Next Article in Journal
Influence of Si Addition on the Chemical and Tribological Performance of TiAlCrN Coating Deposited by Co-Sputtering
Previous Article in Journal
O-Vacancy-Rich ε-MnO2 Synthesized at Hydrophobic Interface: An Efficient Fenton-like Catalyst for Removing Ciprofloxacin from Water
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Crystals
Volume 13
Issue 12
10.3390/cryst13121665
crystals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Development of a Real-Time Boron Concentration Monitoring Technique for Plasma Doping Implantation

by
Su-Young Chai
and
Sung-Hoon Choa
*
Graduate School of Nano IT Design Fusion, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea
*
Author to whom correspondence should be addressed.
Crystals 2023, 13(12), 1665; https://doi.org/10.3390/cryst13121665
Submission received: 18 October 2023 / Revised: 20 November 2023 / Accepted: 21 November 2023 / Published: 6 December 2023
Browse Figures
Versions Notes

Abstract

:
Plasma doping (PLAD) technology is widely used in the semiconductor industry. One of the problems associated with PLAD is precise dosage control and monitoring during the doping process. Excessive boron doping into the n-type poly gate will affect the p-MOSFET threshold voltage. In this study, we develop a novel method for the real-time monitoring of the boron concentration as it penetrates into an oxide film. We attempted to determine whether the real-time monitoring of the boron concentration can be replaced by measuring the thickness of the damaged layer remaining after plasma doping and a cleaning process, since the thickness of the damaged layer can be measured relatively easily in real time by means of ellipsometry. It is found that as the plasma doping energy is increased, the boron concentration increases linearly, with a strong correlation (R2 = 0.98) between the plasma doping energy and the boron concentration. Moreover, there is a close relationship between the plasma doping energy and the thickness of the damaged layer. As the doping energy is increased, the thickness of the damaged layer also increases linearly. We also find a close correlation (R2 = 0.92) between the change in the thickness of the damaged layer and the p-MOSFET threshold voltage. In summary, there are very good correlations between the plasma doping energy and the concentration of boron, the doping energy and the thickness of the damaged layer, and the thickness of the damaged layer and the threshold voltage. It is proven that the concentration of boron penetrating into the oxide layer can be monitored by measuring the thickness of the damaged layer in real time.

