TWI684660B - TiW alloy target and its manufacturing method - Google Patents

Abstract

The present invention provides a TiW alloy target capable of simultaneously suppressing abnormal discharge during sputtering, in addition to suppressing deformation of a target material in a process such as clamping or joining, or abrasion or damage to a wafer by a cutting tool. A TiW alloy target material, which contains 7 mass% to 13 mass% Ti, and the remaining part contains W and inevitable impurities, the average value of the Vickers hardness in the sputtering surface is 550HV ~ 630HV, wherein the content of Ti is better It is 9% by mass to 11% by mass.

Description

TiW alloy target and its manufacturing method

The present invention relates to, for example, a TiW alloy target material that can be used to form a diffusion barrier layer used in a semiconductor element and a method for manufacturing the same.

As semiconductor devices become more integrated and denser, migration of precipitates generated at the contact portion between the Al wiring and the Si substrate becomes a problem. In the contact portion, a thin film containing TiW alloy may be formed as Diffusion barrier. Furthermore, it is known that the thin film containing TiW alloy can be formed by a sputtering method.

The target material used in the sputtering method has a problem that particles are generated when a thin film is formed, and techniques for suppressing the amount of generated particles are being studied. The same is true for TiW alloy targets (hereinafter also simply referred to as "targets"). For example, Patent Document 1 includes TiW alloy phase, W phase, and Ti phase containing 20% or more in terms of area ratio of microstructure. Structure, and the surface roughness of the target material is set to Rmax value of 3 μm or less, thereby improving the unevenness of the sputtering surface of the target material, thereby suppressing the generation of particles.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 5-98435

According to the research of the present inventors, it was confirmed that, as disclosed in Patent Document 1, W powder and hydrogenated Ti powder were mixed and pulverized, and then dehydrogenated by hot isostatic pressing (hereinafter referred to as " HIP") The target material is produced by pressure sintering, and there may be a low-hardness part in the target material, and the target body may be deformed during processing such as chueking or bonding.

The TiW alloy is a so-called hard-to-grind material that is highly likely to crack or be damaged during machining, and if there are high or low hardness parts in the target, it will cause the cutting tool to wear or break the wafer. The surface roughness of the target material obtained at this time becomes large, or the target body may be damaged as the case may be.

In addition, if there is a low-hardness portion including, for example, a pure Ti phase or pure W in the eroded area in the center of the sputtering surface of the target, only the low-hardness portion remains or falls off, and thus, the surface of the eroded area The roughness becomes coarser, and it is easy to cause abnormal discharge during sputtering.

An object of the present invention is to provide a TiW alloy target that can simultaneously suppress abnormal discharge during sputtering in addition to suppressing deformation of the target material in processing such as clamping or joining, or abrasion or damage to the wafer by the cutting tool.

The TiW alloy target of the present invention contains 7 mass% to 13 mass% Ti, and the remainder contains W and inevitable impurities. The average value of Vickers hardness in the sputtering surface is 550HV to 630HV.

In the target of the present invention, the Ti content is more preferably 9% by mass to 11% by mass.

Moreover, the target of the present invention is more preferably the average value of the Vickers hardness is 602HV ~620HV.

The TiW alloy target of the present invention can be obtained by a manufacturing method including: adding Ti powder in such a manner as to contain 7 mass% to 13 mass% Ti and the remainder is W and inevitable impurities The step of mixing with the W powder to obtain a mixed powder; the step of pressing the mixed powder to obtain a shaped body; the step of crushing the shaped body and sieving to obtain a crushed powder of less than 1.5 mm; and the sintering The step of obtaining a TiW alloy sintered body by pressing and sintering the pulverized powder under conditions of a temperature of 1500°C to 1600°C, an applied pressure of 20 MPa to 40 MPa, and a holding time of 1 hour to 10 hours.

