MOSCAP device based on p-dipole material Ga2O3 and preparation method thereof

Abstract

The invention discloses an MOSCAP device based on a p-dipole material Ga2O3 and a preparation method of the MOSCAP device. The method comprises the following steps: firstly, growing a SiO2 interface layer (IL) on a p-Si substrate through a thermal oxidation method; ga2O3 with different cycle numbers is grown on the IL layer through an atomic layer deposition technology, and an HfO2 film is grown in situ. And then, rapidly annealing the device to repair oxide defects between the dielectric layers. And finally, preparing a patterned W electrode, thereby obtaining the MOSCAP device. According to the invention, after the Ga2O3 dipole layer is added, the MOSCAP device shows a relatively low hysteresis curve, only an extremely low equivalent oxide thickness (EOT) is increased, and meanwhile, remarkable VFB forward adjustment is realized. The invention proves that Ga2O3 is a novel p-dipole material with potential, and shows a wide application prospect in multi-threshold technical development of advanced process nodes.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of metal-oxide-semiconductor capacitor (MOSCAP) devices, and in particular to a MOSCAP device based on p-dipole material Ga2O3 and a preparation method thereof. Background Art

[0002] With the continuous advancement of CMOS integration technology, multi-threshold voltage modulation technology has become an important research direction for advanced technology nodes of logic circuits. The traditional solution is to achieve threshold voltage (Threshold Voltage, V t ), such as the transition from planar transistor technology to Fin Field-Effect Transistor (FinFET). However, as advanced process technology enters the Gate-All-Around (GAA) era, the limitation of chip size and the increasing complexity of three-dimensional deposition, lithography and etching processes make it urgent to develop a new technology to achieve multi-threshold voltage.

[0003] In recent years, a method to achieve V t Controllable dipole engineering has attracted wide attention from researchers. This ultrathin dipole layer is usually inserted into SiO2 (IL) and HfO2 (high- k ) layers to adjust the flat band voltage of the transistor. V FB )and V t .according to V t These dipole materials can be divided into two categories: n-type dipole and p-type dipole, which realize NMOS (N-type metal-oxide-semiconductor) devices respectively. V t The forward and reverse controllable modulation. So far, the research on n-dipole materials has been relatively mature, but the research on p-dipole materials is still relatively small. Al2O3, as a common p-dipole material, has been widely used and studied in industry and academia. However, due to the certain inhibition mechanism of Al covering technology, there is also V t Due to the problems of displacement saturation, long-range Coulomb scattering causing degradation of carrier mobility and reliability, it is crucial to explore a new p-dipole material.

[0004] According to the existing dipole formation theory and molecular dynamics calculation prediction, Ga2O3 is expected to become a candidate material for p-dipole. A potential new p-dipole material needs to meet the following characteristics: 1. It has high k value to achieve a lower EOT Sacrificial amount, thereby achieving threshold voltage control of zero film thickness; 2. Can achieve a larger V FB The offset and control range can meet the needs of multi-threshold voltage technology; 3. The prepared film is of high quality to avoid the increase of device leakage current. Summary of the invention

[0005] The purpose of the present invention is to provide a MOSCAP device based on a novel p-dipole material Ga2O3 and a preparation method thereof. The present invention adopts a novel p-dipole substitute material to prepare a MOSCAP device, and by introducing a Ga2O3 dipole layer, a significant flat band voltage ( V FB ) forward shift; the present invention inserts Ga2O3 grown by plasma enhanced atomic layer deposition (PE-ALD) into SiO2 interface layer / HfO2 to construct a MOSCAP device. The preparation process is simple. The prepared MOSCAP device can achieve a large-range forward modulation of the flat-band voltage and achieve threshold control with nearly zero thickness change of the film.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for preparing a MOSCAP device based on p-dipole material Ga2O3 comprises the following steps: (1) Using p-type doped Si with (100) crystal orientation as the substrate, high-temperature thermal oxidation was performed in an O2 atmosphere to grow high-quality SiO2 interface layer (IL) films; (2) on the surface of the SiO2 film obtained in step (1), plasma enhanced atomic layer deposition (PE-ALD) is used to grow Ga2O3 films of different thicknesses to form a dipole layer, and at the same time, HfO2 films are deposited; (3) annealing the device of step (2) in a specific gas environment, temperature, time and specific annealing method to repair oxide defects inside and between the films; (4) After obtaining the device surface in step (3), patterning the contact electrode area by ultraviolet (UV) lithography, and preparing the corresponding electrode on the film surface by electron beam evaporation (EBE) and liftoff process; (5) For the device in step (4), a hydrofluoric acid (HF) solution is used to wet-etch the back of the device to remove the natural oxide layer on the back, and a back electrode of a certain thickness is grown by an EBE process.

