CN113463045B

CN113463045B - Laser pulse deposition system and processing method

Info

Publication number: CN113463045B
Application number: CN202110653625.8A
Authority: CN
Inventors: 秦应雄; 李晓
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-06-11
Filing date: 2021-06-11
Publication date: 2022-10-14
Anticipated expiration: 2041-06-11
Also published as: CN113463045A

Abstract

The invention discloses a laser pulse deposition system and a processing method, and belongs to the technical field of laser. The system comprises a pulse light source, a scanning light path module and a vacuum deposition module which are sequentially connected, wherein a light beam emitted by the pulse light source is incident to the scanning light path module, and is obliquely incident to the vacuum deposition module after being focused by the scanning light path module, the scanning light path module is used for keeping light spots at any position on the surface of a target material in the vacuum deposition module to be uniform in size, and the distance between a substrate and the target material is kept unchanged in the scanning process of the focused light spots on the surface of the target material, so that uniform light spot pulse deposition is realized. The laser pulse deposition system and the processing method provided by the invention control the scanning light path module to carry out pulse sputtering on different areas on the surface of the target material, thereby realizing high-efficiency processing of a large-area and high-uniformity film.

Description

Laser pulse deposition system and processing method

Technical Field

The invention belongs to the technical field of laser, and particularly relates to a laser pulse deposition system and a processing method.

Background

The Pulse Laser Deposition (Pulse Laser Deposition) technology is one of the important technologies for preparing films such as high-temperature superconductors, semiconductors, ferroelectrics, diamond-like carbon, ceramics and the like at present, and the technology has the characteristics of capability of preparing films with high melting points and complex components, clean processing mode, easiness in control and the like. The main principle of the pulse laser deposition technology is to focus ultrafast and ultrastrong pulse laser generated by a pulse laser on the surface of a target material, so that the surface of the target material is instantaneously heated and ablated to further generate high-temperature and high-pressure plasma. And (3) performing directional local adiabatic expansion on the plasma, emitting the plasma to the substrate along the normal direction of the surface of the target material, and depositing to form a film on the substrate.

With the development of the thin film industry technology, new requirements and problems to be solved are also presented for the PLD-prepared thin film. The method is characterized in that: because the distribution of the common laser focusing light is Gaussian distribution, the generated plasma is mainly concentrated in a light spot focusing area, the film with large surface area cannot be prepared, the thickness of the film and the uniformity of components are poor, although the relative movement of the target and the substrate is controlled, the quality of the film is improved to a certain extent, and new problems are provided for the cost and the stability of the system; secondly, due to the complex mechanism of deposition parameters, during the film deposition process, the surface of the film is polluted by particles with micron-submicron scale, which also causes the uniformity of the film to be poor, and although the particles are reduced by a mechanical shielding technology based on different rates, the deposition rate is reduced. The solution is to take the physical process of the interaction between the laser and the target material into consideration, deeply research the generation mechanism of the liquid drop, further adjust the deposition parameters, and fundamentally reduce the pollution of the film particles.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a laser pulse deposition system and a processing method, and aims to solve the problems of small surface area element, poor film uniformity and low film deposition rate in the process of preparing a film by the existing pulse laser deposition technology.

In order to achieve the above object, according to an aspect of the present invention, a laser pulse deposition system is provided, which includes a pulse light source, a scanning light path module, and a vacuum deposition module, which are connected in sequence, wherein a light beam emitted by the pulse light source is collimated and expanded, then enters the scanning light path module, and then enters the vacuum deposition module in an oblique manner after passing through the scanning light path module, the scanning light path module is configured to maintain a uniform size of a light spot at any position on a surface of a target material in the vacuum deposition module, and a distance between a substrate and the target material is maintained unchanged during a scanning process of a focused light spot on the surface of the target material, so as to achieve uniform light spot pulse deposition.

Furthermore, most pulse light sources of common pulse deposition systems in the market are excimer lasers with the wavelength of 248nm, but the pulse deposition systems are large in size and high in price and are difficult to obtain large-area uniform films; the pulse light source used by the invention is a low-energy and high-repetition-frequency all-solid-state laser with low price, and the deposition of the thin-film material can be carried out by adopting the mode of one or a plurality of light source combinations of laser light sources with a plurality of wave bands of 1064nm/1030nm fundamental frequency to 213nm/206nm quintuple frequency and the like. Compared with excimer laser sources, the cost of the deposition system is greatly reduced, and film uniformity, uniformity and particulate matter problems are greatly improved.

