A process for selectively etching a substrate 20 having a molybdenum silicide layer 25 with a resist material 26 on portions of the molybdenum silicide layer 25 is described. The substrate 26 is placed into an etch zone 54 and the process gas comprising SF.sub.6 and HBr is introduced into the etch zone 54. Preferably, the volumetric flow ratio of SF.sub.6 :HBr is from about 1:10 to about 1:1, and more preferably, an oxygen containing gas such as O.sub.2 is added to the process gas. A plasma is generated in the etch zone 54 to form an etch gas from the process gas that anisotropically etches the MoSi.sub.x layer 25 with good selectivity and reduced profile microloading.

BACKGROUND 
The present invention relates to a method for etching molybdenum silicide 
in semiconductor processing. 
Reactive ion etching processes are used to fabricate devices having 
submicron sized features, such as semiconductor integrated circuit chips. 
These processes are used to selectively etch a substrate, where portions 
of the substrate are protected by a patterned etch resistant "resist" 
material, such as photoresist or oxide hardmask. The resist protected 
portions form "features" on the substrate which become part of the 
integrated circuit being processed. Etching is effected by introducing a 
process gas into a chamber and generating a plasma in the chamber to 
create an etch gas from the process gas. The etch gas etches the substrate 
to create volatile etch byproduct compounds, which are then removed from 
the chamber. 
Typically, the process gas is a mixture of gases such as for example a 
mixture of Cl.sub.2 or CCl.sub.4, O.sub.2, and an inert gas such as He or 
Ar. Often a chloroflurocarbon gas is added to the process gas. However, 
there are several problems with these process gases. One problem is that 
chloroflurocarbon gases are environmentally toxic. Thus, processes using 
these gases are subject to strict environmental regulations. 
Another problem is that these gases chemically react with the resist on the 
substrate, and cause relatively thick residues or deposits to form on (i) 
the chamber walls, (ii) the sidewalls of the etched features, and (iii) 
the resist material. This deposit or residue layer can flake off and form 
particles that contaminate the wafers. The contaminant particles are not 
detected until the wafer is fully processed and can results in loss of the 
entire wafer at a cost of $5,000 or more. 
Another problem with these gases is that they etch features having 
"reentrant" profiles. By reentrant profiles, it is meant that the 
sidewalls of the features are inwardly sloped, forming angles of less than 
85.degree. with the substrate. Reentrant profiles are caused by isotropic 
etching or undercutting, which occurs when etching proceeds horizontally 
below the resist layer, instead of vertically through the uncoated 
portions. It is preferable to have features having vertical sidewalls with 
angles close to 90.degree., which occur when the process gas 
anisotropically etches the substrate and etching proceeds vertically 
through the uncoated portions of the substrate. 
Typical reactive ion etching systems can also result in high profile 
microloading. High profile microloading occurs when the cross-sectional 
profile of the features vary as a function of the spacing between the 
features on the substrate. It is desirable to have an etching process that 
provides features with uniform cross-sections regardless of the distance 
between the features, or the density of features. 
It is also desirable to obtain high etch rates and a high etching 
selectivity ratio for process efficacy. The etch selectivity ratio is the 
ratio of the MoSi.sub.x etch rate to the resist etch rate. A high 
selectivity ratio is desirable to avoid excessive etching of the resist 
layer that can result in etching of the substrate below the resist layer. 
Accordingly, there is a need for a method for selectively etching 
molybdenum silicide on semiconductor substrates that minimizes deposits on 
chamber walls; provides substantially anisotropic etching; and provides 
reduced profile microloading. It is also desirable to obtain high etch 
rates and high substrate to resist etch selectivity ratio for process 
efficacy. 
The present invention is directed to a method that satisfies these needs. 
The method allows substantially anisotropic etching of substrates, reduced 
residue deposition, reduced profile microloading, high etch rates and a 
high etch selectivity ratio. 
