Method for in-situ activation of substrate surface in atomic layer deposition chamber

Abstract

The invention belongs to the technical field of semiconductor manufacturing, micro electro mechanical systems and precise optical coating, and particularly discloses a method for activating the surface of a substrate in situ in an atomic layer deposition chamber, which comprises the following steps: selecting a donor substrate and a target substrate to be activated; etching the donor substrate to obtain a donor substrate with high-density hydroxyl groups; placing the donor substrate with the high-density hydroxyl groups and a target substrate to be activated in the same atomic layer deposition process chamber; and inert carrier gas is introduced into the atomic layer deposition process chamber, purging process parameters are controlled, and in-situ activation of the target substrate is completed. According to the method for activating the surface of the substrate in situ in the atomic layer deposition chamber, after the surface of the substrate is activated by the method, protective films such as aluminum oxide and the like are subjected to atomic layer deposition, so that the adhesive force and long-term reliability of the protective films on a whole device can be ensured; and interface engineering technical support is provided for manufacturing of high-performance and high-reliability three-dimensional heterogeneous integrated devices and micro-nano sensors.

Description

Technical Field

[0001] This invention belongs to the fields of semiconductor manufacturing, microelectromechanical systems and precision optical coating technology, and specifically relates to a method for in-situ activation of substrate surface in an atomic layer deposition chamber. Background Technology

[0002] In the manufacturing of semiconductors, microelectromechanical systems and integrated optoelectronic devices, the original silicon surface is usually chemically inert with an extremely low hydroxyl density. This leads to a significant decrease in the adhesion of atomic layer deposition (ALD) films in such areas, forming weak interfacial bonding regions, which in turn affects the mechanical stability, electrical reliability and long-term service life of the devices.

[0003] To address the insufficient surface activity in unetched areas, traditional processes typically incorporate additional surface activation steps, such as plasma treatment and wet chemical treatment. However, plasma treatment easily causes surface atomic damage and increased micro-roughness, and may lead to deformation or defects in the etched microstructures due to high-energy particle bombardment. While plasma surface activation methods are highly efficient, their activation is inherently a high-energy process. Ions, electrons, and ultraviolet photons in plasma generate strong physical sputtering and radiation effects on the substrate surface, inevitably leading to atomic-level surface damage, lattice disturbance, and a significant increase in surface micro-roughness. For regions with already formed precise micro / nano structures, this high-energy bombardment can easily cause defects such as rounded edges, dimensional changes, and even cracks, severely impairing the functionality and reliability of the device. Furthermore, the effectiveness of plasma treatment is affected by the coupling of multiple parameters, including equipment, power, and gas pressure, making uniformity and repeatability control challenging.

[0004] Wet chemical surface activation methods can generate hydroxyl groups under mild conditions, but their biggest drawback is the need to expose the substrate to liquid chemicals. This process not only increases the complexity of the process and the production cycle, but more importantly, it introduces an extremely high risk of contamination. Airborne particles, adsorbed organic molecules, and residual metal ions in the cleaning solution can severely damage the clean surface sought in semiconductor processes. These contaminants become weaknesses at the interface, degrading film performance. Simultaneously, the drying process after wet processing may cause structural adhesion or liquid residue, leading to secondary interface contamination and oxidation, compromising overall surface cleanliness, damaging surface roughness, or destroying the etched fine structures.

[0005] In summary, both global plasma treatment and immersion wet chemical treatment involve the global activation of the entire substrate surface, which disrupts the existing surface physical and chemical states, thus failing to achieve the goal of co-optimization of heterogeneous interfaces. Therefore, there is a need in the art to develop a method for in-situ activation of the substrate surface within an atomic layer deposition chamber, which can effectively solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for in-situ activation of a substrate surface within an atomic layer deposition chamber. After activating the substrate surface, an atomic layer deposition of a protective film such as alumina is performed, which ensures the adhesion and long-term reliability of the protective film on the overall device. At the same time, this method maintains the inherent ultra-clean state and atomic-level roughness of the substrate, providing interface engineering technology support for the manufacture of high-performance, high-reliability three-dimensional heterogeneous integrated devices and micro / nano sensors.

