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Templates for LED wafer processing

Posted In Templates - By Bettye Eddy on Tuesday, March 31st, 2020 With No Comments »

Seren Photonics Ltd is thrilled to announce the launch of its subsequent generation of semi-polar gallium nitride (GaN) on sapphire templates for LED wafer processing.

This modern-day generation of eleven-22 GaN templates is still based totally on Seren’s patented method evolved through Professor Tao Wang’s crew at the University of Sheffield.

The improved overall performance comes approximately via a production improve that now not best improves crystal quality, but additionally enhances manufacturing yield.

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This method has already finished qualification for 2” diameter product and as a part of its development activity, Seren has now tailored the improved method to the development of 4” and six” templates. “With demand for four” and six” accounting for over seventy-five % of the sapphire market for LEDs, they want to provide clients with enterprise preferred four” diameter wafers along with the option to upgrade to six” makes total commercial sense” stated Bedwyr Humphreys Chief Development Officer at Seren Photonics. Four” templates for purchaser sampling are anticipated during Q3 2015, with 6” deliberate to come online at some stage in H1 2016.

Experts in the semi-polar GaN discipline will realize that semi-polar GaN shows anisotropic behavior below x-ray diffraction. What this indicates is that, in contrast to c-aircraft GaN, semi-polar GaN crystal first-class is dependent on the route along the wafer that the measurement is taken. This latest development has conquered this problem yielding a semi-polar GaN layer with isotropic crystal fine. This not best enhances the optical isotropy of the material however also ensures electrical homes inclusive of mobility are also isotropic.

This latest era is now to be had for sampling in 2” diameter or custom sizes. At less than 5um thick, the GaN layer for these semi-polar templates is the thinnest to be had on the market today, making sure minimal wafer bow with most disorder blockading.

Introductory Information About Silicon Nitride Film Stress and Wafer Processing

Low-Stress LPCVD Nitride with a Film Stress of much less than 250 MPa Tensile is frequently used for building Membranes, Cantilever Beams, and other mechanical systems. Low-Stress Nitride is also very powerful as a KOH. The traits of silicon-nitride movies deposited with plasma-better chemical vapor deposition (PECVD) can vary in composition and physical houses. An essential parameter in the fabrication of micro-electro-mechanical systems (MEMS) devices is the control and tailoring of the film stress. In fact, silicon-nitride movie pressure can vary from tensile (as much as 800 MPa) to compressive (-500 MPa), depending on the PECVD deposition situations.

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One of the fundamental constructing blocks in silicon wafer processing and MEMS processing is the capacity to deposit skinny films of cloth onto a wafer. One such deposition technique is LPCVD Silicon Nitride, a skinny film deposition manner that coats all the uncovered regions of the wafer. The difference in mechanical properties between the nitride and the silicon wafer will introduce a “strain” inside the wafer + nitride gadget.

Tensile and Compressive Stress: If there’s an identical amount of nitride on both aspects of the wafer it’ll be in a balanced nation and continue to be flat.

If the nitride is eliminated from one facet of the wafer the system will no longer be in equilibrium and the wafer will bow. If the wafer curves up in the direction of the side with the nitride, the nitride is considered to be tensile. If the wafer curves down away from the facet with the nitride, the nitride is taken into consideration to be compressive.

Selecting the Right Film Stress: Choosing the best movie stress can be essential to yield and overall performance of the device. For instance, if Stoichiometric Nitride (800 Mpa Tensile) is used as a KOH mask, too thick of a movie can lead to micro-cracking and movie failure. Switching to a Low-Stress NItride (two hundred Mpa Tensile) will dispose of microcracking and enhance yield.

Film Stress for MEMS: Having too low of a film stress also can cause troubles for certain programs. Many MEMS foundry programs use silicon nitride as a membrane, diaphragm, or different suspended structure. Insufficient tensile strain can result in structures that may “sag” or “hunch”. Typically, the thinner the nitride, the extra tensile stress is wanted to preserve a suspended shape flat.

Remember, the entire suspended shape ought to be considered a “machine”. If extra compressive movies which include PECVD Oxide are added on the pinnacle of the nitride, extra stress should be constructed into the nitride to atone for it. The complete “device” ought to be tensile.

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Applications Guide: Here are a number of our nitride suggestions for select programs:

KOH Etch Mask: Nitride Thickness (500 to 3000 A)
Film kind: stoichiometric Nitride On Oxide Stress
Target (-300/800 Mpa)

Thickness (500 to ten,000 A)
Film kind: Low Stress Nitride Stress
Target (200 Mpa)

Thickness (500 to 30,000 A)
Film kind: Super Low Stress Nitride Stress
Target (50 Mpa)

Suspended Structures:
Nitride Thickness (Less than 500 A)
Film type: Low Stress Nitride Stress
Target (350 Mpa)

Thickness (500 to one thousand A)
Film type: Low Stress Nitride Stress
Target (300 Mpa)

Thickness (one thousand to 5,000 A)
Film type: Low Stress Nitride Stress
Target (250 Mpa)

Thickness (five,000 to 10,000 A)
Film type: Low Stress Nitride Stress
Target (200 Mpa)

Thickness (10,000 to 15,000 A)
Film kind: Low Stress Nitride Stress
Target (a hundred and fifty Mpa)

Thickness (15,000 to 20,000 A)
Film type: Super Low-Stress Nitride Stress
Target (one hundred Mpa)

Thickness (20,000 to 30,000 A)
Film type: Super Low-Stress Nitride Stress
Target (50 Mpa)

Jessica entered the Semiconductor Manufacturing discipline in 1998 and is now the founding father of Rogue Valley Microdevices in 2003. As Founder and CEO, Jessica has mounted the agency as a world-elegance silicon wafer supplier and MEMS Foundry Services.

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