JP2005154210A - Method for producing quartz crystal thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a quartz crystal thin film which exhibits excellent crystal characteristics, in particular, a quartz crystal thin film grown in such a manner that the AT-cut plane is preferentially oriented in a high yield by using a simple vapor phase reactor. <P>SOLUTION: At least two quartz layers (where the quartz layers are controlled so that each of the quartz layers is composed of a crystal phase and an amorphous phase and the ratio of the crystal phase in the quartz layer on the side farther from a substrate is higher than that of the crystal phase in the quartz layer on the side closer to the substrate) are formed on the surface of the substrate having a lattice constant different from that of the quartz crystal. Then the quartz crystal thin film is epitaxially grown on the surface of the crystal layer on the side farther from the substrate by the reaction of a silicic acid alkoxide and oxygen. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a quartz crystal thin film and a manufacturing method thereof.

  The quartz crystal thin film is used as an oscillator, a vibrator, a surface acoustic wave device for a high frequency filter, an optical waveguide, a semiconductor substrate, or a component thereof. As a method for producing such a useful quartz crystal thin film, a method of polishing a quartz single crystal obtained by a hydrothermal synthesis method into a thin film has been conventionally known. As a manufacturing method, a sol-gel method, a plasma chemical vapor deposition (DVD) method, a sputtering method, a laser ablation method, and the like are known. However, these production methods have problems such as low yield of crystal crystal thin films that are practically satisfactory, or the necessity of managing large-scale equipment and strict production conditions. It is not necessarily advantageous as a manufacturing method.

  Patent Document 1 describes an atmospheric pressure vapor phase epitaxial growth method (AP-VPE) as a method for producing a quartz crystal thin film that can be advantageously used industrially. In this atmospheric pressure vapor phase epitaxial growth method, a quartz crystal thin film is formed on a substrate by reacting silicon alkoxide with oxygen, preferably in the presence of a reaction accelerator such as hydrogen chloride, under atmospheric pressure without using a vacuum apparatus. Is deposited by epitaxial growth. This patent publication further describes the crystallinity of the quartz crystal thin film deposited thereon by providing a buffer layer on the substrate in advance when the quartz crystal thin film is formed on the substrate by atmospheric pressure vapor phase epitaxy. There is a statement to improve.

On the other hand, it is known that a quartz crystal thin film with an AT-cut surface oriented and grown preferentially has a low temperature dependency when used as a vibrator, and is therefore considered an excellent device. However, a method for selectively producing a quartz crystal thin film having such characteristics, in particular, a method for producing by a vapor phase method has not been known so far.
JP 2002-80296 A

An object of the present invention is to provide a method for producing a quartz crystal thin film that makes it possible to produce a quartz crystal thin film exhibiting excellent crystal characteristics at a high yield using a simple gas phase reactor. .
In particular, the present invention provides a method for producing a quartz crystal thin film that makes it possible to produce a quartz crystal film having an AT-cut surface oriented and grown with high yield using a simple gas phase reactor. The purpose is to provide.
It is another object of the present invention to provide a quartz crystal film in which an AT cut surface is preferentially grown.

In the present invention, a crystal substrate having a lattice constant different from that of a crystal crystal has at least two crystal layers (however, each crystal layer is composed of a crystal phase and an amorphous phase, The crystal phase ratio in the crystal layer on the far side is adjusted to be higher than the crystal phase ratio in the crystal layer on the side close to the substrate), and then the surface of the crystal layer on the side far from the substrate In addition, there is a method for producing a crystal crystal film comprising producing a crystal crystal film epitaxially grown by a reaction between silicate alkoxide and oxygen.
The present invention also resides in a quartz crystal film manufactured by the above manufacturing method.

In particular, the present invention provides at least two crystal layers (however, each crystal layer is composed of a crystal phase and an amorphous phase on the surface of a crystalline substrate having a lattice constant different from that of the crystal crystal. The crystal phase ratio in the crystal layer far from the substrate is adjusted to be higher than the crystal phase ratio in the crystal layer near the substrate), and then There is a method for producing a crystal crystal film, which comprises generating a crystal crystal film epitaxially grown so that an AT cut surface is preferentially oriented and grown on the surface by a reaction between silicate alkoxide and oxygen.
The present invention also resides in a quartz crystal film in which the AT cut surface produced by the above production method is grown with a preferential orientation.

