JP2004001147A - Method for manufacturing microcrystal thin film structural body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a planar or three-dimensional thin film structural body having a microcrystal material or a material having amorphous and microcrystal parts gradiently existing. <P>SOLUTION: An amorphous thin film is formed by a composition having a supercooled liquid region and a film forming condition to form an amorphous thin film structural body. The amorphous thin film structural body is maintained in a prescribed structure and heat treatment to generate microcrystal is performed to manufacture the microcrystal thin film structural body. By using a heating and holding method to generate thermal gradient, the microcrystal thin film structural body having specific solute part and the microcrystal part gradiently existing is manufactured. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a thin film structure, and more particularly, as a micromachine such as a microactuator, a probe, a stylus, various sensors such as a microsensor, and a structural part of various probes such as a flow for a scanning type flow microscope. The present invention relates to a method for producing a thin film structure having a microcrystalline structure, which can be used partially or entirely.
[0002]
[Prior art]
In a micromachine, various sensors, various probes, etc., a force acting outside the substrate surface is generated, and various proximity effects, fluid flow, voltage of other electronic circuits, and the like outside the substrate are detected. For this reason, micromachining that applies thin-film deposition technology and microfabrication technology used in semiconductor manufacturing makes it possible to three-dimensionally curve and deform minute planar structures, such as beams, composed of various thin films, such as beams. A thin film structure having a minute three-dimensional structure is now used.
[0003]
As a method of manufacturing such a thin film structure, the present inventors focused on the properties of an amorphous material having a supercooled liquid region, and formed a thin film made of an amorphous material having a supercooled liquid region on a predetermined substrate. Forming a thin film structure having a planar structure in which the thin film processing body is cooled from a supercooled liquid region to room temperature and at least a part of the substrate is removed (Japanese Patent No. 3125048); A thin film structure having a three-dimensional structure in which a thin film structure made of an amorphous material is heated to a supercooled liquid region to be softened, deformed to a predetermined shape by applying an external force to the thin film structure, and then cooled to room temperature. A manufacturing method (Japanese Patent No. 3099066) was developed.
[0004]
By the way, compared to the conventional polycrystalline material having crystal grains of the order of tens to hundreds of microns, it has excellent mechanical properties such as high toughness, and can have higher electrical conductivity than an amorphous material. A microcrystalline material having microcrystals having a size on the order of several tens of microns to nanometers has become known as a material that can obtain many more properties than a crystalline material.
[0005]
However, when manufacturing a planar thin film structure such as a cantilever using a microcrystalline material, film forming conditions such as a substrate temperature and a film forming speed at which a microcrystalline structure is formed during film formation, and a thin film structure are used. Sometimes it is necessary to form a film under such conditions that the stress inside the thin film does not cause deformation or destruction. However, since these conditions cannot be satisfied at the same time, it is not possible to manufacture a thin film structure having a microcrystalline structure and high flatness. It is difficult, and it is even more difficult to accurately produce a three-dimensional microcrystalline structure such as a bent beam. In the method of forming microcrystals at the time of film formation, since the entire thin film becomes microcrystals, it is extremely difficult to manufacture a structure in which an amorphous portion and a microcrystal portion are inclined in a thin film structure. There was a problem.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve such problems in the prior art, and to provide a manufacturing method for manufacturing a planar or three-dimensional thin film structure having a microcrystalline material or a material in which amorphous and microcrystalline portions are inclined. Is to provide.
[0007]
[Means for Solving the Problems]
The present inventors have conducted research on a method of manufacturing a thin film structure having microcrystals. As a result, first, a thin film structure was formed from an amorphous thin film, and then the structure of the amorphous thin film was changed to a glass transition point. As described above, it has been found that a microcrystalline thin film structure can be obtained by performing a heat treatment at a temperature equal to or lower than the crystallization start temperature for a predetermined time and generating microcrystals in the amorphous phase. The invention has been reached.
