JP4090084B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention disclosed in this specification relates to a semiconductor device having an electrode or a wiring whose main component is aluminum or aluminum, and a manufacturing method thereof.
[0002]
[Prior art]
Recently, a technique for manufacturing a thin film transistor (hereinafter referred to as TFT) on an inexpensive glass substrate has been rapidly developed. The reason is that the demand for active matrix liquid crystal display devices has increased.
[0003]
In an active matrix liquid crystal display device, a TFT (referred to as a pixel TFT) is arranged in each of millions of pixels arranged in a matrix, and the charges entering and exiting each pixel electrode are controlled by the switching function of the TFT. is there.
[0004]
Further, a TFT for driving the pixel TFT (referred to as a circuit TFT for convenience) is incorporated in the peripheral drive circuit, and the display pixel portion in which the pixel TFT is disposed and the drive circuit portion in which the circuit TFT is disposed are formed on the same substrate. Integrated circuits formed above are becoming common.
[0005]
That is, such an integrated circuit is formed of millions of pixel TFTs and hundreds or more of circuit TFTs. In such a configuration, of course, a low production yield becomes a problem.
[0006]
For example, if one pixel TFT does not operate, the pixel electrode connected thereto loses its function as a display element. This causes so-called point defects. For example, in the case of a normally black liquid crystal display device, a point defect is displayed as a black dot when white is displayed, which greatly damages the appearance.
[0007]
If the circuit TFT does not operate, all the pixel TFTs to which a drive voltage is applied from the circuit TFT do not function as a switching element. This causes a so-called line defect and becomes a fatal obstacle for the liquid crystal display device.
[0008]
Therefore, the active matrix type liquid crystal display device must be capable of maintaining normal and stable operation of millions of TFTs in the long term.
However, it is very difficult to completely eliminate point defects and line defects.
[0009]
The above point defects and line defects are mainly caused by the unnecessary operation of the TFT. One of the main causes of TFT malfunction is contact failure.
[0010]
A contact failure is a malfunction that occurs when a connection failure occurs between the wiring electrode and the TFT active layer (consisting of a thin film semiconductor layer) or a gate electrode (hereinafter referred to as a contact). That is. In particular, in a planar type TFT, since the wiring electrode and the TFT are electrically connected via a thin opening (contact hole), contact failure is a serious problem.
[0011]
Contact failure is a major cause of early deterioration of semiconductor element characteristics, and the deterioration is accelerated particularly when a large current flows or during high-temperature operation. Therefore, it is said that the reliability of the contact determines the reliability of the semiconductor element.
[0012]
Generally, in the case of a pixel display region in an active matrix liquid crystal display device, the gate electrode is directly pulled out of the pixel display region, so that there is only contact with the active layer of the TFT.
[0013]
In the case of a peripheral drive circuit, there are hundreds of thousands to millions of contacts. In particular, the presence of a gate electrode contact and the increase in temperature associated with a large current operation mean that the contact is required to have a reliability higher than that of the pixel display region.
[0014]
There are three main causes of contact failure.
One of them is that the conductive film forming the wiring electrode and the semiconductor film forming the source / drain of the TFT are not in contact with each other by ohmic junction.
[0015]
This is because an insulating film such as a metal oxide is formed on the bonding surface. Further, the state in the vicinity of the semiconductor film surface (impurity concentration, defect level density, cleanliness, etc.) greatly affects the performance of the contact.
[0016]
As a second cause, the coverage of the conductive film forming the wiring electrode is poor, and the wire is broken in the contact hole.
In this case, improvement is required depending on the film forming method and film forming conditions of the wiring electrode.
[0017]
Further, as a third cause, disconnection of the wiring electrode due to the cross-sectional shape of the contact hole or the like can be cited. The cross-sectional shape of the contact hole is the insulator covered with the contact part (SiN, SiO ₂ Etc.) strongly depends on the etching conditions.
[0018]
In particular, burrs and blowholes (nests) formed by over-etching are serious problems because they significantly deteriorate coverage. As an example, a state in which a gap is formed on the gate electrode will be described with reference to FIG.
[0019]
FIG. 14 is an enlarged view of a contact hole portion for connecting a gate electrode and a wiring of a planar type thin film transistor.
[0020]
In FIG. 14A, reference numeral 101 denotes a metal electrode made of an anodizable material, here a gate electrode made of a material mainly composed of Al (aluminum). A gate insulating film, a semiconductor layer, and the like are present under the gate electrode 101, but are omitted for simplification of the drawing.
[0021]
An anodic oxide film 102 (Al is formed by anodizing the gate electrode 101 in an electrolytic solution. ₂ O _Three As a main component). The anodic oxide film 102 is a very dense and strong film, and protects the gate electrode 101 from heat applied in the heat treatment process, and plays a role of suppressing generation of hillocks and whiskers.
[0022]
Hillocks and whiskers are needle-like or stab-like projections resulting from abnormal growth of aluminum.
[0023]
Further, an interlayer insulating film 103 is formed on the gate electrode 102. As the interlayer insulating film 103, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like can be used.
[0024]
Then, as shown in FIG. 14A, the interlayer insulating film 103 is etched by a wet etching method or a dry etching method to form a contact hole 104.
[0025]
In order to form the contact hole 104, the interlayer insulating film 103, which is a silicide film, must first be etched, and then the anodic oxide film 102 must be etched.
[0026]
However, since the anodic oxide film 102 is a very dense and strong film, etching takes time. For this reason, during isotropic etching, the etching proceeds considerably in the lateral direction, and a hollow portion 105 as shown in FIG. 14B is formed.
[0027]
FIG. 14C shows a state when the wiring electrode 106 is formed in this state. In such a case, as shown in FIG. 14C, the hollow portion 105 cannot be covered with the wiring electrode 106, causing disconnection. Such a state often causes contact failure.
[0028]
Further, if the overetching at the end of the etching of the anodic oxide film is long, the etching of the gate electrode 101 proceeds little by little, and a blow hole may be formed. This also causes contact failure.
