Method and device for sputtering deposition of optical thin film based on double pulse sources

Abstract

The invention discloses an optical thin film sputtering deposition method and device based on double pulse sources, and belongs to the technical field of optical thin film manufacturing in optical manufacturing. According to the method, corresponding deposition parameters are adjusted according to different substrates and target materials, and deposition preparation of various optical thin films is achieved; the double-pulse source is divided into a main source and an auxiliary source, high-energy charge energy particles generated by the main pulse source bombard the surface of a target material, cascade collision occurs in several atomic layers on the surface of the target material, energy exchange occurs between the particles and the target material, and after target material atoms obtain enough energy to overcome own atomic potential barriers, the target material atoms leave the surface of the target material and are deposited on the surface of a substrate to form a thin film; the high-energy particles generated by the auxiliary pulse source bombard the surface of the growing thin film, and the film material molecules and the high-energy particles generate energy and momentum transfer to obtain large kinetic energy, so that the adhesiveness of the thin film is enhanced, and the surface arrangement is more compact. The preparation of multiple optical films can be realized, and meanwhile, the filling density and the use performance of the optical film can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical thin film manufacturing in optical manufacturing, and relates to a sputtering deposition optical thin film method and device based on a double pulse source. Background Art

[0002] Optical thin film refers to a film stack composed of one or more metal films or dielectric films or metal films and dielectric films coated on optical components to change the transmission characteristics of light waves. Optical thin films can reduce or increase the reflection of the surface of optical components, select the spectrum, control polarization and phase and other optical properties, and can also improve the chemical, mechanical, electrical and other properties of the surface of optical components in a targeted manner. It is one of the key technologies indispensable for various optical systems and laser systems. With the advancement of science and technology, the application of optical thin films is becoming more and more extensive, and the requirements are becoming higher and higher, but obtaining uniform and stable optical thin films is a technical challenge we face.

[0003] As an emerging optical thin film preparation technology, ion beam sputtering deposition uses an ion beam with high ion energy to bombard the target material at a certain angle, sputtering the target atoms and depositing them on the substrate. Although the optical film deposited by ion beam sputtering has a strong bond with the substrate, the uniformity and stability of the film deposited on the substrate surface are difficult to guarantee due to the uncertainty of the target material molecular motion trajectory during the sputtering process.

[0004] In addition, the thickness of the optical film is closely related to the optical properties. If the film thickness is not known during the deposition process, it is impossible to ensure that the deposited film meets the requirements. Then it is necessary to rework and perform multiple depositions, which is cumbersome and has low processing efficiency. At the same time, the optical elements after sputtering deposition will be affected by the environment during the multiple handling processes, which will affect the bonding force between the film and the substrate and the stress of the film layer, thereby destroying the film performance. Summary of the invention

[0005] In order to solve the problems in the prior art that the uniformity and stability of thin film deposition cannot be guaranteed and the thickness of the film layer cannot be monitored, the purpose of the present invention is to provide a method and device for sputtering and depositing optical thin films based on a dual pulse source. The method can adjust the corresponding deposition parameters for different substrates and target materials to achieve the deposition preparation of various optical thin films; at the same time, it can improve the filling density and performance of the optical film. The device can realize the integration of sputtering and removal. The main pulse source provides energy to sputter the target atoms out of the target surface; the auxiliary pulse source provides secondary energy to the target atoms to make the film more adherent; in addition, after the film is prepared, the surface of the film can be smoothed and removed to solve the problem that the uniformity and stability cannot be guaranteed, and at the same time, the film stress can be reduced to improve the bonding force between the substrate and the film layer. The present invention also uses a film thickness monitor to monitor the optical thickness of the film layer in real time during the sputtering deposition process to solve the problem that the film thickness cannot be monitored.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] The sputtering deposition method of optical thin film based on dual pulse sources, the pulse source is divided into a main pulse source and an auxiliary pulse source. The high-energy, high-momentum energetic particles generated by the main pulse source bombard the target surface, and cascade collisions occur in several atomic layers on the target surface. The particles and the target exchange energy. When the target atoms obtain enough energy to overcome their own atomic barriers, they leave the target surface; the auxiliary pulse source is used to provide secondary energy to the sputtered target atoms, so that the target atoms move to the substrate to form an optical thin film; at the same time, the secondary energy provided by the auxiliary pulse source can enhance the adhesion of the film and make the molecular arrangement of the surface target more dense; the secondary energy provided by the auxiliary pulse source increases the filling density and refractive index of the optical film, so that the water vapor absorption of the film is reduced, the wavelength drift of the film is reduced, and the absorption and scattering effects of the film layer are correspondingly reduced; the stress σ of the film layer is controlled based on the regulation of the substrate curvature radius, as shown in the following formula:

[0008]

[0009] Where E represents the Young's modulus of the substrate; d represents the thickness of the optical film; v represents the Poisson's ratio of the target; R p R0 represents the radius of curvature of the substrate before the film is deposited.

[0010] Furthermore, according to equations (2), (3), and (4), the optical thickness d of the deposited film is determined by the optical properties that the optical film needs to achieve:

[0011]

[0012] Where R represents the reflectivity of the film; δ represents the phase thickness of the film; n 0-2 Respectively represent the refractive index of air, film layer and substrate; λ represents the wavelength; m is the number of extreme points.

[0013] Analysis of the above formulas (2)(3)(4) shows that the optical thickness of the film layer is related to the optical performance that the film layer needs to achieve. The optical thickness of the film layer is monitored in real time by a film thickness monitor to ensure that the deposited film layer meets the required standards.

[0014] The present invention discloses a sputtering deposition optical thin film device based on a dual pulse source, which is mainly composed of a main pulse source, an auxiliary pulse source, a target platform, a deposition workbench, a light emitting device, a film thickness monitor, a target material and a substrate; the main pulse source, the auxiliary pulse source, the target platform and the deposition workbench are placed in a vacuum chamber; the target material is fixed on the target platform; the substrate is fixed on the deposition workbench; the pulse beam emitted by the main pulse source bombards the surface of the target material to sputter out target material atoms; the pulse beam emitted by the auxiliary pulse source assists the target material atoms to adhere to the surface of the substrate; the light emitting device irradiates the surface of the substrate; and the film thickness monitor monitors the thickness of the film layer deposited on the surface of the substrate in real time.

[0015] The method for thin film deposition using the above-mentioned sputtering deposition optical thin film device based on a dual pulse source comprises the following steps:

[0016] Step 1: wipe the target material and substrate material with a dust-free cloth dipped in a mixed solution of ethanol and ether, and then install them into the target table and workbench in the vacuum chamber respectively; before deposition, drive the auxiliary pulse ion source to clean the target material and substrate to remove surface impurities and reduce film stress;

[0017] Step 2: Start the vacuum pump to evacuate the vacuum chamber; different vacuum degrees are achieved according to the requirements of different optical films;

[0018] Step 3: drive and turn on the power of the main pulse source to bombard the target material; at the same time, turn on the auxiliary pulse source to further provide energy to the sputtered target molecules to achieve deposition on the substrate surface;

[0019] Step 4: Turn on the film thickness monitor; monitor the film thickness in real time until the film meets the optical property requirements; after the film deposition is completed, the auxiliary pulse source can also clean the unstable molecules in the film to ensure the uniformity and stability of the film;

[0020] Step 5: Inspect the film layer. After the film layer is prepared, it is necessary to conduct thickness and performance tests on the prepared film layer to inspect whether the sputtered deposited optical film meets the preset requirements. The film made by the dual-pulse source sputtering deposition method has high uniformity, smooth surface and stable optical properties.

[0021] In the above-mentioned device, the end face of the target table is parallel to the end face of the workbench, and the main pulse source and the target table are on the same plane; the main pulse source can be flipped so that the emitted pulse beam can bombard the surface of the target table; the auxiliary pulse source and the workbench are on the same plane, and the auxiliary pulse can also be flipped so that the pulse beam emitted by the auxiliary pulse source can provide secondary energy to the target material molecules sputtered by the main pulse source to realize the deposition of the target material molecules on the substrate surface to form a film layer.

