Supporting mechanism for simultaneous measurement of double surfaces of large-size wafer and measurement method

Abstract

The invention discloses a supporting mechanism and a measuring method for simultaneous measurement of two sides of a large-size wafer, and the supporting mechanism comprises a frame straight rod, a short cantilever beam rod, a middle bottom beam rod, a frame fixing block, a supporting positioning element, a spring, and a clamping block, and the end part of the frame straight rod and the end part of the short cantilever beam rod are connected through the frame fixing block to form a square frame. The middle bottom beam rod stretches across the short cantilever beam rod and is parallel to the frame straight rod, the middle bottom beam rod is provided with an upper cross beam and a lower cross beam which are parallel to each other, and the supporting and positioning element penetrates out of the upper cross beam and supports a wafer to be detected through the upper end of the supporting and positioning element. A clamping block is arranged on the portion, located on the lower surface of the upper cross beam, of the supporting and positioning element, the spring is arranged between the clamping block and the lower cross beam, and the spring is arranged around the supporting and positioning element. The problems of errors caused by the fact that the wafer needs to be overturned to obtain the overall shape information and measurement errors caused by gravity deformation caused by the large-size wafer in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer geometry measurement, and more specifically to a support mechanism and measurement method for simultaneous measurement of both sides of a large-size wafer. Background Technology

[0002] Semiconductor wafers, as the fundamental material in integrated circuit and chip manufacturing, have evolved from the initial 2-inch wafers to the current 18-inch wafers. As wafer sizes increase and thicknesses decrease, higher constraints are placed on surface characteristic parameters. Larger wafers allow for the production of more integrated circuits on a single wafer, helping to reduce the cost per chip; therefore, large-size wafers have become the mainstream direction in chip manufacturing. However, during quality inspection of large-size wafers, the deformation due to their own weight significantly interferes with the measurement of their geometric morphology parameters.

[0003] Therefore, some existing large-size wafer geometry measurement equipment separates gravity deformation by changing the wafer support method. However, this support method that completely offsets gravity deformation requires flipping the wafer to obtain overall topography information, which introduces new positioning errors. Thus, this support method that requires flipping the wafer introduces additional external force that cannot eliminate gravity deformation, and will also cause measurement errors in the geometry of large-size wafers. Summary of the Invention

[0004] In view of this, the purpose of this invention is to design a support mechanism for simultaneous measurement of both sides of a large wafer, which addresses the measurement error of its geometric morphology parameters caused by the deformation due to the self-weight of the large wafer in the prior art, thereby ensuring the measurement accuracy of the geometric morphology of the large wafer.

[0005] This invention provides a support mechanism for simultaneous double-sided measurement of large-size wafers, comprising a frame straight rod, a short cantilever beam rod, a middle bottom beam rod, a frame fixing block, a support positioning element, a spring, and a locking block. The ends of the frame straight rod and the short cantilever beam rod are connected to form a square frame via the frame fixing block. The middle bottom beam rod spans the short cantilever beam rod and is parallel to the frame straight rod. The middle bottom beam rod has an upper crossbeam and a lower crossbeam that are parallel to each other. The support positioning element extends through the upper crossbeam and supports the wafer to be measured through its upper end. A locking block is provided on the lower surface of the upper crossbeam of the support positioning element. The spring is disposed between the locking block and the lower crossbeam and surrounds the support positioning element.

[0006] Preferably, the supporting positioning element is a precision needle gauge.

[0007] Preferably, the straight frame rod is designed with through holes at both ends, and the short cantilever beam rod is provided with threaded holes at both ends. The spacing of the short cantilever beam is designed according to the spacing of the support points, and through holes are provided on the short cantilever beam rod. The middle bottom beam rod has a "20" shaped structure. The middle bottom beam rod is connected to the short cantilever beam rod by screws to form the main load-bearing part located at the bottom. The rest is left empty, leaving enough space to realize simultaneous measurement of the wafer by dual probes on both sides.