[0008]
The first method for manufacturing a microcrystalline thin film structure according to the present invention includes the steps of: forming an amorphous thin film on a substrate; patterning the amorphous thin film into a predetermined shape; Heating the amorphous thin film at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals in the amorphous thin film; and removing at least a part of the substrate to form a thin film structure. Forming a flat microcrystalline thin film structure.
[0009]
Further, in the second method for manufacturing a microcrystalline thin film structure according to the present invention, a step of forming an amorphous thin film on a substrate; a step of patterning the amorphous thin film into a predetermined shape; A step of cooling at least a part of the thin film and heating the remaining part at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals, and removing at least a part of the substrate, Forming a thin-film structure, wherein a microcrystalline thin-film structure having a flat plate-like shape in which microcrystalline portions and amorphous portions are inclined exists.
[0010]
Further, a third method of manufacturing a microcrystalline thin film structure according to the present invention includes a step of forming an amorphous thin film on a substrate; a step of patterning the amorphous thin film into a predetermined shape; Removing a portion, forming a thin film structure, applying an external force to at least a portion of the thin film structure to cause a deformation of a portion of the amorphous thin film, at least a portion of the thin film structure A step of subjecting a part to heat treatment at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to produce microcrystals, thereby producing a microcrystalline thin film structure having a three-dimensional structure.
[0011]
Further, a fourth method for manufacturing a microcrystalline thin film structure according to the present invention includes the steps of: forming an amorphous thin film on a substrate; patterning the amorphous thin film into a predetermined shape; Removing a portion to form a thin film structure; applying an external force to at least a portion of the thin film structure to cause deformation of a portion of the amorphous thin film; Heating at least a part of the remaining portion and heating the remaining portion at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals, and the microcrystal portion and the amorphous portion have a three-dimensional structure. The present invention is characterized in that a microcrystalline thin film structure that exists in an inclined manner is manufactured.
[0012]
In the present invention, the glass transition point Tg is a temperature at which a transition from a solid phase to a highly viscous supercooled liquid occurs when the temperature of an amorphous thin film is increased. The crystallization start temperature Tx is a temperature at which crystallization starts to be observed when the temperature of the supercooled liquid is increased. Incidentally, the temperature at which crystallization from the supercooled liquid is observed depends on the temperature rise rate at the time of observation, and also depends on the measuring means. In the present invention, the crystallization onset temperature is set to 0.16 ° C./sec by using a differential scanning calorimeter (DSC). Is defined as the crystallization start temperature Tx.
[0013]
In the present invention, the size of the microcrystals in the microcrystalline thin film structure to be manufactured, for example, the particle size, can be selected from various sizes depending on the characteristics of the microcrystalline thin film structure of interest and the application of the microcrystalline thin film structure. It is possible. However, if the size of the crystal is too large, it will be the same as a normal polycrystalline thin film, and the properties of a microcrystalline thin film cannot be obtained.If the size of the crystal is too small, the properties as a crystal will be lost. The properties of the thin film cannot be obtained. Accordingly, the particle size of the microcrystal is preferably about 2,000 nm or less and 1 nm or more, more preferably 1,000 nm or less, more preferably 1 nm or more, and even more preferably 100 nm or less and 1 nm or more.
[0014]
According to the present invention, by forming a film in an amorphous state, film forming conditions such as a substrate temperature can be remarkably relaxed as compared with a case where a microcrystalline thin film is directly formed. In particular, an amorphous alloy having a supercooled liquid region has a low critical cooling rate, and can form an amorphous thin film without particularly cooling the substrate.
[0015]
Further, according to the present invention, after film formation, heat treatment is performed in a supercooled liquid region and microcrystallization is performed, so that the internal stress or elastic stress of the thin film can be relaxed. A thin film structure can be manufactured.
BEST MODE FOR CARRYING OUT THE INVENTION
The substrate used in the method for manufacturing a microcrystalline thin film structure of the present invention can be appropriately selected depending on the use of the microcrystalline thin film structure. For example, single crystal silicon, single crystal silicon provided with an oxide film or a nitride film, Pyrex (registered trademark) (Trademark) glass, a stainless steel plate, or the like.
