CN1610064A - Semiconductor device - Google Patents

Abstract

In the case of using an aluminum alloy thin film as an electrode layer in the manufacture of a liquid crystal display element or a semiconductor element, it is possible to provide a semiconductor element capable of realizing excellent low-resistance ohmic contact characteristics without a so-called cover layer. In a semiconductor element having a substrate, a semiconductor layer formed on the substrate, and an electrode layer constituting wiring or electrodes, there is a portion where the semiconductor layer is directly bonded to the electrode layer, and the electrode layer is made of a transition metal containing nickel, cobalt, iron, etc. aluminum alloy film formation.

Description

semiconductor element

technical field

The present invention relates to a semiconductor element, in particular to a structure of a semiconductor element and a liquid crystal display element excellent in low-resistance ohmic contact characteristics.

Background technique

In recent years, the high integration and high-speed progress of semiconductor elements represented by so-called ICs or liquid crystal display elements for liquid crystal displays having the same structure, such as thin film transistors (Thin Film Transistor hereinafter abbreviated as TFT). Accordingly, device structures using these semiconductors have been improved day by day, and various materials have been developed for semiconductor device constituting materials to realize semiconductor devices having excellent characteristics.

In order to meet such requirements, the applicant provides a kind of aluminum alloy film, which can be used with the ITO film (Indium Tin Oxide, indium tin oxide) used in liquid crystal display, in addition to the research on the aluminum alloy film as the constituent material of the liquid crystal display element. material), etc., can maintain ohmic junction even if energized for a long time, can prevent interdiffusion of silicon and aluminum, has low resistivity characteristics, and has good heat resistance (see Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open No. 2003-89864

The aluminum alloy thin film proposed by the applicant contains 0.5-7.0 at% of at least one element among nickel, cobalt, and iron, 0.1-3.0 at% of carbon, and the rest is aluminum. Utilize the aluminum alloy thin film of such composition, form the electrode layer that constitutes wiring or electrode of liquid crystal display element, can finally make a kind of liquid crystal display element by this, this liquid crystal display element can be directly bonded with transparent electrode, can prevent silicon and aluminum Interdiffusion, low electrical resistance, good heat resistance, and excellent anti-abnormal precipitation characteristics.

In liquid crystal display elements such as semiconductor elements and TFTs, aluminum alloy thin films are often used as described above when forming electrode layers constituting wiring lines or electrodes. This is because high-melting-point materials such as tantalum, chromium, titanium, or their alloys have been used conventionally. However, since such high-melting-point materials have too high resistivity, attention has been paid to aluminum, which has a low resistivity and is easy to process for wiring.

However, when electrode layers are formed using this aluminum alloy thin film, it is known that the following phenomenon occurs at the contact portion of each structural layer of a semiconductor element. Among them, when the electrode layer formed by using an aluminum alloy film is in direct contact with a silicon layer or a semiconductor layer formed of silicon (doped silicon, etc.), there is a tendency for silicon to precipitate into the aluminum alloy film, or there is a tendency for aluminum to form Diffusion in a semiconductor layer formed of silicon, etc., and the diffused aluminum atoms tend to destroy the PN junction formed by the semiconductor layer, and if it is directly bonded to a transparent electrode, it will cause bonding due to the difference in the oxidation-reduction potential of the two materials. resistance changes.

In consideration of such problems, that is, the low-resistance ohmic contact characteristics required by semiconductor elements or liquid crystal display elements, when using an aluminum alloy film as an electrode layer, a so-called covering layer (or contact barrier layer) composed of Mo or Cr, etc. is formed. , the term "covering layer" below is used as a concept including a contact barrier layer) (for example, refer to Non-Patent Document 2).

[Non-Patent Document 2] Tatsuo Uchida, "Next-Generation Liquid Crystal Display Technology", 1st edition, Industrial Research Society Co., Ltd. Nov. 1, 1994, .36-38.

