This invention relates to a clean transfer method and an apparatus therefor, and more particularly to a clean transfer method for transferring an object to be transferred (hereinafter referred to as "transferred object") required for fabricating and/or assembling a product associated with a semiconductor or the like while keeping an operating environment clean and free of contamination, and an apparatus therefor.
In general, a clean transfer system which has been conventionally practiced is constructed in such a manner as shown in FIGS. 1 and 2. More particularly, the system includes a room 100, which is divided into a maintenance chamber 102 and a clean chamber 104 through a partition 106. The maintenance chamber 102 is permitted to communicate with an ambient atmosphere and is provided therein with various processing sections (processing equipments) 108 used for precision film formation required in manufacturing of a semiconductor.
The clean chamber 104 is kept at considerable cleanness as high as Classes 100-10. The term "Class 100" refers to cleanness wherein the number of dust particles having a size of 0.5, .mu.m or higher per 1 ft.sup.3 is 100 or less and the term "Class 10" indicates. cleanness with the number of dust particles having the size of 0.5, .mu.m or higher per 1 ft.sup.3 is 10 or less. An airstream is downwardly introduced from a ceiling of the clean chamber 104 through filter 110 sufficient to ensure the cleanness between the Class 100 and Class 10 into the clean chamber 104, and then discharged from a perforated floor 112. A clean shuttle 114 is movably arranged in the clean chamber 104 and is kept at the cleanness between the Class 10 and Class 1. The term "Class 1" indicates the cleanness wherein the number of dust particles having a size 0.5, .mu.m or more per 1 ft.sup.3 is 1 or less. A transfer port of each of the processing sections 108 is permitted to communicate with the clean chamber 104 through an opening formed through the partition 106 and a peripheral area 116 around the opening is locally kept at cleanness between the Classes 10 and 1.
Delivery of a transferred object 118 such as a semiconductor wafer or the like between the clean shuttle 114 and the processing section 108, as shown in FIG. 2, is carried out by transferring the transferred object 118 from the clean shuttle 114 through the peripheral area 116 to a load lock chamber (preliminary vacuum chamber) 120, closing a shutter for the transfer port, evacuating the preliminary vacuum chamber 120 to a vacuum and then transferring the transferred object to a processing chamber (vacuum chamber) 122 of the processing section 108.
As another conventional clean transfer system, a multi-chamber system which is constructed as shown in FIG. 3 has been used. In the multi-chamber system, a single load lock chamber is commonly used for processing sections 124A, 124B and 124C for sputtering, CVD, etching and the like.
In the conventional clean transfer system shown in FIGS. 1 and 2, it is required that the clean chamber 104 is provided therein with a relatively increased internal space and kept at considerable cleanness as high as between the Class 100 to 10. Unfortunately, it is highly costly to keep the large clean chamber at such high cleanness as described above. Also, in the prior art, it is required to provide each of the processing sections 108 including the processing chamber 122 with the load lock chamber 120, thus, vacuum evacuation of the load lock chamber is indispensable, resulting in the processing section being complicated in structure. Further, the prior art fails to substantially isolate an interior of the clean shuttle 114 and the peripheral area 116 from suspended dust irrespective of an increase in cleanness. Furthermore, vacuum evacuation of the load lock chamber 120 and introduction of air thereinto which are carried out during delivery of the transferred object between the clean shuttle 114 and the processing section 108 cause a rapid variation in pressure, resulting in dust or any foreign matter such as moisture, impurity gas or the like being scattered in the processing section 108 to lead to pollution of the transferred object.
The multi-chamber system shown in FIG. 3 fails to increase the number of the processing sections arranged and provide arrangement of the system with an increased degree of freedom, and is troublesome in maintenance.