The present invention also provides at least two quartz layers on the surface of a substrate having a lattice constant different from that of the quartz crystal (however, each quartz layer is composed of a crystalline phase and an amorphous phase and is far from the substrate). The crystal phase ratio in the crystal layer on the side is adjusted to be higher than the crystal phase ratio in the crystal layer on the side close to the substrate). There is also a laminate in which the grown quartz crystal films are laminated.
The present invention also provides a quartz crystal film in which an AT cut surface is preferentially grown and a laminate having a crystal layer composed of a crystal phase and an amorphous phase on the surface of one side of the crystal crystal film. There is also.
The present invention also resides in a quartz crystal film in which an AT cut surface formed by a vapor deposition method is grown with a preferential orientation.

  By using the method for producing a quartz crystal thin film of the present invention, a quartz crystal thin film exhibiting excellent crystal characteristics, particularly a quartz crystal thin film grown with a preferential orientation of an AT cut surface, can be converted into a simple vapor phase reactor. It becomes possible to manufacture with high yield. Moreover, since the quartz crystal thin film of the present invention has high crystallinity, it exhibits excellent physical properties.

A preferred embodiment of the method for producing a quartz crystal film of the present invention is as follows.
(1) The crystal layer in contact with the surface of the substrate is composed of 1 to 50% crystal phase and 99 to 50% amorphous phase, while the crystal layer in contact with the surface of the crystal crystal film is 5 to 95%. The crystal phase is composed of 95 to 5% amorphous phase, and the ratio of the crystal phase in the latter crystal layer is 4% or more higher than the ratio of the crystal phase in the former crystal layer.
(2) The quartz crystal layer is in contact with the surface of the quartz crystal film, and the lower quartz crystal layer composed of 1 to 50% crystal phase on the side in contact with the surface of the substrate and 99 to 50% amorphous phase. The upper crystal layer is composed of two layers of -95% crystal phase and 95-5% amorphous phase, and the ratio of the crystal phase in the upper crystal layer is the crystal phase in the lower crystal layer 4% or more higher than the above ratio.
(3) The crystal layer is formed by utilizing a reaction between silicate alkoxide and oxygen.
(4) Both the formation of the quartz layer and the production of the quartz crystal film are performed at atmospheric pressure.
(5) The substrate is a Si substrate, a GaAs substrate, or a sapphire substrate.
(6) The substrate is a sapphire substrate having a (110) A plane.

  Next, a method for producing a quartz crystal thin film and a quartz crystal thin film according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a typical layer structure of a laminate including a quartz crystal thin film obtained by the method for producing a quartz crystal thin film of the present invention. That is, the laminated body 10 has a configuration in which a lower crystal layer 12, an upper crystal layer 13, and a crystal crystal thin film 14 are laminated in this order on a substrate 11. The lower crystal layer 12 and the upper crystal layer 13 are formed when the crystal crystal thin film is epitaxially grown on the substrate, particularly when the crystal crystal thin film having the AT cut surface oriented with priority is deposited by epitaxial growth. Since it is understood to exhibit a function (plane orientation control function) that reduces the influence of the substrate while maintaining the influence of the lattice constant of the substrate, in the following, each layer will be referred to as a lower buffer layer and an upper buffer layer. is there.

As the substrate, a crystalline substrate having a lattice constant different from that of quartz crystal is selected. However, the crystalline substrate preferably has a hexagonal crystal structure, or a hexagonal atomic arrangement appears on the surface thereof. Examples of such a crystalline substrate include a Si substrate, a GaAs substrate, and a sapphire substrate, and a sapphire substrate having a (110) A plane is particularly preferable.
The substrate may be transparent or opaque. However, when the quartz crystal thin film is used as an optical element component as a quartz crystal thin film with a substrate without peeling the quartz crystal thin film from the substrate, it is preferable to use a transparent substrate. A preferable thickness range of the substrate is in the range of 50 to 500 μm, and particularly preferably in the range of 100 to 300 μm.

