Method for rapidly judging laser de-bonding interface
By eroding the wafer after laser debonding specific corrosion liquid and measuring the resistance value difference, the problem of complexity and high cost in judging the laser debonding interface in the prior art is solved, and fast and accurate interface judgment is achieved, and process development efficiency is improved.
Patent Information
- Application Number
- CN202510252571.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-03-18
- Filing Date
- 2025-03-05
- Publication Date
- 2025-06-20
AI Technical Summary
In the prior art, when judging the laser debonding interface, there are problems such as expensive detection equipment and complex processes. Especially when the bonding cross-section contains a variety of materials, it is difficult to accurately judge the position of the debonding interface.
By selecting the appropriate corrosion solution, wet corrosion of the debonded wafer, test the corrosion surface resistance value, calculate the difference in the resistance value to judge the position of the debonded interface.
This method can quickly and accurately determine the location of the bonding interface, avoiding the problems of long cycles, low efficiency and high cost of traditional methods, and significantly improving process development efficiency.
Smart Images
Figure CN120184029A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and more particularly, to a method for quickly judging a laser debonding interface. Background Art
[0002] Currently, the development trend of the integrated circuit industry has gradually shifted from the continuous reduction of feature sizes driven by the traditional Moore's law to three-dimensional integration, multi-chip stacking, heterogeneous integration, etc. Among them, the most core process links are wafer bonding, thinning, and debonding processes. The bonding process is to bond two wafers with specific functions through a bonding method, and the debonding process is to successfully separate two wafers to be separated through mechanical peeling, chemical peeling, thermal slip method, laser debonding method, etc. Since at least one wafer has completed most of the manufacturing processes during debonding, the success of the debonding process is very important. If the debonding fails, the wafer has been damaged by the substrate, resulting in huge losses. Based on this, during the development of the debonding process, the accurate judgment of the process effect is extremely important.
[0003] Currently, the laser debonding method has become the current mainstream debonding solution due to its advantages such as non-contact, mature and controllable process, easy to be used in mass production, and compatibility with the integrated circuit industry. The principle of laser debonding is to use a laser with no obvious absorption wavelength in the substrate material to pass through the upper substrate material and reach the bonding interface. The bonding interface is composed of a high transmittance film (usually an insulating dielectric film with a high surface resistance state) and a film with a certain absorption rate (usually a metal film or a carbon film with a low surface resistance state). After the laser is absorbed by the metal film, the temperature of the metal film rises, destroying the adhesion between the metal film and the insulating dielectric film, thereby destroying the bonding interface to achieve the debonding effect.
[0004] Traditional methods for accurately judging the effect of the debonding process require observing the surface and cross-section using methods such as infrared microscopes, scanning electron microscopes, and transmission electron microscopes, which are very time-consuming, laborious, and increase costs. Especially when the bonding cross-section contains multiple materials, the limitations of this method are more obvious.
[0005] When the bonding cross-section structure is relatively simple, consisting of an insulating dielectric film / metal film / insulating dielectric film, the judgment of the debonding interface and the debonding process effect is relatively easy, and only need to observe with a microscope and test the resistance of the surfaces of the two wafers after separation to judge. As Figure 1 shown, after laser irradiation for debonding, there are two possible results for the debonding interface: when the surface of the upper wafer shows a high resistance state, it means that the debonding interface is the interface between the insulating dielectric film / conductive metal film on the surface of the upper wafer; when the surface of the upper wafer shows a low resistance state, it means that the debonding interface is the interface between the conductive metal film / insulating dielectric film on the surface of the lower wafer.
[0006] However, in actual situations, the bonding interface contains multiple layers of conductive metal thin films and insulating dielectric films. For example, Figure 2 as shown, it is a bonding chip with a relatively complex structure. Therefore, simply relying on measuring the surface resistance of the two wafers after debonding cannot accurately determine the position of the debonding interface, nor can it determine whether the process requirements are met. For this reason, it is necessary to cleave the two silicon wafers, and then use methods such as SEM and TEM to observe the cross-section, and compare the observation results with the sample structure to confirm at which interface the debonding occurs. This method has a long cycle, low efficiency, requires cleaving, and high costs, affecting the process development efficiency. Summary of the Invention
[0007] The present invention discloses a method for quickly determining the laser debonding interface to overcome the disadvantages of expensive detection equipment and complex processes in the prior art.