1. Introduction

As semiconductor manufacturing processes become more miniaturized, the power consumption of dynamic random access memory (DRAM) continues to decrease while the speed of the DRAM continues to increase. As the channel lengths of transistors decrease, the leakage current increases due to the short channel effect. Therefore, it is necessary to improve the characteristics of the metal-oxide-semiconductor field-effect transistors (MOSFETs) used in driving circuits. To overcome these issues, dual-poly-gate technology have been used to reduce the power consumption and secure fast operation speeds instead of conventional single-poly-gate technology [1,2,3]. The dual-poly-gate MOSFET is one in which the poly gate of a p-MOSFET is changed from the n-type to the p-type. The n-type poly gate is a buried channel with high hole mobility and a very simple manufacturing process, but it is vulnerable to the short channel effect [4,5]. On the other hand, for the p-type poly gate of a p-MOSFET, the position of the channel changes from a buried channel to a surface channel leading to a lower operating voltage and less leakage current. It is simple to form the p-type poly gate through boron ion implantation at a level of 1 × 1017 ions/cm2 into the n-type poly gate of an existing p-MOSFET [6,7], then the single poly gate which was composed of only n-type MOSFETs is converted into a dual poly gate composed of the n-type and p-type. Boron ion implantation technology at the level of ~1 × 1017 ions/cm2 is therefore required for the dual poly gate.
To form the dual poly gate, low energy and high-dose ion implantation technology are required. Conventional beamline ion implantation technology have difficulty in low energy levels and high-dose implantation, with several issues arising in relation to sub −22 nm technology due to the space charge limit, self-sputtering, and angle limit issues. Therefore, plasma doping (PLAD) technology has emerged as a promising doping strategy due to its various advantages that allow it to overcome the problems associated with beamline implantation [8,9,10,11,12,13,14]. Plasma doping technology enables high dose implantation (~1 × 1017 ions/cm2) with low energy and a high throughput. Therefore, this technology is widely used to manufacture ultra-shallow junctions [15], silicon-on-insulator (SOI) structures [16], flat panel displays [17], image sensors [18], and power semiconductor devices [19]. It can also be applied to various semiconductor processes and device fabrication steps, such as trench doping [20,21] and metallization [22,23,24]. On the other hand, the plasma doping process is relatively complicated and very sensitive to the plasma environment.
The critical problem that occurs when converting the n-type poly gate into the p-type poly gate is boron penetration into the oxide film at the bottom of the gate during the thermal annealing process after boron is implanted into the n-type poly gate [25], which affects the p-MOSFET threshold voltage. When the boron ions penetrate the oxide film, the insulating function of the oxide film is reduced, such that the channel can easily be formed even at a low threshold voltage. Therefore, it is crucial to monitor the concentration of boron penetrating the oxide film during the fabrication process. However, there is no practical technology or equipment capable of measuring these boron concentrations in real time. Secondary ion mass spectrometry (SIMS) is widely used to analyze dopant concentrations given its high detection sensitivity [26,27,28]. However, SIMS is not a continuous and real-time measurement method, and much time is required for the analysis. Therefore, it is necessary to develop a real-time method capable of monitoring boron concentrations.
