B. S. Kwon

Ultrahigh Selective Etching of SiO2 Using an Amorphous Carbon Mask in Dual-Frequency Capacitively Coupled C4F8 / CH2F2 / O2/Ar Plasmas

Highly selective etching of a silicon dioxide layer using a very thin physical-vapor-deposited amorphous carbon layer (PVD-ACL) was investigated in a dual-frequency superimposed capacitively coupled plasma etcher. The following process parameters of the C 4 F 8 /CH 2 F 2 /O 2 /Ar plasmas were manipulated: CH 2 F 2 /(CH 2 F 2 + O 2 ) flow ratio, high frequency (HF) power (P HF ), and low frequency power (P LF ). A wide processing window existed to produce the ultrahigh etch selectivities of a SiO 2 layer using the patterned PVD-ACL mask. The etch gas flow ratio played a critical role in determining the process window for ultrahigh silicon oxide/ ACL etch selectivity due to the disproportionate change in the degree of polymerization on the SiO 2 and ACL surfaces. Etching of the ArF photoresist/bottom antireflective coating (BARC)/SiO x ACL/silicon-oxide-stacked structure allows the use of a very thin PVD-ACL as an etch mask layer for the etching of high aspect ratio silicon dioxide patterns.

Etching characteristics and application of physical-vapor-deposited amorphous carbon for multilevel resist

For the fabrication of a multilevel resist (MLR) based on a very thin, physical-vapor-deposited (PVD) amorphous carbon (a-C) layer, the etching characteristics of the PVD a-C layer with a SiOx hard mask were investigated in a dual-frequency superimposed capacitively coupled plasma etcher by varying the following process parameters in O2∕N2∕Ar plasmas: high-frequency/low-frequency combination (fHF∕fLF), HF/LF power ratio (PHF∕PLF), and O2 and N2 flow rates. The very thin nature of the a-C layer helps to keep the aspect ratio of the etched features low. The etch rate of the PVD a-C layer increased with decreasing fHF∕fLF combination and increasing PLF and was initially increased but then decreased with increasing N2 flow rate in O2∕N2∕Ar plasmas. The application of a 30nm PVD a-C layer in the MLR structure of ArF PR∕BARC∕SiOx∕PVD a-C∕TEOS oxide supported the possibility of using a very thin PVD a-C layer as an etch-mask layer for the TEOS-oxide layer.

Highly selective etching of silicon nitride to physical-vapor-deposited a-C mask in dual-frequency capacitively coupled CH2F2∕H2 plasmas

A multilevel resist (MLR) structure can be fabricated based on a very thin amorphous carbon (a-C) layer (≅80nm) and Si3N4 hard-mask layer (≅300nm). The authors investigated the selective etching of the Si3N4 layer using a physical-vapor-deposited (PVD) a-C mask in a dual-frequency superimposed capacitively coupled plasma etcher by varying the process parameters in the CH2F2∕H2∕Ar plasmas, viz., the etch gas flow ratio, high-frequency source power (PHF), and low-frequency source power (PLF). They found that under certain etch conditions they obtain infinitely high etch selectivities of the Si3N4 layers to the PVD a-C on both the blanket and patterned wafers. The etch gas flow ratio played a critical role in determining the process window for infinitely high Si3N4∕PVD a-C etch selectivity because of the change in the degree of polymerization. The etch results of a patterned ArF photoresisit/bottom antireflective coating/SiOx∕PVD a-C∕Si3N4 MLR structure supported the idea of using a very thin PVD a-C layer a...

Infinitely high etch selectivity during CH2F2/H2 dual-frequency capacitively coupled plasma etching of silicon nitride to chemical vapor-deposited a-C

For fabrication of a multilevel resist (MLR) structure with silicon nitride (Si3N4) and amorphous carbon (a-C) layers, highly selective etching of the Si3N4 layer using a chemical vapor-deposited (CVD) a-C etch mask was investigated by varying the following process parameters in CH2F2/H2/Ar plasmas: etch gas flow ratio, high-frequency source power (PHF), and low-frequency source power (PLF) in a dual-frequency superimposed capacitively coupled plasma etcher. The results of etching the ArF photoresist/bottom antireflective coating/SiOx/CVD a-C/Si3N4 MLR structure showed the possibility of obtaining an infinitely high selective etch process for the Si3N4 layer using a thin CVD a-C etch mask for high aspect-ratio pattern formation. The CH2F2/H2 gas flow ratio was found to play a critical role in determining the process window for infinite Si3N4/CVD a-C etch selectivity, due to the change in the degree of polymerization on Si3N4 and CVD a-C surfaces.

Infinitely high selective inductively coupled plasma etching of an indium tin oxide binary mask structure for extreme ultraviolet lithography

Currently, extreme ultraviolet lithography (EUVL) is being investigated for next generation lithography. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics with a completely different configuration than those of conventional photolithography. This study investigated the etching properties of indium tin oxide (ITO) binary mask materials for EUVL, such as ITO (absorber layer), Ru (capping/etch-stop layer), and a Mo–Si multilayer (reflective layer), by varying the Cl2/Ar gas flow ratio, dc self-bias voltage (Vdc), and etch time in inductively coupled plasmas. The ITO absorber layer needs to be etched with no loss in the Ru layer on the Mo–Si multilayer for fabrication of the EUVL ITO binary mask structure proposed here. The ITO layer could be etched with an infinitely high etch selectivity over the Ru etch-stop layer in Cl2/Ar plasma even with a very high overetch time.

Infinite Etch Selectivity during Etching of SiON with an Extreme Ultraviolet Resist Pattern in Dual-Frequency Capacitively Coupled Plasmas

We investigated the processing window for the etch selectivity of silicon oxynitride (SiON) layers to extreme ultraviolet (EUV) resists and the variation in line edge roughness of EUV resists during etching of SiON/EUV resist structures in a dual-frequency superimposed capacitively coupled plasma etcher. We varied the processing parameters of the CH 2 F 2 /(CH 2 F 2 + N 2 ) gas flow ratio and low frequency source power (P LF ) in CH 2 F 2 /N 2 /Ar plasma and the O 2 flow rate in CH 2 F 2 /N 2 /O 2 /Ar plasma. The CH 2 F 2 /N 2 flow ratio was found to play a critical role in determining the processing window for infinite etch selectivity of SiON/EUV resists due to disproportionate changes in the degrees of polymerization on SiON and EUV resist surfaces. The preferential chemical reaction between hydrogen and carbon in the hydrofluorocarbon (CH x F y ) polymer layer, and the nitrogen and oxygen in the SiON layer, presumably led to the formation of HCN, CO, and CO 2 etch by-products and resulted in smaller steady-state hydrofluorocarbon thicknesses on SiON. As a result, continuous SiON etching due to enhanced SiF 4 formation occurred while the CH x F y layer was deposited on the EUV resist surface. The critical dimension and line edge roughness increased with increasing CH 2 F 2 /(CH 2 F 2 + N 2 ) flow ratio due to an increased degree of polymerization.