JP5526072B2 - Sputtering target and Ti-Al-N film and electronic component manufacturing method using the same - Google Patents

Description

  The present invention relates to a sputtering target suitable for forming a diffusion prevention layer on a semiconductor substrate or the like, a Ti—Al—N film using the sputtering target, and an electronic component manufacturing method.

Recently, a ferroelectric memory (FeRAM) using a ferroelectric thin film as a storage medium has been actively developed, and is expected as an alternative memory for DRAM. In such FeRAM, lead zirconate titanate (solid solution of PbZrO ₃ and PbTiO ₃ (PZT)), barium titanate (BaTiO ₃ (BTO)), barium strontium titanate (Ba _a Sr _1-a TiO 2). ₃ (BSTO)) and the like are used.

In the memory device such as FeRAM using the above-described oxide-based dielectric thin film, a precious metal electrode such as Pt, Ir, Ru, IrO _x , PtO _x , RuO is used instead of the conventionally used polysilicon electrode. Oxide electrodes such as _x have been used, and a structure in which a dielectric thin film is sandwiched between these electrodes has been adopted. In such a device structure, the formation of an oxide-based dielectric thin film requires a temperature of 600 ° C. or higher, which is a particularly high-temperature process among semiconductor processes. Further, since an oxide-based dielectric thin film is formed, the thin film is often formed in an oxygen atmosphere.

  In putting a memory device using an oxide-based dielectric thin film into practical use, for example, it is necessary to combine a semiconductor substrate on which a switching transistor is formed and a memory cell (thin film capacitor) using the oxide-based dielectric thin film. . Specifically, a noble metal electrode, an oxide electrode, and an oxide-based dielectric thin film are sequentially formed on a W plug of a Si substrate on which a transistor is formed. Since the oxide-based dielectric thin film is formed in a high-temperature oxygen atmosphere or the like as described above, oxygen in the dielectric thin film or the electrode is likely to diffuse to the Si substrate side, causing problems such as oxidation of the W plug, for example. It is. Since oxidation of the W plug is accompanied by volume expansion, peeling at the interface occurs.

To prevent this problem, a diffusion prevention layer (barrier layer) is formed between the thin film capacitor using an oxide-based dielectric thin film and the semiconductor substrate to prevent mutual diffusion of these constituent elements (especially oxygen). It is effective to do. In a semiconductor device, a TiN film or a TaN film is generally used as a diffusion prevention layer. However, since these are inferior in oxidation resistance, as a diffusion prevention layer of a semiconductor device having an oxide-based dielectric thin film, a TiN film is used. Ti _1-x Al _x N (Ti—Al—N) film, which is a solid solution of AlN and AlN, is used. The Al composition of the Ti—Al—N film has been shifted to increase the heat resistance, and for example, an alloy composition containing Al in the range of 25 to 50 atomic% is applied. It is coming.

The Ti—Al—N film is thermally and chemically stable and has excellent oxidation resistance. Such a Ti—Al—N film as a diffusion preventing layer is formed by reactive sputtering in a mixed gas atmosphere of Ar and N ₂ using a Ti—Al alloy target. A Ti—Al alloy target used for forming a Ti—Al—N film is generally produced by applying a melting method or a sintering method.

  Since the above-described Ti-Al alloy target is required to reduce the amount of impurities that cause deterioration of element characteristics and generation of dust, a melting method in which a high-purity material is easily obtained is mainly used. Yes. When producing a Ti—Al alloy target by a melting method, first, a Ti material and an Al material are melted by applying a vacuum melting technique such as vacuum arc melting or electron beam (EB) melting, and have a predetermined composition ratio. A Ti—Al master alloy is prepared.

  Next, the Ti—Al mother alloy (ingot) is heated to 1000 ° C. or higher, subjected to hot working such as forging or rolling, and then heat-treated again at a temperature of 1000 ° C. or higher. Here, since the crystal grain size of the Ti-Al alloy constituting the target and its variation affect the generation of dust and the film thickness uniformity of the thin film, it is necessary to recrystallize the Ti-Al alloy after hot working. Heat treatment is required. The target material (Ti—Al alloy material) thus manufactured is machined into a predetermined target shape, and then joined to a backing plate to obtain a target target.

By the way, when a Ti—Al alloy target is produced by a melting method, cracks in the alloy material generated during hot working, particularly cracks and chips generated in the outer peripheral portion of the material are problematic. In the case of Ti alone or Al alone, cracking or chipping hardly occurs even when plastic working is performed. This is because there are few substances that obstruct ductility. In contrast, Ti—Al alloys form intermetallic compounds such as Ti ₃ Al and Al ₃ Ti, and these intermetallic compounds are generally brittle. There is a problem that it is likely to occur.

  For this reason, the Ti-Al alloy material is heated to as high a temperature as possible, and plastic processing is performed in a state in which the mobility of atoms is enhanced, but cracks are sufficiently suppressed even in such a high temperature state. It is not possible to reduce the production yield of the target. In particular, in a Ti—Al alloy containing a large amount of Al (for example, an Al content of 25 to 50 atomic%), since an intermetallic compound is easily formed, the occurrence of cracks during hot working is a problem.

  On the other hand, when a Ti—Al alloy target is produced by a sintering method, a predetermined target shape can be obtained without performing hot working or the like, and the crystal grain size can be reduced. The sintering method has no size dependency and is also effective for making the target composition uniform. However, from the viewpoint of impurities, there is a problem that it is easy to be contaminated with impurity elements during powder production and that the raw material has a large specific surface area, so that gas components are particularly easily adsorbed in large quantities. Gas components such as oxygen and nitrogen cause abnormal discharge during sputtering, which increases the amount of dust and the like. For this reason, it is required to reduce the amount of impurities, particularly the content of gas components such as oxygen and nitrogen, in the sintering target.

  JP-A-2000-273623 discloses a Ti-Al alloy target containing Al in the range of 5 to 65% by mass. Here, the content of alkali metals such as Na and K, Fe, It describes that the content of transition metals such as Ni and Co, and further the content of gas components such as oxygen, carbon, hydrogen and nitrogen are reduced. However, the above publication presupposes a Ti—Al alloy target to which a melting method is applied, and does not describe anything about the purification of the Ti—Al alloy target to which a sintering method is applied. Furthermore, there is no description about improvement of hot workability of the Ti—Al alloy target to which the melting method is applied.

