Helium-assisted low-temperature thin film deposition method and device

Abstract

The invention discloses a helium-assisted low-temperature thin film deposition method and device, and belongs to the technical field of thin film deposition. The method mainly comprises the steps that when reaction gas is introduced into a deposition cavity loaded with a to-be-deposited substrate, helium with the preset flow is introduced into the deposition cavity at the same time; helium and reaction gas are excited through a radio frequency electric field to generate mixed plasmas, low-temperature thin film deposition is carried out in a deposition cavity of the mixed plasmas, helium is preferentially ionized under the action of the radio frequency electric field to generate helium high-energy electrons, the helium high-energy electrons provide energy for dissociation of the reaction gas into the plasmas, and in addition, the reaction gas is separated into the mixed plasmas. Local heat generated in the helium plasma discharging process is conducted to the cavity outer wall cooling device through high thermal conductivity of helium high-energy electrons, and therefore temperature fluctuation in the cavity is reduced. The plasma enhancement and energy transfer characteristics of helium are utilized, and on the premise that the low-temperature deposition temperature is guaranteed, the deposition rate and the film performance are synchronously improved.

Description

Technical Field

[0001] This application relates to the field of thin film deposition technology, and in particular to a helium-assisted low-temperature thin film deposition method and apparatus. Background Technology

[0002] PECVD (Plain Electron Vapor Deposition) technology is widely used in thin film preparation. Among them, low-temperature PECVD, with a deposition temperature below 250°C, is widely used in flexible electronics, polymer-based devices, and advanced semiconductor packaging because it avoids the performance damage to the substrate material caused by high temperatures. However, PECVD deposition technology at low temperatures has a significant technical bottleneck: the low temperature leads to a decrease in the dissociation efficiency of the reactive gases, which in turn causes slow deposition rates and low film density.

[0003] Existing solutions for improving the performance of low-temperature PECVD deposition mainly include increasing radio frequency (RF) power and adjusting the reactive gas ratio. However, increasing RF power will enhance the bombardment damage of the substrate by the plasma, which can easily cause structural damage, especially to flexible substrates or precision devices; while adjusting the reactive gas ratio can only slightly improve the dissociation efficiency and has limited effect on improving the deposition rate and film density.

[0004] Therefore, there is an urgent need to develop new low-temperature PECVD thin film deposition technologies to improve the performance of PECVD deposited thin films in low-temperature environments. Summary of the Invention

[0005] In view of the problems of slow deposition rate and low film density in existing low-temperature deposition thin film technology, this application mainly provides a helium-assisted low-temperature thin film deposition method and apparatus.

[0006] To achieve the above objectives, the first technical solution adopted in this application is: a helium-assisted low-temperature thin film deposition method, which includes: simultaneously introducing a predetermined flow rate of helium into a deposition cavity containing a substrate to be deposited while introducing a reactive gas; generating a mixed plasma by exciting helium and the reactive gas through a radio frequency electric field, and performing low-temperature thin film deposition in the deposition cavity containing the mixed plasma, wherein the helium is preferentially ionized under the action of the radio frequency electric field to generate helium high-energy electrons, which provide energy for the dissociation of the reactive gas into plasma, and the high thermal conductivity of the helium high-energy electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the cavity, thereby reducing the temperature fluctuation in the deposition cavity.

[0007] Optionally, the flow rate of helium is 20 sccm to 50 sccm.

[0008] Optionally, the impurity content of helium gas is no more than 10 ppm.

[0009] Optionally, before generating a mixed plasma by exciting helium and reactive gas with a radio frequency electric field, the vacuum level in the deposition chamber is adjusted to 3 Pa to 15 Pa by an electromagnetic vacuum valve.

[0010] Optionally, the operating frequency and power of the radio frequency electric field can be adjusted according to the characteristics of the deposited thin film.

[0011] Optionally, an automatic impedance matching device can be used to achieve impedance matching between the radio frequency energy corresponding to the radio frequency electric field and the plasma.

[0012] Optionally, the temperature fluctuation within the deposition chamber should not exceed 1°C.

