WO2017154888A1 - イグニッションを安定化することが可能なスパッタリングターゲット - Google Patents
イグニッションを安定化することが可能なスパッタリングターゲット Download PDFInfo
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- WO2017154888A1 WO2017154888A1 PCT/JP2017/008959 JP2017008959W WO2017154888A1 WO 2017154888 A1 WO2017154888 A1 WO 2017154888A1 JP 2017008959 W JP2017008959 W JP 2017008959W WO 2017154888 A1 WO2017154888 A1 WO 2017154888A1
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
- C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3411—Constructional aspects of the reactor
- H01J37/3414—Targets
- H01J37/3423—Shape
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3411—Constructional aspects of the reactor
- H01J37/3414—Targets
- H01J37/3426—Material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3411—Constructional aspects of the reactor
- H01J37/3435—Target holders (includes backing plates and endblocks)
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3488—Constructional details of particle beam apparatus not otherwise provided for, e.g. arrangement, mounting, housing, environment; special provisions for cleaning or maintenance of the apparatus
- H01J37/3491—Manufacturing of targets
Definitions
- the present invention relates to a sputtering target capable of stably performing excitation and generation (also referred to as ignition, plasma ignition, or ignition) of initial plasma at the start of sputtering in sputtering.
- excitation and generation also referred to as ignition, plasma ignition, or ignition
- the wiring of a semiconductor integrated circuit is required to be thinned with each generation, and sputtering, which is a kind of physical vapor deposition, is used to form a thin film that becomes such wiring.
- sputtering which is a kind of physical vapor deposition
- magnetron sputtering in which plasma is controlled by electromagnetic force is often used.
- a target whose film forming process is stable and easy to control is indispensable.
- plasma ignition failure means a state in which plasma cannot be generated (ignition failure).
- a copper wiring is generally used as a wiring of a semiconductor integrated circuit, but in recent years, a sputtering target made of tantalum is often used to form a barrier film for the copper wiring. Since the barrier film is also applied to a wiring hole having a high aspect ratio (ratio of step depth to opening), the barrier film needs to be stably formed as an ultrathin film by controlling the film formation rate. Further, it is necessary to perform sputtering with high power in order to increase the sputtering yield, and a target with a low film formation rate that is advantageous for film thickness control under such conditions is desired. Such film formation control technology plays a part in the development of PVD.
- the tantalum target which is an example of the target for forming the barrier film described above, has a purity of 4N5 (99.995 wt%) from the viewpoint of versatility. In order to suppress an increase in current as much as possible, a product of purity 6N (99.9999 wt%) may be used substantially. In recent years, in order to increase the degree of freedom in wiring design, the use of such ultra-high purity materials is increasing.
- the target is softened by increasing the purity, and it may be difficult to control the quality of the target, such as inhomogeneous texture orientation after plastic working and crystal coarsening during recrystallization by heat treatment. .
- These problems can be solved to some extent by strictly controlling the manufacturing process of the target.
- the use environment of the target becomes more severe, and new problems are introduced. Problems may become apparent.
- a voltage is applied using a target as a cathode, and even electrons or primary electrons jumping out of the target are accelerated by an applied electric field and ionized and collided with introduced Ar gas atoms, thereby turning Ar into plasma, and Ar ions
- Ar ions Is a phenomenon in which the target is the cathode, collides, strikes out the target material, emits secondary electrons, and ionizes Ar again continuously. Ignition is required to generate it.
- the ignition condition of plasma follows the Paschen's law in principle.
- This law generally holds for the relationship between the discharge start voltage and the product of the distance between electrodes and the atmospheric pressure (pd product).
- the discharge start voltage that is, the minimum discharge voltage
- Patent Document 1 discloses a technique for suppressing fluctuation in the impedance of a cathode circuit by forming an annular groove such as a V-shape, an arc, or a square shape on a part of a target surface to increase the surface area of the target.
- Patent Document 2 discloses that a magnetic flux leakage groove is formed in the vicinity of a magnetic flux concentration region of a magnetic target used for magnetron sputtering, so that plasma is also applied to the periphery of the groove so that the effective erosion area of the target is reduced. Disclosure of technology intended for expansion
- Patent Document 3 by forming a plurality of inclined surfaces having a height of 1 to 10 mm on the target surface, ions are incident on the target surface obliquely to improve the film formation rate and to suppress the reattachment of particles to the sputtering surface.
