A method for preparing a standard particle wafer

Abstract

The present invention provides a method for preparing a standard particle wafer, wherein a standard particle sample liquid is first atomized, then vertically sprayed, and finally, after the solvent of the atomized droplets evaporates, a target-set standard particle wafer can be obtained. The preparation method of the present invention can prepare a standard particle wafer with a specified number and a specified size of particles (more than ten nanometers), which can be used for performance verification of a particle detector, and has the advantages of being simple and fast.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor defect detection, and in particular to a method for preparing a standard particle wafer. Background Art

[0002] At present, standard particle wafers are often used in the development and use of semiconductor defect detection equipment. The wafer surface particle detector is an instrument that detects the particle size of the wafer surface based on optical methods. The instrument uses a laser to illuminate the wafer surface. When the light encounters particulate matter, the light will scatter. The number and particle size of the particles are determined by measuring the scattered light, thereby determining the particle size of the wafer surface. During the initial installation and subsequent use of the wafer surface particle detector, standard particle wafers are needed to adjust the accuracy of its particle size test. Standard particles of different sizes are required to calibrate semiconductor defect detection equipment and test the performance of the equipment. However, standard particle wafers are currently only provided by large foreign manufacturers, with prices as high as hundreds of thousands or even millions of yuan, and are difficult to purchase and have a long delivery time. Domestic manufacturers are in urgent need of breaking through this technical barrier.

[0003] In summary, there is an urgent need to develop a method for preparing standard particle wafers. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for preparing a standard particle wafer, which uses a standard particle sample liquid to be atomized first, then sprayed vertically, and finally, after the solvent of the atomized droplets evaporates, a target-set standard particle wafer can be obtained. The preparation method of the present invention can prepare a standard particle wafer with a specified number and a specified size of particles (more than ten nanometers), which can be used for performance verification of a particle detector, and has the advantages of being simple and fast.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] The object of the present invention is to provide a method for preparing a standard particle wafer, the preparation method comprising the following steps:

[0007] Clearly define the target particle size, target spraying area, and target particle density on the blank wafer;

[0008] Preparing a standard particle sample solution, wherein the size of the standard particles in the standard particle sample solution meets the target particle size;

[0009] Atomizing the standard particle sample liquid so that each obtained atomized droplet contains only one standard particle, and vertically spraying the obtained atomized droplets on a target spraying area on the blank wafer;

[0010] After the solvent of the atomized droplets evaporates, a standard particle wafer is obtained.

[0011] The preparation method of the present invention can prepare a standard particle wafer with a specified number and a specified size of particles (above ten nanometers), which can be used for performance verification of a particle detector and has the advantages of being simple and fast.

[0012] It should be noted that, in the preparation method described in the present invention, the target particle density is obtained by adjusting the vertical distance L between the spray port and the target spray area during the vertical spraying process, because after the atomized droplets are emitted from the spraying area, the coverage area of ​​the atomized droplets spreads to the surroundings, and due to the effect of gravity, it will move downward at the same time; the smaller the vertical distance L, the greater the target particle density, and the more particles per unit area on the blank wafer; the larger the vertical distance L, the smaller the target particle density, and the fewer particles per unit area on the blank wafer; however, the specific setting of the vertical distance L needs to be actually adjusted according to the actual vertical spraying equipment used and the operating environment of the vertical spraying, and a specific empirical relationship is obtained through multiple debugging, so it will not be repeated here; the specific debugging content includes the size and shape of the spray port, the pressure of the vertical spraying, etc.

[0013] As a preferred technical solution of the present invention, in the preparation method, each obtained atomized droplet contains only one standard particle, which needs to satisfy the following relationship:

[0014]

[0015] Wherein, C1 is the mass concentration of the standard particle sample solution, in g / cm 3 ;

[0016] ρ0 is the density of the standard particles in the standard particle sample solution, in g / cm 3 ;

[0017] D0 is the diameter of the standard particles in the standard particle sample solution, in μm;

[0018] D is the diameter of a single atomized droplet, in μm;

[0019] X is the proportionality coefficient, satisfying 0.5≤X≤1.5.

[0020] It should be noted that, in the preparation method described in the present invention, the closer the value of the proportional coefficient X is to 1, the higher the proportion of the atomized droplets containing only one standard particle. By ensuring that each atomized droplet obtained contains only one standard particle, the phenomenon of standard particle aggregation will not occur, and the particle uniformity of the standard particle wafer can be improved. In the actual operation process, the diameter of the target particle size (i.e., the diameter D0 of the standard particles in the standard particle sample liquid) and the density of the standard particles in the standard particle sample liquid (such as the density of polystyrene balls) are known. First, determine the diameter D of the atomized droplets that can be achieved by the atomizer, and then prepare the standard particle sample liquid of the corresponding concentration according to the set proportional coefficient X. Based on the actual effect, the atomization parameters of the atomizer can be fine-tuned to adjust the size and flow rate of the atomized droplets to achieve better results.