The present invention can provide a target material that can simultaneously suppress the deformation of the target material in a process such as clamping or joining, or the abrasion or breakage of the wafer by the cutting tool, and can also suppress the abnormal discharge during sputtering. Therefore, it is a useful technique for forming the Al wiring of the semiconductor element and the diffusion barrier layer of the Si substrate described above.

A, B, C ‧‧‧ measuring point

FIG. 1 is an optical microscope observation photograph of the sputtering surface of the target of Example 1 of the present invention.

2 is an optical microscope observation photograph of the sputtering surface of the target material of the comparative example.

The target of the present invention has a feature that the average value of the Vickers hardness specified by the Japanese Industrial Standards (JIS) Z 2244 in the sputtering surface is in the range of 550HV to 630HV. Hereinafter, the "Vickers hardness of the sputtered surface" is also referred to simply as "Vickers hardness".

By setting the average value of the Vickers hardness to 550 HV or more, the target of the present invention can suppress the deformation of the target body during processing such as clamping or joining in machining.

In addition, by setting the average value of the Vickers hardness to 550 HV or more, the target of the present invention can suppress the generation of built-up edges in wafers such as milling machines and lathes, for example. That is, the target of the present invention can suppress the wafer cutting amount gradually becoming larger as the cutting process progresses, can reduce the difference in the size of the target at the start of cutting and the end of cutting, and can also suppress the occurrence of edge accumulation The peeling caused the wafer to break.

On the other hand, if there is a soft part including, for example, pure Ti phase or pure W in the eroded area in the center of the sputtering surface of the target, only the part with low hardness may remain or fall off. The surface roughness of the eroded area becomes rougher, and it is easy to cause abnormal discharge during sputtering. Therefore, in the target of the present invention, the average value of the Vickers hardness is 550 HV or more. In addition, for the same reason as above, the target of the embodiment of the present invention preferably has an average Vickers hardness of 602 HV or more.

By setting the average value of the Vickers hardness to 630 HV or less in the target of the present invention, for example, it is possible to suppress the amount of abrasion of the wafer by a milling machine, a lathe, or the like. That is, in the target material of the present invention, the cutting amount of the wafer gradually decreases as the cutting process progresses, and the difference in the size of the target material between the start of cutting and the end of cutting can be suppressed from increasing, and the damage of the wafer can also be suppressed.

In addition, by setting the average value of the Vickers hardness to 630 HV or less, the target of the present invention can be used for processing such as when it is clamped to a cutting machine and bonded to a backing plate or backing tube. Suppresses damage to the target body. In addition, for the same reason as described above, the target of the embodiment of the present invention preferably has an average Vickers hardness of 620 HV or less.

From the viewpoint of suppressing the deformation of the target material or the abrasion or breakage of the wafer by the cutting tool, as well as the abnormal discharge during sputtering, the Vickers hardness in the present invention refers to the splash of the target material. The average value of the Vickers hardness measured at any three locations on the plated surface is in the range of 550HV to 630HV.

In addition, the target of the present invention preferably has a structure including a TiW alloy having an average Vickers hardness in the range of 550 HV to 630 HV. In addition, from the viewpoint of setting the average value of the Vickers hardness to 602 HV to 620 HV, the target of the embodiment of the present invention is preferably free of Ti phase and W phase in the sputtering surface, that is, Ti phase and W phase. The area ratio is 0 area%. In addition, the area% of the present invention refers to the determination of the concentration of each element obtained by color mapping using a field emission-electron probe microanalyzer (FE-EPMA) The value derived from the distribution.

The target of the present invention has a composition containing 7% by mass to 13% by mass of Ti, and the remainder contains W and inevitable impurities. The content of Ti is defined as 7% by mass to 13% by mass in a range that does not greatly impair the diffusion barrier properties of the Al wiring and the Si substrate. In addition, for the same reason as described above, the Ti content is preferably in the range of 9% by mass to 11% by mass, and more preferably in the range of 10±0.5% by mass.