[0008] Preferably, the precision needle gauge has a diameter of 1mm, a length of 50mm, and is made of stainless steel; the clamping block has a diameter of 2.5mm, a hole diameter of 1mm, a thickness of 2mm, and is made of nylon material.

[0009] Preferably, the frame fixing block is L-shaped with a hollow center and is made of stainless steel.

[0010] Preferably, the upper end of the precision needle gauge is also fitted with a protective hose, which is a small screw-protected silicone sleeve to prevent the precision needle gauge from damaging the wafer.

[0011] Preferably, the positioning method of the wafer to be tested is to use a precision pin gauge to hold the positioning groove of the wafer on one side, and to use two extended precision pin gauges on the other side to prevent the wafer from rotating.

[0012] A measurement method for double-sided measurement of large-size wafers employs a support mechanism as described above for double-sided measurement of large-size wafers to support the wafer under test and performs simultaneous scanning of the double-sided morphology of the wafer using a dual-probe double-sided scanning scheme.

[0013] By adopting the above technical solution, the present invention can achieve the following technical effects: The present invention provides a support mechanism for simultaneous double-sided measurement of large-size wafers. The frame rod and the short cantilever beam are connected by screws to form the frame of the support mechanism. The middle bottom beam and the short cantilever beam of the short cantilever beam are connected by screws. The needle gauge passes through the support positioning hole, the locking block, the spring, and the support positioning hole from top to bottom (the two support positioning holes are coaxial, i.e., the support positioning coaxial hole between the middle bottom beam). The protective hose is sleeved on the upper end of the needle gauge. It can be seen that the outer diameter of the spring, the diameter of the locking block, the diameter of the needle gauge, and the outer diameter of the hose are all less than or equal to the width of the middle bottom beam. The frame of the support mechanism is left empty except for the space occupied by the middle bottom beam. The overall support mechanism components are small and do not obstruct the view, which facilitates the simultaneous measurement of the wafer morphology by two probes. The wafer is placed on the support pin gauge of the support mechanism. The wafer position is adjusted so that it is fixed by the limiting pin gauge (such as the support pin gauge installation). Due to its own weight, the pin gauge moves downward, causing the locking block to compress the spring. The spring generates a reaction force to counteract the self-weight effect of the wafer. This solves the problem in the prior art where changing the wafer support method to separate gravity deformation completely eliminates gravity deformation. The support method requires flipping the wafer to obtain overall morphology information, which introduces new positioning errors. This invention avoids the problem of introducing additional external force or failing to eliminate gravity deformation by flipping the wafer support method. Therefore, this invention solves the problem of measurement error caused by gravity deformation of large-size wafers in the prior art, and also solves the problem of error caused by additional external force introduced by flipping the wafer to obtain overall morphology information in the prior art to avoid measurement errors caused by gravity deformation. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 It is an ideal method for analyzing the self-weight deformation of large-size wafers under basic support conditions.

[0016] Figure 2 It is an ideal choice for support points on large-size wafers.

[0017] Figure 3 This is a three-dimensional schematic diagram of a support mechanism for simultaneous measurement of both sides of a large-size wafer, provided by an embodiment of the present invention.

[0018] Figure 4 This is a top view of a support mechanism for simultaneous measurement of both sides of a large-size wafer, provided in an embodiment of the present invention.

[0019] Figure 5 This is a front view of a support mechanism for simultaneous measurement of both sides of a large-size wafer, provided in an embodiment of the present invention.

[0020] Figure 6 This is a schematic diagram of a support mechanism provided in an embodiment of the present invention, which restores the original shape of a large-size wafer based on the flatness error.

[0021] Figure 7 (a) is a measurement side view provided by an embodiment of the present invention for simultaneous measurement of both sides of a large-size wafer.

[0022] Figure 7 (b) is a top view of a measurement method for simultaneous measurement of both sides of a large-size wafer, provided in an embodiment of the present invention.

