JPH04267359A - Formation of metal layer - Google Patents

Abstract

PURPOSE:To enhance barrier performance of Ti series barrier metal. CONSTITUTION:A Ti layer 9 and a TiN layer 10 are laminated sequentially while covering a contact hole 8 bored through a layer insulation film 7 oppositely to the source/drain region 5 of a MOS transistor. Inert substance, e.g. N2, is then ion implanted to destroy pillar crystal structure of the TiN layer 10 and to produce an amorphous TiN layer 10a. Consequently, a grain boundary providing a high speed diffusion path disappears thus suppressing diffusion of Al or Si. Material such as Al-1%Si is subsequently applied onto the entire surface through sputtering. At that time, the contact hole 8 has good burying characteristics. Furthermore, an Al metal layer 11 is patterned. Excellent barrier performance of the amorphous TiN layer 10a is verified based on measurement results of junction leak current.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a wiring forming method applied to the manufacture of semiconductor devices, etc., and particularly improves resistance to so-called aluminum spikes in contact areas having a barrier metal made of a titanium (Ti) material layer. Concerning how to do so.

0002

BACKGROUND OF THE INVENTION As seen in recent VLSI, ULSI, etc., as the design rules of semiconductor devices are highly reduced, junctions become shallower and contact holes become smaller. Defects such as breakdown or deterioration of the junction or increase in contact resistance are likely to occur due to elution of aluminum (Al) into the diffusion layer and precipitation of silicon (Si) from the electrode wiring material in the contact hole. Therefore, in order to prevent the alloying reaction between the electrode wiring material and the Si substrate and the precipitation of Si, it has become common to provide a barrier metal between the two. This barrier metal is usually a transition metal or its nitride,
In addition to transition metal compounds such as carbides, oxynitrides, and borides,
Made of high melting point metal silicide, alloy, etc. Moreover, its structure is not limited to a single layer, but is often a combination of multiple types of films.

For example, a typical example is a two-layer barrier metal (Ti/TiN type) in which a Ti layer and a TiN layer are laminated in order from the substrate side to the Al type material layer side. Since the Ti layer has a high affinity for oxygen, it has the effect of reducing the natural oxide film formed on the surface of the impurity diffusion layer, making it an excellent contact material from the perspective of stably achieving low-resistance ohmic contact. It is. However, when used alone, it cannot sufficiently function as a barrier metal. This is because even if a single Ti layer is interposed between the Si substrate and the Al-based material layer, both the reaction between Si and Ti and the reaction between Ti and Al proceed. This is because penetration, that is, the occurrence of aluminum spikes, cannot be prevented. On the other hand, the TiN layer is thermodynamically stable with respect to Si and has a higher barrier property than the Ti layer, but it has a problem in that it has particularly high contact resistance with respect to p-type Si. In addition, since the crystal grain size when deposited using vacuum thin film formation technology is around 200 Å and has a columnar structure, Al diffuses through the grain boundaries after heat treatment, resulting in sufficient aluminum spike formation. It cannot be prevented. Also,
When formed directly on a Si substrate, oxygen incorporated into the film as an impurity tends to segregate at the interface with the Si substrate.
It is difficult to make contacts. Therefore, Si
By first forming a Ti layer on a substrate and then laminating a TiN layer, the advantages of both layers are utilized.

In addition, as a measure to further improve barrier properties, in recent years, a two-layer barrier metal (Ti/
TiON type) has also been proposed. This is intended to prevent Al from diffusing into the grain boundaries by segregating oxygen at the grain boundaries of TiN.