[0008] In the above step (1), the doping concentration of the Si substrate is 1.0×10 15 -1.0×10 17 cm -3 The thermal oxidation temperature is set to 500-800°C and the time is 5-10 min. Before thermal oxidation, the natural oxide layer on the surface of the Si substrate is removed using a standard RCA cleaning process.

[0009] In the above step (2), the process conditions for growing Ga2O3 film by plasma enhanced atomic layer deposition PE-ALD are: using trimethylgallium (TMGa) as Ga source, the pulse time is 0.1-2 s, O2 plasma is selected as oxygen source, the RF power is 50-200 W, the time is 0.5-5 s, the deposition temperature is 200-300 ° C, and the deposition rate is 0.05-0.07 nm / cycle; the process conditions for depositing HfO2 film are: using tetrakis(dimethylamino)hafnium (TDMAHf) as Hf source, the pulse time is 0.1-2 s, O2 plasma is selected as oxygen source, the RF power is 50-200 W, the time is 0.5-5 s, the deposition temperature is 200-300 ° C, and the deposition rate is 0.12-0.20 nm / cycle.

[0010] In the above step (2), the thickness of the Ga2O3 film is 0.6-3 nm, and the thickness of the HfO2 film is 4-6 nm.

[0011] In the above step (3), the annealing atmosphere is nitrogen (N2) or argon (Ar), the set annealing temperature is 500-1000°C, the annealing time is 1 ms-15 s, and the annealing method is rapid thermal annealing (RTP) or laser annealing.

[0012] In the above step (4), the lateral size of the contact electrode area is 50-100 μm, and the electrode structure is W (50-100 nm) or TiN (5-10 nm) / W (50-100 nm).

[0013] In the above step (5), the HF solution wet etching time is 1-5 min; after the wet etching, acetone, isopropanol and deionized water are used for ultrasonic cleaning in sequence to remove particles and pollutants on the back, and the acetone, isopropanol and deionized water ultrasonic cleaning time is 2-5 min; the back electrode is Ni (50-100 nm).

[0014] The present invention also provides a MOSCAP device based on p-dipole material Ga2O3 prepared according to the above preparation method and a preparation method thereof. After inserting the Ga2O3 layer, the device sacrifices a very small equivalent oxide thickness (Equivalent Oxide Thickness, EOT ) case, a huge flat-band voltage is achieved V FB Positive offset.

[0015] The principle of the present invention is as follows: The MOSCAP device based on the novel p-dipole material Ga2O3 of the present invention inserts a Ga2O3 dipole layer at the IL / HfO2 interface of the device through PE-ALD technology, introduces p-dipole at the IL / Ga2O3 and Ga2O3 / HfO2 interfaces, thereby reducing the IL / high- k The valence band offset (VBO) of the layer is reduced, thereby realizing the forward large-range modulation of the flat band voltage of the MOSCAP device. At the same time, since the ALD-grown Ga2O3 has a high dielectric constant (~10), the equivalent oxide thickness ( EOT ) is also extremely small, thus enabling threshold control of the film with almost zero thickness variation.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The Ga2O3 film grown by PE-ALD is dense, uniform and has adjustable thickness, achieving extremely small changes before and after the insertion of the dipole layer EOT Increase the amount.

[0017] 2. Through IL / high- k The interfacial insertion of Ga2O3 material introduced p-dipole, thus achieving a huge V FB Positive offset.

