JP3249071B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device having a stacked contact plug structure, and more particularly to a method for stabilizing connection resistance.

[0002]

2. Description of the Related Art Conventionally, there has been known a semiconductor device having a multilayer wiring structure in which a large number of wiring layers are formed on a semiconductor substrate on which a semiconductor element is formed with an interlayer insulating film interposed therebetween. Hereinafter, a conventional method for manufacturing a semiconductor device will be described with reference to FIG. FIG. 4 is a cross-sectional view showing an example of a general structure of a semiconductor device having a conventional multilayer wiring structure.

As shown in FIG. 1, a first interlayer insulating film 2 and a connection hole formed in the first interlayer insulating film 2 are formed on a semiconductor substrate 1 on which a transistor (not shown) is formed. A buried first buried plug 3 made of a high melting point metal such as tungsten, a first interlayer insulating film 2 and a first buried plug 3
A first-layer metal wiring 4 made of a conductive material such as aluminum formed on the buried plug 3; a second interlayer insulating film 2 and a second-layer insulating film formed on the first-layer metal wiring 4; Film 5 and second buried plug 6 made of a refractory metal buried in a connection hole formed in second interlayer insulating film 5.
And a second-layer metal wiring 7 formed on the second interlayer insulating film 5 and the second buried plug 6.

Next, a manufacturing process for realizing the structure of the semiconductor device will be schematically described. First, the semiconductor substrate 1
Then, for example, a transistor having a gate insulating film, a gate electrode, and source / drain regions is formed. Then, a first interlayer insulating film 2 is deposited on the semiconductor substrate 1, and a connection hole reaching the impurity diffusion region 1 a (for example, the source / drain region) of the semiconductor substrate 1 is formed in the first interlayer insulating film 2. . Then, a first buried plug 3 is formed by burying a high melting point metal such as tungsten in the connection hole.
After that, a metal film such as an aluminum alloy film is formed on the first buried plug 3 and the first interlayer insulating film 2 and then patterned to form a first-layer metal wiring 4. After that, the same steps are repeated, and the second interlayer insulating film 4 and the second
A buried plug 6 and a second-layer metal wiring 7 are formed.

[0005]

The structure of the above-described semiconductor device has a structure in which a buried plug and a metal wiring are sequentially stacked in a connection hole of each interlayer insulating film. It is said that the conventional stacked contact plug structure has the following problems.

In this stacked contact plug structure, the embedded plug and the metal wiring of each layer are stacked, so that the embedded plug and the metal wiring are connected in series. Therefore, the resistance in the path connecting the metal wiring of each layer differs depending on the opening area of each connection hole which is the narrowest part in the path. In addition, there is a problem that the contact resistance is largely dependent on the opening area, and a stable connection resistance cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. An object of the present invention is to reduce the dependence of the connection resistance between wirings on the opening area, thereby reducing the variation in connection hole diameter. It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of exhibiting stable connection resistance.

[0008]

Means taken by the present invention to achieve the above object is to increase the contact area between the buried plug and the wiring thereon to thereby reduce the change in the connection resistance due to the variation of the connection hole diameter. To reduce the percentage of

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: forming a first interlayer insulating film on a conductive region of a semiconductor substrate;
Forming a first connection hole reaching the conductive region in the interlayer insulating film; and forming a central portion in the first connection hole.
Forming a recessed first buried plug; and forming on the first buried plug and the first interlayer insulating film
Forming a first wiring having a deep recess in which a height difference is emphasized, and depositing a second interlayer insulating film on the semiconductor substrate on which the first wiring is formed;
The deep recess of the first wiring in the second interlayer insulating film
Forming a second connection hole reaching a region including: a step of forming a second buried plug in the second connection hole; and forming the second buried plug and the second interlayer insulating film. and a step of forming a second wiring on the.

According to this method, there is a height difference between the upper surface of the first buried plug buried in the first connection hole and the upper surface of the first interlayer insulating film. In this state, since the first conductor film is deposited at a low coverage, a deep recess is formed in a region on the first buried plug of the first wiring patterned from the first conductor film. You. After that, when the second buried plug is formed on the first wiring, the contact area between the two becomes extremely larger than the cross-sectional area of the connection hole. Therefore, even if the diameter of the connection hole varies due to the manufacturing process or design, the contact area along the depth direction of the concave portion hardly changes, so that the variation in the contact area as a whole is reduced. That is, a semiconductor device having a stable connection resistance with small opening area dependence is formed. In addition, the presence of the concave portion in the first wiring also reduces the stress from the second embedded plug.