[0007] To achieve the above objectives, the present invention provides a method for in-situ activation of a substrate surface within an atomic layer deposition chamber, comprising the following steps: Step S1: Select the donor substrate and the target substrate to be activated; Step S2: Etch one or more donor substrates with buffer oxide etchant (BOE solution) to obtain donor substrates with high-density hydroxyl groups. Step S3: Place the donor substrate with high-density hydroxyl groups and the target substrate to be activated in the same atomic layer deposition process chamber. Step S4: Inert carrier gas is introduced into the atomic layer deposition process chamber. By controlling the purging process parameters, the inert carrier gas flowing through the surface of the donor substrate with high-density hydroxyl groups transfers the hydroxyl groups on the surface of the donor substrate to the surface of the target substrate to be activated, thereby completing the in-situ activation of the target substrate. Step S5: After the target substrate adsorbs an appropriate amount of hydroxyl groups, the in-situ activation of the target substrate surface is completed. Then, conventional atomic layer deposition film formation process is directly performed on the in-situ activated target substrate surface to prepare a functional thin film.

[0008] By introducing one or more independently prepared donor silicon substrates that have been fully etched with BOE solution, a controlled and gentle purge airflow is used to physically "transfer" or induce the high-density "active hydroxyl groups" on the surface of the donor silicon substrate to the surface of the unetched target substrate. This results in a uniform and appropriate hydroxyl group coverage on the entire target substrate surface, providing consistent and excellent nucleation sites for subsequent ALD deposition of alumina, ultimately improving the overall adhesion while maintaining the original cleanliness and roughness of the surface.

[0009] Preferably, in step S1, the donor substrate is a single-crystal silicon wafer, and the target substrate to be activated is a silicon substrate or a silicon oxide substrate; considering the size of the atomic layer deposition process chamber and the actual application conditions, the length of both the donor substrate and the target substrate to be activated is 3-100mm, the width is 3-100mm, and the thickness is 0.5-5mm.

[0010] Preferably, step S2 specifically involves: etching the donor substrate with a buffer oxide etching solution at a temperature of 20°C for 0.5-5 hours to form hydroxyl groups on the surface of the donor substrate; rinsing with ultrapure water for 5-30 seconds to remove visible water residue on the surface, thereby obtaining a donor substrate with high-density hydroxyl groups. The volume ratio of ammonium fluoride to hydrogen fluoride in the buffer oxide etching solution is 6:1; the volume ratio of the buffer oxide etching solution to the donor substrate is 6:1.

[0011] Preferably, in step S3, the donor substrate with high-density hydroxyl groups and the target substrate to be activated are placed parallel to each other in the atomic layer deposition process chamber; wherein, the donor substrate with high-density hydroxyl groups is placed upstream of the atomic layer deposition process chamber and in the diffusion region perpendicular to the airflow direction, so that the donor substrate with high-density hydroxyl groups is located upstream of the purge airflow; the target substrate to be activated is placed downstream of the atomic layer deposition process chamber.

[0012] Preferably, in step S4, the purging process parameters are as follows: the inert carrier gas is high-purity nitrogen, with a flow rate of 100-500 sccm; the purging time is 1-10 min; the temperature inside the atomic layer deposition process chamber is 373-473 K; and the purity of the high-purity nitrogen is 99.999%. This allows the carrier gas flowing over the donor substrate surface to carry and "transport" gaseous or adsorbed hydroxyl groups, guiding them directionally to the downstream target substrate surface.

[0013] Preferably, in step S5, the functional thin film is an alumina thin film prepared by atomic layer deposition or a thin film of other possible materials.

[0014] The present invention employs the above-described method for in-situ activation of a substrate surface within an atomic layer deposition chamber, and its beneficial effects are as follows: (1) The present invention provides a substrate surface activation method (pretreatment method) for functional group transfer in an ALD chamber without introducing external contamination or damaging the surface, so that the hydroxyl density and state of the donor silicon substrate can be independently optimized by the BOE process and can be reused or replaced, providing a stable and sufficient supply of hydroxyl groups; the entire transfer process is completed in a closed chamber under an inert atmosphere, without the intervention of any liquid or high-energy plasma, completely avoiding external contamination and physical damage to the surface; the target substrate itself does not directly contact any chemical treatment agent, and its original surface cleanliness, micromorphology and etched fine structure are completely preserved, and the required hydroxyl active sites are only supplemented by the gas phase.

[0015] (2) The atomic layer deposition precursor surface in-situ activation method provided by the present invention for enhancing the interfacial bonding strength between thin film and heterogeneous surface specifically controls the gas flow rate, flow direction, pressure and time in the atomic layer deposition process chamber and designs a specific airflow dynamics purging mode, which can drive the high-density active hydroxyl groups on the surface of the etched area of ​​the buffer oxide etchant to be efficiently and uniformly transferred to the unetched substrate surface with low hydroxyl density by means of physical migration and surface diffusion mechanism, thereby realizing the homogenization and activation of surface hydroxyl groups.