[0008] Technical concept of this application:
[0009] When there are multiple layers stacked in the bonding chip, for example, the structures of each layer are as Figure 2 shown, the bonding interface contains multiple layers of conductive metal thin films and insulating dielectric films. When performing the laser debonding process, the laser passes through the transmission layer. After debonding occurs, there will be two possible debonding interfaces, and the resistance patterns on the surfaces of the two wafers after debonding are the same. Simply relying on the surface resistance of the wafers cannot accurately distinguish the debonding interface. At the same time, due to the very thin film thickness in the bonding area, all at the nanometer level, it is also impossible to accurately judge by surface color and microscopic observation. Therefore, simply relying on the surface resistance of the wafers cannot determine which layer is the specific separation surface, and subsequent chip manufacturing cannot be carried out.
[0010] Based on this dilemma, considering that the film resistivity in the bonding area is different, and the corrosion rate for a specific etching solution is different: for example, if the dielectric film uses SiO2, it is extremely easy to be corroded by HF; but for conductive films such as metal films, the corrosion rate of HF is much smaller than that of SiO2. For this reason, the present invention proposes to corrode the debonded wafers with a specific etching solution, and then measure the surface resistance after corrosion, so as to quickly determine the accurate position of the debonding interface.
[0011] The technical solution adopted by the present invention to solve the above technical problems is:
[0012] Based on the above purpose, the present invention discloses a method for quickly determining the laser debonding interface, which includes:
[0013] Select an etching solution according to the film layer structure in the bonding area of the target sample, and the etching solution has different etching efficiencies for different film layer materials in the film layer structure;
[0014] Measure the surface resistance values of the two wafers obtained after laser debonding, and record them as R1 and R2;
[0015] Use an etching solution to perform wet etching on the two wafers after laser debonding, measure the surface resistance values of the two etched wafers, and record them as R'1 and R'2;
[0016] Calculate the difference in the surface resistance values of the two wafers, and judge the debonding interface based on the magnitude of the numerical changes from R1 to R'1 and from R2 to R'2.
[0017] Further, the above wet etching method includes: placing the two wafers in the etching solution for 5 - 10 s and then taking them out, washing and drying.
[0018] Further, the film materials in the above film layer structure include an insulating dielectric film and a conductive film.
[0019] Further, the material of the above insulating dielectric film is SiO2, SiC; the material of the conductive film is a conductive metal film, a metalloid film or a carbon film.
[0020] Further, the etching rate of the above etching solution for the insulating dielectric film is 100 - 900 nm / min, and the etching rate for the conductive film is 1 - 9 nm / min.
[0021] Further, the etching rate of the above etching solution for the wafer substrate material is 0.1 - 0.5 nm / min.
[0022] Further, the above etching solution is any one of HF solution, pyrophosphoric acid solution, sodium hydroxide solution and sodium fluoride solution.
[0023] Further, among the film materials in the above film layer structure, the material of the insulating dielectric film is SiO2, and the material of the conductive film is a conductive metal film or a metalloid film.
[0024] Further, the above etching solution is an HF solution with a concentration of 35 - 45 wt%.
[0025] Further, the method of judging the debonding interface based on the magnitude of the numerical changes from R1 to R'1 and from R2 to R'2 includes:
[0026] First, judge whether the separation surface of the two wafers is an insulating dielectric film or a conductive film according to the numerical values of R1 and R2, and exclude the bonding interfaces that do not conform;
[0027] Then, determine the bonding interface according to the magnitude of the numerical changes of R'1 - R1 and R'2 - R2.
[0028] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0029] The method for quickly judging the laser debonding interface provided by the present invention utilizes the different corrosion efficiencies of different material films in the bonding area for a specific etching solution. After debonding, the change trend of the surface resistance of the wafer after etching by the etching solution is very different. By testing the numerical changes in the resistance of the upper and lower wafer surfaces before and after etching after debonding, the position of the debonding interface can be accurately judged. And for the case where the film layer structure of the bonding interface is more complicated, there is no need to split the film, and only the change in the surface resistance of the upper and lower wafers after etching can be relied on to lock which layer the specific separation surface is. Compared with the traditional SEM and TEM characterization methods after slicing, it can greatly shorten the characterization time, reduce the characterization cost, and improve the development efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.
