A diamond heat spreading substrate for integrated circuits and a method of making the same

Abstract

This application provides a diamond heat dissipation substrate for integrated circuits, comprising a diamond layer, and a seed layer and a metallization layer sequentially deposited on the diamond layer. The seed layer is a metal capable of forming carbides with carbon. It is produced by growing a polycrystalline diamond film on a silicon substrate using MPCVD; then depositing the seed layer onto the diamond sheet using thermal evaporation or PVD; after depositing, heating to 800–1200°C, followed by cooling to 600–1000°C for annealing; and finally depositing the metallization layer to obtain the product. This diamond heat dissipation substrate achieves better bonding by specifically metallizing the diamond, particularly by using a metal seed layer to form carbides with carbon, and by controlling the temperature, time, heating rate, cooling rate, gas environment, gas pressure, and vacuum level. Through specific temperature and annealing treatments, atomic interdiffusion between layers is achieved, improving the bonding strength between layers.

Description

Technical Field

[0001] This application relates to the field of integrated circuit substrate technology, and in particular to a diamond heat dissipation substrate for integrated circuits and a method for preparing the same. Background Technology

[0002] In high-power or high-frequency electronic applications, the heat generated increases with the increasing switching speed of components, leading to a higher heat power density that needs to be dissipated. This is also influenced by the shrinking size of electronic components, resulting in increasingly demanding performance requirements for thermal management components. However, good thermal conductivity itself is not the key factor. Diamond, for example, is widely considered the best thermal conductor in nature. Although it is not conductive in its undoped state, its unique combination of crystal structure and strong covalent electron bonds results in a tremendous thermal conductivity through phonons. This type of heat flow also appears in the form of waves and wave packets in some other insulating materials. Combined with its low dielectric loss, low coefficient of friction, wide spectral transparency, high hardness, and chemical inertness, diamond is undoubtedly a special material choice. This set of specific properties makes diamond an ideal candidate for thermal management tools, especially thermal management devices. However, when using diamond as a thermal management material, uneven contact between the heat-generating component and the heat sink prevents the rapid conduction of excess heat and the suppression of "hot spots," thus severely degrading the performance and efficiency of electronic devices. Summary of the Invention

[0003] This application is made in view of the above-mentioned problems, and its purpose is to provide a diamond heat sink substrate with good thermal management effect that can be used in high power density electronic devices.

[0004] The first aspect of this application provides a diamond heat dissipation substrate for integrated circuits, comprising a diamond layer, and a seed layer and a metallization layer sequentially deposited on the diamond layer, wherein the seed layer is a metal capable of forming carbides with element C.

[0005] The seed layer is at least one of titanium, nickel, and chromium.

[0006] The metallization layer is at least one of gold, copper, and silver.

[0007] The metallization layer further includes an isolation layer located on one side of the seed layer, the isolation layer being at least one of platinum metals.

[0008] The thickness of the seed layer is 10–200 nm, and the thickness of the metallization layer is 50–1000 nm.

[0009] The thickness of the isolation layer is 10–200 nm.

[0010] A second aspect of this application provides a method for fabricating a diamond heat dissipation substrate for integrated circuits, comprising the following steps:

[0011] 1) Growth of polycrystalline diamond thin films on silicon substrates using MPCVD;

[0012] 2) After growth is complete, remove the substrate, use a laser to cut the diamond film into diamond sheets of a certain size, and then perform double-sided grinding, polishing and cleaning on the diamond sheets;

[0013] 3) A seed layer of 10-100 nm is deposited onto the diamond sheet by thermal evaporation or PVD.

[0014] 4) After the plating process is completed, heat to 800-1200℃, hold for 10 minutes, then cool to 600-1000℃ to complete the annealing process;

[0015] 5) Then, metallization layer is deposited in the range of 600 to 1000℃. If an isolation layer is present, isolation layer, isolation layer and metallization layer are deposited one by one.

[0016] 6) After cooling to room temperature, break the vacuum and remove the product.

[0017] The roughness of the diamond sheet after grinding and polishing in step 2) is less than 30 nm.

[0018] The heating and cooling rates in steps 3) and 4) are 1 to 10°C per minute.

[0019] The metallization layer has a coating thickness of 50 nm.

[0020] In step 3), the conditions for thermal evaporation or PVD are 10. -8 Under vacuum conditions, 100 sccm of argon gas is introduced and the temperature is raised to 600–1000°C. A seed layer of 10–100 nm is deposited on the target using a metal target.

