A laminated dielectric material and a method for manufacturing and using the same

Abstract

The application provides a laminated dielectric material and a preparation method and application thereof, and belongs to the technical field of organic electronic devices. The material has a three-layer or multi-layer hafnium oxide (H) / zirconium oxide (Z) / hafnium oxide (H) laminated dielectric structure; the method comprises sequentially sputtering and depositing a hafnium oxide film and a zirconium oxide film, and repeatedly sputtering and depositing in this way; in addition, the material is applied to an organic transistor, and the organic transistor comprises, from bottom to top, a substrate, a dielectric layer (the material), an organic semiconductor layer and source and drain electrodes. The organic transistor has a low working voltage, can reduce the subthreshold swing of the organic transistor to a theoretical physical limit value (even break through the theoretical physical limit value), and the prepared stacked gate dielectric has a high-K dielectric constant and excellent insulation.

Description

Technical Field

[0001] This invention relates to the field of organic electronic device technology, and in particular to a multilayer dielectric material, its preparation method, and its application. Background Technology

[0002] Organic field-effect transistors (OFETs) are fundamental components of integrated circuits, combining organic electronics and optoelectronics. Over the past decade, the development of high-performance organic semiconductor (OSC) materials (including polymers and small molecules) has facilitated the rapid advancement of OFETs. To date, charge carrier mobility in OFETs has exceeded 10 cm⁻¹. 2 V -1 s -1 Its performance already surpasses that of commercial amorphous SiFETs and achieves the electrical performance required for practical device applications. On the other hand, OFETs using OSC as the channel layer have several competitive advantages, including low cost, solution handleability, and excellent inherent flexibility. Therefore, compared to ubiquitous silicon transistors, OFETs are highly promising candidates for flexible and wearable electronics.

[0003] However, power consumption is one of the most critical issues for deploying OFETs in practical applications. Most OFETs typically operate at voltages of tens of volts, far exceeding the operating voltage of benchmark thin-film amorphous silicon devices (<5V), leading to significant dynamic power consumption. Power dissipation generates heat and causes temperature rise. Particularly in circuits composed of high-density OFETs, temperatures rise rapidly, leading to gradual degradation of organic materials and shortened device lifetime. Furthermore, high-voltage bias generates significant interference signals and gate leakage current, increasing static power consumption. More importantly, given the current limitations of flexible battery capacity and safety, high-voltage OFETs are unsuitable for wearable / stretchable technologies. Therefore, reducing the operating voltage of OFETs is a fundamental prerequisite for practical device applications and has gradually become a hot research topic.

[0004] The most critical approach to reducing the operating voltage of an OFET is to reduce the subthreshold swing. This can be achieved by increasing the capacitance of the gate dielectric (including using high-k dielectric materials, solid polymer electrolytes, and reducing the dielectric layer thickness) and reducing the trap density (reducing the trap density of organic semiconductors, reducing interface defects between the OSC and the dielectric, and improving electrode-OSC contact performance). Therefore, introducing a high-k oxide dielectric layer is a highly effective way to reduce the OFET's subthreshold swing and operating voltage. However, existing devices use a single-layer oxide dielectric layer, and their subthreshold swing only approaches the theoretical limit.

[0005] Therefore, this application designs a multilayer dielectric material, its preparation method, and its application. Summary of the Invention

[0006] This invention provides a multilayer dielectric material, its preparation method, and its application, with the aim of solving the aforementioned problems in the prior art.

[0007] To achieve the above objectives, embodiments of the present invention provide a multilayer dielectric material, its preparation method, and its applications. This material has a three- or multi-layer hafnium oxide (H) / zirconia (Z) / hafnium oxide (H) multilayer dielectric structure. The method involves sequentially sputtering and depositing a hafnium oxide thin film and a zirconia thin film, repeating this sputtering deposition process. Furthermore, this material is applied in organic transistors, which include, from bottom to top, a substrate, a dielectric layer (the material), an organic semiconductor layer, and source and drain electrodes. This organic transistor operates at a low voltage, reducing the subthreshold swing of the organic transistor to (or even exceeding) the theoretical physical limit. The prepared stacked gate dielectric exhibits a high K dielectric constant and excellent insulation properties.

