JPH04355918A - Dry etching method for high melting point metal material - Google Patents

Abstract

PURPOSE:To improve the controllability in the neighborhood of the endpoint by a method wherein an etching treatment is conducted in a condition rich in sulphur fluoride gas, and another etching treatment is conducted in the vicinity of the etching endpoint in a hydrogen-bromide-gas rich condition. CONSTITUTION:A wafer W is etched at high speed using HBr/SF6 gas in an etching process to be conducted under the prescribed condition rich in sulphur fluoride gas. A chemical vapor-deposition buried part 1a and an overgrowth part 1b are generated in a contact hole 3, and a high melting point metal material 1, which is the part to be etched, is constituted by the above-mentioned 1a and 1b. Then, the high melting point metal material 1 is etched at low etching speed under the prescribed condition by an etching process which is rich in hydrogen promide gas. By the above-mentioned etching treatment, a burying work is completed, and a a flattened structure is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dry etching high melting point metal materials. The present invention can be applied to various fields using high-melting point metal materials, such as processing and forming a high-melting point metal film or a high-melting point metal compound film during the production of electronic materials (semiconductor devices, etc.). It can be suitably used in some cases.

0002

BACKGROUND OF THE INVENTION In the field of electronic materials, particularly in the field of semiconductor devices, demands for miniaturization and integration are increasing. In addition to this, along with the demand for miniaturization, there is also a demand for high reliability and high speed. For example, in VLSI, W (tungsten), Ti (titanium), Mo (
molybdenum) and other high melting point metals, and their compounds (
Silicide, etc.) are being used as wiring materials. In particular, W has been applied as a suitable material for filling contact holes, etc., and is seen as a promising material that meets the requirements of VLSI.

As a method for forming and processing W, for example, a method for embedding W into a contact hole, a blanket W etch-back method shown in FIG. 3 or a selective W burying method shown in FIG. 4 can be considered.

The method shown in FIG. 3 involves applying W to a substrate 10 such as a semiconductor wafer (for example, a Si substrate), as shown in FIG.
A film is formed on the entire surface of the substrate (W formed on the entire required portion of the substrate in this way is called a blanket W), and
This is a method of burying the contact hole 3 formed in the upper insulating film 2 of SiO2, etc., and then etching it back by dry etching to flatten it as shown in FIG. 3(b). In FIG. 1A, the W portion buried in the contact hole 3 is shown as 1a, and the overgrowth portion formed on the base 10 is shown as 1b. Overgrowth part 1
b occurs because the depths of contact holes on the same substrate are not necessarily the same, and also because it is difficult to stop growth at the exact hole depth. The refractory metal material (W) 1 consisting of both parts 1a and 1b is etched to remove the overgrowth part 1b, leaving only the buried W part 1a as shown in FIG. 1(b), and forming a W wiring (W plug). form.

Similarly, the method shown in FIG.
When using a specific gas such as WF6, Si
Taking advantage of the property that W selectively grows only upward,
The contact hole 3 is filled from the bottom with W, and then filled in as shown in FIG.
) to obtain the structure. In the figure, 1a indicates the selective growth W that fills the inside of the contact hole 3, but at this time, the selective growth W protrudes from the contact hole 3 and a so-called nail head 1d is generated. Therefore, it is necessary to etch back and remove this nail head 1d to obtain the structure shown in FIG. 4(b).

[0006]

[Problems to be solved by the invention] As shown above, FIG.
In any of the techniques shown in FIG.
b (in the case of FIG. 3) or the nail head portion 1d (in the case of FIG. 4) is required, and therefore etchback by dry etching is required.

However, in the etch-back by dry etching, the area of the W portion (the etched portion) of the high melting point metal material 1 rapidly decreases near the interface with SiO2 forming the insulating film 2. The etching rate of W increases. That is, as a result, SiO2
(Insulating film material) It becomes difficult to control the end point of W etching at the interface. JP-A No. 61-95528 discloses a technique in which the high-frequency power source for plasma etching is set to high output at the beginning and then switched to low output, but this does not solve the above-mentioned problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for dry etching high melting point metal materials that can achieve dry etching of high melting point metal materials near the end point with good controllability. It is.

