A method for plasma-assisted tin dioxide production

Abstract

The application provides a plasma-assisted tin dioxide preparation method, which comprises the following steps: pretreating a substrate and then blowing Ar gas; introducing an organic tin precursor; blowing Ar gas to remove the excess precursor; introducing H2O vapor with a flow rate of 1-2 sccm and continuously reacting for 30-60 S to form Sn-OH bonds and hydrolyze residual organic ligands; blowing Ar gas; introducing H2 plasma short pulses with a pulse width of 0.5-2 S and a frequency of 1-5 Hz to react with residual organic carbon on the surface, generate CH4 and remove the CH4, and form Sn-H saturated surface dangling bonds; blowing Ar gas to remove H2 and reaction byproducts; introducing O2 plasma to oxidize Sn-H into SnO2 lattice structure; blowing Ar gas; judging whether the film thickness reaches a target value; if not, returning to step 2; and if yes, cooling and taking out, so that the amount of organic ligand impurities is reduced, and the quality of the tin dioxide film is improved.

Description

Technical Field

[0001] This invention relates to a plasma-assisted method for preparing tin dioxide. Background Technology

[0002] Tin dioxide (SnO2) is an important wide-bandgap semiconductor material with broad application prospects in solar cells, gas sensors, and transparent conductive films due to its excellent photoelectric properties, chemical stability, and high transparency. With the rapid development of microelectronics and optoelectronics technologies, the demand for high-quality tin dioxide thin films is increasing, and its preparation methods have attracted widespread attention.

[0003] Currently, the main methods for preparing tin dioxide thin films include sol-gel method, chemical vapor deposition, magnetron sputtering, and atomic layer deposition (ALD). Among these, ALD has become an important method for preparing high-quality tin dioxide thin films due to its excellent film thickness control precision, good step coverage, and uniformity. CN115584483B discloses a method for preparing tin dioxide thin films using ALD, in which a first oxygen source and a second oxygen source are alternately used as oxygen sources to react with an organic tin metal source. The strong oxidizing power of the second oxygen source is utilized to reduce defects in the crystal structure of the prepared tin dioxide.

[0004] However, existing methods for preparing tin dioxide thin films still have some technical problems: First, in the traditional ALD process for preparing tin dioxide thin films, the organic ligands in the organotin precursor are often difficult to remove completely, and the residual organic impurities will affect the electrical and optical properties of the film; Second, conventional water vapor as an oxidant has limited reactivity and is difficult to achieve complete oxidation at low temperatures, resulting in defects such as oxygen vacancies in the film.

[0005] Therefore, there is an urgent need to develop a method for preparing tin dioxide thin films that can effectively remove organic impurities and improve the crystal quality of the films, in order to meet the application requirements of high-performance electronic and optoelectronic devices. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a plasma-assisted method for preparing tin dioxide, achieving fewer organic ligand impurities and improving the quality of tin dioxide thin films. This objective is achieved as follows: This invention proposes a plasma-assisted method for preparing tin dioxide, comprising: Step 1: Pre-treat the substrate and then purge it with Ar gas for 5-10 seconds; Step 2: Introduce organotin precursor at a flow rate of 0.1-1 sccm for 30-60 seconds to allow precursor molecules to adsorb onto the substrate surface and form a monolayer. Step 3: Perform Ar gas purging for 5-10 seconds to remove excess precursors; Step 4: Introduce H2O vapor at a flow rate of 1-2 sccm for 30-60 seconds to react with the adsorption layer and form Sn-OH bonds, while simultaneously hydrolyzing residual organic ligands; then purge with Ar gas for 5-10 seconds. Step 5: Introduce short pulses of H2 plasma with a pulse width of 0.5-2S and a frequency of 1-5Hz. The plasma reacts with residual organic carbon on the surface to generate CH4, which is then discharged. At the same time, Sn-H saturated surface dangling bonds are formed. Step 6: Purge with Ar gas for 5 seconds to remove H2 and reaction byproducts; Step 7: Introduce O2 plasma at a power of 50-100W for 3-8 minutes to oxidize the Sn-H state to a SnO2 lattice structure; then purge with Ar gas for 5-15 seconds. Step 8: Determine whether the film thickness has reached the target value. If not, return to step 2; otherwise, proceed to the next step. Step 9: Cool down and remove.

[0007] Furthermore, the pretreatment of the substrate in step 1 includes: cleaning the substrate with an ultrasonic cleaning device, cleaning with a mixed solution of acetone, ethanol and deionized water for 5-10 minutes, placing the cleaned substrate into the ALD cavity, evacuating the ALD cavity, and heating it to 60-150°C.

[0008] Furthermore, the cooling and removal in step 9 includes: cooling to room temperature in an N2 atmosphere; and transferring to a glove box.

