JPWO2008018478A1 - Device junction structure - Google Patents

Abstract

In the present invention, when a semiconductor layer such as n + -Si and an Al-based alloy layer are directly bonded, mutual diffusion between Al and Si can be prevented, and ohmic characteristics can be maintained. Provided is a device junction structure capable of ensuring low resistance characteristics. The present invention relates to a device junction structure comprising a semiconductor layer and an Al-based alloy layer bonded directly to the semiconductor layer, wherein the semiconductor layer directly bonded to the Al-based alloy layer is made of Si containing nitrogen. The element has a junction structure characterized by that. The nitrogen content of this Si was 1 × 10 18 to 5 × 10 21 atoms / cm 3.

Description

  The present invention relates to a bonding structure of elements constituting a display device such as a liquid crystal display, and more particularly to a technique for manufacturing an element using an Al-based alloy as a wiring circuit material.

  2. Description of the Related Art In recent years, wiring materials made of aluminum (hereinafter sometimes simply referred to as “Al”)-based alloys are widely used as constituent materials in display devices such as thin-screen televisions typified by liquid crystal displays. This is because the specific resistance value of the Al-based alloy wiring material is low and the wiring process is easy.

For example, in the case of an active matrix type liquid crystal display, a thin film transistor (hereinafter abbreviated as TFT) serving as a switching element is a transparent electrode (hereinafter, referred to as ITO (Indium Tin Oxide)) such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). An element is composed of a transparent electrode layer (sometimes referred to as a transparent electrode layer) and a wiring circuit formed of an Al-based alloy (hereinafter referred to as an Al-based alloy layer). In such an element, there are a portion where the Al-based alloy layer is bonded to the transparent electrode and a portion where the Al-based alloy layer is bonded to n ⁺ -Si (phosphorus-doped semiconductor layer) in the TFT.

When configuring the element as described above, considering the influence of the aluminum oxide formed in the Al-based alloy layer, molybdenum (Mo), titanium (Ti), etc. between the Al-based alloy layer and the transparent electrode layer The refractory metal material is formed as a so-called cap layer. In addition, in joining the semiconductor layer such as n ⁺ -Si and the wiring circuit, the semiconductor layer and the Al-based alloy layer are prevented from interdiffusion between Al and Si by a thermal process during the manufacturing process. A high melting point metal material such as molybdenum (Mo) or titanium (Ti), which is the same as the cap layer, is interposed between the two.

Here, the above-described element structure will be specifically described with reference to FIG. FIG. 1 is a schematic cross-sectional view of an a-Si type TFT relating to a liquid crystal display. In this TFT structure, an electrode wiring circuit layer 2 made of an Al-based alloy wiring material constituting the gate electrode portion G and a cap layer 3 made of Mo, Mo—W, or the like are formed on the glass substrate 1. The gate electrode portion G is provided with a SiNx gate insulating film 4 as protection. On the gate insulating film 4, an a-Si semiconductor layer 5, a channel protective film layer 6, an n ⁺ -Si semiconductor layer 7, a cap layer 3, an electrode wiring circuit layer 2, and a cap layer 3 are sequentially deposited. A drain electrode portion D and a source electrode portion S are provided by appropriately forming a pattern. On the drain electrode portion D and the source electrode portion S, an element surface flattening resin or SiNx insulating film 4 ′ is coated. Further, on the source electrode portion S side, a contact hole CH is provided in the insulating layer 4 ′, and a transparent electrode layer 7 ′ of ITO or IZO is formed in that portion. In the case where an Al alloy wiring material is used for such an electrode wiring circuit layer 2, the transparent electrode layer 7 ′ and the electrode wiring layer 2 between the n ⁺ -Si semiconductor layer 7 and the electrode wiring layer 2 and in the contact hole CH The cap layer 3 is interposed between the two.

  In the element structure shown in FIG. 1, since a cap layer of Mo or the like is formed, an increase in the cost of materials and manufacturing equipment is inevitable, and it has been pointed out that the manufacturing process is complicated.

Therefore, as a technique for omitting the cap layer as described above, a technique has been proposed in which a part of the wiring layer made of an Al-based alloy is nitrided and bonded to the semiconductor layer via the nitrided part (Patent Document). 1), and a technique for nitriding the entire wiring layer made of an Al-based alloy and bonding it to the semiconductor layer has also been proposed (see Patent Document 2).
JP 2003-273109 A JP 2005-123576 A

  However, in response to the above-mentioned Patent Document 1, since the resistance of the nitrided portion of the Al-based alloy is increased, the ohmic characteristics tend not to be satisfied when the semiconductor layer and the Al-based alloy layer are directly bonded. Further, as in Patent Document 2, if all of the Al-based alloy wiring layer is nitrided, the resistance value of the wiring layer itself becomes too large to satisfy satisfactory element characteristics.

