Prepaid cell phones are a great option for people who are looking to avoid the hassles involved with signing a contract and the costly expenses that come with overage charges. These days, you can find a lot of prepaid cell phone plans that can rival the service you would get with a traditional service. Many of the large companies who have the typical two-year contract model offer prepaid or pay as you go methods of mobile phone use.
As a result, there is a lot of choice out there. This is good on the one hand, because it means there is competition and a lot of different companies to choose from, but it also makes it difficult to narrow it down to one company and actually make a choice. You also want to try to find the best deal and that involves comparing postpaid and prepaid cell phone offers to each other to find the best value for your precious money.
The last thing you want to do is pay too much and not use all the cellular minutes you pay for. But you also want to avoid paying too little, so you run out of minutes too soon or have to pay expensive overage minute charges.
Most of the well-known cell phone networks offer post paid as well as prepaid plans. It is worth your while to look at the costs of both, as you keep in mind how many minutes come with each plan. Virgin Mobile offers a pay as you go plan that includes the feature of roll-over minutes, which means you get to carry unused minutes over into the next month and use them. Typically, this can be a welcome feature in a post paid cell phone plan, but as an incentive, often you see a company offering this same feature in a prepaid plan. So keep your eyes open for deals like this, where you can get post paid features in a prepaid plan.
Keep in mind that some prepaid providers charge a daily fee for use of their phone minutes. An example is Verizon. So while their prepaid plans may seem like they're saving you money, you must remember that you will be paying an additional charge for each day you use the phone. In Verizon 's case you pay a dollar a day for use of the phone. Just factor that into your overall calculations and see if it still makes sense and saves you money.
You need to consider numerous factors as you search for the cheapest option for your mobile communications. Look at as many companies as possible and compare and contrast the benefits of each plan. One other thing you should know is that most prepaid cell phone providers do not provide a free cell phone. It is typical for a company to offer a free phone when you upgrade your plan or sign a contract extension. Since there is no contract involved in a prepaid cell phone agreement, that incentive is gone.
Check the prices of the phones that work with each offer. Often you will be able to find a good deal on a cell phone on eBay or Craigslist. It just takes a little time and research. The beauty of the prepaid model is you can screw up and sign up with a service you end up not liking but you don't have to stay with them because you never signed a contract. Thus, there is no cancellation fee, which can be a total rip-off.
Monday, November 10, 2008
Tuesday, October 7, 2008
Epitaxy on Silicon-On-Insulator Technology
Introduction:
As at current, we see that CMOS technology is the driving technology of the microelectronics industry, and the conventional way of fabricating integrated circuits on bulk silicon substrates has illustrated problems such as unwanted parasitic effects, latchup, and the difficulty of making shallow junctions. In the recent years, the advent of Silicon-on-Insulator has proven superior in many aspects to their bulk counterparts, and the benefits include the absence of latch-up, the reduced parasitic source and drain capacitances, the ease of making shallow junctions, radiation hardness, ability to operate at high temperature, improved transconductance and sharper subthreshold slope. There are several approaches available to create SOI wafers, and we discuss two particular techniques over here. First, we seek to illustrate a heteroepitaxy technique through the Ultra-Thin Silicon (UTSi) process where high quality Silicon-on-Sapphire (SOS) material is formed. Next, we look at a homo epitaxy technique called Epitaxial Lateral Overgrowth (ELO) technique which seeks to grow a homogenous crystal laterally on an insulator.
Ultra-Thin Silicon (UTSi) Process
Silicon-on-Sapphire (SOS) material was first introduced in 1964. SOS was recognized for its high speed and low power potential. The usage of Czochralski growth of sapphire crystals and the subsequent deposition of a silicon film in an epitaxial reactor had proved inefficient as there was high defect density due to lattice mismatch with defect densities near the Si-Sapphire interface reaching up to planar faults /cm and line defects/cm. This resulted in low resistivity, mobility, and lifetime near the interface. The silicon film deposited is also under compressive stress at room temperature due to different thermal expansion coefficients which may possibly result in relaxation in the film through crystallographic defects such as microtwins, stacking faults, and dislocations. Such consequences are undesired.[1]
Hence, these reasons advocate the need for better heteroepitaxy technique, and in which the UTSi process is one such potential candidate. The steps involved in a UTSi process are as follows: See Figure 1.
