A method for quickly detecting the depth of CVD single crystal diamond damage layer

Abstract

The invention discloses a method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond. The depth of the damaged layer of a substrate material is tested by a continuous indentation test, and a micro-indentation test method is proposed to evaluate the total damage of a CVD diamond processing surface. The damage caused by the micro-indentation test is small enough to be eliminated during the processing. The method has the characteristics of rapidity, low cost, strong operability, etc., and can be used for rapid detection and evaluation of damaged layers in different processing flows of diamond materials, and has certain guiding significance for optimizing material processing parameters and the processing time of the next process.

Description

Technical Field

[0001] The invention belongs to the technical field of damage layer depth detection, and in particular relates to a method for quickly detecting the depth of a damage layer of an extremely hard semiconductor material CVD single crystal diamond. Background Art

[0002] CVD single crystal diamond is an ideal semiconductor material. Due to the high hardness and high brittleness of single crystal diamond materials, as well as the stringent requirements for the surface quality of semiconductor wafers, the processing of single crystal diamond is a great challenge. Traditionally, the processing of diamond is divided into two steps: rough machining and fine machining. The processing quality during rough machining has a great influence on the final surface quality. Large waves, long cracks, and severe graphitization make the surface quality after rough machining worse, so the damage layer must be removed during fine machining. The main processing stages of rough machining include laser cutting and grinding. Grinding is an effective method for removing the damaged layer after laser cutting, especially for removing the graphitized layer. However, due to the chemical and mechanical activities during grinding, a new damage layer will be introduced, including the graphitized layer and the microcrack layer. The microcrack layer is the damaged layer after laser cutting, and the graphitized layer is the damaged layer after laser cutting. The surface conditions after rough machining are very complicated. Transmission electron microscopy research is very popular in the testing of the damage layer, but its application is limited by the preparation of the specimen.

[0003] A fast and inexpensive detection method for damaged layers (including graphitized layers and microcrack layers) after rough machining is very important. However, testing the graphitized layer is a costly and time-consuming task. The relationship between the graphitized layer and the mechanical properties is not direct and clear. Testing the microcrack layer under the graphitized layer is more difficult than testing the graphitized layer. The indentation method is often used to test material hardness, elastic modulus, fracture toughness, etc., and is widely used. Some studies characterize the depth of the damaged layer of the material by the change in hardness with the depth of indentation, or the change in energy during indentation unloading. However, due to the uncertainty of the damaged layer of the material, complex calculations are required when considering the substrate effect and the damaged layer of the material cannot be accurately characterized.

[0004] Therefore, a fast, low-cost and efficient method for detecting the damage layer depth of diamond substrate materials is of great significance. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to use a continuous indentation method to quickly detect the depth of the damaged layer during material processing, thereby optimizing the processing time of different processes, improving processing efficiency and saving production costs.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for rapidly detecting the depth of a CVD single crystal diamond damage layer comprises the following steps:

[0008] a. Select materials from any processing step in the diamond processing flow as samples, and make them into samples to be tested by cutting;

[0009] b. Fix the cut sample to be tested on the sample holder which is continuously pressed into the test platform by using crystal glue, and cure it to the maximum strength;

[0010] c. Install the sample holder with the sample to be tested on the workbench of the continuous press test platform;

[0011] d. Continuously adjust the distance between the pressure head and the sample to be tested, and when the critical load is reached, determine that the pressure head and the sample to be tested are just in contact;

[0012] e. Use the continuous indentation method to perform indentation test on the sample to be tested, and feed the same indentation depth each time, and keep the load for a specific time. After the time is reached, continue to load until the set loading depth or loading times, and record the change in load after a single feed during the loading process;

[0013] f. As the penetration depth increases, when the load increase suddenly increases, the corresponding number of loading times n when the load increase changes is recorded. 1 , and the penetration depth before the load suddenly increases is recorded as h 1 :

[0014] h 1 = (n 1 -1) ×h 0 (1)

[0015] where h 0 is the depth of single loading, n 1 >2.

[0016] g. The depth h of the damaged layer of the material is: h = h 1 .

[0017] In the step a, the state of the sample to be tested includes but is not limited to the diamond crystal seed used for crystal growth, after crystal growth, after laser cutting, after grinding, and after polishing.

[0018] In the step c, the surface of the sample to be tested is kept parallel to the sample table.

[0019] In the step c, the test platform can move along the three axes of X, Y and Z, and the movement accuracy of the X and Y axes is not less than 0.5 μm, and the movement accuracy of the Z axis pressing direction is not less than 10 nm.

[0020] In the step c, a single-channel force measuring system is installed on the test platform, and the accuracy of the force measuring system is not less than 0.05 mN.

[0021] In step d, the critical contact load N is determined. crit ≤0.1mN.

[0022] In the step d, the indenter is a natural diamond indenter, and the shape of the indenter is a Webster indenter or a spherical indenter, and the roughness Sa of the surface of the indenter is ≤10 nm.

[0023] The radius of the spherical indenter is 1 ~200μm.