A cover layer is formed between a semiconductor layer and an electrode layer, or between a transparent electrode and an electrode layer, for example, in the case of a TFT. This will be specifically described below by taking a schematic cross-sectional view of a so-called a-Si type TFT shown in FIG. 1 as an example. In this type of TFT, a gate electrode 2 made of an aluminum alloy thin film is formed on a glass substrate 1, and a gate insulating layer 3 of SiN (silicon nitride) or the like is formed thereon. Next, in the channel portion, an n-type a-SI layer 5 is formed on the gate insulating layer via the a-Si layer 4 . In addition, on the pixel display side, a transparent electrode made of an ITO film is provided on the gate insulating layer 3 . On the n-type a-Si layer 5 and the transparent electrode 6 of the channel portion, a so-called capping layer 7 mainly made of Mo, Cr, etc. is formed. The drain electrode 8 and the source electrode 9 are formed thereon with an aluminum alloy thin film.

In this way, in a TFT having an electrode layer that uses an aluminum alloy thin film to form wiring or electrodes, a cover layer mainly made of Cr, Mo, etc. is provided in consideration of the ohmic contact characteristics of the above-mentioned resistance related to the contact of the aluminum alloy thin film. This is unavoidable and must be formed when an electrode layer made of an aluminum alloy thin film is used, in other words, when an aluminum-based material is used as a constituent material of the TFT. That is, the process of forming the cover layer is necessary in TFT manufacture, which leads to a complicated stacked structure and increased production cost. In addition, the cover layer is currently provided not only for liquid crystal display elements but also for semiconductor elements such as so-called ICs.

In addition, there has recently been a market trend to exclude the use of Cr as a material constituting the coating layer, and this has begun to place significant restrictions on techniques for forming the coating layer.

Contents of the invention

The present invention has been made against the background of the above circumstances, and its object is to provide a semiconductor element which, when using an aluminum alloy thin film as an electrode layer in the manufacture of a liquid crystal display element and a semiconductor element, does not have a so-called covering layer, and can also achieve excellent low-resistance ohmic contact characteristics.

The present applicant found a semiconductor device structure capable of realizing low-resistance ohmic contact characteristics without forming a cover layer as a result of intensive research on an already developed aluminum alloy thin film (see Patent Document 1), and finally came up with the present invention.

In the present invention, in a semiconductor element having a substrate, a semiconductor layer formed on the substrate, and an electrode layer constituting a wiring or an electrode, there is a portion where the semiconductor layer is directly bonded to the electrode layer, and the electrode layer is made of an aluminum alloy containing a transition metal film formation. In the semiconductor element structure of the present invention, the electrode layer formed of the aluminum alloy thin film can be directly bonded to the semiconductor layer because the aluminum alloy thin film forming the electrode layer contains transition metal.

It is known that this transition metal easily forms a silicide with silicon (Si) constituting a semiconductor. For this reason, transition metals such as Mo, Cr, or W are used as materials constituting the coating layer. In addition, the present inventors themselves have also found that silicon must be contained in the aluminum alloy thin film in order to prevent interdiffusion with silicon.

In addition, as the research on the aluminum alloy thin film developed by the present inventors continues to deepen, it is found that if the aluminum alloy thin film contains a transition metal, even if it is directly bonded to the semiconductor layer, there will be no precipitation of silicon into the aluminum alloy thin film. and the diffusion of aluminum into the silicon layer. That is, it has been shown that only by adding a transition metal to the aluminum alloy thin film, the same effect as that of the so-called coating layer, that is, low-resistance ohmic contact characteristics can be realized.

That is, it is possible to configure a semiconductor element in which an electrode layer formed of an aluminum alloy thin film and a semiconductor layer can be directly bonded without forming a cover layer constituting a barrier layer only by adding a transition metal to the aluminum alloy thin film.

The theory of this phenomenon is currently being verified, but it is speculated that the transition metal contained in the aluminum alloy thin film forms silicide at the interface when the aluminum alloy thin film and the semiconductor layer are directly bonded.

