Search

US-12628589-B2 - Etching method using oxygen-containing hydrofluorocarbon

US12628589B2US 12628589 B2US12628589 B2US 12628589B2US-12628589-B2

Abstract

An etching method for forming a high aspect ratio aperture by selectively etching one or more silicon-containing films in a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films comprises: mounting the substrate in a processing chamber; introducing an etching gas containing a vapor of an oxygen-containing hydrofluorocarbon into the processing chamber; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the high aspect ratio aperture, wherein the oxygen-containing hydrofluorocarbon has a general formula C x H y F z O n , where 2≤x≤13, 1≤y≤15, 1≤z≤21, 1≤n≤3.

Inventors

  • Tomo Hasegawa
  • Vladislav GAMALEEV
  • Nicolas GOSSET

Assignees

  • L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE

Dates

Publication Date
20260512
Application Date
20230224

Claims (19)

  1. 1 . An etching method for forming a high aspect ratio aperture by selectively etching one or more silicon-containing films in a substrate using a patterned mask layer deposited on top of the one or more silicon-containing films, the method comprising: mounting the substrate in a processing chamber; introducing an etching gas containing a vapor of an oxygen-containing hydrofluorocarbon into the processing chamber; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the one or more silicon-containing films so that the one or more silicon-containing films are selectively etched versus the patterned mask layer to form the high aspect ratio aperture, wherein the oxygen-containing hydrofluorocarbon has a general formula C x H y F z O n , where 2≤x≤13, 1≤y≤15, 1≤z≤21, 1≤n≤3, provided that when x=4, y≠3, z≠7, n≠1, wherein the oxygen-containing hydrofluorocarbon has at least one ether group represented by one of following formulas: R 1 —CO—O—CH 2 —R 1 , R 2 —CH 2 —O—CH 2 —R 2 or R 3 —CHF—O—CF 2 —R 1 , wherein R 1 is H, F, C x H 2x+2-z F z or C x F 2x+2 ; R 2 is H, C x H 2x+2-z F z or C x F 2x+2 ; R 3 is F, C x H 2x+2-z F z or C x F 2x+2 , where 2≤x≤3 and 1≤z≤3.
  2. 2 . The method of claim 1 , wherein the oxygen-containing hydrofluorocarbon contains at least one oxygen atom in an ether group or in a carbonyl group.
  3. 3 . The method of claim 1 , wherein the oxygen-containing hydrofluorocarbon is selected from C 4 H 2 F 6 O 2 , C 3 H 2 F 6 O, C 2 H 2 F 4 O, C 2 HF 3 O, C 3 H 5 F 3 O, C 2 H 4 F 2 O, C 5 H 4 F 8 O, C 5 HF 11 O, C 2 H 3 F 3 O, or their isomers.
  4. 4 . The method of claim 1 , wherein the oxygen-containing hydrofluorocarbon is C 4 H 2 F 6 O 2 or its isomers.
  5. 5 . The method of claim 1 , wherein the oxygen-containing hydrofluorocarbon is C 4 H 2 F 6 O 2 , CAS No. 407-38-5.
  6. 6 . The method of claim 1 , wherein the etching gas further includes a vapor of a fluorocarbon or hydrofluorocarbon selected from CF 4 , C 2 F 6 , C 3 F 6 , C 4 F 6 , C 4 F 8 , C 5 F 8 , C 5 F 10 , C 6 F 12 , C 7 F 14 , C 8 F 16 , CH 2 F 2 , CH 3 F, CHF 3 , C 5 HF 7 , C 3 H 2 F 6 , C 3 H 4 F 2 , C 3 F 2 H 4 , C 4 H 2 F 6 , C 4 H 3 F 7 , C 3 HF 4 N, CF 3 I, C 3 F 7 I, C 4 F 9 I, C 4 H 9 F 3 Si, C 5 H 9 F 5 Si or combinations thereof.
