Method and device for controlling warpage of semiconductor wafer
Patent Information
- Application Number
- PCT/KR2025/099555
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-08
- Filing Date
- 2025-03-05
- Publication Date
- 2025-10-02
AI Technical Summary
Current methods for controlling semiconductor wafer warpage, particularly in advanced manufacturing processes with fine line widths and stacked structures, are inefficient and costly, leading to reduced production yield and structural deformation, and there is no effective solution for severe warpage issues in wafer-level packaging processes.
A method and device using a pulsed laser beam with an infrared wavelength to form a modified layer inside the wafer, controlling its position and shape to manage warpage by forming residual stress patterns.
This approach quickly and effectively controls wafer warpage with minimal cost, improving production yield and reducing processing time, especially in ultra-stacked memories and wafer-level packaging, without the need for additional coatings.
Smart Images
Figure KR2025099555_02102025_PF_FP_ABST
Abstract
Description
Semiconductor wafer warpage control method and device
[0001] The present invention relates to a method and device for controlling wafer warpage that inevitably occurs during a semiconductor wafer manufacturing process, and more particularly, to a semiconductor wafer warpage control method and device capable of controlling the warpage of a wafer in a desired direction and size by forming a modified layer inside a semiconductor wafer using a pulsed laser beam having an infrared wavelength and controlling the position and shape of the modified layer.
[0002]
[0003] Recent cutting-edge semiconductor device manufacturing processes are producing semiconductor devices with fine line widths of less than 10 nm and stacked structures of hundreds of layers or more. These semiconductor manufacturing processes involve numerous heat treatment and thin film processes, during which thermal stress and physical stress due to differences in the properties of the stacked thin films naturally accumulate, resulting in wafer warpage. Pressure is applied to the 3D stacked thin films, causing the wafer to bend and deform like a bow, also known as wafer bow. This phenomenon reduces the degree of freedom (DoF) and overlay performance, particularly during the exposure process, and causes structural deformation, preventing proper pattern engraving.
[0004] Figure 1 shows that as NAND flash memory becomes more advanced, wafer warpage increases further. That is, as the number of layers increases to 32, 48, 64, 96, and 128, the degree of wafer warpage increases further. Recently, as the number of layers exceeds 200, wafer warpage has caused serious problems such as reduced production yield. To solve this wafer warpage problem, wafer warpage has been controlled by coating a thin film on the back of the wafer that creates stress opposite to the warpage direction. This additional coating of a thin film for wafer warpage control increases the number of coating processes, which significantly increases additional cost and time. Recently, wafer warpage has reached a serious situation where it can no longer be controlled by this backside coating film formation process. In addition, wafer warpage has become more severe in recent wafer-level packaging processes, such as grinding wafers, bonding wafers, and molding processes, but there is currently no method to control this wafer warpage.
[0005]
[0006] The present invention was created to solve the above-mentioned problems, and the problem to be solved by the present invention is to provide a semiconductor wafer warpage control method and device that can quickly and effectively control the warpage of a wafer by using a pulsed laser beam of an infrared wavelength to focus the laser beam inside the wafer, moving the wafer to form a modified layer inside the wafer, and controlling the height and shape of the modified layer.
[0007] The above objects and various advantages of the present invention will become more apparent to those skilled in the art from the preferred embodiments described below with reference to the accompanying drawings.
[0008]
[0009] A method for controlling warpage of a semiconductor wafer according to one aspect of the present invention for solving the above problem comprises the steps of: focusing a laser beam of a pulsed infrared wavelength into the interior through the back surface of a semiconductor wafer; forming a modified layer in the interior of the semiconductor wafer by utilizing a breakdown phenomenon occurring at a portion where the laser beam of the pulsed infrared wavelength is focused; and changing the formation height or pattern shape of the modified layer to control warpage of the semiconductor wafer.