The present invention has been made in the background as described above, and in the case of directly joining a semiconductor layer such as n ⁺ -Si and an Al-based alloy layer, mutual diffusion of Al and Si can be prevented, and ohmic It is possible to provide a device junction structure that can maintain the characteristics and can secure the low resistance characteristics of the Al-based alloy layer itself. More specifically, even when a thermal history of 250 ° C. or higher is applied, the interfacial reaction at the interface between the semiconductor layer and the Al-based alloy layer is suppressed, the ohmic characteristics are maintained, and the resistance of the Al-based alloy layer is maintained. An object of the present invention is to provide a bonding technique for elements that can have a value of 10 μΩ · cm or less.

  In order to solve the above problems, the present inventors have studied Si for forming a semiconductor layer in order to realize direct bonding between the semiconductor layer and the Al-based alloy layer. As a result, Si contains nitrogen. In this case, it was found that good direct bonding can be realized.

  The present invention relates to a device junction structure comprising a semiconductor layer and an Al-based alloy layer bonded directly to the semiconductor layer, wherein the semiconductor layer directly bonded to the Al-based alloy layer is made of Si containing nitrogen. It was supposed to be.

The nitrogen content of Si forming the semiconductor layer in the present invention is preferably 1 × 10 ¹⁸ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ³ , and preferably 1 × 10 ¹⁸ atoms / cm ³ to 1 ×. More preferably, it is 10 ²⁰ atoms / cm ³ .

  The semiconductor layer in the bonding structure of the element according to the present invention can be made of Si containing nitrogen with a depth of 100 mm or more from the surface side directly bonded to the Al-based alloy layer.

Moreover, it is preferable that the semiconductor layer in this invention consists of amorphous n ^<+>- Si or p ^<+>- Si. In this case, “n” is a semiconductor layer in which electrons are dominant as carriers, “p” is a semiconductor layer in which holes are dominant as carriers, and “ ⁺ ” is Si to This means that the additive element is highly doped. The semiconductor layer in the present invention preferably contains 5 × 10 ¹⁷ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ^{3 of} a dopant selected from phosphorus, boron, and antimony.

Furthermore, the Al-based alloy in the present invention preferably contains 0.5 at% to 10.0 at% of Ni. In addition, it is more preferable to contain 0.1 at% to 0.8 at% of boron. Moreover, when forming the junction structure of the element which concerns on this invention, it is preferable to form Al type alloy layer by sputtering method, and the sputtering target in that case is Al containing 0.5at%-10.0at% of Ni What consists of a system alloy is preferable.
And it is preferable to use the Al type alloy sputtering target which contains boron at 0.1 to 0.8 at% in addition to Ni.

  The present invention relates to a thin film transistor formed from an element having the above-described element junction structure.

In the element structure according to the present invention described above, a gas containing at least one of N ₂ , NH ₃ , and NO _X is introduced into a film formation atmosphere when forming Si as a semiconductor layer by chemical vapor deposition. To form a film.

In addition, in the element structure according to the present invention, when a gas containing N ₂ is introduced to form Si as a semiconductor layer, the film formation is started with a nitrogen partial pressure ratio of 0.001% to 20%, or The film can be formed by adjusting the nitrogen partial pressure ratio to 0.001% to 20% during the film formation.

  The element structure according to the present invention can also be formed by performing heat treatment at 200 ° C. to 500 ° C. in a nitrogen atmosphere after depositing Si as a semiconductor layer.

TFT schematic sectional drawing. The ohmic characteristic evaluation sample schematic. Photomicrograph of Si diffusion heat resistance evaluation. Photomicrograph of Si diffusion heat resistance evaluation. The conceptual graph which shows the nitrogen analysis result in the semiconductor layer by a secondary ion mass spectrometer. The plane conceptual diagram which shows the wiring structure of a TFT element.

  Hereinafter, although the best embodiment in the present invention is described, the present invention is not limited to the following embodiment.

