Patent Application
20060022342
1. Field of the Invention
The present invention relates to a semiconductor device having a novel structure and a method for manufacturing the same; and more specifically to a semiconductor device having multi-layer wirings of a lowered wiring capacity by the use of a low-dielectric-constant film of a novel structure, and a method for manufacturing the same.
2. Related Background Art
With the miniaturization of semiconductor devices in recent years, wiring capacity has increased, and the delay of signals through wirings has become significant. For lowering wiring capacity, the reduction of the resistance of metal wiring, and the use of materials having a low specific dielectric constant as interlayer insulating films can be considered. In general, as a method for reducing the resistance of metal wiring, the change of the metal for wirings from aluminum to copper, which has a lower resistivity, is considered.
On the other hand, in order to lower the specific dielectric constant of the interlayer insulating films, instead of conventional SiO2 (specific dielectric constant ε=4.3) the use of Si—O-based inorganic materials having a low specific dielectric constant, such as fluorine-doped SiOF and HSQ (hydrogen silsesquioxane), organic materials, such as a polyimide-based resin, the mixtures of organic and inorganic materials and the like have been studied.
As a method for lowering the specific dielectric constant of interlayer insulating films, making the above substances or the like porous is also examined. Japanese Patent Application Laid-Open No. 2000-216153 discloses a porous film consisting of an organic-inorganic composite film formed by a plasma CVD method using a mixed gas of a silicon alkoxide and an organic compound. Japanese Patent Application Laid-Open No. 2002-75982 discloses a porous-silica-based film consisting of polyalkylsilazane and polyacrylic acid or the like.
According to these patent gazettes, a low-dielectric-constant material can be formed by making the material porous.
However, since the film quality of porous bodies composed of organic materials or the mixture of organic and inorganic materials is significantly different from the film quality of a silicon oxide film or the like used as the material of interlayer insulating films in conventional semiconductor devices, various new processes are required leading to the rise of costs for manufacturing the semiconductor devices. In addition, there are many materials inferior to conventionally used silicon oxide or the like in the resistance to the semiconductor process and the stability for a long period of time, such as the deterioration of the film quality by organic solvents. Furthermore, when compared with conventionally used silicon oxide, many materials are difficult to perform fine processing using etching. Therefore, using porous bodies composed of organic materials or the mixture of organic and inorganic materials, it is difficult to fabricate semiconductor devices having a high reliability at low costs, compared with conventionally used silicon oxide.
Therefore, an object of the present invention is to provide a semiconductor device having interlayer insulating layers that excels in chemical resistance and fine processability by using a porous body composed mainly of silicon oxide formed from inorganic materials only.
Another object of the present invention is to provide a method for manufacturing the above-described semiconductor device at low costs.
The first aspect of the semiconductor device according to the present invention is a semiconductor device comprising interlayer insulating layers formed on a substrate, and wirings formed in the interlayer insulating layers, wherein the interlayer insulating layers are composed of a porous body having fine pores of a columnar shape and a parent material region consisting mainly of silicon oxide surrounding the pores, and the wirings are composed of a structure wherein columnar substances containing aluminum dispersed in a base material composed of silicon.
The second aspect of the semiconductor device according to the present invention is a semiconductor device comprising interlayer insulating layers formed on a substrate, and wirings formed in the interlayer insulating layers, wherein the interlayer insulating layers are composed of a porous body having fine pores of a columnar shape and a parent material region consisting mainly of silicon oxide surrounding the pores, and the wirings are composed of a region wherein an electrically conducting material is introduced in a portion of the porous body.
The average pore diameter of the above-described fine pores is preferably 1 nm or larger and 15 nm or smaller; and the average distance between the pores is preferably 3 nm or longer and 20 nm or shorter. This is because the higher pore density and the smaller pore diameter make the mechanical strength of the porous body higher, and raise the reliability of the device; and the larger fine pore portion of the porous body lowers the dielectric constant and increases the speed of the device.
