KR102330631B1 - Cylindrical silicon target - Google Patents

Abstract

The cylindrical silicon target is a cylindrical silicon target formed in a cylindrical shape made of polycrystalline silicon, and the longitudinal direction of crystal grains appearing on the outer peripheral surface is arranged along the central axis of the cylinder. Moreover, in the outer peripheral surface of the cylindrical silicon target, when the length of the longest part in the direction along the central axis of each crystal grain is L, and the length of the longest part in the direction orthogonal to the central axis is W, the outer peripheral surface In the range of 100 mm in the circumferential direction x 100 mm in the direction along the central axis, there are 5 or more crystal grains having the length L of 10 mm or more, and the average value of the ratio (L/W) of the length L to the length W of these crystal grains It should be 2.0 or higher.

Description

Cylindrical silicon target {CYLINDRICAL SILICON TARGET}

The present invention relates to a cylindrical silicon target used in a sputtering apparatus.

A sputtering apparatus which sputters while rotating a cylindrical target is known. Such a sputtering apparatus is suitable for film-forming of a large area, and there exists a feature that the use efficiency of a target material is very high. In general, flat-type targets have a usage efficiency of several tens to 30%, whereas in a cylindrical target, sputtering while rotating can provide a very high usage efficiency of about 80%. Moreover, since cooling water can flow inside the cylindrical target, cooling efficiency is high, and it is possible to apply high electric power to a target material, and to form a film|membrane at a high film-forming rate.

As a conventional cylindrical target of silicon|silicone, it describes in patent document 1, for example. In this patent document 1, the cylindrical target which laminated|stacked the target layer which has Si alloy as a main component by the thermal spraying method on the outer peripheral surface of the columnar base|substrate is disclosed.

Japanese Laid-Open Patent Publication No. 5-86462

In order to ensure film-forming uniformity, it is generally required for a target to be substantially the same size as the to-be-processed member etc. which are film-forming object, or to be larger than that. And with the enlargement of the film-forming object, although enlargement of the cylindrical target is also desired, if enlarged, it will become difficult to form a film of uniform film thickness.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cylindrical silicon target capable of forming a film having a uniform film thickness.

The cylindrical silicon target of the present invention is a cylindrical silicon target formed in a cylindrical shape made of polycrystalline silicon, and the longitudinal direction of crystal grains appearing on the outer peripheral surface is arranged along the central axis of the cylinder.

In a cylindrical silicon target, a linear portion along the central axis direction (sputter surface) of the outer peripheral surface faces the film formation surface of the film formation object, and plasma is formed between the opposite portions. And the target particle|grains are emitted from the linear part along the central axis direction from the outer peripheral surface of the cylindrical silicon target, and the linear part moves in a circumferential direction with rotation of the cylindrical silicon target.

As for the cylindrical silicon target of this invention, the longitudinal direction of the crystal grain is arrange|positioned along the central axis of a cylinder, ie, along the direction parallel to the film-forming surface, as for the outer peripheral surface used as a sputtering surface. For this reason, each crystal grain arranged in the central axis direction on the outer peripheral surface of the cylindrical silicon target is emitted (sputtered) at the same timing, and a uniform sputtering rate is obtained in the central axis direction of the cylindrical silicon target, and a uniform film thickness is obtained. can form a film of

In the cylindrical silicon target of the present invention, in the outer circumferential surface, the length of the longest part of each crystal grain in the direction along the central axis is L, and the length of the longest part in the direction orthogonal to the central axis is W. , 5 or more crystal grains having the length L of 10 mm or more in the range of 100 mm in the circumferential direction of the outer peripheral surface × 100 mm in the direction along the central axis, and the ratio of the length L to the length W of these crystal grains (L /W) may have an average value of 2.0 or more.

In the cylindrical silicon target of the present invention, the average crystal grain diameter of the crystal grains in a cross section perpendicular to the central axis is 2 mm or more and 10 mm or less.