  The method for producing a quartz crystal thin film according to the present invention is characterized in that at least two buffer layers are formed on a substrate before producing the quartz crystal thin film. Both of these at least two buffer layers are thin layers composed of a crystalline phase and an amorphous phase. Then, the ratio of the crystal phase in the crystal layer on the side far from the substrate is adjusted to be higher than the ratio of the crystal phase in the crystal layer on the side close to the substrate. Specifically, the buffer layer 12 (lower buffer layer) on the side in contact with the surface of the substrate is composed of a crystal phase of 1 to 50% and an amorphous phase of 99 to 50%. The buffer layer 13 (upper buffer layer) is composed of a 5-95% crystal phase and a 95-5% amorphous phase. However, the ratio of the crystal phase in the upper buffer layer is 4% or more (preferably 5% or more, more preferably 10% or more, and preferably 40% or less, more than the ratio of the crystal phase in the lower buffer layer. Preferably 30% or less). The plurality of buffer layers satisfying the above-described requirements of the plurality of layers used in the method for manufacturing a crystal crystal thin film according to the present invention are control layers for controlling the plane orientation of the crystal crystal thin film grown on the uppermost buffer layer. Acts as

  The crystal layer (buffer layer) composed of a crystalline phase and an amorphous phase can achieve the object of the present invention with only two layers satisfying the above requirements. However, if necessary, three or more layers are provided. Also good. When providing three or more buffer layers, the lowermost layer in contact with the substrate may satisfy the requirements of the lower buffer layer, and the uppermost layer may satisfy the requirements of the upper buffer layer. However, the layer in the middle also needs to be a crystal layer composed of a crystal phase and an amorphous phase, and the ratio of the crystal phase in the intermediate crystal layer is higher than the ratio of the crystal phase in the lowest layer, The ratio is preferably lower than the ratio of the crystal phase in the uppermost layer. When two or more crystal layers (intermediate buffer layers) are present in the middle, the ratio of crystal phases in the upper intermediate buffer layer is higher than the ratio of crystal phases in the lower intermediate buffer layer. Is preferred.

  Each buffer layer preferably has a thickness in the range of 10 to 1000 nm, more preferably in the range of 10 to 300 nm, and particularly preferably in the range of 20 to 200 nm. . Further, it is preferable that the lower buffer layer is thicker than the upper buffer layer.

  It is preferable that at least two crystal layers (buffer layers) on the substrate are formed by a reaction between silicate alkoxide and oxygen. That is, the quartz crystal thin film of the present invention is formed by a method of depositing an epitaxially grown quartz crystal film on the buffer layer by the reaction of silicate alkoxide and oxygen. It is preferable that the buffer layer and the quartz crystal thin film are continuously formed on the substrate using the same raw material.

  The formation of two or more crystal layers (buffer layers) by the reaction of the silicate alkoxide and oxygen and the formation of a crystal crystal thin film on the buffer layers are preferably carried out by atmospheric pressure vapor phase epitaxy. This atmospheric pressure vapor phase epitaxial growth method is described in detail in Japanese Patent Application Laid-Open No. 2002-80296 as described above. Therefore, in this specification, the atmospheric pressure vapor phase epitaxial growth method is only described briefly. For a detailed description of the atmospheric pressure vapor phase epitaxial growth method, refer to the above-mentioned JP-A-2002-80296.

  Atmospheric pressure vapor phase epitaxy is performed by applying atmospheric pressure (in this specification, atmospheric pressure means not only atmospheric pressure but also pressure close to atmospheric pressure (within twice the atmospheric pressure, 1 In this case, the gasified silicate alkoxide and oxygen are brought into contact with each other, and quartz produced by oxidation of the silicate alkoxide is deposited on the substrate. As the silicate alkoxide, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, or a mixture of any combination thereof is used. The oxygen may be an oxygen supply source such as ozone, dinitrogen monoxide, or water. Since the oxidation of the silicate alkoxide is promoted by the presence of a reaction accelerator such as hydrogen chloride, the use of such a reaction accelerator is also preferred.

