E BEAM

E-BEAM EVAPORATION, AN OVERVIEW

During the evaporation process by electron beam “e-beam”, a current passes through a tungsten filament, which by Joule effect and heating promotes the emission of electrons. Then, a high voltage is applied between the filament and the material which is contained in the crucible, this voltage accelerates the released electrons towards the crucible with the material to be evaporated. Finally, a strong magnetic field is applied to focusing these electrons in a beam that transfers the energy of these electrons to the material to be deposited in any substrate.

Deposition of materials by e-beam. In the image on the right, Andrea Conzatti Cantú, a student at the Technological Institute of Orizaba, who is doing her thesis on the development of pH sensors, makes use of the e-beam system of the CIDESI Querétaro clean room.

Deposition and co-deposition of materials in a e-beam system

The e-beam system at the cleanroom at Cidesi Querétaro, “it is one of the most popular ones”, is also equipped with two thermal evaporation systems further the ebeam system, which allows the Microtechnologies team to carry out from one single material deposition to multiple depositions of materials without open the main chamber and loss vacuum which gives them incredible advantages and possibilities in the manufacture of electronic devices.

This system is dedicated to the deposit of metals and some dielectrics. The materials that we have available in the clean room are: Gold, Platinum, Silver, Aluminum, Chromium, Nickel, Tungsten, Aluminum Oxide, Silicon Oxide and Chromium Oxide, mainly.

This ability to deposit different materials allows us to work on the development of sensors and electronic devices for a wide variety of applications such as glucose detection or air pollutant detection sensors, or many others.

From the left image you can see the crucible with gold pellets, also, for the right image you can see the e-beam system with the crucible with Gold after a deposition.

Further to the co-deposition and single deposition of materials, the two extra sources for thermal evaporation, the ebeam system has the following capabilities:

  • Rotation and heating of the sample holder up to 50 rpm. and 650 °C, respectively
  • Simultaneous deposition of up to three four-inch wafers
  • The deposition is controlled by software (PID control), in addition to that the scanning of the electron beam is programmable according to the deposited material.
  • The coated film thickness is monitored by an inficon sensor.
  • Finally, the equipment is supported by a cryogenic pump that allows reaching pressures of up to E-8 Torr that guarantees integrity in the purity of the deposited material.

As mentioned before, the ebeam system has two sources for thermal evaporation of materials. For the thermal evaporation processes. It is important to mention that high vacuum pressure during the deposition is critical and fundamental to obtain good homogeneity on the deposited films.

Finally, the deposition of materials by e-beam and thermal evaporation methods are ideal when developing applications such as diodes or organic-based photovoltaic systems, because the evaporation of materials is carried out at pressures in the range of -6 Torr, which avoids the presence of oxygen and moisture remnants in the main chamber.

The image on the right shows Nickel pellets that would be deposited by e-beam. The image on the left shows a wafer with conductivity and temperature sensors, in which part of the Nickel film was removed by the “lift off” process. These sensors were designed and manufactured in the clean room of CIDESI Querétaro.

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