Furthermore, the scanning light path module comprises a 45-degree reflector, a one-dimensional vibrating mirror, a flat field focusing lens and a movable optical platform unit, light beams emitted by the pulse light source are reflected to the one-dimensional vibrating mirror through the 45-degree reflector and then reflected to the flat field focusing lens through the one-dimensional vibrating mirror, the one-dimensional vibrating mirror deflects within a certain angle range, and the movable optical platform integrally moves the scanning light path module in a dimension perpendicular to the scanning of the one-dimensional vibrating mirror, so that the focusing light spots are uniformly distributed and scanned in a two-dimensional plane.

Has the advantages that: the one-dimensional galvanometer is controlled by a motor to deflect within a certain angle range, light beams are reflected by the one-dimensional galvanometer and then are incident to the flat-field focusing lens at different angles, and focusing light spots with uniform sizes are formed at different positions on the surface of the target material. When the one-dimensional galvanometer controls the focused light spots to move on the surface of the target material in a certain dimension, the movable optical platform drives the scanning light path module to integrally move in parallel in the dimension perpendicular to the scanning of the one-dimensional galvanometer, and the focused light spots are uniformly distributed and scanned in a two-dimensional plane. The moving range of the movable optical platform and the deflection angle of the one-dimensional galvanometer are controlled by a program, so that the processing of films with different sizes is realized, and the film deposition rate and the film deposition uniformity are improved.

Further, the vacuum deposition module comprises a vacuum cavity, a target material and an incidence window; the target material and the target sample are both positioned in a vacuum cavity, and the incidence window is positioned on the vacuum cavity; the target and the incident beam are obliquely arranged, namely the incident beam obliquely enters the surface of the target through the incident window.

Furthermore, the target is a composite target, different areas of the target can be composed of different material units, the distribution of the material units can be designed independently, and through the design of different combinations, the target can deposit a composite multi-component film, and the uniformity of film components of the deposited film can be greatly improved.

Furthermore, the substrate is a movable substrate, and when the high-temperature plasma sputtered from the target deposits as uniformly distributed thin films on the working surface of the current substrate, the working surface of the substrate is moved in parallel by a motor, so that the substrate above the target is a non-deposited material surface. By translating the working surface of the substrate, film deposition at infinity in a certain dimension can be achieved.

Furthermore, the pulse deposition system further comprises a collimation and beam expansion element, which is positioned between the pulse light source and the scanning light path module and is used for collimating and expanding the light beam emitted by the pulse light source.

Furthermore, the pulse deposition system also comprises a diffraction optical element, and a certain inclined phase is superposed on the diffraction optical element, so that after the light beam emitted by the pulse light source is modulated by the inclined phase of the diffraction optical element, the distribution of the focused light spot is changed from a Gaussian shape into a multi-focus combined rectangular light spot with approximately uniform energy distribution.

Has the beneficial effects that: the uniformity of the light field and the temperature field of the multi-focus combined rectangular light spot is close to that of a flat-topped rectangular light spot, and compared with the situation of Gaussian focused light spots, the uniformity of the light field and the temperature field of the focused light spot is obviously improved. Meanwhile, the anti-maladjustment characteristic of the multi-focus combined rectangular light spot is remarkably improved compared with that of a flat-top rectangular light spot. The multi-focus combined rectangular light spots are combined with the scanning light path module, so that the focused light spots are uniformly distributed at any position of the target.

Furthermore, by means of increasing an incidence window on the vacuum cavity, the multi-path laser pulse deposition system is used for pulse deposition of the composite target, scanning light path modules of different light paths can be matched with all-solid-state light sources with different wavelengths, pulse sputtering requirements of different targets and different film components are met, and pulse deposition of the targets is achieved at the same time.

Has the advantages that: through the parallel processing of the double-light-path system and the multi-light-path system, the deposition rate of the deposited film and the surface element of the film are greatly improved, and the uniformity of the film layer of the film can be greatly improved by reducing the generation of liquid drops and particles.