[0009] Furthermore, the organotin precursor in step 2 is selected from at least one of tetradimethylaminotin, tetraethylaminotin, dibutyldiphenyltin, or dibutyldiacetyl tin.

[0010] Furthermore, the introduction of H2O vapor in step 4 includes: when introducing H2O vapor, pulse injection is used, and the duration of a single pulse is 0.1-0.5 seconds.

[0011] Furthermore, in step 7, the introduction of O2 plasma is carried out at a power of 50-100W for 3-8 minutes, including: 30-50W for 1-2 minutes and 80-150W for 2-6 minutes.

[0012] Compared with the prior art, the beneficial effects of the present invention are: the present invention, through plasma-assisted preparation method, especially H2 plasma short pulse treatment, can effectively remove residual organic impurities, improve the purity of the film, solve the problem of difficult removal of residual organic impurities in traditional methods, and achieve higher purity.

[0013] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Example

[0014] Step 1: Pre-treat the substrate and then purge it with Ar gas for 10 seconds; Step 2: Introduce tetradimethylaminotin at a flow rate of 1 sccm for 60 seconds to allow precursor molecules to adsorb onto the substrate surface and form a monolayer. Step 3: Perform Ar gas purging for 10 seconds to remove excess precursors; Step 4: Introduce H2O vapor at a flow rate of 2 sccm for 60 seconds to react with the adsorption layer and form Sn-OH bonds, while simultaneously hydrolyzing residual organic ligands; then purge with Ar gas for 10 seconds. Step 5: Introduce a short pulse of H2 plasma with a pulse width of 2 seconds and a frequency of 5 Hz. The plasma reacts with the residual organic carbon on the surface to generate CH4, which is then discharged. At the same time, Sn-H saturated surface dangling bonds are formed. Step 6: Purge with Ar gas for 5 seconds to remove H2 and reaction byproducts; Step 7: Introduce O2 plasma at a power of 100W for 8 minutes to oxidize the Sn-H state to a SnO2 lattice structure; then purge with Ar gas for 15 seconds. Step 8: Determine whether the film thickness has reached the target value. If not, return to step 2; otherwise, proceed to the next step. Step 9: Cool down and remove. Example

[0015] A plasma-assisted method for preparing tin dioxide, characterized in that it includes: Step 1: Clean the substrate using an ultrasonic cleaning device. Clean with a mixed solution of acetone, ethanol and deionized water for 5 minutes. Place the cleaned substrate into the ALD cavity, evacuate the ALD cavity, heat it to 60°C, and then purge it with Ar gas for 5 seconds. Step 2: Introduce tetraethylammonium tin at a flow rate of 0.1 sccm for 30 seconds to allow precursor molecules to adsorb onto the substrate surface and form a monolayer. Step 3: Perform Ar gas purging for 5 seconds to remove excess precursors; Step 4: Introduce H2O vapor at a flow rate of 1 sccm for 30 seconds to react with the adsorbed layer and form Sn-OH bonds, while simultaneously hydrolyzing residual organic ligands; then purge with Ar gas for 5 seconds. Step 5: Introduce a short pulse of H2 plasma with a pulse width of 0.5 s and a frequency of 1 Hz. The plasma reacts with the residual organic carbon on the surface to generate CH4 and release it. At the same time, Sn-H saturated surface dangling bonds are formed. Step 6: Purge with Ar gas for 5 seconds to remove H2 and reaction byproducts; Step 7: Introduce O2 plasma at a power of 50W for 3 minutes to oxidize the Sn-H state to a SnO2 lattice structure; then purge with Ar gas for 5 seconds. Step 8: Determine whether the film thickness has reached the target value. If not, return to step 2; otherwise, proceed to the next step. Step 9: Cool to room temperature in a N2 atmosphere; transfer to a glove box. Example

[0016] A plasma-assisted method for preparing tin dioxide, characterized in that it includes: Step 1: Pre-treat the substrate and then purge it with Ar gas for 7.5 seconds; Step 2: Introduce dibutyldiphenyltin at a flow rate of 0.55 sccm for 45 seconds to allow the precursor molecules to adsorb onto the substrate surface and form a monolayer. Step 3: Perform Ar gas purging for 7.5 seconds to remove excess precursors; Step 4: Introduce H2O vapor. When introducing H2O vapor, use pulse injection with a single pulse duration of 0.3 s and a flow rate of 1.5 sccm for 45 s. The vapor reacts with the adsorbed layer to form Sn-OH bonds and hydrolyzes residual organic ligands. Then, purge with Ar gas for 7.5 s. Step 5: Introduce a short pulse of H2 plasma with a pulse width of 1.5 s and a frequency of 3 Hz. The plasma reacts with the residual organic carbon on the surface to generate CH4 and release it. At the same time, Sn-H saturated surface dangling bonds are formed. Step 6: Purge with Ar gas for 5 seconds to remove H2 and reaction byproducts; Step 7: Introduce O2 plasma at 45W for 1.5 minutes and then at 115W for 4 minutes to oxidize the Sn-H state to a SnO2 lattice structure; then purge with Ar gas for 10 seconds. Step 8: Determine whether the film thickness has reached the target value. If not, return to step 2; otherwise, proceed to the next step. Step 9: Cool down and remove.

