Sample mounting

About this Process
Process Details
Equipment	Sample Mounting Station
Technology	Temporary bonding
Chemicals Used	Santovac 5, CrystalBond, KMPR

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.

Training modules

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 mounting

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.

Photoresist mounting

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.

Mounting with WaferBond should be performed in the EVG 510.

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.

These methods cannot be used if the sample is smaller than the requirements for the tool or if the wafer will be fragile after the process is complete.

The recommended method of backside protection is using KMPR. Please review the Backside Protection with KMPR SOP for more details.

Another alternative that can be used in very specific applications is using Dicing saw tape. This method is required to load a sample into the ADT 7100 Dicing Saw.

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.

Authorization

Use of the sample mounting station requires an active reservation on the scheduler. To gain access, complete the Sample Mounting Rise, above, and create a helpdesk ticket requesting authorization. An in-person training will be scheduled via the helpdesk system

Equipment that requires mounting

RIE equipment

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
LAM 9400	Good	OK	OK	Poor	N/A	Good
Oxford ICP RIE	Good	OK	OK	Poor	N/A	Good
P5000 RIE	Good	OK	OK	Poor	N/A	Good

Other equipment

• CMP Strasbaugh 6EC
  • Wax used to mount to handle can be found by the tool
• ADT 7100 Dicing Saw
  • Use dicing saw tape to mount