Patent Publication Number: US-2005123860-A1

Title: Dielectric with fluorescent material

Description:
BACKGROUND OF THE INVENTION  
      Substrates have layers of dielectric material that separate conductors at different levels of the substrate. Micro vias pass through layers of dielectric material to electrically connect conductors at different levels. Imprinting tools can be used to help form these vias. A male patterned imprinting tool is pressed through a dielectric layer to make contact with the conductor under the dielectric layer. This forms a trench in the dielectric layer that, when filled with conductive material, creates a via.  
      If the imprinting process leaves some residual dielectric at the bottom of the trench, the conductive material that will fill the trench may not make contact with the underlying conductor. This may prevent the substrate from functioning properly. Additionally, dielectric material from the substrate sometimes sticks to the imprinting tool. This degrades quality of features subsequently formed by the imprinting tool.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side cross sectional view of a substrate according to one embodiment of the present invention.  
       FIG. 2  is a side cross sectional view that illustrates a portion of how the via of the substrate may be formed.  
       FIG. 3   a  is a side cross sectional view that illustrates one example of a result of an imprinting process.  
       FIG. 3   b  is a side cross sectional view that illustrates another example of a result of an imprinting process.  
       FIG. 4  is a schematic view of an embodiment of a detection device for detecting whether there is material at the bottom of the trench formed by the imprinting tool.  
       FIG. 5  is a side cross sectional view that illustrates the second conductor and via that may be formed on the first dielectric layer.  
       FIG. 6  is a schematic diagram of a computer system according to one embodiment of the present invention.  
       FIG. 7  is a schematic view of an embodiment of a detection device for detecting whether there is material from the first dielectric layer stuck on the imprinting tool.  
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is a side cross sectional view of a substrate  100  according to one embodiment of the present invention. The substrate  100  may include a first conductor  102 . The first conductor  102  may be a conductive trace, a conductive core, or another conductor. In some embodiments, the first conductor  102  may comprise copper, aluminum, or other materials.  
      There may be a first dielectric layer  104  that covers at least part of the first conductor  102 . In an embodiment, the first dielectric layer  104  may have a thickness in a range from about 10 microns to about 70 microns. In another embodiment, the first dielectric layer  104  may have a thickness in a range from about 20 microns to about 50 microns. The first dielectric layer  104  may comprise an insulating material, such as an epoxy, an epoxy blend, BT (a blend of Bismaleimide and Triazine resins), polyimide, a polyimide blend, LCP (Liquid Crystal Polymer, aromatic copolyesters), PPO (polyphenylene oxide), Cyanate Ester, PPS (polyphenylene sulfide), or another material or combination of materials. The first dielectric layer  104  may also comprise a fluorescent material. In an embodiment, the fluorescent material may comprise less than about 10 percent of the dielectric material of the first dielectric layer  104 . In another embodiment, the fluorescent material may comprise less than about 2 percent of the dielectric material of the first dielectric layer  104 . The fluorescent material may be a material that absorbs electromagnetic radiation in a first range of wavelengths and in response emits electromagnetic radiation in a second range of wavelengths. The first range may include all or part of the range of wavelengths that make up ultraviolet light in an embodiment. The second range may include all or part of the range of wavelengths that make up visible light in an embodiment. Ultraviolet light may have a wavelength in a range of about 10 nanometers to about 400 nanometers. Visible light may have a wavelength in a range from about 400 nanometers to about 700 nanometers.  
      The first dielectric layer  104  may have side walls  106  that extend from the top to the bottom of the first dielectric layer  104  to define boundaries of a via  110 . These side walls  106  may be vertical, as illustrated in  FIG. 1 , may be slanted so that the via  110  is wider at the top than at the bottom, or may have another configuration.  
      There may be a second conductor  108  on the first dielectric layer  104 . The second conductor  108  may cover all or part of the first dielectric layer  104 . The second conductor  108  may be a conductive trace, a conductive core, or another conductor. In some embodiments, the second conductor  108  may comprise copper, aluminum, or other materials. The substrate  100  may include a via  110 . The via  110  may comprise a conductive material that electrically connects the first conductor  102  to the second conductor  108 . In some embodiments, the via  110  may comprise copper, aluminum, or other materials. The via  110  may simply be part of the same piece of conductive material that comprises the second conductor  108 , and may have been formed at the same time as the second conductor  108  in an embodiment. In another embodiment, the via  110  may be formed separately from the second conductor  108  and have an electrical connection with the second conductor  108 .  