In earlier work by Jeon et al., the possibility of high implantation dose monitoring was briefly introduced [8]. In this study, we systematically investigated whether the real-time monitoring of boron concentrations is possible by measuring the thickness of the damaged layer formed during the p-type poly gate fabrication process. The relationships among the boron concentration, plasma energy, formation of different layers, and the p-MOSFET threshold voltage in the p-type poly gate transistor were investigated in detail.

2. Experimental Section

The p-type poly gate wafers used here were fabricated with p-type silicon wafers (100). A flow chart of the overall process of the p-type poly gate is shown in Figure 1. Firstly, an oxide layer of 1000 Å thickness was deposited onto a silicon wafer using high-speed radical oxidation equipment (RADICAL, TEL, Irvine, CA, USA), after which a 700 Å thick polysilicon layer was deposited using a chemical vapor deposition system (ALPHA303i, TEL, Tokyo, Japan). The poly layer is the n-type, and phosphorus doping at 6.0 × 1020 ions/cm3 was applied. Thereafter, boron doping was conducted using plasma doping equipment (VISTaPLAD, AMAT, Santa Clara, CA, USA), and a doping layer was formed. The conditions for boron doping were a doping energy of 6.85 keV and a boron ion dose of 1.0 × 1017 ions/cm2 during implantation. To investigate the effects of the plasma doping energy on the boron concentration of the oxide layer, different plasma doping energy conditions during the p-type poly gate process were also used, which were 6.75 keV, 6.85 keV, 6.95 keV, and 7.05 keV.
After doping, a cleaning process was conducted using cleaning equipment (Zeta300, TEL, Tokyo, Japan). A wet cleaning process was used because it is difficult to remove a photoresist with high-dose doping using the plasma ashing process. The cleaning process involves heating sulfuric acid (H2SO4) to 95 °C, mixing it with hydrogen peroxide (H2O2), and spraying it on the wafer. The mixing ratio of sulfuric acid to hydrogen peroxide is 1 to 9. Finally, using RTP (rapid thermal process) equipment (Helios, Mattson, Fremont, CA, USA), thermal annealing was conducted up to a temperature of 970 °C for 20 s. with a ramp-up rate of 75 °C/s. During the thermal annealing step, nitrogen (N2) at a flow rate of 15 slm (standard liter per minute) and oxygen (O2) of 30 sccm were flowed into the chamber. Thermal annealing is an important process for activating ions implanted into the poly gate. However, because many ions are implanted near the surface with low energy, some ions can escape from the poly gate during the annealing process. To prevent this phenomenon, a small amount of oxygen flowed into the chamber during the annealing step to form a capping layer on the surface. After fabrication, the thickness of each layer was measured with a transmission electron microscope (TEM) (JEM-F200, JEOL, Tokyo, Japan). The concentrations of boron implanted and oxygen into each layer were analyzed using a SIMS (SC-Ultra, CAMECA, Paris, France) which has a 5% error range of the concentration measurement and a depth resolution of below 1 nm.
Dual poly gate transistors of a p-MOSFET were also fabricated. Changes in the threshold voltage upon changes in the thickness of the damaged layer were analyzed. The fabrication conditions of the p-type poly gate were identical to those shown in Figure 1. In this case, 178,300 mm p-type silicon wafers were used in total. Plasma boron ion implantation was conducted at a doping energy level of 6.85 keV and at a boron ion dose of 1.0 × 1017 ions/cm2 during implantation. The thickness of the damaged layer was measured using an ellipsometer (Atlas, Manometries, Wilmington, MA, USA), and the threshold voltages of the p-MOSFET were measured using a voltage measuring instrument (Keysight AG4082F, AGILENT, Santa Clara, CA, USA).

