JP2915177B2 - Method of manufacturing sputtering target and sputtering target manufactured by this method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high-density wiring board suitable for information processing equipment such as an electronic computer and an electronic exchange, by forming a high-resistivity thin film for forming a resistance element in a circuit by sputtering. The present invention relates to a sputtering target used for the above.

[0002]

2. Description of the Related Art Conventionally, a thin film composed of Cr, Si and O and having a large specific resistance has a small temperature coefficient of resistance, is thermally and chemically stable, and is a very useful thin film for forming a thin film resistance element. Are known. As a means for forming the thin film, Journal of Vacuum Science and Technology Vol. 4 No. 4 (1967), pp. 163 to 170 (J. Vac. Sci. Techno)
l. , 4 (1967) pp163-170), a method of heating and depositing a mixture of a Cr powder and a silicon monoxide (SiO) powder with an electron beam.

Further, as described in JP-A-54-1898 and JP-A-58-82770, reactive sputtering is performed in an oxygen-containing atmosphere using a composite type target or an alloy target comprising Cr and Si to form the thin film. It is stated that it can be obtained.

Further, Shin Solid Films
57 (1979), pages 363 to 366 (Th
in Solid Films, 57 (1979) pp.
363-366), there is also an example in which a mixture of Cr powder and SiO ₂ powder is used as a sputtering target to form the thin film as a powder.

A sputtering target for obtaining a thin film composed of tantalum (Ta), silicon (Si) and oxygen (O), which is different in material system but known as a thin film composed of metal, silicon and oxygen, is used as a sputtering target. ) And S
Japanese Patent Application Laid-Open No. Sho 58-119605 describes an example in which a powder of iO ₂ is formed by pressing under pressure to form a sputtering target.

[0006]

SUMMARY OF THE INVENTION Among the above conventional examples, Cr
In any of the examples for forming a thin film composed of Si and O, the desired thin film can be obtained in a short term,
No consideration is given to the stability over time for obtaining a thin film with good reproducibility over a long period of time, and there is a problem in industrial use because the composition is easily shifted. In the case of a sputtering target formed from metal Ta and SiO _2, a chemical reaction between tantalum and silicon, or tantalum and oxygen occurs at a high temperature, resulting in a very brittle target. There is. For this reason, the relative density does not increase, and even if various measures are taken, 90%
Stay on the order. For this reason, the in-plane distribution and the distribution in the thickness direction of the microvoids included in the sputtering target are likely to occur, and the reproducibility over a long period (stability over time) is also observed.
There is a problem in the point. In addition, the microvoids not only serve as starting points for cracks but also to facilitate the propagation thereof, so that a target material having a low relative density has low mechanical strength and is easily broken during use. In addition, a large gap that can be confirmed with the naked eye causes local concentration of glow discharge during sputtering, and the discharge becomes unstable. When pressure is applied at a high pressure to increase the relative density to 90% or more in order to prevent this, heat is generated due to friction between particles at the time of pressurization, and the progress of the reaction cannot be suppressed. For this reason, the obtained target material is very brittle, and often breaks due to heat generated by electric discharge during sputter film formation, and cannot be used.

An object of the present invention is to provide a sputtering target suitable for mass production for stably forming a large amount of a thin film made of Cr, Si and O with a high specific resistance.

[0008]

The above object is achieved by obtaining a sputtering target composed of Cr, Si and O having a high uniformity and high mechanical strength, that is, a high relative density.
For this reason, Cr and Si, which is a stable oxide, are used as raw materials.
O ₂ powder was used and its particle size was 32 in Tyler number.
A mesh under (with a particle size of 500 μm or less) is selected and, after sufficiently removing water, 20 to 80% by weight.
It mixes in the ratio of Cr to make a raw material powder. Here, in order to prevent a reaction between Cr and Si from occurring due to heating for forming, powder obtained by forming a thin oxide film on the surface of Cr grains by heat treatment may be mixed with SiO ₂ to be used as a raw material powder. Then, the inside of the can is evacuated while being heated to 200 to 800 ° C. while being filled into a sealing can for consolidation with foil of a high melting point metal such as niobium (Nb), and then sealed. The sputtering target is manufactured by pressure molding with a hydraulic press.