[0011] As described in claim 2, the claim
1, in the step of forming the first wiring,
The first wiring is formed from a conductor film deposited under the conditions of the coverage.
Preferably.

According to this method, the first wiring
The depth of the recess formed on the first buried plug is
It is possible to make it larger.

[0013] As described in claim 3, the claim
2, in the step of forming the first wiring, 20
Al deposited by low-temperature sputtering at 0 ° C or lower
It is preferable to form the first wiring from a minium alloy film.
Good.

[0014] By this method, the it is possible to sedimentary small conditions extremely coverage, the first wiring,
Increase the depth of the recess formed on the first embedded plug.
It becomes possible to be crisp .

As set forth in claim 4, claim
Forming a first buried plug in step 1
Then, from the metal film whose film thickness is thinner than the first interlayer insulating film,
By forming the first embedded plug, the central portion can be formed.
Easily forming a first embedded plug having a concave shape
be able to.

As set forth in claim 5, claim
Forming a second buried plug in step 1
Now, a second embedded plug with a concave central part is formed,
In the step of forming the second wiring, the second embedding is performed.
Has a deep recess on the plug
A second wiring can be formed. By this method
In the case of having a multilayer wiring structure of two or more layers,
Form a connection hole on the second buried plug reaching the wiring
And further comprising a second embedded plug and a wiring.
All by stacking up in the same way as
A semiconductor device having a stable connection structure between wiring layers
Will be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

1 to 3 show a method of manufacturing a semiconductor device having a stacked contact plug structure according to an embodiment of the present invention.

First, as shown in FIG. 1, a transistor such as a MOSFET is formed on a semiconductor substrate 1, and the semiconductor substrate 1
A first interlayer insulating film 2 having a thickness of 800 to 1200 nm
Is deposited. Then, a connection hole having a diameter of 0.5 to 0.7 μm reaching the impurity diffusion region 1a such as a source / drain region in the transistor is formed in the first interlayer insulating film 2.
Next, a high melting point metal is deposited in the connection hole with a thickness less than the thickness of the first interlayer insulating film 2, for example, about 350 to 700 nm, and then etched back to remove portions other than the connection hole. . By this step, the first embedded plug 3 having a slightly concave shape near the center is formed in the connection hole.

Next, as shown in FIG. 2, a first conductor film having a thickness of about 600 to 900 nm is deposited on the entire surface of the substrate at a low coverage. For example, when depositing an aluminum alloy film by a sputtering method, a low-temperature sputtering method of 200 ° C. or lower is employed. Then, the first conductive film is patterned, and in this step, the first-layer metal wiring 4 whose central portion is largely recessed is formed on the first embedded plug 3 and the first interlayer insulating film 2 around the first embedded plug 3. You. Here, an aluminum alloy film is used as the first conductor film, and the first conductor film is deposited by a low-temperature sputtering method. At this time, in the deposition of the aluminum alloy film by the low-temperature sputtering method, the aluminum alloy film does not flow as in the case of the high-temperature sputtering method. Moreover, by depositing the aluminum alloy film under a condition of low coverage, that is, low step coverage,
Overhang occurs at the edge of the connection hole, and the deposition rate of the film in the concave portion of the aluminum alloy film becomes extremely low. Therefore, as shown in the drawing, the height difference between the first interlayer insulating film 2 and the first buried plug 3 is emphasized, and the first-layer metal wiring 4 has a deep recess in the connection hole.
It is preferable that t × 2> D × 140%, where t is the deposition thickness of the refractory metal film and D is the diameter of the connection hole.

Next, as shown in FIG. 3, a second interlayer insulating film 5 is formed on the entire surface of the substrate.
A connection hole reaching the metal wiring layer 4 is formed. And
In this connection hole, a high melting point metal such as tungsten is deposited in a thickness less than the thickness of the second interlayer insulating film 5 to form a second buried plug 6. At this time, the second buried plug 6 has a shape in which the center is recessed, but the degree of the recess is the first degree.
The depression of the layer metal wiring 4 is reduced.
Thereafter, a second conductor film made of an aluminum alloy film is deposited on the entire surface of the substrate by low-temperature sputtering, and then the second conductor film is patterned to form a second buried plug 6 and a second interlayer insulating film 5. A second-layer metal wiring 7 is formed thereon. By this step, the second-layer metal wiring 7 whose central portion is largely recessed like the first-layer metal wiring 5 is formed.