[0013] Optionally, after the thin film deposition is completed, the helium and reactive gases introduced into the deposition chamber are stopped, the radio frequency power supply that generates the radio frequency electric field is turned off, and the deposition chamber is kept in a vacuum state for 3 to 5 seconds. After the deposition chamber is kept in a vacuum state for 3 to 5 seconds, the nitrogen inlet valve is opened to allow the pressure in the deposition chamber to rise back to atmospheric pressure, and then the substrate with the thin film deposition completed is removed.

[0014] Optionally, the deposition rate of the thin film is 0.5 nm / s to 2 nm / s.

[0015] The second technical solution adopted in this application is: a helium-assisted low-temperature thin film deposition apparatus, comprising: a helium inlet module, used to simultaneously introduce a predetermined flow rate of helium into the deposition chamber when introducing reactive gas into the deposition chamber loaded with the substrate to be deposited; and a thin film deposition module, used to excite helium and reactive gas to generate plasma through a radio frequency electric field, and to perform low-temperature thin film deposition in the plasma environment of the mixed gas, wherein helium is preferentially ionized under the action of the radio frequency electric field to generate helium high-energy electrons, which provide energy for the reaction gas to dissociate into plasma, and the high thermal conductivity of helium high-energy electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the chamber, thereby reducing the temperature fluctuation in the deposition chamber.

[0016] The beneficial effects that the technical solution of this application can achieve are: by introducing helium into the low-temperature deposition system, utilizing the plasma enhancement and energy transfer characteristics of helium, the dissociation efficiency of the reactive gas and the plasma activity can be improved, and the deposition rate and film performance can be improved simultaneously while ensuring that the deposition temperature does not exceed 250℃. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a specific embodiment of a helium-assisted low-temperature thin film deposition method according to this application; Figure 2 This is a schematic diagram of a specific embodiment of a helium-assisted low-temperature thin film deposition apparatus according to this application.

[0019] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0020] The preferred embodiments of this application will now be described in detail with reference to the accompanying drawings, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of this application.

[0021] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0022] This application specifically relates to a thin film preparation method that uses helium (He) to assist in the deposition of thin films in a low-temperature environment, which is applicable to the thin film manufacturing scenarios of low-temperature sensitive semiconductor devices where the deposition temperature is strictly limited.

[0023] Helium, as an inert gas, possesses high thermal conductivity, moderate ionization energy, and high molecular motion speed, making it suitable as an energy transfer medium and ionization enhancer in plasma environments. This application addresses the challenges of low-temperature deposition by systematically introducing helium into the low-temperature PECVD deposition process. The synergistic effect of helium and reactant gases solves these critical issues.

[0024] The technical solution of this application and how it solves the above-mentioned technical problems will be described in detail below with specific embodiments. The specific embodiments described below can be combined with each other to form new embodiments. The same or similar ideas or processes described in one embodiment may not be repeated in other embodiments.

[0025] Figure 1 This invention illustrates one embodiment of a helium-assisted low-temperature thin film deposition method.

[0026] Figure 1 The helium-assisted low-temperature thin film deposition method shown includes: step S101, introducing a predetermined flow rate of helium into a deposition chamber loaded with a substrate to be deposited while simultaneously introducing a reactive gas into the deposition chamber; step S102, generating a mixed plasma by exciting helium and reactive gas with a radio frequency electric field, and performing low-temperature thin film deposition in the deposition chamber of the mixed plasma, wherein helium is preferentially ionized under the action of the radio frequency electric field to generate helium high-energy electrons, which provide energy for the dissociation of reactive gas into plasma, and the high thermal conductivity of helium high-energy electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the chamber, thereby reducing the temperature fluctuation in the deposition chamber.

[0027] This specific embodiment addresses the problems of low reactive gas dissociation efficiency, slow deposition rate, and poor film performance in existing low-temperature PECVD deposition. This application provides a helium-assisted low-temperature PECVD film deposition method. By introducing helium into the low-temperature deposition system, the plasma enhancement and energy transfer characteristics of helium are utilized to improve the reactive gas dissociation efficiency and plasma activity. Under the premise of ensuring that the deposition temperature does not exceed 250°C, the deposition rate and film performance are improved simultaneously.