[0009]

[Means for Solving the Problems] The present invention provides a method for dry etching high melting point metal materials using hydrogen bromide gas and sulfur fluoride gas, comprising: This is a dry etching method for refractory metal materials in which etching is performed under conditions rich in sulfur fluoride gas at least at the beginning of etching, and etching is performed under conditions rich in hydrogen bromide gas near the end of the etching. The purpose has been achieved.

[0010] In this invention, the high melting point metal material is
It is a general term for high melting point metals such as W, Ti, Mo, alloys containing these metals or other metals, nonmetals, and/or compounds, and compounds of these metals such as silicide.

[0011] In this invention, the sulfur fluoride gas refers to a gas containing fluorine and sulfur as constituent elements. Examples include sulfur hexafluoride SF6, sulfur tetrafluoride SF4, sulfur monofluoride S2 F2, and sulfur difluoride SF2.

In this invention, etching is performed at least initially under conditions rich in sulfur fluoride gas, but at this time, etching may be performed only with sulfur fluoride gas, or with sulfur fluoride gas. Etching may be performed using a mixed gas of hydrogen bromide gas and hydrogen bromide gas under conditions rich in sulfur fluoride gas. The condition rich in sulfur fluoride gas means that the reactive species contributing to etching are mainly fluorine radicals. This allows high-speed etching to be achieved. It is preferable that the sulfur fluoride gas is contained in a flow rate of about 100 to 80%, and from the viewpoint of high-speed etching,
Particularly preferred is flow rate %. Among the sulfur fluoride gases, SF6 is preferable.

In the present invention, etching is performed under conditions rich in hydrogen bromide gas, at least near the end point of etching, but at this time, etching may be performed with only hydrogen bromide gas, or with hydrogen bromide gas and fluoride gas. Etching may be performed using a mixed gas with a sulfur oxide gas and under conditions rich in hydrogen bromide gas. Conditions rich in hydrogen bromide gas mean that the reactive species contributing to etching are primarily bromine radicals. This allows slow etching to be performed. The preferred content of the sulfur fluoride gas at this time is about 0 to 10% in flow rate.

[0014] When switching from conditions rich in sulfur fluoride gas to conditions rich in hydrogen bromide gas, the speed reduction effect may be further enhanced by, for example, simultaneously reducing the high frequency output. Further, the conditions may be changed discontinuously, stepwise, or continuously (such as gradually increasing the hydrogen bromide gas richness). The switching point can be determined at a time set in advance through trials. Further, the end point can be detected by, for example, an emission spectrum. The gas system under each condition is
In addition to the sulfur fluoride gas and/or the hydrogen bromide gas, other gases can also be added for dilution gas and other purposes.

The material to be etched to which the present invention is applied may be a high melting point metal material part for forming a semiconductor device, etc., but it is preferably applied to the etch back of a high melting point metal film. For example, W by blanket W-CVD
It can be suitably used for etching back a film or a selectively grown W film. Since the blanket W-CVD film has a greater problem of drastic reduction in W area when filling contact holes, it can be said that it can be effectively used for etchback in this case.

Any etching device may be used. EC
This can be carried out using any appropriate etching means, such as R etching, RIE, and magnetron etching. The present applicant has proposed in Japanese Patent Application No. 2-10489 a technique for etching a polycide film consisting of a high melting point metal silicide layer and a polycrystalline silicon layer using an etching gas made by adding at least HBr to a fluorine gas. It is carried out.

[0017]

According to the present invention, since etching is first performed under conditions rich in sulfur fluoride gas, high-speed etching can be achieved using fluorine radicals. Further, since etching is performed under conditions rich in hydrogen bromide gas near the end point of etching, etching is performed at a low speed due to bromine radicals, and etching can be realized with good controllability near the end point. Although the etching rate ratio between both conditions differs depending on other conditions, under conditions rich in hydrogen bromide gas, the etching rate can be reduced to 1/2 to 1/3, for example.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. However, it goes without saying that the present invention is not limited to the examples described below.