  For example, a buffer layer (a layer in which a crystalline phase and an amorphous phase coexist) is deposited on the substrate surface by a reaction between silicate alkoxide and oxygen. For example, a quartz crystal thin film is formed by a reaction between the same silicate alkoxide and oxygen. This can be realized by allowing the reaction to proceed at a lower temperature (for example, a temperature lower by 20 to 200 ° C.) than the temperature at which the product is deposited (the temperature of the substrate, the same applies hereinafter). In forming the two or more buffer layers of the present invention, the upper buffer layer is formed at a temperature (for example, 400 to 530) lower than the temperature of the lower buffer layer (for example, 10 to 100 ° C.). At a temperature in the range of ° C. Further, it is preferable to adjust the crystallinity by performing an annealing treatment after the formation of each buffer layer.

  In the method for producing a quartz crystal thin film of the present invention, the two or more buffer layers have a lattice constant intermediate between the lattice constant of the substrate and the lattice constant of the quartz crystal thin film, and in particular, the lower buffer layer has a lattice constant of the substrate. It has a close lattice constant, and the upper buffer layer has a lattice constant close to that of the quartz crystal thin film, and has a function of relaxing the difference between the lattice constant of the substrate and the lattice constant of the quartz crystal thin film.

  On the two or more buffer layers, an epitaxially grown quartz crystal thin film is formed by the reaction of silicate alkoxide and oxygen. This quartz crystal thin film is preferably formed by atmospheric pressure vapor phase epitaxy as in the formation of the buffer layer. However, when the quartz crystal thin film is deposited on the buffer layer, the substrate temperature is preferably set to a temperature 20 to 200 ° C. higher than the substrate temperature when the buffer layer is formed. However, the optimal substrate temperature for the production of the quartz crystal thin film is a temperature in the range of 550 to 600 ° C.

  In the method of manufacturing a quartz crystal thin film of the present invention, when a Si substrate, a GaAs substrate, or a sapphire substrate, particularly a sapphire substrate having a (110) A plane is used as a substrate, an AT cut is formed on two or more buffer layers. A quartz crystal thin film that has been grown with a plane preferentially oriented (that is, with a cut plane preferentially oriented in a direction inclined by about 3 ° on the substrate surface, particularly the (110) A plane of a sapphire substrate), is easily obtained. Generate.

  In addition, the quartz crystal thin film laminated on the substrate via two or more buffer layers has a coefficient of thermal expansion of each of the substrate, the buffer layer, and the quartz crystal thin film by heating or cooling the laminate. Depending on the difference, the substrate and the buffer layer can be separated. Alternatively, using the same temperature control, the substrate can be peeled off with one or more buffer layers attached. The quartz crystal thin film thus peeled off from the substrate is then used as a resonator, vibrator, surface acoustic wave element for high frequency filter, optical waveguide, semiconductor substrate, or parts thereof by performing predetermined processing. Can do. If a transparent substrate is used as the substrate, the quartz crystal thin film can be used as an optical component in a state of being laminated on the substrate.

Tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ : 99.999%] and oxygen [99.999%] on the surface of the optical grade sapphire substrate [(110) A plane, 10 mm × 10 mm] polished on the surface From the above, a quartz crystal thin film was formed under the following conditions using atmospheric pressure vapor phase epitaxy (APVPE) in the presence of hydrogen chloride.

(1) A quartz vertical reactor was prepared, a sapphire substrate was mounted inside the reactor, and the substrate was heated to 500 ° C. Next, nitrogen gas (nitrogen gas diluted tetraethoxysilane gas) passed through tetraethoxysilane heated to 70 ° C. was introduced into the reactor for 30 minutes while maintaining the substrate temperature at 500 ° C. Further, nitrogen gas diluted oxygen gas is introduced into the reactor, and simultaneously hydrogen chloride gas (reaction accelerator) diluted with nitrogen gas is introduced into the reactor to decompose tetraethoxysilane gas, and the produced crystal compound is formed into a substrate. Deposited and grown on top to form a lower buffer layer. The introduction of these gases into the reactor was performed using different gas inlets.
In the reactor, the partial pressures of tetraethoxysilane gas, oxygen, and hydrogen chloride gas are 3.3 × 10 ² Pa, 3.3 × 10 ⁴ Pa, and 1.7 × 10 ² Pa, respectively. Introduced.
The formed lower buffer layer had a thickness of 100 nm and consisted of 10% crystalline phase and 90% amorphous phase.
Next, the introduction of each gas into the reactor was interrupted, and the lower buffer layer was annealed by heating the substrate to 550 ° C. for 15 minutes.

