Novel plasma enhanced atomic layer deposition equipment and plasma assisted atomic layer deposition film method

Abstract

The invention relates to novel plasma enhanced atomic layer deposition equipment and a plasma assisted atomic layer deposition method, the equipment comprises a reaction cavity, a plasma generator is communicated with the reaction cavity, the plasma generator comprises a hollow rectangular tube, a discharge coil is wound on the outer wall of the rectangular tube, and the discharge coil is communicated with the reaction cavity. After the discharge coil is switched on, reaction gas is ionized when passing through the rectangular tube, and obtained ions enter the reaction cavity and are deposited on a preset substrate; the inner wall of the rectangular tube is provided with an insulating layer. According to the equipment, an oxygen-free or low-oxygen-content insulating layer is loaded on the rectangular tube of the plasma generator, bombardment of plasma is resisted in the plasma discharge process, oxygen elements of the rectangular tube are prevented from being brought out, and therefore the oxygen content of nitride and fluoride films is reduced, and the optical performance of the films is improved.

Description

Technical Field

[0001] The invention relates to the technical field of plasma-assisted atomic layer deposition, in particular to a novel plasma-enhanced atomic layer deposition device and a plasma-assisted atomic layer deposition film method. Background Art

[0002] Fluorides are widely used in the semiconductor manufacturing process, especially in the field of optics. Since fluorides have good optical properties, especially high transmittance in the ultraviolet and visible light ranges, they are widely used in the manufacture of optical components such as optical films, reflectors, and lenses. Fluorides can not only effectively reduce the surface reflection of optical components and improve their optical performance, but also extend their service life by improving the corrosion resistance and anti-pollution ability of optical components. In the thin film preparation process, fluorides can be deposited by plasma coating technology, such as sputtering, chemical vapor deposition (CVD), etc.

[0003] As the size of semiconductor devices continues to decrease, traditional coating technologies such as physical vapor deposition (PVD) and chemical vapor deposition (CVD) cannot meet the requirements of devices on high aspect ratio substrates or when the required film thickness is only a few nanometers. On the one hand, traditional coating technologies cannot achieve some fine structures, especially complex and fine surface structures at the nanometer level; on the other hand, for substrates with high aspect ratios, traditional coating technologies cannot meet the conformality requirements. The so-called conformality refers to the step coverage of thin film deposition, the gap filling ability, and the ability to retain the original shape, that is, the thickness of the film deposited on all three-dimensional structures (top, sidewalls, and bottom) is the same, and the original design size ratio is not destroyed, which is also called the common coverage effect.

[0004] In order to solve the above problems, the prior art uses atomic layer deposition (ALD) technology to obtain thin film materials. ALD is the deposition of thin films precisely controlled at the atomic level, and has great potential for producing very thin conformal films, and can control the thickness and composition of the film at the atomic level.

[0005] The main steps are as follows:

[0006] (1) Precursor pulse: The ALD process begins with the introduction of the first precursor into the reaction chamber. This precursor is a gas or vapor containing the chemical elements of the target deposition material that reacts with specific active sites on the wafer surface. The precursor molecules adsorb on the wafer surface to form a saturated molecular layer.

[0007] (2) Inert gas purging: Subsequently, an inert gas (such as nitrogen or argon) is introduced for purging to remove unreacted precursors and by-products, ensuring that the wafer surface is clean in preparation for the next reaction.

[0008] (3) Second precursor pulse: After the purge is completed, the second precursor is introduced to react chemically with the precursor adsorbed in the first step to form the desired deposit. This reaction is usually self-limiting, that is, once all active sites are occupied by the first precursor, no new reaction will occur.

[0009] (4) Inert gas purging again: After the reaction is completed, the surface is purged with inert gas again to remove residual reactants and by-products, restoring the surface to a clean state and preparing for the next cycle.

[0010] The above series of steps constitute a complete ALD cycle. Each time a cycle is completed, an atomic layer is added to the wafer surface. By precisely controlling the number of cycles, the desired film thickness can be achieved.