[0023] The attached diagram is labeled as follows: 1-Straight frame rod, 2-Short cantilever beam rod, 3-Middle bottom beam rod, 4-Frame fixing block, 5-Support positioning precision pin gauge, 6-Spring, 7-Clip block, 8-Screw, 9-Protective hose, 10-Wafer to be tested, 11-Limiting precision pin gauge. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0025] Example

[0026] The following are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the following embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0027] This invention provides reference to [the relevant document]. Figures 1 to 7The first embodiment of the present invention provides a support mechanism for simultaneous double-sided measurement of large-size wafers, comprising: a frame straight rod 1, a short cantilever beam rod 2, a middle bottom beam rod 3, a frame fixing block 4, a support positioning precision pin gauge 5, a spring 6, a locking block 7, a screw 8, a protective hose 9, a wafer to be measured 10, and a limiting precision pin gauge 11; the ends of the frame straight rod 1 and the short cantilever beam rod 2 are connected to form a square frame by the frame fixing block 4, and the middle bottom beam rod 3 spans the short cantilever beam rod 2 and is connected to the frame straight rod 1. Parallel to each other, the intermediate bottom beam has an upper crossbeam and a lower crossbeam that are parallel to each other. The support positioning precision pin gauge 5 passes through the upper crossbeam and supports the wafer 10 to be tested through the upper end of the support positioning precision pin gauge 5. The support positioning precision pin gauge 5 is provided with a locking block 7 on the lower surface of the upper crossbeam. The locking block 7 and the lower crossbeam are provided with a spring 6, which is arranged around the support positioning precision pin gauge 5. The intermediate bottom beam 3 is provided with a limit positioning precision pin gauge 11 near the short cantilever beam 2.

[0028] Among them, the wafer under test 10 has its geometric parameters (warpage, curvature, and total thickness deviation) controlled within the range of 20 / 15μm. Under the nationally recommended three-point support method, the minimum self-weight deformation of a 12-inch ideal sapphire wafer (with a completely flat surface) reaches more than 60μm. Figure 1 As shown, self-weight deformation has a significant impact on the measurement of its geometric parameters. Based on three-point support, considering the scanning probe travels in a straight line, the support points are distributed horizontally and vertically. With four-point support, the minimum self-weight deformation at a distance of 105mm from the ideal wafer's geometric center is still over 20μm. Gradually expanding the support points, in simulation analysis with a 21-point support method (support point spacing 57mm), the self-weight deformation of the 12-inch ideal wafer is approximately 1.446μm, which is more than 46 times lower than the minimum deformation caused by the self-weight of the wafer under traditional three-point support, effectively alleviating wafer self-weight deformation. Compared to the wafer's 20 / 15μm geometric parameter control range, this is more than 10 times smaller, having a negligible impact on its measurement. Further increasing the number of support points does not significantly alleviate wafer self-weight deformation (see...). Figure 2 As shown in the figure, the increase in support points corresponds to a decrease in the distance between support points, which hinders the probe from measuring the geometry of the wafer.

[0029] Taking a 12-inch sapphire ideal wafer as an example, the self-weight deformation under 21-point rigid support is approximately 1.446μm. (See attached manual for details.) Figure 2As shown, it is assumed that the gravity of the wafer is evenly distributed to 21 support points, and each support point bears a gravity of about 0.06564 N. It can be seen that the gravity evenly distributed to each support point of the wafer is extremely small. In order to more realistically restore the true topography of the wafer, a compression spring is selected as the main component providing elastic support to offset the self-weight deformation of the large-size wafer. The spring selected should have a particularly obvious gravity deformation for the wafer, while the deformation caused by the changes in flatness, warp, and total thickness deviation should be as small as possible and can be ignored. Furthermore, it can ensure that the wafer remains in its original state during measurement. Therefore, small springs equal in number to the support points are required, and stainless steel is often selected for the small springs. The spring deformation formula is: (λ represents the deformation, n represents the number of active coils, d represents the wire diameter, G represents the shear modulus of the material, F represents the external force, D represents the mean diameter, and C = D / d represents the spring index). Referring to relevant data, as shown in Table 1, the smallest wire diameter of the standard spring is 0.1 mm, the maximum mean diameter is 1.3 mm, and the longest is 20 mm. After calculation, the deformation λ of this type of spring reaches 4.197 mm under 0.06564 N, and the influence on the flatness, warp, and total thickness deviation change value (≤20 μm) of the wafer itself is extremely small and can be almost ignored. Therefore, this type of small spring is selected, and a preload of 3.9 mm is given to ensure that the support force differences caused by the unevenness of the wafer at each support point are very small.

