Laser marking method for wafer and wafer
By grinding and groove formation on the back of the wafer, combined with laser marking and etching, the problem of the ridges of the character pits periphery after laser marking of the wafer is solved, and the flatness and polishing effect of the wafer are improved.
Patent Information
- Application Number
- CN202411381738.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2024-12-27
AI Technical Summary
During the laser marking process of wafers, bulges are prone to appear on the periphery of the character pit, which affects the flatness of the wafer. It is difficult for the prior art to effectively solve this problem.
By grinding the back of the wafer, a groove covering the area to be marked with laser, and a first etching process is performed after laser marking, so that a step-like morphology is formed between the character pit and the groove, and then a double-purpose process is performed During surface polishing, the polished abrasive particles can slide into the groove to avoid insufficient polished abrasive particles on the periphery of the character pit and suppress the appearance of the bulge.
It effectively improves the flatness of the wafer, avoids the bulge on the outer periphery of the character pit, and ensures the uniformity and effect of the double-sided polishing process.
Smart Images
Figure CN119208208A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present disclosure relate to the field of semiconductor manufacturing technology, and more particularly to a laser marking method for wafers and wafers. Background Art
[0002] Wafers have become the basic material for manufacturing semiconductor devices due to their good electron mobility, thermal conductivity and controllable doping characteristics. Usually, during the wafer manufacturing process, specific information is printed on the back of the wafer in a specific way to facilitate tracking, control and verification of the source of the wafer, and this specific method includes laser marking.
[0003] Currently, when laser marking is performed on the back of a wafer, each character is usually realized by a plurality of character pits arranged in a specific array. The laser irradiation will form a ridge on the periphery of each character pit. Although the wafer is etched after laser marking to remove the ridge, it is found that there are still ridges on the periphery of the character pits after double-sided polishing of the etched wafer. These ridges cause the flatness of the wafer to decrease.
[0004] In view of this, it is currently urgent to provide a laser marking method in which no raised portion appears on the periphery of the character pit after laser marking. Summary of the invention
[0005] In view of this, the embodiments of the present disclosure are intended to provide a laser marking method and wafer for wafers; a wafer can be manufactured in which the periphery of the character pits in the laser-marked characters has no raised portions, thereby improving the flatness of the wafer.
[0006] The technical solution of the embodiment of the present disclosure is implemented as follows: In a first aspect, an embodiment of the present disclosure provides a laser marking method for a wafer, the laser marking method comprising: Grinding the back side of the wafer so that the thickness of the wafer decreases from the center of the wafer to the edge of the wafer; forming a groove on the back side of the wafer, wherein the groove covers the area to be laser marked on the back side of the wafer, and an outline of a first projection of the groove on the back side of the wafer entirely exceeds an outline of a second projection of the area to be laser marked on the back side of the wafer; Performing laser marking on the area to be laser marked; performing a first etching process on the wafer; The wafer is double-sided polished. The depth of the groove is set such that the groove still exists after undergoing the first etching process.
[0007] In some examples, forming a groove on the back side of the wafer includes: An oxidation treatment is performed on the back side of the wafer in the area where the groove is to be formed, and a second etching treatment is performed on the area where the groove is to be formed, so as to form the groove.
[0008] In some examples, the oxidation treatment is achieved by heating the area where the groove is to be formed using a laser, wherein the energy density of the laser is 1×10 2 W / cm 2 Up to 1×10 3 W / cm 2 .
[0009] In some examples, the second etching process is an acid etching process.
[0010] In some examples, the etching solution of the second etching process is an HF solution or a buffered oxide etching solution, wherein the concentration of the HF solution or the HF solution in the buffered oxide etching solution is 45% to 49%, and the duration of the second etching process is 190s to 550s.
[0011] In some examples, the groove has a depth of 1.9 μm to 5.5 μm.
[0012] In some examples, the profile of the first projection exceeds the profile of the second projection by 1 mm to 3 mm in a radial direction of the wafer.
[0013] In some examples, the first etching process is an alkaline etching process.
[0014] In some examples, the etching solution of the first etching process is a KOH solution, and the concentration of the KOH solution is 42% to 47%, and the duration of the first etching process is 200 seconds to 215 seconds.
[0015] In a second aspect, an embodiment of the present disclosure provides a wafer, which is laser marked according to the laser marking method for wafers described in the first aspect, and when the edge removal amount of the wafer is 2 mm, after the laser marking, the total thickness deviation corresponding to the area of the wafer other than the laser marked area is 160 nm to 200 nm.
