1. A resist composition comprising
a polymer which changes its alkali solubility under the action of an acid as a base resin, and
a copolymer comprising recurring units (a) and (b) of the general formula (1) as an additive,
wherein R1 is fluorine or trifluoromethyl, R2 and R3 are hydrogen or a straight, branched or cyclic C1-C20 alkyl group, or R2 and R3 may bond together to form a ring with the carbon atom to which they are attached, and in this case, R2 and R3 together represent a straight, branched or cyclic C2-C20 alkylene group, R4 is hydrogen or an acid labile group,
R5 to R8 are independently selected from the group consisting of hydrogen, fluorine, and a straight, branched or cyclic C1-C20 alkyl group, which may contain at least one ether or ester group, may be substituted with fluorine, and may contain a hydroxy group, or any two of R5 to R8 may bond together to form a ring with the carbon atom(s) to which they are attached, m is 0 or 1, a and b are numbers in the range: 0.2\u2266a\u22660.8, and 0.1\u2266b\u22660.6.
2. The resist composition of claim 1 which is a chemically amplified positive resist composition.
3. The resist composition of claim 2, wherein the base resin is a polymer comprising recurring units having an acid labile group and recurring units having an adhesive group of hydroxy andor lactone ring.
4. The resist composition of claim 1 which is a chemically amplified negative resist composition.
5. The resist composition of claim 1, further comprising at least one member selected from the group consisting of an organic solvent, a basic compound, a dissolution regulator, a crosslinker, and a surfactant.
6. A pattern forming process comprising the steps of:
applying the resist composition of claim 1 onto a substrate to form a coating,
heat treating the coating and exposing it to high-energy radiation, and
developing the exposed coating with a developer.
7. The process of claim 6, wherein the high-energy radiation has a wavelength of 180 to 250 nm.
8. The process of claim 6, wherein the exposing step is by immersion lithography involving exposing the coating to high-energy radiation through a liquid.
9. The process of claim 8, wherein the immersion lithography involves using high-energy radiation having a wavelength of 180 to 250 nm, introducing a liquid between the substrate having a resist coating formed thereon and a projection lens, and exposing the substrate to the high-energy radiation through the liquid.
10. The process of claim 8, wherein the liquid is water.
11. The process of claim 6, wherein the high-energy radiation is an electron beam.
12. The process of claim 11, comprising the steps of:
applying the resist composition of claim 1 onto a mask blank substrate to form a coating,
heat treating the coating and exposing it to high-energy radiation, and
developing the exposed coating with a developer.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of etching a wafer of to form a plurality of staircase structures with reduced local and global asymmetry, the method comprising:
forming a photoresist layer on a plurality of micron-scale semiconductor structures; and
trimming the photoresist layer with a plasma etch process performed in a reverse MESA mode.
2. The method of claim 1, wherein the plasma etch process is a high pressure plasma etch process performed at a pressure of approximately 90 mTorr.
3. The method of claim 1, wherein the plasma etch process is a pulsed plasma etch process performed with an approximately 10 KHz pulse with an approximately 60% duty cycle.
4. The method of claim 1, wherein the plasma etch process is a pulsed, high pressure plasma etch process performed at a pressure of approximately 90 mTorr, with an approximately 10 KHz pulse having an approximately 60% duty cycle.
5. The method of claim 1, further comprising:
subsequent to trimming the photoresist layer, etching layers of a vertical NAND device using a pattern of the trimmed photoresist.
6. A method of etching a wafer of to form a plurality of staircase structures with reduced local and global asymmetry, the method comprising:
forming a photoresist layer on a plurality of micron-scale semiconductor structures;
trimming the photoresist layer with a plasma etch process performed in a reverse MESA mode, wherein the plasma etch process is a high pressure plasma etch process performed at a pressure of approximately 90 mTorr; and
subsequent to trimming the photoresist layer, etching layers of a vertical NAND device using a pattern of the trimmed photoresist.
7. The method of claim 6, wherein the plasma etch process is a pulsed plasma etch process performed with an approximately 10 KHz pulse with an approximately 60% duty cycle.
8. A method of etching a wafer of to form a plurality of staircase structures with reduced local and global asymmetry, the method comprising:
forming a photoresist layer on a plurality of micron-scale semiconductor structures;
trimming the photoresist layer with a plasma etch process performed in a reverse MESA mode, wherein the plasma etch process is a pulsed plasma etch process performed with an approximately 10 KHz pulse with an approximately 60% duty cycle; and
subsequent to trimming the photoresist layer, etching layers of a vertical NAND device using a pattern of the trimmed photoresist.