JP4235114B2 - Sintered body and sputtering target comprising the same - Google Patents

Description

The present invention relates to a sputtering target comprising a sintered body, and now, more particularly, prevention of gas permeation transparent plastic as a protective film for optical, sintered used like the protective film of the Na elution preventing, or the lens surface of the glass and The present invention relates to a sputtering target.

Silicon oxide-based thin films such as SiO ₂ film or SiO _x (1 <X <2) film have excellent electrical insulation and high mechanical strength, so that they are used as barrier films for various optical components, Since it is transparent and excellent in gas barrier properties, it is also used as a protective film for preventing gas permeation of transparent plastic. When such a SiO ₂ film or SiO _x film is formed on a base material, a reactive sputtering method is performed using silicon (Si), silicon monoxide (SiO), and silicon dioxide (SiO ₂ ) as a sputtering target. .

As this reactive sputtering method, a bipolar DC reactive sputtering method and a high-frequency reactive sputtering method are used as typical methods. First, in order to form a thin film by the bipolar DC reactive sputtering method, N ₂ or O ₂ or the like is mixed and introduced into an inert gas such as Ar under reduced pressure conditions, and a DC high voltage is applied between the electrodes. Discharge (glow discharge).

  By such discharge, the inert gas is ionized, collides with the cathode side at high speed, and the substance (target) arranged on the cathode is ejected. The protruding material becomes nitrides or oxides and is deposited on the surface of the substrate to form a thin film.

  On the other hand, in the high frequency reactive sputtering method, a high frequency voltage of 50 kHz or more is applied instead of the direct current high voltage applied in the bipolar direct current reactive sputtering method to cause a high frequency glow discharge. This is a method of forming a thin film on the surface.

  The above-mentioned bipolar DC reactive sputtering method has the advantage that the apparatus and operation are simple and the film forming speed is fast. However, when a high resistance substance or insulator is used as a target, the target is charged by positive ions. Sputtering becomes impossible.

  On the other hand, since the above-described high-frequency reactive sputtering method uses high-frequency discharge, a glow discharge is maintained even when an insulator or the like is used as a target, so that a thin film can be formed. However, the high-frequency reactive sputtering method has a slower film formation rate than the bipolar DC reactive sputtering method, and the power supply configuration is complicated, so that the production cost of the apparatus becomes expensive, and the reliability of the power supply I am worried about maintainability. For this reason, this method has a problem that it is difficult to stably obtain a high-frequency current.

  In order to cope with such a problem, an attempt is made to form a film by a direct current reactive sputtering method on an insulating base material which has been conventionally formed by a high frequency reactive sputtering method. For example, a method is known in which direct reactive sputtering is performed by erasing a part (oxygen component) of a main material (PLZT / PZT system) to reduce resistance.

  Furthermore, in order to reduce the resistance of the sintered body, a method has been proposed in which a conductive material is mixed with an insulating material and sintered to obtain a highly conductive sintered body and subjected to direct current reactive sputtering. (JP 2000-264731 A, JP 2001-5871 A, etc.).

  However, among the above-described methods, the method of providing conductivity to the sintered body by oxygen deficiency limits the substances to which this method can be applied, and cannot be applied to the silicon oxide-based material targeted by the present invention. . Also, in the proposed method of obtaining a sintered body having a high conductivity by mixing and sintering an insulating substance and a conductive substance, a sintered body in which different materials are mixed is used. A film is formed, and the film characteristics change. Furthermore, since it is a mixed sintered body, the specific resistance of the sputtering target is not uniform, and problems such as unstable film formation also occur.

As described above, in order to form a silicon oxide-based thin film, a reactive sputtering method is performed using Si, SiO, and SiO ₂ as sputtering targets. However, Si can be easily reduced in resistance by doping boron (B), phosphorus (P), or antimony (Sb) at the stage of growing a single crystal.

