Patent Publication Number: US-2023140032-A1

Title: Apparatus for thermally processing a substrate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of semiconductor technology, especially an improved rapid thermal processing apparatus for processing a wafer. 
     2. Description of the Prior Art 
     Single wafer rapid thermal processing (RTP) has become one of the key technologies in semiconductor manufacturing due to its faster wafer processing with precise control of the thermal budget. 
     Rapid thermal processing (RTP) is typically performed by irradiating a wafer with light from an array of high-intensity lamps directed at the front face of the wafer on which the integrated circuits are being formed. The radiation is at least partially absorbed by the wafer and quickly heats it to a desired high temperature, for example above 600° C. or in some applications above 1000° C. The radiant heating can be quickly turned on and off to controllably heat the wafer over a relatively short period, for example, of a minute or less or even a few seconds. 
     It is important to control the temperature across the wafer to a closely defined temperature uniform across the wafer. However, the prior art rapid thermal processing often encounters local temperature uniformity, especially at the center of the wafer. 
     SUMMARY OF THE INVENTION 
     It is one object of the present invention is to provide an improved wafer thermal processing apparatus to solve the above-mentioned shortcomings or deficiencies of the prior art. 
     One aspect of the invention provides an apparatus for thermally processing a substrate including a substrate support for holding the substrate, and a plurality of lamps disposed above the substrate support. The plurality of lamps is grouped into concentric lamp zones including a center zone comprised of a center lamp and peripheral lamps surrounding the center lamp. A plurality of reflective sleeves including a center sleeve coupled to the center lamp and peripheral sleeves is coupled to the peripheral lamps, respectively, for directing radiated heat to the substrate during thermal processing. The center sleeve has a surface roughness higher than that of the peripheral sleeves. 
     According to some embodiments, the plurality of lamps is tungsten-halogen lamps. 
     According to some embodiments, the substrate support comprises an edge ring, and the substrate is supported on its periphery by the edge ring. 
     According to some embodiments, the edge ring comprises an annular sloping shelf contacting corner of the substrate. 
     According to some embodiments, the center lamp is surrounded by six peripheral lamps. 
     According to some embodiments, the center sleeve has a surface roughness of about 0.8-3.2 Ra, while the peripheral sleeves have a surface roughness of smaller than 0.4 Ra. 
     According to some embodiments, the center sleeve and the peripheral sleeves comprise copper and gold. 
     According to some embodiments, a transparent quartz window is disposed between the plurality of reflective sleeves and the substrate support. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic cross-sectional view of a single-wafer thermal processing apparatus according to one embodiment of the present invention. 
         FIG.  2    is a top view of a heating source composed of the lamp array in  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the disclosure, reference is made to the accompanying drawings, which form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. 
     Other embodiments may be utilized, and structural, logical, and electrical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be considered as limiting, but the embodiments included herein are defined by the scope of the accompanying claims. 
     Please refer to  FIG.  1    and  FIG.  2   .  FIG.  1    is a schematic cross-sectional view of a single-wafer thermal processing apparatus according to one embodiment of the present invention.  FIG.  2    is a top view of a heating source composed of the lamp array in  FIG.  1   . As shown in  FIG.  1    and  FIG.  2   , the apparatus 1 for thermally processing wafers according to the present invention includes a body  10  and a heating source  20 . According to an embodiment, the heating source  20  covers the body  10  to form an enclosed processing area  30 . 
     According to an embodiment, a substrate support  110  is provided in the body  10  for holding a substrate  101 , for example, a semiconductor substrate or a silicon wafer. According to an embodiment, the substrate support  110  is rotatable. According to an embodiment, the substrate support  110  includes an edge ring  111  and the substrate  101  is supported by the edge ring  111  on its periphery. According to an embodiment, the edge ring  111  includes an annular sloping shelf  112  contacting the lower corner along the periphery of the substrate  101 . It can be seen from  FIG.  1    and  FIG.  2    that the substrate  101  has a smaller diameter  d   1 , the edge ring  111  has a slightly larger outer diameter  d   2 , and the inner diameter of the body  10  is  d   3 , wherein  d   3  is greater than  d   2 , and  d   2  is greater than  d   1 . 
     According to an embodiment, the heating source  20  includes a plurality of densely arranged lamps  210  arranged directly above the substrate support  110 . According to an embodiment, the lamps  210  are tungsten-halogen lamps. As shown in  FIG.  2   , the lamps  210  are divided into a plurality of concentric lamp areas, and the center zone A 1  includes a center lamp  210   a  and peripheral lamps  210   b  surrounding the center lamp  210   a . According to an embodiment, the center zone A 1  contains only seven lamps, and the center lamp  210   a  is surrounded by six peripheral lamps  210   b . 
     According to an embodiment, as shown in  FIG.  1   , the heating source  20  further includes a plurality of reflective sleeves  220  respectively connected to the lower ends of the lamps  210  for directing heat radiation to the substrate  101  during the heat treatment. According to an embodiment, a transparent quartz window  40  is provided between the reflective sleeves  220  and the substrate support  110 . 
     According to an embodiment, the reflective sleeves  220  comprise copper and gold, but not limited thereto. According to an embodiment, the reflective sleeves  220  are composed of copper and gold. The reflective sleeves  220  include a center sleeve  220   a  connected to the center lamp  210   a  and peripheral sleeves  220   b  respectively connected to the peripheral lamps  210   b . The surface roughness of the center sleeve  220   a  is higher than that of the peripheral sleeves  210   b . 
     According to an embodiment, the surface roughness of the inner surface of the center sleeve  210   a  is about 0.8-3.2 Ra (Ra: arithmetic average roughness), and the surface roughness of the inner surface of each peripheral sleeve  210   b  is less than 0.4 Ra. According to an embodiment, the inner surface of the center sleeve  210   a  may be subjected to sandblasting treatment to achieve the desired surface roughness. 
     Since the surface roughness of the center sleeve  210   a  is relatively higher, the reflection of the center sleeve  210   a  can be reduced, thereby improving the local temperature uniformity of the wafer under thermal treatment. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.