Therefore, by adopting the semiconductor element structure of the present invention, since no cladding layer is required, the stacked structure of the element can be simplified, and the cladding layer manufacturing process can be omitted, so that the production efficiency can be improved. In addition, in the above and below, the so-called semiconductor layer of the present invention includes a silicon layer called a semiconductor active layer, a silicon layer such as a doped n+ type or P+ type a-Si layer. In addition, the substrate according to the present invention includes semiconductor substrates such as silicon and glass substrates of liquid crystal display elements. In addition, the semiconductor element of the present invention naturally includes IC and liquid crystal display elements, such as TFT and other commonly-named semiconductor elements, and also includes elements having similar structures.

In addition, the semiconductor element of the present invention may have a portion where the electrode layer and the transparent electrode for liquid crystal display are directly joined. If the aluminum alloy thin film forming the electrode layer contains a transition metal, the electrode potential of the aluminum alloy thin film is on the same level as the oxidation-reduction potential of the transparent electrode material such as tin oxide film or ITO film constituting the transparent electrode. Therefore, the semiconductor element of the present invention is also suitable for liquid crystal display elements. In addition, the "oxidation-reduction potential" refers to the potential at which the oxidation rate and the reduction rate are equal and balanced in the oxidation-reduction reaction of a certain reactant, that is, the equilibrium potential.

The transition metal contained in the aluminum alloy thin film of the semiconductor element related to the present invention is preferably iron, cobalt, nickel, and this is because when these transition metal elements are contained in the aluminum alloy thin film, its oxidation-reduction potential is different from that of the transparent electrode. Very close while being able to ensure heat resistance. One element of these three transition metals may be contained, or two or more elements of these elements may be contained. In addition, at least one or more elements of other transition metals, namely titanium, vanadium, chromium, zirconium, niobium, molybdenum, iron, rhodium, palladium, hafnium, tantalum, tungsten, osmium, iridium, and platinum, can also be used. . This is because these elements are known to easily form silicides.

In addition, in the aluminum alloy thin film forming the electrode layer, it is desirable to contain 0.1 to 7.0 at % of a transition metal. If the content is less than 0.1 at%, there may be a tendency for insufficient silicide formation at the joint interface. The reason for this is not clear, but when the semiconductor layer is directly bonded, silicon and aluminum are interdiffused, and aluminum The oxidation-reduction potential of the alloy thin film is very different from that of the transparent electrode, so the aluminum alloy thin film cannot be directly bonded to the transparent electrode. In addition, it is also because there is a tendency that the heat resistance of the aluminum alloy thin film also disappears. In addition, if it exceeds 7.0 at%, even if an aluminum alloy thin film is formed at a substrate temperature of 200°C, after heat treatment at 300°C for 1 hour in a vacuum, the resistivity value will exceed 20μΩcm, and it will not be possible to form a practical semiconductor element. electrode layer. Therefore, it is preferable that the transition metal content in the aluminum alloy thin film is 0.5-5.0 at%. This is because when iron, cobalt, and nickel are contained as transition metals, if they are less than 0.5 at%, there is a tendency for heat resistance to decrease, and at the same time, the oxidation-reduction potential of the aluminum alloy thin film forming the electrode layer deviates from the transparent oxidation-reduction potential. tend to be serious. In addition, since the resistivity value increases when exceeding 5.0 at%, there is a tendency that the practical low resistance characteristic cannot be maintained.

Furthermore, in the aluminum alloy thin film forming the electrode layer according to the present invention, it is preferable to contain carbon. This is because, if carbon is contained in the aluminum alloy thin film, it is possible to effectively prevent abnormal precipitation that occurs during the thermal process.

When the carbon element is contained, the carbon content is preferably 0.1 to 3.0 at%. This is because if the carbon content is less than 0.1 at%, there is no effect of suppressing abnormal precipitation, and if it exceeds 3.0 at%, the resistivity value increases, and a practical electrode layer in a semiconductor element cannot be formed.

