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| 2. |
- Jonsson, Kerstin, et al.
(författare)
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Oxygen Plasma Wafer Bonding Evaluated by the Weibull Fracture Probability Method
- 2001
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 11:4, s. 364-370
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the oxygen plasma bonding process for fusion bonded silicon wafers has been characterized by a new approach. The mechanical reliability of bonded microstructures was determined using burst tests and Weibull statistic analyses. The fracture characteristic of the bonded system is considered to depend on the stress distribution, the defect distribution and the fracture surface energy at the bond. Using Weibull theory, it is possible to extract the Weibull modulus m and the mean fracture uniform tensile stress per unit length, σfc, from the measured data. These quantities make it possible to compare the joint defect distribution and the fracture surface energy at the bonded interface for the processing conditions under observation. These experiments also demonstrate that it is possible to distinguish between these quantities under certain conditions.The fracture probability for different annealing temperatures has been evaluated and found to agree with previous results from surface energy measurements. It is shown that the bond fracture probability increases with annealing times in the range of 10-100 h. The saturated bond strength value is considerably enhanced by oxygen plasma activation prior to bonding. In this study, plasma activations at room temperature and 300 °C compare to chemical activations in hot nitric acid annealed at 120 °C and 700 °C, respectively. The tendency to form voids at elevated temperatures, e.g. 300 °C, is increased by the oxygen plasma treatment.If the surface energy is considered to be homogeneous over the bonded interface, the Weibull modulus m is an indirect measure of the defect distribution, low m values indicate a wide spectrum of defect types, whereas a high m value narrows the defect distribution responsible for fracture. The Weibull modulus m is shown to be valuable for evaluation of the bonded interface. It is demonstrated that a more scattered defect distribution emerges for in situ bonded wafers as compared to ex situ, and annealing at 300 °C for 90 h as compared to room-temperature storage. However, the defect distribution becomes increasingly more narrow with storage time. These variations may be due to either changes in microcracks or void configuration or inhomogeneities in the fracture surface energy over the bond interface.
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| 4. |
- Jonsson, Lars, et al.
(författare)
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Patterning of tantalum pentoxide, a high epsilon material, by inductively coupled plasma etching
- 2000
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Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 2166-2746 .- 2166-2754. ; 18:4, s. 1906-1910
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Tidskriftsartikel (refereegranskat)abstract
- Integrated capacitors can easily cover a major part of the total chip area which may seriously affect the cost to produce the chip. By using a high epsilon material as the dielectric material, in the capacitor, the size can be reduced significantly. One very promising candidate is tantalum pentoxide (Ta2O5)" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(Ta2O5)(Ta2O5)which has a dielectric constant of about 25. This should be compared to silicon nitride which has a dielectric constant of 8. In order to make integrated capacitors the tantalum pentoxide must be patterned. Results of a study on etching of tantalum pentoxide, silicon dioxide, and polysilicon with a high density plasma, using an inductively coupled plasma source, are presented and compared to results obtained by means of reactive ion etching. The gas used, CHF3," role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">CHF3,CHF3, implies a polymerizing chemistry and the deposition of a fluorocarbon layer is shown to play an important role in the etch process. The fluorocarbon deposition onto the substrate surface is not only affected by the temperature of the substrate itself but also by the temperature of all surfaces that are exposed to the plasma. The process parameters with the strongest influence on the process have been found to be pressure and substrate bias voltage.
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| 5. |
- Köhler, Johan, et al.
(författare)
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A hybrid cold gas microthruster system for spacecraft
- 2001
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Ingår i: Digest of Papers for the 11th Int Conf on Solid-State Sensors and Actuators - Transducers '01 and Eurosensors XV, Munich, Germany, June 10-14. ; , s. 886-889
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Konferensbidrag (refereegranskat)
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| 6. |
- Köhler, Johan, et al.
(författare)
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Silicon fusion bond interfaces resilient to wet anisotropic etchants
- 2001
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 11, s. 359-363
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Tidskriftsartikel (refereegranskat)abstract
- The bond interface in silicon microsystems is sensitive to the subjection to wet anisotropic etchants. Fusion bond interfaces of bonded wafers resilient to potassium hydroxide or tetramethyl ammonium hydroxide etching are obtained using wafers of oxidized silicon bonded to oxidized silicon, where the bond oxide is removed by trifluoromethane plasma etching. Other investigated bond configurations initiate severe damages during etching.
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| 7. |
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| 8. |
- Pasquariello, Donato, et al.
(författare)
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Oxidation and induced damages in oxygen plasma in situ wafer bonding
- 2000
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 147:7, s. 2699-2703
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present our in situ, oxygen plasma‐activated wafer bonding process. By keeping one wafer on the anode and the other on the cathode, we have an asymmetric plasma load on the wafers, making our bonding process interesting for low‐temperature applications where damage or defect‐sensitive active layers are bonded to less sensitive carrier wafers. As a step in optimizing the discharge parameters for plasma bonding applications, the effect of the self‐bias voltage on surface energy, oxidation rates, and damage is investigated. An optimum in surface energy was found at moderate self‐bias voltages, both at room temperature bonding and after low‐temperature annealing at 200°C. This is explained by the fact that at these voltages there is a minimum oxide thickness, which promotes the diffusion of water from the bond interface, and also by the fact that at these voltages we have the best surface cleaning conditions. Also, the surface oxide generated by the oxygen plasma seems to be reactive. With our in situ oxygen‐plasma‐activated wafer bonding process there was a major increase in surface energy for wafers bonded at moderate self‐bias volt‐ages compared to conventional wafer bonding performed in ambient air.
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| 9. |
- Pasquariello, Donato, et al.
(författare)
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Surface energy as a function of self-bias voltage in oxygen plasma wafer bonding
- 2000
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Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; A82, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- A limitation in the use of wafer bonding has been the necessity for high-temperature annealing after contacting the wafers at room temperature. In this paper, we try to find the highest surface energy as a function of self-bias voltage in oxygen plasma-activated wafer bonding, in order to achieve a low-temperature bonding process. The bonding was performed in situ the vacuum chamber. It was found that oxygen plasma has a smoothing effect on the surface roughness, rather independent of the plasma self-bias. However, a moderate self-bias voltage proved to give the highest surface energy for the bonded wafers, both at room-temperature and after annealing at 200°C. We believe that this is due to the fact that a moderate self-bias is the most efficient in removing surface contaminants, like water and hydrocarbons. It was also found that even after annealing at higher temperatures, 480°C and 720°C, the plasma-bonded wafers showed higher surface energy values than wafers bonded in ambient air. This investigation was focused on low-effect plasmas, <200 W, keeping the induced plasma damages at a minimum.
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| 10. |
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