  7. 7 . The method of claim 1 , wherein the etching gas further includes an oxidizing gas selected from O 2 , O 3 , CO, CO 2 , SO, SO 2 , FNO, N 2 , NO, N 2 O, NO 2 , H 2 O, COS or combinations thereof.
  8. 8 . The method of claim 1 , wherein the etching gas further includes an inert gas selected from He, Ar, Xe, Kr or Ne.
  9. 9 . The method of claim 1 , wherein the etching gas further includes an additional gas selected from H 2 , SF 6 , NF 3 , N 2 , NH 3 , Cl 2 , BCl 3 , Br 2 , F 2 , HBr, HCl, PF 3 or combinations thereof.
  10. 10 . The method of claim 1 , wherein an aspect ratio of the high aspect ratio aperture is above 5.
  11. 11 . The method of claim 1 , wherein the one or more silicon-containing films comprise a layer of Si a O b H c C d N e , where a>0, b, c, d and e≥0, selected from silicon oxide, silicon nitride, crystalline Si, poly-silicon, polycrystalline silicon, amorphous silicon, low-k SiCOH, SiOCN, SiC, SiON, or a layer of alternating silicon oxide and silicon nitride (ONON) films or alternating silicon oxide and poly-silicon (OPOP) films.
  12. 12 . The method of claim 11 , wherein a selectivity of the silicon oxide film versus the silicon nitride film in the layer of ONON films ranges from 1:2 to 2:1.
  13. 13 . An etching method for forming a high aspect ratio aperture by selectively etching a silicon oxide film in a substrate using a patterned mask layer deposited on top of the silicon oxide film, the method comprising: mounting the substrate in a processing chamber; introducing an etching gas containing an oxygen-containing hydrofluorocarbon C 4 H 4 F 6 O or C 4 H 2 F 6 O 2 vapor into the processing chamber; converting the etching gas to a plasma; and allowing an etching reaction to proceed between the plasma and the silicon oxide film so that the silicon oxide film is selectively etched versus the patterned mask layer to form the high aspect ratio aperture.
  14. 14 . The method of claim 13 , wherein the oxygen-containing hydrofluorocarbon is C 4 H 2 F 6 O 2 , CAS 407-38-5.
  15. 15 . The method of claim 13 , wherein the etching gas further includes a vapor of a fluorocarbon or hydrofluorocarbon selected from CF 4 , C 2 F 6 , C 3 F 6 , C 4 F 6 , C 4 F 8 , C 5 F 8 , C 5 F 10 , C 6 F 12 , C 7 F 14 , C 8 F 16 , CH 2 F 2 , CH 3 F, CHF 3 , C 5 HF 7 , C 3 H 2 F 6 , C 3 H 4 F 2 , C 3 F 2 H 4 , C 4 H 2 F 6 , C 4 H 3 F 7 , C 3 HF 4 N, CF 3 I, C 3 F 7 I, C 4 F 9 I, C 4 H 9 F 3 Si, C 5 H 9 F 5 Si or combinations thereof.
  16. 16 . The method of claim 13 , wherein the etching gas further includes an oxidizing gas selected from O 2 , O 3 , CO, CO 2 , SO, SO 2 , FNO, N 2 , NO, N 2 O, NO 2 , H 2 O, COS or combinations thereof.
  17. 17 . The method of claim 13 , wherein the etching gas further includes an inert gas selected from He, Ar, Xe, Kr or Ne.
  18. 18 . The method of claim 13 , wherein the etching gas further includes an additional gas selected from H 2 , SF 6 , NF 3 , N 2 , NH 3 , Cl 2 , BCl 3 , Br 2 , F 2 , HBr, HCl, PF 3 or combinations thereof.
  19. 19 . The method of claim 13 , wherein an aspect ratio of the high aspect ratio aperture is above 5.

