Abstract:
The present disclosure relates generally to the field of semiconductor manufacturing. In one example, in a production flow of low-volume, high-precision semiconductor products, a method for controlling critical dimensions of a semiconductor product during a semiconductor processing operation in the production flow, the semiconductor processing operation requiring a desired energy value to achieve the critical dimensions includes: measuring a previously formed critical dimension on the product; calculating a first energy value based on the measured critical dimension and a desired critical dimension for the semiconductor processing operation; and obtaining the desired energy value based on the calculated first energy value and a previously-obtained desired energy for the semiconductor processing operation performed on a prior product in the production flow.

Description:
CROSS-REFERENCE  
       [0001]     This application is related to U.S. patent application Series No. (Attorney Docket No. 24061.170) filed on (Not yet filed). 
     
    
     BACKGROUND  
       [0002]     The present disclosure relates generally to the field of semiconductor manufacturing, and more particularly, to the field of integrated circuit metrology for controlling critical dimensions of features formed on semiconductor wafers.  
         [0003]     With the advancement of semiconductor manufacturing, current semiconductor fabrication design rules allow ultra large scale integration (ULSI) devices to possess submicron features, increased transistor and circuit speeds, and improved reliability. To ensure that the devices are of a desired size, e.g., they do not improperly overlap or interact with one another, the design rules define such things as the tolerances between devices and interconnecting lines, and the widths of the lines. The design rule limitation will often define a desired range for line and spacing dimensions, such as the width of a line or the amount of space between two lines permitted in the fabrication of devices.  
         [0004]     Frequently, dimensional errors indicate certain instability in a critical part of the semiconductor manufacturing processes. Dimensional errors may arise from any number of sources, such as optical (e.g., lens field curvature or lens aberration in a photolithography system), mechanical, or chemical (e.g., thickness non-uniformity of resist coating and anti-reflection coating (ARC)) sources. In one example, lithography machines, which facilitate pattern projection on wafers, may cause dimensional errors by supplying an incorrect energy amount (e.g., the radiation used for exposure). Accordingly, among other things, it is desirable to provide adequate control of the energy dose to ensure that the dimension complies with the predefined specification.  
         [0005]     For those reasons and other reasons that will become apparent upon reading the following detailed description, there is a need for an improved dimension controller. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures.  
         [0007]      FIG. 1  illustrates a simplified lithography system  100  according to one embodiment of the present disclosure.  
         [0008]      FIG. 2  illustrates a process performed by a critical dimension (“CD”) controller according to one embodiment of the present disclosure.  
         [0009]      FIG. 3  illustrates a method provided by the CD controller according to one embodiment of the present disclosure.  
     
    
     DETAILED DESCRIPTION  
       [0010]     The present disclosure relates generally to the field of semiconductor manufacturing, and more particularly, to the field of integrated circuit metrology for controlling critical dimensions of features formed on semiconductor wafers.  
         [0011]     For the purposes of promoting an understanding of the principles of the invention, references will now be made to the embodiments, or examples, illustrated in the drawings and specific languages will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0012]     Referring now to  FIG. 1 , shown therein is a simplified lithography system  100  according to one embodiment of the present disclosure. In this embodiment, the lithography system  100  may comprise one or more wafers  102 , inline process systems  108  and  110 , which may comprise a scanner or other lithography machines known in the art, metrology systems  112  and  114 , which may be any suitable machine known in the art such as CD-scanning electron microscope (CD-SEM), and a CD controller  116 . In this example, the CD controller  116  is a hardware/software system for controlling the critical dimension of the pattern by a feedback mechanism and algorithm through run-to-run process. The CD controller  116  may be designed for producing low-volume and high-quality semiconductor devices. However, it is also contemplated that the CD controller  116  may be used for other circumstances. The CD controller  116  may comprise software programs, such as C, C++, Java or other programs, to implement a process  200 , which will be described in connections with  FIG. 2 .  
         [0013]     Referring now to  FIG. 2 , shown therein is a process  200  performed by the CD controller  116  according to one embodiment of the present disclosure. In this embodiment, the process  200  may include two methods: an inline flow method  202  and a metrology method  204 .  
         [0014]     In one embodiment, the inline flow method  202  is performed by the inline process system  110  and/or the CD controller  116  ( FIG. 1 ). A request is made for the process system  110  to provide an appropriate processing operation, e.g., a predetermined amount of exposure energy. In response, the CD controller  116  may calculate the energy amount according to the method and algorithm in the current disclosure. In one example, the appropriate amount of energy may be calculated as follows: 
 