[0008] In one aspect of the present invention, a stacked dielectric material is provided, wherein the stacked dielectric material is a three-layer or multi-layer hafnium oxide (H) / zirconia (Z) / hafnium oxide (H) stacked dielectric layer.

[0009] Preferably, the thickness of the dielectric layer is 10–100 nm. The dielectric layer thickness in this application ensures good modulation of the transistor channel current. Different dielectric layer thicknesses result in different unit capacitances; and the thickness of the dielectric layer affects the modulation effect of the organic transistor channel current.

[0010] Based on a general inventive concept, embodiments of this invention provide a method for preparing the aforementioned multilayer dielectric material. Using hafnium oxide and zirconium oxide as sputtering targets, argon gas is introduced, and a layer of hafnium oxide film, a layer of zirconium oxide film, a layer of hafnium oxide film…a layer of hafnium oxide film is sequentially sputtered and deposited, repeatedly sputtering and depositing to obtain three or more layers of hafnium oxide (H) / zirconia (Z) / hafnium oxide (H) stacked dielectric layers. Using magnetron sputtering of high-k oxide dielectric layers allows for large-area uniform deposition of thin films at temperatures ranging from room temperature to 600°C. The multilayer dielectric layer integrates the advantages of both dielectric materials, resulting in a dielectric layer with better insulation properties.

[0011] Preferably, the magnetron sputtering pressure is 0.1–1 Pa, the power is 50–2000 W, and the temperature is room temperature to 600°C; the deposition rate is 0.1–100 nm / min, the substrate rotation speed is 1–50 r / min; the argon flow rate is 1–100 sccm; and the annealing temperature is 0–900°C. More preferably, the magnetron sputtering temperature is between room temperature and 500°C, and the annealing temperature is 0–900°C, resulting in better insulation performance of the multilayer dielectric layer.

[0012] Another aspect of the embodiments of the present invention provides the application of the above-described multilayer dielectric material in an organic transistor, wherein the organic transistor comprises the above-described multilayer dielectric material or the multilayer dielectric material obtained by the above-described preparation method.

[0013] Preferably, the organic transistor further includes a substrate, a modification layer, an organic semiconductor layer, and source and drain electrodes.

[0014] Preferably, the modification layer is a polymer film spin-coated onto the multilayer dielectric material, and the polymer film is at least one of PMMA, PS, PVA, PVC, and PVP. Spin-coating the modification layer helps reduce the surface roughness of the sample and improves the growth of subsequent organic semiconductor film layers.

[0015] Preferably, the thickness of the organic semiconductor layer is 10-100 nm; the material of the organic semiconductor layer includes at least one of 2,7-dioctyl[1]benzothiophene[3,2-b]benzothiophene (C8-BTBT), C10-DNTT, pentacene, and polytrihexylthiophene (P3HT).

[0016] Preferably, the source and drain electrodes are Ag electrodes.

[0017] Preferably, the fabrication steps of the organic transistor are as follows:

[0018] S1: Prepare the substrate;

[0019] S2: A multilayer dielectric material is deposited on the substrate by magnetron sputtering to obtain a sample with a dielectric layer;

[0020] S3: Spin-coat a polymer film as a modification layer onto the sample with stacked dielectric layers;

[0021] S4: An organic semiconductor layer is prepared on a sample with a stacked dielectric layer and a modification layer to obtain an intermediate product;