[0022] The detection principle of the film thickness monitor is to emit light through a light emitting device to illuminate the film layer. The reflected light is received by the film thickness monitor to obtain data for analyzing the optical properties of the film layer; the light passes through the spectrometer in the film thickness monitor to divide the incident light into reflected light and transmitted light; the reflected light passes through the photocell to form a contrast electrical signal and enters the display; the transmitted light passes through a high-reflection mirror and is focused by a lens to converge the light beam onto a monochromator, which converts the weakened light signal into an electrical signal, which enters the display as another input signal of the differential amplifier; the two electrical signals are compared to obtain the optical thickness of the film layer.

[0023] The above-mentioned sputtering deposition method of optical thin film based on dual pulse source, the deposition parameters include: the voltage of the main pulse source is 800-1500V, the anode current is 0.3-0.4mA; the voltage of the auxiliary pulse source is 200-400eV, and the anode current is 1.1-1.8mA.

[0024] Beneficial effects:

[0025] 1. The present invention discloses a method and device for sputtering optical thin films based on a dual pulse source. According to different substrates and target materials, the corresponding deposition parameters are adjusted to achieve the deposition preparation of various optical thin films; at the same time, the filling density and performance of the optical thin films can be improved.

[0026] 2. The present invention discloses a method and device for sputtering and depositing optical thin films based on a dual pulse source. The dual pulse source can realize the integration of sputtering and removal. The high-energy charged particles generated by the main pulse source bombard the surface of the target material, and the particles and the target material exchange energy. When the target material atoms obtain enough energy to overcome their own atomic potential barriers, they leave the target material surface and deposit on the substrate surface to form a thin film. The auxiliary pulse source is used to generate high-energy particles to bombard the growing surface of the film. The film material molecules transfer energy and momentum with the high-energy particles to obtain greater kinetic energy, thereby enhancing the adhesion of the film and making the surface arrangement more dense. At the same time, the auxiliary pulse source can clean the substrate and target surface to remove surface impurities before film deposition, which is beneficial to improving the bonding strength between the substrate and the film; after the film is deposited, the auxiliary pulse source can still clean the film surface to ensure the uniformity of the film.

[0027] 3. The present invention discloses a method and device for sputtering deposition of optical thin films based on a dual pulse source. The optical thickness of the thin film is calculated according to the performance requirements of the thin film, and then a film thickness monitor is used to monitor the optical thickness of the optical thin film in real time during the sputtering process. This can achieve precise manufacturing of optical thin films and has the advantages of high processing efficiency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a diagram of a dual pulse source sputtering device for depositing optical thin films;

[0029] Figure 2This is the principle diagram of sputtering deposition;

[0030] Figure 3 Schematic diagram of the optical thin film growth process;

[0031] Figure 4 This is the schematic diagram of the film thickness monitor.

[0032] Among them, 1 is a vacuum pump, 2 is a vacuum chamber, 3 is an auxiliary pulse source, 4 is a light emitting device, 5 is a fixture, 6 is a target platform, 7 is a target material, 8 is a film thickness monitor, 9 is a main pulse source, 10 is a substrate, 11 is a workbench, 12 is a target material molecule, 13 is a spectroscope, 14 is a high reflective mirror, 15 is a lens, 16 is a monochromator, 17 is a display device, and 18 is a photocell. DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to the accompanying drawings.

[0034] Figure 1 The figure is a dual pulse source sputtering deposition optical thin film device, which is composed of a vacuum system, a deposition system and a control system. The vacuum system is composed of a vacuum pump 1 and a vacuum chamber 2, and the deposition system is placed in the vacuum chamber 2; the vacuum pump 1 is controlled by a system control module, and the corresponding vacuum degree is selected according to the characteristics of the target material 7 and the substrate material 10; the deposition system is composed of a main pulse source 9 and an auxiliary pulse source 3, a target stage 6 and a deposition workbench 11, and the target material 7 is fixed on the target stage 6 using a clamp 5, and the substrate material 10 is fixed on the deposition workbench 11 using a clamp 5.