[0005]

[Problem to be solved by the invention] However, TiO
Although barrier properties are improved when an N layer is used, the following new problems arise. The first problem is
The contact resistance increases by more than one order of magnitude compared to a TiN layer that does not contain oxygen. The second problem is that T
This is because after-corrosion is more likely to occur than when an iN layer is used. BCl3 is usually used as a dry etching gas for Al-based material layers and barrier metals.
A chlorine-based gas such as chlorine-based gas is used because this gas reacts with oxygen in the TiON layer to generate Cl2. In addition to these chemical factors, there are also structural factors that cause aftertacrosis. That is, the TiON layer has a rough surface morphology and has poor wettability with the Al-based material layer compared to the TiN layer, so it is easy to provide a place for residual chlorine to remain at the interface with the Al-based material layer. The third problem is the deterioration of step coverage. In recent highly integrated semiconductor devices, the opening diameter of the connection hole opened in the interlayer insulating film to connect the lower layer wiring and the upper layer wiring has become smaller, and the aspect ratio has come to exceed 1. There is. However, as mentioned above, the TiON layer has a rough surface morphology and poor wettability and reactivity with Al-based materials, so even if the Al-based material is deposited by sputtering, the connection holes are not filled uniformly, resulting in ) is likely to occur.

[0006] As described above, with the conventional techniques, it is difficult to form a contact that can simultaneously satisfy the requirements of low resistance, high barrier properties, and excellent step coverage. Therefore, an object of the present invention is to provide a wiring forming method that can simultaneously satisfy these requirements.

[0007]

[Means for Solving the Problems] A wiring forming method of the present invention is proposed to achieve the above-mentioned objects. That is, the wiring forming method according to the first invention of the present application is as follows:
A step of covering at least the bottom and sidewalls of a connection hole opened in an insulating film on a substrate with an amorphous Ti-based material layer, and a step of forming an Al-based material layer so as to fill at least the connection hole. It is characterized by having the following.

A wiring forming method according to a second aspect of the present invention is characterized in that the Ti-based material layer is made amorphous by ion-implanting an inert substance.

[0009]

[Operation] The Ti-based material layer formed by vacuum thin film formation technology usually has a polycrystalline structure consisting of a collection of fine columnar crystals with a grain size of about 200 Å, but in order to improve its barrier properties, It is essential to inactivate grain boundaries, which provide fast diffusion paths for impurities. Conventionally, inactivation has been carried out by, for example, segregating oxygen at grain boundaries, but the problems with the resulting film are as described above using the TiON layer as an example. Therefore, the present inventor proposed the present invention, considering the idea of destroying the polycrystalline structure and eliminating the grain boundaries themselves, rather than inactivating the grain boundaries through oxygen segregation. be. If the grain boundaries are completely eliminated, the state will be amorphous, but in the present invention, the single crystal that makes up the polycrystalline structure is highly fine-grained, and the grain boundaries are substantially fast. If the particles are made so fine that they cannot serve as a diffusion route, the goal will be achieved. Therefore, the term "amorphous" as used in the present invention includes a completely amorphous state and an ultrafine particle state close to the completely amorphous state. In any case, the barrier properties against aluminum spikes are improved, and problems such as deterioration of surface morphology and promotion of after-corrosion do not arise. In the second invention of the present application, ion implantation of an inert substance is performed as a means for achieving the above-mentioned amorphization. According to this method, by appropriately setting conditions such as ion species, implantation energy, dose amount, etc., it is possible to make a thin Ti-based material layer into a desired amorphous state with good controllability.

0010

[Embodiments] Preferred embodiments of the present invention will be described below. This embodiment is an example in which the second invention of the present application is applied to contact formation in the source/drain region of a MOS transistor, and the TiN layer is made amorphous by ion-implanting N2. This process will be explained with reference to FIGS. 1(a) to 1(c).

First, as shown in FIG. 1(a), Si
A field oxide film 2 is formed on the substrate 1 by, for example, the LOCOS method, and a gate oxide film 3 made of silicon oxide or the like is formed in the element formation region defined by the field oxide film 2.
A gate electrode 4 made of DOPOS or the like was formed through the wafer. Next, after performing a first ion implantation to form source/drain regions 5 using the gate electrode 4 as a mask, sidewalls 6 made of silicon oxide or the like are formed in a conventional manner by CVD, RIE, etc. did. Thereafter, a second ion implantation was performed to increase the impurity concentration in a part of the source/drain region 5 using the gate electrode 4 and sidewall 6 as a mask, thereby forming an LDD structure. Furthermore, an interlayer insulating film 7 was formed by depositing silicon oxide or the like on the entire surface of the substrate by, for example, CVD, and then the interlayer insulating film 7 was patterned to open a contact hole 8 facing the source/drain region 5. Subsequently, a Ti/TiN-based two-layer barrier metal was formed. First, the lower Ti layer 9 is formed with an Ar flow rate of 50 SCCM and a gas pressure of 0.47 Pa (3.5
The film was formed to a thickness of about 300 Å by performing sputtering under the following conditions: mTorr), DC sputter power of 4 kW, and substrate temperature of 300°C. In addition, the upper TiN layer 1
0 is an example of N2 flow rate of 50SCCM and gas pressure of 0.
It was formed to a thickness of about 700 Å by performing reactive sputtering under the conditions of 47 Pa (3.5 mTorr), DC sputter power of 6 kW, and substrate temperature of 300°C.

