JP4649964B2 - Photo-vapor chemical growth method and photo-vapor chemical growth apparatus - Google Patents

Description

  The present invention relates to a photo-vapor chemical growth method and a photo-vapor chemical growth apparatus, and more particularly to a photo-vapor chemical growth method and a photo-vapor chemical growth apparatus capable of inducing multiphoton absorption.

  Conventionally, a photo-vapor chemical deposition (photo CVD) method for forming a thin film by irradiation with an excimer laser or the like is used in various semiconductor device manufacturing processes, for example, correction of a mask pattern in a display manufacturing process. Is used as a technique for locally forming a film corresponding to a fine pattern.

  When forming a thin film using such a photo-CVD apparatus, it is necessary to use a separate laser light source having an optimum center wavelength with respect to the light absorption wavelength of the main raw material of the thin film necessary for the photochemical reaction, or Therefore, it is necessary to take measures such as using a tunable laser having a wide wavelength band. As typical laser light sources, there are excimer lasers (KrF laser (wavelength 249 nm), ArF laser (wavelength 193 nm), etc.) and the like, and optical CVD is realized using these (for example, see Non-Patent Document 1). .

D.K.Flynn and J.I.Steinfeld, "Depositionof refractory metal films by rare-gas halide laser photodissociationof metal carbonyls", Journal Applied Physics, 59 (11), 1 June 1986, p.3914-p.3917

  The photochemical reaction in the above-mentioned photo-CVD is based on the assumption of one-photon absorption, and the film-forming method and mechanism of photo-CVD by the multi-photon absorption process have not been sufficiently elucidated theoretically or experimentally. For this reason, there is no specific guideline for realizing a practical photo-CVD method or photo-CVD apparatus that enables film formation with good film quality.

  In view of such a problem, the present invention provides a photo-vapor chemical growth method and a photo-vapor chemical growth apparatus that can form a film using a multiphoton absorption process and have good film quality after film formation. The purpose is to do.

In order to solve the above-described problems, the photochemical vapor deposition method according to the present invention applies a pulse laser beam having a pulse width of 1 ps or less in a source gas atmosphere using an objective lens having a numerical aperture NA exceeding 0.7. Irradiation is performed on the film formation body to form a film.
Further, the present invention is characterized in that, in the above-described photo-vapor chemical growth method, the film formation is performed by inducing a multiphoton absorption process.

  In addition, the photochemical vapor deposition apparatus according to the present invention is a photochemical vapor deposition apparatus in which a film is irradiated with a laser beam in a source gas atmosphere to form a film on the film by a photodissociation reaction. A laser light source that emits a pulsed laser beam having a pulse width of 1 ps or less, and an objective lens that has a numerical aperture NA that is greater than 0.7 for condensing the laser on the film formation target. And

As described above, in the photochemical vapor deposition method and the photochemical vapor deposition apparatus according to the present invention, the pulse width of the laser light source is set to 1 ps or less, and the numerical aperture indicating the focusing performance of the objective lens is set to 0. .7. Here, the objective lens refers to an optical system that focuses light with respect to the film formation position of the film formation target. As a result of intensive studies by the present inventors, when a so-called femtosecond laser having a pulse width of 1 ps or less is used as a light source, the film quality of the structure formed by photo-vapor chemical growth affects the light collection performance of the objective lens. Confirmed to receive. That is, it was found that a finer and more appropriate film-like structure can be formed by using an objective lens having a numerical aperture exceeding 0.7.
In the photochemical vapor deposition method of the present invention, the multiphoton absorption process is induced by the energy condition that induces the multiphoton absorption process, that is, the energy that induces the photodissociation reaction of the target thin film material. It was confirmed that the use of a light source having a wavelength band that produces a fine film-like structure having a resolution exceeding the resolution of the objective lens to be used.

As described above, according to the photochemical vapor deposition method and the photochemical vapor deposition apparatus of the present invention, a film-like structure having a good film quality can be generated.
In addition, in the photo-vapor chemical growth method of the present invention, by generating a film-like structure by inducing a multiphoton absorption process, a fine-shaped structure having a resolution exceeding the resolution of the objective lens can be generated. Can do.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
1A and 1B show a schematic plan configuration and a schematic cross-sectional configuration of an example of a photo-vapor chemical growth apparatus that realizes the photo-vapor chemical growth method according to the present invention, respectively. The photochemical vapor deposition apparatus 20 includes at least a deposition target 13, a vacuum chamber 21 in which film formation is performed by introducing a raw material gas for a thin film to be formed, and a desired degree of vacuum in the vacuum chamber 21. And an optical system 23 having a laser light source 15 made of a pulse laser and the like.

