Substrate surface treatment method and product and application thereof

Abstract

The invention relates to the technical field of semiconductor electrodes, in particular to a substrate surface treatment method and a product and application thereof, and the treatment method comprises the following steps: S1, treating a strontium titanate base material by using a water solvent, and then carrying out corrosion treatment for 45-60 minutes by using a hydrochloric acid solution with the volume fraction of 10%-20% to obtain a pretreated substrate; and S2, carrying out annealing treatment on the obtained pretreated substrate, and cooling to obtain the substrate with the ordered surface step structure. According to the treatment method, the strontium titanate is used as the deposition substrate, the structure of the deposition substrate is similar to that of the perovskite oxide SrRuO3, deposition growth of the SrRuO3 on the deposition substrate can be met, the surface of the strontium titanate is subjected to special treatment before deposition to enable the strontium titanate to have an atomic-scale flat surface and an ordered surface step structure, and then the SrRuO3 is deposited and grown, so that the surface roughness of the electrode is greatly reduced; therefore, the performance of the semiconductor device is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor electrodes, and in particular to a substrate surface processing method, a product thereof and an application thereof. Background Art

[0002] SrRuO3, as a multi-oxide perovskite material, is widely used as the lower electrode of semiconductor devices because it can achieve single crystal film epitaxial growth and has good conductivity. For electrodes, the roughness of the electrode surface will greatly affect the device performance. For example, in the ferroelectric capacitor structure, the roughness of the lower electrode will affect the leakage current of the material, thereby affecting the performance of ferroelectricity; for example, in the memristor, the roughness of the lower electrode will affect the device switching ratio, cycle stability and other parameters. It can be seen that reducing the surface roughness of the lower electrode is an important method to improve the performance of semiconductor devices. However, the surface roughness of SrRuO3 currently used as the lower electrode needs to be improved. The main conventional improvement method is to change the electrode deposition method, such as changing from magnetron sputtering to ion beam sputtering; but its improvement effect is still limited, and it is easy to bring other adverse effects to the electrode crystal structure due to changing the deposition method.

[0003] In view of this, it is indeed necessary to provide a technical solution to the above problems. Summary of the invention

[0004] One of the purposes of the present invention is to provide a substrate surface treatment method in view of the deficiencies in the prior art, so as to solve the problem that the surface of the currently deposited SrRuO3 as a lower electrode material still has a relatively high roughness.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for processing a substrate surface comprises the following steps:

[0007] S1. Treating the strontium titanate substrate with a water solvent, and then performing corrosion treatment with a hydrochloric acid solution having a volume fraction of 10% to 20% for 45 to 60 minutes to obtain a pretreated substrate;

[0008] S2, annealing the pretreated substrate obtained in step S1, cooling it down, and obtaining a substrate with an ordered surface step structure.

[0009] Preferably, in step S1, the reaction temperature of the water solvent treatment is 35-70° C., and the treatment time is 45-60 min.

[0010] Preferably, in step S1, the reaction temperature of the water solvent treatment is 50-70° C., and is accompanied by ultrasonic treatment or stirring treatment.

[0011] Preferably, before the aqueous solvent treatment, the surface of the strontium titanate substrate is pre-cleaned, and the pre-cleaning treatment is: ultrasonic cleaning using a non-aqueous solvent for 5 to 20 minutes.

[0012] Preferably, the non-aqueous solvent is acetone and / or ethanol.

[0013] Preferably, the pre-cleaning treatment is: firstly ultrasonically clean the surface with acetone for 10 to 20 minutes, and then ultrasonically clean the surface with ethanol for 10 to 20 minutes.

[0014] Preferably, in step S2, the annealing temperature is 900-980° C., and the annealing time is 2-3 hours.

[0015] A second object of the present invention is to provide a substrate obtained by processing the substrate surface using the above-mentioned substrate surface processing method.

[0016] The third object of the present invention is to provide a method for preparing a semiconductor lower electrode, comprising the following steps: depositing perovskite oxide on a substrate using a pulsed laser deposition method, wherein the substrate is the substrate described above.

[0017] Preferably, the pulse conditions of the pulse laser deposition method are: laser energy 280-320 mJ, oxygen pressure 18-22 Pa, target substrate distance 40-60 mm, deposition frequency 3-7 Hz, temperature 700-800° C.; the surface roughness Ra of the obtained semiconductor lower electrode is 0.1 nm to 1 nm.