[0029]
In addition, a natural oxide film is formed on the aluminum surface when the gate electrode 101 made of an aluminum electrode is exposed, and the presence of this oxide film also causes contact failure.
[0030]
In order to avoid this problem, other metal materials or silicide materials may be used as the electrode material. However, considering the characteristics of aluminum that it has low resistance, such measures are generally good. Absent.
[0031]
[Problems to be solved by the invention]
An object of the invention disclosed in this specification is to solve the above-described problem and reduce malfunction of a semiconductor device due to contact failure.
[0032]
In particular, it is an object of the present invention to provide a technique for eliminating contact defects when aluminum or a material containing aluminum as a main component is used as an electrode.
[0033]
Then, it is an object to improve long-term reliability of a device using a semiconductor device or a liquid crystal display device by improving contact reliability. Another object is to improve the yield of the manufacturing process by eliminating point defects and line defects in the liquid crystal display device.
[0034]
[Means for Solving the Problems]
One of the configurations of the semiconductor device disclosed in this specification for solving the above-described problem has a configuration in which aluminum or a material containing aluminum as a main component is in contact with each other.
An element belonging to group 12 to 15 is present at a higher concentration in the interface between the two materials and / or in the vicinity thereof than in other regions.
[0035]
In addition, the configuration of a semiconductor device according to another invention is as follows:
Aluminum or a material based on aluminum;
An insulating film formed on the material;
In the structure having
Contact holes are formed in the insulating film,
The aluminum or aluminum-based material and the wiring material are in contact with each other in the contact hole,
An element belonging to Group 12 to 15 is present at a higher concentration than other regions at and / or in the vicinity of the interface between the aluminum or the material mainly composed of aluminum and the wiring material. .
[0036]
In addition, the configuration of other semiconductor devices is as follows:
An insulated gate field effect semiconductor device comprising:
A wiring electrode made of aluminum or a material containing aluminum as a main component and electrically connected to at least a part of the semiconductor device through a contact hole formed in the interlayer insulating film;
The wiring electrode contains an element that substantially provides fluidity to the wiring electrode at a temperature of 450 ° C. or lower.
[0037]
In order to solve the above-described problem, the structure of the method for manufacturing a semiconductor device according to the present invention is as follows.
In forming a configuration in which aluminum or a material mainly composed of aluminum is in contact with each other,
Forming an element belonging to Group 12-15 between the two materials or a layer containing a predetermined amount of the element;
Adding a heat treatment to fluidize the element;
It is characterized by having.
[0038]
Furthermore, another structure of the method for manufacturing a semiconductor device according to the present invention is as follows:
Aluminum or a material based on aluminum;
An insulating film formed on the material;
In the structure having
Forming a contact hole in the insulating film and exposing the aluminum or a material mainly composed of aluminum at a bottom thereof;
Forming a film made of an element belonging to Group 12-15 at least at the bottom of the contact hole, or a film containing a predetermined amount of the element;
Forming a material for forming wiring on the film;
Applying heat treatment to fluidize the elements belonging to Group 12-15,
It is characterized by having.
[0039]
Another structure of the method for manufacturing a semiconductor device according to the present invention is as follows:
Semiconductor materials,
An insulating film formed on the material;
In the structure having
Forming a contact hole in the insulating film and exposing the semiconductor material at a bottom thereof;
Forming a film of an element belonging to Group 12-15 at least at the bottom, or a film containing a predetermined amount of the element;
Forming aluminum or a material mainly composed of aluminum on the film;
Applying heat treatment to fluidize the elements belonging to Group 12-15,
It is characterized by having.
[0040]
In addition, the configuration of other inventions is as follows:
A method for manufacturing an insulated gate field effect semiconductor device, comprising:
Forming a wiring electrode made of aluminum or a material containing aluminum as a main component and electrically connected to at least a part of the semiconductor device through a contact hole formed in the interlayer insulating film;
Heat treating the wiring electrode to provide substantial fluidity to the wiring electrode;
Have
The wiring electrode is characterized by adding one or a plurality of elements that provide fluidity to the wiring electrode at a temperature of 450 ° C. or lower.
[0041]
The invention disclosed in this specification can obtain a remarkable effect particularly when aluminum or a material containing aluminum as a main component is used as a material for forming a wiring.
[0042]
In the present invention, an element belonging to Group 12 to 15 (formerly 2B to 5B) refers to an element that starts with Zn and ends with Bi in the element table shown in FIG. The predetermined amount means an amount introduced by artificially controlling the amount.
[0043]
As the element belonging to Group 12-15, one or more elements selected from germanium, tin, gallium, zinc, indium and antimony are used.
[0044]
In the present invention, when aluminum or a material containing aluminum as a main component is used for the wiring electrode, the temperature in the step of bringing fluidity to the wiring electrode (reflow step) is 450 ° C. in consideration of the heat resistance of aluminum. Must be kept below.
[0045]
Examples of the element that brings fluidity to the wiring electrode at a temperature of 450 ° C. or lower include the elements belonging to the above-mentioned group 12 to 15 such as germanium, tin, gallium, zinc, lead, indium, and antimony. For example, germanium is preferably contained at a concentration of 20 to 40 atomic% with respect to aluminum.
[0046]
The heating means used in the reflow process may be any of means for heating in an electric furnace and means for irradiating intense light such as ultraviolet light and infrared light. For example, a technique called RTA (rapid thermal annealing) is known as a heating means using strong light.
[0047]
In addition, the structure of a method for manufacturing a semiconductor device according to another invention is as follows.
A method for manufacturing an insulated gate field effect semiconductor device, comprising:
Forming a thin film mainly composed of germanium and a thin film composed mainly of aluminum, which are electrically connected to at least a part of the semiconductor device through contact holes formed in the interlayer insulating film; and
And heat-treating the laminated film to bring about substantial fluidity to the laminated film.