The target of the present invention can be obtained by the following manufacturing method, and its general form will be described. In addition, the present invention is not limited to the forms described below.

First, the Ti powder and the W powder are mixed so as to contain 7 mass% to 13 mass% Ti, and the remainder is W and inevitable impurities to obtain a mixed powder. Then, at room temperature (20±15°C defined in JIS Z 8703), the mixed powder is formed into a molded body using, for example, cold isostatic pressing (hereinafter referred to as “CIP”).

Next, after the shaped body is pulverized by, for example, a disk mill, etc., it is sieved to produce a pulverized powder of less than 1.5 mm. Then, the pulverized powder is pressure-sintered to obtain a TiW alloy sintered body, and the target material of the present invention can be obtained by machining the TiW alloy sintered body.

Pressure sintering can be applied to HIP or hot press (hereinafter referred to as "HP"), for example. In addition, the pressure sintering is performed under the conditions of a sintering temperature of 1500°C to 1600°C, an applied pressure of 20 MPa to 40 MPa, and a holding time of 1 hour to 10 hours. The setting of these conditions can be determined according to the specifications of the pressure sintering equipment, and the conditions of low temperature and high pressure are easily applied to HIP, and the conditions of high temperature and low pressure are easily applied to HP. In the present invention, it is preferable to apply HP to the pressure sintering. In addition to suppressing the formation of a pure Ti phase or a pure W phase, a high-density sintered body can also be obtained.

By setting the sintering temperature to 1500° C. or higher, sintering is promoted, and a high-density sintered body can be obtained. In addition, for the same reason as described above, the sintering temperature is preferably set to 1510° C. or higher. In addition, by setting the sintering temperature to 1600°C or less, in addition to being applicable to general-purpose pressure sintering equipment, the formation of crystal grains in the sintered body is also suppressed Long, can obtain a uniform fine structure. In addition, for the same reason as described above, the sintering temperature is preferably set to 1580° C. or lower.

By setting the pressure to 20 MPa or more, sintering is promoted, and a high-density sintered body can be obtained. In addition, by setting the pressure to 40 MPa or less, general-purpose pressure sintering equipment can be applied.

By setting the sintering time to 1 hour or more, sintering is promoted, and a high-density sintered body can be obtained. In addition, by setting the sintering time to 10 hours or less, it is possible to manufacture without hindering the manufacturing efficiency.

By increasing the relative density of the target material, the voids existing in the target material can be reduced, and the unevenness of hardness can be reduced, which helps to improve the machinability. In addition, by increasing the relative density of the target material, the bending resistance of the target material can be increased, which contributes to the suppression of damage to the target material during handling when clamped to a cutting machine or bonded to a back plate or back tube. Therefore, the target of the embodiment of the present invention preferably has a relative density exceeding 101.0%.

Here, the relative density in the present invention refers to the volume density measured by the Archimedes method divided by the mass ratio obtained based on the composition ratio of the target of the present invention. The theoretical density of the element monomers obtained by weighted average, and the value obtained by multiplying the obtained value by 100.

[Example]

Ti powder with a 50% particle size (hereinafter referred to as "D50") of a volume-based cumulative particle size distribution (hereinafter referred to as "D50") and W powder with a D50 of 4.5 μm contain 10% by mass of Ti and the remainder is W and inevitable To obtain mixed powder. Then, the mixed powder was filled in a mold made of rubber, and subjected to CIP treatment under a molding pressure of 2.0 ton/cm ² (≒196.133 MPa) to obtain a molded body.

Next, the shaped body obtained above was crushed and sieved using a disc mill to obtain crushed powder of less than 1.5 mm.

Then, the crushed powder was filled in a pressurized container made of C (carbon), the pressurized container was installed inside the furnace body of the HP device, and pressure sintering was performed under the conditions of 1520°C, 30 MPa, and 2 hours. A TiW alloy sintered body as a target of Example 1 of the present invention was obtained.