The above-described fine pores are preferably formed perpendicularly or substantially perpendicularly to the film surface. This is because if the fine pores are formed at a slant to the film surface, when a metallic material is inserted to form wirings, the wirings also become adversely slanted. The fine pores may be substantially perpendicular to the film surface, and is not required to be perfectly perpendicular.
By thus using silicon oxide, which has been conventionally used, as the major component, chemical resistance and the like of the film can be raised compared with organic materials. The specific dielectric constant can also be lowered by making the silicon oxide porous.
The semiconductor device according to the present invention may contain aluminum oxide in the porous body used as interlayer insulating films.
The first aspect of the method for manufacturing a semiconductor device according to the present invention has a step of preparing a structure wherein columnar substances containing aluminum as the major component are dispersed in a base material consisting mainly of silicon and containing at least aluminum; and a step of removing the columnar substances.
The second aspect of the method for manufacturing a semiconductor device according to the present invention has a step of preparing a structure wherein columnar substances containing aluminum as the major component are dispersed in a base material consisting mainly of silicon and containing at least aluminum; a removing step of removing the columnar substances; and an introducing step of introducing an electrically conductive material in a portion of the regions in the pores of the porous bodies having columnar pores formed by the removing step.
The third aspect of the method for manufacturing a semiconductor device according to the present invention has a step of preparing a structure wherein columnar substances containing aluminum as the major component are dispersed in a base material consisting mainly of silicon and containing at least aluminum; a first removing step of removing the columnar substances; a second removing step of removing a portion of the porous bodies having columnar pores formed by the first removing step; and an introducing step of introducing an electrically conductive material in porous-body-removed portions formed by the second removing step.
The step of preparing the structure is preferably a step of preparing a structure wherein the columnar substances are dispersed in the base material perpendicularly, or substantially perpendicularly to the film surface.
In such methods for manufacturing a semiconductor device, the processes of conventional wiring-burying methods, such as the removal of interlayer insulating layers, the burying of a wiring metal and planarization, can contingently omitted, and a semiconductor device using multi-layer wirings can be manufactured easily at low costs.
The history to reach the present invention will be described. The present inventors conducted research on fine structures using aluminum, and happened to reach the above-described findings.
Specifically, the present inventors found that when silicon was added during the formation of an aluminum film on a substrate using a method for forming a film of a material in a non-parallel state, such as a sputtering method, there was a case wherein aluminum of a columnar structure was spontaneously formed in the matrix of silicon substantially perpendicularly to the substrate under predetermined conditions. It was also found that when the film on which the aluminum of the columnar structure was formed was immersed in a solvent that preferentially dissolves aluminum than silicon, and oxidized, a porous body consisting mainly of silicon oxide was formed which was inorganic material wherein fine pores of a diameter of several nanometers (silicon oxide porous body) was formed.
It was also found, by the measurement of the specific dielectric constant of thus prepared silicon oxide porous body, that the specific dielectric constant lowered compared with conventional non-porous silicon oxide.
It was also possible to introduce metallic materials (including carbon nanotubes) in a porous body consisting mainly of silicon oxide (silicon oxide porous body) using an electrodeposition method, a VLS (vapor liquid solid) method or the like.
It was also found that thus prepared silicon oxide porous body had chemical resistance substantially equivalent to the chemical resistance of conventionally used silicon oxide.
Thus, the present inventors conducted repetitive studies on the bases of the above findings, and reached the present invention.
The embodiment of a semiconductor device and a method for manufacturing the same according to the present invention will be described in detail below.
<Constitution of Semiconductor Device>
In
As
As
The porous body 10 is composed mainly of silicon oxide, and the composition thereof to all the elements other than oxygen is preferably 0.1 atomic % or more and 30 atomic % or less aluminum, and 70 atomic % or more and 99.9 atomic % or less silicon. Although the material of the porous body 10 preferably consists of silicon oxide, it may contain small quantities of various elements, such as argon (Ar), nitrogen (N) and hydrogen (H). Although the material of the porous body 10 is preferably porous, it may also contain crystalline materials.