[0011] In order to reduce the deposition temperature and expand the raw material range of the precursor, plasma-assisted atomic layer deposition (PEALD) technology has been developed. This technology uses plasma-enhanced atomic layer deposition equipment. The main cavity of the equipment adopts a dual-cavity (vacuum chamber + reaction chamber) hot-wall reaction chamber design. The substrate and the reaction chamber wall are irradiated and heated by the heating components in the vacuum chamber at the same time. The substrate and the reaction chamber can be heated to 450°C. The substrate is equipped with an additional high-temperature module and can be heated to more than 600°C separately. The reaction chamber can be used to deposit 8-inch (200 mm) substrates and is compatible with substrates below 8 inches. A plasma generator is connected between the vacuum chamber and the reaction chamber. The plasma generator ionizes the reaction gas under the action of the electric field to produce ions, which enter the reaction chamber to participate in the chemical reaction process.

[0012] The main manufacturers and equipment models of plasma enhanced atomic layer deposition equipment are shown in Table 1. These equipment are suitable for preparing high-precision, pinhole-free, and highly conformal nano-thin films (Al 2 O 3 ,TiO 2 ,SiO 2 ,Ta 2 O 5 ,ZnO,ZrO 2 etc.), have a high reaction rate and controllability, but cannot successfully prepare fluoride films that meet the optical performance requirements.

[0013] Table 1 Main manufacturers and equipment models of plasma enhanced atomic layer deposition equipment

[0014] Manufacturer model Beneq (Finland) TFS200 Oxford Instruments (UK) FlexAL 2.0 Picosun (Finland) R-200Advanced Shenyang Scientific Instrument Co., Ltd. PEALD-200 Jiangsu Microguide Nanotechnology Co., Ltd. PEALD-300 Summary of the invention

[0015] The purpose of the present invention is to overcome the problem that the existing PEALD technology cannot prepare fluoride films that meet the optical performance requirements, and to provide a new plasma enhanced atomic layer deposition device and a method for plasma assisted atomic layer deposition of thin films. The inventors found through experiments that the main reason why the optical performance of the fluoride film prepared by the existing PEALD technology does not meet the standards is that the elemental composition of the film is different from that of the target film. Further elemental analysis found that this difference is mainly manifested in the oxygen content, that is, the fluoride film with substandard optical performance contains an oxygen content higher than 10% (atomic percentage). Although the entire reaction chamber has adopted a vacuum system as much as possible and no new oxygen-containing source has been introduced, the oxygen content in the fluoride film still cannot be controlled below 10% (atomic percentage).

[0016] After a long period of thinking and exploration, the inventor believes that in the existing plasma enhanced atomic layer deposition equipment, the plasma generator connected between the vacuum chamber and the reaction chamber, whose plasma matrix tube is made of quartz material, may produce oxygen ions during the plasma discharge process, and then enter the reaction chamber with the reaction gas source to participate in the formation of the fluoride film. Therefore, the inventor tried to add a barrier layer to the inner wall of the existing quartz matrix tube and found that it can significantly reduce the oxygen content in the fluoride film. On this basis, the inventor further improved the material and structure of the matrix tube, and successfully prepared a fluoride film with optical properties that meet the requirements.

[0017] The specific plan is as follows:

[0018] A novel plasma enhanced atomic layer deposition device comprises a reaction chamber, wherein a sample stage is arranged in the reaction chamber, and the sample stage is connected to a lifting mechanism and a rotating mechanism, so that the lifting and rotating of the sample stage can be realized;

[0019] The reaction chamber is connected to a vacuum system and an exhaust system. The vacuum system is connected to the reaction chamber through a vacuum pump to maintain the air pressure environment required for the reaction. The exhaust system is connected to the reaction chamber through a pipeline to exhaust waste gas after the reaction.