Alternatively, a sputtering target is manufactured by molding the mixed raw material powder by a normal press, mounting the mixture on a die, and press-molding by a hot press.

[0010]

The Cr and SiO ₂ powders are selected so that the particle size of each powder is 32 mesh or less (particle size of 500 μm or less), and these are mixed in a ratio of 20 to 80 wt% Cr and sufficiently stirred. And a uniform mixed raw material powder can be obtained. By using this mixed raw material powder, local Cr and S
A sintered body having a very small variation in the ratio of iO ₂ can be manufactured. Also, a natural oxide film is formed on the surface of the Cr particles only by leaving the Cr powder in the air due to the inherent properties of Cr.
In order to prevent a chemical reaction between r and Si in SiO ₂ , it is possible to stably manufacture without generating a brittle compound or destruction of the sintered body due to a volume change at the time of compound formation. Further, a more reliable effect can be obtained by forming an oxide film on the surface of the Cr particles by heat treatment. Since both are stable at the pressure at a high temperature, during molding by high pressure conditions of temperature and 1000 kg / cm ² at about 1200 ° C. is between Cr particles SiO ₂
Has a mixed two-phase structure in which the space between Cr particles is almost completely filled with SiO _2, so that the relative density of the sintered body becomes 95% or more. Further, the Nb foil, which is a reaction preventing layer lined with the sealing can, reacts with the material of the sealing can and the raw material powder to mix the constituent elements of the sealing can into the press molded body or to prevent the surface of the press molded body from being mixed. To prevent the sealing can from being removed from the container. Such a reaction prevention treatment is also necessary for a die when performing pressure molding by a hot press. Due to the overall effect of these production methods, local variation in the ratio of Cr and SiO _{2 in} the sintered body is small, so that the sintered body is very homogeneous and has a relative density of 95% or more and high mechanical strength. A sintered body can be obtained. A thin film obtained by using the present sputtering target having such characteristics has a small in-plane distribution of film characteristics, and can obtain a thin film with good reproducibility over a long period of time.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

Example 1 As shown in FIG. 1, the particle size of a Cr powder having a purity of 99.5% or more as a raw material is 120 mesh or less, and the particle size of a SiO ₂ powder having a purity of 99.5% or more is 200 mesh. Screen each as follows. Since the Cr powder has relatively little moisture adsorption, it may be used as it is as a raw material powder after sorting if care is taken in storage. In addition, when there is a concern about moisture adsorption during storage, the water can be reliably removed by stirring while heating at about 200 ° C. in the air, and at the same time, an oxide film is formed on the entire surface of the Cr particles, In the reaction with SiO ₂ .
If the heating at the time of the drying is set to a high temperature exceeding 300 ° C., the surface oxidation of the Cr particles becomes remarkable, and the oxygen content of the entire target is affected, so that the above temperature range is appropriate. The SiO ₂ powder is always heated to 800 ° C. or more and stirred in an atmosphere or a dry atmosphere such as nitrogen to remove water. Depending on the manufacturing method, the SiO ₂ powder may contain about 10% by weight of water in the form of water of crystallization. In addition, since the water in the atmosphere adsorbs considerably during storage, it is necessary to remove the water as much as possible. Drying at a high temperature as described above is essential. If water remains in the SiO ₂ powder, it becomes water vapor at a high temperature of about 1000 ° C. during sintering, and the Cr powder is extremely oxidized to a brittle oxide.