[0016] (3) After the pretreatment method in this invention is completed, there is no need to break the vacuum or transfer the substrate. The standard ALD cycle can be directly cut into the same chamber to achieve seamless connection from surface activation to film formation, thereby improving the overall process efficiency and reducing process redundancy.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of the method for activating the substrate surface in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the placement of the silicon substrate with high-density hydroxyl groups and the target substrate to be activated into the cavity in an embodiment of the present invention. Figure 3 This is a graph showing the refractive index fitting results obtained from the ellipsometric spectrum in the experimental example of this invention; Figure 4 The XPS depth profile of the narrow spectrum peaks of the alumina thin film prepared by atomic layer deposition (ALD) after BOE solution etching in the experimental example of this invention shows the variation trend of sputtering time (depth); where a is the change of Si 2p peak position, b is the change of O 1s peak position, and c is the change of Al 2p peak position. Figure 5 The peak fitting results of the Al 2p spectrum at four representative depths in XPS depth profiling of the alumina thin film deposited by ALD on the BOE solution-etched substrate in this embodiment of the invention; where a is the film surface, b is at a depth of about 5.77 nm, c is at a depth of about 11.55 nm, and d is at a depth of about 13 nm (near the interface region). Figure 6 This is a figure showing the fitted measured results of elemental composition at different depths of the substrate etched by BOE solution and deposited by ALD in the experimental example of this invention. Figure 7These are atomic force microscopy (AFM) images of the surface morphology of the BOE solution-etched substrate, the target-treated substrate, and the untreated control substrate after 120 cycles of ALD coating in the experimental examples of this invention; where a is the untreated control substrate, b is the BOE solution-etched substrate, and c is the target-treated substrate. Figure 8 This is a figure showing the measured results of fitting the elemental proportions at different depths of the untreated control substrate and the target treated substrate in the experimental examples of this invention using ALD deposition of alumina thin films. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0021] Example like Figure 1 As shown, a method for in-situ activation of a substrate surface within an atomic layer deposition chamber includes preparing a donor silicon substrate enriched with sufficient hydroxyl groups, determining a suitable gas flow distribution and appropriate chamber pressure to promote diffusion and avoid turbulence formation, specifically including the following steps: Step S1: Select the donor substrate and the target substrate to be activated; A single-crystal silicon wafer was selected as the donor substrate (silicon substrate), and it was cut into 15×15×0.5mm pieces using a diamond cutter. 3 .

[0022] The target substrate to be activated is a silicon substrate or a silicon oxide substrate; the target substrate to be activated has a length of 15 mm, a width of 15 mm, and a thickness of 0.5 mm.

[0023] Step S2: Etch the three silicon substrates with BOE solution to obtain a silicon substrate with high-density hydroxyl groups; The BOE solution was prepared with a volume ratio of 6:1 to silicon substrate. The volume ratio of ammonium fluoride to hydrogen fluoride in the buffer oxide etching solution was 6:1. The silicon substrate was etched with the BOE solution at a temperature of 20°C for 1 hour to form high-density hydroxyl groups on the surface of the silicon substrate. After rinsing with ultrapure water for 10 seconds, the substrate was wiped dry with a clean cloth to remove visible water residue. The resulting silicon substrate with high-density hydroxyl groups was then immediately placed into the atomic layer deposition process chamber. Step S3, as follows Figure 2 As shown, a silicon substrate with high-density hydroxyl groups and a target substrate to be activated are placed parallel to each other in the same atomic layer deposition process chamber. In this process, a silicon substrate with high-density hydroxyl groups is placed upstream of the atomic layer deposition process chamber and in a diffusion region perpendicular to the airflow direction, while the target substrate to be activated is placed downstream of the atomic layer deposition process chamber.

[0024] Step S4: High-purity nitrogen gas (99.999% purity) is introduced into the atomic layer deposition process chamber at a flow rate of 200 sccm for 5 minutes. The temperature inside the atomic layer deposition process chamber is 373 K. The airflow path and dynamic conditions are precisely controlled to determine a suitable airflow distribution and appropriate chamber pressure to promote diffusion and avoid turbulence. The high-purity nitrogen gas flowing over the silicon substrate surface with high-density hydroxyl groups carries and "transports" the gaseous or adsorbed hydroxyl groups on the silicon substrate surface with high-density hydroxyl groups, and directs them to the target substrate surface to be activated downstream of the atomic layer deposition process chamber, so that the target substrate surface to be activated is physically adsorbed to form a hydroxyl layer.