(2) Next, the substrate temperature is lowered to 450 ° C., the introduction of each gas is resumed, the tetraethoxysilane gas is decomposed over 30 minutes, and the generated crystal is deposited on the lower buffer layer on the substrate. And an upper buffer layer was formed.
The formed upper buffer layer had a thickness of 50 nm and consisted of 25% crystal phase and 75% amorphous phase.
Next, the introduction of each gas into the reactor was interrupted, and the upper buffer layer was annealed by heating the substrate to 570 ° C. for 15 minutes.

(3) Finally, the introduction of each gas is resumed while maintaining the substrate at 570 ° C., the tetraethoxysilane gas is decomposed over 60 minutes, and the generated crystal is deposited on the upper buffer layer on the substrate. Then, it was epitaxially grown to form a quartz crystal thin film. The formed quartz crystal thin film had a thickness of 11 μm.

(4) The formed quartz crystal thin film was peeled off from the substrate using temperature control, and X-ray diffraction and X-ray pole figure measurement were performed. Line pole figure figure was obtained. From these results, it was confirmed that this quartz crystal thin film was inclined about 3 ° from the (001) plane direction, that is, preferentially oriented to a so-called AT cut plane. Further, since the half-value width of this X-ray diffraction diagram was narrow, it was confirmed that this quartz crystal thin film had high crystallinity.

  Furthermore, when the above-mentioned quartz crystal thin film was subjected to waveform measurement by a network analyzer, oscillation of a fundamental wave of 150 MHz was confirmed as shown in FIG. It is known that the thickness and the oscillation frequency satisfy the following relationship in the case of a quartz crystal thin film that is correctly oriented to AT cut.

[Equation 1]
Oscillation frequency f (MHz) = 1666 / film thickness (μm)

  The quartz crystal thin film satisfies the above relational expression, and from this measurement, it was confirmed that the quartz crystal thin film was preferentially oriented on the AT cut surface.

It is a figure which shows the typical layer structure of the quartz crystal thin film obtained with the manufacturing method of the quartz crystal thin film of this invention. It is an X-ray diffraction pattern of the quartz crystal thin film obtained in the example. It is a X-ray pole figure figure of the crystal crystal thin film obtained in the example. It is the measurement figure obtained by the waveform measurement by the network analyzer of the crystal crystal thin film obtained in the Example.

Explanation of symbols

10 Laminated body 11 Substrate 12 Lower crystal layer (lower buffer layer)
13 Upper crystal layer (upper buffer layer)
14 Quartz crystal thin film

Claims (20)