The method of the present invention comprises selectively etching a 
substrate having a molybdenum silicide layer with a resist material on 
portions of the molybdenum silicide layer. The method comprises the steps 
of: 
(a) placing a substrate into an etch zone; 
(b) introducing a process gas comprising SF.sub.6 and HBr into the etch 
zone, the volumetric flow ratio of SF.sub.6 :HBr being from about 1:10 to 
about 1:1; and 
(c) generating a plasma in the etch zone to form an etch gas from the 
process gas, wherein the etch gas selectively etches the molybdenum 
silicide layer on the substrate. 
Preferably, the process gas further comprises an oxygen containing gas. 
Preferably, the volumetric flow ratio of SF.sub.6 :HBr:oxygen containing 
gas is selected so that the sidewalls of the etched features are smooth 
and form angles of at least about 85.degree. with the substrate. More 
preferably, the flow ratio is selected so that the molybdenum silicide to 
resist etching selectivity ratio is greater than about 0.6, and most 
preferably, the flow ratio is selected so that molybdenum silicide etch 
rate is greater than about 500 .ANG./minute.

DESCRIPTION 
The present invention is directed to a reactive ion etching process for 
selectively etching a substrate having a molybdenum silicide layer and a 
resist material on portions of the molybdenum silicide layer, by using a 
process gas comprising SF.sub.6 and HBr. Preferably, an oxygen containing 
gas is added to the process gas. The process gas is introduced into an 
etching zone containing the substrate. A plasma is generated from the 
process gas to form an etch gas which selectively etches the substrate. 
With reference to FIGS. 1a and 1b, the substrate 20 can be a metal, glass, 
or ceramic wafer 22 such as a semiconductor wafer. Typically, the 
substrate 20 is a silicon or gallium arsenide wafer 22 having a plurality 
of layers 24 thereon. The layers 24 can include metal, oxide, nitride, and 
silicide layers, the upper layer 25 being a molybdenum silicide layer. 
Typically, the molybdenum silicide layer has a composition of MoSi.sub.x, 
with x being about 2. However, the MoSi.sub.x layer can also be 
nonstoichiometric and can contain other metals or alloys. 
A resist material 26, such as photoresist or oxide hardmask, which is 
substantially resistant to etching is applied on top of the substrate 
layers 24. The resist 26 can be applied in a patterned overlay as shown in 
FIG. 1a. The resist 26 overlay protects portions of the substrate 20, so 
that after the substrate 20 is etched, the protected portions of the 
substrate 20 form features 28 that are part of the semiconductor device 
being processed. The features 28 have widths or thicknesses from about 0.6 
to about 1 micron. The features 28 also have sidewalls 30 that form angles 
32 with the surface of the substrate 20. The features 28 can either be 
"dense" or closely packed on the substrate 20, with the spans 34 between 
the features 28 being about 0.8 microns in width, or the features 28 can 
be "open" or spaced apart with the spans 34 being about 20 microns wide. 
With reference to FIG. 2, an apparatus 50 suitable for practicing the 
present invention comprises an etching chamber 52 having an etch zone 54. 
The substrate 20 is typically placed on a cathode or susceptor 56 in the 
etch chamber 52. Process gas is introduced into the etch chamber 52 
through the gas inlet 58. Thereafter, the gas passes through a 
"showerhead" diffuser plate 60 which distributes the process gas in the 
etch zone 54. A focus ring 62 can be used to maintain the plasma 
substantially in the etch zone 54. 
A barrier or pumping plate 70 with a plurality of exhaust holes 72 
therethrough separates the etching chamber 52 into two zones, an etching 
zone 54 and a non-etching zone 74. The exhaust holes 72 are in fluid 
communication with a vacuum pump through the exhaust hole 76 for 
withdrawing spent process gas and volatile etch-byproduct compounds from 
the etching chamber 52. The apparatus 50 can be a magnetically enhanced 
reactor, having a magnetic coil 80 around the etching chamber 52 to 
magnetically enhance the plasma formed in the etching zone 54. 
