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Controlled laser thermocracking of dielectrics

#3337


Development of controlled CO- or CO2-laser -based technique for thermal cracking of dielectric wafers to chips

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics

Status
3 Approved without Funding

Registration date
01.08.2005

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • NPO Lavochkin, Russia, Moscow reg., Khimki

Collaborators

  • University of Aveiro, Portugal, Aveiro\nUniversity of Ioannina, Greece, Ioannina\nGlasTech Produktions- und Verfahrenstechnik GmbH, Austria, Hausmening\nNortheast Science & Technology, USA, MA, East Sandwich\nKorea Polytechnic University, Korea, Kyonggi-do\nLBE, France, Issy les Moulineaux\nBeams, Inc., Japan, Tokyo\nUniversity of Twente, The Netherlands, Enschede

Project summary

Nowadays, the world electronic industry reorients its efforts towards production of decreasingly smaller chips for processors and LEDs while imposing more stringent requirements on cut edge quality.

Most of the methods existing now for the cutting of dielectric wafers to chips rely on the laser scribing process [1]. Along with this, the principal tendency consists of the usage of lasers emitting as short as possible wavelengths (excimer, IV harmonic of neodymium laser) and very short pulses (less than 100 ns) [1]. These characteristics are required to make a narrow groove penetrating then into the wafer depth to crack it down to chips. Such a technology is capable of manufacturing chips sized as 350x350 m. Yet, it has a set of limitations:

  • Because of the thermal and physical coupled effects of the laser upon the chip elements, there is no doubt that the kerf between the chips packed, for instance, onto a sapphire wafer gets not contractible.
  • The chip’s edges will have microirregularities.

However, there is a technology free of the above-listed disadvantages. This is the high-efficiency controlled laser thermocracking technique [1] built around the process in which the wafer surface is heated locally by a laser beam to strong thermal stresses initiating controllable microcracks. The profits observed along with this are the virtually zero cut width (virtually zero kerf) and “mirror-class” quality (without microdefects) of cut edges. This technology has been approved successfully [1] on polycrystalline quartz and monocrystalline sapphire, borosilicate glasses. As a rule, such efforts were mainly based on CO2 lasers. Yet, the technology, though certainly promising, has three problems to deal with.
  • Because of the low penetration depth for CO2 laser, the microcrack is not deep.
  • The high-quality of the cutoff edges will prohibit intercrossing cuts much required to produce miniature components.
  • The maximum thickness of material that can be cut is limited.

Hence, it is much topical to find correct solutions to the above problems.

Project objectives:


1. Make a pilot laser facility for controlled thermal cracking of dielectrics based on:
  • cw CO laser as a principal cutting tool;
  • pulsed CO2 laser as a non-contact tool initiating microdefects;
  • controlled crack-finishing unit.
2. Calculate and make an optical channel for optimal laser power distribution on a dielectric being cut.
3. Perform a complex of thermal and mechanical coupled calculations determining optimal modes of wafer thermocracking depending on the laser type.
4. Perform experimental works on optimization of the modes of power-controlled CO laser thermocracking of dielectrics.
5. Starting from the specific features and characteristics of the proposed technique, determine its principal application fields. Estimate the capabilities of the controlled laser thermocracking technique in application to other materials relevant to the nuclear instrument-making and electronic industries.

This project fully complies with ISTC objectives and represents a logical continuation of the ISTC project #2130 since its main result - the automatic tunable CO laser – will find a powerful application to the precession cutting of any types of sheet glass (for LCD displays) and wafers made of various materials to chips to meet the ever-growing demand in the world market [1-25].

The project will provide highly qualified specialists of the RFNC-VNIIEF and Lavochkin Association employed formerly in nuclear R&D programs with an alternative employment; it also encourages the weapon developers in Russia to join the international scientific community.


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