  Furthermore, regarding the film formation process using the conventional Ti—Al alloy target, the instability of the plasma state during film formation is a problem. That is, when reactive sputtering is performed using a conventional Ti—Al alloy target, if the film is continuously formed for a long time, the plasma becomes unstable, resulting in a problem that the discharge is cut off. Further, when the plasma state becomes unstable, the number of occurrences of abnormal discharge increases. These cause a decrease in device yield. For this reason, in the sputtering process using a Ti—Al alloy target, there is a strong demand for stabilization of plasma and further reduction of abnormal discharge.

  The present invention has been made to cope with such a problem. In a Ti—Al alloy target used when forming a Ti—Al—N film or the like, the target is obtained after reducing the amount of impurities. An object of the present invention is to provide a sputtering target capable of increasing the production yield of the film and further improving the film quality. More specifically, an object of the present invention is to provide a sputtering target that can increase the production yield of a melting target that can be highly purified.

The sputtering target of the present invention is a sputtering target made of a melting material of a Ti—Al alloy containing Al in the range of 5 to 50 atomic%, and the Zr content and the Hf content of the target are each 100 ppb or less. And the variation of the Zr content and the Hf content of the target as a whole is 20% or less, respectively .

  Zr and Hf are the same 4A group elements as Ti and have an affinity for Ti, and therefore are easily present as impurities in the Ti material. When such Zr and Hf are present at a relatively high concentration in the Ti—Al alloy material, cracking and chipping are likely to occur during hot working. On the other hand, for example, by reducing the Zr content and Hf content in the Ti-Al alloy material subjected to hot working, as well as variations in these contents, cracks and cracks during hot working, etc. Occurrence can be suppressed. Therefore, according to the Ti—Al alloy target satisfying the above-described Zr content and Hf content, the production yield can be improved.

  According to the sputtering target of the present invention, for example, while reducing the amount of impurities in the Ti-Al alloy target used when forming a Ti-Al-N film or the like, the production yield of the target is increased, It is possible to improve the film quality.

It is principal part sectional drawing which shows one structural example of the electronic component (thin film capacitor) which has the Ti-Al-N film | membrane formed into a film using the sputtering target of this invention as a diffusion prevention layer.

Hereinafter, modes for carrying out the present invention will be described. The sputtering target of the present invention is made of a Ti—Al alloy containing Al in the range of 5 to 50 atomic%. For example, Ti—Al—N (Ti ₁ ) used as a diffusion prevention layer (barrier layer) having excellent oxidation resistance. _-x Al _x N (0.05 ≦ x ≦ 0.5)) The film is applied.

  When the Al composition in the sputtering target (Ti—Al alloy target) made of the Ti—Al alloy is less than 5 atomic%, the effect of improving the oxidation resistance cannot be sufficiently obtained. For example, a Ti—Al—N film formed using a Ti—Al alloy target having an Al composition of less than 5 atomic% is likely to oxidize and adheres to the film formed thereon, for example, the lower electrode of a thin film capacitor. Decreases and peeling easily occurs. As the Al composition increases, the oxidation resistance in the high temperature region improves, so the Al composition is preferably 25 atomic% or more.

  However, if the Al composition is set too high, the oxidation resistance deteriorates, and oxygen and other mobile ions can easily pass through the Ti—Al—N film as the diffusion preventing layer. -Al composition in Al alloy target shall be 50 atomic% or less. On the other hand, if the Al composition exceeds 50 atomic%, the resistivity of the Ti—Al—N film also increases, leading to degradation of device characteristics. Also from such a point, the Al composition is 50 atomic% or less.

Al in the Ti—Al—N film not only enhances its oxidation resistance, but also functions as an oxygen trap material. For example, when an electrode film made of a conductive oxide such as SrRuO ₃ (SRO) is formed on a Ti—Al—N film, oxygen in the conductive oxide diffuses into a film formation substrate such as a semiconductor substrate. This can be suppressed. The Al composition (Al content) in the Ti—Al alloy target is particularly preferably in the range of 25 to 50 atomic% in order to improve the oxidation resistance, heat resistance, barrier properties and the like of the diffusion prevention layer.

  The first sputtering target in the present invention is a Ti-Al alloy target having an Al composition as described above, wherein the oxygen content is 500 ppm or less, the nitrogen content is 50 ppm or less, and the carbon content is 100 ppm or less. Variations in the oxygen content, nitrogen content, and carbon content as a whole are each 20% or less. Such a 1st Ti-Al alloy target exhibits an effect especially with respect to the sintering target which comprises the sintered compact of Ti-Al alloy.

  That is, the sintered Ti—Al alloy target can easily obtain a target of a desired size and a desired shape without performing hot working like a melting target, and can achieve a finer crystal grain size. On the other hand, the conventional sintering target using Ti-Al alloy powder has a drawback that it is difficult to sufficiently reduce the amount of impurities, particularly gas components such as oxygen, nitrogen, and carbon. On the other hand, by applying the manufacturing method of the present invention described in detail later, it becomes possible to obtain a Ti-Al alloy target, particularly a sintered target, in which the contents of oxygen, nitrogen and carbon are sufficiently reduced. .

  Oxygen, nitrogen, and carbon present as impurities in the Ti—Al alloy target all cause abnormal discharge during sputtering, which increases the amount of dust and the like. For this reason, in the first Ti—Al alloy target, the oxygen content is 500 ppm or less, the nitrogen content is 50 ppm or less, and the carbon content is 100 ppm or less. When the content of oxygen, nitrogen and carbon exceeds the above range, the amount of dust generated is greatly increased.

  Oxygen present in the Ti—Al alloy target promotes the oxidation of the Ti—Al—N film obtained by sputtering the target, and the adhesion force of, for example, the lower electrode of the thin film capacitor formed thereon is increased. Reduce. In addition, the oxidation resistance of the Ti—Al—N film itself is reduced. Also from such a point, the oxygen content of the Ti—Al alloy target is set to 500 ppm or less. More preferably, the oxygen content of the target is 300 ppm or less. However, if oxygen is completely removed from the Ti—Al alloy target, the anti-diffusion performance of the resulting Ti—Al—N film may be lowered. Specifically, the oxygen content of the Ti—Al alloy target is preferably in the range of 10 to 500 ppm, more preferably in the range of 10 to 300 ppm.

