Jonas Tiren

Fracture testing of silicon microelements in situ in a scanning electron microscope

Fracture testing of silicon cantilever beams (thicknesses 10–20 μm) was performed in situ in a scanning electron microscope by means of an equipment specially designed for this purpose. Beams of various sizes and orientations (〈011〉 and 〈001〉) were manufactured in Si (100) wafers by two different micromachining procedures. The beams were tested by simple bending to fracture, and a number of fundamental fracture parameters were determined from an analytical model of elastic fracture. To verify its validity, the model was utilized to evaluate an experimental E modulus, which was found to agree well with previous results. Fracture limits, fracture strains, and initiating flaw sizes were determined. The maximum fracture limit was very high; about 10 GPa. The strengths of different beams scattered from this value down to practically zero strength, with an average close to 4 GPa. The corresponding fracture strains and initiating flaw sizes were 6% and 3 nm, respectively (maximum strength), and 2% and 17 nm (ave...

Deep level transient spectroscopy analysis of fast ion tracks in silicon

Deep level transient spectroscopy measurements of electron traps in MeV proton‐ and alpha‐irradiated n‐type silicon have been performed. Six deep levels are found in proton‐irradiated samples, while only three appear after alpha irradiation. The influence of the irradiation dose on the defect production is investigated together with the depth concentration profiles. The profiles scale with the nuclear energy deposition, but in the case of the doubly negative charged state of the divacancy at EC −0.24 eV, the peak concentration at the end of the track is less pronounced relative to the tail region towards the surface. It is proposed that the singly negative charged state at EC −0.42 is more probable in a highly distorted lattice and it is shown that the formation of the singly negative charged state of the divacancy dominates the defect production for higher doses.

A batch-fabricated non-reverse valve with cantilever beam manufactured by micromachining of silicon

A batch-fabricated non-reverse valve has been manufactured in silicon with micromachining tools, i.e., electrochemical doping-selective etching in KOH and anisotropic etching in EDP. The valve simply consists of a cantilever beam that can take two positions, one letting a gas or a fluid through the valve, the other forced by the pressure to close on of the two inlet holes. The valve features fast response, small size, batch manufacturing and small dead volumes, and also shows an application of the mechanical strength of silicon. A simple theory is used to predict the basic characteristics of the valve.

Fabrication of three-dimensional silicon structures by means of doping-selective etching (DSE)

Abstract Despite its early discovery, doping-selective etching (DSE) of silicon sensor and actuator structures has not been widely used. The potential advantages of DSE are IC compatibility, new degrees of freedom in three-dimensional micromachining and full exploitation of the excellent mechanical properties of silicon. The mechanisms of DSE are both chemical and electrochemical in nature, and can be described as a ‘race’ between dissolution and passivation of the reaction products. The process has been monitored by studying the current-voltage characteristics of homogeneous silicon wafers. Model experiments on basic sensor structures, such as thin membranes and cantilever beams, have been performed. It is shown that the sequence in patterning the structures is crucial in determining the detailed geometry. This is partly expected due to the well-known anisotropy of alkaline etchants. Some as yet unreported effects of anisotropy will be subject to further investigations. Conclusively, DSE offers new and interesting possibilities in the fabrication of sensor and actuator elements.

Batch processing of laterally mobile structures in single-crystalline silicon

Abstract The introduction of elements free to move in the lateral wafer directions may have a great impact on the evolution of silicon micromechanics. Such laterally mobile structures allowing rotation and sliding motion can be used in sensor and actuator applications that have been inaccessible so far due to performance or cost limitations of present technology. This paper deals with the possibility of making these structures in single-crystalline silicon and outlines some fabrication processes using lamination of two oxidized wafers to form a sacrificial layer that will attach the mobile structure to the substrate, and a lamination of silicon surfaces to attach the overlay to the substrate. Both the mobile structure and the overlay will then have anisotropic properties, which gives new possibilities when designing three-dimensional mobile structures.

Investigations of evaporated silicon p-n junctions and their application to junction field-effect transistors

p‐n junctions formed by vacuum evaporation of silicon on crystalline silicon have been investigated. The junctions were formed by ion implantation of 49BF+2 in the evaporated silicon films. Subsequently, an isochronal heat treatment in the range of 600–850 °C was performed and its influence on the doping distributions and corresponding diode behavior was studied. Secondary‐ion mass spectrometry was used to investigate the resulting boron distributions. A sharp decrease in the boron concentration was found at the interface for the sample annealed at 850 °C.The fabricated p‐n junctions were evaluated by measuring the current‐voltage characteristics. Comparisons were made to ordinary diffused p‐n junctions in bulk silicon. Using the current‐voltage measurements, the leakage current and the ideality factor of the diodes were extracted. The reverse currents were also measured and show a nonsaturating behavior. The resistivity of the films were investigated as a function of anneal temperature, and it was found ...