[0018] The beneficial effects of the present invention are as follows: the treatment method provided by the present invention uses strontium titanate as a deposition substrate, which is similar in structure to the perovskite oxide SrRuO3, and can satisfy the deposition and growth of SrRuO3 thereon. Before deposition, the surface of strontium titanate is specially treated to make it have an atomic-level flat surface and an ordered surface step structure, and then SrRuO3 is deposited and grown, and the surface roughness of the obtained electrode is greatly reduced, thereby ensuring the performance of the semiconductor device. Specifically, for the treatment of the surface of strontium titanate, a water solvent is first used for treatment, so that the SrO surface is hydrolyzed into Sr(OH)2, and then hydrochloric acid is used for corrosion to remove the generated Sr(OH)2, and the obtained step structure is more stable and not easy to form small surface protrusions. After annealing treatment, a strontium titanate substrate with an ordered surface step and a single TiO2 termination surface can be obtained, and SrRuO3 is deposited on the substrate to obtain a semiconductor lower electrode, whose roughness is reduced by at least 10 times, solving the problem of high surface roughness of the currently deposited SrRuO3 film. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram of the lattice structure of strontium titanate.

[0020] Figure 2 The surface morphology and surface step height variation diagram of the strontium titanate substrate of Example 1 of the present invention, wherein (a) is a 3D modeling diagram of the surface morphology of the strontium titanate substrate under an atomic force microscope (AFM); (b) is a 1 μm 2 Surface morphology of the strontium titanate substrate surface under AFM; (c) is the average height map of the strontium titanate substrate surface along the step direction.

[0021] Figure 3 This is a surface morphology image of the semiconductor lower electrode obtained in Example 1 of the present invention under AFM.

[0022] Figure 4 This is a surface morphology image of the semiconductor lower electrode obtained in Comparative Example 1 of the present invention under AFM. DETAILED DESCRIPTION

[0023] In order to make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects are described in further detail below, but the embodiments of the present invention are not limited thereto.

[0024] The present invention provides a method for processing a substrate surface, comprising the following steps:

[0025] S1. Treating the strontium titanate substrate with a water solvent, and then performing corrosion treatment with a 10% to 20% volume fraction hydrochloric acid solution for 45 to 60 minutes to obtain a pretreated substrate;

[0026] S2, annealing the pretreated substrate obtained in step S1, cooling it down, and obtaining a substrate with an ordered surface step structure.

[0027] After the hydrolysis reaction, hydrochloric acid is used for treatment, so that the Sr(OH)2 generated on the surface can react with the acid to remove the SrO layer on the surface, thereby obtaining a single TiO2 surface. The inventors have found that the step structure obtained by using hydrochloric acid alone is more stable, the surface flatness is higher, and it is not easy to form small surface protrusions compared to the corrosion treatment of hydrochloric acid mixed with other acids (such as nitric acid).

[0028] The hydrochloric acid etching treatment time can be 45 to 50 minutes, 50 to 55 minutes or 55 to 60 minutes. The hydrochloric acid concentration is preferably controlled to be between 10% and 20% by volume to avoid the acid concentration being too high and damaging the subsurface structure of the substrate after long-term immersion. In particular, under the premise of sufficient hydrolysis, the effect of the hydrochloric acid etching treatment can be guaranteed, and the extension of the hydrochloric acid etching treatment time due to insufficient hydrolysis can be avoided. Excessive hydrochloric acid immersion will cause the acid to damage the subsurface structure of the substrate, increase the surface roughness, and result in poor performance of the lower electrode finally generated.

[0029] The substrate obtained by the above treatment of the present invention is then deposited with perovskite oxide, and the obtained sample has better performance as a semiconductor lower electrode.

[0030] Compared with substrates of other materials, the present invention uses strontium titanate as the substrate, which is more conducive to the subsequent deposition and growth of SrRuO3 thin films, and the surface roughness of the obtained lower electrode is lower, thereby ensuring the performance of the semiconductor device.

[0031] In some embodiments, in step S1, the reaction temperature of the water solvent treatment is 35 to 70°C, and the treatment time is 45 to 60 minutes. Compared with the reaction at room temperature, increasing the reaction temperature of the system helps to increase the reaction rate, allowing the SrO surface to be hydrolyzed more fully, laying the foundation for subsequent acid corrosion. Specifically, the reaction temperature of the water solvent treatment can be 35 to 40°C, 40 to 50°C, 50 to 60°C or 60 to 70°C. Preferably, the reaction temperature of the water solvent treatment is 50 to 70°C. At the same time, the water solvent treatment is accompanied by ultrasonic treatment or stirring treatment, which is more conducive to the hydrolysis reaction of the SrO surface.