  As shown in FIG. 1A, the vacuum chamber 21 includes a main chamber 1 and a plurality of side ports, and flanges 2a to 2h connectable to the side ports are arranged symmetrically. In the main chamber 1, the film formation body 13 is stored at a substantially central position, and as shown in FIG. 1B, the film formation body 13 is appropriately held above or below the position where the film formation body 13 is attached. A moving means 11 for scanning the laser beam, a two-dimensional stage such as a so-called xy stage, or a three-dimensional stage is attached. In addition, a light transmissive window 12 is provided on the flange on the side opposite to the flange on which the moving means 11 is provided in order to introduce laser light.

  At least one of the side ports is connected by an open / close valve that can independently connect to the main chamber. In this example, the raw material gas storage 5 is connected to the flange 2f in the main chamber 1 via the variable leak valve V2. By opening and closing the valve V2 as necessary, the main chamber 1 can be appropriately supplied and filled with the source gas.

On the other hand, the exhaust means 7 of the exhaust system 22 is connected to at least another other side port, in the illustrated example, the flange 2g, via the valve V1 and the variable leak valve V3, so that the exhaust in the main chamber 1 is appropriately performed. To be done.
This exhaust system 22 is mainly composed of an exhaust means 7 composed of a rotary pump or the like and an abatement device 10, and surplus source gas exhausted by the exhaust means 7 is excluded as indicated by an arrow a through a valve V5. It is guided to the device 10 and absorbed. Finally, the exhaust gas is led to the exhaust duct through the valve V6 as indicated by arrows b and c. In addition, when using a rotary pump, as shown in FIG. 1, an oil mist eliminator, so-called oil and a wrap 8, are attached so that the oil does not contaminate the detoxifying material. Further, the air may be branched between the oil trap 8 and the valve V5, and air may be introduced through the variable leak valve V4.

In the optical system 22 that introduces laser light into the main chamber 1, the laser light guided from the laser light source 15 such as a pulse laser through the mirror 16 is appropriately focused on, for example, the glass substrate of the film formation target 13. At least an objective lens 14 is provided. Further, if necessary, an observation window 3 for observing whether or not a film is appropriately formed on the film formation target 13 is provided, for example, on the flange 2a.
As described above, when the objective lens 14 is stored in the main chamber 11, the deposition target 11 is fixed, the objective lens 14 is connected to the scanning stage, and the objective lens 14 itself is scanned. Alternatively, the scanning may be performed on the film formation target 11.
Further, it is more desirable that an auxiliary optical system and control system having an autofocus function are added to the objective lens 14.

  The objective lens 14 may be installed outside the vacuum chamber. However, when installing outside the vacuum chamber, an objective lens in which spherical aberration generated by the window 12 is corrected in advance is used so as to minimize deterioration of the light collecting performance by the beam introduction window 12. In any case, the numerical aperture NA of the objective lens is assumed to exceed 0.7. The objective lens may be configured by a condensing optical system including a plurality of lens groups and an optical medium other than the lens as long as a desired numerical aperture can be obtained.

The laser light source 15 made of a pulse laser has a pulse width of 1 ps or less. In addition, it is desirable that the energy condition is such that, for example, the power can be adjusted so that the multiphoton absorption can be induced in the film forming process. Specifically, a light source such as a Ti: Sapphire laser is applicable. The pulse width is 1 ps or less, preferably 500 fs or less, and more ideally 300 fs or less.
In order to induce multiphoton absorption, a light intensity of a certain level or more is required. However, if the pulse width can be set shorter, the light intensity within one pulse can be further increased. As a result, the multiphoton can be generated with lower energy. It is expected that absorption can be induced. In addition, if the pulse width is shorter, heat conduction to the adjacent lattice is less likely to occur during the multi-photon absorption process, so that the influence of heat in the film formation process can be reduced, resulting in light It becomes easier to control the dissociation reaction.

As a raw material used for the photo-vapor phase chemical growth method of the present invention,
1) High vapor pressure and easy vaporization 2) It is desirable to be able to absorb laser light and induce photodissociation reaction.
For example, considering the formation of a Cr film, Cr (CO) ₆ is suitable.
Cr (CO) ₆ → Cr + 6CO
The photodissociation reaction can be used. Cr (CO) ₆ is a solid powder near room temperature, but has a relatively high vapor pressure of 27 Pa, and therefore has a property of being easily sublimated. Further, if there is a strong light absorption band in the vicinity of a wavelength of 260 nm to 279 nm and the irradiated laser beam is 400 nm, it is considered that a photodissociation reaction can be induced by two-photon absorption.
Table 1 below shows the relationship between other applicable raw materials and film forming conditions.