[0016]
In the method for manufacturing a microcrystalline thin film structure according to the present invention, as a method for forming an amorphous thin film on a substrate, a physical vapor deposition method such as sputtering or vapor deposition such as high-frequency magnetron sputtering, or a chemical vapor deposition method such as CVD method. A known method such as a method can be used. Using such a thin film forming method, a thin film of an amorphous material having a supercooled liquid region is formed on a substrate. The type of the amorphous material used here is not limited as long as it has a supercooled liquid region and can achieve the object of the present invention, and various amorphous metal alloys such as Zr- In addition to Cu-Al and Pd-Cu-Si, various amorphous materials can be used.
[0017]
In the method of manufacturing a nanocrystalline thin film structure according to the present invention, the thin film formed on the substrate as described above is patterned into a predetermined shape and manufactured. For the patterning, a known fine processing technique such as wet etching using hydrofluoric acid or potassium hydroxide solution or dry etching such as RIE (reactive ion etching) can be used.
[0018]
In the method for manufacturing a nanocrystalline thin film structure according to the present invention, the patterned amorphous thin film is heated and heat-treated in a supercooled liquid region. When the non-quality thin film exceeds the glass transition temperature, it becomes a supercooled liquid state of 10 ¹¹ to 10 ¹³ Pa · s, and the stress inside the thin film can be removed. By maintaining the amorphous thin film in the temperature range of the supercooled liquid state, microcrystals can be generated from the phase in the supercooled liquid state.
[0019]
FIG. 1 is a time-temperature transformation diagram in which the crystallization start time at each temperature is determined by DSC for two types of amorphous thin films. In order to generate microcrystals, heat treatment may be performed so as to reach a crystallization region at the upper right of the line in FIG. The heat treatment time can be shortened near Tx because the crystallization proceeds quickly, while the heat treatment for a relatively long time is required near Tg because the crystallization is slow. Note that crystallization by such heat treatment can be confirmed by a method such as observing generation of microcrystalline particles by electron microscope observation, or finding diffraction lines by electron beam diffraction.
[0020]
In order to generate a good microcrystalline phase, the temperature range Tx-Tg of the supercooled liquid region is desirably 10 ° C or more, more desirably 20 ° C or more. Further, by having a relatively wide supercooled liquid region, the heating step of the thin film is stabilized, so that the step can be simplified.
[0021]
In the method for producing a microcrystalline thin film structure of the present invention, known heating means such as infrared heating, laser heating, and high-frequency heating can be used as the heating means used for the overheat treatment. In this heat treatment, the entire thin film structure can be heat-treated to microcrystallize the entire structure. In addition, by giving a temperature difference to the thin film structure during the heat treatment, the amount of generated microcrystals is inclined. It can also be a microcrystalline inclined thin film structure.
[0022]
In order to give a temperature difference to the thin film structure in the heat treatment of the thin film structure, a method of bringing a cooling material into contact with the thin film structure and performing local cooling can be used. For example, during the heat treatment, a cooling member is brought into contact with a predetermined position on the amorphous thin film pattern to generate a thermal gradient in the amorphous thin film pattern or the thin film structure. By performing the heat treatment in such a state, the portion having a higher temperature is more crystallized, and the portion in contact with the cooling agent remains amorphous, and the amorphous portion follows the thermal gradient. It is possible to realize a structure made of an amorphous-microcrystalline material in which microcrystalline portions are inclined. When a jig is used to deform the thin film structure into a three-dimensional shape, the jig can be used as a cooling member.
[0023]
In the method for manufacturing a microcrystalline thin film structure according to the present invention, when the thin film structure is heated and heat-treated in a supercooled liquid region, the thin film structure is deformed by applying stress, and the internal stress caused by the deformation is reduced. After being removed by this heat treatment, this is cooled to obtain a three-dimensional structure with deformation maintained. As a method of applying a stress to obtain a three-dimensional structure by deforming the thin film structure, a method of mechanically applying a stress using a jig or the like, or a method of applying an electrostatic force between the thin film structure using an electrode layer or the like. A method of applying a magnetic stress, a method of applying a magnetic stress between the thin film structure using a magnetic material, and a method of forming the thin film structure into layers having different coefficients of thermal expansion depending on purposes, and a method of applying a thermal expansion between layers. Each method described in Japanese Patent No. 3099066, such as a method of deforming by a bimetal effect due to a difference, can be used.
