However, the growth procedure of hBN is not compatible with current semiconductor technology due to the high temperature requirement for its growth. Thus, new growth methods for hBN or different types of BN for practical applications should be developed. In this work, we introduce the growth of high-quality hBN, nanocrystalline hBN and amorphous BN by varying the growth temperature.
On the other hand, the growth at lower temperature induced nanocrystalline hBN (around 700 oC) and amorphous BN (below 400 oC). Amorphous BN consists of sp2 boron and nitrogen elements with random orientation of BN bonds. These results are important studies that are the basis for future BN application research. Also, BN films grown at low temperatures can contribute to industrial application research.
An interesting property of amorphous BN is a very low dielectric constant of less than 2, indicating that it can be used as an ultra-low dielectric material in the back-end-of-line (BEOL) of integrated circuits. We also compare the structure and dielectric properties of hBN, nanocrystalline hBN and amorphous BN.
Research Background for the Boron Nitride (BN)
Overview
Background for BN allotropes
Preparation of Hexagonal Boron Nitride (hBN)
- Top-down approach for hBN synthesis
- Bottom-up approach for hBN growth via chemical vapor deposition (CVD)
Outlook of BN
High Crystalline hBN Growth via Thermal CVD
Abstract
Experimental section for high crystalline hBN
- Introduction of thermal CVD system
- Characterizations
- Surface crystallographic characterization (Low Energy Electron Diffraction, LEED)
Results and discussion
- Characterization of epitaxially grown multilayer hBN
- Application of epitaxially grown hBN
Conclusion
Low Temperature Growth of Boron Nitride
Abstract
The reduction in processing speed due to increased resistance and capacitance delay is a major obstacle to downscaling electronics. Minimizing the dimensions of interconnects (the metal wires that connect different electronic components on a chip) is essential for device miniaturization. So far, research has mainly focused on reducing the resistance of scaled interconnects, because the integration of dielectrics using low-temperature deposition processes compatible with complementary metal-oxide-semiconductors is technically challenging.
Specifically, the International Roadmap for Devices and Systems recommends the development of dielectrics with κ values less than 2 by 2028. Here we report three-nanometer-thick amorphous boron nitride films with ultralow κ values of 1.78 and 1.16 (close to that of air, κ = 1) at operating frequencies of 100 kilohertz and 1 megahertz, respectively. The films are mechanically and electrically robust, with a breakdown strength of 7.3 megavolts per centimeter, which exceeds requirements.
Cross-sectional imaging reveals that amorphous boron nitride prevents the diffusion of cobalt atoms into silicon under very harsh conditions, unlike reference barriers. Our results show that amorphous boron nitride has excellent low-κ dielectric properties for high-performance electronics.
Experimental section
- Si substrate cleaning
- Growth of a-BN
- Characterization
- Ellipsometry
- High-resolution Rutherford backscattering and high-resolution elastic recoil detection
- Density measurement
- Breakdown-voltage and dielectric-constant measurement
- Diffusion-barrier performance
- Molecular dynamic simulations and computations
At the end of deposition, the borazine flow and plasma generation were terminated and the furnace was cooled to room temperature using 20 sccm of H2 gas. The analysis chamber, maintained at a base pressure of 5 × torr, was equipped with an electron analyzer (R3000, Scienta) and an X-ray absorption spectroscopy detector with a delay filter to facilitate operation in PEY mode. To investigate the elemental composition of the thin films, high-resolution Rutherford backscattering spectrometry (HR-RBS) was performed by irradiating samples with a 450-keV He + beam generated by an RBS system (HRBS-V500; Kobe Steel) .
A magnetic sector analyzer with a high resolution of 1.2 keV was used for the measurements of the thin films. Peaks corresponding to the relevant elements (B, N, O, and Si) were observed in the HR-RBS spectra. The areal density (atoms per square centimeter) was measured, allowing the calculation of the a-BN film density by taking into account the element thickness.
