JP3222453B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device with an improved etching process. INDUSTRIAL APPLICABILITY The present invention can be generally used for manufacturing a semiconductor device having a step of etching a high melting point metal silicide, and can be used, for example, in manufacturing a semiconductor device having a so-called high melting point metal polycide structure as a gate structure. .

[Summary of the Invention]

The present invention provides a method of manufacturing a semiconductor device, using pure hydrogen bromide gas or gas system was mixed rare gas hydrogen bromide or a gas-based mixed with N ₂ or O ₂ to, refractory metal By performing the silicide etching, it is possible to stably achieve etching with a good shape without using a harmful gas such as a fluorinated hydrocarbon compound.

[Conventional technology and its problems]

2. Description of the Related Art When manufacturing a semiconductor device, a technique including a step of etching a high-melting-point metal silicide is used. For example, metal silicide has been used as a gate material due to a demand for higher speed of an integrated circuit such as an LSI. This is because metal silicide has a resistance value about one digit smaller than that of polysilicon, and is therefore advantageous for speeding up. When metal silicide is used as a gate material and the reactivity with the underlying gate insulating film becomes a problem, it is often used as a so-called polycide structure in which metal silicide is stacked on polysilicon.

As described above, when manufacturing a semiconductor device using metal silicide, it is necessary to perform the metal silicide etching process. Conventionally, various methods have been developed and put into practical use for metal silicide etching techniques. Among them, currently the mainstream is fluorinated hydrocarbon gas,
That is, a method using a so-called Freon-based gas (Freon F113 or the like) called Freon or Freon as an etching gas. However, CFC-based gases cause environmental problems such as depletion of the ozone layer.
It is certain that it will not be usable in the future. Under such circumstances, there is an urgent need for anisotropic processing of metal silicide, for example, for etching a gate material having a polycide structure, a technique capable of performing the etching processing using a gas system other than a chlorofluorocarbon-based gas. I have.

The present applicant has been diligently conducting various research and development on this point, but depending on the gas system, the etching shape is affected by the change in the amount of reaction products due to the size of the area to be etched, and anisotropic processing is as desired. There are problems that do not progress,
It is not always easy to develop a new etching gas system.

In particular, in a polycide structure in which polysilicon is present under the metal silicide, two materials having different etching behaviors must be processed, and an etching gas between the metal silicide and polysilicon must be processed due to a difference in vapor pressure of a reaction product. Often, it is necessary to switch between conditions. For microwave plasma etching technology of metal polycide structure, especially tungsten polycide structure,
Monthly Semiconductor World, October 1989, 126-130
Although described on the page, the etching gas used here is also a fluorine-containing gas such as C ₂ Cl ₃ F ₃ and C ₂ ClF ₅ , and does not solve the problem of the harmful gas.

On the other hand, as a conventional technique for etching polysilicon,
There are documents showing RIE technology using hydrogen bromide gas (Moritak
a Nakamura et al. `` Variable Profile poly-Si Etching
with Low Temperature RIE and HBr gas '', 1988 DRY P
ROCESS SYMPOSIUM, II-5, Proceedings 58-63). However, this document does not mention the applicability of the refractory metal silicide to etching. It is presumed that the technique of this document did not consider the control of the accelerating voltage or the like, and therefore could not be considered to be used for silicide. In particular, the possibility of application to a high melting point metal polycide structure has not been suggested at all. Even if the technique disclosed in this document is simply used for etching the refractory metal silicide, there is a problem in good etching shape and etching stability.

[Object of the invention]

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a method for manufacturing a semiconductor device having an etching step using a gas system that can realize stable etching with a good shape without using a harmful gas.

[Means and actions for solving the problems]

The method of manufacturing a semiconductor device according to the present invention includes, first, a step of forming a convex portion made of a laminated film on a substrate by etching a laminated film made of a high-melting-point metal silicide and an underlying polysilicon film. In a method for manufacturing a semiconductor device, pure hydrogen bromide gas, or a gas system in which hydrogen bromide is mixed with a rare gas, or a gas system in which N ₂ or O ₂ is mixed with these gases is a reaction product of silicon. While forming the side wall protective film by the by-products, the upper refractory metal silicide is removed by etching, and subsequently, under the same conditions, the lower silicon film is etched under the same conditions, whereby the refractory metal silicide and The above-mentioned problem is solved by performing anisotropic etching of a laminated film made of the underlying silicon film to form a projection made of the laminated film. A.

The method of manufacturing a semiconductor device according to the present invention includes, secondly, a step of forming a projection made of the laminated film on the substrate by etching the laminated film composed of the high melting point metal silicide and the underlying polysilicon film. the method of manufacturing a semiconductor device, using pure hydrogen bromide gas or gas system was mixed rare gas hydrogen bromide or a gas-based mixed with N ₂ or O ₂ to, the sidewalls protected by a side reaction products While forming a film, while etching the laminated film composed of the refractory metal silicide and the underlying silicon film, the step of etching is performed by the refractory metal silicide and the refractory metal bromide which is a reaction product. The high-melting-point metal silicide in the upper layer is removed by etching under the acceleration voltage Vdc.
c) etching the underlying silicon film underneath to perform anisotropic etching of the laminated film composed of the refractory metal silicide and the underlying silicon film to form a convex portion composed of the laminated film. This solves the problem described above.