In the range of 100 mm in any circumferential direction of the outer peripheral surface × 100 mm in the direction along the central axis, the longest part of the crystal grains in the direction (longitudinal direction) along the central axis includes 5 or more crystal grains, the length L of which is 10 mm or more, and the length L is 10 By using a cylindrical silicon target having a crystal structure in which the average value of the ratio (L/W) of each crystal grain ratio (L/W) of mm or more is 2.0 or more, the area ratio of the crystal grains along the central axis on the outer peripheral surface (opposing surface) of the cylindrical silicon target can be sufficiently high, , a film having a uniform film thickness can be formed.

According to the cylindrical silicon target of the present invention, since crystal grains arranged in the central axis direction on the outer circumferential surface can be released at the same timing, a uniform sputtering rate is obtained in the central axis direction, and a film of uniform film thickness can be formed. can

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the cylindrical silicon target of embodiment of this invention.
It is a schematic diagram of the manufacturing apparatus used for manufacture of a polycrystalline silicon ingot.
It is a schematic diagram explaining the film-forming conditions of an Example.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the cylindrical silicon target of this invention is described with reference to drawings. In addition, embodiment shown below is an example of the cylindrical silicon target which concerns on this invention.

The cylindrical silicon target 10 of this embodiment shown in FIG. 1 consists of polycrystalline silicon, is formed in the cylindrical shape, and an outer peripheral surface turns into a sputtering surface. In such a cylindrical cylindrical silicon target 10, a linear portion of the outer peripheral surface along the central axis O direction is disposed to face the film formation surface 15 to be formed, and the linear portion and the film formation surface 15 are disposed. ), a plasma is formed between the opposing portions. Then, target particles are emitted from a linear portion opposite to the film-forming surface 15, and with the rotation of the cylindrical silicon target 10, the linear portion is sequentially moved in the circumferential direction while the film-forming surface 15 is rotated. make a film on the

As for the cylindrical silicon target 10 of this embodiment, the longitudinal direction of the crystal grain of polycrystalline silicon which appears on the outer peripheral surface is arrange|positioned along the central axis O of a cylinder, as shown in FIG. That is, since the crystal structure along the longitudinal direction of the crystal grains in a direction parallel to the film-forming surface 15 of the film-forming target is formed on the outer peripheral surface of the cylindrical silicon target 10 used as the sputtering surface, it faces the film-forming surface 15. The longitudinal direction of each crystal grain is arrange|positioned along the linear part of the outer peripheral surface to do. For this reason, crystal grain boundaries can be reduced as much as possible in the linear portion, and each crystal grain arranged along the central axis (O) direction is emitted (sputtered) at the same timing. Accordingly, a uniform sputtering rate is obtained in the central axis O direction, and a film having a uniform film thickness can be formed on the entire surface of the film formation surface 15 .

Moreover, in the outer peripheral surface of the cylindrical silicon target 10, the length of the longest part in the direction along the central axis O of each crystal grain of polycrystalline silicon is L, and in the direction orthogonal to the central axis O When the length of the longest part is W, there are 5 or more crystal grains whose length L is 10 mm or more in the range of 100 mm in the circumferential direction of the outer peripheral surface x 100 mm in the direction along the central axis O, and these length L are 10 mm When the average value of the ratio (L/W) of the length L and the length W of the crystal grains equal to or greater than 2.0 is 2.0 or more, the cylindrical silicon target 10 is an area ratio of the crystal grains along the central axis O in the outer peripheral surface of the cylindrical silicon target 10 can be made sufficiently high, and a film having a uniform film thickness can be formed on the entire surface of the film formation surface 15 .

Next, one Embodiment of the method of manufacturing the cylindrical silicon target 10 of the structure mentioned above is demonstrated. In the present embodiment, a polycrystalline silicon ingot having a long crystal structure in the uniaxial direction is cast, the polycrystalline silicon ingot is cored, and the outer periphery and the cross section are further ground with a universal grinding machine to form a cylindrical shape. By doing so, the cylindrical silicon target 10 is manufactured. The crystal structure elongated in the uniaxial direction is formed by growing crystals in the cooling direction by controlling the solidification start temperature, the solidification rate, the temperature gradient at the time of solidification, and the like in the unidirectional solidification method.