In the interlayer insulating layer 3, at least a part may be composed of a porous body 10 consisting mainly of silicon oxide, and a part of the interlayer insulating layer 3 may be composed of a conventionally used low-dielectric-constant film.
The wiring 4 is characterized to be composed of a structure wherein columnar substances containing aluminum are dispersed in a base material containing silicon; to be composed of a metallic material buried in a plurality of fine pores in the interlayer insulating layer 3; or to be composed of a metallic material buried in a hole formed by a part where the interlayer insulating layer 3 has been removed. Although the metallic material composing the wiring 4 is preferably Al or Cu, which has a low resistivity and low costs, a single element metal such as Ag, Au, Mo and W, or an alloy formed by mixing two or more metals can also be used. Furthermore, CNT (carbon nanotube) may also be used.
Although the protective insulating layer 2 is preferably composed of an insulator such as SiN, it may be not used if there are no problems in the operation of the semiconductor device.
<Method for Manufacturing Semiconductor Device>
The method for manufacturing a semiconductor device according to the present invention will be described below.
Here, the example wherein a via, which is a vertical wiring, is formed in the interlayer insulating layer will be described.
(First Step)
The first step is a step for preparing a structure wherein columnar substances consisting mainly of aluminum are dispersed in a material consisting mainly of silicon and containing at least aluminum substantially perpendicularly to the film surface.
For example, aluminum and silicon are provided, and using a method that can form a substance in a non-equilibrium state, such as a sputtering method, a structure consisting of an aluminum-silicon mixture (aluminum-silicon mixed film) 20 wherein aluminum columnar structures 23 are dispersed in a matrix of silicon 22 is formed on a semiconductor substrate 21 as
When the aluminum-silicon mixed film 20 is formed using such a method, as shown in
Specifically, the aluminum columnar structures 23 shown in
In the mixed film of aluminum and silicon, the quantity of silicon in the formed film is 20 to 70 atomic %, preferably 25 to 65 atomic %, and more preferably 30 to 60 atomic % to the total quantity of aluminum and silicon. If the quantity of silicon is within such a range, an aluminum-silicon mixed film 20 wherein aluminum columnar structures 23 are dispersed in the region of silicon 22 can be obtained.
The atomic percent indicating the proportion of aluminum and silicon indicates the proportion of the numbers of silicon and aluminum, and is also described as atom % or at %. For example, it is a value when the quantities of silicon and aluminum in the aluminum-silicon mixed film are quantitatively analyzed using an inductively coupled plasma emission spectrometry method (ICP method).
(Second and Third Steps)
These steps include a step for removing the aluminum columnar structures 23 (columnar substances) from the aluminum-silicon mixed film 20 (structure) after the above-described first step, and a step for oxidizing the structure after the removing step simultaneously with or after the removing step.
For example, as
Furthermore, as
Although the solutions used in the etching of the aluminum columnar structures 23 include acids such as phosphoric acid, sulfuric acid, hydrochloric acid and a chromic acid solution, which dissolve aluminum but little dissolve silicon, an alkali such as sodium hydroxide can also be used if there are no adverse impacts in the formation of fine pores by etching, and the types of the acid or alkali are not specifically limited. The mixture of several kinds of acid solutions or several kinds of alkali solutions can also be used. The etching conditions, such as solution temperature, solution concentration and etching time can be suitably selected depending on the porous body to be formed.
(First Step)
The first step is a step for preparing a structure wherein columnar substances consisting mainly of aluminum are dispersed in a material consisting mainly of silicon and containing at least aluminum substantially perpendicularly to the film surface.
For example, aluminum and silicon are provided, and using a method that can form a substance in a non-equilibrium state, such as a sputtering method, a structure wherein aluminum columnar structures 33 are dispersed in the matrix of silicon 32 on a semiconductor substrate 31, that is an aluminum-silicon mixed film 30 is formed as
(Second and Third Steps)
These steps consist of a removing step for removing columnar structures consisting mainly of Al, and a step for oxidizing the structures after the removing step simultaneously to or after the removing step.