Amount of Energy=(DefaultEnergy+ReticleEnergy)*ToolRatio+Correction 
 
         [0015]     DefaultEnergy is a predetermined amount of exposure energy (expose dose, energy, or dose) for the system  110 , such as a best known method supplied by a tool supplier.  
         [0016]     ReticleEnergy is a predetermined amount of expose energy for the product being processed and the reticle being used. It may also be determined by a combination of a product identification and a reticle identification. In one example, the ReticleEnergy may be obtained from Table 1 as follows:  
                                                 TABLE 1                                   RETICLE ID   PRODUCT ID   RETICLE ENERGY                                        F123A   ABC 849   −0.65           F124A   ABC 849   −1.02           F125A   ABC 849   −0.4           F125A   ABC 850   −0.83                      
 
         [0017]     The Reticle ID refers to specific reticle (photomask, or mask). Product ID refers to a certain product being manufactured.  
         [0018]     ToolRatio is an amount determined by performances of different inline process tools. In one example, ToolRatio may be obtained from Table 2 as follows:  
                               TABLE 2                       EQUIPMENT ID   LINESPACE ID   TECHNOLOGY   TOOL RATIO   CONTROLLER ID                   NPD7C1   VIA   T094AHE       100 VIAX11-DTV       NPD7C5   VIA   S049ACA       106 CDMON       NPD7C5   M3   S049       115 IMP913       NPD7C5   M2   S049AAA       104 IMPX13       NPD7C5   M1   E738-S049AHA       91.603 MET113-                       E738       NPD7C5   M1   S049   91.603   MET113                  
 
         [0019]     Equipment ID identifies a particular photolithography equipment. Linespace ID identifies a specific patterning feature. Technology identifies a certain semiconductor process (e.g., 0.13 micron LOGIC). Tool Ratio is a value associated with the identified piece of equipment (from Equipment ID).  
         [0020]     Correction represents a compensatory energy value. In one example, Correction may be obtained from Table 3 as follows:  
                                             TABLE 3                       EQUIPMENT                   ID   PRODUCT ID   MASK LEVEL   CORRECTION                                NPABA3   TMH552   130A   0.0321       NPABC4   CEHM3S   130C   −0.0116       NPABC4   TME913A-EAZN   130A   −0.0334       NPABC4   TME913A-T3EAZN   130A   −0.018       NPABC4   TME913A-T4EAZN   130A   −0.0098                  
 
         [0021]     Mask Level represents a structural layer in a semiconductor wafer patterned by a corresponding mask.  
         [0022]     As will be described in connections with  FIG. 3  and the metrology method  204 , some of the parameters, such as ReticleEnergy, ToolRatio, and Correction, may be adjusted after feedback is provided to the CD controller  116 .  
         [0023]     Referring now to  FIG. 3 , according to one embodiment of the present disclosure, the metrology method  204  provided by the CD controller  116  begins at step  206 , where the CD controller calculates desired energy. In one embodiment, the step  206 , the CD controller  116  calculates the desire energy according to two formulas. First, Adjusted Energy may be calculated as follows: 
 
Adjusted Energy=(CD target−CD mean)*CD slope 
 
         [0024]     “CD target” may represent the targeted CD of the wafer. In one example, a 0.13 micron semiconductor product may comprise a CD of 0.13 micron.  
         [0025]     “CD mean” may represent the average (mean) of the measured CD data. After a wafer has been processed by the inline process system  110  of  FIG. 1 , a machine operator may transfer the wafer to the CD-SEM metrology system  112  of  FIG. 2  to measure the CD on the wafer. The measurement, which may be conducted by any known method, may utilize a microscope to obtain several sample points from the wafer.  
         [0026]     “CD slope” may be obtained by dividing the Amount of Energy (pursuant to the method  202 ) by the CD target.  
         [0027]     In furtherance of the example, Desired Energy may then be calculated by a feedback system. In one example, Desired Energy for the next run (represented by n+1, while n refers to the current run) may be calculated according to the following formula: 
 
Desired Energy ( n+ 1)=weight*Desired Energy ( n )+(1-weight)*(Final Energy+Adjusted Energy) 
 
