Ki-Seon Park

Development of New TiN/ZrO2/Al2O3/ZrO2/TiN Capacitors Extendable to 45nm Generation DRAMs Replacing HfO2 Based Dielectrics

New ZrO₂/Al₂O₃/ZrO₂ (ZAZ) dielectric film was theoretically designed and successfully demonstrated to be applicable to 45nm DRAM devices. ZAZ dielectric film is a combined structure from tetragonal ZrO₂ and amorphous Al ₂O₃. Thus prepared ZAZ TFT capacitors showed very small Tox.eq value of 6.3Aring and low leakage current less than 1fA/cell. It was also confirmed that ZAZ TFT capacitor was thermally robust during backend full thermal process by applying it to the final DRAM product in mass production

Oxidation Characteristics of TiN Film as a Barrier Metal for Bottom-Electrode Ru Film Fabricated from Tris-(2,4-octanedionato)ruthenium

Bottom-electrode Ru films were fabricated on barrier metal TiN films by the reaction of tris-(2,4-octanedionato)ruthenium [Ru(od)3, Ru(C8H13O2)3] precursor and O2 gas. It was observed that the film incorporated the undesirable impurity of oxygen that could oxidize the TiN underlayer during postthermal treatments. To evaluate the oxidation characteristics of barrier metal TiN by the incorporated oxygen, samples with the Ru/TiN film stack were annealed in N2 ambient up to 700°C for 60 s by rapid thermal processing (RTP). No sign of TiN oxidation was observed in analyses by X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy. This was also confirmed by measuring the electrical resistance of a contact hole plugged with poly-Si and connected to the Ru/TiN stack, which shows an acceptable value below 1.3×103 Ω. We also investigated the oxidation characteristics of the Ru/TiN stack by atmospheric O2 gas. The samples were annealed in O2 ambient by RTP at 500°C, 600°C, and 700°C for 60 s. The Ru film began to oxidize to RuO2 at 500°C. With increasing temperature, further oxidations of Ru and TiN occurred simultaneously. Finally, at 700°C, Ru and TiN oxidized completely to RuO2 and rutile TiO2 phases, respectively. These results demonstrate the ease of oxidation of Ru and TiN films in O2 ambient.

23.5 A 4Gb LPDDR2 STT-MRAM with compact 9F2 1T1MTJ cell and hierarchical bitline architecture

Spin-transfer torque magnetic RAM (STT-MRAM) is one of the most promising nonvolatile memories with guaranteed high-speed read and write operations. Along with performance improvements in the tunnel magnetoresistance (TMR) and the magnetic tunnel junctions (MTJ) required switching current, there have also been reports on high-capacity (up to tens of Mb) STT-MRAM [1–4]. In [2] a perpendicular-TMR (pMTJ) device is used to reduce the switching current and a high-speed current sense amplifier is proposed. In [3] a 54nm 2T-1MTJ 14F2-cell is proposed that uses a high-density DRAM process: self-aligned contact and plug process. However, the unit cell area of STT-MRAM is still much larger than that of DRAM, making STT-MRAM not cost-competitive to contemporary DRAM.

Reliability of MIM HAO capacitor for 70nm DRAM

In order to verify the package reliability of a MIM HAO capacitor module, mass production 256M DDR processes with 0.1 /spl mu/m design rule were adopted. The capacitor dielectrics used were HAH and Hf/sub x/Al/sub y/O/sub z/ and showed Tox.eq of 12/spl Aring/ and Lc of<0.2 fA/cell, respectively. With proper thermal compensation for adjusting the cell Vt, we could get a high probe test yield, and high package yield when a MIM HAO capacitor was introduced instead of an SIS Al/sub 2/O/sub 3/ capacitor. With package samples, the refresh time of the device did not degrade after IR and EFR stresses, and finally, we could confirm the reliability of MIM HAO capacitors at package level through long term operation lifetime testing.

4Gb perpendicular STT-MRAM with compact cell structure and beyond

Since the discovery of a theoretical idea of spin-transfer torque (STT) [1], STT-MRAM has attracted a great interest as a candidate of universal memory.

Investigation on the compositionally graded Hf/sub x/Al/sub y/O/sub z/ films for TiN based DRAM capacitor

New concept of capacitor dielectric thin film was successfully demonstrated through graded Hf/sub x/Al/sub y/O/sub z/ dielectric thin film accompanied by post ozone annealing for the application to DRAM capacitor. MIM capacitor with graded Hf/sub x/Al/sub y/O/sub z/ dielectric films showed drastically reduced leakage current and highly improved breakdown voltage by 0.45-0.75V maintaining the same EOT value. In the case of graded film with Hf/Al=1.5/1, EOT showed very small value of 12.3/spl Aring/ and leakage current could be maintained as low as 1E/sup -16/A/cell at +1.0V.

Development of highly robust nano-mixed Hf/sub x/Al/sub y/O/sub z/ dielectrics for TiN/Hf/sub x/Al/sub y/O/sub z//TiN capacitor applicable to 65nm generation DRAMs

TIT capacitor with Nano-mixed Hf/sub x/Al/sub y/O/sub z/ dielectric was successfully demonstrated to be applicable to 65nm DRAM devices. Nano-mixed Hf/sub x/Al/sub y/O/sub z/ thin film by ALD(Atomic Layer Deposition) showed an excellent thermal stability even up to 700/spl deg/C without any leakage current degradation. Moreover, Nano-mixed films revealed lower leakage current than laminate due to effective nano-scale mixing of HfO/sub 2/ and Al/sub 2/O/sub 3/TiN/Hf/sub x/Al/sub y/O/sub z//TiN capacitor turned out to be applicable to 65nm DRAM showing low EOT of 11/spl Aring/ and low leakage of 1 fA/cell.