Dry etching method
Disclosed is a dry etching method for a laminated film in which at least one silicon layer and at least one silicon oxide layer are laminated together. The dry etching method includes generating a plasma gas from a dry etching agent and etching the laminated film with the plasma gas under the application of a bias voltage. The dry etching agent contains an unsaturated hydrofluorocarbon represented by the following formula: C 3 H x F y where x is an integer of 1 to 5; y is an integer of 1 to 5; and x and y satisfy a relationship of x+y=4 or 6, and iodine heptafluoride. The volume of the iodine heptafluoride in the dry etching agent is 0.1 to 1.0 times the volume of the unsaturated hydrofluorocarbon in the dry etching agent.
1. A dry etching method for a laminated film, the laminated film comprising at least one silicon layer and at least one silicon oxide layer laminated together, the dry etching method comprising:
applying a mask with an opening to the laminated film;
generating a plasma gas from a dry etching agent;
bringing the plasma gas into contact with the laminated film through the opening of the mask; and
etching the laminated film with the plasma gas under the application of a bias voltage, thereby forming a through hole in the laminated film in a direction perpendicular to an in-plane direction of the laminated film,
wherein the dry etching agent comprises:
an unsaturated hydrofluorocarbon represented by the following formula: C 3 H x F y where x is an integer of 1 to 5; y is an integer of 1 to 5; and x and y satisfy a relationship of x+y=4 or 6; and
iodine heptafluoride, wherein the volume of the iodine heptafluoride in the dry etching agent is 0.1 to 1.0 times the volume of the unsaturated hydrofluorocarbon in the dry etching agent.
2. The dry etching method according to claim 1 , wherein the unsaturated hydrofluorocarbon is at least one selected from the group consisting of C 3 HF 5 , C 3 H 2 F 4 and C 3 HF 3 .
3. The dry etching method according to claim 1 , wherein the bias voltage is 500 V or higher.
4. The dry etching method according to claim 1 , wherein the dry etching agent further comprises an inert gas, and wherein the total amount of the unsaturated hydrofluorocarbon and the iodine heptafluoride in the dry etching agent is 2 to 95 vol %.
5. The dry etching method according to claim 4 , wherein the dry etching agent essentially consists of the unsaturated hydrofluorocarbon, the iodine heptafluoride and the inert gas.
6. The dry etching method according to claim 1 , wherein the concentration of the unsaturated hydrofluorocarbon in the dry etching agent is 1 to 90 vol %.
7. The dry etching method according to claim 6 , wherein the concentration of the unsaturated hydrofluorocarbon in the dry etching agent is 10 to 50 vol %.
8. The dry etching method according to claim 1 , wherein the laminated film comprises a plurality of silicon layers and a plurality of silicon oxide layers alternately laminated together.
9. The dry etching method according to claim 1 , wherein the ratio of an etching rate of the silicon layer to an etching rate of the silicon oxide layer is in a range of 67 to 150%.
10. The dry etching method according to claim 1 , wherein the through hole is formed with a hole diameter ratio of 30% or lower as determined by the following equation:
Hole
diameter
ratio
=
Diameter
of
through
hole
in
laminated
film
Diameter
of
opening
mask
×
100
%
.