Abstract:
The present invention provides a method of super flat chemical mechanical polishing (SF-CMP) technology, which is a method characterized in replacing laser lift-off in a semiconductor fabricating process. SF-CMP has a main step of planting a plurality of polishing stop points before polishing the surface, which is characterized by hardness of the polishing stop points material being larger than hardness of the surface material. Therefore, the present method can achieve super flat polishing surface without removing polishing stop points.

Description:
FIELD OF INVENTION  
       [0001]    The present invention relates to the semiconductor field, using chemical mechanical polishing technology in the semiconductor fabricating process to produce flat surface, more specifically, a method to replace laser lift-off in a semiconductor fabricating process. 
       BACKGROUND  
       [0002]    In a conventional method of producing a flip-chip light emitting diode element, depositing a plurality of epitaxy layers on a sapphire growing substrate to produce an epitaxy wafer. On the epitaxy wafer, a plurality of light emitting diode elements are produced. The epitaxy wafer is cut to produce an element die. Flip-chip connects the element die to a fixing plate. The flip-chip connecting comprises fixing the element die at the fixing plate by connecting at least one electrode of the element die to at least one pad of the fixing plate. 
         [0003]    Now there is a film light emitting diode element to replace flip-chip light emitting diode element, and in comparison to the flip-chip light emitting diode element, film GaN light emitting diode element has advantages of a low heat resistance, uniform current in n-type layer and p-type layer, and low cost. For the film light emitting diode element, the epitaxy wafer is directly bonded to a conductive carrier substrate. Then decomposing GaN with the use of excimer laser, and by so removes sapphire substrate and keeping the active region. 
         [0004]    The above-described method of removing sapphire substrate is called the laser lift-off, which is disclosed in U.S. Pat. No. 6,455,340, 7,001,824 and 7,015,117. At present, the laser lift-off is the only applied method of film GaN light emitting diode element, but the laser lift-off is incompatible with the conventional process. Therefore, the method has disadvantages of expensive equipments and laser causing processing damages. 
         [0005]    If the laser lift-off is replaced by conventional chemical mechanical polishing (CMP) technology, in comparison to the laser lift-off the technology does not require laser equipments and the usage of laser lift-off technology. It can achieve low costs and easy application. However, when applying the conventional CMP technology, if a plane to be polished is too large, location variables of two sides and center of the plane will be too large. Therefore, the required standard of flat plane during mass production of semiconductor devices cannot be achieved, which will lower the yield of the semiconductor device production. Thus, the present invention provides a method of super flat chemical mechanical polishing technology. The method overcomes the problem of large location variables of two sides and center of the plane from the conventional CMP, and provides advantages of low costs, easy application and better yield. 
       SUMMARY OF INVENTION  
       [0006]    The present invention provides a method of super flat chemical mechanical polishing (SF-CMP) technology, which is a method characterized in replacing laser lift-off in a semiconductor fabricating process. SF-CMP has a main step of planting a plurality of polishing stop points before polishing the surface, which is characterized by hardness of the polishing stop points&#39; material being larger than hardness of the material that needs to be removed. Therefore, the present method can achieve super flat polishing surface without removing polishing stop points. The method comprises the following steps: (a) providing a first material for forming a first layer; (b) providing a second material for forming a second layer on a side of the first layer; (c) etching the second layer for producing a plurality of trenches exposing surface of the first layer; (d) filling a third material, which has hardness larger than the first material and the second material, in the trenches to form a plurality of polishing stop points; (e) removing the third material outside the trenches, and exposing surface of the second layer; (f) bonding surface of the second layer on a conductive fourth material; and (g) polishing the first material to expose the second layer material by mechanical or chemical mechanical polishing method. Wherein the etching step is Inductively Coupled Plasma, the third material is diamond film or Diamond Like Carbon film, and removing is by mechanical or chemical mechanical polishing. 
