JPH0665213B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and its manufacturing method.

B. Prior Art Semiconductor devices such as dynamic RAM (random access)
For example, a so-called salicide structure in which a silicide is formed in a self-aligned manner is known as one method of forming a silicide layer of a refractory metal on the surface of a polysilicon gate or a diffusion layer. This salicide structure is expected to realize high speed and high integration. An example of FIG. 5 will be described along the manufacturing process.

First, as shown in FIG. 5A, a field oxide film 2 is formed in a predetermined pattern on one main surface side of a P-type silicon substrate 1 by a LOCOS (Local Oxidation of Silicon) method, and P serving as a channel stopper is formed immediately below the field oxide film 2. The type semiconductor region 3 is formed. Then, after growing the gate oxide film 4, CVD
Polysilicon is deposited on the entire surface by the (Chemical Vapor Deposition) method, and then this polysilicon layer is processed by the photoetching method to form the polysilicon gate 5
And

Next, as shown in FIG. 5B, the oxide film deposited on the entire surface by the CVD method is processed by RIE (Reactive Ion Etching), and spacers 8 and 9 made of SiO ₂ are formed on the side surface of the gate 5.
To a predetermined width.

Further, phosphorus ions are implanted using the polysilicon gate 5 and the spacers 8 and 9 as a mask to form N ⁺ type semiconductor regions 6 and 7 on both sides of the gate 5 which will be source and drain regions.
Are self-aligned.

Then, as shown in FIG. 5C, a refractory metal (for example, titanium) 10 is deposited on the entire surface by sputtering.

Then, as shown in FIG. 5D, under normal pressure (near 760 Torr), heat treatment is performed in the presence of an inert gas by an electric furnace or a lamp annealer such as a halogen lamp, and the refractory metal 10 and the exposed silicon layer (ie, , The gate 5, and the source and drain regions 6 or 7) are selectively alloyed with titanium silicide layers 11, 12 and 13 on the surface of the silicon layer.

Then, as shown in FIG. 5E, titanium that has not reacted with silicon is removed by etching with an ammonia solution or the like, and the silicide layer 11,
Expose 12 and 13. This silicide layer is further heat-treated at 700 ° C. or higher to obtain a stable composition (TiSi ₂ ).

Next, as shown in FIG. 5F, contact holes 15 and 16 are formed by photoetching at predetermined portions (on the source and drain regions in the drawing) of the insulating film (for example, phosphosilicate glass film) 14 attached to the entire surface, and further the sputtering method is used. The aluminum or the like attached to the entire surface is processed by photo-etching to form the electrodes 17, 18 and various wirings.

The semiconductor element obtained by the manufacturing process as described above (here, MOSFET (Metal Oxide Semiconductor Field Ef
As a result of various investigations by the present inventor, it was found that there are the following problems.

That is, first, in the titanium silicide layers 12 and 13 of the titanium silicide layers, which are in contact with the electrodes 17 and 18 such as Al or Al alloy, titanium silicide reacts with Al to form a film of a new composition at the interface, As a result, the contact resistance between the two changes and the reliability of the semiconductor element deteriorates. In addition, importantly, since titanium silicide and Al are in contact with each other, electromigration of Al (the movement or deformation of the electrode or wiring due to the movement of Al electrons) easily occurs. Further, some oxidation of titanium silicide is unavoidable at the time of its formation, so that the contact resistance with the wiring material changes or increases, which also accelerates the deterioration of the reliability of the element.

Although such a defect remarkably impairs the characteristics of the silicide layer, it is a fact that no effective countermeasure for that can be found conventionally.

C. An object of the present invention is to provide a semiconductor device in which contact resistance is made uniform and stable, and electromigration is prevented and side is stabilized, and a manufacturing method thereof.

D. Structure of the Invention That is, the present invention, a silicide layer formed of a refractory metal and silicon formed on a region of higher impurity concentration than the semiconductor substrate formed on one main surface of the semiconductor substrate or on polysilicon, A semiconductor device having a nitride layer made of a nitride of silicide formed simultaneously with the silicide layer on the silicide layer.

The present invention also includes a step of forming a refractory metal on a region of a higher impurity concentration than that of the semiconductor substrate formed on one main surface of the semiconductor substrate or on polysilicon, and a nitrogen atmosphere or nitrogen containing under reduced pressure. Forming a laminated structure of a silicide layer made of the refractory metal and silicon and a nitride layer of silicide on the region or the polysilicon by heat treatment at a predetermined temperature in an atmosphere A method for manufacturing a device is provided.

E. Embodiment An embodiment of the present invention will be described in detail below with reference to FIGS.

1 and 2 show a semiconductor device according to this embodiment, for example, a MOSFET for a dynamic RAM. This M
The OS transistor has a part in common with the transistor shown in FIG. 5F, but the common part is given the same reference numeral and the description thereof is omitted.

