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(2009-09-25 12:23:16)







Paradigm shift in compound semiconductor Production since the introduction of the laser dicing



This paper will address the impact of multi beam laser dicing on the dicing procession capability in the backend of line, as well as the advantages which it brings for manufacturing optimization such as cycle time reduction, cost reduction, wafer and dicing field improvement, and elimination of backside processes.




Return of investment


For several years now, technology leading compound semiconductor companies have introduced multi beam laser dicing to replace the conversional mechanical die separation technology such as sawing and scribe and break. Upon the installation of a multi beam laser dicing system, the obviously advantages of using such a laser dicing process become evident. The dicing kerfs have been reduced to below 20 um in many cases, with no chipping on either front or backside. As showed in figure 1 below, this increase in capability then allow the street size to be reduced down to 26um, allowing more die per wafer. 





This is achieved by using a unique multi beam technology, demonstrated in figure 2, which reduces the power density, minimizes the thermal load, and reduces the kerf width in the wafer.

这是采用独特的多光束技术实现的,图2显示了其工作原理,降低了功率密度 ,减小了热负载,缩小了刻线宽度。

The higher speed of dicing has led to a productivity increase of 5 – 8 times, compared with any other conventional separation system, 3- 5 times any other laser dicing concept. This increase in through-put is to a large extent achieved by using multi beam technology, which minimizes the number of traverses needed to dice through a wafer. This strong increase in through-put, together with street width reduction ,no dicing field loss and high up time(97%),allows a return of investment usually within 3 to 6 months.





Multiple Beam Laser Process

When using any dicing system to separate the die, it is the trade-off of quality and speed, independent of the technology. Currently available industrial lasers can deliver high amounts of power. However ,when exerted at such high levels onto a thin wafer substrate, the material is not only separated, but may also be damaged severely. To get a good quality cut (no chipping or cracks) with a minimal heat affected zone, low laser power levels need to be used. Normally as a result, material removal rates and therefore dicing speed is lowered and the laser capability with respect to the available power is far from optimized. The multi beam does address these concerns.



The basic principle is to split the main laser beam up into a plurality of laser beams, each having a low power level and therefore not compromising the cut quality, and working concurrently as a group of beams, keeping both the material removal rate and the dicing speed high. Initially, semiconductor manufacturers had concerns over the visual appearance and the extent of the heat affected zone (HAZ) of the die after laser dicing. The advantage of a multibeam laser dicing process does not eliminate the HAZ, but clearly minimizes this effect. In addition ,the recast generated by the first beam, which is of low power and intensity, thermally isolates the substrate for the subsequent following beams. See figure 3 below.




Chip side healing (CSH)

Having a slightly rougher but more regular dicing edge compared to S&B or sawing, questions arose if the die strength and package reliability of laser diced die hand changed. In fact, the die strength is fully recovered, and even exceeds the reference die strength of current separation technologies after laser dicing, in combination with a post process step. See figure 4 below.

和常规的S&B 和锯相比,有轻微的粗糙,如果die的延长和封装的可靠性出现变化,那就会引起其它问题。实际上,die的延伸是完全可以恢复的,即使超出了当前分离技术的参考延伸,还可以和后续的处理结合来消除。



Usually after the multiple bam lasers dicing technology has been integrated into full production, additional capabilities of this unique dicing technology have been explored. Apart from the primary advantages, the secondary advantages may have an even larger contribution to the efforts of companies to reduce costs and improve yield.


The secondary advantages can include a significant reduction of labor costs, as no post visual inspection is needed as in traditional dicing processes. This allows significantly less operator intervention, thus allowing one operator to manage an increased number of machines.

Additionally, expensive and time consuming backstreet etching can be eliminated by using the full potential of the multiple laser beam technology. Whereas for most dicing technologies the thick backside metal needs etching, the multibeam laser dicing cuts Au or Cu back metals of 5-10 um.


此外,完全发挥多光束的的能力,则可以减少用于蚀刻backstreet,隔离区的时间和费用。然而对于较厚的被板金属,是需要蚀刻的,对大部分的划片技术来说。多光束激光划片可以切5-10um后的Au 或Cu 被板金属。



Laser dicing options


Along with the melt ejection, laser dicing technologies, sub-surface laser dicing technologies have been introduced. The sub surface technology focuses laser pulses inside the wafer substrate, modifying the crystalline structure, weakening and creating stress without material removal. Afterwards the wafer can be separated by expansion or with aid of a breaking device. Several advantages over mechanical scribe and break can also be achieved utilizing this technology but do not offer the major advantages that multi-beam ablation offer.  The performance comparison of the traditional scribe & break, laser subsurface and the multiple beam ablations are illustrated below in figure 6.




A multiple beam, sub surface laser dicing technology is currently being developed, which will improve the productivity of such a process significantly.



In addition, the versatility of the (ablative) melt ejection, multiple beam laser dicing technology to dice various types of substrates, a range of substrate thicknesses, and various wafer surface passivations, all on the same machine platform, has become a welcome enhancement of manufacturing capabilities. Next to these advantages, this technology also enables several roadmap requirements such as die shrinkage, flip chip wafer technology and the trend towards thinner wafers (down to 30-50um). With the list of applications still growing, multiple beam laser dicing is currently able to offer a solution for dicing different types of substrates and materials used in semiconductor manufacturing and solar cells, including GaAs, CuW, GaP, Ge, InP, LiTaO3,Si,and SiC, with various front and backside passivations and or metallization.

此外,熔融喷射的多功能性,多光束激光划片技术可以切割各种基材,各种厚度,各种表面,在一台设备上,这样的设备在提高制造能力中受到欢迎。此外,还可以用来做标记,以满足die收缩率,倒装晶片技术和晶片越来越薄(小到30-50 um)的趋势的需求。应用的范围还在扩大,目前可以处理的材料有:GaAs, CuW, GaP, Ge, InP, LiTaO3,Si,and SiC,带有不同的钝化和金属化的前后表面。



In summary, a multiple beam laser dicing system is not just a different dicing solution; it is a paradigm shift in dicing technology that enables compound semiconductor manufacturers to increase and broaden their capability and capacity in both front – and backend, increase dicing yield, and reduce the overall cost and cycle time, while addressing challenges in their product roadmaps.




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