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= Proximity Effect Correction =
= Proximity Effect Correction =
Apart from conversion to V30 the prime use of Beamer is to do Proximity Effect Correction (PEC). This is done through the PEC node. The PEC node has a quite a few options and different ways to define a Point Spread Function (PSF). The PSF is a radially symmetric function around the beam spot that defines dose received by the resist both due to the incident beam but also from scattered electrons. The PSF used in Beamer can be defined in two ways; either based on gaussian functions where the user supplies the parameters used to define the functions, or the PSF can be based on Monte Carlo simulations of electron scattering. In any case the PSF is mainly dependent on beam energy (acceleration voltage) and substrate material. The JEOL 9500 system is always used at 100 kV, the Raith eLine system can however be used at any acceleration voltage between 1 and 30 kV. The PSF changes drastically with acceleration voltage and it is very important to use a PSF generated at the correct acceleration voltage. Beamer comes with its own Monte Carlo simulator called Tracer. In Tracer one can set up a substrate material stack and simulate electron scattering at the desired acceleration voltage. The PSF can be output as a file and loaded into Beamer for PEC.
Apart from conversion to V30 the prime use of Beamer is to do Proximity Effect Correction (PEC). This is done through the PEC node. The PEC node has a quite a few options and different ways to define a Point Spread Function (PSF). The PSF is a radially symmetric function around the beam spot that defines dose received by the resist both due to the incident beam but also from scattered electrons. The PSF used in Beamer can be defined in two ways; either based on gaussian functions where the user supplies the parameters used to define the functions, or the PSF can be based on Monte Carlo simulations of electron scattering. In any case the PSF is mainly dependent on beam energy (acceleration voltage) and substrate material. The JEOL 9500 system is always used at 100 kV, the Raith eLine system can however be used at any acceleration voltage between 1 and 30 kV. The PSF changes drastically with acceleration voltage and it is very important to use a PSF generated at the correct acceleration voltage. Beamer comes with its own Monte Carlo simulator called Tracer. In Tracer one can set up a substrate material stack and simulate electron scattering at the desired acceleration voltage. The PSF can be output as a file and loaded into Beamer for PEC.
=Dose variations=
== Dose variation defined by datatype or layertype ==
[[File:beamer7.jpg|400px|right]]
When designing your pattern, you can define a dose variation either by defining different areas in different GDS datatype or in different layertype.
In both cases you import the GDS-file as usual into BEAMER, importing all layers. The layers should be visible when you view the GDSfile:
If you defined different doses by different GDS layers, you should tick 'Datatype to Class' under 'Advanced' when you convert to v30.
If you defined different doses by different layer type, you should tick 'Layer to Class' under 'Advanced' when you convert to v30.
View the v30-file and make sure all variations have been converted correctly.
In the jdf-file, manually create a shot modulation (similar to the jdi-file created by PEC) that fits to the number of layers in your v30-file. This shot modulation should be defined in the end of the jdf-file (see the sdf- and jdf-file manual). In the example below, the three layers (green, blue and red in the BEAMER viewer to the right) are defined to have shot modulation from -20 % to + 20 % of the base-dose:
<br clear="all" />
<pre>
JOB/W  'TEST',4        ; 4 inch wafer
PATH DTU5M
  ARRAY    (0,1,0)/(10000,3,10000)
    ASSIGN  P(1)-> ((*,*),SHOT1)     
  AEND
PEND
LAYER    1
P(1)  'fredrikpnov1507prox.v30'
SPPRM 4.0,,,,1.0,1
STDCUR 0.22  ;nA
SHOT1:  MODULAT  (( 0, -20) , ( 1, 0) , ( 2, 20))
END
</pre>
== Dose variation defined by an array in jdf file ==
Another even faster way to define dose modulation (if you have less than 10-15 different doses) is to repeat the pattern (v30-file) in an array with different doses in the jdf file, just type the dose modulation you wish to apply to every chip in the array:
<pre>
JOB/W  'TEST',4        ; 4 inch wafer
PATH DTU5M
  ARRAY    (-10000,2,10000)/(10000,1,10000)
    ASSIGN  P(1)-> ((1,1),SHOT1)
    ASSIGN  P(1)-> ((1,2),SHOT2)
    ASSIGN  P(1)-> ((2,1),SHOT3)
    ASSIGN  P(1)-> ((2,2),SHOT4)     
  AEND
PEND
LAYER    1
P(1)  'tjulahej.v30'
SPPRM 4.0,,,,1.0,1
STDCUR 0.22  ;nA
SHOT1:  MODULAT  (( 0, -20))
SHOT2:  MODULAT  (( 0, -10))
SHOT3:  MODULAT  (( 0, 0))
SHOT4:  MODULAT  (( 0, 10))
END
</pre>
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