The remarkable structure of this MOS transistor is that the surfaces of the silicide (eg, titanium silicide) layers 11, 12, and 13 are nitrided by the method described below, and the nitride layers 20 and 21,
It has been converted to 22. These nitride layers are shown shaded in FIG. Where the silicide layers 11, 12,
Since 13 and the nitride layers 20, 21, and 22 are simultaneously formed in the same step as described later, the diffusion of silicon into titanium can be controlled by the nitriding reaction.

By forming such a nitride layer of titanium silicide on the surface of the titanium silicide layer, the electrodes 17 and 18 of Al or Al alloy (or refractory metal) and the silicide layers 12 and 13 do not come into direct contact with each other. The above nitride layers 21, 22
Will intervene. As a result, the reaction between Al on the electrode side and the silicide is prevented during electrode formation, etc., and the contact resistance between the two does not substantially change. In this case, the electric resistance of the titanium silicide nitride is 13 to 16 μΩ-cm, which is sufficiently low, so that the contact resistance is not increased. In addition, the nitride layer also has a function of preventing the underlying titanium silicide from being oxidized, which also contributes to the improvement of the contact resistance.

In addition, since the nitride layers 21 and 22 (further 20) have a property of causing less electromigration than Al, Al that tends to occur between titanium silicide and Al.
It is possible to effectively prevent the electromigration.
In this sense, the nitride layer also functions as a barrier for electromigration.

As described above, the nitride layers 21 and 22 (and 20) are formed on the upper layers (particularly Al electrodes) and the titanium silicide layers 12 and 13 (and 1).
It has a function of preventing undesired interaction with (1) and can improve the reliability of the semiconductor device. The nitride materials 21 and 22 act as an etching mask for the underlying silicon when the contact holes 15 and 16 are formed by etching.

In the above MOSFET, the thickness of the polysilicon gate may be 4500Å as a whole, and the thickness of the titanium silicide layer may be 1200Å including the surface nitride layer.

Next, the method for manufacturing the semiconductor device according to the present embodiment will be explained with reference to FIG.

The process of FIGS. 3A to 3C is almost the same as the process of FIGS. 5A to 5C, and thus the description thereof is omitted, but the thickness of the polysilicon layer 5 is, for example, about 4500Å, the thickness of the metal titanium film 10 is about 10. Is, for example, about 1200Å.

In the next step of FIG. 3D, under reduced pressure (for example, 10 ⁻² Tor
r), in an atmosphere containing N ₂ or N _2, using an electric furnace or a lamp annealer such as a halogen lamp, for example, 550 to 600.
Heat to ℃. As a result, titanium silicide layers 11, 12 and 13 are formed on the surface regions of the silicon layers 5, 6 and 7, respectively, and at the same time, the nitride layers 20, 21 and 22 of titanium silicide formed of N ₂ are formed on the surfaces thereof. Are formed respectively. That is, a silicidation reaction occurs at the interface between the titanium 10 and the silicon layer, and at the same time, a nitriding reaction by N ₂ in the atmosphere occurs at the surface layer portion of the titanium 10. This nitriding reaction controls the diffusion of the underlying silicon to the surface and also occurs inside the silicide layer. The silicide layers 11, 12 and 13 having a nitride layer on the surface may be formed to a thickness of about 1200 Å including the nitride layer (however, the thickness of the nitride layer is 1000 Å
degree).

Then, as shown in FIG. 3E, titanium that has not reacted with silicon,
And titanium nitride or titanium-rich silicide (not shown in FIG. 3D) is removed by etching with ammonia solution or the like. This selectively leaves the nitride layers 20, 21 and 22 on the silicide layers 11, 12 and 13 in approximately the same pattern, respectively. Here, chemically stabilized titanium nitride is difficult to process and difficult to remove easily by etching, so the pressure and temperature of the atmosphere in the heat treatment of the step of FIG. 3D should be adjusted appropriately. It prevents the formation of chemically stable titanium nitride.

Then, heat treatment is performed at 700 ° C. or higher in the same atmosphere as that used in the step of FIG. 3D. This allows the nitride layer 2
Nitriding of 0, 21 and 22 further progresses sufficiently in a nitrogen atmosphere, and the underlying silicide layers 11, 12 and 13 change to a stable composition (TiSi ₂ ).

Next, as shown in FIG. 3F, an insulating film 14 is deposited on the entire surface, and after the contact holes 15 and 16 are formed, electrodes 17 and 18 made of Al or the like are formed.
Are provided (see FIG. 1).

By the process described above, the silicide layer having the surface nitride layer can be formed on the surface of the silicon layer.