[0048]
In the above structure, a so-called alloy layer is formed by combining the thin film mainly composed of germanium and the thin film mainly composed of aluminum formed in the contact hole by heat treatment. . Of course, this alloy layer easily exhibits fluidity by a reflow process at a temperature of 450 ° C. or lower.
[0049]
At this time, the heating means used in the reflow process may be either a means for heating in an electric furnace or a means for irradiating strong light such as ultraviolet light or infrared light. For example, a technique called RTA (rapid thermal annealing) is known as a heating means using strong light.
[0050]
DETAILED DESCRIPTION OF THE INVENTION
For example, in the configuration shown in FIG. 1, when the wiring 317 made of aluminum is brought into contact with the gate electrode 208 made of aluminum, the gate contact hole is formed as shown in FIG. As shown in B), a germanium film 300 and an aluminum film 315 are laminated. Then, heat treatment (reflow process) is performed.
[0051]
By the reflow process, a mixed layer 320 made of aluminum and germanium is formed as shown in FIG. By forming the mixed layer 320, gaps between the contact portions are filled, and a natural oxide film formed on the exposed surface of the electrode 208 made of aluminum is eliminated, so that a good contact is formed.
[0052]
【Example】
[Example 1]
The present embodiment relates to a manufacturing process of a thin film transistor, and shows an example in which a reflow process is performed using an alloy composed of aluminum, germanium, and copper as a wiring electrode. An example of a manufacturing process of a thin film transistor (TFT) in this embodiment is shown in FIGS.
[0053]
FIG. 2 is a process diagram for manufacturing the structure of FIG. The manufacturing process will be described with reference to FIG.
First, as shown in FIG. 2A, a glass substrate 201 having an insulating surface is prepared, and silicon oxynitride (SiO 2) serving as a base film is prepared. _x N _y 202) is formed to a thickness of 2000 mm.
[0054]
As a substrate, a quartz substrate can be used in addition to a glass substrate. In an integrated circuit having a multilayer structure, an appropriate insulating film can also be used as a substrate. As the base film, a silicon oxide film or a silicon nitride film can be used.
[0055]
An amorphous silicon film having a thickness of 500 mm (not shown) is formed thereon by a plasma CVD method or a low pressure thermal CVD method, and is crystallized by an appropriate crystallization method. This crystallization may be by heating or by laser light irradiation. Alternatively, a method of adding an element (for example, Ni) that promotes crystallization during crystallization may be used.
[0056]
Next, the crystalline silicon film obtained by crystallizing the amorphous silicon film is patterned to form the island-shaped semiconductor layer 203 constituting the active layer.
[0057]
On top of this, a silicon oxide film 204 that functions as a gate insulating film later is formed to a thickness of 1500 mm. The silicon oxide film 204 may be formed by a plasma CVD method or a low pressure thermal CVD method.
[0058]
Next, a metal thin film 205 made of aluminum or a material mainly composed of aluminum is formed to a thickness of 4000 mm. This aluminum film 205 will later constitute the gate electrode 208. Of course, in addition to aluminum, an anodizable material such as tantalum or niobium can be used.
[0059]
Next, anodization is performed in the electrolytic solution using the aluminum film 205 as an anode. As the electrolytic solution, an ethylene glycol solution of 3% tartaric acid neutralized with aqueous ammonia and adjusted to PH = 6.92 is used. Further, the treatment is performed under the conditions of a formation current of 5 mA and an ultimate voltage of 10 V using platinum as a cathode.
As a result, a dense anodic oxide film (not shown) is formed on the surface of the aluminum film 205. The thickness of the anodic oxide film having a dense film quality can be controlled by controlling the voltage application time.
[0060]
This dense anodic oxide film has an effect of improving the adhesion between the photoresist to be formed next and the aluminum film 205. (Fig. 2 (A))
[0061]
When the structure of FIG. 2A is obtained in this way, a resist mask (not shown) is arranged and the aluminum film 205 is patterned. Then, an aluminum pattern (not shown) constituting the gate electrode 208 and the anodic oxide films 206 and 207 is formed later.
[0062]
Next, a second anodic oxidation is performed to form a porous anodic oxide film 206. The electrolytic solution is a 3% oxalic acid aqueous solution, the above aluminum pattern is used as an anode, platinum is used as a cathode, and a formation current of 2 to 3 mA and an ultimate voltage of 8V are processed.
[0063]
At this time, anodic oxidation proceeds in a direction parallel to the substrate. This is because a resist mask (not shown) exists on the upper surface, and anodic oxidation does not proceed there.
[0064]
Here, the length of the porous anodic oxide film 206 is controlled by controlling the voltage application time. In this embodiment, the thickness of the anodic oxide film 206 is 0.7 μm.
[0065]
Further, after removing the resist mask with a dedicated stripping solution, a third anodic oxidation is performed to obtain the state of FIG.
[0066]
At this time, an electrolytic solution is used in which 3% of an ethylene glycol solution of tartaric acid is neutralized with ammonia water and adjusted to PH = 6.92. And it processes as a formation current 5-6mA and the ultimate voltage 100V by using platinum as a cathode.
[0067]
The anodic oxide film 207 formed at this time is very dense and strong. Therefore, it has an effect of protecting the gate electrode 208 from damage caused in a subsequent process such as a doping process or heat of the heating process.
[0068]
In this anodic oxidation process, the electrolytic solution penetrates into the porous anodic oxide film 206, so that the anodic oxide film 207 is formed around the aluminum pattern. In FIG. 2B, the aluminum pattern remaining without being anodized becomes a substantial gate electrode 208.
[0069]
Next, an impurity is implanted into the island-shaped semiconductor layer 203 by ion doping. Here, P (phosphorus) is used as an impurity in order to manufacture an N-channel TFT. Note that B (boron) is used to form a P-channel TFT.