[0016] The embodiments of the present disclosure provide a laser marking method and a wafer for a wafer; in the present disclosure, the back side of the wafer is ground to reduce the thickness of the wafer from the center to the edge of the wafer, and then a groove is formed on the back side of the wafer, and the groove covers the area to be laser marked on the back side of the wafer, and then when the wafer is subjected to a first etching process after the area to be laser marked is laser marked, a step-like morphology is formed between the periphery of the character pit in the character formed after the laser marking and the groove, and then when the wafer is double-sided polished, the polishing abrasive grains can slide into the groove along the back side of the inclined wafer W and fall into the above-mentioned character pit, thereby avoiding the phenomenon of insufficient polishing abrasive grains on the periphery of the above-mentioned character pit, suppressing the appearance of ridges on the periphery of the character pit, and improving the flatness of the wafer W. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 A schematic diagram of a ridge appearing on the periphery of a character pit in the related art; Figure 2 A schematic flow chart of a laser marking method for wafers provided in an embodiment of the present disclosure; Figure 3 A schematic diagram of a back side of a wafer after grinding according to an embodiment of the present disclosure; Figure 4 A schematic diagram of the positional relationship between the groove and the area to be laser marked provided in an embodiment of the present disclosure; Figure 5 A schematic diagram of the back side structure of a wafer after laser marking provided by an embodiment of the present disclosure; Figure 6 A schematic diagram of the back side structure of a wafer after a first etching process provided by an embodiment of the present disclosure; Figure 7 A schematic diagram of double-sided polishing of a wafer provided in an embodiment of the present disclosure. DETAILED DESCRIPTION
[0018] The technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure.
[0019] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present disclosure are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products or apparatuses.
[0020] In the embodiments of the present disclosure, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present disclosure should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.
[0021] In addition, unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The words "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components.
[0022] The basic principle of laser marking on wafers is: the laser generator emits high-energy continuous laser, and the focused laser acts on the printing material, causing the material on the wafer surface to melt instantly or even vaporize. By controlling the path of the laser on the surface of the wafer material, the required graphic mark is formed.
[0023] Specifically, the above-mentioned laser includes infrared laser, CO2 laser or solid laser, etc.
[0024] In the related art, when a wafer is subjected to double-sided polishing after laser marking, ridges often appear around the periphery of the character pits in the characters formed by the laser marking.
[0025] After studying this, the inventor found that the reasons why the above-mentioned ridges appear on the periphery of the character pits after laser marking on the wafer include: On the one hand, when the wafer is etched after laser marking, tiny protrusions or warping are easily generated on the periphery of the character pits during the etching process.
[0026] Specifically, the purpose of etching the wafer after laser marking is to remove silicon slag or melt produced during the laser melting process around the character pit. During the laser melting process, the surface of the area around the character pit will undergo slight single-crystal silicon denaturation or oxidation, resulting in a different etching removal rate between this area and other areas on the wafer. Therefore, during the etching process, tiny bulges or warping are easily produced around the character pit.
[0027] On the other hand, during the double-sided polishing process, the polishing abrasive particles acting on the periphery of the character pits may be insufficient, as shown in the following example. Figure 1 shown.
[0028] When polishing slurry is supplied between the polishing pad 1 and the wafer W to perform double-sided polishing on the wafer W, polishing abrasive particles (shown as black circles in the figure) contained in the polishing slurry fall into the character pit D, causing the outer periphery of the character pit D ( Figure 1 The polishing abrasive grains (shown as the dotted ellipse in the figure) are insufficient, so the polishing rate corresponding to the periphery of the character pit D is lower than the polishing rate of other areas on the back of the wafer W, which leads to a reduction in the polishing amount corresponding to the periphery of the character pit D compared with the polishing amount of other areas on the back of the wafer W, thereby causing the above-mentioned tiny protrusions or warps to transform into higher protrusions 2. It can be understood that the protrusions 2 on the periphery of the character pit D will cause the flatness of the wafer W to deteriorate.
[0029] It should be noted that the above-mentioned polishing slurry includes an alkaline slurry using colloidal silica as polishing abrasive particles.
[0030] In view of this, the inventors hope to provide a laser marking method for wafers, which can suppress the phenomenon of insufficient polishing abrasive particles at the periphery of the character pit D during the double-sided polishing process to avoid the appearance of a raised portion 2 at the periphery of the character pit D.
[0031] Specifically, see Figure 2 The laser marking method for wafers provided in the present disclosure includes the following steps.
[0032] In step S201 , the back side of the wafer W is ground so that the thickness of the wafer decreases from the center of the wafer W to the edge of the wafer W.
