A method for estimating the service life of a planar sputtering target with a back plate

Abstract

The application discloses a kind of backplate's plane sputtering target service life estimation method, mainly for the whole original thickness is relatively thin, after separating unbinding, easy to produce warping, target edge does not sputter or almost does not sputter backplate's plane sputtering target material.The specific method is to separate sputtering target and backplate by heating, to determine the deepest sputtering track of sputtering target by mold silica gel, to the difference between the maximum edge thickness and the minimum thickness of the deepest sputtering track as the maximum thickness difference, and to use it as a reference to estimate the remaining minimum thickness consumption sputtering power consumption, and then to estimate the service life of sputtering target.The method of the application is simple to operate, suitable for manufacturers without precision measuring instruments such as three-coordinate instrument and three-dimensional scanner, providing guidance for the estimation of the service life of backplate's plane target, and ensuring the safe use of sputtering target.

Description

Technical Field

[0001] This invention belongs to the field of magnetron sputtering and relates to a method for estimating the service life of a planar sputtering target with a backplate. Background Technology

[0002] Magnetron sputtering is a type of physical vapor deposition (PVD). It has advantages such as simple equipment, easy control, large coating area, and strong adhesion, and is widely used in the preparation of various materials such as metals, semiconductors, and insulators.

[0003] As a key raw material for magnetron sputtering, the target material is preferentially sputtered by ions on the surface of the target material during planar magnetron sputtering due to the effect of orthogonal electromagnetic fields on sputtered ions. This forms sputtering trenches and produces uneven etching on the sputtered surface. In specific tracks or areas, sputtering will occur preferentially, forming the deepest sputtering track of the sputtering target. Once these areas are penetrated, the target material is scrapped.

[0004] For most planar sputtering targets, they are typically bonded to a backplate, which serves purposes such as fixing the target and dissipating heat. If sputtering continues after the target has been penetrated, it will further sputter onto the backplate material, causing contamination of the sputtered coating product and damage to the backplate or even the equipment.

[0005] For planar targets such as precious metal or magnetic targets, the initial thickness is typically 1-5 mm, considering both cost reduction and improved magnetic permeability. Due to this thinness, the remaining thickness during actual use is often even lower than for other targets, in order to improve efficiency. Therefore, a simple and quick way to determine the remaining thickness of the preferred sputtering area and predict the target's lifespan is essential to avoid product scrap and reduce production costs.

[0006] CN103572222A discloses a method for determining the sputtering lifetime of a sputtering target. The method involves determining a linear relationship between sputtering power consumption and the minimum remaining thickness of the target; setting a standard remaining thickness for the target; and substituting the standard remaining thickness into the linear relationship to determine the sputtering lifetime of the target. The patent uses a coordinate measuring machine to measure the remaining thickness at points along two mutually perpendicular directions, and the lowest point on the two curves is taken as the minimum remaining thickness of the target. However, this method has a small sample size, and the selected lowest points along the two mutually perpendicular directions cannot represent the minimum remaining thickness of the target. If more samples are needed, other side profiles need to be measured, resulting in low efficiency. Furthermore, this method is only applicable to circular targets.

[0007] CN105525264A discloses a method for obtaining the remaining sputtering time of a target material. The method provides a target material with a known initial thickness; partially sputters the target material and records the sputtering time; measures the remaining thickness of the target material after partial sputtering to obtain a minimum remaining thickness, and obtains a maximum sputtering thickness based on the minimum remaining thickness; the remaining sputtering time of the target material is obtained based on the product of the initial thickness and the sputtering time, and the ratio of the product to the maximum sputtering thickness. This method is only applicable to rectangular and circular targets and requires calculation based on a known initial thickness. In actual production, the thickness of most planar bonding targets is a theoretical thickness calculated based on weight, without an accurate initial thickness value, and the original target material thickness may vary at different locations.

[0008] CN111428417A discloses a method for predicting the lifespan of a sputtering target. This method uses 3D scanning to acquire morphological images of the target before and after sputtering. A surface erosion curve is generated by combining these two images. The original thickness and minimum remaining thickness of the target are obtained from the surface erosion curve. A functional relationship is constructed between the minimum remaining thickness, sputtering power consumption, and the original thickness of the target. The lifespan of the target is then predicted using this functional relationship. This method calculates the lifespan by superimposing the back surface morphological curves before and after sputtering, requiring the back surfaces of the target to be completely superimposed before and after sputtering.

