A cadmium sulfide target and a method for manufacturing the same

Abstract

The application belongs to the technical field of sputtering targets, and discloses a cadmium sulfide target and a preparation method thereof. The cadmium sulfide target contains cadmium sulfate, and the mass content of the cadmium sulfate is greater than 0.1 and less than or equal to 0.5. The cadmium sulfide powder and the cadmium sulfate powder are sequentially subjected to mixing, loading into a mold, vacuumizing, heating, heat preservation, and cooling to obtain the cadmium sulfide target. In the heat preservation process, the target is subjected to pressurizing and pressure maintaining after being heat preserved for 20-50 minutes. In the mixing process, the cadmium sulfide powder and the cadmium sulfate powder are mixed by using a ball milling process. Specifically, the cadmium sulfide powder and the cadmium sulfate powder are put into a ball milling barrel for dry mixing, the ball-to-material ratio is 1:1.2-1.5, and the ball milling time is 3-6 hours. The application provides a preparation method of the cadmium sulfide target. The cadmium sulfate and the cadmium sulfide are mixed by using the ball milling process, the distribution uniformity of the cadmium sulfate in the cadmium sulfide target is improved, and the sputtering efficiency of the target and the uniformity of the sputtering film are further improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sputtering targets, in particular to a cadmium sulfide target and a preparation method thereof. BACKGROUND

[0002] Cadmium sulfide is an important semiconductor material in the field of photocatalytic reactions, has a relatively narrow band gap so as to be capable of responding in the visible light range, can greatly utilize sunlight, and has great development potential in the field of photocatalysis. The cadmium sulfide semiconductor is a material widely applied in the fields of optics, photoelectricity, optical storage and the like. The cadmium sulfide semiconductor has excellent photoelectric performance, an easily controlled energy band structure and high electron mobility, and therefore is widely applied in illumination, information display, solar cells and the like. The cadmium sulfide target itself is not conductive, and is usually doped to be conductive, and is applied by sputtering.

[0003] For example, Chinese patent 201711237510.0 discloses a high-conductivity cadmium sulfide target and a preparation method thereof. The high-conductivity cadmium sulfide target comprises cadmium sulfide and anhydrous cadmium sulfate, and the content of the anhydrous cadmium sulfate is 50 ppm to 10000 ppm.

[0004] The application can obviously improve the conductivity of the cadmium sulfide target by adding the anhydrous cadmium sulfate into the cadmium sulfide powder. The patent application discloses two preparation methods of two cadmium sulfide targets doped with cadmium sulfate.

[0005] (1) The cadmium sulfide powder is added into a cadmium sulfate solution, soaked for a period of time, and then subjected to centrifugation, drying, crushing and grinding. Then, the cadmium sulfide target is subjected to target pressing treatment in a hot-pressing sintering furnace. After cooling, the furnace is opened and the material is discharged, and the high-conductivity cadmium sulfide target is obtained.

[0006] (2) The cadmium sulfide powder and the anhydrous cadmium sulfate powder are mixed, and then subjected to target pressing treatment in a hot-pressing sintering furnace. After cooling, the furnace is opened and the material is discharged, and the high-conductivity cadmium sulfide target is obtained.

[0007] The two methods have advantages and disadvantages. The first method causes uneven distribution of cadmium sulfate in the centrifugation process, and the second method has a small content and causes uneven micro-resistivity.

[0008] The patent limits the content of the anhydrous cadmium sulfate. When the content of the anhydrous cadmium sulfate exceeds 0.1, the distribution of the cadmium sulfate in the cadmium sulfide target becomes uneven, directly affecting the sputtering efficiency and the uniformity of the film. Therefore, the patent adopts the cadmium sulfate with a content of 50 ppm to 10000 ppm to be doped in the cadmium sulfide target.

[0009] However, with the development of technology, the sputtering performance of the thin film is required to be higher and higher, in order to further improve the uniformity of the thin film, a cadmium sulfide target with more than 10000ppm of cadmium sulfate and uniform distribution is needed to meet the sputtering performance requirements of the thin film. SUMMARY

[0010] One of the purposes of the present application is to provide a cadmium sulfide target to solve the technical problem of insufficient conductivity of the cadmium sulfide target in the prior art, which is difficult to meet the growing sputtering performance requirements of the thin film.

