Room Temperature Temporary Bonding/ Debonding Processes for 2.5/ 3D integration

1. Room Temperature Temporary Bonding/ Debonding Processes for 2.5/ 3D integration Tim McCrone Applications Engineer SUSS MicroTec Inc. 430 Indio Way Sunnyvale, CA IWLPC, November 11

2. Preview 2.5 and 3D Thin Wafer Introduction Material Requirements Current Material Solutions Market Overview

3. 2.5 and 3D Technologies Source:

4. Material Requirements No outgassing for Vacuum Processes Temperature stability must be greater than 250°C minimum, though some customers ask for as high as 350°C+ Compatible with all standard chemical processes for lithography, etch, and plating Low stress bonding and debonding to prevent damage to the thinned wafer

5. Material Requirements Largest Barrier is Cost of Ownership Lowering the cost of ownership requires a minimized cost of materials Lower inputs through the use of improved recipes saving solvent or adhesive. Effectively recycle carriers using tape, solvent, or plasma processes Increase throughput of tools by lowering process complexity and optimizing idle times

6. Bonding Flowchart TEMPORARY BONDING Flip Wafer Apply Adhesive or Release Layer (Spin Coat, Laminate Dry Film) Cure Adhesive or Release Layer (Temperature, Plasma) Device Wafer Liquid Phase or Thermocompression Bond Cure Adhesive – Optional(Temperature, UV) Apply Adhesive or Release Layer (Spin Coat, Laminate Dry Film) Cure Adhesive or Release Layer (Temperature, Plasma) Carrier DEBONDING: MECHANICAL OR LASER ASSISTED AT ROOM TEMPERATURE Thinned Device Wafer Flip Wafer Flip Wafer Clean Carrier(Wet, Plasma) Carrier Attach Wafer Stack to Tape Frame Mechanical- or Laser Assisted Debonding at Low / Room Temperature Clean Device Wafer on Tape Frame Peel Adhesive(De-taping)

7. Different Bonding Methods Adhesives can be broken down into various groups: Whether the material is a thermoset or a thermoplastic If it debonds at the carrier or the device interface What the debond methods the material can use are There are many different materials manufactures in the space, and all materials have their own advantages

8. Polymer Types Thermoplastics are materials that soften at a higher temperature. These take advantage of thermocompression bonding. Thermoset materials undergo an irreversible cross linking with temperature. These can be fully liquid or only partially reflow while crosslinking to have a self leveling effect

9. Debond Methods Low stress and no heat prevents solder deformation or diffusion during debonding

10. Debonding Methods Carrier release allows for low debond forces that are not dependent on the topography. The device wafer must be cleaned such that no residue remains. Carrier release allows for the use of mechanical or laser debonding Carrier Side Release

11. Debonding Methods Device release allows for low cost device cleaning after debond The adhesive must come free of device topography without a high application of force Device side release still requires for effective recycling of the carrier wafer. Device Side Release Clean, 50µm thindevice wafer Adhesive on carrier Bumps on device wafer SEM images from

12. Mechanical Debonding Mechanical debonding applies force to the carrier wafer, while minimizing the force applied to the device wafer. By initiating a flaw in the bond surface and controlling the force applied to the carrier wafer the carrier and the device can be separated Controlling the debond front prevents damage to either the carrier or the device wafer.

13. Eximer Laser Debonding Pulsed Excimer laser line beam Optional UV- absorption layer Eximer laser debonding produces zero force on the device wafer. The material’s absorption of the energy forces the substrates apart. Since the carrier and device wafers have already been separated by the mechanical force of the gas the wafers separate from eachother easily Substrates must use glass carriers. Ideally CTE matched glasses should be used to prevent excessive stress. Only the top 200-300nm of material is removed. Glas Carrier (UV-absorbing) Adhesive Device Wafer

14. Excimer Laser Debonding Laser debond carriers can be recycled quickly using an O2 plasma. Device wafers can be cleaned using the appropriate solvent or a tape peel process.

15. Device Wafer Cleaning Challenges for cleaning include finding appropriate tape with the required chemical resistance or protecting the tape, and optimizing the recipe for minimal solvent consumption Understanding and improving the clean recipe to minimize the amount of solvent used is important to reducing the COO

16. Market Overview Debond / Clean (20-50% of CoE) Temporary Bond (50-80% of CoE) Normalized Cost of Equipment* / Wafer ProcessQualificationat Institute Level andon Customer Samples Qualifiedfor / in Productionon SUSS Equipment Maturity *Cost of Equipment (CoE) includes: Bonder / Debonder / Device Wafer Cleaner Carrier cleaning / recycling is not considered

17. Market Overview Typical throughput has increased for bonding from 15-20 wafers. The cost of ownership for bonding has improved primarily because of reductions in complexity of the process and cycle times Mechanical debonding throughput is 20 wafers per hour Eximer laser debonding processes have a 40 wafer per hour throughput Cleaning tools for thin wafers on tape frames have 20 wafer per hour throughputs. The primary cost of ownership for cleaning comes from how efficient the solvent is.

18. SÜSS MicroTec Lithography GmbH Ferdinand-von-Steinbeis Ring 10 75447 Sternenfels www.suss.com