For example, as
Specifically, the silicon oxide porous body 30a shown in
(Fourth Step)
The fourth step is an introducing step for introducing an electrically conductive material in a part of regions in the fine pores 34 of the porous body 30a having the columnar fine pores 34 formed in the above removing step.
For example, as
Here, although a method to electrodeposit an electrically conductive material selectively on the region other than the masked region with the resist 35 is described, a method wherein the base material in the place to be electrodeposited (wiring region) is changed, as
After removing the resist 35 using a remover as
The first and third steps are repeated to manufacture a semiconductor device having multi-layered wirings as shown in
(First Step)
The first step is a step for preparing a structure wherein columnar substances consisting mainly of aluminum are dispersed in a material consisting mainly of silicon and containing at least aluminum substantially perpendicularly to the film surface.
For example, aluminum and silicon are provided, and using a method that can form a substance in a non-equilibrium state, such as a sputtering method, a structure wherein aluminum columnar structures 43 are dispersed in the matrix of silicon 42 on the semiconductor substrate 41, that is an aluminum-silicon mixed film 40 is formed as
(Second and Third Steps)
These steps consist of a first removing step for removing columnar structures consisting mainly of Al, and a step for oxidizing the structures after the first removing step simultaneously to or after the first removing step.
For example, as
(Fourth Step)
The fourth step is a second removing step for removing a part of the porous body 40a having columnar fine pores 44 obtained in the first removing step.
For example, as
(Fifth Step)
The fifth step is an introducing step for introducing an electrically conductive material in a region 46 after removing the porous body formed in the above second removing step.
For example, as
A semiconductor device having multi-layered wirings as shown in
The present invention will be specifically described below referring to examples.
The first example is an example of a semiconductor device wherein porous films having fine pores perpendicular to a substrate consisting mainly of silicon oxide are used as interlayer insulating layers, and wirings are formed by burying aluminum in the fine pores in the porous film. Here, an example of forming a via, which is a vertical wiring, is formed in the interlayer insulating layers will be described.
As described above,
First, on a semiconductor substrate on which semiconductor elements such as MOSFET, wiring layers and element isolating regions (not shown) were formed, an aluminum-silicon mixture (mixed film) 20 containing 60 atomic % aluminum relative to the total quantity of aluminum and silicon as shown in
The aluminum-silicon mixture 20 was observed using an FE-SEM (field emission scanning electron microscope). The surface viewed from diagonally above has aluminum columnar structures arranged two-dimensionally surrounded by the silicon region as
Next, as
Next, the aluminum-silicon mixture on which the resist 24 was formed was immersed in a 5 wt % solution of phosphoric acid for 4 hours to remove the portion of the aluminum columnar structures 23, and the region of silicon 22 was oxidized to form fine pores 25 as shown in
In such a method for forming the metal wirings (via) 26, fine pores of a diameter of up to about 5 nm substantially perpendicular to the substrate are formed only in the open portion of the resist 24, and on the region where the resist is formed the metal wirings (via) 26 are formed perpendicularly to the semiconductor substrate 21. Therefore, if the open portion of the resist 26 can be formed, the metal wirings (via) 26 of diameters up to about 5 nm can be formed. Specifically, since there is no limitation of forming the metal wiring (via) portion by fine processing of the interlayer insulating layers, this method can form finer metal wirings (via) than conventional methods.
Next, the phosphoric-acid-etched aluminum-silicon mixed film (porous body composed of a material consisting mainly of silicon oxide) 20a was observed using an FE-SEM (field emission scanning electron microscope). On the surface of the porous body 20a region other than the metal wiring (via) region 26 viewed from the diagonally above, as the silicon oxide porous body of
Since the fabricated porous body 20a is more porous than regular silicon oxide, it has a lowered specific dielectric constant. As a result, wiring delay can be reduced compared with a semiconductor device manufactured using regular silicon oxide. Since the porous film of the present invention is composed of an inorganic material consisting substantially of Si—O, chemical resistance is improved over a porous film composed of an organic material or the mixture of inorganic and organic materials.