Thereafter, Cr and SiO ₂ powders each adjusted to a predetermined weight were sufficiently mixed to obtain a raw material powder.
Here, in a composition in which the mixing ratio of the raw material powders is significantly different, such as 20% by weight or less Cr and 80% by weight or more, uniform mixing of the raw material powders becomes difficult, and even in the sputtering target, Cr or SiO ₂ is reduced. Easy to be unevenly distributed. For this reason, the composition of the sputtering target needs to be in the range of 20 wt% Cr to 80 wt% Cr. In order to suppress the reaction such as alloying with the mixed powder under high temperature and high pressure, it is packed in a steel sealing can sealed with niobium (Nb) or tantalum (Ta) foil having a thickness of several tens of μm. The air in the container is exhausted over several hours while heating at a temperature in the range of 800 ° C. The higher the temperature, the more quickly and surely the gas can be evacuated. It is desirable that the evacuation is performed until the pressure in the container becomes 0.01 Pa or less, and if it is 0.001 Pa or less, there is a sufficient effect to prevent excessive oxidation during sintering due to residual air and moisture, and a sputtering target The reproducibility of various characteristics is also good. After the evacuation is completed, the container is hermetically welded and sintered by a hot isostatic press at a temperature of 1000 ° C. to 1400 ° C. and a pressure of 1000 to 1200 kg / cm ² . After sintering, it is gradually cooled to room temperature over 10 hours or more, and after completion of cooling, the compacting can is mechanically cut and removed to take out the sintered compact. By this sintering step, the volume of the sealing can is reduced by about 10 to 20%. When the relative density of the obtained molded body was measured, it became clear that a density of 98% was obtained. Thereafter, the formed body is machined into a predetermined shape, washed and dried with an organic solvent, pure water, or the like, and a target is bonded to a backing plate to facilitate attachment to a sputtering apparatus, thereby completing the process.

Example 2 A sputtering target can be manufactured by exactly the same process as in Example 1 even when the particle size of the raw material powder is 32 mesh under Cr and 200 mesh under SiO _2. The local uneven distribution of the powder was conspicuous, and the relative density was slightly lower than that of the above example and was about 96%. When using the sputtering target, sufficient attention must be paid to the reproducibility of film quality, and it was possible to use the sputtering target as a sputtering target by adjusting the film forming conditions according to the fluctuation.

[Example 3] In the same manner as in Example 1, raw material powders are prepared and uniformly mixed at an expected ratio, then filled in a mold having a desired shape, and pressed at a pressure of about 400 kg / cm ^2. Powder molding. This was attached to a carbon container and the degree of vacuum in the container was set to 0.
Exhaust to 01 Pa. Thereafter, at a temperature of 1300 ° C., about 260 k is applied through a carbon spacer coated with boron nitride.
g / cm ² of pressure was applied to the compact,
Hold for hours. According to this method, a sputtering target equivalent to that of Example 1 could be obtained.

In this manufacturing method, since a sputtering target having a small relative density can be obtained by lowering the pressure and sintering, a sputtering target having a relative density of about 80% is manufactured.
Although discharge was performed at a power density of 3.0 W / cm ^2, the target was broken by a few minutes of discharge, and was not practical. On the other hand, no signs of damage due to electric discharge were observed in any of the targets having a relative density of 95% or more, including those described in Examples 1 and 2, produced by any method.

Example 4 The surface of the target having a composition of 66% by weight of Cr-34% by weight of SiO ₂ obtained in Examples 1, 2 and 3 was polished and observed with an optical microscope. As shown, the structure is such that Cr grains 1 are scattered in SiO ₂ . This is because S
The structure is such that iO ₂ has fluidity and flows between the Cr particles 1 to almost completely fill the voids. When a sample having such a structure is subjected to X-ray fluorescence analysis, as shown in FIG.
And SiO ₂ , the characteristic X-ray intensity of Cr 4 and Si
Since the characteristic X-ray intensity 3 of O ₂ is reversed with a sharp rise and fall, it is clear that no mutual diffusion has occurred and a clear boundary exists. It is considered that this is because the natural oxide film or the thermal oxide film on the surface of the Cr grains acted as a barrier for preventing mutual diffusion under high temperature and high pressure in the sintering process. The relative density of the sintered body having such a structure (the theoretical density in this case was 4.06 g / cm ³ ) was about 98%, which was a sufficiently high value.

Example 5 The mechanical strength of a target sintered under the same conditions while changing the particle size of the Cr and SiO ₂ powders was compared. As shown in Table 1, the mechanical strength was the particle size of the Cr powder. And the larger the Cr grains, the more brittle. Under the conditions shown in Table 1, cracks occur at the stage of machining after sintering,
It could not be evaluated as a sputtering target.
However, a rectangular sputtering target was manufactured using the conditions in Table 2 and RF power was applied thereto at a power density of 3.1 W / cm ² , thereby generating a glow discharge. However, it could be used without any abnormality. Therefore, the upper limit of the particle size of the Cr powder is between 1 and 2 in the conditions in the table, and it is clear that finer than 2 can sufficiently withstand use.