[0020] A gas delivery system is connected to the reaction chamber through a pipeline, so as to deliver the reaction gas to the reaction chamber. A plasma generator is provided on the connecting pipeline between the gas delivery system and the reaction chamber. The plasma generator comprises a hollow rectangular tube, and a discharge coil is wound around the outer wall of the rectangular tube. After the discharge coil is turned on, the reaction gas is ionized when passing through the rectangular tube, and the obtained ions enter the reaction chamber and are deposited on a pre-set substrate. The inner wall of the rectangular tube has an insulating layer, and the insulating layer does not contain oxygen.

[0021] Furthermore, the insulating layer is any one of silicon nitride, aluminum nitride and silicon carbide, and has a thickness of 5 to 10 microns.

[0022] Furthermore, the insulating layer is an insulating polymer with a thickness of 5 to 10 micrometers, and the melting point of the insulating polymer is higher than 300°C.

[0023] Furthermore, the insulating polymer is any one of ECCtreme ECA fluoropolymer resin, polytetrafluoroethylene, and ethylene-chlorotrifluoroethylene copolymer.

[0024] Furthermore, the rectangular tube includes a quartz tube body and a polytetrafluoroethylene coating attached to the inner wall of the quartz tube body, or the rectangular tube includes a ceramic body and a polytetrafluoroethylene coating attached to the inner wall of the ceramic body.

[0025] Further, the rectangular tube comprises an insulating polymer body, the melting point of the insulating polymer is higher than 300° C., and is preferably any one of ECCtreme ECA fluoropolymer resin, polytetrafluoroethylene, and ethylene-chlorotrifluoroethylene copolymer; or,

[0026] The rectangular tube comprises an insulating body, and the material of the insulating body is any one of silicon nitride, aluminum nitride and silicon carbide.

[0027] The present invention also protects a method for plasma-assisted atomic layer deposition of thin films, which uses the novel plasma-enhanced atomic layer deposition device to perform atomic layer deposition, comprising the following steps:

[0028] S1, placing a substrate in the reaction chamber, wherein the reaction chamber is not used for depositing a peroxide film;

[0029] S2, evacuate the reaction chamber so that the vacuum degree in the reaction chamber reaches 3*10 -5 When the pressure drops below 500 Torr, the plasma generator is turned on, and the reaction gas is introduced to grow a thin film on the substrate.

[0030] Furthermore, the reaction gas includes a gas generated after a reaction source is heated, and the reaction source is an aluminum source or a magnesium source, preferably trimethylaluminum or di(cyclopentadienyl)magnesium.

[0031] Furthermore, the reaction gas includes NH 3 , sulfur hexafluoride.

[0032] Beneficial effects: The novel plasma enhanced atomic layer deposition equipment provided by the present invention improves the matrix tube in the plasma generator so that the inner wall of the matrix tube has an insulating layer to prevent the oxygen element in the matrix tube from being taken out during the discharge process and entering the fluoride and nitride films, thereby obtaining a film product with an oxygen content of less than 1.5 at.% (atomic percentage), thereby improving the optical properties of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0034] Figure 1 It is a schematic diagram of a partial structure of a device provided in Embodiment 1 of the present invention;

[0035] Figure 2 This is a test diagram of the optical properties of a thin film provided by an embodiment of the present invention;

[0036] Figure 3 This is a thin film element distribution diagram provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. In the examples, those without specifying specific techniques or conditions are carried out according to the techniques or conditions described in the literature in this area or according to the product specification. Those without specifying the manufacturer of reagents or instruments used are all conventional products that can be obtained commercially. In the following examples, if not clearly stated, "%" refers to weight percentage.

[0038] Example 1

[0039] A novel plasma enhanced atomic layer deposition device comprises a reaction chamber, wherein a sample stage is arranged in the reaction chamber, and the sample stage is connected to a lifting mechanism and a rotating mechanism, so that the lifting and rotating of the sample stage can be realized;

[0040] The reaction chamber is connected to a vacuum system and an exhaust system. The vacuum system is connected to the reaction chamber through a vacuum pump to maintain the air pressure environment required for the reaction. The exhaust system is connected to the reaction chamber through a pipeline to exhaust waste gas after the reaction.