Next, such steps are repeated to form a multi-layered semiconductor device as shown in
Since the interlayer insulating layers of thus manufactured semiconductor device are composed of porous bodies consisting mainly of silicon oxide, the specific dielectric constant can be lowered, and the wiring capacity can be reduced.
By the use of such a manufacturing method, a metallic material can be buried in the interlayer insulating layers without performing the conventionally used wiring-metal burying process (Damascene process), including the etching of interlayer insulating layers, the plating of metallic materials, and the surface polishing by CMP; and the interlayer insulating layers having a flat surfaces can be formed. Therefore, since the number of process steps decreases, the costs of the semiconductor device can be reduced.
The second example is an example of a semiconductor device wherein porous films having fine pores perpendicular to a substrate consisting mainly of silicon oxide are used as interlayer insulating layers, and metal wirings (via) are formed by burying Cu in the fine pores. Here, an example of forming a via, which is a vertical wiring, is formed in the interlayer insulating layers will be described.
As described above,
First, on a semiconductor substrate 31 on which semiconductor elements such as MOSFET, wiring layers and element isolating regions (not shown) were formed, an aluminum-silicon mixture (mixed film) 30 containing 60 atomic % aluminum to the total quantity of aluminum and silicon as shown in
The aluminum-silicon mixture 30 was observed using an FE-SEM (field emission scanning electron microscope). The surface viewed from diagonally above has aluminum columnar structures 63 arranged two-dimensionally surrounded by the silicon region 62 as
Next, the aluminum-silicon mixture 30 was immersed in a 5 wt % phosphoric acid solution for 4 hours to remove the portion of the aluminum columnar structures 33, and the region of silicon 32 was oxidized to form fine pores 34a. As a result, a porous body 30a composed of the material consisting mainly of silicon oxide 32a was fabricated on the entire surface of the film as
Next, the phosphoric-acid-etched aluminum-silicon mixed film (porous body composed of a material consisting mainly of silicon oxide) 30a was observed using an FE-SEM (field emission scanning electron microscope). On the surface viewed from the diagonally above, as the silicon oxide porous body of
Since the fabricated porous body 30a is more porous than regular silicon oxide, it has a lowered specific dielectric constant. As a result, wiring delay can be reduced compared with a semiconductor device manufactured using regular silicon oxide. Since the porous film of the present invention is composed of an inorganic material consisting substantially of Si—O, chemical resistance is improved over a porous film composed of an organic material or the mixture of inorganic and organic materials.
Next, a resist 35 was applied onto the region other than the metal wiring (via) portion of thus fabricated porous body (interlayer insulating layer) 30a as
Next, Cu was selectively deposited in the fine pores 34 in the metal wiring (via) portion on which the resist 35 was not applied using electroplating (electrodeposition process). As a result, a structure, wherein the wiring material 36 was buried in a part of the porous body 30a, as shown in
By repeating such steps several times, a multi-layered semiconductor device as shown in
Since the interlayer insulating layers of thus manufactured semiconductor device are composed of porous bodies consisting mainly of silicon oxide, the specific dielectric constant can be lowered, and the RC delay can be prevented.
By the use of such a manufacturing method, since a metallic material is directly buried in the pores of the interlayer insulating layers, the etching process of the interlayer insulating layers can be omitted. Therefore, since the number of process steps decreases, the costs of the semiconductor device can be reduced.
Furthermore, in such a method for forming the metal wirings (via), the metal wirings (via) perpendicular to the substrate are formed only in the open portion of the resist. Therefore, since there is no limitation of forming the metal wiring (via) portion by fine processing of the interlayer insulating layers, this method can form finer metal wirings (via) than conventional methods.
