Alternative process schemes for double patterning that eliminate the intermediate etch step

Lithography options and challenges for sub-45nm node interconnect layers

“…The full lithography process is done twice per layer, with even an extra intermediate etch step in between (not to mention extra hard mask materials that may be required). This problem can, however, be circumvented by novel material developments [3]. Double exposure, also called contrast enhancement lithography, requires the development of a "memory-free" photoresist, which is not available currently [4].…”

“…However this second exposure is less critical in terms of CD and overlay. The dual development process is an attractive solution for very regular designs (such as memory), and can be considered as an alternative to spacer defined double patterning [3]. The negative tone developer by itself offers great possibility to enhance process windows for contact, via and trench layers.…”

Cure-induced photoresist distortions in double patterning

“…[13][14][15][16]18,[20][21][22][23][27][28][29][30][31][32][33][34] For double imaging generality, any pattern distortions need to be assessed for severity and possible correction within a given set of design rule constraints. To date, the majority of double imaging implementations have been demonstrated using highly regular structures such as pitch-split line/space arrays or crossed-grid contact hole arrays.…”

“…Without stabilization, the first resist pattern will swell or dissolve on application of the second resist film, or undergo additional exposure and development during the patterning of the second resist. Numerous chemical, 3,6,[9][10][11][12][13] photochemical, [1][2][3][4]14 thermal, 8 and ion-beam 5,7,15 stabilization methods have recently been described.…”

“…1͒. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Stabilization of the first photoresist pattern before processing of the second resist pattern is necessary in double imaging. Without stabilization, the first resist pattern will swell or dissolve on application of the second resist film, or undergo additional exposure and development during the patterning of the second resist.…”