On Tuesday my post included information on dicing Low-k wafers; however on Thursday I discovered additional information presented in Semicon China in 2012. I will visit ALSI at Semicon West 2012 to confirm the information contained and to find out more about their technology.
Basically it is a multi-beam technology which will allow for a clean singulation of the top layers. Subsequent singulation can be performed using a standard dicing blade.
The question then becomes which mechanical dicing blade to use and how deep to cut into the tape. As stated in a previous post dicing tape selection is more than simply looking for a tape with high peel strength pre-UV and a low peel strength tape post-UV. Peel strength is a metric which does not tell the whole story. The missing aspects will be the modulus of the tape and tack testing results.
If you would like to learn more about this then please contact me and I would be happy to discuss both aspects and how they relate to dicing tape selection.
Thursday, July 5, 2012
Tuesday, July 3, 2012
Dicing Low-K Materials
Dicing Low-k materials is challenging. The conventional approach using one or multiple dicing blades created issues of front side chipping or layers would peel away causing device failure. In an article in 2004 Synova proposed a full cut approach using a laser cooled by water.
Below is an example of the results which are quite impressive indeed on a low-K wafer.
ADT and Disco both developed approaches whereby the wafer is grooved with a laser and then the wafer is diced using a mechanical blade.
Low-k materials requires a new approach to singulation. What is often missed in discussions on singulation is dicing tape.
Dicing tape is more than a "sticky support" for a water jet application the wrong dicing tape will cause dies to fly off and for the groove and dice solution dicing tape plays a critical role as the wrong tape could cause backside chipping or die fly off. If you have any questions regarding which tape might be right for your process please contact me.
Below is an example of the results which are quite impressive indeed on a low-K wafer.
ADT and Disco both developed approaches whereby the wafer is grooved with a laser and then the wafer is diced using a mechanical blade.
Dicing tape is more than a "sticky support" for a water jet application the wrong dicing tape will cause dies to fly off and for the groove and dice solution dicing tape plays a critical role as the wrong tape could cause backside chipping or die fly off. If you have any questions regarding which tape might be right for your process please contact me.
DBG Process
The conventional dicing process consists of mounting a wafer on to a medium (wax or tape) and then connecting either to a hoop ring (set of concentric expansion rings) or a ring frame (either stainless steel or plastic) and then dicing through the material. In the conventional process the dicing process is the process of singulation where a chip or die is separated from the wafer. Their are issues with this process which affect yield.
One of the largest of these issues is backside chipping. Backside chipping has many potential root causes but the effect is the same lower die strength.
The chart above is a test on dies ranging from 10um to 25um thick. The results clearly demonstrate that backside chipping (conventional) reduces die strength. Reduced die strength may result in failure during subsequent steps in ultra-thin chips. So what is the answer?
One potential answer is DBG (Dice Before Grind). This process was developed in 1999 by Toshiba and two suppliers stepped up to deliver the solution Disco Corporation and LINTEC Corporation.
1999 DBG Press Release
The above illustration shows the steps in the DBG process. Disco supplies the half-cut dicer (blades) and grinder (grind wheels) and LINTEC supplies the back grind tape laminator (back grind tape) and wafer mounter (pick-up tape). Links to all of the products are listed below.
Back Grind Tape Laminator and Mounter
Half-Cut Dicer and Grinder
Investing in new systems may not be cost effective for smaller companies so there are vendors who offer to process DBG wafers. Contact me for a list of companies who can supply this service. In addition this process can be done using manual equipment on a smaller scale. I can not publish the results or technique here but it there has been significant data collected using semi-auto Disco and LINTEC equipment and if you contact me I would be happy to help design a more cost effective process for lower wafer volumes.
The decision to use the DBG process really depends on the thickness of the die, the package design, and the effect chipping (front side and back side) have on device performance. DBG may not be for every application, but for applications requiring ultra-thin strong dies it will increase die strength and ultimately positively impact yield.
One of the largest of these issues is backside chipping. Backside chipping has many potential root causes but the effect is the same lower die strength.
A Study on Chip Thinning Process for Ultra Thin Memory Devices (Toshiba)
Link to the Toshiba White PaperThe chart above is a test on dies ranging from 10um to 25um thick. The results clearly demonstrate that backside chipping (conventional) reduces die strength. Reduced die strength may result in failure during subsequent steps in ultra-thin chips. So what is the answer?
One potential answer is DBG (Dice Before Grind). This process was developed in 1999 by Toshiba and two suppliers stepped up to deliver the solution Disco Corporation and LINTEC Corporation.
1999 DBG Press Release
The above illustration shows the steps in the DBG process. Disco supplies the half-cut dicer (blades) and grinder (grind wheels) and LINTEC supplies the back grind tape laminator (back grind tape) and wafer mounter (pick-up tape). Links to all of the products are listed below.
Back Grind Tape Laminator and Mounter
Half-Cut Dicer and Grinder
Investing in new systems may not be cost effective for smaller companies so there are vendors who offer to process DBG wafers. Contact me for a list of companies who can supply this service. In addition this process can be done using manual equipment on a smaller scale. I can not publish the results or technique here but it there has been significant data collected using semi-auto Disco and LINTEC equipment and if you contact me I would be happy to help design a more cost effective process for lower wafer volumes.
The decision to use the DBG process really depends on the thickness of the die, the package design, and the effect chipping (front side and back side) have on device performance. DBG may not be for every application, but for applications requiring ultra-thin strong dies it will increase die strength and ultimately positively impact yield.
Monday, July 2, 2012
Introduction to Dicing Tapes
Introduction to Dicing Tapes
Dicing Tapes are used in the semiconductor manufacturing process to hold a silicon wafer in place during dicing. Dicing tapes come in two basic varieties, UV and Non-UV. The Non-UV dicing tape is for larger chip sizes while the UV dicing tape generally is used for smaller chip sizes or thinner dies.
The world’s first UV curable dicing tape was developed by FSK Corporation of Japan in 1984. They later changed their name to LINTEC Corporation and are now the largest sellers of UV Curable Dicing Tape worldwide.
Selecting a dicing tape is not always easy in semiconductor manufacturing. While dicing parameters (blade, speed, depth of cut, and RPM) can play a big part in determining cut quality dicing tape does play a role. A dicing tape which is “soft” and “thick” is not a good match for thin dies or brittle devices. It is like dicing on a pillow. Unfortunately almost all tape manufacturers do not list the relatively softness or modulus of the tapes and therefore a user must try several different types to find the type that best fits for the user.
For more information on LINTEC go to http://www.lintec-usa.com/.
The world’s first UV curable dicing tape was developed by FSK Corporation of Japan in 1984. They later changed their name to LINTEC Corporation and are now the largest sellers of UV Curable Dicing Tape worldwide.
Selecting a dicing tape is not always easy in semiconductor manufacturing. While dicing parameters (blade, speed, depth of cut, and RPM) can play a big part in determining cut quality dicing tape does play a role. A dicing tape which is “soft” and “thick” is not a good match for thin dies or brittle devices. It is like dicing on a pillow. Unfortunately almost all tape manufacturers do not list the relatively softness or modulus of the tapes and therefore a user must try several different types to find the type that best fits for the user.
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