The current density-voltage (J-V) and capacitance-frequency (C-f) characteristics of the films in metal/a-BN/n-Si stacks were measured using a Tektronics K4200A-SCS parameter analysis system and a Karl Suss PA -200DS semi -automatic probe station. After device fabrication, capacitance-voltage units in the parameter analyzer system were used to perform the C-f measurements. We performed the C–f measurements in the frequency range 1 kHz–10 MHz with a holding bias of 0.5 V and an alternating current.
The measured capacitance values did not change significantly as a function of the applied voltage of 0.5 V. At high frequencies exceeding 5 MHz, significant noise levels were observed in the capacitance, probably due to the low impedance of the a-BN capacitor. Then, the J–V characteristics of both film samples were determined using the original measurement units of the parameter analyzer system.
To evaluate the performance of the films as diffusion barriers, ~3 nm thick samples of a-BN and TiN (deposited by radiofrequency sputtering) were deposited on Si substrates. Throughout the simulation, the temperature of the substrate was kept constant using a Nose-Hoover thermostat in a canonical NVT ensemble at temperature T = 673 K. The extended Tersoff potential for BN was used to describe the chemical processes ( such as bond formation and dissociation ) among the atomic species involved.21 This model potential is specifically designed to correctly describe the dependence of bonding in B, N, and B-N systems on coordination and chemical environment.
Results and discussion
- Introduction of BN thin film deposition
- Optimization of BN thin film deposition
- Microscopic observation
- Spectroscopic measurement and calculation
- Angle-dependent near-edge X-ray absorption fine structure (NEXAFS) measurement
- Electronic properties
- Diffusion barrier test
9 confirms the amorphous structure of BN films and the calculated diffraction pattern corresponding to the result in Fig. Raman spectra of a-BN and crystalline three-layer hexagonal-BN (for comparison) show that the h-BN E2g mode at 1373 cm-1 is absent in a-BN (Fig. 8c).25, 26 Fourier transform infrared spectroscopy (FTIR) spectrum in Fig. 8d shows that there is an absorption peak near 1370 cm-1 attributed to the transverse optical mode. of BN in a-BN.
Detailed chemical and density analysis was performed with Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA) - the results of which are shown in the figure. Analysis of reduced radial distribution function obtained from electron diffraction data and chemical mapping of a-BN film cross section. The Raman spectrum of the bare SiO2/Si substrate is identical to that of a-BN - suggesting that no distinct h-BN crystal mode is present in a-BN.; (d) FT–IR spectrum measured using s-polarized radiation at an incidence angle of 60°; (e) PEY-NEXAFS spectra for the B K edge of a-BN, measured at incident angles of 30°, 55° and 70° - showing no orientation dependence.
Thus, information regarding the relative orbitals in h-BN layers can be obtained by changing the incident angle of X-rays.28 NEXAFS spectra obtained for a BN sample at incident angles of 30°, 55° and 70° is shown in figure. The relative dielectric constants (k) for a-BN and h-BN, for comparison, at different frequencies are shown in Figure. The low k values of a-BN are attributed to non-polar bonds between BN and also absence of order that prevents dipole alignment even at high frequencies.
The k-values for a-BN compare extremely favorably with other reports in the literature, as shown in Table 2. We confirmed the electrical measurements of k-values with those obtained by measuring the refractive index of a-BN with spectroscopic ellipsometry measuring and using the relationship: n2 = k.21 The refractive indices of h-BN and a-BN at 633 nm wavelength were found to be 2.16 and 1.37 respectively, as indicated by the green stars in Figure. In addition, the nano-scratch test results showed that the BN films were well attached to the Si substrate, and the strength of the BN films was similar to that of the Si substrate.