[0028] Specifically, this application introduces helium into the low-temperature thin film deposition process, increasing the deposition rate by 30% to 60% compared to traditional low-temperature deposition methods. For example, when depositing a 500nm SiO2 thin film, this application takes 250 to 300 seconds, while the traditional process takes 400 to 500 seconds. Therefore, compared to traditional low-temperature deposition technologies, the technology of this application significantly improves production efficiency. Furthermore, helium is an inert gas and does not chemically react with the reactant gases or the substrate, eliminating the risk of impurity introduction. This application also achieves precise control of the deposition rate and thin film performance by adjusting the flow ratio of helium to reactant gases, resulting in strong process controllability. Moreover, using this method for low-temperature thin film deposition does not require large-scale modifications to existing PECVD equipment; only the addition of a helium supply module is needed for upgrades, reducing equipment investment costs and improving technological compatibility.

[0029] exist Figure 1 In the embodiment shown, the helium-assisted low-temperature thin film deposition method includes step S101, in which a predetermined flow rate of helium is simultaneously introduced into the deposition chamber while a reaction gas is introduced into the deposition chamber that has been loaded with a substrate to be deposited.

[0030] In one specific embodiment of this application, the flow rate of helium is 20 sccm to 50 sccm.

[0031] In one specific embodiment of this application, the impurity content of helium is no more than 10 ppm.

[0032] In a specific example of this application, to ensure deposition quality, the substrate is pretreated before the reactive gas is introduced into the deposition chamber containing the substrate to be deposited. This pretreatment involves creating a uniform temperature field on the substrate. The specific procedure is as follows: First, the substrate to be deposited is placed in the positioning groove of the heater in the deposition chamber. At this time, the dimensional tolerance between the positioning groove and the substrate is controlled within ±0.5mm, and it is necessary to ensure that the deviation of the center of the substrate from the axis of the heater is ≤0.5mm, so as to avoid quality problems caused by uneven plasma bombardment in the future.

[0033] Then, the deposition chamber is closed, and the mechanical pump of the vacuum pumping system is started to extract the air from the deposition chamber, reducing the vacuum level of the deposition chamber to 1×10⁻⁶ within 30-40 seconds. -3 The pressure is kept below 1 Pa to ensure the deposition chamber is in a vacuum environment before deposition. This is because gases such as O2 and N2 in the air will react with the substrate during plasma excitation to form oxide impurities, contaminating the substrate surface. Simultaneously, during the vacuuming process, a vacuum gauge provides real-time data feedback to ensure the vacuum level within the deposition chamber. When the vacuum level within the deposition chamber reaches 1 × 10⁻⁶ Pa, the pressure is reduced to 1 × 10⁻⁶ Pa. -3After the vacuum state stabilizes for 10-30 seconds, a mixture of helium and reactive gas is introduced into the deposition chamber.

[0034] Specifically, to achieve precise proportioning and uniform mixing of helium and reactive gases, thereby laying the foundation for subsequent plasma co-ionization, this application introduces a mixture of helium and reactive gases into the deposition chamber through the following processing steps: First, configure the helium and reactant gas sources. Specifically, use 5N high-purity helium with an impurity content ≤10ppm and a purity of 99.999% as the helium source. The reactant gas needs to be selected according to the film material. For example, when depositing SiO2, use silane SiH4 with a purity of 99.999% and nitrous oxide N2O with a purity of 99.999% as the reactant gas. When depositing Si3N4, use silane with a purity of 99.999% and ammonia NH3 with a purity of 99.999% as the reactant gas.

[0035] Secondly, the flow rates of each gas are controlled separately by independent flow meters in the gas supply unit with an accuracy of ±0.1 sccm. The helium flow rate is set to 20 sccm to 50 sccm, and the reaction gas flow rates are matched according to a predetermined ratio. For example, during SiO2 deposition, the silane flow rate is 800 sccm to 2000 sccm and the nitrous oxide flow rate is 100 sccm to 300 sccm, with a flow ratio of 8:1; during Si3N4 deposition, the silane flow rate is 800 sccm to 1500 sccm and the ammonia flow rate is 200 sccm to 300 sccm, with a flow ratio of 5:1.

[0036] exist Figure 1 In the embodiment shown, the helium-assisted low-temperature thin film deposition method includes step S102, in which a mixed plasma is generated by exciting helium and reactive gas through a radio frequency electric field, and low-temperature thin film deposition is performed in the deposition cavity of the mixed plasma. In this method, helium is preferentially ionized under the action of the radio frequency electric field to generate high-energy helium electrons. These high-energy helium electrons provide energy for the dissociation of the reactive gas into plasma. Furthermore, the high thermal conductivity of the high-energy helium electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the cavity, thereby reducing temperature fluctuations within the deposition cavity.