         [0028]     In the above formula, Final Energy may be equal to the Amount of Energy obtained by the method  202  or other defined energy amount. The weight may be a value provided by a system user from such things as previous experience or other available data.  
         [0029]     At step  208 , an accumulator is used to calculate the Amount of Energy. In one embodiment, the CD controller  116  calculates the accumulated error between CD target and CD mean, according to the following formulas.  
         [0030]     The following calculations may be utilized:  
                 R   ⁡     (   t   )       =       R   ⁡     (     t   -   1     )       +   1       ,     
     ⁢       if   ⁢           ⁢       mask   tth     ⁡     (   t   )         ∉     {       mask     1   ⁢   th       ,     mask     2   ⁢   nd       ,   …   ⁢           ,     mask       R   ⁡     (     t   -   1     )       ⁢   th         }               (   a   )                     F   j     ⁡     (   t   )       =         F   j     ⁡     (     t   -   1     )       +   1       ,       if   ⁢           ⁢       f   jk     ⁡     (   t   )         ∉     {       f   j1     ,     f   j     ,     f   j3     ,   …   ⁢           ,       f   jk     ⁡     (     t   -   1     )         }               (   b   )                 N   ⁡     (   t   )       =       ∑     j   =   1       R   ⁡     (   t   )         ⁢       F   j     ⁡     (   t   )                 (   c   )                   Q     (   i   )       ⁡     (   t   )       =       ∑     j   =   1       R   ⁡     (   t   )         ⁢       ∑     k   =   1         F   j     ⁡     (   t   )         ⁢         Q   ~     jk     (   i   )       ⁡     (   t   )                   (   d   )                     Q   ~     jk     (   i   )       ⁡     (   t   )       =       ln   ⁢           ⁢       d   jk     ⁡     (   t   )         -     ln   ⁢           ⁢     f   jk                 (   e   )                   d   jk     ⁡     (   t   )       =           d   _     jk     ⁡     (   t   )           K   jk     ⁡     (   t   )                 (   f   )                     d   _     jk     ⁡     (   t   )       =           d   _     jk     ⁡     (     t   -   1     )       -       d   jk   last     ⁡     (   t   )       +       d   jk   new     ⁡     (   t   )                 (   g   )                   Q     (   i   )       ⁡     (   0   )       =         F   j     ⁡     (   0   )       =         K   jk     ⁡     (   0   )       =       N   ⁡     (   0   )       =       R   ⁡     (   0   )       =         d   jk     ⁡     (   0   )       =           d   _     jk     ⁡     (   0   )       =   0                       (   h   )             
 
         [0031]     Where: 
        Q (i) (t): accumulated tool distinction since last update for a same tool and a same control ID;     R(t): accumulated reticle number after last update for a same tool and a same control ID;     F i (t): accumulated number of exposure energy since last update for the j th  mask with a same tool and a same control ID;     K ij (t): accumulated number of same run since last update for the j th  mask under a same tool and a same control ID. Same run represents for runs of a same exposure energy. A repeating measurement does not account for same run;     N(t): accumulated number of runs since last update for a same tool and a same control ID. Same run only account for once;     f jk : exposure energy for k th  run and j th  mask with a same tool and a same control ID;     d jk   last : previous desire energy of a lot for k th  run and j th  mask with a same tool and a same control ID (only for a situation when a same lot is measured more than once); and     d jk   new : latest desire energy of a lot for k th  run and j th  mask with a same tool and a same control ID.        
 
         [0040]     Accordingly, K ij (t) may be obtained as follows: 
 
 Whenever any new CD data (d jk   new (t)) is obtained, check CDMEAN j   old (t):  
         If   ⁢           ⁢       CDMEAN   j   old     ⁡     (   t   )       ⁢           ⁢   exists   ⁢           ⁢   already     ,     then   ⁢           ⁢     {                 K   jk     ⁡     (   t   )       =       K   jk     ⁡     (     t   -   1     )         ,       if   ⁢           ⁢       K   jk     ⁡     (     t   -   1     )         ≠   0                       K   jk     ⁡     (   t   )       =   1     ,       if   ⁢           ⁢       K   jk     ⁡     (     t   -   1     )         =   0                     d   jk   last     ⁡     (   t   )       =         CDMEAN   j   old     ⁡     (   t   )       +       w   jk     ×   Δ   ⁢           ⁢     CD   last     ×     slope   i                         d   jk   new     ⁡     (   t   )       =         CDMEAN   j   new     ⁡     (   t   )       +       w   jk     ×   Δ   ⁢           ⁢     CD   new     ×     slope   i                 }     ⁢           ⁢   otherwise     ,       (         CDMEAN   j     ⁡     (   t   )       ⁢           ⁢   does   ⁢           ⁢   not   ⁢           ⁢   exist     )     ⁢           ⁢     {                 K   jk     ⁡     (   t   )       =         K   jk     ⁡     (     t   -   1     )       +   1       ,                   d   jk   last     ⁡     (   t   )       =   0                   d   jk   new     ⁡     (   t   )       =         CDMEAN   j   new     ⁡     (   t   )       +       w   jk     ×   Δ   ⁢           ⁢     CD   new     ×     slope   i                 }           
         End   ⁢           ⁢   If     ⁢             ⁢                 
 
