JPH11145112A - Patterning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a formation of a pattern consisting of fine lines and spaces without residual metal leaving and other remainder, by processing a dry etching on the third layer using a mixture of chlorine containing gas and oxygen gas. SOLUTION: A silicon oxidized film 2 is formed on a semiconductor board 1. On the silicon oxidized film 2, a WSi layer 3 as the first metal layer, a Tin layer 4 as the second metal layer, and a low resistance precious metal layer 5 consisting of a Pt layer 5a and an Au layer 5b as the third metal layer are stacked by an evaporation method or by a sputtering method in turn. Next, a mixture of Cl2 gas and O2 gas is provided having helicon plasma of flow rate by 1:2, and a low resistance precious metal layer 5 is processed through dry etching masked by an oxide mask 6. By this process, a pattern consisting of fine lines and spaces can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a patterning method suitable for forming a laminated metal wiring of a semiconductor device and the like, and more particularly to a method for preventing the re-adhesion of Au and Ti materials to the side walls of the laminated metal wiring and the like and residues. It relates to a patterning method.

[0002]

2. Description of the Related Art Conventionally, aluminum material is mainly used for wiring of a semiconductor device. However, as the frequency and the degree of integration increase, delay due to resistance of metal wiring and deterioration due to stress migration and electromigration occur. It has been a problem. For this reason, gold (A) having low wiring resistance and excellent resistance to both migrations
Noble metal materials such as u) and platinum (Pt) are used as materials for gate electrodes and wirings of semiconductor devices for ultrahigh frequency. For example, for a gate electrode of a compound semiconductor device, tungsten silicide (WSi) or molybdenum (M
o) Refractory metal layer made of, for example, titanium nitride (TiN)
Or a barrier metal layer made of titanium (Ti) or the like and Au
Alternatively, there are many structures in which low-resistance noble metal layers made of Pt or the like are sequentially laminated. The barrier metal layer is formed as a barrier against diffusion of noble metal atoms in the low-resistance noble metal layer to the high-melting metal layer or the underlayer, to improve adhesion between the high-melting metal layer and the low-resistance noble metal layer, and to improve migration resistance. Is what it is.

[0003] Such a three-layer metal wiring is formed by patterning. A conventional patterning method will be described. 2A to 2C are sectional views showing a conventional patterning method in the order of steps. In the conventional patterning method, first, as shown in FIG. 2A, after a silicon oxide film 12 is formed on a semiconductor substrate 11, a thickness of 100 μm is formed on the silicon oxide film 12 as a refractory metal layer.
WSi layer 13 having a thickness of 50 nm as a barrier metal layer.
A 50 nm thick Pt layer 15a and a 400 nm thick AN
The u layer 15b is sequentially formed into a stacked film by a vapor deposition method or a sputtering method. Then, a photoresist mask 16 is formed on the low-resistance noble metal layer 15 by a lithography technique.

Next, as shown in FIG. 2 (b), an inert gas such as an argon (Ar) gas is ionized, accelerated by an electric field, and sputter-etched using the photoresist mask 16 as a mask. , The Au layer 15b and the Pt layer 15a are etched. As the ion milling method, an oblique milling method in which ions are incident obliquely with respect to the thickness direction of the substrate is often used so that the Au and Ti materials once removed do not adhere to the side walls. For example, ion milling is performed with the ion incident direction inclined at 40 ° with respect to the thickness direction of the substrate.

Then, as shown in FIG. 2C, using a photoresist mask 16, an Au layer 15b and a Pt layer 15a as masks, a carbon tetrafluoride (CF ₄ ) gas and a sulfur hexafluoride (SF ₆ ) gas are used. The TiN layer 14 and the WSi layer 13 are etched by a reactive ion etching (RIE) method using a mixed gas of TiO ₂ or a mixed gas of chlorine (Cl ₂ ) gas and CF ₄ gas to form a laminated metal wiring. ing.

Another patterning method has been proposed (JP-A-3-38825). 3A to 3C are cross-sectional views showing the patterning method described in JP-A-3-38825 in the order of steps. The patterning method described in this publication will be described. However, for the sake of comparison with the present invention, the type and thickness of each film or layer may be different from those described. In the patterning method described in this publication, first, after a silicon oxide film 22 is formed on a semiconductor substrate 21, a 100-nm thick refractory metal layer is formed on the silicon oxide film 22.
WSi layer 23, 50 nm thick as barrier metal layer
100N thick TiN layer 24 and low-resistance noble metal layer
The Au thin film 25 having a thickness of 10 nm is sequentially stacked and deposited by a vapor deposition method or a sputtering method. Then, a photoresist pattern 27 having an opening is formed on the Au thin film 25 by a lithography technique. And a photoresist pattern 2
An Au pattern 28 having a thickness of 700 nm is formed in the opening 7 by plating using the Au thin film 25 as an electrode.