For this reason, usually, a doped Si powder can be formed by a DC reactive sputtering method using a DC sputtering apparatus while introducing oxygen. On the other hand, when a sintered body of SiO or SiO ₂ is used as a sputtering target, the material is not conductive, and thus the film is formed by a high frequency reactive sputtering method.

  When a film is formed by direct-current reactive sputtering using doped Si, the film forming speed is increased, but the reactive sputtering conditions are easily changed, and as a result, the film characteristics of the formed silicon oxide are It will vary. Furthermore, there is a problem that doped Si is easily cracked when high output is applied.

On the other hand, in the case of forming a _{SiO X (1 <X <2} ) film or SiO ₂ film, SiO close to the film composition, the use of SiO ₂ as a target, since the amount of oxygen introduced into the atmosphere can be reduced, film properties Can be homogenized. As described above, since SiO and SiO ₂ are insulating materials with low conductivity, it is necessary to use a high-frequency reactive sputtering apparatus. For this reason, compared with direct current | flow reactive sputtering method, there exists a problem that the film-forming speed | rate is slow and it is difficult to enlarge the sintered compact.

The present invention has been made in view of the problems in forming a conventional silicon oxide thin film by a reactive sputtering method, and is applied to a DC reactive sputtering apparatus by reducing the resistivity of a sintered body. can make it in, along with ensuring the deposition rate, ensures stable film properties to be formed, not in the further use of dissimilar materials, it is possible to form a thin film having a single composition, baked An object is to provide a bonded body and a sputtering target comprising the same.

In order to solve the above-mentioned problems, the present inventors have made various studies on the method for forming a silicon oxide-based thin film. As a result, if a conductive sintered body can be produced, this can be used as a sputtering target. Thus, it was noted that a silicon oxide thin film can be formed by applying a sputtering apparatus using a DC power source.

  As a result, the stability of the film characteristics to be formed can be ensured, and at the same time, the film forming speed can be increased to improve the productivity and a good sputtering rate (film forming efficiency) can be obtained.

In the above examination, when the doped Si powder and the SiO powder or the mixed powder of SiO and SiO ₂ are mixed and sintered, a part of “SiO” is “Si + SiO ₂ ” inside or on the surface of the SiO powder. It was found that it decomposes thermally.

  That is, by mixing and sintering Si, which is heavily doped with SiO, which is an insulator, as a conductor, good conductivity can be obtained by the interaction of Si mixed with pyrolyzed Si.

Furthermore, even if these are mixed and sintered, a silicon oxide film having the same composition is formed by any of reactive sputtering, Si, SiO, and SiO ₂ powder. There is no effect. Thereby, it is possible to eliminate the change in film characteristics and the non-uniformity of the specific resistance of the sputtering target, which has been a problem in the conventional mixed sintering.

This invention is completed based on said knowledge, and makes the summary the sputtering target which consists of the sintered compact of following (1)-(4) and the sintered compact of (5).

(1) A sintered body obtained by molding a raw material powder in which silicon powder doped with boron, phosphorus or antimony and silicon monoxide powder are mixed in an amount of 20% or more by mass% .

(2) 20% to 80% by weight of silicon powder (Si) doped with boron (B), phosphorus (P) or antimony (Sb) is contained, and the balance is raw material powder made of silicon monoxide (SiO). It is a sintered body characterized by being molded.

(3) 20% to 80% of silicon powder (Si) doped with boron (B), phosphorus (P) or antimony (Sb) is contained by mass%, with the balance being silicon monoxide (SiO) or silicon monoxide A sintered body comprising a mixture of silicon dioxide (SiO and SiO ₂ ), and a raw material powder having a silicon monoxide (SiO) content of 20% or more in the mixture.

It is desirable that the sintered bodies (1) to (3) have a bulk density of 95% or higher after sintering.

The sintered bodies (1) to (3) preferably have a specific resistance of 8 Ω · cm to 4 × 10 ⁻³ Ω · cm .

(4) A sputtering target comprising the sintered body of (1) to (3 ) above.