  Although it is a balance with the vapor pressure of the raw material, if the vapor pressure of the supplied raw material gas is low and an appropriate film quality cannot be obtained, the temperature of the entire chamber is adjusted so that a more appropriate vapor pressure can be obtained. A temperature control device may be added. Alternatively, it is also effective to provide a more appropriate film forming condition by using a structure in which the film formation substrate can be directly heated.

  The film formation is based on a photodissociation reaction by multiphoton absorption, but is not limited thereto. For example, as the number of photons increases, the threshold energy for starting the reaction may exceed the ablation threshold of the film formation substrate. In this case, a crystal for generating harmonics is inserted at the output end of the light source system to generate harmonics such as second harmonics and third harmonics, and this is used for film formation, which is apparently necessary for the reaction. The number of photons can be reduced, the threshold energy of the photodissociation reaction can be lowered, and appropriate film forming conditions can be obtained.

Based on the schematic configuration shown in FIG. 1, a photo-vapor chemical growth apparatus having the configuration of the present invention was prepared, and the actual film formation results are shown below.
First, BK7 (optical glass) is used as a film formation target, a pulse laser light source having a wavelength of 400 nm, a repetition frequency of 1 kHz, and a pulse width of 100 fs is used. The numerical aperture NA of the objective lens is 0.95, and the fluence (unit area is A Cr structure was deposited on the deposition target under the condition that the temporal integration value of the passing radiant flux was 0.08 J / cm ² . FIG. 2 shows an observation photograph of the formed structure by SEM (Scanning Electron Microscope).
In this example, film formation was performed while changing the scanning speed. In FIG. 2, the upper structure is formed at a scanning speed of 0.5 μm / s, the central structure is formed at a scanning speed of 0.25 μm / s, and the lower structure is formed at a scanning speed of 0.1 μm / s. It can be seen that when the scanning speed is slowed, a film-like structure is clearly formed.
Moreover, the result of having analyzed the structure shown in FIG. 2 by EDX (Energy Diffusion X-ray: Energy dispersive X-ray analyzer) is shown in FIG. From this analysis result, it was confirmed that the structure had a significant Cr content. In other words, it was confirmed that Cr (CO) ₆ was appropriately decomposed by irradiation with the focused femtosecond laser, and Cr was deposited to form a film.
Furthermore, the line width of the structure was about 570 nm, and as a result of multiphoton absorption, it was confirmed that a structure smaller than the spot diameter (˜1 μm) of the focused laser beam could be produced.
It should be noted that when the scanning speed is relatively high at 0.5 μm / s, a clear film-like structure is not confirmed, but this is due to the generation speed by the photodissociation reaction of the source gas, and at the same scanning speed. By repeating the reciprocating irradiation, a structure similar to the case where the scanning speed is relatively slow, such as about 0.1 μm / s, is generated.

Next, in order to investigate how the structure to be generated changes depending on the focusing performance of the objective lens that collects the laser light, each objective lens having a numerical aperture NA = 0.7, 0.4 is set. The structure was produced using this method.
First, an objective lens having a numerical aperture NA = 0.7 is formed on a film-forming body made of BK7, the fluence is set to 0.22 J / cm ^{2, which} is about three times the example in FIG. 2, and other conditions are described above. The film was formed in the same manner as in the example of FIG. The observation photograph figure by SEM of the produced | generated structure in this case is shown in FIG.4 and FIG.5. 4 shows the case where the scanning speed is 0.5 μm / s and 0.25 μm / s, and FIG. 5 shows the case where the scanning speed is 0.1 μm / s.
From this result, a relatively clear structure is generated by slowing the scanning speed. However, when the numerical aperture NA is 0.95, a granular structure, that is, a homogeneous structure is obtained at NA = 0.7. It can be seen that the structure is not film quality, and the denseness as seen when NA = 0.95 cannot be confirmed. This was the same even when the reciprocating irradiation was repeated.

Similarly, using an objective lens with a numerical aperture NA = 0.4, the fluence was similarly 0.22 J / cm ² , and the other conditions were the same as in FIGS. 2, 4 and 5 described above. FIGS. 6 to 8 show observation photographs of the generated structure in this case by SEM. In FIG. 6, when the scanning speed is 0.5 μm / s, in FIG. 7, the scanning speed is 0.25 μm / s, and in FIG. 8, the scanning speed is 0.1 μm / s. Respectively. From these results, it can be seen that the generated structure has a more granular feeling than the example of NA = 0.7. It was the same even when the reciprocating irradiation was repeated.

