Process for etching, and chamber cleaning and a gas therefor

Abstract

The present invention relates to a process for cleaning chambers of apparatus used for semiconductor manufacturing with a gas mixture comprising or consisting of fluorine, nitrogen and argon as well as said gas mixtures.

Claims

1. A process for cleaning a treatment chamber of an apparatus used for semiconductor manufacturing, the process comprising cleaning the treatment chamber with an etching gas, wherein the etching gas is a gas mixture consisting of around 30% (v/v) fluorine, nitrogen greater than or around 30% (v/v) to equal to or less than 45% (v/v) and argon in a range of equal to or greater than 25% (v/v) to less than or around 40% (v/v), relative to the total composition of fluorine, argon, and nitrogen as 100% (v/v).

2. The process of claim 1 wherein the gas mixture consists of around 30% (v/v) fluorine, around 30% (v/v) nitrogen and around 40% (v/v) argon.

3. The process of claim 1 wherein the gas mixture is used in a main chamber cleaning step.

4. The process of claim 1 wherein the pressure in the chamber is in the range between 1 and 3.5 Torr.

5. The process of claim 1 wherein the process is plasma-assisted using a remote plasma source with a frequency from 100 KHz to 1 GHz.

6. The process of claim 1 wherein the apparatus is optimized for the use of NF.sub.3 as etching gas.

7. The process of claim 1 wherein an inorganic material selected from the group consisting of amorphous Si, Si.sub.3N.sub.4, SiO.sub.xN.sub.y wherein 0<x≤3 and 0≤y≤4, SiO.sub.2, TaN, TiN and W is removed by etching with the etching gas.

8. The process of claim 7 wherein SiO.sub.2 is removed by etching with the etching gas.

9. The process of claim 5, wherein the process is plasma-assisted using a remote plasma source with a frequency around 400 KHz.

Description

EXAMPLES

(1) 1. Determination of Etch Rates:

(2) The etch rates were determined in situ by reflectrometry using a 645 nm laser directed to the sample. The etch rate was calculated by dividing the thickness of the film by the time when the removal endpoint was detected.

(3) 2. Samples:

(4) The size of the samples was a 200 mm wafer. The investigated material was deposited on a 150 nm thermal SiO.sub.2 layer to allow interferometric measurement. The SiO.sub.2 samples were deposited on bulk silicon since their optical properties allow interferometric measurements.

(5) 3. Chamber Cleaning Experiments on Alta-CVD

(6) The experiments were performed on an AltaCVD Tool with a two-chamber system with “Brooks VX400” loader. Chamber PM2 was used for doped/undoped poly-Si films. The heater temperature was set to 400° C., the wall temperature was 55° C.

(7) An MKS “Paragon” remote plasma source optimiszed for NF.sub.3 was used with a frequency of 400 kHz. The dissociated ions and radicals enter the chamber near the slit valve and flow between heater and shower head. The remote plasma source was usually ignited in the presence of pure argon. Directly after the plasma was in a stable condition, the gas mixture comprising fluorine was introduced.

(8) The respective gas mixture was delivered to the machine from gas cylinders with the size of 10 l. The apparatus was equipped with a “Brooks GF 125” digital mass flow controller, metal sealed, VCR suitable for all kind of corrosive gases.

(9) A cleaning process was than performed with three individual cleaning steps (pre-clean, main clean and post clean) for a combined time of 45 s.

Example 1: Chamber Cleaning with Different F.SUB.2./Ar/N.SUB.2 .Mixtures

(10) A 1-2 μm thick PETEOS-film was deposited on 200 mm Si-substrates and thickness measured with spectrometer (OMT)/ellipsometer (tencor UV1280SE), 49 points, 10 mm edge exclusion. Wafers were loaded into the chamber. SiO.sub.2-etch rates were calculated after measuring post-etch TEOS film thickness.

(11) For each example, the main cleaning step (second row) was done with the pure etching gas mixture while the pre- and post-cleaning steps were performed with the addition of 1140 and 850 sccm (“standard cubic centimeter”), respectively. The other parameters (step time t, pressure p and respective flow rates of argon, etching gas and total gas) are given in the table below.

(12) Example 1a shows the inventive mixture whereas the comparative examples 1b and 1c were performed with gas mixtures outside the claimed range.

(13) Results:

(14) TABLE-US-00001 Example 1: F2/N2/Ar (30%/45%/25%) t p Ar Etch gas Total Etch Rate F-Gas [s] [Torr] [sccm] [sccm] [sccm] [nm/mm] [g] 5 3 1140 450 1590 1343 12 3 0 1660 1860 12 4 850 930 1780

(15) TABLE-US-00002 Example 1a: F2/N2/Ar (30%/30%/40%) t p Ar Etch gas Total Etch Rate F-Gas [s] [Torr] [sccm] [sccm] [sccm] [nm/mm] [g] 5 3 1140 450 1590 1253 0.30 12 3 0 1860 1860 12 4 850 930 1780

(16) TABLE-US-00003 Comparative Example 1b: F2/N2/Ar (30%/20%/50%) t p Ar Etch gas Total Etch Rate [s] [Torr] [sccm] [sccm] [sccm] [nm/min] 5 3 1140 450 1590 1127 12 3 0 1860 1860 12 4 850 930 1780

(17) TABLE-US-00004 Comparative Example 1c: F2/N2/Ar (30%/50%/20%) t p Ar Etch gas Total Etch Rate [s] [Torr] [sccm] [sccm] [sccm] [nm/min] 5 3 1140 450 1590 1098 12 3 460 1400 1860 12 4 1080 700 1780

(18) The results show that surprisingly, the etch rate shows an unexpected maximum value of 1253 nm/min for the inventive gas mixture F.sub.2/N.sub.2/Ar (30%/30%/40% each v/v) and another unexpected maximum of 1343 nm/min for a gas mixture F2/N2/Ar (30%/45%/25% each v/v). Variation of the nitrogen and argon content just outside the claimed range results in a decrease of etch rate. The inventive gas mixture of experiment 1a leads to etch rates more than 10% higher than the next best result with the gas mixture of comparative experiment 1b.

Comparative Example 2: Chamber Cleaning with NF.SUB.3./Ar Mixtures

(19) Three different cleaning processes were performed with different NF.sub.3/Ar mixtures as shown in the table below. All other parameters were identical to the ones referred to in Experiment 1.

(20) Results:

(21) TABLE-US-00005 Comparative Experiment 2 (NF3/Ar) t p Ar NF3 Total SiO2 Rate F-Gas [s] [Torr] [sccm] [sccm] [sccm] [nm/mm] [g] 5 3 1500 90 1590 1123 0.37 12 3 1500 360 1860 12 4 1600 180 1780 5 3 1500 90 1590 846 0.25 12 3 1620 240 1860 12 4 1660 120 1780 5 3 1500 90 1590 621 0.18 12 3 1700 160 1860 12 4 1700 80 1780

(22) The results show that the inventive gas mixture of experiment 1a leads to etch rates more than 10% higher than the next best result with the NF.sub.3/Ar gas mixture of comparative experiment 2. Additionally, the consumption of fluorine (calculation based on the total weight of fluorine atoms consumed, last column) is clearly higher in the best result of Comparative Example 2 compared to the consumption calculated for result with the inventive mixture of Experiment 1a.