[0070]
First, the first ion doping is performed in the state of FIG. P (phosphorus) is implanted at an acceleration voltage of 60 to 90 kV and a dose of 0.2 to 5 × 10. ¹⁵ Atom / cm ² To do. In this embodiment, the acceleration voltage is 80 kV and the dose amount is 1 × 10. ¹⁵ Atom / cm ² Ion doping is performed as follows.
[0071]
As a result, the gate electrode 208 and the porous anodic oxide film 206 serve as a mask, and regions 209 and 210 to be the source / drain later are formed in a self-aligned manner. (See Fig. 2 (C))
[0072]
Next, as shown in FIG. 2C, the porous anodic oxide film 206 is removed and a second doping is performed. The second implantation of P (phosphorus) is an acceleration voltage of 60 to 90 kV and a dose of 0.1 to 5 × 10. ¹⁴ Atom / cm ² To do. In this embodiment, the acceleration voltage is 80 kV and the dose amount is 1 × 10. ¹⁴ Atom / cm ² And
[0073]
Then, the gate electrode 208 serves as a mask, and low-concentration impurity regions 211 and 212 having a lower impurity concentration than the source region 209 and the drain region 210 are formed in a self-aligned manner.
[0074]
At the same time, since no impurity is implanted immediately below the gate electrode 208, a region 213 functioning as a TFT channel is defined in a self-aligned manner. Further, an offset region (not shown) where a gate voltage is not applied is formed by the thickness of the anodic oxide film 207.
[0075]
The low concentration impurity region 212 has an effect of suppressing the formation of a high electric field between the channel region 213 and the drain region 210. This region is generally referred to as an LDD (lightly doped drain) region.
[0076]
Next, laser annealing and thermal annealing are performed by irradiation with KrF excimer laser light. In this embodiment, the energy density of the laser light is 250 to 300 mJ / cm. ² The thermal annealing is performed at 300 to 450 ° C. (1 hr).
[0077]
By this annealing process, the crystallinity of the island-shaped semiconductor layer 203 damaged in the ion doping process can be improved. At this time, the crystallinity can be further improved by adding a hydrogenation treatment at 350 ° C. for 1 hour.
[0078]
Next, as shown in FIG. 2D, a first interlayer insulating film 214 made of a silicon oxynitride film is formed by a plasma CVD method. The interlayer insulating film 214 may be a silicon oxide film or a silicon nitride film. Further, a multilayer structure of these insulating films may be used.
[0079]
Next, as shown in FIG. 1A, contact holes for electrically connecting the source and gate electrodes and the TFT are formed. In this embodiment, this contact hole is formed by a wet etching method using buffered hydrofluoric acid.
[0080]
At this time, the source contact portion and the gate contact portion are simultaneously formed. That is, a contact hole for the semiconductor layer and a contact hole for the gate electrode are formed simultaneously. This technique is a desirable means for reducing the number of times of patterning and simplifying the process.
[0081]
First, in the source contact portion, the first interlayer insulating film 214 and the gate insulating film 204 are etched in this order, and the source region 209 of the island-shaped semiconductor layer 203 is exposed. In this state, the etching is still in progress because the etching rate of the anodic oxide film 207 is small in the gate contact portion.
[0082]
Further, when the anodic oxide film 207 is etched with a hydrofluoric acid-based etchant, the etching proceeds non-uniformly, so that the etching of the gate electrode 208 also proceeds simultaneously from the portion where the etchant penetrates.
[0083]
Therefore, when the etching of the anodic oxide film 207 is completed, over-etching proceeds in the source contact hole portion, and the gate electrode 208 is eroded in the gate contact hole portion, and each contact hole portion has the structure shown in FIG. Such a hollow portion is formed.
[0084]
Such a state inevitably occurs although it is a problem of a degree, and becomes a big cause of contact failure.
[0085]
In order to solve this problem, it is necessary to form each contact hole individually. However, if each contact hole is formed individually, the number of photolithography processes increases, which is disadvantageous in terms of process simplification (cost reduction).
[0086]
In the present embodiment, the following configuration is employed in order to reliably form a contact when the state shown in FIG.
[0087]
First, after forming a contact hole as shown in FIG. 1A, an extremely thin film 300 of germanium is formed by plasma CVD as shown in FIG. 1B.
[0088]
The film forming conditions are as follows. The film thickness of the germanium film 300 is 200 to 300 mm.
Deposition temperature ... 200 ℃
Deposition gas ... GeH _Four : 20SCCM H ₂ : 380SCCM
Deposition pressure ... 1.0 torr
Applied power: 20W
[0089]
Next, a metal thin film 315 is formed to a thickness of 4000 mm by sputtering. In this embodiment, an aluminum film in which 2 wt% of copper is added to aluminum is formed as the metal thin film 315. The reason why copper is added is to suppress generation of hillocks and whiskers due to abnormal growth of aluminum.
[0090]
In the state of FIG. 1 (B), the hollow portion and the blow hole cannot be completely covered, so there is a high possibility that the contact hole is broken. At this time, a state where attention is paid only to the contact hole provided in the upper part of the gate electrode 208 will be described with reference to FIG.
[0091]
FIG. 3 shows a cross-sectional shape of the contact hole 401 provided in the interlayer insulating film 214 formed on the gate electrode 208, and a germanium film 300 and a metal thin film 315 are formed in the contact hole 401. That is, in FIG. 1B, this corresponds to an enlarged cross-sectional view of the contact hole above the gate electrode 208.
[0092]
In the deposited state, as shown in FIG. 3A, the metal thin film 315 is likely to have a disconnection due to poor coverage at the bottom of the contact hole 401 (inside the circle indicated by 402).
[0093]
In addition, it is difficult to form a thick film on the side wall of the contact hole 401 by sputtering, and it is often extremely thinner than a desired film thickness (inside a circle indicated by 403).
[0094]
In addition, at the entrance of the opening portion of the contact hole 401, the deposited metal thin film 315 protrudes (in a circle indicated by 404), and depending on circumstances, the opening closes the entrance of the opening portion. (Cusp) may be formed.