The element according to the present invention includes a semiconductor layer and an Al-based alloy layer directly bonded to the semiconductor layer, and the semiconductor layer directly bonded to the Al-based alloy layer is Si containing nitrogen. . The nitrogen content is preferably 1 × 10 ¹⁸ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ³ , and preferably 1 × 10 ¹⁸ atoms / cm ³ to 1 × 10 ²⁰ atoms / cm ^3. More preferred.

When the nitrogen content of Si is less than 1 × 10 ¹⁸ atoms / cm ³ , interdiffusion between Al and Si tends to occur, and the interface reaction tends not to be sufficiently suppressed. Specifically, when a thermal history of 250 ° C. or higher is applied, an interface reaction tends to occur, and direct bonding tends to be difficult. On the other hand, if it exceeds 5 × 10 ²¹ atoms / cm ³ , the on current in the transistor characteristics when the element is formed tends to decrease, and the on / off ratio tends to decrease. When the nitrogen content of Si is 1 × 10 ¹⁸ atoms / cm ³ to 1 × 10 ²⁰ atoms / cm ³ , the silicon has a heat resistance of 280 ° C. or more, and an on / off ratio which is a switching characteristic of the element is 5 You will be able to remove more than digits.

  In the device junction structure according to the present invention, the entire semiconductor layer is preferably made of Si having the nitrogen content described above, but a part of the semiconductor layer may be made of Si having the nitrogen content. . For example, the depth of 100 mm or more from the surface of the semiconductor layer directly bonded to the Al-based alloy layer is made of Si containing nitrogen. In short, if the semiconductor layer in the portion directly bonded to the Al-based alloy layer has Si with the above nitrogen content, mutual diffusion between Al and Si can be prevented and ohmic characteristics can be maintained.

As a method of adding nitrogen to Si forming the semiconductor layer, SiH ₄ , PH _3, etc. diluted with argon are used when the semiconductor layer is formed by chemical vapor deposition, so-called CVD (Chemical Vapor Deposition). In addition to gas, a method of adding an appropriate amount of N ₂ gas, NH ₃ gas, or NO _X gas alone or in combination can be employed. In addition, as a method of incorporating nitrogen into a part of the semiconductor layer, when forming a film by CVD, the timing of adding N ₂ and NH ₃ gas in addition to the introduced gas such as hydrogen diluted SiH ₄ and PH ₃ is set. There is a method of performing heat treatment in a nitrogen atmosphere after controlling or forming a semiconductor layer. For example, when nitrogen is contained in a semiconductor layer in a TFT manufacturing process of a liquid crystal display, either the entire semiconductor layer or a part of the surface of the semiconductor layer may be used, but the increase or decrease in the number of steps in the manufacturing process or the difficulty in adjusting the nitrogen content In consideration of the above, it is preferable to adopt a method that can easily cope with the current manufacturing process.

More specifically, when N ₂ gas is added to a film forming atmosphere for forming Si as a semiconductor layer by chemical vapor deposition (CVD), the film is formed with a nitrogen partial pressure ratio of 0.001% to 20%. Or by adjusting the nitrogen partial pressure ratio to 0.001% to 20% in the middle of the film formation, Si that becomes the semiconductor layer can contain nitrogen. This nitrogen partial pressure ratio is a partial pressure ratio when nitrogen gas is introduced into the atmosphere in which Si is formed, and if it is less than 0.001%, it is heat resistant even if other film formation conditions in CVD are changed. This is because it becomes impossible to achieve a nitrogen content (1 × 10 ¹⁸ atoms / cm ³ ) that can secure the above. On the other hand, if it exceeds 20%, the resistance of the semiconductor layer increases and the transistor characteristics tend to deteriorate. The nitrogen partial pressure ratio is obtained from the actual flow rate based on the conversion factor. When nitrogen is contained in this CVD film formation, nitrogen can be contained in the entire semiconductor layer, or nitrogen can be contained in a part of the semiconductor layer. When ammonia (NH ₃ ) gas is used instead of this nitrogen gas, the partial pressure ratio is preferably 0.001 to 2%.

As another method, after forming Si to be a semiconductor layer, nitrogen may be contained in Si of the semiconductor layer by performing a heat treatment at 200 ° C. to 500 ° C. in a nitrogen atmosphere. When nitrogen is contained in Si of the semiconductor layer by heat treatment in this nitrogen atmosphere, the semiconductor layer has a nitrogen content that continuously decreases from the surface of the semiconductor layer in the depth direction. The nitrogen atmosphere in the present invention refers to a deliberately controlled environment using a gas containing nitrogen as a main component, for example, a gas species such as N ₂ gas, NH ₃ gas, or NO _X gas, preferably nitrogen. Is an environment having a partial pressure of 90% or more, more preferably 99% or more.