[0041] A gas delivery system is connected to the reaction chamber through a pipeline to deliver the reaction gas to the reaction chamber. A plasma generator is provided on the connecting pipeline between the gas delivery system and the reaction chamber. Figure 1 As shown, the plasma generator includes a hollow rectangular tube, the outer wall of which is wound with a discharge coil. When the discharge coil is turned on, the reaction gas is ionized when passing through the rectangular tube, and the obtained ions enter the reaction chamber and are deposited on a pre-set substrate; the inner wall of the rectangular tube has an insulating layer, and the insulating layer does not contain oxygen.

[0042] Example 2

[0043] This embodiment improves the rectangular tube on the basis of Embodiment 1. The rectangular tube includes a quartz tube body and a polytetrafluoroethylene coating attached to the inner wall of the quartz tube body. The coating thickness is 5 microns. The coating is sprayed onto the existing quartz rectangular tube. The quartz rectangular tube is a hollow cylinder. A layer of polytetrafluoroethylene coating is plated inside the hollow cylinder. Then, a sealing ring is added to the upper and lower ends of the rectangular tube, which is connected to the reaction chamber through a flange. The structures of other parts such as the reaction chamber are existing technologies.

[0044] Example 3

[0045] Based on Example 1, this embodiment improves the rectangular tube. The rectangular tube includes a ceramic tube body and a polytetrafluoroethylene coating attached to the inner wall of the ceramic tube body. The coating is sprayed onto the existing ceramic rectangular tube. The coating thickness is 5 microns. The ceramic rectangular tube is a hollow cylinder. A layer of polytetrafluoroethylene coating is plated inside the hollow cylinder. Then, a sealing ring is added to the upper and lower ends of the rectangular tube, which is connected to the reaction chamber through a flange. The specific structure of other parts such as the reaction chamber is the existing technology.

[0046] Example 4

[0047] Based on Example 1, this embodiment improves the rectangular tube, which is a polytetrafluoroethylene rectangular tube, a hollow cylinder, and then adds a sealing ring at both ends of the rectangular tube, which is connected to the reaction chamber through a flange. The specific structure of the reaction chamber and other parts is the existing technology.

[0048] Example 5

[0049] The new plasma enhanced atomic layer deposition equipment in Example 3 and Example 4 were used to deposit aluminum nitride films, with trimethylaluminum (TMA) as the Al precursor and NH3 / Ar as the reaction gas, and the introduction time was 0.1 and 13 s respectively. 2 As purge gas. TMA purge time is 4s, NH 3 The purge time of / Ar was 6s. The carrier gas of TMA was high purity N 2 , flow rate is 120sccm, NH 3 The carrier gas of plasma is Ar. Ar and NH 3 The flow rates of and were 160 and 30 sccm respectively. The plasma power was 2500 W. The deposition temperature was 300 °C.

[0050] The main process parameters are shown in Table 2. The specific steps are as follows:

[0051] First, the temperature of the reaction chamber was raised to 300°C, and the temperature of TMA was raised to 25°C. TMA was introduced for 0.1s and then turned off, and nitrogen was introduced to purge the process chamber for 4s. The plasma generator was turned on, the power was set to 2500W, 160sccm of argon and 30sccm of ammonia were introduced, and then turned off after 13s, and then nitrogen was introduced to purge the chamber for 6s.

[0052] Table 2 Aluminum nitride process parameters

[0053] Parameter (unit) value Source bottle temperature (℃) 25 Substrate temperature (℃) 300 Trimethylaluminum introduction time (s) 0.1 Post-purge time of trimethylaluminum (s) 4 Ammonia injection time (s) 13 Ammonia post-purge time (s) 6 Argon gas flow rate (sccm) 160 Ammonia flow rate (sccm) 30 Plasma power (W) 2500

[0054] Example 6

[0055] The novel plasma enhanced atomic layer deposition equipment in Example 3 and Example 4 were used to deposit magnesium fluoride thin films, di(cyclopentadienyl)magnesium [Mg(Cp) 2 ] as a magnesium source and sulfur hexafluoride (SF 6 ) plasma as a fluorine source. Mg(Cp) 2 The precursor was kept at 90°C. SF 6 The plasma power was 800 W. High purity nitrogen (99.999%) was used as carrier gas and purge gas. Mg(Cp) 2 When the nitrogen flow rate is 100 sccm, the SF 6 The plasma flow rate is 50 sccm. The process sequence is: Mg(Cp) 2 3s of inlet, 6s of nitrogen purge, SF 6 Plasma was introduced for 10 seconds and nitrogen was purged for 8 seconds. The deposition temperature was 300°C.