[0030] Table 1 Deformation corresponding to different types of springs under a 12-inch wafer

[0031] Spring type Valid number of laps Wrap ratio Deformation λ / mm 0.1*1.4*20 28 13 4.19677 0.15*3*15 9 19 2.80674 0.15*3*20 12.5 19 3.89826 0.2*4*20 13 19 3.04064 0.2*4*15 9 19 2.10506

[0032] Among them, there are two border straight rods 1 and two short cantilever beam rods 2, with a width of 4 mm and a thickness of 8 mm. 1.3-mm through holes are designed at both ends of the straight rods, and M1.2X4 threaded holes are designed at both ends of the short cantilever beam rods. The distance between the short cantilever beam rods is 57 mm, the width is 2.5 mm, and 1.3-mm through holes are designed on the short cantilever beams. The border of the support mechanism is formed by connecting with M1.2X8 screws. There are five middle bottom beam rods 3, which are roughly in the shape of "廿" but do not extend beyond the left and right sides, with a width of 2.5 mm. The cross bar is designed with 5 equally spaced support positioning coaxial holes with a diameter of 1.1 mm according to the support point spacing, and M1.2x4 threaded holes are designed at the top of the vertical rods. The main part of the support mechanism is formed by connecting with M1.2X10 screws to the short cantilever beams of the short cantilever beam rods 2. The space inside the border of the support mechanism where the middle bottom beam rods are not placed is left empty. The middle bottom beam rods are thin to ensure as little occlusion as possible, which helps the probe to perform double-sided simultaneous scanning of the wafer.

[0033] The springs 6 are 21 in number, selected from the above calculations as 0.1*1.3*20 type; the support positioning precision pin gauges 5 are 21 in number, made of bearing steel, selected as 1x50 type (diameter 1mm, length 50mm), with a chamfered end designed to support the wafer to prevent scratching the wafer; the clamping block 7 is designed with a diameter of 2.5mm, a hole diameter of 1mm, and a thickness of 2mm, and is made of nylon material. The springs are placed on the crossbar of the middle bottom beam between the support positioning coaxial holes. The pin gauges pass through the coaxial holes between the middle bottom beams and the springs. Due to the elasticity of the clamping block, the pin gauges can be fixed by the clamping block, making the springs, clamping blocks, pin gauges, and support positioning coaxial holes coaxial. During this process, the pin gauges support the wafer and also serve as guide rods for the springs, preventing the springs from becoming unstable.

[0034] Please refer to the instruction manual appendix. Figure 3-5 The second embodiment of the present invention provides a gravity deformation-resistant support mechanism for simultaneous measurement of both sides of a large-size wafer. The mechanism is designed and assembled in a "wire frame" manner. The middle bottom beam serves as a support for the spring. The structure is small, which minimizes obstruction and leaves enough space to enable simultaneous measurement of both sides of the probe.

[0035] Please refer to the instruction manual appendix. Figure 3-5 The third embodiment of the present invention provides a method for fixing a gravity deformation-resistant support mechanism for simultaneous measurement of both sides of a large-size wafer. This support mechanism can be placed in any measuring device to perform wafer geometry measurement according to this fixing method.