Step 1: Grow a relatively thick film of silicon on sapphire. Silane (SiH4) is commonly used as the source of silicon for SOS growth. Its pyrolysis reaction in a carrier hydrogen gas, SiH4 --> Si + 2H2, results in the deposition of a silicon layer over the sapphire substrate. The deposition temperature is usually kept below 1050 deg C in order to prevent the autodeposition of aluminum from the sapphire substrate to the silicon layer. The desired silicon orientation is , which has been achieved on various sapphire orientations, i.e., , , .
Step 2: Implantation of Si into the silicon film is carried out to amorphize the bottom 2/3 of the silicon film, with the exception of a thin superficial layer, where the original defect density is the lowest.
Step 3: A low temperature thermal annealing step is then used to induce solid-phase regrowth of the amorphized silicon, using the top silicon layer as a seed.
Step 4: The silicon film is then thinned to the desired thickness by thermal oxidation, and the subsequent HF strip of the SiO. What remains is the final product of Silicon-on-Sapphire (SOS).
It has been demonstrated that UTSi process is capable of delivering relatively defect-free and stress free SOS material in which devices with a high effective mobility can be made.
One application of the UTSi process is seen in UTSi CMOS transistors. As seen from Figure 2, the fabrication process is much simpler since the deep implants and guard regions are unnecessary thanks to the insulating sapphire substrate, and undesired effects such as leakage currents, latchup, and the RF parasitics are eliminated since the devices now sit on an insulating layer. The performance of the CMOS process is enhanced by as much as two generations of process geometry reduction. The advantages of forming CMOS transistors in the ultra thin silicon layer over insulating sapphire include the following:
* Elimination of substrate capacitance, which allows higher speed at lower power and avoids voltage dependent capacitance distortions
* Fully depleted operation, improving linearity, speed, and low voltage performance
* Excellent isolation which allows integration of multiple RF functions without crosstalk
UTSi circuits are produced that compete in the rapidly expanding wireless and fiber optic markets at higher frequencies and data rates with lower power consumption than standard bulk CMOS, SiGe and GaAs circuits, while still using standard CMOS equipment and processing.
Epitaxial Lateral Overgrowth (ELO) Technique
This technique allows the homoepitaxial growth of silicon on silicon, with the focus placed on growing the crystal laterally on the insulator. In ELO, we can perform this in an atmospheric or in a reduced-pressure epitaxial reactor. The technique consists of the epitaxial growth of silicon from seeding windows over SiO islands or devices capped with an insulator.
The steps involved in a ELO technique are as follows: See Figure 3.
Step 1: An oxide layer is grown on the (100) silicon wafer. Next, patterning is carried out on the oxide to demarcate the windows. The edges of the windows are oriented along the direction.
Step 2: Cleaning of the wafer is carried out
Step 3: Wafer is loaded into an epitaxial reactor and submitted to a high-temperature hydrogen bake to remove the native oxide from the seeding windows.
Step 4: Epitaxial growth is performed next, using e.g: SiHCl +H+ HCL gas mixture.
Step 5: Apply an in-situ HCl etch step to remove any crystallites that may be formed on the oxide due to nucleation of small silicon crystals with random orientation during the epitaxial growth.
Step 6: Once the small nuclei are removed, a new epitaxial growth step is performed, followed by an etch step, and this repeats until the oxide is covered by epitaxial silicon.