- the technology is disclosed.
- Patent Document 4 by forming a recess in the outer peripheral portion where the plasma density on the target surface is low, foreign matter that easily accumulates at a portion where the plasma density is low adheres in the recess, preventing protrusion of the foreign matter from the surface, Disclosed is a technique for preventing an abnormal discharge from occurring between the two.
- Patent Document 5 discloses a technique for forming a distributed structure of imprint (uneven shape) by pressing a tool having a protrusion on a side surface of a target, and the structure tries to prevent falling or peeling of an adhered material. It is. Also in this document, the purpose of pressing and deforming the tool on the surface of the target is to prevent the falling and peeling of the deposit, and not to stabilize the initial ignition of the plasma. Naturally, specific pressing conditions, structures, and target characteristics suitable for stabilizing the initial ignition of plasma are not disclosed.
- the present invention has been made in view of the circumstances as described above, and in the initial plasma ignition (ignition) at the time of sputtering, there is no retry (reignition) due to defective ignition or stop of the apparatus, and the like. It is an object to provide a sputtering target capable of starting sputtering. In particular, it is an object of the present invention to provide a sputtering target capable of stably starting sputtering even under conditions that are disadvantageous to ignition such as a high-purity material and a reduction in introduced gas.
- the sputtering target of the present invention can reduce the ignition failure rate of ignition (plasma ignition) even under conditions such as reduction of introduced gas and shortened voltage application time, and can stably start a sputtering process. Make it possible. As a result, the downtime of the apparatus can be shortened, which can contribute to an improvement in throughput and cost performance.
- the sputtering target of the present invention has a flat portion and a tapered portion on the sputtering surface.
- the sputtering surface means a surface exposed to the plasma of the sputtering target.
- the taper portion means a portion that is chamfered between the outer peripheral end of the sputtering surface of the sputtering target and the side surface of the target, and is a portion that does not substantially contribute to film formation or contributes little.
- the flat part means a part of the sputtering surface that substantially contributes to film formation excluding the taper part.
- the flat part of the target that is perpendicular to the vertical line connecting the target and the target on which the film is to be formed by sputtering. This refers to the surface to be sputtered.
- the sputtering target of the present invention is characterized in that crystal strain processing is applied to the above-described taper portion of the sputtering surface.
- a KAM (Kernel Average Misoration) value can be used as an index.
- the taper portion has an average crystal strain of 0.5 ° or more as the KAM value. is there.
- the KAM value is obtained by analyzing the result of electron beam backscattering (EBSD) measurement, as will be described in detail later.
- EBSD electron beam backscattering
- the KAM value of the tapered portion is determined at a predetermined position of the tapered portion. Evaluation is based on the EBSD measurement result of the cross section.
- the KAM mapping image is obtained by measuring the KAM mapping image obtained from the EBSD measurement according to the present invention in order of 200 ⁇ m in the depth direction with a measurement range of 200 ⁇ m in the vertical direction (depth direction) and 1200 ⁇ m in the horizontal direction (direction parallel to the surface) It is calculated as an average value for each region divided every time, but in the present invention, “at least the surface portion of the taper portion has a crystal distortion of 0.5 ° or more on average as a KAM value” It means that the average KAM value calculated from the measurement range of 200 ⁇ m in length and 1200 ⁇ m in width closest to the surface in the cross section is 0.5 ° or more.
- Such a portion having a crystal distortion in the tapered portion is likely to cause an electron avalanche when generating plasma, and thus can greatly contribute to the generation and stabilization of ignition.
- the shape and energy level change that occurs when crystal strain is applied reduces the penetration depth when primary charged particles (Ar ions, electrons) enter the target,
- One factor is considered to be that it is possible to improve the probability of secondary electron emission because the energy of the primary charged particles propagates to electrons near the target surface.
- impurities and gas components are precipitated in the crystal grain boundary portion.