[0036] Specifically, in this embodiment, the frame fixing block 4 is L-shaped, 10mm thick, and has an 8.1x4mm space carved out along the left and lower sides. The upper wall is 5mm wider than the lower wall and is made of stainless steel. The four frame fixing blocks respectively hold the four corners of the support mechanism frame to prevent it from shaking. At the same time, the width of the wall extending from the top can place the entire support mechanism in the measuring equipment.

[0037] Please refer to the instruction manual appendix. Figure 5 The fourth embodiment of the present invention provides a method for preventing wafer damage during placement in an anti-gravity deformation support mechanism for simultaneous measurement of both sides of a large-size wafer, which uses a flexible tube to cover one end of the needle gauge to support the wafer.

[0038] Specifically, in this embodiment, one end of the support positioning precision needle gauge 5 is chamfered, and the protective hose 9 is a 1*2*3 type silicone rubber hose (1mm aperture, 2mm outer diameter, 3mm length), with one end spherically closed. The hose is fitted onto the chamfered end of the needle gauge to support the wafer, thus providing double protection against scratches on the wafer.

[0039] Please refer to the instruction manual appendix. Figure 3-5 The fifth embodiment of the present invention provides a wafer positioning method, which achieves physical positioning of the wafer through three positioning precision pin gauges 11.

[0040] Specifically, in this embodiment, the wafer 10 to be tested, as can be seen from relevant manufacturing processes, is positioned using "V"-shaped or "U"-shaped positioning grooves, with a groove depth of approximately 2-3 mm. The intermediate bottom beam 3 is placed on the three intermediate bottom beams in the middle and on both sides, with a pair of 1.1 mm diameter coaxial holes added near the edge. The intermediate bottom beam in the middle is designed with its coaxial holes 149.5 mm from its center, while the intermediate bottom beams on both sides are designed with their coaxial holes 100 mm from their centers. First, the positioning pins on the intermediate bottom beam in the middle are installed (using the same method as the support positioning pins described above). The positioning pins extend beyond the support positioning pins, and a protective flexible tube 9 (5 mm in length) is fitted over them. The wafer is moved and rotated so that its positioning groove contacts the positioning pins. Next, the positioning pins on the intermediate bottom beams on both sides are installed, and the wafer to be tested is adjusted to contact the positioning pins on both sides. It should be noted that in other embodiments, other limiting positions may be used, which are not specifically limited here, but these solutions are all within the protection scope of this invention.

[0041] Please see Figures 3 to 6 The sixth embodiment of the present invention provides a gravity deformation-resistant support method for simultaneous measurement of both sides of a large-size wafer. This mechanism can also be called a "conformal mechanism". This mechanism can effectively restore the wafer morphology according to the flatness error of the wafer itself.

[0042] Specifically, in this embodiment, the distance between the crossbars of the intermediate bottom beam 3 is designed to be 18.1mm, the spring 6 is selected as 0.1*1.3*20 model, and the clamping block 7 is 2mm thick and 2.5mm in diameter, with the diameter of the clamping block being larger than the outer diameter of the spring. The spring is placed between the coaxial holes supporting the intermediate bottom beam, and the clamping block is placed between the crossbar support positioning hole and the spring on the intermediate bottom beam. The needle gauge passes through the coaxial hole of the intermediate bottom beam, the clamping block, and the spring, and is fixed by the clamping block, thereby giving the spring a pre-compression deformation of 3.9mm as calculated in the first embodiment above. This pre-compression deformation is much greater than the wafer's own curvature, warpage, and total thickness deviation (≤20μm). When the wafer to be tested is placed on the supporting needle gauge, its own weight compresses the needle gauge, causing it to move downwards and compress the clamping block and the spring. Because the spring itself has a certain pre-compression deformation, the spring can ensure that each support point is in contact with the wafer based on its own elasticity. Figure 5 As shown, the difference in support force at each support point due to the unevenness of the wafer is very small, thus offsetting the bending deformation caused by the wafer's own weight. Therefore, the support mechanism can effectively restore the original shape of the wafer. In addition, when measuring wafers of other materials, the amount of spring deformation caused by the wafer's own weight can be calculated according to the calculation method in the first example above, and the adjustment block can be used to apply the corresponding preload to the spring at the position of the needle gauge.

