method.

[Problems to be Solved by Conventional Techniques and Inventions] Conventionally, when an insulating layer is grown on a semiconductor crystal substrate represented by Si, use of a Si oxide film (SiO _{X to} SiO ₂ ) is mainly used. (“Insulating Films on Semiconductors”, Spring
er-Verlag, Berlin, Heidelberg, New York 1981: Ed.M.Sc
hulz & G.Persl etc.) On the other hand, in order to expand the device characteristics and commercialization, applications other than Si oxide film, such as CaF ₂ (T.Asano & H.Ishiwara,
J. Appl. Phys. 55 (1984) 3566, etc.), ZrO ₂ (Y. Ohsa
ka, T.Imura, Y.Nishibayashi, & F.Nishiyama, J.Appl.Phy
s. 63 (1988) 581) has been actively researched and developed for epitaxial growth of ceramic films on Si substrates. These ceramic films are formed by a vapor deposition method, a sputtering method, or a CVD method. In a vapor deposition method using a ceramic material as a vapor deposition source, the ceramic material is generally a high melting point material, and thus is often vapor-deposited by electron beam heating.

In general, in a sputtering method, a CVD method, or an oxidation-reactive deposition method using a metal deposition source, a film is formed in a high-pressure gas atmosphere, generally at a pressure of 10 ^-5 Torr or more, so that the substrate is used. The cleanliness of the Si crystal surface becomes a problem.

Even in a vapor deposition method using a ceramic material as an evaporation source (electron beam heating), since the ceramic material material is always in a molten state, for example, in the case of oxide ceramics, oxygen is selectively selected from the molten material in a high vacuum. It is easy to leave. The released oxygen quickly covers the surface of the Si substrate and deteriorates the crystallinity of the grown film. In addition, the oxygen content of the raw material often becomes smaller than the stoichiometric composition.

When oxygen is considered as an atmosphere gas in the film forming process and a gas released from the raw material, at a normal film forming temperature (> 400 ° C.), the clean surface of the Si crystal is easily oxidized, and SiO _x
A layer is formed.

Since the SiO _X layer takes an amorphous state, that is, its structure is random, the ceramic material layer to be formed on it is a polycrystalline film that does not reflect the structure of the substrate Si crystal at all or has a random priority in the plane. It often becomes an alignment film.

The same can be said for the formation of a ceramic material other than an oxide.

The present invention provides a ceramic material film epitaxially grown while keeping the surface of the semiconductor crystal substrate clean, and only by the interaction between the substrate surface and the grown film, that is, without being affected by the impurity layer, It is an object to provide a method by which a layer can be produced on a substrate.

[Means for Solving the Problems] In order to solve the above technical problems, the present invention provides a sintered body, powder or powder of one or more ceramic materials to be epitaxially grown on a clean surface of a semiconductor crystal substrate. The crystal is evaporated and scattered by a pulse laser beam in a vacuum higher than 1 × 10 ⁻⁷ Torr, and a substrate temperature of 600 to 8
A method for epitaxially growing the ceramic thin film on a clean surface of the semiconductor crystal substrate maintained at 00 ° C. Further, in the method of forming a ceramic film on the semiconductor substrate, the clean surface of the semiconductor crystal substrate may further include one or more types of the ceramic crystal or a chemical bond between the semiconductor crystal and the ceramic material by the epitaxial growth. After being covered with the generated transient crystal, a reactive gas for ensuring a volatile component of the ceramic body is supplied at a pressure of 1 × 10 ⁻⁷ Torr or more, and the ceramic film is crystal-grown. The present invention provides a method for producing a ceramic thin film on a semiconductor substrate, characterized in that the method comprises: Further, a method for forming a ceramic thin film on a silicon substrate is preferable. Further, the ceramic body is preferably a fluorite-type oxide or a perovskite-type oxide. Further, it is preferable to form a thin film of CeO ₂ of a fluorite-type oxide ceramic body or SrTiO ₃ of the perovskite-type ceramic body on a semiconductor substrate.

In the method for forming a ceramic material thin film on a semiconductor substrate according to the present invention, a pulsed laser beam is applied to a desired ceramic material (target) in the high vacuum to evaporate the components of the ceramic material instantaneously and intermittently. By being scattered and deposited on the substrate surface without supplying a reactive gas, the degree of vacuum during the film forming process hardly changes, and the surface of the semiconductor crystal substrate heated to 600 to 800 ° C. The ceramic material film can be formed under the high vacuum sufficient to keep the material clean.

