| Method of optimizing seasoning recipe for etch process -> Monitor Keywords |
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  Method of optimizing seasoning recipe for etch processRelated Patent Categories: Data Processing: Generic Control Systems Or Specific Applications, Specific Application, Apparatus Or Process, Product Assembly Or Manufacturing, Particular Manufactured Product Or Operation, Integrated Circuit Production Or Semiconductor FabricationThe Patent Description & Claims data below is from USPTO Patent Application 20060293781. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10/652,403 filed on Aug. 29, 2003, which claims priority to Korean Application No. 2002-57194, filed on Sep. 19, 2002, the disclosures of which are incorporated herein by reference in their entirety. TECHNICAL FIELD OF THE INVENTION [0002] The present invention relates to a dry etching method for fabricating a semiconductor device, and more particularly, to a method of optimizing a seasoning recipe for a dry etch process. BACKGROUND [0003] As semiconductor devices become more highly integrated, the design rules are reduced. Thus, in a dry etch process, it is important to have a high etch selectivity and a high anisotropy to properly etch a wafer. Also, it is important to be able to reproduce the same etch for each wafer that passes through the dry etch process. [0004] In a dry etch process, the initial set of wafers that are processed can be spoiled when the dry etch processing chamber is not stabilized. In other words, if the ambient atmosphere within the chamber has not reached steady state, an unsteady etch rate can result. This problem also occurs after a series of wafers have been processed or the dry etch process remains idle for a period of time between etch processes. Thus, a "seasoning process" is performed to prevent these problems by using a test wafer before a main etch process. Here, "seasoning process" means a process of etching a test wafer before performing a main etch process in the same chamber. In a conventional method, a recipe for a seasoning process is the same as that of a main etch process. However, immediately after finishing the seasoning process, the ambient atmosphere in the chamber may still not be stabilized, which results in an unsteady etch rate in the main etch process. [0005] FIG. 1 is a graph showing experimental results obtained using a conventional dry etch process. In FIG. 1, the results of two test cases are shown. In case 1, a seasoning process was performed using a test wafer with an oxide layer in a dry etch chamber. Then, a main etch process was performed in the same chamber using a run wafer having a polysilicon layer and a tungsten silicide layer sequentially stacked on the wafer. Further, the run wafer included a hard mask pattern formed on the tungsten silicide layer. In the main etch process, the tungsten silicide layer was etched using the hard mask pattern by supplying Cl.sub.2 and SF.sub.6. An end-point detection time was determined as the time when the tungsten silicide layer was completely etched, as measured using an optical emission spectroscopy. Next, the polysilicon layer was etched by supplying HBr and O.sub.2. In a seasoning process (which was performed before the main etch process), a test wafer with an oxide layer was etched by supplying the same etch gases, under the same conditions and with the same sequences, as in the main etch process. [0006] In case 2, the same main etch process was used as in case 1. However, in the seasoning process of case 2, a test wafer having a polysilicon layer was etched. Further, the main etch recipe used in case 2 was identical with that of case 1. In case 1 and case 2, each of the main etches were repeatedly performed on multiple wafers of at least one lot. [0007] As illustrated in FIG. 1, with case 1, after the seasoning process was performed with respect to the test wafer with the oxide layer, an end-point detection time in the first main etch process was determined to be greater than the end-point detection times of subsequently processed wafers. As subsequent wafers were processed through the main etch process, the end-point detection time gradually decreased and stabilized. Furthermore, in case 2, after performing a seasoning process with respect to the test wafer with the polysilicon layer, an end-point detection time of a first main etch process was determined to be less than the end-point detection times of subsequently processed wafers. As subsequent wafers were processed through the main etch process, the end-point detection time gradually increased and stabilized. Thus, as is apparent from FIG. 1, although a seasoning process was performed in the conventional dry etch process with respect to a test wafer by using the same etch recipe with that of the main etch process, the conventional method did not provide a constant etch rate for the main etch process. [0008] Therefore, a need exists for a reproducible dry etch process that reduces the number of wafers that are spoiled during the start-up of a dry etch process. SUMMARY OF THE INVENTION [0009] The present invention is directed to methods for providing a reproducible dry etch process by optimizing a seasoning recipe. According to one embodiment of the present invention, a