“Cosmetics As a Potential Source of Particulate Contamination in the Clean Room”, 1993 ():
Since the early 1980’s, all major semiconductor manufacturers invoked the “no-cosmetics” policy. This had some severe psychological effects on the female workforce which comprised ~90% of the wafer fab employees. In the interest of business (as well as wafer yield), this policy was upheld. This paper discusses some of the psychological responses by the fab operators. Several experiments were performed which indicated that cosmetics presented a source of particulate contamination but at the same time cosmetics can prevent skin flaking. However, the use of cosmetics by both men and women could be detrimental to the cleanroom even when the personnel may not actually be wearing the cosmetics in the clean room. This paper is to raise the level of awareness to the problem of cosmetics in the clean room and to offer some clean room protocol procedures that can minimize and possibly eliminate much of the human contaminants. Cosmetics in the clean room is not restricted to the female workforce. Men are also guilty of using cosmetics while in the clean room. This paper examines this problem and suggests cleanroom guidelines.
Background: The space program requires 100% electronic uptime on all major systems. In 1985 one of the shuttle missions was scrubbed because mission guidelines did not allow lift off with only 4⁄5 computers operational. The cost of the aborted mission was in excess of $30.83$101985 million and the cost of the removal and replacement of the defective component was ~$1,541,400.45$500,0001985. Failure analysis of the shuttle component found corrosion of the semiconductor metallization as a result of human contamination (spittle, in this particular instance).14 Similar accounts are described by FAA computers and banking computers failing for similar defects in their CPU IC’s.
The space shuttle incidence has caused NASA and FAA to personally audit prime semiconductor contractors. They found that 1–3% of all semiconductor devices had some form of human contamination. Since human-related contamination is more of a reliability issue, military specs are now in place to require all microcircuits to be chemically analyzed for any on-die contaminants prior to sealing.
…The second task was to develop experiments that could be repeated as often as necessary to illustrate that cosmetics were a serious source of contamination. The experiment was simply having operators with and without cosmetics performing simple wafer handling chores: wafer inspections at an inspection station next to the Aeronca particle monitor. This test was repeated several times per week, using different operators with different skin types. Figures 2 & 3 summarize the results of this testing. Both men and women were tested across all 3 fabs. In Figure 2, women of all skin types generated more particles when not wearing makeup. This would seem normal since nearly all cosmetics (or, more specifically, make-up) has a moisturizer base which keeps the skin less dry in the harsh conditions of the clean room. The one exception is that women classified as having oily skin flaked about the same, with or without cosmetics. This is because the skin will not slough off as much since the skin has its own built in moisturizing system, called keratin17. Similarly, women with dark skin tend to have less dryness because of the excess skin pigmentation which also acts as a moisturizer.
…Even cosmetics that are used to protect the skin find their way to the microcircuit (or other products relating to clean rooms). In an unrelated experiment in which Advanced Micro Devices was in the process of developing a new site-wide wafer fab protocol spec, the training department began dry-runs of the series of classes involving the new, more rigid clean room procedures. One of the classes involved selected wafer fab operators and the purpose was to demonstrate the proper method to put on the clean room attire. However, the gloves were treated with a phosphorescent powder (the same type used by the police to “lift” fingerprints). Some of the older operators could feel the powder but they passed it off as being part of a new style of glove. After all the participants were in their proper clean room attire (including the gloves), the trainer discussed various protocol rules with the operators. About a half hour later the trainer informed everyone that the gloves had been lightly dusted. One by one, each person stood in front of a full length mirror while the trainer scanned their body with a black light. With few exceptions, there were yellow fingerprints allover their smocks as well on unprotected areas such as their faces and arms. This test was to illustrate that human contamination can find its way to the work area even with all possible protective measures in force.
…Many of the contaminants in cosmetics are harmless to the wafer fab. But as this paper has illustrated, most cosmetics of all types contain chemicals and compounds that can be devastating to semiconductor processing. The EDS illustrations of Figures 4 through 9 show an abundance of easily ionized elements with low 1st ionization potential. The lower this potential, the easier it is for that element to combine with other elements. Also, Table 1 shows the common elements in body fluids (or skin tissue) which also have low first ionization potential. As in the case of the space shuttle where the defect was latent, that is, it occurred after the device had been tested and was in the field, many of the defects caused by cosmetics can also be latent. It is these defects for which we have more concern. The immediate defects are usually caught at the manufacturer’s facility or even at the subsystem level. Most of the highly ionized metallic elements can cause immediate damage such as metal shorts, breakdowns in the oxides, threshold shifts, and various resistance changes.
…To illustrate the effects of cosmetics on the parametric values of the semiconductors, several wafers were contaminated with after shave, talc, eye liner, lipstick, blush, mascara residue, moisturizer, and skin flakes/hair…These are just a few of the types of parameter changes that can occur when cosmetics (and cosmetics on skin) come in contact with a semiconductor device in the clean room.