The heating temperature of the substrate is preferably 600 to 800 ° C., but the temperature at which the epitaxially grown film does not become polycrystalline depends on the type of the ceramic material to be grown, for example,
In the CeO ₂ film, at 600 ° C. or less, the polycrystalline film is formed under any conditions, and in the SrTiO ₃ film, 700 ° C. or more is preferable.
For the aTiO ₃ film, 650 ° C. or higher is preferable.

After the surface of the semiconductor crystal is once covered with the ceramic material film, the surface becomes stable against a reactive gas such as oxygen. For example, when forming an oxide ceramic material film, it is easy to ensure oxygen deficiency in the crystal film generated at high temperature and high vacuum, and to easily and stably increase the crystallinity and characteristics of the crystal film. Become.

For ceramic materials that are unstable at high temperature and high vacuum, use a ceramic material that is stable at high temperature and high vacuum, and after forming a film, the desired ceramic material is placed in a stable gas atmosphere. The film formation process can be performed by changing the conditions.

[Operation] In the method for producing a ceramic thin film on the surface of a semiconductor crystal substrate according to the present invention, since the surface of the semiconductor crystal substrate is kept under a clean high vacuum during the film forming process, the ceramic structure flying from the target material is formed. Interaction occurs only with the element, and a ceramic crystal film can be grown on the substrate surface in a clean atmosphere. That is, the growth of the desired ceramic film is not hindered by the generation of the surface oxide layer.

In the method of the present invention in which a desired ceramic material (target) is irradiated with a pulsed laser beam to form a film on the substrate surface, a continuous wave laser or electron beam heating or resistance heating is used to deposit the target material as in the case of depositing the target material. Since the target is not constantly heated, or even kept in a molten state, the atmosphere during the film forming process is very clean.

After the semiconductor crystal substrate is once covered with the ceramic film, there is no need to pay attention to the reaction between the substrate surface and the reactive gas, etc., and the deposition atmosphere, especially the gas pressure, can be set freely. Will be possible.

The method for producing a ceramic film according to the present invention has made it possible to produce an oxide thin film with excellent reproducibility and excellent characteristics.

Furthermore, the method for producing a ceramic of the present invention includes, for example,
It is easily useful for producing an oxide thin film such as a photodetector and a transistor.

Next, the method of forming the ceramic material film on the substrate according to the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

[Example 1] CeO ₂ was used as a ceramic material, and Si (001) was used as a semiconductor substrate.
Select a substrate with (110) and (111) planes and a substrate temperature of 600 to 800
The film forming process was performed at a temperature of about ℃. The degree of vacuum and under a following atmosphere 1 × 10 ^-7 Torr during film formation, 1 × 10 ^-7 high under a high vacuum atmosphere from Torr, also during formation of oxygen 1 × 10 ^-7 Torr, constantly supplied The film formation process was performed in the atmosphere set. in this case,
Except for the conditions in which oxygen was forcibly supplied, the presence of O ₂ gas in the film formation chamber during film formation was not confirmed by gas mass spectrometry. CeO ₂ formed under the above three types of film formation conditions
The following various measurements were performed on the film.

The crystallinity of the CeO ₂ film was compared by high-speed electron diffraction and X-ray diffraction. In the film formation under a high vacuum, the base pressure of 2 × 10 ⁻⁹ Torr before the start of the film formation increased to 5 × 10 ⁻⁹ Torr during the film formation.

CeO ₂ is deposited on the target under the above three conditions.
Using a CeO ₂ sintered body, an ArF excimer laser (80 mJ, 2 Hz) was focused on the target. Note that CeO ₂ is a stable material having the original fluorite-type structure even under the temperature and vacuum of the present embodiment.

 Table 1 shows the results.

An epitaxially grown CeO ₂ film was obtained only under conditions where the pressure during film formation was low and the surface of the Si substrate was kept clean. The cleanliness of the Si substrate surface was confirmed by RHEED immediately before film formation. In particular, a CeO ₂ single crystal film without twins was obtained on the surface of the Si (111) substrate. When the substrate temperature was lower than 600 ° C., the CeO ₂ film grew into a polycrystalline film under any conditions.

