The National Committee for Employer Support of the Guard and Reserve has presented Lattice Materials with an award recognizing the company for its commitment to national security, protecting liberty and freedom by supporting employee participation in America’s National Guard and Reserve force.  The Patriotic Employer Award was presented to the company by Hank Adams, Bozeman ESGR Area Chairman after being nominated by the Company’s Purchasing Manager, Captain Russ Parker, who will soon be deployed to Iraq for Operation New Dawn. Lattice Materials’ President, Don Profota, has fostered a culture of respect and support for the U.S. armed forces and works closely with the Company’s military members to ensure they are able to attend all scheduled military training and schools without a loss of pay or benefits and without problems due to work scheduling.  Lattice Materials’ support extends throughout the organization with each employee playing a role in the creation of a powerful and resolute support system.  Lattice Materials is the world leader in silicon and germanium infrared optical blanks, curves and thin film materials and is located in Bozeman, Montana. The Company has been serving the aerospace and defense industries with quality materials for over 20 years.

Lattice Materials Published in Solar Novus

Lattice Materials was just published in Solar Novus! Please take a few minutes to read through the article below:

http://www.solarnovus.com/index.php?option=com_content&view=article&id=1049:silicon-resistivity-key-to-solar-efficiency&catid=38:application-tech-features&Itemid=246

Silicon Resistivity: Key to Solar Efficiency

By Peter Brown, Lattice Materials

In the quest to improve efficiency and reduce costs associated with solar energy, what goes into a solar cell at the very beginning is just as important as the energy that comes out. When the process begins, highly purified silicon is paramount.

Highly purified silicon (Si, >99.999% purity) is a well-known material for applications such as semiconductors, solar cells, and infrared optical components, both transmissive (lenses) and reflective (mirrors). The physical characteristics of the silicon are important, but they vary from one application to another. Physical characteristics include optical transmission, resistivity, type (N or P), orientation, carrier lifetime, index of refraction and purity.

Looking at the table below, resistivity is the one characteristic that’s of primary importance across the board (with the exception of reflective optics).

	Electronics	Solar Power Generation	Transmissive Optics	Reflective Optics
Optical Transmission	N	N	P	N
Resistivity	P	P	P	N
Type (N or P)	P	P	S	N
Orientation	P	S	S	S
Carrier Lifetime	P	P	N	N
Index of refraction	N	N	P	N
Purity	P	P	P	P

Relevance of common silicon specifications, by application
P=primary. S=secondary. N=no importance

Resistivity is important in solar power generation because it shows the degree to which a material tends to impede the flow of electrical current. (Note that it is related to, but not equivalent with, resistance, expressed in Ohms.) Resistance is measured for an individual electrical component; i.e., the voltage applied across the component, divided by the amount of current conducted with that voltage applied. Resistivity is a bulk characteristic of the material itself, regardless of how that material is eventually processed into an electrical component.

Low resistivity materials conduct electricity better than high resistivity materials. For example, silver, an excellent conductor, has a resistivity of 1.59×10^-8 Ohms·cm, whereas glass, an insulator, has a resistivity of 10¹⁰ to 10¹⁴ Ohms·cm. The middle contains pure silicon, a semiconductor with a theoretical resistivity of 6.40×10⁴Ohms·cm when no dopants are added.

Dopants and resistivity

When Czochralski growth is used in solar wafer manufacturing, it must contain the proper dopant at the right quantity in order to produce silicon that can be used in solar wafers. Without the dopant, the silicon is useless for the solar industry.

Nearly all applications for silicon require the addition of dopants to produce the particular resistivity required. Dopants are either P type (typically boron) or N type (phosphorous, arsenic, or antimony). Dopants are added to the silicon as part of the crystal growth process, most commonly Czochralski growth (Cz). The amount of dopant added is very small, typically in the parts per billion to parts per thousand range. The following table lists some values of resistivity, and the dopant concentrations that produce these values:

P (Boron)				N (Phosphorous)
Resistivity ohm-cm	ppba	atoms/cm3	atoms/gm Si	ppba	atoms/cm3	atoms/gm Si
100	2.6	1.35 EE+14	5.6 EE+13	0.86	4.2 EE+13	1.8 EE+13
10	27	1.35 EE+15	5.6 EE+14	8.8	4.4 EE+14	1.9 EE+14
1	290	1.45 EE+16	6.2 EE+15	96	4.8 EE+15	2.1 EE+15
0.1	5500	2.8 EE+17	1.2 EE+17	1550	7.8 EE+16	3.4 EE+16
0.005	410000	2.0 EE+19	8.6 EE+18	240000	1.2 EE+19	5.3 EE+18

The actual amount of dopant added to the silicon is very small. For example, a typical solar application calls for P type material, with resistivity > 1 ohm-cm. From the table, we can see that this resistivity corresponds to 6.2 x 10¹⁵ atoms of boron per gram of silicon. For a 50 kg charge of silicon in the Cz furnace, this doping level equals about 5.5 milligrams of boron dopant.

