Patent Publication Number: US-2006013954-A1

Title: Method for improving atomic layer deposition process and the device thereof

Description:
RELATED APPLICATIONS  
      The present application is based on, and claims priority from, Taiwan Application Serial Number 93121391, filed Jul. 16, 2004, the disclosure of which is hereby incorporated by reference herein in its entirety.  
     FIELD OF THE INVENTION  
      The present invention relates to a method for improving a semiconductor process and a device thereof, and more particularly, to a method for improving an atomic layer deposition process and a device thereof.  
     BACKGROUND OF THE INVENTION  
      Due to the rapid development of the semiconductor industry various process technologies and applied materials have been greatly developed for continuously enhancing the integration degree and the operation performance of the devices in the integrated circuit. As the device size has been minimized, the aspect ratio of the contact and the via has also greatly increased, resulting in increased difficulty in operating the deposition process. Hence, how a conformal metal layer is formed in the contact and via with the increased aspect ratio has become one of the key subjects in the development of the sub-micron process.  
      Nowadays, an atomic layer deposition (ALD) process is a popular method for forming a conformal metal layer. Reference is made to  FIGS. 1A  to  1 C, which are cross-sectional diagrams of the wafer during different stages of the atomic layer deposition process according to the prior art. As shown in  FIG. 1A , a precursor reactant  120  is introduced into a chamber until the surface of the wafer  100  is saturated with the precursor reactant  120 . The excess precursor reactant  120  is then exhausted. Next, as shown in  FIGS. 1B and 1C , another precursor reactant  140  is introduced, reacts with the precursor reactant  120  adsorbed on the surface of the wafer  100 , and then a product  160  is formed on the surface of the wafer  100 . Subsequently, the unreacted precursor reactant  140  and by-product are exhausted. The product  160  is controlled to be a monolayer deposited on the surface of the wafer  100  during the atomic layer deposition process, so the product  160  is conformally formed in the contact or the via. However, the deposition rate of the metal layer is very slow when using the atomic layer deposition process, and the thickness of resultant metal layer is very thin, typically about 0.5 angstroms (Å) to 3 Å. If the thickness of resultant metal layer needs to be several tens of Å, the atomic layer deposition process must be repeated several tens of times, and the throughput is severely affected.  
     SUMMARY OF THE INVENTION  
      Hence, it is an aspect of the present invention to provide a method for improving an atomic layer deposition process and a device thereof, so as to deposit a conformal metal layer and to increase the throughput of the process.  
      According to the aforementioned aspect of the present invention, a device for improving an atomic layer deposition process is provided, which has a shield for dividing a chamber into a plurality of sub-chambers, a plurality of gas injecting plates disposed correspondingly above the sub-chambers for introducing precursor gases required in different steps into the sub-chambers, and a revolving spindle. The revolving spindle is connected to a plurality of susceptors and rotated to move the susceptors from one sub-chamber into another sub-chamber. A plurality of wafers can be simultaneously transferred into the device to perform the deposition process, and then by rotating operations, the atomic layer deposition process is completed. The desired thickness can be achieved by controlling rotation numbers. Therefore, the operation time of the deposition process can be reduced effectively, so as to increase the throughput of the process.  
      In addition, a method for improving an atomic layer deposition process is provided, which utilizes a shield that consists essentially of an inert gas to divide a chamber into a plurality of sub-chambers, and introduces precursor gases required in different steps into the sub-chambers. Next, a wafer is transferred into a sub-chamber to perform a gas adsorption step in which the deposition process gases are adsorbed on the surface of the wafer. The wafer is then moved into another sub-chamber to perform a main deposition step. Afterwards, another wafer is transferred into the sub-chamber of the gas adsorption step. Therefore, the gas adsorption step and the film deposition step can be simultaneously performed on a plurality of wafers, so as to increase the throughput and the process effectively. Furthermore, the reaction steps in different stages are performed in different sub-chambers, so the step of changing precursor gases is not necessary. Hence, the operation time and steps of the process can be greatly reduced, and the throughput of the process can be increased effectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
       FIGS. 1A  to  1 C are cross-sectional diagrams of the wafer during different steps of the atomic layer deposition process according to the prior art;  
       FIG. 2  is a schematic diagram of the device for improving the atomic layer deposition process in accordance with a preferred embodiment of the present invention; and  
       FIG. 3  is a flow chart of the method for improving the atomic layer deposition process in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      In order to increase the throughput of the atomic layer deposition process and more effectively utilize the process precursor gases, the present invention provides a method for improving an atomic layer deposition process and a device thereof. Hereinafter, the preferred embodiments are described in detail with the accompanying drawings.  