Description

TECHNICAL FIELD The present invention relates to plasma-etching methods using oxygen-containing hydrofluorocarbons based plasma etching chemistry as an etchant for anisotropic etching of SiO2, Si3N4, stack of alternating SiO2 and Si3N4 films, and other Si-containing films with high etch rates, high selectivity to a mask material and forming patterns with a defined profile in high aspect ratio structures, and, in particular, to the plasma-etching methods using oxygen-containing hydrofluorocarbons having a formula CxHyFzOn, where 2≤x≤10, 1≤y≤15, 1≤z≤21, 1≤n≤3, preferably, at least one oxygen atom is incorporated to the hydrofluorocarbon in an ether or carbonyl group. BACKGROUND Improvements in terms of control of deposited polymer film profile to finely etch patterns with a defined profile, high etch rate of silicon-containing (e.g., SiO2, Si3N4 or alternating combination of SiO2 and Si3N4) films, and high selectivity to mask material (e.g. amorphous carbon, amorphous silicon, doped amorphous carbon or amorphous silicon) are expected in high-aspect-ratio contact and channel etching for applications such as 3D NAND and DRAM memory fabrication. Nowadays, silicon and silicon-based dielectrics are key components of any semiconductor device. Limitations in scaling down of transistors together with constant need in a considerable increase of memory capacity resulted in move of semiconductor industry from 2D type of structures to 3D integration. Production of semiconductor devices with vertical architectures, such as 3D NAND or DRAM, brings new fabrication challenges. One of the major problems related to the fabrication of 3D semiconductor devices (such as 3D NAND) is increasing height of elements, which requires etching of structures (apertures, holes, pillars, etc.) in dielectric with a high aspect ratio (ratio of height to width of structure). In more details, 3D NAND fabrication process requires deep etching of silicon oxide or alternated layers of silicon nitride and oxide, with well-defined profiles, and a soft landing onto the underlying (bottom) layer, which is a very challenging process even using state of the art devices. Therefore, etching process should feature high silicon oxide and nitride etch rates in order to maintain high production yield while etch rate of hard mask and bottom landing layers should be maintained as low as possible to avoid damage and various defects. The control of the hole etched profile (usually thin lateral size and straight vertical profile are desired) became recently one of the most important factors and challenges in fabrication of complex 3D semiconductor structures. To keep a defined profile it is required to minimize negative processing effects and defects such as bowing, twisting, or other pattern distortions. These defects are mainly coming from poor control of polymer film which is deposited during the etching process to protect parts of structure which are not intended to be etched (e.g., sidewall of hole or mask). The part of sidewall with not enough deposited polymer-based protection film may be distorted during high-aspect etching process leading to formation of mentioned above defects. Therefore, fine etching process tuning including precise control the polymer passivation conformality is necessary to ensure a good protection of the sidewalls while avoiding the clogging of the mask or an etch stop at the bottom of the holes during etching process. Although there are numbers of prior arts for SiO2 or Si3N4 etching by fluorocarbon gases, most of etching gas mixtures disclosed in prior art include molecular O2 gas. For example, U.S. Pat. No. 6,069,092 to Imai et al. discloses dry etching using fluorocarbon gas mixed with inert gas and oxygen. U.S. Pat. No. 5,626,775 A to Roberts et al. discloses etching of silicon dioxide or silicon nitride using trifluoroacetic acid and its oxygen-containing derivatives, and the etching chemical is mixed with oxygen. U.S. Pat. No. 7,153,779 B2 to Trapp et al. discloses etching of silicon oxide layer for high aspect ratio contact application using organic fluorocarbons including nitrogen-containing gases. U.S. Pat. No. 6,540,930 B2 to Kesari et al. discloses usage of perfluoroketones having 4 to 7 carbons mixed with oxygen to remove deposits and etch dielectrics and metals in a vapor reactor (non-plasma process). Various oxygen-containing compounds have been used as etching gas to etch SiO2 or Si3N4. US 2019/0345385 A1 to Oomori et al. discloses usage of CF3—CxHyFzO (where x=2 or 3; y=1, 2, 3, 4 or 5 and z=2x−1−y) and having one oxygen-containing three-membered ring, to etch silicon-based materials. JP2000038580 to Kumagai et al. discloses usage of CF3CFHOCF2H to etch silicon-based materials. That patent is pending and the target molecule is a specific formula and structure. JP6773110B2 to Matsuura et al. discloses the usage of R—CF—O—CH2—R (methylether-based fluorocarbons) to etch silicon oxide and prevent the neck growth (pattern