When the particle size of Cr and SiO ₂ powders is large, local Cr and SiO ₂
, The reproducibility of the film characteristics of the thin film deteriorates. Therefore, the particle sizes of the Cr and SiO ₂ powders used as the raw materials need to be finer than 32 mesh from this point, and the SiO ₂ powder is equivalent to or better than the Cr powder in terms of uniform mixing. Need to be fine. However, the mechanical strength saturates even if the Cr powder is too thin, and the amount of oxygen increases more than the expected amount due to the increase in the oxide layer accompanying the increase in the surface area of the Cr particles. Since the influence of the relatively large amount becomes remarkable, there is no advantage even if it is smaller than 1000 mesh under. The finer the SiO ₂ powder, the more the amount of adsorbed water increases, and the cohesion of the particles becomes remarkable, effectively giving the same result as the coarse powder. Therefore, when actually manufacturing a sputtering target, both the Cr and SiO ₂ powders should be 3 in consideration of the impurity content of the raw material powder, the ease of handling, and the characteristics of the target.
The range of 2 to 1000 mesh under is the optimum particle size.

[0020]

[Table 1]

[Embodiment 6] 127 × 381 mm square Cr
-A SiO ₂ sintered target was manufactured and attached to a substrate moving film forming type sputtering apparatus, and a thin film was formed by discharging with RF power of 1.5 kW. The sheet resistance distribution of the obtained thin film was 127 mm square. It was ± 3% or less on the substrate. Further, the film forming reproducibility under a constant film forming condition was examined by the present apparatus, and the relationship between the cumulative number of batches and the average sheet resistance value is shown in FIG. From this figure, the relationship 5 by the composite type target having the same outer shape by combining the Cr plate and the SiO ₂ plate increases each time the batches overlap, and the number of batches that can obtain the thin film having the above-described sheet resistance and its distribution characteristics Was about 20 batches, but in Example 6 using the sputtering target according to the present invention, the number of batches reached 300 batches or more, and significant improvement in mass productivity was confirmed. In addition, through these studies, there was no sign that the present sintered target was destroyed by electric discharge, and it was confirmed that the above-mentioned conditions for the production were appropriately set.

Example 7 A sputtering target was manufactured by changing the mixing ratio of Cr and SiO ₂ powder in the range of 55 to 80% by weight of Cr, and a Cr—Si—O thin film was formed by RF sputtering using these targets. Formed. FIG. 5 shows the specific resistance in the as-formed state. As is clear from this figure, a thin film having a specific resistance of 1 μΩ · m, which is equivalent to a generally known NiCr (nichrome) thin film, has a composition of 80 wt% Cr in the sputtering target of the present invention. And a thin film in a high resistivity region, which was conventionally difficult to obtain stably, is made of SiO ₂
Can be easily obtained over a wide range by increasing the amount of.

From the viewpoint of the specific resistance of the obtained thin film, the range of 50 to 80% by weight of Cr is particularly useful as the target composition. On the other hand, if the Cr content is less than 20% by weight, the obtained thin film becomes substantially an insulator, which is outside the object of the present invention. Thus, from the viewpoint of the properties of the obtained thin film, the composition of the sputtering target according to the present invention needs to be in the range of 20 wt% Cr to 80 wt% Cr, and in particular, 50 to 80 wt% Cr is preferable. It is.