As described above, the nitrogen-containing Si is preferably a so-called dopant, that is, n ⁺ -Si or p ⁺ -Si, and has an amorphous crystal form. Such a semiconductor layer preferably contains 5 × 10 ¹⁷ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ^{3 of} a dopant selected from phosphorus, boron, and antimony. This is because when Si is highly doped with phosphorus, boron, and antimony, ohmic characteristics can be secured in direct bonding with the Al-based alloy layer. When the doping amount is 5 × 10 ¹⁷ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ³ , although depending on the dopant species and the activation heat treatment conditions, the transistor characteristics of the device can be sufficiently secured. Depending on the type of dopant, even higher doping exceeding 5 × 10 ²¹ atoms / cm ³ is possible. However, in the case of an amorphous Si semiconductor element, the activation rate of the dopant does not increase, so it is not practical.

  In addition, introduction | transduction of each dopant seed | species to Si can be performed by well-known methods, such as what is called a thermal diffusion method and an ion implantation method. And about the dopant seed | species in Si, and its content, it can measure with a secondary ion mass spectrometer (Dynamic SIMS).

  When forming the element of the present invention, the Al-based alloy layer is preferably an Al-based alloy containing Ni (nickel). The present invention is effective even if the Al-based alloy layer is pure Al. However, if the Al-based alloy contains Ni, it is easy to reduce the resistance of the Al-based alloy layer itself to 10 μΩ · cm or less. This is because it is easy to realize direct bonding with good element characteristics. Specific examples of the Al-based alloy containing Ni include an Al-Ni alloy, an Al-Ni-B (boron) alloy, an Al-Ni-C (carbon) alloy, an Al-Ni-Nd (neodymium) alloy, Al-Ni-La (lanthanum) alloy etc. are mentioned. And it is preferable that this Ni content is 0.5 at%-10.0 at%. When Nd and La are used, the Ni content is preferably 0.5 at% to 2.0 at%. The content of B, C, Nd, and La is preferably 0.1 at% to 1.0 at%.

Furthermore, the Al-based alloy is more preferably an Al—Ni—B alloy containing 0.1 at% to 0.8 at% of B (boron). The Al—Ni—B alloy having such a composition enables direct bonding with a transparent electrode layer such as ITO or IZO, and also allows direct bonding with a semiconductor layer such as n ⁺ -Si. It is possible to form an element having a low junction resistance when directly bonded to a layer or a semiconductor layer and having excellent heat resistance. When this Al—Ni—B alloy is employed, the Ni content is preferably 4.0 at% or more and the B content is preferably 0.80 at% or less. More preferably, the Ni content is 3.0 at% to 6.0 at%, and the B content is 0.20 at% to 0.80 at%. This is because the Al—Ni—B alloy having such a composition is provided with excellent heat resistance characteristics against each thermal history in the manufacturing process of the element. The Al-based alloy of the present invention desirably contains Al at least 75 at% from the viewpoint of low resistance characteristics. The Al-based alloy layer has no particular problem even if it is subjected to nitriding treatment or oxidation treatment.

  If the junction structure of the element according to the present invention described above is used, the interface reaction of the interface between the semiconductor layer and the Al-based alloy layer is suppressed, the ohmic characteristics are maintained, and the resistance value of the Al-based alloy layer is 10 μΩ. -Since it becomes an element which can be made into cm or less, it can be said that it is suitable for forming a thin film transistor (TFT). In addition, the junction structure of the element according to the present invention is a very suitable element structure when forming a so-called bottom gate TFT in which the gate electrode is located on the substrate side.

Next, examples of the present invention will be described. In Example 1, as the Al-based alloy layer, a pure Al film (specific resistance value 2.8 μΩ · cm), an Al-5.0 at% Ni alloy film (specific resistance value 4.0 μΩ · cm), Al-5. Using three types of 0 at% Ni-0.4 at% B film (specific resistance value 4.2 μΩ · cm), a semiconductor layer made of Si was directly bonded, and the characteristics of the element were evaluated (Comparative Example) Is an Al-5.0 at% Ni-0.3 at% C film (with a specific resistance value of 4.8 μΩ · cm). As characteristic evaluation, the ohmic characteristics and Si diffusion heat resistance described below were investigated. The specific resistance value of each film is a single film (thickness of about 0.3 μm) formed on a glass substrate by sputtering (magnetron sputtering apparatus, input power 3.0 W / cm ² , argon gas flow rate 100 sccm, argon pressure 0.5 Pa). ), And after heat treatment at 300 ° C. for 30 minutes in a nitrogen gas atmosphere, measurement is performed using a four-terminal resistance measurement device.