      The substrate  100  may include second and/or third dielectric layers  112 ,  114  as well. For example, the first conductor  102  may partially or completely cover the second dielectric layer  112 . The third dielectric layer  114  may cover the second conductor  108 . Additionally, the substrate  100  may include numerous other structures or layers, such as additional vias, additional conductors, additional dielectric layers, and other features.  
       FIG. 2  is a side cross sectional view that illustrates a portion of how the via  110  of the substrate  100  may be formed according to one embodiment of the present invention. An imprinting tool  202  with one or more features  204  may be pressed into the first dielectric layer  104  to transfer the features  204  on the imprinting tool  202  to the first dielectric layer  104 . Note that for simplicity, only the first dielectric layer  104  and the first conductor  102  are illustrated in  FIG. 2 . Other parts (not shown) of the substrate  100  may also be connected to the first dielectric layer  104  and first conductor  102  at this point. The one or more features  204  of the imprinting tool  202  may be part of a male pattern that imprints the first dielectric layer  104  with various depressions to allow later formation of lines, traces, vias, or other features through a process such as electroplating or another process. The first dielectric layer  104  on the first conductor  102  may be softened at the time it contacts the imprinting tool  202 . In an embodiment, the first dielectric layer  104  may comprise epoxy, and may be softened with heat, such as being raised to a temperature in a range of about 150 degrees Celsius to about 160 degrees Celsius. In other embodiments where the first dielectric layer  104  may comprise different materials, different temperatures may be used to soften the first dielectric layer  104 , or different methods may be used to soften the first dielectric layer  104 .  
       FIG. 3   a  is a side cross sectional view that illustrates one example of a result of an imprinting process such as described with respect to  FIG. 2 . Pressing the imprinting tool  202  into the first dielectric layer  104  has resulted in formation of a trench  302  in the first dielectric layer  104 . The trench  302  is defined by sidewalls  106  of the first dielectric layer  104  and may have various shapes, as discussed above with respect to  FIG. 1 . In the example illustrated in  FIG. 3 , the male feature  204  of the imprinting tool  202  has not reached all the way through the first dielectric layer  104  to the first conductor  102 . Some dielectric material  304  of the first dielectric layer  104  remains at the bottom of the trench  302 . Such remaining material  304  may prevent successful formation of a via  110  that electrically connects the first conductor  102  with the second conductor  108 . The material  304  may be in a very thin layer, such as a micrometer or less. This makes it difficult to detect since it is substantially optically transparent, and so thin that mechanical probes may penetrate it to reach the first conductor  102  to result in a false reading that the material  304  is not there.  
       FIG. 3   b  is a side cross sectional view that illustrates another example of a result of an imprinting process such as described with respect to  FIG. 2 . Like the example of  FIG. 3   a , in the example of  FIG. 3   b , pressing the imprinting tool  202  into the first dielectric layer  104  has resulted in formation of a trench  302  in the first dielectric layer  104 . The trench  302  is defined by sidewalls  106  of the first dielectric layer  104  and may have various shapes, as discussed above with respect to  FIG. 1 . In the example illustrated in  FIG. 3   b , the male feature  204  of the imprinting tool  202  has reached substantially all the way through the first dielectric layer  104  to the first conductor  102 . Substantially no dielectric material of the first dielectric layer  104  remains at the bottom of the trench  302 . This allows a via  110  to properly electrically connect the first conductor  102  with the second conductor  108 .  
       FIG. 4  is a schematic view of an embodiment of a detection device  400  for detecting whether there is material  304  at the bottom of the trench  302  formed by the imprinting tool  202 . A radiation source, such as UV source  402  may be used to generate radiation  404  directed at the trench  302  in the first dielectric layer  104 . The radiation  404  may be in the first range of wavelengths that is absorbed by the fluorescent material in the first dielectric layer  104 . In response to radiation  404  striking the material  304 , the fluorescent material within any material  304  remaining at the bottom of the trench  302  may emit electromagnetic radiation  406  in a second range of wavelengths. This radiation  406  may be detected by a detector  408 . The detector  408  may be a device such as a charge coupled device (“CCD”) connected to a microscope, where the microscope may be oriented to allow detection of radiation  406  emitted by material  304  at the bottom of the trench  302 , and to not receive or to filter out radiation emitted by fluorescent material in the rest of the first dielectric layer  104 . The first dielectric layer  104  and the first conductor  102  may be held in place by a stage (not shown) that is capable of accurately positioning the first dielectric layer  104  and the first conductor  102  relative to the source  402  and detector  408 . Such stages are known and available, for example, for SEM, e-beam exposure tools, wafer stepper/scanner stages, and interferometer applications.  