The process conditions can be varied during the etching process. For 
example, when etching multiple layers 24 and 25 of the substrate 20, 
typically the process has multiple stages. The process conditions for each 
stage depends upon the composition of the layer that is being etched. 
Furthermore, when the substrate 20 is etched in multiple stages, the 
progress of the etch is monitored by monitoring the composition of the gas 
withdrawn from the chamber using a optical emission technique. When the 
composition of the withdrawn gas changes, it signifies that one layer has 
been etched through and the second layer is being etched. At this time, 
the composition of the process gases and other process conditions can be 
changed to provide greater etching efficiency for the layer being etched. 
For example, when etching MoSi.sub.x deposited on a silicon layer, the 
"main" etch or the etching of the MoSi.sub.x layer 25 was typically 
carried out about zero to ten seconds after a rise in the SiF emission 
spectra was observed. 
To use the apparatus 50, a substrate 20 is placed on the cathode 56, and a 
process gas comprising SF.sub.6 and HBr is introduced through the gas 
inlet 58 into the etch zone 54. The process gas can further comprise an 
oxygen containing gas such as O.sub.2, O.sub.3, CO, CO.sub.2, H.sub.2 O 
and mixtures thereof. Preferably the oxygen containing gas is O.sub.2. 
SF.sub.6 is the primary etchant, and the HBr and the oxygen containing gas 
are included to provide better control of feature profile, etch 
selectivity ratio, and etch rates. A plasma is generated in the etch zone 
54 to form an etch gas from the process gas, which selectively etches the 
substrate 20. The flow of the etch gas is shown by the arrows 82. 
The composition of the process gas is controlled by adjusting the 
volumetric flow ratio of SF.sub.6 to HBr to oxygen containing gas. By 
"volumetric flow ratio" it is meant the ratio of the volume per unit time 
of one gas to the volume per unit time of a second gas. 
Preferably, the volumetric flow ratio of SF.sub.6 :HBr:oxygen containing 
gas is selected so that the sidewalls 30 of the features 28 have smooth 
surfaces without jagged or rough edges and so that the sidewalls 30 form 
angles 32 of at least about 85.degree. with the wafer 22. Preferably, the 
ratio is selected so that the sidewalls 30 form angles 32 of about 
85.degree. to 90.degree. with the wafer 22. Features 28 having 
perpendicular sidewalls 30 are desired for optimum integrated circuit 
design and performance. More preferably, the volumetric flow ratio of 
SF.sub.6 to HBr to oxygen containing gas is selected so that the 
molybdenum silicide etch rate is greater than about 500 .ANG./minute. Most 
preferably the flow ratio is selected so that the molybdenum silicide to 
resist etching selectivity ratio is greater than about 0.6. 
As explained in the examples provided below, it has been found that a 
volumetric flow ratio of SF.sub.6 :HBr from about 1:10 to about 1:1 
provides suitable etch rates, good feature profiles, and good etch 
selectivity ratio. Within this range, SF.sub.6 and HBr flow ratios from 
about 3:17 to about 7:13 are more preferable, and a flow ratio of about 
1:3 is most preferable, providing features having profile angles 32 from 
about 85.degree. to 9020 and an etch selectivity greater than 0.6. It is 
believed that the addition of oxygen provides higher etch rates and 
reduces the amount of residue deposit formed on the chamber walls and on 
the sidewalls 30 of the features 28. Preferably, the volumetric flow ratio 
of SF.sub.6 to oxygen containing gas is from about 0.1:1 to about 100:1, 
more preferably, the flow ratio is from about 1:1 to about 10:1, and most 
preferably, the flow ratio is from about 1:1 to about 3:1. 
The process gas should be introduced at a sufficient rate so that the rate 
of etching the substrate 20 is greater than about 500 .ANG. per minute. 
For the apparatus 50, tile total flow rate of SF.sub.6 and HBr is 
preferably from about 50 to about 100 sccm and more preferably about 80 
sccm. However, the optimum flow rate can vary depending on the reactor 
size and flow characteristics. 
