Dry etch resistance

Initial studies of the dry-etch resistance of these resists showed that PFEMA had an etching rate in a CCl plasma (p = 0.2 torr, P = 600 W) about threeotimes lower (i.e. 380 X/min) than that of aluminum (i.e. 1200 A/min). 

Materials that exhibit enhanced solubility after exposure to radiation are defined as positive resists. The mechanism of positive resist action in most of these materials involves either main-chain scission or a polarity change. Positive photoresists that operate on the polarity change principle have been widely used for over three decades in the fabrication of VLSI devices and they exhibit high resolution and excellent dry etching resistance. Ordinarily, the chain scission mechanism is only operable at photon wavelengths below 300 nm where the energy is sufficient to break main chain bonds. 

Copolymer Approach to Design of Sensitive Deep-UV Resist Systems with High Thermal Stability and Dry Etch Resistance... 

The methacrylate units incorporated in the polymer chain give excellent UV transmission, while the a-methylstyrene units provide good dry etch resistance and high thermal stability. 

The dry etch resistance of P(MI-VBC) was compared with that for several commercial resists using a variety of etch gases (02, SFg, and CF4) under RIE conditions. The etch rate data given in Table V are presented as the ratio of the resist etch rate relative... 

When MCA is copolymerized with MMA, the resulting copolymer etches faster than PMMA, consistent with the PMCA and MCN/MCA results. Incorporation of MCA, a monomer with a-chlorine, has the effect of decreasing plasma etch resistance, as is observed for the MCA homopolymer. Sensitization by chlorine appears to be general (see Tables I, III, and VI), except for the case where the chlorine is Incorporated onto the aromatic side chain group. This effect was observed previously by Taylor and Wolf for other polymer systems. ( ) The C-Cl bond strength is lower than that for C-H and C-F, and there is much evidence that this bond can be easily cleaved, even in the solid state. (, ) This weaker side chain group leads to lower dry-etch resistance. 

The etch rate measurements for positive and negative-behaving e-beam resists are found in Table V. It is apparent that the etch resistance is lower the more sensitive the positive resist. The exception would be PMCN, which exhibits better dry-etch resistance than that which would be predicted based on e-beam sensitivity alone. Where e-beam sensitivity and etch resistance are needed, copolymerization becomes very important. This has been demonstrated for the MCN/MMA and MCA/MCN model copolymer systems in references 9 and 10, respectively. 

In general, the photoresists exhibit greater dry-process resistance than the vinyl polymers of Table II. The greater dry-etch resistances of photoresists is attributed to the aromatic nature of the crosslinking agents, photoactive components, and novolac resins (positive photoresists only). In addition, the... 

Acrylate resists such as polymethylmethacrylate (PMMA) have been used extensively in electron beam lithography because of their excellent resolution and contrast, despite their limited dry etch resistance and low sensitivity (1). Copolymers of PMMA, containing chemical groups more sensitive to radiation induced degradation, have also been studied and have shown up to a four-fold improvement in sensitivity (2). One approach has been to form a crosslinked gel, in-situ on the wafer, which contains radiation sensitive crosslinks and leads to improved sensitivity and improved contrast during development (3-7). 

Enhancement of Dry-Etch Resistance of PDly(butene-l sulfone)... 

The positive photoresists based on a novolac matrix resin and a diazo-quinone sensitizer evolved from materials originally designed by Kalle Corporation in Germany to produce photoplates used in the printing industry. These positives photoresists have become the workhorses of the microelectronics industry because of their high resolution and dry etch resistance. 

Incorporation of aromatic rings into polymer structures results in improvement in dry etch resistance 43, 44). Consequently, negative resists based... 

However conventional positive electron beam resists like PMMA(4) or PBS(5.) do not have excellent dry etching resistance. The electron beam sensitivities of these positive resists primarily result from radiation-induced degradation of polymer main chains. If the main chain bonding force of these polymers is weakened in order to improve sensitivities, the dry etching resistances of these polymers will decrease. In such cases, sensitivity to electron beam exposure and dry etching resistance are in a trade-off relationship. 

Rai and Shepherd( ) have showed that polystyrene has good sputtering resistance. It is well known that the incorporation of phenyl groups into resist polymers or the use of aromatic polymers such as polystyrene or novolacs enhances the dry etching resistance of the polymer. 

---