      In an embodiment, if the detector  408  detects an intensity of radiation  406  in the second range of wavelengths greater than a selected threshold intensity, the detection device  400  may determine that material  304  exists at the bottom of the trench  302 , and that formation of the trench  302  has failed. In such a case, the first dielectric layer  104  may be further processed to remove the material  304 , or may be discarded. In some embodiments, further processing to remove the material  304  may include one or more of a plasma etch, a reactive ion etch, a wet chemical etch, a salt bath, a laser ablation, or another processing method. After such processing, the detection device  400  may be used again to ensure that the processing successfully removed the material  304 .  
      In an embodiment, if the detector  408  detects less than the threshold intensity of radiation in the second range of wavelengths while radiation  404  from the source  402  is directed at the trench, this may mean that substantially no material  304  is at the bottom of the trench  302 . Thus, further processing may be performed to form the via  110 , the second conductor  108 , and the rest of the substrate  100 .  
       FIG. 5  is a side cross sectional view that illustrates the second conductor  108  and via  110  that may be formed on the first dielectric layer  104  and the first conductor  102  after the detector  408  detects less than the threshold intensity of radiation in the second range of wavelengths. In an embodiment, a conductive material such as aluminum or copper may be electroplated on the first dielectric layer  104  and the first conductor  102 . In such an embodiment, the second conductor  108  and via  110  may be different areas of a single contiguous piece of material, rather than separate, discrete structures. The rest of the substrate  100  may then be formed, to result in the substrate  100  illustrated and discussed in  FIG. 1 .  
       FIG. 6  is a schematic diagram of a computer system  602  according to one embodiment of the present invention. The computer system  602  may include the substrate  100  described above. A die  604  may be connected to the substrate  100  by connectors such as solder balls  606  or other connectors. The substrate  100  may be connected to a structure such as a printed circuit board (“PCB”)  608  by connectors such as solder balls  610  or other connectors. Additionally, the computer system  602  may include a memory  604  and/or a mass storage unit  614 , which may be connected to the PCB  608 . The memory  604  may be any memory, such as random access memory, read only memory, or other memories. The mass storage unit  614  may be a hard disk drive or other mass storage device. The computer system  602  may also include other components such as input/output units, a microprocessor, or other components.  
       FIG. 7  is a schematic view of an embodiment of a detection device  700  for detecting whether there is material  710  from the first dielectric layer  104  stuck on the imprinting tool  202 . The imprinting tool  202  may be tested by the device  700  after the tool  202  has imprinted a pattern on the first dielectric layer  104  a number of times. Material  710  from the first dielectric layer  104  may stick to the imprinting tool  202  as the tool  202  imprints the dielectric  104 . The detection device  700  is similar to the detection device  400  described with respect to  FIG. 4 . A radiation source, such as UV source  702  may be used to generate radiation  704  which is directed at the imprinting tool  202 . The radiation  704  may be in the first range of wavelengths that is absorbed by the fluorescent material in any material  710  from the first dielectric layer  104  stuck on the imprinting tool  202 . In response, the fluorescent material within the material  710  may emit electromagnetic radiation  706  in a second range of wavelengths. This radiation  706  may be detected by a detector  708 . The detector  708  may be a device such as a charge coupled device (“CCD”).  
      In an embodiment, if the detector  708  detects an intensity of radiation  706  in the second range of wavelengths greater than a selected threshold intensity, the detection device  700  may determine that material  710  from the first dielectric layer  104  has stuck to the imprinting tool  202 . In such a case, maintenance (such as cleaning the tool  202 ) may be performed on the imprinting tool  202 . In some embodiments, such maintenance or cleaning may include one or more of a plasma etch, a reactive ion etch, a wet chemical etch, a salt bath, a laser ablation, or another processing method. After such processing, the detection device  700  may be used again to ensure that the processing successfully removed the material  710 .  
      In an embodiment, if the detector  708  detects less than the threshold intensity of radiation in the second range of wavelengths while radiation  704  from the source  702  is directed at the tool  202 , this may mean that substantially no material  710  has stuck to the tool  202  and/or that no maintenance will be performed on the tool  202  at this time.  
      The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. This description and the claims following include terms, such as left, right, top, bottom, over, under, upper, lower, first, second, etc. that are used for descriptive purposes only and are not to be construed as limiting. The embodiments of a device or article described herein can be manufactured, used, or shipped in a number of positions and orientations. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above teaching. Persons skilled in the art will recognize various equivalent combinations and substitutions for various components shown in the Figures. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.