As integration of circuits increases, required feature size becomes smaller and smaller. Defect control becomes tighter
due to decrease in defect size that affects the images printed on the wafer and increase in possibility to be killer defect
like 2-face bridge defect. Therefore, particle sources from all processes should be controlled extremely.
Especially for dry etching process, Alumina ceramic has been widely used for plasma resistance material such as
electrode covering plate and insulator. However, they can be etched under 'F' series plasma condition as well, even in
small amounts. It has been reported that non-volatile by-products from etch ceramic can be particle sources to be killer
defect. Therefore, selection of ceramic materials must be important for particle control in dry etch process.
This paper pertains to testing etch resistance differences in Alumina (Al2O3) and Yttria (Y2O3) ceramic materials
depending on various density and surface roughness. Ceramic surface microstructures change after plasma treatment was
observed with scanning electron microscope (SEM) and ceramic erosion rate after plasma treatment was measured with
Embedded-attenuated phase shift masks (EAPSMs) have been an indispensable enabling technology for <130 nm node device fabrication. The precise etching of MoSiON is a key process in high quality phase shift mask manufacturing. Fluorine-based plasma chemistry has been used widely to date, but it is difficult to control CD (Critical Dimension) and phase uniformity. This stems mainly from the large Cr undercut and surface roughness due to the reaction of fluorine radicals with the phase shifting layer. In this paper, etch characteristics of the MoSiON layer using CF4, O2, and He in an inductively coupled plasma (ICP) were examined for the manufacturing of phase shift masks for 90-nm node design rules. The dependency of etch parameters such as ICP power, bias power (DC bias voltage), pressure, CF4 concentration, and O2 concentration on the etch properties of MoSiON were tested. We have investigated vertical slope, surface morphology, and minimum CD bias. This optimized process condition showed that intra-mask phase uniformity was below 1% (3-sigma) over a 135 mm × 135 mm mask area and transmittance uniformity was 8.68% ± 0.09%. CD uniformity was 5.5nm (3-sigma), CD linearity was 5.0nm over 300nm to 1300nm, and Cr-to-MoSiON CD bias was 2.0nm. The MoSiON profile was nearly vertical and the surface morphology was very clean.
The etch characteristics of MoSiON were investigated when chlorine was utilized as the main etch gas in an ICP dry etch system. MoSiON and glass are easily etched with fluorine-based plasmas such as: CF4, SF6, and CHF3. These plasma chemistries generate carbon-containing and fluorine-containing polymers as byproducts, which can be responsible for generating particles or hard defects on the mask during the MoSiON etch step. They also cause damage to the glass surface, manifesting themselves as a phase or transmission errors.
In this paper, new plasma chemistry was applied to etch MoSiON, and its characteristics were examined focusing on the effects of each parameter. These parameters included: ICP power, bias power, pressure, and gas concentration. It is difficult to etch MoSiON with good selectivity to Cr because MoSiON and Cr can be etched simultaneously after the photoresist layer has been removed. It will be shown how to increase the selectivity to Cr using an optimized process leveraging a new hardware modification. The etch characteristics of the chlorine plasma will also be compared to that of fluorine plasmas. It was found that using a chlorine plasma to etch MoSiON instead of a fluorine plasma yields good etch properties and good morphology.
In the photomask manufacturing, dry etch process is one of important process and the etch process mainly affects CD uniformity, skew, and Cr slope. We will present newly developed dry etcher system using TCP (transformer coupled plasma) source and its Cr etch performance. We will investigate the performance of TCP source for the uniformity, linearity, and loading effects. CD uniformity of 0.8 um Cr space pattern at 11 x 11 arrays with 135 x 135 mm2 area is below 8 nm and 15 nm in 3 sigma in case of ZEP7000 and IP3500 as resists, respectively. The skew (ASI - ADI) linearity of clear and dark CDs from 0.4 um to 2 um is below 35 nm in case of IP3500. The Cr loading characteristics of TCP source is investigated and the etch process parameter dependence on the loading is verified.