An example of the manufacturing apparatus 101 of a polycrystalline silicon ingot is shown in FIG. This manufacturing apparatus 101 is equipped with the floor heater 21 under the floor, the cooling plate 31 is formed on it, The lower supply pipe|tube 32 of the argon gas for cooling is provided in this cooling plate 31. is connected. A quartz mold 41 is placed on the cooling plate 31 , and a lower heater 22 and an upper heater 23 are formed on the outer periphery of the mold 41 . In addition, a plurality of thermocouples 51 are formed for each predetermined depth position of the mold 41, and based on the temperature result by the thermocouple 51, the bottom heater 21, the lower heater 22 and the upper heater ( 23) allows individual output adjustment.

Further, in the manufacturing apparatus 101, an upper supply pipe 61 disposed toward the upper surface of the mold 41 and a diffusion plate 62 having a large number of pores are formed, and the upper supply pipe 61 and the diffusion plate are formed. Argon (Ar) gas is supplied to the periphery of the mold 41 through 62 . The entire mold 41 and the heaters 21 to 23 are covered with the heat insulating material 71 .

Next, the method of casting a polycrystalline silicon ingot using the manufacturing apparatus 101 comprised in this way is demonstrated.

First, a silicon raw material (not shown) is charged into the inside of the mold 41 . As the silicon raw material, for example, a bulky chunk obtained by pulverizing high-purity silicon having a purity of 99.9999% is used. Moreover, dopants, such as boron (B), are added to a silicon raw material as needed.

When argon gas is supplied to the periphery of the mold 41 through the upper supply pipe 61, the periphery of the mold 41 is maintained in an atmosphere excluding oxygen. Then, in an atmosphere excluding oxygen, the silicon raw material charged into the mold 41 is heated and melted by the heaters 21 to 23 to obtain a silicon melt 80 .

Next, while adjusting the output of the heaters 21 to 23 , an argon gas for cooling is introduced into the cooling plate 31 from the lower supply pipe 32 to cool the bottom of the mold 41 , whereby the silicon in the mold 41 is The melt 80 is partially and sequentially solidified over time at a solidification rate of 0.1 to 0.3 mm/min from the bottom to the top of the mold 41 in the vertical direction with respect to the bottom surface of the mold 41 . To grow a polycrystalline silicon ingot having a one-way solidified casting structure. In addition, by unidirectional solidification, impurities such as oxygen are collected at the end (upper) of the ingot and concentrated in the final solidified part, so that by cutting this part, a polycrystalline silicon ingot with a small amount of impurities can be obtained.

The polycrystalline silicon ingot thus obtained has a crystal structure elongated in the uniaxial direction, and the longitudinal direction of each crystal grain is arranged along the uniaxial direction. For this polycrystalline silicon ingot, the longitudinal direction of the crystal grains (growth direction) is changed to the longitudinal direction (growth direction) of the crystal grains by cutting out the central part of the cylinder in the longitudinal direction (central axis (O) direction) of the crystal grains, and then grinding the outer periphery and the cross section. A cylindrical silicon target 10 disposed along O) is obtained.

To form a film having a uniform film thickness on the entire surface of the film formation surface 15 using the cylindrical silicon target 10, not only the crystal orientation in the direction (uniaxial direction) along the central axis O, but also the central axis ( It is preferable to consider the crystal orientation of the cross-section perpendicular to O). That is, it is desirable not only to obtain crystal grains in which the same crystal orientation continues in the direction along the central axis O of the outer peripheral surface of the cylindrical silicon target 10, but also to continue the same crystal orientation in a cross section perpendicular to the central axis O. do. Specifically, the crystal orientation in which the average crystal grain diameter of the crystal grains is 2 mm or more and 10 mm or less in a cross section perpendicular to the central axis O is preferable. If the average crystal grain diameter of the crystal grains in the cross section perpendicular to the central axis O is 2 mm or more, it becomes possible to form a film having a uniform film thickness on the entire surface of the film formation surface 15 . On the other hand, when the average crystal grain diameter exceeds 10 mm, cracks are likely to occur when the polycrystalline silicon ingot is processed to obtain the cylindrical silicon target 10 . Considering forming a film having a uniform film thickness, more preferably, the average grain size is 2 mm or more and 7 mm or less.