[0035] Figure 2 The main pulse source bombards the target material, and the target material molecules gain energy and overflow the target material surface. The auxiliary pulse source provides secondary energy to reach the surface of the base material. The target material molecules diffuse and aggregate on the surface of the base material to form stable nuclei and then form an optical film on the surface of the base material, such as Figure 3 shown. Figure 4 The schematic diagram of the film thickness monitor is shown in Figure 1. The light passes through the spectroscope 13 in the film thickness monitor, and the incident light is divided into reflected light and transmitted light. The reflected light passes through the photocell 18 to form a contrast electrical signal and enters the display 17; the transmitted light passes through the high reflective mirror 14 and is focused by the lens 15 to converge the light beam onto the monochromator 16. The monochromator 16 converts the weakened light signal into an electrical signal, which enters the display 17 as another input signal of the differential amplifier. The two electrical signals are compared to obtain the optical thickness of the film layer.

[0036] Example 1

[0037] This embodiment is used for the deposition of optical thin films on the surfaces of optical elements such as optical mirrors and hard and brittle materials in optical systems. For example, when a tantalum dioxide optical film is deposited on the surface of a high-reflection quartz mirror in a solar simulator, the film reflectivity is required to reach 99%. The corresponding deposition parameters are selected according to the substrate and the target material; the optical properties that the optical film needs to achieve determine the optical thickness of the film layer deposition.

[0038] The method for thin film deposition using a dual pulse source sputtering deposition optical thin film device is specifically implemented in the following steps:

[0039] Step 1: Wipe the tantalum dioxide target 7 and the quartz substrate 10 with a dust-free cloth dipped in a mixed solution of ethanol and ether, and then install them into the target table 6 and the workbench 11 in the vacuum chamber 2 respectively and fix them with a clamp 5; before deposition, drive the auxiliary pulse source 3 to clean the surface of the single crystal silicon 7 and the silicon carbide substrate 10 to remove surface impurities and reduce film stress.

[0040] Step 2: Start the vacuum pump 1 to evacuate the vacuum chamber 2; according to the requirements of the optical film of the tantalum dioxide target material 7 and the quartz substrate 10, the vacuum degree is 1.33×10 -6 Pa.

[0041] Step 3: Drive and turn on the power of the main pulse source 9 to bombard the tantalum dioxide target 7; at the same time, turn on the auxiliary pulse source to further provide energy to the sputtered tantalum dioxide molecules to achieve deposition on the surface of the quartz substrate 10.

[0042] Step 4: Turn on the film thickness monitor 8; monitor the film thickness in real time until the tantalum dioxide film meets the optical property requirements. After the film deposition is completed, the auxiliary pulse source 3 can also clean the unstable molecules in the film to ensure the uniformity and stability of the film.

[0043] Step 5: Test the film layer: After the tantalum dioxide film layer is prepared, the performance of the prepared film layer needs to be tested. The tantalum dioxide film layer prepared by the dual pulse source sputtering deposition method has a high degree of uniformity, a smooth surface and stable optical properties.

[0044] The deposition parameters in this embodiment include: the voltage of the main pulse source is 500V, and the anode current is 0.5mA; the voltage of the auxiliary pulse source is 200V, and the anode current is 1.2mA.

[0045] In this embodiment, the quartz substrate sputtering deposition of tantalum dioxide film material is a high reflection film with a central wavelength of 632.8nm. The experiment finally achieved a central wavelength reflectivity greater than 99.99%, a transmittance of 0, and an optical film thickness of 150nm.

