Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of U.S. Ser. No. 09/033,180 filed Mar. 2, 1998, now U.S. Pat. No. 6,041,735 which is a Continuation-in Part of U.S. Ser. No. 08/996,260 filed Dec. 22, 1997, now 5,975,011. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to semiconductor integrated circuits, and more particularly, to an apparatus and method for fabricating a spherical-shaped semiconductor integrated circuit. 
     Conventional integrated circuits, 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 layers are processed onto the semiconductor wafer surface. Once completed, the wafer is then cut into one or more chips and assembled into packages. Although the processed chip includes several layers fabricated thereon, the chip still remains relatively flat. 
     A fabrication facility is relatively expensive due to the enormous effort and expense required for creating flat silicon wafers and chips. For example, manufacturing the wafers requires several high-precision steps including creating rod-form polycrystalline semiconductor material; precisely cutting ingots from the semiconductor rods; cleaning and drying the cut ingots; manufacturing a large single crystal from the ingots by melting them in a quartz crucible; grinding, etching, and cleaning the surface of the crystal; cutting, lapping and polishing wafers from the crystal; and heat processing the wafers. Moreover, the wafers produced by the above processes typically have many defects which are largely attributable to the difficulty in making a single, highly pure crystal due to the above cutting, grinding and cleaning processes as well as due to the impurities, including oxygen, associated with containers used in forming the circuits formed on these wafers become smaller. 
     Another major problem associated with modern fabrication facilities for flat chips is that they require extensive and expensive equipment. For example, dust-free clean rooms and temperature-controlled manufacturing and storage areas are necessary to prevent the wafers and chips from defecting and warping. Also, these types of fabrication facilities suffer from a relatively inefficient throughput as well as an inefficient use of the silicon. For example, facilities using in-batch manufacturing, where the wafers are processed by lots, must maintain huge inventories to efficiently utilize all the equipment of the facility. Also, because the wafers are round, and the completed chips are rectangular, the peripheral portion of each wafer cannot be used. 
     Still another problem associated with modern fabrication facilities is that they do not produce chips that are ready to use. Instead, there are many additional steps that must be completed, including cutting and separating the chip from the wafer: assembling the chip to a lead frame which includes wire bonding, plastic or ceramic molding and cutting and forming the leads, positioning the assembled chip onto a printed circuit board; and mounting the assembled chip to the printed circuit board. The cutting and assembly steps introduce many errors and defects due to the precise requirements of such operations. In addition, the positioning and mounting steps are naturally two-dimensional in character, and therefore do not support curved or three dimensional areas. 
     Therefore, due to these and various other problems, only a few companies in the world only can successfully manufacture conventional flat chips. Furthermore, the chips must bear a high price to cover the costs of manufacturing, as well as the return on initial capital and investment. 
     In U.S. Pat. No. 5,955,776, assigned to the same assignee as the present application and hereby incorporate by reference, a method and apparatus for manufacturing spherical-shaped semiconductor integrated circuits is disclosed. The present invention is specific to an apparatus and method for performing metal deposition on the circuits. 
     SUMMARY OF THE INVENTION 
     The present invention, accordingly, provides an apparatus and method for performing material (e.g. metal) deposition on semiconductor devices. In one embodiment, the apparatus provides an enclosure for defining a chamber. The chamber includes a metallic portion such as a conductor coil powered by a voltage generator. A gas, having a suspension of particles for treating the semiconductor devices, is introduced into the chamber and the powered conductor coil converts the as to inductively coupled plasma and vaporizes the particles. The particles can then be deposited on the semiconductor devices. 
     Several advantages result from the foregoing. For one, the semiconductor devices can be continuously introduced into the chamber to reduce or eliminate the need for a clean room environment. Also, the chamber can be maintained at a relatively high temperature above conventional semiconductor material warping or melting points. Further, the method of the present invention can be carried out in a relatively small space and eliminates the requirements for assembly and packaging facilities. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of the apparatus of the present invention. 
     FIG. 2 is a graph of temperature and vapor flux vs location for defining a deposition area in the apparatus of FIG.  1 . 
     FIG. 3 is an expanded, sectional view of the apparatus of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1 the reference numeral  8  refers, in general, to a processing device including a hollow outer sphere  10  having an inlet opening  10   a  and an outlet opening  10   b  located diametrically opposite the inlet opening  10   a.  One end of a horizontally extending inlet conduit  12  registers with the inlet opening  10   a  of the sphere  10 , and one end of a generally U-shaped outlet conduit  14  registers with the outlet opening  10   b.  It is understood that the conduits  12  and  14  are connected to the sphere  10  in any known manner and, alternately, can be formed integrally with the sphere. 
