Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2000-08-23
2003-08-05
Gordon, Paul P. (Department: 2121)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S109000, C700S110000, C702S084000, C438S005000
Reexamination Certificate
active
06604012
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 1999-46227 filed on Oct. 23, 1999, which is hereby incorporated by reference in its entirety for all purposes.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for dispatching lots and an apparatus for the same, and more particularly to a method for dispatching lots in which processing equipment and/or processing conditions in a succeeding process are variably arranged according to the result of a preceding process, in a semiconductor manufacturing condition in which a plurality of processes are sequentially performed with respect to a same lot, and an apparatus for the same.
2. Description of the Related Art
Generally, semiconductor integrated circuit devices using a wafer are manufactured by a number of processes such as diffusion, photo, etching, oxidation, thin film, and metal processes. The order of performing the above-mentioned processes are determined by the kind of semiconductor integrated circuit device to be manufactured, and in a predetermined processing order, the results of the preceding process directly or indirectly influences the result of the succeeding process. For example, the accuracy of the photo process significantly affects the quality of a wafer obtained by the subsequent etching process.
Further, because semiconductor integrated circuit devices are mass-produced, a plurality of identical processing equipment simultaneously performing the same functions are commonly utilized in each manufacturing process.
In such manufacturing conditions of the semiconductor integrated circuit devices, when a wafer lot dispatches from a preceding process to a succeeding process, maintaining quality and production rate become an important factor to be considered. Especially, in the case when the result of a preceding process directly influences its succeeding process, a lot dispatching which uses to its highest degree the quality relationship between the preceding and succeeding processes contributes to the improvement of quality and production rate.
In view of the lot dispatching process, it is important to determine to which equipment among a plurality of equipment in a succeeding process a wafer lot should be dispatched, as some equipment in the succeeding process maintain the level of quality obtained in a preceding process while others deteriorate or improve the quality of the wafers. Further, even identical processing equipment lack consistency in their efficiency and performance, thus resulting in inconsistent processing quality. Especially, since wafers are generally finely processed in the semiconductor manufacturing processes, a minute difference in the efficiency and performance by the equipment in succeeding processes drastically influences the quality of wafers. Thus, dispatching a wafer lot to a succeeding process having a number of processing equipment is an important matter to be considered.
In relation to the lot dispatching, it should be further noted that the most suitable processing conditions should be applied for improving the quality and productivity of wafers in a succeeding process. Respective processes have their own processing conditions to be applied for processing the wafer lots. One processing condition is a combination of various processing condition elements such as pressure, temperature, and amount of the gas. As such, the quality of wafers obtained from a process is affected largely by suitability of the processing conditions applied in the process. Hence, the processing conditions of respective processes need to be most suitably applied to obtain best quality of the wafers.
FIG. 1
shows the concept of a lot dispatching commonly applied in a semiconductor manufacturing line. Such conventional lot dispatching is classified as fixed recipe. In such lot dispatching, lots waiting to be dispatched to a succeeding process from a preceding process are dispatched at random to one of the processing equipment designated from No.
1
to No. k without particularly considering the relationship between the results of the preceding process and/or the performance characteristics of the succeeding processing equipment. Such conventional random dispatching relies on the experience of engineers, which can not ensure consistently good quality. Further, in the conventional lot dispatching method, the processing error of the preceding process is not systemically compensated or reduced in the succeeding process.
Further, in determining processing conditions of a succeeding process, a single fixed processing condition which does not take into account the relationship between the result of the preceding process and the manufacturing conditions required in the succeeding process has been conventionally implemented. Also, in the conventional method, if it is evaluated that the existing processing condition deteriorates quality or productivity, an engineer analyzes the cause and makes appropriate changes in the processing condition. However, control of the processing conditions is not systematically accompanied in the conventional semiconductor manufacturing process.
As a result, because of the absence of the systematic analysis with respect to the relation between the results of the preceding process and the equipment and processing conditions of the succeeding process needed for improving quality and productivity, a most suitable lot dispatching method cannot be obtained. And, due to the efficiency limit of the processing equipment and the dispersion (including the accidental dispersion) of the input elements of the preceding and succeeding processes, it is difficult to obtain a predictable constant quality and productivity. Thus, defect rate of a wafer lot tends to be enlarged as the wafer lot is processed by succeeding processes. Further, conventionally, the selection of the processing equipment and the processing condition depended on the trial and error judgement of engineers, and frequent replacement of engineers or processing equipment resulted in more inconsistencies in the manufacturing process, as can be understood in view of FIG.
1
. For example, when critical dimension (CD) is utilized to analyze qualities of wafer lots in a succeeding process, inferior quality caused by the succeeding process is determined to be greater than its preceding process.
A conventional technology related to a lot dispatching method is disclosed by U.S. Pat. No. 5,841,677. The patent discloses an optimization-based dispatching rule that can be used in manufacturing a semiconductor integrated circuit using equipment that needs a batch run and/or long processing time. According to the patent, when an expected waiting time which is needed for completing the preceding process with respect to a WIP lot is longer than the allowed waiting time, the lot is instantly processed in the succeeding process. In the opposite case, WIP lots are not dispatched until the allowed lots of the preceding process arrive, rather they are dispatched after the lots are merged together with the allowed lots to become a batch.
However, the patent only discloses the fact that the preceding processing equipment is efficiently used by the dispatching rule and that the waiting time should be minimized for dispatching, and does not refer to the systematic approach about the relationship between the result of the preceding process and the equipment and process conditions of the succeeding process in regard to maintaining consistent quality and productivity.
SUMMARY OF THE INVENTION
The present invention is therefore directed to a method of dispatching lots which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
It is a first object of the present invention to provide a lot dispatching method and system for dispatching a respective lot to a succeeding processing equipment most suitable for maintaining consistent quality, according to the systematic analytic result o
Chae Hee-Sun
Cho Dae-Sik
Kang Hee-Se
Kim Seok-Hyun
Kwak Doh-Soon
Gordon Paul P.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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