[0009] CN116222465A discloses a method for testing the minimum remaining thickness of a pot-shaped target and a method for predicting its lifetime. The method uses a three-angle coordinate measuring machine to measure the simulated curve of the unsputtered target and the surface erosion curve of the pot-shaped target after sputtering. Then, based on the simulated curve of the unsputtered target and the surface erosion curve of the pot-shaped target after sputtering, the closest point is determined. The minimum remaining thickness is calculated based on the closest point. The lifetime of the target is predicted based on the correspondence between the actual thickness used and the sputtering power consumption. This method also requires the acquisition of original target size information for modeling and is suitable for situations where the target surface or non-sputtered surface should have consistent or good overlap before and after sputtering.

[0010] CN111060044A discloses a method for measuring the thickness of weldable target materials using a water-immersion C-scan device. This method utilizes C-scan software and ultrasonic longitudinal wave pulse reflection technology, taking the interface wave peak position as the starting point. The sound velocity of the target material is measured using a known target blank thickness. After subsequent bonding with a backing plate and processing, or after magnetron sputtering, the thickness of the target material at this point is measured using the already measured sound velocity. However, this method requires point-by-point measurement, necessitating accurate positioning of the lowest point of the sputtering trajectory. Furthermore, it introduces a certain degree of error compared to actual measurements, making it unsuitable for measuring thickness values ​​required for life assessment.

[0011] In summary, the above methods for assessing the lifespan of planar sputtering targets with backplates have the following three problems: ① Existing methods generally rely on measuring instruments such as coordinate measuring machines (CMMs) and 3D scanners to measure the dimensional data of the target before and after sputtering. However, in actual use, planar sputtering targets are usually bound to a backplate, making it impossible to obtain thickness information directly. The thickness difference before and after sputtering can only be obtained through surface erosion curves when the sputtering surfaces do not overlap. Furthermore, the high cost and portability of the aforementioned dimensional measurement equipment limit the data collection required for lifespan assessment by ordinary manufacturers. ② Before sputtering, to ensure high-quality sputtering surfaces, contact measurement operations should be avoided as much as possible. In addition, since the planar sputtering target is still bound to the backplate at this time, it is generally impossible to accurately obtain the thickness data before sputtering. The theoretical thickness value or C-scan measurement value is usually used. However, the problem of confirming the location of the lowest point of the track thickness during C-scan thickness measurement remains unresolved. Additionally, the original thickness of the target varies at different locations, making it unreasonable to use the theoretical thickness or C-scan measurement value as a reference. ③ For planar targets such as precious metal targets or magnetic targets, considering the reduction of target material costs and the improvement of magnetic permeability, the original thickness of the target material is generally 1-5mm. Due to the thin overall thickness, warping is likely to occur after unbinding due to stress release and other reasons, which affects the flatness of the bonding surface after unbinding. Therefore, the method of comparing the difference of the surface erosion curve of the sputtered surface by overlapping the morphological trajectory of the non-sputtered surface before and after sputtering is not applicable.

[0012] Based on existing methods for assessing the service life of sputtering targets, it is of great significance to develop a method for predicting the service life of planar sputtering targets with backplates. Summary of the Invention

[0013] To address the shortcomings of existing technologies, this invention provides a method for estimating the lifespan of a planar sputtering target with a backplate. The backplate is separated from the target, and the deepest sputtering trajectory after sputtering is confirmed using mold silicone. The thickness of the deepest sputtering trajectory and the edge path thickness are measured using a micrometer. The maximum edge thickness is taken as the original thickness of the sputtering target, and the minimum thickness of the deepest sputtering trajectory is taken as the remaining thickness of the target. The maximum thickness difference of the sputtering target is obtained. This maximum thickness difference is used as a reference for the maximum consumed thickness during sputtering to estimate the sputtering power consumption of the remaining thickness, thereby predicting the target's lifespan. This method extracts thickness data from the target after separation from the backplate, reducing the steps of pre-sputtering thickness measurement or solving the problem of unmeasurable pre-sputtering thickness. The method of using mold silicone to locate the lowest remaining thickness of the target is fast and accurate. The measurement method is simple and effective, and the obtained consumed thickness value is more reasonable. Using this value as a reference, the obtained sputtering lifespan is more reliable. This method is suitable for estimating the lifespan of a planar sputtering target with a backplate, providing manufacturers without coordinate measuring machines, 3D scanners, or other testing equipment with the possibility of independently predicting the lifespan of this type of target.

