13  EP 2 000 008 B1 14  strate transport mechanism 360 correspond to similar 2- digit reference numerals identifying similar elements in the embodiment of FIG. 1. With reference to FIG. 4, sys- tem310includesinput andtake- up rolls374, 386located outside of the reaction chamber housing 330. Additional input/output turning guides 338 are provided within iso- lationzone320. Substrate312isfedthrough one ormore slits, wiper valves, or other flow- constricting entrance and/or exit passageways 340, 342. Positioning the input and take-up rolls 374, 386 outside of reaction chamber 330 may ease roll loading and unloading. [0043] In an alternative embodiment (not shown), the input and take-up rolls 374, 386 may be placed in sepa- rate vacuum chambers or load-locks adjacent the first and second ends 376, 384 of reactor housing 330. Ad- ditional process modules maybeprovided between input roll 374 and reaction chamber 330 and/or between reac- tion chamber 330 and take-up roll 386 such that the thin film coating process would comprise just one module in a larger substrate processing system. For example, a preheating stage or other functionalization module may be providedbetween input roll374and reactionchamber 330. Examples of pre-treating or functionalizing steps useful with ALD coating system 310 include vac uum processingto speed up out-gassing of substrate 312 be- forecoating; ultra-violetlight treatment; ozone treatment, e.g., for making normally-hydrophobic plastic films hy- drophilictoenhance orenable ALDprocessing;exposure to a plasma or other source of radicals; and cleaning steps. Other process modules, such as lithography and other patterningsteps, non- ALDdepositionsuch assput- tering,and other surface finishing andcoating steps,may also be utilized. [0044] System 310 includes adjustable turning guides 364, 366that aremovable toward andawayfromdividers 334, 336 and isolation zone 320 to change a substrate dwell time within the precursor zones 314, 316. The lo- cation of turning guides 364, 366 may be adjusted inde- pendentlyor ingroups, andmay becontrolledbyacontrol system 310 to change dwell time as process ne eds change over time. In FIG. 4, three different groups of turning guides are shown in each precursor zone, each group having a different dwell time. Adjusting dwell time may facilitate nucleation for certain precursors, and may improve precursor penetration in porous surfaces. Sim- ilarly, dividers 334, 336 may be movable along the same direction as adjustable turning guides 364, 366 (i.e., up anddown), tochange the substrate dwell timein isolation zone 320. [0045] System 310 further includes a precursor recy- cling subsystem 400 located upstream of a junction 404 of the pumping/exhaust lines from first and second pre- cursorzones 314, 316. Subsystem400includes first and second traps 410, 420 flanked by a pair of three-way valves 430, 432, or their equivalent, to enable one of the traps410,420tobeselectively interposedinthe pumping line 440between the precursor zone 316and pump 358. A first one of the valves 430 includes two outlets, one being connected to the inlet of first trap 410and the other connected to the inlet of second trap 420. Similarly, sec- ond valve 432 includes two inlets; one connected to the outlet offirst trap410 and theother to the outletof second trap 420. FIG. 4 shows the left- hand sides of valves 430, 432 being closed and the right-hand sides open, so that second trap 420 is interposed in the pumping line 440 andservingasa precursor trap. Meanwhile, first trap410 is isolated from the pumping line 440, as indicated by blackened shut-off valves on the left-hand side of each three-way valve 430, 432. First trap 410 is operating in a regenerative mode, wherebythe trap410 is being heat- ed to release previously trapped precursor material into a precursor supply/recycling line 450. Isolation valves 462, 464 are provided between supply outlets of respec- tive traps 410, 420 and a downstream supply junction 470ofthesupplyoutletsin supply/recycling line 450. The position of valves 430, 432, 462, and 464 may be re- versedfromwhatisshowninFIG. 4,sothat first trap410 functions as the inline precursor trap, and second trap 420 operates as a precursor source. In the embodiment shown, one half of subsystem 400 is always operating as a trap, and the other half as a supply component of precursor delivery system 326. [0046] A second subsystem (not shown) may be pro- vided in the first precursor zone exhaust line upstream of junction 404 for trapping and recycling first precursor in a similar manner. [0047] Suitable traps 410, 420 for subsystem400may include simple inline liquid nitrogen traps or, more pref- erably, cryogenic "waterpumps" modified to pump a pre- cursor, rather than water, at suitable pressures and tem- peratures. Suitable cryogenicwaterpumps preferablyin- clude built-in heaters for regeneration capability. Exam- ple of cryogenic waterpumps include the Polycold $^{®}$ PFC water vapor cryopump and the CTI- Cryogenics$^{®}$ Low- Profile Waterpump™, both sold by Brooks Automation (www.brooks.com). Cryogenic waterpumpsare normally configured to pump in a low vacuum environment, but may be modified or adjusted to work in the operating pressure ranges of methods described herein. For some precursors the trap operating temperature may range from 100-150° Kelvin, while for others, it may range be- tween 150° and 300° Kelvin. Higher trapping tempera- tures may enable certain metal halide precursor chemi- cals to be trapped, while allowing other materials, such as background water vapor, solvents, and inert gas, to pass, thereby improving the purity of trapped precursor. [0048] The systems and methods described herein may exhibit little or no coating of moving machine parts, including the payoutandtake-up spools72, 82, 172, 182, 272, 282, 372, 382 and turning guides 64, 66, 164, 166, 364, 366, since each of these parts is either resident in only one zone of the system, or entirely outside of the zones. Unlike conventional ALD systems, high- speed pulse valves are not required in the systems described herein and, in theory, maintenance requirements would be minimal. 8