[0032] In some embodiments, the surface of the strontium titanate substrate is pre-cleaned before the aqueous solvent treatment, and the pre-cleaning treatment is: ultrasonic cleaning for 5 to 20 minutes using a non-aqueous solvent. The surface pre-cleaning treatment of the strontium titanate substrate can remove organic attachments on the substrate surface to ensure sufficient hydrolysis of the subsequent SrO surface. The use of a non-aqueous solvent can, on the one hand, be more conducive to removing organic attachments, and on the other hand, avoid premature reaction of water with the SrO surface, which affects the subsequent hydrolysis process. Specifically, the non-aqueous solvent uses acetone and / or ethanol.

[0033] Preferably, the pre-cleaning treatment is: firstly ultrasonically clean the surface with acetone for 10 to 20 minutes, and then ultrasonically clean the surface with ethanol for 10 to 20 minutes.

[0034] In some embodiments, in step S2, the annealing temperature is 900-980°C, and the annealing time is 2-3h. The annealing temperature can be 900-920°C, 920-940°C, 940-960°C or 960-980°C; the annealing time is 2-3h. The annealing temperature and time are controlled within the above range to avoid excessively high temperature or too long annealing time, which will cause the SrO surface to regenerate, resulting in a decrease in the purity of the single TiO2 termination surface, and the height of the step cannot match the spacing between adjacent titanium dioxide surfaces, affecting the generated step structure, thereby affecting the deposition and growth of SrRuO3, resulting in the surface roughness of the obtained lower electrode being still too large.

[0035] Specifically, the present invention also provides a method for preparing a semiconductor lower electrode, comprising the following steps: depositing a perovskite oxide on a substrate using a pulsed laser deposition method, wherein the substrate is the substrate described above. The perovskite oxide mainly refers to SrRuO3, and the structure of SrRuO3 is more similar to that of SrTiO3. Compared with depositing SrRuO3 using other substrates (such as NdGaO3), the substrate provided by the present invention has better compatibility with SrRuO3.

[0036] In some embodiments, the pulse conditions of the pulse laser deposition method are: laser energy 280-320 mJ, oxygen pressure 18-22 Pa, target substrate distance 40-60 mm, deposition frequency 3-7 Hz, temperature 700-800°C; the surface roughness Ra of the obtained semiconductor lower electrode is 0.1 nm-1 nm, and Rq is 0.2 nm-1 nm.

[0037] Preferably, the pulse conditions of the pulse laser deposition method are: laser energy 30mJ, oxygen pressure 20Pa, target substrate distance 50mm, deposition frequency 5Hz, temperature 750℃; under the preferred conditions, the surface roughness Ra of the semiconductor lower electrode obtained can be lower than 0.5nm, even below 0.2nm; Rq is lower than 0.7nm, and can reach below 0.3nm. The use of this pulse condition to deposit SrRuO3 has better matching with the substrate structure of the present invention, and is more conducive to obtaining a lower electrode with lower roughness.

[0038] The present invention and its beneficial effects will be described in further detail below in conjunction with specific embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0039] Example 1

[0040] A method for processing a substrate surface comprises the following steps:

[0041] 1) firstly ultrasonically clean the strontium titanate substrate with acetone for 10 minutes, and then ultrasonically clean it with ethanol for another 10 minutes to obtain a pre-cleaned strontium titanate substrate;

[0042] 2) placing the strontium titanate substrate in 60° C. deionized water for ultrasonic vibration for 50 minutes, and then performing corrosion treatment with a 10% by volume hydrochloric acid solution for 50 minutes to obtain a pretreated substrate;

[0043] 3) In an air atmosphere, the pretreated substrate is placed in an annealing furnace for annealing at a temperature of 980° C. for 3 h, and then slowly cooled to room temperature to obtain a substrate with an ordered surface step structure.

[0044] The substrate obtained as above is used to deposit SrRuO3 to prepare a semiconductor lower electrode. The preparation method is: SrRuO3 is deposited and grown on the substrate using a pulsed laser deposition method. The pulse conditions are: laser energy 300mJ, oxygen pressure 20Pa, target substrate distance 50mm, deposition frequency 5Hz, temperature 750℃; after deposition and growth, the temperature is slowly cooled to room temperature to obtain a semiconductor lower electrode.