[0010] According to one embodiment, the pulsed infrared wavelength laser beam has a wavelength in the range of 1 μm to 3 μm.
[0011] In one embodiment, the pulsed infrared wavelength laser beam has a pulse width of 10 ns to 500 nsec and a frequency of 10 kHz to 500 kHz.
[0012] According to one embodiment, the formation height of the modified layer is formed in a region of 10 to 100 μm from the upper surface of the semiconductor wafer or 10 to 100 μm from the lower surface of the semiconductor.
[0013] According to one embodiment, the shape of the modified layer is any one of an X-axis directional pattern formed along the X-axis direction, a Y-axis directional pattern formed along the Y-axis direction, a lattice directional pattern formed along both the X-axis and Y-axis directions, and a local region pattern formed only in a local region.
[0014] According to one aspect of the present invention for solving the above problem, a semiconductor wafer warpage control device comprises a wafer support for supporting a semiconductor wafer so that its back surface faces upward, a wafer transfer unit for transferring the semiconductor wafer in the x-axis and y-axis, a laser beam size control unit for controlling the size of a pulsed infrared laser beam, a laser beam transmission unit for transmitting the pulsed infrared laser beam toward the semiconductor wafer, and a laser beam focus forming unit for focusing the pulsed infrared laser beam on the inside of the semiconductor wafer to form a laser modification layer on the inside of the semiconductor wafer.
[0015] According to one embodiment, the semiconductor wafer warpage control device further includes an infrared camera for confirming the formation of the laser modified layer.
[0016] According to one embodiment, the warpage state of the semiconductor wafer can be measured in advance by a wafer warpage measurement unit before the back surface of the semiconductor wafer is supported upward by the wafer support.
[0017] According to one embodiment, the wafer warpage measurement unit may include one of a displacement sensor and a refractometer.
[0018]
[0019] When using the semiconductor wafer warpage control method and device according to the present invention, compared to the existing warpage control method using thin film coating, it takes less time and costs less, can increase the yield, and has the effect of greatly improving the production yield in the production of ultra-stacked memories, the production of ultra-fine pattern devices, and wafer-level packaging processes, where warpage is currently a major problem due to the very large amount of wafer warpage control. In addition, the semiconductor wafer warpage control method and device according to the present invention has the advantage of being able to control wafer warpage at a very low cost because it requires almost no consumable costs.
[0020]
[0021] Figure 1 is a drawing for explaining the problem of semiconductor wafer warpage that occurs in the semiconductor wafer manufacturing process.
[0022] FIG. 2 is a drawing for explaining a method for forming a modified layer inside a semiconductor wafer according to one embodiment of the present invention.
[0023] FIG. 3 is a drawing for explaining a wafer warpage control method using a semiconductor wafer internal modification layer according to one embodiment of the present invention.
[0024] FIG. 4 is a drawing showing examples of pattern shapes for controlling semiconductor wafer warpage according to one embodiment of the present invention.
[0025] Figure 5 is a schematic diagram related to semiconductor wafer warpage measurement.
[0026] Figure 6 is a schematic diagram of a semiconductor wafer warpage control device according to one embodiment of the present invention.
[0027] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. It should be noted that the attached drawings and examples are simplified and illustrative, intended to assist those skilled in the art in understanding the present invention.
[0028] FIG. 2 is a drawing for explaining a method for forming a semiconductor wafer internal modification layer according to an embodiment of the present invention, FIG. 3 is a drawing for explaining a wafer warpage control method using a semiconductor wafer internal modification layer according to an embodiment of the present invention, FIG. 4 is a drawing showing examples of pattern shapes for semiconductor wafer warpage control according to an embodiment of the present invention, FIG. 5 is a schematic diagram related to semiconductor wafer warpage measurement, and FIG. 6 is a schematic diagram of a semiconductor wafer warpage control device according to an embodiment of the present invention. In some drawings (FIGS. 2 and 4), the wafer is expressed by enlarging a portion thereof, and for convenience, only a portion of the cross-section of the laser modification layer (100) and the wafer (W) is simplified and shown.
