New Chemical Vapor Delivery Systems for Surface Cleaning


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Conventional aqueous wet cleaning methods in semiconductor manufacturing are facing tremendous challenges, with decreasing line widths and high aspects ratio features on the order of a few nanometers. Water and other liquids have surface tensions that frequently prevent complete penetration into nanometer-sized trenches and vias now being fabricated on semiconductor wafers and other substrates. This problem is accentuated by the fact that particle sizes leading to Killer defects are now on the order of 10 nm or less. Nanometer-sized particles can adhere to a surface with a relatively strong force of over a million times its weight. An effective cleaning technique for submicron particle removal will require complete penetration of the device features to surround and dislodge particles, but at the same time not damage the features or etch the surface.



Solid State Phenomena (Volume 195)

Edited by:

Paul Mertens, Marc Meuris and Marc Heyns




D. Alvarez Jr et al., "New Chemical Vapor Delivery Systems for Surface Cleaning", Solid State Phenomena, Vol. 195, pp. 25-29, 2013

Online since:

December 2012




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[2] 50 Flow Rate (slm) Beginning Solution Conc Ending Solution Conc H2O2 Conc in Gas Stream.



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[2] 50 Figure 1. Flow rate study of Hydrogen Peroxide delivery without pre-humidification. A new technology that is capable of generating and delivering stable concentrations of H2O2 vapor has been developed. The method utilizes a membrane pervaporator consisting of an ionic fluoropolymer containing 10-50 nm sized pores. Ultra-high purity compositions are delivered because only water and hydrogen peroxide molecules pass through the pores. Pervaporation devices are used in series, where pre-loading a carrier gas first with water and then flowing through a pervaporater filled with H2O2/H20 mix enables a controlled H2O2/H2O ratio to be delivered to a process. Here, pre-humidification with water vapor ensures maintanance of the liquid source concentration which not only ensures process control but also has safety ramifications. Figure 2 shows stable delivery of a ~30% H2O2 solution at 40C. The average H2O2 concentration was 700ppm with a standard deviation of 16ppm. For the solution, the beginning concentration average was 33. 4% and the final concentration average was 33. 2%. This demonstrates the ability to control the hydrogen peroxide mass transfer rate while maintaining a relatively stable liquid solution concentration. Figure 2. H2O2 Output at 40°C with 30% Solution The output of a ~70% H2O2 solution held at 40C is shown in Figure 3. The average H2O2 concentration was 2583ppm with a standard deviation of 23ppm. For the solution, the beginning concentration average was 69. 1% and the final concentration average was 69. 9%. Figure 3. H2O2 Output at 40°C with 70% Solution With both tests, the hydrogen peroxide measurement was just below the theoretical value expected from Raoult's Law solution. Dilute Ammonia/Water Vapor Delivery Oxide and Silicon loss during cleaning can no longer be tolerated, therefore dilute chemistries are being sought. Dilute solutions of ammonia/water delivered from the vapor phase is a promising candidate for emerging applications. Ammonia mass transfer through a membrane delivery system was examined. Data in Figure 4 show dilute ammonia concentrations delivered from a liquid 0. 5% NH4OH/Water solution at 30º C. Mass transfer rates can be adjusted by varying flow rate. In a subsequent test, ammonia concentration in the liquid solution was varied to study the effects on the delivered concentration. Results show Figure 5 that higher vapor phase concentrations may be obtained by adjusting solution concentration. However, these results demonstrate that the membrane acts as an attenuation device, as the delivered concentrations are less than would be expected from a liquid solution with the use of a bubbler. Figure 4. Concentration of delivered ammonia starting from a 0. 5% NH4OH solution. Figure 5. Concentration of ammonia delivered at various source solution concentrations. Isopropanol/Water Vapor Delivery Vapor iso-propanol/water solutions show promise in the removal of residual organic compounds from surfaces as well as stain-free drying. Initial studies were undertaken to examine delivery of this two-component mixture. Iso-propanol concentrations in a water solution were varied in order to look at changes in delivered iso-propanol concentrations. Results in Figure 6 demonstrate the viability of the new membrane technology for delivery of a wide range of iso-propanol concentration. Figure 6. Concentration of IPA vapor delivered at various solution concentrations. Various aspects of multi-component vapor delivery will be discussed along with the viability of new membrane delivery systems for emerging surface cleaning applications.