[0022] S5: Source and drain electrodes are prepared by thermal deposition on the surface of the intermediate product to obtain an organic transistor.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] (1) This invention utilizes magnetron radio frequency sputtering to achieve large-area, low-temperature, and simple fabrication of dielectric layer thin film stacked structures—hafnium oxide and zirconium oxide stacked dielectric layers. This stacked structure is not limited to three-layer stacks, but can also be a repeating superlattice structure of H / Z / H / Z / ... / H. The superlattice structures of these two materials are used in organic transistors. Organic transistors have low operating voltages, and most importantly, they can reduce the subthreshold swing of organic transistors to the theoretical physical limit (or even exceed the theoretical physical limit). The prepared stacked gate dielectric has a high K dielectric constant and excellent insulation properties. It is difficult or even impossible to achieve this effect by stacking any other two dielectric materials.

[0025] (2) The present invention is based on an organic transistor with an oxide stacked gate dielectric, which can operate at a voltage as low as 3V and achieve a current switching ratio of 10. 7 The subthreshold swing amplitude SS can reach or even exceed the theoretical limit of 60mV / decade. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the low-SS organic transistor in Embodiment 1 of the present invention;

[0028] Figure 2 This is a transfer curve diagram of the low-SS organic transistor in Embodiment 1 of the present invention;

[0029] Figure 3 This is the output curve of the low-SS organic transistor in Embodiment 1 of the present invention;

[0030] Figure 4 This is a gate-drain current curve of the low-SS organic transistor in Embodiment 1 of the present invention;

[0031] Figure 5 This is a transfer curve diagram of the low-SS organic transistor in Embodiment 2 of the present invention;

[0032] Figure 6 This is the transfer curve of the organic transistor based on monolayer hafnium oxide in Comparative Example 1 of the present invention;

[0033] Figure 7 This is the transfer curve of the organic transistor based on monolayer zirconium oxide in Comparative Example 2 of this invention. Detailed Implementation

[0034] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] This invention addresses existing problems by providing a multilayer dielectric material, its preparation method, and its applications.

[0038] Example 1

[0039] This embodiment uses a hafnium oxide / zirconia / hafnium oxide multilayer dielectric material, which is prepared through the following steps:

[0040] Multilayer dielectric materials were fabricated on a cleaned single-crystal Si substrate using magnetron sputtering. Hafnium oxide and zirconium oxide were used as sputtering targets, respectively mounted on targets A and B of the magnetron cavity. Multilayer dielectric films were then fabricated using radio frequency sputtering at a pressure less than 8 × 10⁻⁶. -4 During the sputtering process, high-purity argon gas (Ar) was introduced at a flow rate of 30 sccm (introduction rate). The working pressure was set to 0.3 Pa and the working voltage to 45 V. The substrate rotation speed was adjusted to 20 r / min. First, a hafnium oxide thin film was obtained by sputtering with a hafnium oxide target for 5 min. Then, a zirconium oxide thin film was obtained by sputtering with a zirconium oxide target for 5 min. After that, another hafnium oxide thin film was obtained by sputtering with a hafnium oxide target for 5 min. This process was repeated to sputter a three-layer stacked dielectric layer with a total thickness of 50 nm.

[0041] The organic transistor in this embodiment has the following structure: Figure 1 As shown, from bottom to top, it includes a single-crystal Si substrate, a three-layer stacked dielectric layer (the dielectric layer is made of the dielectric material prepared above), a C8-BTBT organic semiconductor layer, and Ag source and drain electrodes.

[0042] The above-mentioned method for fabricating organic transistors includes the following steps:

[0043] (1) Clean the 1.5*1.5cm monocrystalline silicon substrate with detergent, deionized water, deionized water, deionized water and isopropanol in sequence for 15 minutes, and then blow it dry with high-purity nitrogen airflow.

