Quantitative calibration method

Abstract

The application provides a quantitative calibration method, and belongs to the technical field of wafer testing, and specifically comprises the following steps: S1: obtaining standard data of a standard wafer sample; S2: measuring the standard wafer sample data to obtain first test data; S3: fixing a plurality of stickers with different quantitative thicknesses on an adsorption support needle, and respectively measuring the standard wafer sample data to obtain second test data; the sticker is provided with an opening at the adsorption support needle to prevent the adsorption air holes of the adsorption support needle from being blocked, and the position of the adsorption support needle in the wafer warping degree measuring instrument is relatively fixed; and S4: generating correction data of the wafer warping degree measuring instrument according to the standard data, the first test data, the second test data and the quantitative thickness. Through the processing scheme, the wafer warping degree measuring instrument adopting the capacitive thickness measurement principle is accurately corrected.

Description

Technical Field

[0001] This invention relates to a wafer warpage measuring instrument, and more specifically to a quantitative calibration method. Background Technology

[0002] The LBW (Wafer Warp Measurement) device is a non-contact, non-destructive silicon wafer warp measurement instrument. It utilizes the principle of capacitance thickness measurement to obtain silicon wafer Thickness / Bow / Warp / GBIR parameter information (Thickness: thickness deviation, Bow: curvature, Warp: warp, GBIR: flatness). During use, the LBW device may experience intermittent horizontal drift in the Bow / Warp measurement. Currently, there are two solutions:

[0003] The first method involves calibrating the distance from the lower surface of the wafer to the lower probe using software. However, the manufacturer does not provide software adjustment permissions, so the correction can only be made by the manufacturer. The correction process usually takes 3-7 days. However, after the Bow / Warp measurement level is abnormal, the correction can only be maintained for three days after the manufacturer modifies the software parameters.

[0004] The second method involves blindly adjusting the position of the support pin. The height of the pin can be manually adjusted, but the working space for the pin is limited, and manual adjustment cannot ensure accuracy (there is no quantitative relationship between the number of screw turns and the change in the height of the pin). The result after adjustment is highly random, and a lot of time is required to verify the adjustment effect.

[0005] Therefore, both of the above methods will affect the stability of the machine and the factory's production capacity. Summary of the Invention

[0006] Therefore, in order to overcome the shortcomings of the prior art, the present invention provides a quantitative calibration method for accurately correcting a wafer warpage measuring instrument that uses the principle of capacitance thickness measurement.

[0007] To achieve the above objectives, the present invention provides a quantitative calibration method for calibrating a wafer warpage measuring instrument that uses the principle of capacitance thickness measurement, comprising: S1: acquiring standard data of a standard wafer sample;

[0008] S2: Measure the standard wafer data to obtain first test data; S3: Fix multiple stickers of different quantitative thicknesses on the adsorption support pin, and measure the standard wafer data respectively to obtain second test data; the stickers are provided with openings at the adsorption support pin to prevent clogging of the adsorption pores of the adsorption support pin, and the position of the adsorption support pin in the wafer warpage measuring instrument is relatively fixed; S4: Generate calibration data for the wafer warpage measuring instrument based on the standard data, the first test data, the second test data, and the quantitative thickness.

[0009] In one embodiment, the standard data includes standard reference surface data and standard median surface data. The standard median surface data is the surface data formed by the median line of the standard wafer sample, and the standard reference surface data is the surface data formed by the reference line. The median line is the thickness center curve of the wafer, and the reference line is a reference line generated by fitting the median line.

[0010] In one embodiment, the reference line is a reference line generated by least-squares fitting of the median line.

[0011] In one embodiment, the length and width of the sticker are between 1 and 2 cm.

[0012] In one embodiment, the sticker is a resin sticker.

[0013] In one embodiment, the quantitative thickness is 10–80 μm.