Moreover, in the cylindrical silicon target 10 of this embodiment, the same average crystal grain diameter can be obtained in the cross section of arbitrary positions including the cross section perpendicular|vertical with respect to the central axis O.

In addition, when casting a polycrystalline silicon ingot, if the solidification rate is made gentle (in the above embodiment, if the solidification rate is made slower than 0.1 mm/min), the crystal grains are not only uniaxial, but also orthogonal to the uniaxial direction. It grows large also in the uniaxial direction, and long and short crystal grains are mixed in the uniaxial direction, making it difficult to grow a polycrystalline silicon ingot having a long crystalline structure in the uniaxial direction. On the other hand, even when the solidification rate is set to a rate exceeding 0.3 mm/min, a polycrystalline silicon ingot having a crystal structure elongated in the uniaxial direction cannot be obtained.

In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of this invention, it is possible to add various changes.

For example, in the above embodiment, a polycrystalline silicon ingot having a crystal structure elongated in the uniaxial direction is cast using the manufacturing apparatus 101 shown in FIG. A polycrystalline silicon ingot may be manufactured using a manufacturing apparatus having a different structure, such as pulling-up continuous unidirectional solidification casting, which is produced by pulling up a silicon ingot of polycrystalline silicon using seed crystals while unidirectionally solidifying from the silicon melt.

Example

The results of confirmation experiments performed to confirm the effectiveness of the present invention will be described.

Using the same apparatus as the manufacturing apparatus 101 shown in FIG. 2, the polycrystalline silicon ingot which has a crystal structure elongate in uniaxial direction was manufactured. Hereinafter, referring to FIG. 2 , a material obtained by adding boron (B) having a purity of 99.99% as a dopant to high purity silicon (Si) having a purity of 99.9999% as a raw material is used, and this is charged into a mold 41 made of quartz. Then, argon (Ar) gas was introduced, the pressure in the furnace was set to 6700 Pa, and the raw material was heated and melted by the heaters 21 to 23 to obtain a silicon melt 80 . Then, the silicon melt 80 is maintained at 1480° C. to 1510° C., which is just above the melting point of silicon, by temperature control by the thermocouple 51, and in this state, the bottom surface of the mold 41, the mold 41 The bottom surface of the mold 41 is cooled with argon gas introduced through the cooling plate 31 while adjusting the outputs of the heaters 21 to 23 at the lower part and the upper part of the mold 41, and the inside of the mold 41 is By sequentially solidifying molten high-purity silicon from the bottom surface of the mold 41 toward the top of the mold 41 partially and over time, a unidirectionally solidified casting structure in the vertical direction with respect to the bottom surface of the mold 41 A polycrystalline silicon ingot having

The polycrystalline silicon ingot has dimensions of 180 mm in diameter x 220 mm in height, and is a high-purity polycrystalline silicon ingot containing boron for a dopant in a proportion of 200 ppm. Moreover, four types of polycrystalline silicon ingots were formed by adjusting the solidification rate to 0.01-1 mm/min.

Specifically, the solidification rate of polycrystalline silicon ingot No. 1 shown in Table 1 was 0.50 mm/min, the solidification rate of polycrystalline silicon ingot No. 2 was 0.05 mm/min, and the solidification rate of polycrystalline silicon ingot No. 3 was 0.15 mm. /min, the solidification rate of polycrystalline silicon ingot No. 4 was 0.28 mm/min, and the solidification rate of polycrystalline silicon ingot No. 5 was 0.30 mm/min.

After coring the obtained polycrystalline silicon ingot to a diameter of 135 mm in the axial direction (height direction), the outer peripheral surface and the cross section were ground with a universal grinding machine, and a cylindrical shape having an outer diameter of 155 mm, an inner diameter of 135 mm, and a length (height) of 199.8 mm A silicon target was fabricated. Then, observation of the crystal structure on the outer peripheral surface of the obtained cylindrical silicon target was performed, and for each crystal grain within the range of 100 mm in an arbitrary circumferential direction of the outer peripheral surface × 100 mm in the direction along the central axis, in the direction along the central axis. The dimension of the length L of the longest part in in and the length W of the longest part in the direction orthogonal to the length L was measured with the noggis. Then, the average value of the number of crystal grains having a length L of 10 mm or more within the range and the ratio (L/W) of each crystal grain having a length L of 10 mm or more was calculated.