In addition, according to the study of the present inventors, when the semiconductor element related to the present invention is formed, when the aluminum-nickel contains carbon as the aluminum alloy thin film, it has been confirmed that the content of nickel is preferably 0.5 to 5 at%. From a practical point of view, it is more desirable to be in the range of 2..0 to 4.0 at%. This is because if nickel is less than 2.0 at%, the difference between the oxidation-reduction potential value of the transparent electrode and the oxidation-reduction potential value of the aluminum alloy thin film tends to increase significantly, and the heat resistance at 350° C. or higher tends to deteriorate. In addition, when nickel exceeds 4.0 at%, the resistivity value tends to increase, and the resistivity value after heat treatment at 300° C. for 1 hour in vacuum may exceed 10 μΩcm. In addition, it was confirmed that when carbon is contained in aluminum-cobalt or aluminum-iron, the content of cobalt or iron is preferably in the range of 2.0 to 5.0 at%. This is because, if it is within this content range, an electrode layer with low resistivity and good heat resistance can be formed, especially if it is used in a liquid crystal display element, it can form a liquid crystal display suitable for a large screen or high definition. .

As described above, according to the present invention, when an aluminum alloy thin film is used as an electrode layer in the manufacture of a semiconductor element, excellent low-resistance ohmic contact characteristics can be realized even without a so-called cover layer. Also, the semiconductor element of the present invention is suitable for a liquid crystal display element because the electrode layer can be directly bonded to the transparent electrode even in a liquid crystal display element including a transparent electrode made of an ITO film.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a conventional TFT.

Fig. 2 is a cross-sectional view of a test sample for examining bonding characteristics.

Fig. 3 shows measurement curves of the results of bonding characteristics of each electrode layer.

Fig. 4 is a graph showing the relationship between the reverse current value and the heat treatment temperature of each electrode layer when a voltage of -1V is applied.

FIG. 5 is a perspective view of a test sample for measuring durability against energization with a transparent electrode.

FIG. 6 is an Arrhenius plot for measuring energization durability due to temperature.

FIG. 7 is a cross-sectional photograph of the joint portion between the electrode layer and the transparent electrode observed in Example 1 and Example 2. FIG.

FIG. 8 is a TEM photograph showing a cross section of a junction between an electrode layer and a Si layer in Example 1. FIG.

FIG. 9 is a TEM photograph showing the cross section of the junction between the electrode layer and the transparent electrode in Example 1. FIG.

FIG. 10 is an enlarged photograph of a cross section of a junction in FIG. 9 .

FIG. 11 is a graph showing the relationship between the junction resistance and the potential difference with ITO.

Detailed ways

Preferred embodiments of the present invention will be described below based on Examples and Comparative Examples. First, the result of examining the bonding characteristics between the electrode layer and the semiconductor layer when the structure of the semiconductor element according to the present invention is adopted will be described. Fig. 2 is a cross-sectional view of an experimental sample for examining the bonding characteristics.

The test sample shown in FIG. 2 has a laminated structure of an electrode layer 10 (0.2 μm thick), an n-type Si substrate 20 (625 μm thick), and a p-type a-Si layer 30 (0.1 μm thick, with a resistivity value of 5 to 10 Ωcm). , the terminals L1 and L2 are connected to the outer surface of the electrode layer 10 and the electrode layer 10 ′ of the p-type a-Si layer 30 . The electrode layer 10 ( 10 ′) of the test sample was formed by using the aluminum alloy thin film of each composition shown in Table 1. The bonding characteristics were checked by measuring the current flowing between the terminals when a voltage was applied between the terminals, and how the bonding characteristics changed was also checked by heat-treating the formed electrode layer 10 .

[Table 1] Electrode layer Al Ni C Mo Cu Si Example 1 96.8 3.0 0.2 - - - Conventional example 2 - - - 100 - - Comparative example 1 98.5 - - - 0.5 1.0 Comparative example 2 100 - - - - -

(at%)

The electrode layer in Example 1 is an aluminum alloy thin film containing nickel and carbon, and in Conventional Example 1, molybdenum is used to form the coating layer as the electrode layer. In addition, as comparative examples, electrode layers were formed using an aluminum alloy thin film containing silicon and copper (comparative example 1) and an aluminum thin film composed only of aluminum (comparative example 2). In addition, the heat treatment of each electrode layer was carried out by leaving the test sample in a nitrogen atmosphere at different temperatures of 250° C., 300° C., and 350° C. for 1 hour.

