Etching Gas

Examples 1 to 3 and Comparative Examples 1 and 2

[0053]There are shown examples where etching was conducted on an interlaminar insulating film (SiO2) by using an etching gas of the present invention for contact hole-fabrication.

[0054]As a sample, a SiO2 interlaminar insulating film 22 was formed on a single crystal silicon wafer 21. The sample was put to use upon forming on the SiO2 film a resist mask 23 having apertures to serve as an etching mask. A sample before etching is shown in FIG. 1A.

[0055]A schematic cross section of an apparatus used in the experiment is shown in FIG. 2. By using a high-frequency source 3 (13.56 MHz, 50 W), etching gases (difluoroacetyl fluoride (CHF2COF), oxygen (O2), argon (Ar)) having been supplied from a gas inlet at flow rates shown in Table 1 were excited in a sapphire tube 7 attached to the top of a reaction chamber 1 thereby generating active species. The active species were supplied into the chamber by the flow of gas, upon which etching was conducted on a sample 12 fixed by a sample holder 11. Among the gas specimens, CHF2COF, CF3COF and CF4 were introduced from a first gas inlet while O2 was introduced from a second gas inlet, through a mass flow controller (though not shown).

[0056]The temperature of the substrate (or the sample holder 11) was set at 25° C., the pressure was set at 2.67 Pa (0.02 Torr), and the RF power density was set at 2.2 W/cm2. A discharged gas was diluted with nitrogen supplied at 5 L/min on a discharge side of a mechanical booster pump, and then the concentration of CF4 was quantified by calibration curve method with the use of FT-IR. Results of the above are shown in Table 1. Incidentally, “ND” shown in the Table refers to less than the floor limit for detection (0.05 volume %). The etching rate (Å/min) was determined in such a manner as to divide film thicknesses obtained before and after etching by an etching time. The film thicknesses were measured by an optical interferotype film-thickness meter. A sample after etching (in the case of having facets) is shown in FIG. 1B.

TABLE 1 Flow Flow CH4 Rate Rate Etching Selection Concentration of Gas 1 of Gas 2 Rate Ratio to Aspect Patterning in Discharged Gas 1 SCCM Gas 2 SCCM Å/min Resist Ratio Profile Gas Example 1 CHF2COF 50 None — 4058 6 6 or No facet, Less than more Good side floor limit for wall detection Example 2 CHF2COF 10 Ar 200 4121 6 6 or No facet, Less than more Good side floor limit for wall detection Example 3 CHF2COF 50 O2 10 15598 7 6 or No facet, Less than more Good side floor limit for wall detection Comparative CF3COF 50 None — 3218 5 6 or Partially 0.11% Example 1 more having facets and gouges in side wall Comparative CF4 50 None — 608 4 5 Partially 0.18% Example 2 having facets and gouges in side wall CHF2COF: Difluoroacetyl fluoride CF3COF: Trifluoroacetyl fluoride O2: Oxygen Ar: Argon CF4: Carbon tetrafluoride

EXPLANATION OF REFERENCE NUMERALS

[0057]1 Chamber

[0058]2 Earth

[0059]3 High-frequency source

[0060]4 First gas inlet

[0061]5 Second gas inlet

[0062]6 Third gas inlet

[0063]7 Sapphire tube

[0064]8 Induction coil

[0065]9 Electronic pressure meter

[0066]10 Discharged-gas line

[0067]11 Sample holder

[0068]12 Sample

[0069]21 Silicon wafer

[0070]22 SiO2 interlaminar insulating film

[0071]23 Resist mask

[0072]24 Facets