Photolithography

In the following sections, we begin with a description of photolithography, then focus on a number of methods developed in our laboratory and conclude with some other non-traditional techniques. More extensive descriptions of traditional approaches are reviewed elsewhere [78]. 

Photolithography is the most commonly used microlithographic technique [2, 78]. In photolithography, a substrate, spin-coated with a thin layer of photo- 

In addition to conventional photoresist polymers, Langmuir-Blodgett (LB) films and SAMs [79-81] have been used as resists in photolithography. In such applications, photochemical oxidation, cross-linking, or generation of reactive groups are used to transfer micropatterns from the photomask into the mono-layers [82-84]. 

After a thin film is deposited onto a substrate, the next step is constructing a structure from this layer of thin film according to a designed pattern that must be transferred onto the substrate. This is done through a technique called photolithography. 

Photomask with transparent and opaque regions that define device patterns. 

Note that the discussion here is in the context of positive PR. An opposite or negative PR is also possible the PR becomes insoluble in the developer after exposure and remains soluble in the absence of exposure. 

Photolithography process using contact aligner, (a) Ultraviolet exposure of photoresist with photomask, (b) Pattern on photomask is transferred to photoresist after development. 

In addition to the high resolution obtained with a visible light source, this method based on the phonon-assisted process has several advantages, including  

Based on the results outlined above, a prototype machine for producing commercial products has been constructed in collaboration with industry [53]. As shown in Fig. 1.27, it occupies an area as small as 1 m. It uses a conventional Xe lamp 

It should be pointed out that a metallic photomask may sacrifice the resolution due to diffraction of the plasmonic wave. To solve this problem, the plasmonic wave 

Examples of the patterns fabricated by this machine are a 40 nm-linewidth linear pattern (Fig. 1.28a), a high-aspect-ratio pattern (Fig. 1.28b), a pattern with a minimum linewidth of 22 nm realized by making high-resolution photoresist (Fig. 1.28c), two-dimensional arrays of rings and disks (Fig. 1.28d, e), and so on [53]. This machine has been made available for public use since April 2006. Examples of its use include the fabrication of a two-dimensional array of room-temperature operated nanophotonic NOT gates composed of InAs QDs (refer to Fig. 1.11), linear and curved Si optical waveguides, and so on. 

Although the prototype machine of Fig. 1.27 is fully automatic and can be used to fabricate a variety of devices, a more compact and simple machine is sufficient 

Schematic illustration of nanocasting and SEM images of (a) a natural lotus leaf and (b) its positive PDMS replica [75]. 

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Figure 14.15 Outline of the photolithography process for producing integrated circuit chips.

Phosphine(s), chirality of, 314 Phosphite, DNA synthesis and, 1115 oxidation of, 1116 Phospholipid, 1066-1067 classification of, 1066 Phosphopantetheine, coenzyme A from. 817 structure of, 1127 Phosphoramidite, DNA synthesis and, 1115 Phosphoranc, 720 Phosphoric acid, pKa of, 51 Phosphoric acid anhydride, 1127 Phosphorus, hybridization of, 20 Phosphorus oxychloride, alcohol dehydration with. 620-622 Phosphorus tribromide, reaction with alcohols. 344. 618 Photochemical reaction, 1181 Photolithography, 505-506 resists for, 505-506 Photon, 419 energy- of. 420 Photosynthesis, 973-974 Phthalic acid, structure of, 753 Phthalimide, Gabriel amine synthesis and, 929... 

Registiy of Mass Spectral Data, 412 Replication (DNA). 1106-1107 direction of, 1107 error rate during. 1107 lagging strand in, 1107 leading strand in, 1107 Okazaki fragments in, 1107 replication fork in, 1107 Replication fork (DNA), 1107 Reserpine, structure of, 65 Residue (protein), 1027 Resist, photolithography and, 505-506... 

The minimum size of the monochrome pixels (we consider color in Section 13.7.3) that can be fabricated using OLEDs is dictated primarily by the ability to pattern the electrode which is deposited on top. OLEDs are not sufficiently robust to withstand the normal processes of photolithography. Among the schemes which have been suggested for high resolution patterning is one in which the substrate is pne-pattemed to provide its own shadow mask [1911. By this means, pixel sizes down to 300 p have been demonstrated, and a lower limit of about 100 p is estimated. 

Photolithography and microfabrication can be combined to manufacture well-defined, micro-... 

Chemical vapor deposition Plasma etching Photoresist Photolithography Resistance heating Ion implantation Spin-on glass deposition Cathodic arc Ion plating... 

Metal is then deposited into the opened vias (openings) in the oxide layer and over its surface. During the subsequent photolithography process, it is patterned to form the desired electrical interconnections. These two steps are repeated for each succeeding level to produce additional levels of interconnections. Finally, a protective overcoat of oxide/nitride is applied (passivation), and vias are opened so that the wires eonnectlng the IC chip to its carrier package can be bonded to output pads. 

Fabrication was done by photolithography and deep reactive ion etching (DRIB). The catalyst was inserted by sputtering. Such a prepared microstructure was sealed with a Pyrex cover. The bonded micro device was placed on a heating block containing four cartridge heaters. Five thermocouples monitored temperature on the back side. A stainless-steel clamp compressed the device with graphite sheets. 

Microfabrication is achieved by photolithography and isotropic etching of glass using HF [4—13]. Thermal bonding serves for interconnection. Holes are drilled in the top plate for connection to the fluidic peripherals. 

Two microstructured layers of the 2x2 chip were fabricated by photolithography and wet etching in glass (Figure 4.11) [23,24]. These top and bottom layers and a third thinner layer containing holes as conduits were thermally bonded to yield the chip. The way of guiding the micro charmels, as described above, is referred to as two-level crossing. 

The chip is made from glass by photolithography and wet etching followed by thermal bonding. 

This chip version is typically made in glass and has the great advantage that the flow can be directly visualized [40,44—46]. Fabrication is achieved by photolithography and wet-chemical etching followed by thermal bonding of the plates covered with a thin layer of solder [47]. 

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