In addition, the thin film formation conditions when forming each electrode layer are input power 3.0W/cm ² , argon gas flow rate 100ccm, and argon gas pressure 0.5Pa. Using a magnetron sputtering device, the film formation time is about 60sec, and the formation time is about 2000 Å. (0.2 μm) thick film, the substrate temperature was set to 100°C.

Figure 3 shows the junction characteristics of each electrode layer. 3(A), (B), (C) and (D) show the measurement results of Example 1, Conventional Example 1, Comparative Example 1 and Comparative Example 2, respectively. In addition, in the curves of the respective measurement results, the thin dotted line indicates the case of no heat treatment (as-depO), the thick dotted line indicates the case of 250°C heat treatment, the thin solid line indicates the case of 300°C heat treatment, and the thick solid line indicates the case of heat treatment at 300°C. The line shows the case of heat treatment at 350°C.

First, looking at FIG. 3(D), it can be seen that when the electrode layer was formed only with aluminum in Comparative Example 2, it was confirmed that the PN junction was destroyed in the state without heat treatment, and with the negative applied voltage (in FIG. 2, the terminal When a negative voltage is applied to the L1 side), the reverse current also increases. In addition, when the electrode layer is formed using the Al-Cu-Si-based aluminum alloy thin film of Comparative Example 1 (FIG. 3(C)), since Si is contained, the PN is maintained without heat treatment or heat treatment at 250°C. The state of the junction that rectifies when the applied voltage changes from negative to positive. However, when heat treatment was performed at 300° C. and 350° C., it was confirmed that the normal PN junction was not maintained, and the reverse current also increased as the negative applied voltage increased.

In addition, referring to FIG. 3) (B), it can be seen that when the electrode layer was formed using molybdenum in Conventional Example 1, it was confirmed that a normal PN junction was maintained regardless of the presence or absence of heat treatment. Then, looking at Fig. 3(A), it can be seen that when the electrode layer is formed by using the Al-Ni-C aluminum alloy thin film of Example 1, in the heat treatment at 300°C and 350°C, as the negative applied voltage increases, , since the reverse current does not increase significantly, the reverse saturation current is maintained, so it shows that the PN junction has nothing to do with whether there is heat treatment, and basically maintains a normal state.

Next, the reverse current value at each heat treatment temperature will be described based on the inspection results of the bonding characteristics between each electrode layer and semiconductor layer shown in FIG. 3 . FIG. 4 shows the reverse current value (average value of 4 measured values) when the negative applied voltage in FIG. 3 is -1V, and the curve drawn with the heat treatment temperature as the horizontal axis.

Referring to FIG. 4 , it can be seen that the reverse current value at an applied voltage of -1 V is greatly changed by heat treatment in the case of comparative example 2 where only aluminum is used. In addition, in the case of the Al-Cu-Si system of Comparative Example 1, when the heat treatment was performed at 300° C. or higher, the reverse current value also changed greatly. In addition, in the case of molybdenum in Conventional Example 1, it was confirmed that there was almost no change in the reverse current value regardless of the presence or absence of heat treatment. Then, in the case of the Al-Ni-C system of Example 1, it was confirmed that at the heat treatment temperatures of 300°C and 350°C, although there was a certain change in the reverse current value, it was not the same as in Comparative Examples 1 and 2. large reverse current value changes. In addition, the reverse current value shown in Fig. 4 is the value at the junction area (0.04cm ² ) of the test sample shown in Fig. The reverse current value in the semiconductor element is estimated to be smaller than the value shown in FIG. 4 .

