JPS60130165A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a connection electrode of high reliability by a method wherein, in mounting a connection electrode to a diffused region provided in a semiconductor substrate, an insulation film is adhered over the entire surface, and a window part is bored by corresponding to the diffused region, where a laminated body of a Pt silicide layer and an Mo film is buried, and an Al wiring layer is adhered over the entire surface including it. CONSTITUTION:An N type region 2 is diffusion-formed in the surface layer part of the P type Si substrate 1, and the following process is taken in mounting the connection electrode to a part of the surface of the region. In other words, a PSG film 3 is adhered over the entire surface including the region 2, and the window part is bored by corresponding to the position of connection electrode mounting, where the connection electrode made of a Pt silicide layer 11 in the lower layer, and an Mo film 12 in the upper layer is buried by making its surface almost even with the film 3. Thereafter, an Al electrode 15 abutting against this electrode is adhered over the entire surface. Or, a Ti nitride film can be adhered on the film 12. Either case produces an electrode generating no contact failure for a long time by decreasing the contact resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION +a+ Technical Field of the Invention The present invention relates to a semiconductor device, and particularly relates to the structure of an electrode connected to a semiconductor substrate (substrate).

(I)) Prior Art and Problems As is well known, in semiconductor devices such as semiconductor integrated circuits (ICs), semiconductor elements, resistors, etc. are formed on a semiconductor substrate, and wiring layers derived from these elements are formed on the top surface. There are many.

Aluminum (AI) films or aluminum-silicon alloy (Al/Si: Si content 1 to 2%) films have been used for the wiring layer, and aluminum is inexpensive (M is a highly conductive abrasive material). This is because the material has strong adhesion to the insulating film and is easily patterned.

However, as ICs become more highly integrated and miniaturized, such as LSI and VLSI, the electrode windows become smaller and the steps on the sides of the electrode window openings become steeper, making it difficult to make stable connections for electrode wiring. Figure 1 shows a cross-sectional view of the electrode part to explain this, in which 1 is a p-type silicon substrate, 2 is an n-type silicon region, and 3 is a phosphosilicate glass (PSG) film. An insulating film, 4 an electrode window, and 5 aluminum wiring.

As shown in the figure, the aluminum wiring 5 is connected to the layer portion S of the electrode window.
The constriction is severe and the wire is likely to break at this part. This is also due to the poor coverage of sputtering, and aluminum films are mainly deposited by sputtering, and it is difficult to deposit by chemical vapor deposition (CVD). be.

Furthermore, when an aluminum-silicon alloy film is brought into direct contact with a silicon substrate as shown in Figure 1, the silicon (Si>) in the film diffuses into the aluminum due to the heat treatment during the wafer process, and the silicon substrate is exposed to the contact surface. As the layer grows epitaxially, it becomes a heterogeneous silicon layer and the contact resistance increases, and a pn junction is formed in the contact with the p-type epitaxial silicon layer containing aluminum, resulting in a significant increase in the contact resistance.

Therefore, recently, an electrode structure having a cross section as shown in FIG. 2 has come to be used. In the structure of this example, 6 is a molybdenum silicide (MoSi2) film, and this Mo
A Si2 film 6 is interposed between the silicon region 2 and the aluminum wiring 5 to prevent contact failure from occurring.

However, when a silicide film such as the MoSi bifurcated film 6 is deposited in direct contact with the silicon layer, contact resistance increases, especially contact resistance with the p-type silicon layer. Moreover, if heat treatment is performed for a long time, aluminum from the aluminum wiring gradually penetrates the thin MoSi2 film 6 and comes into contact with silicon, destroying the shallow junction and causing a contact failure. In addition, the electrode structure shown in FIG. 2 also has a shoulder portion S of the electrode window, as in FIG.
Needless to say, the wire is easily broken due to the constriction.

(C1 Object of the Invention) The present invention eliminates these problems and proposes a semiconductor device having an extremely reliable electrode structure.

fdl Structure of the Invention The purpose of the invention is to provide an insulating film forming a window formed on a semiconductor substrate, a metal silicide film formed in the window, and an insulating film formed on the metal silicide film and forming a window in the window. This is achieved by a semiconductor device having an embedded first conductive layer and a second conductive layer formed in the first conductive layer.

<e+　Embodiments of the invention Examples will be described in detail below with reference to nine drawings.

3 and 4 show cross-sectional views of the connection electrode structure according to the present invention, in which the electrode window is almost buried in a molybdenum (Mo) film 12 via a platinum silicide film 11, It has a structure in which aluminum wiring 15 is formed on the upper surface and connected. In addition, the electrode structure shown in FIG. 4 is buried with a conductive polycrystalline silicon film 13 through a platinum silicide film 11, and a titanium nitride (TiN) film is placed on top of it as a reaction prevention film.
) with a film 14 interposed therebetween, and an aluminum wiring 1 on its upper surface.
It has a structure in which 5 are connected. In these electrode structures, a palladium silicide film may be used instead of the platinum silicide 19+1, and a tungsten film may be used instead of the No film 120.
W) Film, MoSi2 H'A+ 1/l/silicide (TaSi2) Ij% may be used. By doing so, an electrode with low contact resistance can be obtained, and contact failure is less likely to occur even when used for a long time.

Second, the structure according to the present invention does not deposit a silicide film, but deposits platinum and converts it into silicide through low-temperature heat treatment, so it has good contact with the silicon layer.