  In addition, nitrogen present in the Ti—Al alloy target causes deterioration in characteristics of the obtained Ti—Al—N film or the like, and in particular, causes variations in specific resistance. Also from such a thing, the nitrogen content of a Ti-Al alloy target shall be 50 ppm or less. More preferably, the nitrogen content of the target is 30 ppm or less. Similarly, the carbon present in the Ti—Al alloy target causes a bad influence on the sinterability of the target, and therefore the carbon content of the target is set to 100 ppm or less. The carbon content is more preferably 60 ppm or less.

  Regarding the presence forms of oxygen, nitrogen, and carbon in the Ti—Al alloy target, if the oxygen content, nitrogen content, and carbon content of the target as a whole vary, the resulting thin film (Ti—Al—N The characteristics of the film etc.), for example, the in-plane uniformity of the resistivity decreases. In addition, the diffusion prevention performance of the Ti—Al—N film tends to vary. For this reason, the variation of the oxygen content, the nitrogen content, and the carbon content of the target as a whole is 20% or less. The variation in the content of these gas components is more preferably 10% or less.

  Further, the first Ti—Al alloy target has an Mg content of 50 ppm or less, an Mn content of 50 ppm or less, and an Si content of 100 ppm or less, and the Mg content, Mn content, and Si content as a whole target. It is preferable that the amount variation is 20% or less. Since each element of Mg, Mn and Si stably adsorbs gas components in the Ti-Al alloy target, that is, oxygen, nitrogen and carbon to prevent degassing, the content of each of these elements is within the above-mentioned range. It is preferable that The more preferable contents of each element of Mg, Mn and Si are 30 ppm or less for Mg, 30 ppm or less for Mn, and 50 ppm or less for Si, respectively.

  In addition, if the variation of each content of Mg, Mn and Si as a whole target is large, degassing is prevented and the uniformity of characteristics of the obtained thin film is deteriorated. Is preferably 20% or less. The variations in Mg content, Mn content, and Si content are more preferably 10% or less.

  Here, the oxygen content, the nitrogen content, the carbon content, the Mg content, the Mn content, the Si content, and the variation of the content of each of these elements in the Ti—Al alloy target are as follows. It refers to the calculated value. That is, for example, when the target is disk-shaped, each position at a distance of 50% from the central portion of the target and four straight central portions that divide the circumference evenly through the central portion (a total of eight locations), and Specimens were collected from a total of 17 locations at 90% distance from the center (total of 8 locations), and the content of each element in these 17 test samples was measured, and the average of these measured values. Values are the oxygen content, nitrogen content, carbon content, Mg content, Mn content, and Si content of the Ti-Al alloy target.

  Furthermore, the variation of each content of oxygen, nitrogen, and carbon, and the variation of each content of Mg, Mn, and Si, from the maximum value and the minimum value of the content (each measured value) of each element of each test piece, It is determined based on {(maximum value−minimum value) / (maximum value + minimum value)} × 100 (%). The oxygen and nitrogen contents are values measured by an inert gas-thermal conductivity method, and the carbon content is a value measured by a high-frequency combustion-infrared absorption method. The contents of Mg, Mn and Si are values measured by ICP-emission spectroscopic analysis.

  In the first Ti—Al alloy target described above, the average crystal grain size of the Ti—Al alloy is preferably 10 mm or less, more preferably 5 mm or less, and the variation of the average crystal grain size as a whole target is 20% or less. It is preferable that As described above, when the crystal grains of the Ti—Al alloy are relatively fine and the variation of the average crystal grain size of the target as a whole is small, the generation of dust during sputter deposition can be suppressed.

  When the Ti-Al alloy crystal grains become coarse, erosion is different due to the difference in the plane orientation, so that the crystal grains are uneven at the adjacent grain boundary part and concentrated on the convex part, resulting in reattachment of sputtered particles. . A large amount of dust is abruptly generated when the deposits deposited in this way peel off or cause abnormal discharge. When the average crystal grain size of the Ti—Al alloy exceeds 10 mm, the above-described height difference of the unevenness becomes very large, and a large number of dusts are likely to be generated, resulting in a decrease in device yield. In addition, when the crystal grain size of the target as a whole varies, unevenness is likely to occur in the grain boundary portion as well, increasing the amount of dust generated and increasing the in-plane thickness of the thin film obtained. Uniformity is reduced.

  For this reason, in the first Ti—Al alloy target, the average crystal grain size of the Ti—Al alloy is preferably 10 mm or less, and more preferably 5 mm or less which is effective for sudden dust suppression. It is desirable. The average crystal grain size variation of the entire target is preferably 20% or less, which can improve in-plane uniformity such as the film thickness of the thin film and is effective for reducing dust. The variation in average crystal grain size is more preferably 10% or less. By these, it becomes possible to improve the manufacturing yield of Ti—Al—N film and the like, and consequently the device yield using the Ti—Al—N film.

  In addition, about the average crystal grain diameter of the Ti-Al alloy target and its dispersion | distribution, it is preferable to satisfy the same value also in the 2nd and 3rd Ti-Al alloy target mentioned later.

Here, the average crystal grain size of the Ti—Al alloy is a value obtained as follows. First, similarly to the measurement of the impurity content, specimens are sampled from 17 positions of the target, and the surface of each specimen is etched with an etching solution of HF: HNO ₃ : H ₂ O = 1: 1: 1. Then, the structure is observed with an optical microscope. A circle having a known area is drawn on the optical micrograph, and the number of crystal grains completely included in the circle (number A) and the number of crystal grains cut by the circumference (number B) are counted. The measurement magnification is preferably set so that the number of crystal grains completely contained in the circle is 30 or more. The total number N of crystal grains in the circle is number A + number B / 2. From the total number N of crystal grains in the circle and the area A of the circle, the average area per crystal grain is obtained by A / N, and the diameter of this average area is defined as the average grain size.