[0014] In one embodiment, fixing a sticker of a predetermined thickness onto an adsorption support pin includes: cleaning the surface of the adsorption support pin using a volatile solvent as the cleaning agent; making holes on the sticker to be applied that correspond to the pores of the adsorption support pin; aligning the openings of the sticker with the pores on the adsorption support pin, smoothing the surface, and checking that there are no air bubbles or curling on the contact surface between the sticker and the adsorption support pin; if no air bubbles or curling are found, the sticker is completely fixed onto the adsorption support pin.

[0015] In one embodiment, the calibration steps include: adjusting the relative position of the standard wafer sample between the capacitors, wherein the standard wafer sample is located at a second position between the capacitors; performing a standard wafer test on the standard wafer sample located at the second position to generate real-time capacitance data corresponding to the second position; when it is determined that the real-time capacitance data is not the first test data, determining a quantitative thickness of the sticker based on the difference between the real-time capacitance data and the first test data, fixing the sticker of the quantitative thickness on the adsorption support pin, and then performing the standard wafer test; when it is determined that the real-time capacitance data is the first test data, the calibration is completed.

[0016] Compared with the prior art, the advantages of this invention are: it transforms the uncontrollable screw rotation adjustment of the support pin height into an intuitive sticker thickness adjustment, and the resin material does not damage the wafer. It is easy to operate, and the change in sticker thickness is the height adjustment amount, which is quantitative and more clear. In addition, it can also alleviate the fluctuation of measurement values ​​caused by vibration of equipment hardware structure to a certain extent during the measurement process, thereby improving the authenticity and accuracy of wafer measurement. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of wafer warpage measurement in a wafer warpage measuring instrument;

[0019] Figure 2 yes Figure 1 A magnified view of the adsorption support pin in the middle;

[0020] Figure 3 This is a schematic diagram of the capacitance thickness measurement parameters of a wafer warpage measuring instrument.

[0021] Figure 4 This is a magnified view of the sticker at the adsorption support pin in an embodiment of the present invention. Detailed Implementation

[0022] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0023] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0025] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0026] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0027] The LBW device (Wafer Warpage Measurement Instrument) is a non-contact, non-destructive silicon wafer warpage measurement device that uses the principle of capacitance thickness measurement to obtain silicon wafer Thickness / Bow / Warp / GBIR parameter information.

[0028] like Figure 1 and Figure 2 As shown, platform 5 (Stage) is a fixed base, and adjustable screw 3 is fixed on platform 5. The adjustable screw 3 has an adsorption vent 2 inside, and an air tube 4 communicating with the adsorption vent 2 is also inside the adjustable screw 3. The wafer 1 can be fixed by the adsorption air tube 4 through negative pressure adsorption. By adjusting the adjustable screw 3, the upper surface of the adsorption vent 2 can be adjusted, thereby adjusting the position of the wafer between the capacitors. The adjustable screw 3, the adsorption vent 2, and the air tube 4 together form an adsorption support pin (adsorption support pin) supporting the wafer 1.

[0029] like Figure 3 As shown, the median line M is the thickness center curve of the wafer, and the reference line N is a reference line obtained by fitting the median line M. In one embodiment, the reference line N is a reference line fitted to the median line M using the least squares method. BOW represents curvature, which is the maximum distance between the median line M and the reference line N. WARP represents warpage, which is the difference between the maximum and minimum values ​​between the median line M and the reference line N. S is the scanning area of ​​the capacitive probe, d1 is the distance from the upper probe of the capacitor to the upper surface of the wafer, d2 is the thickness of the wafer (silicon wafer), d3 is the distance from the lower probe of the capacitor to the lower surface of the wafer, d is the capacitor pitch, a is the distance from the median line M to the upper surface of the wafer, b is the distance from the median line M to the lower surface of the wafer, ε1 is the air dielectric constant at d1, ε2 is the dielectric constant at the wafer (silicon wafer), and ε3 is the air dielectric constant at d3.

[0030] When a wafer is placed between the plates of a fixed capacitor, the capacitance of the silicon wafer is... Since d1 + d3 = d - d2 and ε1 = ε3, therefore Therefore, the thickness of the silicon wafer can be determined by measuring the silicon wafer capacitance C according to this formula.