The way it works

In the Cz process, the silicon and dopant are loaded into a quartz crucible, melted, and stabilized at about 1400°C. A seed crystal is then dipped into the melt, and as it is slowly pulled upward out of the melt the silicon/dopant mixture freezes onto the seed in perfect crystalline structure. Since the solubility of the dopant is higher in the molten silicon than the solid crystal ingot, the dopant is more concentrated in the melt as the crystal is pulled and the melt consumed. The result is that the bottom of the ingot contains a higher dopant concentration than the top of the ingot, and therefore resistivity decreases from the top to the bottom of the ingot.

Czochralski (Cz) Growth For Solar Wafer Manufacturing

If the dopant concentration, and thus resistivity, varies beyond the required specifications over the length of the ingot, it will have a negative impact on process yield. For this reason, techniques have been developed to allow for controlling silicon and dopant amounts in the melt over the course of the run, and thus create a more uniform resistivity profile.

Lattice Materials Silicon Growth Room

Thermal donors, and the affects of annealing on resistivity

The Cz growth process introduces a small amount of free oxygen atoms into the silicon crystal. This oxygen diffuses out of the quartz (silicon dioxide) crucible that contains the molten silicon. These oxygen atoms are also known as thermal donors, and behave as an N-type dopant. That is, they counteract the dopant effect of a P-type ingot, or magnify the dopant’s effects in an N-type ingot.

In wafer processing, a typical process is to eliminate these thermal donors by annealing the wafers at temperatures above 1000 °C, and then quenching the wafers quickly through the critical temperature range (400-750 °C) where thermal donors are created. By removing the thermal donors, the targeted resistivity is better controlled.

Silicon ingots are often annealed after growth for stress relief. If an ingot is not grown slip-free (i.e., it has dislocations in the crystal lattice), it will have inherent stresses that contribute to fractures and chips during the manufacturing process. This is especially true of polycrystalline silicon, in which there is no single crystal lattice in the ingot. These stresses can be relieved through annealing of the ingot prior to processing. This annealing can also have the effect of reducing local variations in resistivity across the ingot.

Silicon Ingots

As new techniques for controlling the uniformity of resistivity across an ingot are discovered, it will be crucial for wafer manufacturers to adopt those techniques. The solar industry is evolving very quickly and only those manufacturers who stay on the cusp of technology will maintain a competitive advantage.

About the Author

Peter Brown is Manager of Sales and Marketing at Lattice Materials. Specialists in precisely controlling resistivity in silicon ingots for over twenty years, Lattice Materials routinely provides Czochralski crystal growth seeds for the solar industry. Lattice Materials also manufactures polish-ready infrared and reflective optics and provides a wide range of thin-film deposition materials.

Copyright © 2010 Novus Media Today, LLC. All Rights Reserved.

Press Release - Witness Sample Stocking Program

Check out the new Lattice Materials press release on our witness sample stocking program: http://www.prnewswire.com/news-releases/thin-film-coating-witness-samples-now-being-stocked-by-lattice-materials-96903564.html

Thin Film Coating Witness Samples Now Being Stocked by Lattice Materials

 

BOZEMAN, Mont., June 22 /PRNewswire/ -- In response to growing demand for rapid delivery and competitive pricing, Lattice Materials recently started stocking thin film coating witness samples for its customers. The program takes the burden and expense of inventory off the company's customers and improves their experience with Lattice.

As Peter Brown, Sales and Marketing Manager at Lattice Materials explained, "The witness sample stocking program saves our customers money in three ways:

1. They can buy in smaller quantities than if we ran a polishing operation just for their order; because we make the witness samples in bulk, they can enjoy quantity discounts without having to buy in large lots.
2. They can get extremely fast delivery, without having to pay any expedite fees;
3. Because delivery is within a few days, they can stock much smaller quantities and save on inventory costs."

Lattice Materials has built its reputation on high quality and consistent performance in its products – from infrared optical parts to thin film deposition materials. The stocking program has made the same quality and performance available without the hassle of lead times.

Brown continued, "Lattice is proud of our 20-year history of specialized support of germanium and silicon in infrared optics and coating applications. The witness sample stocking program is one more example of Lattice's leadership in these strategic materials."

The witness sample stocking program goes hand in hand with the company's new sputtering target stocking program. Low resistivity and undoped targets have been made available in common round sizes.

