Sergio A. Ajuria

Furnace formation of silicon oxynitride thin dielectrics in nitrous oxide (N2O): The role of nitric oxide (NO)

We have studied the growth kinetics of the N2O furnace oxynitridation process demonstrating the importance of input flow rate, and therefore gas residence time, in determining the final film thickness and the nitrogen concentration. This dependence on residence time can explain the variation in the tendency to thickness saturation observed in the film growth data reported by several groups. Using published gas phase kinetic data, we have shown that, for a 950 °C oxynitridation process, N2O decomposes into N2, O2, and NO before reaching the wafer load. Again using published information, we have derived a simple equation which describes the subsequent reaction between NO and O2 to produce NO2 as the gas flows down the tube. This reaction results in loss of NO by an amount which depends on the gas residence time and therefore on the input gas flow rate and the dimensions of the system. Since it can be argued that NO2 does not contribute to nitridation, this system‐dependent loss of NO can explain the variation in the reported film growth data. Combining our experimental data and model, we find that the peak nitrogen concentration in the film depends linearly on the NO gas phase concentration. Further, the oxynitride grows more slowly as the NO concentration increases supporting the idea that oxidation sites are blocked by nitrogen as oxynitridation time increases.

Growth and surface chemistry of oxynitride gate dielectric using nitric oxide

Oxynitride films grown on preoxidized (100) silicon surfaces in a nitric oxide (NO) ambient at 950 °C have been investigated using x‐ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), and cross‐sectional transmission electron microscopy (XTEM). Compared to N2O oxynitride, NO oxynitride exhibits very different surface chemistry, interface properties, and growth mechanisms. The etch back of NO and N2O oxynitride films allows control of sample thickness for the XPS measurements. NO oxynitride has the interfacial nitrogen (Nint) sharply peaked on the Si substrate side of the interface, while it is broad and on the dielectric side of the interface for the N2O oxynitride. The N(1s) XPS results reveal a clear distinction between N2O oxynitride and NO oxynitride. Near the Si/dielectric interface the NO oxynitride shows primarily Si≡N bonds, while the N2O films showed a N(1s) binding energy peak that is in‐between that of Si≡N bonds and Si2=N—O bonds. Furth...

Relationship between growth conditions, nitrogen profile, and charge to breakdown of gate oxynitrides grown from pure N2O

We studied the relationship between the growth conditions, the nitrogen profile, and the charge to breakdown of N2O oxynitrides grown in a RTP and in a conventional furnace. RTP oxynitride shows nitrogen accumulation at the Si/SiO2 interface. On the other hand, furnace oxynitride shows almost uniform nitrogen distribution in the bulk, resulting in poor charge to breakdown characteristics. We find that two‐step oxynitridation processes provide nitrogen accumulation at the Si/SiO2 interface and result in better electrical properties than those of one‐step oxynitrides.

Furnace grown gate oxynitride using nitric oxide (NO)

Gate oxynitride was grown in NO for the first time. This approach can provide a tight N accumulation near the Si/SiO/sub 2/ interface. Much lower thermal budget is required for an NO process than for an N/sub 2/O process to produce an oxynitride with useful properties. Submicron MOSFETs with NO oxynitride showed superior current drive characteristics and comparable hot carrier immunity to those with N/sub 2/O oxynitride. >

Evaluation of Interfacial Nitrogen Concentration of RTP Oxynitrides by Reoxidation

We prepared oxynitrides with different interfacial nitrogen concentration ([N int ]) using RTP. Reoxidation kinetics of these oxynitrides was studied. It was found that reoxidation thickness strongly depends on the [N int ]. The reoxidation kinetics can be used for the evaluation of [N int ]

Gate oxynitride grown in nitric oxide (NO)

Gate oxynitride was grown in NO for the first time. This approach can provide a tight N accumulation near the Si/SiO/sub 2/ interface. Much lower thermal budget is required for an NO process than an N/sub 2/O process to produce an oxynitride with useful properties. Submicron MOSFETs with NO oxynitride showed superior current drive characteristics and comparable hot carrier immunity to those with N/sub 2/O oxynitride.<<ETX>>

Scaling of poly-encapsulated LOCOS for 0.35 /spl mu/m CMOS technology

We demonstrate the scaling of Poly-Encapsulated LOCOS (PELOX) for 0.35 /spl mu/m CMOS technology without detrimental effects on gate oxide and shallow source/drain junction integrity. As-grown birds beak punchthrough is shown to fundamentally limit the scalability of LOCOS-based schemes for narrow nitride features. A quantitative comparison of birds beak punchthrough is made between LOCOS, Poly-Buffer LOCOS (PBL), and PELOX. The PELOX scalability is emphasized by evaluating the impact of the polysilicon-sealed cavity length for narrow nitride features. We present the realization of a 1 /spl mu/m active/isolation pitch fully meeting the geometry and off-leakage requirements of 0.35 /spl mu/m CMOS technologies (VDS/spl les/5 V). This field-implant-free isolation module avoids unnecessary process complexity by successfully integrating scaled PELOX with the split well-drive-in scheme. A highlight of this new approach is that the NMOSFET characteristics are largely width-independent down to 0.3 /spl mu/m dimensions. >

Oxynitride gate dielectric grown in nitric oxide (NO): the effect of reoxidation on dielectric reliability of the active edge

Reoxidation of an oxynitride gate dielectric grown by NO anneal of thermal oxide has been studied. This process has demonstrated /spl sim/3-5X improvement of Q/sub BD/ of active edge intensive capacitors in comparison to thermal oxide, N/sub 2/O and NO oxynitride. This improvement is believed to be due to the reduction of local thinning of the gate dielectric at the field oxide edge which also reduces local build-up of positive charge near the gate electrode at the isolation edges.

Kinetic analysis of silicon oxidations in the thin regime by incremental growth

The scaling of dry thermal oxides into the thin (<400 A) range continues to motivate studies of the rapid initial oxidation rate of silicon unaccounted for by a linear‐parabolic model. In this paper, silicon oxidation kinetics in this unresolved regime are studied by the incremental reoxidation of thin thermally grown and deposited silicon oxide layers on silicon. It is found that the reoxidation rates of thermally grown oxides in the thin regime rapidly decrease with increasing oxide thickness. In contrast, the reoxidation rates of deposited oxides are faster, and nearly thickness independent. It is also found that the reoxidation rates of thin thermal oxides can be significantly increased by inert thermal annealing. Existing thin‐regime oxidation models are evaluated in light of these experimental findings, and it is concluded that only models invoking stress suppression of early oxidation kinetics can reconcile all experimental observations. In further support of a stress argument, the time and tempera...

Low-defect-density and high-reliability FETMOS EEPROM's fabricated using furnace N/sub 2/O oxynitridation

The superior characteristics of floating-gate electron tunneling MOS (FETMOS) EEPROMs fabricated using a furnace N/sub 2/O oxynitridation process are described. These devices exhibited about eight times better endurance and good data retention characteristics while maintaining defect density comparable to that of the control thermal oxide devices. These devices also showed very good thickness uniformity across the wafer and wafer-to-wafer.<<ETX>>