[0024]

According to the present invention, it is possible to obtain a uniform sputtering target without a bias in the mixing ratio of Cr and SiO ₂ . In addition, the present target has high mechanical strength and can withstand a long-time discharge, so that the usable time of the target can be ten times or more that of the conventional target. Furthermore, by using this target, a thin film having a desired specific resistance can be obtained with good reproducibility in a state where the film quality distribution in the substrate is small, so that when this thin film is formed as a resistive element, an error in element resistance can be reduced. In addition, the circuit characteristics of the thin film circuit can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing process of a Cr—SiO ₂ sintered target according to the present invention;

FIG. 2 is a view showing a microstructure of a Cr—SiO ₂ sintered target according to the present invention;

FIG. 3 is a diagram showing a result of a line analysis by X-ray fluorescence from A to A ′ in FIG. 2;

FIG. 4 is a diagram showing a change in specific resistance associated with the use of a sintered target according to the present invention as compared with that of a composite target having the same shape;

FIG. 5 is a diagram showing the mixing ratio dependency of the specific resistance of a thin film obtained by a sintering target in which the mixing ratio of SiO ₂ powder is changed.

[Explanation of symbols]

1 ... Cr particle, 2 ... SiO ₂ , 3 ... Detection intensity of fluorescent X-ray of Si, 4 ... Detection intensity of fluorescent X-ray of Cr, 5 ... Variation of thin film sheet resistance due to consumption in composite target, 6
... Fluctuation of thin film sheet resistance due to wear in the target according to the present invention. Is shown.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor ▲ Kusu ▼ Mochi Akihiro 1st Horiyamashita, Hadano-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Kanagawa Plant (72) Inventor Chiba ▲ Yoshi ▼ Takataka Takashi, Shimane Prefecture -2 Inside Hitachi Metals Co., Ltd. (72) Inventor Akitoshi Hiraki 2107-2 Yasugi-cho, Yasugi-shi, Shimane Prefecture Inside Hitachi Metals Co., Ltd. (56) References JP-A-2-54760 (JP, A) JP-A-4 -14203 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14/34 C22C 1/05 H01L 21 / 203,21 / 285

Claims (4)

(57) [Claims] 1. A sputtering method manufactured by sintering a powder of metallic chromium (Cr) and a powder of silicon dioxide (SiO2) under pressure.
In the method of manufacturing the target, the particle size of both powders
Is less than 30 mesh (particle size 500 μm or less)
The particle size of silicon dioxide (SiO2) powder is metallic chromium
Use the same or finer particle size as (Cr) powder
, Metal chromium (Cr) powder in air at 100-30
Heat to a temperature of 0 ° C. to remove water and remove silicon dioxide (Si
O2) powder in air at a temperature of 800-1200 ° C
Heat to remove water and combine both powders of metallic chromium (Cr)
The weight ratio of the powder is mixed to a ratio in the range of 20 to 80% ,
By sintering the mixed powder under pressure, the mixing ratio
The ratio of the actual density to the theoretical density (relative density) is 9
A method for producing a sputtering target , wherein the sintered integral material is 5% or more . 2. A metal chromium (Cr) powder and silicon dioxide
Sputter produced by sintering (SiO2) powder under pressure
A ring target with a particle size of 30
Ash or less (particle size 500 μm or less) and diacid
Particle size of powder of silicon oxide (SiO2) is metallic chromium (Cr)
Of the same or finer particle size as
Chromium (Cr) powder at 100-300 ° C in air
Heated to a temperature to remove moisture, silicon dioxide (SiO
The powder of 2) is heated to a temperature of 800 to 1200 ° C in the atmosphere.
Moisture is removed by heating, and both are powdered metallic chromium (Cr)
The weight ratio of the powder is mixed in the range of 20-80%,
By sintering the mixed powder under pressure, the mixing ratio
The ratio of the actual density to the theoretical density (relative density) is
Sputtering target with a sintered integral of 95% or more . 3. A sputtering target according to claim 1.
During the pressure sintering in the production method of the above , after sufficiently mixing the powder of metal chromium (Cr) and the powder of silicon dioxide (SiO 2) as raw materials, a lining for preventing a reaction with the raw materials is provided. Raw material powder is filled in a sealed can, and the inside of the can is heated to 0.01 Pa while heating the can at 200 to 800 ° C.
A method for producing a sputtering target, comprising evacuating to the following degree of vacuum, sealing, and sintering by hot isostatic pressing. Using the sputtering target according to 4. The method of claim 2, 1-1000 Ri by the RF sputtering method
Chromium (Cr) and silicon (S
Electricity formed by forming a thin film composed of i) and oxygen (O)
Circuit .