[0056] The main process parameters are shown in Table 3. The specific steps are as follows:

[0057] First, raise the temperature of the reaction chamber to 300°C and add Mg(Cp) 2 The temperature was raised to 90°C. Mg(Cp) 2 The plasma generator was turned on, the power was set to 800 W, 50 sccm of sulfur hexafluoride gas was introduced, and it was turned off after 10 seconds, and then nitrogen was introduced to purge the chamber for 8 seconds.

[0058] Table 3 Magnesium fluoride process parameters

[0059] Parameter (unit) value Source bottle temperature (℃) 90 Substrate temperature (℃) 300 Magnesium bis(cyclopentadienyl) injection time (s) 3 Magnesium bis(cyclopentadienyl) purge time (s) 6 Sulfur hexafluoride injection time (s) 10 Sulfur hexafluoride purge time (s) 8 Sulfur hexafluoride flow rate (sccm) 50 Nitrogen flow rate (sccm) 100 Plasma power (W) 800

[0060] Comparative Example 1

[0061] Conventional plasma enhanced atomic layer deposition equipment, namely R200 equipment produced by Picosun, was used to deposit aluminum nitride film, and the specific process was the same as that in Example 5.

[0062] Comparative Example 2

[0063] A conventional plasma enhanced atomic layer deposition device, R200 produced by Picosun, was used to deposit the magnesium fluoride film. The specific process was the same as that in Example 6.

[0064] Performance Testing

[0065] (1) Optical performance

[0066] The magnesium fluoride films prepared in Example 6 and Comparative Example 2 were subjected to optical tests. Figure 2 As shown, it is found that the magnesium fluoride film prepared by Example 6 using the improved equipment has a lower refractive index due to the rectangular tube with PTFE coating, and the refractive index at a wavelength of 643nm is 1.39, which is consistent with the refractive index of the standard oxygen-free magnesium fluoride film. Comparative Example 2 uses conventional plasma enhanced atomic layer deposition equipment to prepare a magnesium fluoride film with a higher refractive index, close to the refractive index of magnesium oxide, proving that the magnesium fluoride film prepared by conventional plasma enhanced atomic layer deposition equipment has a higher oxygen content.

[0067] (2) Elemental analysis

[0068] The elemental analysis of the magnesium fluoride film prepared in Example 6 and Comparative Example 2 is shown in Table 4. The elemental distribution of the film produced by the equipment in Example 4 in Example 6 and the magnesium fluoride film prepared in Comparative Example 2 is shown in Table 4. Figure 3 .

[0069] Table 4 Oxygen content of magnesium fluoride film

[0070] sample Oxygen content (at.%) Comparative Example 2 15.5 Example 6 (using the equipment of Example 3) 1.3 Example 6 (Using the equipment of Example 4) 1.3

[0071] from Figure 3 It can be seen from Table 4 that the magnesium fluoride film prepared in Example 6 has a lower oxygen content, while the magnesium fluoride film prepared in Comparative Example 2 has an oxygen content of 15.5% (atomic percentage), which further explains the results of the optical test.

[0072] Elemental analysis was performed on the aluminum nitride films prepared in Example 5 and Comparative Example 1. The results are shown in Table 5.

[0073] It can be seen from Table 5 that the oxygen content of the aluminum nitride film prepared in Example 5 is relatively low, while the oxygen content of the magnesium fluoride film prepared in Comparative Example 2 is 15.5% (atomic percentage), which is similar to the change in the oxygen content of the magnesium fluoride film. It can be inferred that the optical performance of the aluminum nitride film prepared in Example 5 is better than that of Comparative Example 2.