[0031] Figure 1 A schematic diagram of debonding a bonding sheet with a relatively simple structure in the prior art is shown;
[0032] Figure 2 A schematic diagram of debonding a bonding sheet with a relatively complex structure in the prior art is shown;
[0033] Figure 3 The structure diagram of the bonding sheet in Embodiment 1 of the present invention is shown;
[0034] Figure 4 The position diagram of the separation surface after laser debonding in Example 1 of the present invention is shown;
[0035] Figure 5 The infrared microscope pictures of the separated surfaces after laser debonding in Example 1 of the present invention are shown, wherein the left picture is the upper wafer and the right picture is the lower wafer;
[0036] Figure 6 The position diagram of the separation surface after laser debonding in Example 2 of the present invention is shown;
[0037] Figure 7 The diagram shows the position of the separation surface after laser debonding in Example 3 of the present invention. DETAILED DESCRIPTION
[0038] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For specific conditions not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.
[0039] The present invention will be further described in detail below through specific examples in conjunction with the accompanying drawings.
[0040] Example 1
[0041] The present application provides a method for quickly judging the laser debonding interface. The structure of the target bonded sample to be analyzed is as Figure 3 shown. The bonding interface is composed of SiO2 and a conductive metal film. The entire sample involves three materials: silicon, metal or metal nitride, and SiO2. This sample has been debonded into an upper wafer and a lower wafer by the laser debonding method.
[0042] The method for the laser debonding interface includes:
[0043] (1) Select the etching solution:
[0044] According to the film layer structure of the bonding area of the target sample, an HF solution with a concentration of 40 wt% is selected as the etching solution. The etching efficiency of this etching solution for the three film layer materials of silicon, metal or metal nitride, and SiO2 and the typical surface resistance change trend after HF etching are shown in Table 1:
[0045] Table 1. Etching efficiency of HF for each layer material
[0046]
[0047] (2) Measure the surface resistance before etching:
[0048] The four-probe resistance measurement method is used to measure the surface resistance values R1 and R2 of the upper wafer and the lower wafer, as shown in Table 2.
[0049] (3) Wet etching:
[0050] The upper wafer and the lower wafer are placed in the HF etching solution for 10 s and then taken out, washed and dried.
[0051] (4) Measure the surface resistance after etching:
[0052] Using the same method, measure the surface resistance values R'1 and R'2 of the upper wafer and the lower wafer after etching, as shown in Table 2.
[0053] Table 2. Resistance values of the upper and lower wafers before and after HF etching
[0054]
[0055] (5) Determine the debonding interface:
[0056] After laser debonding, there are four possible debonding surfaces:
[0057] a. 2 / 3 interface: The bonding surface between the second-layer SiO2 film and the third-layer conductive metal film;
[0058] b. 3 / 4 interface: The bonding surface between the third-layer conductive metal film and the fourth-layer SiO2 film;
[0059] c. 4 / 5 interface: The bonding surface between the fourth-layer SiO2 film conductive metal film and the fifth-layer conductive metal film;
[0060] d. 5 / 6 interface: The bonding surface between the fifth-layer conductive metal film and the sixth-layer SiO2 film.
[0061] In laser debonding, the surface directly in contact with the silicon wafer is difficult to separate. Therefore, the situations of the 1 / 2 interface and the 6 / 7 interface do not occur.
[0062] As shown in Table 2, the resistance of the separated surface of the unetched upper wafer is 600 Ω, indicating that the separated surface of the upper wafer is a conductive metal film; the resistance of the separated surface of the lower wafer > 60 MΩ, indicating that the separated surface of the lower wafer is a SiO2 film. It can be judged that the separated surface is between the conductive metal film 3 / SiO2 film 4; or between the conductive metal film 5 / SiO2 film 6.
