JP2922058B2 - Thin film making method and thin film making equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming technique,
In particular, the present invention relates to a thin film forming method and a thin film forming apparatus for forming a thin film by irradiating a target with excitation light.

[0002]

2. Description of the Related Art Several techniques for forming a thin film using light are known. In light CVD, a source gas containing a constituent element of a thin film is irradiated with light having a specific wavelength, and a specific component is activated to grow the thin film on a substrate. Generally, various lasers are used as a light source. The wavelength of light, and thus the type of laser, is selected according to the source gas, the element to be deposited, and the like.

Recently, laser molecular beam epitaxy (MBE)
The technology called is actively researched. Laser MBE
In this method, a laser beam is focused and irradiated on a predetermined target to cause ablation to form a thin film of a target material on a substrate.

[0004] Ablation is a phenomenon in which a target material is scattered from a locally generated high-temperature plasma state. An excimer laser is often used as a laser for causing ablation.

[0005] In photo-CVD, gas is used as the source of the constituent elements of the thin film. The gas source is generally a compound of a target constituent element, and when this compound is decomposed, an element other than the target element is also generated. Other constituent elements in the source gas or impurities contained in the source gas may affect the quality of a thin film to be formed.

Further, since the source gas is handled at a relatively high pressure, the activated source gas does not immediately disappear even if the laser irradiation is stopped. For this reason, when trying to accurately control the thickness of the thin film, the growth of the film may not be stopped immediately.

In laser MBE, a target is ablated in a relatively high vacuum. Therefore, if laser irradiation is stopped, ablation stops immediately,
The growth of the thin film stops. Therefore, highly accurate control of the film thickness is relatively easy.

A solid target is mainly used as a source for growing a thin film. By using a target substance or a solid target of a constituent element thereof, it is easy to suppress impurities. in this way,
Laser MBE has several advantages over photo-CVD.

[0009]

The laser mainly generates a laser beam having a spot-shaped cross section. In the laser MBE, such a laser beam is condensed and irradiated on a target surface. From the target irradiated with laser light,
The target constituent material is released in a cone shape with the irradiation point at the top.

When a molecular beam from such a point source is received by a planar substrate, the thickness of the thin film on the substrate is the thickest at the point closest to the point source, and becomes thinner as the distance from the point source increases. Become.

[0011] The substrate is placed in a satellite orbit (planetary motion).
Although it is possible to form a thin film having a relatively uniform film thickness on the surface by moving the substrate, the driving mechanism of the substrate becomes complicated. Further, in order to drive the substrate in a satellite orbit, the size of a reaction chamber for depositing a film becomes large. Therefore, there is a limit in producing a large-area thin film.

It is important to form a thin film on a large-area surface by controlling the film thickness uniformly and with high precision in order to exhibit the function of the thin film. However, the normal laser MB
In E, it is not easy to grow a thin film having a uniform thickness on a large area surface.

An object of the present invention is to provide a thin film forming method capable of growing a thin film having a uniform film thickness on a large-area surface and controlling the film thickness accurately. Another object of the present invention is to provide a thin film forming apparatus having a uniform film thickness on a large-area substrate and capable of accurately controlling the film thickness.

[0014]

According to the present invention, there is provided a thin film forming method comprising the steps of: arranging a base substrate for thin film growth facing a target; and irradiating the target with synchrotron radiation to ablate the target material. And causing it to occur.

Further, the thin film forming apparatus of the present invention comprises a reaction chamber capable of evacuating, a target holding mechanism arranged in the reaction chamber for holding a target, and a base substrate facing the target. And a SR introducing means for introducing synchrotron radiation into the reaction chamber.

[0016]

The ablation can be caused by using synchrotron radiation (SR light) instead of laser light. SR light includes light in a wide wavelength range from the X-ray region to the visible light region. For this reason, it is possible to form a thin film similar to the laser MBE using an excimer laser using the SR light. Since the wavelength range is wide, a thin film forming substance can be selected from a wider range of materials.