[0031] This application provides a quantitative calibration method for calibrating a wafer warpage measuring instrument that uses the capacitance thickness measurement principle, comprising the following steps:

[0032] S1: Obtain standard data for standard wafer samples.

[0033] In one embodiment, the standard data includes standard reference surface data and standard median surface data. The standard median surface data is the surface data formed by the median line of a standard wafer sample, and the standard reference surface data is the surface data formed by a reference line. The median line is the thickness center curve of the wafer, and the reference line is a reference line generated by fitting the median line. The Bow / Warp value at a specified location on the wafer can be obtained based on the standard reference surface data and the standard median surface data of the standard wafer sample. The median line M will differ at different specified locations on different wafers, so a suitable Bow / Warp value can be selected as a reference based on the ease of measurement. In one embodiment, the reference surface can be obtained by fitting the (d3+b) values ​​of each measurement point.

[0034] S2: Measure standard wafer data to obtain the first test data.

[0035] Measure standard wafer data to obtain the first test data, which can be capacitance data or other data such as Thickness / Bow / Warp / GBIR.

[0036] S3: Fix multiple stickers of different quantitative thicknesses on the adsorption support pin, measure the data of the standard wafer respectively, and obtain the second test data; the stickers are provided with openings at the adsorption support pin to prevent blockage of the adsorption probe's adsorption pores, and the position of the adsorption support pin in the wafer warpage measuring instrument is relatively fixed.

[0037] By attaching a sticker of a predetermined thickness above the adsorption support pin, the relative position of the wafer between the capacitors is changed, i.e., d3 is altered. In one embodiment, fixing the sticker of a predetermined thickness to the adsorption support pin includes the following steps: cleaning may be performed first. Figure 1 For cleaning the surface of the adsorption support pin, volatile solvents such as ethanol can be used. Make holes on the sticker to be attached that correspond to the pores on the adsorption support pin. Align the holes on the sticker with the pores on the adsorption support pin, smooth the surface, and check that there are no air bubbles or curling at the contact surface between the sticker and the adsorption support pin. If no air bubbles or curling are found, the sticker is completely fixed to the adsorption support pin and subsequent operations can proceed. The holes in the sticker at the adsorption support pin also help maintain wafer stability during platform operation.

[0038] In one embodiment, such as Figure 4As shown, when the sticker 6 is attached to the suction support pin, the adjustable screw 3 is adjusted to the lowest position and locked.

[0039] S4: Generate calibration data for the wafer warpage measuring instrument based on the standard data, the first test data, the second test data, and the quantitative thickness.

[0040] When the standard data includes standard reference surface data and standard median surface data, the calibration data includes calibration reference surface data and calibration median surface data.

[0041] Taking a standard wafer with a thickness of 780μm (defined by the factory report on the Bow value) as an example, using the above steps, stickers of different quantitative thicknesses are fixed on the adsorption support pins. The standard wafer sample is then tested to generate second test data. The standard data, first test data, second test data, and quantitative thickness are then used to generate the calibration reference surface data and calibration median surface data for the wafer warpage measuring instrument. After data fitting, using a 45μm sticker, the Bow value can be calibrated upward by 1μm, and using an 80μm sticker, the Bow value can be calibrated upward by 2μm, until it meets the value defined in the standard wafer report. The calibration is then complete.

[0042] In one embodiment, the calibration steps for the LBW device include:

[0043] Step 1: Adjust the relative position of the standard wafer sample between the capacitors. At this point, the standard wafer sample is in the second position between the capacitors. Changing the relative position of the wafer between the capacitors can adjust the Bow / Warp measurement level.

[0044] Step two: Perform standard wafer testing on the standard wafer sample located at the second position to generate real-time capacitance data corresponding to the second position.

[0045] Step 3: When it is determined that the real-time capacitance data is not the first test data, the quantitative thickness of the sticker is determined based on the difference between the real-time capacitance data and the first test data. The sticker of the quantitative thickness is fixed on the adsorption support pin, and then the standard sheet test is performed. When it is determined that the real-time capacitance data is the first test data, the calibration is completed.