[0095]
Therefore, in this embodiment, a reflow process is performed after the film formation process of the metal film 315. This process is a process for fluidizing the metal thin film 315 by heating to ensure contact between the electrode 208 made of aluminum and the film 315 made of aluminum.
[0096]
This reflow process needs to be performed in the temperature range of 375 to 450 ° C. in consideration of the heat resistance of the gate electrode 208 made of aluminum (in this embodiment, since it is protected by the anodic oxide film 207, it is more heat resistant than usual). Is increasing).
[0097]
In this embodiment, heat treatment is performed at 450 ° C. for 1 hour in an electric furnace. At this time, the treatment atmosphere may be a vacuum, an inert atmosphere such as nitrogen, or a hydrogen atmosphere.
[0098]
By this heat treatment, a reaction first occurs at the interface between a germanium film (not shown) and the metal thin film 315, and an alloy layer 320 having a composition of aluminum, copper, and germanium is formed.
[0099]
This reaction gradually proceeds by the diffusion of germanium and aluminum, and eventually the vicinity of the lower layer of the metal thin film 315 has a composition containing germanium. For this reason, fluidity is exhibited at a temperature of 400 ° C., and the reflow process proceeds.
[0100]
By this reflow process, the vicinity of the lower layer of the metal thin film 315 has fluidity, and is covered without disconnecting the gap portion or the gap of the blow hole. Therefore, all the disconnection portions or poor contact portions of the metal thin film 315 are short-circuited and can be completely electrically connected to the gate electrode 208 (or the source region 209).
[0101]
FIG. 3B shows an enlarged cross-sectional view of the contact hole after the reflow process. The metal thin film 315 having fluidity temporarily by the reflow process covers the disconnection portion or the contact failure portion and fills the inside of the contact hole. Note that an alloy layer 320 is formed under the metal thin film 315.
[0102]
In addition, the natural oxide film present on the exposed surface of the gate electrode 208 is also removed in the reflow process, and contact failure due to the presence can be suppressed.
[0103]
As shown in FIG. 4, the eutectic point of aluminum and germanium is at least 424 ° C., but the fluidization of germanium can be performed at about 400 ° C. However, it is preferable from the reproducibility of the effect that the heating temperature in this reflow process is 375 degreeC or more. Further, the upper limit is preferably set to 450 ° C. or less in consideration of the heat resistance of aluminum.
[0104]
After the above steps, the metal thin film 315 and the alloy layer 320 are patterned to form the source electrode 316 and the gate electrode 317.
[0105]
Note that the reflow process may be performed after the source electrode 316 and the gate electrode 317 are formed by this panning.
[0106]
Next, a second interlayer insulating film 318 is formed. In this embodiment, first, the source electrode 316 and the gate electrode 317 are covered with a silicon nitride film or a silicon oxynitride film (not shown). This corresponds to a buffer film for depositing a resin material with good adhesion.
[0107]
A material made of resin is stacked thereon as the second interlayer insulating film 318. Since this resin material can be selected from those having a relative dielectric constant lower than that of silicon oxide or silicon nitride, it is possible to reduce the influence of the capacitance formed between the transparent electrode to be formed later and the TFT.
[0108]
In addition, since the material made of resin used for the second interlayer insulating film 318 is excellent in planarizing the upper surface of the device, a uniform voltage can be applied to the liquid crystal (not shown) from the transparent electrode.
[0109]
Finally, a transparent electrode 319 made of ITO is formed, and a thin film transistor (TFT) disposed in a pixel region of an active matrix liquid crystal display device as shown in FIG. 1C is manufactured.
[0110]
Since the TFT manufactured according to the process of this embodiment shows a good contact regardless of the shape of the contact hole, there is no fear of a problem such as a malfunction of the TFT due to the disconnection of the wiring or the electrode.
[0111]
The structure shown in this embodiment can be used not only for an active matrix liquid crystal display device but also for an EL display device, an EC display device, and other thin film integrated circuits.
[0112]
[Example 2]
This example shows an example in which a titanium film is formed before and after the reflow process in Example 1. An example of a manufacturing process of a thin film transistor (TFT) in this example is the same as that in Example 1, and thus description thereof is omitted.
[0113]
First, the case where a titanium film is formed before the reflow process will be described. In this case, after the contact hole is formed as shown in FIG. 1A, a 500 mm thick Ti (titanium) film is formed next. Since Ti is excellent in coverage with respect to unevenness, it is possible to cover a hollow portion and a blow hole to some extent.
[0114]
In addition, the Ti film has an effect of preventing the formation of silicide by reacting aluminum, which is a component of wiring to be formed later, with silicon, which is a component of the active layer, in the source region. Furthermore, the titanium film and the aluminum film are characterized by a small contact angle (good wettability).
[0115]
Therefore, a more reliable contact can be realized by first maintaining good ohmic contact with the Ti film and then performing the reflow process after forming the wiring electrode.
[0116]
Next, a case where a titanium film is formed after the reflow process will be described. In this case, in FIG. 1B, a titanium film (not shown) is formed on the metal thin film 315 to a thickness of 500 mm. This Ti film has the effect of increasing the ohmic contact between the output terminal and the wiring electrode when taking out the current.
[0117]
Example 3
In the first embodiment, as shown in FIG. 1B, a metal thin film 315 to be a wiring electrode is formed on the germanium film 300. On the contrary, in this embodiment, the metal thin film 315 is formed on the metal thin film 315. An example in which a germanium film 300 is formed is shown. The description will be made with reference to FIG.
[0118]
When the state shown in FIG. 1A is obtained, first, a metal thin film 315 to be a wiring electrode is formed. Then, a germanium film 300 is formed thereon. The film forming conditions may be in accordance with the first embodiment. Of course, a tin film, a gallium film, a zinc film, or the like may be used in addition to the germanium film.
[0119]
With the configuration as in this embodiment, since the surface of the metal thin film 315 containing aluminum as a main component is covered with the germanium film 300, it is not exposed to the atmosphere. That is, since no insulator is formed on the surface of the metal thin film 315, good ohmic contact can be ensured with the subsequent extraction electrode.
[0120]
Further, in the reflow process, the surface state and surface shape of the metal thin film 315 are greatly affected, and therefore the insulator formed on the surface of the metal thin film 315 becomes a factor that hinders the reflow of the metal thin film 315. The present embodiment is also an effective means in eliminating such factors.
[0121]
In carrying out this embodiment, it is preferable to combine a structure in which a titanium film is provided as a base film in the contact hole as shown in the second embodiment. This is because when the bottom of the contact hole is a silicon film, silicide is formed between the metal thin film mainly composed of aluminum.
[0122]
Further, a sandwich structure such as germanium film-metal thin film-germanium film can be formed in combination with the first embodiment. In this case, the reflow process can be performed more reliably.
[0123]
Example 4
This embodiment is an example in which a sputtering method is used as a method for forming the film 300 in the configuration shown in Embodiment 1. In this embodiment, when the metal thin film (aluminum film) 315 is formed by sputtering, a target having a germanium film formed on the surface thereof is used.
[0124]
When such a target is used, a germanium film 300 is first formed, and then an aluminum film 315 is formed.
[0125]
In this embodiment, by controlling the film thickness of the germanium film formed on the target, it is possible to control the film thickness of the germanium film 300 and the fluidization state in the reflow process.
[0126]
Example 5
This example shows an example in which a metal element other than germanium is used for aluminum or a wiring electrode mainly composed of aluminum in Example 1 or Example 2. An example of a manufacturing process of a thin film transistor (TFT) is the same as that in Example 1, and thus the description thereof is omitted.
[0127]
Examples of the element having the same effect as germanium used in Example 1 or Example 2 include elements belonging to Group 12 to 15 such as tin, gallium, zinc, lead, indium, and antimony.
[0128]
Here, as reference examples, FIGS. 4 to 10 show aluminum, germanium (Ge), tin (Sn), gallium (Ga), zinc (Zn), lead (Pb), indium (In), and antimony (Sb). The binary phase diagram of the alloy which consists of each element is shown.
[0129]
In this embodiment, since the wiring material is mainly composed of aluminum, the temperature of the reflow process needs to be 450 ° C. or lower. According to each phase diagram, it can be seen that if each element except antimony is present at a concentration substantially below that of aluminum, it can exist in a liquid phase state without precipitates even at 450 ° C.
Ge: 25-32 atomic% (Fig. 4)
Sn: 85 atomic% or more (Fig. 5)
Ga: 45 atomic% or more (Fig. 6)
Zn: 65 atomic% or more (Fig. 7)
Pb: 99 atomic% or more (Fig. 8)
In: 98 atomic% or more (Fig. 9)
[0130]
The concentration of these various elements is a value obtained from the content of each element having a eutectic point in the phase diagram. Actually, since it has fluidity at a temperature less than the eutectic point, it can have a concentration range of ± several tens of percent, preferably ± 15%, more preferably ± 25%.
[0131]
In FIG. 10, the alloy of aluminum and antimony does not enter a liquid phase state at 450 ° C., but if it is a thin film, it is presumed that the temperature at which it enters the liquid phase decreases, so it can be used as a reflow material. .
[0132]
Example 6
The present embodiment shows an example in which the heat treatment in the reflow process is performed by RTA (rapid thermal annealing). An example of a manufacturing process of a thin film transistor (TFT) in this example is the same as that in Example 1, and thus description thereof is omitted.
[0133]
RTA is an annealing method in which an object to be processed is irradiated with intense light such as infrared light or ultraviolet light with a lamp or the like. This feature is that the temperature rise rate and the temperature fall rate are fast and the processing time is as short as several seconds to several tens of seconds, so that only the outermost thin film can be heated. That is, for example, only the thin film on the glass substrate can be annealed at an extremely high temperature of about 1000 ° C.
[0134]
The reason why the reflow process must be performed at 450 ° C. or less in Example 1 is that the heat resistance of the gate electrode made of aluminum is taken into consideration.
[0135]
However, if the RTA technique shown in this embodiment is applied, heating at a temperature exceeding the heat resistance of the gate electrode becomes possible, so that the allowable range of the reflow temperature is expanded. Therefore, the range of selection of the metal element used for reflow can be expanded.
[0136]
Further, since the RTA process is performed in a very short time of several seconds to several tens of seconds, it is a very effective means from the viewpoint of productivity.
[0137]
Example 7
This embodiment shows an example of a method of adding germanium to a wiring electrode containing aluminum as a main component by a sputtering method. An example of a manufacturing process of a thin film transistor (TFT) in this example is the same as that in Example 1, and thus description thereof is omitted.
[0138]
In order to perform the reflow process at a temperature of 450 ° C. or lower, preferably 400 ° C. or lower, the germanium content is desirably 20 to 40 atomic%. The addition concentration of germanium is a value obtained on the basis of the germanium content (30 atomic%) where the eutectic point exists in FIG. In practice, a value of 20 to 40 atomic% would be reasonable because it will have fluidity at temperatures below the eutectic point.
[0139]
First, when a contact hole is formed in the interlayer insulating film, a wiring electrode mainly composed of aluminum containing 20 to 40 atomic% germanium is directly formed. In this embodiment, germanium grains are placed on an aluminum target to which 2% copper is added, and sputtering is performed. Of course, sputtering may be performed by the method shown in the fourth embodiment.
[0140]
In this way, it is possible to easily form a wiring electrode that can be reliably reflowed.
[0141]
In this case, the composition contains germanium immediately after the start of film formation, but gradually does not contain germanium. However, since reflow is a phenomenon that has only to occur on the surface that is in contact with the hollow portion or the blowhole, such a composition does not cause a problem.
