Photolithographic processing steps

Figure 1. Typical photolithographic processing steps necessary to pattern SiOt layer on a Si substrate. Key A, thermal oxidation B, photoresist deposition C, resist exposure through photomask and D, develop photoresist.

In most cases, the vertical-stacking process begins at the wafer stage where the normal bond pads are first redistributed toward the edges of the die by several photolithographic process steps shown in Figures 5.14 and 5.15 and described as follows. 

Abstract A crucial problem in the manufacturing of high aspect ratio structures in the microchip production is the collapse of photoresist patterns caused by imbalanced capillary forces. A new concept to reduce the pattern collapse bases on the reduction of the capillary forces by adsorption of a cationic surfactant. The application of a cationic surfactant rinse step in the photolithographic process leads to a reduction of the pattern collapse. Physicochemical investigations elucidate the mechanism of surfactant adsorption... 

To investigate whether the rinse with cationic surfactants does affect the pattern collapse, the photolithographic process as described in Experimental was performed without surfactant rinse and with an additional rinse step with four different concentrations of the surfactant. The results of these experiments have been discussed in detail by Wun-nicke et al. [21], Here only a short summary is given. 

The investigation of the pattern collapse in the photolithographic process revealed that a short rinse step with cationic surfactant solutions yields a maximum pattern collapse reduction at a surfactant concentration far below the cmc. The rinsing time had no influence on the pattern collapse. 

Figure 1.2. Basic steps of the photolithographic process (J) oxidizing, (2) spin coating, (3) exposing, 4) developing, etching, and (6) stripping.

Figure 5.16 Novel fabrication process for the third generation of micromachined electrospray emitter tips silicon support wafer (blue), 200 nm thick silicon dioxide etch-release layer (white) which is patterned using a HF-based wet-etch step, single polySi micro-nib layer (red) housing the reservoir and the nib tip which is defined using either a chlorine- or an SF6-based dry etch and single UV photolithographic masking step (black).

The next procedure is the heart of the photolithographic process. A photoresist layer is spin cast over the silicon wafer from solution. It is then given a preliminary set of processing steps (such as baking at elevated temperatures) following the procedures recommended by the manufacturer. The material... 

Chip is attached face down and wire bonded to the interposer. A thin elastomer, sandwiched between the chip and interposer, cushions the chip and the solder-ball interconnects, relieving stresses (see Fig. 1.13). The interposer generally consists of a metallized, flexible polyimide tape on which are formed electrical connections by photolithographic processes. As a final step, the exposed wire bonds and edges of the chip are molded with epoxy. 

Photolithography is the workhorse of the semiconductor device manufacturing industry. Figure 2 shows the processing steps involved in the fabrication of a p-n junction. Similar processes are used in the fabrication of a MOSFET. The key steps in any photolithographic process are as follows ... 

Figure 3 Schematic diagrams showing photolithographic processes that utilize (a) double exposure and (b) double development steps.

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