Abstract:
A front opening unified pod for preventing the contamination of wafers due to outgassing. The front opening unified pod includes a front opening unified pod body and a cleaning apparatus. The front opening unified pod has an opening section and a base plate within the opening section and the base plate facing each other. The cleaning apparatus has at least an air-blasting element installed inside the front opening of the unified pod body. An air supplying system connected to the air-blasting element provides a stream of air.

Description:
BACKGROUND OF INVENTION 
   1. Field of Invention 
   The present invention relates to a semiconductor fabrication process and equipment. More particularly, the present invention relates to a front opening unified pod and associated method for preventing outgassing pollution. 
   2. Description of Related Art 
   Following the rapid increase in the level of integration for semiconductor devices, accuracy in dimension as well as material composition in each fabricating step has become increasingly important. Any minor error or pollution may lead to serious production loss or scrapping of a large quantity of wafers. 
   In semiconductor production, the processing station used for fabricating semiconductor devices typically includes a plurality of modules (for example, processing transport storage/safety link/gaseous reactant). In addition, the processing station may include a wafer transfer system for transporting wafers between various processing modules and the storage modules. In general, wafers are retrieved from a wafer carrier using a specially designed robotic blade and transferred to a processing chamber for a reaction. After the reaction, the wafer is transferred from the reaction chamber back to the wafer carrier so that a subsequent processing step can be initiated. 
   A conventional 8-inch wafer uses a type of wafer carrier called a standard mechanical interface (SMIF). However, as manufacturing technology continues to improve, the size of wafer that can be processed has increased to 12 inches. To accommodate larger wafers such as the 12-inch wafers, a specially designed wafer carrier called the front opening unified pod (FOUP) has been developed. The FOUP has an air-sealed chamber for holding wafers so that dust particles suspended in the air are prevented from polluting the wafers. When wafers need to be loaded into a piece of processing equipment, the door of the FOUP is opened so that a robotic blade is permitted to pick up a wafer inside the sealed chamber. 
     FIG. 1  is a top view of a conventional wafer-processing semiconductor fabrication station. As shown in  FIG. 1 , the processing station  100  includes a reaction chamber  102 , a load-locking area  104 , a mini-environment area  106 , a couple of robotic blades  108 ,  110  and a front opening unified pod base  112 . 
   Before carrying out a reaction process, the front opening unified pod  114  needs to be secured tightly to the front opening unified pod base  112 . To transfer wafers into the reaction chamber  102 , the robotic blade  108  inside the mini-environment area  106  is used to pick up a wafer inside the front opening unified pod  114  and then the wafer is downloaded onto a wafer boat  116  inside the load-locking area  104 . Thereafter, the robotic blade  110  is used to transport the wafer boat  116  into the reaction chamber  102 . After the processing reaction, the robotic blade  110  is again used to move the wafer boat  116  out and then the robotic blade  106  is again used to transfer the wafer inside the wafer boat  116  into the front opening unified pod  114 . The aforementioned steps are repeated until all the wafers inside the front opening unified pod  114  have been processed. 
   In the aforementioned process, a single wafer is reacted each time. However, most front opening unified pods are capable of holding a few tens of wafers. Hence, it takes some time to process the whole batch of wafers inside the front opening unified pod. If the processed wafers inside the front opening unified pod generate some outgassing, the gas (for example, phosphene) that diffuses out of the wafer may fill up the entire space within front opening unified pod leading to some contamination of the untreated wafers. Through such contamination, yield of the processing reaction will drop. 
   SUMMARY OF INVENTION 
   Accordingly, one object of the present invention is to provide a front opening unified pod and associated method for preventing wafer pollution due to outgassing so that the product yield is increased. 
   To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a front opening unified pod capable of preventing outgassing pollution. The front opening unified pod includes at least a front opening unified pod body and a cleaning apparatus. The front opening unified pod body has an opening section and a base plate. The base plate and the opening section face each other. The cleaning apparatus includes at least an air-blasting element set up inside the front opening unified pod body and an air supplying system connected to the air-blasting element to provide a continuous stream of air on demand. 