[0044] (2) Hafnium oxide / zirconia / hafnium oxide / zirconia / hafnium oxide dielectric layers are sequentially deposited on the substrate by magnetron sputtering to obtain an intermediate sample with stacked dielectric layers; the magnetron sputtering process and parameters in this step are the same as the preparation steps and parameters of the dielectric materials mentioned above;

[0045] (3) Then, an organic semiconductor layer was prepared by thermal evaporation deposition of C8-BTBT. The deposition rate was controlled at 1.5 nm / min and the deposition time was controlled at 10 min to obtain an organic semiconductor film with a thickness of 15 nm. The sample rotation speed was controlled at 20 r / min to obtain an intermediate product with a dielectric layer and an organic semiconductor layer.

[0046] (4) Ag source and drain electrodes are prepared by thermal evaporation on intermediate products with dielectric layer and organic semiconductor layer to obtain organic transistors with steep subthreshold swing.

[0047] The organic transistor of this embodiment was tested, and its transfer curve is shown in the figure below. Figure 2 As shown in the figure, the device operates at a voltage of only 3V, and the current switching ratio reaches 10. 7 Calculations show that the subthreshold swing SS reaches the theoretical limit, which is only 60mV / decade; its output curve is shown in the figure below. Figure 3 As shown in the figure, a good ohmic contact is formed between the organic semiconductor and the Ag electrode. Its gate-drain current curve is shown below. Figure 4 As shown.

[0048] Example 2

[0049] This embodiment uses a hafnium oxide / zirconia / hafnium oxide / zirconia / hafnium oxide multilayer dielectric material, which is prepared through the following steps:

[0050] Multilayer dielectric materials were fabricated on a cleaned single-crystal Si substrate using magnetron sputtering. Hafnium oxide and zirconium oxide were used as sputtering targets, respectively mounted on targets A and B of the magnetron cavity. Multilayer dielectric films were then fabricated using radio frequency sputtering at a pressure less than 8 × 10⁻⁶. -4 During the sputtering process, high-purity argon gas (Ar) was introduced at a flow rate of 30 sccm. The working pressure was set to 0.3 Pa and the working power to 100 W. The substrate rotation speed was adjusted to 20 r / min. Hafnium oxide, zirconium oxide, hafnium oxide, zirconium oxide, and hafnium oxide targets were sputtered sequentially for 5 min each to obtain a five-layer stacked dielectric film of hafnium oxide / zirconia / hafnium oxide / zirconia / hafnium oxide. The total thickness of the multilayer stacked dielectric layer obtained by sputtering was about 50 nm.

[0051] The organic transistor in this embodiment comprises, from bottom to top, a single-crystal Si substrate, a five-layer stacked dielectric layer (the dielectric layer is made of the dielectric material prepared above), a C8-BTBT organic semiconductor layer, and four parts: Ag source and drain electrodes.

[0052] The above-mentioned method for fabricating organic transistors includes the following steps:

[0053] (1) Clean the 1.5*1.5cm monocrystalline silicon substrate with detergent, deionized water, deionized water, deionized water and isopropanol in sequence for 15 minutes, and then blow it dry with high-purity nitrogen airflow.

[0054] (2) Hafnium oxide / zirconia / hafnium oxide / zirconia / hafnium oxide dielectric layers are sequentially deposited on the substrate by magnetron sputtering to obtain an intermediate sample with stacked dielectric layers; the magnetron sputtering process and parameters in this step are the same as the preparation steps and parameters of the dielectric materials mentioned above;

[0055] (3) An organic semiconductor layer was then prepared by thermal evaporation deposition of C8-BTBT. The deposition rate was controlled at 1.5 nm / min and the deposition time was controlled at 10 min to obtain an organic semiconductor film with a thickness of 15 nm. The sample rotation speed was controlled at 20 r / min to obtain an intermediate product with a dielectric layer and an organic semiconductor layer.

[0056] (4) Ag source and drain electrodes are prepared by thermal evaporation on intermediate products with dielectric layer and organic semiconductor layer to obtain organic transistors with steep subthreshold swing.