Ablation by SR light has the following additional features. The SR light includes abundantly a wavelength component (about 1 to 10 nm) which is much shorter than the wavelength (about 200 nm) of an excimer laser mainly used in the laser MBE. For this reason, it is considered that the plasma generated by the SR light is in a higher ionization state than the plasma generated by the excimer laser, and the density can be made more uniform.

The SR light is emitted in a tangential direction of the electron orbit of the SR light source and on a plane formed by the electron orbit. The directivity of SR light is extremely high, for example, the divergence angle perpendicular to the plane is about 1 mrad, and its thickness is 1 mm or less.
Therefore, when SR light is used, ablation can be generated without using a condenser lens or a mirror.

Since the density of particles scattered by ablation can be made uniform, it is easy to make the thickness of the thin film to be made uniform. Further, since SR light having a linear cross section can be easily obtained, linear ablation can be generated without using an optical system.

Therefore, a thin film having a width corresponding to the length of the straight line can be manufactured. It is also clear that the growth of the thin film stops immediately when the entry of the SR light is stopped.

[0021]

FIG. 1 schematically shows a thin film forming apparatus according to an embodiment of the present invention. The main configuration of the thin film forming apparatus includes a reaction chamber 1, a slit chamber 2, an optical system chamber 3, and an SR light source 14.

The thin film forming apparatus is connected to the SR light source 14 and introduces the SR light 5 emitted from the electrons orbiting the electron orbit 15 in the SR light source. The reaction chamber 1, the slit chamber 2, and the optical system chamber 3 are connected to the SR light source 14 so as to form a continuous space.

The SR light source 14 is maintained in a high vacuum of 10 ^-9 torr or less, and the optical system chamber 3 has a bulb V2.
And an exhaust device P2 is connected through the outlet to exhaust air to a similar high vacuum. Light in a wavelength range from infrared light emitted from electrons orbiting the electron orbit 15 to soft X-rays enters the reaction chamber 1 through the optical system chamber 3 and the slit chamber 2.

The SR light source 14 is provided with a means for controlling the accumulated current value of electrons circling the electron orbit 15.
The amount of generated SR light can be controlled. Further, the SR light source 14 is provided with a means for controlling the critical wavelength of the SR light 5, and can select an optimal wavelength for causing a target to undergo ablation. For example, by changing the magnetic field, the electron energy can be changed.

In the reaction chamber 1, a solid target 4, which is a material for forming a thin film, is disposed so as to block SR light. When the solid target 4 is irradiated with the SR light, ablation occurs from the irradiated portion.

For this reason, since the degree of vacuum in the reaction chamber 1 is reduced, an exhaust device P1 is connected to the reaction chamber 1 via the valve V1. The evacuation device P2 connected to the optical system chamber 3 performs differential evacuation to generate S
A high vacuum in the R light source 14 is maintained.

The electron orbit 15 has a circular orbit, for example.
The generated SR light has a disk-like shape, and a part thereof, for example, a part having a width of several cm is introduced into the reaction chamber 1 via the optical system chamber 3. In the figure, the SR light has a linear cross section that is long in a direction perpendicular to the paper surface.

When the linear portion of the solid target 4 is irradiated with the SR light 5 having such a linear cross section, linear ablation occurs on the surface of the solid target 4 and the target material is scattered radially. To deposit on the surface of the substrate 6. Since the SR light 5 has a linear cross section that is long in the direction perpendicular to the plane of the paper, deposition on the substrate 6 also occurs in a band-shaped area that is long in the direction perpendicular to the plane of the paper.

In order to increase the width of the belt-like region where the deposition occurs and perform uniform deposition, a linear drive mechanism 10 that can move in the left-right direction on the paper is provided in the holding mechanism that holds the substrate 6. By reciprocating the linear drive mechanism 10 right and left, a thin film having a uniform thickness can be deposited on a desired region on the substrate 6.

The linear drive mechanism 1 for performing a linear motion
Although 0 is exemplified, a mechanism for driving the base in the length direction of the long object may be used instead of the reciprocating motion in order to perform deposition on the underground of the long object. Further, by controlling the linear drive mechanism, a thin film having a gradually changing thickness can be deposited on the substrate 6. Such a thin film whose thickness changes gradually can be used for a variable filter or the like.