         [0007]    The present invention also provides a method of producing film light emitting diode element, the method comprising the following steps: (a) providing a first material for forming a first layer; (b) providing a second material of a semiconductor material, for forming a second layer acting as an active region on a side of the first layer; (c) etching the second layer for producing a plurality of trenches exposing surfaces of the first layer; (d) covering a layer medium; (e) filling a third material, which has hardness larger than the first material and the second material, in the trenches to form a plurality of polishing stop points; (f) providing a fourth material for forming a first electrode layer on surfaces of the second layer; (g) bonding the first electrode layer on a conductive carrier; (h) removing the first layer; and (i) forming a plurality of second electrodes on surfaces of the second material after removing the first layer. Wherein the first material is a sapphire; the second material is semiconductor material of Group Ill-V or Group II-VI; third material is diamond film, Diamond Like Carbon (DLC) film; the etching in Step (c) is Inductively Coupled Plasma etching; the removing in Step (h) is by mechanical or chemical mechanical polishing; the first electrode layer is p-type; and the second electrode layer is n-type. The above method further comprises a step of performing surface roughening on a polished surface or a step of forming two-dimensional photonic crystals after polishing. 
         [0008]    Since an embodiment of the present invention is planting diamond material in active regions of light emitting diodes to form a plurality of polishing stop points. Therefore the present invention calls it a diamond shoulder light emitting diode structure. 
         [0009]    An embodiment of the present invention specifies in removing substrate of film device. An advantage of using diamond films in light emitting devices is better thermal dissipation. In addition, in another embodiment of the present invention, planting diamond film surrounding the active region can prevent active region from being removed in the step of removing top layer material or bottom layer material of active region. More specifically, in an embodiment of a film light emitting diode element producing, all semiconductor fabrication steps are related to film light emitting diode element, and polishing stop points are a key method for protecting the active region during mechanical or chemical-mechanical removing sapphire layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0010]    The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
           [0011]      FIG. 1  describes conventional chemical mechanical polishing technology. 
           [0012]      FIG. 2  describes a plane after applying super flat chemical mechanical polishing technology. 
           [0013]      FIG. 3  describes a tilted top view of stop point distribution according to one embodiment of the present invention. 
           [0014]      FIG. 4  describes a cross-sectional view of an initial sample according to one embodiment of the present invention. 
           [0015]      FIG. 5  describes a cross-sectional view of an initial sample after etching according to one embodiment of the present invention. 
           [0016]      FIG. 6  describes a cross-sectional view of an initial sample after covering diamond film according to one embodiment of the present invention. 
           [0017]      FIG. 7  describes a cross-sectional view of an initial sample after forming first electrode layer according to one embodiment of the present invention. 
           [0018]      FIG. 8  describes a cross-sectional view of an initial sample after bonding conductive carrier according to one embodiment of the present invention. 
           [0019]      FIG. 9  describes a cross-sectional view of an initial sample after mechanical or chemical mechanical polishing according to one embodiment of the present invention. 
           [0020]      FIG. 10A  describes a cross-sectional view of an initial sample after roughening active region surface according to one embodiment of the present invention. 
           [0021]      FIG. 10B  describes a cross-sectional view of an initial sample after forming two-dimensional photonic crystal on active region surfaces according to one embodiment of the present invention. 
           [0022]      FIG. 11A  describes a cross-sectional view of forming second electrode in  FIG. 10A  according to one embodiment of the present invention. 
           [0023]      FIG. 11B  describes a cross-sectional view of forming second electrode in  FIG. 10B  according to one embodiment of the present invention. 
           [0024]      FIG. 12A  describes a cross-sectional view of cutting light emitting device of  FIG. 11A  according to one embodiment of the present invention. 
           [0025]      FIG. 12B  describes a cross-sectional view of cutting light emitting device of  FIG. 11B  according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]      FIG. 1  presents a conventional semiconductor structure, which comprises active region  130 , electrode layer  140  and carrier  150 . When applying conventional chemical mechanical polishing technology, if a plane to be polished is too large, location variables of two sides and center of the plane will be too large. Therefore, a distance between L the two sides of the plane is proportional to the variable V. 