- the grain boundary portion where the impurities and gas components are deposited becomes a portion where the probability of secondary electron emission is locally increased compared to the surrounding structure, and discharge is promoted by promoting secondary electron emission from this portion. It can also be considered that the probability of occurrence can be improved.
- FIG. 1 shows the sputtering surface of the sputtering target, and the lower drawing of FIG. 1 shows a cross section of the sputtering target.
- FIG. 1 is merely one form for easy understanding, and the present invention is not limited by this form.
- the present invention includes various modifications other than those described below.
- Crystal strain is introduced at least into the taper portion on the sputtering surface side of the target, but it may be formed not only in the taper portion but also across flat portions and side surfaces.
- the target When the target is placed facing the wafer and the crystal strain is introduced into the flat part that is parallel to the wafer surface, it must be introduced into the part that is less involved in film formation (low erosion region). Is preferred.
- the sputter rate of the material differs depending on the crystal plane orientation, but the crystal grain orientation is disturbed in the crystal strain introduced portion, so the sputter rate is different compared to the crystal strain non-introduced portion. This is because if these both parts are mixed in the part contributing to the film formation on the flat surface, the uniformity of the film thickness is adversely affected.
- the amount of magnetic flux leakage may change at the crystal strain introduction portion, and the influence on the current-voltage change during film formation may increase.
- the region where no erosion occurs is where the primary charged particles (Ar ions, electrons) that contribute to the ignition do not enter the target or the amount of reattachment of the film is large. The effect is considered extremely low.
- crystal strain is introduced only to the taper part, or whether it is introduced across the taper part and the flat part, the taper part and the side surface, or the taper part, the flat part and the side surface, depends on the specifications of the sputtering apparatus. Therefore, it can be appropriately selected according to the specifications. In order to avoid the above-described problems related to film thickness uniformity and leakage magnetic flux, it is safe to introduce crystal strain only in the tapered portion.
- the sputtering target of the present invention has an average KAM value of 0.5 ° or more in at least the surface portion of the taper portion when evaluated using the KAM value as an index of crystal strain.
- the average KAM value on the surface of the tapered portion is preferably 1.0 ° or more, and more preferably 1.5 ° or more.
- the evaluation of the KAM value in the present invention is performed in order to prevent the KAM value from being evaluated excessively from the value reflecting the original crystal orientation due to the presence of the crystal grain boundary, and to increase the reliability of the measurement evaluation.
- the value is set to 5 °.
- an evaluation value of 5 ° or more is not obtained by the KAM value evaluation method of the present invention.
- the upper limit of a desirable KAM value that exhibits the effects of the present invention is 3 °.
- At least a depth of about 0.4 mm from the surface must have a crystal strain that is an average of 0.5 ° or more as a KAM value. Is desirable. If the depth of the portion having this crystal strain is insufficient, the number of sites such as grain boundaries that can be considered to contribute to stabilization of plasma ignition when erosion progresses is considered to be insufficient. Become.
- Crystal strain introduced into at least the taper can be introduced by any means capable of imparting strain to the crystal structure, and plastic deformation such as cold forging, rolling, pressing (pressing), etc. Machining, and in some cases, cutting under predetermined conditions can also be used.
- knurling with a press using a tool such as a pressing piece having a knurling-shaped protrusion can easily introduce crystal strain without greatly changing the target shape before and after processing, and the amount of strain to be introduced. Is preferable in that it can be controlled with relatively high accuracy.
- the amount of strain introduced can be controlled by processing conditions such as the pressing force and angle of the pressing piece, and the number of pressings.
- the optimum processing conditions for achieving a crystal strain of 0.5 ° or more on average as the KAM value on the surface of the tapered portion are different depending on the target material, the material of the tool, and the knurling shape of the tool.
- the knurling pitch is increased, the number of contact points per unit area is reduced. Therefore, when the pressing force is the same, the larger the pitch, the larger the amount of strain entering the target.
- a pressing piece having a knurling shape with a vertex angle of 30 to 120 ° and a pitch of 0.1 to 5 mm is pressed against the taper portion of the target with a pressing force of a cutting depth of 0.5 to 5 mm. Can do.
- the pattern of the pressing piece is transferred to the tapered portion at a depth corresponding to the pressing force, and a pattern in which the apex of the quadrangular pyramid is flat is formed.