That is, according to the present invention, as the etching gas used in the etching step, a pure hydrogen bromide gas, a gas system in which hydrogen bromide is mixed with a rare gas, or a gas system in which these are mixed with N ₂ or O ₂ is used. Therefore, there is no need to use chlorofluorocarbon-based gas, so that it is possible to determine environmental problems and harmful gas regulations. And if the atom that contributes to the etching is bromine, it is less responsive than chlorine or fluorine,
With an etching gas containing a hydrogen bromide gas, for example, an undercut or the like hardly occurs, and good etching can be stably performed. Also, when the polycide structure is etched, it is not necessary to change the etching conditions, and an advantageous process can be performed.

In the present invention, as an etching gas used in the etching step, pure hydrogen bromide (HBr) gas can be preferably used, and a gas system in which hydrogen bromide is mixed with a rare gas such as Ar, He, Xc, or Kr is used. Can be used. Furthermore, N ₂
As a gas system mixed with O ₂ and O ₂ , it is possible to make use of these reactivities to exert, for example, a side wall protecting effect of the etching material.

In addition, bromine (Br ₂ ) gas can be considered as one that generates reactive bromine atoms, but it has a boiling point (easy to condense),
Hydrogen bromide is superior in terms of toxicity and other ease of handling.

The etching means can be suitably applied to dry etching such as RIE and plasma etching, and the etching conditions can be appropriately selected according to the type of the material to be etched, the gas system to be used, and the desired etching process.

In the present invention, as the high melting point silicide to be etched, for example, tungsten silicide (WSi
₂ ), molybdenum silicide (MoSi _{2 and the} like), titanium silicide (TiSi _{2 and the} like), tantalum silicide (TaSi _{2 and the} like), and other silicides of various refractory metals can be used. Tungsten silicide is suitably used as a gate material, and etching it is one preferred embodiment of the present invention.

The present invention may be implemented so as to process by partially removing the high melting point metal silicide, or may be implemented so as to completely remove the high melting point metal silicide.

In the present invention, it is preferable to perform the etching under ion energy such that a reaction product such as a refractory metal silicide or a bromide thereof can be sputtered.

Although the mechanism at the time of etching in the present invention is not necessarily clear, the high melting point silicide itself or a reaction product generated by reacting the high melting point silicide with a bromine atom provided from hydrogen bromide is sputtered, and etching is performed by the sputter. (Or will be started). It is not clear whether the sputter occurs only at the beginning of the reaction or during the process of chemically etching, but at least the refractory metal silicide or the high-melting metal bromide which is the reaction product is sputtered by ions that can be sputtered. Etching under an accelerating voltage Vdc yields favorable results.

According to the study of the present inventors, it is preferable that the acceleration voltage Vdc be 300 volts or more. Further, etching can preferably proceed in the range of 300 volts to 500 volts.
The acceleration voltage Vdc is determined, for example, by the difference between the substrate to be etched and the plasma potential in the case of plasma etching, and determines the incident energy of ions. Such an accelerating voltage Vdc of the DC voltage component is applied by a self-bias without being specially applied depending on the device condition, but it may be controlled so as to be in the range of the accelerating voltage Vdc. .

In the etching step of the present invention, a bromide of silicon is generated. In the present invention, the bromide can be used for protecting the side wall of the structure to be etched. In addition, various members of the device, for example, a cathode covers and or residual gas and carbon present in such a mask sputtering was oxygen, side reaction product of a nitrogen (e.g., Si _x O _y and Si _x N _y
) Can be used for sidewall protection. Since such by-products are generally generated unless strictly prevented, they can be used for side wall protection by setting conditions corresponding to the etching conditions. . If it is desired to further obtain the side wall protection effect, N ₂ or O ₂ may be added to the gas system as described above. When such shape control is performed, optimal conditions can be determined for each desired shape.

Next, according to the method of the present invention, even when etching the polycide structure in which the polysilicon layer is present under the high melting point metal, the etching can be continuously performed using the same gas system under the same conditions. Therefore, in manufacturing a semiconductor device having a process including etching of a polycide structure,
It can be said that it can be preferably used.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Needless to say, the present invention is not limited to the embodiments described below, and can take various aspects.

In the present embodiment, the present invention is applied to the manufacture of a semiconductor device using a W (tungsten) silicide film as a gate structure material, in particular, a W polycide structure composed of a W silicide film and a polysilicon film underlying the W silicide film.

That is, as shown in FIG. 1A, the structure to be etched in this embodiment is formed on the gate insulating film 2 on the substrate 1.
It has a polycide structure in which a polysilicon film 3 and W silicide (WSi _x ), which is a high melting point silicide 4, are laminated. In particular, the polycide structure in this embodiment uses polysilicon doped with impurities, so-called DOPOS, as the polysilicon film 3 under the high-melting-point silicide 4. Further, the substrate 1 of this example is a silicon substrate, and the gate insulating film 2 is an SiO ₂ film. In FIG. 1A, reference numeral 5 denotes a photoresist (P
R).