With constant pressure to maintain higher levels of thin film coating performance at lower costs, the Lattice Materials stocking programs are an invaluable resource. Ordering only what is needed and having it arrive just in time is an exceptionally valuable proposition in this increasingly competitive industry.

Lattice Materials is the world leader in germanium and silicon infrared optical blanks, curves, CNC machined parts and thin film deposition materials. Parts made by Lattice Materials are found in products such as night-vision goggles, infrared cameras, missiles and the most advanced military aircraft in the world. The company's global sales and support network ensures top quality service and ease of transaction. Lattice Materials is ISO 9001:2008 certified and ITAR compliant. For more information, please visit www.LatticeMaterials.com.

This release was issued on behalf of the above organization by Send2Press(R), a unit of Neotrope(R).http://www.Send2Press.com

SOURCE Lattice Materials

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New Curve Generator Has Arrived!

Lattice Materials just took delivery of its new Optipro eSX 200, five axis optical machining center. This outstanding and industry leading curve generator will allow the company to realize a significant increase in both capacity and tolerances.



The machine has the capability to spherical grind, edge and also provide various CNC milling functions. Spherical generating work on this machine can be done from 5mm up to 300mm diameter (depending on the radius configuration).

With the Optipro eSX 200 curve generator, Lattice Materials has gained the ability to produce prepolish surface finishes on large diameter parts (150mm to 300mm) utilizing D15 and D7 resin bond tooling. We also now have the ability to produce sag tolerances of +/-1 micron depending on radius configuration.

This machine is already being taken advantage of by several of Lattice Materials' largest customers.  They are extremely impressed by our capabilities and as always, our customer care. 

One of the company's UK customers said: "We've never had a problem with your materials. We basically take it straight from the packaging to pre-polish and we don't even need to inspect them first."

That's proof of the Lattice Materials quality guarantee in action.

Visit Lattice Materials online for more information or to request a quote. 

You may also call (406) 586-2122.

Lattice Materials Announces Stocking of Sputtering Targets

Starting immediately, sputtering targets in most popular round sizes will be available for immediate shipping from Lattice Materials. Customers will get the same high quality material and consistent target performance that Lattice Materials has always provided.  

You can now order small quantities of targets that will be immediately shipped.  Customers will save money by keeping inventory as well as minimum order levels very low. Low resistivity and undoped targets are available.


Low Resistivity Targets:              Undoped Targets:
· Monocrystalline                        · Monocrystalline
· P-Type, Boron Doped                · Undoped/Intrinsic Si
· Resistivity 0.005-0.020 Ohm cm  · Diameters: 2", 3"
· Diameters: 2", 3", 4", 6" and 8"   · Resistivity >1 Ohm cm
· Thickness: 0.125", 0.250"          · Thick: 0.125", 0.250"

Call or go online today for your custom quote!

(406) 586-2122        www.latticematerials.com

Lattice Materials Announces Stocking of Thin Film Coating Witness Samples

Thin Film Coating Witness Samples are now in stock at Lattice Materials! Cut inventory, costs and save time through this new program.

Keep your coating department running and reduce your costs by ordering our standard silicon coating witness samples. You get the same high quality and consistent performance that Lattice Materials has always provided.

"We wanted to give our customers another reason to do business with Lattice. The easier we can make their operations, the more value they will see in us." said Peter Brown of Lattice Materials. Peter is the Manager of Sales and marketing for the company and has been working to make Lattice even easier to work with.

Lattice Materials has set the industry standard for quality and ease of transaction. Ask around, our reputation precedes us!

Call or go online today for your custom quote!

(406) 586-2122        www.latticematerials.com

Germanium optical products now at much lower prices from Lattice Materials!

Bozeman, Mont., USA - Lattice Materials has strived for over 20 years to provide highly competitive pricing on its products. Now, due to process and supply chain improvements, the company has been able to reduce Germanium blank prices substantially. 

Having been highly competitive in Silicon products for quite some time, the Lattice Materials name has become synonymous with dedication to quality, consistency and fast turn-around. With the new capabilities, the company expects Germanium products to occupy a vastly increased portion of the business.

"Germanium is a superior material for infrared optical applications," commented Peter Brown, Manager of Sales and Marketing at Lattice Materials, before continuing, "The new pricing levels allow us to be truly competitive internationally. We're really excited and the response from our customers so far has been tremendous."

Lattice Materials has the manufacturing expertise to create parts with virtually any characteristics that the customer requires - from windows to curves to complex machined shapes. All parts are subjected to rigorous quality inspections before shipment to ensure a quality product every time. The company is ISO certified, licensed with the Department of State and fully compliant with ITAR laws and regulations.

Call or go online today for your custom quote!

(406) 586-2122        www.latticematerials.com