Patent Application
20160079176
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-185307, filed Sep. 11, 2014, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a semiconductor device.
In connection with miniaturization of semiconductor devices, the width and height of interconnects of semiconductor integrated circuits have been reduced. Therefore, when a metal interconnect is used, the interconnect resistance is increased due to the interface inelastic scattering of electrons.
To solve the problem, use of a graphene interconnect is suggested. Normally, a graphene film used for a graphene interconnect can be formed by growing graphene from a catalytic layer.
However, it is not easy to form a graphene film of good quality in a desired region. Thus, a semiconductor device which realizes acquisition of an excellent graphene film, and its manufacturing method are desired.
In general, according to one embodiment, a method of manufacturing a semiconductor device, the method includes: forming a first film having a first melting point; forming a pattern of a second film on an upper surface of the first film, the second film having a second melting point lower than the first melting point; and forming a graphene film on the upper surface of the first film, the graphene film being formed from a side surface of the pattern of the second film.
Embodiments will be described hereinafter with reference to the accompanying drawings.
This specification explains the method for manufacturing the semiconductor device according to the embodiment with reference to
Firstly, as shown in
On the underlying catalytic film 13, a first catalytic film (first film) 14 is formed. The first catalytic film 14 functions as a catalyst for growing graphene, and has a first melting point which is relatively high.
A metal film is employed for the first catalytic film 14. The metal film used for the first catalytic film 14 is formed of a main metal element and an additional element for making the melting point of the metal film (first catalytic film 14) higher than the melting point of the main metal element. The main metal element is selected from cobalt (Co) and nickel (Ni). The additional element can be divided into two groups.
An additional element which forms a chemical compound is categorized as the first group. In this case, silicon (Si) or titanium (Ti) can be used for the additional element. Thus, the metal film used for the first catalytic film 14 is formed of Co—Si, Co—Ti, Ni—Si or Ni—Ti.
An additional element which forms a solid solution is categorized as the second group. In this case, iridium (Ir) or ruthenium (Ru) can be used for the additional element. Thus, the metal film used for the first catalytic film 14 is formed of Co—Ir, Co—Ru, Ni—Ir or Ni—Ru.
Subsequently, as shown in
A metal film is employed for the second catalytic film 15. The metal film used for the second catalytic film 15 can be divided into two cases as follows.
In the first case, the metal film used for the second catalytic film 15 is formed of a single metal element. The single metal element is selected from cobalt (Co) and nickel (Ni). Thus, the metal film used for the second catalytic film 15 is formed of Co or Ni.
In the second case, the metal film used for the second catalytic film 15 is formed of a main metal element and an additional element for making the melting point of the metal film (second catalytic film 15) lower than the melting point of the main metal element. In this case, a solid solution is formed by the additional element. The main metal element is selected from cobalt (Co) and nickel (Ni). The additional element is selected from indium (In), manganese (Mn) and copper (Cu). Thus, the metal film used for the second catalytic film 15 is formed of Co—In, Co—Mn, Co—Cu, Ni—In, Ni—Mn or Ni—Cu.
In the next step, as shown in
Next, as shown in
Now, this specification explains the graphene film 17 obtained by the step shown in
In general, graphene grows from a side surface (facet) of a step. A catalytic film is employed for an underlying region having a step. However, when a catalyst having a low melting point is used, a catalytic material (catalytic metal) easily moves. Therefore, the catalytic material aggregates. As a result, a facet is formed in many places in the catalytic film. Thus, discontinuous graphene is formed. When a catalyst having a high melting point is used, a catalytic material (catalytic metal) has difficulty in moving. Therefore, the graphene growth is insufficient.
In the present embodiment, the first catalytic film 14 is formed by using a catalytic material which has a high melting point. The second catalytic film 15 is formed on the first catalytic film 14 by using a catalytic material which has a low melting point. Since the melting point of the second catalytic film 15 is low, graphene grows from the side surface (facet) 15a of the second catalytic film 15. Since the melting point of the first catalytic film 14 is high, the graphene formed on the upper surface of the first catalytic film 14 is flat. Therefore, it is possible to effectively form the graphene film 17 which has a large area and is excellent in flatness and continuousness. In addition, the graphene film 17 grows from the side surface 15a of the second catalytic film 15. The distance between the lower surface and the upper surface of the graphene film 17 corresponds to the distance between the lower edge and the upper edge of the side surface 15a of the second catalytic film 15.