Ohmic characteristics: The ohmic characteristics were evaluated by preparing the evaluation sample shown in FIG. 2 (FIG. 2A shows a sample cross-sectional view, and FIG. 2B shows a sample plan view). First, a 500-nm n ⁺ -Si semiconductor layer 2 was formed on a glass substrate 1 (Corning Corporation: # 1737) by CVD (manufactured by Samco Corporation: PD-2202L). The film formation conditions for the n ⁺ -Si semiconductor layer 2 are as follows: RF 100 W (0.31 W / cm ² ), SiH ₄ gas (hydrogen dilution) flow rate 300 ccm, phosphorus (P) component-containing gas (hydrogen dilution) flow rate 50 ccm, substrate temperature An n ⁺ -Si semiconductor layer 2 having a thickness of 300 mm was formed at 300 ° C. Then, an Al-based alloy layer 3 was formed to a thickness of 2000 mm by sputtering (magnetron sputtering apparatus, input power 3.0 W / cm ² , argon gas flow rate 100 sccm, argon pressure 0.5 Pa). Then, an evaluation sample in which the Al-based alloy layer 3 was formed by photolithography using a 1000 μm long × 300 μm wide electrode pad with a pad spacing of 50 μm was produced. And ohmic characteristic was evaluated by performing the current-voltage measurement in the range of + 5V--5V between both the electrode pads formed in this evaluation sample. The evaluation method of the ohmic characteristics is based on the measured current-voltage graph, where an evaluation sample in which the correlation between the current and the voltage is linear is evaluated as having an ohmic junction. Those having a non-correlated correlation were evaluated as x not having an ohmic junction.

Si diffusion heat resistance: As an evaluation sample of this characteristic, an n ⁺ -Si semiconductor layer (300 mm) was formed on a glass substrate by CVD (same conditions as in the above ohmic characteristics), and sputtering (magnetron) was performed on the semiconductor layer. A sputtering apparatus, an input power of 3.0 W / cm ² , an argon gas flow rate of 100 sccm, and an argon pressure of 0.5 Pa were used to form each Al alloy layer (2000 kg).

The nitrogen content in the n ⁺ -Si semiconductor layer is such that N ₂ gas is added at a partial pressure ratio of 0 in addition to SiH ₄ gas diluted with hydrogen and an introduction gas of phosphorus (P) component-containing gas at the time of film formation by CVD. It adjusted by adding so that it might become the range of 0.001 to 20%.

  And after setting heat processing temperature for every 10 degreeC in the temperature range of 200-380 degreeC for each evaluation sample and performing heat processing for 30 minutes in nitrogen gas atmosphere, phosphoric acid type Al etching liquid (Kanto Chemical Co., Ltd.) Made by immersing in an Al mixed acid etchant / composition (volume ratio) phosphoric acid: succinic acid: acetic acid: water = 16: 1: 2: 1) for 10 minutes. Dissolved to expose the semiconductor layer. The exposed surface of the semiconductor layer was observed with an optical microscope (200 times) to examine whether mutual diffusion between Si and Al occurred.

  3 and 4 show typical optical micrographs on the exposed semiconductor layer surface. FIG. 3 shows the surface of the semiconductor layer where no interdiffusion is observed (evaluation result: ◯), and FIG. 4 shows the trace of interdiffusion (black spots in the photograph) (evaluation result: x). 3 and 4 are images used as a reference when determining the presence or absence of mutual diffusion, and do not show the observation results of this example.

Tables 1 to 3 show the characteristics evaluation results. Sample No. 1-1 to 1-3 are cases where nitrogen is contained in the Si semiconductor layer. 1-4 to 1-7 are cases where the Si semiconductor layer does not contain nitrogen. Table 1 shows a case where the nitrogen content of the Si semiconductor layer is 4 × 10 ¹⁹ atoms / cm ³ , Table 2 shows a case where the nitrogen content is 1 × 10 ¹⁸ atoms / cm ³ , and Table 3 shows a case where 1 × 10 ²⁰ atoms / cm ³ is used. Shows the results of the case. The nitrogen content here is an average value.