After the process gas is introduced into the etch zone 54, a plasma is 
generated in the etch zone 54 to form an etch gas from the process gas for 
etching the substrate 20. The power flux of the plasma should be from 
about 0.21 w/cm.sup.2 to about 0.57 w/cm.sup.2. Thus, the power used to 
generate the plasma is typically from about 150 to about 400 watts, and 
more preferably about 250 to about 300 watts for a 6 inch (15.25 cm) 
diameter wafer. 
The plasma may be enhanced by a method such as electron cyclotron 
resonance, magnetically enhanced reactors and inductively coupled plasma. 
Preferably, a magnetically enhanced ion reactor is used. The magnetic 
field in the reactor induced by the magnetic coil 80 must be sufficiently 
strong to increase the density of the ions formed in the plasma, but not 
so strong as to induce charge-up damage, which would damage features such 
as CMOS gates. Typically, the magnetic field on the surface of the 
substrate 20 is from about 10 to about 100 Gauss, more preferably from 
about 20 Gauss to about 80 Gauss, and most preferably about 75 Gauss. 
Typically, the chamber is maintained at a pressure of from about 1 mTorr to 
about 300 mTorr, preferably from about 50 mTorr to 250 mTorr, and more 
preferably from 100 to 160 mTorr. Lower pressures provide more uniform 
etching, at the expense of lower etch rates. 
The cathode 56 can also be heated using a heating source, such as a lamp, 
underneath the cathode 56. The cathode 56 is preferably heated to 
temperatures sufficiently high to volatilize etching by-products, and 
sufficiently low so that the thin layer of passivating deposit 90 that 
forms on the sidewalls 30 of freshly etched features 28 is not 
volatilized. Typically, the cathode 56 is heated to a temperature of about 
20.degree. to about 100.degree. C., and more preferably at a temperature 
of about 65.degree. C. A flow of helium on the back of the substrate 20 at 
a pressure of about 4 Torr, can be used to control the temperature of the 
substrate 20. 
The chamber wall 96 should be also heated so that less deposit forms on the 
walls 96. The chamber wall 96 typically is heated to a temperature from 
about 45.degree. C. to about 100.degree. C., and more typically to a 
temperature of about 65.degree. C. 
EXAMPLES 
The following examples demonstrate the efficacy of the present invention. 
These examples are undertaken using a magnetically enhanced reactive ion 
reactor, and in particular, a "PRECISION 5000" system with a "PHASE II 
POLYETCH" chamber kit, fabricated by Applied Materials, Santa Clara, 
Calif. 
Silicon wafers having a diameter of about 150 mm (6 inches) and a thickness 
of 0.73 mm were used for these experiments. The wafers 22 had a layer 25 
of MoSi.sub.x of thickness 3400 .ANG.. Underneath the molybdenum 
disilicide layer was a 1000 .ANG. layer of polysilicon, and below the 
polysilicon layer was a 2000 .ANG. of silicon oxide. The molybdenum 
silicide layer was coated with a patterned overlay of "G-line KALLE PR" 
photoresist, fabricated by Hoechst, Germany. The photoresist lines had 
widths of about 0.8 .mu.m and occupied about 50% of the total area of the 
wafer. 
After etching, the thickness of the photoresist layer 26 remaining on the 
substrate 22, the smoothness of the sidewalls 30, the angles 32 between 
the sidewalls 30 and the substrate 22 and the amount of residue 90 
remaining were evaluated from scanning electron microscope photos of the 
etched wafers. Etch rates were calculated by measuring the depth of the 
features 28 in etched substrates 20. 
Residual resist 26 and sidewall deposition 90 were removed by dry stripping 
in combination with a wet process. The dry stripping was carried out in a 
"GASONICS" resist stripper for two minutes using an oxygen and CF.sub.4 
plasma. In the wet stripping process, the substrate was dipped for about 
five minutes in a solution comprising one part 30% conc. NH.sub.4 OH, two 
parts 30% conc. H.sub.2 O.sub.2, and seven parts water, heated to about 
50.degree. C. to 70.degree. C. 