[0014] The above-mentioned objective of the present invention is achieved as follows:

[0015] A method for estimating the service life of a planar sputtering target with a backplate includes the following steps:

[0016] 1. Separation of backplate and sputtering target: The sputtering target and backplate are separated by heating. After separation, the solder on the back of the sputtering target is removed.

[0017] 2. Confirmation of the deepest sputtering track: Inject liquid silicone from the mold into the sputtering track of the target material. After the silicone solidifies, remove the solid silicone and place it horizontally. Use ink pad to lightly contact the protruding part of the silicone. Then, put the silicone back into the sputtering track of the target material in its original position and press it lightly. The area that is stained with ink pad is the deepest sputtering track. The mold silicone should be made of a material with a hardness of 50-70 degrees.

[0018] 3. Confirmation of measurement data points for edge and deepest sputtering track: Use a needle micrometer to measure the thickness data of the edge and deepest sputtering track. The more measurement points, the better. When the area with ink stains on the deepest sputtering track is a point, the thickness data must be included in the measurement. When the area with ink stains is a line or a surface, the measurement points are evenly distributed.

[0019] 4. Measure the thickness data of multiple edges of the sputtering target and the thickness data of multiple deepest sputtering tracks of the sputtering target: Use a needle micrometer to measure the thickness of the edges and the deepest sputtering tracks. During measurement, keep the micrometer caliper perpendicular to the measuring surface and move the needle slightly back and forth and left and right near the test point to ensure that the value obtained when measuring the edge thickness is the largest value near the test point or the value obtained when measuring the deepest sputtering track thickness is the smallest thickness value near the test point.

[0020] 5. Target sputtering lifetime estimation: The sputtering power consumption of the sputtering target at the time of unbinding is x1. After unbinding, the maximum thickness value y1 of each point on the edge of the target is measured, the minimum thickness value y2 of each point on the deepest sputtering track is measured, the maximum thickness consumed by sputtering on the sputtering surface is y1-y2, and the maximum thickness consumed per unit power consumption is (y1-y2) / x1. Then the power consumption after sputtering at the minimum remaining thickness of the target is x2=y2 / ((y1-y2) / x1), where x2 represents the remaining lifetime of the target in terms of sputtering power consumption. The total lifetime of the target is x1+x2=x1+y2 / ((y1-y2) / x1).

[0021] Furthermore, the original sputtering target and backplate are connected by brazing and polymer welding. The backplate and target are separated by heating. After the target and backplate are separated, the solder on the surface of the sputtering target is first scraped off with a silicone block. Then, a triangular wire drawing machine is used to treat the back surface with 100-200 grit sandpaper to remove any remaining solder.

[0022] Furthermore, when separating the backplate from the sputtering target, high-temperature tape is applied to the sputtering surface of the target, and the target is placed face down in a bonding furnace for heating. After the solder melts, the backplate is separated from the sputtering target.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) This invention does not rely on expensive measuring instruments such as coordinate measuring machines and 3D scanners. The method of determining the deepest sputtering track position by molding silicone is fast and accurate, and simple to operate. It is suitable for manufacturers to independently estimate the service life of planar sputtering targets with backplates.

[0025] (2) In this invention, the backplate and the target of a planar sputtering target with a backplate are separated by heating. The maximum value of the edge thickness of the sputtering target after separation is taken as the original sputtering target thickness, and the minimum value of the thickness of the deepest sputtering track is taken as the remaining thickness of the target. The difference between the two is the maximum thickness difference, which is taken as the maximum sputtering consumption thickness. This method is more reasonable than calculating the maximum sputtering consumption thickness based on the theoretical thickness or average thickness of the original target. The target life prediction is safer and more accurate. Attached Figure Description

[0026] Figure 1 Example 1 of this invention obtains the deepest sputtering trajectory of a nickel-platinum target.