According to another aspect of the present invention, there is provided a processing method based on the above laser pulse deposition system, including the following steps:

(1) Building the laser pulse deposition system, and calculating the output power of a light beam according to the characteristics of target components;

(2) Controlling the light beam to be collimated and focused on different positions of the surface of the target by moving the scanning light path module;

(3) And adjusting the scanning speed of the one-dimensional galvanometer and the displacement speed of the movable optical platform to control the stay time of the focusing light spots at different positions of the target material so as to obtain different stoichiometric ratios of the components of the film.

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

(1) The laser pulse deposition system and the processing method provided by the invention control the scanning light path module to carry out pulse sputtering on different areas on the surface of the target material, thereby realizing high-efficiency processing of a large-area and high-uniformity film.

(2) The laser pulse deposition system and the processing method provided by the invention realize the preparation of the multi-component film by controlling the combination of the composite target design and the scanning range of the scanning light path module.

(3) According to the invention, the multi-focus combined rectangular light spot is designed through the diffractive optical element, so that the light field uniform distribution is greatly improved, the generation of large-particle substances in the process of depositing a film is reduced, and the consistency quality of the film layer is improved; the multi-focus combined rectangular light spot has good anti-detuning characteristic, and the uniformity of the deposited large-area film is improved.

(4) The laser light source is an all-solid-state pulse laser, and compared with an excimer laser used in other technologies, the laser reduces the device cost.

(5) The invention uses the combination of a multi-channel laser pulse deposition system and all-solid-state light sources with different working wavelengths, meets the sputtering requirements of different target materials, further increases the size of the deposited film and greatly improves the film deposition efficiency.

Drawings

FIG. 1 is a schematic structural diagram of a pulsed laser deposition system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a one-dimensional galvanometer scanning target according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the present invention illustrating the scanning optical path module controlled by the motor to move and scan the target material;

FIG. 4 is a schematic view of the surface composition distribution of the composite target of the present invention;

FIG. 5 is a schematic view of the present invention with a focused spot scanning on a target;

FIG. 6 is a schematic diagram of the motion of a parallel movable substrate structure according to the present invention;

FIG. 7 (a) is a plot of the modulated optical field of a laser beam without the diffractive optical element;

FIG. 7 (b) is a diagram illustrating a light field distribution of four focus combined rectangular spots modulated by a diffractive optical element according to the present invention;

FIG. 8 is a schematic diagram of parallel processing of a dual-beam laser pulse deposition system according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a laser pulse deposition system which comprises a pulse light source, a scanning light path module and a vacuum deposition module which are sequentially connected, wherein light beams emitted by the pulse light source are collimated and expanded and then are incident to the scanning light path module, and then are obliquely incident to the vacuum deposition module after passing through the scanning light path module, the scanning light path module is used for keeping light spots at any position on the surface of a target material in the vacuum deposition module to be uniform in size, so that the distance between a substrate and the target material is kept unchanged in the scanning process of the surface of the target material, and uniform light spot pulse deposition is realized.

The invention also provides a processing method based on the laser pulse deposition system, which comprises the following steps:

(1) Building the laser pulse deposition system, and calculating the output power of the light beam according to the characteristics of the target components;

(3) And adjusting the scanning speed of the one-dimensional galvanometer and the displacement speed of the movable optical platform to control the dwell time of the focused light spots at different positions of the target material so as to obtain different stoichiometric ratios of the components of the film.

Examples

As shown in fig. 1, a novel laser pulse deposition system provided in an embodiment of the present invention includes a high repetition frequency, low energy all-solid-state laser 1, a 45 ° reflector 2, a first motor and a guide rail 3 for moving a movable optical platform 7, a one-dimensional galvanometer 4, a second motor 5 for driving the galvanometer to vibrate, a standard flat-field focusing lens 6, the movable optical platform 7, an incident window 8, a vacuum cavity 9, a target 10, a substrate 11, a diffractive optical element 12, a collimation and beam expansion element 13, a rotating shaft 14, and a rotating shaft 15 with a motor.

The light beam emitted by the all-solid-state laser 1 is collimated by the collimation and beam expansion unit 13, then enters the diffraction optical element 12, is modulated by the diffraction optical element 12, and then is transmitted to the reflector 2, is reflected by the reflector 2, then enters the one-dimensional vibrating mirror 4, is reflected by the vibrating mirror 4 to the flat field focusing mirror 6, and enters the target 10 through the entrance window 8 after being focused by the flat field lens 6. High-temperature high-pressure plasma is excited on the surface of the target material 10. The plasma is directionally and locally adiabatically expanded and is emitted to the substrate 11 along the normal direction of the surface of the target 10, and finally the plasma is deposited on the substrate 11 to form a uniform and consistent film.

The movable optical platform 7 is connected with a support on the guide rail, and is controlled by the first motor 3 to move back and forth on the guide rail along the optical axis direction, so that the effect that the focused light spot on the target working surface 10 moves in a certain dimension (y axis in the figure) is realized.

The one-dimensional galvanometer 4 is connected with a second motor 5, the galvanometer 4 is controlled to deflect within a certain angle range through the second motor 5, and the process of two-dimensional scanning of a focused light beam on the surface of the target is realized by matching with a movable optical platform 7. Under the specific situation of large surface element films and the like, the working length (x axis in the figure) of a scanning light spot can be freely adjusted by adopting galvanometer scanning. The traditional laser pulse deposition system adopts a rotary target material to realize the effect of moving light spots on the surface of the target material, and the combination of the movable optical flat 7, the one-dimensional scanning galvanometer 4 and the flat field focusing lens 6 is adopted in the invention, so that the focusing at any position on the surface of the target material can be realized, the adjustment speed is high, the real-time light spot position adjustment is facilitated, and the film deposition rate is improved.

In the embodiment shown in fig. 2, when the second motor 5 controls the one-dimensional galvanometer 4 to rotate to the position of the dotted line in the figure, the reflected light path of the galvanometer is changed to the position shown by the dotted line, and the incident light beam and the optical axis angle of the flat field focusing mirror 6 are changed to focus on different positions on the surface of the target 10 at the same latitude. The second motor 5 is programmed and controlled, the deflection angle of the one-dimensional galvanometer 4 is adjusted, the scanning range of the focusing light spot on the working surface of the target 10 can be adjusted, and the change of the scanning light spot in the scanning direction (x direction in the figure) is realized.

Fig. 3 shows that in the embodiment, when the first motor 3 drives the movable optical platform 7 to drive the optical path scanning device to integrally move to the position of the dotted line, the optical path of the system is changed from the solid line to the dotted line, so as to realize the function of changing the focused light spot on the surface of the target 10 back and forth along a certain dimension (y direction in the figure). The function of scanning any position on the surface of the target material 10 is realized by combining the angular deflection of the one-dimensional galvanometer 4 to adjust the position change of the focused light spot in the other vertical dimension (x direction in the figure) and controlling the first motor 3 and the second motor 5 to cooperatively move. Compared with the traditional pulse deposition system, the method can realize the preparation of large-surface element deposition films, and can flexibly adjust the size of the prepared surface element.

Fig. 4 shows a composite target composition distribution for the surface of the target 10, with different letters a, b, c representing the desired composition for deposition of a multi-component film. The uniformity and the film rate of the deposited film can be improved by designing the distribution areas of different components on the target. The present invention provides a planar distribution of one of the different component structures, and may include other types of distributions.

For a traditional pulse laser deposition system, the phenomenon of off-axis deflection can be generated after a light beam passes through a focusing lens system, and spot distortion can occur on the surface of a target material relative to an ideal plane. In this embodiment, for the flat-field lens, the image plane is a plane, and the laser beam can form a focused spot with a uniform size in the whole target plane.

Fig. 5 shows that when the scanning speed of the galvanometer is equal angular speed, the focused light spot forms a focused light spot with uniform size on the target 10. The uniform size of the focused spots can enable the surface of the target material 10 to generate plasma with uniform state distribution, and the uniformity of the deposited film on the substrate 11 is greatly improved.

In the embodiment shown in fig. 6, the movable substrate structure is moved in such a manner that the substrate material is stored on the spindle 14 on one side of the substrate before the pulsed laser deposition is started, and the starting end of the substrate material is connected to the spindle 15 having the third motor. When the plasma excited by the target 10 is deposited as a uniform thin film on the substrate 11, the motor-controlled spindle 15 starts to rotate, so that the substrate material on which the thin film deposition has been completed is stored on the spindle 15, and the spindle 14 is driven to further release the undeposited substrate material stored on the spindle 14, so that the state of the undeposited thin film on the substrate 11 is maintained. By the rotation of the

rotating shafts

14 and 15, the deposited film can be infinitely extended in a certain dimension while the distance between the substrate and the target is kept unchanged.