     A hollow inner sphere  20  extends within the sphere  10  in a coaxial, slightly spaced relationship to define a substantially spherical passage  21  therebetween. The inner sphere  20  has an inlet opening  20   a  and an outlet opening  20   b  registering with a chamber  22  defined by the interior of the sphere, with the outlet opening  20   b  being located diametrically opposite the inlet opening  20   a.  One end of a horizontally extending inlet conduit  24  registers with the inlet opening  20   a  of the inner sphere  20 , and is connected to the sphere  10  in any known manner. The inlet conduit  24  extends within the inlet conduit  12  in a spaced relation thereto to define, with the inlet conduit  12 , a cylindrical inlet passage  26  that communicates with the passage  21 . Although not shown in the drawings, it is understood that the conduit  24  is supported within the conduit  12  in any known manner such as by struts, or the like. A nipple  28 , or the like, is connected to the distal end portion of the inlet conduit  12  to introduce a first fluid into the passage  26 ,and the distal end of the inlet conduit  24  is open so as to provide an inlet to receive one or more additional fluids. For example, first fluid introduced into the passage  26  via the nipple  28  could be a cooling fluid and the fluids introduced into the inlet conduit  24  could be a plasma gas and a process gas which function in a manner to be described. 
     A second inlet opening  20   c  and a second outlet opening  20   d  are formed through the inner sphere  20 . The openings  20   c  and  20   d  are diametrically opposed and extend in a ninety degree, angularly spaced, relation to the openings  20   a  and  20   b.  A pair of diametrically opposed openings  10   c  and  10   d  are formed through the outer sphere  10  and are aligned with the openings  20   c  and  20   d,  respectively, of the inner sphere  20 . 
     A vertically extending inlet conduit  30  extends through the opening  10   c  in the outer sphere  10  and registers with the opening  20   c  of the inner sphere  20 . A vertically extending outlet conduit  32  extends through the opening  10   d  in the outer sphere  10  and registers with the opening  20   d  in the inner sphere  20 . A conduit  34  extends within the outlet conduit  32 , through the opening  10   d  in the outer sphere, and also registers with the opening  20   d  of the inner sphere  20 . The diameter of the conduit  34  is less than that of the outlet conduit  32  so as to form a cylindrical passage  36  which also registers with the opening  20   d  of the inner sphere  20 . Although not shown in the drawings, it is understood that the conduit  34  is supported within the conduit  32  in any known manner such as by struts, or the like. 
     An electrical conductor  40  is coiled around the outer surface of the conduit  12  The conductor  40  is connected to a radio frequency (RF) power generator  42 , an impedance matching network  44 , and a control panel  46  for creating a radio frequency signal in connection with a plasma process that may be performed in connection with the chamber  22  as described below. The RF generator  42 , matching network  44 , and control panel  46  are conventional devices for producing plasma torches. 
     In operation, a plurality of members  50 , each of a semiconductor material, are introduced into the inlet conduit  30  and pass into the chamber  22  in the inner sphere  20 . The members  50  are preferably of a generally technique disclosed shape in the above-identified and presently incorporated U.S. Pat. No. 5,955,776. After traversing the interior of the chamber  22 , the members  50  pass through the outlet opening  20   d  in the inner sphere  20  before discharging from the chamber  22  through the conduit  32 . The introduction and discharge of the members  50  in this manner is controlled to prevent the accumulation of a relatively large number of members in the chamber  22  at the same time. To this end, a fluid, such as an inert carrier gas, is introduced into the conduit  34  and therefore passes upwardly, as viewed in the drawing, into the chamber  22 , with the velocity of the gas being controlled so that the discharge of the members  50  through the conduit  32  is controlled. 
     During this flow of the members  50  through the chamber, one or more gases are selectively introduced into the inlet end of the inlet conduit  24  and thus flow directly into the chamber  22 . The particular gases that are introduced into the chamber depends on the specific desired treatment of the members  50 . As an example, a high-purity argon gas is introduced into the conduit  24  and passes into and through the chamber  22  in a direction that extends approximately ninety degrees to the direction of the passage of the members  50  through the chamber. This gas (hereinafter referred to as a “plasma gas”) establishes a toroidal plasma torch region  52 , shown enclosed by the phantom lines in the drawing, through which the members  50  pass. The plasma gas therefore passes over the members  50  in the chamber and comes into intimate contact with the members. The velocity and mass flow of the plasma as introduced into the chamber  22  in this manner is controlled so that the plasma gas passes through the chamber, exits the chamber through the outlet opening  20   b  in the inner sphere  20 , and passes into the conduit  14  for discharge. The conduit  14  also asserts a negative pressure, thereby reducing the atmospheric pressure inside the chamber  22 . 