- the processing is usually performed at room temperature without heating, but the essential purpose of the processing of the present invention is to control the amount of crystal strain on the surface to be processed.
- the processing may be performed under the condition of heating.
- the introduction of crystal strain into the taper portion of the target may be achieved by performing cutting processing of an arbitrary shape under the condition that an appropriate strain can be applied to the taper portion.
- cutting conditions suitable for the cutting tool to give intentional crystal strain to the taper part are set as compared with the case of performing simple cutting. It is necessary to keep in mind.
- the surface of the tapered portion Processing that introduces an average strain of 0.5 ° or more as the KAM value can be smoothly performed.
- the technique of the present invention can be suitably applied to a tantalum target having a purity of 4N5 (99.995%) or higher for forming a barrier film for copper wiring.
- purity 4N5 (99.995%) means that Ta ingot is analyzed by glow discharge mass spectrometry (GDMS), and Na, Al, Si, K, Ti, Cr, Mn, Fe, Co , Ni, Cu, Zn, Zr means that the total value is less than 50 wtppm.
- the KAM value as an index of the amount of crystal distortion is adjacent to a predetermined analysis pixel in an inverse pole mapping (IPF) image that is a crystal orientation mapping for each crystal grain obtained from EBSD. It is defined as a value obtained by calculating the average of the azimuth differences with all the pixels.
- IPF inverse pole mapping
- an observation sample 201 surrounded by a broken line is cut out from the taper portion, and the taper surface on the sample observation surface is cut out.
- the region 202 from the first to the predetermined depth of the hatched portion is measured by EBSD.
- the IPF image of the entire observation region obtained as a result is calculated according to the above-described definition, and converted into a KAM value spatial mapping image. If a crystal grain boundary portion is included in the extracted pixel at the time of calculating the KAM value, the KAM value calculated using the pixel becomes an extremely large value, which is originally based on the orientation difference of the crystal grains. As a result, an evaluation value that is not appropriate as a KAM value that should be calculated is calculated. Therefore, in order to eliminate such calculation errors due to crystal grain boundaries, in the present invention, as described above, the maximum KAM value is limited to 5 ° for evaluation.
- FIG. 2B is an example of the KAM mapping image of the part of FIG.
- the KAM mapping image is an image in which a local KAM value at a predetermined place is represented by a difference in color tone (shading on the drawing).
- the sputtering target of the present invention has a taper portion taper portion.
- the KAM value is larger toward the upper side of the surface closer to the surface, that is, the crystal strain introduced into the target structure is larger, and the crystal strain is relatively smaller at a certain depth or more. It is what.
- the sputtering target of the present invention shows a tendency that the KAM value gradually decreases in the depth direction from the surface of the tapered surface of the taper portion.
- evaluation is performed by setting an average KAM value evaluation region every 200 ⁇ m in the depth direction from the surface as shown in FIG.
- a direction perpendicular to the depth direction in the average KAM value evaluation region That is, the length in the direction along the tapered surface is set to 1200 ⁇ m, which is sufficiently longer than the depth direction.
- a rectangular region of 200 ⁇ m in the depth direction set in this way and 1200 ⁇ m in the direction along the tapered surface is defined as a unit region for evaluating the average KAM value in the present invention.
- the KAM value will be different for the same sample, but it is sufficient compared to the crystal grain in the SEM image observed by EBSD. It is common to perform KAM analysis with small pixels set (otherwise KAM values, which are quantities based on local grain orientation differences, are not accurately measured) and appropriate Those skilled in the art who are familiar with the provisions of standards and the like necessary for evaluating the crystal grain size and the like can appropriately set the observation field magnification and the like. Needless to say, the analysis in the present invention is appropriately set in consideration of them.
- the KAM value of the sample is evaluated after specifically performing the following processing.
- Surface treatment of sample for KAM value evaluation ⁇
- Place resin use resin that dissolves in acetone, etc. for accurate surface retention and load adjustment.
- the ignition stability at the time of ignition is evaluated by performing an ignition test according to the following procedure and conditions.
