New perspectives on IC miniaturisation
The evolution of the integrated circuits has had a significant impact on several application fields, where the nano-size and high speed of electronic devices play an important role, such as medical, biological and chemical analysis as well as telecommunications. However, further miniaturisation of IC components is restricted by mechanical stress build-up in the layers and substrates during processing that seriously affect the device performance and reliability. Therefore, stress should be continuously monitored, and action should be taken to minimise it. Otherwise, lattice strains can reach levels in excess of the critical values for dislocation formation, thus resulting in the device degradation. Transmission Electron Microscopy (TEM) plays a key role in the microelectronics industry. It provides an effective means for stringent research, development and production, when morphological / analytical investigational tools become less effective, due to device size reduction. The expected spread of TEM used in the semiconductor industry will also promote and extend the range of applications of the various analytical capabilities of this instrument. The technique of Convergent Beam Electron Diffraction (CBED), is capable of investigating the lattice strains in crystals. However, this application has so far been of limited use, as the procedure requested to extract the local strain tensor from the TEM/CBED pattern is largely manual, thus requiring long analysis times. Under the STREAM project a software package has been developed that digitally acquires the diffraction patterns and yields the strain tensor in the corresponding nano-regions of the structure. The software package has a built-in "CBED pattern-to-strain value" routine, which speeds up the strain measuring procedure, passing from a "days long evaluation" to at least a "matter of hours" evaluation, approaching industry standards' response times. The routine use of the TEM/CBED method to analyse strains will allow the optimisation of the processes, in order to avoid device failure due to dislocation generation. The reduction of device failure due to stress will not only have economic benefits, but also will result in a cut in the waste products, with direct effects on environment control.
