Abstract:
A defect detection method is disclosed, in which the method includes: providing a semiconductor sample, wherein the semiconductor sample comprises at least one defect; utilizing a failure analysis for detecting at least one suspected area on the backside of the semiconductor sample; utilizing a physical energy for forming a plurality of reference marks around the suspected area on the backside of the semiconductor sample; and utilizing the reference marks for determining the relative location of the defect on the front side of the semiconductor sample.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a defect detection method, and more particularly, to a method of detecting defects on the backside of a semiconductor sample.  
         [0003]     2. Description of the Prior Art  
         [0004]     In the semiconductor fabricating process, some small particles and defects are unavoidable. As the size of devices shrinks and the integration of circuits increases gradually, those small particles or defects have an even greater effect on the properties of the integrated circuits. In order to improve the reliability of semiconductor devices, a plurality of tests and failure analyses are performed continuously to find the root cause of the defects or particles. Then, process parameters can be tuned correspondingly to reduce a presence of defects or particles so as to improve the yield and reliability of the semiconductor fabricating process.  
         [0005]     Please refer to  FIG. 1 .  FIG. 1  is a schematic diagram of a method of defect detection  10  according to the prior art. As shown in  FIG. 1 , a sampling  12  is first performed to select a semiconductor wafer as a sample for following defect detection and analysis in advance. Next, a defect inspection  14  is performed. Normally, a proper defect inspection machine is utilized to scan in a large scale to detect all defects on the semiconductor wafer. Since there are too many defects on a semiconductor wafer, a manual defect review with the SEM cannot be directly performed for all defects in practice. Hence, a manual defect classification  16  is typically performed before the defect review  18 . After separating the defects into different defect types, some defects are sampled for the defect review  18 . Next, a defect root cause analysis  20  may be performed in advance according to the result of the defect review  18  to attempt to reduce the defect generation.  
         [0006]     In the prior art technology, the biggest problem lies in the determination of defects from the samples. Typically, there may be thousands of defects found in the defect inspection  14 . However, engineers are only able to pick a portion of the defects, such as  50  to  100 , to perform the defect review  18  and the following defect analysis. In general, the determination of the killer defects, which often have a large impact on the yield of fabrication processes, is totally dependent upon the personal experience of the engineers and most of the time, the engineers are only able to randomly pick up some samples for the defect review  18 . Thus, in most cases, since the samples in the defect review  18  are picked up randomly, it is obvious that only a few effective samples are valid and most parts of the defect review  18  are meaningless and ultimately, this leads to a huge waste of time and effort, and a great reduction in the accuracy of the following defect analysis.  
         [0007]     In addition to most defects that are located on the surface of the semiconductor wafer, which can be analyzed by a front side approach to perform a failure analysis, some defects strongly related to fabrication processes are located on the bottom layer or backside of the wafer and normally, defects that are hidden within the wafer are the most difficult to detect, especially for chips with multi-layer metal wires. Hence, a backside approach referred to as the layout navigation system has been recently introduced to perform a much more accurate failure analysis for determining the location of the defect. Nevertheless, circuit layout diagrams needed for the layout navigation system are highly confidential materials for most companies and are difficult to obtain. Consequently, the difficulty of obtaining the circuit layout diagrams often increases fabrication time and cost, and influences the reliability, electrical performance, yield, and overall production when the fabs are performing defect analysis. Therefore, there has been a strong demand for developing a defect detection method for solving the above-mentioned problems.  
       SUMMARY OF INVENTION  
       [0008]     It is therefore an objective of the present invention to provide a defect detection method to improve the time and cost of utilizing the conventional layout navigation system for performing defect detection on the backside of the semiconductor sample.  
         [0009]     According to the present invention, a defect detection method includes the following steps: providing a semiconductor sample, wherein the semiconductor sample comprises at least one defect; utilizing a failure analysis for detecting at least one suspected area on the backside of the semiconductor sample; utilizing a physical energy for forming a plurality of reference marks around the suspected area on the backside of the semiconductor sample; and utilizing the reference marks for determining the relative location of the defect on the front side of the semiconductor sample.  
         [0010]     According to the present invention, another defect detection method is disclosed, in which the method includes: providing a semiconductor sample, wherein the semiconductor sample comprises at least one defect; utilizing a failure analysis for detecting at least one suspected area on the backside of the semiconductor sample; utilizing a first physical energy for forming a plurality of first reference marks around the suspected area on the backside of the semiconductor sample; and utilizing a second physical energy and the first reference marks to form a plurality of second reference marks on the front side of the semiconductor sample for determining the relative location of the defect.  