As described above, according to the present embodiment, a buried plug having a thickness less than the thickness of the interlayer insulating film is formed in the connection hole formed in the interlayer insulating film, and a plug having a low covering rate is further formed thereon. Since the metal wiring made of the aluminum alloy film is formed under the conditions, it is possible to form the metal wiring having a shape in which the central portion is largely depressed. For this reason, the contact area between the metal wiring and the buried plug in the upper layer increases. Even if the diameter of the connection hole varies, the depth of the concave portion of the wiring hardly changes, so that the contact area according to the depth does not change. That is, even if the diameter of the connection hole varies, the degree of change in the contact area due to the variation is reduced. Therefore, a stable connection resistance with little dependence on the opening area can be realized.

Although stress is applied to the first-layer metal wiring 4 by the second buried plug 6 in the upper layer made of tungsten, since the center of the first-layer metal wiring 4 is largely recessed, Stress on the wiring and the like from the upper tungsten plug is also reduced.

In the above embodiment, the high melting point metal film is buried in the connection hole by the etch-back method, but may be buried by the selective CVD method.

[0025]

According to the first to fifth aspects of the present invention, as a method of manufacturing a semiconductor device having a stacked contact plug structure, a metal film thinner than an interlayer insulating film is formed in a connection hole. After burying and forming a buried plug, a conductive material is deposited thereon at a low coverage to form a wiring, and an upper-layer buried plug or the like is further formed thereon. By increasing the contact area between the semiconductor device and the buried plug thereon, it is possible to realize a method of manufacturing a semiconductor device having a stable connection resistance with a small opening area dependency.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a process of forming a first embedded plug in a manufacturing process of a semiconductor device having a stacked contact plug structure according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a process of depositing a first conductive film for forming a first wiring layer in a manufacturing process of the semiconductor device according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a process of depositing a second conductor film for forming a second wiring layer in the manufacturing process of the semiconductor device according to the embodiment of the present invention.

FIG. 4 is a sectional view of a conventional semiconductor device having a stacked contact plug structure.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 1a impurity diffusion region 2 first interlayer insulating film 3 first buried plug 4 first layer metal wiring 5 second interlayer insulating film 6 second buried plug 7 second layer metal wiring

Claims (5)

(57) [Claims] Forming a first interlayer insulating film on a conductive region of a semiconductor substrate; and forming a first interlayer insulating film on the first interlayer insulating film to reach the conductive region.
A step of forming a connection hole, forming a first buried plugs recessed central portion to the first connection hole, on said first buried plug and the first interlayer insulating film Forming a first wiring having a deep concave portion in which a height difference is emphasized ; depositing a second interlayer insulating film on the semiconductor substrate on which the first wiring is formed; The deep recess of the first wiring in the second interlayer insulating film;
Forming a second connection hole reaching a region including a portion ; forming a second buried plug in the second connection hole; and forming the second buried plug and the second interlayer insulating layer the method of manufacturing a semiconductor device and a step of forming a second wiring on the film. 2. A method for manufacturing a semiconductor device according to claim 1.
At In the step of forming the first wiring, under the condition of low coverage,
Forming the first wiring from the deposited conductor film;
A method for manufacturing a semiconductor device. 3. A method for manufacturing a semiconductor device according to claim 2.
At In the step of forming the first wiring, a low temperature of 200 ° C. or less
Aluminum alloy deposited by hot sputtering
Forming the first wiring from a film;
Manufacturing method of body device. 4. A method for manufacturing a semiconductor device according to claim 1.
At In the step of forming the first buried plug, the first
The first filling from a metal film thinner than the interlayer insulating film.
Manufacturing a semiconductor device characterized by forming a plug
Construction method. 5. A method for manufacturing a semiconductor device according to claim 1.
At In the step of forming the second embedded plug, the central portion
Forming a second buried plug with a recess, In the step of forming the second wiring, the second embedding is performed.
Has a deep recess on the plug that emphasizes the height difference
Semiconductor device, wherein a second wiring is formed.
Manufacturing method.