JPH04320029A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a contact structure of high diffusion barrier performance by forming a film decomposed by reaction of a high melting point metal film and Si between a high melting point metal film and a silicon layer before nitriding treatment of a high melting point metal film. CONSTITUTION:An SiO2 9 is formed by thermal oxidation over the surface of a necessary region of a high-doped diffusion layer 5 exposed by contact hole formation, and a Ti film 5 is deposited over the whole surface by sputtering. R.T.A heat treatment is made in an N2 atmosphere for about 700 deg.C 30sec to nitrify most of the Ti layer 5 into a TiN film 7. At this time, a TiSi2 layer 6 is formed between the TiN film 7 and the high-doped diffusion layer 3. Thereafter, an Al film 8 is formed over the whole face, the part other than an unnecessary region is patterned together with the TiN film 7 by photoetching. Hereupon, the Ti layer 5 reduces the SiO2 layer 9 gradually, and some of the TiSi2 layer 6 is formed. This process enables suppression of restriction in nitride film thickness and deterioration in junction characteristics.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for forming contact holes for forming wiring in a semiconductor device using a nitrided high melting point metal film as a barrier metal.

0002

[Prior Art] When forming Al wiring between conductive layers of a semiconductor device, the conventional method is to bond a sputtered Al film containing Si directly to a high concentration diffusion layer on a Si substrate exposed at a contact hole. there were. Recently, Si
It has become a problem that the characteristics deteriorate due to the intrusion (spike) of Al into the substrate and the precipitation of high-resistance Si lumps at the bonding interface. Therefore, as shown in FIG. 3, a second metal film (barrier metal film) 7 for restricting the diffusion of Al or Si is formed between the high concentration diffusion layer 3 and the Al film 8 to solve the above problem. A solution is being considered.

One of the methods is to form a titanium nitride (TiN) film 7 as a barrier metal film between the high concentration diffusion layer 3 and the Al film 8, as shown in FIG. A method for manufacturing this structure is shown in sequence in FIG. First, as shown in FIG. 5(a), a Ti film 5 is formed on the entire surface of the high-concentration diffusion layer 3 in a state in which a necessary portion of the high concentration diffusion layer 3 is exposed by forming a contact hole, and then in a nitrogen (N2) gas atmosphere. A short heat treatment is performed to cause the Ti film 5 to react with N2 gas, as shown in Fig. 5(b).
), a TiN film 7 is formed as a barrier metal, and as shown in FIG.
The N film 7 is removed and a TiN film structure shown in FIG. 4 is formed.

0004

However, according to the above-mentioned method, as shown in FIG.
A silicite reaction occurs between TiSi2 and Ti film 5.
Layer 6 is formed.

[0005] Here, the TiSi2 layer 6 has a lower ability to restrict the aforementioned diffusion of Al or Si than the TiN film 7. Furthermore, the formation of the TiSi2 layer 6 promotes the diffusion of Ti into the high concentration diffusion layer 3, and the thicker the TiSi2 film 6, the worse the junction characteristics.

[0006] The TiN film 7 and TiS on this high concentration diffusion layer
Formation of the i2 film 6 proceeds as shown in FIG. Figure 2 (
A Ti film 5 formed on the silicon layer 1 as shown in a)
is heat-treated in a N2 atmosphere, and a TiN film 7 is formed on its surface due to a reaction with N2, while a TiN film 7 is formed at the interface with the silicon layer 1 due to a reaction between silicon and Ti.
An iSi2 film 6 is formed. These reactions are shown in Figure 2(b)
) as shown by the arrows, and the reaction ends when the Ti film necessary for both reactions is used up, as shown in FIG. 2(c).

Under the heat treatment conditions necessary for forming a TiN film, the reaction between the silicon layer and Ti occurs at the same time as the formation of the TiN film since they are in contact with each other. Ti as a condition
A TiSi2 film having a thickness of N or more is formed. TiSi2
Generally speaking, the thicker the film, the more likely the bonding characteristics will deteriorate if the bonding depth is the same.

For this reason, the film thickness of TiSi2 is determined so as not to affect the bonding characteristics.
This limits the film thickness, which affects the ability to prevent Al or Si diffusion.

In other words, if a sufficiently thick TiN film is to be formed using the above method, the TiSi2 film will also become thick, resulting in deterioration of the bonding characteristics.

[0010] Furthermore, let us assume that the deterioration of the bonding properties is caused by Ti.
Even if the diffusion of Ti during Si2 formation can be suppressed by optimizing the formation conditions, in order to increase the TiN film thickness, it is necessary to increase the thickness of the sputtered Ti film, as shown in Figure 2 (a). The diameter of a contact opening that allows a Ti film to be formed with good coverage increases, making it difficult to form an element having fine contacts.

An object of the present invention is to suppress the silicidation reaction that occurs simultaneously with the nitridation reaction of a high-melting point metal, and to form a necessary nitride film regardless of the formation of silicide.

0012

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a structure between the high melting point metal film and the silicon layer (which has a higher generation energy than the oxide of the high melting point metal) before nitriding the high melting point metal film. By forming a film that has a high melting point and is decomposed by the reaction between the high melting point metal and Si, the formation of silicide during the formation of the nitride film is suppressed.