         [0011]     According to the present invention, another defect detection method is disclosed, in which the method includes: providing a semiconductor sample, wherein the semiconductor sample comprises at least one defect; utilizing a failure analysis for detecting at least one suspected area on the backside of the semiconductor sample; utilizing a physical energy for forming a plurality of reference marks around the suspected area on the backside of the semiconductor sample; and utilizing abnormal voltage contrast results and the reference marks for determining the relative location of the defect on the front side of the semiconductor sample.  
         [0012]     In contrast to the conventional defect detection method, the present invention utilizes a first utilizes a failure analysis to determine the location of a suspected area on the backside of the semiconductor sample and after locating a physical energy damage signal, utilizes a non-contact physical energy to form a plurality of destructive reference marks around the suspected area on the backside of the semiconductor sample for marking the location of the defect, thereby greatly improving the difficulty, cost, and time of utilizing the conventional layout navigation system for performing defect detection on the backside of the semiconductor sample.  
         [0013]     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 DRAWINGS  
       [0014]      FIG. 1  is a schematic diagram of a defect detection method according to the prior art.  
         [0015]      FIG. 2  is a perspective diagram showing the means of examining a defect on the backside of the semiconductor sample.  
         [0016]      FIG. 3  is a perspective diagram showing the upward view of the front side of the semiconductor sample according to the first embodiment of the present invention.  
         [0017]      FIG. 4  through  FIG. 6  are perspective diagrams showing the means of examining the defect on both backside and front side of a semiconductor sample.  
         [0018]      FIG. 7  is a perspective diagram showing the means of examining the defect on the front side of the semiconductor sample according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]     Please refer to  FIG. 2 .  FIG. 2  is a perspective diagram showing the means of examining a defect on the backside of a semiconductor sample  100 . As shown in  FIG. 2 , a semiconductor sample  100  is first provided, in which the semiconductor sample  100  can be a semiconductor wafer, die, or chip according to different stage of the fabrication process. Preferably, a semiconductor wafer is utilized as an example in the present invention. The semiconductor sample  100  includes a front side  102  and a backside  104 , and at least a defect  106  or a suspected spot. The defect  106  or the suspected spot can be detected by utilizing a failure analysis technique, such as a hot spot analysis, IR OBIRCH analysis, or emission analysis to track a suspected signal produced on the backside  104  of the semiconductor sample  100  and finally locate the location of a suspected area.  
         [0020]     In an example of utilizing a photo-emission microscope to perform an OBIRCH analysis, a laser is first provided to scan the backside  104  of the semiconductor sample  100 . During the scanning process, a portion of the laser energy is converted to heat energy and if any defect or hole is present on the semiconductor sample  100 , the heat transfer of the area around the defect will become different than other areas of the same sample, thereby causing partial temperature transformation and forming abnormal signals. Additionally, a constant voltage can be utilized to connect to two ends of the semiconductor sample  100  and by relating the variation of the electrical current provided by the constant voltage with the pixel intensity of the image formed and relating the location of the pixel with the location scanned by the laser beam during an electrical current variation, the location of the defect can be determined. Consequently, the present invention is able to determine the location of the defect within a circuit and effectively examine problems such as short circuit or electrical leakage.  
         [0021]     Next, a non-contact physical energy is utilized to form a plurality of destructive reference marks  122  around the suspected area on the backside  104  of the semiconductor sample  100 . In other words, by utilizing the failure analysis such as the hot spot analysis, IR OBIRCH analysis, and emission analysis to first determine the location of the suspected area on the backside  104  of the semiconductor sample  100  and locating a physical energy damage signal, a laser emission device  120  is then utilized to form a plurality of reference marks  122  around the defect  106  on the backside  104  of the semiconductor sample  100  for determining the location of the defect  106 .  
         [0022]     Preferably, the reference marks  122  formed around the defect  106  on the backside  104  of the semiconductor sample  100  are observed from the front side  102  of the semiconductor sample  100 . Please refer to  FIG. 3 .  FIG. 3  is a perspective diagram showing the upward view of the front side  102  of the semiconductor sample  100  according to the first embodiment of the present invention. In general, the thickness of a semiconductor wafer is roughly between 9000 angstroms (Å) to 14000 angstroms and in order to accurately determine the location of the reference marks  122  on the front side  102  of the semiconductor sample  100 , users are able to adjust the strength of the laser beam source for forming a plurality of destructive reference marks  122  on the backside  104  of the semiconductor sample  100  and then observe the reference marks  122  from the front side  102  of the semiconductor sample  100 .  