In addition, under the same conditions as described above, TiW alloy sintered bodies as targets of Inventive Example 2 to Inventive Example 10 were also obtained.

Ti powder having a D50 of 30 μm and W powder having a D50 of 4.5 μm are mixed so as to contain 10% by mass of Ti and the remainder is W and inevitable impurities to obtain a mixed powder. Then, the mixed powder was filled in a mold made of rubber, and subjected to CIP treatment under a molding pressure of 2.0 ton/cm ² (≒196.133 MPa) to obtain a molded body.

Next, the shaped body obtained above was crushed and sieved using a disc mill to obtain crushed powder of less than 1.5 mm.

The pulverized powder was filled in a soft steel pressurized container, vacuum degassed at a temperature of 450°C, and subjected to pressure sintering by HIP under the conditions of 1180°C, 100 MPa, and 2 hours to obtain a comparative example. TiW alloy sintered body of the target.

From the position of each sintered body obtained above as a sputtering surface, a test piece was taken by machining, and the Vickers hardness and relative density were measured. In addition, as this In the TiW alloy sintered bodies of samples No. 1 to No. 10 of the invention examples, it was confirmed that there was no abrasion or breakage of the wafer during the machining for forming the target shape. In addition, during the machining process, there is no fall-off of the TiW sintered body, so it is also possible to expect the suppression of abnormal discharge during sputtering. In addition, there is no case where the TiW sintered body is deformed or damaged during processing such as clamping with a cutting machine.

The Vickers hardness is based on JIS Z 2244, using MVK-E manufactured by Akashi Corporation, with a measurement load of 9.8N.

In addition, the relative density is a theory obtained by dividing the bulk density measured by the Archimedes method by the weighted average of element monomers calculated based on the mass ratio obtained from the composition ratio of each target. Density and multiply the value by 100. In addition, the measurement was carried out using an electronic hydrometer SD-120L manufactured by Kensei Industry Co., Ltd.

As shown in Table 1, Sample No. 11 as a comparative example is a metal structure in which the Ti phase shown in white part shown in FIG. 2 is dispersed in the W phase in a matrix, and it is confirmed that the Vickers hardness is lower than Soft part of 550HV.

On the other hand, Samples No. 1 to No. 10, which are Inventive Examples 1 to 10, included only the TiW alloy phase represented by the gray portion in FIG. 1, and there were no soft parts observed in Comparative Examples It can be confirmed that, in addition to adjusting the Vickers hardness to the range of 550HV to 630HV, the relative density also has a high value.

With this, the target of the present invention can be expected to suppress the deformation or damage of the target body in addition to the wear and damage of the wafer during machining.

A, B, C ‧‧‧ measuring point

Claims (4)

A TiW alloy target material, which contains 7 mass% to 13 mass% Ti, and the remainder contains W and inevitable impurities, and the average value of the Vickers hardness in the sputtering surface is 550HV to 630HV. The TiW alloy target as described in item 1 of the patent application scope, in which the Ti content is 9% by mass to 11% by mass. The TiW alloy target material according to item 1 or item 2 of the patent application scope, wherein the average value of the Vickers hardness is 602HV~620HV. A method for manufacturing a TiW alloy target, comprising: a step of obtaining a mixed powder by mixing Ti powder with W powder in such a manner as to contain 7 mass% to 13 mass% Ti and the remainder is W and inevitable impurities The step of pressing the mixed powder at normal temperature to obtain a shaped body; the step of crushing the shaped body and then sieving to obtain a crushed powder with a particle size of less than 1.5 mm; and the sintering temperature of 1500°C~ A step of obtaining a TiW alloy sintered body by pressing and sintering the pulverized powder under the conditions of 1600° C., an applied pressure of 20 MPa to 40 MPa, and a holding time of 1 hour to 10 hours.

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