         [0041]     In one example, the above calculations may be realized by applying a dynamic 3-dimensional array: the X axis may represent the control ID, while the Y-Z axes may represent exposure energy and contribution, respectively.  
                                                                                                             Reticle Number   Exposure Energy Number   f jk (t)             d   jk   last     ⁡     (   t   )                       d   jk   new     ⁡     (   t   )             K jk (t)   {overscore (d)} jk (t)   d jk (t)               Q   ~     jk     (   i   )       ⁡     (   t   )                                                                     j = 1   k = 1   f j1               d   11   last     ⁡     (   t   )                       d   11   new     ⁡     (   t   )             K 11 (t)   {overscore (d)} 11 (t)   d 11 (t)               Q   ~     11     (   i   )       ⁡     (   t   )                 j = 1   k = 2   f j2               d   12   last     ⁡     (   t   )                       d   12   new     ⁡     (   t   )             K 12 (t)   {overscore (d)} 12 (t)   d 12 (t)               Q   ~     12     (   i   )       ⁡     (   t   )                 j = 1         ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮             j = 1   k = F 1 (t)   f 1F     1     (t)               d     1   ⁢       F   1     ⁡     (   t   )         last     ⁡     (   t   )                       d     1   ⁢       F   1     ⁡     (   t   )         new     ⁡     (   t   )             K 1F     1     (t) (t)   {overscore (d)} 1F     1     (t) (t)   d 1F     1     (t) (t)               Q   ~       1   ⁢     F   1         (   i   )       ⁡     (   t   )                 j = 2   k = 1   f 21               d   21   last     ⁡     (   t   )                       d   21   new     ⁡     (   t   )             K 21 (t)   {overscore (d)} 21 (t)   d 21 (t)               Q   ~     21     (   i   )       ⁡     (   t   )                 j = 2   k = 2   f 22               d   22   last     ⁡     (   t   )                       d   22   new     ⁡     (   t   )             K 22 (t)   {overscore (d)} 22 (t)   d 22 (t)               Q   ~     22     (   i   )       ⁡     (   t   )                 j = 2         ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮             j = 2   k = F 2 (t)   f 2F     2     (t)               d     2   ⁢       F   2     ⁡     (   t   )         last     ⁡     (   t   )                       d     2   ⁢       F   2     ⁡     (   t   )         new     ⁡     (   t   )             K 2F     2     (t) (t)   {overscore (d)} 2F     2     (t) (t)   d 2F     2     (t) (t)               Q   ~       2   ⁢     F   2         (   i   )       ⁡     (   t   )                       ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮             J = R(t)   k = 1   f R1               d   R1   last     ⁡     (   t   )                       d     R   ⁢   1     new     ⁡     (   t   )             K R1 (t)   {overscore (d)} R1 (t)   d R1 (t)               Q   ~       R   ⁢   1       (   i   )       ⁡     (   t   )                 J = R(t)   k = 2   f R2               d   R2   last     ⁡     (   t   )                       d   R2   new     ⁡     (   t   )             K R2 (t)   {overscore (d)} R2 (t)   d R2 (t)               Q   ~     R2     (   i   )       ⁡     (   t   )                 J = R(t)         ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮               ⋮             J = R(t)   k = F R (t)   f RF     R     (t)               d       RF   R     ⁡     (   t   )       last     ⁡     (   t   )                       d       RF   R     ⁡     (   t   )       new     ⁡     (   t   )             K RF     R     (t) (t)   {overscore (d)} RF     R     (t) (t)   d RF     R     (t) (t)               Q   ~         (     R   ⁢   F     )     R       (   i   )       ⁡     (   t   )                                                The   ⁢           ⁢   total   ⁢           ⁢     Q   :       Q     (   i   )       ⁢           ⁢     (   t   )           =       ∑     j   =   1       R   ⁡     (   t   )         ⁢       ∑     k   =   1       k   =     Fj   ⁡     (   t   )           ⁢         Q   ~     jk     (   i   )       ⁢           ⁢     (   t   )                                         Final   ⁢           ⁢   Tool   ⁢           ⁢     Drift   :           ⁢     q   t     (   i   )           =     EXP   ⁡     (         Q     (   i   )       ⁢           ⁢     (   t   )         R   ⁡     (   t   )         )                                     New   ⁢           ⁢   Tool   ⁢           ⁢     Ratio   :       TR     (   i   )       ⁢           ⁢     (   new   )           =       q   t     (   i   )       ×     TR     (   i   )       ⁢           ⁢     (   old   )                              
 
