A method for eliminating the backside suction pen mark of super back seal product after epitaxy
By cleaning the suction pen every 12 hours and adjusting the vacuum pressure to -70Kpa to -60Kpa, combined with a management system and regular spot checks, the problem of suction pen marks on the back of the super back-sealed product after the outer edge is solved, improving product yield and the lifespan of the suction pen.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI SEMICON WAFER TECH CO LTD
- Filing Date
- 2022-08-25
- Publication Date
- 2026-07-10
AI Technical Summary
In silicon epitaxy, pen marks appear on the back of the super-back-sealed product after epitaxy, resulting in poor appearance and scrapping of the epitaxial product. Existing technologies lack effective removal methods.
Clean the suction pen every 12 hours and adjust the pressure regulating valve connected to the negative pressure suction line to a vacuum pressure of -70Kpa to -60Kpa. Combine this with the use of a management system and regular spot checks to ensure the cleanliness and lifespan of the suction pen.
It effectively removes the pen marks on the back of the epitaxial wafer, avoids silicon wafer scratches and pen marks, improves product yield, and achieves effective management and maintenance of the pen.
Smart Images
Figure CN115602593B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, specifically a method for removing ink from a pen. Background Technology
[0002] In silicon epitaxy, a back seal layer is required on the back of the substrate. Typically, a layer of silicon dioxide (ITO) is used as the back seal layer. Supersealing products, however, have a double-layer back seal structure, where an ITO layer is further covered by a polycrystalline silicon (poly) layer. In other words, during the CVD process for supersealing products, APCVD is first performed on the back of the silicon wafer to form a silicon dioxide film, followed by LPCVD to form a polycrystalline silicon film. Thus, the back of the silicon wafer is wrapped by two thin films, with the outermost layer being a polycrystalline silicon film.
[0003] Existing super-sealed products have been found to have pen marks on the back after the outer layer is applied, which cannot be detected before the outer layer is applied, resulting in defective appearance of the outer layer product and its scrapping.
[0004] Research has shown that the ink marks appearing after epitaxy are caused by contaminants from the ink pen adhering to the back of the silicon wafer during visual inspection. Skipping visual inspection may result in defective products with damage to the back side being shipped out.
[0005] Currently, there is no method to overcome the ink absorption caused by the extension of the pen. Summary of the Invention
[0006] To address the problems existing in the prior art, the present invention provides a method for eliminating pen marks on the back of a super-sealed product after the outer edge has been extended, thereby solving at least one of the above-mentioned technical problems.
[0007] To achieve the above objectives, the present invention provides a method for eliminating suction pen marks on the back of a super-sealed product after the outer edge has been extended. The method is characterized in that the suction pen is cleaned every 12 hours, and a pressure regulating valve is installed between the suction pen and the negative pressure suction pipeline, wherein the vacuum pressure of the suction pen is adjusted to -70Kpa to -60Kpa.
[0008] This invention patent achieves the elimination of suction mark after epitaxy. It addresses the problem of insufficient suction force from the suction pen, which causes micro-friction between the silicon wafer and the pen, resulting in scratches on the wafer surface. Simultaneously, it avoids the suction mark problem caused by excessive suction force. Furthermore, it was discovered that the cleaning frequency of the suction pen also has a significant impact on suction mark formation.
[0009] More preferably, the cleaning method for the suction pen is to repeatedly apply the suction pen to a clean silicon wafer surface and observe it with a spotlight until the suction marks on the suction pen disappear, at which point the suction pen is clean.
[0010] A further preferred embodiment includes a cleaning tank for cleaning the suction pen, the top of which is fitted with a hanging bracket for suspending the suction pen, and the hanging bracket is fitted with hooks for suspending the suction pen via hanging rings.
[0011] It facilitates the hanging and fixing of the pen.
[0012] A further preferred embodiment includes a pen-collecting management system, which includes a pen-collecting holder for inserting and placing pens, the pen-collecting holder having an inclined slot, and a timer and an indicator light installed next to the slot;
[0013] An indicator light will show whether the ink pen in the slot needs cleaning.
[0014] This facilitates better control over the pen suction.
[0015] More preferably, the timer is connected to a controller, and the controller controls the connected indicator light.
[0016] If the timer determines that more than 12 hours have passed since the last cleaning, the indicator light will show that cleaning is required.
[0017] More preferably, the pressure regulating valve is connected to a controller, the controller is connected to a memory, and the memory stores the cleaning time of the suction pen and the suction force of the suction pen.
[0018] This facilitates the traceability of information later on.
[0019] A further preferred embodiment includes a pen usage rate recording system, which includes a counter for the number of times the pen is used and a timer;
[0020] A display screen is installed next to the slot, which is used to display the number of times the counter has been used and the time recorded by the timer.