In order to uniformly diffuse the deposited material deposited on the substrate 6 or to promote crystallization of the deposited material, it is preferable to mount a heater 8 on the substrate holding mechanism.

The irradiation of the SR light 5 gradually consumes the surface of the target 4. The target 4 is attached to a rotation mechanism 7, and by rotating the rotation mechanism 7,
A fresh surface of the target 4 can be supplied to the SR light irradiation area.

In order to deposit different substances,
It is sufficient that the rotation mechanism 7 can be driven in the axial direction, a plurality of targets 4 are provided on the axis, and a desired target is supplied to the SR light irradiation area. The rotation mechanism 7
A plurality of combinations of the target and the target 4 may be provided.

The slit chamber 2 is for adjusting the SR light intensity that causes ablation. For example, the slit rotating plate 9 having an opening of a predetermined variable shape is rotated to periodically block the SR light 5.

The irradiation amount of the SR light 5 can be adjusted by adjusting the irradiation time of the SR light 5 or by changing the width of the slit. Note that the SR light 5 is continuous light emitted from an electron packet orbiting the electron orbit 15, and the light emission cycle at the fixed position is several ns to several 1s.
00 ns. Since the emission cycle of the SR light 5 is sufficiently short, the irradiation time of the SR light is controlled by controlling the slit rotating plate 9.

An optical apparatus 11 such as a lens or a mirror is inserted into the optical system chamber 3. SR light has high directivity, but has a divergence angle depending on its wavelength. The divergence angle increases as the wavelength increases. Important components for ablating the target are very short ultraviolet (VUV) light and soft X-rays, but long-wavelength UV light and visible light are also effective.

The soft X-ray which is a characteristic component of the SR light has a width of about 1 mm in the vertical direction (the thickness direction of the disk), but spreads more with longer wavelength components. The optical device 11 is used to converge the long wavelength component of the SR light.

In the configuration shown in the figure, a cylindrical lens 11 having a band-shaped slit in the center is used. The long wavelength component spread to the lens portion is bent in the optical axis direction by the refraction of the lens. The short-wavelength component traveling on the axis passes through the central slit of the lens 11 and travels.

While the target 4 is irradiated with the SR light 5, the target constituent material is scattered from the target 4, so that the degree of vacuum of the reaction chamber 1 is reduced. By providing an exhaust device P1 in the reaction chamber 1 and connecting an exhaust device P2 to the optical system chamber 3, differential evacuation is performed to maintain the degree of vacuum in the SR light source 14 at a high vacuum.

A gate valve 12 is provided between the reaction chamber 1 and the slit chamber 2 to separate the reaction chamber 1 from the vacuum on the SR light source 14 side. When the gate valve 12 is closed, the reaction chamber 1 is disconnected,
The substrate 6 on which the thin film has been formed can be taken out or the target 4 can be replaced.

Of course, at the time of these exchanges, the reaction chamber 1
A spare part to be temporarily taken in and out of the spare chamber connected to the reaction chamber 1 is accommodated so that the inside of the reaction chamber 1 is not exposed to the atmospheric pressure.

Although not shown, the reaction chamber 1 has a quartz oscillator for controlling the film thickness and an R for measuring the electron beam diffraction similar to those used in a laser MBE apparatus or the like.
HEED and the like are provided. Further, a gas supply duct may be provided in the reaction chamber 1 to supply an oxygen gas when depositing an oxide thin film and a nitrogen gas or the like when depositing a nitride.

Hereinafter, the target rotating mechanism 7, the slit rotating plate 9, and the optical device 11 will be described in more detail with reference to FIGS. As shown in FIG. 2, the target rotation mechanism 7 includes a motor 21, a bellows 22, a vacuum flange 24, and a combination target 23. The combination target 23 is composed of targets of four different substances. Each target has a width wider than the width of the SR light, and only one of the targets can be selectively irradiated with the SR light. With such a combination target,
For example, Bi ₂ O ₂ , Sr, CuO ₃ , and Ca can be selectively deposited.