[0021] The beneficial effects of this application are as follows: The diamond heat dissipation substrate achieves better bonding by performing specific metallization on diamond, especially by using a metal seed layer to form carbides with C element, and controlling the temperature, time, heating rate, cooling rate, gas environment, gas pressure, vacuum degree, etc. Through specific temperature and annealing treatment, atomic interdiffusion between layers is achieved, thereby improving the bonding force between layers. Attached Figure Description

[0022] Figure 1 This is a microscope image of the diamond heat dissipation substrate obtained by the preparation method of this application at 100 micrometers.

[0023] Figure 2This is a microscope image of the diamond heat dissipation substrate prepared in Comparative Example 1 at 100 micrometers. Detailed Implementation

[0024] The following detailed description, with appropriate reference to the accompanying drawings, discloses an embodiment of a diamond heat dissipation substrate for integrated circuits and a method for fabricating the same, according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0025] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0027] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0030] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0031] A diamond heat dissipation substrate for integrated circuits includes a diamond layer, and a seed layer and a metallization layer sequentially deposited on the diamond layer, wherein the seed layer is a metal capable of forming carbides with element C.

[0032] In some embodiments, the seed layer is at least one of titanium, nickel, and chromium.

[0033] In some embodiments, the metallization layer is at least one of gold, copper, and silver.

[0034] In some embodiments, the metallization layer further includes an isolation layer located on one side of the seed layer, the isolation layer being at least one of platinum metals.

[0035] In some embodiments, the thickness of the seed layer is 10–200 nm, and the thickness of the metallization layer is 50–1000 nm.

[0036] The thickness of the isolation layer is 10–200 nm.

[0037] A method for fabricating a diamond heat dissipation substrate for integrated circuits includes the following steps:

[0038] 1) Growth of polycrystalline diamond thin films on silicon substrates using MPCVD;

[0039] The specific growth method is as follows:

[0040] 1. Clean the silicon substrate by sonicating it sequentially with acetone, alcohol, and water for 30 minutes each time;

[0041] 2. After cleaning, the silicon substrate is ultrasonically treated with diamond micro powder for 30 minutes. After ultrasonic treatment, it is placed in deionized water and ultrasonically treated for 30 minutes to remove excess diamond micro powder.

[0042] 3. Then, diamond growth is carried out in MPCVD at a temperature of 600-1000℃, a methane ratio of 0-10%, and a hydrogen flow rate of 100-1000 sccm.

[0043] Furthermore, the growth process parameters are as follows: 100–1000 sccm of hydrogen, 0–100 sccm of methane, gas pressure 10–200 torr, microwave power 600–6000 W, and temperature 600–1000 °C. After the diamond has grown to the required thickness, it is cooled and removed. The heating rate is 1–10 °C per minute. The cooling rate is 1–10 °C per minute.

[0044] In MPCVD diamond growth, specific gas pressure and microwave power are used to ensure excellent diamond growth.

[0045] 2) After growth is complete, remove the substrate, use a laser to cut the diamond film into diamond sheets of a certain size, and then perform double-sided grinding, polishing and cleaning on the diamond sheets;

[0046] Depending on the required size, the diamond undergoes laser cutting, grinding, and polishing processes, such as cutting it into diamond sheets with a diameter of 20mm x 20mm and a thickness of 300 micrometers. The diamond sheets are then ultrasonically treated with acetone, alcohol, and water in that order for 30 minutes each. Acetone removes organic matter, alcohol removes substances soluble in alcohol, and deionized water removes acetone, alcohol, and substances soluble in water.

[0047] 3) A seed layer of 10-100 nm is deposited onto the diamond sheet by thermal evaporation or PVD.

[0048] Specifically, the conditions for thermal evaporation or PVD are 10. -8 Under vacuum conditions, 100 sccm of argon gas is introduced and the temperature is raised to 600–1000°C. A seed layer of 10–100 nm is deposited on the target using a metal target.

[0049] For example, a diamond sheet is placed in PVD and sputtered with a titanium layer of 10-100 nm using a titanium target at an temperature of 600-1000°C.

[0050] The use of thermal evaporation or PVD to deposit the seed layer is also a key factor, as other methods are difficult to achieve. Through extensive experimental research, these two methods provide higher energy, which is beneficial for metal adhesion to the diamond plate, thus achieving the seed layer required in this application.

