Abstract:
According to the present invention, a process of the present invention is performed with stagnated process gas in a chamber. The process comprises the steps of supplying process gas into a chamber, blocking process gas entry and exit from the chamber so as to stagnate the supplied gas therein, and performing the process. As a result, a process time can be significantly reduced, thereby maximizing yield and reducing the substantial amount of the process gas.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device using a diffusion process and an annealing process. 
     BACKGROUND OF THE INVENTION 
     In general, a diffusion process is performed to form a necessary layer and an annealing process is performed to recover crystalinity and stabilize physical property. During these processes, parameters such as temperature, gas, pressure, and reaction time are controlled to form a necessary layer. 
     In such a diffusion process, a desirable layer is formed in accordance with the kinds of gas and the thickness of the layer is decided in accordance with the reaction time. After process conditions such as temperature and pressure, are determined, a reaction gas is introduced to form a layer or to diffuse an impurity onto a layer. Since a conventional diffusion process is performed by introducing and simultaneously exhausting a gas (impurity source gas), this leads to a very long process time and a large amount of gas can be consumed. If the process is performed by raising internal temperature of the chamber, the gas is fast dissolved and the amount of dissolved gas increases to shorten the process time. However, as a semiconductor device structure has become highly integrated requiring a shallow junction, there is a limit to use this kind of method. 
     Recently, a PH 3  annealing process using a sheet-fed or a vertical furnace has been used to increase the capacitance of a semiconductor device. 
     FIG. 1 is a flow chart showing the steps of an annealing process in accordance with a conventional method for manufacturing a semiconductor device, and FIG. 2 is a diagram for depicting a conventional method for manufacturing a semiconductor device. 
     Referring to FIGS. 1-2, a conventional semiconductor device manufacturing process is performed by flowing a process gas. As shown in FIG. 2, the process gas is continuously supplied from a process gas supply apparatus  502  into a chamber  500  where a semiconductor manufacturing process is performed, and the supplied process gas is continuously exhausted from the chamber  500  through an exhausting apparatus  504 . That is, the conventional semiconductor device manufacturing process is performed with a first valve  510  installed on a supply line  506  combining the process gas supply apparatus  502  with the chamber  500 , and a second valve  512  installed on an exhausting line  508  combining the chamber  500  with the exhausting apparatus  504  being opened. 
     The conventional PH 3  annealing process, as shown in FIG. 1, includes the steps of loading a semiconductor wafer into a chamber (S 1000 ), setting process conditions in the chamber (S 1005 ), forming process gas flow (S 1010 ), performing an annealing process (S 1015 ), then, blocking process gas and purging the inside of the chamber (S 1020 ), dropping internal temperature of the chamber (S 1025 ), and unloading the semiconductor wafer from the chamber (S 1030 ) when the annealing process is completed. 
     FIG. 3 is a graph showing a difference between the semiconductor device capacitance acquired through an annealing process of FIG.  1  and the capacitance without an annealing process. 
     Referring to FIG. 3, the semiconductor device capacitance “A” acquired through the PH 3  annealing process is higher than the capacitance “B” acquired without the PH 3  annealing process. A conventional PH 3  annealing process is performed at a high temperature (about 750° C.) for 3 hours and uses PH 3  of 1.5 l/min. Accordingly, this PH 3  annealing process taking a long time, results in lower yield. The time for flowing process gas practically takes 50% and more out of total time for performing a conventional PH 3  annealing process. Since the process is performed by continuously supplying the process gas, a lot of the process gas can be wasted. That is, PH 3  of 270 l is used while performing one time of the annealing process. 
     Consequently, a conventional a semiconductor device manufacturing process has drawbacks such as a long process time, low yield, and waste of process gas. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method for manufacturing a semiconductor device which can reduce process time and the amount of process gas used. 
     According to the present invention, a method for manufacturing a semiconductor device by performing a predetermined process with respect to a predetermined object in a chamber by using process gas comprises the steps of supplying the process gas into the chamber, blocking the chamber so as to stagnate supplied process gas in the chamber, and performing the process. 
     According to the present invention, the step of performing the process further comprises the steps of determining whether the amount of the process gas in the chamber is less than a threshold and supplying more process gas into the chamber, if the process gas is less than the threshold, and then repeating the blocking step. 
     In the preferred embodiment, the process is a diffusion process or an annealing process. 
     A present invention process is performed by stagnating process gas in a chamber, so that a process time can be significantly reduced. As a result, it is possible to maximize yield and to substantially reduce the amount of the process gas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate the present invention and, together with the description, further serve to explain the principle of the invention and to enable those skilled in the pertinent art to make and use the invention. 