[0029] Although FIG. 2 is a drawing for explaining the present invention, the following is provided with reference to FIG. 2 in relation to a conventional wafer cutting process. A pulsed laser beam (110) is focused onto the inside of a wafer (W) through a focusing lens (120). When the peak power of the focused pulsed laser beam is sufficiently large, a strong breakdown phenomenon occurs at the focus position, causing instantaneous melting, vaporization, and plasma phenomena, thereby changing the structure of the silicon wafer. When this breakdown phenomenon is continuously generated by moving the wafer (W) or the laser beam (110), a modification layer (100) is formed by the laser beam (110). The actual appearance of the modification layer (100) is as shown in the cross-sectional photograph in (c) of FIG. 2. After continuously forming such a modified layer (100) inside the wafer (W), if a slight impact is applied to the wafer (W), the modified layer (100) acts as a crack point, enabling the wafer (W) to be cut. This is called laser stealth cutting, and is currently widely used in the industry as a method for cutting wafer dies.
[0030] In the case of the present invention, unlike the existing process for laser stealth cutting, it is characterized in that the warpage of the wafer (W) is controlled by precisely controlling the height and shape of the modified layer (100).
[0031] Continuing with reference to FIG. 2, if the output and frequency of the laser beam (110), the moving speed of the wafer (W) or the laser beam (110), and the on / off of the laser beam (110) are precisely controlled, the height (s) of the modified layer (100), the length (l) of the modified layer (100), and the spacing (d) between the modified layers can be adjusted, as shown in FIG. 2. In addition, the formation height (h) of the modified layer can be adjusted by adjusting the focus position of the laser beam (LB). At this time, the laser beam (110) used is an infrared wavelength laser beam with good transmittance to the silicon wafer (W). Preferably, a laser beam having a wavelength in the range of 1 μm to 3 μm is good. In order to effectively form the modified layer (100) inside the wafer (W), a pulsed laser beam (110) must be used, and a short pulse width is used to create sufficient peak power. Preferably, the pulse width should be between 10 ns (nanoseconds) and 500 ns. And the frequency should be between 10 kHz and 500 kHz.
[0032] In addition, the shape of the laser beam is also important for the formation of a stable modified layer. An ideal Gaussian shape is desirable, and the beam quality factor (M) is 2 ) is preferably 1.5 or less. In order to form the modified layer (100), the wafer (W) or the focus lens (120) of the laser beam must be moved in the direction of the arrow (130). The moving speed of the wafer (W) or the focus lens (120) of the laser beam is preferably 10 mm / sec to 1000 mm / sec. If it is too slow or too fast, a problem occurs in the quality of the modified layer (100).
[0033] FIG. 3 is a drawing for explaining a wafer warpage control method using a semiconductor wafer internal modification layer according to one embodiment of the present invention.
[0034] Referring to FIG. 3 together with FIG. 2, (a) of FIG. 3 shows a case where a modified layer (100a) is formed at a position close to the lower part of the wafer (W1) (i.e., a position relatively closer to the lower surface than the upper surface, and having a distance of h1 from the lower surface), and (b) of FIG. 3 shows a case where a modified layer (100b) is formed at a position close to the upper part of the wafer (W2) (i.e., a position relatively closer to the upper surface than the lower surface, and having a distance of h2 from the upper surface).
[0035] As shown in (a) of Fig. 3, when the focus position of the laser beam is focused to a position close to the lower part of the wafer (W1) and the wafer (W1) or the focus lens (120) of the laser beam is moved, a laser modified layer (100a) is formed at that position. The volume of the modified layer (100a) expands due to laser breakdown at that position of the wafer (W1), and as a result of this volume expansion and the formation of strong residual stress, the wafer (W1) is warped upward (i.e., becomes convex downward), as shown in (c) of Fig. 3.