[0051] It is important to emphasize that the following conditions must be met: temperature 600–1000℃, time 1–100 min, heating rate 1–10℃ / min, cooling rate 1–10℃ / min, gas environment (argon, nitrogen, and hydrogen are used in the experiment), pressure 1–100 torr, and vacuum level 10. -8 This is mainly reflected in the preparation process of the seed layer and the metallization layer, and is mainly reflected in the PVD process. The diamond roughness needs to be below 30nm, and preferably in the range of 1 to 10nm. Under appropriate conditions, it may cause severe blistering of the electroplated metal (referring to the outermost metallization layer).

[0052] 4) After the plating is completed, heat to 800-1200℃ and hold for 10 minutes. This temperature range is to generate carbides. Too high a temperature will generate too many carbides and reduce thermal conductivity, while too low a temperature will generate too few carbides and not meet the requirements. Then cool down to 600-1000℃ to complete the annealing treatment. This temperature condition was obtained through a large number of experimental studies to ensure the effect of the seed layer of this application is achieved.

[0053] Specifically, annealing is performed at 600–1000°C for 30 minutes, or preferably at 700–900°C.

[0054] Annealing can cause diamond to form a carbide complex with strong adhesion.

[0055] 5) Then, metallization layer is deposited in the range of 600 to 1000℃. If an isolation layer is present, the isolation layer is deposited first. This temperature range was obtained through a large number of experimental studies. If the temperature is too low, the adhesion will be poor. If the temperature is too high, the adhesion will also be poor.

[0056] The diamond surface is coated with a titanium-platinum metal layer. We need to sputter titanium first, then platinum, and then gold. The titanium layer is to improve the bonding strength, the platinum layer is to isolate the upper and lower layers, and the gold layer is for subsequent welding. Different metal layers will play different roles.

[0057] 6) After cooling to room temperature, break the vacuum and remove the product.

[0058] In some embodiments, the roughness of the diamond sheet after grinding and polishing in step 2) is below 30 nm. A roughness of 1-10 nm is preferred to improve sputtering uniformity.

[0059] In some embodiments, the heating and cooling rates in steps 3) and 4) are 1 to 10°C per minute.

[0060] In some embodiments, the metallization layer has a deposition thickness of 50 nm.

[0061] Example

[0062] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0063] Example 1

[0064] 1. Silicon wafers to be used.

[0065] 2. After cleaning, the silicon wafer is ultrasonically treated with diamond micro powder for 30 minutes.

[0066] 3. Place the processed silicon wafer into an MPCVD chamber for diamond film growth. The growth process parameters are: hydrogen: 100 sccm, methane: 10 sccm, gas pressure: 10 torr, microwave power: 600 W, temperature: 600 °C. After the diamond film reaches the required thickness, cool it down and remove it. The heating rate is 5 °C per minute, and the cooling rate is 5 °C per minute.

[0067] 4. The grown diamond is then processed through cutting, grinding, and polishing to achieve the required specifications, such as a diamond substrate with a diameter of 20mm x 20mm and a thickness of 300 micrometers.

[0068] 5. Sonicate the diamond substrate with acetone, alcohol and water in sequence for 30 minutes each.

[0069] 6. After cleaning, place the diamond substrate into the PVD.

[0070] 7. Evacuate the PVD to 10°C. -8 pa.

[0071] 8. Introduce 100 sccm of argon gas. Heat the sample to 600℃ at a rate of 5℃ per minute.

[0072] 9. Sputtering titanium target to prepare a titanium layer (seed layer) on the surface of a diamond substrate, such as sputtering 10nm.

[0073] 10. After sputtering, heat the sample to 800°C at a rate of 5°C per minute. Hold at this temperature for 10 minutes, then cool to 600°C at a rate of 5°C per minute.

[0074] 11. Then begin sputtering a platinum layer, such as sputtering 10nm.

[0075] 12. Then begin sputtering a gold layer, such as sputtering 50nm.

[0076] 13. After cooling to room temperature, break the vacuum and remove the sample.

[0077] Example 2

[0078] 1. Silicon wafers to be used.

[0079] 2. After cleaning, the silicon wafer is ultrasonically treated with diamond micro powder for 30 minutes.