      Reference is made to  FIG. 2 , which is a schematic diagram of the device for improving the atomic layer deposition process in accordance with a preferred embodiment of the present invention. As shown in  FIG. 2 , a shield  210  is disposed in a chamber  200  and divides the chamber  200  into a first sub-chamber  204  and a second sub-chamber  208 . The shield  210  may consist essentially of an inert gas, such as argon (Ar), helium (He) or nitrogen (N 2 ). A first gas injecting plate  234  and a second gas injecting plate  238  are directly disposed above the first sub-chamber  204  and the second sub-chamber  208 , respectively, for introducing a first precursor gas  254  and a second precursor gas  258 . A first susceptor  274  and a second susceptor  278  are disposed correspondingly below the first gas injecting plate  234  and the second gas injecting plate  238 , respectively. Therefore, a plurality of wafers may be processed simultaneously in the chamber, and different reaction steps may be performed in different sub-chambers. In this preferred embodiment, the first sub-chamber  204  is employed for performing a gas adsorption step of the first precursor gas  254  in the atomic layer deposition process, and the second sub-chamber  208  is employed for performing a main deposition step. In an example of forming a metal tungsten (W) film, the first precursor gas  254  may be a silane (SiH 4 ) gas, a borane (B 2 H 6 ) gas or a combination thereof, and the second precursor gas  258  may be a tungsten hexafluoride (WF 6 ) gas. Due to the precursor gas adsorption step and the deposition step are performed in different sub-chambers, respectively, the shield  210  separates and prevents the first precursor gas  254  and the second precursor gas  258  from mixing and contacting with each other. Therefore, it is not necessary to perform the step of exhausting excess precursor gases in the atomic layer deposition process of the prior art. The steps required in the atomic layer deposition process can be effectively reduced, so as to increase the throughput.  
      In addition, the foregoing device further has a revolving spindle  290  that connects with the first susceptor  274  and the second susceptor  278 . After rotating the revolving spindle  290  to an appropriate angle, the first susceptor  274  can be moved from the first sub-chamber  204  into the second sub-chamber  208 , and the second susceptor  278  can be moved from the second sub-chamber  208  into the first sub-chamber  204 . After a second wafer  268  is transferred to the first sub-chamber  204  and the first precursor gas adsorption step is completed, in other words, the first precursor gas adsorbed on the surface of the second wafer  268  reaches saturation, the spindle  290  is rotated to move the second wafer  268  into the second sub-chamber  208  to perform a deposition step; and simultaneously, the first wafer  264  is transferred into the first sub-chamber  204  to perform the gas adsorption step of the first precursor gas  254 . Hence, by controlling the revolving spindle  290 , a plurality of wafers perform the gas adsorption step and the deposition step continuously and in turn until the desired thickness of the metal layer is obtained. Moreover, the shield  210  consisting essentially of the inert gas is not only employed for preventing the first precursor gas  254  and the second precursor gas  258  from mixing with each other but also employed for removing the unreacted precursor gas on the wafer. For example, when the second wafer  268  is moved from the first sub-chamber  204  into the second sub-chamber  208 , the unreacted first precursor gas  254  on the second wafer  268  can be removed, and when the second wafer  268  is moved from the second sub-chamber  208  into the first sub-chamber  204 , the second precursor gas  258  that is unreacted with the first precursor gas  254  on the second wafer  268  can be removed. As a result, an additional removal step is not necessary, and the operation time of the process can be greatly reduced, thereby increasing throughput.  
      In the aforementioned preferred embodiment, the chamber is divided into the first sub-chamber and the second sub-chamber; however, a plurality of shields can be further disposed in the chamber to divide the chamber into a plurality of the first sub-chambers and a plurality of the second sub-chambers depending on the size of the chamber and the requirement of the process. By controlling the revolving spindle, a plurality of wafers perform the gas adsorption step and the deposition step in the first sub-chamber and the second sub-chamber continuously and in turn for increasing the throughput and the process effectively. Therefore, the present invention is not limited herein.  
      Reference is made to  FIG. 3 , which is a flow chart of the method for improving the atomic layer deposition process in accordance with a preferred embodiment of the present invention. As shown in  FIG. 3 , the step  300  is first performed, which introduces an inert gas to form at least one shield in a chamber, and the shield divides the chamber into at least one first sub-chamber and at least one second sub-chamber, wherein the inert gas is selected from the group consisting of argon, nitrogen and helium. Next, the step  310  and the step  330  are performed, which introduce a first precursor gas and a second precursor gas into the first sub-chamber and the second sub-chamber, respectively, to perform an atomic layer deposition process. And then in the step  350 , a wafer is transferred into the first sub-chamber to perform the first precursor gas adsorption step. After the surface of the wafer is saturated with the first precursor gas, a spindle is rotated to move the wafer into the second sub-chamber in the step  370 , and the adsorbed first precursor gas reacts with the adsorbed second precursor gas to form a film. In addition, the inert gas is also employed to remove the unreacted first precursor gas and the unreacted second precursor gas on the surface of the wafer. Afterward, another wafer is transferred into the first sub-chamber, for simultaneously processing a plurality of wafers to increase the operation rate of the process. Besides, the step  350  and the step  370  can be repeated to increase the deposition thickness of the film.  
      Therefore, according to the aforementioned preferred embodiments, one advantage of the method for improving an atomic layer deposition process and the device thereof is that the first precursor gas adsorption and the film deposition can be simultaneously performed on a plurality of wafers, thereby increasing the throughput and the process effectively. Moreover, the gas adsorption step and the deposition step are performed in different sub-chambers, respectively, so it is not necessary to change the precursor gases required in different steps repeatedly, thereby effectively reducing the step of changing precursor gases. Furthermore, when the wafers are reciprocated between the sub-chambers, the shield consisting essentially of the inert gas is employed for removing the unreacted precursor gas on the wafer. Therefore, the operation time of the atomic layer deposition process can be greatly reduced, increasing the throughput.  
      As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative rather than limiting of the present invention. It is intended that various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.