Method for producing microparticles
Silicon microcarriers suitable for fluorescent assays as a well as a method of producing such microcarriers are provided. The method includes the steps of providing a SOI wafer having a bottom layer of monocristalline silicone, an insulator layer and a bottom layer of monocristalline silicon, delineating microparticles, etching away the insulator layer and then depositing an oxide layer on the wafer still holding the microparticles before finally lifting-off the microparticles.
1. A method for producing microparticles suitable as support for fluorescent assays, comprising the steps of:
(a) providing a wafer having a sandwich structure comprising a bottom layer, an insulator layer lying over the bottom layer and a top layer lying over the insulator layer;
(b) etching the top layer to delineate microparticles which are thereby formed on the insulator layer;
(c) etching away the insulator layer to remove all of the insulator layer;
(d) depositing a layer on the wafer that is holding the microparticles, whereby mechanical forces that are capable of detaching the microparticles from the wafer are avoided; and
(e) lifting-off the microparticles from the wafer, wherein step (d) occurs after step (c) and before step (e).
2. The method of claim 1 , wherein the wafer is a SOI wafer.
3. The method of claim 1 , wherein the deposition of the dielectric material in step (d) includes plasma-enhanced chemical vapor deposition, by evaporation or by sputtering.
4. The method of claim 1 , wherein step (e) is performed by sonication.
5. The method of claim 1 , further comprising the step of attaching a ligand to the microparticle.
6. The method of claim 1 , wherein the layer of step (d) includes a dielectric material.
7. The method of claim 6 , wherein the dielectric material is an oxide or a nitride.
8. The method of claim 6 , wherein the dielectric material is silicon dioxide.
9. The method according to claim 1 , wherein the layer of step (d) includes a polymer or a metal.
10. The method of claim 9 , wherein the polymer is parylen.
11. The method of claim 9 , wherein the metal is selected from the group consisting of the following:
aluminium, chromium, gold and silver.
12. The method of claim 1 , wherein step (b) includes the steps of:
(i) spin coating a photosensitive resist layer onto the wafer;
(ii) delineating the surface layout of the microparticles on the photosensitive layer using photolithography techniques; and
(iii) etching the top layer.
13. The method of claim 12 , wherein step (iii) includes deep silicon etching.
14. The method of claim 12 , wherein step (iii) includes use of the Bosch process.
15. The method of claim 12 , wherein the photosensitive resist layer is negative or positive photoresist.