3. Results and Discussion

During the fabrication of the p-type poly gate shown in Figure 1, it was expected that different layers would form sequentially based on each fabrication step. A schematic illustration of the formation of each layer is presented in Figure 2. In particular, during the boron implantation process, a doping layer is formed on the polysilicon layer. This doping layer can be divided into two layers: a dopant-rich layer and a damaged layer. The dopant-rich layer is a layer in which the boron is deposited on the poly layer, and the damaged layer is a layer in which damage occurs as boron is implanted into the poly layer. Finally, during the cleaning process, the dopant-rich layer is removed, leaving only the damaged layer.
To analyze each layer during the fabrication of the poly gate wafer in detail, a TEM analysis was conducted during each fabrication step. Figure 3 exhibits cross-sectional TEM images of the poly-gate region in the wafer after the plasma doping, cleaning, and thermal annealing processes, respectively. Figure 3a shows the TEM cross-sectional image of the poly-gate region after the plasma doping process. As shown in Figure 3a, the oxide layer and poly layer are clearly observed after plasma doping. In the poly layer, a doping layer with a thickness of 170 Å was also observed. It was found that the doping layer consisted of a dopant-rich layer with a thickness of 105 Å and a damaged layer with a thickness of 65 Å. The dopant-rich layer is a layer doped over the poly layer. The damaged layer is a layer in which ions are implanted into the poly layer, with damage occurring due to ion implantation.
Figure 3b shows a TEM image after the completion of the cleaning process. After cleaning, the dopant-rich layer was removed and disappeared. It was found that among the doping layers, only a damaged layer with a thickness of 65 Å remained after cleaning. It is expected that depending on the cleaning conditions, the thickness of the removed dopant-rich layer and the thickness of the remaining damaged layer can be changed. Figure 3c shows an image taken after the thermal annealing process. It can be seen that the thickness of the damaged layer was 55 Å, decreasing by approximately 10 Å after the thermal annealing process. When boron ions were implanted, fluorine ions were also implanted with the boron ions. The implantation of fluorine ions stemmed from BF3 gas, which was used to obtain a stable bonding structure and to generate the boron ions. Therefore, it is thought that the thickness of the damaged layer decreased by 10 Å as the fluorine ions disappeared through the thermal annealing process. It can be seen from the TEM image that the removed dopant-rich layer and the remaining damaged layer can be clearly distinguished.
To support the TEM analysis results, each layer was also analyzed using a SIMS. The concentrations of boron ions in the oxide layer, the poly layer, and the doping layer were analyzed after the plasma doping, cleaning, and thermal annealing processes, respectively. Figure 4 exhibits the boron concentration of each layer in the depth direction after the plasma doping, cleaning, and thermal annealing processes. The dotted line in Figure 4 indicates the boron concentration after the plasma doping process. The boron concentration decreased linearly with the depth direction. The thickness of the doping layer was approximately 170 Å, which is identical to the TEM measurement.
The blue line in Figure 4 indicates the changes in the boron concentration after the thermal annealing process. After thermal annealing, the boron concentration increased in the damaged layer, but the boron concentration in the poly layer decreased linearly to around 500 Å in the depth direction. From 550 Å in the depth direction, the boron concentration in the poly layer did not change much. This phenomenon is indicative of the diffusion of boron ions during the thermal annealing process. In particular, the boron concentration in the oxide film increased slightly, which is attributed to the penetration of boron into the oxide film layer. The oxide layer plays a very important role as an insulating film. Therefore, the boron penetration into the oxide film will affect the electrical activation characteristics of the p-MOSFET and in particular will cause a change in the threshold voltage. Therefore, it is very important to monitor the amount of boron ions penetrating the oxide layer in real time.