[0025] If the hydroxyl distribution on the surface of the target substrate does not meet the preset requirements, repeat step S4 until the hydroxyl distribution on the surface of the target substrate meets the preset requirements, and then the in-situ activation of the target substrate is completed. Step S5: Atomic layer deposition is performed directly on the surface of the target substrate after in-situ activation to obtain a highly adhesive and dense alumina protective film.

[0026] The target substrate that has completed in-situ activation was used to prepare an alumina monolayer film by ALD deposition for 120 cycles: the precursor was trimethylaluminum (TMA), the carrier gas flow rate was 300 sccm, the deposition rate was 0.1 nm / s, the pressure in the atomic layer deposition process chamber at the beginning of the coating was 0.1 Torr, the internal and external pressure difference was 12 Torr, and the deposition temperature was kept constant at 373 K.

[0027] Comparative Example 1 The silicon substrate with high-density hydroxyl groups obtained after completing step S4 in the embodiment was used to prepare an alumina monolayer film by ALD deposition for 120 cycles: the precursor was trimethylaluminum (TMA), the carrier gas flow rate was 300 sccm, the deposition rate was 0.1 nm / s, the pressure in the atomic layer deposition process chamber at the beginning of the film deposition was 0.1 Torr, the internal and external pressure difference was 12 Torr, and the deposition temperature was constant at 373 K.

[0028] Comparative Example 2 Select the same batch of single-crystal silicon wafers as those in step S1 of the embodiment as the substrate (silicon substrate), and cut them into 15×15×0.5mm pieces using a diamond cutter. 3 .

[0029] A single layer of alumina was prepared on a silicon substrate by ALD deposition in 120 cycles: the precursor was TMA, the carrier gas flow rate was 300 sccm, the deposition rate was 0.1 nm / s, the pressure in the atomic layer deposition process chamber at the beginning of the deposition was 0.1 Torr, the pressure difference between the inside and outside was 12 Torr, and the deposition temperature was constant at 373 K.

[0030] Experimental Example In the examples, the target substrate that has undergone in-situ activation was subjected to ALD deposition of an alumina monolayer film (target treatment substrate), the silicon substrate with high-density hydroxyl groups in Comparative Example 1 was subjected to ALD deposition of an alumina monolayer film (BOE solution etched substrate), and the silicon substrate in Comparative Example 2 was subjected to ALD deposition of an alumina monolayer film (untreated control substrate) for performance testing.

[0031] (1) The ellipsometric spectrum of the alumina monolayer film at incident wavelengths of 300-1200 nm was tested. δ By applying the Cauchy dispersion relation and Urbach tail absorption fitting to ellipsometric spectra, parameters such as the refractive index, film thickness, and film uniformity of the alumina monolayer film were obtained.

[0032] like Figure 3 As shown, the actual thicknesses of the alumina monolayer films deposited by ALD on the BOE solution-etched substrate, the target-processed substrate, and the untreated control substrate are 13.2 nm, 12.7 nm, and 12.0 nm, respectively.

[0033] As can be seen from the above, the substrate etched by BOE solution is rich in hydroxyl groups, which facilitates nucleation. The resulting alumina film is thicker, has a higher refractive index, and is denser and of better quality. The target treatment substrate, which has hydroxyl groups transferred from the surface of the BOE solution etched substrate, is also rich in hydroxyl groups to a certain extent. Therefore, the refractive index of the alumina film deposited on the target treatment substrate is higher than that of the alumina film deposited on the untreated control substrate.

[0034] (2) XPS was used to test the depth distribution of the alumina monolayer film to the substrate, and the elemental distribution information of the alumina film was obtained; and the microscopic surface morphology of the BOE solution etched substrate, the target treatment substrate, and the untreated control substrate after 120 cycles of ALD deposition was characterized.

[0035] like Figures 4-6 As shown, in the BOE solution etching of the substrate, an alumina monolayer film deposited by ALD was observed at a depth of 13 nm at the interface. Significant chemical shifts of all three elements (Si, O, and Al) were observed near the interface between the film and the substrate. Al exhibited diverse valence states, indicating a high level of impurities in the film. Furthermore, throughout the overall depth analysis, carbon was consistently present, with an increased content at the interface, indicating the persistent contamination introduced during etching. And as... Figure 7As shown in b, the root mean square roughness (R) of the BOE solution etched substrate surface is... q The wavelength increases to 1.14 nm, which is relatively large and will cause greater scattering loss. Therefore, the decrease in surface cleanliness caused by direct etching will inevitably affect the optical performance of the thin film.