Next, as shown in FIG. 3 (b), after the photoresist pattern 27 is peeled off, the Au pattern 28 is used as a mask to react using a mixed gas of Ar gas and oxygen (O ₂ ) gas. Ion beam etching (RIB
The Au thin film 25 is etched by the method E).

Then, as shown in FIG. 3C, using the Au pattern 28 and the Au thin film 25 as a mask, the TiN layer 24 and the WSi layer 23 are formed by a RIBE method using a mixed gas of Ar gas and SF ₆ gas. Is etched to form a laminated metal wiring.

According to this patterning method, the ABE is performed by a RIBE method using a mixed gas of Ar gas and O ₂ gas.
Since the u thin film 25 is etched, the etching rate ratio between the Au thin film 25 and the TiN layer 24 is large, and no problems such as residue and base surface roughness occur.

[0010]

However, the above-mentioned conventional patterning method has the following problems.

In the patterning method using the ion milling method, a pattern composed of fine lines and spaces cannot be formed without causing re-adhesion on the side wall of the metal wiring. In the case where ions are made incident in parallel with the thickness direction of the substrate, the ions can be made incident on fine regions, so that a fine pattern can be formed. However, the removed Au and Pt materials are sputtered again. And reattach to the side walls of the wiring. When the re-adhesion occurs, the re-adhesion may be a particle generation source, or the re-adhesion may be peeled off, causing a short circuit between the wiring patterns to cause an electric short circuit and a leak.

On the other hand, when ions are incident in a direction inclined with respect to the thickness direction of the substrate, re-adhesion can be prevented, but the side of the wiring pattern enters the shadow of the photoresist mask 16 to prevent the ions from re-adhering. Thus, no ions are incident on this region. Therefore, the Au layer 15b and the Pt layer 15a on the side of the wiring pattern remain without being removed. Then, when the TiN layer 14 and the WSi layer 13 are etched as they are, the Au layer 15b and the Pt layer 15a on the side of the wiring pattern serve as a mask, and a metal residue and a residue 17 are generated. To prevent this, the Au layer 15b and the Pt
When the milling time of the layer 15a is extended, the low-resistance noble metal layer 15 and the TiN
Since the ratio of the milling speed with the layer 14 is as small as about 2, T
A large step is formed in the iN layer 14 and the WSi layer 13, and an electric short circuit and a leak occur between the wiring patterns. Further, in this method, since there is a region where ions are not incident at all, there remains a problem that a pattern including fine lines and spaces is not formed.

In the patterning method described in JP-A-3-38825, the Au thin film 2 is formed by a RIBE method using a mixed gas of Ar gas and O ₂ gas.
Since No. 5 is etched, it does not react with the etched Au material and cannot be volatilized and removed. For this reason, reattachment to the side wall occurs. Further, when the ion beam is irradiated from a direction inclined with respect to the thickness direction of the substrate, a fine pattern is not formed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and does not cause the re-adhesion of Au and Pt materials to the side walls of the laminated metal wiring, and provides fine lines and spaces free of metal residues and residues. An object of the present invention is to provide a patterning method capable of forming a pattern consisting of:

[0015]

A patterning method according to the present invention comprises a first metal layer, a second metal layer formed on the first metal layer, and a second metal layer formed on the first metal layer. The method for patterning a laminate comprising the formed third metal layer includes a step of dry-etching the third metal layer using a mixed gas containing a gas containing chlorine and an oxygen gas. Features.

In the present invention, since a mixed gas containing a gas containing chlorine and an oxygen gas is used when dry-etching the third metal layer, a compound having high volatility is generated by dry-etching. In addition, a fine pattern can be formed without causing re-adhesion to the side wall, residue and metal residue.

[0017] The second metal layer may contain Ti, and the third metal layer may be made of at least one metal material selected from the group consisting of gold and platinum. By forming the third metal layer from at least one metal material selected from the group consisting of gold and platinum, AuCl _x , PtCl _x and PtC having high volatility by dry etching.
Since l _x O _y is generated, re-adhesion of the side wall is prevented. In addition, by including Ti in the second metal layer, the difference in etching rate between the second metal layer and the third metal layer is increased, so that a fine pattern can be easily formed.

Further, the present invention can include a step of dry-etching the second metal layer and the first metal layer using a gas containing halogen.

The laminate is formed on a wafer, and in the step of dry-etching the third metal layer, the third metal layer is dry-etched by setting the temperature of the wafer to 70 to 250 ° C. It is desirable to have a process.

Further, in the step of dry-etching the second metal layer and the first metal layer, the temperature of the wafer is set to -30 to 50 ° C., and the second metal layer and the first metal layer are etched. It is desirable to have a step of dry etching.

