Conformal MOCVD Deposition of GeSbTe in High Aspect Ratio Via Structure for Phase Change Memory Applications

Abstract

We have demonstrated conformal deposition of amorphous GeSbTe films in high aspect ratio structures by MOCVD. SEM analysis showed the as-deposited GeSbTe films had smooth morphologies and were well controlled for void free amorphous conformal deposition. GeSbTe films adhere well to SiO2, TiN, and TiAlN. The morphology and adhesion are stable in 420°C post process. By annealing at 365°C, amorphous GeSbTe films converted into crystalline GeSbTe with polycrystalline grain sizes of 5nm. Film resistivity in the crystalline phase ranged from 0.001 to 0.1 Ω-cm, suitable for device applications. Phase change devices fabricated with confined via structures filled with MOCVD GeSbTe showed cycle endurances up to 1×1010 with a dynamic set/rest resistance of two orders of magnitude.

Phase-change properties of GeSbTe thin films deposited by plasma-enchanced atomic layer depositon

“…Recently, a number of studies have been carried out to investigate the deposition of phase-change materials by ALD and CVD techniques [9][10][11][12][13][14][15]. It has been reported that the precursor and substrates have an important influence on the microstructure and composition of Ge-Sb-Te films.…”

MOCVD GST for high speed and low current Phase Change Memory

“…We have previously reported MOCVD GST films that are conformal, smooth, and have a high density [10][11][12][13]. Our MOCVD GST films can be made to have very low oxygen impurities as shown in Fig.1 and have relatively low carbon and nitrogen incorporation as reported in Ref.…”

“…[11]. We have made many GST compositions by MOCVD for use in PCM devices [10]. As shown in the GST compositional phase diagram (Fig.…”

“…3 (a) and (b) show that GST 325 and GST 415 are capable to fill 15nm and 20nm holes, respectively. The compositions of the GST filled holes are uniform [10].…”

“…A very small, sub-20nm confined cell also shows potential of improving cycle endurance for DRAM applications due to its small size and thus lower energy used for reset [5]. Smooth and conformal processes such as CVD (Chemical Vapor Deposition), MOCVD and ALD (Atomic Layer Deposition) must be developed for GST alloys to fill confined device structures [6][7][8][9][10][11][12]. Currently the most advanced PCM devices with a GST filled 20nm node size confined cell structure use Ge-doped Sbrich SbTe alloys [5].…”