         [0023]     Next, an optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), or focused ion beam (FIB) microscope is utilized to examine the front side  102  of the semiconductor sample  100 . According to different circumstances, a physical (such as a plasma etching process) or chemical (such as solutions) approach is utilized to perform a delayer process for determining the location and cause of the defect  106 .  
         [0024]     According to another embodiment of the present invention, a non-contact physical energy can also be utilized to form a plurality of destructive reference marks on both the front and back sides of a semiconductor sample for determining the location of the defect. Please refer to  FIG. 4  through  FIG. 6 .  FIG. 4  through  FIG. 6  are perspective diagrams showing the means of examining the defect on both the backside and front side of the semiconductor sample  200 .  
         [0025]     Similar to the first embodiment, a semiconductor sample  200  is provided, in which the semiconductor sample  200  includes a front side  202 , a backside  204 , and at least one defect  206  or a suspected spot. Next, a failure analysis, such as a hot spot analysis, IR OBIRCH analysis, or emission analysis is utilized to determine the location of the suspected area on the backside  204  of the semiconductor sample  200  and after locating the physical energy damage signal, a laser emission device  220  is utilized to form a plurality of reference marks  222  around the defect  206  on the backside  204  for marking the location of the defect  206 , as shown in  FIG. 5 . Next, the laser emission device  220  is utilized again for forming a plurality of reference marks  224  on the front side  202  of the semiconductor sample  200 . Preferably, this procedure can be performed repeatedly until the reference marks  224  on the front side  202  approach the reference marks  222  on the backside  222  and the reference marks  222  and  224  finally overlap each other, as shown in  FIG. 6 .  
         [0026]     Next, an optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), or focused ion beam (FIB) microscope is utilized to examine the front side  202  of the semiconductor sample  200  and according to different circumstances, and a physical or chemical delayer process is then utilized for determining the location and cause of the defect  206 .  
         [0027]     Additionally, the present invention also utilizes a constant voltage to connect to a semiconductor sample and determine the location of the defect on the front side of the semiconductor sample by observing the electrical current change generated by the voltage. Please refer to  FIG. 7 .  FIG. 7  is a perspective diagram showing the means of examining the defect on the front side of the semiconductor sample. First, a semiconductor sample  300  is provided, in which the semiconductor sample  300  includes a front side  302 , a backside (not shown), and at least one defect  306  or a suspected spot. Next, a failure analysis technique, such as a hot spot analysis, IR OBIRCH analysis, or emission analysis is utilized to determine the location of the suspected area on the backside of the semiconductor sample  300 , and after locating the physical energy damage signal relating to the suspected area, a laser emission device (not shown) is utilized to form a plurality of reference marks  322  around the defect  306  on the backside of the semiconductor sample  300 .  
         [0028]     Next, a constant voltage is provided to form a plurality of electrical currents for connecting to two ends of the semiconductor sample  300 , in which one end of the semiconductor sample  300  is connected to a voltage source V CC  whereas the other end is connected to ground. When the laser emission device is utilized, a portion of the laser energy will be transformed into heat energy and if a defect is present on the semiconductor sample, the heat transfer around the defect will be different from other areas without the defect, thereby causing partial temperature change and forming a plurality of destructive reference marks. Hence after the destructive reference marks are formed, the constant voltage can be utilized to connect to the semiconductor sample  300 , and by obtaining abnormal voltage contrast results of the area in proximity to the defect  306 , the location of the defect  306  can be determined from the front side  302  of the semiconductor sample  300 .  
         [0029]     In contrast to the conventional method of detecting defects within a semiconductor sample, the present invention first utilizes a failure analysis to determine the location of a suspected area on the backside of the semiconductor sample and after locating a physical energy damage signal, a non-contact physical energy is utilized to form a plurality of destructive reference marks around the suspected area on the backside of the semiconductor sample for marking the location of the defect. Next, approaches including laser markings or measuring abnormal voltage contrast results can be utilized to form a plurality of corresponding reference marks on the front side of the semiconductor sample or to emphasize the location of the defect. Finally, an optical microscope, scanning electron microscope, transmission electron microscope, or focused ion beam microscope is utilized in coordination with physical or chemical delayer processes to examine the front side of the semiconductor sample and analyze the location and cause of the defect. As a result, the present invention is able to greatly reduce the difficulty, cost, and time of utilizing the conventional layout navigation system for performing defect detection on the backside of the semiconductor sample.  
         [0030]     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.