  Thus, the average particle diameter of each test piece (total 17 pieces) is obtained, and the average value of these values is taken as the average crystal grain diameter of the sputtering target of the present invention. Further, regarding the variation of the average crystal grain size, {(maximum value−minimum value) / (maximum value + minimum value)} from the maximum value and the minimum value of the average grain size of each test piece (a total of 17 pieces). It is determined based on × 100 (%).

The above-described first Ti—Al alloy target can be obtained with good reproducibility by applying, for example, the manufacturing method shown below. First, a high-purity Ti material of 3N or higher and a high-purity Al material of 4N or higher are prepared, weighed so as to have a desired composition ratio, and then dissolved under a vacuum of, for example, 1 × 10 ⁻² Pa or lower. Then, a Ti—Al master alloy (Ti _1-x Al _x (x = 0.05 to 0.5)) having a desired composition is prepared. For melting the Ti raw material and the Al raw material, it is preferable to apply a vacuum arc melting method, an EB melting method, a cold exclusive melting method or the like. By setting the atmosphere during the vacuum melting to 1 × 10 ⁻² Pa or less. The amount of gas components such as oxygen, nitrogen, and carbon can be sufficiently reduced.

  Next, the Ti—Al mother alloy described above is pulverized by the rotating electrode method. In other words, a Ti—Al alloy powder having a desired composition is produced by applying the rotating electrode method. According to the rotating electrode method, a Ti—Al alloy powder having a desired particle size is obtained while maintaining the characteristics of a Ti—Al master alloy having a small amount of gas components (oxygen, nitrogen and carbon contents) obtained by vacuum melting. Can be obtained. The particle diameter of the Ti—Al alloy powder by the rotating electrode method is preferably 500 μm or less. When the particle diameter of the Ti—Al alloy powder exceeds 500 μm, there is a possibility that it cannot be sufficiently densified in the subsequent sintering step.

  Next, such a Ti—Al alloy powder is sintered by applying hot pressing, HIP, plasma discharge sintering, etc., and a sintered body of Ti—Al alloy as a target material is produced. The sintering of the Ti—Al alloy powder is preferably performed in a vacuum at a temperature of 1000 to 1500 ° C. for 3 hours or more. When the sintering temperature is less than 1000 ° C. or the sintering time is less than 3 hours, a sufficiently high density sintered body cannot be obtained, and the amount of gas components in the sintered body also increases. There is a fear. On the other hand, when the sintering temperature exceeds 1500 ° C., Ti—Al alloy crystals grow abnormally, the average crystal grain size of the sintered body becomes coarse, and the variation in average crystal grain size also increases. Furthermore, it adversely affects the variation in the content of gas components and Mg, Mn, Si and the like.

  Then, the target material (sintered material of Ti—Al alloy) as described above is machined into a desired target shape and joined to a backing plate made of Al, Cu, or an alloy thereof, etc. A sputtering target (Ti-Al alloy target) is obtained. That is, after using a target material made of a sintered body, the amount of each gas component of oxygen, nitrogen, and carbon is sufficiently reduced, and a Ti-Al alloy target that suppresses variation in the content thereof is highly reproducible. Can be obtained.

  Note that diffusion bonding, brazing bonding, or the like is employed for bonding the target and the backing plate. The brazing joining is preferably performed using a known In-based or Sn-based bonding material (brazing material). Further, when an Al-based backing plate is used, the brazing temperature is set to 600 ° C. or lower. This is because the melting point of Al is 660 ° C., and when it exceeds 600 ° C., plastic deformation tends to occur. Further, instead of using a separate backing plate, an integrated sputtering target in which the backing plate shape is formed simultaneously when the target is manufactured may be used.

  The second sputtering target in the present invention is a Ti-Al alloy target having the Al composition described above, wherein the Zr content and the Hf content are each 100 ppb or less. In such a second Ti—Al alloy target, it is preferable that variations in the Zr content and the Hf content of the target as a whole are 20% or less, respectively. The second Ti—Al alloy target is particularly effective for a melting target including a melting material of Ti—Al alloy.

  That is, when the cracking and chipping occurred when the conventional Ti-Al alloy melting ingot was hot-worked, it was compared with the normal part using various methods such as EPMA, SIMS, and GDMS. It has been found that the content of Zr and Hf is greatly different in the part where cracks and cracks are generated as compared with the normal part. Zr and Hf are the same 4A group elements as Ti and have an affinity for Ti, and thus are easily present as impurities in the Ti material. If such Zr and Hf are present in a relatively high concentration in the molten ingot of the Ti—Al alloy, they concentrate and precipitate at the grain boundary part, so cracks and cracks may occur during hot working. It tends to occur.

  Therefore, in the second Ti—Al alloy target, for example, the Zr content and the Hf content in the molten ingot of the Ti—Al alloy subjected to hot working, and thus the Zr content and the Hf content in the Ti—Al alloy target. Each amount is 100 ppb or less. By using a Ti—Al alloy material in which the contents of Zr and Hf are each 100 ppb or less, it is possible to suppress the occurrence of cracks and chips during hot working. In other words, if the content of Zr or Hf in the Ti—Al alloy material exceeds 100 ppb, a lot of cracks and chips are generated during hot working, and the production yield of the Ti—Al alloy target is greatly reduced. More preferably, the contents of Zr and Hf are 50 ppb or less, respectively.

  Also, even when the Zr and Hf contents in the Ti—Al alloy material vary, cracking and chipping are likely to occur during hot working, and in particular, locally on the outer periphery of the Ti—Al alloy material. Cracks are likely to occur. Such a phenomenon becomes prominent when the variation of the target as a whole exceeds 20%. Therefore, in the second Ti—Al alloy target, the variation of the Zr and Hf contents is preferably 20% or less. It is more preferable that the variation in the contents of Zr and Hf is 10% or less. Note that, in the second Ti—Al alloy target, the contents of Zr and Hf and variations thereof are determined in the same manner as the gas component amounts and variations in the first Ti—Al alloy target.

  Further, in the second Ti—Al alloy target, the gas component amount (oxygen, nitrogen, carbon) and its variation, and the average crystal grain size of the Ti—Al alloy and its variation are also expressed as the first Ti—Al alloy target. It is preferable to control similarly to. By these, generation | occurrence | production of dust can be suppressed and the in-plane uniformity of the characteristic of a thin film obtained, or a film thickness can be improved.

  The third sputtering target in the present invention is a Ti-Al alloy target having the Al composition described above, wherein the Cu content is 10 ppm or less and the Ag content is 1 ppm or less. In such a third Ti—Al alloy target, it is preferable that the variation of the Cu content and the Ag content as the whole target is 30% or less, respectively. The third Ti—Al alloy target is effective even for a target comprising either a melting material or a sintered material of a Ti—Al alloy.

  That is, Cu and Ag are elements showing the highest ionization rate in the periodic table. If such elements are present in a relatively high concentration in the Ti-Al alloy target, these elements (Cu and Ag) themselves ionize and return to the target during sputter deposition, causing self-sustained discharge. become. When such a self-sustaining discharge occurs, the plasma becomes unstable during film formation for a long time, or abnormal discharge is induced to increase the amount of dust generated.

  Therefore, in the third Ti—Al alloy target, the Cu content is set to 10 ppm or less and the Ag content is set to 1 ppm or less. By using such a Ti—Al alloy target, it is possible to stabilize the plasma state during continuous film formation for a long time and to suppress the generation of dust due to abnormal discharge. In other words, when the Cu content in the Ti—Al alloy target exceeds 10 ppm, the continuous discharge is adversely affected, abnormal discharge increases, and a lot of sudden dust is generated. The same is true when the Ag content exceeds 1 ppm. The Cu content in the Ti—Al alloy target is more preferably 5 ppm or less, and the Ag content is more preferably 500 ppb or less.

  In addition, when the content of Cu and Ag in the Ti-Al alloy target varies, the uniformity of characteristics such as the film thickness and specific resistance of the obtained thin film increases, In the Ti-Al alloy target No. 3, it is preferable that variation in Cu and Ag contents is 30% or less. The variation in the content of these elements is more preferably 15% or less. Note that, in the third Ti—Al alloy target, the contents of Cu and Ag and variations thereof are obtained in the same manner as the gas component amounts and variations in the first Ti—Al alloy target.

  Further, in the third Ti—Al alloy target, the gas component amount (oxygen, nitrogen, carbon) and its variation, and the average crystal grain size of the Ti—Al alloy and its variation are also expressed by the first Ti—Al alloy target. It is preferable to control similarly to. By these, it becomes possible to further enhance the dust suppressing effect and the uniformity of the thin film characteristics. In addition, when applying a melting material to the third Ti—Al alloy target, it is preferable to control the contents of Zr and Hf and their variations in the same manner as the second Ti—Al alloy target. As a result, the production yield of the target can be increased.

  The second and third Ti—Al alloy targets described above can be obtained with good reproducibility, for example, by applying the following manufacturing method. Here, the dissolution target will be mainly described.

First, a high purity Ti material (for example, acicular Ti) of 4N or more is prepared, and this is dissolved, for example, by EB. At this time, the inside of the vacuum chamber for EB melting is preferably a vacuum atmosphere of 1 × 10 ⁻⁵ Pa or less, and EB melting is preferably repeated three times or more. By performing EB dissolution under such conditions, the contents of Zr and Hf, and Cu and Ag in the Ti material can be reduced to a predetermined value or less. In particular, since Zr and Hf are difficult to separate from Ti, for example, the number of repetitions of EB dissolution is preferably 5 or more.

  On the other hand, as for the Al material, when reducing only the content of Zr or Hf, a commercially available Al material of 4N or higher may be used as it is, but when reducing the content of Cu or Ag, Al of 4N or higher may be used. The material is preferably treated three or more times, for example using a zone refining method. By applying such treatment, the content of Cu or Ag can be reduced to a predetermined value or less.

Next, the Ti material and the Al material that have been treated as described above are weighed so as to have a desired composition ratio, and then melted by applying, for example, a vacuum arc melting method, an EB melting method, a cold exclusive melting method, or the like. Then, an ingot of a Ti—Al master alloy (Ti _1-x Al _x (x = 0.05 to 0.5)) having a desired composition is produced. The size of the ingot is preferably in the range of 100 to 300 mm in diameter. Here, the main crucible used for vacuum melting is Cu. However, if the crucible is used, the molten ingot is solidified, and the Cu may be slightly diffused from the Cu crucible to the surface of the ingot. There is. In order to prevent such diffusion of Cu, it is preferable to use an Au crucible.

  When applying a sintered target to the third Ti—Al alloy target, the Ti—Al alloy ingot as described above is pulverized by the rotating electrode method, and this Ti—Al alloy powder is processed as described above. The third Ti—Al alloy target made of a sintered material can be obtained by sintering at step S2.

  Next, the obtained Ti—Al alloy ingot is subjected to plastic working such as hot forging or rolling. By using a Ti—Al alloy ingot with a reduced content of Zr or Hf, it is possible to suppress the occurrence of cracks and chips during hot working. Moreover, it is preferable to make the processing rate in this case into the range of 50 to 98%. Furthermore, the heat treatment temperature and the holding time at the time of hot working are important in controlling the variation in the content of Zr and Hf and the content of Cu and Ag. Specifically, the heat treatment temperature is preferably in the range of 1100 to 1500 ° C., and the holding time at such temperature is preferably 3 hours or more.

  That is, if the heat treatment temperature during hot working is less than 1100 ° C., cracking or chipping is likely to occur during plastic working. On the other hand, when the heat treatment temperature exceeds 1500 ° C., the crystal grain size of the Ti—Al alloy becomes coarse, and it becomes impossible to sufficiently control the average crystal grain size that is important as a characteristic required for the target. Furthermore, since Cu and Ag having a high diffusion coefficient appear positively on the surface portion of the material, the variation in their contents tends to increase.

  The Ti—Al alloy material (melting / working material) as the target material thus produced is subjected to a heat treatment for 2 hours or more at a temperature of 1000 to 1500 ° C. to recrystallize the Ti—Al alloy. The heat treatment temperature for recrystallization is preferably in the range of 1000 to 1500 ° C. in order to suppress coarsening of crystal grains. After the heat-treated Ti—Al alloy material is machined into a desired target shape, the target sputtering target (Ti—Al alloy) is formed by joining with a backing plate made of Al, Cu, or an alloy thereof. Target).

  In other words, the production yield of Ti-Al alloy target can be greatly increased because it is possible to suppress the occurrence of cracks and chips during hot working after using a target material made of melted and processed material. It becomes. Furthermore, it is possible to obtain a Ti—Al alloy target with sufficient reproducibility while sufficiently reducing the contents of Cu and Ag and suppressing variations in the contents. The method described above is applied to the joining with the backing plate.

  Note that impurity elements other than the above-described elements in the sputtering target (Ti—Al alloy target) of the present invention may be included to some extent at a level of a general high-purity metal material. As for the purity of the Ti—Al alloy target, the purity represented by [100− (total content of Fe, Ni, Cr, Na, K, U, Th)] × 100 (%) is 99.9% or more. It is preferable.

The sputtering target (Ti—Al alloy target) of the present invention is used for forming a Ti—Al—N film (Ti _1-x Al _x N film (0.05 ≦ x ≦ 0.5)), for example. is there. Such a Ti—Al—N film can be obtained, for example, by performing reactive sputtering in a mixed gas of Ar and N ₂ using the Ti—Al alloy target of the present invention. The obtained Ti—Al—N film has excellent properties as a diffusion preventing layer, and the number of dust contamination is greatly reduced. That is, by using the Ti—Al alloy target of the present invention, a diffusion prevention layer (Ti—Al—N film) having excellent characteristics and quality can be obtained with high yield.

  The Ti—Al—N film described above has excellent barrier properties against various elements including oxygen, particularly barrier properties at high temperatures, and has a low resistance of 200 μΩ · cm or less. Therefore, by using such a Ti—Al—N film as a diffusion prevention layer between the semiconductor substrate and various elements, for example, interdiffusion of oxygen and other elements due to high temperature annealing (for example, 600 ° C. or more) is prevented. Can do. Further, since the oxidation of the Ti—Al—N film itself can be prevented, it is possible to suppress a decrease in adhesion at the interface with the element constituent layer. That is, peeling of the element constituent layer can be suppressed.

  The Ti—Al—N film described above is suitable as a diffusion prevention layer for the semiconductor substrate. Specifically, it is particularly effective for semiconductor memories such as FeRAM and DRAM, which are a combination of a semiconductor substrate on which a switching transistor is formed and a thin film capacitor (memory cell) using a dielectric thin film made of a perovskite oxide. is there.

  FIG. 1 is a cross-sectional view showing a configuration example of an electronic component (a semiconductor memory such as FeRAM or DRAM) having a Ti—Al—N film formed using the Ti—Al alloy target of the present invention as a diffusion prevention layer. is there. In the figure, reference numeral 1 denotes a semiconductor substrate (Si substrate) on which a switching transistor (not shown) is formed, and has a W plug 2 electrically connected to a switching transistor (not shown). A Ti—Al—N film 3 formed using the above-described sputtering target of the present invention is formed on the semiconductor substrate 1 as a diffusion preventing layer, and a thin film capacitor 4 is further formed thereon.

The thin film capacitor 4 includes a lower electrode 5, a dielectric thin film 6, and an upper electrode 7 that are sequentially formed on the Ti—Al—N film 3. The lower electrode 5 includes noble metals such as Pt, Au, Pd, Ir, Rh, Re, Ru, and alloys thereof (Pt—Rh, Pt—Ru, etc.), SrRuO ₃ , CaRuO ₃ , BaRuO _3, and these Conductive perovskite oxides such as solid solution systems (for example, (Ba, Sr) RuO ₃ and (Sr, Ca) RuO ₃ ) are used. The constituent material of the upper electrode 7 is not particularly limited, but it is preferable to use a noble metal (including an alloy), a conductive perovskite oxide, or the like, similarly to the lower electrode 5.

As the dielectric thin film 6, a dielectric material having a perovskite crystal structure is suitable. Examples of such a dielectric material include a perovskite oxide represented by ABO ₃ . In particular, barium titanate (BaTiO ₃ (BTO)), a part of the A site element (Ba) of the BTO is replaced with an element such as Sr or Ca, and a part of the B site element (Ti) is replaced with Zr. A perovskite oxide (such as BSTO) substituted with an element such as Hf, Sn or the like is preferably used.

The dielectric thin film 6 includes a perovskite oxide other than BTO or BSTO, for example, a simple perovskite oxide such as SrTiO ₃ , CaTiO ₃ , BaSnO ₃ , BaZrO ₃ , Ba (Mg _1/3 Nb _2/3 ). It is also possible to apply composite perovskite oxides such as O ₃ and Ba (Mg _1/3 Ta _2/3 ) O ₃ , and their solid solution systems. It goes without saying that a slight deviation from the stoichiometric ratio is allowed for the composition of the perovskite oxide.

  In such a semiconductor memory, the thin film capacitor 4 is satisfactorily formed on the semiconductor substrate 1 without deteriorating its characteristics by the diffusion preventing layer made of the Ti—Al—N film 3 having excellent barrier characteristics and oxidation resistance. be able to. In particular, peeling between the lower electrode 5 of the thin film capacitor 4 and the Ti—Al—N film 3, peeling between the Ti—Al—N film 3 and the W plug 2, etc. can be satisfactorily suppressed. The thickness of the Ti—Al—N film 3 is preferably as thin as possible within the range in which the diffusion preventing effect can be obtained. Specifically, the thickness is preferably in the range of 10 to 50 nm.

  Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1
First, 4N5 Ti material and 4N Al material were prepared, and these were weighed so as to have a composition of Ti-30 atomic% Al. Next, these were melted in a vacuum of 1 × 10 ⁻² Pa or less by a vacuum arc melting method to produce a Ti—Al alloy ingot having a diameter of 80 mm. After processing this Ti—Al alloy ingot into an electrode material having a diameter of 70 mm and a length of 100 mm, Ti—Al alloy powder having an average particle diameter of 300 μm is obtained by a rotating electrode method (rotation speed: 8000 rpm or more) using this electrode material. Was made.

  Next, the above-described Ti—Al alloy powder was filled into a carbon mold having an inner diameter of 130 mm and sintered using a hot press apparatus. Hot press sintering was performed in a vacuum at 1200 ° C. for 5 hours, at a heating rate of 10 ° C./min, and at a pressure of 25 MPa. After the Ti-Al alloy sintered body thus obtained is machined, it is brazed to an Al backing plate and further machined to obtain a Ti-Al alloy target having a diameter of 127 mm and a thickness of 5 mm. Got.

  Each content of oxygen, nitrogen, and carbon and variations thereof, and each content of Mg, Mn, and Si and variations thereof of the Ti—Al alloy target thus obtained were measured. The measuring method is as described above. As the measuring apparatus, TC-436 manufactured by LECO was used for oxygen and nitrogen, CS444 manufactured by LECO was used for carbon, and SPS-1200A manufactured by Seiko Denshi Kogyo was used for Mg, Mn and Si. Furthermore, the average crystal grain size and the variation of the Ti—Al alloy target were measured and evaluated. The measuring method is as described above. These results are shown in Tables 1 and 2. And this Ti-Al alloy target was used for the characteristic evaluation mentioned later.

Example 2
First, a 3N5 Ti material and a 4N Al material were prepared and weighed so as to have a composition of Ti-45 atomic% Al. Subsequently, these were melt | dissolved by the cold exclusive method in the vacuum of 1 * 10 ^<-2 > Pa or less, and the Ti-Al alloy ingot with a diameter of 80 mm was produced. After processing this Ti-Al alloy ingot into an electrode material having a diameter of 70 mm and a length of 100 mm, a Ti-Al alloy powder having an average particle diameter of 150 μm is obtained using this electrode material by a rotating electrode method (rotation speed: 10000 rpm or more). Was made.

  Next, the above-described Ti—Al alloy powder was filled into a carbon mold having an inner diameter of 130 mm and sintered using a hot press apparatus. Hot press sintering was performed in vacuum under the conditions of 1400 ° C. × 5 hours, a heating rate of 10 ° C./min, and a pressure of 30 MPa. After the Ti-Al alloy sintered body thus obtained is machined, it is brazed to an Al backing plate and further machined to obtain a Ti-Al alloy target having a diameter of 127 mm and a thickness of 5 mm. Got.

  Each content of oxygen, nitrogen, and carbon and variations thereof, and each content of Mg, Mn, and Si and variations thereof of the Ti—Al alloy target thus obtained were measured. The measuring method is as described above. Furthermore, the average crystal grain size and the variation of the Ti—Al alloy target were measured and evaluated. The measuring method is as described above. These results are shown in Tables 1 and 2. And this Ti-Al alloy target was used for the characteristic evaluation mentioned later.

Example 3
First, a 2N5 Ti material and a 3N Al material were prepared and weighed so as to have a composition of Ti-35 atomic% Al composition. Next, these were melted in a vacuum of 1 × 10 ⁻² Pa or less by a vacuum arc melting method to produce a Ti—Al alloy ingot having a diameter of 80 mm. After processing this Ti-Al alloy ingot into an electrode material having a diameter of 70 mm and a length of 100 mm, a Ti-Al alloy powder having an average particle diameter of 450 μm is obtained by a rotating electrode method (rotation speed: 5000 rpm or more) using this electrode material. Was made.

  Next, the above-described Ti—Al alloy powder was filled into a carbon mold having an inner diameter of 130 mm and sintered using a hot press apparatus. Hot press sintering was performed in vacuum under the conditions of 1700 ° C. × 5 hours, a heating rate of 10 ° C./min, and a pressure of 25 MPa. After the Ti-Al alloy sintered body thus obtained is machined, it is brazed to an Al backing plate and further machined to obtain a Ti-Al alloy target having a diameter of 127 mm and a thickness of 5 mm. Got.

  Each content of oxygen, nitrogen, and carbon and variations thereof, and each content of Mg, Mn, and Si and variations thereof of the Ti—Al alloy target thus obtained were measured. The measuring method is as described above. Furthermore, the average crystal grain size and the variation of the Ti—Al alloy target were measured and evaluated. The measuring method is as described above. These results are shown in Tables 1 and 2. And this Ti-Al alloy target was used for the characteristic evaluation mentioned later.

Comparative Example 1
First, a Ti—Al alloy material having a Ti-30 atomic% Al composition was produced by powder metallurgy. After this Ti—Al alloy material was machined, it was brazed to an Al backing plate and further machined to obtain a Ti—Al alloy target having a diameter of 127 mm × thickness of 5 mm.

  Each content of oxygen, nitrogen, and carbon and variations thereof, and each content of Mg, Mn, and Si and variations thereof of the Ti—Al alloy target thus obtained were measured. The measuring method is as described above. Furthermore, the average crystal grain size and the variation of the Ti—Al alloy target were measured and evaluated. The measuring method is as described above. These results are shown in Tables 1 and 2. And this Ti-Al alloy target was used for the characteristic evaluation mentioned later.

Using each Ti—Al alloy target according to Examples 1 to 3 and Comparative Example 1 described above, a Ti—Al—N film having a thickness of 100 nm was formed on a 4-inch Si substrate by reactive sputtering. As the sputtering gas, a mixed gas of Ar ₁₀ sccm and N ₂ 20 sccm was used, and the sputtering conditions were a substrate-target distance: 150 mm, back pressure: 1 × 10 ⁻⁵ Pa, DC output: 2 kW, and sputtering time: 10 min. The number of arc generations during sputter deposition under such conditions, and the film thickness uniformity and the number of dusts of each Ti—Al—N film obtained were measured and evaluated.

  The number of arc occurrences was measured using a micro arc counter. The number of dusts was measured using a dust measuring device WM3. Further, regarding the film thickness uniformity of the Ti—Al—N film, the film thickness was measured at a 5 mm interval from the end with respect to the substrate diameter using a coating step meter, and from the maximum value and the minimum value of these values. , [(Maximum film thickness−minimum film thickness) / (maximum film thickness + minimum film thickness) × 100 (%)] was obtained. These results are shown in Table 3. In addition, each measured value is an average value at the time of carrying out sputtering film-forming on three Si substrates.

