Tungsten etching mechanisms in CF4/O2 reactive ion etching plasmas

Abstract

I n situ x-ray photoelectron spectroscopy (XPS), etch rate measurements, and optical emission spectroscopy have been used to examine the etching characteristics of tungsten in CF4/O2 reactive ion etching plasmas. It is found that the etch rate maximum of tungsten occurs at a proportion of oxygen in excess of that required to produce the maximum gas phase fluorine atom concentration, and this cannot be explained by using an etch mechanism model similar to that developed for silicon. XPS results have been used to identify tungsten oxyfluoride (WOF4) on the etched surface, and a model for tungsten etching is proposed that involves tungsten oxyfluoride as an important etch product.

Effect of CO and CO2 addition to the CF4/O2 gas system on the etching of a low-pressure chemical vapor deposition tungsten film

“…The etch rate of SiO 2 increased gradually up to 30% of O 2 , while that of W increased sharply reaching its maximum value of 302 nm/min at 50% of oxygen in feed gas. Recently, Oehrlein et al 11,13 reported that F and O atoms were adsorbed on the tungsten surface as the oxygen in feed gas increases up to 35% and produced WOF 4 . For tungsten etching, the gas phase species in a CF 4 /O 2 plasma analyzed by MS were CO 2 , COF, COF 2 , and WF 5 observed at mass numbers of 44, 47, 66, and 107, respectively.…”

Using an 80% CF4+20% CO2 gas mixture to recover aged anode wires in proportional chambers

“…Then the oxygen radicals were mostly generated due to dissociation of CO 2 in collisions with avalanche electrons near of the wire. As was shown in [13][14][15][16][17][18][19][20], an effective etching gas mixture has a ratio of fluorine and carbon atoms in the range of 0.8 oF/C o4.0. To optimize the recovery processes we chose 80%CF 4 þ 20%CO 2 which has F/C ¼3.2.…”

“…DC glow discharge and RF-plasmas based on CF 4 /O 2 have been widely used in integrated circuits production [15][16][17]. For example, to etch tungsten or silicon compounds in a DC glow discharge, a negative potential is applied to a substrate in electrical contact with the wafer.…”

Interactive effects in reactive ion etching of W1−xGex

“…Among the various deposition processes chemical vapor deposition ͑CVD͒ is most attractive because of its potential for good step coverage and selective filling of small features from the bottom up. 1 Recently, W-CVD via reduction of WF 6 by GeH 4 was shown to be quite promising compared to the more common WF 6 /H 2 and WF 6 /SiH 4 processes. 2 It shows excellent W/Si interface integrity, low contact resistance and superior step coverage.…”

“…One essential question is the possible impact of the Ge component on the dry etch behavior of the WGe alloy compared to that of pure W. Previously, the RIE characteristics of pure W in CF 4 , CF 4 /O 2 , SF 6 , SF 6 /O 2 , CF 2 Cl 2 , and Cl 2 plasmas have been investigated. [3][4][5][6][7][8][9] The general picture emerging from these studies is temperature dependent dry etch behavior. There is a gradual shift from ion-induced anisotropic etching below 0°C to much more chemical etching with isotropic features at room temperature ͑RT͒ and higher temperatures.…”