[0036] In contrast, by using a controlled, gentle purge airflow, the high density of "active hydroxyl groups" on the donor silicon substrate surface can be physically "transferred" or induced to the unetched target substrate surface, thereby achieving a uniform and moderate hydroxyl coverage across the entire substrate surface. This provides consistent and excellent nucleation sites for subsequent ALD deposition of alumina, ultimately improving the overall bonding strength while maintaining the original cleanliness and roughness of the surface.

[0037] like Figure 7 a in Figure 7 As shown in c, the surface roughness of the target processed substrate is similar to that of the untreated control substrate, with Rq = 0.790 nm for the target processed substrate and Rq = 0.723 nm for the untreated control substrate. Figure 8 As shown, compared with the alumina film deposited on the untreated control substrate, the alumina film deposited on the target treated substrate has an increased interface width and a stoichiometric ratio closer to 2:3, indicating that the alumina film deposited on the target treated substrate is of higher quality.

[0038] And such as Figure 7 As shown, the method for in-situ activation of the substrate surface within the atomic layer deposition chamber in this embodiment of the invention has almost no impact on the sample surface quality, thus avoiding the drawbacks of plasma treatment that can easily cause surface atomic damage and increased micro-roughness.

[0039] Therefore, the present invention employs the above-mentioned method for in-situ activation of the substrate surface within an atomic layer deposition chamber. After activating the substrate surface using this method, an atomic layer deposition of alumina or other protective films is performed, which ensures the adhesion and long-term reliability of the protective film on the overall device. At the same time, this method maintains the inherent ultra-clean state and atomic-level roughness of the substrate, providing interface engineering technology support for the fabrication of high-performance, high-reliability three-dimensional heterogeneous integrated devices and micro / nano sensors.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for in-situ activation of a substrate surface within an atomic layer deposition chamber, characterized in that, Includes the following steps: Step S1: Select the donor substrate and the target substrate to be activated; Step S2: Etch one or more donor substrates with buffer oxide etchant to obtain donor substrates with hydroxyl groups. Step S3: Place the donor substrate with hydroxyl groups and the target substrate to be activated in the same atomic layer deposition process chamber; Step S4: Inert carrier gas is introduced into the atomic layer deposition process chamber. By controlling the purging process parameters, the inert carrier gas flowing through the surface of the donor substrate with hydroxyl groups transfers the hydroxyl groups on the surface of the donor substrate to the surface of the target substrate to be activated, thereby completing the in-situ activation of the target substrate. Step S5: Perform atomic layer deposition directly on the surface of the target substrate after in-situ activation to prepare a functional thin film.

2. The method for in-situ activation of a substrate surface within an atomic layer deposition chamber according to claim 1, characterized in that: In step S1, the donor substrate is a single-crystal silicon wafer, and the target substrate to be activated is a silicon substrate or a silicon oxide substrate; the length of both the donor substrate and the target substrate to be activated is 3-100mm, the width is 3-100mm, and the thickness is 0.5-5mm.

3. The method for in-situ activation of a substrate surface within an atomic layer deposition chamber according to claim 1, characterized in that, Step S2 is as follows: The donor substrate is etched with buffered oxide etching solution at a temperature of 20°C for 0.5-5 hours to form hydroxyl groups on the surface of the donor substrate. After rinsing with ultrapure water for 5-30 seconds, the visible water residue on the surface is removed, and a donor substrate with hydroxyl groups is obtained. The volume ratio of ammonium fluoride to hydrogen fluoride in the buffer oxide etching solution is 6:1; the volume ratio of the buffer oxide etching solution to the donor substrate is 6:

1.

4. The method for in-situ activation of a substrate surface within an atomic layer deposition chamber according to claim 1, characterized in that: In step S3, the donor substrate with hydroxyl groups and the target substrate to be activated are placed parallel to each other in the atomic layer deposition process chamber; wherein, the donor substrate with hydroxyl groups is placed upstream of the atomic layer deposition process chamber and in the diffusion region perpendicular to the gas flow direction, and the target substrate to be activated is placed downstream of the atomic layer deposition process chamber.

5. The method for in-situ activation of a substrate surface within an atomic layer deposition chamber according to claim 1, characterized in that, In step S4, the specific purging process parameters are as follows: the inert carrier gas is high-purity nitrogen, with a flow rate of 100-500 sccm; the purging time is 1-10 min; and the temperature inside the atomic layer deposition process chamber is 373-473 K. The purity of the high-purity nitrogen gas is 99.999%.

6. The method for in-situ activation of a substrate surface within an atomic layer deposition chamber according to claim 1, characterized in that: In step S5, the functional thin film includes an alumina thin film prepared by atomic layer deposition.

Images