[0021] The counter and the timer are connected to a controller, which wirelessly controls a signal light installed on the pen; the signal light is a wireless signal light.
[0022] After the controller analyzes the number of times each suction pen is used and the usage time, it displays the suction pens that are suitable to continue working.
[0023] Avoid using a single suction pen for too long.
[0024] In a further preferred embodiment, the suction pen is randomly inspected every month of use. The inspection method involves attaching the suction pen to the polished surface of a lightly doped silicon wafer, using the OISF process to convert contaminants on the suction pen into OISF traces, observing the OISF traces and calculating the OISF density to determine the specific condition of the suction pen.
[0025] A further preferred step in the OISF process is to perform wet oxygen thermal oxidation on lightly doped silicon wafers in a furnace tube for 2 hours at an oxidation temperature of 1100°C, followed by etching with Secco solution or Wright solution.
[0026] Further optimization is that when OISF traces are clearly visible under visual inspection, it is directly determined that the device cannot continue to be used, and microscopic examination is not required.
[0027] Under visual inspection, traces of OISF are visible but not clear. Microscopic examination is used to assist in the determination. If the OISF density is >400 particles / cm³, it indicates a potential problem. 2 It was determined that the product could not be used any further; OISF density < 400 particles / cm³ 2 It was determined that it could continue to be used.
[0028] OISF marks are oxidation-induced stacking faults, a type of defect that can be detected using spotlights and microscopes after the OISF defect detection process when there is contamination or scratches on the surface of the silicon wafer. Attached Figure Description
[0029] Figure 1 This is a partial structural schematic diagram of a specific embodiment 1 of the present invention;
[0030] Figure 2 A microscope illustration of the surface of the new suction pen;
[0031] Figure 3 Microscopic image of the surface of an old suction pen that has been used for more than 3 years;
[0032] Figure 4 This is a comparison chart of the results of Experiment 1 of the present invention;
[0033] Figure 5 This is a comparison chart of the results of Experiment 2 of the present invention.
[0034] Wherein: 1 is a slot, 2 is a display screen, 3 is a timer, and 4 is an indicator light. Detailed Implementation
[0035] The present invention will now be further described with reference to the accompanying drawings.
[0036] For a specific embodiment 1, see [link / reference] Figure 1 The suction pen is cleaned every 12 hours, and a pressure regulating valve is installed between the suction pen and the negative pressure suction pipeline, adjusting the vacuum pressure of the suction pen to -70Kpa to -60Kpa. This invention patent achieves zero suction pen marks after epitaxy. This invention controls the suction force of the suction pen to prevent micro-friction between the silicon wafer and the suction pen, which can scratch the silicon wafer surface. It also avoids the problem of suction pen marks caused by excessive suction force. Furthermore, it was discovered that the cleaning frequency of the suction pen also has a significant impact on suction pen marks.
[0037] Experiment 1: Survey of Old Pens
[0038] An old suction pen with 400,000 test samples was selected. The suction pens were examined under a spotlight and a microscope on the third day after cleaning and 12 hours after cleaning. The results are as follows:
[0039]
[0040] Experiment 2: Comparison of new and old suction pens
[0041] One new suction pen was selected (for testing 1000 samples). The suction pen was examined under a spotlight and a microscope on the third day after cleaning and 12 hours after cleaning. The results are as follows:
[0042]
[0043] As can be seen from the two experiments above:
[0044] 1. On the 3rd day after cleaning, the old suction pen can still show clear and complete suction pen marks, indicating that when testing the super back seal product, the current cleaning frequency is no longer sufficient to meet the product's needs.
[0045] 2. Regardless of whether the absorbent pen is new or old, cleaning can significantly remove the absorbent pen marks. Under visual inspection, OISF traces are significantly reduced, and under microscopic inspection, the OISF density is reduced by half.
[0046] 3. Based on the above experiments, for the super back-sealed product, the cleaning frequency of the suction pen should be adjusted to once every 12 hours.
[0047] Experiment 3: Vacuum pressure test for pen suction. The results of different vacuum pressures for pen suction are as follows:
[0048] vacuum pressure Performance -5KPa The silicon wafer won't hold, and it will fall off. -10 kPa The silicon wafer won't hold, and it will fall off. -20KPa The silicon wafer won't hold, and it will fall off. -30KPa The silicon wafer won't hold, and it will fall off. -40KPa It can hold a silicon wafer, and the surface has scratches. -50KPa It can hold a silicon wafer, and the surface has scratches. -60KPa It can hold silicon wafers without scratching. -70KPa It can hold silicon wafers without scratching. -100KPa There are pen marks
[0049] The cleaning method for the suction pen is to repeatedly apply the suction pen to a clean silicon wafer surface and observe it with a spotlight until the suction marks on the suction pen disappear, at which point the suction pen is clean.