[0024]
As shown in FIG. 1, the time for heating and holding the thin film in the supercooled liquid region varies greatly depending on the heating temperature, and also differs depending on the type of material constituting the thin film, the thickness of the thin film, the conditions for forming the thin film, and the like. It will be. Generally, the temperature is maintained for about 10 ² to 10 ⁴ seconds in such a temperature range. Thereby, the stress in the thin film processing body can be sufficiently removed and the crystal can be microcrystallized, thereby achieving the object of the present invention. After the heat treatment, the thin film is cooled from the supercooled liquid region to room temperature. As the cooling means, means such as natural cooling by heat radiation, cooling by introducing a cooling gas, cooling by contact with a cooling board, and the like can be used.
[0025]
In the method for manufacturing a microcrystalline thin film structure according to the present invention, at least a part of the substrate is removed. As a method for removing at least a part of the substrate, a known fine processing technique represented by wet etching or dry etching as described above can be used. The removal of at least a part of the substrate can be performed after the heat treatment in order to prevent deformation during the heat treatment and obtain a planar nanocrystalline structure. Further, at least a part of the substrate may be removed before the heat treatment, and the structure may be deformed by applying a stress during the heat treatment to obtain a predetermined three-dimensional structure.
[0026]
In the production of the microcrystalline thin film structure of the present invention, before forming a thin film made of an amorphous material having a supercooled liquid region on a substrate, the substrate is formed into a predetermined shape as described in Japanese Patent No. 3125048. A patterned sacrificial layer can be formed. In this case, a thin film planar structure is obtained by forming an amorphous thin film on a substrate so as to cover the sacrifice layer and removing the sacrifice layer instead of removing at least a part of the substrate. Can be.
[0027]
The patterned sacrificial layer can be formed by uniformly applying a resist on the main surface of the substrate by spin coating or the like, and then performing exposure and development through a mask made of Cr. Furthermore, after forming polysilicon or the like uniformly on the main surface of the substrate by means such as CVD, a protective film made of a resist may be formed on the polysilicon film and wet-etched.
[0028]
The thickness of the thin film processing body constituting the microcrystalline thin film structure of the present invention is not particularly limited, and can be formed to any thickness within a range having a supercooled liquid region depending on the application. In particular, when the thickness of the thin-film planar processing body is in the range of 1 to 20 μm, it has a supercooled liquid region as described above and has a strength suitable for use in various sensors and various probes. Therefore, a microcrystalline thin film structure suitable for various sensors and various probes can be provided by forming a thin film planar processed body, and a thin film before being processed into a thin film planar processed body to 1 to 20 μm. .
[0029]
(Example 1)
As shown in FIG. 2, an amorphous thin film 2 of 5 μm thick Pd-based thin film metallic glass (Pd ₇₆ Cu ₇ Si ₁₇ , subscript is atomic%) is formed on a silicon substrate 1 by the following semiconductor process. Patterned.
[0030]
First, a polyimide film was formed on the main surface of the substrate to a thickness of 5 μm by spin coating. Next, a patterning layer was formed by patterning the polyimide film by RIE (reactive ion etching). Next, a silicon oxide layer was formed to a thickness of 1 μm on the back surface of the substrate by a thermal oxidation method. Next, a thin film made of metallic glass having the above composition was formed to a thickness of 2 μm on the main surface of the substrate by a sputtering method so as to cover the thin film made of the metallic glass with the patterning layer. Next, the substrate was immersed in potassium hydroxide to remove the patterning layer, and the thin film was patterned to form a processed thin film.
[0031]
FIG. 3 shows the results of measuring the differential thermal curve of the amorphous thin film 2 with a differential scanning calorimeter at a temperature rising rate of 0.16 ° C./sec. In the figure, the glass transition temperature Tg is 637 K, the crystallization start temperature Tx is 669 K, and a supercooled liquid region exists between Tx and Tg.