[0063] Put the upper and lower wafers into HF for etching, and measure the resistance of the separated surfaces of the etched upper and lower wafers. The resistance of the separated surface of the upper wafer increases slightly, and the resistance of the separated surface of the lower wafer decreases significantly. As shown in Table 2, it can be seen that the resistance of the separated surface of the etched upper wafer is 6 kΩ, with a small change range, indicating a low etching rate; while the resistance of the etched lower wafer is 100 Ω, and the resistance changes from over-range (> 60 MΩ) to 100 Ω, indicating a very fast etching rate, and the detected is the metal film layer below the film layer. It can be inferred that the position of the separated surface after debonding is between the conductive metal film 3 / SiO2 film 4, that is, the position of the separated surface is as Figure 4 shown. The reason is that: Since HF has a strong etching effect on silicon oxide and a poor etching effect on metals, through HF etching, the SiO2 on the surface of the lower wafer is stripped, exposing the conductive metal film 5 on the surface. Therefore, the resistance on the separated surfaces of the upper and lower wafers has changed as described above.
[0064] (7) Conclusion verification:
[0065] Use infrared to observe the separated surfaces of the upper and lower wafers, as Figure 5As shown, the results indicate that the separation plane is indeed between the conductive metal film 3 and the SiO2 film 4.
[0066] Example 2
[0067] This application provides a method for quickly judging the laser debonding interface. The structure of the target bonded sample for analysis is also as Figure 3 shown. The bonding interface is composed of SiO2 and a conductive metal film. The entire sample involves three materials: silicon, metal, and SiO2. This sample has been debonded into an upper wafer and a lower wafer by the laser debonding method (the laser intensity used is different from that in Example 1).
[0068] The method for quickly judging the laser debonding interface includes:
[0069] (1) Select a 45wt% HF solution as the etching solution;
[0070] (2) Place the upper wafer and the lower wafer in the HF etching solution for 10 s, then take them out, wash, and dry.
[0071] (3) Measure the surface resistance before and after etching
[0072] Using the four-probe resistance measurement method, measure the surface resistance values R1, R2, R’1, and R’2 of the upper wafer and the lower wafer before and after etching, as shown in Table 3.
[0073] Table 3. Resistance values of the upper and lower wafers before and after HF etching
[0074]
[0075] (4) Judge the debonding interface
[0076] As shown in Table 3, the resistance of the separation plane of the unetched upper wafer is >60 MΩ, indicating that the separation plane of the upper wafer is the SiO2 film; the resistance of the separation plane of the lower wafer is 500 Ω, indicating that the separation plane of the lower wafer is the conductive metal film. It can be judged that the separation plane is between the SiO2 film 2 and the conductive metal film 3; or between the SiO2 film 4 and the conductive metal film 5.
[0077] Put the upper and lower wafers into HF for etching, and measure the resistance of the separation plane of the etched upper and lower wafers. The resistance of the separation plane of the upper wafer decreases significantly, and the resistance of the separation plane of the lower wafer increases slightly. As shown in Table 3, it can be seen that the resistance of the separation plane of the etched upper wafer is only 70 Ω, and the change trend is large (from >60 MΩ beyond the range to 70 Ω), indicating that its etching rate is extremely fast, and the detected is the metal film layer above the film layer; while the lower wafer is 4000 Ω, and the change amplitude is small, indicating that its etching rate is low, and the detected is the metal film layer. It can be inferred that the position of the separation plane after debonding is between the SiO2 film 4 and the conductive metal film 5, that is, the position of the separation plane is as Figure 6As shown in the figure. The reason is that since HF has a strong corrosive effect on silicon dioxide but a relatively poor corrosive effect on metals, through HF corrosion, the SiO2 on the upper wafer surface is stripped, exposing the conductive metal film 3 on the surface. Therefore, the above-mentioned change in resistance occurs on the separated surface between the upper and lower wafers.
[0078] Example 3
[0079] This application provides a method for quickly judging the laser debonding interface, and the structure of the target bonded sample for analysis is also as Figure 3 shown. This bonding interface is composed of SiO2 and a conductive metal film. The entire sample involves three materials: silicon, metal, and SiO2. This sample has been debonded into an upper wafer and a lower wafer by the laser debonding method (the laser intensity used is different from that in Examples 1 and 2).
[0080] The method for quickly judging the laser debonding interface includes:
[0081] (3) Select a 35wt% HF solution as the etching solution;
[0082] (4) Place the upper and lower wafers in the HF etching solution for 10 s and then take them out, wash and dry.
[0083] (3) Measure the surface resistance before and after etching
[0084] Adopt the four-probe resistance measurement method to measure the surface resistance values R1, R2, R'1, and R'2 of the upper and lower wafers before and after etching, as shown in Table 4.