The electrical breakdown strength of a-BN was extracted by measuring the current density with applied bias (Figure 11d) on vertical sandwich type devices. Since the thickness of a-BN is 3 nm, the breakdown field is found to be 7.3 MV-cm-1 – this is almost twice that of h-BN (see Table 1) and the highest reported for materials with dielectric constants of less than 3 nm. then 2, as shown in figure. We therefore tested the diffusion barrier properties of a-BN by depositing 80 nm cobalt film on a-BN and annealing the Co/a-BN/Si devices in vacuum for 1 h at 600 °C.
These annealing conditions are extremely harsh and under similar conditions severe diffusion of cobalt into Si occurs when industry standard TiN is used as a barrier layer (Figure 12). In contrast, no diffusion of Co or silicide formation was observed with α-BN in cross-sectional TEM results shown in Figure.
Kitahara, A.; Yasuno, S.; Fujikawa, K., Study of the thickness and density of thin films by high-resolution Rutherford backscattering spectrometry and X-ray reflectivity. Los, J.; Kroes, J.; Albe, K.; Gordillo, R.; Katsnelson, M.; Fasolino, A., Extended Tersoff potential for boron nitride: energetic and elastic properties of pristine and defective h-BN. Al-Ghalith, J.; Dasmahapatra, A.; Krol, P.; Meletis, E.; Dumitric|, T., Compositional and structural atomistic investigation of amorphous Si–B–N networks of interest for high-performance coatings.
F.; Fukarek, W.; Mändl, S.; Möller, W., Phase identification of boron nitride thin films by polarized infrared reflection spectroscopy. In "Incompressible" pore effect on the mechanical behavior of low-K dielectric films, Materials Research Society Symposium - Proceedings "Incompressible" pore effect on the mechanical behavior of low-K dielectric films, Boston, MA, United States, Boston, MA, United States, 2002; pp 567-572. Grill, A., Structural characterization of porous low-k thin films prepared by different techniques using x-ray porosimetry.
The purpose of my research is to clarify the relationship between the needs of the semiconductor company and boron nitride thin film. Growth of single, multilayer hexagonal boron nitride (h-BN) on Pt, Cu metal substrate and Al2O3, SiO2 substrate using chemical vapor deposition (CVD) method. Deposition of amorphous boron nitride using PE-CVD, and characterization of the intrinsic properties of amorphous boron nitride.
Seokmo Hong, Chang-Seok Lee, Min-Hyun Lee, Yeongdong Lee, Kyung Yeol Ma, Gwangwoo Kim, Seong In Yoon, Kyuwook Ihm, Ki-Jeong Kim, Tae Joo Shin, Sang Won Kim, Eun-chae Jeon, Hansol Jeon , Ju-Young Kim, Hyung-Ik Lee, Zonghoon Lee, Aleandro Antidormi, Stephan Roche, Manish Chhowalla*, Hyeon-Jin Shin* & Hyeon Suk Shin*. Yan Wang, Jong Chan Kim, Yang Li, Kyung Yeol Ma, Seokmo Hong, Minsu Kim, Hyeon Suk Shin, Hu Young Jeong & Manish Chhowalla*. Gwangwoo Kim, Sung-Soo Kim, Jonghyuk Jeon, Seong In Yoon, Seokmo Hong, Young Jin Cho, Abhishek Misra, Servet Ozdemir, Jun Yin, Davit Ghazaryan, Matthew Holwill, Artem Mishchenko, Daria V.
Ming Huang、Mandakini Biswal、Hyo Ju Park、Sunghwan Jin、Deshun Qu、Seokmo Hong、Zhili Zhu、Lu Qiu、Da Luo、Xiaochi Liu、Zheng Yang、Zhongliu Liu、Yuan Huang、Hyunseob Lim、Won Jong Yoo、Feng Ding、 Yeliang Wang、Zonghoon Lee 和 Rodney S. 蓝宝石上单取向多层六方氮化硼的晶圆级和无皱外延生长。用于操纵表面等离子体和增强拉曼光谱能力的六方氮化硼/金基底。