Next, we analyzed the oxygen concentration of each layer using SIMS. Figure 5 shows the SIMS profile of the oxygen concentration for each process step including plasma doping, cleaning, and thermal annealing. As shown in the figure, a high oxygen concentration was observed in the doping layer after the doping process (dotted line). After the cleaning process (orange-colored line), however, the oxygen disappeared, i.e., the dopant-rich layer was removed by the cleaning process, which is identical to the process found by the SIMS analysis of the boron concentration in Figure 4. It can be seen that the oxygen concentration is high in the dopant-rich layer. The reason for the high oxygen concentration in the dopant-rich layer is that the dopant-rich layer was exposed to atmospheric air after the boron-doping process, with the oxygen in the atmosphere then combined with the boron ions in the dopant-rich layer. The oxygen was not observed in the poly layer such that the poly layer can be clearly distinguished, supporting the results of the previous TEM and SIMS analyses. After the thermal annealing process (blue line), the oxygen concentration in the damaged layer was high because a capping layer was formed due to the small amount of oxygen introduced during the thermal annealing step [29]. Finally, it can be seen that the oxygen concentration in the oxide layer was very high such that the oxide layer could be clearly distinguished, which is strong evidence supporting the previous TEM and SIMS analyses results.
Next, we analyzed the silicon concentration of each layer using SIMS. Figure 6 shows the SIMS profile of the silicon concentration for each process step including plasma doping, cleaning, and thermal annealing. As shown in the figure, a low silicon concentration was observed in the doping layer after the doping process (dotted line). After the cleaning process (orange-colored line), however, the silicon disappeared, i.e., the dopant-rich layer was removed by the cleaning process, showing the similar results found by the SIMS analysis of the boron concentration in Figure 4. It can be seen that the silicon concentration is low in the dopant-rich layer. The reason the silicon concentration is low in the dopant-rich layer is because a large amount of boron is deposited. Also, it can be seen that a large amount of boron is deposited, so the silicon concentration of the damaged layer is low, and the silicon concentration of the poly layer and the oxide layer are the same.
Figure 7 exhibits the changes in the boron concentration of the oxide layer under different plasma doping energy conditions during the p-type poly gate process. The doping energy levels used were 6.75 keV, 6.85 keV, 6.95 keV, and 7.05 keV. The boron concentrations in the oxide layer at the different doping energies of 6.75, 6.85, 6.95 keV, and 7.05 keV were 7.5 × 1012, 8.1 × 1012, 8.9 × 1012, and 1.0 × 1013 ions/cm2, respectively. As the doping energy was increased, the boron concentration of the oxide layer increased. The correlation between the doping energy and the boron concentration of the oxide layer (R2) is 0.98, indicating that the correlation is very strong. Therefore, it is clear that the concentration of boron that penetrated the oxide layer was closely related to the doping energy.
Next, the thickness of the damaged layer was measured while varying the plasma doping energy during the p-type poly gate process. As shown in Figure 8, for different doping energy levels of 6.75 keV, 6.85 keV, 6.95 keV, and 7.05 keV, the measured thicknesses of the damaged layer were 63.0 Å, 65.4 Å, 66.4 Å, and 68.2 Å, respectively. As the doping energy increased, the thickness of the damaged layer increased linearly. That is, the higher the doping energy, the deeper the boron ions were implanted, such that the thickness of the damaged layer also increased. Moreover, the correlation between the doping energy and the thickness of the damaged layer (R2) is 0.97, which is a very strong correlation. Therefore, the thickness of the damaged layer was closely related to the doping energy.
Next, dual poly gate transistors for a p-MOSFET were fabricated and the p-MOSFET threshold voltages (PMOS Vt) were measured for 178 samples. The thicknesses of the damaged layers of the samples were also measured. Figure 9 shows the p-MOSFET threshold voltages for different thicknesses of the damaged layers; these are divided into eight box plots ranging from 63 Å to 70 Å. For the damaged layer thicknesses of 62 Å, 63 Å, 64 Å, 65 Å, 66 Å, 67 Å, 68 Å, 69 Å, and 70 Å, the average p-MOSFET threshold voltages were –0.737 V, −0.736 V, −0.738 V, −0.730 V, −0.726 V, −0.722 V, −0.719 V, and −0.710 V, respectively. The p-MOSFET threshold voltage decreased as the thickness of the damaged layer increased. Also, the relationship between the thickness of the damaged layer and the p-MOSFET threshold voltage showed a strong correlation (R2 = 0.92), as demonstrated in Figure 10. As a result, it was found that the p-MOSFET threshold voltage varied linearly with the thickness of the damaged layer.
In conclusion, it was found that there were good correlations between the concentration of boron that penetrated the oxide film and the doping energy, the doping energy and the thickness of the damaged layer, and the thickness of damaged layer and the p-MOSFET threshold voltage. Therefore, it is possible to monitor the boron concentration penetrating an oxide film in real time by measuring the thickness of the damaged layer, which can be measured by non-destructive optical methods such as ellipsometry and spectroscopic reflectometry in real time.

