JP3361893B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a silicide electrode formed on a diffusion layer by self-alignment and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the miniaturization of LSIs, the wiring width is decreasing and the source / drain diffusion layers are becoming shallower. Therefore, the electric resistance of the wiring material, the diffusion layer and the like increases, which is one of the causes for increasing the signal transmission delay. As one method of reducing such a transmission delay, a technique of siliciding the gate electrode and the source / drain diffusion layers has been proposed.

A conventional semiconductor device in which a silicide layer is formed on the source / drain diffusion layers by self-alignment and a method of manufacturing the same will be described with reference to FIG. The source / drain diffusion layers formed in self-alignment silicide layer on generally salicide (Salicide: s elf- ali gned sili ci
de ) is called. First, on the silicon substrate 10, L
The element isolation film 12 is formed by the OCOS method. Then, after forming the gate oxide film 14 by thermal oxidation, the polysilicon 16 and the tungsten silicide (WSi) which will become the gate electrode are formed.
_x ) film 18 is continuously formed, and the polysilicon film 16 is doped by phosphorus (P) ion implantation.

Next, an HTO (high tem) for suppressing the reaction between the gate electrode 24 and the metal film during the later salicide formation.
After forming a perarure oxide film 20 and an antireflection film 22 for preventing halation in a lithography process when processing a gate electrode (FIG. 4A), a gate electrode 24 is formed by lithography and etching. . After processing the gate electrode 24, the HTO film 20 is left on the gate electrode 24 and the antireflection film 22 is removed (FIG. 4).
(B)).

Next, after forming an HTO film to be a side wall, the HTO film is etched back to form the side wall 2.
8 is formed. In order to form the source / drain diffusion layer 30, first, an oxide film 32 serving as a protective film is formed by thermal oxidation. Next, ion implantation is performed through the oxide film 32 to dope the impurities to be the source / drain diffusion layers 30 and activate by heat treatment (FIG. 4C).

Thereafter, the oxide film 32 is removed by a pretreatment using a hydrofluoric acid (HF) -based aqueous solution, and a titanium (Ti) film 3 for salicizing the source / drain diffusion layer 30 is formed.
4 is deposited. Next, the sample on which the Ti film 34 is deposited is heat-treated to silicify the deposited Ti film 34 (FIG. 4).
(D)). At this time, the HTO film 20 and the sidewall 28
Alternatively, since the Ti film 34 on the element isolation film 12 does not react with these underlying oxide films, the source / drain diffusion layer 3
Only the Ti film 34 deposited on 0 is silicidized in a self-aligned manner to form the silicide layer 36.

By removing the unreacted Ti film 34, a series of salicide forming steps are completed (see FIG. 4).
(E)). By forming salicide on the source / drain diffusion layer 30 in this manner, a shallow diffusion layer with low resistance can be formed.

[0008]

However, in the above-described conventional semiconductor device and the manufacturing method thereof, it is necessary to perform pretreatment with an HF-based aqueous solution immediately before the deposition of the Ti film 34 in order to remove the oxide film 32. , The HTO film 20 is a thermal oxide film having a normal etching rate for an HF-based aqueous solution.
Since it is about double, there is a problem that the HTO film 20 is removed by this pretreatment.

When the HTO film 20 is completely removed, the Ti film 3 is directly formed on the WSi _x film 18 of the gate electrode 24.
4 is deposited, and the WSi _x film 18 and Ti are deposited by the subsequent heat treatment.
There is a problem that the film 34 reacts. Also, WSi
_The reaction between the _x film 18 and the Ti film 34 causes the reaction layer to diffuse laterally, and as shown in FIG. 5A, the silicide layer 36 and the gate electrode 24 formed on the source / drain diffusion layer 30. There was a problem that and could be short-circuited by the bridge.

Further, when the wiring layer 40 is formed as an upper layer using the HTO film 20 as an interlayer insulating film, there is a problem that the gate electrode 24 and the wiring layer 40 are short-circuited. An object of the present invention is to provide a semiconductor device in which a gate electrode and a source / drain diffusion layer or a gate electrode and a wiring layer are not short-circuited when a source / drain diffusion layer is salicided, and a manufacturing method thereof.

[0011]

The object In order to achieve the above object, according to the metal film deposited on a base substrate, and a silicide electrode formed the starting substrate and the locally reacted by heat treatment, is formed on the upper surface of the gate electrode, A silicon oxynitride film that does not react with the metal film, or a silicon nitride film ,
The etching rate of the silicon oxynitride film or the silicon nitride film with respect to the hydrofluoric acid aqueous solution is
After the drain / drain diffusion layer is formed, it is removed with an aqueous solution of hydrofluoric acid.
It is achieved by a semiconductor device characterized in that the etching rate of the silicon thermal oxide film with respect to the hydrofluoric acid aqueous solution is slower.

[0012]

In the above semiconductor device, the refractive index of the silicon oxynitride film or the silicon nitride film is larger than 1.7 and smaller than 2.7, and the silicon oxynitride film or The semiconductor device is characterized in that the light absorption coefficient of the silicon nitride film is larger than 0.3 with respect to the light source wavelength of the exposure device used for patterning the gate electrode.

Further, in the above semiconductor device, the gate electrode is formed of polycrystalline silicon or tungsten polycide in which tungsten silicide is deposited on polycrystalline silicon. . In the above semiconductor device,
The silicide electrode is achieved by a semiconductor device characterized by being titanium silicide, cobalt silicide, or nickel silicide.

In addition, a conductive film deposition step of depositing a conductive thin film to be a gate electrode on a base substrate, and silicon having a slower etching rate for a hydrofluoric acid aqueous solution than a thermal oxide film on the conductive thin film. Oxynitride film, or
An insulating film depositing step of depositing a silicon nitride film, the silicon
Con oxynitride film, or processing the silicon nitride film及<br/> beauty the conductive thin film, a gate electrode forming step of forming the gate electrode, said to be formed a silicide electrode on a base substrate region An oxide film removing step of removing the oxide film with the hydrofluoric acid-based aqueous solution, and depositing a metal film on the underlying substrate from which the oxide film has been removed, and performing heat treatment to remove the oxide film from the underlying substrate. An electrode forming step of reacting the metal film to locally form the silicide electrode is accomplished by a method of manufacturing a semiconductor device.

[0016]

[0017]

According to the present invention, since the silicon oxynitride film that does not react with the metal film is used as the interlayer insulating film, the silicide layer can be selectively formed by the usual salicide forming process. In addition, since the insulating film that does not react with the metal film is deposited on the gate electrode, the metal film and the gate electrode do not react with each other in the salicide process, and the gate electrode and the source / drain diffusion layer are prevented from short-circuiting. can do.

Further, by using a silicon oxynitride film or a silicon nitride film as the insulating film,
It is possible to prevent a short circuit between the gate electrode and the source / drain diffusion layer without significantly changing the conventional semiconductor process or manufacturing apparatus. Further, since a silicon oxynitride film or a silicon nitride film, which has a slower etching rate with an HF-based aqueous solution, is deposited on the gate electrode as compared with an HTO film or an oxide film formed by thermal oxidation,
Since the silicon oxynitride film or the silicon nitride film on the gate electrode is not completely removed in the oxide film removal step when depositing the metal film for forming the salicide, the metal film and the gate electrode react in the salicide process. Therefore, it is possible to prevent the gate electrode and the source / drain diffusion layer from being short-circuited.

Further, the refractive index is larger than 1.7 and smaller than 2.7, and the light absorption coefficient is 0.3 with respect to the light source wavelength of the exposure device used for patterning the gate electrode.
By forming a larger silicon oxynitride film or silicon nitride film on the gate electrode, it can be used not only as a reaction suppressing film in the later salicide process but also as an antireflection film. In this case, a separate process for forming the antireflection film is not required, and the manufacturing process of the semiconductor device can be shortened.

The structure of the semiconductor device described above can be applied to a semiconductor device using polycrystalline silicon or tungsten polycide for the gate electrode. Further, the above structure of the semiconductor device can be applied to a semiconductor device in which salicide is formed by titanium silicide, cobalt silicide, and nickel silicide.

Further, a conductive thin film to be a gate electrode is deposited on the base substrate, and an insulating film having a slower etching rate with respect to the hydrofluoric acid aqueous solution than the thermal oxide film is deposited on the conductive thin film. A gate electrode is formed by processing a conductive thin film, the oxide film in the region where the silicide electrode is to be formed on the underlying substrate is removed by a hydrofluoric acid-based aqueous solution, and a metal film is deposited on the underlying substrate from which the oxide film has been removed. Then, the underlying substrate and the metal film in the region where the oxide film has been removed by the heat treatment are reacted with each other to locally form the silicide electrode. Therefore, the metal film and the gate electrode react with each other to form the gate electrode and the source / drain diffusion layer. It is possible to manufacture a semiconductor device in which no short circuit occurs.

By using a silicon oxynitride film or a silicon nitride film as the insulating film deposited on the conductive thin film, a semiconductor device can be manufactured without significantly changing the conventional semiconductor process or manufacturing device. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic sectional view showing the structure of a semiconductor device according to an embodiment of the present invention,
2A and 2B are process cross-sectional views showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 3 is a view showing a method for forming a wiring layer in a semiconductor device according to an embodiment of the present invention.

In the semiconductor device according to the present embodiment, an insulating film which is hard to be etched by an HF-based aqueous solution and functions as an antireflection film for preventing halation in lithography when processing the gate electrode is formed on the gate electrode. It is characterized by being accumulated. That is, the gate electrode 24 for controlling the channel current is formed on the silicon substrate 10 via the gate oxide film 14. A silicon oxynitride (SiON) film 38 is formed on the gate electrode 24, which is difficult to be etched by an HF-based aqueous solution and functions as an antireflection film for preventing halation in lithography when processing the gate electrode 24. Has been done. The silicide layer 3 is formed on the source / drain diffusion layer 30 by self-alignment.
6 is formed.

Next, a method of manufacturing the semiconductor device according to this embodiment will be described. First, LOCO is placed on the silicon substrate 10.
The element isolation film 12 is formed by the S method. Next, after the gate oxide film 14 is formed by thermal oxidation, the polysilicon 16 which will be the gate electrode and the WSi _x film 18 are continuously formed, and the polysilicon film 16 is doped by phosphorus (P) ion implantation.

Then, a SiON film 38 that suppresses the reaction between the metal film and the gate electrode during the subsequent salicide formation is formed by the plasma CVD method (FIG. 2A). In addition, S
It is desirable to form the iON film 38 under the following conditions. That is, the optical constant of the formed SiON film 38 is 1.7 <n with respect to the light source of the exposure apparatus.
The film is formed under the condition that <2.7 and 0.3 <k <1.0 are satisfied. Here, n is a refractive index and k is an absorption coefficient.

By setting the optical constants in this way, the SiON film can also be used as an antireflection film when processing the gate electrode. The etching rate of the SiON film 38 with respect to the HF-based aqueous solution also changes depending on the film forming conditions, but it is desirable to deposit the SiON film under the condition that the etching rate is slower than that of the thermal oxide film. This is because if the etching rate of the SiON film 38 is high, the SiON film 38 may be completely removed in the oxide film removal step in the subsequent salicide formation, and the gate electrode and the source / drain diffusion layer may be short-circuited. is there.

Table 1 shows an example of the relationship among the film forming conditions of the SiON film, the etching rate (E / R), the refractive index (n), and the absorption coefficient (k).

[0029]

[Table 1] As can be seen from Table 1, as the gas flow rate ratio of SiH ₄ / N ₂ O is increased, the etching rate is decreased and the refractive index and the absorption coefficient are increased. Therefore, by setting the upper limit of the flow rate ratio from the relationship with the refractive index and setting the lower limit of the flow rate ratio from the absorption coefficient and the etching rate, it is possible to form a SiON film that satisfies the above conditions. In the example of Table 1, by forming the SiON film under the film forming conditions of Sample 4, for example, the etching rate is about 1 / th that of the thermal oxide film.
At the same time as 3, it is possible to obtain a film having a sufficient refractive index and absorption coefficient to be used as an antireflection film.

After depositing the SiON film 38, the pattern of the gate electrode 24 is transferred by lithography, and the SiON film 38 and the WSi _x film 1 are formed by reactive ion etching.
8. Polysilicon 16 is continuously processed to form gate electrode 2
4 is formed (FIG. 2B). Next, after forming an HTO film to be a sidewall, the HTO film is etched back to form a sidewall 28.

In order to form the source / drain diffusion layer 30, first, an oxide film 32 serving as a protective film is formed by thermal oxidation. Next, ion implantation is performed through the oxide film 32 to dope the impurities to be the source / drain diffusion layers 30 and activate by heat treatment (FIG. 2C). After that, the oxide film 32 is removed by pretreatment using an HF-based aqueous solution. At this time, the SiON film 3 is formed on the gate electrode 24.
8 is deposited, but as described above, the SiON film 38
Is higher than HTO film and oxide film formed by thermal oxidation.
Since the etching rate of the F-based aqueous solution is slow, SiO
The N film 38 is entirely removed, and the gate electrode 24 is not exposed.

After that, a Ti film 34 for salicide on the source / drain diffusion layer 30 is deposited, and the Ti film 34 is silicified by heat treatment. At this time, SiON
Since the Ti film 34 on the film 38, the sidewall 28 or the element isolation film 12 does not react with the underlying oxide film, only the Ti film 34 deposited on the source / drain diffusion layer 30 is silicided in a self-aligned manner. (FIG. 2 (d)).

Next, the unreacted Ti film 34 is removed to complete the salicide formation process (see FIG. 2).
(E)). On the wiring formed by the gate electrode 24 on the element isolation film 12, as shown in FIG.
A wiring layer 40 such as a film may be formed. At this time as well, since the WSi _x film 18 of the gate electrode 24 is completely covered with the SiON film 38, the gate electrode 24 and the wiring layer 40 may be short-circuited. Can be prevented.

On the element isolation film 12, FIG.
, The SiON film 3 on the gate electrode 24 is intentionally
8 is removed to remove the gate electrode 24 and the wiring layer 40.
May be directly wired. In this case, for example, the SiON film 38 may be removed in the region connecting the gate electrode 24 and the wiring layer 40 before processing the gate electrode.
In this case, the metal film reacts with the gate electrode 24 to form the reaction layer 42 in the subsequent salicide process. However, the gate electrode 24 formed in the element isolation region is sufficiently removed from the source / drain diffusion layer 30. Since there is a distance, the gate electrode 24 and the source / drain diffusion layer 30 will not be short-circuited by the bridge even if the reaction layer 42 diffuses laterally due to the reaction.

As described above, according to the present embodiment, the SiON film 38 having a predetermined optical constant is formed on the gate electrode 24 instead of the conventional HTO film, so that the reaction in the salicide process which will be performed later can be prevented. Since it can be used not only as a deterrent film but also as an antireflection film, a separate process for forming the antireflection film is not required, and the semiconductor manufacturing process can be shortened.

Since the SiON film 38 has a slower etching rate by the HF-based aqueous solution than the HTO film or the oxide film formed by thermal oxidation, in the oxide film removing step before depositing the Ti film 34, the gate electrode is removed. Since the upper SiON film 38 is not entirely removed and the gate electrode 24 is not exposed, the Ti film 34 and the WSi _x film 18 of the gate electrode 24 do not react in the salicide process, and the gate electrode 24 and the source are not reacted. It is possible to prevent the / drain diffusion layer 30 from being short-circuited.

Further, the SiON film 38 has excellent compatibility with the manufacturing process of the silicon device, and since it is not necessary to significantly change the manufacturing apparatus for film formation, it can be easily incorporated in the manufacturing process. . Further, TiN is formed on the wiring by the gate electrode 24 on the element isolation film 12.
Even when the wiring layer 40 such as a film is formed, the gate electrode 24
Since the WSi _x film 18 is completely covered with the SiON film 38, it is possible to prevent the gate electrode 24 and the wiring layer 40 from being short-circuited.

Various modifications are possible without being limited to the above-mentioned embodiments of the present invention. For example, in the above-described embodiment, Si is formed on the gate electrode as a reaction suppressing film and an antireflection film during salicide formation.
Although the ON film is formed, the film is not limited to the SiON film as long as the film has a predetermined optical constant and the etching rate for the HF-based aqueous solution is slower than that of the thermal oxide film. For example, the same effect can be obtained by using a silicon nitride (SiN) film.

In the above embodiment, the gate electrode material is W
Although the tungsten polycide gate made of Si _x / polysilicon is used, the material is not limited to the gate electrode material. For example, a gate electrode made of a polysilicon single layer, another polycide electrode, or the like may be used. Further, although the Ti film is used as the metal forming the salicide in the above-mentioned embodiment, the salicide may be formed by using another metal film. For example, a cobalt (Co) film may be deposited to form cobalt silicide, or a nickel (Ni) film may be deposited to form nickel silicide.

[0040]

As described above, according to the present invention, as compared with the HTO film or the oxide film formed by thermal oxidation, the insulating film having a slower etching rate by the HF aqueous solution is deposited on the gate electrode. Since the insulating film on the gate electrode is not entirely removed in the oxide film removing step when depositing the metal film for forming the metal film, the metal film and the gate electrode do not react in the salicide step, It is possible to prevent a short circuit between the gate electrode and the source / drain diffusion layer.

Further, on the gate wiring on the element isolation film,
A wiring layer such as a TiN film may be formed in a later step, but since the gate wiring is completely covered with the insulating film at this time as well, it is possible to prevent a short circuit between the gate wiring and the wiring layer. it can. In addition, a conventional HTO is formed on the gate electrode.
By forming an insulating film having a predetermined optical constant instead of a film, it can be used not only as a reaction suppressing film in a later salicide process but also as an antireflection film. It is possible to shorten the manufacturing process of the semiconductor device without requiring the additional process.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a structure of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing the structure of a semiconductor device according to another embodiment of the present invention.

4A to 4C are process cross-sectional views showing a conventional method for manufacturing a semiconductor device.

FIG. 5 is a diagram illustrating a problem in a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

10 ... silicon substrate 12 ... device isolation film 14 ... gate oxide film 16 ... polysilicon film 18 ... WSi _x film 20 ... HTO film 22 ... antireflection film 24 ... gate electrode 28 ... side wall 30 ... source / drain diffusion layer 32 ... Oxide film 34 ... Ti film 36 ... Silicide layer 38 ... SiON film 40 ... Wiring layer 42 ... Reaction layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01L 29/78 301S (56) References JP-A-4-342141 (JP, A) JP-A-63-316476 (JP, A) JP-A-5-3256 (JP, A) JP-A-5-94966 (JP, A) JP-A-4-137621 (JP, A) JP-A-7-142424 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/28 301 H01L 29/78 H01L 21/336

Claims (5)

(57) [Claims] 1. A silicide electrode formed by locally reacting a metal film deposited on a base substrate with the base substrate by heat treatment, and silicon oxyde formed on the upper surface of a gate electrode and not reacting with the metal film. a nitride film, or a silicon nitride film
And the etching rate of the silicon oxynitride film or the silicon nitride film with respect to an aqueous solution of hydrofluoric acid is
After the drain / drain diffusion layer is formed, it is removed with an aqueous solution of hydrofluoric acid.
A semiconductor device characterized by being slower than an etching rate of a silicon thermal oxide film for an aqueous solution of hydrofluoric acid. 2. The semiconductor device according to claim 1, wherein the silicon oxynitride film or the silicon nitride film has a refractive index higher than 1.7 and 2.
Smaller than 7, and the light absorption coefficient of the silicon oxynitride film or the silicon nitride film with respect to the light source wavelength of the exposure device used when patterning the gate electrode,
A semiconductor device characterized by being greater than 0.3. 3. The semiconductor device according to claim 1, wherein the gate electrode is made of polycrystalline silicon or tungsten polycide in which tungsten silicide is deposited on polycrystalline silicon. apparatus. 4. The semiconductor device according to claim 1, wherein the silicide electrode is titanium silicide, cobalt silicide, or nickel silicide. 5. A conductive film deposition step of depositing a conductive thin film to be a gate electrode on a base substrate, and silicon having a slower etching rate for a hydrofluoric acid aqueous solution than a thermal oxide film on the conductive thin film. An insulating film deposition step of depositing an oxynitride film or a silicon nitride film, and a gate electrode forming step of processing the silicon oxynitride film or the silicon nitride film and the conductive thin film to form the gate electrode An oxide film removal step of removing the oxide film in the region where the silicide electrode is to be formed on the underlying substrate with the hydrofluoric acid-based aqueous solution; and depositing a metal film on the underlying substrate from which the oxide film has been removed, An electrode forming step of locally reacting the underlying substrate with the metal film in a region where the oxide film is removed by heat treatment to locally form the silicide electrode. The method of manufacturing a semiconductor device according to claim.