Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
2001-01-10
2002-11-19
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C134S001300, C510S175000, C510S176000
Reexamination Certificate
active
06482750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and to a semiconductor device manufactured thereby, and more particularly, to a cleaning process of a semiconductor substrate.
2. Description of the Background Art
Adsorption and elimination of particles onto and from the surface of a semiconductor substrate are usually explained by an electrostatic phenomenon. When the surface of the semiconductor substrate and the surfaces of particles are charged with the same polarity, particles leave from the surface of the semiconductor substrate by electrostatic repulsion. In an alkaline cleaning fluid, the surface of the semiconductor substrate and the surfaces of particles are charged with the same polarity.
Accordingly, in the course of manufacture of a semiconductor device, an alkaline cleaning fluid; for example aqueous ammonium hydroxide or a mixed hydrogen peroxide liquid (hereinafter called “APM”), has been widely used for a process of cleaning a semiconductor substrate.
Tungsten used as material of a wire has the property of reacting vigorously with an oxidizing agent such as hydrogen peroxide until dissolution. For this reason, a semiconductor substrate having tungsten exposed thereon cannot be cleaned by use of APM.
A solution of hydroxide has been used as a cleaning fluid in the process of cleaning a semiconductor substrate having tungsten or an alloy thereof (hereinafter called “tungsten-based members”) exposed thereon.
Here, the hydroxides include ammonium hydroxide, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide (hereinafter called “TMAH”). From the viewpoint of protection of a semiconductor substrate from metal contamination, use of ammonium hydroxide or TMAH, which does not contain any metal atoms, is preferable in cleaning the semiconductor substrate.
Since a solution of ammonium hydroxide (hereinafter called “aqueous ammonium”) has the property of dissolving silicon, aqueous ammonium cannot be used for cleaning a semiconductor substrate having exposed thereon a silicon-based member such as polycrystalline silicon (hereinafter called “polysilicon”), amorphous silicon, a silicon oxide film, or a silicon substrate.
For these reasons, the alkaline cleaning fluid cannot be used for cleaning a semiconductor substrate having both a tungsten-based member and a silicon-based member exposed thereon.
In order to clean the semiconductor substrate having exposed the tungsten-based member and exposed the silicon-based member, a compound expressed by the following chemical formula (I) or (II), which is served as a silicon corrosion inhibitor, is added to the cleaning fluid containing an aqueous hydroxide, or an aqueous ammonium, for example.
HO-{(EO)x-(PO)y}z-H (I)
R-[{(EO)x-(PO)y}z-H]m (II)
wherein “EO” designates an oxyethyethylene group, and “PO” designates an oxypropylene group. “R” designates a residue formed by eliminating hydrogen atoms from a hydroxyl group of alcohol or amine, or a residue formed by eliminating hydrogen atoms from an amino acid. “x” and “y” are integers satisfying x/(x+y)=0.05 to 0.4, and “z” and “m” are positive integers.
Next, a conventional method of manufacturing a semiconductor device using the foregoing cleaning fluid will be described.
With reference to
FIGS. 1A
to
1
C, a first conventional method of manufacturing a semiconductor device will be described. More specifically, a method of forming a gate electrode of a MOS transistor will be described.
As shown in
FIG. 1A
, a gate insulating film
2
, a polysilicon film
11
, a barrier metal layer
21
, and a tungsten film
31
are formed on a semiconductor substrate
1
, in the sequence.
Next, as shown in
FIG. 1B
, a resist pattern
51
is formed on the tungsten film
31
, and an interconnection pattern (gate electrode)
41
is formed by dry etching with the resist pattern
51
as a mask.
Next, as shown in
FIG. 1C
, the resist pattern
51
is removed by plasma ashing (ashing), thereafter resist residues
61
are remained on the top of the gate electrode
41
. Although not shown, the resist residues
61
are remained on the both sides of the gate electrode
41
.
Finally, the semiconductor substrate is cleaned in a subsequent cleaning step, in which the semiconductor substrate
1
is cleaned by use of the previously-described cleaning fluid. Thus, the resist residues
61
are removed from the semiconductor substrate
1
, and a semiconductor device is manufactured.
With reference to
FIGS. 2A
to
2
C, a second conventional method of manufacturing a semiconductor device will be described. More specifically, a method of forming a source region and a drain region of a MOS transistor will be described.
With reference to
FIG. 2A
, the interconnection pattern (gate electrode)
41
is formed on the gate insulating film
2
formed on the semiconductor substrate
1
, by the same method as that illustrated in
FIGS. 1A
to
1
C.
Further, a resist pattern
52
is formed on the gate electrode
41
and on the gate insulating film
2
around the gate electrode
41
.
Next, ions are implanted into the semiconductor substrate
1
(as indicated by arrows shown in
FIG. 2A
) with the resist pattern
52
as a mask. Thus, although not shown, a source region or a drain region of a MOS transistor is formed in the semiconductor substrate
1
.
Subsequently, although not shown, the resist pattern
52
is removed by plasma ashing, thereafter resist residues
62
are remained on the gate insulating film
2
on the semiconductor substrate
1
, as shown in FIG.
2
B.
Finally, although not shown, the semiconductor substrate
1
is cleaned in cleaning step, more specifically, in which the semiconductor substrate
1
is cleaned by use of the previously-described cleaning fluid. Thus, the resist residues
62
are removed from the semiconductor substrate
1
, and the semiconductor device is manufactured.
As shown in
FIG. 2C
, there may be a case in which, after side walls
71
have been formed on the both sides of the gate electrode
41
, ions are implanted into the semiconductor substrate
1
. Even in such a case, a silicon-based member or a tungsten-based member may become partially exposed through pin holes formed in the side walls
71
. For this reason, the semiconductor substrate
1
is cleaned by use of the previously-described cleaning fluid, to thereby remove the resist residues
63
.
In the cleaning step of the conventional methods, however, there are problems as follows.
In a case where the cleaning fluid has a high hydroxide content, the silicon inhibitor cannot be added to the cleaning fluid at high concentration. The reason for this is that, if both the silicon corrosion inhibitor and hydroxide are added to the cleaning fluid at high concentrations, the cleaning capability of the cleaning fluid is resultant degraded.
More specifically, in the cleaning step of the semiconductor substrate having a silicon-based member and a tungsten-based member exposed thereon, use of the cleaning fluid cannot be attained both a high cleaning capability and a high silicon corrosion prevention effect simultaneously.
In order to remove particles from the semiconductor substrate
1
, the previously-described cleaning step is often carried out several times.
Further, in a case where plural transistors having different electrical properties are formed on the semiconductor substrate
1
, the steps illustrated in
FIGS. 2A
to
2
C (i.e., the step of forming a resist pattern, the step of implanting ions, the step of removing a resist pattern, and a cleaning step) must be carried out several times.
Here, a hydroxide, which is contained in the cleaning fluid, has the property of eluting tungsten slightly.
Therefore, in the case that the semiconductor substrate
1
must be cleaned several times as mentioned above, an amount, to which the tungsten film
31
is eluted by use of the previously-described cleaning fluid, exceeds an allowable range. As a result, which may cause f
Deo Duy
McDermott & Will & Emery
Mitsubishi Denki Kabushiki Kaishi
Utech Benjamin L.
LandOfFree
Method of manufacturing semiconductor device including a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing semiconductor device including a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing semiconductor device including a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2946798