Repair method for phase shift mask in semiconductor device

Details Repair method for phase shift mask in semiconductor device Repair method for phase shift mask in semiconductor device

1999-09-10

2001-12-11

Rosasco, S. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Radiation modifying product or process of making

Radiation mask

C204S192340, C216S066000

Reexamination Certificate

active

06329106

ABSTRACT:

FIELD OF INVENTION
The present invention relates to a repair method for phase shift mask in a semiconductor device, and more particularly to a repair method for half-tone phase shift mask in a semiconductor device.
BACKGROUND OF THE INVENTION
The half-tone phase shift mask has been used in the photolithography process having high resolution so as to fabricate a fine contact hole or a fine patterning. Especially, when an i-line exposure equipment is used in the process, a phase shift layer provided to the half-tone phase shift mask is formed of a material such as MoSi, MoSiN or MoSiON that transmits approximately 4~12% of light and shifts phase of the light.
FIG. 1
is a cross-sectional view showing a general half-tone phase shift mask.
Referring to
FIG. 1
, a phase shift layer
13
that transmits approximately 4~12% of light and shifts phase of the light by 180°, is formed on a quartz substrate
11
. The phase shift layer
13
is formed of one selected among MoSi, MoSiN and MoSiON, and with thickness of approximately 1,000~1,400A. The phase shift layer
13
is partially patterned so as to act as a contact hole or a pattern mask. At this time, an E-beam writing method is applied to patterning of the phase shift layer
13
.
However, as shown in
FIG. 2
, a bridge
15
occurs as a phase shift layer at an unwanted region during patterning the phase shift layer
13
. The bridge
15
is removed by the following methods.
Firstly, the bridge
15
can be removed by a focused ion beam (hereinafter “FIB”) method. According to this method, Ga ions (Ga
+
) having high energy, i.e. 50~100 KeV are implanted to the bridge
15
, thereby to drop off the bridge
15
from the quartz substrate
11
.
On the other hand, the second repairing method uses a blue laser having long wavelength. A laser having wavelength of approximately 488 nm is applied to the bridge
15
, and then the bridge
15
is welded and removed.
However, the following problems occurred in a repair process using the FIB device. Since the FIB repair method is generally applied to Cr mask, it is difficult to remove the bridge made of the phase shift layer having a property of matter, which is different from that of Cr. In other words, the phase shift layer such as MoSi, MoSiN and MoSiON has a stronger bonding force than that of Cr. Therefore, it takes many hours to remove the bridge
15
. As a result, referring to
FIGS. 4 and 5
, residues
15
a
remain of the bridge
15
and also repair by-products
16
formed around the residue
15
a
even after a selected time is passed. Herein, the by-products
16
is formed by a reaction between Ga Ions, i.e. ion source of the FIB repair and Si ions, one component of the phase shift layer which comprises the bridge
15
having excellent reactivity with respect to Ga ions. The repair by-products
16
are not easy to remove by the FIB repair method.
Furthermore, if the FIB repair process is performed for a long time to remove the residue
15
a
of the bridge completely, the Ga ions (Ga
+
) having high energy are continuously focused at the quartz substrate
11
of the outside of the bridge
15
or the repair by-products
15
a
. As shown in
FIG. 6
, the Ga ions (Ga
+
) having high energy are continuously focused on a surface of the quartz substrate
11
, thereby pitting some portions (H) of the quartz substrate
11
.
Moreover, if the FIB repair process is performed for a long time, the Ga ions (Ga
+
) having high energy may permeate inside the quartz substrate
11
with high energy, then the Ga ion (Ga
+
) functions as a mask. Therefore, a defect occurs in the pattern on semiconductor substrate.
In the meantime, a method by emitting the blue laser has low accuracy during the repair process since a laser has its inherent characteristic of diffraction. Therefore, edges of repaired portions are removed ununiformly. Thus, if the repaired portions are not removed uniformly, it is difficult to use them as masks for forming a high resolution pattern. Since the phase shift layer as mentioned previously has a strong bonding force, powerful energy and long time are required to remove the bridge by the blue laser.
SUMMARY OF THE INVENTION
Accordingly, it is one object of the present invention to prevent generation of the repair by-products during the repair process of the phase shift layer.
It is another object of the present invention to prevent defects on the quartz substrate during the repair process of the phase shift layer.
It is further an object of the present invention to repair only a portion to be removed.
It is still one object of the present invention to repair defected portions on the phase shift mask in a short time.
To accomplish the above objects, the present invention provides a repair method for phase shift mask in a semiconductor device so as to remove a bridge formed between a phase shift layer on a quartz substrate, comprising the steps of: first repairing the bridge by implanting a charging ion according to a focused ion beam (“FIB”) method; and second repairing the first repaired bridge portion by emitting laser and then removing the bridge.
Herein, in the step of first repairing the bridge, the charging ion is Ga ion (Ga
+
) and the laser is a blue laser. In the step of first repairing the bridge, the Ga ions (Ga
+
) are implanted such that the cohesion property of the entire bridge is weakened. The Ga ions (Ga
+
) are implanted by energy of approximately 25~35 KeV with beam current of approximately 45~55 pA and ion concentration of 10
15
~2×10
15
ions/cm
2
.
Further, the bridge is first repaired so that the bridge is divided in the shape of a lattice. In the step of first repairing the bridge, a boundary between the phase shift layer and the bridge is repaired. A line width of the first repaired portion is preferably shown as an integral number times of the minimum line width repairable by the FIB device. The Ga ions (Ga
+
) are implanted with a relatively high energy of 140~150 pA.
According to another embodiment of the present invention, a repair method for phase shift mask in a semiconductor device so as to remove a bridge formed between a phase shift layer on a quartz substrate, comprises the steps of: first repairing the bridge by emitting a blue laser to a center of the bridge; and second repairing the first repaired bridge portion by implanting a charging ion according to a focused ion beam (“FIB”) method.
Herein, the laser used in the step of first repairing the bridge is a blue laser, and the charging ion used in the step of second repairing the bridge is Ga ion (Ga
+
). In the step of second repairing the bridge, the Ga ions (Ga
+
) are implanted with energy of 20~40 KeV.


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