[0032]
The amorphous thin film 2 is heated at a crystallization temperature Tx for 120 seconds in a heat treatment environment in which the amorphous thin film 2 is reduced in pressure to 10 ⁻³ Pa or less to prevent oxidation using infrared rays as a heating means. And cooled to room temperature at a cooling rate of 10 ° C./min. The softening in the supercooled liquid region during the heating reduced the internal stress of the thin film and hardened the thin film structure by crystallization.
[0033]
After cooling, the silicon substrate was partially immersed in an aqueous solution of potassium hydroxide heated to 80 ° C. for 2 hours to remove a part of the silicon substrate, thereby obtaining a planar cantilever microcrystalline thin film structure 3 shown in FIG. Was. The microcrystallinity of the thin film structure 3 thus obtained was confirmed by observation with an electron microscope by the presence of microcrystalline particles. In addition, the presence of diffraction lines due to microcrystals was confirmed by electron beam diffraction.
[0034]
(Example 2)
In the same manner as in Example 1, an amorphous thin film patterned by a known method such as a semiconductor process was formed on a silicon substrate 1 and subsequently patterned on the substrate 1 as shown in FIG. The cooling member 4 was brought into contact with a part of the amorphous thin film 2. In the present embodiment, a stainless steel member that is sufficiently larger than the plate 1 is used as the cooling member 4. In addition, if necessary, a cooling pipe (not shown) may be connected to the cooling member 4, and a cooling device for circulating a refrigerant in the pipe may be provided.
[0035]
In the state where the cooling member 4 shown in FIG. 5 is in contact with the crystallization start temperature Tx (669K) by infrared heating under the reduced pressure of 10 ⁻³ Pa or less in order to prevent oxidation, as in Example 1. Heating for 250 seconds, the portion cooled by the cooling member 5 does not crystallize, and the thin-film structure 5 of FIG. 6 made of an amorphous-microcrystalline gradient material whose degree of crystallinity increases with distance from the cooling member. Was made. The softening in the supercooled liquid region passing during the heating reduced the internal stress of the thin film structure 5 and strengthened the structure by crystallization. Electron microscopic observation of the portion of the obtained thin film structure 5 having a large degree of crystallinity confirmed that the film was well microcrystallized. In addition, diffraction lines due to microcrystals were confirmed by electron beam diffraction.
[0036]
(Example 3)
FIG. 7 shows an amorphous cantilever-shaped thin film structure 6 made of a Zr-based thin film metallic glass (Zr ₇₅ Cu ₁₅ Al ₆ , subscript is atomic%) having a thickness of 5 μm used in the present example. This cantilever-shaped thin film structure 6 was produced as follows. First, as in Example 1, a polyimide film is formed on the main surface of the substrate 1 to a thickness of 5 μm by a spin coating method, and a patterning layer is formed on the silicon substrate by RIE (reactive ion etching). did. Next, a silicon oxide layer was formed to a thickness of 1 μm on the back surface of the substrate by a thermal oxidation method. Next, a thin film made of metallic glass having the above composition is formed to a thickness of 2 μm on the main surface of the substrate by sputtering so as to cover the patterning layer, and the patterning layer is removed by immersing the substrate in potassium hydroxide. At the same time, a thin film processed body was formed by patterning the thin film, and then a portion of the silicon substrate was removed by immersing the thin film in a potassium hydroxide aqueous solution heated to 80 ° C. for 2 hours, as shown in FIG. A cantilever-shaped thin film structure 6 was obtained.
[0037]
The amorphous thin planar structure 6, as shown in FIG. 8, is deformed by a stainless member 7, at the crystallization starting temperature Tx (713K), by a known heating means such as infrared heating, 10 ^- Heating was performed for 110 seconds under a reduced pressure of ³ Pa or less, softening in a supercooled liquid region passing during heating reduced the internal stress and hardened the structure by crystallization, and after cooling, shown in FIG. The microcrystalline thin film structure 8 having a three-dimensional structure was manufactured. Observation with an electron microscope of the obtained thin film structure 8 confirmed that it was microcrystallized. In addition, diffraction lines due to microcrystals were confirmed by electron beam diffraction.