[0033] like Figure 3 As shown, the back side of the wafer W is ground so that the thickness of the wafer W is reduced from the center of the wafer W to the edge of the wafer W. That is, after the grinding process, the morphology of the back side of the wafer W is as shown in FIG. Figure 3 The "V" shape in the middle.
[0034] Of course, in some examples, the present disclosure only limits the thickness of the wafer W to decrease from the center of the wafer W to the edge of the wafer W after the grinding process, but does not limit the morphology of the back side of the wafer W to Figure 3 The "V" shape and other shapes that satisfy the requirement that the thickness of the wafer W decreases from the center of the wafer W to the edge of the wafer W also fall within the protection scope of the present disclosure.
[0035] In step S202, a groove is formed on the back side of the wafer W, wherein the groove covers the area to be laser marked on the back side of the wafer W, and an outline of a first projection of the groove on the back side of the wafer W as a whole exceeds an outline of a second projection of the area to be laser marked on the back side of the wafer W.
[0036] like Figure 4 As shown, in the present disclosure, a groove 401 (shown as a dashed rectangle in the figure) is provided to cover the area 402 to be laser marked (shown as a dotted rectangle in the figure), and the outline of the first projection of the groove 401 on the back side of the wafer W (the dashed box in the figure) as a whole exceeds the outline of the second projection of the area 402 to be laser marked on the back side of the wafer W (the dashed box in the figure).
[0037] In step S203, laser marking is performed on the area to be laser marked.
[0038] It should be noted that the laser marking method used in the present disclosure is a laser marking method, which is used to quickly perform laser marking on the above-mentioned area to be laser marked.
[0039] In addition, in the present disclosure, a solid-state laser is selected for laser marking to minimize the thermal damage to the wafer W as much as possible.
[0040] In step S204, a first etching process is performed on the wafer; It should be noted that the first etching process is performed on wafer W after laser marking on the back side of wafer W, mainly to remove the damage caused to wafer W after the grinding process, and to clean up the impurities generated in the groove 401 after laser marking, so as to avoid affecting the polishing effect of the subsequent double-sided polishing process.
[0041] In step S205, the wafer W is double-sided polished. The depth of the groove 401 is set such that the groove 401 still exists after the first etching process.
[0042] like Figure 5 As shown, after a groove 401 is formed on the back side of the wafer W, a character pit D is formed after laser marking is performed in the area 402 to be laser marked.
[0043] After laser marking, the wafer W is subjected to a first etching process, wherein Figure 6 The filling region W1 shown in FIG. 4 is a portion removed after the first etching process, and the groove 401 still exists after the first etching process.
[0044] It can be understood that after the first etching process, the groove 401 and the periphery of the character pit D form a stepped morphology ( Figure 6 ), so Figure 7As shown, during the double-sided polishing process, after polishing slurry is supplied between the polishing pad P and the back of the wafer W, the polishing abrasive particles can slide down to the above-mentioned groove 401 through the tilted back of the wafer W and under the action of their own gravity, and fall into the character pit D through the step between the groove 401 and the outer periphery of the character pit D.
[0045] It should be noted that although the polishing abrasive particles will still fall into the character pit D, the polishing abrasive particles will continuously slide toward the groove 401 during the double-sided polishing process. Therefore, there will be no problem of insufficient polishing abrasive particles on the periphery of the character pit D. Furthermore, during the double-sided polishing process, after the portion corresponding to the groove 401 is removed, the polishing rate of the periphery of the above-mentioned character pit D can be kept consistent with the polishing rate of other areas on the back side of the wafer W, thereby ensuring that the overall polishing amount of the back side of the wafer W except for the laser-marked area is consistent, suppressing the appearance of the above-mentioned protrusion 2, and improving the flatness of the wafer W.
[0046] It should be noted that in the present disclosure, the groove 401 still exists after the first etching process, and the groove 401 can be removed after the double-sided polishing process.
[0047] In the present disclosure, the back side of wafer W is ground to reduce the thickness of wafer W from the center to the edge of wafer W, and then a groove 401 is formed on the back side of wafer W, and the groove 401 covers the area to be laser marked on the back side of wafer W. Then, after laser marking is performed on the area to be laser marked, a first etching process is performed, so that a step-like morphology is formed between the periphery of the character pit in the character formed after laser marking and the groove 401. Then, when double-sided polishing is performed on wafer W, the polishing abrasive grains can slide along the inclined back side of wafer W into the groove 401 and fall into the character pit D, thereby avoiding the phenomenon of insufficient polishing abrasive grains on the periphery of the character pit D, suppressing the appearance of a raised portion 2 on the periphery of the character pit D, and improving the flatness of wafer W.