[0011] Another purpose of the present application is to provide a cadmium sulfide target, which can make the content of more than 10000ppm of cadmium sulfate in the cadmium sulfide target be uniformly distributed, further improve the conductivity of the target and the sputtering efficiency and uniformity of the thin film, and meet the higher sputtering performance requirements of the thin film.

[0012] To achieve the above purpose, the present application provides a cadmium sulfide target, which contains cadmium sulfate, and the mass content of the cadmium sulfate is >0.1 and ≤0.5.

[0013] Preferably, in the above-mentioned cadmium sulfide target, the mass content of the cadmium sulfate can be selected as 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5.

[0014] The present application also discloses a preparation method of the above-mentioned cadmium sulfide target, wherein cadmium sulfide powder and cadmium sulfate powder are sequentially mixed, loaded into a mold, vacuumized, heated, heat preserved, and cooled to obtain the cadmium sulfide target.

[0015] In the process of heat preservation, the pressure is applied and the pressure is maintained after heat preservation for 20-50min.

[0016] In the process of heat preservation, the pressure is applied and the pressure is maintained after heat preservation for 20-50min.

[0017] In the ball milling step, the grinding balls are of four sizes, with diameters of 30, 20, 10, and 5mm, and a weight ratio of 1:1:1:1.

[0018] Preferably, the preparation method of the above-mentioned cadmium sulfide target comprises the following specific steps:

[0019] Step 1: cadmium sulfide powder and cadmium sulfate powder are weighed according to the mass ratio of 99.89-99.5:0.11-0.5 and loaded into a ball mill barrel for dry grinding mixing, the ball-to-material ratio is 1:1.2-1.5, and the ball milling time is 3-6h;

[0020] Step 2: the mixed material in step 1 is loaded into a mold, and then put into a vacuum hot pressing furnace;

[0021] Step 3: vacuumize to a vacuum degree of ≤10 Pa in the furnace, start heating, and heat to 810-880℃ at a rate of 8-12℃ / min, and keep for 2-4h, and after keeping for 20-50min, pressurize and keep pressure, the pressure is 30-50MPa, and the keeping pressure time is 45-70min;

[0022] Step 4: after the temperature drops to room temperature, the vulcanized cadmium target material is demolded.

[0023] Further, the purity of the cadmium sulfide powder and the cadmium sulfate powder is 4N or above.

[0024] Further preferably, the ball milling barrel is made of polyurethane, stainless steel or zirconium material.

[0025] Further preferably, the grinding ball is a zirconium ball, a silicon dioxide ball or a stainless steel ball.

[0026] Beneficial effects

[0027] Compared with the prior art, the present application has at least the following advantages:

[0028] (1) The present application provides a vulcanized cadmium target material, the mass content of cadmium sulfate in which is >0.1 and ≤0.5, and it has stronger conductivity;

[0029] (2) The present application provides a preparation method of a vulcanized cadmium target material, which mixes cadmium sulfate and vulcanized cadmium through a ball milling process, improves the uniformity of the distribution of cadmium sulfate in the vulcanized cadmium target material, and further improves the sputtering efficiency of the target material and the uniformity of the sputtered film;

[0030] (3) The present application adopts a specific ball milling mixing process of ball-to-material ratio and ball milling time, which ensures the uniform distribution of cadmium sulfate in the vulcanized cadmium powder;

[0031] (4) The present application adopts the operation of keeping temperature for a period of time before pressurizing in the heat keeping stage, compared with the operation of starting to pressurize in the heating stage in the prior art, which can effectively avoid the cracking of the target material, because the vulcanized cadmium and cadmium sulfate have the phenomenon of thermal expansion and contraction during heating, which will cause the cracking of the target material if pressurizing is started in the heating stage or just after heating to the heat keeping temperature, and the internal part of the target material has not reached the heat keeping temperature due to heat transfer, and the thermal expansion and contraction phenomenon still exists, and the cracking of the target material will also occur; therefore, the present application adopts the operation of keeping temperature for a period of time to ensure that the internal part of the target material has reached the heat keeping temperature before pressurizing, which can effectively avoid the cracking of the target material. DETAILED DESCRIPTION

[0032] The application will be further described in connection with the following examples which do not limit the application in any way.

[0033] In order to illustrate the technical contents of the application, the following further describes the embodiments.

[0034] The following examples and comparative examples all use a ball mill barrel with four kinds of zirconium balls and polyurethane balls with diameters of 30, 20, 10, and 5 mm respectively and a weight ratio of 1:1:1:1.