- Ignition test ⁇ First step "Gas stable" (5 sec) Ar gas is introduced at 5 sccm. ⁇ Second step “Ignition” (1 sec (5 sec until ignition)) While introducing 5 sccm of Ar gas, 1000 W is applied with a DC power source.
- Vacuum degree: 0.2 to 0.3 mTorr ⁇ 3rd step "evacuation” (10sec) A vacuum is drawn in the chamber (degree of vacuum: 1 to 3 ⁇ Torr). The ignition test is performed with the above three steps as one cycle.
- the success or failure of the ignition is determined based on whether or not the actual power is reached within 5 seconds from the start of application in the second step “ignition”. If the ignition is not successful within 5 seconds, the process returns to the beginning of the “ignition” in the second step, and the set power is applied again. If the ignition is not successful even after the application of the set power is repeated four times in the “ignition” of the second step, it is determined that the ignition has failed and the process is stopped.
- a conventional target serving as a comparative example was produced by the following procedure.
- a tantalum raw material having a purity of 99.995% or more was melted by electron beam and cast into an ingot.
- this ingot was cold-tightened and forged and then cut into a billet.
- the billet was cold-kneaded and forged and then recrystallized at 900 to 1000 ° C., and cold-kneaded and forged again and then recrystallized and annealed at 900 to 1000 ° C.
- the forged ingot is cold-rolled, subjected to strain relief and recrystallization heat treatment at 900 to 1000 ° C., and further, a workpiece rotation speed of 200 rev / min and a cutting depth of 0.2 mm / rev are applied to the outer periphery of the sputter surface.
- a taper portion was formed by lathe processing at, and a tantalum sputtering target having a diameter of 444 mm and a sputtering surface diameter of 406 mm was obtained.
- the final strain removal and recrystallization heat treatment has almost no distortion in the target material before the final processing, and a slight distortion is introduced into the tapered portion by the subsequent lathe processing of the normal tapered surface.
- no intentional crystal strain is introduced into either the sputtering surface or the side surface.
- the crystal distortion of the cross section of the taper portion of the target was analyzed by KAM value analysis by setting the maximum KAM value to 5 ° in units of 200 ⁇ m in length and 1200 ⁇ m in width in the same manner as in Example 1 described later. Even when taking an evaluation region up to 1 mm in the depth direction (5 unit regions from the surface to the depth direction), the crystal strain remains at an average KAM value of 0.41 ° to 0.46 °, The results were below 0.5 ° in all evaluation areas.
- the sample for performing EBSD measurement for the evaluation of the KAM value is a sample suitable for the measurement paying attention to the crystal strain by the surface treatment process of the KAM value evaluation sample described above as in the examples described later. It was. Next, the ignition stability was evaluated for the target by the ignition test described above, and the ignition failure rate of the ignition was examined. As a result, the ignition failure rate was 100%.
- Example 1 In a tantalum sputtering target having a diameter of 444 mm and a sputtering surface diameter of 406 mm manufactured in the same manner as in Comparative Example 1, a pressing piece having a knurling shape with an apex angle of 90 ° and a pitch of 2 mm is 1.0 mm on the outer periphery of the sputtering surface. Intentional crystal strain was introduced into the tapered portion of the sputtering target by performing a knurling process of pressing with a pressing force. A photograph of this target is shown in FIG. 4 (the left is an overall view and the right is an enlarged view of a tapered portion). A lattice shape was formed in the tapered portion by this pressing process.
- the sample for performing EBSD measurement for the evaluation of the KAM value is obtained by appropriately performing the mirror polishing of the surface and the chemical etching process by the surface treatment process of the value evaluation sample for the KAM value described above. It was set as the sample suitable for the measurement which paid its attention to.
- the crystal distortion of the cross section of the taper portion was evaluated by KAM value analysis using EBSD with the maximum KAM value set to 5 ° in units of 200 ⁇ m in length and 1200 ⁇ m in width.
- a region having an average KAM value of 0.5 ° or more set as an effective crystal strain amount in the invention is a region from the surface to a depth of 1.4 mm (seven unit regions from the surface to the depth direction).
- the measurement evaluation of the KAM value is performed using a crystal orientation analyzer OIM6.0-CCD / BS manufactured by TSL (the same applies to the above-described comparative example and the following examples).
