In thin-film work, as in any field involving the extensive use of chemicals, the potential toxicity of materials should always be carefully considered. While most materials commonly used in thin-film applications are relatively safe, there are instances where distinctly hazardous substances must be handled.
It is prudent for thin-film workers to investigate the potential toxicity of a material before using it. The technical literature on thin films, typically focused on physical and chemical properties, often omits discussion of toxicity.
For instance, thorium fluoride, oxyfluoride, and oxide are widely discussed in the literature, but their radioactivity went unacknowledged for a long time. Nowadays, the hazards associated with these materials are well-recognized, and they are being gradually phased out, though some high-power infrared applications still require their use. Similarly, certain thallium salts, which are effective in the far infrared, are particularly toxic.
Manufacturers’ literature is becoming an increasingly valuable source of information on material toxicity, and in cases of uncertainty, consulting the manufacturer is essential. While toxic materials remain sealed in their containers, the risk is minimal.
However, as soon as the container is opened, the potential for material escape introduces significant danger. A primary goal when using toxic materials is to confine them to a well-defined space where appropriate precautions can be implemented.
If material escapes this space and creates dangerous concentrations outside, accidents may become unavoidable. In such cases, the entire laboratory might need to be considered a danger zone, necessitating special precautions, including extensive cleaning protocols and possibly requiring personnel to wear protective clothing and respirators.
To mitigate risks, machines used in production can be isolated from the rest of the workspace with dust-containment cabinets equipped with air circulation and filtration systems. During the thin-film process, most evaporated material typically deposits as a coating inside the machine or on jigs and fixtures, often forming a powdery residue. The greatest danger arises during subsequent cleaning, particularly when solvents and cleaning fluids with harmful vapors are used.
A sound rule for working with hazardous chemicals is to minimize the total quantity stored on the premises, especially the amount kept outside of safe storage. This practice not only limits the potential scale of disasters but also reduces the likelihood of leaks, even in the absence of other precautions. Additionally, it alleviates psychological stress related to handling dangerous substances.
It is important to note that many poisons act cumulatively. While small doses received during brief experiments may seem harmless, repeated exposure over several years can cause irreparable harm. For this reason, research workers may safely conduct occasional experiments with hazardous processes, but production workers—who may operate these processes daily for extended periods—require stringent safety standards. The production environment must prioritize worker safety, ensuring precautions are thorough and clearly communicated without inducing unnecessary alarm.
In emergencies, laboratories may need to be evacuated quickly. To facilitate this, hazardous materials should be securely contained, and their locations clearly documented. Proper housekeeping is essential. Thin-film workers in industrial settings should ensure that the medical officer is informed about the materials in use so that necessary precautions are in place before any issues arise.
Legal requirements for handling hazardous materials exist, but they may not always represent sufficient precautionary measures. It is advisable to apply the same rigorous safety protocols as those observed in chemical laboratories, even when materials are not explicitly classified as dangerous.