Some points we should note is that the epitaxial growth proceeds from the seeding windows both vertically and laterally, and the silicon crystal is limited by the and facets. When two growth fronts, seeded from opposite sides of the oxide, join together, a continuous silicon-on-insulator film is formed, which contains a low-angle subgrain boundary where the two growth fronts meet. A groove is observed over the centre of the SOI area. When more growth is done, this groove disappears.
As much as this is a simple technique to have homoepitaxial growth, a major disadvantage is the nearly 1:1 lateral-to-vertical growth ratio. On the other hand, the thick ELO film allows the design engineer to obtain SOI films of different thickness easily simply by polishing the wafers to required depths as needed. Also, the low defect density and low thermal budget needed to implement a ELO-SOI is considered superior to other technologies such as SIMOX (Separation by Implanted Oxygen) or other SOI processes for submicron devices.
Applications for this technique have been seen in three-dimensional and double-gate devices.
Variations in ELO technique has been witnessed in “tunnel epitaxy”, “confined lateral selective epitaxy” (CLSEG) or “pattern-constrained epitaxy” (PACE) whereby a “tunnel” of SiO is created, forcing the epitaxial silicon to propagate laterally instead of vertically. In effect, a 7:1 lateral-to-vertical growth ratio has been obtained, which is more efficient than the original approach
Orginally Written Article @ http://flashg-soitechnology.blogspot.com/
By: Jimmy Lee
As at current, we see that CMOS technology is the driving technology of the microelectronics industry, and the conventional way of fabricating integrated circuits on bulk silicon substrates has illustrated problems such as unwanted parasitic effects, latchup, and the difficulty of making shallow junctions. In the recent years, the advent of Silicon-on-Insulator has proven superior in many aspects to their bulk counterparts, and the benefits include the absence of latch-up, the reduced parasitic source and drain capacitances, the ease of making shallow junctions, radiation hardness, ability to operate at high temperature, improved transconductance and sharper subthreshold slope. There are several approaches available to create SOI wafers, and we discuss two particular techniques over here. First, we seek to illustrate a heteroepitaxy technique through the Ultra-Thin Silicon (UTSi) process where high quality Silicon-on-Sapphire (SOS) material is formed. Next, we look at a homo epitaxy technique called Epitaxial Lateral Overgrowth (ELO) technique which seeks to grow a homogenous crystal laterally on an insulator.
Ultra-Thin Silicon (UTSi) Process
Silicon-on-Sapphire (SOS) material was first introduced in 1964. SOS was recognized for its high speed and low power potential. The usage of Czochralski growth of sapphire crystals and the subsequent deposition of a silicon film in an epitaxial reactor had proved inefficient as there was high defect density due to lattice mismatch with defect densities near the Si-Sapphire interface reaching up to planar faults /cm and line defects/cm. This resulted in low resistivity, mobility, and lifetime near the interface. The silicon film deposited is also under compressive stress at room temperature due to different thermal expansion coefficients which may possibly result in relaxation in the film through crystallographic defects such as microtwins, stacking faults, and dislocations. Such consequences are undesired.[1]
Hence, these reasons advocate the need for better heteroepitaxy technique, and in which the UTSi process is one such potential candidate. The steps involved in a UTSi process are as follows: See Figure 1.
Step 1: Grow a relatively thick film of silicon on sapphire. Silane (SiH4) is commonly used as the source of silicon for SOS growth. Its pyrolysis reaction in a carrier hydrogen gas, SiH4 --> Si + 2H2, results in the deposition of a silicon layer over the sapphire substrate. The deposition temperature is usually kept below 1050 deg C in order to prevent the autodeposition of aluminum from the sapphire substrate to the silicon layer. The desired silicon orientation is , which has been achieved on various sapphire orientations, i.e., , , .
Step 2: Implantation of Si into the silicon film is carried out to amorphize the bottom 2/3 of the silicon film, with the exception of a thin superficial layer, where the original defect density is the lowest.
