Technical Note

Waxless Mounting Wafer Polishing Templates
for Single Sided Polishing Machines

(TSK-America, Gigamat, Cybeq, Siltec, Spitfire, SpeedFam IPEC, Strasbaugh, Peter Wolters)

 

Waxless Mounting Polishing Templates


    POLISHING TEMPLATES

    Polishing Templates from PR Hoffman are a waxless mounting assembly used for single-sided polishing of silicon wafers and other semiconductor wafer materials. We use a buffed porous film material (1000 and 7000) or a non-porous material (1450) based on the application needs. When the surface of the material is wet, the surface tension between the wafer and the film provides the necessary adhesion to hold the wafer in place while the head moves to the polishing surface. To insure that the wafer stays on the head during polishing, we add a custom FR-4 template. The buffed films allow the wafer to rotate in the pocket.

Each template is designed to your specific polishing machine and wafer (diameter, initial and final thickness). We use CNC machinery to manufacture templates for any size and shape part up to 486 mm (19-1/8") - larger sizes may be available upon request.

PR Hoffman has been manufacturing and suppling lapping and polishing machinery, carriers, and process expertise to the semiconductor, optics, quartz and other industries since 1936. Our polishing templates reflect our sensitivity to the needs of the semiconductor industry and its specific needs. The concerns of flatness, cleanliness, and consistency are foremost in our material selection and manufacturing methods.

Polishing Templates in all three materials should be loaded to about 5 PSI. As the pressure approaches 15 PSI, the pore structure is over-compressed resulting in "high points" where some material will not compress any more and other areas that still compress a little bit more -- causing less than desirable surface profile.

To request a quotation, please supply the following information:

    Wafer Diameter:                                             Head Diameter:                             

    Thickness before Polish:                                     Thickness after Polish:                             


Polishing Templates
Comparison of Pad Materials:     NAPCON; 1000, 1000-DM, 7000, 1450, & BP-107
(Typical Data - not for specification. - contact factory)


Thickness
1000
520 micron ±20
1000-DM
525 micron ±15


7000
590 micron ±30
1450
610 micron ±50
BP-107
390 micron ±30

Pore Height
1000 (& -DM)
300-390 micron
7000
300-390 micron
1450
n/a - not open
BP-107
100-190 micron
Pore height dimension is measured without the substrate that pad material is mounted on.    Substrate on 1000 film is 125 micron. On 7000 and 1450 films it is 200 micron. NAPCON-1000 and NAPCON 7000 are "Buffed" pads, NAPCON-1000-DM is machined, and NAPCON-1450 is un-buffed (as cast).


Pore Diameter
1000 (& -DM)
35 to 55 micron
7000
33 to 53 micron
1450
n/a - not open
BP-107
41 to 51 micron
The pore diameter is recorded from measurement made at top of pore opening. While both 1000 and 7000 film pore measurements are similar the shape of open pore below top opening is different. On 1000 film the pore opening becomes wider toward bottom of pore such as a coke bottle. When pressure is applied to this type construction the pad material is easily deflected or folded down (compressed). The 7000 film’s pore diameter remains much the same from top opening to bottom of open pore. More like a cylinder. This creates a more rigid construction allowing for less compression or deflection. The amount of wafer that can be pressed into this type construction is less than 1000 film. The pore structure of 1450 film is similar to 7000 but is not detailed as this is a closed-cell material.


Pore Density
(percent %)
1000 (& -DM)
18 to 28
7000
20 to 30
1450
n/a - not open
BP-107
18 to 28


Deflection

1000 (& -DM)
at 5 psi, 0.0023" est.
at 15 psi, 0.0046"
7000
at 5 psi, 0.0012" est.
at 15 psi, 0.0015"
1450
at 5 psi, 0.0006" est.
at 15 psi, 0.00079"
BP-107
at 5 psi, T.B.D.
at 15 psi, T.B.D.

Compressibility
 (percent %)
 
27 to 37
 
6 to 20
 
3 to 7
 
13 to 23
We believe deflection is a more accurate comparison than measuring compression. Compression is a percentage gained by taking overall height (including various sub-straight heights) into distance material gives. Deflection however is an actual measurement from a controlled down force. For example, at 5 psi, 1000 film will deflect about 60 micron, while 7000 film deflection is about 30 micron, and 1450 film deflection is about 15 micron. As pressure is increased on 1000 film it will continue to deflect, but 7000 and 1450 films tends to "bottom out" above 5 psi.

Surface Friction
1000-DM has a smoother surface than 1000, and thus will allow more rotation (under light loading) which is desired for prime silicon wafer manufacturing. With pad material in a dry state 1000 film has less friction than 7000. We have not been able to control moisture evaporation well enough to test under wet conditions. We also have not developed a formulated procedure other than placing a known weight on pad surface positioned at a controlled angle and monitor the time required for weight to travel a measured distance.

Specific Gravity
( g/cm3 )
 1000 (& -DM)
0.41 to 0.51
 7000
0.58 to 0.68
 1450
0.67 to 0.75
 BP-107
0.76 to 0.86
Microphotographs

Surface / Profile

No Surface view for
1450 as it is closed-cell

 1000 (& -DM)

7000

 1450

 BP107

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conditioning brush carriers for double-sided planetary polishing machines from PR Hoffman!  
  1517 Commerce Ave., Carlisle, PA   17015
  Phone: +1 (717) 243-9900      Fax: +1 (717) 243-4542
  Email:  prhoff@prhoffman.com