Patent Publication Number: US-6335291-B1

Title: System and method for plasma etch on a spherical shaped device

Description:
CROSS REFERENCE 
     This patent is a divisional of U.S. Ser. No. 09/350.045 filed Jul. 8, 1999, which claims the benefit of U.S. Ser. No. 60/092,343 filed Jul. 10, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to semiconductor integrated circuits, and more particularly, to an apparatus and method for etching a semiconductor integrated circuit such as on a spherical-shaped semiconductor device. 
     Conventional integrated circuit devices, or “chips,” are formed from a flat surface semiconductor wafer. The semiconductor wafer is first manufactured in a semiconductor material manufacturing facility and is then provided to a fabrication facility. At the latter facility, several processing operations are performed on the semiconductor wafer surface. 
     One common processing operation is etching. Conventionally, whole wafers are completely coated with a layer or layers of various materials such as silicon nitride, silicon dioxide, or a metal. The unwanted material is then selectively removed by etching through a mask, thereby leaving, for example, selectively removed by etching through a mask, thereby leaving, for example, various patterns and holes in a thermal oxide where diffusions are to be made. For another example, etching can be used to create long stripes of aluminum for electrical interconnects between individual circuit elements. In addition, various patterns must sometimes be etched directly into the semiconductor surface. Examples include: circular holes or short grooves where trench capacitors are to be made in silicon; mesas that are required in the silicon dielectric isolation process; and small, flat depressions in GaAs where the gate metal is to be deposited. 
     While most etching processes use a mask, a few procedures do not involve any local masking. These procedures include etching whole semiconductor slices to remove damage and/or to polish the surface, and etching slices or chips to delineate crystallographic defects. In addition, before the advent of planar technology, a variety of germanium and silicon etching steps were used for removing damage from junctions. 
     There are many different kinds of etching processes. One such type is plasma etching. Plasma etching, and combination plasma/reactive ion etching, are performed in a low-pressure gaseous plasma, and are most commonly used in fine-geometry applications. Plasma etching generally involves fewer safety hazards and spent chemical disposal problems, but the additional cost of plasma equipment is a deterrent to its use when fine-line definition is not necessary. 
     In U.S. Pat. No. 5,995,776 filed on May 16, 1997, a method and apparatus for manufacturing spherical-shaped semiconductor integrated circuit devices is disclosed. It is desired to provide an apparatus and method for performing plasma etching process on a spherical-shaped device to create the integrated circuit thereon. 
     SUMMARY 
     Provided herein is a system and method for performing plasma etch on a spherical shaped device. In one embodiment, the system includes a processing tube for providing a reactive chamber for the spherical shaped substrate. A plasma jet is located adjacent to the processing tube. The plasma jet includes a pair of electrodes, such as a central cathode and a surrounding anode, for producing a plasma flame directed towards the reactive chamber. The central cathode may, for example, be powered by a radio frequency power source. As a result, the reactive chamber supports non-contact etching of the spherical shaped substrate by the plasma flame from the plasma jet. 
     In some embodiments, the system also includes a cooling system for cooling at least a portion of the plasma jet. 
     In some embodiments, the plasma jet includes a directional nozzle for directing the plasma flame towards a central portion of the reactive chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The figure describes a system and method for etching a spherical shaped integrated circuit device according to one embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following disclosure provides many different embodiments, or examples, for implementing different features. Techniques and requirements that are only specific to certain embodiments should not be imported into other embodiments. Also, specific examples of processing gases and component shapes and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention from that described in the claims. 
     Referring to the figure, the reference numeral  10  designates, in general, a system for etching a device, such as a spherical-shaped semiconductor integrated circuit device  12 . For the sake of example, the device  12  could be of the same type formed according to the technique disclosed in the above-identified U.S. Pat. No. 5,955,776. 
     The device  12  moves through an inner chamber  13  of a processing tube  14  with a carrier gas (not shown). The device  12  may move according to a pipeline process flow from one processing station to another, such that the system  10  is merely one processing operation in a series of operations. The device  12  eventually resides near a central portion of the inner chamber  13 , without contacting the processing tube  14 . 
     The device  12  may, in some embodiments, be carried and/or levitated by a plasma flame  16  inside the chamber  13 . Furthermore, the device  12  may be rotated by the plasma flame and/or the carrier gas to facilitate processing operations. For example, the plasma flame  16  may provide an upward force, as seen in the figure, to the device  12  to counteract a downward force of the device due to gravity. 
     The system  10  includes an atmospheric pressure plasma jet, designated generally by the reference numeral  20 . The plasma jet  20  produces the uniform low-temperature plasma flame  16  at about 100-275° C. for materials processing on the device  12 . The plasma jet  20  includes two coaxial electrodes: a center cathode  22  and a surrounding anode  24 . The surrounding anode  24 , in the present embodiment, is attached to a grounded power supply  26 . The center cathode  22  is coupled to a radio frequency (“RF”) source  28  operating at 13.56 MHZ frequency and between 40-500 Watts of RF power. Process gases  30  are injected into the processor  10  through an inlet  32 , where the plasma jet heats the gas. 
     For the sake of example, the process gases  30  may include helium, oxygen and carbon tetrafluoride, which are fed into an annular space  34  between the two electrodes  22 ,  24 . Responsive to the power created between the electrodes  22 ,  24 , the process gases  30  form the plasma flame  16 , which is directed towards the chamber  13  through a nozzle portion  36 . The nozzle portion  36  serves to direct the plasma flame  16  towards a central portion of the chamber  13 , and specifically, towards the device  12 . 
     Any direct current (“DC”) voltage between the plasma flame  16  and either electrode  22 ,  24  is the same and relatively small. The various ions and free radicals that are generated in the plasma flame  16  diffuse to the electrode  22 ,  24  and device  12  surfaces, where they can react with the material being etched to form volatile products that are pumped away. 
     A cooling system  40  is also provided with the system  10 . The cooling system, in the present embodiment, includes a water inlet  42 , a water outlet  44 , and a cooling sleeve  46 . The cooling sleeve  46  wraps around and surrounds the anode  24 . It is understood, however, that different cooling arrangements and cooling fluids can be used for different embodiments, as necessary. 
     It is understood that several variations may be made in the foregoing. For example, different shaped devices can be etched in the above-described system. Additional modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.