Sample mounting or temporary bonding refers to a variety of techniques for laminating the device substrate to a handle wafer. There are two reasons for mounting a sample to a handle: 1) because the sample is smaller than the tool chuck (e.g. a 4" wafer on a 6" chuck or a small piece on a full wafer), or 2) to add mechanical support for fragile material during processing. For thin substrates (< 200 μm) the handle may be applied early and remain with the substrate through all levels of processing. Alternatively, the handle may be applied for a specific process step only. Common processing techniques that prompt the use of a handle include reactive ion etching and DRIE, grinding and lapping, and any process for which the substrate size is smaller than the handling requirements of the tool being used.
|About this Process|
|Equipment||Sample Mounting Station|
|Chemicals Used||Santovac 5, CrystalBond, KMPR|
This online course covers the fundamentals of sample mounting at the LNF and is also required for checkout on most plasma etch tools; see the tools checkout procedure for more details.
- Full course for initial training
- Link to unlocked course for later review
Supported mounting methods
The LNF supports several mounting methods using a variety of different materials. There are pros and cons to each of these methods, please read the documentation fully before choosing a method.
|Mounting Material||Temperature Range||Removal||Thermal Conductance||Material Compatibility||Notes|
|Santovac 5||Acetone||Good||Reacts with PR||Recommended mounting method|
|Crystalbond 555||< 50°C||DI, PRS2000||OK||Reacts with PR||Recommended for release processes|
|Crystalbond 509||< 120°C||Acetone||OK||Reacts with PR|
|Photoresist||PRS 2000, Acetone||Poor||Not recommended|
|KMPR||< 300°C||Remover PG||Good||Backside protection (no carrier)|
|WaferBond CR200||Xylenes, Acetone, IPA||OK||Good for long-term mounting|
Santovac 5 mounting
Santovac 5 is a viscous hydrocarbon oil that can be used to attach the sample to a carrier wafer. This is the recommended method of mounting for RIE processes. Please review the Santovac 5 SOP for more details.
Crystalbond is a wax that can be used to attach the sample to a carrier wafer. There are two types of Crystalbond: Low temperature 555 and High temperature 509. Please review which material is best suited to your process. For more information, please review the Crystalbond SOP.
Mouting to a carrier using photoresist is not recommended for most applications, particularly where excess heat may be generated or the sample will be placed in a high vacuum environment. If you think you still need to use photoresist to mount, please contact staff via the helpdesk ticket system for assistance.
WaferBond CR 200
WaferBond CR 200 is a material that can be used to mount a sample to a carrier for long term processing. This method is recommended for fragile samples or samples that will undergo a several processing steps before releasing. For more details, review the WaferBond datasheet.
Handle wafer alternatives
In certain situations, a carrier wafer may be unnecessary, but the back of the wafer still needs to be protected. Examples include etching small holes through a wafer.
Sample mounting station
There is a sample mounting station located in 1480B which can be used for a variety of the mounting methods described above. It contains the equipment and lab-provided materials needed for many of these mounting methods including two vacuum hotplates that can be used to mount samples without trapped air pockets between the sample and handle wafer. The only processes that are not performed here are mounting with KMPR, Dicing Tape, and WaferBond. The guidelines for using this station can be found here
Using the vacuum hotplate
This section explains how to use the vacuum hotplate for mounting wafers.
Equipment that requires mounting
The following RIE equipment may require that a sample be mounted to a carrier. The recommended process for this equipment is Santovac 5, but other alternatives are possible. The following table lists some of these alternatives.
|Tool||Santovac 5||Crystalbond 555||Crystalbond 509||Photoresist||KMPR||WaferBond CR200|
|STS Pegasus 4||Good||Good||Good||Poor||Good||Good|
|STS Pegasus 6||Good||Good||Good||Poor||Good||Good|
|STS Glass Etcher||Good||Poor||OK||Poor||N/A||Good|
|Oxford ICP RIE||Good||OK||OK||Poor||N/A||Good|