Archive for July, 2013

PostHeaderIcon Reverse LATTICE CPLD Source code

The same memory type but built with newer technologies such as 0.9 µm in the Microchip PIC16CR57 microcontroller [124] and 1.0 µm in the Motorola MC68HC705C9A microcontroller [23] requires deprocessing because the top bit-line metal wires obstruct observation of the transistors (Figures 59 and 60).

NAND Mask ROM memory type with metal layer programming (see Figure 22) was used in the NEC µPD78F9116 microcontroller [125] fabricated with 0.35 µm technology. As all the internal layers were planarised, deeper layers cannot be observed unless the top metal layer is removed (Figure 61). This was accomplished by using Nitrox etching for the passivation layer followed by treatment in a 33% water solution of KOH to etch the top aluminium metal layer but preserving the interconnection layer which is probably made out of tungsten (because when the HCl solution was used to etch the top metal layer, the interconnection layer was etched away as well).

PostHeaderIcon Reverse DSP CPLD IC Chip program

Layout reconstruction requires the images of all the layers inside the chip to be combined. The images are normally taken automatically using a motorised stage to move the sample and special software to combine all the images together.

Normally, for semiconductor chips fabricated with 0.13 µm or smaller technology, images are created using a SEM which has a resolution better than 10 nm.

PostHeaderIcon Read Lattice CPLD embeded firmware

The main disadvantage of high resolution microscopes is the short working distance between the objective and a specimen, especially at high magnifications (about 0.3 mm with 100× objective). As a result partially decapsulated chips cannot be observed and full decapsulation of the die is required. Using microscopes with a long working distance, for example the Mitutoyo FS70 [121] with 13 mm working distance on 200× objective, helps solve this problem but at a cost: the resolution is at most 0.4 µm because the NA cannot be high.

Another problem of the high-resolution objectives is a very short depth of focus, which makes the out-of-focus planes look blurred, thus reducing the image quality. This is more noticeable on multilayer chips where the distance between the top and the bottom layer is more than 1 µm.

Confocal microscopy reduces this effect as all out-of-focus planes become dark or appear in different colours depending from their depth. Such confocal systems are very expensive, especially the ones that use laser scanning, and therefore can be afforded by relatively large labs only. Even second-hand confocal microscopes start from £10,000.