[0018] 3. Through XPS valence band spectrum and core level fine spectrum, the band alignment analysis of IL / HfO2 and IL / Ga2O3 / HfO2 heterostructures was carried out, proving that Ga2O3 is a highly promising p-dipole material from the perspective of valence band step change.

[0019] 4. In the present invention, the Ga2O3 film grown based on ALD is amorphous and has a high dielectric constant. It is inserted between SiO2 / HfO2 as a dipole layer, and can achieve a flat band voltage positive adjustment of 1.09-1.59 V at the same thickness. However, the traditional Al2O3 as a p-dipole material can generally only achieve a flat band voltage shift of 0.1-0.5 V at the same thickness (0.6-3nm). The present invention solves the problem of the V FB The problem of regulation volume saturation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the p-Si / SiO2 substrate structure of an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the thin film structure of a p-Si / SiO2 / Ga2O3 / HfO2 device according to an embodiment of the present invention.

[0022] Figure 3 It is a schematic structural diagram of spin coating a photoresist mask layer on a device according to an embodiment of the present invention.

[0023] Figure 4 FIG. 4 is a schematic diagram of the structure of a MOSCAP device according to an embodiment of the present invention.

[0024] Figure 5 This is a capacitance-voltage curve diagram of a device according to an embodiment of the present invention tested at 1 MHz.

[0025] Figure 6 FIG. 1 is a graph showing the flat-band voltage and equivalent oxide thickness of a device according to an embodiment of the present invention as a function of the thickness of the dipole layer.

[0026] Figure 7 This is a graph showing the variation of conductance extracted by the parallel conductance method with test frequency for a device according to an embodiment of the present invention.

[0027] Figure 8 FIG. 4 is a distribution diagram of interface trap defects in an energy band of a device according to an embodiment of the present invention.

[0028] Fig. 9 Schematic diagram of the energy band alignment of the dielectric layer of the device of an embodiment of the present invention; a) 0nm Ga2O3, b) 10 cycles, c) 20 cycles, d) 30 cycles. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto. Example

[0030] A MOSCAP device based on a novel p-dipole material Ga2O3 is prepared in the following steps: (1) A p-type doped Si substrate with a (100) orientation and a doping concentration of 1.0×10 15 cm -3 The natural oxide layer on the surface of the Si substrate was removed using a standard RCA cleaning process. A 2 nm thick high-quality SiO2 film was grown by thermal oxidation at 600 °C for 5 min in an O2 atmosphere using a tube furnace. The resulting structure is shown in Figure 1 As shown; (2) On the surface of the SiO2 film obtained in step (1), PE-ALD technology was used, with TMGa as the Ga source, pulse time of 0.2 s, O2 plasma selected as the oxygen source, RF power of 100 W, time of 1 s, deposition temperature at 250 °C, deposition rate of 0.65 nm / cycle, and Ga2O3 film was grown for 0 / 10 / 15 / 20 / 30 cycles to form a dipole layer. At the same time, TDMAHf was used as the Hf source, pulse time of 0.2 s, O2 plasma selected as the oxygen source, RF power of 100 W, time of 4 s, deposition temperature at 250 °C, deposition rate of 0.15 nm / cycle, and HfO2 film was deposited for 40 cycles, as shown in FIG. Figure 2 As shown; (3) annealing the device of step (2) in a rapid thermal annealing furnace (RTP) in a N2 atmosphere at 800°C for 15 s to repair oxide defects within and between the films; (4) After obtaining the device surface in step (3), the contact electrode region is patterned by ultraviolet (UV) lithography, such as Figure 3 As shown, a 50 nm W electrode is patterned on the film surface by EBE and liftoff processes; (5) For the device in step (4), the back of the device was wet-etched with HF solution for 2 min to remove the natural oxide layer on the back. Acetone, isopropanol and deionized water were used for ultrasonic cleaning at 40 W for 3 min to remove particles and contaminants on the back. A 50 nm Ni back electrode was grown by EBE process to obtain the following: Figure 4 The MOSCAP device with p-Si / IL / Ga2O3 / HfO2 / W structure is shown.