[0027] Figure 2 : Schematic diagram of the edge measurement point and the deepest sputtering trajectory measurement point of the nickel-platinum target in Embodiment 1 of the present invention.

[0028] Figure 3 Example 2 of this invention obtains the deepest sputtering trajectory of the platinum target.

[0029] Figure 4 : Schematic diagram of the measurement points at the edge of the platinum target and the measurement point at the deepest sputtering trajectory in Embodiment 2 of the present invention.

[0030] Figure 5 : Cross-sectional view of the planar sputtering target with backplate of the present invention after untying. Detailed Implementation

[0031] The present invention will be further illustrated below through specific implementation examples, but this does not limit the present invention in any way. Any changes or improvements made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0032] Example 1

[0033] This embodiment provides a method for estimating the service life of a planar sputtering target with a backplate, including:

[0034] Step (1): Separate the backplate of a circular planar nickel-platinum sputtering target with a backplate from the sputtering target (the theoretical thickness of the nickel-platinum target is 3mm, and the sputtering power consumption of the target is 90kWh): Use high-temperature tape to stick to the sputtering surface of the nickel-platinum target, place the sputtering surface of the nickel-platinum target downwards in the bonding heating furnace for heating, and after the solder is heated and melted, separate the backplate from the nickel-platinum sputtering target. Use a silicone block to initially scrape off the solder on the nickel-platinum welding surface. After the nickel-platinum target cools down, remove the high-temperature tape. Finally, use a triangular wire drawing machine to perform surface treatment on the welding surface of the nickel-platinum target to remove the solder that has not been scraped off. The surface treatment uses sandpaper with a grit of 150.

[0035] Step (2), confirmation of the deepest sputtering trajectory of the nickel-platinum target: Inject liquid mold silicone into the sputtering trajectory of the separated nickel-platinum target. After the silicone solidifies, remove the solid silicone and place it horizontally. Lightly contact the protruding parts of the silicone with ink pad, and then place the silicone back into the sputtering trajectory of the nickel-platinum target in its original position. The area where the ink pad is applied is the deepest sputtering trajectory. The mold silicone is selected from materials with a hardness of 60 degrees. The deepest sputtering trajectory of the nickel-platinum target is obtained as follows: Figure 1 .

[0036] Step (3), confirmation of measurement data points for the edge and deepest sputtering track of the nickel-platinum target: Use a micrometer to measure the thickness data of the edge and the deepest sputtering track. Select 20 points evenly distributed along the circumference to measure the edge thickness. Include the points with ink residue on the deepest sputtering track in the measurement. Divide the line with ink residue and take points for measurement, for a total of 20 points. Measure the thickness data of multiple deepest sputtering tracks of the sputtering target: Use a micrometer to measure the thickness of the edge and the deepest sputtering track. During measurement, keep the micrometer caliper perpendicular to the measuring surface. Slightly move the caliper tip back and forth and left and right near the test point to ensure that the value obtained when measuring the edge thickness is the largest value near that test point or the value obtained when measuring the deepest sputtering track thickness is the smallest thickness value near that test point. The thickness measurement data is shown in Table 1. A schematic diagram of the measurement points for the edge and the deepest sputtering track of the nickel-platinum target is shown below. Figure 2 .

[0037] Table 1

[0038]

[0039]

[0040] Step (4), target sputtering lifetime estimation: the sputtering power consumption of the nickel-platinum sputtering target when untied is x1 = 90kWh. After untiing, the maximum thickness value of each point on the edge of the nickel-platinum target is measured as y1 = 3.122mm, and the minimum thickness value of each point on the deepest sputtering track is y2 = 1.245mm. The maximum thickness consumed by sputtering on the nickel-platinum sputtering surface is y1-y2 = 3.122-1.245 = 1.877mm. Then the power consumption (remaining lifetime, expressed as sputtering power consumption) after sputtering at the minimum remaining thickness of the nickel-platinum target is x2 = y2 / ((y1-y2) / x1) = 59.7kWh. The total lifetime of the nickel-platinum target is x1 + x2 = x1 + y2 / ((y1-y2) / x1) = 149.7kWh.

