Photolithography with polymethyl methacrylate (PMMA)

Abstract

Polymethyl methacrylate (PMMA) is widely used as an electron beam resist but is not used as a photoresist because of its insensitivity to electromagnetic radiation with wavelengths longer than about 300 nm. In this paper we describe a technique for performing conventional photolithography with high molecular weight PMMA at the widely used 365 nm i-line wavelength. The technique involves photosensitizing PMMA with Irgacure 651-a commercially available photo-initiator that can cause PMMA strands to cross-link. Optimum amount of Irgacure can produce a negative tone photoresist with adequate photosensitivity and plasma etch resistance. We describe this technique in detail with complete processing conditions and discuss the effects of varying Irgacure 651 concentration in PMMA as well as changes in UV exposure dose. We also show example structures patterned with commonly available materials and equipment. Finally, we show that it is possible to carry out gradient lithography with this approach, in order to produce structures in relief in photosensitive PMMA.

Gadolinium-Based Hybrid Ultra-Low-Background Material for Protecting the Darkside20k Dark Matter Detector from Background Neutrons

“…Attempts to incorporate the nano-sized powder compound Gd 2 O 3 (20 -80 nm) did not lead to the required results. Despite the nanoscale character of the grains, considering the large density difference in densities (r Gd O 2 3 = 7.407 g/cm 3 [18], r PMMA = 1.18 g/cm 3 [9]) and long thermal polymerization process (12 h to 20 days, depending on the size of the product) the nanosized Gd 2 O 3 particles agglomerated and sedimented during the process of polymerization. In these experiments the difference in the gadolinium concentration over the HM thickness of 5 cm exceeded one order of magnitude.…”

Inherently UV Photodegradable Poly(methacrylate) Gels

“…To date, no positive gel-based photoresists have been demonstrated, even though gels offer advantages over established procedures using linear polymers such as PMMA. [37] First, no designated step is required to remove irradiated polymer fragments from the copper surface using a solvent ("developer"), since the degraded organogel dissolves into the solvent released upon gel degradation. Second, the inherently photodegradable organogels can be removed with affordable UV lamps, whereas PMMA typically requires X-ray or electron beams to degrade efficiently.…”

“…Second, the inherently photodegradable organogels can be removed with affordable UV lamps, whereas PMMA typically requires X-ray or electron beams to degrade efficiently. [37] To test the suitability of inherently photodegradable organogels as a photoresist, we coated a copper circuit board with a thin film of organogel (200 µm). The organogel film was then spatially degraded with UV light for 10 min using a photomask and immersed into 0.5 m aq.…”

Visible Light Induced Degradation of Poly(methyl methacrylate‐co‐methyl α‐chloro acrylate) Copolymer at Ambient Temperature

“…[ 1–3 ] Cost‐effective, transparent, and lightweight nature of PMMA combined with excellent resistance to environmental conditions and scratches makes it a suitable alternative for a variety of indoor and outdoor applications. [ 4–11 ] Hence, the demand for PMMA production in the industry has been consistently increasing per year. [ 12,13 ] According to statistics, PMMA consumption is expected to reach up to around 4 M tons in 2027.…”