Etching gas

Abstract

We provide an etching gas containing 1,1,1,2-tetrafluoroethane that is less prone to side etching. [Solution] The etching gas includes 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds.

Description

Technical Field

[0001] The present disclosure relates to an etching gas containing 1,1,1,2-tetrafluoroethane.

Background Art

[0002] As an etching gas, 1,1,1,2-tetrafluoroethane is known.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although 1,1,1,2-tetrafluoroethane is known as an etching gas, the inventors have found that there is a problem of causing side etching. When side etching occurs, it becomes difficult to obtain a desired processed shape.

[0005] An object of the present disclosure is to provide an etching gas containing 1,1,1,2-tetrafluoroethane in which side etching hardly occurs.

Means for Solving the Problems

[0006] The present disclosure includes the following aspects. [Item 1] An etching gas comprising 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds. [Section 2] The fluorocarbon compound having a double bond is the etching gas described in item 1, wherein the number of double bonds is one. [Section 3] The etching gas according to item 1 or 2, wherein the fluorocarbon compound having a double bond has 2 or 3 carbon atoms. [Section 4] The etching gas according to any one of claims 1 to 3, wherein the fluorocarbon compound having a double bond comprises at least one compound selected from the group consisting of 1-chloro-1,2-difluoroethene, 1-chloro-1-fluoroethene, and 3,3,3-trifluoropropene. [Section 5] The etching gas according to any one of items 1 to 4, wherein the concentration of the fluorocarbon compound having one or more double bonds relative to the total of 1,1,1,2-tetrafluoroethane and the fluorocarbon compound having one or more double bonds is 1 volume ppm or more and less than 400 volume ppm. [Section 6] The etching gas according to any one of items 1 to 5, wherein the concentration of the fluorocarbon compound having one or more double bonds relative to the total of 1,1,1,2-tetrafluoroethane and the fluorocarbon compound having one or more double bonds is 50 ppm by volume or more and 300 ppm by volume or less. [Section 7] Furthermore, an etching gas as described in any one of items 1 to 6, including an inert gas. [Section 8] The inert gas is argon, as described in item 7. [Section 9] The etching gas described in any one of items 1 to 8, wherein the concentration of 1,1,1,2-tetrafluoroethane in the etching gas is 1.0% by volume or more and 20% by volume or less. [Effects of the Invention]

[0007] According to the etching gas of this disclosure, side etching is suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram illustrating the side etch rate. [Modes for carrying out the invention]

[0009] The etching gases of this disclosure include 1,1,1,2-tetrafluoroethane, fluorocarbon compounds having one or more double bonds, and inert gases.

[0010] A mixed gas containing 1,1,1,2-tetrafluoroethane can suppress side etching, particularly during hole etching, by containing one or more fluorocarbon compounds having double bonds.

[0011] The fluorocarbon compounds having the double bond described above are typically hydrofluoroolefins (HFOs).

[0012] Examples of hydrofluoroolefins (HFOs) include 2-chloro-1,1-difluoroethene (HFO-1122), (E / Z)1-chloro-1,2-difluoroethene (HFO-1122a), trifluoroethene (HFO-1123), 1-chloro-2-fluoroethene (HFO-1131), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 3,3,3-trifluoropropene (HFO-1243zf), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze), 1,3,3,3-tetrafluoropropene (HFO-1234zd), and 1,2,3,3,3-pentafluoropropene (HFO-1336mzz).

[0013] In one embodiment, the fluorocarbon compound having a double bond has one double bond.

[0014] In one embodiment, the fluorocarbon compound having a double bond has 2 or 3 carbon atoms.

[0015] In a preferred embodiment, the fluorocarbon compound having a double bond contains at least one compound selected from the group consisting of 1-chloro-1,2-difluoroethene, 1-chloro-2-fluoroethene, and 3,3,3-trifluoropropene. The fluorocarbon compound having a double bond is preferably 1-chloro-1,2-difluoroethene, 1-chloro-2-fluoroethene, or 3,3,3-trifluoropropene. The fluorocarbon compound having a double bond may be used alone or in combination of two or more.

[0016] The concentration of the fluorocarbon compound having a double bond relative to the total of 1,1,1,2-tetrafluoroethane and the fluorocarbon compound having one or more double bonds is 1 volume ppm or more, preferably 5 volume ppm or more, more preferably 10 volume ppm or more, still more preferably 50 volume ppm or more, for example, 100 volume ppm or more. By including 1 volume ppm or more of the fluorocarbon compound having a double bond, side etching is suppressed. Also, the concentration of the fluorocarbon compound having a double bond may be less than 500 volume ppm, preferably 400 volume ppm or less, more preferably 300 volume ppm or less, for example, 200 volume ppm or less or 100 volume ppm or less. By setting the concentration of the fluorocarbon compound having a double bond to less than 500 volume ppm, pore clogging during etching can be suppressed. The concentration of the fluorocarbon compound having a double bond may be more than 1 volume ppm and less than 500 volume ppm, preferably 5 to 400 volume ppm, more preferably 50 to 300 volume ppm.

[0017] The etching gas of the present disclosure may contain an inert gas. The inert gas is used as a so-called dilution gas.