[0038]
(Example 4)
The member 7 shown in FIG. 8 is a cooling member having a large heat capacity, and the other components are the same as those of the third embodiment, whereby the thin film three-dimensional structure of FIG. The body 9 was made. Electron microscopic observation of the portion of the obtained thin film structure 4 having a large degree of crystallinity confirmed that the film was well microcrystallized. In addition, diffraction lines due to microcrystals were confirmed by electron beam diffraction.
[0039]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the thin film planar structure or the thin film three-dimensional structure provided with the material in which the quantity of a microcrystal or a microcrystal changes with inclination can be manufactured. Properties suitable for each part, such as increasing the fracture toughness by microcrystallization at the base where stress is concentrated, and maintaining the amorphous part at the tip where abrasion resistance and high hardness are required Therefore, a thin film structure applicable to various uses such as various microprobes, nano / micromachines such as end effectors of micromanipulators, and the like can be realized.
[Brief description of the drawings]
FIG. 1 is a time-temperature transformation diagram showing the crystallization start time at each temperature for two types of amorphous thin films.
FIG. 2 is a view showing an amorphous thin film patterned on a substrate.
FIG. 3 is a diagram showing a differential heat curve of an amorphous thin film measured by a differential scanning calorimeter.
FIG. 4 is a view showing a planar cantilever-shaped microcrystalline thin film structure.
FIG. 5 is a diagram showing that heat treatment is performed by applying a temperature gradient by bringing a cooling member into contact with an amorphous thin film patterned on a substrate.
FIG. 6 is a view showing a thin film structure composed of an amorphous-microcrystalline gradient material.
FIG. 7 is a diagram showing a cantilever-shaped thin film structure.
FIG. 8 is a view showing a state in which a heat treatment is performed while deforming an amorphous thin film planar structure with a stainless member.
FIG. 9 is a diagram showing a structure of a microcrystalline thin film having a three-dimensional structure.
FIG. 10 is a view showing a thin film three-dimensional structure made of an amorphous-microcrystalline gradient material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Thin film, 3 ... Cantilever-shaped microcrystalline thin film structure, 4 ... Cooling member, 5 ... Thin film structure, 6 ... Amorphous cantilever shape Thin film structure, 7: Stainless steel member, 8: Microcrystalline thin film structure having a three-dimensional structure, 9: Thin film three-dimensional structure made of an amorphous-microcrystalline gradient material.

Claims (4)

Forming an amorphous thin film on the substrate;
Patterning the amorphous thin film into a predetermined shape,
A step of heating the patterned amorphous thin film at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals in the amorphous thin film;
Removing at least a part of the substrate to form a thin film structure. Forming an amorphous thin film on the substrate;
Patterning the amorphous thin film into a predetermined shape,
A step of cooling at least a part of the amorphous thin film and heating the remaining part at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals,
Removing at least a portion of the substrate to form a thin film structure;
A method for producing a microcrystalline thin film structure, comprising: Forming an amorphous thin film on the substrate;
Patterning the amorphous thin film into a predetermined shape,
Removing at least a portion of the substrate to form a thin film structure;
Applying an external force to at least a part of the thin film structure to cause deformation of a part of the amorphous thin film,
A step of heating at least a part of the thin film structure at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals,
A method for producing a microcrystalline thin film structure, comprising: Forming an amorphous thin film on the substrate;
Patterning the amorphous thin film into a predetermined shape,
Removing at least a portion of the substrate to form a thin film structure;
Applying an external force to at least a part of the thin film structure to cause deformation of a part of the amorphous thin film,
Cooling at least a part of the amorphous thin film and heating the remaining part at a temperature equal to or higher than the glass transition point and equal to or lower than the crystallization start temperature for a predetermined time to generate microcrystals. A method for manufacturing a thin film structure.

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