Next, the results of examination of the bonding properties between the electrode layer formed using the aluminum alloy thin film of Example 1 and the transparent electrode composed of an ITO film will be described. First, the results of measurement of energization durability when the electrode layer of Example 1 was bonded to an ITO film will be described.

Fig. 5 shows the measurement method of energization durability. Electrode layers (0.2 μm thick) were cross-formed on transparent electrodes 40 (0.2 μm thick) made of ITO film (In ₂ O ₃ -10 wt% SnO ₂ ), and electricity was supplied from terminals indicated by arrows. The energization durability measurement is performed by measuring the resistance between the terminals and measuring the energization time until the resistance between the terminals changes. The measurement environment of the energization durability is in an air atmosphere at 85°C. For comparison with Example 1, the electrode layers of Al (aluminum)-Nd (neodymium) shown in Table 2 were also measured.

[Table 2] Electrode layer Al Ni C Mo Example 1 96.8 3.0 0.2 - Comparative example 3 98.0 - - 2.0

The energization durability was measured by energizing for 200 hours at two current values of 10 μA and 1 mA. In addition, the electrode layer of Comparative Example 3 was measured in two cases, one in which it was directly bonded to the transparent electrode, and the other in which one of the constituent materials of the coating layer was formed between the electrode layer and the transparent electrode. Cr film (0.05 μm thick) to form the junction. Table 3 shows the results of the energization durability when the energization time during which the inter-terminal resistance changes occurs.

[table 3] Electrode layer electric current Cr film Power Durability Example 10μA - 200h no change 1mA - 200h no change Comparative example 3 10μA none After 40 hours, the resistance is almost unchanged, and then there is a certain resistance value at 200b hours 1mA none After 130 hours, the resistance value becomes larger Comparative example 3 10μA have 200h no change 1mA have 200h no change

As shown in Table 3, for the electrode layer of Comparative Example 3 interposed by the Cr film serving as the coating layer, the resistance value between the terminals did not change even after 200 hours of energization (the resistance value between the terminals was 6E=03Ω). . However, when the electrode layer of Comparative Example 3 was directly bonded to the transparent electrode without the Cr film, it was confirmed that after 40 hours with a current of 10 μA, the resistance between the terminals increased (from the initial resistance value between terminals 6E+3Ω to 2.5E +5Ω). Furthermore, it was confirmed that after 130 hours at a current of 1 mA, the inter-terminal resistance increased significantly (from the initial inter-terminal resistance value of 4E+3Ω to 4E+7Ω). In addition, the electrode layer of Example 1 did not change in the inter-terminal resistance value (the inter-terminal resistance value was 5E+3Ω) even when energized for 200 hours.

Next, the test results of the temperature-dependent energization durability will be described. The temperature-dependent energization durability was measured for the electrode layers of Example 1 and Comparative Example 3 (without the Cr film) described above. The measurement method is to take the current value as 3mA, and the time when the resistance value of the junction reaches twice the initial value is taken as the life. And the temperature at the time of energization was set to 85 degreeC, 100 degreeC, 150 degreeC, 200 degreeC, and 250 degreeC, and performed. Fig. 6 is a graph showing the Arrhenius plot of the life time of the junction part measured at each temperature when the resistance rise time is measured and the reciprocal of the temperature maintained at the time of energization. In FIG. 6 , the vertical axis represents life time, and the horizontal axis represents 1000/absolute temperature. From the slope of the first-order straight line extrapolated from the Arrhenius plot, the activation energy for increasing the resistance at the junction was calculated to be 1.35 eV for Example 1 and 0.42 eV for Comparative Example 3. From this result, it was confirmed that the electrode layer of Example 1 had activation energy about 3.3 times that of Comparative Example 3. In addition, it can be predicted from FIG. 5 that the endurance life of Comparative Example 3 at 85° C. during continuous energization is only about 2 hours, while that of Example 1 is even about 70,000 hours.

