Fluent material handling – with receiver or receiver coacting mea – With signal – indicator – recorder – inspection means or exhibitor
Reexamination Certificate
2000-06-09
2001-07-31
Douglas, Steven O. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
With signal, indicator, recorder, inspection means or exhibitor
C141S098000, C141S065000
Reexamination Certificate
active
06267158
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sealed container, a storage apparatus, an electronic part conveyance system for storage or conveyance of an electronic part and a method of storage and conveyance of an electronic part in a process of production of a semiconductor device, a liquid crystal display device, a magnetic disk, etc., more particularly relates to a sealed container, a storage apparatus, and an electronic part conveyance system and a method of storage and conveyance of an electronic part able to inhibit formation of a native oxide film on the surface of a silicon wafer.
2. Description of the Related Art
In the process of production of a semiconductor device, the wafer is washed and dried before treatment such as oxidation and film formation. Also, when moving a wafer to a different treatment system or when storing a wafer temporarily between production steps, the wafer is usually exposed to the atmosphere in a clean room. Under the above situation, a thin native oxide film of as much as several nm grows on the surface of the wafer.
As factors affecting the growth rate of the native oxide film, the concentration of oxygen, concentration of moisture, temperature, and, in addition, the composition and surface conditions of the wafer can be mentioned.
Along with the miniaturization and higher integration of semiconductor devices, the effect of the thin native oxide film on the characteristics of semiconductor devices has increased and even a native oxide film having a thickness of about 0.5 nm is now being considered a problem. Especially, when forming a refractory metal silicide on a polysilicon electrode or when forming a silicide on the surface of source/drain regions and other impurity diffusion layers (SALICIDE; self-aligned silicide process), any native oxide film present becomes an obstacle to forming a uniform silicide. Also, if a native oxide film having a thickness of more than 0.5 nm is present, it influences the dielectric breakdown voltage of a gate oxide film.
Devices for performing a washing treatment on the wafer in a nitrogen gas atmosphere to inhibit growth of such a native oxide film or deposition of organic material etc. are for example described in Japanese Unexamined Patent Publication (Kokai) No. 3-242932, Japanese Unexamined Patent Publication (Kokai) No. 4-124825, Japanese Unexamined Patent Publication (Kokai) No. 5-160095, and Japanese Unexamined Patent Publication (Kokai) No. 6-181191.
However, according to these prior arts, although the washing process is performed in a nitrogen gas atmosphere and the growth of the native oxide film is inhibited, after the washing, the wafer is exposed to the atmosphere and then stored in a carrier box. After this, the inside of the carrier box is purged with nitrogen gas and the wafer is moved to the equipment of the next process under conditions where the growth of the native oxide film is inhibited. Therefore, there has been a problem that the native oxide film grows when the wafer is moved between the treatment equipment and the carrier box.
Therefore, several apparatuses for inhibiting the growth of a native oxide film on a wafer by performing all the conveyance between treatment devices in a nitrogen gas atmosphere have been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. 5-82622 discloses a mechanical interface, comprising a body casing of a wafer treatment device for storing the wafer treatment device and filled with clean air and a carrier box (pod) able to engage with the body casing air-tightly, enabling the inside of the pod to be filled with high purity nitrogen gas each time a pod is set at the body casing.
Also, Japanese Unexamined Patent Publication (Kokai) No. 10-64861 discloses a wafer washing apparatus enabling all of the conveyance from a washing treatment to a treatment device of the next step to be performed in an inert gas, preferably, in a nitrogen gas atmosphere, and a method of washing a wafer using this apparatus. This method of washing first attaches a carrier box of a wafer to a treatment box containing a wafer washing unit and seals the inside of the treatment box and the carrier box air-tightly by the casings of the two boxes. In the air-tight state, a bottom plate of the carrier box is moved in the treatment box using an elevator in the treatment box. Due to this, the wafer is loaded in the treatment box in a nitrogen atmosphere. The wafer is unloaded by the reverse procedure.
According to this washing method or apparatus, the wafer is no longer exposed to the atmosphere after the wafer is washed and until conveyed to the apparatus of the next production step, so the growth of a native oxide film due to the oxygen and moisture in the atmosphere can be inhibited.
Further, Japanese Unexamined Patent Publication (Kokai) No. 10-321714 discloses a conveyable sealed container, for a wafer used during the process of production of a wafer, which is able to completely replace the gas inside the container in an extremely short time and an atmosphere replacement device for a sealed container and a method of replacing an atmosphere. This conveyable sealed container has a plurality of vent holes along facing inner sides of the casing. When nitrogen is supplied, a laminar flow of nitrogen is formed in the container. Therefore, the gas to be replaced is efficiently exhausted and the gas being supplied (nitrogen) fills the container in an extremely short time.
According to the apparatuses or the methods described in the above Japanese Unexamined Patent Publication (Kokai) No. 5-82622, Japanese Unexamined Patent Publication (Kokai) No. 10-64861, and Japanese Unexamined Patent Publication (Kokai) No. 10-321714, it is possible to inhibit the growth of the native oxide film on a wafer when moving, conveying, or temporarily storing the wafer in the process of production of the wafer.
However, according to the above conventional apparatuses or methods, it is difficult to make completely air-tight the joinder between the part accommodating the wafer treatment device (for example, the above described body casing or treatment box) and the conveyable container (for example, the above described carrier box or container).
For improving the air-tightness of the joinder, the material of the joinder, comprised of metal, plastic, etc., is mechanically polished or otherwise treated or the joinder is achieved by vacuum adhesion or mechanical clamping via an O-ring or other packing.
Even by these methods, the center line mean roughness of the surface at the joinder is for example about several 10 &mgr;m. It is difficult to eliminate the roughness of the surface microscopically. Therefore, a slight leak occurs. Also, when these apparatuses are used, since vacuum exhaust and gas replacement are repeated, if fine particles detach from the surface of the joinder due to the change of the inside pressure or an effect of the gas flow, the air-tightness of the join will decline further.
Therefore, even if the container in which the wafer is held is filled with for example high purity nitrogen as an inert gas to decrease the concentration of oxygen and concentration of moisture in the container, the concentration of oxygen and the concentration of moisture will increase along with the elapse of time.
FIG. 5
shows an example of the change of the concentration of oxygen and the concentration of moisture in a sealed container along with the elapse of time. As shown in
FIG. 5
, if the container is sealed and held after the concentration of oxygen and the concentration of moisture are made about 10 ppm, both when that the joinder part is plastic and is aluminum, the concentrations of oxygen and moisture remarkably increase after the elapse of about one week. As described above, even if a wafer is stored in a sealed container in the state where the concentrations of oxygen and moisture are lowered, the conditions are present for easier growth of a native oxide film along with time.
To prevent this, there is the method of continuously passing a lar
Douglas Steven O.
Kananen Ronald P.
Rader Fishman & Grauer
Sony Corporation
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