Waterborne dispersion composition
Methods and apparatus for etching a high aspect ratio feature in a stack on a substrate are provided. The feature may be formed in the process of forming a 3D NAND device. Typically, the stack includes alternating layers of material such as silicon oxide and silicon nitride or silicon oxide and polysilicon. WF 6 is provided in the etch chemistry, which substantially reduces or eliminates problematic sidewall notching. Advantageously, this improvement in sidewall notching does not introduce other tradeoffs such as increased bowing, decreased selectivity, increased capping, or decreased etch rate.
1. A process for making a waterborne dispersion composition made using an extruder-based continuous process comprising the steps of:
(A) providing an extruder;
(B) feeding a mixture of:
(i) at least one vinyl acetate copolymer;
(ii) at least one compatibilizer selected from the group consisting of rosin acid, rosin ester, phenolic resin, and combinations thereof; and
(iii) a dispersing agent that is an alkyl carboxylic acid
into the extruder;
(C) feeding a first water addition to the mixture of step (B) in the extruder to provide a polymer continuous dispersion;
(D) feeding at least one base to the mixture of step (C) in the extruder; and
(E) feeding a second water addition to the mixture of step (D) in the extruder to form a water continuous dispersion that is wax-free and comprises
(i) from 80 wt % to 90 wt % vinyl acetate copolymer, and
(ii) less than 1.5 wt % dispersing agent, based on the solids weight percent of the water continuous dispersion.
2. The process of claim 1 , wherein each of the components: (i) at least one vinyl acetate copolymer; (ii) at least one compatibilizer; and (iii) at least one dispersing agent are fed into the extruder separately.
3. The process of claim 1 , wherein the components: (i) at least one vinyl acetate copolymer; (ii) at least one compatibilizer; and (iii) at least one dispersing agent are fed into the extruder together.
4. The process of claim 1 , wherein the extruder has a first feeding zone near the front end of the extruder, a second feeding zone near the middle of the extruder, and a third feeding zone near the back end of the extruder.
5. The process of claim 4 , wherein the temperature of the first feeding zone is from 90° C. to 150° C.
6. The process of claim 5 , wherein the temperature of the second feeding zone is from 90° C. to 150° C.
7. The process of claim 6 , wherein the temperature of the third feeding zone is from 80° C. to 150° C.
8. The process of claim 1 , wherein the dispersion produced by the process has a shelf stability of greater than 1 year at room temperature and has a particle size of less than 2 microns.
9. The process of claim 1 , wherein the at least one vinyl acetate copolymer is an ethylene vinyl acetate copolymer and fed into the extruder at a concentration of from 80 weight percent to 90 weight percent of total solids.
10. The process of claim 1 , wherein the at least one compatibilizer is a highly dimerized rosin acid and is fed into the extruder at a concentration of from 5 weight percent to 30 weight percent of total solids.
11. The process of claim 1 , wherein the at least one dispersing agent is oleic acid and is fed into the extruder at a concentration from 0.1 weight percent to 5 weight percent of total solids.
12. The process of claim 1 , wherein the amount of water fed into the extruder to the first water addition is from 3.5 weight percent to 6 weight percent of the total solids and first water addition.
13. The process of claim 1 , wherein the at least one base is potassium hydroxide and is fed into the extruder at a concentration of from 80 percent to 120 percent neutralization of the theoretical acid value of the components.
14. The process of claim 1 , wherein the amount of water fed into the extruder in the second water addition is greater than or equal to 3.5 weight percent of the total solids, first and second water additions.
15. A heat seal coating for food packaging or for industrial packaging comprising the dispersion composition made by the process of claim 1 .
16. The process of claim 1 , wherein the water continuous dispersion comprises from 0.66 wt % to 0.75 wt % of the dispersing agent.
17. The process of claim 16 comprising (D) feeding the at least one base separately from the (C) feeding the first water addition.
18. The process of claim 17 comprising (E) feeding the second water addition separately from the (D) feeding the at least one base.
19. The process of claim 18 wherein step (D) occurs after step (C) and step (E) occurs after step (D).