[0037] In one specific embodiment of this application, before generating a mixed plasma by exciting helium and reactive gas with a radio frequency electric field, the vacuum level in the deposition chamber is adjusted to 3 Pa to 15 Pa by an electromagnetic vacuum valve.

[0038] In one specific embodiment of this application, the operating frequency and power of the radio frequency electric field are adjusted according to the characteristics of the deposited thin film.

[0039] In one specific embodiment of this application, an automatic impedance matching device is used to achieve impedance matching between the radio frequency energy corresponding to the radio frequency electric field and the plasma.

[0040] In one specific embodiment of this application, the temperature fluctuation within the deposition chamber is no greater than 1°C.

[0041] In one specific embodiment of this application, the deposition rate of the thin film is 0.5 nm / s to 2 nm / s.

[0042] Specifically, before generating a mixed plasma by exciting helium and reactive gases with a radio frequency electric field, the vacuum level of the cavity is first adjusted to 3Pa~15Pa by an electromagnetic vacuum valve with a response time ≤0.5s. The specific value here is not limited in this application because different vacuum levels are used for depositing different thin films. For example, a vacuum level of 8Pa±0.2Pa is usually used for depositing SiO2, and a vacuum level of 6Pa±0.2Pa is usually used for depositing Si3N4. The vacuum level range set in this application can balance the plasma density and ensure the migration ability of active groups.

[0043] Subsequently, plasma is excited by a radio frequency electric field, and low-temperature, high-efficiency deposition is achieved by utilizing the enhanced ionization and thermal conductivity advantages of helium. The specific implementation steps and principles of helium thin film deposition are as follows: First, a 13.56MHz radio frequency power supply is started, and the radio frequency power is adjusted to 500W~800W according to the characteristics of the deposited thin film. Furthermore, an automatic impedance matching device with a matching time ≤0.5s is used to achieve impedance matching between the radio frequency energy and the plasma. This is because helium is preferentially ionized in the radio frequency electric field to generate high-energy electrons. These high-energy electrons provide sufficient energy for the dissociation of reactive gases; for example, silane dissociates into SiH3 under high-energy electron bombardment. + SiH2 + Because of the presence of active groups, the dissociation efficiency of this application can be increased from 40%~60% in traditional low-temperature processes to 80%~90%. Simultaneously, the high thermal conductivity of helium allows for rapid conduction of localized heat generated by plasma discharge. This localized heat is then transferred to the outer wall of the cavity, and through the synergistic effect of the outer wall cooling device, the internal temperature fluctuation of the cavity is kept ≤±1℃, thus avoiding uneven heating of the substrate due to localized overheating. Simultaneously, the reactive gas ionizes under the action of a radio frequency electric field to form plasma. Based on the thin film characteristics, the deposition temperature of the deposition cavity is maintained between 100℃ and 250℃. After reaching the predetermined temperature, thin film deposition is performed. The deposition time is determined according to the target thin film thickness. In this application, the deposition rate can reach 0.5nm / s~2nm / s; for example, the deposition time for a 500nm SiO2 thin film is 300s.

[0044] In one specific embodiment of this application, after thin film deposition is completed, the helium and reactive gases introduced into the deposition chamber are stopped, the radio frequency power supply generating the radio frequency electric field is turned off, and the deposition chamber is kept in a vacuum state for 3-5 seconds. After the deposition chamber is kept in a vacuum state for 3-5 seconds, the nitrogen inlet valve is opened to allow the pressure in the deposition chamber to rise back to atmospheric pressure, and then the substrate with the completed thin film deposition is removed.

[0045] Specifically, after deposition is complete, the helium and reactive gas supply is stopped, the RF power supply is turned off, and the chamber is kept in a vacuum state for 3-5 seconds. Then, the nitrogen inlet valve is opened, and high-purity nitrogen (99.999% purity) is slowly introduced at a rate of 0.05 MPa / min. After the chamber pressure steadily rises to atmospheric pressure, the substrate is removed, completing the thin film deposition. At this point, the pressure increase rate needs to be ≤0.1 MPa / min to prevent sudden pressure changes from causing the thin film to peel off from the substrate.

