JPH07201826A - Dry-etching method - Google Patents

Abstract

PURPOSE:To obtain a dry-etching method whereby the etching rates of TiN films are increased and the formation of a through hole is performed appropriately in a multilayer wiring having the TiN films. CONSTITUTION:In the case of the etching of a multilayer metallic wiring having TiN films 103, 105, the mixture gas of SF6 with a fluorocarbon-based gas is introduced into an etching chamber, and to the space between the electrodes on one of which a semiconductor substrate having the TiN films 103, 105 is put, an RF power is fed for the TiN films to be etched. In this case, it is preferable that the flow rate of SF6 is 10-30sccm and the flow rate of CF4 as the fluorocarbon based gas is 20-60sccm and the pressure of the etching chamber is 20-60 Pa and the density of the RF power is 2.2-4.4W/cm<2>. Thereby, the etching rates of the TiN films are increased, and the depositions which can not be removed from the inner sidewall of a through hole is prevented from being generated on it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for a TiN (titanium nitride) film used for semiconductor devices.

[0002]

2. Description of the Related Art Generally, a TiN film is used as an upper layer or a lower layer of a metal wiring in a semiconductor device as a measure against migration of a metal wiring such as aluminum. For example, in the metal wiring shown in FIG.
01 on Ti film 502, TiN film 503, Al-Si-
A Cu film 504 and a TiN film 505 are sequentially formed using a sputtering technique, a photoresist 506 is applied thereon, and a pattern is formed using a lithography technique. As shown in FIG. 5B, a TiN film 505, an Al—Si— layer, and a TiN film 505 were formed on this semiconductor substrate by using a general reactive ion etching apparatus using chlorine-based gas such as Cl ₂ and BCl ₃ .
The Cu film 504, the TiN film 503, and the Ti film 502 are etched to form wiring.

However, in this etching method, a Ti film,
In etching the TiN film, photoresist 506
The etching rate is 100Å /
There was a problem that you could only get about min. As a method for solving this problem, Japanese Patent Laid-Open No. 3-239323 discloses that the TiN film can be etched at a high speed by etching the TiN film using a mixed gas of CF ₄ and N ₂ or SF ₆ and N _2. It has been shown that

In recent years, in order to cope with higher integration and higher speed of semiconductor devices, a multilayer structure of wiring has been required.
Here again, the wiring is applied with a laminated metal wiring as a measure for preventing stress migration and electromigration. In such a laminated structure, through holes for connecting the upper and lower metal wirings to each other can be formed. Required. FIG. 6 is a diagram showing a part of the process. First, as shown in FIG. 6A, the silicon oxide film 6 is formed.
01 on Ti film 602, TiN film 603, Al-Si-
After forming a metal wiring having a laminated structure including a Cu film 604 and a TiN film 605 by a general lithography technique or etching technique, an interlayer insulating film 606 such as a silicon oxide film is formed, a photoresist 607 is applied, and lithography is performed. A pattern of through holes is formed by a technique.

Subsequently, as shown in FIG. 6B, a general RIE (reactive ion etching) apparatus is used to add O to a fluorocarbon-based gas such as CF ₄ or CHF _3.
2 , the interlayer insulating film 606 is etched by using an etching gas to which an inert gas such as Ar is added, and the through hole 6
08 is formed. At this time, the TiN film 605 on the upper portion of the lower layer wiring is also etched at the same time in order to suppress the resistance between the upper layer wiring formed in the next step and the lower layer wiring. Finally, as shown in FIG. 6C, the Al-Si-Cu film 60 is formed.
9. A TiN film 610 is sequentially formed, and an upper wiring is formed by using a general lithography and etching technique to complete a multilayer wiring.

However, this method of forming a through hole has a problem in that a step break is likely to occur when the Al-Si-Cu film 609 is formed and a short circuit occurs between wirings. Further, the interlayer insulating film 606 is etched to form the through hole 608, and then the Al--Si--Cu film 6 is formed.
When etching the TiN film on 04, CF ₄ , CH
When etching with F ₃ or an etching gas in which O ₂ is added to these, the etching rate of the TiN film is 200
Only Å / min was obtained, and there was a problem in mass productivity. As a method of increasing the etching rate, CF ₄ , CH
The etching rate of the TiN film is increased to about 500 Å / min by etching with an etching gas in which Ar is added to F ₃ , but the TiN film is removed and Al-Si is removed.
The Cu film is also sputter-etched, and aluminum-based deposits adhere to the sidewalls of the through holes. This deposit cannot be removed even by treating it with plasma or chemicals, and if the upper wiring is formed with the deposit remaining in the through hole, the reliability of the device will decrease. was there.

As a method for solving this problem, Japanese Unexamined Patent Publication No.
No. 102331 discloses a method of forming through holes. FIG. 7 is a diagram showing a part of the process. First,
As shown in FIG. 7A, A is formed on the silicon oxide film 701.
An l-Si-Cu film 702 is formed at 7,000 Å, and then a TiN film 703 is formed at 700 Å. Wiring is formed from this by general lithography technology and etching technology. Then, an interlayer insulating film 704 such as a silicon oxide film is grown,
A photoresist is applied, a through-hole pattern is formed in the photoresist by an exposure technique, and a fluorine gas such as CHF ₃ that provides etching selectivity between the interlayer insulating film 704 and the TiN film 703 is used as an etching gas. The through hole 705 is formed by etching.

After removing the photoresist, the surface of the interlayer insulating film 704 is sputter-etched by Ar using an RIE apparatus. As a result, as shown in FIG. 7B, a tapered side wall surface of approximately 45 ° is formed in the through hole opening. Finally, etching is performed with a fluorine-based gas such as SF _{6 which} provides etching selectivity between the Al-Si-Cu film 702 and the bottom surface of the through hole 705 as shown in FIG. 7C. It is possible to expose the Al-Si-Cu surface without the TiN film and the deposit. Further, since the opening of the through hole 705 is formed into a taper shape by Ar sputter etching, it is possible to form a wiring without breaks in the wiring formation in the next step.

[0009]

However, Japanese Unexamined Patent Publication No. 3-2.
T by CF ₄ , N ₂ shown in Japanese Patent No. 39323
Since an etching rate of only about 200 to 250 Å / min can be obtained by etching the iN film, CF ₄ , CHF
Similar to the etching of the TiN film by ₃ , there was a problem in mass productivity. Further, the etching of the TiN film by SF ₆ and N ₂ has a problem that the resistance to stress migration and electromigration is lowered because the etching of the TiN film progresses in the direction parallel to the substrate.

Further, in the method of forming a through hole disclosed in Japanese Patent Application Laid-Open No. 4-102331, when Ar sputter etching is performed by the RIE apparatus, Ar has energy due to the cathode drop voltage, so that the substrate surface is affected. Therefore, the etching rate in the vertical direction hardly becomes zero.
That is, the TiN film is etched together with the interlayer insulating film by Ar sputter etching, and finally the Al-S film is formed.
The i-Cu film is also sputter-etched and deposited on the side wall of the through hole, and since the deposit 706 cannot be removed by any treatment, there is a problem that the reliability of the device is lowered. In addition, etching of the TiN film is performed by SF
₆ If it is performed alone, the etching of the TiN film also progresses in the direction parallel to the substrate, and the TiN film on the Al-Si-Cu wiring other than the opening of the through hole is also etched. There is a problem that the resistance to migration and electromigration is reduced. An object of the present invention is to provide a dry etching method for increasing the etching rate and preventing deposition of irremovable reaction products on the sidewalls of through holes even when they are formed.

[0011]

According to the dry etching method of the present invention, a TiN film is etched using a mixed gas of SF ₆ and a fluorocarbon type gas. In this case, TiN
When etching the metal wiring of the laminated film including the film or forming the connection portion between the wiring of the laminated film including the TiN film, the interlayer film is etched and subsequently the TiN film forming the upper layer of the laminated film is formed. Applied when etching.
For example, the dry etching method of the present invention has a pair of electrodes in a chamber, a mixed gas of SF ₆ and a fluorocarbon-based gas is introduced into the chamber, and T
A semiconductor substrate having an iN film is placed, and RF power is supplied between both electrodes to etch the TiN film. In this case, the flow rate of SF ₆ is 10 to 30 sccm, and the flow rate of CF ₄ as the fluorocarbon gas is 20 to 60 sccc.
m, pressure 20 to 60 Pa, RF power density 2.2 to
It is preferably 4.4 W / cm ² .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a semiconductor substrate when the dry etching method of the present invention is applied to the formation of metal wiring having a laminated structure. First, as shown in FIG. 1A, a Ti film 102 having a film thickness of 300 Å and a 10
A TiN film 103 having a film thickness of 00Å, an Al-Si-Cu film 104 having a film thickness of 5000Å, and a TiN film having a film thickness of 250Å
The film 105 is sequentially formed by a sputtering method. Then, a photoresist 106 is applied and a pattern is formed by a lithographic technique.

Subsequently, this semiconductor substrate is etched using the cathode couple type RIE apparatus shown in FIG.
This RIE device has a chamber 2 having a gas supply at the top.
01 is provided with an upper electrode 202 and a lower electrode 203 inside,
An RF power source 205 is connected to the lower electrode 203 via a matching box 204. Then, the semiconductor substrate W is placed on the lower electrode 203.

In this etching, first, SF ₆ (flow rate 10 sccm) and CF are used as etching gas.
_The TiN film 105 is etched under the conditions of ₄ (flow rate 20 sccm), pressure 20 Pa, and RF power density 3.3 W / cm ² . Subsequently, Cl ₂ (flow rate 30 sccm) and BC
Al—Si—Cu film 10 under the conditions of l ₃ (flow rate 70 sccm), pressure 30 Pa, and RF power density 3.8 W / cm ^2.
Etching 4 is performed. Further, the TiN film 103 is made of TiN.
Under the same etching conditions as the film 105, finally the TiN film 10
2 is etched under the same etching conditions as the Al-Si-Cu film 104. As a result, metal wiring having a required pattern is formed as shown in FIG.

FIG. 3 shows the CF ₄ flow rate dependency of the etching rate when etching the TiN film described above. The etching rate is 2000 to 3000 Å / min.
It can be seen that the etching rate is 10 times or more that of the conventional technique. Here, according to the study by the present inventor, the conditions under which the TiN film can be etched at a high etching rate are not limited to the above etching conditions, but SF ₆ (flow rate 10 to 30 sccm) and CF ₄ (flow rate 20 to 60 sccm). ), A pressure of 20 to 60 Pa, and an RF power density of 2.2 to 4.4 W / cm ² in an appropriate combination, it has been confirmed that the TiN film can be etched at an etching rate of 1500 Å / min or more. Further, it is possible to obtain equivalent performance by using CHF ₃ in addition to CF ₄ .

FIG. 4 is a schematic sectional view of a semiconductor substrate when the dry etching method of the present invention is applied to the formation of through holes. First, as shown in FIG. 4A, a Ti film 402, a TiN film 403, and an Al film are formed on the silicon oxide film 401.
A —Si—Cu film 404 and a TiN film 405 are formed by sputtering, and a wiring having a laminated structure is formed by a lithography technique and an etching technique. Next, an interlayer insulating film 404 such as a silicon oxide film is formed, a photoresist 407 is applied, and a through hole pattern is formed by a lithography technique. Then, the interlayer insulating film 406 is formed by HF liquid or the like.
Isotropically etched to 40 to 60% of the film thickness. The etching at this time can be performed by wet etching with an HF solution or the like, or by RIE treatment with CF ₄ or O ₂ .

This semiconductor substrate is etched using the cathode couple type RIE apparatus shown in FIG. That is,
As shown in FIG. 4B, CF ₄ (flow rate 20 sccm) and CHF ₃ (flow rate 4) are conditions under which the interlayer insulating film 406 can be selectively etched with respect to the TiN film 405.
0sccm), pressure 20Pa, RF power density 5.5W
Etching is performed at / cm ² . Next, TiN film 405
SF ₆ (flow rate 10 sccm), CF ₄ (flow rate 20 sccm)
cm), pressure 20 Pa, RF power density 3.3 W / cm
Etching is performed under the condition of ² .

Then, after removing the photoresist 407, as shown in FIG. 4C, the Al-Si-Cu film 4 is formed.
09 and a TiN film 410 are sequentially formed, an upper wiring is formed by using a general lithography and etching technique, and a multi-layer wiring is completed. In this embodiment, the through hole 40
Since isotropic etching is first performed in the formation of No. 8, step disconnection does not occur when forming the wiring of the upper layer.
Further, since the TiN film 405 exposed by the formation of the through hole 408 is etched at a higher speed than in the past and the reaction product is not deposited on the sidewall of the through hole 408, the reliability of the device is greatly improved as compared with the conventional one. It is possible to improve.

[0019]

As described above, according to the present invention, the TiN
By etching a film or a laminated film of metal wiring including a TiN film using a mixed gas of SF ₆ and a fluorocarbon-based gas, there is an effect that high-speed etching can be realized. In particular, when a TiN film is etched in forming a through hole that is a connecting portion between wirings of a laminated structure, a reaction product that cannot be removed is not deposited on the side wall of the through hole. This also has the effect of significantly improving the reliability of the device. In addition, a chamber has a pair of electrodes, a mixed gas of SF ₆ and a fluorocarbon-based gas is introduced into the chamber, a semiconductor substrate having a TiN film is placed on one of the electrodes, and an RF electrode is placed between the electrodes. In dry etching in which electric power is supplied to etch the TiN film, the flow rate of SF ₆ is 10 to 30 sccm, the flow rate of CF ₄ as a fluorocarbon-based gas is 20 to 60 sccm, and the pressure is 20 to 60.
By setting the Pa and RF power densities to 2.2 to 4.4 W / cm ² , it is possible to realize etching at high speed without depositing an irremovable reaction product.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an etching method of the present invention in the order of steps.

FIG. 2 is a schematic configuration diagram of an RIE device for carrying out the method of the present invention.

FIG. 3 is a diagram showing a relationship between a TiN etching rate and a gas flow rate in the method of the present invention.

FIG. 4 is a cross-sectional view showing a step of forming a through hole by the etching method of the present invention.

FIG. 5 is a cross-sectional view showing a conventional etching method in the order of steps.

FIG. 6 is a cross-sectional view showing a method of forming a conventional through hole in the order of steps.

FIG. 7 is a cross-sectional view showing a conventional improved through-hole forming method in process order.

[Explanation of symbols]

 101 Silicon oxide film 102 Ti film 103 TiN film 104 Al-Si-Cu film 105 TiN film

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display area // C23F 4/00 E 8417-4K

Claims (5)

[Claims] 1. A dry etching method comprising etching a TiN film using a mixed gas of SF ₆ and a fluorocarbon-based gas. 2. The dry etching method according to claim 1, wherein the metal wiring of the laminated film including the TiN film is etched. 3. When forming a connection portion between wirings of a laminated film containing a TiN film, the interlayer film is etched, and then the TiN film forming the upper layer of the laminated film is mixed with SF ₆ and a fluorocarbon-based gas. A dry etching method characterized by etching using a gas. 4. A chamber is provided with a pair of electrodes, a mixed gas of SF ₆ and a fluorocarbon-based gas is introduced into the chamber, and a semiconductor substrate having a TiN film is placed on one of the electrodes, and both electrodes are placed. A dry etching method in which RF power is supplied to etch the TiN film. 5. The flow rate of SF ₆ is 10 to 30 sccm, and the flow rate of CF ₄ as the fluorocarbon gas is 20 to 60.
The dry etching method according to claim 4, wherein the sccm is 20 to 60 Pa, the RF power density is 2.2 to 4.4 W / cm ² .