[0045] Example 2

[0046] A method for processing a substrate surface comprises the following steps:

[0047] 1) firstly ultrasonically clean the strontium titanate substrate with acetone for 20 minutes, and then ultrasonically clean it with ethanol for another 20 minutes to obtain a pre-cleaned strontium titanate substrate;

[0048] 2) placing the strontium titanate substrate in 35° C. deionized water for ultrasonic vibration for 60 minutes, and then performing corrosion treatment with a 20% by volume hydrochloric acid solution for 60 minutes to obtain a pretreated substrate;

[0049] 3) In an air atmosphere, the pretreated substrate is placed in an annealing furnace for annealing at a temperature of 950° C. for 3 h, and then slowly cooled to room temperature to obtain a substrate with an ordered surface step structure.

[0050] The substrate obtained as above is used to deposit SrRuO3 to prepare a semiconductor lower electrode. The preparation method is: SrRuO3 is deposited and grown on the substrate using a pulsed laser deposition method. The pulse conditions are: laser energy 280mJ, oxygen pressure 18Pa, target substrate distance 40mm, deposition frequency 3Hz, temperature 700℃; after deposition and growth, the temperature is slowly cooled to room temperature to obtain a semiconductor lower electrode.

[0051] Example 3

[0052] A method for processing a substrate surface comprises the following steps:

[0053] 1) firstly ultrasonically clean the strontium titanate substrate with acetone for 15 minutes, and then ultrasonically clean it with ethanol for another 15 minutes to obtain a pre-cleaned strontium titanate substrate;

[0054] 2) placing the strontium titanate substrate in 70° C. deionized water for ultrasonic vibration for 45 minutes, and then soaking it in a 15% by volume hydrochloric acid solution for corrosion treatment for 45 minutes to obtain a pretreated substrate;

[0055] 3) In an air atmosphere, the pretreated substrate is placed in an annealing furnace for annealing at a temperature of 900° C. for 2 h, and then slowly cooled to room temperature to obtain a substrate with an ordered surface step structure.

[0056] The substrate obtained as above is used to deposit SrRuO3 to prepare a semiconductor lower electrode. The preparation method is: SrRuO3 is deposited and grown on the substrate using a pulsed laser deposition method. The pulse conditions are: laser energy 320mJ, oxygen pressure 22Pa, target substrate distance 60mm, deposition frequency 7Hz, temperature 800℃; after deposition and growth, the temperature is slowly cooled to room temperature to obtain a semiconductor lower electrode.

[0057] Example 4

[0058] Different from Example 1, the water solvent treatment time in this example is 30 minutes.

[0059] For the rest, please refer to Example 1 and will not be described again here.

[0060] Example 5

[0061] Different from Example 4, the acid etching treatment time of this example is 75 minutes.

[0062] For the rest, please refer to Example 4 and will not be described again here.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that the strontium titanate substrate used in this comparative example is not treated and is directly used for depositing SrRuO3. The deposition conditions can be found in Example 1 and will not be described again here.

[0065] Comparative Example 2

[0066] Different from Example 1, the annealing temperature of this comparative example is 1050°C.

[0067] For the rest, please refer to Example 1 and will not be described again here.

[0068] Comparative Example 3

[0069] Different from Example 1, the annealing time of this comparative example is 4 hours.

[0070] For the rest, please refer to Example 1 and will not be described again here.

[0071] Comparative Example 4

[0072] The difference from Example 1 is that the substrate base material of this comparative example is NdGaO3, and other surface treatment methods refer to Example 1 and are not described again here.

[0073] Comparative Example 5

[0074] The difference from Example 1 is that the acid used for the corrosion treatment in this comparative example is a mixture of 10% by volume hydrochloric acid and 10% by volume nitric acid. For other surface treatment methods, refer to Example 1 and will not be described in detail here.

[0075] Comparative Example 6

[0076] The difference from Example 1 is that the acid used for the corrosion treatment in this comparative example is 30% by volume hydrochloric acid. For other surface treatment methods, refer to Example 1 and will not be described in detail here.

[0077] The substrates and semiconductor lower electrodes obtained in the above-mentioned Examples 1 to 5 and Comparative Examples 1 to 6 were subjected to morphological characterization and roughness testing.

[0078] The morphology characterization results of Example 1 are as follows Figure 2 As shown. Figure 2 As can be seen from Figure (b), the substrate obtained by the present invention presents a step structure; Figure 2 Figure (c) and Figure 1 By comparison, it can be seen that the step height of the substrate of the present invention is 0.4 nm, which is Figure 1 The distances between adjacent TiO2 surfaces are consistent, indicating that the substrate surface is terminated by a single TiO2 surface at this time, and the surface treatment method of the present invention can effectively remove the SrO surface.