[0085] Table 4. Resistance values of the upper and lower wafers before and after HF etching
[0086]
[0087] (4) Judge the debonding interface
[0088] As shown in Table 4, the resistance of the separated surface of the unetched upper wafer is >60 MΩ, indicating that the separated surface of the upper wafer is a SiO2 film; the resistance of the separated surface of the lower wafer is 450 Ω, indicating that the separated surface of the lower wafer is a conductive metal film. It can be judged that the separated surface is between the SiO2 film 2 / conductive metal film 3; or between the SiO2 film 4 / conductive metal film 5.
[0089] The upper and lower wafers are placed in HF for etching, and the separated surfaces of the etched upper and lower wafers are subjected to resistance testing. The resistance of the separated surface of the upper wafer exceeds the range (>60 MΩ), and the resistance of the separated surface of the lower wafer increases slightly. As shown in Table 4, it can be seen that the resistance of the separated surface of the etched upper wafer still exceeds the range, indicating that the detected material is the silicon wafer under the film layer; while the resistance of the lower wafer is 5000 Ω with a small change range, indicating that its etching rate is low and the detected material is the metal film layer. It can be inferred that the separated surface position after debonding is between the SiO2 film 2 and the conductive metal film 3, that is, the separated surface position is as Figure 7 shown. The reason is that since HF has a strong etching effect on silicon dioxide and a poor etching effect on metals, through HF etching, the SiO2 on the surface of the upper wafer is stripped, exposing the silicon on the surface. Therefore, the upper wafer remains high-resistance, and the metal film of the lower wafer is also damaged to a certain extent, resulting in an increase in the resistance of the lower wafer before and after etching.
[0090] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method for quickly determining a laser debonding interface, characterized in that: It includes: Selecting a etching solution according to the film layer structure of the target sample bonding area, wherein the etching solution has different etching efficiencies on different film layer materials in the film layer structure; The surface resistance values of the two wafers obtained after laser debonding were measured and recorded as R1 and R2; Using the etching solution to wet-etch the two wafers after laser debonding, and testing the surface resistance values of the two wafers after etching, and recording them as R'1 and R'2; The debonding interface is determined based on the magnitude of the change in the values from R1 to R'1 and from R2 to R'2.
2. The method for rapidly determining a laser debonding interface according to claim 1, characterized in that: The wet etching method comprises: placing the two wafers in the etching solution for 5-10 seconds, then taking them out, washing them and drying them.
3. The method for rapidly determining a laser debonding interface according to claim 2, characterized in that: The film layer materials in the film layer structure include an insulating dielectric film and a conductive film.
4. The method for rapidly determining a laser debonding interface according to claim 3, characterized in that: The material of the insulating dielectric film is SiO2 or SiC; the material of the conductive film is a conductive metal film, a metalloid film or a carbon film.
5. The method for rapidly determining a laser debonding interface according to claim 4, characterized in that: The corrosion efficiency of the etching solution on the insulating dielectric film is 100-900 nm / min, and the corrosion efficiency on the conductive film is 1-9 nm / min.
6. The method for rapidly determining a laser debonding interface according to claim 4, characterized in that: The etching efficiency of the etching solution on the wafer substrate material is 0.1-0.5nm / min.
7. The method for rapidly determining a laser debonding interface according to claim 5 or 6, characterized in that: The etching solution is any one of HF solution, pyrophosphoric acid solution, sodium hydroxide solution and sodium fluoride solution.
8. The method for rapidly determining a laser debonding interface according to claim 3, characterized in that: Among the film layer materials of the film layer structure, the material of the insulating dielectric film is SiO2, and the material of the conductive film is a conductive metal film or a metal-like film.
9. The method for rapidly determining a laser debonding interface according to claim 7, characterized in that: The etching solution is an HF solution with a concentration of 35-45wt%.
10. The method for rapidly determining a laser debonding interface according to claim 1, characterized in that: Methods for determining a debonded interface based on the magnitude of the change in values from R1 to R'1 and from R2 to R'2 include: First, according to the values of R1 and R2, determine whether the separation surface of the two wafers is an insulating dielectric film or a conductive film, and exclude the bonding interface that does not meet the requirements; Then, the bonding interface is determined based on the numerical variation range of R'1-R1 and R'2-R2.