By performing dry etching at an appropriate temperature of the wafer on which the laminated body is formed, the reactivity and etching rate of the etched material are increased, so that a pattern having a desired shape can be formed more easily. be able to.

The second metal layer comprises a Ti layer and a Ti layer.
One type of metal layer selected from the group consisting of N layers may be used.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the embodiment of the present invention will be specifically described below with reference to the accompanying drawings. FIG.
3A to 3C are cross-sectional views illustrating a patterning method according to the first embodiment of the present invention in the order of steps. In the method of the present embodiment, first, a silicon oxide film 2 having a thickness of 500 nm is formed on a semiconductor substrate 1 as shown in FIG. Next, on the silicon oxide film 2, a WSi layer 3 having a thickness of 100 nm as a first metal layer, a TiN layer 4 having a thickness of 50 nm as a second metal layer, and a 50 nm thickness as a third metal layer. Pt layer 5a and thickness 400 nm
Are sequentially formed by an evaporation method or a sputtering method. The TiN layer 4 becomes a barrier metal layer, and the Pt layer 5a
And the Au layer 5b constitute the low-resistance noble metal layer 5. Next, a thickness of 500 n made of SiO _{2 is formed} on the Au layer 5b.
m is grown, and a photoresist film pattern is formed on the insulating film by lithography. Then, using a photoresist film pattern as a mask, the RIE apparatus is used to dry the insulating film using a mixed gas of carbon tetrafluoride (CF ₄ ) gas, fluorohydrocarbon (CHF ₃ ) gas, and argon (Ar) gas. By etching, an oxide film mask 6 is formed. After that, the photoresist film pattern is removed.

Next, as shown in FIG. 1B, a mixed gas of Cl ₂ gas and O ₂ gas is supplied at a flow ratio of 1: 2 by a helicon plasma etching apparatus, and the pressure is set to 0.1.
1Pa, Helicon plasma source power 1000W
(13.56 MHz), RF bias power 500W
(13.56 MHz), and using the oxide mask 6 as a mask, the Au layer 5b and the Pt constituting the low-resistance noble metal layer 5
The layer 5a is dry-etched.

Since the mixed gas of Cl ₂ gas and O ₂ gas has high reactivity with Au and Pt materials, the highly volatile Au chloride (AuCl _x ) and Pt chloride (PtCl _x ) and chloride of Pt (PtCl _x
O _y ) are generated. For this reason, reattachment to the side wall does not occur.

Also, by using a mixed gas of Cl ₂ gas and O ₂ gas, the selectivity of the etching rate between the low-resistance noble metal layer 5 and the TiN layer 4 is increased. This is because TiN containing Ti can be obtained by using this mixed gas.
This is because the layer 4 is oxidized and its etching rate decreases. FIG. 4 is a graph showing the relationship between the oxygen gas ratio on the horizontal axis and the selectivity on the vertical axis. In FIG. 4, the solid line indicates the selectivity between the Au layer and the TiN layer,
The dashed line indicates the selectivity between the Au layer and the SiO ₂ layer. As shown in FIG. 4, even if the oxygen gas ratio increases, the Au layer and the S
Although the selectivity with the iO ₂ layer does not change much, the Au layer and the T
The selectivity with the iN layer is significantly increased. In the dry etching under the above conditions, the etching rate of the Au layer 5b was 250 nm / min and the etching rate of the Pt layer 5a was 100 nm / min, whereas the etching rate of the TiN layer 4 was only 10 nm / min. . Therefore, the dry etching is completely stopped on the TiN layer 4, so that the remaining Au layer 5b and Pt layer 5a are small,
The surface of the N layer 4 becomes smooth.

After the Au layer 5b and the Pt layer 5a are dry-etched, as shown in FIG. 1C, a mixture of a carbon tetrafluoride (CF ₄ ) gas and a sulfur hexafluoride (SF ₆ ) gas is formed. Ti by reactive ion etching (RIE) using a gas or a mixed gas of Cl ₂ gas and CF ₄ gas
The N layer 4 and the WSi layer 3 are etched to form a laminated metal wiring.

In the method of this embodiment, Cl ₂ gas and O ₂
Since the low-resistance noble metal layer 5 is dry-etched using a gas mixture with a gas, a compound having high volatility is generated as described above, so that re-adhesion to the side wall does not occur.
Further, the selectivity of the etching rate between the low-resistance noble metal layer 5 and the TiN layer 4 is high, and the dry etching of the low-resistance noble metal layer 5 on the TiN layer 4 is completely stopped. For this reason,
High perpendicularity of pattern shape.