Next, as an example, the implantation energy is 50ke.
N2 ions were implanted into the entire surface of the substrate under conditions of V and a dose of 5 x 1015 atoms/cm2, as shown in Figure 1(b).
As shown in FIG. 2, the TiN layer 9 was changed to an amorphous TiN layer 9a.

Furthermore, by sputtering, Al-1%
A Si layer was deposited to a thickness of about 4000 Å. The sputtering conditions were, for example, an Ar flow rate of 100 SCCM, a gas pressure of 0.47 Pa (3.5 mTorr), a DC sputtering power of 22.7 kW, and a substrate temperature of 200°C. At this time, the entire surface of the substrate was covered with the Al-1%Si layer, and the inside of the contact hole 8 was also filled uniformly without forming any cavities. Finally, the Al-1%Si layer, the amorphous TiN layer 10a, and the Ti layer 9 are simultaneously patterned by performing dry etching using a chlorine-based mixed gas such as BCl3/Cl2-based gas. 1(c), an Al-based wiring pattern 11 was formed. After completion of this dry etching, no after-corrosion was observed as remarkable as when a TiON layer was used as the upper layer of the barrier metal of the two-layer structure.

In order to confirm the barrier properties of the amorphous TiN layer 10a in the MOS transistor formed as described above, a voltage of -5.5V was applied to the gate electrode of the MOS transistor which was maintained at a predetermined temperature for 30 minutes. was applied to measure the junction leakage current. As a result, the MOS transistor did not exhibit any increase in junction leakage current even after annealing at 600°C. This means that 600
This means that the amorphous TiN layer 10a functions as an effective barrier metal without reacting with Al even at temperatures as high as 0.degree. C., thereby preventing Al from penetrating into the source/drain regions 5.

By the way, the present invention is not limited to the above-described embodiments; for example, the ion implantation to make the TiN layer 9 amorphous is not carried out over the entire surface of the substrate, but may be carried out using a suitable mask, for example. It is also possible to perform this only in the vicinity of the contact portion via the contact portion. Furthermore, the inert substance to be injected is not limited to the above-mentioned N2, as long as it does not cause a significant change in the chemical properties of TiN.
For example, ions of Ar, H2, Ti, etc. can also be implanted.

[0016]

As is clear from the above description, by applying the present invention, it is possible to form a contact with low resistance and excellent barrier properties and step coverage. therefore,
The present invention is extremely suitable for manufacturing semiconductor devices that require high integration and high performance based on fine design rules.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example in which the second invention of the present application is applied to the manufacture of a MOS transistor according to the process order, in which (a) an interlayer insulating film in which a contact hole is formed is covered and a Ti (b) is a state in which the TiN layer has been made amorphous by ion implantation; (c)
1 and 2 respectively show a state in which an Al-based wiring pattern is formed.

[Explanation of symbols]

1...Si substrate 4...Gate electrode 5...Source/drain region 7...
-Interlayer insulating film 8...Contact hole 9...Ti layer 10...TiN layer 10a...Amorphous TiN layer 11...Al-based wiring pattern

Claims (2)

[Claims] 1. Covering at least the bottom and sidewalls of a connection hole opened in an insulating film on a substrate with an amorphous titanium-based material layer, and coating an aluminum-based material so as to fill at least the connection hole. 1. A wiring forming method, comprising the step of forming a layer. 2. The wiring forming method according to claim 1, wherein the titanium-based material layer is made amorphous by ion-implanting an inert substance.