스퍼터링을 이용한 고품질 AlN 박막 성장과 평가

스퍼터링을 이용한 고품질 AlN박막 성장 및 평가. 스퍼터링을 이용한 고품질 AlN박막 성장 및 평가. 4장에서는 펄스 스퍼터링을 사용하여 AlN 박막의 성장을 연구했습니다.

Aluminum nitride

Crystal structure

Physical properties

Applications

In chapter 3, the fundamental growth principle of the reactive gas DC magnetron sputtering method for the growth of AlN thin films was described. By changing the growth rate, it is confirmed that the composition of the thin film is changed. EDS results were confirmed to intuitively confirm the stoichiometric composition change of the thin film as shown in figure 3.3.

200W As a result, it is confirmed that the plasma effect affects the stoichiometric composition of the thin film by increasing the Al supply. It was also confirmed that the correct amount of Al is important for the crystallinity of the thin film. In the results in Figure 3.2, the change of the transparency and surface roughness of the sample was observed at conditions of different plasma strength.

It has been reported that the preferred orientation change of AlN was observed depending on the reactive gas mixing ratio [4]. The influence of the thin layer was analyzed in terms of the stoichiometric composition according to the change of the amount of Al supply. The reactive gas DC magnetron sputtering plasma power in Chapter 3 affected the Al supply.

As a result, the composition of the thin film was changed and affected the crystallinity. Consequently, the results show that the plasma power in the PSD also affects the Al supply, which affects the film composition. In regions of low plasma power, the plasma power increases and the crystallinity of the thin film increases by increasing the energy of the Al molecules.

It was also confirmed that the appropriate amount of Al is important for the crystallinity of the thin film. Variation of the stoichiometric composition of AlN thin films grown using reactive DC magnetron sputtering.

Figure 1.2 The schematics of AlN thin films of applications such as DUV-LED [15], Heat-sink [16], SAW sensor [17], RF filter [18], transparent

Growth method for AlN thin films

Outline of thesis

Sputtering parameters such as plasma power, gas flow ratio, substrate temperature, and gas flow ratio are controlled to enhance the crystallinity of the AlN thin films. In Chapter 4, exploiting the effects of sputtering conditions mentioned in Chapter 3, the growth conditions of AlN thin films using pulsed sputter deposition are optimized. Effect of sputtering pressure on the crystalline quality and residual stress of AlN films deposited at 823 K on nitrided sapphire substrates by reactive pulsed DC sputtering.

Experimental Equipment

DC discharge

The discharge continues, but the number of electrons in this region is still insufficient. Plasma resistance decreases with increasing current (increasing ions and electrons) in a conventional glow discharge. Sputtering is processed in the anomalous glow discharge region where the voltage increases as a function of current.

Sputtering yield

Magnetron sputter

Reactive gas sputter

Pulsed sputtering deposition (PSD)

The no-arc condition is related to the duty cycle and Figure 2.4 shows their relationship. If τoff.crit > τoff.crit and τon < τon.crit are not present, arc discharge occurs due to charge accumulation and dielectric surfaces.

Figure 2.3 V-I graph of pulsed unipolar DC discharge

X-ray diffraction (XRD)

In the case of sputtering using a reactive gas as in this study, the sputtering process is modified by the reaction of the target surface. To summarize the results so far, by changing the growth rate, it can be observed that the amount of Al was controlled by plasma power. In the experiment in which the plasma power was fixed, the tendency of the growth rate to decrease with the increase of the nitrogen flow rate is not explained by (1) phenomenon of gas flow ratio.

For example, if the growth rate is determined by the supplied amount of growth element, the growth rate of the thin film increases as the nitrogen supply increases while the plasma power is constant (constant Al supply amount). When controlling the gas flow ratio, a smooth surface is observed due to increased N and decreased Al input. In previous chapters, the sputtering parameters affected the Al supply and changed the stoichiometric composition of the film.

The growth rate was measured using a contact profiler and the color change of the film was observed using a camera. 3] However, high-energy Al atoms induce residual strain, which is expected to affect the crystal quality of the thin film. Samples in the high plasma power range (600–800 W) were similarly observed in Chapter 3, although the color of the thin film was observed to be dark, but Al peaks were not confirmed.

As the growth temperature increases, the FWHM of the thin film is reduced from 0.57 to 0.28 degrees due to the increase in surface motion length. The substrate growth temperature in the PSD affected both crystal quality and lattice strain due to the increase in surface motion length. The plasma power affected the amount of Al and the chemical stoichiometry of the film, as well as the migration length and plasma damage.

Atomic force microscopy (AFM)

Field emission scanning electron microscope (FE-SEM)

Since it is a measurement method that uses electrons, there is also a limitation that a sample is a conductor. It is used for the surface morphology of AlN thin films at an electron voltage of 15 kV.

