Which of the following statement is true for the lift off process?
I. After lift off process, the material is deposited at the sites which are not protected by photoresist
II. Lift off process gives a better result if the bilayer of photoresist is used instead of a single layer of photoresist
III.Lift off process is temperature dependent
IV. Quick evaporation of solvents during lift off may create a problem of redeposition
V. Deposition of material on the sidewalls creates a fence-like structure on the substrate
I, II, III, IV, V
I, III, IV, V
I, II, IV, V
I, II, III, IV
The correct statement is: I, II, IV, V
To find the true statement for the lift-off process among the given options, we will examine each statement one by one.
I. After lift-off process, the material is deposited at the sites which are not protected by photoresist.
This statement is true. In the lift-off process, the photoresist is patterned to create a mask on the substrate. The areas covered by the photoresist are protected, and the material is deposited only in the areas not covered by the photoresist. After deposition, the photoresist is removed, leaving behind the deposited material only at the desired sites.
II. Lift-off process gives a better result if the bilayer of photoresist is used instead of a single layer of photoresist.
This statement is not true. The use of a bilayer of photoresist is not directly related to the quality of the lift-off process. The choice of single or bilayer photoresist primarily depends on the specific requirements of the fabrication process, such as pattern resolution and process compatibility.
III. Lift-off process is temperature dependent.
This statement is true. The lift-off process can be influenced by temperature. Higher temperatures can enhance the solubility of the photoresist, aiding in its removal. However, excessively high temperatures can also affect the stability and integrity of the photoresist or lead to undesired reactions, so careful control of temperature is necessary.
IV. Quick evaporation of solvents during lift-off may create a problem of redeposition.
This statement is true. During the lift-off process, the solvents used to dissolve the photoresist can evaporate quickly. If the solvents evaporate before the photoresist is completely lifted off, there is a possibility of redeposition of the dissolved resist material on the substrate. This can lead to contamination and affect the quality of the final patterned structure.
V. Deposition of material on the sidewalls creates a fence-like structure on the substrate.
This statement is true. In some cases, during the lift-off process, material can deposit not only on the unprotected areas but also on the sidewalls of the patterned photoresist. This can result in the formation of a "fence-like" structure, where the deposited material forms vertical walls along the edges of the patterned features.
Based on the analysis above, the statements that are true for the lift-off process are I, III, IV, V. Therefore, the correct answer is option II, III, IV, V.