JPH05259294A - Formation of wiring - Google Patents

Abstract

PURPOSE:To produce a connection hole having a superior step coverage in a method for forming a wiring of an integrated circuit or the like. CONSTITUTION:After a dielectric film 12 has been formed to cover the surface of a substance 10 to be connected made of a semiconductor substrate or a wiring layer, a resist layer 30 having a hole 30a is formed on the dielectric film 12. A recess corresponding to the hole 30a is formed on the dielectric film 12 by anisotropic dry etching with the use of the resist layer 30 as a mask. Then this is also subjected to isotropic dry etching with the use of the resist layer 30 as a mask. This causes the recess to be deformed into a pot-shaped recess 32b with its opening progressively increased in size toward the outside. Thereafter, an internal hole 32c is formed by anisotropic etching with the use of the resist layer 30 as a mask, whereby a connection hole 32 made up of the recess 32b and the internal hole 32c is obtained. After the resist layer 30 has been removed, a wiring layer that extends from the inside to the outside of the connection hole 32 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming method used for manufacturing an integrated circuit such as an LSI, and more particularly to anisotropic etching, isotropic etching and the like when forming a contact hole in an insulating film by selective etching. By performing anisotropic three-step etching, a connection hole with good step coverage can be obtained.

[0002]

2. Description of the Related Art Conventionally, as a wiring forming method for an LSI or the like,
It is known that a connection hole is formed as shown in FIG. That is, the insulating film 1 of silicon oxide or the like is formed so as to cover the surface of the connected body 10 formed of the semiconductor substrate or the wiring layer.
After forming 2, the concave portion 14a is formed in the insulating film 12 by isotropic etching using the resist layer as a mask, and then the inner hole 14b is formed by anisotropic etching using the same resist layer as the mask. Then, after removing the resist layer, a wiring material is applied to the inside of the connection hole 14 formed of the concave portion 14a and the inner hole 14b and the upper surface of the insulating film 12 to perform patterning, thereby wiring from the inside of the connection hole 14 to the outside. Form the layers.

In the connection hole forming method shown in FIG. 7, the connection hole 1
Since a sharp edge is formed at the opening end portion A of No. 4, there is a problem that the step coverage of the wiring material is not good and the wiring layer from the inside of the connection hole 14 to the outside is easily broken.

As a first method for solving such a problem, there is known a method of removing a sharp edge of the opening end A by isotropic etching after forming a connection hole (for example, a special method). Japanese Unexamined Patent Publication No. 64-84222, Japanese Patent Laid-Open No.
-116129 gazette).

As a second method for solving the above problems, as shown in FIG. 8, a silicon oxide film 12A, a silicon nitride film 12B and an amorphous silicon film 12C are formed on a silicon substrate 10A. A method is known in which after forming the three-layer film 13, the connection hole 14 is formed in the three-layer film 13 by isotropic etching and anisotropic etching in the same manner as described with reference to FIG. No. 1-280317).

In the isotropic etching process of the three-layer film 13,
A portion corresponding to the opening end of the connection hole 14 is processed so as to gradually increase the opening size. For this reason, when the wiring layer 16 is formed after the formation of the connection hole 14, the opening end of the connection hole 14 is smooth, so that the wiring layer 16 can be prevented from being broken.

[0007]

According to the above-mentioned first method, the size of the contact hole becomes too large during the second isotropic etching, and the surface layer of the wiring layer is removed in the contact hole. There was an inconvenience. For example, as shown in FIG. 7, the connected body 10 is a wiring layer, and WSi ₂ , M is formed on the wiring layer.
When the surface layer 10a of oSi ₂ , TiW or the like is formed, if the second isotropic etching is performed using a fluorine-based gas such as CF ₄ , NF ₃ or the like, the surface layer 1 is formed in the connection hole 14.
0a is often etched away. Without the surface layer 10a, it becomes difficult to form a good ohmic contact with the upper wiring layer.

Further, according to the above-mentioned second method, when the wiring layer 16 is made of Al or an Al alloy, excess silicon supplied from the amorphous silicon layer 12C is deposited in the wiring layer 16 to form the silicon nodules SN. To do.
This silicon nodule SN is connected to the connection hole 2 of the insulating film 18.
0 may be blocked and a low resistance connection with the upper wiring layer 22 may be obstructed. The generation of the silicon nodules SN is more remarkable when a refractory metal silicide such as WSi ₂ or MoSi ₂ is arranged as a barrier metal layer under the wiring layer 16. Since the three-layer film 13 is formed in the second method,
There is also a problem that the process becomes complicated.

An object of the present invention is to provide a novel wiring forming method capable of easily obtaining a connection hole having good step coverage.

[0010]

The wiring forming method according to the present invention comprises: (a) a step of forming an insulating film to cover the surface of a body to be connected; and (b) a hole exposing a part of the insulating film. Forming a resist layer having the same on the insulating film; and (c)
Forming a recess in the insulating film corresponding to a hole in the resist layer by anisotropic etching using the resist layer as a mask; and (d) isotropic using the resist layer as a mask after the anisotropic etching. And (e) anisotropically using the resist layer as a mask after the isotropic etching, by performing anisotropic etching to transform the recessed portion into a pot-shaped recessed portion whose opening size gradually increases toward the outside. Forming an inner hole that is continuous with the pot-shaped recess and reaches a part of the connected body by performing a reactive etching,
(F) After removing the resist layer, a step of forming a wiring layer extending from the connected body to the insulating film via a connection hole formed of the pot-shaped recess and the inner hole is included.

[0011]

According to the method of the present invention, the isotropic etching is performed after the anisotropic etching to form the pot-shaped concave portion whose opening size gradually increases toward the outside. When the wiring material is applied after the hole is formed, the opening end of the connection hole has a smooth shape, so that the step coverage is improved and the disconnection can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 6 show a wiring forming method according to an embodiment of the present invention. Steps (1) to
(6) will be sequentially described.

(1) After forming an insulating film 12 of silicon oxide or the like on a semiconductor substrate of silicon or the like or a wiring layer 10 of a wiring layer of Al alloy or the like, an insulating film 12 of silicon oxide or the like is formed on the insulating film 12 by a well-known spin coating method or the like. Then, a resist layer 30 is formed.
Then, a hole 30a corresponding to a desired connection hole is formed in the resist layer 30 by photolithography.

(2) Next, a recess 32a corresponding to the hole 30a is formed in the insulating film 12 by anisotropic dry etching using the resist layer 30 as a mask. The anisotropic dry etching process is, for example, reactive ion etching (RIE).
Can be performed by using an apparatus, and as a processing gas, C
HF ₃ / He / O ₂ or CF ₄ / CHF ₃ / Ar can be used.

(3) Next, the resist layer 30 is used as a mask to perform isotropic etching to transform the concave portion 32a outward so as to be transformed into a pot-shaped concave portion 32b whose opening size gradually increases. The isotropic etching process can be performed using a chemical dry etching (CDE) device or a parallel plate type plasma etching device, and the processing gas is CF.
₄ / O ₂ , NF ₃ or SF ₆ can be used.
When the isotropic etching is performed using the parallel plate type plasma etching apparatus, it is preferable to perform the etching at a relatively high pressure using a gas that does not form the sidewall protection film.

As an example, a depth of about 400 [nm] is obtained by using an RIE device using CHF ₃ / He / O ₂ as a processing gas.
After forming the concave portion 32a, isotropic etching of about 200 [nm] was performed using a CDE device using CF ₄ / O ₂ as a processing gas, and a preferable pot-like shape with rounded open end was formed. As a result, the concave portion 32b was obtained. On the other hand, isotropic etching of about 200 [nm] was performed using a CDE apparatus using CF ₄ / O ₂ as a processing gas without forming the recess 32a. Only a relatively shallow recess with an edge at the open end as shown was obtained.

(4) Next, anisotropic etching using the resist layer 30 as a mask is performed in the same manner as in FIG. 2 to form an inner hole 32c which is continuous with the recess 32b and reaches the connected body 10. The connection hole 32 including the recess 32b and the inner hole 32c is obtained.

(5) Next, the resist layer 30 is removed by an ashing process or the like, and a cleaning process is performed if necessary.

(6) Thereafter, a wiring material such as an Al alloy is deposited on the inside of the connection hole 32 and on the insulating film 12 by a sputtering method or the like. At this time, since the opening end of the connection hole 32 has a smooth and rounded shape, the step coverage of the wiring material becomes extremely good and disconnection can be prevented. Next, the deposition layer of the wiring material is patterned by the selective etching process to form the wiring layer 34 extending from the connection target 10 to the insulating film 12 through the connection hole 32.

The above-mentioned anisotropic, isotropic and anisotropic three-step etching does not necessarily have to be performed by different etching apparatuses, and the same apparatus can be used by changing etching conditions such as gas components and pressure. You may do it.

[0021]

As described above, according to the present invention, since a connection hole with good step coverage can be obtained by three-step etching including anisotropic etching, isotropic etching and anisotropic etching, It is possible to obtain the effect of preventing disconnection and connection failure that occur in the wiring layers from the inside to the outside.

In addition, (a) since the third step is anisotropic etching, the size of the connection hole becomes too large,
There are advantages that the wiring surface layer is not undesirably removed in the connection hole, and that the (b) insulating film has a single-layer structure, so that the process is simple.

[Brief description of drawings]

[Figure 1]

FIG. 6 is a substrate cross-sectional view showing a wiring forming method according to an embodiment of the present invention.

FIG. 7 is a substrate cross-sectional view for explaining a conventional connection hole forming method.

FIG. 8 is a sectional view of a substrate for explaining a conventional wiring forming method.

[Explanation of symbols]

10: Connected object, 12: Insulating film, 30: Resist layer, 3
2: Connection hole, 34: Wiring layer.

Claims (1)

[Claims] 1. A process of forming an insulating film covering a surface of an object to be connected, and a resist layer having a hole exposing a part of the insulating film is formed on the insulating film. And (c) forming a recess in the insulating film corresponding to a hole in the resist layer by anisotropic etching using the resist layer as a mask, and (d) the resist layer after the anisotropic etching. Performing isotropic etching with the mask as a mask to transform the concave portion into a pot-shaped concave portion whose opening size gradually increases toward the outside, and (e) the resist layer after the isotropic etching. Forming an inner hole which is continuous with the pot-shaped recess and reaches a part of the connected body by performing anisotropic etching using the mask as a mask, and (f) after removing the resist layer, Pan-shaped recess and inside Wiring formation method comprising forming a wiring layer extending on the insulating film connecting hole from the object to be connected via a consisting.