     FIG. 1 is a flow chart showing the steps of an annealing process in accordance with a conventional method for manufacturing a semiconductor device; 
     FIG. 2 is a diagram for depicting a conventional method for manufacturing a semiconductor device; 
     FIG. 3 is a graph showing difference between semiconductor device capacitance acquired through an annealing process of FIG.  1  and capacitance without an annealing process; 
     FIG. 4 is a diagram for depicting a method for manufacturing a semiconductor device in accordance with the present invention; 
     FIG. 5 is a schematic view of an annealing system applying a method for manufacturing a semiconductor device in accordance with the present invention; 
     FIG. 6 is a flow chart showing the steps of a method for manufacturing a semiconductor device in accordance with the present invention; and 
     FIG. 7 is a graph showing semiconductor device capacitance acquired through an annealing process of FIG. 6 applying a method for manufacturing a semiconductor device in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to accompanying drawings FIGS. 4-7. 
     FIG. 4 is a diagram illustrating a method for manufacturing a semiconductor device in accordance with the present invention. 
     Referring to FIG. 4, a semiconductor device manufacturing process is performed with stagnated process gas in a chamber  10 . After supplying the process gas from a process gas supply apparatus  12  into the chamber  10 , a first valve  20  installed on a supply line  16  and a second valve  22  installed on an exhausting line  18  are locked to stagnate the process gas supplied into the chamber  10 . When the process is ended, the process gas is exhausted from the chamber  10  by an exhausting apparatus  14 . In this regard, by stagnating the process gas in a chamber, high reaction efficiency of the process gas can be obtained. 
     The reactivity of the process gas, for example, increases during the diffusion or annealing processes, so that a process can be performed in a short period of time. Since the process is performed with stagnated process gas in the chamber  10 , the amount of the process gas stagnated therein may become lacking as time progresses. In order to remedy this drawback, the amount of the gas is measured and, if less than a threshold, more process gas is supplied to the chamber so as to continuously perform the process. 
     FIG. 5 is a schematic view of an annealing system applying a method for manufacturing a semiconductor device in accordance with the present invention. 
     Referring to FIG. 5, an annealing system  30  includes a chamber  40 , a tank  45 , and an exhausting apparatus  55  such as a booster pump and a dry pump. A mass flow controller  50  for controlling the amount of process gas supplied from the tank  45  into the chamber  40  and a first valve  65  are installed on a supply line  60  combining the chamber  40  with the tank  45 . A second valve  75  is installed on an exhausting line  70  combining the chamber  40  with the exhausting apparatus  55 . The annealing system  30  supplies process gases such as PH 3  from the tank  45  into the chamber  40 , for the annealing process. 
     FIG. 6 is a flow chart showing the steps of a semiconductor device manufacturing process in accordance with the present invention. 
     As shown in FIG. 6, a PH 3  annealing process using an annealing system  30  can apply a method of the present invention. Referring to FIGS. 5-6, this annealing process comprises the steps of loading a semiconductor wafer into a chamber  40  (S 100 ), setting internal process conditions of the chamber  40  (S 105 ), supplying process gas (PH 3 ) into the chamber  40  (S 110 ), blocking a supply line  60  and an exhausting line  70  to stagnate the process gas in the chamber  40  (S 115 ), performing an annealing process (S 120 ), purging the inside of the chamber  40  (S 200 ), dropping internal temperature of the chamber  40  (S 205 ), and unloading the semiconductor wafer from the chamber  40  (S 210 ) when the annealing process is ended. In particular, in accordance with the present invention, the process gas is supplied into the chamber  40  and then a first valve  65  and a second valve  75  are locked to stagnate the supplied process gas therein. That is, the present invention method is performed by stagnating the process gas in the chamber  40 . 
     FIG. 7 is a graph showing the semiconductor device capacitance acquired through an annealing process of FIG. 6 applying a method of the present invention. 
     This PH 3  annealing process is performed at about 750° C. for 30 minutes by using PH 3  of 1.5 l/min, so that the capacitance is equal to that of a conventional method, as shown in FIG.  7 . That is, a process time and the amount of process gas used can be significantly reduced compared to a conventional PH 3  annealing process. 
     As mentioned above, during the PH 3  annealing process of this invention, it is determined that whether the process gas stagnated in the chamber  40  is less than a threshold while performing the annealing process. If less than the threshold, additional process gas is then supplied into the chamber  40 . As a result, this process can be continuously performed. This is provided in case the amount of process gas is reduced and lacking in the chamber  10  as time progresses, because the present invention process is performed with stagnated process gas in the chamber. That is, the amount of the process gas in the chamber  10  is measured while performing a process and, if it is less than the threshold, more process gas is supplied to the chamber so as to continuously perform the process. Also, the interval of process gas resupply time can be set by a test. 
     As described above, since a process of this invention is performed with stagnated process gas in a chamber, a process time can be significantly reduced. As a result, it is possible to maximize yield and reduce the amount of the process gas. 
     While the invention has been described with respect to particular embodiment above, it will be understood by those skilled in the art that modifications may be made without departing from the spirit and scope of the present invention.