[0021] As a preferred technical solution of the present invention, the standard particle sample solution is obtained by diluting the standard particle stock solution and satisfies the following relationship:

[0022] C1=C0 / k

[0023] Where C0 is the mass concentration of the standard particle stock solution, in g / cm 3 ; k is the dilution multiple.

[0024] In the present invention, the dilution factor k is related to the diameter D of the atomized droplets. 3 That is, the larger the diameter of the atomized droplets, the larger the volume of the atomized droplets, and the larger the dilution factor k, can ensure that each atomized droplet contains only one standard particle.

[0025] As a preferred technical solution of the present invention, after the atomization and before the vertical spraying, the obtained atomized droplets are homogenized; the homogenization process is performed by blowing air so that the obtained atomized droplets are in a turbulent state and are uniformly distributed in a spatial area.

[0026] As a preferred technical solution of the present invention, the diameter of the target particle size is 0.03-10μm, that is, the diameter D0 of the standard particles in the standard particle sample solution is 0.03-10μm, for example, 0.03μm, 0.05μm, 0.1μm, 0.2μm, 0.4μm, 0.5μm, 0.8μm, 1μm, 2μm, 5μm, 6μm, 8μm or 10μm, etc., but are not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0027] As a preferred technical solution of the present invention, the target particle density is 10-200 particles / cm 2 , for example 10 / cm 2 , 50 pieces / cm 2 , 80 pieces / cm2 , 100 pieces / cm 2 , 130 pieces / cm 2 , 150 pieces / cm 2 , 180 pieces / cm 2 or 200 pcs / cm 2 The above numerical range is not limited to the above numerical values, and other numerical values ​​not listed are also applicable.

[0028] As a preferred technical solution of the present invention, the standard particles in the standard particle sample solution are polystyrene spheres; and the solvent in the standard particle sample solution is water.

[0029] As a preferred technical solution of the present invention, the mass concentration C1 of the standard particle sample solution is (0.1-100)E-5g / cm 3 , for example 0.1E-5g / cm 3 , 0.5E-5g / cm 3 , 1E-5g / cm 3 、10E-5g / cm 3 、20E-5g / cm 3 、30E-5g / cm 3 , 50E-5g / cm 3 、60E-5g / cm 3 、80E-5g / cm 3 or 100E-5g / cm 3 The above numerical range is not limited to the above numerical values, and other numerical values ​​not listed are also applicable.

[0030] As a preferred technical solution of the present invention, the diameter D of a single atomized droplet is 1-10 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the blank wafer is vacuum adsorbed on a wafer carrier, and the wafer carrier is provided with a temperature control device and a rotating device; the temperature control device is used to control the temperature of the blank wafer; the rotating device is used to adjust the sprayed area of ​​the blank wafer.

[0032] It should be noted that, in actual operation, the atomized droplets of the standard particle sample liquid are sprayed vertically on the target spraying area on the blank wafer, and the temperature of the wafer carrier is adjusted by a temperature control device, thereby controlling the temperature of the blank wafer to ensure that the atomized droplets can evaporate within a predetermined time and only retain the standard particles on the blank wafer; moreover, when the entire blank wafer needs to be sprayed, the blank wafer can be driven to rotate by the rotation of the wafer carrier with the help of a rotating device, thereby ensuring the uniformity of the spraying concentration of the entire blank wafer.

[0033] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0034] The preparation method of the present invention can prepare a standard particle wafer with a specified number and a specified size of particles (above ten nanometers), which can be used for performance verification of a particle detector and has the advantages of being simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a particle size distribution curve obtained by the method for preparing the standard particle wafer described in Example 1 of the present invention;

[0036] Figure 2 This is a particle distribution position diagram obtained by the method for preparing the standard particle wafer described in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0038] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0039] Example 1

[0040] This embodiment provides a method for preparing a standard particle wafer, and the preparation method comprises the following steps:

[0041] The target particle size on the blank wafer is 0.2 μm, the target spraying area is the entire blank wafer, and the target particle density is 120 ± 10 particles / cm 2 ;

[0042] Polystyrene beads with an average diameter of 0.204 μm were selected as standard particles, and the density ρ0 of the standard particles was 1.050 g / cm 3 , prepare the mass concentration C0 to be 0.02g / cm 3 Take 50 μL of the standard particle stock solution (solvent is water) and dilute it to 20 mL, that is, the dilution factor k is 400, and the mass concentration C1 is 5E-5 g / cm 3Standard particle sample solution;

[0043] The standard particle sample liquid is atomized by a nebulizer, and the diameter D of a single atomized droplet is controlled to be 5 μm. According to the relationship The proportionality coefficient X is calculated to be 0.701, which satisfies 0.5≤X≤1.5, thus ensuring that each atomized droplet contains only one standard particle;

[0044] The obtained atomized droplets are homogenized by blowing air so that the atomized droplets are in a turbulent state and are uniformly distributed in a spatial region;

[0045] The atomized droplets after homogenization are vertically sprayed on the target spraying area on the blank wafer; the blank wafer is vacuum adsorbed on the wafer stage, and the wafer stage is provided with a temperature control device and a rotating device; the temperature control device is used to control the temperature of the blank wafer; the rotating device is used to adjust the sprayed area of ​​the blank wafer, and when the entire blank wafer needs to be sprayed, the blank wafer can be driven to rotate by the rotation of the wafer stage with the help of the rotating device, so as to ensure the uniformity of the spraying concentration of the entire blank wafer;

[0046] After the solvent of the atomized droplets evaporates, a standard particle wafer is obtained.