   The air-blasting element is set up on the base plate. The air-blasting element can be an air filter or a nozzle. The air-blasting element may blow out inert gas or nitrogen. 
   In this invention, a cleaning apparatus is installed on the sidewall of the base plate inside the front opening unified pod facing the opening section. The air ejected from the cleaning apparatus carries any gases diffused from the wafer away from the front opening wafer pod and hence prevents the pollution of unprocessed wafers. Furthermore, the front opening unified pod has a very simple design and hence requires no major alteration of the processing station and incurs no major cost. In addition, the front opening unified pod of this invention can be mounted or dissembled with ease so that its application is convenient. Moreover, the air-blasting element has a filtering action for maintaining the interior of the front opening unified pod at a definite level of cleanliness. 
   This invention also provides a method of preventing wafer pollution due to the outgassing of processed wafer inside a front opening unified pod. First, a plurality of wafers is loaded into a front opening unified pod having a cleaning apparatus capable of producing a stream of air therein. Thereafter, an unprocessed wafer is transferred to a reaction chamber and then the wafer is processed. After that, the processed wafer is returned to the front opening unified pod. The aforementioned steps are repeated until all the wafers inside the front opening unified pod are processed. All through the processing operations, the cleaning apparatus keeps blowing a jet of air out so that the air inside the front opening wafer pod is constantly flushed out and thus preventing the unprocessed wafer from being contaminated. 
   The cleaning apparatus includes at least an air-blasting element set up inside the front opening unified pd pod body and an air supplying system connected to the air-blasting element to provide a continuous stream of air on demand. The air-blasting element is set up on a base plate inside the front opening unified pod. The air-blasting element can be an air filter or a nozzle. The air-blasting element may blow out inert gas or nitrogen. 
   In this invention, the cleaning apparatus is used to carry the gases diffused from the processed wafer away from the front opening unified pod throughout the processing period. Hence, the unprocessed wafers inside the front opening unified pod are prevented from any contamination. Furthermore, the front opening unified pod has a very simple design and hence requires no major alteration of the processing station and incurs no major cost. In addition, the front opening unified pod of this invention can be mounted or dissembled with ease so that its application is convenient. Moreover, the air-blasting element has a filtering action for maintaining the interior of the front opening unified pod at a definite level of cleanliness. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a top view of a conventional wafer-processing semiconductor fabrication station. 
       FIG. 2  is a schematic three-dimensional view of the structure of a front opening unified pod according to this invention. 
       FIG. 3  is a top view showing a wafer-processing semiconductor fabrication station that incorporates a front opening unified pod according to this invention. 
   

   DETAILED DESCRIPTION 
   Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     FIG. 2  is a schematic three-dimensional view of the structure of a front opening unified pod according to this invention. As shown in  FIG. 2 , the front opening unified pod  200  includes a front opening wafer pod body  202  and a cleaning apparatus  204 . The cleaning apparatus  204  includes, for example, a plurality of air-blasting elements  206   a  to  206   d , an air supplying system  208  and a set of pipelines  210  and  212 . 
   The air-blasting elements  206   a  to  206   d  are set up inside the front opening unified pod  202  such that the air-blasting elements  206   a  and  206   b  are spread out alternately along the left and right side of a base plate  202   b  facing the opening  202   a . For example, the air-blasting elements  206   a  and  206   b  are set up on one side of the base plate  202   b  with a distance between the two. Similarly, the air-blasting elements  206   c  and  206   d  are set up on the other side of the base plate  202   b  with a distance between the two. However, the pair of air-blasting elements  206   a ,  206   b  alternates in height level with the pair of air-blasting elements  206   c ,  206   d . The air-blasting elements  206   a  to  206   d  are, for example, air nozzles or air filters fabricated using resinous or ceramic material. The air blowing out of the air-blasting elements  206   a  to  206   d  preferably produces a laminar flow  216  so that the gases diffusing from processed wafers  214  are blown away smoothly. In addition, the air blown out from the air-blasting elements  206   a  to  206   d  also purges any impurities suspended in the air inside the front opening unified pod  200 . The air from the air-blasting elements  206   a  to  206   d  is provided by an air supplying system  208  such as a clean compressed air tank or an inert gas tank (that holds nitrogen, helium, neon, argon, krypton or xenon). The pipelines  210  and  212  connect the air-blasting elements  206   a  to  206   d  to the air supplying system  208 . The pipeline  210  connects the two air-blasting elements  206   a  and  206   b  while the pipeline  212  connects the two air-blasting elements  206   c  and  206   d.    