The sintered body of the present invention is characterized in that silicon monoxide contains 20 to 80% of Si powder doped with B, P or Sb by mass%. More preferably, the content is 30 to 60%. By including the doped Si powder, this sintered body has conductivity, so that it can be used as a target for a sputtering apparatus of a DC power source.

  When reactive sputtering is used as a cathode (target) of a sputtering apparatus, variations in film characteristics are reduced, and a good sputtering rate can be obtained.

  By including the doped Si powder, there are portions where the Si powders are in contact with each other and show conductivity, but a part of SiO is thermally decomposed inside or on the surface of the SiO powder during mixed sintering.

  At this time, the electrical conductivity is further improved by thermally diffusing the dope element, B, P or Sb in the conductive Si powder into the thermally decomposed Si. This point can be confirmed by an experiment conducted by the inventors from an experimental result in which the specific resistance of the sintered body rapidly decreases as the sintering temperature is increased.

  In the sintered body of the present invention, when the content of the doped Si powder is less than 20%, the specific resistance of the sintered body is not sufficiently lowered even when sintered at a high temperature. This is because the particle distribution of the doped Si powder becomes too “rough”. For this reason, the lower limit of the content of the doped Si powder is 20%, preferably 30%.

  On the other hand, when the content of the doped Si powder exceeds 80%, the characteristics of SiO are lost, and the characteristics of the film formed are uneven and, like the Si target, defects such as being easily cracked when high power is input. . For this reason, the upper limit of the content of the doped Si powder is set to 80%, preferably 60%.

In the case of mixed sintering, even if the doped Si powder and SiO ₂ powder are mixed and sintered without mixing SiO, the bulk density of 95% required for the target cannot be achieved.

However, if SiO powder is present during hot pressing, a bulk density of 95% or more can be sufficiently achieved. Since the sublimation temperature of SiO is as low as about 1200 ° C., it becomes glassy with hot pressing. Therefore, when SiO is mixed in the raw material powder, the SiO penetrates into the gap between the Si powder and the SiO ₂ powder, This is presumably because a glassy sintered body is formed.

From the above, in the sintered body of the present invention, mixing of doped Si powder and SiO powder as a raw material powder is essential. However, in order to adjust the oxygen concentration of the target, it is also effective to mix SiO ₂ powder with a mixed raw material of doped Si powder and SiO powder. Even in this case, the content of the SiO powder needs to be 20% or more in order to make the film characteristics of the target uniform without losing the characteristics of SiO. Desirably, it is 30% or more.

In addition, in this sintered body , it is desirable to make the average particle diameter of the raw material powder finer from the viewpoints of improving the sinterability, homogenizing the conductive properties and homogenizing the film composition. On the other hand, if the raw material powder becomes too fine, a problem of poor mixing occurs. Therefore, the average particle size of the raw material powder is desirably in the range of 1 to 20 μm.

The specific resistance of the doped Si powder contained in the sintered body of the present invention is preferably set to 0.01 Ω · cm (high resistivity) to 0.0001 Ω · cm (low resistivity). . This is because if the resistance becomes too high, sufficient conductive properties cannot be secured, and if the resistance becomes too low, the material cost becomes too expensive.

  The doping method using B, P or Sb is not particularly limited as long as it is a method usually employed in the stage of growing a silicon single crystal. The doping amount of B, P or Sb is added so that the grown Si single crystal satisfies the above specific resistance.

The sintered body of the present invention contains 20 to 80% of Si powder doped with SiO powder, that is, SiO powder or mixed powder of SiO and SiO _2, and mixed well. While the obtained powder is pressed at a pressure of 100 kg / cm ² or more, it is preferably produced by pressure firing at a temperature of 1250 to 1400 ° C.

If the sintering temperature is too high, dissolution of the Si powder occurs and a good sintered body cannot be obtained. On the other hand, if the sintering temperature is too low, the sintering is insufficient, and the doping elements of B and P Thermal diffusion is not sufficiently performed. For this reason, in the production of the sintered body of the present invention, the sintering temperature is desirably 1250 to 1400 ° C, and more desirably 1300 to 1400 ° C.