[0047] The standard particle wafer prepared in this embodiment was tested for particle quantity and size using a particle analyzer from KLA. The obtained particle size distribution curve is shown in the figure below: Figure 1 As shown in the figure, it can be seen that the peak characteristics of the particle size in the particle size distribution curve are obvious, among which the peak size is 0.205μm, which meets the requirement of the target particle size of 0.2μm; the obtained particle distribution position diagram is shown in Figure 2 As shown in the figure, it can be seen that the target spraying area is the entire blank wafer and the distribution uniformity is good. According to computer statistics, the total number of particles is 20755 and the number per unit area is 127 / cm 2 , meeting the target particle density of 120±10 / cm 2 requirements.

[0048] It should be noted that the preparation method of the standard particle wafer described in the present invention is uniformly controlled by a control system, and the control system can adjust the power of the atomization device, the height of the wafer carrier, the temperature of the wafer carrier, etc.; the mass concentration C0 of the standard particle stock solution is input into the control system, the diameter D of the atomized droplets is selected (generally the default value), and the target particle density of the blank wafer is set, and the control system will automatically calculate the dilution factor k and the recommended height of the wafer carrier, the temperature control temperature and other parameters; according to the calculation results given by the control system, after the standard particle sample solution is prepared, the operating system is connected, the blank wafer is placed, and the operation of the preparation method can be started; after the solvent of the atomized droplets vertically sprayed on the blank wafer evaporates, the standard particle wafer can be obtained, which can be used for performance verification of the particle detector.

[0049] The preparation method of the present invention can prepare a standard particle wafer with a specified number and a specified size of particles (above ten nanometers), which can be used for performance verification of a particle detector and has the advantages of being simple and fast.

[0050] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0051] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0052] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0053] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a standard particle wafer, characterized in that: The preparation method comprises the following steps: Clearly define the target particle size, target spraying area, and target particle density on the blank wafer; Preparing a standard particle sample solution, wherein the size of the standard particles in the standard particle sample solution meets the target particle size; Atomizing the standard particle sample liquid so that each obtained atomized droplet contains only one standard particle, and vertically spraying the obtained atomized droplets on a target spraying area on the blank wafer; After the solvent of the atomized droplets evaporates, a standard particle wafer is obtained; In the preparation method, in order to make each obtained atomized droplet contain only one standard particle, the following relationship needs to be satisfied: ； Wherein, C1 is the mass concentration of the standard particle sample solution, in g / cm 3 ; ρ0 is the density of the standard particles in the standard particle sample solution, in g / cm 3 ; D0 is the diameter of the standard particles in the standard particle sample solution, in μm; D is the diameter of a single atomized droplet, in μm; X is the proportionality coefficient, satisfying 0.5≤X≤1.

5.

2. The preparation method according to claim 1, characterized in that The standard particle sample solution is obtained by diluting the standard particle stock solution and satisfies the following relationship: C1=C0 / k Where C0 is the mass concentration of the standard particle stock solution, in g / cm 3 ; k is the dilution multiple.

3. The preparation method according to claim 1, characterized in that: After the atomization and before the vertical spraying, the obtained atomized liquid droplets are homogenized; the homogenization process is performed by blowing air so that the obtained atomized liquid droplets are in a turbulent state and are uniformly distributed in a spatial area.

4. The preparation method according to claim 1, characterized in that: The target particle size has a diameter of 0.03-10 μm.

5. The preparation method according to claim 1, characterized in that: The target particle density is 10-200 particles / cm 2 .

6. The preparation method according to claim 1, characterized in that: The standard particles in the standard particle sample solution are polystyrene beads; and the solvent in the standard particle sample solution is water.

7. The preparation method according to claim 1, characterized in that: The mass concentration C1 of the standard particle sample solution is (0.1-100)E-5g / cm 3 .

8. The preparation method according to claim 1, characterized in that: The diameter D of a single atomized droplet is 1-10 μm.

9. The preparation method according to claim 1, characterized in that: The blank wafer is vacuum-adsorbed on a wafer carrier, and the wafer carrier is provided with a temperature control device and a rotating device; the temperature control device is used to control the temperature of the blank wafer; the rotating device is used to adjust the sprayed area of ​​the blank wafer.

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