P. T. Liu

Eliminating dielectric degradation of low-k organosilicate glass by trimethylchlorosilane treatment

The interaction between low-k organosilicate glass (OSG) and photoresist removal is investigated. O2 plasma ashing and chemical wet stripper are commonly performed to remove photoresist (PR) in integrated circuit fabrication. However, O2 plasma or wet stripper will attack function groups and cause Si–OH group formation in OSG film during PR removal processing. The Si–OH groups often lead to moisture uptake and consequently dielectric degradation will occur in OSG film. Trimethylchlorosilane (TMCS) treatment can negate the damage in the OSG film after the PR removal process. In addition, chemical TMCS can react with Si–OH groups and reduces moisture uptake so that the dielectric characteristic of OSG can be maintained. Hence, TMCS treatment is a promising method for photoresist removal.

A Novel Approach of Fabricating Germanium Nanocrystals for Nonvolatile Memory Application

A nonvolatile memory device embedded with Ge nanocrystal dots is fabricated by the thermal oxidation of Si 0 . 8 Ge 0 . 2 combined with a rapid thermal annealing at 950°C in N 2 gas. The tunnel oxide in the nonvolatile memory is controlled to be 4.5 nm thick and embedded with 5.5 nm Ge nanocrystals. A low operating voltage, 5 V, is implemented and a significant threshold-voltage shift, 0.42 V, is observed. When the electrons are trapped in the Ge nanocrystals, the effect of Coulomb blockade prevents the injection and storage of more electrons and decreases the leakage current. Also, the retention characteristics are tested to be robust.

A distributed charge storage with GeO2 nanodots

In this study, a distributed charge storage with GeO2 nanodots is demonstrated. The mean size and aerial density of the nanodots embedded in SiO2 are estimated to be about 5.5 nm and 4.3×1011 cm−2, respectively. The composition of the dots is also confirmed to be GeO2 by x-ray absorption near-edge structure analyses. A significant memory effect is observed through the electrical measurements. Under the low voltage operation of 5 V, the memory window is estimated to ∼0.45 V. Also, a physical model is proposed to demonstrate the charge storage effect through the interfacial traps of GeO2 nanodots.

Low-power memory device with NiSi2 nanocrystals embedded in silicon dioxide layer

A metal-oxide-semiconductor structure with NiSi2 nanocrystals embedded in the SiO2 layer has been fabricated. A pronounced capacitance-voltage hysteresis was observed with a memory window of 1 V under the 2 V programming voltage. The processing of the structure is compatible with the current manufacturing technology of semiconductor industry.

The effect of ammonia plasma treatment on low-k methyl-hybrido-silsesquioxane against photoresist stripping damage

Abstract The integration process, low-k hybrid-organic-siloxane-polymers (HOSP) and photoresist stripping process have been investigated. The dielectric properties of HOSP films are degradated after photoresist removal. This is because photoresist stripping processes destroy the functional groups and induce moisture uptake in HOSP films. In this study, NH3-plasma treatment was used for HOSP films to form a thin nitrogen-containing layer, preventing HOSP films from O2 plasma ashing and chemical wet stripper damage during photoresist removal. The leakage current is decreased significantly and the dielectric constant is maintained at a low value after photoresist removal. These experimental results show that NH3 treatment is a promising technique to enhance the resistance of HOSP films to the photoresist stripping process.

CMP of low-k methylsilsesquiazane with oxygen plasma treatment for multilevel interconnect applications

The effect of oxygen plasma treatment on methylsilsesquiazane (MSZ) dielectric was investigated for chemical mechanical planarization (CMP) process. Oxygen plasma treatment was implemented before CMP. Experimental resultshave shown that the polishing rate of MSZ film with O 2 plasma pretreatment is increased as much as two order of magnitude more than that of MSZ without O 2 plasma pretreatment. Moreover, the electrical properties of post-CMP MSZ are close to those of an as-cured MSZ. These results indicate that the modified surfaces resulting from O 2 plasma treatment increase the polishing rate of MSZ. After polishing, the MSZ film still maintains a low-k duality.

Memory effect of oxide/SiC:O/oxide sandwiched structures

The memory effects of the oxide/oxygen-incorporated silicon carbide (SiC:O)/oxide sandwiched structure were investigated. The memory window is decreased with the increase of the oxygen content in the SiC:O film due to the reduction of dangling bonds. A concise model is proposed to explain the reduction of dangling bonds with increasing oxygen content. Also, a higher breakdown voltage is observed with less oxygen content in the SiC:O film, which is attributed to the high barrier height induced by electron trapping in the SiC:O film.

Improvement of low dielectric constant methylsilsesquioxane by boron implantation treatment

The organic silsesquioxane, methylsilsesquioxane (MSQ), exhibits a low dielectric constant because of its lower film density compared with thermal oxide. In this study, boron implantation treatment is investigated in order to improve the quality of MSQ. The small size of boron atoms do not damage the chemical bonding of the MSQ film. In addition, the formation of densified surfaces after boron implantation can reduce the probability of moisture uptake into the MSQ. Therefore, the leakage current of MSQ film is significantly decreased and the low-k properties of MSQ film can be maintained.

Effects of Ar/N2 Flow Ratio on Sputtered-AlN Film and Its Application to Low-Voltage Organic Thin-Film Transistors

In this work, we applied a low-temperature (150 °C) alumina nitride (AlN) film as the gate dielectric in organic thin-film transistors (OTFTs). It was found that the Poole–Frenkel-type leakage can be suppressed by increasing the nitrogen gas ratio in the deposition process. The thin and low-leakage AlN dielectric was characterized and then utilized in pentacene-based OTFTs. The proposed AlN dielectric greatly lowers the OTFT operating voltage ( 105) were also obtained for the AlN-OTFTs.

Study on SONOS nonvolatile memory technology using high-density plasma CVD silicon nitride

With the replacement of silicon nitride in an oxide/nitride/oxide (ONO) gate-stacked structure, trap-rich high-density plasma chemical vapor deposited (HDPCVD) SiN x shows a more significant threshold-voltage shift (memory window) than that of conventional low pressure (LP)CVD Si 3 N 4 . Also, low-temperature (200°C) deposited HDPCVD silicon nitride shows a good retention characteristic, the same as high-temperature (780°C) LPCVD Si 3 N 4 . With the optimization of thickness in the gate-stacked ONO structure, low-voltage and reliable operation, lower than 5 V. is realizable.