[0036] In contrast, when the focus position of the laser beam is focused to a position close to the upper part of the wafer (W2) as shown in (b) of FIG. 3 and the wafer (W2) or the focus lens (120) of the laser beam is moved, the laser modified layer (100b) is formed at that position. The volume of the modified layer (100b) due to laser breakdown occurs at that position of the wafer (W2), and as a result of this volume expansion and the formation of strong residual stress, the wafer (W2) is warped downward (i.e., becomes convex upward), as shown in (d) of FIG.
[0037] In (a) and (c) of FIG. 3 and (b) and (d), the degree of warpage is proportional to the amount of the modified layer (100a), and the degree of warpage is greater the closer the formation height (h) of the modified layer (100) is formed to the lower surface of the wafer (W1) (in the case of (a) and (c)) or the closer it is formed to the upper surface of the wafer (W2) (in the case of (b) and (d)). It is preferable that the formation heights (h1, h2) of the modified layers (100a, 100b) for effective warpage control be between 10 µm and 100 µm. As a result of the experiment, when the height of the modified layer (100a, 100b) is less than 10 µm, there is a high possibility of causing damage to the surface of the wafer (W1, W2), and when the height of the modified layer (100a, 100b) exceeds 100 µm, there is a disadvantage in that the size of the warpage is reduced. As a result, it is desirable to control the degree of warpage of the wafer (W1, W2) by maintaining the formation height (h1, h2) of the modified layer (100a, 100b) at 10 µm to 100 µm and controlling the length (l, see FIG. 2) and interval (d) of the modified layer (100a, 100b) to control the total amount of the modified layer (100a, 100b).
[0038] FIG. 4 is a drawing showing examples of pattern shapes for controlling warpage of a semiconductor wafer according to one embodiment of the present invention.
[0039] The pattern shown in (a) of Fig. 4 is a grid pattern, which is formed symmetrically left and right so that warpage can be uniformly adjusted over the entire wafer area, and is an appropriate pattern when adjusting the warpage of the wafer up and down. The amount of warpage can be appropriately adjusted by adjusting the x-axis pitch (△x) and the y-axis pitch (△y). The x-axis pitch (△x) is the spacing in the x-axis direction between wafer modification layers formed along the y-axis, and the y-axis pitch (△y) is the spacing in the y-axis direction between wafer modification layers formed along the x-axis. The smaller the pitch, the greater the amount of warpage, and the larger the pitch, the smaller the amount of warpage.
[0040] The x-axis pattern and y-axis pattern shown in (b) and (c) of Fig. 4 are used when the modified layer is formed in only one direction to greatly increase the warpage in a specific direction. The x-axis pattern shown in (b) of Fig. 4 causes a large left-right warpage with respect to the x-axis, and the y-axis pattern shown in (c) causes a large left-right warpage with respect to the y-axis. In order to locally increase the warpage, a local area pattern can be used as in (d) of Fig. 4. Although a y-axis pattern is exemplified in (d), not only a y-axis pattern but also an x-axis pattern or a lattice pattern can be formed in a local area. In the various patterns of Fig. 4, the vertical direction of the warpage can be controlled by patterning by determining whether the formation height (h) of the modified layer is to be close to the upper surface or close to the lower surface (see Fig. 3). In other words, the vertical direction of the bending is controlled by the height of the formation of the modified layer (see Fig. 3), and the left and right directions of the x-axis and y-axis are controlled by the shape of the pattern (see Fig. 4).
[0041] FIG. 5 is a schematic diagram related to semiconductor wafer warpage measurement, and FIG. 6 is a schematic diagram of a semiconductor wafer warpage control device according to one embodiment of the present invention.