[0046] Example 2

[0047] This embodiment is used for the deposition of optical thin films on the surfaces of optical elements such as optical mirrors, hard and brittle materials in optical systems. For example, when silicon dioxide is deposited on the surface of silicon carbide lenses in the Shenguang ignition device, the reflectivity is required to reach more than 98%. The corresponding deposition parameters are selected according to the silicon carbide substrate and the silicon dioxide target; the optical properties that the optical thin film needs to achieve determine the optical thickness of the film layer deposition.

[0048] The method for thin film deposition using a dual pulse source sputtering deposition optical thin film device is specifically implemented in the following steps:

[0049] Step 1: Wipe the silicon dioxide 7 and silicon carbide substrate 10 materials with a dust-free cloth dipped in a mixed solution of ethanol and ether, and then load them into the target table 6 and the workbench 11 in the vacuum chamber 2 respectively and fix them with a clamp 5; before deposition, drive the auxiliary pulse source 3 to clean the silicon dioxide 7 and the silicon carbide substrate 10 to remove surface impurities and reduce film stress.

[0050] Step 2: Start the vacuum pump 1 to evacuate the vacuum chamber 2; according to the requirements of the optical film of the single crystal silicon and silicon carbide substrate materials, the vacuum degree is 1.0×10 -6 Pa.

[0051] Step 3: Drive and turn on the power of the main pulse source 9 to bombard the single crystal silicon 7 target; at the same time, turn on the auxiliary pulse source to further provide energy to the sputtered single crystal silicon molecules to achieve deposition on the bottom surface of the silicon carbide substrate 10.

[0052] Step 4: Turn on the film thickness monitor 8; monitor the film thickness in real time until the silicon dioxide film meets the optical property requirements. After the film deposition is completed, the auxiliary pulse source 3 can also clean the unstable molecules in the film to ensure the uniformity and stability of the film.

[0053] Step 5: Test the film layer: After the silicon dioxide film layer is prepared, the performance of the film layer needs to be tested. The film made by the ion beam sputtering deposition method of the dual pulse source has a high degree of uniformity, a smooth surface and stable optical properties.

[0054] The deposition parameters in this embodiment include: the voltage of the main pulse source is 1250V, and the anode current is 60mA; the voltage of the auxiliary pulse source is 300V, and the anode current is 1.2mA.

[0055] In this embodiment, the silicon carbide substrate is sputtered to deposit silicon dioxide material, which is a high reflective film with a central wavelength of 1064nm, achieving a central wavelength reflectivity of more than 99.86%, a transmittance of 0, and an optical film thickness of 300nm.

[0056] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for sputtering optical thin films based on a dual pulse source, characterized in that: The pulse source is divided into a main source and an auxiliary source. The high-energy, high-momentum energetic particles generated by the main pulse source bombard the target surface, and cascade collisions occur in several atomic layers on the target surface. The particles exchange energy with the target. When the target atoms obtain enough energy to overcome their own atomic barriers, they leave the target surface. The auxiliary pulse source can provide secondary energy to the sputtered target atoms, so that the target atoms move to the substrate to form an optical film. At the same time, the secondary energy provided by the auxiliary pulse source can enhance the adhesion of the film and make the molecular arrangement of the surface target more dense. The secondary energy provided by the auxiliary pulse source increases the filling density and refractive index of the optical film, so that the water vapor absorption of the film is reduced, the wavelength drift of the film is reduced, and the absorption and scattering effects of the film layer are reduced accordingly. The stress σ of the film layer is controlled based on the regulation of the substrate curvature radius, as shown in the following formula: Where E represents the Young's modulus of the substrate; d represents the thickness of the optical film; v represents the Poisson's ratio of the target; R p R0 represents the radius of curvature of the substrate before the film is deposited.

2. The method for sputtering optical thin films based on a dual pulse source as claimed in claim 1, characterized in that: According to equations (2), (3), and (4), the optical thickness d of the deposited film is determined by the optical properties that the optical film needs to achieve: Where R represents the reflectivity of the film; δ represents the phase thickness of the film; n 0-2 Respectively represent the refractive index of air, film layer and substrate; λ represents the wavelength; m is the number of extreme points.

