JP4283189B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method suitable for manufacturing a semiconductor device using Co silicide for each electrode such as a gate electrode, a source electrode, and a drain electrode in a MOS transistor.

  In general, in a Si semiconductor device including a MOS transistor or the like, Co silicide which is a compound of Co and Si which is a refractory metal is widely used as a material for a gate electrode, a source electrode and a drain electrode.

  Conventionally, to form an electrode made of Co silicide, a Co film is deposited on the Si surface of the gate region, the source region, and the drain region, or Co and Si are deposited at the same time, and then heat treatment is performed to perform Co silicide. (For example, refer to Patent Document 1).

At that time, after depositing Co, it is also covered with a cap layer made of TiN or the like to protect the Co surface that is easily oxidized and prevent an increase in electric resistance (see, for example, Patent Document 2). In this case, the cap layer is removed after the Co silicide is generated, and then a method of depositing a SiO ₂ film or a Si ₃ N ₄ film as a hard mask and a surface protection is mainly used.

9 to 11 are cutaway side views showing a main part of a semiconductor device at process points for explaining a conventional process.
See Fig. 9 (1)
A gate insulating film 2 made of SiO ₂ is formed on the Si substrate 1, then a gate electrode 3 made of polycrystalline Si is formed on the gate insulating film 2, and then the side surfaces of the gate electrode 3 and one of the Si substrates 1 are formed. part insulating film 4 is formed of a thin SiO ₂ to then form a cyclic Doworu 5 made of SiO _2, then forming a source region 6 and drain region 7, then depositing a Co film 8 on the entire surface Then, a cap layer 9 made of TiN is formed on the Co film 8.

See Fig. 10 (2)
A heat treatment is performed to react the Co film 8 with the gate electrode 3 made of polycrystalline Si and the Si substrate 1 to form a Co silicide film 10, and then the cap layer 9 and the unreacted Co film 8 are removed.

See Fig. 11 (3)
A protective film 12 made of SiO ₂ or Si ₃ N ₄ is formed on the entire surface.

  By the way, in recent years, there has been a demand for shortening of the product manufacturing time, so that simplification of the process is desired. For example, even when the Co silicide film 10 is formed, the oxidation of the surface of the Co film 8 is suppressed. The cap layer 9 can be easily formed, and the unreacted Co film 8 deposited on the side wall 5 can be reliably and easily removed so as not to remain as a residue. It is needed.

  In the conventional process, the cap layer 9 and the unreacted Co film 8 are removed at the same time by immersing them in a solution. However, when this method is employed, the unreacted Co film 8 and the cap layer 8 are removed. In many cases, 9 cannot be completely removed and a residue is formed, and such a residue causes a leak current.

  In addition, when the above solution is used, it is necessary to clean the solution. However, the semiconductor device having a fine pattern cannot be sufficiently dried, and depending on the remaining moisture, oxidation and contamination in the gas phase may occur. It is expected that this reaction will become more apparent with the progress of pattern miniaturization in the future. Therefore, in the semiconductor device manufacturing process, cleaning with a solution at a stage where a fine pattern exists on the surface must be avoided.

  In general, Co is easily oxidized, which increases the resistance of the semiconductor device and leads to deterioration of characteristics. Therefore, in the process of forming the Co silicide film 10, the cap layer 9 is formed on the Co film 8 to perform heat treatment. In this case, it is indispensable to protect the surface, and the number of processes is inevitably increased.

In addition, the process from the deposition of the Co film 8 to the deposition of the cap layer 9 must be performed in a vacuum, or a surface cleaning step must be interposed between the treatments. There are many restrictions on the formation, and a complicated process that goes against the simplification of the process is required. Further, with respect to the wiring for the gate, source, and drain, the contact hole that opens in the interlayer insulating film and fills it. The formation of conductive plugs is becoming difficult due to the increase in aspect ratio due to miniaturization, which contributes to the poor conductivity of semiconductor devices, so miniaturization can be achieved without increasing the aspect ratio. Is also needed.
JP 2000-243726 A JP 2000-174273 A

  In the present invention, the manufacturing process of a semiconductor device having a Co silicide electrode is simplified, and the thickness of the Co silicide film and the cap layer can be controlled to reduce the aspect ratio in the contact hole. The generation of the residue of unreacted Co during the formation of N is eliminated, and the Co oxide is easily removed so that the cleanliness can be maintained.

  In the method of manufacturing a semiconductor device according to the present invention, the principle of forming an electrode composed of a Co silicide film is that an unnecessary Co film or Co oxide film is reacted with a carboxyl group to generate a carboxylate, The acid salt is based on the fact that it can be easily volatilized by heat treatment or energy beam irradiation.

FIG. 1 is an explanatory diagram for explaining the principle of the present invention.
Stage (1)
A CoSi film 22, a Co film 23, and a Co oxide film 24 are formed on the Si substrate 21. The Co oxide film 24 is naturally generated because the Co film 23 is easily oxidized.
Stage (2)
By using acetic acid (CH ₃ CHOOH) as a gaseous material having a carboxyl group for converting Co oxide and Co into a carboxylate, the Co oxide film 24 is exposed to the acetic acid vapor to adsorb the acetic acid. To form a carboxylate salt of
Stage (3)
Heat treatment or energy beam irradiation is performed to volatilize the Co carboxylate.
Stage (4)
Co and carboxyl groups are easily reacted, whereas Si has low reactivity with carboxyl groups, so that it remains on the surface and forms a cap layer 25 made of stable SiO ₂ .

In the above process, when the Si substrate 1 is exposed to a gaseous substance having a carboxyl group, or oxides of Co and Si are formed on the surface by heating while supplying oxygen during the exposure, The oxide is volatilized and removed by the gaseous substance having a carboxyl group, but SiO ₂ remains.

By utilizing this phenomenon, it is possible to control the thickness of the CoSi film 22 and the thickness of the cap layer 25 made of SiO _{2 serving as a} protective film with considerable flexibility.

  Further, since the Co film 23 can be easily removed by becoming a volatile carboxylate by being exposed to a gaseous substance having a carboxyl group, for example, the Co film 23 is deposited on the side wall in the gate. Co removal is also facilitated.

  Further, since the Co oxide film 24 can be removed by using a carboxyl group in the same manner as the Co film 23, even if the surface of the completed CoSi film 22 is in an oxidized state, the oxide film can be easily removed. Since it can be removed, the surface of the CoSi film 22 can be easily cleaned at any stage.

From where it said, is in the manufacturing method of a semiconductor device according to the present invention, the steps of forming a Co silicide by heating after depositing or Co depositing Co and Si simultaneously on Si, then, carboxyl A protective film made of SiO ₂ is heated while being exposed to a gaseous substance having a group or after being exposed, and Co is volatilized as a carboxylate and Co is oxidized as a carboxylate and Si is oxidized. it you are basically the composed contains the steps of.

By adopting the above means, when the Co film is silicided, the SiO ₂ film naturally generated on the surface serves as a cap layer, that is, a protective layer, and can prevent the Co silicide film from being oxidized.

Further, the cap layer made of SiO ₂ formed on the surface can be used as a hard mask film in the subsequent process, and it is not necessary to separately provide a cap layer as in the prior art.

Furthermore, since the thickness of the Co silicide film and the thickness of the cap layer made of SiO ₂ can be controlled, it is possible to make the interlayer insulating film thin by adjusting the gate height to be low, Accordingly, since the aspect ratio can be reduced without increasing the contact hole, it is easy to secure a process margin in etching.

  Furthermore, the Co film or Co oxide film deposited on the sidewall can be easily removed by exposure to a gaseous substance having a carboxyl group, so that the residue is small and the surface is clean. The Co silicide film can be easily formed, and when the Co silicide film is formed, the semiconductor device is exposed to an oxygen-containing environment such as the atmosphere, and there is no need to pay much attention to the transfer to the next process. And environment management becomes easier.

  2 to 4 are side sectional views showing the principal part of the semiconductor device in the main points of the process for explaining the process of forming the Co silicide electrode according to the present invention. The symbols used in FIGS. And the same symbol represent the same part or have the same meaning.

See Fig. 2 (1)
A gate insulating film 2 made of SiO ₂ is formed on the Si substrate 1, then a gate electrode 3 made of polycrystalline Si is formed on the gate insulating film 2, and then the side surfaces of the gate electrode 3 and one of the Si substrates 1 are formed. A thin insulating film 4 made of SiO ₂ is formed on the surface, then a side wall 5 made of SiO ₂ is formed, then a source region 6 and a drain region 7 are formed, and then a Co film 8 is deposited on the entire surface. . It should be noted here that it is not necessary to form the cap layer 9 (see FIG. 9) for preventing the Co film 8 from being oxidized.

See Fig. 3 (2)
Heat treatment is performed to cause the Co film 8 to react with the gate electrode 3 made of polycrystalline Si and the Si substrate 1 to form a Co silicide film 10 and to expose to a gaseous substance having a carboxyl group.

In this step, the unreacted Co film 8 is removed, and at the same time, a protective film 11 made of SiO ₂ is formed on the Co silicide film 10. The protective film 11 can be used as a hard mask in the next process as required.

See Fig. 4 (3)
A protective film 12 made of SiO ₂ or Si ₃ N ₄ is formed on the entire surface.

  FIG. 5 is an explanatory view of a main part showing an apparatus for forming Co silicide according to the present invention, in which 31 is a main body, 32 is a wafer mounting table, and 33 is acetic acid employed as a gaseous substance having a carboxyl group. A vapor supply pipe, 34 is an oxygen supply pipe, 35 is an exhaust pipe, 36 is an acetic acid container, 37 is a heater, 38 is an acetic acid solution, 39 is a wafer, and the atmosphere in the wafer 39 and the body 31 can be heated. It is like that.

In the illustrated apparatus, the inside of the main body 31 is evacuated through an exhaust pipe 35. Acetic acid vapor is fed from the air feed pipe 33 as a gaseous substance having a carboxyl group and supplied to the surface of the wafer 39. Acetic acid is vaporized by heating the acetic acid solution 38 in the acetic acid container 36 with a heater 37. In order to volatilize the Co carboxylate, the wafer 39 is heated to about 250 ° C. In order to oxidize the surface of the wafer 39 as necessary, oxygen is supplied from the oxygen air supply pipe 34 while the wafer 39 is heated. Thereafter, the wafer 39 can be exposed to acetic acid vapor to perform surface treatment, and the thickness of the protective film made of the Co silicide film and SiO ₂ can be controlled.

  FIG. 6 is a main part explanatory view showing another example of an apparatus for forming Co silicide according to the present invention. The same symbols as those used in FIG. 5 represent the same parts or have the same meanings. To do.

  The apparatus shown in FIG. 4 differs from the apparatus shown in FIG. 3 only in the heat source for heating the wafer 39, and the other configurations are exactly the same. As a heat source, an energy beam such as an ion beam is used without using a heater. In the case of an ion beam, the carboxylate can be volatilized by setting the irradiation energy to 100 eV or more.

  FIG. 7 is a diagram showing the results of an experiment conducted to explain the effect of the present invention. An analysis experiment based on X-ray photoelectron spectroscopy (XPS) was conducted to obtain a Co / Si interface. It is the result of investigating elements present in the vicinity.

  The sample used here is a sample obtained by applying a sputtering method to a Co film having a thickness of 20 nm on a Si substrate before processing, and acetic acid vapor while heating to 340 ° C. before processing. The surface condition after exposure to was compared.

  In this experiment, the detection depth was 4 nm to 5 nm, the time when the sample was exposed to acetic acid vapor was 2 hours, and the analysis was carried out by transporting the sample to the atmosphere. C is also included. The main elements detected by this measurement were Co, O, C, and Si as the base.

From the data on the untreated sample, it can be seen that a natural oxide film is formed on the Co surface in the initial state. In the spectrum of the electronic state Si2s, a slight peak of SiO _x that is considered to exist at the Co / Si interface is recognized. It is considered that a silicidation reaction occurred at the interface with Si and Si was leached to the detection depth by XPS. From the spectrum of the electronic state Co2p, a peak of Co alone is recognized together with the Co natural oxide film, and the thickness of the natural oxide film is recognized to be 5 nm or less.

For the surface after the sample is heated to 340 ° C. and exposed to acetic acid vapor, from the Co2p spectrum, the peak of Co—O or Co—OH is below the detection limit, and only the peak due to Co alone is present. From this, it can be seen that the Co natural oxide film existing on the surface disappeared. In addition, since the peak indicating SiO ₂ is remarkably increased in the spectra of O1s and Si2s, it is recognized that a SiO ₂ film of about _{2 to 3} nm is formed in the vicinity of the surface.

FIG. 8 is an explanatory diagram showing the element ratio in the vicinity of the surface obtained from the XPS spectrum shown in FIG. It can be seen that after the wafer is exposed to acetic acid vapor at 340 ° C., Co is almost lost and SiO ₂ is dominant. Further, it has been shown to be effective in reducing C contamination, and considering that the sample is transported to the atmosphere as described above, it can be seen that there is almost no residual C contained in acetic acid.

From the above experimental results, Co / Si having a Co oxide film on the surface is exposed to acetic acid vapor and heated, whereby the Co oxide disappears and a SiO ₂ film is formed on the outermost surface. Was confirmed.

It is explanatory drawing for demonstrating the principle of this invention. It is a principal part cutting side view showing the semiconductor device in the process important point for demonstrating the formation process of Co silicide electrode by this invention. It is a principal part cutting side view showing the semiconductor device in the process important point for demonstrating the formation process of Co silicide electrode by this invention. It is a principal part cutting side view showing the semiconductor device in the process important point for demonstrating the formation process of Co silicide electrode by this invention. It is principal part explanatory drawing showing the apparatus which forms Co silicide by this invention. It is principal part explanatory drawing showing the other example of the apparatus which forms Co silicide by this invention. It is a diagram which shows the result of the experiment conducted in order to demonstrate the effect of this invention. It is explanatory drawing showing the element ratio of the surface vicinity calculated | required from the XPS spectrum shown as FIG. It is a principal part cutting side view showing the semiconductor device in the process important point for demonstrating the conventional process. It is a principal part cutting side view showing the semiconductor device in the process important point for demonstrating the conventional process. It is a principal part cutting side view showing the semiconductor device in the process important point for demonstrating the conventional process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Si substrate 2 Gate insulating film 3 Gate electrode 4 Insulating film 5 Side wall 6 Source region 7 Drain region 8 Co film 9 Cap layer 21 Si substrate 22 CoSi film 23 Co film 24 Co oxide film 25 Cap layer made of SiO ₂

Claims (5)

Forming a Co silicide by heating after depositing or Co depositing Co and Si simultaneously on Si,
Subsequently, heating is performed while being exposed to a gaseous substance having a carboxyl group or after being exposed, and Co is volatilized as a carboxylate and Co is oxidized as SiO ₂ by being oxidized as SiO _2. A method for manufacturing a semiconductor device, comprising: a step of forming a protective film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the heating is irradiation with an energy beam. During or before exposure to a gaseous substance having a carboxyl group, heating is performed while introducing oxygen to form a Co oxide film and a SiO ₂ film on the surface, and the Co oxide film is volatilized as a carboxylate and SiO _{2. 2. The} method of manufacturing a semiconductor device according to claim 1, wherein the protective film made of is left and the film thickness of the Co silicide and the protective film made of SiO2 are controlled. 2. The method of manufacturing a semiconductor device according to claim 1, wherein when the MOS transistor is formed, the Co deposited on the side wall of the gate is exposed to a gaseous substance having a carboxyl group to be oxidized and removed. . When Co oxide is generated on the surface of Co silicide in advance, it is exposed to a gaseous substance having a carboxyl group and heated to remove the oxidized Co and generate a protective film made of SiO ₂ to keep the surface clean. The method of manufacturing a semiconductor device according to claim 1.

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