Moreover, the crystal structure observation of the whole cross-section perpendicular|vertical with respect to the central axis of each cylindrical silicon target was performed, the length of the longest part of each crystal grain was measured with a noggis, and the average was computed.

In addition, three pieces of cylindrical silicon targets manufactured under the same conditions were prepared, and as shown by the dashed-dotted line in Fig. 3, the three pieces of cylindrical silicon targets were placed in a backing tube 11 made of titanium (Ti) with indium (In). was bonded to prepare a cylindrical silicon target 10A having an outer diameter (Do) = 155 mm, an inner diameter (Di) = 135 mm, and an overall length (L0) = 600 mm.

And sputtering was performed to the glass substrate using this cylindrical silicon target 10A. As shown in FIG. 3 , sputtering is performed on a sheet 91 having a length of L1 = 450 mm and a glass substrate 92 having a width of S = 20 mm in the central axis (O) direction of a cylindrical silicon target 10A. was carried out in a row at equal intervals, and the output was 8.3 kW/m to form a silicon thin film aiming at a film thickness of 500 nm on the surface of each glass substrate 92 . And the film thickness of each glass substrate 92 was measured one point at a time using the level difference measuring device, and the dispersion|variation in the film thickness of the glass substrate 92 of 5 sheets was calculated. The variation in the film thickness was calculated from the following formula using the average value of five points of the measured film thickness, and the maximum and minimum values among five points of the measured film thickness.

Variation in film thickness (±%) = {(maximum value - minimum value) ÷ (average value of 5 points)} × 100 ÷ 2

A result is shown in Table 1.

As can be seen from Table 1, among the outer peripheral surfaces of the cylindrical silicon target, there are 5 or more crystal grains having a length L of 10 mm or more appearing within the range of 100 mm in the circumferential direction x 100 mm in the direction along the central axis, and these length L are 10 mm With respect to crystal grains that are larger than or equal to, in the cylindrical silicon target of No. 3 or No. 4 in which the average value of the ratio (L/W) is 2.0 or more, the variation in the film thickness can be suppressed to less than 7%, in the central axis direction of the cylindrical silicon target. In this, a film having a more uniform film thickness can be formed. Also in No. 5, there were 5 or more crystal grains having a length L of 10 mm or more, the average value of the ratio (L/W) was 2.0 or more, and a film having a uniform film thickness was formed with a film thickness variation of 8.4%. . Moreover, in No.3, No.4, and No.5 with low dispersion|variation in film thickness, the average crystal grain diameter of the crystal grain of a cross section was also 2 mm or more and 10 mm or less.

10, 10A: Cylindrical silicon target
11: Backing tube
15: film formation surface
21: floor heater
22: lower heater
23: upper heater
31: cooling plate
32: lower supply pipe
41 : mold
51: thermocouple
61: upper supply pipe
62: diffuser plate
71: insulation material
80: silicon melt
91: sheet
92: glass substrate
101: apparatus for manufacturing polycrystalline silicon ingot

Claims (3)

A cylindrical silicon target formed in a cylindrical shape made of polycrystalline silicon, wherein the longitudinal direction of crystal grains appearing on the outer circumferential surface is arranged along the central axis of the cylinder,
The outer peripheral surface is a sputter surface,
In the outer peripheral surface, when the length of the longest part in the direction along the central axis of each crystal grain is L and the length of the longest part in the direction orthogonal to the central axis is W, the outer peripheral surface is 100 mm in the circumferential direction x there are 5 or more crystal grains having the length L of 10 mm or more within a range of 100 mm in the direction along the central axis, and the average value of the ratio (L/W) of the length L to the length W of these crystal grains is 2.0 or more Cylindrical silicon target, characterized in that. delete The method of claim 1,
A cylindrical silicon target, wherein an average crystal grain diameter of the crystal grains in a cross section perpendicular to the central axis is 2 mm or more and 10 mm or less.

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