[0041] Example 2

[0042] This embodiment provides a method for estimating the service life of a planar sputtering target with a backplate, including:

[0043] Step (1): Separate a rectangular planar platinum sputtering target backplate from the sputtering target (the theoretical thickness of the platinum target is 4mm, and the sputtering power consumption of the target is 5400kWh): Use high-temperature tape to stick to the sputtering surface of the platinum target, place the platinum target with the sputtering surface facing down in the bonding heating furnace for heating, and after the solder is heated and melted, separate the backplate from the platinum sputtering target. Use a silicone block to initially scrape off the solder on the nickel-platinum welding surface. After the platinum target cools down, remove the high-temperature tape. Finally, use a triangular wire drawing machine to perform surface treatment on the welding surface of the platinum target to remove the solder that has not been scraped off. The surface treatment uses 200 grit sandpaper.

[0044] Step (2), confirmation of the deepest sputtering trajectory of the platinum target: Inject liquid mold silicone into the separated platinum target sputtering trajectory. After the silicone solidifies, remove the solid silicone and place it horizontally. Lightly contact the protruding part of the silicone with ink pad. Then, place the silicone back into the target sputtering trajectory in its original position and press it lightly. The area that is stained with ink pad is the deepest sputtering trajectory. The mold silicone is selected with a hardness of 70 degrees. The obtained deepest sputtering trajectory is as follows: Figure 3 .

[0045] Step (3), confirmation of measurement data points for the edge and deepest sputtering track of the platinum target: The thickness data of the edge and deepest sputtering track are measured using a needle micrometer. The edge thickness is measured at 20 points evenly distributed along both the length and thickness directions. The ink points on the deepest sputtering track are included in the measurement. The lines with ink are measured at 20 points evenly distributed. Measurement of multiple deepest sputtering track thickness data of the sputtering target: The thickness of the edge and deepest sputtering track is measured using a needle micrometer. During measurement, the micrometer caliper should be kept perpendicular to the measuring surface. The needle tip should be slightly moved back, forth, left, and right near the test point to ensure that the value obtained when measuring the edge thickness is the largest value near the test point or the value obtained when measuring the deepest sputtering track thickness is the smallest thickness value near the test point. The thickness measurement data is shown in Table 2. The schematic diagram of the edge measurement points and deepest sputtering track measurement points of the platinum target is shown in Table 2. Figure 4 .

[0046] Table 2

[0047]

[0048] Step (4), estimated sputtering lifetime of platinum target: The sputtering power consumption of the sputtering target when untied is x1 = 5400 kWh. After untiing, the maximum thickness value of each point on the edge of the target is y1 = 4.134 mm, the minimum thickness value of each point on the deepest sputtering track is y2 = 1.072 mm, and the maximum thickness consumed by sputtering on the sputtering surface is y1-y2 = 4.134-1.072 = 3.062 mm. Then the power consumption (remaining lifetime, expressed as sputtering power consumption) after sputtering at the minimum remaining thickness of the target is x2 = y2 / ((y1-y2) / x1) = 1890.5 kWh, and the total lifetime of the target is x1+x2 = x1+y2 / ((y1-y2) / x1) = 7290.5 kWh.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that step (1) did not use a silicone block to initially scrape off the solder on the nickel-platinum welding surface and the residual solder after the subsequent triangular wire drawing machine surface treatment. Therefore, the edge and track data of the nickel-platinum target material measured in step (3) are shown in Table 3.

[0051] Table 3

[0052]

[0053] Based on the above data, the estimated sputtering lifetime of the nickel-platinum target is as follows: the sputtering power consumption of the sputtering target when untied is x1 = 90 kWh. After untiing, the maximum thickness value of each point on the edge of the target is measured to be y1 = 3.591 mm, the minimum thickness value of each point on the deepest sputtering track is y2 = 1.462 mm, and the maximum thickness consumed by sputtering on the sputtering surface is y1 - y2 = 3.591 - 1.462 = 2.129 mm. Therefore, the power consumption and remaining lifetime after sputtering at the minimum remaining thickness of the target is x2 = y2 / ((y1 - y2) / x1) = 61.8 kWh, and the total lifetime of the target is x1 + x2 = x1 + y2 / ((y1 - y2) / x1) = 151.8 kWh.

