Chemical Control


Different kinds of chemicals are used for device processing in the NFF cleanroom. Some chemicals are dangerous when mixed with other chemicals or heated while others are dangerous on their own. NFF users should have a good understanding of all the chemicals they intend to use. They should know what to do when accidents, such as chemical spills, occur. In general, safe chemical use can be achieved through proper training, proper labeling, proper storage and segregation, and proper transport. All chemicals used in the NFF are controlled items. No chemicals can be brought in or taken out without permission. At HKUST, the Health, Safety and Environment Office (HSEO) also plays an important role in chemical safety. For more details, please visit

Bringing in Chemicals
  1. Users who wish to bring in any chemicals into the laboratory, they have to first submit an application for Safety Assessment on Users Requested Process, (or Safety Assessment) to NFF management for approval.
  2. Approved chemicals may be stored in the NFF for a certain period of time only. Once that period expires, those chemicals must be removed from the laboratory.
  3. The owners of the chemicals are responsible for their disposal.
Taking out Chemicals

A formal written notice must be given to NFF management for approval if a chemical is to be taken out of the laboratory for use elsewhere. The notice must include a declaration of responsibility and liability in relation to safety and be signed by the project supervisor.

Standard and Special Items
  1. All chemicals used in the NFF are classified into two groups, namely Standard and Special items. Standard items refer to the chemicals that are supported and provided by the NFF. (See Tables 1 – 6 for a full list)
  2. Special items refer to any other chemicals that are not listed in Tables 1 – 6. The NFF is not responsible for the provision of those items.

Table 1 - Standard Photoresists

Item Photoresist Applications and Characteristics
PR-1 HPR504 g-line +ve PR, For normal thickness (1.0 ~ 1.5um)
PR-2 HPR506 g-line +ve PR, For thick film thickness (2 ~ 3um)
PR-3 SPR660 i-line +ve PR, For normal thickness (1.0 ~ 1.2um)
PR-4 FH 6400L g-line +ve PR, For normal thickness (1.0 ~ 1.2um)
PR-5 AZ9260 i-line +ve PR, For spray coating
PR-6 AZ4620 g-line +ve PR, For thick film thickness (~6um)
PR-7 AZ4903 g-line +ve PR, For thick film thickness (25 ~100um)
PR-8 AZ5206E 310-405nm dual-tone PR, For normal thickness (0.8 ~ 1.2um)
PR-9 AZ5214E 310-405nm dual-tone PR, For normal thickness  (1.3 ~  2um)
PR-10 AZ7908 i-line +ve PR, For normal thickness (0.6 ~ 0.8 um)

Table 2 - Standard Developers

Item Developer Applications and Characteristics
D-1 FHD-5 For PR-1 to PR-6; PR-8 to PR-10
D-2 AZ400K For PR-7

Table 3 – Standard Organic Solvents

Item Organic Solvent Applications and Characteristics
S-1 MS2001 +ve Photoresist stripper for PR1 to PR10
S-2 HMDS Adhesion promoter for positive photoresist processing
S-3 Acetone Cleaning, and lift-off
S-4 Isopropyl Alcohol (IPA) Cleaning
S-5 FH-ER Back and front side rinsing
S-6 MEK For spray coating
S-7 PGMEA For spray coating and photoresist dilution

Table 4 – Standard Acids

Item Acid Applications and Characteristics
A-1 Acetic Acid For Aluminum etch
A-2 Hydrochloric Acid (HCI) For RCA2 and decontamination
A-3 Phosphoric Acid For Nitride removal and Aluminum etch
A-4 Sulfuric Acid For photoresist stripping, and piranha clean
A-5 Nitric Acid For Aluminum etch
A-6 777 Pad Etch For etching Silicon Dioxide
A-7 Freckle Etch For Silicon residue removal
A-8 CEP-200 For Chrome etch
A-9 Hydrofluoric Acid (HF) For Oxide etch, and piranha cleaning
A-10 Buffered Oxide Etchant BOE For Oxide etch

Table 5 – Standard Bases

Item Base Applications and Characteristics
B-1 Ammonium Hydroxide For RCA1
B-2 Sodium Thiosulphate For neutralization of Potassium Iodide (KI) solution
B-3 Tetramethlammonium Hydroxide 25% (TMAH) For Silicon etch (used at wetstation G and J only)

Table 6 – Miscellaneous

Item Miscellaneous Applications and Characteristics
M-1 Hydrogen Peroxide (H2O2) For cleaning and photoresist stripping
M-2 Potassium Hydroxide (KOH) Pellet For Silicon etch
M-3 Potassium Iodide For Gold etch etc.
M-4 Iodine For Gold etch