[0013]

[Operation] As described above, the present invention forms a second film between the high melting point metal film and the silicon layer, so that it is difficult to form a nitride film barrier layer that is conventionally introduced into the contact region by thermal nitridation. This makes it possible to sufficiently suppress the limitations on nitride film thickness and the deterioration of bonding properties caused by silicide reactions.
It becomes possible to form contacts with higher diffusion barrier performance than before.

Furthermore, the refractory metal film required to obtain the necessary nitride film can be made much thinner than in the conventional example, and the desired structure can be formed with good coverage.

[0015]

[Example] Figure 1 shows a thin TiSi2 layer according to the present invention.
An example of a method for forming a contact with an iN barrier metal layer is shown.

First, as shown in FIG. 1(a), a SiO2 layer 9 of about 50 Å is formed by thermal oxidation on the surface of the high concentration diffusion layer 3 where the required region is exposed by forming a contact hole, and then the entire surface is Then, a Ti film 5 of about 500 Å is deposited by sputtering.

Thereafter, as shown in FIG. 1(b), the R.I.C. T. A. Perform heat treatment,
Most of the Ti layer 5 is nitrided to form a TiN film 7. At this time, a TiSi2 layer 6 of 100 Å or less is formed between the TiN film 7 and the high concentration diffusion layer 3. Thereafter, as shown in FIG. 1(c), an Al film 8 is formed on the entire surface, and areas other than unnecessary areas are patterned together with the TiN film 7 by photolithography.

TiN film 7 and TiSi2 formed by this method
Formation of the film 6 proceeds as shown in FIG.

First, as shown in FIG. 6(a), the Ti layer 5 formed on the silicon layer 1 via the SiO2 layer 9 is
Due to the heat treatment inside, the formation of a TiN layer progresses from the surface. On the other hand, between the Ti layer 5 and the silicon layer 1 is a SiO2 layer 9.
Due to the presence of Ti, as shown in Fig. 2(b)
It does not react in the same way as the N layer. However, here, the Ti layer 5 is
Gradually reduce the SiO2 layer 9 and some TiSi2
Layer 6 is formed.

However, this TiSi2 layer 6 is as shown in FIG. 2(b).
The resulting TiSi2 is much thinner than the case shown in
This means that the TiN layer 7 is formed more quickly than the layer 6. As shown in FIG. 6(c), when the SiO2 layer 9 is completely reduced, the TiN layer 7 is formed to be sufficiently thicker than the TiSi2 layer 6.

In other words, the TiSi2 reaction shown in the conventional example is suppressed by the presence of the SiO2 layer 9, making it easier for the TiN reaction to occur, making it possible to form a thicker TiN layer from the same Ti film than in the conventional example. Furthermore, SiO2 layer 9
Since it becomes a TiSi2 layer, the contact resistance does not increase,
Furthermore, since diffusion of Ti atoms toward the substrate side can be suppressed, deterioration of bonding characteristics can also be suppressed.

Therefore, it becomes easier to form the necessary diffusion barrier TiN layer 7 while suppressing the deterioration of the bonding characteristics, and it is possible to form a better contact than before.

The SiO2 layer 9 used here to suppress the TiSi2 reaction has a formation energy higher than that of the oxide of the high melting point metal used, and is reduced as a result to become a TiSi2 or other conductive material layer. It is not limited to this. Moreover, in order to form this SiO2 layer 9 to the necessary thickness, it is not necessary to use thermal oxidation.
Other methods such as VD, sputtering, etc. can be used. Furthermore, the thickness of this SiO2 layer is preferably about 50 Å, but is not limited to this as long as the desired structure can be obtained.

Furthermore, the Al film 8 is used for low-resistance wiring between elements, and this manufacturing method can also be applied to wiring materials other than Al.

[0025]

As explained in detail above, according to the present invention, in the formation of a nitride film barrier layer conventionally introduced into a contact region by thermal nitridation, limitations on nitride film thickness and deterioration of bonding characteristics due to silicide reaction can be avoided. can be sufficiently suppressed, and it becomes possible to form a contact structure with higher diffusion barrier performance than before.

In addition, the refractory metal film required to obtain the necessary nitride film can be made much thinner than in the conventional example, which has the advantage that the desired structure can be formed with good coverage and the diameter of the contact opening can be reduced. There is.

[Brief explanation of drawings]

FIG. 1: Cross-sectional view of the manufacturing process of an embodiment of the present invention

[Fig. 2] Diagram explaining the drawbacks of the conventional example

[Fig. 3] Illustration of conventional example (Part 1)

[Fig. 4] Illustration of conventional example (Part 2)

[Figure 5] Cross-sectional view of the conventional manufacturing process

[Figure 6] TiN, TiSi2 film explanatory diagram

[Explanation of symbols]

1 Silicon substrate 2 Element isolation insulating film 3 High concentration diffusion layer 4 Intermediate insulation film 5 Ti film 6 TiSi2 film 7 TiN film 8 Al film 9 SiO2 film

Claims (3)

[Claims] 1. A method for manufacturing a semiconductor device, in which the surface of a high melting point metal film formed so that at least a portion thereof is in contact with the surface of a silicon semiconductor substrate is converted into a titanium nitride film by a heat treatment reaction in a nitrogen gas atmosphere. A semiconductor device characterized in that, before the heat treatment, a film having a property of delaying the reaction between the high melting point metal and silicon is formed between the surface of the silicon semiconductor substrate and the high melting point metal film. Production method. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the film having a property of delaying the reaction between the high melting point metal and the silicon is an SiO2 film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the high melting point metal is titanium.