         [0027]      FIG. 2  shows a semiconductor structure having stop point  260 , the semiconductor structure comprises a distance L 210  between two sides of a plane to be polished, variable V 220 , active region  230 , electrode layer  240 , carrier  250  and stop point width a 270 . Also in the present invention, after applying an embodiment of the super flat chemical mechanical polishing technology, when after planting a plurality of polishing stop points  260 , variable V of the entire plane can be controlled within standards required in semiconductor fabricating process. The method comprises the following steps: (a) providing a first material for forming a first layer; (b) providing a second material for forming a second layer on a side of the first layer; (c) etching the second layer for producing a plurality of trenches exposing surface of the first layer; (d) filling a third material, which has hardness larger than the first material and the second material, in the trenches to form a plurality of polishing stop points; (e) removing the third material outside the trenches, and exposing surface of the second layer. Furthermore, the present embodiment still can be like the step of removing the first material and control the variable V to be within standards required in semiconductor fabricating process. 
         [0028]      FIG. 3  presents a cross-sectional view of stop point distribution according to one embodiment the present invention. As described above, a distance between the two sides of the plane is proportional to the variable. Therefore, a variable within the standard range can be obtained by controlling sizes of the stop points and distances between the stop points. Evidently, the stop points in the present embodiment can be circles, triangles, rectangles or of other geometrical shapes. 
         [0029]    According to an application of the present invention, another embodiment is disclosed in  FIG. 4-FIG .  12 , which is a method of fabricating a film semiconductor light emitting device. The method comprise the following steps: (a) providing a first material for forming a first layer  410 ; (b) providing a second material of a semiconductor material, for forming a second layer  230  acting as an active region on a side of the first layer (as shown in  FIG. 4 ); (c) etching the second layer for producing a plurality of trenches  510  exposing surfaces of the first layer (as shown in  FIG. 5 ); (d) covering a layer medium  620 ; (e) filling a third material  610  , which has hardness larger than the first material and the second material, in the trenches to form a plurality of polishing stop points (as shown in  FIG. 6 ); (f) removing the third material  610  and medium material  620  outside the trenches and providing a fourth material for forming a first electrode layer  710  on surfaces of the second layer (as shown in  FIG. 7 ); (g) bonding the first electrode layer on a conductive carrier  810  (as shown in  FIG. 8 ); (h) removing the first layer exposing a plurality of polishing stop points  910  (as shown in  FIG. 9 ); and (i) forming a plurality of second electrodes  1110  on surfaces of the second material after removing the first layer (as shown in  FIG. 11 ). The present embodiment further comprises roughening active region surfaces  1010  as in  FIG. 10A  or forming two-dimensional photonic crystal  1020  on active region surfaces as in  FIG. 10B . Finally, like shown in  FIG. 12A  or  12 B, cutting the light emitting device. In the embodiment described above, the first material can be sapphire; the second material can be GaN or GaInN, the second material semiconductor material of Group III-V or Group II-VI; the etching in Step (c) is Inductively Coupled Plasma etching; wherein the third material can be diamond film or Diamond Like Carbon (DLC) film; the removing in Step (h) is by mechanical or chemical mechanical polishing; the first electrode layer is p-type and the second electrode layer is n-type. An embodiment of the present invention is a diamond shoulder light emitting diode referred as  1210 . 
         [0030]    The semiconductor device structure produced according to one embodiment of the present invention, comprise: a conductive carrier; a semiconductor material layer; a superhard material, wherein the superhard material has at least a surface adjacent to the semiconductor material layer; a first electrode layer located on a surface of the semiconductor material layer; and a second electrode layer located on another surface of the semiconductor material layer opposing the first electrode layer. Wherein the semiconductor material layer comprises InGaP, AlInGaN, AlInGaP, AlGaAs, GaAsP or InGaAsP; the superhard material comprises diamond, Diamond Like Carbon (DLC), Titanium Nitride (TiNx) or Titanium Tungsten (TiWx) alloy; and the conductive carrier comprises copper, silicon, silicon carbide or GaAs.