[0035] Example 1

[0036] A cadmium sulfide target was prepared by the following steps:

[0037] Step 1: cadmium sulfide powder and cadmium sulfate powder were weighed according to a mass ratio of 99.89:0.11, and were loaded into a ball mill barrel for dry grinding and mixing, with a ball-to-material ratio of 1:1.2 and a ball milling time of 6 h;

[0038] Step 2: the material after mixing in step 1 was loaded into a mold, and then was placed into a vacuum hot pressing furnace;

[0039] Step 3: vacuum was drawn to a vacuum degree in the furnace of ≤10 Pa, heating was started, and the temperature was raised to 880℃ at a rate of 12℃ / min, and was kept for 2 h. After 20 min of keeping, pressure was applied and kept, with a pressure of 50 MPa and a pressure keeping time of 45 min;

[0040] Step 4: after the temperature dropped to room temperature, the cadmium sulfide target was demolded.

[0041] Example 2

[0042] A cadmium sulfide target was prepared by the following steps:

[0043] Step 1: cadmium sulfide powder and cadmium sulfate powder were weighed according to a mass ratio of 99.5:0.5, and were loaded into a ball mill barrel for dry grinding and mixing, with a ball-to-material ratio of 1:1.5 and a ball milling time of 3 h;

[0044] Step 2: the material after mixing in step 1 was loaded into a mold, and then was placed into a vacuum hot pressing furnace;

[0045] Step 3: vacuum was drawn to a vacuum degree in the furnace of ≤10 Pa, heating was started, and the temperature was raised to 810℃ at a rate of 8℃ / min, and was kept for 4 h. After 40 min of keeping, pressure was applied and kept, with a pressure of 45 MPa and a pressure keeping time of 70 min;

[0046] Step 4: after the temperature dropped to room temperature, the cadmium sulfide target was demolded.

[0047] Example 3

[0048] A cadmium sulfide target is prepared by the following steps:

[0049] Step 1: cadmium sulfide powder and cadmium sulfate powder are weighed according to a mass ratio of 99.8:0.2, and are loaded into a ball mill barrel for dry grinding and mixing, with a ball-to-material ratio of 1:1.3, and a ball milling time of 4h;

[0050] Step 2: the mixed material after Step 1 is loaded into a mold, and then is placed into a vacuum hot pressing furnace;

[0051] Step 3: vacuum is drawn to a vacuum degree in the furnace of ≤10Pa, heating is started, and the temperature is raised to 850℃ at a rate of 10℃ / min, and is kept for 3h, and after 30min of keeping, pressure is applied and kept, with a pressure of 40MPa and a keeping time of 55min;

[0052] Step 4: after the temperature drops to room temperature, the cadmium sulfide target is demolded.

[0053] Example 4

[0054] A cadmium sulfide target is prepared by the following steps:

[0055] Step 1: cadmium sulfide powder and cadmium sulfate powder are weighed according to a mass ratio of 99.8:0.2, and are loaded into a ball mill barrel for dry grinding and mixing, with a ball-to-material ratio of 1:1.3, and a ball milling time of 4h;

[0056] Step 2: the mixed material after Step 1 is loaded into a mold, and then is placed into a vacuum hot pressing furnace;

[0057] Step 3: vacuum is drawn to a vacuum degree in the furnace of ≤10Pa, heating is started, and the temperature is raised to 850℃ at a rate of 10℃ / min, and is kept for 3h, and after 50min of keeping, pressure is applied and kept, with a pressure of 40MPa and a keeping time of 55min;

[0058] Step 4: after the temperature drops to room temperature, the cadmium sulfide target is demolded.

[0059] Comparative Example 1

[0060] It is substantially the same as Example 3, except that Step 1 is changed to: cadmium sulfide powder and cadmium sulfate powder are weighed according to a mass ratio of 99.8:0.2, and are loaded into a blender for stirring and mixing, with a stirring time of 4h.

[0061] Comparative Example 2

[0062] The procedure is basically the same as that of Example 3, except that in the step 3, the vacuum is drawn to a vacuum degree of ≤10 Pa in the furnace, the heating is started, the temperature is raised to 850℃ at a rate of 10℃ / min, and the temperature is kept for 3h, the pressurization and pressure keeping are carried out after 10min of keeping the temperature, the pressurization pressure is 40MPa, and the pressure keeping time is 55min.