In the silicidation reaction of FIG. 3D, the nitriding reaction on the surface of the silicide is advantageous because it prevents the oxidation of the silicide. For this reason, it is preferable to reduce the pressure in the reaction vessel in advance as described above. Further, the heat treatment for stabilizing the silicide described in FIG. 3E also improves the state of the interface with the underlying silicon, strengthens the silicide, and prevents film peeling. Therefore, in the case of the structure like this example,
When the electrode 17 or 18 is used as a bit line or a data line, the film peeling of the silicide is fatal, but such a situation does not occur at all in the stabilization treatment of this example.

FIG. 4 shows a cross section of the device at a position different from that of FIG. 1, but here, the insulating film 14 is provided with a contact hole on the nitride layer 20 on the silicide layer 11 provided on the polysilicon gate 5. 23 is formed, and an electrode 24 of Al or the like is provided here.

The presence of the silicide layer 11 improves the signal transmission speed of the polysilicon gate 5, and the contact resistance with the electrode 24 is uniformized and stabilized by the nitride layer 20, and no film peeling occurs. It is particularly effective when used as a word line.

Although the present invention has been illustrated above, the above examples can be further modified based on the technical idea of the present invention.

For example, the nitride layer described above may be provided on the surface of the silicide, but may extend to the inside of the silicide as described above. As the metal for silicidation, other refractory metals such as tungsten and tantalum can be used in addition to the above titanium. The electrode or wiring material on the silicide is not limited to Al, but may be an Al alloy such as Al-Si or a refractory metal such as tungsten. Further, although the above-mentioned example relates to a laminated structure of silicide-silicon, the present invention is not limited thereto, and is applicable to a case where a nitride layer is formed on a gate surface made of silicide alone, for example. is there. Further, in the silicidation reaction involving nitridation described above, for example, NH ₃ can be used as another nitrogen-containing atmosphere in addition to N ₂ for the nitriding reaction. It should be noted that the present invention is not limited to the above-described elements
It can be applied to other ICs such as (read only memory), and the application place may be any place where the silicide layer is formed.

F. As described above, according to the present invention, since the nitride layer is formed on at least the surface of the silicide layer, the interaction between the electrode or the wiring material deposited on the silicide layer and the silicide is prevented,
The contact resistance between them can be made uniform or stable. Moreover, the electromigration can be prevented by the nitride layer, and the nitride layer can prevent the oxidation of the silicide. Further, in the present invention, since the silicide layer and the nitride layer of silicide are simultaneously formed in the same process, the diffusion of the underlying silicon into the refractory metal (titanium) can be appropriately controlled by the nitriding reaction.
A desired silicide layer can be obtained and the manufacturing cost can be suppressed. Furthermore, since the pressure and temperature of the atmosphere during the heat treatment are appropriately adjusted so that chemically stable metal nitride (titanium nitride) is not formed, the metal nitride formed in unnecessary portions can be easily removed. can do.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a sectional view of a semiconductor device, and FIG. 2 is a plan view of FIG. 1 (however, an insulating layer on the front surface side is shown. (Omitted), FIGS. 3A, 3B, 3C, 3D, 3E, and 3F are cross-sectional views showing a method of manufacturing a semiconductor device in the order of steps, and FIG. 4 is another portion of the semiconductor device. FIG. FIG. 5A, FIG. 5B, FIG. 5C, FIG. 5D, FIG. 5E and FIG. 5F are cross-sectional views showing a conventional method of manufacturing a semiconductor device in the order of steps. In the reference numerals shown in the drawings, 5 ... Polysilicon gate 6, 7 ... N ⁺ type semiconductor region (diffusion layer) 8, 9 ... Spacer 10 ... Titanium 11, 12, 13 ... Titanium silicide layer 15, 16, 23 ... Contact holes 17, 18, 24 ... Electrodes such as Al 20, 21, 22 ... Nitride layers.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number for FI Technical indication H01L 29/784 (56) References JP-A-60-153121 (JP, A) JP-A-57- 72383 (JP, A) JP-A-56-167365 (JP, A)

Claims (4)

[Claims] 1. A silicide layer composed of a refractory metal and silicon formed on a region of a semiconductor substrate having a higher impurity concentration than that of the semiconductor substrate or formed on one main surface of the semiconductor substrate, and on the silicide layer. And a nitride layer formed of a nitride of silicide formed simultaneously with the silicide layer. 2. A step of forming a refractory metal on a region having a higher impurity concentration than that of the semiconductor substrate formed on one main surface of the semiconductor substrate or on polysilicon, and a nitrogen atmosphere or nitrogen containing under reduced pressure. Forming a laminated structure of a silicide layer made of the refractory metal and silicon and a nitride layer of silicide by heat treatment at a predetermined temperature in an atmosphere on the region or the polysilicon. Device manufacturing method. 3. The method for manufacturing a semiconductor device according to claim 2, wherein the heat treatment is performed in a temperature range of approximately 550 to 600 ° C. 4. The heat treatment according to claim 2 or 3, wherein the heat treatment is performed at a pressure of about 10 ⁻² Torr.
A method of manufacturing a semiconductor device according to item.