This paper reports new deposition model of boron impurity considered formation of oxide film during

deposition process. Finally, we have considered the impurity concentration change in silicon surface and found

that diffusion coefficient in the thin oxide film increases more 100 times than the thick oxide film. The result

contributes to get the accurate simulation value. This new boron deposition model will apply to find the

formation condition of base layer in fabrication process of high-frequency transistor.

It is able to simulate the deposition process through oxide film by SILVACO TCAD (semiconductor process

simulation tools), but the simulation results did not give the accurate values.

At silicon surface, always exists the natural oxide film or oxide film formed during boron deposition process,

and boron impurity diffuses through the oxide film into silicon

Fig.1 Impurity flow in deposition process of boron impurity

In silicon surface, boron impurity concentration is not fixed, it increase gradually and oxide film thickness is

increased. Therefore, we have shown intuitionally the impurity concentration in atmosphere, oxide film and

silicon as Fig.1. Where N

is impurity concentration in oxide

film, N

is impurity concentration in silicon. The corresponding mathematical model can write as follows. If

Where k

D

film.

Then, at the Si-SiO

interface, the impurity concentration relationship in oxide film and silicon determined by

segregation coefficient as follows equation (2).

(3)

Here N

- boron impurity concentration in silicon

D

- diffusion coefficient of the boron impurity changing due to concentration in silicon

t - deposition time

Starting condition (impurity concentration before the deposition) is as follows

The impurity concentration of the starting wafer is 4×10

, major facets is {111} plane and substrate is n-

type silicon. As shown in Fig.2, since surface impurity concentration is about 10

, junction depth is

0.077μm and sheet resistance is 1.3×10

Ω/□, the difference between simulation result and actually

measurement value is very large. Because diffusion coefficient used in simulating is incorrect.

Fig.2 Deposition simulation (concentration distribution) result by SILVACO TCAD(950℃)

The diffusion coefficient in oxide film explained as follows:

activation-energy. The difference between simulation result of boron deposition process with default value and

the actually measurement values is very large. So we have assumed that k

is 100, impurity concentration is

3×10

cm

interface. The simulation result at 950℃ shows in Fig.3.

Fig.3 Impurity concentration distribution of boron deposition by simulation

15. Tiago Davi Curi Busarello, Marcelo Godoy Simões, José Antenor Pomilio, Chapter 2 - Semiconductor

Diodes and Transistors, Editor(s): Muhammad H. Rashid, Power Electronics Handbook (Fifth Edition),

Butterworth-Heinemann, 2024, Pages 17-52, https://doi.org/10.1016/B978-0-323-99216-9.00027-5.

16. Xiaoyue Wang, Chi Liu, Yuning Wei, Shun Feng, Dongming Sun, Huiming Cheng, Three-dimensional

transistors and integration based on low-dimensional materials for the post-Moore’s law era, Materials

films grown by PECVD under epitaxial and microcrystalline conditions, Applied Surface Science

Advances, Vol. 18, 2023, 100508, https://doi.org/10.1016/j.apsadv.2023.100508.

18. N. Lambert, A. Taylor, P. Hubík, J. Bulíř, J. More-Chevalier, H. Karaca, C. Fleury, J. Voves, Z. Šobáň,

D. Pogany, V. Mortet, Modeling current transport in boron-doped diamond at high electric fields

including self-heating effect, Diamond and Related Materials, Vol. 109, 2020, 108003,