John Sudijono

Dual-layer inorganic SiON bottom ARC for 0.25-μm DUV hard mask applications

Inorganic SiON BARC has been used widely in I-line lithography and 248nm DUV lithography because of its good photo performance and tunable reflective index (n) and extinction coefficient (k) on specific substrates. Conventional single layer SiON BARC on poly, WSix or Al (TiN) has successfully enhanced CD control. However, when applying single layer SiON BARC on top of oxide hard mask, tight thickness control of hard mask becomes a major issue in order to maintain the substrate reflectivity for good photo performance. Dual layer SiON BARC presented in this paper resolves the issue with wide range of hard mask thickness control. Unlike conventional organic BARC where the absorption is the primary mechanisms and the conventional single layer inorganic BARC where phase shift cancellation is dominant, the dual layer BARC uses both phase shift cancellation and light absorption mechanism. The design of dual layer BARC is that top layer serves as phase shift cancellation layer and bottom layer serves as light absorption layer with high k value. Therefore, with fixed bottom absorption layer, top layer n and k and thickness can be fine tuned to get the best photo performances. The advantages of dual layer SiON BARC are that there is no need for the tight BARC thickness control as in the case of single layer SiON BARC as well as for hard mask thickness control. Since the light is all absorbed by the bottom BARC layer, the periodical phenomena of light passing through transparent hard mask film does not exist. Detail information of setting up dual layer SiON BARC by both simulation and experiment are described here. The comparison between dual layer BARC and single layer BARC shows that smaller swing ratio and tighter CD control can be obtained in the case of dual layer BARC. Similarly, the comparison between dual layer SiON BARC and organic BARC shows that smaller iso-dense bias and better resist profile can be obtained with dual layer SiON BARC.

Via Resistance Reduction using “Cool” PVD-Ta Processing

Different processes, including cool physical vapor deposition (PVD), of Ta barrier and Cu seed deposition were compared in Cu interconnect development. In the cool Ta process, the substrate temperature was 100°C in the standard process. With the cool process, via resistance (0.19 μm in via size) was reduced by about 25%, although 40% thicker Ta was measured at the via bottom. This was not in agreement with the common understanding that the thicker the Ta film is, the higher the via resistance. Blank film studies suggested that a mixed texture of α- and β-Ta was formed at via bottom in the new Ta/Cu process. X-ray diffraction spectra clearly exhibited the existence of α-Ta in addition to the β-Ta, where the latter is usually observed in the standard process. Electron diffraction spectra further supported the claim of mixed α-/β-Ta formation at via bottom. Moreover, Rutherford backscattering data suggested that the mixed α-/β-Ta had even higher thermal stability.

Hydrogen Concentration Analysis in Pecvd and Rtcvd Silicon Nitride Thin Films and It's Impact on Device Performance

In this paper the impact of the ESL (Etch Stop layer) nitride on the device performance especially the threshold voltage (Vt) has been studied. From SIMS analysis, it is found that different nitride gives different H concentration, [H] in the Gate oxide area, the higher [H] in the nitride film, the higher H in the Gate Oxide area and the lower the threshold voltage. It is also found that using TiSi instead of CoSi can help to stop the H from diffusing into Gate Oxide/channel area, resulting in a smaller threshold voltage drift for the device employed TiSi. Study to control the [H] in the nitride film is also carried out. In this paper, RBS, HFS and FTIR are used to analyze the composition changes of the SiN films prepared using Plasma enhanced Chemical Vapor deposition (PECVD), Rapid Thermal Chemical Vapor Deposition (RTCVD) with different process parameters. Gas flow ratio, RF power and temperature are found to be the key factors that affect the composition and the H concentration in the film. It is found that the nearer the SiN composition to stoichiometric Si 3 N 4 , the lower the [H] in SiN film because there is no excess silicon or nitrogen to be bonded with H. However the lowest [H] in the SiN film is limited by temperature. The higher the process temperature the lower the [H] can be obtained in the SiN film and the nearer the composition to stoichiometric Si 3 N 4 .

Effect of deposition conditions on the properties of HDP-CVD-fluorinated silicon oxide (SiOF)

Fluorinated silicon oxide (SiOF) has been deposited by the high density plasma chemical vapor deposition technique using a SiH4/SiF4/O2/Ar plasma. The effect of the SiF4:O2 flow rate ratio together with the substrate rf bias and the source rf bias were investigated systematically. By varying the SiF4 flow rate ratio together with the substrate rf bias and the source rf bias were investigated systematically. By varying the SiF4 flow rate, the concentration of fluorine in the SiOF can range from approximately 5 at percent to approximately 12 at percent. At low SiF4:O2 flow ratios, the fluorine incorporates primarily as -Si-F in the oxide to changes in the SiOF microstructure, which result in modifications to the properties of this low-k material. An increased substrate rf bias did not affect the density of the oxide. However, the among of incorporated fluorine and the net deposition rate are both reduced. The source rf has no effect on the density of the oxide and the amount of incorporated fluorine. The main effect is a slight increase in the deposition rate.