[0042] In order to control the warpage of the wafer (W), it is very important to measure the degree of warpage of the wafer (W). Therefore, before controlling the warpage of the wafer using a wafer warpage control device on a peninsula as shown in FIG. 6, it is preferable to perform a wafer warpage measurement step as shown in FIG. 5 to determine the degree of wafer warpage. The wafer warpage measurement step is performed using a wafer support (220) on which the wafer (W) is seated and a wafer warpage measurement unit (210) for measuring wafer warpage. The wafer support (220) must support the wafer (W) so that no external force is applied to it, and can be supported using a precision-machined plane with high flatness or by placing the wafer on three pins. It is preferable that the three pins be located midway between the center and the periphery of the wafer, rather than at the periphery of the wafer. In the case of a 300 mm wafer, a point about 75 mm from the center is preferable, and in the case of a 200 mm wafer, a point about 50 mm from the center is preferable. As a warpage measuring device (210), a displacement sensor for measuring the height of a wafer (W) can be used, or a deflectometer that takes a deflection image with a camera and determines the degree of warpage can be used. The deflectometer has the advantage of being able to quickly determine the degree of warpage with just a few pictures taken with a camera.
[0043] As shown in Fig. 5, after the degree of warpage of a wafer (W) is measured using a wafer warpage measuring device (210) on a wafer support (200), a wafer warpage adjustment step is performed using a device shown in Fig. 6 to correct the warpage. The transition from the wafer warpage measuring step of Fig. 5 to the wafer warpage adjustment step of Fig. 6 can be performed automatically using a transfer robot.
[0044] The wafer warpage adjustment step of FIG. 6 is performed while the wafer (W) is seated on the wafer chuck (330) on the wafer transfer unit (320). The wafer (W) is turned over and seated on the wafer chuck (330), so that the back surface (WB) of the wafer (W) faces upward. At this time, a protective member such as a film may be used to protect the surface of the wafer on which the semiconductor element pattern is formed. The protected wafer is turned over and firmly fixed to the wafer chuck (330). At this time, the wafer chuck (330) uses vacuum or static electricity to hold the front surface of the wafer flat. The wafer firmly fixed to the wafer chuck (330) is moved in the x-axis and y-axis to form a modified layer at an appropriate location inside the wafer. The diameter of the laser beam (LB) emitted from the laser generation unit (311) can be adjusted through the laser beam size adjustment unit (312). The larger the diameter of the laser beam (LB), the smaller the focus can be. Therefore, in order to form a precise laser modification layer, it is desirable to increase the diameter of the laser beam to 5 mm or more. The laser beam output through the laser beam size adjustment unit (312) is transmitted to the laser beam focus forming unit (315) through the laser beam transmission unit (314). An optical fiber and a reflective mirror can be used as the laser beam transmission unit (314). Alternatively, a galvanic scanner that moves two reflective mirrors at high speed to scan the laser beam at high speed can be used. The laser beam is focused at a certain position inside the wafer through the laser beam focus forming unit (315). At this time, in order to create a focus of a sufficiently small size, it is desirable to use a lens with a magnification of 10 times or more. In addition, when the galvanic scanner is used as the laser beam transmission unit (314), it is desirable to use an f-θ lens or a telecentric lens. An infrared camera (313) may be installed to check the process of forming a modified layer by a laser beam in real time.Since infrared rays have the characteristic of penetrating silicon, using an infrared camera (313) has the advantage of being able to monitor the formation process of the modified layer in real time. In addition, it can be used to check whether the desired pattern has been properly formed after the formation of the modified layer. Since the laser beam used for modification is also infrared, it is preferable to install a filter that blocks the laser wavelength used in front of the infrared camera (313). When an optical fiber is used as the laser beam transmission unit (314), the laser beam size adjustment unit (312) is installed at the rear end of the laser beam transmission unit (314), and the laser beam with the adjusted size is introduced into the laser beam focus formation unit (315). If the diameter of the laser beam coming from the laser generation unit (310) is sufficiently large or the magnification of the focus lens is sufficiently large, the laser beam size adjustment unit (312) may be omitted.