At this time, low-temperature heat treatment is important in order not to change the device characteristics, and platinum silicide films and Balajiu J. silicide films are suitable for this purpose.

Furthermore, in the electrode structure in which the aluminum J1 film is directly deposited on the platinum silicide film 11, the aluminum wiring layer is easily corroded. It is thought that this is because, due to the presence of platinum, the residue of the chlorine gas used when etching the aluminum film turns into hydrochloric acid during the water washing process, etching the aluminum. However, this structure solves that problem,
Reliability is further improved.

Next, FIGS. 5 to 7 show cross-sectional views in the order of steps for forming electrodes in the embodiment shown in FIG. 3. As shown in FIG. 5, after forming an electrode window 4 on the PSG film 3, platinum (Pt) is deposited to a thickness of 200 to 400 layers by vapor deposition or spacing, and heat-treated at a temperature of 350 to 450°C. A platinum wrinkled side (PTSI or PT2 Si) film 11 is formed using the following steps.

Since the PT deposited on psclffJ3 remains unreacted after the heat treatment, it is removed by etching with aqua regia after the heat treatment. The metal +4 material used here needs to be a material that can be turned into silicide by low-temperature heat treatment at 500°C or less.
Platinum or palladium (Pct) are preferred materials.

Next, as shown in FIG. 6, Mol*x2 is deposited by bias sputtering so that the electrode window is almost buried. The excess Mo film deposited on the pscH layer 3 is removed by etching using a known photoprocess.

In this case, when depositing by bias sputtering, the deposition and etching proceed simultaneously, and the etching progresses quickly on the side surfaces of the electrode window, so that the Mo film 12 is laminated on the side surfaces in a gentle one-term diagonal shape.

Note that low pressure (0.2 Torr) is used instead of the bias sputtering method.
The M0 film 12 may be deposited by a CVD method (approximately R).

In that case, silicon substrate 1 is heated to 350 to 450'c, and molybdenum pentachloride is heated to 1a in argon or hydrogen.
a L, to be deposited. Since it is a CVD method, the coating properties are good. In addition, the silicide film is made using the CVD method. In that case, for example, molybdenum pentachloride and monosilane are thermally decomposed and deposited.

In addition, this buried layer is preferably made of a material that has low resistivity even without high-temperature heat treatment. W film exemplified above.

) josi2 film and TaSi2 film are such materials with low resistivity.

Next, as shown in FIG. 7, aluminum wiring 15 having a thickness of 5,000 to 7,000 layers is deposited by sputtering and patterned to complete the electrode wiring layer.

Next, FIGS. 8 to 11 show cross-sectional views in the order of steps for forming electrodes in the embodiment shown in FIG. 4. First, as shown in FIG. 5 of the above example, after forming an electrode window 4 on the PSG film 3 as shown in FIG. Adhered, temperature 350
A platinum silicide (PLSi or Ph Si) film 11 is formed by heat treatment at ~450°C. Alternatively, palladium silicide (P[]2Si) may be formed.

Next, as shown in FIG. 9, a polycrystalline silicon film 13 doped with n-type impurities is deposited by low pressure CVD.

If the thickness of the PSG film 3 is 1 tt m, then 1 to 1.5
The polycrystalline silicon film is deposited to a thickness of approximately μm, almost burying the electrode window, and deposited on the excess PSG layer 3.
It is removed by reactive ion etching using a Freon-based gas mainly composed of 4 gases. At this time, since the film is deposited by the CVD method using a reduced pressure of about 0.2 Torr, it has good FH resistance and is sufficiently laminated on the side surfaces of the electrode windows.

Next, as shown in FIG. 10, the film thickness is 1000-2000.
Deposit TiNIRI4 by sputtering. TiNI
]ff is formed by sputtering natanium in a mixed gas of nitrogen gas and argon gas. Thereafter, as shown in FIG. 11, aluminum wiring 15 is deposited on the upper surface by sputtering and patterned. Then, TiN1
'J becomes a diffusion prevention film that prevents the diffusion of aluminum and silicon.

An increase in contact resistance due to diffusion of aluminum and silicon in the lever and connection electrode is prevented, and a flattened aluminum wiring layer is formed.

(``) Effects of the Invention As is clear from the above explanation, according to the present invention, the contact resistance value is stable with little fluctuation even after long-term heat treatment, and a flat aluminum wiring layer with no disconnection is achieved. This greatly contributes to improving the reliability of ICs.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional connection electrode, FIGS. 3 and 4 are cross-sectional views of a connection electrode according to the present invention, and FIG.
7 to 7 are sequential cross-sectional views of the process of forming the connection electrode shown in FIG. 3, and FIGS. 8 to 11 are sectional views of the process of forming the connection electrode shown in the 41st recess. In the figure, 1 is a P-type silicon substrate, 2 is an n-type silicon region, 3 is a PSG film (insulating B'J), and 4 is an electrode window. 5.15 is an aluminum arrangement spring layer, 11 is platinum lizard, 12 is a molybdenum film, 13 is a conductive polycrystalline silicon film, and 14 is a titanium nitride film. Figure 1 - Figure B Figure 2 Figure 3 Column 51 Figure 7

Claims (1)

[Claims] An insulating film having a window formed on a semiconductor substrate, a metal silicide film formed in the window, and a first conductive layer formed on the metal silicide film and embedded in the window. and a second conductive layer formed on the first conductive layer.