[0142]
Needless to say, a sputtering method using an existing target formed of an alloy of aluminum and germanium or a laminated structure may be used. In addition, the wiring electrode may have a multilayer structure including a layer containing germanium and a layer not containing germanium.
[0143]
The metal thin film formed in this way easily exhibits fluidity by a reflow process at 375 to 450 ° C. for 1 hour, so that the burrs and blowholes in the contact hole can be reliably coated without disconnection. . A reliable contact can be formed.
[0144]
Example 8
This embodiment shows an example in which a thermal CVD method is used as a method of forming the germanium film 300 or the metal thin film 315 containing germanium in the configuration shown in FIG. Since a manufacturing process of a thin film transistor (TFT) in this embodiment is the same as that in Embodiment 1, the description thereof is omitted.
[0145]
When the contact hole is formed as shown in FIG. 1A, a metal thin film 315 mainly composed of aluminum containing 20 to 40 atomic% germanium is directly formed. In this embodiment, DMAH (dimethyl aluminum hydride) and GeH which are alkyl metals are used as film forming gases. _Four Is used.
[0146]
As a film forming gas, GeH _Four If only is used, only a germanium film can be formed as the film 300.
[0147]
Here, the film forming temperature is set to 250 to 270 ° C. In this case, the film formation rate is about 4500 L / min. The resistivity is close to the bulk and is 2.95 μΩcm.
[0148]
The metal thin film 315 thus formed easily exhibits fluidity by the reflow process. Therefore, it is possible to cover the punched portion in the contact hole and the blow hole without breaking, and a reliable contact can be formed.
[0149]
Example 9
In the first embodiment, the germanium film 300 is formed by the plasma CVD method. However, the germanium film 300 may be formed by the sputtering method. In this embodiment, an example of using a multi-chamber (cluster tool) structure apparatus having a configuration as shown in FIG. 11 as a sputtering apparatus will be described.
[0150]
The sputtering apparatus having a multi-chamber structure shown in FIG. 11 can continuously deposit thin films having different compositions by providing targets having different compositions (including different elements) in each reaction chamber.
[0151]
Here, a simple configuration of the sputtering apparatus shown in FIG. 11 will be described. Reference numeral 10 denotes a substrate to be processed, 11 a common chamber serving as an apparatus main body, and 12 a transfer mechanism for transferring the substrate 10. The substrate 10 is carried in / out from load lock chambers 13 and 14 attached to the apparatus main body 11. Reference numerals 15 and 16 denote substrate transport cassettes installed in the load lock chambers 13 and 14, respectively. Further, the load lock chambers 13 and 14 are hermetically shut off from the common chamber 11 by gate valves 17 and 18.
[0152]
The common chamber 11 is provided with a first reaction chamber 19, a second reaction chamber 20, and a third reaction chamber 21, and the first to third reaction chambers are gate valves 22, 23, 24, respectively. Thus, the common chamber 11 is hermetically shut off. Reference numeral 25 denotes a heating chamber, which is used when preheating is performed as a pretreatment when a thin film is formed on the substrate 10. The heating chamber 25 is also hermetically shut off from the common chamber 11 by a gate valve 26.
[0153]
Next, an example of forming a laminated structure composed of thin films having different compositions using the sputtering apparatus configured as described above will be described.
[0154]
For example, an aluminum (Al) target is provided in the first reaction chamber 19, a germanium (Ge) target is provided in the second reaction chamber 20, and a tin (Sn) target is provided in the third reaction chamber 21. . Then, it is possible to obtain a desired stacked structure such as a Ge—Al—Sn stacked structure or an Al—Ge—Sn stacked structure by continuously forming a film using each target without opening to the atmosphere.
[0155]
In the reflow process, the surface shape and surface state of the metal thin film subjected to the reflow process are important factors that greatly affect the reflow process. For example, a natural oxide is immediately formed on the surface of a thin film containing aluminum as a main component in the atmosphere, and this natural oxide also becomes a factor that hinders reflow. Further, since the natural oxide is insulative, it also inhibits ohmic contact with other conductive thin films.
[0156]
However, in this embodiment, metal thin films having different compositions can be laminated without being exposed to the atmosphere, and the above-described problems are not caused. In particular, since the aluminum surface is easily oxidized, the method of this embodiment that can be laminated without opening to the atmosphere is very effective.
[0157]
Example 10
In Example 4, an example in which a germanium film is formed by sputtering is shown. However, in the case of Example 4, if the film forming process is performed once, the germanium film disappears from the surface of the used target. sell.
[0158]
That is, in order to carry out this embodiment continuously, a dedicated target (a target in which an aluminum film and a germanium film are laminated in the minimum amount necessary for carrying out this embodiment once) is prepared. An operation such as performing replacement as needed becomes necessary, which causes problems in terms of throughput and cost.
[0159]
As one of the solutions, it can be considered that the sputtering apparatus has “a function of forming a germanium film on the target itself”. That is, the film forming process may be repeated in the following steps.
[0160]
(1) A Ge / Al laminated film is formed using a first target.
(2) When film formation is completed, the first target is switched to the second target simultaneously with switching the substrate to be processed.
(3) While the Ge / Al laminated film is formed using the second target, a germanium film is formed on the first target in another reaction chamber.
[0161]
By repeating the above steps, it is possible to always use an aluminum target having a germanium film deposited on its surface. In this case, a multi-chamber as shown in FIG. 11 can be used. Moreover, the sputtering apparatus used in the present invention can also include a target switching mechanism and a film forming apparatus for forming a germanium film on the target.
[0162]
Example 11
In this embodiment, the fact that the reflow process according to the present invention is an extremely effective technique for the disconnection failure of the wiring inside the contact hole will be described with experimental facts. An example in which the treatment atmosphere of the reflow process is a hydrogen atmosphere will also be mentioned. The SEM photograph of FIG. 12 is used for the description.
[0163]
12A, 12B, and 12C show a cross section inside the contact hole. The inner diameter of the contact hole is about 2 μm, and the interlayer insulating film is about 0.8 μm. The wiring structure that embeds the contact hole is Ti (500 mm) / Al-Si (10000 mm) / Sn (50 mm) from the bottom.