The combination target 23 is mounted on a shaft 25, and by expanding and contracting the bellows 22,
Any target can be selected. The motor 21 rotates the shaft 25 to change the irradiation position of the target 23.

With such a target rotating mechanism, S
It exposes a fresh surface of the target to the R light, and allows a desired target to be selected from a plurality of targets.

FIG. 3 shows a configuration example of the slit rotating plate 9. In the slit chamber 2, the SR light is
Through the paper in the direction perpendicular to the paper. Slit rotating plate 9
Includes a disk 34 in which a slit 31 is formed, and a motor 3
Rotated by 2.

As the motor 32 rotates, the SR light periodically passes through the slit rotating plate 9. By adjusting the passage time of the SR light, the SR light irradiation intensity is adjusted. SR
In order to adjust the light intensity, it is preferable that the opening angle of the slit 31 can be variably adjusted.

For example, the disk 34 is composed of two plates,
The opening angle of the slit 31 can be adjusted by providing an opening on one of them and adjusting the relative angle between the two. It is also possible to provide a plurality of types of disks 34 and select a desired disk.

FIG. 4 shows an example of the configuration of a cylindrical lens which is an example of optical equipment. Cylindrical lens 11
Has a focal length in the Y direction in the figure and has no convergence effect in the X direction. Therefore, the SR light 5 incident on the cylindrical lens 11 is converged only in the vertical direction in the drawing.

An opening slit 37 is formed at the center of the cylindrical lens 11.
SR light 5 incident on the slit passes through the slit 37 as it is. Since soft X-rays and VUV light having a short wavelength have a small divergence angle, they are almost incident on the central opening slit 37, are not refracted by the cylindrical lens 11, and are not absorbed by the cylindrical lens 11. The converging action of the cylindrical lens 11 is set to UV light having a wavelength longer than approximately 200 nm.

According to such a configuration, the SR light of a long wavelength having a large divergence angle can be efficiently irradiated on the target. When a shorter wavelength SR light is to be converged, it is preferable to use a mirror instead of a lens having strong absorption. For example, a longitudinal cylindrical mirror is suitable.

A process for forming a thin film on the substrate 6 using the thin film forming apparatus shown in FIG. 1 will be briefly described below. The substrate 6 is mounted on a substrate holding mechanism and heated to a desired temperature by the heater 8. After evacuating the reaction chamber 1 to a predetermined vacuum degree,
Open the gate valve 12 and move the reaction chamber 1 to the SR light source 1
Connect to 4 side. The slit rotating plate 9 is rotated to introduce the SR light 5 into the reaction chamber 1 via the optical system chamber 3 and the slit chamber 2.

When the SR light 5 irradiates the surface of the target 4, ablation occurs at the irradiation position, and the constituent material of the target 4 scatters radially. The scattered target constituent material is deposited on the surface of the substrate 6 to form a thin film. By driving the linear drive mechanism 10 during the deposition to change the position of the substrate 6 left and right, a thin film having a uniform thickness is formed on the substrate 6.

When laminating a plurality of types of thin films, a combination target is used as the target 4, a thin film having a desired thickness is deposited, the target is replaced, and another type of thin film is deposited. The thickness of the deposited thin film is RHE (not shown).
Measure by ED device.

When a relatively thick thin film is formed, the deposited film thickness is monitored based on the thickness of the thin film deposited on the crystal oscillator provided on the substrate 6 side. After depositing a desired thin film, the gate valve 12 is closed, and the substrate 6 is taken out through the preliminary chamber.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
The optical system chamber 3 is not always necessary, and the optical device 11 can be omitted.

The substance deposited by the ablation of SR light can be widely selected from insulators, semiconductors, and metals. Further, the slit arranged in the slit chamber 2 does not need to have a rotating plate configuration. For example, the slit may be provided on a flat plate and driven by a linear drive mechanism or the like.

