Method of cleaning glass substrates
A method of cleaning thin glass substrates comprises applying a sequence of chemical washing steps as the thin glass substrate is being conveyed in a conveyance direction. In addition, surfaces of the glass substrate may be treated to enhance electrostatic discharge properties of the glass substrates.
1. An in-line method of removing contaminants from a surface of a glass substrate comprising the steps of:
conveying the glass substrate with a conveying device along a conveyance direction, wherein during the conveying at least one surface of the glass substrate is subjected to a surface treatment comprising, sequentially:
a) exposing the at least one surface of the glass substrate to a liquid discharge comprising ozonated water;
b) exposing the at least one surface of the glass substrate to a liquid discharge of a first base solution, wherein ultrasonic energy is applied to the first base solution at a frequency in a range from about 20 kHz to about 200 kHz;
c) exposing the at least one surface of the glass substrate to a liquid discharge of a second base solution;
d) exposing the at least one surface of the glass substrate to a liquid discharge of a first acid solution to remove metallic ions from the at least one surface of the glass substrate, wherein the first acid solution comprises HCl; and
e) drying the at least one surface of the glass substrate.
2. The method according to claim 1 , further comprising increasing an average surface roughness of the glass substrate by exposing the glass substrate to a liquid discharge of a second acid solution after step d).
3. The method according to claim 2 , wherein the second acid solution comprises HF.
4. The method according to claim 2 , wherein the second acid solution comprises an ammonium bifluoride solution having a molar concentration in a range from about 0.2 M to about 2 M.
5. The method according to claim 2 , wherein the average surface roughness Ra of the glass substrate after increasing the average surface roughness of the glass substrate is in a range from equal to or greater than about 0.2 nm to about 0.8 nm.
6. The method according to claim 1 , wherein the first base solution comprises NH 4 OH:H 2 O 2 :H 2 O having a mixture ratio in a range from about 1:1:5 to about 1:2:80 by volume.
7. The method according to claim 1 , wherein the first base solution is at a temperature in a range from about 40° C. to about 80° C. and the glass substrate is exposed to the first base solution for a time in a range from about 1 minute to about 30 minutes.
8. The method according to claim 1 , wherein a pH of the first base solution is greater than about 10.
9. The method according to claim 1 , further comprising applying megasonic energy to the second base solution at a frequency in a range from about 850 kHz to about 1.2 MHz.
10. The method according to claim 1 , wherein the glass substrate comprises less than 1.6×10 12 atoms/cm 2 of Na, K, Fe, Cu and Zn within 5 nm of the at least one surface after step e).
11. The method according to claim 1 , wherein the at least one surface of the glass substrate comprises less than 0.02 particles/cm 2 having an effective diameter greater than 0.3 microns after step e).
12. An in-line method of removing contaminants from a surface of a glass substrate comprising the steps of:
conveying the glass substrate with a conveying device along a conveyance direction, wherein during the conveying at least one surface of the glass substrate is subjected to a surface treatment comprising, sequentially:
a) exposing the at least one surface of the glass substrate to a liquid discharge comprising ozonated water;
b) exposing the at least one surface of the glass substrate to a liquid discharge of a first base solution;
c) exposing the at least one surface of the glass substrate to a liquid discharge of a second base solution;
d) exposing the at least one surface of the glass substrate to a liquid discharge of a first acid solution to remove metallic ions from the at least one surface of the glass substrate, wherein the first acid solution comprises HCl;
e) drying the at least one surface of the glass substrate; and
wherein an average surface roughness of the glass substrate is increased by exposing the glass substrate to a liquid discharge of a second acid solution.
13. The method according to claim 12 , wherein exposing the glass substrate to a liquid discharge of a second acid solution is performed after step c).
14. The method according to claim 12 , wherein exposing the glass substrate to a liquid discharge of a second acid solution is performed before step c).
15. The method according to claim 12 , wherein the second acid solution comprises HF.
16. The method according to claim 12 , wherein the second acid solution comprises an ammonium bifluoride solution having a molar concentration in a range from about 0.2 M to about 2 M.
17. The method according to claim 12 , wherein the glass substrate comprises less than 1.6×10 12 atoms/cm 2 of Na, K, Fe, Cu and Zn within 10 nm of the at least one surface after step e).
18. The method according to claim 12 , wherein the at least one surface of the glass substrate comprises less than 0.02 particles/cm 2 having an effective diameter greater than 0.3 microns after step e).
19. The method according to claim 12 , further comprising applying ultrasonic energy to the first base solution at a frequency in a range from about 20 kHz to about 200 kHz.
20. The method according to claim 12 , further comprising applying megasonic energy to the second base solution at a frequency in a range from about 850 kHz to about 1.2 MHz.