[0164]
The reason why the wiring is formed to be considerably thick is to produce a sample in which the reflow effect can be confirmed more remarkably. The wiring having a three-layer structure was continuously formed by using a multi-chamber sputtering apparatus as shown in FIG.
[0165]
After the wiring structure having the above structure was formed, the cross section of the contact hole was observed by SEM for the substrate subjected to the reflow process under the following conditions.
(A) Initial state before reflow process
(B) State after 450 ° C., 1 hour reflow process in nitrogen atmosphere
(C) State after 450 ° C., 1 hour reflow process in 3% hydrogen atmosphere
[0166]
First, FIG. 12A shows an initial contact hole cross section before the reflow process, and in this state, a disconnection failure of the wiring material is confirmed at the bottom of the contact hole (a region near the hole side wall). The reflow process of the present invention is a technique for improving such disconnection failure.
[0167]
Next, FIG. 12B shows a cross section of a contact hole after a reflow process at 450 ° C. for 1 hour in a nitrogen atmosphere. From FIG. 12B, it can be seen that the wiring shape is generally smooth due to the reflow effect. In addition, even in the initial state, the disconnection failure is improved due to the flow of the wiring material due to reflow.
[0168]
Further, FIG. 12C shows a contact hole cross section after a reflow process at 450 ° C. for 1 hour in a 3% hydrogen atmosphere (diluted with nitrogen). As is apparent from FIG. 12C, it can be confirmed that the overall wiring shape becomes gentler and the contact state of the wiring material inside the contact hole is extremely good.
[0169]
As described above, comparing FIGS. 12A, 12B, and 12C, the reflow process of the present invention is clearly an effective technique for improving the disconnection failure of the wiring inside the contact hole. Can understand.
[0170]
In particular, it can be seen that by making the treatment atmosphere of the reflow process a hydrogen atmosphere, fluidization of the wiring material is promoted and a more reliable contact shape can be realized. Although the reason why the fluidization of the wiring is promoted when the reflow process is performed in a hydrogen atmosphere is not clear, the present inventors hinder the fluidization of the wiring material due to the natural oxide on the wiring surface due to the reduction effect of hydrogen. It is estimated that it was removed to the extent that it does not become.
[0171]
【The invention's effect】
When a contact is formed on a wiring electrode containing aluminum as a main component, a reliable contact can be formed by the action of the element by applying a reflow process using an element such as germanium or tin.
[0172]
As a result, good contact can be obtained even when a hollow portion or a blow hole is formed in the contact hole, and the reliability of the TFT can be greatly improved.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams illustrating a manufacturing process of a TFT of Example 1, and an explanatory diagram of a reflow process. FIGS.
2 is a diagram showing a manufacturing process of a TFT of Example 1. FIG.
3 is a view showing a cross section of a gate contact hole of Example 1. FIG.
FIG. 4 is a binary phase diagram of an alloy composed of aluminum and germanium.
FIG. 5 is a binary phase diagram of an alloy made of aluminum and tin.
FIG. 6 is a binary phase diagram of an alloy of aluminum and gallium.
FIG. 7 is a binary phase diagram of an alloy composed of aluminum and zinc.
FIG. 8 is a binary phase diagram of an alloy of aluminum and lead.
FIG. 9 is a binary phase diagram of an alloy of aluminum and indium.
FIG. 10 is a binary phase diagram of an alloy composed of aluminum and antimony.
11 is a diagram showing a configuration of a sputtering apparatus of Example 9. FIG.
12 is an electron micrograph showing a cross section of the thin film of Example 11. FIG.
FIG. 13 shows a periodic table of elements.
FIG. 14 is an enlarged cross-sectional view of a conventional contact hole.
[Explanation of symbols]
101 Gate electrode
102 Anodized film
103 Interlayer insulation film
104 Contact hole
105
106 Wiring electrode
201 Glass substrate (or quartz substrate)
202 Base film (silicon oxynitride film)
203 Island-like semiconductor layer
204 Gate insulating film (silicon oxide film)
205 Metal thin film
206 Porous anodic oxide film
207 Dense anodic oxide film
208 Gate electrode
209 Source area
210 Drain region
211 Low concentration impurity region
212 Low concentration impurity region
213 channel formation region
214 First interlayer insulating film (silicon oxynitride film)
300 Film made of element for reflow or film containing the element
315 Metal thin film
316 Source electrode
317 Gate electrode
318 Second interlayer insulating film (resin material)
319 Transparent electrode
401 Contact hole

Claims (5)

Forming an insulated gate field effect semiconductor device;
Forming an interlayer insulating film on the insulated gate field effect semiconductor device;
Forming a contact hole reaching a part of the insulated gate field effect semiconductor device in the interlayer insulating film;
Forming a first film having any of germanium, tin, gallium, zinc, lead, indium, and antimony electrically connected to a part of the insulated gate field effect semiconductor device in the contact hole;
A metal film containing aluminum as a main component on the first film, and a second film containing any of germanium, tin, gallium, zinc, lead, indium, and antimony on the metal film in a vacuum. After forming continuously without opening,
A method for manufacturing a semiconductor device, wherein heat treatment is performed to provide fluidity to a stacked film of the first film, the metal film, and the second film. In claim 1 ,
A method for manufacturing a semiconductor device, wherein a part of the insulated gate field effect semiconductor device is a semiconductor layer. In claim 1 ,
The method for manufacturing a semiconductor device, wherein a portion of said insulated gate field effect semiconductor device is a Gate electrode. In any one of Claim 1 thru | or 3 ,
The method for manufacturing a semiconductor device, wherein the heat treatment is performed by RTA (rapid thermal annealing). In any one of Claims 1 thru | or 4 ,
A method for manufacturing a semiconductor device, wherein the heat treatment is performed in a hydrogen atmosphere.

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