The following examples demonstrate that a process according to the present 
invention has a high etch rate (greater than 500 .ANG. per minute), good 
substrate to resist selectivity, and satisfactory sidewall profile of the 
features formed below the resist. Also, the process provides greatly 
reduced amounts of deposit on the chamber walls and on the sidewalls of 
the freshly etched channels. Furthermore, existing reactive-ion etching 
equipment can be used. 
EXAMPLES 1 AND 2 
Examples 1 and 2 were run to determine the feasibility of using SF.sub.6 
and HBr for etching MoSi.sub.x layers. In Example 1, a wafer (as described 
above) was etched in a single stage process using 25% SF.sub.6 (20 sccm) 
and 75% HBr (60 sccm). A chamber pressure of 100 mTorr, a power level of 
200 Watts, and a magnetic field of 75 Gauss was used. The cathode and wall 
temperature were both maintained at 65.degree. C. The wafer was etched for 
about 652 seconds to remove the MoSi.sub.x layer. This experiment 
demonstrated the feasibility of using SF.sub.6 and HBr to etch the 
MoSi.sub.x layer. 
In Example 2, a wafer was etched using the same ratio of SF.sub.6 (20 sccm) 
and HBr (60 sccm), and in addition, 8 sccm of oxygen was added to the 
process gas in order to improve etching rates. The chamber pressure, power 
level, magnetic field, cathode temperature, and wall temperature were the 
same as in Example 1. In this example, the MoSi.sub.x layer etched through 
in about 239 seconds. Thus, the addition of oxygen to the process gas 
improved the etching rate. 
EXAMPLES 3-12 
Examples 3-12 were run in order to optimize the etching process conditions 
by using a factorial design study involving a L.sub.9 (3.sup.4) orthogonal 
matrix. Four process variables, namely (i) power, (ii) SF.sub.6 :HBr 
ratio, (iii) O.sub.2 flow rate, and (iv) chamber pressure were each varied 
at three levels as shown in Table I. The total volumetric flow rate of 
SF.sub.6 :HBr was maintained at about 80 sccm. The magnetic field was 
maintained at 75 Gauss. The cathode temperature and chamber wall 
temperature were both maintained constant at 65.degree. C., and helium was 
flowed at a pressure of 4 Torr on the backside of the wafer to cool the 
wafer. 
TABLE I 
______________________________________ 
L.sub.9 (3.sup.4) ORTHOGONAL MATRIX CONDITIONS 
Level 
Variables I II III 
______________________________________ 
SF.sub.6 %.sup.1 
15 25 35 
(SF.sub.6 :HBr ratio) 
(3:17) (1:3) (7:13) 
Pressure (mTorr) 
100 130 160 
O.sub.2 (sccm) 
2 6 10 
Power (watts) 
200 250 300 
______________________________________ 
Notes: 
.sup.1 The percent of SF.sub.6 was the percent with respect to the HBr 
content, so 25% SF.sub.6 level means the process gas includes 25% SF.sub. 
and 75% HBr, or that the SF.sub.6 :HBr ratio was 1:3. 
Table II shows the process conditions and experimental results for Examples 
3 through 12. Examples 3 through 11 were based on the L.sub.9 orthogonal 
matrix process conditions. Example 12 had the same process conditions as 
Example 3 and was run to determine the accuracy of the experimental 
results obtained for Example 3. 
FIG. 3a shows the change in etch rate of (i) MoSi.sub.x and polysilicon, 
and (ii) photoresist with change in SF.sub.6 to HBr volumetric flow rate. 
The MoSi.sub.x /polysilicon and photoresist etch rates for Examples 6, 7, 
and 8 which used 25% SF.sub.6 were averaged and plotted against the 
SF.sub.6 percentage in question. Although the etching rates increased with 
increase in SF.sub.6, the MoSi.sub.x etch rate did not change at the same 
rate as the photoresist etch rate. 
