X-ray rocking curve analysis of ion implanted mercury cadmium telluride

Junction formation by ion implantation is a critical step in producing high quality infrared focal plane arrays in mercury cadmium telluride (MCT). We have analyzed the structural properties of MCT implanted with B at doses of 10¹⁴ and 10¹⁵ cm⁻² using double and triple crystal x-ray diffraction (DCD and TCD) to monitor the disorder and strain of the implanted region as a function of processing conditions. TCD (333) reflections show that a distinct tensile peak is produced by the high dose implant while the low dose implant shows only a low angle shoulder on the substrate peak. A preliminary association of the low angle shoulder with point defects has been made since no extended defects have been observed in the low dose range. For the high dose implant, extended defect formation has been reported and may be responsible for the tensile peak. After annealing, the low angle shoulder on the low dose implant has disappeared, while the high dose implant exhibits an increase in the tensile strain from 6.5 × 10⁻⁴ to 9.3 × 10⁻⁴ after 24 h of annealing and then decreases in tensile strain to 7.3 × 10⁻⁴ after 48 h of annealing. It is believed the changes in strain are associated with the Oswald ripening and dissolution of extended defects, which has been observed during annealing of ion implanted Si.     

Mercury interstitial generation in ion implanted mercury cadmium telluride

Junction formation and stability in ion implanted mercury cadmium telluride critically depend on the ability to generate Hg interstitials. The creation of Hg interstitials is found to strongly depend on the preferred lattice position of the element implanted. Elements that substitute onto the cation sublattice create significantly more Hg interstitials than elements that sit interstitially or on the anion sublattice. Recoils from implant damage also contribute to Hg interstitial formation in heavier mass implants (Z ≥ of mass Zn), but appear to have negligible influence on interstitial generation in implants of lighter ions. The combination of implanting ions of large mass and high solubility on the cation sublattice produces strong Hg interstitial sources. Implants with these ions can form deep junctions even in heavily doped substrates. Junction stability is also improved with the stronger interstitial source.     

开关DC-DC变换器的自适应占空比跨周期控制方法

针对脉冲跨周期调制(PSM)开关DC-DC变换器输出电压纹波较大的问题,该文提出一种新型的自适应占空比跨周期(ADPS)控制方法。在ADPS控制的变换器中,轻载下,每个周期变换器控制脉冲的占空比与该周期开始时输出电压与参考电压误差的平方根近似成正比;负载越轻,变换器的输出电压纹波越小。研究表明,ADPS控制的DC-DC变换器不仅具有比PSM控制的变换器更低的输出电压纹波,同时具有优异的鲁棒性和瞬态响应能力。     

Plasma cleaning of plastic ball grid array package

An investigation of O₂, Ar and Ar/H₂ plasma cleaning was carried out on plastic ball grid array (PBGA) substrates to study its effects on surface cleanliness, wire bondability and molding compound/solder mask adhesion. Optimization of the plasma cleaning process parameters was achieved using the contact angle method and verified by auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and wedge pull tests. It was found that both the wedge bond quality and moisture sensitivity of a 225 I/O PBGA package were improved after plasma cleaning. Furthermore, atomic force microscopy (AFM) characterization and XPS analysis revealed that the solder mask has undergone plasma-induced surface modification. Cross-contamination of Au and F traces on the solder mask that has occurred during plasma cleaning was identified by XPS. This study has demonstrated the benefits and consequences of plasma cleaning for a PBGA package.