Note that the nitrogen content of the Si semiconductor layer was measured by a secondary ion mass spectrometer (Dynamic SIMS) in the case of 4 × 10 ¹⁹ atoms / cm ³ or more. When nitrogen in the semiconductor layer is measured by a secondary ion mass spectrometer (Dynamic SIMS), an analysis result as shown in FIG. 5 is obtained. FIG. 5 shows an example of measurement results obtained by analyzing nitrogen in a depth direction by a secondary ion mass spectrometer using a semiconductor layer (source or drain) formed of n ⁺ -Si containing nitrogen. As shown in FIG. 5, when nitrogen is contained in a part of Si of the semiconductor layer, in the part of the Si semiconductor layer containing nitrogen, the nitrogen is in a part corresponding to the thickness of the part containing nitrogen. Detected. The nitrogen content (concentration) is specified by the average value of the measured values corresponding to the upper base portion of the trapezoidal peak as shown in FIG.

In addition, when the nitrogen content is 1 × 10 ¹⁸ atoms / cm ³ , it is below the detection limit of the secondary ion mass spectrometer, and therefore, in the depth direction of the Si semiconductor layer by the X-ray photoelectron spectrometer (XPS). Sputtering is performed for about 50 to 100 mm, and then the sputtered part is measured with an X-ray photoelectron spectrometer (XPS) and compared with the integrated intensity of the nitrogen detection peak obtained from the result of measuring the sample with a known nitrogen content. The nitrogen content was calculated. This nitrogen content can be measured by either a secondary ion mass spectrometer or an X-ray photoelectron spectrometer, but if the content is near the detection limit of the secondary ion mass spectrometer, the measurement In some cases, measurement by an X-ray photoelectron spectrometer is performed from the viewpoint of reliability of values.

From the results of Tables 1 to 3, it was found that when the n ⁺ -Si semiconductor layer contains nitrogen, the reaction at the bonding interface is suppressed even when a thermal history of 250 ° C. or higher is applied. Further, as shown in Table 2, when the nitrogen content was 1 × 10 ¹⁸ atoms / cm ³ , it was confirmed that the diffusion heat resistance tends to be lower by 10 to 20 ° C. than the results of Table 1. On the other hand, as shown in Table 3, when the nitrogen content was 1 × 10 ²⁰ atoms / cm ³ , it was confirmed that the diffusion heat resistance tends to be higher by 40 to 50 ° C. than the results of Table 2. Furthermore, when the nitrogen content exceeds 1 × 10 ²⁰ atoms / cm ³ , the on / off ratio, which is the switching characteristic of the element, tends not to be obtained by 6 digits. For example, the on / off ratio when the on current is 10 ⁻⁴ A and the off current is 10 ⁻¹⁰ A is 6 digits. However, since such on / off ratio cannot be maintained, the nitrogen content is 1 × 10 ^20. It is considered practical to use atoms / cm ³ or less.

  Next, in Example 2, the results of a detailed investigation of the Si diffusion heat resistance and the switching characteristics (on / off ratio) of the elements with respect to the Al-based alloys of various compositions and the Si semiconductor layers with varying nitrogen contents. Will be explained.

  The Al-based alloys evaluated in Example 2 are sample Nos. Shown in Tables 4 and 5. 2-1 to Sample No. There are 9 types of 2-9.

And in this Example 2, it evaluated like the method demonstrated in the said Example 1 about six types samples from which the nitrogen content of a semiconductor layer differs. Further, the Si semiconductor layer, P (phosphorus) is contained about ^{2 × 10 18 ~5 × 10 18} atoms / cm 3, and a highly doped ⁿ + -Si.

Switching characteristics: The switching characteristics of the elements were measured by measuring the on / off ratio. The evaluation sample was produced according to the following procedure.

