During the transport of sawn wafers, or of wafers generally, which are optionally separated into individual chips and arranged on a flexible carrier film, for example a sawing film, of a wafer frame, in conventional wafer transport containers, also referred to as wafer boxes or multi-frame shippers, damage to the wafers can occur.
The damage may be induced for example by touch. Here, for example, organic and/or inorganic contamination of the wafer surface, for example as a result of touching during transport, can lead to electrical faults or bonding problems. As a further consequence, inorganic contaminants such as ions can also lead to yield losses. A further risk point resulting from the wafer being touched may be scratches or imprints, which can adversely affect reliability.
Furthermore, the damage may be induced for example by vibrations and/or shocks. Owing to a flexibility of the sawing film, vibrations during transport can be transmitted to said sawing film. The vibrations induced (in the sawing film) can result in edges of the separated chips striking one another, resulting in so-called chipping, which can result in reliability problems. Likewise, there is the risk of chip losses resulting for example from slow detachment of the chips from the sawing film.
Touch prevention has hitherto been achieved for example by means of cassette-like vertical frame shippers (vertical in this context means that the wafers are arranged vertically in relation to a standing surface of the frame shipper) with a large slot spacing or horizontal frame shippers (horizontal means that the wafers are arranged horizontally in relation to a standing surface of the frame shipper) with the use of wafer intermediate inserts, or through the use of individual wafer boxes.
In the case of vertical frame shippers, the slot spacing is however not actually large enough that touch prevention can be 100% guaranteed.
In the case of horizontal frame shippers, some mechanical damage to the wafer surfaces has hitherto been partially prevented through the use of wafer intermediate inserts composed of paper or plastics-coated paper or by means of plastics films.
The use of individual wafer boxes could possibly solve the problem of vibrations, but would be very expensive with regard to packaging material and/or transportation costs, and furthermore would not be production-friendly with regard to a logistical process. A further effect would be an absence of automated handling of the wafers, and an increased storage volume of the packaged goods in-house and for the customer.
All of these already existing solutions are firstly very expensive and secondly do not afford one hundred percent protection of the wafer surface during transport. Furthermore, all wafer intermediate inserts comprise ionic contaminants or ionic components (for example sodium (Na) and/or potassium (K)) which, in the case of certain technologies, can lead to problems.
If the wafers (for example mounted on the wafer frame) are shipped to the customer or in-house having been packaged in the conventional manner in wafer boxes, round foam blanks are typically used to fill the boxes. These can lead to additional costs, for example inter alia in the so-called “bare die” business sector, that is to say in the marketing of unhoused, uninstalled chips (also referred to as dies), because the round foam blanks are normally not reusable.
Furthermore, particles from the foam can contaminate the wafer surface. Furthermore, the foam may release organic gases which, after removal from storage, can give rise to problems during further processing of the wafers (for example in a die bonding process).
Thus, during conventional transport, the filling of the wafer boxes with round foam blanks can result in a risk of particle or chemical contamination and in increased costs.