Cost-effective processing of a piezoresistive MEMS cantilever sensor

In this paper cost-effective methods for fabrication of a piezoresistive cantilever sensor for industrial use are focused. The intended use of the presented cantilever is a medical application. A closer description of the cantilever design is given. The low-cost processing sequence is presented and each processing step is explained in detail. Results from electrical probing and mechanical strength test are given. The results demonstrate that the chosen low-cost processing route results in high yield and a mechanical robust device

Through Silicon Vias in MEMS packaging, a review

Trough Silicon Via (TSV) is a key enabling technology to achieve the integration of various dies by exploiting the third dimension. This allow the integration of heterogeneous chips in a single package (2.5D integration) or to achieve higher integration densities of transistors (3D integration). These vertical interconnections are widely used for both IC and MEMS devices. This paper reviews TSV technology focusing on their implementation in MEMS sensors with a broad overview on the various fabrication approaches and their constraints in terms of process compatibility. A case study of an inertial MEMS sensor will then be presented.publishedVersio

Wafer bonding process for zero level vacuum packaging of MEMS

It is well known that the packaging of electronic devices is of paramount importance, none more so than in MEMS were fragile mechanical elements are realized. Among the different approaches, wafer to wafer bonding guarantees the advantages of the wafer scaling and provides protection of the devices during the final phase of fabrication. Direct bonding, also known as fusion bonding, is seldom implemented in MEMS fabrication due to the high surface quality required, the high temperature involved and the compulsory wet activation process. In this paper a direct bonding process for MEMS inertial sensor without the need of any wet activation step is presented.acceptedVersio

Wafer bonding process for zero level vacuum packaging of MEMS

It is well known that the packaging of electronic devices is of paramount importance, none more so than in MEMS were fragile mechanical elements are realized. Among the different approaches, wafer to wafer bonding guarantees the advantages of the wafer scaling and provides protection of the devices during the final phase of fabrication. Direct bonding, also known as fusion bonding, is seldom implemented in MEMS fabrication due to the high surface quality required, the high temperature involved and the compulsory wet activation process. In this paper a direct bonding process for MEMS inertial sensor without the need of any wet activation step is presented.acceptedVersio

Non-destructive wafer-level bond defect identification by scanning acoustic microscopy

Metal-based thermocompression bonding enables the creation of hermetic seals formed at relatively low processing temperatures and occupying a small portion of the device area. In the current study we have investigated the application of scanning acoustic microscopy (SAM) for assessing the quality of metal thermocompression bonds, both by evaluating its capabilities of localizing areas of poor bonding, and by finding defects in the integrity of the bond seal. Wafer laminates containing a test vehicle of sealing frames with pre-defined defects in the bond metal layer were sealed by Au–Au and Al–Al thermocompression bonding. Employing SAM, an area of five chips of poor bonding was identified non-destructively on the Al–Al laminate. Line defects of width 3.6 µm and point defects of diameter 22.4 µm have also been identified by SAM. The dicing yield for sealing frames was above 96 % for all frames of widths 100–400 µm and for both bond metal systems. The average bond strength was 31.5 ± 11.9 MPa for Al–Al thermocompression bonds and 37.3 ± 9.7 MPa for Au–Au thermocompression bonds. Scanning acoustic microscopy operates non-destructively and proved to be an extremely useful tool complementing current state-of-the-art methods for bond quality assessment.acceptedVersio

Cost-effective processing of a piezoresistive MEMS cantilever sensor

In this paper cost-effective methods for fabrication of a piezoresistive cantilever sensor for industrial use are focused. The intended use of the presented cantilever is a medical application. A closer description of the cantilever design is given. The low-cost processing sequence is presented and each processing step is explained in detail. Results from electrical probing and mechanical strength test are given. The results demonstrate that the chosen low-cost processing route results in high yield and a mechanical robust device

Cost-effective processing of a piezoresistive MEMS cantilever sensor

In this paper cost-effective methods for fabrication of a piezoresistive cantilever sensor for industrial use are focused. The intended use of the presented cantilever is a medical application. A closer description of the cantilever design is given. The low-cost processing sequence is presented and each processing step is explained in detail. Results from electrical probing and mechanical strength test are given. The results demonstrate that the chosen low-cost processing route results in high yield and a mechanical robust device

Plastic Deformation of Thin Si Membranes in Si-Si Direct Bonding

The effect of bond anneal in Si-Si direct bonding of laminates With thin membranes suspending closed cavities is studied. For membranes of a certain size and thickness, it is found that the under-pressure in the cavity during bond anneal leads to plastic deformation of the membrane. By controlling the cavity pressure it is found that the Si crystal of the membrane can be kept intact during bond anneal.acceptedVersio

Metal Films for MEMS Pressure Sensors: Comparison of Al, Ti, Al-Ti Alloy and Al/Ti Film Stacks

Thermo-mechanical stability of metal structures is one of the key factors affecting accuracy of micro-electromechanical (MEMS) piezoresistive pressure sensors. In this work, we present the measurement results of stress and hysteresis for the following metals deposited in the same sputtering equipment -Al, Ti, Al-Ti alloy and stacks of Al/Ti films-enabling, for the first time, a direct comparison between their thermo-mechanical properties supported with analysis of surface morphology (grain size, hillocks and voids).acceptedVersio

Cost-effective processing of a piezoresistive MEMS cantilever sensor

In this paper cost-effective methods for fabrication of a piezoresistive cantilever sensor for industrial use are focused. The intended use of the presented cantilever is a medical application. A closer description of the cantilever design is given. The low-cost processing sequence is presented and each processing step is explained in detail. Results from electrical probing and mechanical strength test are given. The results demonstrate that the chosen low-cost processing route results in high yield and a mechanical robust device