[0031] The MOSCAP device based on the novel p-dipole material Ga2O3 prepared in this embodiment is based on the p-dipole induced by the Ga2O3 insertion layer, so that compared with the control device (device without Ga2O3 insertion), the capacitance-voltage curve of the MOSCAP device has a significant positive drift, and the drift increases with the increase of the thickness of the inserted Ga2O3 and tends to saturation, as shown in FIG. Figure 5 As shown. The device’s Δ V FB and EOT The trend of parameters changing with the number of ALD cycles of Ga2O3 is as follows Figure 6 As shown, by inserting 10-30 cycles of Ga2O3 layer, MOSCAP device only sacrifices 0.05-0.36 nm EOT In the case of V FB Forward controllable drift. The conductance extracted by the capacitance-frequency test of the MOSCAP device with Ga2O3 inserted for 20 cycles in this embodiment ( G ) and frequency ( ω ) and the distribution of device interface trap defects in the energy band extracted by the parallel conductivity method are shown in Figure 7 and Figure 8 As shown, the interface trap defect level of the MOSCAP device in this embodiment is 10 12 eV -1 cm -2 It is of the same performance level as other p-dipole material MOSCAP devices reported.

[0032] The band alignment diagrams of IL / HfO2 and IL / Ga2O3 / HfO2 heterostructures drawn by XPS valence band spectra and core level fine spectra are shown in Fig. 9 As shown. The VBO at the interface of the control SiO2 / HfO2 device is 1.02. After adding 10 / 20 / 30 cycles of Ga2O3, Ga2O3 forms p-dipole at the interface of SiO2 and HfO2, respectively, which makes the VBO between SiO2 and HfO2 drop to 0.81 / 0.69 / 0.62 eV, respectively. This is consistent with the positive drift trend of the capacitance-voltage curve of the electrical test, confirming that ALD Ga2O3 is a p-dipole material with great potential. This new p-dipole material achieves huge V FB Positive regulation makes up for the shortcomings of insufficient p-dipole materials and provides a new potential optional material for the development of future multi-threshold technology. Example

[0033] A MOSCAP device based on a novel p-dipole material Ga2O3 is prepared in the following steps: (1) A p-type doped Si substrate with a (100) orientation and a doping concentration of 1.0×10 17 cm -3 The natural oxide layer on the surface of the Si substrate was removed using a standard RCA cleaning process. A 3 nm thick high-quality SiO2 film was grown by thermal oxidation at 800 °C for 3 min in an O2 atmosphere using a tube furnace. The resulting structure is shown in Figure 1 As shown; (2) On the surface of the SiO2 film obtained in step (1), PE-ALD technology was used, with TMGa as the Ga source, a pulse time of 0.5 s, O2 plasma selected as the oxygen source, RF power of 150 W, time of 2 s, deposition temperature at 270 °C, and deposition rate of 0.70 nm / cycle, to grow Ga2O3 films for 0 / 10 / 15 / 20 / 30 cycles to form a dipole layer. At the same time, TDMAHf was used as the Hf source, with a pulse time of 0.4 s, O2 plasma selected as the oxygen source, RF power of 150 W, time of 5 s, deposition temperature at 270 °C, and deposition rate of 0.17 nm / cycle, and HfO2 films were deposited for 20 cycles, as shown in FIG. Figure 2 As shown; (3) annealing the device of step (2) in a laser annealing device in a N2 atmosphere at a high temperature of 700°C for 1 ms to repair oxide defects inside and between the films; (4) After obtaining the device surface in step (3), the contact electrode region is patterned by ultraviolet (UV) lithography, such as Figure 3 As shown, a 70 nm W electrode was patterned on the film surface by EBE and liftoff processes; (5) For the device in step (4), the back of the device was wet-etched with HF solution for 3 min to remove the natural oxide layer on the back. Acetone, isopropanol and deionized water were used for ultrasonic cleaning at a power of 60 W for 2 min to remove particles and contaminants on the back. A 70 nm Ni back electrode was grown by EBE process to obtain the following: Figure 4 The MOSCAP device with p-Si / IL / Ga2O3 / HfO2 / W structure is shown.

[0034] The performance characteristics of the MOSCAP device based on the novel p-dipole material Ga2O3 prepared in this embodiment are similar to those in Embodiment 1, and will not be described in detail here.