[0080] 3. Place the processed silicon wafer into an MPCVD chamber for diamond film growth. The growth process parameters are: hydrogen 1000 sccm, methane 100 sccm, gas pressure 200 torr, microwave power 6000w, and temperature 1000℃. After the diamond film reaches the required thickness, cool it down and remove it. The heating rate is 10℃ per minute, and the cooling rate is 10℃ per minute.

[0081] 4. The grown diamond is then processed through cutting, grinding, and polishing to achieve the required specifications, such as a diamond substrate with a diameter of 20mm x 20mm and a thickness of 300 micrometers.

[0082] 5. Sonicate the diamond substrate with acetone, alcohol and water in sequence for 30 minutes each.

[0083] 6. After cleaning, place the diamond substrate into the PVD.

[0084] 7. Evacuate the PVD to 10°C. -8 pa.

[0085] 8. Introduce 100 sccm of argon gas. Heat the sample to 1000℃ at a rate of 10℃ per minute.

[0086] 9. Sputter titanium target to prepare a nickel layer (seed layer) on the surface of a diamond substrate, such as sputtering 10nm.

[0087] 10. After sputtering, heat the sample to 1200℃ at a rate of 1-10℃ per minute. Hold at this temperature for 10 minutes, then cool to 1000℃ at a rate of 10℃ per minute.

[0088] 11. Then begin sputtering a gold layer, such as sputtering 50nm.

[0089] 12. After cooling to room temperature, break the vacuum and remove the sample.

[0090] Example 3

[0091] 1. Silicon wafers to be used.

[0092] 2. After cleaning, the silicon wafer is ultrasonically treated with diamond micro powder for 30 minutes.

[0093] 3. Place the processed silicon wafer into an MPCVD chamber for diamond film growth. The growth process parameters are: hydrogen: 500 sccm, methane: 40 sccm, gas pressure: 100 torr, microwave power: 3600 W, temperature: 850℃. After the diamond film reaches the required thickness, cool it down and remove it. The heating rate is 6℃ per minute, and the cooling rate is 6℃ per minute.

[0094] 4. The grown diamond is then processed through cutting, grinding, and polishing to achieve the required specifications, such as a diamond substrate with a diameter of 20mm x 20mm and a thickness of 300 micrometers.

[0095] 5. Sonicate the diamond substrate with acetone, alcohol and water in sequence for 30 minutes each.

[0096] 6. After cleaning, place the diamond substrate into the PVD.

[0097] 7. Evacuate the PVD to 10°C. -8 pa.

[0098] 8. Introduce 100 sccm of argon gas. Heat the sample to 850℃ at a rate of 6℃ per minute.

[0099] 9. Sputter titanium target to prepare a nickel layer (seed layer) on the surface of a diamond substrate, such as sputtering 10nm.

[0100] 10. After sputtering, heat the sample to 1000℃ at a rate of 7℃ per minute. Hold at this temperature for 10 minutes, then cool to 880℃ at a rate of 10℃ per minute.

[0101] 11. Then begin sputtering a copper layer, such as sputtering 50nm.

[0102] 12. After cooling to room temperature, break the vacuum and remove the sample.

[0103] Example 4

[0104] 1. Silicon wafers to be used.

[0105] 2. After cleaning, the silicon wafer is ultrasonically treated with diamond micro powder for 30 minutes.

[0106] 3. Place the processed silicon wafer into an MPCVD chamber for diamond film growth. The growth process parameters are: hydrogen: 400 sccm, methane: 30 sccm, gas pressure: 90 torr, microwave power: 3500 W, temperature: 980℃. After the diamond film reaches the required thickness, cool it down and remove it. The heating rate is 8℃ per minute, and the cooling rate is 5℃ per minute.

[0107] 4. The grown diamond is then processed through cutting, grinding, and polishing to achieve the required specifications, such as a diamond substrate with a diameter of 20mm x 20mm and a thickness of 300 micrometers.

[0108] 5. Sonicate the diamond substrate with acetone, alcohol and water in sequence for 30 minutes each.

[0109] 6. After cleaning, place the diamond substrate into the PVD.

[0110] 7. Evacuate the PVD to 10°C. -8 pa.

[0111] 8. Introduce 100 sccm of argon gas. Heat the sample to 700℃ at a rate of 1–10℃ per minute.

[0112] 9. Sputtering titanium target to prepare a titanium layer (seed layer) on the surface of a diamond substrate, such as sputtering 10nm.