When the low resistance noble metal layer 5 is etched, the pressure is set to 0.5 Pa and the temperature of the semiconductor substrate 1 is set to 150 Pa.
It is good also as ° C. By increasing the temperature of the semiconductor substrate 1, the reactivity between the mixed gas and the Au and Pt materials is improved, and the highly volatile Au chloride (AuCl _x ), Pt chloride (PtCl _x ) and Pt chloride are highly volatile. Oxide (PtCl _x O _y )
Are easily produced. Therefore, the etching rate is improved, and re-adhesion to the side wall does not occur, so that the verticality of the etched shape is improved. When the temperature of the semiconductor substrate 1 is lower than 70 ° C., the angle of the etching shape is 60 °.
It becomes difficult to form a fine line and space pattern because of the following. On the other hand, if the temperature of the semiconductor substrate 1 exceeds 250 ° C., side etching occurs in the Au layer 5b or side etching similar to a notch occurs in the interface between the Au layer 5b and the Pt layer 5a, so that the laminated metal wiring is constricted. And a step is easily formed. Therefore, when dry etching the low-resistance noble metal layer 5, the temperature of the semiconductor substrate 1 is desirably 70 to 250 ° C.

When etching the TiN layer 4 and the WSi layer 3, the temperature of the semiconductor substrate 1 may be set to 25 ° C. If the temperature of the semiconductor substrate 1 at this time is lower than −30 ° C., the etching rate of each layer decreases. On the other hand, when the temperature of the semiconductor substrate 1 exceeds 50 ° C., the TiN layer 4 and W
Side etching may occur in the Si layer 3. Therefore, when etching the TiN layer 4 and the WSi layer 3, the temperature of the semiconductor substrate 1 is desirably -30 to 50C.

Although the helicon plasma etching apparatus is used in the method of the present embodiment, the present invention is not limited to this. Inductively coupled plasma (IC
P) Etching equipment, RIBE equipment and magnetron R
An IE device or the like may be used. Further, at the time of dry etching of the low-resistance noble metal layer, the pressure is preferably low in order to increase the volatility of the generated compound,
It is desirable that: The gas used at this time may be any gas containing chlorine, such as BCl ₃ and SiCl ₄ . Further, an inert gas may be added to a mixed gas of the gas containing chlorine and the O ₂ gas.

In this embodiment, an oxide film made of SiO ₂ is used as a mask for dry-etching the low-resistance noble metal layer 5. However, a photoresist mask and a metal mask containing Ti are used. Is also good.

[0033]

As described in detail above, according to the present invention,
Since the third metal layer is dry-etched using a mixed gas containing a gas containing chlorine and an oxygen gas,
A highly volatile compound is generated by etching, and a pattern consisting of fine lines and spaces can be formed without causing re-adhesion to the side wall. In addition, when Ti is contained in the second metal layer, Ti is oxidized by dry etching, and the etching rate of the second metal layer is reduced, so that a pattern in which the remaining metal and the residue are further reduced is formed. And the surface of the second metal layer becomes smooth. Furthermore, by performing dry etching with the temperature of the wafer on which the laminated body is formed being appropriate, the reactivity and etching rate of the etched material are increased, so that a pattern having a desired shape can be more easily formed. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a patterning method according to an embodiment of the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing a conventional patterning method in the order of steps.

FIG. 3 is a sectional view showing a patterning method described in JP-A-3-38825 in the order of steps.

FIG. 4 is a graph showing a relationship between an oxygen gas ratio and a selection ratio.

[Explanation of symbols]

 1, 11, 21; semiconductor substrates 2, 12, 22; silicon oxide films 3, 13, 23; WSi layers 4, 14, 24; TiN layers 5, 15; low-resistance noble metal layers 5a, 15a; Au layer 6; oxide mask 16; photoresist mask 25; Au thin film 27; photoresist pattern 28;

Claims (6)

[Claims] 1. A laminate comprising a first metal layer, a second metal layer formed on the first metal layer, and a third metal layer formed on the second metal layer. A method of patterning a body, comprising: a step of dry-etching said third metal layer using a mixed gas containing a gas containing chlorine and an oxygen gas. 2. The method according to claim 1, wherein the second metal layer contains Ti, and the third metal layer is made of at least one metal material selected from the group consisting of gold and platinum. 3. The patterning method according to item 1. 3. The patterning method according to claim 1, further comprising a step of dry-etching the second metal layer and the first metal layer using a gas containing halogen. 4. The step of dry-etching the third metal layer, wherein the laminate is formed on a wafer,
4. The patterning method according to claim 1, further comprising a step of dry-etching the third metal layer at a temperature of the wafer of 70 to 250 ° C. 5. 5. The step of dry-etching the second metal layer and the first metal layer, wherein the laminate is formed on a wafer, wherein the temperature of the wafer is -30 to 5
5. The patterning method according to claim 1, further comprising a step of dry-etching the second metal layer and the first metal layer at 0 ° C. 5. 6. The patterning according to claim 2, wherein the second metal layer is one kind of metal layer selected from the group consisting of a Ti layer and a TiN layer. Method.