[0063] Comparative Example 3

[0064] The procedure is basically the same as that of Example 3, except that in the step 3, the vacuum is drawn to a vacuum degree of ≤10 Pa in the furnace, the heating is started, the temperature is raised to 850℃ at a rate of 10℃ / min, and the temperature is kept for 3h, the pressurization and pressure keeping are carried out after 10min of keeping the temperature, the pressurization pressure is 40MPa, and the pressure keeping time is 55min.

[0065] Comparative Example 4

[0066] The procedure is basically the same as that of Example 3, except that in the step 1, the ball-to-material ratio is 1:1.

[0067] Comparative Example 5

[0068] The procedure is basically the same as that of Example 3, except that in the step 1, the ball-to-material ratio is 1:1.7.

[0069] Performance test

[0070] Test method: the relative density of the target material is tested by the Archimedes drainage method; the resistivity of the target material is tested by a four-probe resistivity meter.

[0071] The relative density and resistivity of the cadmium sulfide target materials prepared in Examples 1-5 and Comparative Examples 1-5 are tested according to the above test method, and the results are shown in Table 1.

[0072] Table 1 Relative density and resistivity of cadmium sulfide target materials prepared in Examples 1-5 and Comparative Examples 1-5

[0073]

[0074]

[0075] According to the results in Table 1, it can be seen that:

[0076] According to the comparison of the data in Examples 1-3, it can be seen that the amount of cadmium sulfate has a relatively obvious influence on the conductivity of the cadmium sulfide target material, and according to the comparison of the data in Example 3 and Comparative Example 1, it can be seen that in the case of the same amount of cadmium sulfate, the mixing method has a huge influence on the conductivity of the target material, and the ball milling method used in the present application to mix the cadmium sulfate and cadmium sulfide can make the distribution of the cadmium sulfate in the cadmium sulfide target material more uniform, thereby improving the relative density and conductivity of the target material.

[0077] The target material of the comparative example 2 is cracked due to the pressurization during the temperature rising process, which is caused by the thermal expansion and contraction of the CdS and CdSO4 powders during the heating process.

[0078] According to the data comparison of the example 3 and the comparative example 3, the incomplete heat preservation during the target material preparation process and the pressurization also have certain influences on the density and the conductivity of the target material.

[0079] According to the data comparison of the example 3 and the comparative examples 4 and 5, the ball-to-material ratio during the ball milling process has a great influence on the mixing degree of the CdSO4 and CdS powders; the specific ball-to-material ratio and the ball milling process can effectively improve the relative density and the conductivity of the target material.

[0080] The examples presented herein are merely selected from the combinations of all possible examples. The appended claims should not be limited by the examples described herein. Some numerical ranges in the claims include the sub-ranges within the ranges, and the variations in the ranges should also be covered by the appended claims.

Claims

1. A cadmium sulfide target, characterized in that: The cadmium sulfide target contains cadmium sulfate, and the mass content of the cadmium sulfate is greater than 0.1 and less than or equal to 0.5; The preparation method of the cadmium sulfide target comprises the following specific steps: Step 1: Weighing cadmium sulfide powder and cadmium sulfate powder in a mass ratio of 99.89 to 99.5:0.11 to 0.5 and placing them into a ball mill for dry grinding and mixing, with a ball-to-material ratio of 1:1.2 to 1.5 and a ball milling time of 3 to 6 hours; in the ball milling step, the grinding balls are of four sizes, with diameters of 30, 20, 10, and 5 mm, respectively, and a weight ratio of 1:1:1:1; Step 2: Place the mixed material from step 1 into a mold and then place it in a vacuum hot press furnace; Step 3: Evacuate the furnace until the vacuum degree is ≤10Pa, turn on the heating, and heat it to 810-880℃ at 8-12℃ / min and keep it for 2-4h. After keeping it for 20-50min, pressurize and hold the pressure. The pressurization pressure is 30-50MPa and the holding time is 45-70min. Step 4: After the temperature drops to room temperature, demoulding is performed to obtain a cadmium sulfide target.

2. The cadmium sulfide target according to claim 1, characterized in that The purity of the cadmium sulfide powder and the cadmium sulfate powder is 4N or higher.

3. The cadmium sulfide target according to claim 1, characterized in that The ball mill barrel is made of polyurethane, stainless steel or zirconium.

4. The cadmium sulfide target according to claim 1, characterized in that The grinding balls are zirconium balls, silicon dioxide balls or stainless steel balls.

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