[0046] Specifically, when the LBW device experiences a horizontal drift in Bow / Warp measurement during use, for example, if the standard Bow value is 4μm and the measured Bow value after drift is 5μm, the Bow value has drifted upward by 1μm. A 45μm sticker can be used to calibrate the Bow value upward by 1μm. After the sticker is applied, the data measured by the LBW device during use will be accurate until the Bow value drifts again.

[0047] The above method transforms the uncontrollable screw rotation adjustment of the adsorption support pin height into a direct adjustment of the sticker thickness. The resin material does not damage the wafer, the operation is simple, and the change in sticker thickness is the height adjustment amount, providing a more quantitative and precise measurement. Furthermore, it can mitigate some of the measurement fluctuations caused by vibrations in the equipment hardware, improving the authenticity and accuracy of wafer measurements. The entire process is simple and convenient, effectively solving the problem of horizontal drift in LBW equipment Bow / Warp measurements, ending the current maintenance monopoly on this issue, and promptly restoring factory production capacity.

[0048] In one embodiment, the reference line is a reference line generated by least-squares fitting of the median line.

[0049] In one embodiment, the length and width of the sticker are between 1 and 2 cm.

[0050] In one embodiment, the sticker is a resin sticker.

[0051] In one embodiment, the quantitative thickness of a single-layer sticker is 10–80 μm. In another embodiment, multiple layers of stickers can be stacked to achieve the thickness required to adjust the offset.

[0052] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A quantitative calibration method for calibrating a wafer warpage measuring instrument that uses the capacitance thickness measurement principle, characterized in that, include: S1: Obtain standard data for standard wafer samples; S2: Measure the data of the standard wafer to obtain the first test data. The first test data may be capacitance data, or other data such as thickness deviation, bow curvature, warp, and GBIR flatness. S3: Fix multiple stickers of different quantitative thicknesses on the adsorption support pin, measure the data of the standard wafer respectively, and obtain the second test data; the stickers are provided with openings at the adsorption support pin to prevent blockage of the adsorption pores of the adsorption support pin, and the position of the adsorption support pin in the wafer warpage measuring instrument is relatively fixed. S4: Generate calibration data for the wafer warpage measuring instrument based on the standard data, the first test data, the second test data, and the quantitative thickness; The standard data includes standard reference surface data and standard median surface data. The standard median surface data is the surface data formed by the median line of the standard wafer sample, and the standard reference surface data is the surface data formed by the reference line. The median line is the thickness center curve of the wafer, and the reference line is a reference line generated by fitting the median line. The sticker is a resin sticker; The quantitative thickness is taken as 10~80μm; The calibration steps include: The relative position of the standard wafer sample between the capacitors is adjusted, at which point the standard wafer sample is located in the second position between the capacitors; The standard wafer sample located at the second position is tested as a standard wafer to generate real-time capacitance data corresponding to the second position; When the real-time capacitance data is determined not to be the first test data, the quantitative thickness of the sticker is determined based on the difference between the real-time capacitance data and the first test data. The sticker of the quantitative thickness is fixed on the adsorption support pin, and then the standard sheet test is performed. When the real-time capacitance data is determined to be the first test data, the calibration is completed.

2. The quantitative calibration method according to claim 1, characterized in that, The reference line is generated by fitting the median line using the least squares method.

3. The quantitative calibration method according to claim 1, characterized in that, The length and width of the sticker are between 1 and 2 cm.

4. The quantitative calibration method according to claim 1, characterized in that, Fixing the sticker of a predetermined thickness onto the adsorption support pin includes: Clean the surface of the adsorption support needles using a volatile solvent as the cleaning agent; Make holes on the sticker to be attached that correspond to the air holes of the adsorption support pin; Align the opening of the sticker with the pores on the adsorption support pin, smooth the surface, and check that there are no air bubbles or curling on the contact surface between the sticker and the adsorption support pin; if no air bubbles or curling are found, the sticker is completely fixed on the adsorption support pin.

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