| AVS 64th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS+TF-ThA |
| Session: | Plasma Enhanced ALD |
| Presenter: | Jesse Kalliomäki, Picosun Oy, Finland |
| Authors: | J. Kalliomäki, Picosun Oy, Finland V. Kilpi, Picosun Oy, Finland T. Malinen, Picosun Oy, Finland H. Enami, Hitachi High-Technologies Corp., Japan N. Mise, Hitachi High-Technologies Corp., Japan H. Hamamura, Hitachi R&D Group, Japan T. Usui, Hitachi R&D Group, Japan |
| Correspondent: | Click to Email |
Due to continuous feature size scaling down and change to the 3D structures new process innovations are now required more than ever. Conformal film formation of Al compounds such as AlN is one of the key technologies. AlN is widely used in thermal management applications and due to its compatibility with III–V compounds it has shown growing interest e.g. as interface material. There is also huge potential for AlN in MEMS manufacturing. PEALD at low temperature is one of the suitable solutions for these applications.
We have earlier reported the superiority of low pressure microwave ECR(M-ECR) plasma for Si substrate nitridation at low temperature [1]. In present study, AlN film properties were evaluated for demonstrating the advantage of the newly combined tool with the M-ECR plasma and the leading ALD system from Picosun. TMA (Trimethylaluminum) was used as Al precursor while nitrogen plasma was generated with M-ECR plasma generator to form AlN. Film properties such as density, crystallinity and conformality were studied. Composition of film was analyzed by XPS with Ar sputter.
AlN film properties were investigated as a function of deposition temperature as shown in Fig. 1. The film density increases with deposition temperature and at 200°C the density is 3.09g/cm3, which is consistent for literature values for bulk AlN [2]. It was shown that longer N2 plasma exposure time improved film density. The temperature series in Fig. 1 shows that the growth rate was 0.57Å/c and 0.54Å/c at 100 and 250ºC, respectively. Interestingly, it was found a thickness dependent crystallization. For 20nm films deposited between 100 and 250ºC showed an amorphous structure, whereas 30nm film thickness and above show crystalline structure (verified by XRD) and higher roughness, see Fig. 2. Good quality films with conformality of < 0.5% (1σ non-uniformity) for 300mm wafer and high purity (C<1%, O<3%) were achieved. Efficient generation of the radicals and ions by M-ECR plasma at low pressure [3] is supposed to improve the film properties.
The step coverage obtained in this study at AR 1:20 is >90% as shown in Fig. 3. This is promising for 3D device fabrication where conformal coating of high aspect ratios is crucial. From these results, PEALD with M-ECR plasma can be one of the most advantageous solutions for next generation devices and opens the possibilities for beyond-silicon CMOS devices.
[1] H.Hamamura et al., 16th International Conference on Atomic Layer Deposition (ALD2016)
[2] JCPDF 00-003-1144 (AlN)
[3] H.Enami et al., submitted to ALD2017