FIG. 3b shows the etch selectivity ratio as a function of SF.sub.6 content. 
The etch selectivity ratio was calculated by dividing the average 
MoSi.sub.x /polysilicon etch rate by the average resist etch rate. The 
graph was U-shaped with a maximum etch selectivity ratio greater than 0.75 
at 25% SF.sub.6 content. 
TABLE II 
__________________________________________________________________________ 
PROCESS CONDITIONS AND RESULTS OF EXAMPLES 3-12 
Examples 3 4 5 6 7 8 9 10 11 12 
__________________________________________________________________________ 
SF.sub.6 (%) 15.00 
15.00 
15.00 
25.00 
25.00 
25.00 
35.00 
35.00 
35.00 
15.00 
O.sub.2 (sccm) 2.00 
6.00 10.00 
6.00 10.00 
2.00 
10.00 
2.00 6.00 2.00 
Pressure (mTorr) 100.00 
130.00 
160.00 
100.00 
130.00 
160.00 
100.00 
130.00 
160.00 
100.00 
Power (Watts) 200.00 
250.00 
300.00 
300.00 
200.00 
250.00 
250.00 
300.00 
200.00 
200.00 
MoSi.sub.x and Polysilicon Etch Rate 
435.64 
835.44 
1205.48 
1147.83 
992.48 
923.08 
1419.35 
1227.91 
1152.84 
445.95 
(.ANG./min).sup.1 
Photoresist Etch Rate (.ANG./min).sup.2 
564.00 
1088.00 
1518.00 
1547.00 
850.00 
873.00 
1723.00 
1820.00 
988.00 
630.00 
Selectivity Ratio.sup.3 
0.77 
0.77 0.79 0.74 1.17 
1.06 
0.82 0.67 1.17 0.71 
Profile Angle Center Dense.sup.4 (.degree.) 
84.00 
87.50 
90.50 
87.00 
90.50 
86.00 
91.50 
92.00 
93.00 
82.00 
Profile Angle Center Open.sup.4 (.degree.) 
78.00 
87.00 
91.00 
82.00 
87.00 
84.00 
91.00 
92.50 
92.00 
77.50 
Profile Angle Edge Dense.sup.4 (.degree.) 
83.00 
88.00 
91.50 
89.00 
92.00 
88.00 
92.00 
93.50 
91.50 
82.00 
Profile Angle Edge Open.sup.4 (.degree.) 
78.00 
84.50 
91.50 
83.00 
88.00 
84.00 
90.50 
90.50 
93.00 
78.50 
__________________________________________________________________________ 
.sup.1 Combined etch rate for MoSi.sub.x and polysilicon layers. 
.sup.2 Calculated assuming the initial thickness of photoresist was 1.38 
microns. 
.sup.3 Selectivity ratio = (MoSi.sub.x and polysilicon etch 
rate)/(photoresist etch rate). 
.sup.4 Profile angle for the central and edge areas of the wafer and for 
"dense" and "open" feature densities. The dense regions of the wafer had 
closely spaced features, the average span or distance between the feature 
being about 0.8 microns, while the open areas had features spanned by 
distances of about 20 microns. 
FIG. 4 shows the change in feature profile angle 32 with change in 
percentage of SF.sub.6 for dense (closely packed features) and open areas, 
and for the center and edge areas of the wafer 22. The profile angles are 
averages of the experimental results listed in Table II. In general, 
angles 32 from about 85.degree. to about 92.degree. were obtained. From 
15% to 25% SF.sub.6 content, the profile angle 32 was between 84.degree. 
to 86.degree. in the open areas of the wafer 22 and between 87 to 
90.degree. in the dense wafer regions. At 35% SF.sub.6 the features 28 had 
profile angles of about 90.degree.. The graph also shows profile 
microloading, namely, the variation in profile angle 32 for dense and open 
areas of the wafer 22. As seen form the graph, a maximum variation was 
observed between the open and dense features on the wafer 22. 