- the ignition stability was evaluated for the target by the ignition test described above, and the ignition failure rate of ignition ((number of ignition failures / number of times of ignition) ⁇ 100) was examined.
- the ignition failure rate was 12%, and the ignition characteristics were significantly improved as compared with the target (Comparative Example 1) having no crystal distortion in the tapered portion.
- Example 2 In a tantalum sputtering target (purity of 4N5 or more) having a diameter of 444 mm and a sputter surface diameter of 406 mm manufactured in the same manner as in Comparative Example 1, a pressing piece having a knurling shape with a vertex angle of 90 ° and a pitch of 1 mm is formed on the outer periphery of the sputter surface.
- a pressing piece having a knurling shape with a vertex angle of 90 ° and a pitch of 1 mm is formed on the outer periphery of the sputter surface.
- a lattice shape was formed in the tapered portion by this pressing process.
- the crystal distortion effective in the present invention was determined by analyzing the crystal distortion of the cross section of the taper portion using EBSD in the same manner as in Example 1 and setting the maximum KAM value to 5 ° in units of 200 ⁇ m in length and 1200 ⁇ m in width.
- a region having an average KAM value of 0.5 ° or more set as a strain amount is a region from the surface to a depth of 0.8 mm (four unit regions from the surface to the depth direction), and the average KAM value in this region is 0. It was 5 ° to 2.2 °.
- sputtering was performed on the target under the same conditions as in Example 1, and the ignition failure rate of the ignition was examined by the same evaluation method as in Example 1. As a result, the ignition failure rate was 17%. A significant improvement in the ignition characteristics was observed.
- Example 3 In a tantalum sputtering target (purity 4N5 or more) having a diameter of 444 mm and a sputter surface diameter of 406 mm manufactured in the same manner as in Comparative Example 1, a V-shaped cross-sectionally processed groove is concentrically formed by lathe processing on the tapered portion on the outer periphery of the sputter surface. Formed. At this time, lathe machining was performed with a workpiece rotation speed of 200 rev / min and a cutting depth of 0.5 mm / rev, with a groove width of 2 mm, a depth of 2 mm, and a groove length of an outer circumference of about 1294 mm and an inner circumference of about 1281 mm.
- the crystal distortion effective in the present invention was determined by analyzing the crystal distortion of the cross section of the taper portion using EBSD in the same manner as in Example 1 and setting the maximum KAM value to 5 ° in units of 200 ⁇ m in length and 1200 ⁇ m in width.
- a region having an average KAM value of 0.5 ° or more set as a strain amount is a region from the surface to a depth of 0.4 mm (two unit regions from the surface to the depth direction), and the average KAM value in this region is 0. It was 5 ° to 1.1 °.
- sputtering was performed on the target under the same conditions as in Example 1, and the ignition failure rate of the ignition was examined by the same evaluation method as in Example 1. As a result, the ignition failure rate was 43%.
- the sputtering target of the present invention can reduce the ignition failure rate of ignition (plasma ignition) even under conditions such as reduction of introduced gas and shortened voltage application time, and can stably start a sputtering process. Make it possible. Thereby, the downtime of the apparatus can be shortened, which can contribute to an improvement in throughput and cost performance.
- the sputtering target of the present invention is useful for forming a thin film for electronic devices.