[0024] In the step e, the single pressing depth is 10-100 nm, the holding time is 1-30 s, and the number of pressing times is 3-100 times.

[0025] The beneficial effects of the present invention are:

[0026] (1) The method for rapidly detecting the depth of the damaged layer of CVD single crystal diamond adopted by the present invention tests the depth of the damaged layer of the substrate material through a continuous indentation test, and proposes a micro-indentation test method to evaluate the total damage of the CVD diamond processing surface. The damage caused by the micro-indentation test is small enough to be eliminated during the processing. The method has the characteristics of rapidity, low cost, and strong operability, and can be used for rapid detection and evaluation of the damaged layer in different processing flows of diamond materials, which has certain guiding significance for optimizing material processing parameters and the processing time of the next process.

[0027] (2) The present invention adopts a continuous indentation method to perform indentation testing on the sample. The same indentation depth is fed each time, and the total damage of the CVD single crystal diamond processing surface can be quickly evaluated by the micro-indentation test method. The accuracy of damage layer detection is better than that of single loading, and the detection accuracy of the damage layer can be improved by reducing the depth of single indentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The processing state and surface roughness of the CVD diamond to be tested in the present invention;

[0029] Figure 2 It is a schematic diagram of the continuous pressing method of the present invention;

[0030] Figure 3 The size and tip morphology of the diamond indenter of the present invention;

[0031] Figure 4 The time load curves recorded during the CVD diamond testing process in different states of the present invention;

[0032] Among them, Table 1 is the test parameter table. DETAILED DESCRIPTION

[0033] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0034] The present invention provides a method for quickly detecting the depth of a damaged layer of a CVD single crystal diamond. Figures 1 to 4 shown.

[0035] The method for quickly detecting the depth of a CVD single crystal diamond damage layer comprises the following steps:

[0036] a. Select materials from any processing step in the diamond processing flow as samples, and cut them into rectangular or other shaped samples of the same specifications to be tested; in this embodiment, the states of the selected diamonds include but are not limited to diamond crystal seeds for crystal growth, after crystal growth, after laser cutting, after grinding, after polishing, etc.

[0037] b. Fix the cut sample to be tested on the sample holder which is continuously pressed into the test platform by using crystal glue, and then cure it to the maximum strength.

[0038] c. The sample holder with the sample to be tested is mounted on the workbench of the continuous indentation test platform, and the surface of the sample to be tested is required to be parallel to the sample platform to ensure that the diamond indenter is vertically pressed into the sample to be tested; in addition, the test platform can move along the three axes of X, Y, and Z, and the movement accuracy of the X and Y axes is not less than 0.5μm, and the movement accuracy of the Z axis indentation direction is not less than 10nm.

[0039] The test platform is also equipped with a single-channel force measurement system with an accuracy better than 0.05mN. The single-channel force measurement system includes a force sensor, a data acquisition card and an amplifier.

[0040] d. Continuously adjust the distance between the pressure head and the sample to be tested. When the critical load is reached, determine whether the pressure head and the sample to be tested are just in contact. Determine the critical load of contact. N crit ≤0.1mN;

[0041] In this embodiment, the indenter is a natural diamond indenter, and the shape of the indenter is a Webster indenter or a spherical indenter. The roughness Sa of the surface of the indenter is ≤10 nm, and the radius of the spherical indenter is 1-200 μm.

[0042] e. Perform an indentation test on the sample using a continuous indentation method, feeding the same indentation depth each time, and holding the load for a specific time. After the time is reached, continue loading until the set loading depth or loading number is reached, and record the change in load after a single feed during the loading process. In this embodiment, the single indentation depth is 10-100nm, the holding time is 1-30s, and the number of indentations is 3-100 times.

[0043] f. Due to the existence of the depth of the damaged layer, in the initial stage of loading, the change in load after a single load of different times is relatively small. As the penetration depth increases, the increase in load at a certain time suddenly increases. The corresponding number of loading times when the load increase changes is recorded. 1 , and the penetration depth before the load increase suddenly changes is defined as h 1 :

[0044] h 1 = (n 1 -1) ×h 0 (1)

[0045] where h 0 is the depth of single loading, n 1 >2;

[0046] Then the material damage depth h can be quickly obtained:

[0047] h = h 1 ;

[0048] And the accuracy of the test can be increased or decreased by changing the depth of a single press.

[0049] The following is specifically described in conjunction with embodiments:

[0050] Example 1

[0051] like Figure 1 The following are the CVD single crystal diamond samples in different processing states and the corresponding three-dimensional roughness. The size of the sample is 7×7×1mm. 3 , diamonds in different states are fixed on the sample stage by crystal glue, and then the sample stage is installed on the continuous press-in test platform.

[0052] Figure 2 The figure shows the loading method of the continuous indentation test platform. The indenter is perpendicular to the sample to be tested. The diamond indenter is fixed on the force sensor. The resolution of the force sensor is 0.01mN, the stiffness is 40 N / μm, the natural frequency is 27KHz, and the maximum load capacity is 500N. The loading direction is driven by a high-precision linear motor with an accuracy of 10nm.

