Method suitable for etching hydrophillic trenches in a substrate
View Patent ↗A method suitable for etching hydrophilic trenches into a substrate, such as silicon, is provided. The method comprises etching and sidewall passivation processes for achieving anisotropy. Sidewalls of the etched trench are made hydrophilic during the etch by virtue of a hydrophilizing dopant in a passivating gas plasma. The method is useful for etching ink supply channels in inkjet printheads.
1. A method of fabricating an inkjet printhead comprising the steps of:
(i) providing a wafer substrate having a drop ejection side and an ink supply side;
(ii) etching a plurality of trenches partially through said drop ejection side of said wafer;
(iii) filling said trenches with photoresist;
(iv) forming a plurality corresponding nozzles, ejection actuators and associated drive circuitry on said drop ejection side of said wafer using lithographically masked etching techniques;
(v) etching a plurality of corresponding ink supply channels from said ink supply side of said wafer to said photoresist, said etching comprising an etching process using an etching gas plasma and a passivation process using a passivating gas plasma, wherein said passivating gas plasma comprises a hydrophilizing dopant; and
(vi) stripping said photoresist from said trenches to form nozzle inlets, thereby providing fluid connection between said ink supply side and said nozzles.
2. The method of claim 1 , wherein said substrate is silicon.
3. The method of claim 1 , wherein said etching gas plasma is generated in a plasma etching reactor, and said substrate is etched in said reactor.
4. The method of claim 1 , wherein ink supply channel sidewalls resulting from the etch have a contact angle of less than 50°.
5. The method of claim 1 , wherein the hydrophilizing dopant comprises a boron-containing compound, a phosphorus-containing compound or combinations thereof.
6. The method of claim 1 , wherein the hydrophilizing dopant comprises a compound selected from the group consisting of B 2 H 6 , PH 3 , trimethyl borate (TMB), trimethyl phopshite (TMP) or combinations thereof.
7. The method of claim 1 , wherein ink supply channel sidewalls resulting from the etch comprise phosphosilicate glass (PSG), borosilicate glass (BSG), borophosphosilicate glass (BPSG) or combinations thereof.
8. The method of claim 1 , wherein the ink supply channels have a depth of over 100 micron.
9. The method of claim 1 , wherein a plurality of ink supply channels are etched into said substrate simultaneously, the positions of said ink supply channels being defined by a mask layer disposed on said substrate.
10. method of claim 9 , wherein said mask layer is an oxide layer or a photoresist layer.
11. The method of claim 10 , wherein the substrate: mask selectivity is at least 30:1.
12. The method of claim 9 , wherein the etch rate is at least 4 micron/mm.
13. The method of claim 1 comprising simultaneous etching and passivation processes, wherein a single etching and passivating gas plasma comprises said etching gas plasma and said passivating gas plasma.
14. The method of claim 13 , wherein said etching and passivating gas plasma comprises:
(a) a passivating gas comprising oxygen;
(b) an inert sputtering gas;
(c) a fluorinated etching gas; and
(d) a hydrophilizing dopant.
15. The method of claim 14 , wherein said inert sputtering gas is argon.
16. The method of claim 14 , wherein said fluorinated etching gas is selected from the group consisting of SF 6 , NF 3 and mixtures thereof.
17. The method of claim 1 comprising alternating etching and passivation processes.
18. The method of claim 17 , comprising the steps of:
(i) etching into said substrate using an etching gas plasma, said etching gas plasma comprising:
(a) a fluorinated etching gas; and
(b) an inert sputtering gas;
(ii) passivating exposed surfaces of the substrate using a passivating gas plasma, said passivating gas plasma comprising:
(a) a silicon-containing deposition gas; and
(b) a hydrophilizing dopant;
(iii) alternatingly repeating steps (i) and (ii).
19. The method of claim 18 , wherein said inert sputtering gas is argon.
20. The method of claim 18 , wherein said fluorinated etching gas is selected from the group consisting of SF 6 , NF 3 and mixtures thereof.
21. The method of claim 18 , wherein said silicon-containing deposition gas comprises SiH 4 .
22. The method of claim 18 , wherein said passivating gas plasma further comprises a gas selected from O 2 , N 2 , N 2 O, NH 3 or combinations thereof.
23. The method of claim 18 , wherein the passivation step deposits, on the exposed surfaces, a phosphosilicate glass (PSG), a borosilicate glass (BSG), a borophosphosilicate glass (BPSG) or combinations thereof.