- Target body 101 Sputter surface flat portion 102 Sputter surface taper portion 110 Backing plate 210 Target body 211 Backing plate
Abstract
Description
1)スパッタ面にフラット部とテーパ部を備えたスパッタリングターゲットにおいて、前記テーパ部の少なくとも表面部分がKAM値として平均0.5°以上の結晶歪を有することを特徴とするスパッタリングターゲット、
2)前記テーパ部のKAM値として平均0.5°以上の結晶歪を有する領域が表面から深さ0.4mm以上の領域に達していることを特徴とする前記1)に記載のスパッタリングターゲット、
3)前記KAM値として平均0.5°以上の結晶歪を有する部分が前記テーパ部のみであることを特徴とする前記1)または2)に記載のスパッタリングターゲット、
4)前記テーパ部の結晶歪を有する部分の形状が最大深さ500μm、幅1mm以下、ピッチ2mm以下のナーリング形状であることを特徴とする前記1)~3)のいずれか一に記載のスパッタリングターゲット、
5)純度4N5以上のタンタルからなることを特徴とする前記1)~4)のいずれか一に記載のスパッタリングターゲット。
(KAM値の値評価用試料の表面処理)
・切断機を使い、EBSD測定に適した大きさにサイズに調整
・正確な面保持と荷重調整のため、樹脂込め(アセトン等で溶解する樹脂を使用)
・以下の機械研磨により、表層部の凸凹、傷および加工変質層を除去
-面出し、面削りによる粗研磨(耐水ぺーパー)
-バフによる精密研磨1(9μm、3μm、1μm ダイヤモンド粒子)
-バフによる精密研磨2(0.1μm、0.05μm コロイダルシリカ)
・樹脂溶解、試料取り出し
・ケミカルエッチング液(フッ酸、硝酸、塩酸の混合液)で表面処理
・アセトンもしくはエタノールで超音波洗浄を施し研磨剤等を洗浄
(点火試験)
・第1ステップ「ガス安定」(5sec)
Arガスを5sccm導入する。
・第2ステップ「イグニッション」(1sec(点火まで5sec))
Arガスを5sccm導入したまま、DC電源で1000W印加する。
(真空度:0.2~0.3mTorr)
・第3ステップ「真空引き」(10sec)
チャンバ内の真空引きを行う(真空度:1~3μTorr)。
上記3ステップを1サイクルとして、点火試験を実施する。イグニッションの成否は、第2ステップの「イグニッション」において、印可開始から5sec以内に実電力に到達したかで判断する。5sec以内にイグニッションが成功しなかった場合、第2ステップの「イグニッション」の始めに戻り、設定電力を再度印加する。この第2ステップの「イグニッション」で設定電力の印加を4回繰り返してもイグニッションが成功しない場合は点火失敗と判断し、処理を停止する。
まず、比較例となる従来型のターゲットを以下の手順により作製した。純度99.995%以上のタンタル原料を電子ビーム溶解し、これを鋳造してインゴットとした。次に、このインゴットを冷間で締め鍛造した後切断し、ビレットとした。このビレットを冷間でこねくり鍛造した後900~1000℃で再結晶焼鈍し、再度冷間こねくり鍛造した後900~1000℃で再結晶焼鈍を実施した。次に、鍛造インゴットを冷間圧延し、900~1000℃での歪取り兼再結晶熱処理を行い、さらにスパッタ面の外周部にワーク回転速度200rev/min、切込み深さ0.2mm/revの条件での旋盤加工によってテーパ部を形成し、直径444mm、スパッタ面の直径が406mm、のタンタルスパッタリングターゲットとした。このターゲットでは、最後の歪取り兼再結晶熱処理により、最終加工前のターゲット素材では殆ど歪が無い状態となっており、その後の通常のテーパ面の旋盤加工よってテーパ部に僅かな歪が導入されるとは考えられるものの、それ以外にはスパッタ面、側面のいずれにも意図的な結晶歪を導入していないものである。
比較例1と同様に作製した直径444mm、スパッタ面の直径が406mmのタンタルスパッタリングターゲットにおいて、スパッタ面外周のテーパ部に、頂点角度90°、2mmピッチのナーリング形状を有する押し付け駒を1.0mmの押し付け力で押し付けるナーリング加工を行うことにより、スパッタリングターゲットのテーパ部に意図的な結晶歪を導入した。このターゲットの写真を図4(左は全体図、右はテーパ部拡大図)に示す。この押し付け加工によりテーパ部には格子形状が形成された。そして、このテーパ部より、EBSD測定を行い、KAM値の評価を行う試料を準備した。KAM値の評価のためにEBSD測定を行うための試料は、前述したKAM値の値評価用試料の表面処理工程により、表面の鏡面研磨+ケミカルエッチング処理を適切に行うことで、本来の結晶歪に着目した測定に適した試料とした。