Example 1 In this example, the present invention is applied to the formation of a W film, which is a high melting point metal film, in the production of miniaturized and integrated semiconductor devices such as VLSI devices. In particular, this invention is utilized to fill W into contact holes formed in an interlayer insulating film.

In this example, HB is used as the etching gas.
By performing step etching using r (hydrogen bromide) gas and SF6 gas, etching can be performed with good controllability at the end point.

In this example, a magnetic field microwave etcher was used. An example of conditions for implementation in this case is shown below. In the case of this example, in Step 1, that is, an etching process under conditions rich in sulfur fluoride gas, W was replaced with HBr/S
Perform high-speed etching with F6 gas (or SF6 gas alone). The specific conditions are as follows. (Step 1) Pressure: 10mT Gas system used: SF6 = 50SCCM or HBr
/SF6 =10/40SCCM microwave power: 25
0mA RF bias: 40W

The material to be etched in this example is shown in FIG.
As shown in a of FIG.
A blanket W is used to fill the contact hole 3 formed in the upper interlayer insulating film 2 (SiO2 film here).
It is made by CVD. In addition to the CVD buried portion 1a in the contact hole 3, an overgrowth portion 1b is formed, and in FIG. This structure is etched under the gas-based conditions described above. As a result, etching is performed centering on fluorine radicals, and therefore high-speed etching is performed. It is thought that W mainly evaporates as fluoride. As a result, b in Fig. 1
As shown in FIG. 2, a structure is obtained in which only a thin portion of the overgrowth portion remains as a thin film portion 1c near the end point of etching.

Next, in step 2, that is, an etching step under conditions rich in hydrogen bromide, the high melting point metal material 1 (W part) is etched at a low etching rate under the following specific conditions. (Step 2) Pressure: 10mT Gas system used: HBr=50SCCM or HBr/SF
6 =45/5SCCM Microwave power: 200mA RF bias: 20W

In step 2, the structure shown in c in FIG. 2, which is the state in which step 1 in FIG.
) is etched at low speed under the above conditions. The etching rate in step 2 could be reduced to about 0.5 to 0.3 of the etching rate in step 1. Here, etching is performed mainly by bromine radicals, and W is thought to mainly volatilize as bromide. This etching results in a well-filled and flattened structure, as shown in FIG. 2d. In this step 2, the RF bias was set to 20 W, which was half of that in step 1, because it was desired to minimize the contribution of ionic etching. however,
If the RF bias is lowered, the etching rate may drop too much, so in such a case, it may be better to use a gas system containing a certain amount of SF6 instead of HBr alone.

In this step 2, etching is performed at a low speed, so the controllability of the etching end point is extremely good. Therefore, etching near the interface between the insulating film 2 made of SiO2 and the high melting point metal material 1 (W part) can be achieved satisfactorily. Further, since HBr gas has lower reactivity with W than SF6, the etching rate of W can be changed by changing the flow rate ratio of HBr/SF6 gas, and thereby the controllability of the end point can also be adjusted. Therefore, it is possible to further improve controllability.

It should be noted that the process conditions and the like in the above embodiments are merely examples, and it goes without saying that various conditions can be changed, and various embodiments can be adopted.

[0027]

According to the method of dry etching high melting point metal materials of the present invention, dry etching of high melting point metal materials can be achieved with good controllability near the end point.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an etching process under conditions rich in sulfur fluoride gas in Example-1.

FIG. 2 is a cross-sectional view showing an etching process under conditions rich in hydrogen bromide gas in Example-2.

FIGS. 3(a) and 3(b) are sectional views showing conventional examples.

FIGS. 4(a) and 4(b) are sectional views showing conventional examples.

[Explanation of symbols]

1 High melting point metal material

Claims (1)

[Claims] 1. A method for dry etching a high melting point metal material using hydrogen bromide gas and a sulfur fluoride gas, the method comprising: dry etching a high melting point metal material using hydrogen bromide gas and a sulfur fluoride gas; A dry etching method for refractory metal materials in which etching is performed under conditions rich in gas, and at least near the end point of etching is performed under conditions rich in hydrogen bromide gas.