4. Conclusions

In this study, we investigated a new technique of the real-time monitoring of the concentration of boron penetrating an oxide film, which influences the threshold voltage of a p-type poly gate transistor. We investigated whether the measurement of the boron concentration can be replaced by measuring the thickness of the damaged layer remaining after plasma doping and a cleaning process. It was found that there was a strong correlation between the boron concentration and the plasma doping energy. As the plasma doping energy was increased, the boron concentration increased linearly. Also, there was a close relationship between the plasma doping energy and the thickness of the damaged layer. As the doping energy increased, the thickness of the damaged layer also increased linearly. Finally, it was found that there was a good correlation between the thickness of the damaged layer and the threshold voltage of the transistor. The threshold voltage decreased as the thickness of the damaged layer increased. In conclusion, there were good correlations among the plasma doping energy and the concentration of boron, the doping energy and the thickness of the damaged layer, and the thickness of the damaged layer and the threshold voltage, indicating that the concentration of boron penetrating the oxide layer can be monitored by measuring the thickness of the damaged layer in real time using non-destructive optical methods such as ellipsometry and spectroscopic reflectometry.

Author Contributions

Conceptualization, S.-Y.C. and S.-H.C., methodology and investigation, S.-Y.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.

Acknowledgments

This research was conducted with the support of a Seoul National University of Science and Technology academic research grant.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Lee, S.; Kwong, D.L. Dual Poly-Si Gate Metal Oxide Semiconductor Field Effect Transistors Fabricated with High-Quality Chemical Vapor Deposition HfO2 Gate Dielectrics. Jpn. J. Appl. Phys. 2003, 42, 7256. [Google Scholar] [CrossRef]
  2. Liu, X.-Y.; Lin, X.; Cao, C.-W.; Sun, Q.-Q.; Lin, P.-C.; Bian, Y.-J.; Xing, C.; Wang, P.-F.; Zhang, D.W. Investigation of Single-Transistor Active Pixel Image Sensor Compatible with Dual-Poly-Gate Technology. In Proceedings of the 2012 Symposium on Photonics and Optoelectronics, Shanghai, China, 21–23 May 2012; pp. 1–4. [Google Scholar] [CrossRef]
  3. Son, N.J.; Oh, Y.; Kim, W.; Jang, S.M.; Yang, W.; Jin, G.; Kim, K. A unique dual-poly gate technology for 1.2-V mobile DRAM with simple in situ n/sup+/-doped polysilicon. IEEE Trans. Electron Devices 2004, 51, 1644–1652. [Google Scholar] [CrossRef]
  4. Hu, G.; Bruce, R. Design tradeoffs between surface and buried-channel FET’s. IEEE Trans. Electron Devices 1985, 32, 584–588. [Google Scholar] [CrossRef]
  5. Abe, Y.; Oishi, T.; Shiozawa, K.; Tokuda, Y.; Satoh, S. Simulation study on comparison between metal gate and polysilicon gate for sub-quarter-micron MOSFETs. IEEE Electron Device Lett. 1999, 20, 632–634. [Google Scholar] [CrossRef]
  6. Qin, S.; Hu, Y.J.; McTeer, A. PLAD (Plasma Doping) on 22 nm Technology Node and Beyond Evolutionary and/or Revolutionary. In Proceedings of the International Workshop on Junction Technology, Shanghai, China, 14–15 May 2012; pp. 1–11. [Google Scholar]
  7. Qin, S.; Brumfield, K.; Liu, L.J.; Hu, Y.J.; McTeer, A.; Hsu, W.H.; Wang, M. Plasma Chemistry Study of PLAD Processes. In Proceedings of the 19th International Conference on Ion Implantation Technology, Valladolid, Spain, 25–29 June 2012; pp. 380–385. [Google Scholar]
  8. Jeon, Y.; Koo, I.; Oh, J.; Lee, S.B.; Butterbaugh, J.; Jin, S.; Lee, J.; Rouh, K.; Ju, M.; Jeon, S.; et al. Key Technologies for Ultra High Dose CMOS Applications. In Proceedings of the 17th International Conference on Ion Implantation Technology, Monterey, CA, USA, 8–13 June 2008; pp. 133–136. [Google Scholar]
  9. Renau, A.; Scheuer, J.T. Comparison of Plasma Doping and Beamline Technologies for Low Energy Ion Implantation. In Proceedings of the 14th International Conference on Ion Implantation Technology, Taos, NM, USA, 22–27 September 2002; pp. 151–156. [Google Scholar]