Next, the observation results of the bonding interface between the electrode layer and the transparent layer electrode in Example 1 and Comparative Example 2 will be described. Figure 7 shows the cross-sectional view of two electrode layers joined to a transparent electrode made of ITO film and energized for about 1 hour (current about 1mA) observed by FIB (Focused Ion Beam)-SEM and metal microscope. The preparation conditions of this sample are the same as those described in the above-mentioned Example 1 and Comparative Example 2, so the description thereof will be omitted.

7(A) is a cross section in the case of Comparative Example 1, and (B) is a cross section in the case of Example 1. FIG. Looking at these cross-sections, it can be seen that in Comparative Example 1, deterioration and peeling occurred at the junction of the Al film and ITO film after energization, and in the case of Example 1, no deterioration was observed even after energization.

Next, the results of measuring the oxidation-reduction potentials of Cr, Mo, and ITO films, which are the coating layer constituent materials of Example 1, Comparative Examples 2 and 3, will be described. The measurement of the oxidation-reduction potential was performed by forming a thin film having a predetermined thickness (0.2 μm) with various compositions on a glass substrate, and then cutting the glass substrate to obtain a potential measurement sample. Then, the surface of the potential measurement sample was masked to expose an area equivalent to 1 cm ² to form a measurement electrode. The oxidation-reduction potential was measured with a 3.5% sodium chloride aqueous solution (liquid temperature: 27 ² C), and silver/silver chloride as a reference electrode. In addition, the ITO film used the film of the composition of _In2O3-10wt % _{SnO2 .} Table 4 shows the results.

[Table 4] sample Oxidation-reduction potential (V) Example 1 -1.02 Comparative example 2 -1.64 Comparative example 3 -1.58 Cr -0.78 Mo -0.51 ITO film -0.82

As shown in Table 4, it was confirmed that the oxidation-reduction potential of Example 1 was very close to the oxidation-reduction potential of the ITO film compared with Comparative Examples 2 and 3.

The above results show that by forming the electrode layer of the semiconductor element using the aluminum alloy thin film of Example 1, it is possible to manufacture a semiconductor element capable of achieving excellent low-resistance ohmic contact characteristics without the conventionally used cover layer. Moreover, since the junction characteristic with transparent electrodes, such as an ITO film, is very good, it turns out that it is also very suitable for the structure of a liquid crystal display element.

Finally, regarding the junction characteristics of the electrode layers in Example 1, the detailed observation of the junction and the inspection results of junction resistance will be described again. Fig. 8 is a photo of the joint portion of the electrode layer and Si layer observed with a transmission electron microscope (TEM) in Example 1, and Figs. A photograph of the joint between the electrode layer and the transparent electrode.

The photo in Figure 8 is a p-type a-Si layer (the white part with a thickness of about 80nm in the middle part in the photo) laminated on the surface of an n-type Si substrate (the black part in the lower half of the photo), and then on the p-type Si substrate. The surface of the a-Si layer forms the electrode layer of Example 1 (the upper half of the photo is about 200nm thick), and such a sample is prepared and heat-treated at a temperature of 250° C. for 1 hour, and then processed so that The cross section of the sample was observed with FIB, and then observed with TEM (magnification: 100,000 times) to obtain a photograph. In addition, for several parts of the section, electron beam diffraction images are used to determine the crystal structure and identify the tissue of this part. According to the cross-sectional observation of FIG. 8, when the electrode layer and the Si layer of Example 1 are bonded and then heat-treated, an intermetallic compound of Al3Ni (the part marked with 4 in the photograph) is precipitated on the interface between the electrode layer and the Si layer.