The third example is an example of a semiconductor device wherein porous films having fine pores perpendicular to a substrate consisting mainly of silicon oxide are used as interlayer insulating layers, and Cu was buried in the region after removing a part of the porous films as metal wirings.
As described above,
First, on a semiconductor substrate on which semiconductor elements such as MOSFET, wiring layers and element isolating regions (not shown) were formed, an aluminum-silicon mixture (mixed film) 40 containing 60 atomic % aluminum to the total quantity of aluminum and silicon as shown in
The aluminum-silicon mixture 40 was observed using an FE-SEM (field emission scanning electron microscope). The surface viewed from diagonally above has aluminum columnar structures arranged two-dimensionally surrounded by the silicon region as
Next, the aluminum-silicon mixture 30 was immersed in a 5 wt % phosphoric acid solution for 4 hours to remove the portion of the aluminum columnar structures 33, and the region of silicon 42 was oxidized to form fine pores 44. As a result, a porous body 40a composed of the material consisting mainly of silicon oxide 42a was fabricated on the entire surface of the film as
Next, the phosphoric-acid-etched aluminum-silicon mixed film (porous body composed of a material consisting mainly of silicon oxide) 40a was observed using an FE-SEM (field emission scanning electron microscope). On the surface viewed from the diagonally above, as the silicon oxide porous body of
Since the fabricated porous body 40a is more porous than regular silicon oxide, it has a lowered specific dielectric constant. As a result, wiring delay can be reduced compared with a semiconductor device manufactured using regular silicon oxide. Since the porous film of the present invention is composed of an inorganic material consisting substantially of Si—O, chemical resistance is improved over a porous film composed of an organic material or the mixture of inorganic and organic materials.
Next, a resist 45 was applied onto the region other than the metal wiring portion of thus fabricated porous body (interlayer insulating layer) 40a. Here, a regular photolithography process was used to pattern the resist 45. Furthermore, the interlayer insulating layer was etched using dry etching to form a wiring-burying region. As a result, as
Next, Cu was selectively deposited as the wiring material (metallic material) 47 on the porous-body-removed region 46, which was a wiring-burying region, and as
By repeating such steps several times, a multi-layered semiconductor device as shown in
Since the interlayer insulating layers of thus manufactured semiconductor device are composed of porous bodies consisting mainly of silicon oxide, the specific dielectric constant can be lowered, and the RC delay can be prevented.
The multi-layered semiconductor device as shown in
The fourth example is an example of a semiconductor device wherein porous films having fine pores perpendicular to a substrate consisting mainly of silicon oxide are used as interlayer insulating layers, and Cu was buried as metal wirings (via) in the fine pores. Here, an example wherein the via, which are vertical wirings, are formed in the interlayer insulating layer will be described.
As described above,
First, as
Next, aluminum-silicon mixture (mixed film) 70 containing 60 atomic % aluminum to the total quantity of aluminum and silicon, as shown in
The aluminum-silicon mixed film 70 was observed using an FE-SEM (field emission scanning electron microscope). The surface viewed from diagonally above has aluminum columnar structures arranged two-dimensionally surrounded by the silicon region as
Next, the aluminum-silicon mixed film 70 was immersed in a 5 wt % phosphoric acid solution for 4 hours to remove the portion of the aluminum columnar structures 73, and the region of silicon 72 was oxidized to form fine pores 75. As a result, a porous body 70a composed of the material consisting mainly of silicon oxide 72a was fabricated on the entire surface of the film as
Next, the phosphoric-acid-etched aluminum-silicon mixed film (porous body composed of a material consisting mainly of silicon oxide) 70a was observed using an FE-SEM (field emission scanning electron microscope). On the surface viewed from the diagonally above, as the silicon oxide porous body of
Since the fabricated porous body 70a is more porous than regular silicon oxide, it has a lowered specific dielectric constant. As a result, wiring delay can be reduced compared with a semiconductor device manufactured using regular silicon oxide. Since the porous film of the present invention is composed of an inorganic material consisting substantially of Si—O, chemical resistance is improved over a porous film composed of an organic material or the mixture of inorganic and organic materials.