Figure 2.9 Different types of electron interactions with specimen and related detection modes [11]

Energy dispersive X-ray spectrometer (EDS)

Cathodoluminescence (CL)

When electrons and holes meet and recombine in a semiconductor, they emit light or heat. Typical examples of non-luminescent recombination are defects involving externally added impurity atoms, natural defects, dislocations, and defect complexes, and inherent defects in compound semiconductors are interstitial atom, vacancy, and antisite defect. All of these defects have energy levels that are different from those of the lattice-filled atoms and usually form one or more energy levels in the band gap of the semiconductor.

Energy levels in the band gap effectively recombine transporters, especially if the position of the energy level is near the middle of the band gap.

Fourier transform infrared (FTIR)

In this study, it is used for the luminescence property of AlN such as defect and direct band gap. Proceedings of the 51st Annual Technical Conference, Chicago, April Society of vacuum coaters: a digital library. In general sputtering, the fundamental sputtering parameters such as plasma power and gas flow rate are relatively simple compared to other thin film growth methods.

A total sputtered number of metal atoms (R) in the reactive gas sputtering process is given by equation 3.1 as follows [1]. Where J is the ion current density, q is the amount of charge, Ym is the sputtering yield of the target, θ is the ratio of the surface of the target reacted with the reactive gas, Yc is the sputtering yield of the compound formed by reacting with the reactive gas . In this chapter, controlled AlN films as a basic parameter of DC reactive gas sputtering are investigated as a basic experiment for high-quality AlN thin films.

Experimental details

Influence of plasma power on reactive gas DC magnetron

Growth rate variation
Surface change
Composition variation
Crystallinity

Transparent thin films were observed in the samples grown on plasma power (P<200W) (figure 3.2 (a) and (b)). This indicates that the thin film has a tensile strain in the c-axis direction, and the plasma force has a lattice strain ratio.

Figure 3.1 Growth rate of films with plasma power from 75 to 300W at N 2 /Ar flow ratio of 3/10

Influence of gas flow ratio on the reactive gas DC magnetron

Growth rate variation
Surface change
Crystallinity and composition variation

Conclusion

In Chapter 3, AlN thin films on an ITO/SiO2 substrate were investigated by reactive gas magnetron sputtering. The plasma power and gas flow ratio (increasing N2 gas flow rate) in the DC jet spray were controlled. The growth rates varied with the sputtering parameters, confirming that the amount of Al stock was controlled.

Epitaxy of an Al Droplet-free AlN Layer with Step Current Functions by Molecular Beam Epitaxy, Chinese Physics Letter.

Pulsed Sputtering Deposition of AlN Thin Films

Experiment details

Influence of plasma power on pulsed sputtering deposition of

Al amount supply
Migration length
Plasma damage
Lattice constant
Al-N cluster

Influence of gas pressure on pulsed sputtering deposition of AlN

Influence of growth temperature on pulsed sputtering deposition

Conclusion

Gas pressure could reduce the residual stress relative to the mean free path of Al molecules, but high gas pressure caused poor crystallinity due to low energy Al atoms. Using these, a thin film approaching 0 residual strain was fabricated at a growth temperature of 500℃, an Ar/N2 gas flow ratio of 3/2, and a plasma power of 300 W. The effect of sputtering power on the surface properties and crystal quality of AlN ﬁlms deposited with by pulsed direct reactive spraying.

Growth and characterization of aluminum nitride coatings prepared by pulsed direct current reactive unbalanced magnetron sputtering.

Characterizations of AlN Thin Films

Experimental details
Surface morphology
Refraction index
Luminescence property
Relative permittivity
Electrical resistivity
Conclusion

The surface of AlN thin films by PSD has low roughness, transparency in the visible area. As a result, there are similar characteristics compared to AlN thin films studied in the past, which indicate that the research and development of devices using AlN thin films by PSD is possible. Optical and dielectric properties of dc magnetron sputtered AlN thin films related to deposition conditions.

In this study, the growth and evaluation of AlN thin films were investigated with a view to their wider application. The AlN thin films were deposited by sputtering of two types, such as DC mode and Pulsed DC mode. The characterization of AlN thin films using PSD was investigated, such as surface morphology, refractive index, relative permittivity, luminescence property and electrical resistance.

Subject: Property of AlN thin film on ITO/SiO2 substrate by DC magnetron reactive sputtering. 4] Choi, J., Ko, D., Cho, S., Lee, S., & Chang, J., A study on the change of crystallinity by heat treatment of AlN thin films grown by pulsed sputter deposition Phys. new: Sae Mulli, (accepted). 11] Cho, S., Choi, J., Ko, D., Lee, S., Lee, M., & Chang, J., “Influence of Sputtering Parameters on AlN Thin Film by Pulse Sputter Deposition at room temperature", 4th International Conference on Advanced Electromaterials, Jeju, Republic of Korea, November, 2017.

12] Choi, J., Ko, D., Cho, S., Lee, S., & Chang, J., “Characterization of Annealed AlN Layers Grown by Pulsed Sputter Deposition”, The 4th International Conference on Advanced Electromaterials, Jeju, Republic of Korea, November 2017.