[0079] The roughness test results of Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Tables 1 and Figures 3-4 As shown. Figure 3 and Figure 4 It can be seen from the comparison that after the substrate is processed by the present invention and SrRuO3 is deposited again, the roughness is greatly reduced, which can reach more than 10 times.

[0080] Table 1 Roughness test results

[0081]

[0082]

[0083] It can be seen from the roughness test results of the above-mentioned embodiments 1 to 5 and comparative examples 1 to 6 that, compared with untreated strontium titanate substrates or other treated substrates, the strontium titanate substrate with a step structure obtained after treatment of the present invention is used to deposit SrRuO3, which can ensure the uniform deposition of SrRuO3. The surface roughness of the final product is more than 10 times lower than that of the product obtained from the conventional untreated substrate, and the roughness is also greatly reduced compared with other treated substrates (such as comparative examples 4 to 6). This is mainly due to the higher compatibility of the substrate of the present invention with SrRuO3.

[0084] During the substrate surface treatment process, the control of annealing temperature and time will also affect the subsequent SrRuO3 deposition effect. As can be seen from the comparison results of Example 1 and Comparative Examples 2 to 3, when the annealing temperature is high or the annealing time is too long, the roughness improvement of the final product is limited. This may be because the high temperature and long time will cause the strontium oxide surface to regenerate, and the surface structure of the obtained substrate is not terminated with a single TiO2, which ultimately affects the deposition of SrRuO3.

[0085] In addition, before annealing, the treatment conditions of the strontium oxide surface also need to be regulated. As can be seen from the comparison between Example 1 and Examples 4 to 5 and Comparative Examples 5 to 6, when the water solvent treatment time is not enough, the surface SrO is not fully hydrolyzed, and the subsequent acid corrosion treatment is also insufficient. Even if the acid treatment time is extended, the SrO layer cannot be well treated. On the contrary, the structure of the substrate base material is destroyed due to the excessively long acid treatment time, thereby increasing the surface roughness of the substrate.

[0086] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for treating a substrate surface, characterized in that: The following steps are involved: S1. Treating the strontium titanate substrate with a water solvent, and then performing corrosion treatment with a 10% to 20% volume fraction hydrochloric acid solution for 45 to 60 minutes to obtain a pretreated substrate; S2, annealing the pretreated substrate obtained in step S1, cooling it down, and obtaining a substrate with an ordered surface step structure.

2. The method for treating a substrate surface according to claim 1, characterized in that: In step S1, the reaction temperature of the water solvent treatment is 35-70° C., and the treatment time is 45-60 min.

3. The method for treating a substrate surface according to claim 2, characterized in that: In step S1, the reaction temperature of the water solvent treatment is 50-70° C., and is accompanied by ultrasonic treatment or stirring treatment.

4. The method for treating a substrate surface according to claim 1 or 2, characterized in that: Before the water solvent treatment, the surface of the strontium titanate substrate is pre-cleaned. The pre-cleaning treatment includes: using a non-aqueous solvent to perform ultrasonic cleaning for 10 to 40 minutes.

5. The method for treating a substrate surface according to claim 4, characterized in that: The non-aqueous solvent used is acetone and / or ethanol.

6. The method for treating the substrate surface according to claim 5, characterized in that: The pre-cleaning treatment is: first use acetone to perform ultrasonic cleaning for 10 to 20 minutes, and then use ethanol to perform ultrasonic cleaning for 10 to 20 minutes.

7. The method for treating a substrate surface according to claim 1, characterized in that: In step S2, the annealing temperature is 900-980°C, and the annealing time is 2-3 hours.

8. A substrate, characterized in that The substrate is obtained by treating the substrate surface using the substrate surface treating method according to any one of claims 1 to 7.

9. A method for preparing a semiconductor lower electrode, characterized in that: The following steps are involved: Perovskite oxide is deposited on a substrate using a pulsed laser deposition method, wherein the substrate is the substrate as claimed in claim 8.

10. The method for preparing a semiconductor lower electrode according to claim 9, characterized in that: The pulse conditions of the pulse laser deposition method are: laser energy 280-320 mJ, oxygen pressure 18-22 Pa, target-substrate distance 40-60 mm, deposition frequency 3-7 Hz, temperature 700-800° C.; the surface roughness Ra of the obtained semiconductor lower electrode is 0.1 nm-1 nm.

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