  10. Raj, D.M.; Godet, L.; Chamberlain, N.; Hadidi, K.; Singh, V.; Papasouliotis, G.D. Optimization and Control of Plasma Doping Processes. AIP Conf. Proc. 2011, 1321, 142. [Google Scholar]
  11. Kouzminov, D.; Cournoyer, J.; Norasetthekul, S.; Muthuraman, H.; Gao, Q. Quantitative aspects of PLAD sidewall doping characterization by SIMS and APT. Microsc. Microanal. 2019, 25, 511–516. [Google Scholar] [CrossRef] [PubMed]
  12. Qin, S. Plasma Doping (PLAD) for Advanced Memory Device Manufacturing. In Proceedings of the 2014 20th International Conference on Ion Implantation Technology (IIT), Portland, OR, USA, 26 June–4 July 2014; pp. 1–6. [Google Scholar]
  13. Van Den Berg, J.; Rossall, A.; England, J. Arsenic Plasma Doping in Si Characterized by High Resolution Medium Energy Ion Scattering Depth Profile Analysis. In Proceedings of the 2018 22nd International Conference on Ion Implantation Technology (IIT), Würzburg, Germany, 16–21 September 2018; pp. 263–266. [Google Scholar]
  14. Van Den Berg, J.; Rossall, A.; England, J. Characterization of arsenic plasma doping and postimplant processing of silicon using medium energy ion scattering. J. Vac. Sci. Technol. B 2019, 37, 032901. [Google Scholar] [CrossRef]
  15. Jones, E.C.; Cheung, N.W. Characteristics of sub-100-nm p/sup+//n junctions fabricated by plasma immersion ion implantation. IEEE Electron Device Lett. 1993, 14, 444–446. [Google Scholar] [CrossRef]
  16. Ma, X.; Liu, W.; Chen, C.; Zhan, D.; Song, Z.; Feng, S. A high-quality SOI structure fabricated by low-temperature technology with B+/H+ co-implantation and plasma bonding. Semicond. Sci. Technol. 2006, 21, 959. [Google Scholar] [CrossRef]
  17. Bernstein, J.D.; Qin, S.; Chan, C.; King, T.J. Hydrogenation of polycrystalline silicon thin film transistors by plasma ion implantation. IEEE Electron Device Lett. 1995, 16, 421–423. [Google Scholar] [CrossRef]
  18. Moon, C.R.; Jung, J.; Kwon, D.W.; Yoo, J.; Lee, D.H.; Kim, K. Application of plasma-doping (PLAD) technique to reduce dark current of CMOS image sensors. IEEE Electron Device Lett. 2007, 28, 114–116. [Google Scholar] [CrossRef]
  19. Raj, D.; Grivna, G.; Loechelt, G.; Gao, Q. PLAD (Plasma Doping) for p-type Deep Trench Doping in Power Device Applications. In Proceedings of the 2018 22nd International Conference on Ion Implantation Technology (IIT), Würzburg, Germany, 16–21 September 2018; pp. 42–45. [Google Scholar]
  20. Qian, X.Y.; Cheung, N.W.; Lieberman, M.A.; Brennan, R.; Current, M.I.; Jha, N. Conformal implantation for trench doping with plasma immersion ion implantation. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 1991, 55, 898–901. [Google Scholar] [CrossRef]
  21. Jung, L.M.; Do, S.W.; Kim, J.M.; Kong, S.H.; Nam, K.H.; Lee, Y.H. Ultra-Shallow Junction Formation by Plasma doping and Excimer Laser Annealing. ECS Trans. 2009, 19, 87. [Google Scholar] [CrossRef]
  22. Anders, A. Metal plasma immersion ion implantation and deposition: A review. Surf. Coat. Technol. 1997, 93, 158–167. [Google Scholar] [CrossRef]
  23. Srivastava, A.; Downey, R.; Persing, H.; Yoshida, N.; Han, K.; Maynard, H. Exploration of PLAD Aluminum Implants for Work Function Adjustment. In Proceedings of the 2014 20th International Conference on Ion Implantation Technology (IIT), Portland, OR, USA, 26 June–4 July 2014; pp. 1–4. [Google Scholar]
  24. Xu, Q.; Zou, W.; Xu, G.; Tang, S.; Tao, G.; Salimian, S.; Ye, T. Band-edge work function obtained by plasma doping TiN metal gate for nMOS device application. IEEE Trans. Electron Devices 2018, 65, 2400–2405. [Google Scholar] [CrossRef]
  25. Oh, J.G.; Lee, J.K.; Hwang, S.H.; Cho, H.J.; Sohn, Y.S.; Sheen, D.S.; Pyi, S.H.; Lee, S.W.; Hahn, S.H.; Jeon, Y.B.; et al. Characterization of B2H6 Plasma Doping for Converted p+ Poly-Si Gate. In Proceedings of the 16th International Conference on Ion Implantation Technology, Marseille, France, 11–16 June 2006; pp. 25–28. [Google Scholar]