3. The method for sputtering optical thin films based on a dual pulse source as claimed in claim 1, characterized in that: The thickness of the optical film is detected in real time, and the surface of the optical film is smoothed and removed through an auxiliary pulse source.

4. A device for implementing the method according to claims 1 to 3, characterized in that: The invention mainly comprises a main pulse source (9), an auxiliary pulse source (3), a target platform (6), a deposition workbench (11), a light emitting device (4), a film thickness monitor (8), a target material (7) and a substrate (10); the main pulse source (9), the auxiliary pulse source (3), the target platform (6) and the deposition workbench (11) are placed in a vacuum chamber (2); the target material (7) is fixed on the target platform (6); the substrate (10) is fixed on the deposition workbench (11); the pulse beam emitted by the main pulse source (9) bombards the surface of the target material (7) to sputter target material atoms; the pulse beam emitted by the auxiliary pulse source (3) assists the target material atoms to adhere to the surface of the substrate (10); the light emitting device (4) irradiates the surface of the substrate (10); and the film thickness monitor (8) monitors the thickness of the film layer deposited on the surface of the substrate (10) in real time.

5. The device according to claim 4, characterized in that: The end surface of the target platform (6) is parallel to the end surface of the deposition workbench (11); the main pulse source (9) and the target platform (6) are on the same plane; the main pulse source (9) can be flipped so that the emitted pulse beam can bombard the surface of the target platform (6); the auxiliary pulse source (3) and the deposition workbench (11) are on the same plane; similarly, the auxiliary pulse source (3) can be flipped so that the pulse beam emitted by the auxiliary pulse source (3) can provide secondary energy to the target material molecules (12) sputtered by the main pulse source (9), so that the target material molecules (12) are deposited on the substrate surface to form a film layer.

6. The device according to claim 4, characterized in that: The detection principle of the film thickness monitor (8) is to emit light through a light emitting device to illuminate the film layer, and the light after reflection is received by the film thickness monitor to obtain data for analyzing the optical characteristics of the film layer; the light passes through a spectroscope in the film thickness monitor to divide the incident light into reflected light and transmitted light; the reflected light passes through a photocell to form a contrast electrical signal and enters the display instrument; the transmitted light passes through a high-reflection mirror and is focused by a lens to converge the light beam onto a monochromator, and the monochromator converts the weakened light signal into an electrical signal, which serves as another input signal of a differential amplifier and enters the display instrument; the two electrical signals are compared to obtain the optical thickness of the film layer.

7. A method for thin film deposition using the device as claimed in claim 4, characterized in that: The following steps are included: Step 1: wipe the target material (7) and the substrate (10) with a dust-free cloth dipped in a mixed solution of ethanol and ether, and then respectively place them into the target table (6) and the workbench (11) in the vacuum chamber (2); before deposition, drive the auxiliary pulse ion source (3) to clean the target material (7) and the substrate (10) to remove surface impurities and reduce film stress; Step 2: Start the vacuum pump (1) to evacuate the vacuum chamber (2); different vacuum degrees are achieved according to the requirements of different optical films; Step 3: driving and turning on the power of the main pulse source (9) to bombard the target material (7); and simultaneously turning on the auxiliary source (3) to further provide energy to the sputtered target molecules so as to achieve deposition on the substrate surface; Step 4: Turn on the film thickness monitor (8); monitor the film thickness in real time until the film meets the optical property requirements; after the film deposition is completed, the auxiliary pulse source (3) is also used to clean the unstable molecules in the film to ensure the uniformity and stability of the film; Step 5: Inspect the film layer. After the film layer is prepared, the thickness and performance of the prepared film layer need to be tested to verify that the sputtered deposited optical film meets the preset requirements.

8. The thin film deposition method according to claim 7, wherein: The voltage of the main pulse source is 800-1500V, and the anode current is 0.3-0.4mA; The voltage of the auxiliary pulse source is 200-400 eV, and the anode current is 1.1-1.8 mA.

Images