First, an Al-based alloy film having a thickness of 3000 mm was formed on a glass substrate (Corning Corporation: # 1737) using an Al-based alloy target having each composition. The sputtering conditions were as follows: substrate heating temperature 100 ° C., DCPower 1000 W (3.1 W / cm ² ), argon gas flow rate 100 sccm, and argon pressure 0.5 Pa. Subsequently, the Al-based alloy film was etched by photolithography to form a gate wiring width of 50 μm and a gate electrode width of 15 μm (see FIG. 6). Photolithographic conditions were such that the Al-based alloy film surface was coated with a resist (TFR-970: manufactured by Tokyo Ohka Kogyo Co., Ltd./application conditions: spin coater 3000 rpm, post-baking resist thickness 1 μm target) and pre-baked (110 ° C. 1.5 minutes), a predetermined pattern film was placed, and an exposure process (Mask Anyler MA-20: Mikasa Co., Ltd./exposure conditions 15 mJ / cm ² ) was performed. Subsequently, the film was developed with an alkali developer containing tetramethylammonium hydroxide having a concentration of 2.38% and a liquid temperature of 23 ° C. (hereinafter abbreviated as TMAH developer). 110 ° C., 3 minutes), and circuit formation is performed with a phosphoric acid mixed acid etching solution (manufactured by Kanto Chemical Co., Inc./composition phosphoric acid: nitric acid: acetic acid: water = 16: 1: 2: 1 (capacity ratio)) went. By forming the circuit under such conditions, the circuit was controlled to have a taper angle of 45 °.

After the etching treatment, the resist was removed with a stripping solution (ST106: manufactured by Tokyo Ohka Kogyo Co., Ltd.), and after forming the gate wiring circuit, a SiNx film having a thickness of 2200 mm was formed by RF sputtering. The film forming conditions were a substrate heating temperature of 350 ° C., RF Power 1000 W (3.1 W / cm ² ), an argon gas flow rate of 90 sccm, a nitrogen gas flow rate of 10 sccm, and a pressure of 0.5 Pa. Further, amorphous i-Si and phosphorus-doped n ⁺ -Si were formed on this insulating layer as needed by CVD. The film formation conditions for i-Si (non-doped Si film) were a substrate heating temperature of 300 ° C., RF Power 100 W (0.31 W / cm ² ), SiH ₄ flow rate (10% argon gas dilution) 300 sccm, and a thickness of 2000 mm. The film formation conditions of nitrogen-added n ⁺ -Si (P (phosphorus) doped film) were: substrate heating temperature 200 ° C., RF Power 100 W (0.31 W / cm ² ), SiH ₄ flow rate (8% argon gas dilution) 300 sccm, The nitrogen gas flow rate (0 sccm, 1 sccm, 10 sccm, 20 sccm, 20 sccm, 40 sccm, 100 sccm) is changed with respect to the phosphorus (P) component-containing gas flow rate (8% argon gas dilution) 50 sccm, and the nitrogen-containing n ⁺ having a thickness of 500 mm is changed. A -Si layer was formed. For the nitrogen content of the n ⁺ -Si layer formed at each nitrogen gas flow rate, the measurement method shown in Example 1 was analyzed.

Thereafter, an Al-based alloy film having the same composition as that first formed on the glass substrate was formed on the n ⁺ -Si layer with a thickness of 2000 mm. The film forming conditions were the same as those for the gate wiring.

Then, a source wiring, a drain wiring, and an electrode were formed by photolithography. The photolithography conditions are the same as those for the gate wiring. At this time, after etching the Al-based alloy film, dry etching of the n ⁺ -Si layer was performed. The dry etching conditions are RF
Power 50W, SF ₆ gas flow rate 30sccm, pressure 10Pa. Thereafter, the resist was removed with a stripping solution (ST106: manufactured by Tokyo Ohka Kogyo Co., Ltd.).

Next, a passivation SiNx insulating film having a thickness of 2500 mm was formed, and only the gate, source, and drain electrode portions were exposed by dry etching. Dry etching conditions were RF Power 100W, SF ₆ gas flow rate 30 sccm, O ₂ gas flow rate 5 sccm, and pressure 10 Pa. Under the above conditions, a transistor having a channel width of 25 μm and a channel length of 5 μm was formed (see FIG. 6).

  About the evaluation sample produced as mentioned above, the on / off ratio of the switching characteristic of an element was measured by the 3 terminal method. Vg-Id measurement was performed using a B1500A apparatus manufactured by Agilent Technologies. The on / off ratio was calculated from the Id values at Vg = −10V and + 20V.

  The Si diffusion heat resistance was the same as the method described in Example 1. Tables 4 and 5 show the results of the Si diffusion heat resistance evaluation (Table 4) and on / off ratio measurement (Table 5) in the Si-based semiconductor layers with different Al-based alloys and nitrogen contents. .