[0046] Figure 2 This paper illustrates a specific embodiment of a helium-assisted low-temperature thin film deposition apparatus according to this application.

[0047] exist Figure 2 In the specific embodiment shown, the helium-assisted low-temperature thin film deposition apparatus mainly includes: a helium inlet module 201, used to simultaneously introduce a predetermined flow rate of helium into the deposition chamber when introducing the reactive gas into the deposition chamber loaded with the substrate to be deposited; and a thin film deposition module 202, used to excite helium and reactive gas to generate plasma through a radio frequency electric field, and to perform low-temperature thin film deposition in the plasma environment of the mixed gas. In this module, helium is preferentially ionized under the action of the radio frequency electric field to generate helium high-energy electrons, which provide energy for the reactive gas to dissociate into plasma. Furthermore, the high thermal conductivity of helium high-energy electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the chamber, thereby reducing temperature fluctuations within the deposition chamber.

[0048] In one specific embodiment of this application, the helium-assisted low-temperature thin film deposition apparatus provided in this application can be used to perform the helium-assisted low-temperature thin film deposition method described in any of the above embodiments. Its implementation principle and technical effects are similar, and will not be repeated here.

[0049] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0050] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A helium-assisted low-temperature thin film deposition method, characterized in that, include: When the reactive gas is introduced into the deposition chamber that has been loaded with the substrate to be deposited, a predetermined flow rate of helium is simultaneously introduced into the deposition chamber. A mixed plasma is generated by exciting the helium gas and the reactive gas with a radio frequency electric field, and a low-temperature thin film is deposited in the deposition cavity of the mixed plasma. Under the action of the radio frequency electric field, the helium gas is preferentially ionized to generate high-energy helium electrons. These high-energy helium electrons provide energy for the dissociation of the reactive gas into plasma. Furthermore, the high thermal conductivity of the high-energy helium electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the cavity, thereby reducing the temperature fluctuation in the deposition cavity.

2. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, The flow rate of the helium gas is 20 sccm to 50 sccm.

3. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, The impurity content of the helium gas is no more than 10 ppm.

4. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, Before generating a mixed plasma by exciting the helium and the reactive gas with a radio frequency electric field, the vacuum level in the deposition chamber is adjusted to 3 Pa to 15 Pa by an electromagnetic vacuum valve.

5. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, The operating frequency and power of the radio frequency electric field are adjusted according to the characteristics of the deposited thin film.

6. The helium-assisted low-temperature thin film deposition method according to claim 5, characterized in that, The impedance matching between the radio frequency energy corresponding to the radio frequency electric field and the plasma is achieved by an automatic impedance matching device.

7. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, The temperature fluctuation within the deposition chamber is no greater than 1°C.

8. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, After the thin film deposition is completed, the helium gas and the reactive gas introduced into the deposition chamber are stopped, the radio frequency power supply that generates the radio frequency electric field is turned off, and the deposition chamber is kept in a vacuum state for 3 to 5 seconds. as well as, After maintaining a vacuum state in the deposition chamber for 3 to 5 seconds, the nitrogen inlet valve is opened to allow the pressure in the deposition chamber to rise back to atmospheric pressure, and then the substrate with the completed thin film deposition is removed.

9. The helium-assisted low-temperature thin film deposition method according to claim 1, characterized in that, The deposition rate of the thin film is 0.5 nm / s to 2 nm / s.

10. A helium-assisted low-temperature thin film deposition apparatus, characterized in that, include: A helium inlet module is used to simultaneously introduce a predetermined flow rate of helium into a deposition chamber that has been loaded with a substrate to be deposited when introducing a reactive gas into the deposition chamber. A thin film deposition module is used to excite the helium gas and the reactive gas to generate plasma through a radio frequency electric field, and to perform low-temperature thin film deposition in the plasma environment of the mixed gas. The helium gas is preferentially ionized under the action of the radio frequency electric field to generate helium high-energy electrons. The helium high-energy electrons provide energy for the reactive gas to dissociate into plasma. Furthermore, the high thermal conductivity of the helium high-energy electrons is used to conduct the local heat generated during the helium plasma discharge process to the cooling device on the outer wall of the cavity, thereby reducing the temperature fluctuation within the deposition cavity.

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