[0035] In the above, the present invention uses a device with a Ga2O3 thickness of 0 as a control group. Compared with the control group, the MOSCAP device after adding the Ga2O3 dipole layer exhibits a lower hysteresis curve and only increases the equivalent oxide thickness by a very low amount ( EOT ), while achieving significant V FB Positive regulation overcomes the traditional Al2O3 dipole material V FB The present invention proves that Ga2O3 is a new type of p-dipole material with potential, and shows broad application prospects in the development of multi-threshold technology at advanced process nodes.

[0036] The present invention adopts the above-mentioned embodiment as the preferred implementation mode of the present invention, which is not used to limit the protection scope of the present invention. Any other modifications, changes, substitutions, combinations and simplifications made without departing from the essence and principles of the present invention shall be regarded as equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a MOSCAP device based on p-dipole material Ga2O3, characterized in that: The following steps are involved: (1) Using p-type doped Si with (100) crystal orientation as the substrate, high-temperature thermal oxidation was performed in an O2 atmosphere to grow a high-quality SiO2 interface film; (2) on the surface of the SiO2 film obtained in step (1), a Ga2O3 film of a certain thickness is grown by plasma enhanced atomic layer deposition (PE-ALD) to form a dipole layer, and then a HfO2 film is deposited; (3) annealing the device obtained in step (2) to repair oxide defects within and between the thin films; (4) On the surface of the device obtained in step (3), a contact electrode area is patterned by ultraviolet UV lithography, and a corresponding electrode is prepared on the surface of the film by electron beam evaporation (EBE) and liftoff process; (5) For the device in step (4), the back of the device is wet-etched with a hydrofluoric acid solution to remove the natural oxide layer on the back, and a back electrode of a certain thickness is grown by an electron beam evaporation (EBE) process.

2. The preparation method according to claim 1, characterized in that In step (1), the doping concentration of the Si substrate is 1.0×10 15 -1.0×10 17 cm -3 The thermal oxidation temperature is set to 500-800 °C and the time is 5-10 min. Before thermal oxidation, the natural oxide layer on the surface of the Si substrate is removed using a standard RCA cleaning process.

3. The preparation method according to claim 1, characterized in that In step (2), the process conditions for growing Ga2O3 film by plasma enhanced atomic layer deposition PE-ALD are: using trimethylgallium TMGa as Ga source, the pulse time is 0.1-2 s, O2 plasma is selected as oxygen source, the RF power is 50-200 W, the time is 0.5-5 s, the deposition temperature is 200-300 ° C, and the deposition rate is 0.05-0.07 nm / cycle; the process conditions for depositing HfO2 film are: using tetrakis(dimethylamino)hafnium TDMAHf as Hf source, the pulse time is 0.1-2 s, O2 plasma is selected as oxygen source, the RF power is 50-200 W, the time is 0.5-5 s, the deposition temperature is 200-300 ° C, and the deposition rate is 0.12-0.20 nm / cycle.

4. The preparation method according to claim 1, characterized in that In step (2), the thickness of the Ga2O3 film is 0.6-3 nm, and the thickness of the HfO2 film is 2-6 nm.

5. The preparation method according to claim 1, characterized in that In step (3), the annealing atmosphere is nitrogen or argon, the set annealing temperature is 500-1000°C, the annealing time is 1 ms-15 s, and the annealing method is laser annealing or rapid thermal annealing RTP.

6. The preparation method according to claim 1, characterized in that In step (4), the lateral dimension of the contact electrode region is 50-100 μm, the electrode is W or TiN / W, the thickness of TiN is 5-10 nm, and the thickness of W is 50-100 nm.

7. The preparation method according to claim 1, characterized in that In step (5), the HF solution wet etching time is 1-5 min; after the wet etching, acetone, isopropanol and deionized water are used for ultrasonic cleaning in sequence to remove particles and contaminants on the back of the device, and the ultrasonic time is 2-5 min respectively; the back electrode is Ni with a thickness of 50-100 nm.

8. A MOSCAP device based on p-dipole material Ga2O3, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 7.

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