Next, Cu was selectively deposited as the wiring material (metallic material) 76 in the pores in which Pd was formed using electroless plating. As a result, as
By repeating such steps several times, a multi-layered semiconductor device as shown in
Since the interlayer insulating layers of thus manufactured semiconductor device are composed of porous bodies consisting mainly of silicon oxide, the specific dielectric constant can be lowered, and the RC delay can be prevented.
By the use of such a manufacturing method, since a metallic material is directly buried in the pores of the interlayer insulating layers, the etching process of the interlayer insulating layers can be omitted. Therefore, since the number of process steps decreases, the costs of the semiconductor device can be reduced.
Furthermore, in such a method for forming the metal wirings (via), the metal wirings (via) perpendicular to the substrate are formed only in the open portion of the resist. Therefore, since there is no limitation of forming the metal wiring (via) portion by fine processing of the interlayer insulating layers, this method can form finer metal wirings (via) than conventional methods.
The multi-layered semiconductor device as shown in
Next, preliminary experiments on the structure consisting of aluminum-silicon mixture 20, 30, 40, 64 and 70 used in the present invention will be described. The structure include a matrix portion consisting mainly of Al as a first material, and Si as a second material.
An Al thin wire wherein the Al structural portion surrounded by Si is a columnar structure having a diameter 2r of 3 nm, a distance 2R of 7 nm and a length L is 200 nm (refer to columnar aluminum portion 21 in
First, a method for fabricating the Al thin wire will be described.
An Al—Si mixed film containing 55 atomic % Si to the total quantity of Al and Si, of a thickness of about 200 nm, was formed on a glass substrate using an RF magnetron sputtering method. As the target, a 4-inch Al target, on which eight 15-mm-square Si chips 13 was placed, was used. Sputtering was performed using an RF power source under conditions of an Ar flow rate of 50 sccm, a charge pressure of 0.7 Pa, and an input power of 1 kW. The substrate temperature was a room temperature.
Here, although an Al target, on which eight 15-mm-square Si chips 13 were placed, was used as the target, the number of Si chips is lot limited thereto, but can be changed depending on the conditions of sputtering as long as the content of Si in the AlSi mixed film is nearly 55 atomic %. The target is not limited to an Al target on which Si chips are placed, but may be an Si target on which Al chips are placed, or may be a target formed by sintering Si and Al powders.
Next, the content (atomic %) of Si to the total quantity of Al and Si in thus obtained Al—Si mixed film was analyzed using ICP (inductively coupled plasma emission spectrometry). As a result, the content of Si to the total quantity of Al and Si was about 55 atomic %. Here, for the convenience of measurement, an Al—Si mixed film deposited on a carbon substrate as the substrate was used.
The Al—Si mixed film was observed using an FE-SEM. On the surface viewed from immediately above the substrate, circular Al nanostructures surrounded by Si were two-dimensionally arranged. The pore diameter in the Al nanostructure portion was 3 nm, and the average distance between the centers thereof was 7 nm. When the cross-section was observed using an FE-SEM, the height was 200 nm, and each Al nanostructure portion was independent from each other.
When the sample was observed using X-ray diffraction, no Si peak indicating crystallinity was found, proving that the Si was amorphous.
Therefore, Al—Si nanostructure including Al thin wires of a distance 2R of 7 nm, a diameter 2r of 3 nm and a height L of 200 nm surrounded by Si could be fabricated.
As Comparative Sample A, an Al—Si mixed film containing 15 atomic % Si to the total quantity of Al and Si of a thickness of about 200 nm was formed on a glass substrate using a sputtering method. As the target, a 4-inch Al target, on which two 15-mm-square Si chips 13 was placed, was used. Sputtering was performed using an RF power source under conditions of an Ar flow rate of 50 sccm, a charge pressure of 0.7 Pa, and an input power of 1 kW. The substrate temperature was a room temperature.