[0043] Please refer to the instruction manual appendix. Figure 7The sixth embodiment of the present invention provides a method for simultaneous measurement of both sides of a large-size wafer, wherein the measurement probe is a color confocal probe.

[0044] Specifically, in this embodiment, the color confocal probe is model IFS2403-0.4, with a diameter of 8mm, a resolution of 16nm, a measurement range of 2.5mm, and two sensor references. Figure 7 (a) shows a coaxial mounting system. The corresponding guide rails are controlled to move at the same speed to simultaneously scan the topography of both sides of the wafer. For specific design of the movement path, refer to [reference needed]. Figure 7 (b) As indicated by the arrow markings, the probe has a step distance of 5.5 mm along the direction of the middle bottom beam and a step distance of 11 mm perpendicular to the direction of the middle bottom beam. This method avoids the positioning error introduced by flipping the wafer and ensures that more areas of the wafer are scanned.

[0045] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A support mechanism for simultaneous measurement of both sides of a large-size wafer, characterized in that, The device includes a frame straight rod, a short cantilever beam rod, a middle bottom beam rod, a frame fixing block, a support positioning element, a spring, and a locking block. The ends of the frame straight rod and the short cantilever beam rod are connected to form a square frame through the frame fixing block. The middle bottom beam rod spans the short cantilever beam rod and is parallel to the frame straight rod. The middle bottom beam rod has an upper crossbeam and a lower crossbeam that are parallel to each other. The support positioning element extends through the upper crossbeam and supports the wafer under test through its upper end. The support positioning element has a locking block on the lower surface of the upper crossbeam. The spring is disposed between the locking block and the lower crossbeam and is arranged around the support positioning element.

2. The support mechanism for simultaneous double-sided measurement of large-size wafers according to claim 1, characterized in that, The supporting positioning element is a precision needle gauge.

3. The support mechanism for simultaneous double-sided measurement of large-size wafers according to claim 2, characterized in that, The straight frame rod is designed with through holes at both ends, and the short cantilever beam rod is provided with threaded holes at both ends. The spacing of the short cantilever beam is designed according to the spacing of the support points, and through holes are provided on the short cantilever beam rod. The middle bottom beam rod has a "20" shaped structure. The middle bottom beam rod is connected to the short cantilever beam rod by screws to form the main load-bearing part located at the bottom. The rest of the part is left empty, leaving enough space to realize simultaneous measurement of the wafer by dual probes on both sides.

4. The support mechanism for simultaneous double-sided measurement of large-size wafers according to claim 2, characterized in that, The precision needle gauge has a diameter of 1mm, a length of 50mm, and is made of stainless steel; the clamping block has a diameter of 2.5mm, a hole diameter of 1mm, a thickness of 2mm, and is made of nylon material.

5. The support mechanism for simultaneous double-sided measurement of large-size wafers according to claim 1, characterized in that, The frame fixing block is L-shaped with a hollow center and is made of stainless steel.

6. The support mechanism for simultaneous double-sided measurement of large-size wafers according to claim 2, characterized in that, The upper end of the precision needle gauge is also fitted with a protective hose, which is a small screw-protected silicone sleeve to prevent the precision needle gauge from damaging the wafer.

7. The support mechanism for simultaneous double-sided measurement of large-size wafers according to claim 2, characterized in that, The wafer under test is positioned by using a precision pin gauge to hold the wafer in the positioning groove on one side, and using two extended precision pin gauges on the other side to prevent the wafer from rotating.

8. A measurement method for double-sided measurement of a large-size wafer, characterized in that, The support mechanism for simultaneous measurement of both sides of a large-size wafer, as described in any one of claims 1-7, is used to support the wafer under test and a dual-probe dual-side scanning scheme is used to simultaneously scan the morphology of both sides of the wafer.

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