In the above manner, the graphene film 17 is formed. Subsequently, a patterning process is applied to the graphene film 17 by lithography and etching. Thus, a plurality of graphene interconnects 17a are formed as shown in
As explained above, in the present embodiment, it is possible to form a graphene film which has a large area and is excellent in flatness and continuousness by forming the second catalytic film (second film) 15 having the second melting point which is lower than the first melting point on the first catalytic film (first film) 14 having the first melting point. Thus, a good interconnect having a low resistance can be obtained by using the above-mentioned graphene film to form the interconnect.
In the above embodiment, in the chip region including the graphene interconnects 17a, the second catalytic film 15 may be removed ultimately. However, in the dicing region, the structure shown in
Now, this specification explains a first modification example of the present embodiment. The basic structures are the same as the embodiment. Thus, the explanation of the structures explained in the embodiment is omitted.
Firstly, as shown in
Subsequently, as shown in
In the next step, as shown in
Subsequently, as shown in
In the above manner, the graphene film 17 is formed. After the formation, a patterning process is applied to the graphene film 17 in the same manner as the embodiment. Thus, the plurality of graphene interconnects 17a are formed in the same manner as
In this modification example, in the same manner as the embodiment, it is possible to form a graphene film which has a large area and is excellent in flatness and continuousness by forming the second catalytic film (second film) 15 having the second melting point which is lower than the first melting point on the first catalytic film (first film) 14 having the first melting point. Thus, a good interconnect having a low resistance can be obtained by using the aforementioned graphene film to form the interconnect.
In this modification example, the second catalytic film 15 on the liftoff pattern 21 is removed by the liftoff process. Thus, the upper surface of the first catalytic film 14 is little-etched, and maintains a surface state which is excellent in flatness. By forming a graphene film on the surface which is excellent in flatness, a graphene film of good quality can be obtained.
Now, this specification explains a second modification example of the embodiment. The basic structures are the same as the embodiment. Thus, the explanation of the structures explained in the embodiment is omitted.
In this modification example, an aggregation inhibiting film 31 is formed on the pattern of the second catalytic film 15 before the graphene film 17 is formed in the step of
As stated above, the second catalytic film 15 has a low melting point, and easily moves. Therefore, when the graphene film 17 is formed, the second catalytic film 15 may deform in the neighboring region of the side surface 15a of the second catalytic film 15. In this modification example, the aggregation inhibiting film 31 is provided to restrict the move of the second catalytic film 15. In other words, the aggregation of the second catalytic film 15 is restricted. In this modification example, it is possible to prevent the second catalytic film 15 from deforming in the neighboring region of the side surface 15a. From a different point of view, the graphene film 17 can be surely grown from the side surface 15a of the second catalytic film 15.
The aggregation inhibiting film 31 is selectively provided on the predetermined part of the second catalytic film 15. The predetermined part includes the neighboring region of the side surface 15a of the pattern of the second catalytic film 15. Therefore, the region in which the aggregation inhibiting film 31 is not formed is a free surface. In this region, the move of the second catalytic film 15 is not restricted. Thus, as shown in
As described above, in this modification example, the aggregation inhibiting film 31 is provided to prevent the second catalytic film 15 from deforming in the neighboring region of the side surface 15a of the second catalytic film 15. Thus, it is possible to form an excellent graphene film.
Now, this specification explains a third modification example of the embodiment. The basic structures are the same as the embodiment. Thus, the explanation of the structures explained in the embodiment is omitted.
In the above-described embodiment, the side surface 15a of the second catalytic film 15 is perpendicular. In this modification example, the side surface 15a of the second catalytic film 15 is inclined. In this manner, the side surface 15a of the second catalytic film 15 may be inclined. A graphene film 17 may be grown from the inclined surface.
Even when the side surface 15a of the second catalytic film 15 is inclined, the graphene film 17 grows from the side surface 15a. Thus, the distance between the lower surface and the upper surface of the graphene film 17 corresponds to the distance between the lower edge and the upper edge of the side surface 15a of the second catalytic film 15.
In the above embodiment, the first catalytic film 14 is used for the first film. This means that the first film functions as a catalyst at the time of graphene growth. However, the first film does not necessarily have to function as a catalyst. For example, tungsten (W) or a titanium nitride (TiN) may be used for the first film.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-185307 | Sep 2014 | JP | national |