[0018] The inert gas is not particularly limited as long as it is inert to 1,1,1,2-tetrafluoroethane and fluorocarbon compounds having double bonds. Examples of inert gases include nitrogen or noble gases. Examples of noble gases include helium, neon, argon, xenon, and krypton. Argon is preferred as the inert gas. The inert gas may be used alone or in combination of two or more.

[0019] The etching gas of this disclosure may contain additive gases.

[0020] Examples of additive gases include oxygen and hydrogen.

[0021] The oxygen concentration in the etching gas may be, for example, 1.0 to 20% by volume, preferably 2.0 to 10% by volume, and more preferably 2.0 to 5.0% by volume. Preferably, oxygen is used in an amount of 50 to 150% of 1,1,1,2-tetrafluoroethane, more preferably 80 to 120%, for example, the same amount.

[0022] The concentration of hydrogen in the etching gas may be, for example, 0.1 to 10% by volume, preferably 0.1 to 1.0% by volume, and more preferably 0.1 to 0.50% by volume. Preferably, hydrogen is used in an amount of 10 to 20% of 1,1,1,2-tetrafluoroethane.

[0023] The concentration of 1,1,1,2-tetrafluoroethane in the etching gas is preferably 1.0 to 20% by volume, more preferably 1.0 to 20% by volume.

[0024] The etching gas of this disclosure is preferably used for dry etching.

[0025] The etching gas of this disclosure can etch various substrates. Examples of substrates include SiO2 and SiN.

[0026] (Etching method) Etching using the etching gas of this disclosure can be carried out using conventional etching methods, preferably dry etching methods. The etching conditions can be, for example, the following conditions. Flow rate: 5-500 sccm, preferably 10-300 sccm; • Discharge power: 200-1000W, preferably 300-600W; • Bias power: 10-2000W, preferably 100-1000W; • Pressure (gauge pressure): 30 mTorr or less (3.99 Pa or less), preferably 2 to 10 mTorr (0.266 to 1.33 Pa); ·Electron density: 10 9 ~10 13 cm -3 Preferably 10 10 ~10 12 cm -3 ; • Electronic temperature: 2-9 eV, preferably 3-8 eV; • Wafer temperature: -40 to 100°C, preferably -30 to 50°C; Chamber wall temperature: -30 to 300°C, preferably 20 to 200°C. [Examples]

[0027] The etching gases of this disclosure will be described in more detail below through the following examples, but this disclosure is not limited to these examples.

[0028] A mixed gas of 1,1,1,2-tetrafluoroethane and fluorocarbon compounds was prepared in the amounts shown in the table below. The fluorocarbon compounds used were 1-chloro-1,2-difluoroethene (HFO-1122a), 1-chloro-2-fluoroethene (HFO-1131), and 3,3,3-trifluoropropene (HFO-1243zf). Mixed gas 0 contains only 1,1,1,2-tetrafluoroethane and does not contain any fluorocarbon compounds.

[0029] [Table 1]

[0030] Using the above mixed gases 1-12 and the comparison gas, SiO2 and SiN films on a silicon wafer were etched. Specifically, after introducing the mixed gas and additive gas through a gas inlet connected to the upper electrode, etching was performed by exciting the process gas with a high-frequency power supply (13.56 MHz, 0.22 W). The film thickness was 100 μm. The flow rates of each gas are shown in the table below.

[0031] After etching, the edge face of the silicon wafer was observed using a scanning electron microscope (SEM) to determine the side etching rate. The relative ratio of the side etching rate to that of the comparative example is shown in the table below. The side etching rate R is the ratio of the amount of side etching a to the diameter b of the hole shown in Figure 1, and is calculated using the following formula. R=a / b

[0032] [Table 2] [Industrial applicability]

[0033] The etching gas of this disclosure is suitably used in fields where more precise etching is required, such as the semiconductor field.

Claims

1. An etching gas comprising 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds.

2. The etching gas according to claim 1, wherein the fluorocarbon compound having a double bond has one double bond.

3. The etching gas according to claim 1, wherein the fluorocarbon compound having the double bond has two or three carbon atoms.

4. The etching gas according to claim 1, wherein the fluorocarbon compound having a double bond comprises at least one compound selected from the group consisting of 1-chloro-1,2-difluoroethene, 1-chloro-1-fluoroethene, and 3,3,3-trifluoropropene.

5. The etching gas according to claim 1, wherein the concentration of the fluorocarbon compound having one or more double bonds relative to the total of 1,1,1,2-tetrafluoroethane and the fluorocarbon compound having one or more double bonds is 1 volume ppm or more and less than 400 volume ppm.

6. The etching gas according to claim 1, wherein the concentration of the fluorocarbon compound having one or more double bonds relative to the total of 1,1,1,2-tetrafluoroethane and the fluorocarbon compound having one or more double bonds is 50 ppm by volume or more and 300 ppm by volume or less.

7. Furthermore, the etching gas according to claim 1, further comprising an inert gas.

8. The etching gas according to claim 7, wherein the inert gas is argon.

9. The etching gas according to claim 1, wherein the concentration of 1,1,1,2-tetrafluoroethane in the etching gas is 1.0 volume% or more and 20 volume% or less.

Images