Recently dry etcher system is a key process technology in preparation of photomask for next generation microelectronic device and endpoint detection system is an important part of the dry etch process, because mask CD control of Cr mask is more critical issues than before. In this paper, we describe real time endpoint system which is operated by optical emission multiple wavelength absorption for dry etch process of binary photomask. The end point detection system absorbs optical emission signal in real time, using optical cable from plasm chamber in dry etcher, and the signal is absorbed 200-800nm wavelength for a lot of grating manufactured by etch angel. The signal detects endpoint of process by association of one or several wavelength. We have tested newly developed EPD system and installed at PKLs dry etcher system, using various open area Cr mask with ZEP70000 resist. This study showed that multiple wavelength absorption technique is enough to detect endpoint down to 2 percent Cr loading masks and the EPD signal reproducibility was within 2 percent of EPD time at the same patterned masks.
There is considerable interest in phase shift masks as a route to extending the resolution, contrast, and depth of focus of lithographic tools beyond what is achievable with the normal chrome mask technology. A problem that has so far hindered the introduction of phase shift masks has been the difficulty of phase and transmittance control when a phase shift mask is applied to practical use. Also, to apply phase shift layer (MoSiON), it remains that effects several critical mask parameters including sidewall slope, surface roughness, and critical dimension. For these reasons, this process requires a high degree of control of the etch process of shift layer. So in this paper, we described a technique for the fabrication of phase shift masks by etch rate of a MoSiON layer. Etching experiments of MoSiON were performed using different fluorinated gas mixtures. Four of them, CF4/O2/He, SF6/O2/He, CHF3/O2/He and Cl2/CF4/O2/He were chosen for high etch rate, sidewall slope, and surface morphology. Each added gases had a unique property on the etch rate, anisotropy, surface roughness and sidewall morphology. Result indicates that vertical slope and smooth surface are obtained using the Cl2/ CF4/O2/He and SF6/O2/He mixture. With increasing O2 flow rate to the SF6/O2/He Plasma and added Cl2 gas to the CF4/O2/He Plasma, the MoSiON etching profile becomes anisotropic without undercutting and trench profile. It is probably due to both increasing etch rate and sidewall passivation of Cl2 ion flux. When Cl2 gas was added to the CF4/O2/He Plasma, the small addition of chlorine was enough to protect the exposed sidewall of the undercutting, therefore, higher flow rate of chlorine had to be added to protect the sidewall of the undercutting by forming a sidewall passivation layer. These results show that both increasing O2 flow rate to the SF6/O2/He Plasma and the addition of Cl2 to the CF4/O2/He plasma are necessary in order to achieve a vertical profile and a smooth surface morphology.
The Cr etch rate is affected by Cr density to be etched at the photomask. Different mask-to-mask and within-mask pattern densities have made difficult to control the final CD. We have tested loading effect using binary Cr mask with ZEP7000 photoresist. The loading effect was evaluated for the masks fabricated at the various dry etch conditions with different within-mask Cr loading. The Cr etch rate and selectivity was observed at various process conditions and relations between parameters of dry etch process and Cr loading were evaluated. The horizontal and the vertical Cr etch rates were investigated and the process parameter dependence on the Cr loading was analyzed. The horizontal and the vertical photoresist etch rates were evaluated for the photoresist loading effect. The cause of mask-to-mask loading and within-mask loading are mainly from Cr loading and photoresists loading, respectively. The Cr loading is mainly affected by source power, pressure, and Cl2/O2 ratio. In our system, within-mask Cr loading is strongly dependent on the process parameters when the selectivity of Cr to PR is below 1. If uniformity and selectivity are acceptable, high DC bias, high ga flow, low pressure, and high Cl2/O2 ratio are recommended to reduce loading effect.
The Cr etch rate is affected by Cr density to be etched at the photomask and the Cr loading effect has become main obstacles to overcome for the next generation photomask process. Different mask-to-mask and within-mask pattern densities have made difficult to control the final CD (critical dimension). We have tested loading effect using binary Cr mask with ZEP7000 (3000 angstroms) photoresist. The loading effect was evaluated for the masks fabricated at the same process condition with the different mask-to-mask Cr loading and different within-mask Cr loading. The CD variations of dark field and clear field were observed and the phenomenological approach was proposed for the loading effect by some simplified equations.