FIG. 7 (a) is a diagram showing the Gaussian distribution of the initial spot of the pulse beam; fig. 7 (b) shows a four-focus combined rectangular spot distribution diagram generated by the pulse beam through the diffractive optical element tilt phase modulation. In FIG. 7 (a), we can see that the spot distribution of the Gaussian distribution has a sharp change from the central intensity to the edge intensity during pulse deposition, and we can only use a small area part in the center. And the central light intensity is unevenly distributed, which causes uneven distribution of sputtered high-temperature and high-pressure plasma after expansion and uneven distribution of the irradiation film layer. In fig. 7 (b), the uniformity of the light field and the temperature field of the four-focus combined rectangular light spot is close to that of the flat-topped rectangular light spot, and compared with the case of the gaussian focused light spot, the uniformity of the light field and the temperature field of the focused light spot is obviously improved. Meanwhile, the anti-maladjustment characteristic of the four-focus combined rectangular light spot is remarkably improved compared with that of a flat-top rectangular light spot. When the four-focus combined rectangular light spot is used for pulse deposition, the utilization rate of the light spot is improved, and the uniformity of a deposited film is greatly improved.

FIG. 8 shows one form of parallel processing of a dual-optical-path laser pulse deposition system, where the pulse deposition focused spots can be applied to the same region or different regions during parallel processing of a multi-optical-path scanning device. In the figure, the double-optical-path system acts on different areas of the target during deposition, and the deposition rate and the area of the deposited film are improved in multiples. Due to the interaction between plasmas generated by the double light beams, the generation of liquid drops and particles is reduced, and the uniformity of the film layer is greatly improved.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A laser pulse deposition system is characterized by comprising a pulse light source, a scanning light path module and a vacuum deposition module which are sequentially connected, wherein a light beam emitted by the pulse light source is incident to the scanning light path module, and is obliquely incident to the vacuum deposition module after being focused by the scanning light path module;

the pulse light source is an all-solid-state laser; the scanning light path module comprises a 45-degree reflector, a one-dimensional vibrating mirror, a flat field focusing lens and a movable optical platform, a light beam emitted by a pulse light source is reflected to the one-dimensional vibrating mirror through the 45-degree reflector, and then is reflected to the flat field focusing lens through the one-dimensional vibrating mirror, the one-dimensional vibrating mirror deflects within a preset angle range, and the movable optical platform is used for integrally moving the scanning light path module in a dimension perpendicular to the scanning of the one-dimensional vibrating mirror so as to realize uniform distribution scanning of focusing light spots in a two-dimensional plane;

the vacuum deposition module comprises a vacuum cavity, a target material, a substrate and an incidence window; the target material and the substrate are both positioned in the vacuum cavity, and the incidence window is positioned on the vacuum cavity; the target and the incident beam are obliquely arranged, namely the beam is obliquely emitted to the surface of the target through the incident window;

the device also comprises a collimation and beam expansion element and a diffraction optical element, wherein the collimation and beam expansion element is positioned between the pulse light source and the scanning light path module and is used for collimating and expanding beams of light beams emitted by the pulse light source, the diffraction optical element is positioned between the collimation and beam expansion element and the scanning light path module, and after the light beams are subjected to tilt phase combination modulation by the diffraction optical element, focused light spots are changed into multi-focus combined rectangular light spots with approximately uniform energy distribution from Gaussian distribution.

2. The laser pulse deposition system of claim 1, wherein the target is a composite target, and different regions of the target are comprised of different material units.

3. The laser pulse deposition system of claim 1, wherein the substrate is a movable substrate that moves parallel to the target.

4. The laser pulse deposition system of claim 1, further comprising a plurality of pulsed light sources and a plurality of scanning light path modules, wherein a light beam emitted by each pulsed light source is incident on a corresponding scanning light path module, focused by the scanning light path module and then obliquely incident on the vacuum deposition module, each scanning light path module corresponds to an incident window of the vacuum deposition module, and the plurality of scanning light path modules are matched with pulsed light sources of different wavelengths to meet the pulse sputtering requirements of different targets and achieve simultaneous pulse deposition of the targets.

5. A method of processing a laser pulse deposition system according to any of claims 1 to 4, comprising the steps of:

(2) Controlling the light beam to be collimated and focused on different positions on the surface of the target by moving the scanning light path module;