[0057] The organic transistor of this embodiment was tested, and its transfer curve is shown in the figure below. Figure 5 As shown in the figure, the device operates at a voltage of only 3V, and the current switching ratio is close to 10. 8 Calculations showed that the subthreshold swing SS exceeded the theoretical limit, and the minimum subthreshold swing SS... min =46mV / decade.

[0058] Comparative Example 1

[0059] Hafnium oxide monolayer was prepared by the following steps using hafnium oxide monolayer as the dielectric material:

[0060] Hafnium oxide dielectric material was prepared on a cleaned single-crystal Si substrate using magnetron sputtering. Hafnium oxide was used as the sputtering target, mounted on the A target of the magnetron cavity. A multilayer dielectric film was then prepared by radio frequency sputtering at a pressure less than 8 × 10⁻⁶. -4During the sputtering process, high-purity argon gas (Ar) was introduced at a flow rate of 30 sccm. The working pressure was set to 0.3 Pa and the working voltage to 45 V. The substrate rotation speed was adjusted to 20 r / min. After sputtering for 25 min, a hafnium oxide dielectric film with a thickness of about 50 nm was obtained.

[0061] The organic transistor in this comparative example comprises, from bottom to top, a single-crystal Si substrate, a hafnium oxide dielectric layer (the dielectric material of which is the dielectric material prepared above), a C8-BTBT organic semiconductor layer, and an Ag source and drain electrode.

[0062] The above-mentioned organic transistor is fabricated by the following steps:

[0063] (1) Clean the 1.5*1.5cm monocrystalline silicon substrate with detergent, deionized water, deionized water, deionized water and isopropanol in sequence for 15 minutes, and then blow it dry with high-purity nitrogen airflow.

[0064] (2) A hafnium oxide dielectric layer was deposited on the substrate by magnetron sputtering to obtain an intermediate sample with a 50 nm hafnium oxide dielectric layer; the magnetron sputtering process and parameters were the same as the preparation steps and parameters of the dielectric material described above.

[0065] (3) Then, an organic semiconductor layer was prepared by thermal evaporation deposition of C8-BTBT. The deposition rate was controlled at 1.5 nm / min and the deposition time was controlled at 10 min to obtain an organic semiconductor film with a thickness of 15 nm. The sample rotation speed was controlled at 20 r / min to obtain an intermediate product with a dielectric layer and an organic semiconductor layer.

[0066] (4) Ag source and drain electrodes are prepared on intermediate products with dielectric layer and organic semiconductor layer by thermal evaporation to obtain organic transistors based on a single layer of hafnium oxide dielectric layer.

[0067] The sample with a hafnium oxide dielectric layer prepared by the above method was applied to a transistor to obtain an organic transistor based on a single layer of hafnium oxide. The transfer curve of the organic transistor was tested, and the results are as follows. Figure 6 As shown.

[0068] Comparative Example 2

[0069] It is prepared by using monolayer zirconium oxide as the dielectric material through the following steps:

[0070] Zirconia dielectric material was prepared on a cleaned single-crystal Si substrate using magnetron sputtering. Zirconia was used as the sputtering target, mounted on a B target in a magnetron cavity. Multilayer dielectric films were then fabricated using radio frequency sputtering at a pressure less than 8 × 10⁻⁶. -4During the sputtering process, high-purity argon gas (Ar) was introduced at a flow rate of 30 sccm. The working pressure was set to 0.3 Pa and the working voltage to 45 V. The substrate rotation speed was adjusted to 20 r / min. After sputtering for 25 min, a zirconium oxide dielectric film with a thickness of about 50 nm was obtained.

[0071] The organic transistor in this comparative example comprises, from bottom to top, a single-crystal Si substrate, a zirconium oxide dielectric layer (the dielectric material of which is the dielectric material prepared above), a C8-BTBT organic semiconductor layer, and Ag source and drain electrodes.