[0113] 10. After sputtering, heat the sample to 1000℃ at a rate of 6℃ per minute. Hold at this temperature for 10 minutes, then cool to 700℃ at a rate of 9℃ per minute.

[0114] 11. Then begin sputtering a copper layer, such as sputtering 50nm.

[0115] 12. After cooling to room temperature, break the vacuum and remove the sample.

[0116] Comparative Example 1

[0117] 1. Silicon wafers to be used.

[0118] 2. After cleaning, the silicon wafer is ultrasonically treated with diamond micro powder for 30 minutes.

[0119] 3. Place the processed silicon wafer into an MPCVD reactor for diamond film growth. The growth process parameters are as follows: hydrogen: 100–1000 sccm; methane: 0–100 sccm; gas pressure: 10–200 torr; microwave power: 600–6000 W; temperature: 600–1000℃. After the diamond film reaches the required thickness, cool it down and remove it. The heating rate is 1–10℃ per minute. The cooling rate is 1–10℃ per minute.

[0120] 4. The grown diamond is then processed through cutting, grinding, and polishing to achieve the required specifications. For example, a diamond substrate with a diameter of 20mm x 20mm and a thickness of 300 micrometers.

[0121] 5. Sonicate the diamond substrate with acetone, alcohol and water in sequence for 30 minutes each.

[0122] 6. After cleaning, place the diamond substrate into the PVD.

[0123] 7. Evacuate the PVD to a vacuum of 10 to the power of -8 Pa.

[0124] 8. Introduce 100 sccm of argon gas. Heat the sample to 600–1000℃. The heating rate is 1–10℃ per minute.

[0125] 9. Sputtering titanium target to prepare a titanium layer (seed layer) on the surface of a diamond substrate. For example, here we sputter 10nm.

[0126] 10. Then we begin sputtering a platinum layer. For example, here we sputter 10nm.

[0127] 11. Then we begin sputtering a gold layer. For example, here we sputter 50nm.

[0128] 12. After cooling to room temperature, break the vacuum and remove the sample.

[0129] Compared to the examples, the metal layer preparation process in Comparative Example 1 lacked the high-temperature annealing step, resulting in poor adhesion and obvious peeling under a microscope.

[0130] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a diamond heat dissipation substrate for integrated circuits, characterized in that... This includes the following steps: 1) Growth of polycrystalline diamond thin films on silicon substrates using MPCVD; 2) After growth is complete, remove the substrate, use a laser to cut the diamond film into diamond sheets of a certain size, and perform double-sided grinding, polishing and cleaning on the diamond sheets to make the roughness of the diamond sheets below 30nm. 3) Place the diamond sheet in 10 -8 Under vacuum conditions, argon gas is introduced, and the temperature is raised to 600-1000°C at a rate of 1-10°C per minute. A seed layer of 10-100 nm is deposited on the seed layer by thermal evaporation or PVD. The seed layer is a metal that can form carbides with carbon. 4) After the plating is completed, heat to 800-1200°C at a heating rate of 1-10°C per minute, hold for 10 minutes, and then cool to 600-1000°C at a cooling rate of 1-10°C per minute to complete the annealing process, so as to form carbides between the seed layer and the diamond sheet. 5) Then, a metallization layer is deposited in the range of 600~1000℃; 6) After cooling to room temperature, break the vacuum and remove the product.

2. The preparation method according to claim 1, characterized in that, The metallization layer has a coating thickness of 50 nm.

3. A diamond heat dissipation substrate for integrated circuits, characterized in that, The diamond heat dissipation substrate is prepared by the method for preparing a diamond heat dissipation substrate for integrated circuits according to any one of claims 1-2. The diamond heat dissipation substrate includes a diamond layer, and a seed layer and a metallization layer sequentially deposited on the diamond layer. The seed layer is a metal that can form a carbide with element C.

4. The diamond heat dissipation substrate according to claim 3, characterized in that, The seed layer is at least one of titanium, nickel, and chromium.

5. The diamond heat dissipation substrate according to claim 3 or 4, characterized in that, The metallization layer is at least one of gold, copper, and silver.

6. The diamond heat dissipation substrate according to claim 3, characterized in that, The metallization layer further includes an isolation layer located on one side of the seed layer, the isolation layer being at least one of platinum metals.

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