比較例1と同様に作製した直径444mm、スパッタ面の直径が406mmのタンタルスパッタリングターゲット(純度4N5以上)において、スパッタ面外周のテーパ部に、頂点角度90°、1mmピッチのナーリング形状を有する押し付け駒を0.5mmの押し付け力で押し付けるナーリング加工を行うことにより、スパッタリングターゲットのテーパ部に意図的な結晶歪を導入した。この押し付け加工によりテーパ部には格子形状が形成された。このテーパ部断面の結晶歪を、実施例1と同様にEBSDを用い、縦200μm、横1200μm単位で最大KAM値を5°に設定してKAM値分析を行ったところ、本発明において有効な結晶歪量として設定される平均KAM値0.5°以上の領域は表面から深さ0.8mmまでの領域(表面から深さ方向へ4つの単位領域)であり、この領域における平均KAM値は0.5°~2.2°であった。次に、このターゲットに対して実施例1と同じ条件でスパッタリングを実施し、実施例1と同じ評価法でイグニッションの点火失敗率を調べたところ、点火失敗率は17%であり、この例でもイグニッション特性の大きな向上が見られた。
比較例1と同様に作製した直径444mm、スパッタ面の直径が406mmのタンタルスパッタリングターゲット(純度4N5以上)において、スパッタ面外周のテーパ部に、断面V字型の加工溝を旋盤加工にて同心円状に形成した。この際、ワーク回転速度200rev/min、切込み深さ0.5mm/revの条件で、溝の幅は2mm、深さは2mm、溝の長さは外周約1294mm、内周約1281mmとした旋盤加工を行うことにより、スパッタリングターゲットのテーパ部に意図的な結晶歪を導入した。このテーパ部断面の結晶歪を、実施例1と同様にEBSDを用い、縦200μm、横1200μm単位で最大KAM値を5°に設定してKAM値分析を行ったところ、本発明において有効な結晶歪量として設定される平均KAM値0.5°以上の領域は表面から深さ0.4mmまでの領域(表面から深さ方向へ2つの単位領域)であり、この領域における平均KAM値は0.5°~1.1°であった。次に、このターゲットに対して実施例1と同じ条件でスパッタリングを実施し、実施例1と同じ評価法でイグニッションの点火失敗率を調べたところ、点火失敗率は43%であった。
101 スパッタ面フラット部
102 スパッタ面テーパ部
110 バッキングプレート
210 ターゲット本体
211 バッキングプレート
Claims (5)
- スパッタ面にフラット部とテーパ部を備えたスパッタリングターゲットにおいて、前記テーパ部の少なくとも表面部分が、KAM値として平均0.5°以上の結晶歪を有することを特徴とするスパッタリングターゲット。
- 前記テーパ部のKAM値として平均0.5°以上の結晶歪を有する領域が表面から深さ0.4mm以上の領域に達していることを特徴とする請求項1に記載のスパッタリングターゲット。
- 前記KAM値として平均0.5°以上の結晶歪を有する部分が前記テーパ部のみであることを特徴とする請求項1または2に記載のスパッタリングターゲット。
- 前記テーパ部の結晶歪を有する部分の形状が最大深さ500μm、幅1mm以下、ピッチ2mm以下のナーリング形状であることを特徴とする請求項1~3のいずれか一項に記載のスパッタリングターゲット。
- 純度4N5以上のタンタルからなることを特徴とする請求項1~4のいずれか一項に記載のスパッタリングターゲット。
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SG11201807455XA SG11201807455XA (en) | 2016-03-09 | 2017-03-07 | Sputtering target capable of stabilizing ignition |
KR1020187026267A KR102224969B1 (ko) | 2016-03-09 | 2017-03-07 | 이그니션을 안정화하는 것이 가능한 스퍼터링 타깃 |
JP2018504500A JP6496879B2 (ja) | 2016-03-09 | 2017-03-07 | イグニッションを安定化することが可能なスパッタリングターゲット |
CN201780015348.XA CN108779554B (zh) | 2016-03-09 | 2017-03-07 | 能够使点燃稳定的溅射靶 |
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SG11201807455XA (en) | 2018-09-27 |
US11193199B2 (en) | 2021-12-07 |
KR20180110109A (ko) | 2018-10-08 |
TW201738402A (zh) | 2017-11-01 |
EP3406756A1 (en) | 2018-11-28 |
EP3406756A4 (en) | 2019-09-18 |
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