[0017] Comparative Example 1 This comparative example does not involve H2 plasma treatment; the remaining steps are the same as in Example 1.

[0018] The following results were obtained after analyzing the elemental composition of the thin film using X-ray photoelectron spectroscopy:

[0019] Data Result Analysis and Proof: The data shows that the carbon residue in Comparative Example 1 is as high as 7.85%, which indicates that the hydrolysis reaction cannot completely remove the macromolecular organic ligands in the precursor during the conventional ALD cycle. After the introduction of H2 plasma, the carbon content decreased significantly, proving that H2 plasma can react with the residual organic carbon on the surface to generate volatile methane, effectively cleaning the growth interface.

[0020] In Example 2, due to the short pulse width and low frequency, the reaction between hydrogen groups and surface ligands was insufficient, and 2.42% of carbon remained.

[0021] Although the pulse width and frequency were increased in Example 1, the excessively long pulse and high frequency caused oversaturation of the surface Sn-H bonds or slight physical bombardment damage, reducing the carbon content to 1.15%, but not to the maximum.

[0022] In Example 3, the pulse width and frequency achieved the optimal balance. Combined with the pulsed H2O injection in step 4, the H2 plasma can fully cover the surface active sites with a pulse width of 1.5 s. Its carbon residue is only 0.32%, which basically reaches the detection limit. Moreover, the tin-oxygen ratio of 1:1.99 is closest to the stoichiometric ratio of ideal tin dioxide.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A plasma-assisted method for preparing tin dioxide, characterized in that, include: Step 1: Pre-treat the substrate and then purge it with Ar gas for 5-10 seconds; Step 2: Introduce organotin precursor at a flow rate of 0.1-1 sccm for 30-60 seconds to allow precursor molecules to adsorb onto the substrate surface and form a monolayer. Step 3: Perform Ar gas purging for 5-10 seconds to remove excess precursors; Step 4: Introduce H2O vapor at a flow rate of 1-2 sccm for 30-60 seconds to react with the adsorption layer and form Sn-OH bonds, while simultaneously hydrolyzing residual organic ligands; then purge with Ar gas for 5-10 seconds. Step 5: Introduce short pulses of H2 plasma with a pulse width of 0.5-2S and a frequency of 1-5Hz. The plasma reacts with residual organic carbon on the surface to generate CH4, which is then discharged. At the same time, Sn-H saturated surface dangling bonds are formed. Step 6: Purge with Ar gas for 5 seconds to remove H2 and reaction byproducts; Step 7: Introduce O2 plasma at a power of 50-100W for 3-8 minutes to oxidize the Sn-H state to a SnO2 lattice structure; then purge with Ar gas for 5-15 seconds. Step 8: Determine whether the film thickness has reached the target value. If not, return to step 2; otherwise, proceed to the next step. Step 9: Cool down and remove.

2. The plasma-assisted tin dioxide preparation method according to claim 1, characterized in that, The pretreatment of the substrate in step 1 includes: cleaning the substrate with an ultrasonic cleaning device, cleaning with a mixed solution of acetone, ethanol and deionized water for 5-10 minutes, placing the cleaned substrate into the ALD cavity, evacuating the ALD cavity, and heating it to 60-150℃.

3. The plasma-assisted tin dioxide preparation method according to claim 2, characterized in that, The cooling and removal process in step 9 includes: cooling to room temperature in an N2 atmosphere; and transferring to a glove box.

4. The plasma-assisted tin dioxide preparation method according to claim 1, characterized in that, The organotin precursor in step 2 is selected from at least one of tetradimethylaminotin, tetraethylaminotin, dibutyldiphenyltin, or dibutyldiacetyl tin.

5. The plasma-assisted tin dioxide preparation method according to claim 1, characterized in that, The introduction of H2O vapor in step 4 includes: when introducing H2O vapor, pulse injection is used, and the duration of a single pulse is 0.1-0.5 seconds.

6. The plasma-assisted tin dioxide preparation method according to claim 5, characterized in that, In step 7, the O2 plasma is introduced at a power of 50-100W for 3-8 minutes, including: 30-50W for 1-2 minutes and 80-150W for 2-6 minutes.

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