[0048] for Figure 2 In some possible implementations of the technical solution shown, the forming of the groove 401 on the back side of the wafer W includes: An oxidation treatment is performed on the back surface of the wafer W in the region where the groove 401 is to be formed, and a second etching treatment is performed on the region where the groove 401 is to be formed, so as to form the groove 401 .
[0049] In the specific implementation process, the area on the back side of the wafer W where the above-mentioned groove 401 is to be formed is oxidized, so that oxides such as silicon oxide can be produced in the area where the groove 401 is to be formed. Then, after performing a second etching process, these oxides such as silicon oxide can be removed to form the groove 401.
[0050] In the present disclosure, by first performing an oxidation treatment on the area where the groove 401 is to be formed and then performing a second etching treatment, the shape and depth of the groove 401 can be accurately controlled. In addition, the position of the groove 401 can also be accurately controlled to avoid displacement.
[0051] In addition, the area on the back side of the wafer W where the groove 401 is to be formed is oxidized and then subjected to a second etching process, so that the rate of forming the groove 401 can be increased.
[0052] In addition, in the present disclosure, the method for forming the groove 401 is not limited to the above-mentioned technical solution. For example, in a specific implementation process, the back side of the wafer W except for the area where the groove 401 is to be formed can be covered with a mask, and then an etching method is used to only etch the area where the groove 401 is to be formed to form the groove 401.
[0053] For the above-mentioned embodiments, in some examples, the above-mentioned oxidation treatment is achieved by heating the area where the above-mentioned groove 401 is to be formed by using a laser, wherein the energy density of the above-mentioned laser is 1×10 2 W / cm 2 Up to 1×10 3 W / cm 2 .
[0054] In order to oxidize the area on the back side of the wafer W where the groove 401 is to be formed, in the present disclosure, a laser is used to heat the area where the groove 401 is to be formed to generate oxides such as silicon oxide.
[0055] In addition, in order to prevent damage to the areas other than the area where the groove 401 is to be formed in the wafer W during the heating process, such as the denaturation or oxidation of the single crystal silicon, the energy density of the laser is limited to 1×10 2 W / cm 2 Up to 1×10 3 W / cm 2 That is to say, in the present disclosure, the area on the back side of the wafer W where the groove 401 is to be formed is heated by a relatively low-energy laser, so that the efficiency of the oxidation treatment can be improved while the area where the groove 401 is to be formed is oxidized.
[0056] For the above-mentioned embodiments, in some examples, the second etching process is an acid etching process.
[0057] After the area on the back side of the wafer W where the groove 401 is to be formed is oxidized to generate oxides such as silicon oxide, acid etching in the present disclosure can quickly remove the oxides, thereby forming the groove 401 .
[0058] Specifically, the etching solution of the second etching treatment is an HF solution or a buffered oxide etch (BOE) solution, and the concentration of the HF solution or the HF solution in the buffered oxide etch solution is 45% to 49%, and the duration of the second etching treatment is 190s to 550s.
[0059] In this case, the generated oxides can be quickly removed by using an HF solution. In the present disclosure, an HF solution with a concentration of 45% to 49% is used to remove the oxides, which can ensure that the oxides are removed without causing damage to the wafer W.
[0060] On the other hand, using BOE solution to remove the oxide can make the etching rate constant and uniform. This is because BOE solution is a mixture of hydrofluoric acid (HF) and ammonium fluoride (NH4F). During the etching process, ammonium fluoride (NH4F) acts as a buffer to maintain the H+ concentration in the BOE solution relatively stable, thereby ensuring that the activity of HF remains consistent during the etching process, thereby making the etching rate uniform.
[0061] It should be noted that the etching solution of the second etching process in the present disclosure is not limited to HF solution, and other acidic solutions that can remove the above oxides without damaging the wafer W can also be used as the etching solution of the second etching process in the present disclosure.
[0062] In the present disclosure, the second etching rate and the consistency of the depth of the groove 401 can be ensured by precisely controlling the concentration of the HF solution, thereby avoiding errors in subsequent processing steps that affect the flatness of the wafer W.
[0063] for Figure 2 In the technical solution shown, in some possible implementations, the depth of the groove 401 is 1.9 μm to 5.5 μm.
[0064] In the present disclosure, the depth of the groove 401 is defined to provide a reference for the etching amounts corresponding to the subsequent first etching process and the second etching process, so as to ensure that there is no excessive erosion during the first etching process and the second etching process.
