Sputter Deposition
Reference Guide
Every material has a recommended maximum power density for operation. Applying power greater than the recommended maximum can cause damage to the target or the magnetron. Common types of damage include:
- Delamination of the target from the backing plate.
- Crack formation in the target.
- Arc damage to magnetron head components due to shorting from indium bond material that has leaked from the target into the magnetron head
Angstrom Engineering® recommends the following best practices for operation to minimize damage to targets and magnetrons:
- Ramp the power up and down slowly to allow the target to adjust to the power.
- For a given material, only work up to the maximum power found in the table below.
- Operate sputter sources by controlling on time and power.
- These values are recommended under the assumption that the cathodes have adequate water flow
Material |
Max Power Density (W/sq in) |
| Low-temperature materials (such as In & Sn) | 10 |
| Si (undoped & N-type), Mn, most oxides, nitrides, and bonded targets* | 20 |
| Ni & Ni compounds | 25 |
| SiO2 (unbonded), LiF | 30 |
| P-Type Silicon (Si) | 40 |
| Fe, Ti**, V, Zr | 50 |
| Cr, Co | 80 |
| Ag, Au, Nb**, Pt, Ta**, W | 100 |
| Al, Mo** | 150 |
| Cu | 200 |
* Some bonded targets have a lower power density limit. Do not immediately use the maximum power when first using a target.
** Refractory metals retain heat.
If a voltage creep is seen, this
means that the target is
becoming resistive and that
too much power is being
applied.
3 important things to consider
1. Source power is treated as a percentage of the power supply’s maximum available output. Therefore, if you have a 1000 W power supply, you would set it to 18.2% for an output of 182 W. A 300 W power supply would require a setting of 60.67% for an output of 182 W.
2. Unique material maximum sputter yield: The number of atoms the plasma can dislodge in a given time. Don’t chase a rate. Instead, determine the amount of TIME you will need to achieve your desired film thickness when applying a set POWER for a specific material and target area.
3. In a bonded target: Yield is limited both by the power density of the material you are sputtering, and the power density of the material that forms the bond to the backing plate.
Our Recommendation
Controlling Time & Power
Step 1
Determine the maximum power density of sputter target (material and target area) and your desired film thickness.
Step 2
Slowly ramp up power, taking 3-5 minutes to reach the material’s suggested maximum power.
Indium Tin Oxide has a power density of 19 W/sq in so a Ø2 in target has a max power of 61 W. Tantalum has a power density of 97 W/sq in so a Ø3 in target has a max power of 684 W
Step 3
The rate measured at the material’s maximum power is the maximum rate. Determine how much time you will need at this power setting to reach your desired film thickness. Alternatively, run at a fixed power for a fixed period of time at a known pressure and then perform a physical measurement of the film thickness to determine your time and power effective rate. The rate will typically scale linearly with power (half the power is half the rate) and desired thickness is a factor of time (twice the time, twice the thickness).
Step 4
Slowly ramp down power (over 3-5 minutes for conductive materials and 7-10 minutes for bonded targets and fragile materials such as Silicon and Indium Tin Oxide). Removing power too quickly can result in damage to targets and sources due to thermal shock.
At 61 W, the Indium Tin Oxide target is depositing at a rate of 0.5 Å/s. If a thickness of 200 Å is the desired thickness, the user will need 400 seconds (6 minutes, 40 seconds) at 61 W power to achieve it.
At 684 W, the Tantalum is depositing at a rate of 2.5 Å/s. If a thickness of 1000 Å is the desired thickness, the user will need 400 seconds (6 minutes, 40 seconds) to achieve it.