[0054] Comparative Example 2

[0055] The difference from Example 2 is that the silicone material used in step (2) has a hardness of 30. After solidification, the silicone material is relatively soft. When the solid silicone is long, the middle part of the solid silicone will preferentially contact the track due to gravity after being contaminated with ink. The solid silicone is not easy to put back into the track in place. At this time, the position of the deepest sputtering track is incorrect, the deepest sputtering track cannot be found, and the lifespan cannot be estimated.

[0056]

[0057] The results above show that the method described in this invention can provide a method for estimating the service life of a planar sputtering target with a backplate.

[0058] Examples 1-2 utilize a needle micrometer to measure the thickness of the edge and deepest sputtering track of the separated sputtering target. The deepest sputtering track obtained through the mold silicone is more accurate. The method is simple to operate and suitable for manufacturers without measuring instruments such as coordinate measuring machines or 3D scanners. It provides guidance for estimating the service life of planar targets with backplates, ensures the safe use of sputtering targets, and provides a reference for assessing the safe service life of similar sputtering targets.

Claims

1. A method for predicting the service life of a planar sputtering target with a backplate, characterized in that, The sputtering target is a thin target with an overall original thickness of 1-5 mm. The method includes the following steps: Step 1: Separate the sputtering target and the backplate by heating. After separation, remove the solder on the back of the sputtering target. Step 2: Confirm the deepest sputtering track of the sputtering target using the mold silicone, measure multiple thickness data of the edge of the sputtering target, and measure multiple thickness data of the deepest sputtering track of the sputtering target. Step 3, estimate the lifespan of the sputtering target. The estimation method includes: When the sputtering target is untied, the sputtering power consumption is x1. After untiing, the maximum thickness value y1 of each point on the edge of the target is measured, the minimum thickness value y2 of each point on the deepest sputtering track is measured, the maximum thickness consumed by sputtering on the sputtering surface is y1-y2, the maximum thickness consumed per unit power consumption is (y1-y2) / x1, then the power consumption after sputtering at the minimum remaining thickness of the target is x2=y2 / ((y1-y2) / x1), where x2 represents the remaining lifetime of the target in terms of sputtering power consumption, and the total lifetime of the target is x1+x2=x1+ y2 / ((y1-y2) / x1); in: In step 1, the original sputtering target and the backplate are connected by brazing and polymer welding. The backplate and target are separated by heating. After the target and the backplate are separated, the solder on the surface of the sputtering target is initially scraped off with a silicone block. Then, the back side is surface treated with a triangular wire drawing machine to remove the solder that was not scraped off. In step 2, the process of confirming the deepest sputtering trajectory of the sputtering target using mold silicone includes: Inject the liquid silicone from the mold into the sputtering track of the target material after separation. After the silicone solidifies, remove the solid silicone and place it horizontally. Use ink to lightly contact the protruding parts of the silicone. Then, place the silicone back into the sputtering track of the target material in its original position and press it lightly. The area that is stained with ink is the deepest sputtering track.

2. The method according to claim 1, characterized in that: In step 1, the sputtering target is a planar sputtering target, and the sputtering surface and the bonding surface are both the same surface and parallel to each other before bonding.

3. The method according to claim 1, characterized in that, In step 2, a needle micrometer is used to measure the thickness of the edge of the sputtering target and the thickness of the deepest sputtering track. During the measurement, the micrometer caliper is kept perpendicular to the measuring surface, and the needle tip is moved slightly back and forth and left and right near the test point to ensure that the value obtained when measuring the edge thickness is the maximum value near the test point and the value obtained when measuring the thickness of the deepest sputtering track is the minimum value near the test point.

4. The method according to claim 3, characterized in that: When using a needle micrometer to measure the thickness of the edge of the sputtering target and the deepest sputtering track, and when the areas stained with ink are lines and surfaces, a multi-point measurement method with equal distribution is adopted.

5. The method according to claim 4, characterized in that: When the point on the deepest sputtering track where ink is smeared is taken as a point, the thickness data must be included in the measurement.

6. The method according to any one of claims 1-5, characterized in that: The hardness of the silicone used in the mold is 50-70 degrees.

7. The method according to any one of claims 1-5, characterized in that: The target material can be circular, square, or irregular in shape.

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