  At least two crystal layers on the surface of a crystalline substrate having a lattice constant different from that of the crystal crystal (however, each crystal layer is composed of a crystal phase and an amorphous phase, and the crystal on the side far from the substrate) The ratio of the crystal phase in the layer is adjusted to be higher than the ratio of the crystal phase in the crystal layer on the side close to the substrate), and then on the surface of the crystal layer on the side far from the substrate, A method for producing a quartz crystal film, comprising producing an epitaxially grown quartz crystal film by a reaction between an alkoxide and oxygen.   The crystal layer in contact with the surface of the substrate is composed of 1 to 50% crystal phase and 99 to 50% amorphous phase, while the crystal layer in contact with the surface of the crystal crystal film is 5 to 95% crystal phase. 2. The composition according to claim 1, comprising 95 to 5% of an amorphous phase, wherein the ratio of the crystal phase in the latter crystal layer is 4% or more higher than the ratio of the crystal phase in the former crystal layer. Of manufacturing a quartz crystal film.   The crystal layer is composed of a lower crystal layer composed of 1 to 50% crystal phase on the side in contact with the surface of the substrate and 99 to 50% amorphous phase, and 5 to 95% in contact with the surface of the crystal crystal film. The crystal phase in the upper crystal layer is composed of two layers of the upper crystal layer and the crystal phase in the lower crystal layer. The method for manufacturing a quartz crystal film according to claim 1, wherein the height is also increased by 4% or more.   4. The method for producing a quartz crystal film according to claim 1, wherein the quartz layer is formed by utilizing a reaction between silicate alkoxide and oxygen.   The method for producing a crystal crystal film according to any one of claims 1 to 4, wherein the formation of the crystal layer and the production of the crystal crystal film are both performed at atmospheric pressure.   6. The method for producing a quartz crystal film according to claim 1, wherein the substrate is a Si substrate, a GaAs substrate, or a sapphire substrate.   A quartz crystal film manufactured by the manufacturing method according to claim 1.   At least two crystal layers on the surface of a crystalline substrate having a lattice constant different from that of the crystal crystal (however, each crystal layer is composed of a crystal phase and an amorphous phase, and the crystal on the side far from the substrate) The ratio of the crystal phase in the layer is adjusted to be higher than the ratio of the crystal phase in the crystal layer on the side close to the substrate), and then on the surface of the crystal layer on the side far from the substrate, A method for producing a crystal crystal film, comprising: producing a crystal crystal film epitaxially grown so that an AT cut surface is preferentially oriented and grown by a reaction between an alkoxide and oxygen.   The crystal layer in contact with the surface of the substrate is composed of 1 to 50% crystal phase and 99 to 50% amorphous phase, while the crystal layer in contact with the surface of the crystal crystal film is 5 to 95% crystal phase. 9. The amorphous phase of 95 to 5% is formed, and the ratio of the crystal phase in the latter crystal layer is 4% or more higher than the ratio of the crystal phase in the former crystal layer. Of manufacturing a quartz crystal film.   The crystal layer is composed of a lower crystal layer composed of 1 to 50% crystal phase on the side in contact with the surface of the substrate and 99 to 50% amorphous phase, and 5 to 95% in contact with the surface of the crystal crystal film. The crystal phase in the upper crystal layer is composed of two layers of the upper crystal layer and the crystal phase in the lower crystal layer. The method for manufacturing a quartz crystal film according to claim 8, wherein the height is also increased by 4% or more.   The method for producing a quartz crystal film according to any one of claims 8 to 10, wherein the quartz layer is formed by utilizing a reaction between a silicate alkoxide and oxygen.   The method for producing a quartz crystal film according to any one of claims 8 to 11, wherein the formation of the quartz layer and the production of the quartz crystal film are both performed at atmospheric pressure.   The method for producing a quartz crystal film according to any one of claims 8 to 12, wherein the substrate is a Si substrate, a GaAs substrate, or a sapphire substrate.   The method for manufacturing a quartz crystal film according to any one of claims 8 to 13, wherein the substrate is a sapphire substrate having a (110) A plane.   A quartz crystal film in which an AT cut surface manufactured by the manufacturing method according to claim 8 is preferentially oriented and grown.   At least two crystal layers on the surface of the substrate having a lattice constant different from that of the crystal crystal (however, each crystal layer is composed of a crystal phase and an amorphous phase, and the crystal layer on the side far from the substrate) The crystal phase ratio is adjusted to be higher than the crystal phase ratio in the crystal layer on the side close to the substrate). A laminated body in which is laminated.   The laminate according to claim 16, wherein the substrate is a Si substrate, a GaAs substrate, or a sapphire substrate.   The laminate according to claim 16, wherein the substrate is a sapphire substrate having a (110) A plane.   A laminate having a quartz crystal film in which an AT cut surface is preferentially grown and a quartz crystal layer composed of a crystalline phase and an amorphous phase on a surface of one side of the quartz crystal film. A crystal crystal film in which an AT cut surface formed by vapor deposition is preferentially grown.

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