The effect by using the sintered compact of this invention is demonstrated based on a specific Example.

In the examples, Si powder having a specific resistance adjusted to 0.0004 Ω · cm by doping with B was used. Both the Si powder and the SiO powder were finely pulverized until the average particle size became 10 μm or less. This Si powder was contained in the SiO powder in a range of 10 to 90%, and the obtained powder was subjected to pressure sintering at 1400 ° C. for 2 hours while applying a pressure of 9.8 MPa (100 kgf / cm ² ). Thereafter, it was machined to φ6 inch × t5 mm to obtain a sputtering target.

  The surface resistivity and density ratio of each sintered body obtained under the above conditions were measured, and further, using this sintered body as a target, reactive sputtering using a direct current power source was performed to form a silicon monoxide film ( SiO film) was formed, the sputtering rate of the film thickness per unit time was measured, and variations in film characteristics were observed.

  The surface resistivity is measured by a four-terminal method, and the density ratio is represented by (bulk density / theoretical density) × 100%. Variations in film characteristics are observed from measurement results such as transmittance and refractive index. The measurement results and observation results are shown in Table 1.

  From the results of Table 1, as specified in the present invention, by including the doped Si powder in the SiO powder in the range of 20 to 80%, it can be seen that the variation in film characteristics is also good along with the sputtering rate. I understand.

Further, as a reference test, a sintered body was manufactured using SiO ₂ powder under the same conditions as described above, and the obtained sintered body was machined to form a sputtering target to form a SiO ₂ thin film. At this time, the same measurements and observations were made, but the surface resistivity of the sintered body was 10 ⁷ Ω · cm or more and the sputter rate was poor. It is confirmed that it is the same as the case of 1.

As described above, according to the sintered body of the present invention, the resistivity of the sintered body can be lowered and applied to a DC reactive sputtering apparatus, and the film forming speed can be ensured and stable film characteristics can be ensured. .

If the sintered body of the present invention is used, the resistivity of the sintered body can be lowered and applied to a DC reactive sputtering apparatus, so that the film forming speed is ensured and the film characteristics to be formed are stabilized, Furthermore, a thin film having a single composition can be formed without using different materials. For this reason, if a sputtering target made of this sintered body is used, a sputtering reaction with a good variation in sputtering rate and film characteristics is guaranteed. Accordingly, the present invention can be widely applied as an optical protective film for preventing gas permeation of transparent plastic, for preventing Na elution of glass, or for forming a silicon oxide thin film used as a protective film for a lens surface.

Claims (10)

A sintered body characterized by molding a raw material powder in which silicon powder doped with boron, phosphorus or antimony and silicon monoxide powder are mixed in an amount of 20% or more by mass% . The sintered body according to claim 1, which has a bulk density of 95% or more after sintering . 2. The sintered body according to claim 1, wherein the raw material powder has an average particle diameter of 1 to 20 μm. A sintered body characterized by containing 20 to 80% of silicon powder doped with boron, phosphorus or antimony by mass%, with the remainder formed from raw material powder made of silicon monoxide. The sintered body according to claim 4, which has a bulk density of 95% or more after sintering . 20 to 80% of silicon powder doped with boron, phosphorus or antimony is contained by mass%, and the balance is made of silicon monoxide or a mixture of silicon monoxide and silicon dioxide, and the content of silicon monoxide in this mixture is A sintered body characterized by molding a raw material powder of 20% or more. The sintered body according to claim 6, wherein a bulk density after sintering is 95% or more. The specific resistance is 8 Ω · cm to 4 × 10 ⁻³ Ω · cm, The sintered body according to claim 1 . A sputtering target comprising the sintered body according to claim 1.   The sputtering target according to claim 9, wherein the sputtering target is used for reactive sputtering using a direct current power source.