         [0042]     Following the update of ToolRatio, used variables Q (i) , {tilde over (Q)} (i) , F j , K jk , N, R, d jk , d jk  may be reset under the following conditions: run to run automatic update (V2.0), initialization, manual F/B update (V1.0), or manual update following lens cleaning.  
         [0043]     Referring again to  FIG. 3 , at step  210 , a determination is made as to whether the ToolRatio may be adjusted. In one example, the following table may be used to determine whether ToolRatio may be adjusted.  
                                           Exponential               Accumulator       Product Count Range   abs(q t   (i)  − 1)   Action                   N t    (i)  ≧3 and N t   (i)  &lt;5   &gt;0.03   PE Determines 1. Adjust               2. Reset       N t   (i)  ≧5 and N t   (i)  &lt;10   &gt;0.02   Adjust by system       N t   (i)  ≧10   &gt;0.01   Adjust by system       N t   (i)  ≧15       Adjust by system                  
 
         [0044]     If the ToolRatio remains unadjusted, step  212  may update the Correction value. The step  212  of the method  204 , which updates Correction, may utilize the following formula: 
 
New Correction Energy=Desired Energy ( n+ 1)−(DefaultEnergy+1)−(DefaultEnergy+ReticleEnergy)*ToolRatio 
 
         [0045]     The parameters from the above equation, which may be stored in a database  222 , have already been described in connections with the method  202  and the step  206 .  
         [0046]     If the ToolRatio is adjusted, step  214  of the method  204  adjusts the ToolRatio value and at step  216 , a desired energy table is created. At step  218  the ReticleEnergy is updated accordingly.  
         [0047]     An example of utilizing the methods  202  and  204  will now be described. In this example, it can be assumed:  
         [0048]     ToolRatio of the tool APHO1 is 98.7%,  
         [0049]     ReticleEnergy of the product and layer TM1234-130A is 1.37,  
         [0050]     Correction of APHO1 and TM1234-130A is 0.32,  
         [0051]     For the sake of simplification, the accumulator is assumed to be 1.06,  
         [0052]     DefaultEnergy, which may be 55, is entered by the user.  
         [0053]     Now, pursuant to the method  202 , 
 
Amount of Energy=(55+1.37) *0.987+0.32=55.9572 mj (mini joule)  
 
         [0054]     Then, pursuant to the method  204  and assume that Desired Energy (n) is 55 and DefaultEnergy is 55,  
               Adjusted   ⁢           ⁢   Energy     =       ⁢       (       CD   ⁢           ⁢   Target     -     CD   ⁢           ⁢   Mean       )     *   CD   ⁢           ⁢   Slope                 =       ⁢       (     0.13   -   0.128     )     *   100                 =       ⁢   0.2             
               Desired   ⁢           ⁢   Energy   ⁢           ⁢     (     n   +   1     )       =       ⁢       Desired   ⁢           ⁢     Energy   ⁡     (   n   )       *     (     1   -   weight     )       +                     ⁢     (       Final   ⁢           ⁢   Energy     +     Adjusted   ⁢           ⁢   Energy       )                 =       ⁢       55   *   0.9     +       (     55.9572   +   0.2     )     *   0.1                   =       ⁢     49.5   +   5.61572                 =       ⁢   55.17572             
 
         [0055]     Then, pursuant to the step  210  of the method  204 , assessment will be made with respect to whether ToolRatio may be adjusted. If no adjustment is necessary, then following the step  212  of the method  204 , New Correction is as follows: 
 
New Correction Energy=Desired Energy ( n+ 1)−(DefaultEnergy+ReticleEnergy)*ToolRation=55.17572−(55+1.37)*0.987=−0.46174 
 
         [0056]     On the other hand, if ToolRatio is adjusted, the step  214  of the method  204  may be followed: 
 
New ToolRatio of APHO1=0.987*1.06=1.04622 
 
         [0057]     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. Accordingly, all such modifications are intended to be included within the scope of this invention.