[0045] As a result, according to the present invention, a modified layer is formed inside a wafer using a pulsed laser beam of an infrared wavelength, and by controlling the height and shape of the modified layer, the warpage of the wafer can be effectively controlled up and down and left and right, and the process for this has the advantage of being simple and the processing speed is very fast.
[0046] The semiconductor wafer warpage control method and device according to the present invention can be applied to various processes. For example, the semiconductor wafer warpage control method and device according to the present invention can be applied to a multilayer NAND memory manufacturing process, a multilayer DRAM memory manufacturing process, a 10 nm or less fine pattern device manufacturing process, a wafer-level packaging process, and the like.
[0047] It should be noted that the above description merely exemplifies preferred embodiments of the present invention, and therefore, those skilled in the art may make modifications and variations to the present invention without changing the gist of the invention, and the scope of the present invention is defined by the claims below.
[0048] <Explanation of symbols>
[0049] 100: Modified layer
[0050] 110: Pulse wave laser beam
[0051] 120: Focusing lens
[0052] W: Wafer
[0053] s: height of the modified layer
[0054] l: length of the modified layer
[0055] d: spacing between modified layers
[0056] h: Formation height of the modified layer
Claims
1. A method for controlling warpage of a semiconductor wafer, A step of focusing a pulse wave infrared wavelength laser beam into the interior through the back surface of a semiconductor wafer; A step of forming a modified layer inside the semiconductor wafer by utilizing the breakdown phenomenon occurring at the focused portion of the pulse wave infrared wavelength laser beam; and A method for controlling warpage of a semiconductor wafer, characterized in that it comprises a step of changing the formation height or pattern shape of the modified layer to control warpage of the semiconductor wafer.
2. In claim 1, A semiconductor wafer warpage control method, characterized in that the laser beam of the pulse wave infrared wavelength has a wavelength in the range of 1 ㎛ to 3 ㎛.
3. In claim 1, A semiconductor wafer warpage control method, characterized in that the laser beam of the pulse wave infrared wavelength has a pulse width of 10 ns to 500 nsec and a frequency of 10 kHz to 500 kHz.
4. In claim 1, A method for controlling warpage of a semiconductor wafer, characterized in that the formation height of the modified layer is formed in an area of 10 to 100 μm on the upper surface of the semiconductor wafer or 10 to 100 μm on the lower surface of the semiconductor.
5. In claim 1, A method for controlling warpage of a semiconductor wafer, characterized in that the shape of the above-mentioned modified layer is any one of an X-axis pattern formed along the X-axis direction, a Y-axis pattern formed along the Y-axis direction, a lattice pattern formed along both the X-axis and Y-axis directions, and a local area pattern formed only in a local area.
6. A wafer support that supports the back surface of a semiconductor wafer so that it faces upward; A wafer transfer unit for transferring the semiconductor wafer in the x-axis and y-axis; A laser beam size adjustment unit for adjusting the size of a pulse wave infrared laser beam; A laser beam transmission unit that transmits the pulse wave infrared laser beam toward the semiconductor wafer; and A semiconductor wafer warpage control device, characterized by including a laser beam focus forming unit that focuses the pulse wave infrared laser beam onto the inside of the semiconductor wafer to form a laser modification layer on the inside of the semiconductor wafer.
7. In claim 6, the semiconductor wafer warpage control device, A semiconductor wafer warpage control device, characterized in that it further includes an infrared camera for confirming the formation of the laser modified layer.
8. In claim 6, A semiconductor wafer warpage control device, characterized in that the warpage state of the semiconductor wafer is measured in advance by a wafer warpage measurement unit before the back surface of the semiconductor wafer is supported upward by the wafer support.
9. In claim 8, A semiconductor wafer warpage control device, characterized in that the wafer warpage measurement unit includes one of a displacement sensor and a refractometer.