The substrate holding mechanism is not limited to the illustrated one. What is important is that a disk-shaped SR light generated from the SR light source 14 is extracted to a predetermined width, and is irradiated on a linear region on the target to generate ablation in the linear region of the predetermined width, thereby forming a target structure on the substrate. Is to deposit material. Since an ablation source having a predetermined width can be obtained, it is easy to form a thin film having a uniform thickness even on a large-area substrate.

It will be apparent to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0060]

As described above, according to the present invention,
By using the SR light as the excitation light, a thin film forming method and a thin film forming apparatus having a novel configuration are provided.

By using a wide SR light, a uniform thin film can be formed on a large-area substrate.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a configuration example of a target rotating mechanism used in the thin film forming apparatus of FIG.

FIG. 3 is a plan view showing a configuration example of a slit rotating plate used in the thin film forming apparatus of FIG.

FIG. 4 is a perspective view showing a configuration example of an optical apparatus used in the thin film forming apparatus of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Slit chamber 3 Optical system chamber 4 Target 5 SR light 6 Substrate 7 Rotating mechanism 8 Heater 9 Slit rotating plate 10 Linear drive mechanism 11 Optical equipment (cylindrical lens, cylindrical mirror) 12 Gate valve 14 SR light source 15 Electronic trajectory V Valve P Exhaust device 21 Motor 22 Bellows 23 Combined target 24 Vacuum flange 25 Axis 31 Slit 32 Motor 33 Beam duct 34 Disk

Continuation of the front page (56) References JP-A-3-56670 (JP, A) JP-A-3-288422 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14 / 00-14/58 H01L 21 / 203,21 / 285

Claims (13)

(57) [Claims] 1. A method for forming a thin film, comprising: arranging a base substrate for thin film growth facing a target; and irradiating the target with synchrotron radiation to cause ablation of the target material. 2. The method according to claim 1, wherein the target has a cylindrical surface, and the synchrotron radiation is applied to the target as a beam having a linear cross section parallel to the axis of the cylinder. . 3. The method according to claim 1, wherein a plurality of types of the targets are prepared, and the step of causing the ablation includes a step of exchanging the targets and stacking a plurality of types of films.
3. The method for forming a thin film according to any one of items 2 to 3. 4. A reaction chamber (1) capable of evacuating, a target holding mechanism arranged in the reaction chamber for holding a target, and a substrate holding for holding a base substrate facing the target. A thin film forming apparatus comprising: a mechanism; and SR introducing means for introducing synchrotron radiation (5) into the reaction chamber. 5. The thin film forming apparatus according to claim 4, wherein said SR introducing means introduces synchrotron radiation having an elongated linear cross section in a direction substantially parallel to the substrate surface. 6. The thin film forming apparatus according to claim 4, wherein said SR introducing means includes a rotary plate having a slit. 7. The thin film forming apparatus according to claim 4, wherein said substrate holding mechanism has a mechanism capable of moving a substrate in a direction in which synchrotron radiation light travels. 8. The target holding mechanism has an axial direction substantially parallel to the substrate surface and substantially perpendicular to the traveling direction of the synchrotron radiation, is rotatable around the axial direction, and moves along the axial direction. The thin film forming apparatus according to any one of claims 4 to 7, further comprising a possible target holder. 9. The method according to claim 4, wherein said SR introducing means includes means for controlling an electron orbit and a current value stored in the electron orbit.
9. The thin-film forming apparatus according to any one of 8. 10. The apparatus according to claim 4, wherein said SR introducing means includes means for controlling electron energy of electrons stored in an electron orbit.
10. The thin film forming apparatus according to any one of claims 9 to 9. 11. The apparatus according to claim 4, wherein said SR introducing means includes an optical member for converging the synchrotron radiation having a relatively long wavelength in one direction substantially perpendicular to the traveling direction of the synchrotron radiation. A thin film forming apparatus according to any one of the above. 12. The thin-film forming apparatus according to claim 11, wherein the optical member has a cylindrical lens provided with a slit in the center. 13. An apparatus according to claim 11, wherein said optical member includes a longitudinal cylindrical mirror.