Dry etching was performed under the following etching conditions.

Etching gas: HBr, flow rate 10 SCCM Gas pressure: 1.0 Pa RF power: 300 W Etching temperature: 15 ° C. Etching equipment: Discharge parallel plate plasma etching equipment Under these conditions, the ion acceleration voltage Vdc was 300 V.
The preferred range of the acceleration voltage is 300 to 500 V, and the lower limit is used in the present embodiment. However, considering the influence on the underlying layer, the smaller the acceleration voltage Vdc is, the more preferable it is.
The accelerating voltage Vdc at which the necessary sputtering is performed is 300 V, which is close to the minimum. This aims to achieve desired etching while minimizing the influence on the underlying layer. If the acceleration voltage Vdc exceeds 500V,
Depending on the conditions, carbonization of the resist may proceed.

In this embodiment, the ion species generated in the HBr plasma are accelerated by the voltage Vdc, etching the DOPOS a WSi _x or polysilicon 3 is a refractory metal silicide 4. Bromine atoms are less reactive than atoms such as fluorine and chlorine that have been used in the past, so they are less likely to undercut, thus preventing scuffing of etched sidewalls and making it more anisotropic. Processing can be performed.

In this embodiment, since the bromide of W (WBr _x ) has a low vapor pressure, it is considered that the etching proceeds by the sputtering with the high Vdc. Also, among the reaction products, SiBr _x
Is unstable due to unstable bonding, so the cathode cover (generally Si
O ₂ ) Reacts with oxygen O coming out, etc., and more stable Si _x O _y
It is considered that a side reaction product is formed. It is considered that such a side reaction product becomes a sidewall protective film during the etching and contributes to improving the etching shape.

FIG. 1B shows the shape after the etching as described above. Reference numeral 6 in the drawing schematically depicts a side wall protective film made of a by-product.

In the present embodiment, the metal silicide 4 is a high melting point metal.
In the etching of both layers of WSi _x and DOPOS which is polysilicon 3, good anisotropic etching could be realized in one step without changing discharge conditions at all.

As described above, in this embodiment, the present invention is applied to the etching of the polycide structure so that the high-melting-point silicide layer and the polysilicon layer can be continuously etched under the same conditions. This proves to be extremely effective in etching the structure.

However, when the present invention is used for etching the polycide structure as in this embodiment, the etching of the polysilicon 3 under the high melting point silicide 4 is performed in two steps by changing the conditions, such as performing the etching at a lower pressure than the high melting point silicide 4. Of course, it may be done.

〔The invention's effect〕

As described above, in the method for manufacturing a semiconductor device of the present invention, since the high-melting metal silicide is etched using at least a gas containing hydrogen bromide, it is not necessary to use a problematic gas such as a fluorocarbon-based gas, and The etching can be stably performed with a simple shape, and can be effectively performed by an easy process when applied to, for example, etching of a polycide structure.

[Brief description of the drawings]

1 (a) and 1 (b) show an embodiment of the etching method of the present invention. FIG. 1 (a) shows a sectional structure before etching, and FIG. 1 (b) shows a sectional structure after etching. It is. 1 ... substrate, 2 ... gate insulating film, 3 ... polysilicon (DOPOS film), 4 ... high melting point silicide (WSI _x film).

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-82120 (JP, A) JP-A-3-127826 (JP, A)

Claims (2)

(57) [Claims] In a method of manufacturing a semiconductor device, a method of manufacturing a semiconductor device having a step of forming a convex portion made of a laminated film on a substrate by etching a laminated film made of a refractory metal silicide and a polysilicon film underlying the same is provided. Hydrogen gas, or a gas system in which hydrogen bromide is mixed with a rare gas, or
Using a gas system in which N ₂ or O ₂ is mixed, while forming a sidewall protective film by a side reaction product which is a reaction product of silicon, an upper layer high-melting metal silicide is removed by etching, and then continuously, Under the same conditions, by etching the underlying silicon film, the anisotropic etching of the laminated film composed of the refractory metal silicide and the underlying silicon film is performed to form a convex portion composed of the laminated film. A method for manufacturing a semiconductor device. 2. A method of manufacturing a semiconductor device, comprising the step of forming a convex portion made of a laminated film on a substrate by etching a laminated film made of a refractory metal silicide and a polysilicon film as a base thereof. Hydrogen gas, or a gas system in which hydrogen bromide is mixed with a rare gas, or
Using a gas system in which N ₂ or O ₂ is mixed, while etching the laminated film composed of the refractory metal silicide and the underlying silicon film while forming a side wall protective film by a by-product, an etching step is performed. The high-melting metal silicide and the high-melting metal silicide in the upper layer are etched away under the accelerating voltage Vdc of ions that can be sputtered with the high-melting metal silicide and the reaction product. Etching the lower silicon film underneath to perform anisotropic etching of the laminated film composed of the refractory metal silicide and the underlying silicon film to form a convex portion composed of the laminated film. A method for manufacturing a semiconductor device, comprising: