JP2001274241A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) [Problem] To provide a low-dielectric-constant insulating film in which problems such as poisoned vias are suppressed. SOLUTION: A first insulating film formed on a first wiring layer and having a region containing nitrogen formed on a surface thereof, a second insulating film made of an SOG-based material provided on the first insulating film, Second
A third insulating film provided on the insulating film, a second wiring layer provided on the third insulating film, and a first insulating film provided for connecting the first wiring layer and the second wiring layer The above object is achieved by a semiconductor device comprising: a connection hole penetrating the second insulation film and the third insulation film; and a plug provided in the connection hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method of manufacturing the same. More specifically, the present invention relates to a semiconductor device in which a low dielectric constant insulating film is used as an insulating film between wiring layers and a plug is formed in a connection hole opened in the film, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, there has been a need for a technique for controlling a step which increases due to high integration and high density of a semiconductor device, and further flattening the semiconductor device by embedding the step. In addition, as the performance of semiconductor devices becomes higher, it is indispensable to reduce the capacitance between wiring layers. From this viewpoint, the use of a low dielectric constant insulating film as an insulating film between wiring layers has attracted attention. Currently, inorganic insulating films, especially HSQ (Hydrog
en Silsesquioxane) membranes are of interest.

FIGS. 5A to 5C are cross-sectional views showing the steps of a conventional method for manufacturing a semiconductor device.

First, a first wiring layer 2 made of AlCu is formed on an oxide film (not shown) formed on a semiconductor substrate 1. Next, plasma TEOS (Tetraethylorthosili)
cate) -The first insulating film 3 having a thickness of 100 to 200 nm is formed on the first wiring layer 2 by the CVD method or the plasma SiH ₄ -CVD method (see FIG. 5A).

Next, a predetermined thickness (40) is formed on the first insulating film 3.
An HSQ film (0-600 nm) is applied, baked at 350 ° C., and sintered at 400 ° C. to form the second insulating film 4 (see FIG. 5B).

Next, a third insulating film 5 used as a polishing sacrificial film for planarization is formed on the second wiring layer 4 by plasma TEOS-CVD or plasma SiH ₄ -CVD.
It is formed with a thickness of 1000 to 2000 nm. Further, the thickness is 600 to 10 by a chemical mechanical polishing (CMP) method.
The third insulating film 5 is flattened to have a thickness of 00 nm. Next, after forming a connection hole by a photo / etch process,
The plug 6 is formed by filling the connection hole with tungsten. Further, a semiconductor device is formed by forming the second wiring layer 7 on the third insulating film 5 (see FIG. 5C).

In the above method, there is a problem that poisoned vias and the like are generated at the time of plug formation due to moisture adsorbed on the surface of the first insulating film. Therefore, good electrical characteristics between the wiring layers could not be obtained stably. The poisoned via refers to a phenomenon in which a gas generated by a reaction between moisture and HSQ causes voids in a plug and the connection hole is not completely filled, thereby increasing the resistance between wiring layers.

To solve this problem, Japanese Patent Laid-Open No.
In JP-A-335458, a region containing nitrogen is formed on the side wall by implanting nitrogen ions into the side wall of a second insulating film which is a low dielectric constant insulating film made of HSQ. This nitrogen-containing region blocks moisture in the second insulating film, thereby preventing poisoned via due to ejection of gas into the connection hole.

[0009]

However, since the opening of the connection hole is extremely fine, it has been extremely difficult to uniformly implant nitrogen ions into the side wall of the connection hole. Therefore, it has been desired to provide a method for manufacturing a semiconductor device applicable to a mass production process.

[0010]

Thus, according to the present invention, a first insulating film formed on a first wiring layer and having a region containing nitrogen formed on a surface thereof, and a first insulating film provided on the first insulating film. Second insulating film made of an SOG-based material, a third insulating film provided on the second insulating film, a second wiring layer provided on the third insulating film, a first wiring layer, and a second wiring A semiconductor device comprising: a first insulating film provided to connect the layers; a connection hole penetrating the second insulating film and the third insulating film; and a plug provided in the connection hole. Provided.

Further, according to the present invention, the first wiring layer is formed on the first wiring layer.
Forming an insulating film, irradiating the surface of the first insulating film with plasma containing nitrogen gas to form a region containing nitrogen on the surface of the first insulating film, and forming SOG on the first insulating film.
Forming a second insulating film made of a base material; forming a third insulating film on the second insulating film;
Forming a connection hole penetrating the insulating film and the third insulating film, forming a plug in the connection hole, and forming a second wiring layer on the third insulating film. A method for manufacturing a semiconductor device is provided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor device according to the present invention and a method for manufacturing the same will be described.

First, in the present invention, the first wiring layer may be a gate electrode, a source electrode, a drain electrode or the like formed on a semiconductor substrate (for example, a silicon substrate or the like), and is formed on the substrate. The uppermost wiring layer of the multilayer wiring may be used. Further, the first wiring layer may be formed on the semiconductor substrate via an insulating film such as a silicon oxide film.

As a material constituting the first wiring layer, A
1, metals such as Cu, Ti, W, alloys such as AlCu,
Polysilicon, polysilicon and high melting point metal (W, Ti
And the like). The thickness of the first wiring layer depends on the material to be used, design rules, and the like.
It is preferably from 0 to 500 nm.

Further, a metal nitride layer such as a TiN layer or a WN layer may be formed in order to improve the adhesion between the first wiring layer and the underlying layer below the first wiring layer.

Next, a first insulating film is formed on the first wiring layer. A region containing nitrogen is formed on the surface of the first insulating film. By forming the nitrogen-containing region, generation of moisture generated from the first insulating film can be suppressed. Therefore, a poisoned via or the like generated by a reaction between the material forming the second insulating film to be formed later and the water. The problem described above can be suppressed.

The first insulating film is made of, for example, TEOS, SiH
_{For example,} a silicon oxide film formed using a material such as ₄ can be used. It is preferable that the thickness of the first insulating film is 50 to 300 nm.

The method for forming the first insulating film is not particularly limited, and includes plasma TEOS-CVD, plasma SiH ₄ −
CVD method and the like can be mentioned.

Further, the first insulating film is irradiated with plasma containing nitrogen gas in order to form a region containing nitrogen on the surface thereof. Here, the plasma may be a plasma of a mixed gas with another gas such as a helium gas, an argon gas, and a hydrogen gas other than the nitrogen gas. It is preferable to include another gas since plasma discharge can be stably generated and as a result, the surface of the first insulating film can be uniformly processed. The mixing ratio of the nitrogen gas and the other gas is preferably in the range of 0.5: 1 to 1: 0.5.

The plasma is generated at a predetermined frequency from 1 to 10 T
Irradiation is preferably performed at a pressure of orr for 1 to 3 minutes.
In the case of nitrogen gas alone, the flow rate is 300 to 1000 sc
cm, and in the case of a mixed gas, the nitrogen gas is set to 100 to 500 sccm, and the other gas is set to 100 to 500 sccm.
Preferably, it is 500 sccm.

Further, it is preferable that the frequency is a high frequency of 13.56 MHz and a low frequency of 350 kHz. By using two frequencies, at low frequencies, the plasma follows the irregularities of the first insulating film, reaches the space between the small gaps, and can perform the processing using the plasma. On the other hand, at high frequencies, the plasma generation efficiency can be increased, so that the processing efficiency can be improved. The power at high frequency is 100 to 600 W, and the power at low frequency is 50 to 300 W.
It is preferably W.

In the plasma treatment, the first insulating film is 40
Preferably, it is heated to 0 to 500C. By heating within this range, a region containing nitrogen on the surface of the first insulating film can be formed more efficiently, and deterioration of characteristics of the first wiring layer due to heat can be prevented.

The plasma device that can be used for the plasma processing is not particularly limited, and any known device can be used. For example, a parallel plate anode bonding type RF plasma device, and a diffusion type plasma device such as ECR or helicon wave can be used.

Next, a second insulating film made of an SOG material is formed on the first insulating film.

As the SOG-based material, a material which reacts with moisture adsorbed on the surface of the first insulating film to generate a gas by a heat treatment after the formation of the second insulating film is used. In particular,
Examples include HSQ, parylene, BCB, Teflon (registered trademark), polyimide, and amorphous carbon. Second
It is preferable that the thickness of the insulating film is 300 to 700 nm on the first insulating film where the first wiring layer is not present.

Here, since a region containing nitrogen is formed on the surface of the first insulating film, moisture adsorbed on the surface is removed and the surface becomes hydrophobic. As a result, the generation of a Si—OH bond (this bond releases water vapor at 300 ° C. or more) caused by the reaction between the material constituting the second insulating film and moisture is suppressed, and stable Si—O
-Si or Si-H bonds can be maintained. Therefore, problems such as poisoned via due to degassing of water vapor or the like can be suppressed.

As a method of forming the second insulating film, a known coating method such as a spin coating method can be used. According to this coating method,
The concave portion of the first insulating film is preferentially filled with the second insulating film,
The thickness of the second insulating film is reduced on the protrusion.

The applied second insulating film is 380 to 500
It is preferred to sinter at ℃. In addition, before sintering,
Baking at ~ 350 ° C is more preferred. here,
It is preferable to perform the sintering and baking while flowing a large amount of nitrogen gas at 250 to 500 ° C. (for example, 15 liters / minute). Thereby, the oxygen concentration in the second insulating film can be suppressed to about 100 ppm or less. as a result,
It is possible to suppress generation of a Si—OH bond caused by a reaction between moisture and a material forming the second insulating film.
Therefore, problems such as poisoned vias can be suppressed.

The second insulating film may be formed on the first wiring layer without forming the first insulating film. In this case, it is necessary to irradiate plasma to form a region containing nitrogen in a portion where the first wiring layer is not formed.

Next, a third insulating film is formed on the second insulating film. The third insulating film may be composed of a silicon oxide film, a silicon nitride film, and a laminated film thereof. Third
The thickness of the insulating film only needs to be at least enough to fill a step formed on the surface of the second insulating film. For example, 150
It can be formed with a thickness of about 0 to 2000 nm.

Further, it is preferable that the surface of the third insulating film is flattened by means such as a CMP method.

Next, in order to connect the first wiring layer and a second wiring layer to be formed later, connection holes penetrating therethrough are formed in the first insulating film, the second insulating film and the third insulating film. Is provided. The method for forming the connection hole is not particularly limited, and a known etching method can be used.

A plug is formed in this connection hole. This plug is made of, for example, a metal such as W. The plug can be formed by a known method such as a blanket CVD method. Specifically, first, T as a barrier layer
forming an i film with a thickness of 20 to 50 nm by a sputtering method,
Next, a TiN film as an adhesion layer is formed by sputtering or CV.
It is formed to a thickness of 5 to 20 nm by the D method, and further, W
After a thickness 300~700nm by CVD film, thereby forming plugs in the connection hole by etching back using an etchant such as SF _6.

Next, a second wiring layer is formed on the third insulating film. As a material for forming the second wiring layer, Al,
Examples include metals such as Cu, Ti and W, alloys such as AlCu, polysilicon, and silicide of polysilicon and a high melting point metal (W, Ti, etc.). The thickness of the second wiring layer varies depending on the material to be used, design rules, and the like.
It is preferably 00 nm.

A known cover film may be formed on the second wiring layer.

By repeatedly laminating the above structure, a multilayer wiring of two or more layers can be formed.

[0037]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Embodiment 1 A method for manufacturing a semiconductor device of Embodiment 1 will be described with reference to FIGS.

First, a silicon oxide film (not shown) was formed on the semiconductor substrate 1. The first wiring layer 2 made of Al was formed on the silicon oxide film. The thickness of the first wiring layer 2 was 400 to 500 nm. Next, the entire surface of the semiconductor substrate 1 including the first wiring layer 2 is covered with TEOS-CVD or Si.
The first insulating film 3 was formed by the H ₄ -CVD method (FIG. 1).
(A)). The thickness of the first insulating film 3 is 100 to 20
It was 0 nm.

Next, with the semiconductor substrate 1 heated over the entire surface of the first insulating film 3, plasma of nitrogen gas was irradiated (FIG. 1).
(B)). For the plasma irradiation, a parallel plate anodic bonding type RF plasma processing apparatus shown in FIG. 2 was used. The surface of the first insulating film 3 was irradiated with plasma by applying two frequencies of a high frequency and a low frequency to the upper electrode 15 and the lower electrode 16 of this device. By this irradiation, a region containing nitrogen could be formed on the surface of the first insulating film 3.

More specifically, a high frequency (13.56 MHz)
z) is applied from the lower electrode 16 and a low frequency (350 kHz) is applied.
z) was applied from the upper electrode 15 via the low-pass filter 18. Between the two electrodes, the nitrogen gas flowing out of the gas diffusion unit 19 was brought into a plasma state, and the surface of the first insulating film was irradiated with the plasma. Other conditions for the plasma treatment are as follows: power is 300 W at high frequency and 2 W at low frequency.
00W, pressure 5.0 Torr, nitrogen gas flow rate 60
0 sccm, the reaction temperature was 400 ° C., and the treatment time was about 1 minute.

In FIG. 2, reference numeral 12 denotes a semiconductor substrate, 13 denotes a susceptor, 14 denotes a lamp, and 17 denotes an RF electrode.

Here, the amount of water adsorbed on the surface of the first insulating film before and after plasma irradiation was measured. The measurement was performed by TDS (thermal desorption spectroscopy). The results are shown in FIG. As can be seen from FIG. 3, the amount of moisture released from the first insulating film can be reduced by performing plasma irradiation. This is probably because the surface of the first insulating film became hydrophobic by containing nitrogen.

Next, an HSQ film was formed by a spin coating method so that the thickness on the first insulating film on which the first wiring layer was not formed was 400 nm. The HSQ film was baked at 350 ° C. and sintered at 400 ° C. to form the second insulating film 4. The sintering was performed under a large amount of nitrogen gas atmosphere of 15 liter / min. Thereby, the oxygen concentration in the second insulating film could be suppressed to 100 ppm or less.

Next, a third insulating film 5 is formed on the entire surface of the second insulating film 4.
Silicon oxide film having a thickness of 1500 to 2000 nm
And a thickness of 600 to 100 by the CMP method.
It was flattened to have a thickness of 0 nm (see FIG. 1C).

Next, connection holes were opened in the first insulating film 3, the second insulating film 4, and the third insulating film 5 on the first wiring layer 2. A plug 6 made of W was formed in the connection hole by a normal blanket CVD method. Specifically, first, a Ti film as a barrier layer is formed with a thickness of 20 to 50 nm by a sputtering method, and then a TiN film as an adhesion layer is formed with a thickness of 5 to 20 nm by a sputtering method or a CVD method. After forming a W film on the entire surface with a thickness of 300 nm by the CVD method,
A plug was formed in the connection hole by etching back using SF ₆ as an etchant.

Thereafter, the AlC is placed at a predetermined position on the plug 6.
A semiconductor device was obtained by forming the second wiring layer 7 made of u (see FIG. 1D). The thickness of the second wiring layer 7 is 4
It was 00-500 nm.

FIG. 4A shows the relationship between the resistance of the plug of the obtained semiconductor device and the yield. In the figure, TH means the diameter of the plug.

Comparative Example 1 A semiconductor device was formed in the same manner as in Example 1, except that the first insulating film was not irradiated with plasma. FIG. 4B shows the relationship between the resistance of the plug and the yield of the obtained semiconductor device.

As can be seen from a comparison between FIGS. 4A and 4B, the variation in the resistance value of the plug could be suppressed by irradiating the plasma. Therefore, it was found that the plug of Example 1 had more stable characteristics.

Example 2 A semiconductor device was formed in the same manner as in Example 1 except that the first insulating film was irradiated with plasma composed of a mixed gas of nitrogen gas and argon gas (volume ratio 1: 1). In this example, more stable plasma was obtained than in Example 1, and the surface of the first insulating film could be uniformly processed.

[0052]

According to the present invention, SOG is formed on the first insulating film.
Forming a hydrophobic region containing nitrogen on the surface of the first insulating film by irradiating the surface of the first insulating film with plasma containing nitrogen gas before forming the second insulating film made of a system material; Can be. For this reason, it is possible to suppress problems such as poisoned vias caused by the reaction between the SOG-based material and moisture. That is, since the generation of gas due to the reaction between the SOG-based material and the moisture can be suppressed, the connection hole can be embedded finely with the plug. As a result, it is possible to provide a semiconductor device including a plug with less variation in resistance.

[Brief description of the drawings]

FIG. 1 is a schematic process sectional view of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a schematic sectional view of a plasma processing apparatus used in the example.

FIG. 3 is a graph showing the amount of water released from the surface of a first insulating film of Example 1 and Comparative Example 1.

FIG. 4 is a graph showing characteristics of plugs of Example 1 and Comparative Example 1.

FIG. 5 is a schematic sectional view of a process in a method for manufacturing a conventional semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 first wiring layer 3 first insulating film 4 second insulating film 5 third insulating film 6 plug 7 second wiring layer 12 semiconductor substrate 13 susceptor 14 lamp 15 upper electrode 16 lower electrode 17 RF electrode 18 low-pass filter 19 Gas diffusion unit

Continued on front page F-term (reference) AD05 AD06 AD10 AD11 AH02 AH05 BD02 BD04 BD10 BD19 BF02 BF25 BF29 BH16 BJ02 BJ05

Claims (4)

[Claims] A first insulating film formed on the first wiring layer and having a region containing nitrogen formed on a surface thereof; and a second insulating film made of an SOG-based material provided on the first insulating film. , Second
A third insulating film provided on the insulating film, a second wiring layer provided on the third insulating film, and a first insulating film provided for connecting the first wiring layer and the second wiring layer A connection hole penetrating the second insulation film and the third insulation film, and a plug provided in the connection hole. 2. A step of forming a first insulating film on a first wiring layer, and irradiating a surface of the first insulating film with a plasma containing nitrogen gas to form a region containing nitrogen on the surface of the first insulating film. Forming and forming a second SOG-based material on the first insulating film.
Forming an insulating film, forming a third insulating film on the second insulating film, forming connection holes penetrating the first insulating film, the second insulating film, and the third insulating film; A method for manufacturing a semiconductor device, comprising: a step of forming a plug in a hole; and a step of forming a second wiring layer on a third insulating film. 3. The method according to claim 2, wherein the plasma is a mixed gas plasma of a nitrogen gas, a helium gas, an argon gas or a hydrogen gas. 4. The method according to claim 1, wherein the first insulating film has a thickness of 40.
The production method according to claim 2, wherein the composition is heated to 0 to 450 ° C. 5.