method is provided for determining an optimized seasoning recipe for a dry etch process. The method comprises (a) selecting a critical value of reproducibility; (b) selecting a main etch recipe; (c) selecting a preliminary seasoning recipe; (d) etching a test wafer using the preliminary seasoning recipe in a dry etch chamber; (e) performing a main etch process for a plurality of run wafers in the dry etch chamber using the main etch recipe, and determining an end-point detection time of each run wafer; (f) determining an initial dispersion and a standard deviation using the determined end-point detection times; (g) comparing the initial dispersion to the critical value of reproducibility; and (h) selecting the preliminary seasoning recipe as a seasoning recipe for the etch process, if the initial dispersion is less than or equal to the critical value of reproducibility. In addition, the method comprises changing the preliminary seasoning recipe and repeating steps (c)-(h), if the initial dispersion is greater than the critical value of reproducibility. [0010] According to another embodiment of the present invention, the critical value of reproducibility is set to be proportional to the standard deviation. The critical value of reproducibility is 1 to 6 time(s) of the standard deviation. The initial dispersion is an absolute value of difference between an end-point detection time of a first run wafer and a third run wafer. The standard deviation is calculated by using end-point detection times of a fourth run wafer through at least a tenth run wafer. [0011] According to another embodiment of the present invention, the test wafer may include an oxide layer or a polysilicon layer formed on a substrate. The run wafer may include a polysilicon layer and a tungsten silicide layer which are sequentially stacked on a substrate. The end-point detection time is determined when the tungsten silicide layer is substantially or completely etched. The main etch recipe and the preliminary seasoning recipe use the same etch gas. In addition, the same etch gas may be a mixed gas of HBr and O.sub.2. Flow rates of the HBr and O.sub.2 may be changed when resetting a preliminary seasoning recipe. In yet another embodiment of the invention, a method for optimizing a seasoning recipe for a dry etch process comprises the steps of (a) selecting a preliminary seasoning recipe; (b) etching one or more test wafers using the preliminary seasoning recipe in a dry etch chamber and then performing a main etch process for a plurality of run wafers in the dry etch chamber using a main etch recipe to determine an end-point detection time of each run wafer; and (c) processing the end-point detection times of the run wafers to determine one or more optimization parameters; and (d) evaluating the optimization parameters to determine whether to (i) use the preliminary seasoning recipe as a seasoning recipe for the dry etch process or to (ii) modify the preliminary seasoning recipe and repeat steps (b)-(d) using the modified seasoning recipe. [0012] These and other embodiments, features, aspects, and advantages of the present invention will be described and become apparent from the following detailed description of the preferred embodiments when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is a graph showing experimental results obtained by performing a conventional dry etch process. [0014] FIG. 2 is a flow chart showing a method of optimizing a seasoning recipe according to an embodiment of the present invention. [0015] FIG. 3 is a graph showing experimental results obtained using a dry etch method with an optimal seasoning recipe, according to an embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0016] The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may be embodied in many different forms and nothing herein should be construed as any limitation to the scope of the invention. The embodiments described herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. [0017] FIG. 2 is a flow diagram illustrating a method for optimizing a seasoning recipe for a dry etch process according to an embodiment of the present invention. Initially, a critical value of reproducibility A is set (step 1). Preferably, the critical value of reproducibility A is proportional to a standard deviation of measured end-point detection times (as explained below), and preferably corresponds to about 1 to 6 times the standard deviation. Next, a main etch recipe is set (step 2). The main etch recipe means etch conditions such as kinds of etch gases, flow rates of etch gases, process pressure, process temperature and an etch sequence, which are used in the main etch process. [0018] Next, a preliminary seasoning recipe is set (step 3). The preliminary seasoning recipe can be modified on the basis of the main etch recipe. A preliminary seasoning process is then performed in a dry etch chamber using the preliminary seasoning recipe to etch about 1 to 2 test wafers (step 4). Continue reading... Full patent description for Method of optimizing seasoning recipe for etch process Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of optimizing seasoning recipe for etch process patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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