[0072] The above-mentioned organic transistor is fabricated by the following steps:

[0073] (1) Clean the 1.5*1.5cm monocrystalline silicon substrate with detergent, deionized water, deionized water, deionized water and isopropanol in sequence for 15 minutes, and then blow it dry with high-purity nitrogen airflow.

[0074] (2) A zirconium oxide dielectric layer was deposited on the substrate by magnetron sputtering to obtain an intermediate sample with a 50 nm hafnium oxide dielectric layer; the magnetron sputtering process and parameters were the same as the preparation steps and parameters of the dielectric material described above.

[0075] (3) Then, an organic semiconductor layer was prepared by thermal evaporation deposition of C8-BTBT. The deposition rate was controlled at 1.5 nm / min and the deposition time was controlled at 10 min to obtain an organic semiconductor film with a thickness of 15 nm. The sample rotation speed was controlled at 20 r / min to obtain an intermediate product with a dielectric layer and an organic semiconductor layer.

[0076] (4) Ag source and drain electrodes are prepared on intermediate products with dielectric layer and organic semiconductor layer by thermal evaporation to obtain organic transistors based on a single-layer zirconium oxide dielectric layer.

[0077] The sample with a zirconium oxide dielectric layer prepared by the above method was applied to a transistor to obtain an organic transistor based on a single layer of hafnium oxide. The transfer curve of the organic transistor was tested, and the results are as follows. Figure 7 As shown.

[0078] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a multilayer dielectric material in organic transistors, characterized in that, The stacked dielectric material is hafnium oxide / zirconia / hafnium oxide / zirconia / hafnium oxide; wherein the stacked dielectric layer is composed of alternating hafnium oxide layers and zirconia layers, and the top and bottom layers are both hafnium oxide layers; the organic transistor includes the stacked dielectric material, and the organic transistor operates at a voltage of 3V and has a subthreshold swing of less than 60mV / decade; The method for preparing the stacked dielectric material is as follows: using hafnium oxide and zirconium oxide as sputtering targets, argon gas is introduced, and a hafnium oxide thin film and a zirconium oxide thin film are sequentially sputtered and deposited by magnetron sputtering. This process is repeated to obtain three or more hafnium oxide / zirconia / hafnium oxide stacked dielectric layers.

2. The application according to claim 1, characterized in that, The thickness of the stacked dielectric layer is 10~100 nm.

3. The application according to claim 1, characterized in that, The magnetron sputtering pressure is 0.1~1 Pa, the power is 50~2000 W, the temperature is room temperature to 600 ℃, the deposition rate is 0.1~100 nm / min, the substrate rotation speed is 1~50 r / min, the argon flow rate is 1~100 sccm, and the annealing temperature is 0~900 ℃.

4. The application according to claim 1, characterized in that, The organic transistor also includes a substrate, a modification layer, an organic semiconductor layer, and source and drain electrodes.

5. The application according to claim 4, characterized in that, The modification layer is a polymer film spin-coated onto the laminated dielectric material, and the polymer film is at least one of PMMA, PS, PVA, PVC, and PVP.

6. The application according to claim 4, characterized in that, The thickness of the organic semiconductor layer is 10~100 nm; the organic semiconductor layer material includes at least one of C8-BTBT, C10-DNTT, pentacene, and P3HT.

7. The application according to claim 4, characterized in that, The source and drain electrodes are Ag electrodes.

8. The application according to claim 1, characterized in that, The specific steps for fabricating the organic transistor are as follows: S1: Prepare the substrate; S2: A multilayer dielectric material is deposited on the substrate by magnetron sputtering to obtain a sample with a dielectric layer; S3: Spin-coat a polymer film as a modification layer onto a sample with stacked dielectric layers; S4: An organic semiconductor layer is prepared on the sample having a stacked dielectric layer and a modification layer to obtain an intermediate product; S5: Source and drain electrodes are prepared by thermal deposition on the surface of the intermediate product to obtain an organic transistor.

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