  26. Teo, H.W.; Wang, Y.; Ong, K.; Mo, Z.Q. SIMS Analysis of Ultra-Shallow Boron Implant. In Proceedings of the 2021 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA), Singapore, 15 September–15 October 2021; pp. 1–4. [Google Scholar]
  27. Fearn, S.; McPhail, D.S. High resolution quantitative SIMS analysis of shallow boron implants in silicon using a bevel and image approach. Appl. Surf. Sci. 2005, 252, 893–904. [Google Scholar] [CrossRef]
  28. Qin, S. Front-side and back-side secondary ion mass spectrometry analyses on advanced doping processes for ultra-large scale integrated circuit: A case study. Thin Solid Films 2023, 766, 139654. [Google Scholar] [CrossRef]
  29. Zhang, X.; Connelly, D.; Takeuchi, H.; Hytha, M.; Mears, R.J.; Rubin, L.M.; Liu, T.J.K. Effects of oxygen-inserted layers and oxide capping layer on dopant activation for the formation of ultrashallow p-n junctions in silicon. J. Vac. Sci. Technol. B 2018, 36, 061211. [Google Scholar] [CrossRef]
Crystals 13 01665 g001
Figure 1. Process flowchart used to form the p-type poly gate wafer.
Figure 1. Process flowchart used to form the p-type poly gate wafer.
Crystals 13 01665 g001
Crystals 13 01665 g002
Figure 2. Layer formation process for the p-type poly gate.
Figure 2. Layer formation process for the p-type poly gate.
Crystals 13 01665 g002
Crystals 13 01665 g003
Figure 3. Cross-sectional TEM images overlaying poly silicon layers: (a) after plasma doping, (b) after cleaning, and (c) after annealing.
Figure 3. Cross-sectional TEM images overlaying poly silicon layers: (a) after plasma doping, (b) after cleaning, and (c) after annealing.
Crystals 13 01665 g003
Crystals 13 01665 g004
Figure 4. SIMS profile of the boron concentration after doping, after cleaning, and after annealing.
Figure 4. SIMS profile of the boron concentration after doping, after cleaning, and after annealing.
Crystals 13 01665 g004
Crystals 13 01665 g005
Figure 5. SIMS profile of the oxygen intensity after doping, after cleaning, and after annealing.
Figure 5. SIMS profile of the oxygen intensity after doping, after cleaning, and after annealing.
Crystals 13 01665 g005
Crystals 13 01665 g006
Figure 6. SIMS profile of the silicon intensity after doping, after cleaning, and after annealing.
Figure 6. SIMS profile of the silicon intensity after doping, after cleaning, and after annealing.
Crystals 13 01665 g006
Crystals 13 01665 g007
Figure 7. Correlation between the plasma doping energy and the boron concentration in the oxide layer.
Figure 7. Correlation between the plasma doping energy and the boron concentration in the oxide layer.
Crystals 13 01665 g007
Crystals 13 01665 g008
Figure 8. Correlation between the plasma doping energy and the thickness of the damaged layer.
Figure 8. Correlation between the plasma doping energy and the thickness of the damaged layer.
Crystals 13 01665 g008
Crystals 13 01665 g009
Figure 9. Box plot showing the relationship between PMOS Vt and the damaged layer thickness.
Figure 9. Box plot showing the relationship between PMOS Vt and the damaged layer thickness.
Crystals 13 01665 g009
Crystals 13 01665 g010
Figure 10. Correlation between PMOS Vt and the damaged layer thickness.
Figure 10. Correlation between PMOS Vt and the damaged layer thickness.
Crystals 13 01665 g010
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Chai, S.-Y.; Choa, S.-H. Development of a Real-Time Boron Concentration Monitoring Technique for Plasma Doping Implantation. Crystals 2023, 13, 1665. https://doi.org/10.3390/cryst13121665

AMA Style

Chai S-Y, Choa S-H. Development of a Real-Time Boron Concentration Monitoring Technique for Plasma Doping Implantation. Crystals. 2023; 13(12):1665. https://doi.org/10.3390/cryst13121665

Chicago/Turabian Style

Chai, Su-Young, and Sung-Hoon Choa. 2023. "Development of a Real-Time Boron Concentration Monitoring Technique for Plasma Doping Implantation" Crystals 13, no. 12: 1665. https://doi.org/10.3390/cryst13121665

APA Style

Chai, S.-Y., & Choa, S.-H. (2023). Development of a Real-Time Boron Concentration Monitoring Technique for Plasma Doping Implantation. Crystals, 13(12), 1665. https://doi.org/10.3390/cryst13121665

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop