JPH04267337A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a contact hole without a metal crown by forming a contact hole through dry etching and thereafter by injecting a reactive ion obliquely into the contact hole to conduct an etching treatment. CONSTITUTION:An insulating film 12, substrate wiring Al film 13 and insulating film 14 are formed on a semiconductor substrte 11. A resist film is formed by application and thereafter an etchback is conducted so that the insulating film 14 is flattened. Then, a resist mask 15 is formed on this insulating film 14. A highly accurate contact hole 16 is formed in the insulating film 14 by RIE with intense ionicity via resist mask 15. Subsequently, such device as reactive ion-beam etching device capable of applying reactive ions with a directional property is used to inject the reactive ion 20 into the contact hole 16 at an angle larger than a predetermined angle theta so that Al crown 17 stuck to the sidewall of the resist mask 15 and insulating film 14 in the contact hole 16 is removed by etching.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing semiconductor devices such as VLSIs, and more particularly to the formation of contact holes without metal crowns.

0002

[Prior Art] In the manufacturing process of semiconductor integrated circuits, especially in the VLSI manufacturing process, pattern dimensions are becoming smaller and smaller.
The processing accuracy of dry etching is also becoming more stringent than before. Even in lithography technology, there are problems such as difficulty in patterning when forming contact holes when there is a large step difference in the base, and flattening or smoothing (hereinafter collectively referred to as flattening) has become essential. There is. Normally, planarization is performed by coating and forming a resist film on a surface having a step and etching it back. Then, to connect the wiring, a resist mask is formed on the flattened surface, contact holes are formed by dry etching, such as RIE (reactive ion etching), and then wiring material is deposited over the entire surface including the contact holes. , formed by CVD etc. (for example, forming an Al film,
Alternatively, a tungsten buried layer is formed in the contact hole by forming blanket tungsten (W) and etching back or selective tungsten CVD, and then forming an Al film on the entire surface), and then patterning to form a base conductive film, e.g. Upper layer wiring connected to the Al (or Al alloy) film is formed.

0003

[Problems to be Solved by the Invention] However, due to the above-mentioned planarization, new problems are occurring in dry etching. For example, in RIE, since the incident energy of reactive ions is used, sputtering of the underlying metal film during over-etching becomes a problem. That is, as shown in FIG. 3A, an insulating film 2 such as SiO2 and a base Al (or an Al alloy such as Al-Si) are formed on a semiconductor substrate 1 on which an element is formed.
A film 3, for example, an insulating film 4 such as a SiN film by plasma CVD, is sequentially formed, and after planarization, a contact hole 6 is formed in the insulating film 4 by RIE through a resist mask 5. During over-etching, the underlying Al (or Al The alloy film 3 is sputtered, evaporated and diffused to form an Al deposit 7 called an Al crown on the inner wall surface of the hole. In severe cases, this Al crown 7 remains even after the resist mask 5 is removed, as shown in FIG. 3B, and causes trouble in the subsequent wiring process.

[0004] This Al crown 7 is reduced by reducing overetching, but as shown in FIG. 4, after planarization, the Al (or Al alloy) film pattern 3 on the top of the step
If contact holes 6A and 6B reaching A and the Al (or Al alloy) film pattern 3B at the bottom of the step are simultaneously formed by RIE, the shallower the contact hole 6A, the more excessive over-etching will occur because the thickness of the insulating film 4 to be processed is different. Therefore, Al crown 7 in shallow contact hole 6A
occurrence cannot be prevented.

In particular, when forming the contact hole 6 by RIE, the stronger the ionicity (that is, the incident energy of reactive ions), the more accurate the contact hole can be obtained.
On the other hand, because of its strong ionicity, an Al crown 7 is generated. Furthermore, if the extent of the Al crown 7 is slight, it may be accidentally removed when removing the resist mask 5 or during post-processing, but the removed Al crown 7 becomes dust and has a negative impact on semiconductor device manufacturing. It is something that gives rise to As described above, the problem of the Al crown 7 essentially occurs when the thickness of the insulating film 4 to be processed by planarization etc. differs depending on the location, and a solution to this problem has been desired.

In view of the above-mentioned points, the present invention provides a method for manufacturing a semiconductor device that makes it possible to form a contact hole without a so-called metal crown.

[0007]

[Means for Solving the Problems] The present invention provides a base metal film 1
A step of forming a contact hole 16 in the insulating film 14 on the insulating film 14 by dry etching, and a step of etching away the metal crown 17 produced by the dry etching by injecting reactive ions 20 obliquely into the contact hole 16. It is characterized by having.

[0008]

[Operation] In the present invention, after forming the contact hole 16 by dry etching, the contact hole 1
By etching the hole 6 by obliquely injecting reactive ions 20 into the hole 6, only the metal crown 17 formed on the inner wall surface of the hole is selectively removed without affecting the base metal film 13. Therefore, a contact hole without a metal crown is formed.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In this example, as shown in FIG. 1A, an insulating film 12, an Al (or Al alloy) film 13 as a base wiring, and an insulating film 14 are sequentially formed on a semiconductor substrate 11 on which elements are formed. Here, in order to flatten the surface level difference (not shown), after a resist film is applied and formed, etchback is performed to flatten the insulating film 14. Then, a resist mask 1 with a predetermined pattern is placed on this insulating film 14.
form 5.

Next, as shown in FIG. 1B, the insulating film 14 is removed by highly ionic RIE through the resist mask 15.
A highly precise contact hole 16 is formed in. Since this contact hole 16 is shallow, excessive overetching is performed when other deep contact holes are simultaneously formed, and as a result, the underlying Al (or Al alloy) film 13 is sputtered and a so-called Al crown 17 is generated. still,
This Al crown 17 is attached to the side walls of the insulating film 14 and the resist mask 15, and contains Al, C, and F as its components.
, O, etc. Since it cannot be removed even by ashing, it is thought that stable Al, F, and Al2O3 are also contained, but they are difficult to remove by radical reactions.

Next, as shown in FIG. 2C, a device capable of directionally irradiating reactive ions, such as RIBE (reactive ion beam etching), is used to irradiate the semiconductor substrate 11 with contact holes 16. θ=tan when the hole diameter is A and the hole depth is B for
The reactive ions 20 are incident at an angle larger than the angle θ expressed by -1 (A/B), and the Al deposited on the resist mask 15 and the side wall of the insulating film 14 in the contact hole is
The crown 17 is removed by etching. Since the angle θ is determined by the aspect ratio of the contact hole 16, it may be appropriately determined depending on the contact hole 16 in which the Al crown 17 is formed. The Al crown 17 attached to the side wall of the insulating film 14 is not particularly problematic;
Since ions adhering to the side walls of the resist film 15 pose a problem, directional reactive ions 20 are obliquely incident on the contact hole 16 so that they adhere to at least the side walls of the resist mask 15 and form an Al crown. 17 is removed.

[0013] As the reactive gas, Cl2, BCl3
, a chlorine-based gas containing Cl such as HCl, or a mixed gas of a rare gas such as Ar and a chlorine-based gas, etc. can be used. In order to uniformly inject the reactive ions 20 into the resist mask 15 and the sidewalls of the insulating film 14, the semiconductor substrate 11 (so-called wafer) may be rotated or the direction of the wafer may be changed during etching.

Thereafter, as shown in FIG. 2D, the resist mask 15 is removed, and a wiring material such as an Al film is deposited on the entire surface including the inside of the contact hole 16 by vapor deposition or the like.
Next, patterning is performed to form an Al upper layer wiring 18 connected to the underlying Al (or Al alloy) film 13.

Alternatively, after the process shown in FIG. 2C (not shown), a tungsten buried layer is formed in the contact hole 16 by, for example, forming a blanket tungsten layer and performing etching back or selective tungsten CVD. Next, an Al film is formed in contact with the tungsten buried layer,
After patterning, the base A is formed through the tungsten buried layer.
An Al upper layer wiring connected to the Al (or Al alloy) film 13 is formed.

According to the above-described manufacturing method, after the contact hole 16 is formed in the insulating film 14 on the Al (or Al alloy) film 13 by RIE, an apparatus capable of directionally irradiating reactive ions such as RIBE is used. By obliquely injecting the reactive ions 20 using the method, the Al crown 17 generated by RIE can be etched away. Moreover, in this case, only the Al crown 17 attached to the side wall of the hole is removed, and the underlying Al (or Al alloy) film 13 facing the contact hole 16 is not affected by etching at all. Therefore, after that, through the contact hole 16, the Al upper layer wiring 18 and the underlying Al (or Al
(Alloy) can be well connected to the membrane 13.

In the above example, the Al-based film 1 is used as the base metal film.
3 was used, but the present invention is also applicable to cases where W, WSix, etc. are used.

[0018]

According to the present invention, it is possible to form a contact hole without a metal crown, and the upper layer wiring and the underlying metal film can be well connected through the contact hole. Therefore, it is suitable for application to, for example, the manufacture of ultra-LSIs that require fine contact holes.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram (Part 1) of an example of the present invention.

FIG. 2 is a manufacturing process diagram (Part 2) of an example of the present invention.

FIG. 3 is a manufacturing process diagram for explaining the conventional method.

FIG. 4 is a cross-sectional view for explaining the conventional technology.

[Explanation of symbols]

1 Semiconductor substrate 2 Insulating film 3 Al (or Al alloy) film 4 Insulating film 5 Resist mask 6 Contact hole 7 Al crown 11 Semiconductor substrate 12 Insulating film 13 Al (or Al alloy) film 14 Insulating film 15 Resist mask 16 Contact hole 17 Al crown 18 Upper layer wiring 20 Reactive ions

Claims (1)

[Claims] 1. A step of forming a contact hole by dry etching in an insulating film on a base metal film, and etching a metal crown produced by the dry etching by injecting reactive ions obliquely into the contact hole. A method for manufacturing a semiconductor device, comprising a step of removing.