From the results of Table II, an optimum ratio of SF.sub.6 :HBr was 
determined to be about 1:3. It was also determined that as the oxygen flow 
rate increases, the profile angle 32, etch rates, and selectivity ratio 
all increased. With increase in power, the profile angle and etch rates 
increase and the selectivity ratio decreased, and with increase in 
pressure, the profile angle and the selectivity ratio both increased. 
These results were used to determine optimum process conditions which were 
used for the Examples below. 
EXAMPLES 13 AND 14 
In these examples, two step etching processes were run with a main etch 
step and an overetch step as identified in Table Ill. The main etch 
process parameters were determined from the design matrix study. In the 
main etch step, the SF.sub.6 :HBr volumetric flow ratio was maintained at 
1:3, and flow ratio of SF.sub.6 :O.sub.2 was maintained at about 10:3. 
These process conditions provided he best results. 
In both Examples 13 and 14, the overetch step was carried out to etch the 
underlying polysilicon layer below the MoSi.sub.x layer, and was started 
about 10 seconds after peaking of the silicon spectra. In Example 13, 
overetching was carried out using pure HBr, and in Example 14 a mixture of 
gasas comprising HBr, Cl.sub.2, He, and O.sub.2 was used. 
TABLE III 
__________________________________________________________________________ 
MAIN ETCH OVERETCH 
OVERETCH 
CONDITIONS FOR 
CONDITIONS 
CONDITIONS 
EXAMPLES FOR FOR 
DESCRIPTION 13 AND 14 EXAMPLE 13 
EXAMPLE 14 
__________________________________________________________________________ 
SF.sub.6 (sccm) 
20 -- -- 
HBr (sccm) 60 80 30 
O.sub.2 (sccm) 
6 -- -- 
Cl.sub.2 (sccm) 
-- -- 10 
70% He/30% -- -- 6 
O.sub.2 (sccm) 
Pressure (mTorr) 
150 50 100 
B-Field (gauss) 
75 75 75-100 
Power (watts) 300 250 150 
Time (sec) 216 (EP) 90 360 
MoSi.sub.x Etch Rate 
1000 -- -- 
(.ANG./min) 
MoSi.sub.x Uniformity.sup.1 
.+-.12.5% -- -- 
Photoresist Etch Rate 
1390 -- -- 
(.ANG./min) 
Photoresist Uniformity 
.+-.6.3% -- -- 
Helium Cooling Pressure: 
4 Torr 
Wall Temperature: 
65.degree. C. 
Cathode Temperature: 
65.degree. C. 
Endpoint Wavelength: 
4415.ANG. (SiF line) 
Focus Ring Diameter: 
155 mm 
Number of Gas Plate Holes: 
13 
__________________________________________________________________________ 
gases comprising HBr, Cl.sub.2, He, and O.sub.2 was used. The gases in 
Example 14 resulted in pullback of the resist 26 and gave jagged 
MoSi.sub.x feature profiles in the open areas of the wafer. Only the pure 
HBr overetch was able to give smooth feature profiles. Thus, a pure HBr 
overetch provided the best results. 
After etching, the typical profile angle 32 of the etched features 28 were 
measured by SEM to be about 87.degree.. The polysilicon layer was slightly 
undercut, the maximum oxide underlayer loss was about 1330.ANG., and the 
maximum resist loss was measured at about 6000.ANG.. 
After etching, oxygen was introduced into the etching zone, and reacted 
with the residual photoresist layer for about two minutes. Then a 
five-minute wet stripping process using one part 30% NH.sub.4 OH, two 
parts 30% H.sub.2 O.sub.2, and seven parts water heated 50.degree. C. was 
used to remove residual photoresist. 
The present invention has been described in considerable detail with 
reference to certain preferred versions thereof, however, other versions 
are possible. Therefore, the spirit and scope of the appended claims 
should not be limited to the description of the preferred versions 
contained herein.