[0053] Figure 3 A natural diamond indenter is used, with a tip radius of 50μm, an angle of 90°, and a tip surface roughness of 10nm. After the test equipment and samples are ready, the first step is to calibrate the tool. The determination of tool calibration is determined by the force signal. When the contact force between the diamond indenter and the sample to be tested is greater than 0.0025N, it is determined that the sample to be tested and the diamond indenter are just in contact, and the tool calibration is completed.

[0054] As shown in Table 1, after the tool setting is completed, a continuous press-in test is performed. The test parameter table is shown in Table 1. Each feed is 50 nm, loaded 10 times, and then unloaded until the contact force is 0. The number of unloading times is recorded, and the holding time for each loading and unloading is 10 s.

[0055] Figure 4 The time-load curves are recorded during the test of CVD diamond seed, after crystal growth, after laser cutting, after grinding and after polishing. Due to the high hardness of diamond, the influence of amorphous, graphitized and cracked produced during the processing can reduce the strength of the material; as the loading depth increases, when the influence of the depth of the damaged layer becomes smaller, the contact force is mainly affected by the material below the damaged layer. In the holding stage, the differences between different samples can also be obtained. The contact force of the sample increases after pressing, and the contact force will slowly decrease in the partial holding stage. Figure 4 The position indicated by the arrow is the position where the increase in contact force suddenly changes. Therefore, the depth of the damage layer of different types of diamond can be obtained by formula (1). At the same time, it can be concluded that the damage layer depth after laser processing is the largest, followed by grinding, and the damage layer after polishing is the smallest. The damage layers of the seed crystal and the material after crystal growth are basically the same and higher than the damage layer after polishing.

[0056] The present invention adopts a continuous pressing method to perform indentation test on the sample, and feeds the same pressing depth each time, the accuracy of damage layer detection is better than that of single loading, and the detection accuracy of the damage layer can be improved by reducing the depth of single pressing, and the total damage of the CVD single crystal diamond processing surface can be quickly evaluated by the micro-indentation test method. The damage caused by the micro-indentation test is small enough and can be eliminated during the processing, and has the characteristics of rapidity, low cost, strong operability, etc.; at the same time, it can be used for rapid detection and evaluation of the damage layer in different processing flows of diamond materials, and has a certain guiding significance for optimizing material processing parameters and the processing time of the next process.

[0057] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the invention claimed for protection. The scope of protection claimed for the present invention is defined by the attached claims and their equivalents.

[0058] In the description of the present invention, it is necessary to understand that the terms "front", "rear", "left", "right", "center", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the protection content of the present invention.

[0059]

Claims

1. A method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond, characterized in that: The following steps are involved: a. Select materials from any processing step in the diamond processing flow as samples, and make them into samples to be tested by cutting; b. Fix the cut sample to be tested on the sample holder which is continuously pressed into the test platform by using crystal glue, and cure it to the maximum strength; c. Install the sample holder with the sample to be tested on the workbench of the continuous pressure test platform, and keep the surface of the sample to be tested parallel to the sample table; d. Continuously adjust the distance between the pressure head and the sample to be tested, and when the critical load is reached, determine that the pressure head and the sample to be tested are just in contact; e. Use the continuous indentation method to perform indentation test on the sample to be tested, and feed the same indentation depth each time, and keep the load for a specific time. After the time is reached, continue to load until the set loading depth or loading times, and record the change in load after a single feed during the loading process; f. As the penetration depth increases, when the load increase suddenly increases, the corresponding loading number n1 when the load increase changes is recorded, and the penetration depth before the load increase suddenly increases is recorded as h1: h1= (n1-1) ×h0(1) Where h0 is the depth of single loading, n1>2; g. The depth h of the damaged layer of the material is: h=h1.

2. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 1, characterized in that: In the step a, the states of the sample to be tested include diamond crystal seeds for crystal growth, after crystal growth, after laser cutting, after grinding, and after polishing.

3. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 1, characterized in that: In the step c, the test platform can move along the three axes of X, Y and Z, and the movement accuracy of the X and Y axes is not less than 0.5 μm, and the movement accuracy of the Z axis pressing direction is not less than 10 nm.

4. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 1, characterized in that: In the step c, a single-channel force measuring system is installed on the test platform, and the accuracy of the force measuring system is not less than 0.05 mN.

5. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 1, characterized in that: In step d, the critical load of the contact is determined N crit ≤0.1mN.

6. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 1, characterized in that: In the step d, the indenter is a natural diamond indenter, and the shape of the indenter is a Webster indenter or a spherical indenter, and the roughness Sa of the surface of the indenter is ≤10 nm.

7. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 6, characterized in that: The radius of the spherical indenter is 1~200μm.

8. The method for rapidly detecting the depth of a damaged layer of a CVD single crystal diamond according to claim 6, characterized in that: In the step e, the single pressing depth is 10-100 nm, the holding time is 1-30 s, and the number of pressing times is 3-100 times.

Images