     During the passage of the plasma gas through the chamber  22 , the RF coil  40  is activated and the plasma gas, in combination with RF current from the coil, becomes an inductively coupled plasma. As a result, relatively high energy is created and applied to the region  52  in the chamber  22 . Since this formation of an inductively coupled plasma, and the resultant creation of relatively high energy is well known in the art it will not be described in any further detail. 
     A suspension of fine powder particles  56  is also selectively introduced into the inlet end of the inlet conduit  24  and thus flows directly into the chamber  22 . The plasma gas is used to suspend the particles  56  and inject the particles into a central portion of the region  52 . The particles  56  can be metals, such as Al, Cu, W, or Ti. Alternatively, the particles  56  may be alumina, silica, nitrides, or a mixture of materials (e.g., a mechanical alloy). As a result, the processing device  8  may be the sole tool used to coat semiconductor spherical integrated circuits. The size of the particles  56  are in the micron to submicron range so that they can fully melt and subsequently vaporize in the inductively coupled plasma. The purity of the initial powder is essential for forming the resulting thin films of extra high purity. 
     Alternatively, a metal organic compound (e.g., Al containing metal organics such as trimethyl-aluminum, dimethyl-aluminum-hydride, or tri-isobutyl-aluminum) can be introduced into the plasma gas. Further, a mixture of metal organics and an inert gas (e.g., Ar or N 2 ) can be used to facilitate formation of inductively coupled plasma. The metal organics are injected in a controlled portion of region  52  and the inductively coupled plasma is formed therein. As a result of the metal organic dissolution, a thin layer of metal e.g., Al) material is formed on the surface of the members  50 . This aver can be used as a contact layer as described below. 
     Referring also to FIG. 2, a central portion si of the region  52  graphically represented as the area between boundaries r 1  and r 2  and hereinafter designated deposition area r 1 -r 2 ) has less density of plasma as opposed to the outer regions of the toroidal plasma discussed in greater detail below. The boundary r 1  of the deposition area r 1 -r 2  is defined as the location in which the vapor flux of the particles  56  starts solidifying, while sufficient flux of the vapor still exists. The boundary r 2  is defined as the location in which the temperature in the chamber is less than the melting point of silicon so as not to melt the members  50 . 
     The particles  56  injected to the plasma region become vaporized by high temperatures existing within the region  52 . The temperature range within the thermal atmospheric inductively coupled plasma is may vary from about 5,000K to above 15,000K, depending on the power and frequency supplied by the RF generator  42 . In the preferred embodiment, the RF generator  42  produces a maximum RF power of 2 kW and a working frequency of 13.56 MHz. It is understood, however, that other RF powers and frequencies may also be used. 
     Referring to FIG. 3, the particles  56  passing through the region  52  start melting  60  and subsequently vaporize  62 . The resultant vapor travels further through the region  52  into the deposition area r 1 -r 2 . The members  50  also pass through the deposition area r 1 -r 2  for a duration long enough for depositing a thin film  70 . The rate at which the members  50  travel can be adjusted by the flow of gas through the conduit  34 , described in greater detail above. Also, the members  50  spin to facilitate uniform film coverage. One example of a thin film that can be made by the described technique is a thin metal (e.g., Ti) contact layer for use in a contact stack such as Ti/TiN/Al. 
     The apparatus and method of the present invention leads to several advantages. For one, the continuous flow of the members  50  through the chamber  22  reduces or eliminates the need for batch processing. Also, the chamber can be selectively maintained at a relatively high temperature at or above the warping or melting temperature of the members  50 , by controlling the amount of inductively coupled plasma gas formed in the chambers. Further, the spherical shape of the members  50  provide much greater surface area on which the process gas acts, when compared to the surface area of a conventional flat semiconductor. Also, the method of the present invention can be carried out in a relatively small space and eliminates the requirements for large facilities. 
     It is understood that several variations may be made in the foregoing. For example, several separate inductively coupled plasma torches can be installed to increase the process throughput. Also the members  50  may have the thermal silicon oxide or other elements of an integrated circuit already formed thereon. Other 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.

Technology Category: 5