[0074] Table 5 Oxygen content of aluminum nitride film

[0075] sample Oxygen content (at.%) Comparative Example 1 12.6 Example 5 (using the equipment of Example 3) 1.1 Example 5 (Using the equipment of Example 4) 1.0

[0076] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0078] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A novel plasma enhanced atomic layer deposition device, comprising a reaction chamber, characterized in that: A sample stage is provided in the reaction chamber, and the sample stage is connected to a lifting mechanism and a rotating mechanism, so that the lifting and rotating of the sample stage can be realized; The reaction chamber is connected to a vacuum system and an exhaust system. The vacuum system is connected to the reaction chamber through a vacuum pump to maintain the air pressure environment required for the reaction. The exhaust system is connected to the reaction chamber through a pipeline to exhaust waste gas after the reaction. A gas delivery system is connected to the reaction chamber through a pipeline, so as to deliver the reaction gas to the reaction chamber. A plasma generator is provided on the connecting pipeline between the gas delivery system and the reaction chamber. The plasma generator comprises a hollow rectangular tube, and a discharge coil is wound around the outer wall of the rectangular tube. After the discharge coil is turned on, the reaction gas is ionized when passing through the rectangular tube, and the obtained ions enter the reaction chamber and are deposited on a pre-set substrate. The inner wall of the rectangular tube has an insulating layer, and the insulating layer does not contain oxygen.

2. The novel plasma enhanced atomic layer deposition device according to claim 1, characterized in that: The insulating layer is any one of silicon nitride, aluminum nitride and silicon carbide, and has a thickness of 5 to 10 microns.

3. The novel plasma enhanced atomic layer deposition device according to claim 1, characterized in that: The insulating layer is an insulating polymer with a thickness of 5 to 10 micrometers. The melting point of the insulating polymer is higher than 300°C.

4. The novel plasma enhanced atomic layer deposition device according to claim 3, characterized in that: The insulating polymer is any one of ECCtreme ECA fluoropolymer resin, polytetrafluoroethylene, and ethylene-chlorotrifluoroethylene copolymer.

5. The novel plasma enhanced atomic layer deposition device according to claim 4, characterized in that: The rectangular tube includes a quartz tube body and a polytetrafluoroethylene coating attached to the inner wall of the quartz tube body, or the rectangular tube includes a ceramic body and a polytetrafluoroethylene coating attached to the inner wall of the ceramic body.

6. The novel plasma enhanced atomic layer deposition device according to claim 1, characterized in that: The rectangular tube comprises an insulating polymer body, wherein the melting point of the insulating polymer is higher than 300° C., and the insulating polymer is preferably any one of ECCtreme ECA fluoropolymer resin, polytetrafluoroethylene, and ethylene-chlorotrifluoroethylene copolymer; or The rectangular tube comprises an insulating body, and the material of the insulating body is any one of silicon nitride, aluminum nitride and silicon carbide.

7. A method for plasma-assisted atomic layer deposition of thin films, characterized in that: Atomic layer deposition is performed using the novel plasma enhanced atomic layer deposition device described in any one of claims 1 to 6.

8. The method for plasma-assisted atomic layer deposition of thin films according to claim 7, characterized in that: The following steps are involved: S1, placing a substrate in the reaction chamber, wherein the reaction chamber is not used for depositing a peroxide film; S2, evacuate the reaction chamber so that the vacuum degree in the reaction chamber reaches 3*10 -5 When the pressure drops below 500 Torr, the plasma generator is turned on, and the reaction gas is introduced to grow a thin film on the substrate.

9. The method for plasma-assisted atomic layer deposition of thin films according to claim 8, characterized in that: The reaction gas includes a gas generated by heating a reaction source, wherein the reaction source is an aluminum source or a magnesium source, preferably trimethylaluminum or di(cyclopentadienyl)magnesium.

10. The method for plasma-assisted atomic layer deposition of thin films according to claim 8, characterized in that: The reaction gas includes any one of NH3 and sulfur hexafluoride.

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