Example 2 SrT on Si (001) substrate under high vacuum of about 5 × 10 ⁻⁹ Torr
An iO ₃ film was prepared. SrTiO ₃ sintered body was used as the target material, with a laser output of 80 mJ and a pulse frequency of 2 Hz.
The target material was irradiated with a laser to perform a film forming process. Table 2 shows the results of film formation at various temperatures.

The epitaxial growth orientation predicted from the lattice constant of SrTiO ₃ (a = b = c = 3.9 °) and the lattice constant of Si (a = b = c = 5.4 °) agreed with the results obtained in Example 2.

[Example 3] BaTiO was formed on the Si (001) substrate surface under the same conditions as in Example 2.
_Three films were made. Table 3 shows the results.

Of the obtained epitaxial hexagonal BaTiO ₃ (100) film,
The half width of the rocking curve of the (200) X-ray diffraction peak was 0.98 °.

Example 4 CeO ₂ has a fluorite-type structure stably at a temperature and a pressure on the order of the film forming conditions of Example 1, but causes slight oxygen deficiency.

Therefore, to ensure oxygen deficiency, it is sufficient to supply about 1 × 10 ⁻⁷ Torr of oxygen during film formation. After epitaxially growing a CeO ₂ (110) film on the Si (001) surface at a substrate temperature of 650 ° C. and a vacuum of 5 × 10 ⁻⁹ torr at a film pressure of 200 °, the substrate is blown with 1 × 10 ⁻⁷ torr of oxygen, and subsequently , CeO ₂ was grown.

In the high-speed electron diffraction observation of the formed CeO ₂ film, no change was observed in which the growth of the CeO ₂ (110) film was disturbed by oxygen introduction during the growth.

[Effects of the Invention] The following remarkable technical effects have been obtained by the processing method for forming a ceramic thin film on a semiconductor plate according to the present invention.

First, the ceramic target is instantaneously and intermittently evaporated and scattered by a pulsed laser beam in a high vacuum higher than 1 × 10 ⁻⁷ Torr, so that the film formation atmosphere is maintained in a high vacuum. Fabrication can be performed. A fabrication method can be provided.

Secondly, the present invention provides a manufacturing method capable of growing a ceramic film while keeping the surface of the semiconductor crystal substrate clean since the film formation atmosphere is kept at a high vacuum.

Third, since the surface of the semiconductor crystal substrate is clean, the ceramic film can be epitaxially grown only by the interaction between the substrate surface and the growth film, that is, without being affected by the impurity layer.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tadashi Tsukahara 3-15-5 Shimotakaido, Suginami-ku, Tokyo (56) References JP-A-1-97318 (JP, A) JP-A-4-92816 (JP, A)

Claims (5)

(57) [Claims] 1. The method of claim 1, wherein a sintered body, powder or crystal of one or more ceramic materials to be epitaxially grown on a clean surface of the semiconductor crystal substrate is evaporated and scattered by a pulse laser beam in a vacuum higher than 1 × 10 ⁻⁷ Torr. A method for producing a ceramic film on a semiconductor substrate, wherein the ceramic thin film is epitaxially grown on a clean surface on the semiconductor crystal substrate maintained at a substrate temperature of 600 to 800 ° C. in the high vacuum. 2. The method for producing a ceramic film on a semiconductor substrate according to claim 1, further comprising the step of forming a clean surface of said semiconductor crystal substrate by one or more types of said ceramic crystal or said semiconductor crystal by said epitaxial growth. After being covered with the transient crystal formed by the chemical bonding with the ceramic material, a reactive gas for ensuring a volatile component of the ceramic body is supplied at a pressure of 1 × 10 ⁻⁷ Torr or more, and the ceramic film is formed. 2. The method for producing a ceramic thin film on a semiconductor substrate according to claim 1, wherein crystal growth is performed to stabilize the crystal structure of the epitaxially grown film. 3. The method for producing a ceramic thin film on a semiconductor substrate according to claim 1, wherein said semiconductor crystal substrate is silicon. 4. The method for producing a ceramic thin film on a semiconductor substrate according to claim 1, wherein the ceramic body film is a fluorite-type oxide or a perovskite-type oxide. 5. The fluorite-type oxide ceramic body according to claim 1,
4. The method for producing a ceramic thin film on a semiconductor substrate according to claim 1, wherein the ceramic body is made of CeO ₂ or the perovskite-type ceramic body is made of SrTiO ₃ .