  As is clear from Table 3, it can be seen that the Ti—Al alloy targets according to Examples 1 to 3 all have a smaller number of arcs and the number of dusts is significantly reduced as compared with Comparative Example 1. . Moreover, it turns out that the Ti-Al-N film | membrane formed into a film using the Ti-Al alloy target by Examples 1-3 is excellent in the in-plane uniformity of a film thickness.

Example 4 and Comparative Example 2
First, seven types of Ti—Al alloy ingots (Ti-10 atomic% Al composition) in which the contents of Fe, Ni, Cr, Cu and Ag were changed were prepared. These Ti—Al alloy ingots are adjusted by changing the number of times of Ti material EB dissolution, the number of times of Al material zone refining, and the like.

  Next, these Ti—Al alloy ingots were subjected to heat treatment at 1100 ° C. × 3 hr, followed by continuous hot forging. Thereafter, heat treatment was performed under the conditions of 1100 ° C. × 2 hr for recrystallization, and Ti—Al alloy materials as target materials were respectively produced. Each of these target materials was machined, brazed to an Al backing plate, and further machined to obtain Ti-Al alloy targets each having a diameter of 300 mm and a thickness of 5 mm.

  Using each Ti—Al alloy target thus obtained, a Ti—Al—N film was formed by sputtering under the same conditions as in Example 1. Then, the number of arc occurrences during the sputtering film formation and the number of dusts of the obtained Ti—Al—N films were measured and evaluated in the same manner as in Example 1. These results are also shown in Table 4. In addition, each measured value is an average value at the time of carrying out sputtering film-forming on 10 Si substrates.

  As is clear from Table 4, the Ti-Al alloy targets (Samples 1 to 5), both of which have a low Cu content and a low Ag content, all have a small number of arcs generated, and the number of dust generated is also the Cu content and Ag content. It turns out that it is reduced significantly compared with Ti-Al alloy target (samples 6-7) with much content.

Example 5, Comparative Example 3
First, six types of Ti—Al alloy ingots (Ti-20 atomic% Al composition) having different Cu and Ag contents were prepared. These Ti—Al alloy ingots are adjusted by changing the number of times of EB melting of the Ti material, the number of times of zone refining of the Al material, and the material of the crucible. Moreover, Cu and Ag were added as needed, and content and dispersion | variation were adjusted.

  Next, these Ti—Al alloy ingots were subjected to heat treatment at 1100 ° C. × 3 hr, followed by continuous hot forging. Thereafter, heat treatment was performed under the conditions of 1100 ° C. × 2 hr for recrystallization, and Ti—Al alloy materials as target materials were respectively produced. Each of these target materials was machined, brazed to an Al backing plate, and further machined to obtain Ti-Al alloy targets each having a diameter of 300 mm and a thickness of 5 mm.

  Each content of Cu and Ag of each Ti—Al alloy target thus obtained and their variations were measured. The measuring method is as described above. Next, a Ti—Al—N film was formed by sputtering under the same conditions as in Example 1 using each Ti—Al alloy target. Then, in the same manner as in Example 1, the number of arc occurrences during sputtering film formation and the in-plane uniformity of the dust number and film thickness of each Ti—Al—N film obtained were measured and evaluated. These measurements and evaluation results are shown in Table 5. Each evaluation result is an average value when sputtering is performed on 10 Si substrates.

  As is clear from Table 5, according to the Ti-Al alloy target in which both the Cu content and the Ag content are small and their variation is small, it is possible to reduce the number of dust generation and the film thickness. It can be seen that a Ti—Al—N film having excellent in-plane uniformity can be obtained with good reproducibility.

Example 6 and Comparative Example 4
First, acicular Ti (3N material, 3N5 material, 4N material) and 4N Al material having different purity were prepared. For the Ti material, the number of EB dissolutions of the prepared needle-like Ti was changed to produce several types of Ti ingots. Such Ti material and Al material were weighed so as to have a composition of Ti-10 atomic% Al. Subsequently, these were melt | dissolved by the cold exclusive method in the vacuum of 1 * 10 ^<-2 > Pa or less, and the Ti-Al alloy ingot was produced.

  Next, these Ti—Al alloy ingots were subjected to heat treatment at 1100 ° C. × 3 hr, followed by continuous hot forging. After hot forging, the state of cracking and chipping of the alloy material was visually confirmed and evaluated. The evaluation results of cracks and cracks are shown in Table 6 with those having cracks and chips of 10 to 30 mm, △ with cracks and chips of 1 to 10 mm, and ◯ with cracks and chips of 1 mm or less. . Furthermore, the weight of the Ti—Al alloy material after hot forging was measured.

  The Ti-Al alloy material whose appearance was confirmed was subjected to heat treatment (recrystallization heat treatment) at 1100 ° C. × 2 hr, and then machined to obtain a Ti—Al alloy target having a diameter of 300 mm × thickness of 10 mm. Obtained. The weight of each Ti—Al alloy target thus obtained was measured. Then, the target yield (target weight / ingot weight × 100%) was determined from the target weight and the ingot weight. These results are shown in Table 6.

  As is apparent from Table 6, the Ti-Al alloy target having the Zr content and the Hf content within the scope of the present invention has little cracking and chipping during hot working, resulting in a target yield. I understand that it is expensive.

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... W plug, 3 ... Ti-Al-N film, 4 ... Thin film capacitor, 5 ... Lower electrode, 6 ... Dielectric thin film, 7 ... Upper electrode

Claims (6)

A sputtering target composed of a melting material of Ti-Al alloy containing Al in a range of 5 to 50 atomic%,
Sputtering target, wherein the Zr content and Hf content of the target Ri der less 100ppb respectively, and the variation of the Zr content and Hf content of the overall target is 20% or less, respectively. The sputtering target according to claim 1 , wherein
A sputtering target, wherein the target is bonded to a backing plate. A Ti—Al—N film manufacturing method, wherein a Ti—Al—N film is formed using the sputtering target according to claim 1 . A method for manufacturing an electronic component, comprising the step of forming a Ti—Al—N film using the sputtering target according to claim 1 . In the manufacturing method of the electronic component of Claim 4 ,
The method of manufacturing an electronic component, wherein the Ti—Al—N film is a diffusion prevention layer. In the manufacturing method of the electronic component of Claim 4 or Claim 5 ,
The method of manufacturing an electronic component, wherein the electronic component is a semiconductor memory.

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