Step 3: A low temperature thermal annealing step is then used to induce solid-phase regrowth of the amorphized silicon, using the top silicon layer as a seed.
Step 4: The silicon film is then thinned to the desired thickness by thermal oxidation, and the subsequent HF strip of the SiO. What remains is the final product of Silicon-on-Sapphire (SOS).
It has been demonstrated that UTSi process is capable of delivering relatively defect-free and stress free SOS material in which devices with a high effective mobility can be made.
One application of the UTSi process is seen in UTSi CMOS transistors. As seen from Figure 2, the fabrication process is much simpler since the deep implants and guard regions are unnecessary thanks to the insulating sapphire substrate, and undesired effects such as leakage currents, latchup, and the RF parasitics are eliminated since the devices now sit on an insulating layer. The performance of the CMOS process is enhanced by as much as two generations of process geometry reduction. The advantages of forming CMOS transistors in the ultra thin silicon layer over insulating sapphire include the following:
* Elimination of substrate capacitance, which allows higher speed at lower power and avoids voltage dependent capacitance distortions
* Fully depleted operation, improving linearity, speed, and low voltage performance
* Excellent isolation which allows integration of multiple RF functions without crosstalk
UTSi circuits are produced that compete in the rapidly expanding wireless and fiber optic markets at higher frequencies and data rates with lower power consumption than standard bulk CMOS, SiGe and GaAs circuits, while still using standard CMOS equipment and processing.
Epitaxial Lateral Overgrowth (ELO) Technique
This technique allows the homoepitaxial growth of silicon on silicon, with the focus placed on growing the crystal laterally on the insulator. In ELO, we can perform this in an atmospheric or in a reduced-pressure epitaxial reactor. The technique consists of the epitaxial growth of silicon from seeding windows over SiO islands or devices capped with an insulator.
The steps involved in a ELO technique are as follows: See Figure 3.
Step 1: An oxide layer is grown on the (100) silicon wafer. Next, patterning is carried out on the oxide to demarcate the windows. The edges of the windows are oriented along the direction.
Step 2: Cleaning of the wafer is carried out
Step 3: Wafer is loaded into an epitaxial reactor and submitted to a high-temperature hydrogen bake to remove the native oxide from the seeding windows.
Step 4: Epitaxial growth is performed next, using e.g: SiHCl +H+ HCL gas mixture.
Step 5: Apply an in-situ HCl etch step to remove any crystallites that may be formed on the oxide due to nucleation of small silicon crystals with random orientation during the epitaxial growth.
Step 6: Once the small nuclei are removed, a new epitaxial growth step is performed, followed by an etch step, and this repeats until the oxide is covered by epitaxial silicon.
Some points we should note is that the epitaxial growth proceeds from the seeding windows both vertically and laterally, and the silicon crystal is limited by the and facets. When two growth fronts, seeded from opposite sides of the oxide, join together, a continuous silicon-on-insulator film is formed, which contains a low-angle subgrain boundary where the two growth fronts meet. A groove is observed over the centre of the SOI area. When more growth is done, this groove disappears.
As much as this is a simple technique to have homoepitaxial growth, a major disadvantage is the nearly 1:1 lateral-to-vertical growth ratio. On the other hand, the thick ELO film allows the design engineer to obtain SOI films of different thickness easily simply by polishing the wafers to required depths as needed. Also, the low defect density and low thermal budget needed to implement a ELO-SOI is considered superior to other technologies such as SIMOX (Separation by Implanted Oxygen) or other SOI processes for submicron devices.
Applications for this technique have been seen in three-dimensional and double-gate devices.
