E Beam Lithography
Electron-beam lithography (often abbreviated as e-beam lithography, EBL) is the practice of scanning a focused beam of electrons to draw custom shapes on a surface covered with an electron-sensitive film called a resist. Electron Beam Lithography (EBL) allows users to write patterns with extremely high resolution, smaller than 10nm in size. Important parts of E- Beam Lithography
- Electron Gun
- Vacuum System
- Control System
Advantages of E Beam Lithography System
- The resolution is not limited by diffraction; minimum feature is written on the nanoscale.
- Can write smaller features than: X-ray Lithography and Photolithography.
- Pattern is written directly to the wafer.
- Used to develop, specialized devices and Prototype devices.
- Can be used to make masks.
Disadvantages of E Beam Lithography System
- Not an efficient process for industrial processing.
- Takes multiple hours to pattern an entire wafer.
- Machines are Costly.
- System is more complex than Photolithography System.
- Scattering and Overexposure results in minimum feature being larger.
Application of E- Beam Lithography
E Beam lithography technique is generally used for research purpose not much from commercial prospective.
- Advanced processing techniques.
- Future processing equipment.
- Can convert SEM to be used as an EBL Machine.
- Minimum resolution is slightly larger.
- Used with Photolithography and X-ray Lithography to create next generation devices.
X- Ray Lithography
The photolithography has its resolution limited by diffraction effects. To improve the resolution, therefore, the diffraction effects are reduced by reducing the wavelength. However, if the wavelength is reduced further, all optical materials become opaque because of the fundamental absorption, but transmission increases again in the X-ray region. This led to the requirement of X-rays for lithography purpose. In X-ray lithography an X-ray source illuminates a mask, which casts shadows on to a resist-covered wafer. The mask and resist material for X-ray lithography are mainly determined by the absorption spectra of these materials in the X-ray region.
Advantages of X-Ray Lithography
- Resolves diffraction.
- Shorter wavelengths (.1-10 nm).
- Smaller features.
Disadvantages of X-Ray Lithography
- Thin X-ray masks.
- Time consuming.
Application of X-Ray Lithography
- Create transistors with smaller features.