Comparative Sample A was observed using an FE-SEM. On the surface viewed from immediately above the substrate, the Al portions were not circular, but rope-shaped. In other words, the fine structure wherein Al columnar structures were evenly dispersed in the Si region could not be formed. Furthermore, the size thereof far exceeded 10 nm. When the cross-section was observed using an FE-SEM, the width of the Al portion exceeded 15 nm. The content (atomic %) of Si to the total quantity of Al and Si in thus obtained Al—Si mixed film was analyzed using ICP (inductively coupled plasma emission spectrometry). As a result, the content of Si to the total quantity of Al and Si was about 15 atomic %.
As Comparative Sample B, an Al—Si mixed film containing 75 atomic % Si to the total quantity of Al and Si of a thickness of about 200 nm was formed on a glass substrate using a sputtering method. As the target, a 4-inch Al target, on which fourteen 15-mm-square Si chips 13 was placed, was used. Sputtering was performed using an RF power source under conditions of an Ar flow rate of 50 sccm, a charge pressure of 0.7 Pa, and an input power of 1 kW. The substrate temperature was a room temperature.
Comparative Sample B was observed using an FE-SEM. On the surface viewed from immediately above the substrate, no Al portions were observed. On the cross-section observed using an FE-SEM, the Al portions were not clearly observed. The content (atomic %) of Si to the total quantity of Al and Si in thus obtained Al—Si mixed film was analyzed using ICP (inductively coupled plasma emission spectrometry). As a result, the content of Si to the total quantity of Al and Si was about 75 atomic %.
Only the number of Si chips was changed from the case when Comparative Sample A was fabricated to prepare the samples containing 20 atomic %, 35 atomic %, 50 .atomic %, 60 atomic % and 70 atomic %. The nanostructures wherein Al columnar structures are evenly dispersed are indicated with o and the nanostructures wherein Al columnar structures are evenly dispersed are indicated with x in the following Table 1.
By thus adjusting the Si content to the total quantity of Al and Si to 20 atomic % or more and 70 atomic % or less, the pore diameter of the fabricated Al nanostructures can be controlled, and the Al thin wires of an excellent linearity can be fabricated. For the evaluation of the structures, the use of a TEM (transmission electron microscope) or the like in addition to an SEM is recommendable. Furthermore, as Comparative Sample C, an Al—Si mixed film containing 55 atomic % Si to the total quantity of Al and Si of a thickness of about 200 nm was formed on a glass substrate using a sputtering method. As the target, a 4-inch Al target, on which eight 15-mm-square Si chips 13 was placed, was used. Sputtering was performed using an RF power source under conditions of an Ar flow rate of 50 sccm, a charge pressure of 0.7 Pa, and an input power of 1 kW. The substrate temperature was 250° C.
Comparative Sample C was observed using an FE-SEM. On the surface viewed from immediately above the substrate, no clear boundary between Al and Si was observed. In other words, no Al nanostructures were found. Specifically, if the substrate temperature was excessively high, it is considered that the film for forming such Al nanostructures cannot be grown, because the sample is changed to a more stable state.
In order to obtain the structure wherein columnar materials are dispersed, it is also preferable to set the composition of the target to Al:Si=55:45 or the like.
As described above, when the columnar substances consisting mainly of aluminum are removed from a structure wherein the columnar substances consisting mainly of aluminum is dispersed substantially perpendicularly to the film surface in a base material consisting mainly of silicon and containing at least aluminum, and further the base material consisting mainly of silicon is oxidized, a porous body having fine pores substantially perpendicular to the substrate consisting substantially of silicon oxide can be formed; and by use of porous body as the interlayer insulating layer, a semiconductor device having a reduced wiring capacity can be formed.
The present invention can also provide a method for easily manufacturing the above-described semiconductor device.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001-317682 | Oct 2001 | JP | national |
This is a continuation-in-part application of U.S. patent application Ser. No. 10/271,472 filed on Oct. 15, 2002.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10271472 | Oct 2002 | US |
| Child | 10986939 | Nov 2004 | US |