The photo in Fig. 9 is to form the electrode layer of Example 1 on the surface of a transparent electrode (the black part with a thickness of about 150nm on the lower side of the middle in the photo) made of ITO film (In ₂ O ₃ -10wt% SnO ₂ ) (The whitish part with a thickness of about 200nm on the upper middle side in the photo), such a sample is prepared, heat-treated at 300°C for 1 hour, and then processed so that the cross-section of the sample can be observed with FIB, and then reused TEM (magnification: 100,000 times) was observed to obtain a photograph. FIG. 10 is an enlarged photograph (magnification: 1,000,000 times) of the junction interface in FIG. 9 . Using the enlarged photograph of FIG. 10 , it was confirmed that there was a kelp-shaped precipitate between the transparent electrode side (the lower black portion in the photograph) and the electrode layer side (the upper white portion in the photograph). This precipitate was shown to be an Al3Ni intermetallic compound identified in FIG. 8 . In addition, the oxidation-reduction potential of Al3Ni confirmed in Figs. 8 to 10 was checked and found to be -0.73V.

Next, the results of the junction resistance evaluation will be described. The relationship diagram drawn in Fig. 11 is that the electrode layers of embodiment 1, comparative example 3 and the laminated structure of pure Al film and Cr film are respectively bonded to the ITO film, and the resistance value is measured, and its measurement result is compared with the respective obtained results. The difference between the oxidation-reduction potential value of the electrode layer and the oxidation-reduction potential value of the ITO film is drawn as a curve. The measurement method is to make the sample shown in Figure 5, and measure the resistance value of the sample without heat treatment (as-depo) and with heat treatment (after annealing at different temperatures such as 200°C, 250°C, and 300°C for 1 hour).

The measurement of junction resistance was performed using the sample shown in FIG. 5 formed perpendicular to the electrode layer 10 (0.2 μm thick) on a transparent electrode 40 (0.2 μm thick) composed of an ITO film (In2O3-10 wt% SnO2) , energize from the terminal of the arrow part, measure the resistance, and calculate the joint resistance of the film overlapping part (10 μm × 10 μm. For the electrode layer of the laminated structure of the pure Al film and the Cr film, a 0.2 μm electrode layer is formed on a 0.03 μm Cr film. Pure Al film. In addition, using the oxidation-reduction potential values shown in Table 4, the potential difference between ITO and each electrode layer was calculated, and each junction resistance value was plotted using this as the horizontal axis (Fig. 11).

Referring to FIG. 11 , it was confirmed that the junction resistance was very low in the case of an electrode formed via a Cr film having a potential approximately the same as the oxidation-reduction potential of ITO. In the case of the electrode layers of Example 1 and Comparative Example 3, it was confirmed that the junction resistance value of Example 1 in which the potential difference was not too large was low, and the junction resistance value of the electrode layer of Comparative Example 3 was significantly increased by heat treatment. big.

According to the results of FIGS. 8 to 11, it can be inferred that the electrode layer of Example 1 has a value close to the oxidation-reduction potential of the ITO film because of its oxidation-reduction potential itself, so the junction resistance when it is joined to the transparent electrode of the ITO film is also low. Furthermore, by performing heat treatment, Al3Ni intermetallic compounds are precipitated on the joint interface, thereby realizing excellent joint characteristics. The reason can be considered that since the oxidation-reduction potential (-0.73V) of Al3Ni is a value close to the oxidation-reduction potential (-0.82V) of the transparent electrode of the ITO film, it is not easy to cause an electrochemical reaction with the ITO film and will not cause joint damage, etc.

Claims (6)

1. A semiconductor element having a substrate, a semiconductor layer formed on the substrate, and an electrode layer constituting wiring or electrodes, characterized in that, having a portion where the semiconductor layer is directly bonded to the electrode layer, The electrode layer is formed of an aluminum alloy film containing a transition metal. 2. The semiconductor element according to claim 1, wherein The electrode layer has a portion directly bonded to a transparent electrode for liquid crystal display. 3. The semiconductor element according to claim 1 or 2, wherein The transition metal is at least one or more elements of iron, cobalt and nickel. 4. The semiconductor element according to any one of claims 1 to 3, wherein The aluminum alloy film contains 0.1-7.0 at% transition metal. 5. The semiconductor element according to any one of claims 1 to 4, characterized in that, The aluminum alloy thin film contains carbon. 6. The semiconductor element according to claim 5, wherein The aluminum alloy film contains 0.1-3.0 at% carbon.

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