[0065] for Figure 2In the technical solution shown, in some possible implementations, the outline of the first projection exceeds the outline of the second projection by 1 mm to 3 mm in the radial direction of the wafer.
[0066] In this case, grooves 401 can be formed on the periphery of the character pit D, thereby avoiding the phenomenon of insufficient polishing abrasive particles on the periphery of the character pit D during the double-sided polishing process, thereby preventing the above-mentioned raised portion 2 from appearing on the periphery of the character pit D to affect the flatness of the wafer W.
[0067] for Figure 2 In the technical solution shown, in some possible implementations, the first etching treatment is an alkaline etching treatment.
[0068] In the present disclosure, an alkaline etching method is used to remove Figure 6 It is understood that the alkaline etching process used in the present disclosure can also remove the filled area W1. Figure 6 While filling the area W1 shown in FIG. 4 , impurities in the area where the groove 401 is located are cleaned to prevent the impurities from scratching the back side of the wafer W and affecting the polishing effect in the subsequent double-sided polishing process.
[0069] For the above-mentioned embodiments, in some examples, the etching solution of the above-mentioned first etching treatment is a KOH solution, and the concentration of the above-mentioned KOH solution is 42% to 47%, and the duration of the first etching treatment is 200s to 215s.
[0070] In the present disclosure, the etching solution of the first etching process is preferably a KOH solution with a concentration of 42% to 47%, so as to ensure the etching effect of the second etching process and not cause additional etching damage to the wafer W.
[0071] It should be noted that the etching solution of the first etching treatment in the present disclosure is not limited to KOH solution, and other alkaline solutions that can achieve the above technical effects can also be used as the etching solution of the first etching treatment in the present disclosure.
[0072] Finally, the present disclosure provides a wafer, which is laser marked according to the laser marking method for wafers described in the aforementioned technical scheme, and when the edge removal amount of the above-mentioned wafer is 2 mm, after the above-mentioned laser marking, the total thickness deviation (Total Thickness Variation, TTV) corresponding to the area of the above-mentioned wafer except the laser marked area is 160nm to 200nm.
[0073] It should be noted that the technical solutions described in the embodiments of the present disclosure can be combined arbitrarily without conflict.
[0074] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.
Claims
1. A laser marking method for a wafer, characterized in that: The laser marking method comprises: Grinding the back side of the wafer so that the thickness of the wafer decreases from the center of the wafer to the edge of the wafer; forming a groove on the back side of the wafer, wherein the groove covers the area to be laser marked on the back side of the wafer, and an outline of a first projection of the groove on the back side of the wafer entirely exceeds an outline of a second projection of the area to be laser marked on the back side of the wafer; Performing laser marking on the area to be laser marked; performing a first etching process on the wafer; The wafer is double-sided polished. The depth of the groove is set such that the groove still exists after undergoing the first etching process.
2. The laser marking method for wafer according to claim 1, characterized in that: The forming of a groove on the back side of the wafer comprises: An oxidation treatment is performed on the back side of the wafer in the area where the groove is to be formed, and a second etching treatment is performed on the area where the groove is to be formed, so as to form the groove.
3. The laser marking method for wafer according to claim 2, characterized in that: The oxidation treatment is achieved by heating the area where the groove is to be formed using a laser, wherein the energy density of the laser is 1×10 2 W / cm 2 Up to 1×10 3 W / cm 2 .
4. The laser marking method for wafer according to claim 2, characterized in that: The second etching process is an acid etching process.
5. The laser marking method for wafer according to claim 4, characterized in that: The etching solution of the second etching treatment is an HF solution or a buffered oxide etching solution, wherein the concentration of the HF solution or the HF solution in the buffered oxide etching solution is 45% to 49%, and the duration of the second etching treatment is 190s to 550s.
6. The laser marking method for wafer according to claim 1, characterized in that: The depth of the groove is 1.9 μm to 5.5 μm.
7. The laser marking method for wafer according to claim 1, characterized in that: The outline of the first projection exceeds the outline of the second projection by 1 mm to 3 mm in the radial direction of the wafer.
8. The laser marking method for wafer according to claim 1, characterized in that: The first etching process is an alkaline etching process.
9. The laser marking method for wafer according to claim 8, characterized in that: The etching solution of the first etching process is a KOH solution, and the concentration of the KOH solution is 42% to 47%, and the duration of the first etching process is 200s to 215s.
10. A wafer, characterized in that: The wafer is laser marked according to the laser marking method for wafers according to any one of claims 1 to 9, and when the edge removal amount of the wafer is 2 mm, after the laser marking, the total thickness deviation corresponding to the area of the wafer other than the laser marked area is 160 nm to 200 nm.