From these results, when the numerical aperture of the objective lens is NA = 0.7, it is slightly improved as compared with the case of NA = 0.4, but a granular structure is also observed. It can be seen that the Cr structure manufactured with NA = 0.95 is not a granular structure but a film-like structure.
Actually, when a structure with NA = 0.95 is observed by SEM, a surface state in which light is reflected is observed, but the structure manufactured with a numerical aperture NA ≦ 0.7 is dark. Observed, the latter is expected to be diffusely reflected. Therefore, the generated structure is presumed to be an aggregate of small crystal grains, and it can be said that a result supporting it was obtained from an actual SEM image.

  As described above, the tendency that the generated film has a granular structure when the numerical aperture NA of the objective lens is low does not change even when manufactured at any fluence. It can be concluded that the structure can be generated. In general, if the fluence is the same, it is estimated that an equivalent structure can be produced even if the numerical aperture NA is changed. However, from the above results, it is not necessary to produce a film-like structure with fluence alone. The value energy and the film quality cannot be explained, and in the production of the structure, it is necessary to perform the production with sufficient consideration of the light collecting performance, that is, the numerical aperture NA is a value exceeding at least 0.7. I know you need to do that.

Summarizing the above results, the following points can be cited as effects of the present invention. That is,
1) By setting the numerical aperture NA of the objective lens, which is the condensing performance of the irradiation laser light that induces the photodissociation reaction, to a value exceeding 0.7, an appropriate film quality is formed, and the film having a fine shape A shaped structure can be provided. Good film quality can be formed with a relatively simple configuration of appropriately selecting an objective lens.
2) When using the multiphoton absorption process, if the number of photons corresponding to the required photodissociation reaction matches, photodissociation reaction can be induced with various source gases, and film can be formed accordingly. Therefore, film formation corresponding to various source gases can be realized with one light source.
3) In the case of a photochemical growth method using multiphoton absorption, film formation can be performed with a resolution higher than the spot size of the focused light beam (the size of the diffraction limit), and the film structure having a finer shape You can get things.
4) From the results of the above 1) and 2), a complicated configuration such as installing a special optical system or preparing a number of light sources in the photochemical vapor deposition apparatus is unnecessary, and is relatively inexpensive. Good film formation can be performed with the apparatus configuration.

  Note that the present invention is not limited to the above-described example, and it is possible to use a laser light source of another wavelength band, or to use various other materials as a deposition target and a deposition source gas. Needless to say, various modifications and changes can be made without departing from the scope of the present invention.

1A is a schematic plan view of an example of a photochemical vapor deposition apparatus according to the present invention. FIG. B is a schematic cross-sectional configuration diagram of an example of a photo-vapor chemical growth apparatus according to the present invention. It is an observation photograph figure by the electron microscope of the Cr structure by the Example of the photo-vapor-phase chemical growth method of this invention. It is an analysis figure by the energy dispersive X-ray analyzer of the Cr structure by the Example of the photo-vapor-phase chemical growth method of this invention. It is an observation photograph figure by the scanning electron microscope of the Cr structure by the comparative example of a photo-vapor-phase chemical growth method. It is an observation photograph figure by the scanning electron microscope of the Cr structure by the comparative example of a photo-vapor-phase chemical growth method. It is an observation photograph figure by the scanning electron microscope of the Cr structure by the comparative example of a photo-vapor-phase chemical growth method. It is an observation photograph figure by the scanning electron microscope of the Cr structure by the comparative example of a photo-vapor-phase chemical growth method. It is an observation photograph figure by the scanning electron microscope of the Cr structure by the comparative example of a photo-vapor-phase chemical growth method.

Explanation of symbols

  1. Main chamber, 2a. Flange, 2b. Flange, 2c. Flange, 2d. Flange, 2e. Flange, 2f. Flange, 2g. Flange, 2h. 2. flange; Window, 4. 4. Vacuum gauge, 5. Deposition material storage unit, 6. lighting Exhaust means, 8. Oil trap, 9; Flow meter, 10. 10. Exclusion device, Moving means, 12. Windows, 13. Deposition target, 14. Objective lens, 15. Laser light source, 20. 20. Photo-vapor phase chemical growth apparatus, Vacuum chamber, 22. Exhaust system, 23. Optical system

Claims (3)

Film formation is performed by irradiating a deposition target with a pulsed laser beam having a pulse width of 1 ps or less using an objective lens having a numerical aperture NA exceeding 0.7 in a source gas atmosphere. Photo-vapor phase chemical growth method. 2. The photochemical vapor deposition method according to claim 1, wherein the film formation is performed by inducing a multiphoton absorption process. In a photochemical vapor deposition apparatus in which a film is irradiated with a laser beam in a source gas atmosphere to form a film on the film by a photodissociation reaction.
A laser light source that emits pulsed laser light having a pulse width of 1 ps or less;
An optical chemical vapor deposition apparatus characterized by comprising at least an objective lens having a numerical aperture NA of greater than 0.7 for condensing the laser on the film formation target.