Variations in ELO technique has been witnessed in “tunnel epitaxy”, “confined lateral selective epitaxy” (CLSEG) or “pattern-constrained epitaxy” (PACE) whereby a “tunnel” of SiO is created, forcing the epitaxial silicon to propagate laterally instead of vertically. In effect, a 7:1 lateral-to-vertical growth ratio has been obtained, which is more efficient than the original approach
Orginally Written Article @ http://flashg-soitechnology.blogspot.com/
By: Jimmy Lee
Saturday, September 27, 2008
Satellite TV Codes
Watching television anywhere and anytime is now very easy.Those who have computers such as desktop, laptop or even a pocket PC that has a PCTV device can get into to any television channel and watch the show that they have been anticipating for.Aside from the local channels,you can also watch other international shows from the National Geographic and Animal planet.More than that, you can also tune in to your favorite FM radio or Internet radio frequencies.This is provided that you are within an area where there is an Internet access to your ISP or within a Wifi zone.
Another chance for you to be able to watch clear television shows is through the satellite TV.Satellite TV operates when the satellite dish is able to receive signals or transmissions that bounce back to earth.The signal is relayed to the antenna that in turn decodes it. The final output or message is the picture that you see on your television screen.The package of the satellite TV comes with a satellite dish and an antenna. This is controlled with the use of the remote control that also comes with the package.
In order to get good signal for your television, you should set the right and proper satellite TV codes for it.The satellite TV codes are usually set up when the satellite TV is installed but there are times when these codes needed to be changed.When browsing through the Internet, you can find several sites that can offer free satellite TV codes.All you have to do is to download the application appropriate for your satellite TV and to key in the satellite codes.Once you have established the satellite TV codes,you can already start watching.
Here are some of the websites where you can get the latest satellite TV codes that are always in binary format. One is the dss-keys.This site updates their TV codes from time to time.Another site is the satellitekeys,where they even allow you to download an application where you are taught on how to properly key-in your TV codes.One more site that you can check out when looking for satellite codes is the dsstestersite.This site is a subsidiary of the original site. You can send questions and inquires to this site if the original site is down.You also have the option of checking satjunkies.This is another site that might be helpful for you since it has a forum where you can ask questions regarding satellite TV codes. Joining the forum is easy and free. You just create an account to be able to log in.
Again,there are more sites in the Internet that you can search for regarding the satellite TV codes.There are those that come free while there are those that you can avail in minimal price.There are also several sites that accept online discount coupons when purchasing for the satellite codes.Just make sure that you avail from valid suppliers to continue your access to the shows that you are waiting for.
By: Marcus Rolland
Another chance for you to be able to watch clear television shows is through the satellite TV.Satellite TV operates when the satellite dish is able to receive signals or transmissions that bounce back to earth.The signal is relayed to the antenna that in turn decodes it. The final output or message is the picture that you see on your television screen.The package of the satellite TV comes with a satellite dish and an antenna. This is controlled with the use of the remote control that also comes with the package.
In order to get good signal for your television, you should set the right and proper satellite TV codes for it.The satellite TV codes are usually set up when the satellite TV is installed but there are times when these codes needed to be changed.When browsing through the Internet, you can find several sites that can offer free satellite TV codes.All you have to do is to download the application appropriate for your satellite TV and to key in the satellite codes.Once you have established the satellite TV codes,you can already start watching.
Here are some of the websites where you can get the latest satellite TV codes that are always in binary format. One is the dss-keys.This site updates their TV codes from time to time.Another site is the satellitekeys,where they even allow you to download an application where you are taught on how to properly key-in your TV codes.One more site that you can check out when looking for satellite codes is the dsstestersite.This site is a subsidiary of the original site. You can send questions and inquires to this site if the original site is down.You also have the option of checking satjunkies.This is another site that might be helpful for you since it has a forum where you can ask questions regarding satellite TV codes. Joining the forum is easy and free. You just create an account to be able to log in.
Again,there are more sites in the Internet that you can search for regarding the satellite TV codes.There are those that come free while there are those that you can avail in minimal price.There are also several sites that accept online discount coupons when purchasing for the satellite codes.Just make sure that you avail from valid suppliers to continue your access to the shows that you are waiting for.
By: Marcus Rolland
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