Table 4 and the results shown in Table 5, when the nitrogen content of the Si semiconductor layer is increased, there is a tendency that Si diffusion heat resistance is high, on / off ratio even 5 digits (on / off ratio of 10 ^five values A tendency to become) was observed. In particular, when the nitrogen content is from the order of 10 ¹⁸ atoms / cm ^{3 to the} order of 10 ²¹ atoms / cm ³ , the on / off ratio becomes 5 digits or more, and the Si diffusion heat resistance becomes 280 ° C. or more, excluding pure Al. It has been found. However, when the nitrogen content was on the order of 10 ²² atoms / cm ³ , the on / off ratio was 4 digits. From the results of Table 4 and Table 5, it is desirable that the nitrogen content of the Si semiconductor layer is on the order of 10 ¹⁸ atoms / cm ³ to 10 ²¹ atoms / cm ³ . Also, Al-5.0 at% Ni-0.4 at% B alloy (sample No. 2-3), Al-3.0 at% Ni-0.4 at% B alloy (sample No. 2-6), Al- From the results of 3.2 at% Ni-0.2 at% B alloy (Sample No. 2-7) and Al-2.0 at% Ni-0.4 at% B alloy (Sample No. 2-8), 10 ¹⁹ atoms. It was confirmed that a 6-digit on / off ratio can be realized in the / cm ³ order or 10 ²⁰ atoms / cm ³ order. Judging from the results shown in Tables 1 to 5, it is considered practically desirable that the nitrogen content of the Si semiconductor layer is in the order of 10 ¹⁸ atoms / cm ³ to 10 ²¹ atoms / cm ^3. It was.

According to the present invention, even if a cap layer is omitted and a semiconductor layer such as n ⁺ -Si and an Al-based alloy layer are directly bonded, mutual diffusion between Al and Si can be prevented and ohmic characteristics can be maintained. Therefore, an element having the low resistance characteristic of the Al-based alloy layer itself can be realized.

Claims (14)

In a junction structure of an element comprising a semiconductor layer and an Al-based alloy layer that is directly joined to the semiconductor layer,
A semiconductor junction structure directly bonded to an Al-based alloy layer is Si containing nitrogen, wherein the element has a junction structure. 2. The device junction structure according to claim 1, wherein the nitrogen content of Si is 1 × 10 ¹⁸ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ³ . The element junction structure according to claim 1, wherein the nitrogen content of Si is 1 × 10 ¹⁸ atoms / cm ³ to 1 × 10 ²⁰ atoms / cm ³ .   4. The device junction structure according to claim 1, wherein the semiconductor layer is made of Si containing nitrogen at a depth of 100 mm or more from the surface side directly joined to the Al-based alloy layer. 5. The element junction structure according to claim 1, wherein the semiconductor layer is made of amorphous n ⁺ -Si or p ⁺ -Si. 6. The device junction structure according to claim 5, wherein the semiconductor layer contains a dopant selected from phosphorus, boron, and antimony at 5 × 10 ¹⁷ atoms / cm ^{3 to} 5 × 10 ²¹ atoms / cm ³ .   The Al-based alloy contains 0.5 at% to 10.0 at% of Ni, according to any one of claims 1 to 6. The device according to claim 7, wherein the Al-based alloy contains 0.1 at% to 0.8 at% of boron.   A thin film transistor formed from an element comprising the element junction structure according to claim 1. In an element formation method for forming a junction structure of an element comprising a semiconductor layer and an Al-based alloy layer directly bonded to the semiconductor layer,
An element characterized in that a film containing at least one of N ₂ , NH ₃ , and NO _X is introduced into a film formation atmosphere when forming a Si layer as a semiconductor layer by chemical vapor deposition. Forming method. The element formation method according to claim 10, wherein the film formation is started at a nitrogen partial pressure ratio of 0.001% to 20% when Si film to be a semiconductor layer is formed by introducing a gas containing N ₂ . The element forming method according to claim 10, wherein the nitrogen partial pressure ratio is adjusted to 0.001% to 20% from the middle of the film formation when forming the Si layer as a semiconductor layer by introducing a gas containing N ₂ . In an element formation method for forming a junction structure of an element comprising a semiconductor layer and an Al-based alloy layer directly bonded to the semiconductor layer,
A method for forming an element, characterized by performing heat treatment at 200 ° C. to 500 ° C. in a nitrogen atmosphere after depositing Si to be a semiconductor layer. A sputtering target for forming a junction structure of an element according to claim 7,
An Al-based alloy sputtering target containing Ni at 0.5 at% to 10.0 at%.