   To operate the front opening unified pod  200 , the air supplying system  208  is turned on to provide a constant flow of air (for example, gaseous nitrogen) into various air-blasting elements  206   a  to  206   d  through the pipelines  210  and  212 . The air flowing out of the air-blasting elements  206   a  to  206   d  is filtered before going into the front opening wafer pod  200 . Furthermore, the air from the air-blasting elements  206   a  to  206   d  creates a laminar flow inside the front opening unified pod  200  so that any diffused gases from the processed wafer are flushed out. In other words, a high degree of cleanliness is maintained inside the front opening wafer pod  200 . 
   In the aforementioned embodiment of this invention, a total of four air-blasting elements are used. However, the actual number of air-blasting elements should depend on the actual design. In addition, the air-blasting elements are set up on the left and right side of the base plate facing the opening of the front opening unified pod body. Obviously, the air-blasting elements can also be set up on the top and the bottom side of the base plate or some other positions. Furthermore, the air-blasting elements can even be installed all over the base plate. 
     FIG. 3  is a top view showing a wafer-processing semiconductor fabrication station that incorporates a front opening unified pod according to this invention. As shown in  FIG. 3 , the processing station  300  includes a reaction chamber  302 , a load-locking area  304 , a mini-environment area  306 , a couple of robotic blades  308 ,  310 , a front opening unified pod base  312  and a front opening unified pod  314 . The front opening unified pod  314  is set up on the front opening unified pod base  312  and a cleaning apparatus  316  is installed inside the front opening unified pod  314 . 
   To transfer wafers into the reaction chamber  302 , the robotic blade  308  inside the mini-environment area  306  is used to pick up a wafer inside the front opening unified pod  314  and then the wafer is downloaded onto a wafer boat inside the load-locking area  304 . Thereafter, the robotic blade  310  is used to transport the wafer boat into the reaction chamber  302 . 
   After the processing reaction, the robotic blade  310  is again used to move the wafer boat out of the reaction chamber  302  and then the robotic blade  308  is again used to transfer the wafer from the mini-environment area  306  into the front opening unified pod  314 . The aforementioned steps are repeated to bring all the unprocessed wafers to the reaction chamber  302  and return all processed wafers back to the front opening unified pod  314 . Throughout the period from the transport of the first unprocessed wafer to the reaction chamber  302  to the return of the last processed wafer to the front opening unified pod  314 , the cleaning apparatus  316  is turned on. Thus, air from the air supplying system  316   c  carried by the pipeline  316   b  is blown into the front opening unified pod  314  via the air-blasting elements  316   a . When outgassing does occur in the processed wafers, the diffused gas (for example, phosphene) from the wafers is blown out of the front opening unified pod  314  by the air from the air-blasting elements  316   a . Therefore, the unprocessed wafers inside the front opening unified pod  314  are prevented from contamination leading to a drop in product yield. 
   In this invention, a cleaning apparatus is installed to carry any gases diffused from the processed wafer away from the front opening unified pod throughout the processing period. Hence, the unprocessed wafers inside the front opening unified pod are prevented from any contamination. 
   Furthermore, the front opening unified pod has a very simple design and hence requires no major alteration of the processing station and incurs no major cost. 
   In addition, the front opening unified pod of this invention can be mounted or dissembled with ease so that its application is convenient. Moreover, the air-blasting element has a filtering action for maintaining the interior of the front opening unified pod at a definite level of cleanliness. It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.