[0050] It also includes a cleaning tank for cleaning the absorbent pen, the top of which is fitted with a hanging bracket for suspending the absorbent pen, and the hanging bracket is fitted with hooks for suspending the absorbent pen via hanging rings. This facilitates the hanging and securing of the absorbent pen.
[0051] It also includes a pen-collecting management system, which includes a pen-collecting holder for inserting and placing pens. The pen-collecting holder has an inclined slot 1, and a timer 3 and an indicator light 4 are installed next to the slot 1. The indicator light 4 indicates whether the pen in the slot needs to be cleaned. This facilitates better control over the pens.
[0052] The timer 3 is connected to the controller, which controls the indicator light. When the timer determines that more than 12 hours have passed since the last cleaning, it controls the indicator light to display that cleaning is required.
[0053] The pressure regulating valve is connected to a controller, which is connected to a memory. The memory stores the cleaning time and suction power of the suction pen, facilitating future information traceability.
[0054] It also includes a pen usage recording system, which includes a counter for the number of times the pen has been used and a timer. A display screen 2 is installed next to the slot 1, which displays the number of uses by the counter and the time recorded by the timer. The counter and the timer are connected to a controller, which wirelessly controls indicator lights installed on the pen. These indicator lights are wireless. After analyzing the number of uses and usage time of each pen, the controller displays the pens that are suitable for continued use, thus avoiding prolonged use of a single pen.
[0055] Every month, the suction pens are randomly inspected. The inspection method involves attaching the suction pen to the polished surface of a lightly doped silicon wafer, and using the OISF process to convert contaminants on the suction pen into OISF traces. The OISF traces are observed and the OISF density is calculated to determine the specific condition of the suction pen. The OISF process involves humidifying the lightly doped silicon wafer in a furnace tube for 2 hours at a temperature of 1100°C, using either Secco or Wright solutions for etching.
[0056] The above detection method utilizes the characteristics of OISF. When there is contamination on the surface of the silicon wafer, OISF will be induced. After heat treatment and selective etching, OISF can be observed using a spotlight and microscope, that is, the traces of contaminants from the suction pen are transformed into OISF traces.
[0057] If OISF traces are clearly visible under visual inspection, the device is deemed unusable and microscopic examination is unnecessary. If OISF traces are visible but unclear under visual inspection, microscopic examination is used to assist in the determination. If the OISF density is >400 particles / cm³, further examination is required. 2 It was determined that the product could not be used any further; OISF density < 400 particles / cm³ 2 It was determined that it could continue to be used. Microscopic examination (optical interference microscope, 100x).
[0058] OISF marks are oxidation-induced stacking faults, a type of defect that can be detected using spotlights and microscopes after the OISF defect detection process when there is contamination or scratches on the surface of the silicon wafer.
[0059] During the research and development process, the surface of the suction pen was examined using an optical microscope, revealing that even brand new suction pens (see...) Figure 2It's still an old suction pen that's been used for more than 3 years (see...) Figure 3 The surface condition is indistinguishable and cannot be used as a method for testing the suction pen; at the same time, it is impossible to detect residual dirt and particles on the suction pen.
[0060] Attempts to manipulate the back of the silicon wafer using the OISF process also failed to reproduce the pen marks, thus rendering it unusable as a method for testing pen marks.
[0061] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for eliminating pen marks on the back of a super-sealed product after the outer edge has been sealed, characterized in that, The suction pen is cleaned every 12 hours, and a pressure regulating valve is installed between the suction pen and the negative pressure suction pipeline. The vacuum pressure of the suction pen is adjusted to -70Kpa~-60Kpa. It also includes a pen-collecting management system, which includes a pen-collecting holder for inserting and placing pens. The pen-collecting holder has an inclined slot, and a timer and an indicator light are installed next to the slot. Indicator lights indicate whether the ink pen in the slot needs cleaning. The timer is connected to a controller, and the controller controls the connected indicator light; The pressure regulating valve is connected to the controller, and the controller is connected to the memory. The memory stores the cleaning time of the suction pen and the suction power of the suction pen. It also includes a pen usage rate recording system, which includes a counter for the number of times the pen is used and a timer; A display screen is installed next to the slot, which is used to display the number of times the counter has been used and the time recorded by the timer. The counter and the timer are connected to a controller, which wirelessly controls a signal light installed on the pen; the signal light is a wireless signal light. After the controller analyzes the number of times each suction pen is used and the usage time, it displays the suction pens that are suitable to continue working. Every month after use, the suction pen is randomly inspected. The inspection method is to attach the suction pen to the polished surface of a lightly doped silicon wafer, use the OISF process to convert the contaminants on the suction pen into OISF traces, observe the OISF traces and calculate the OISF density to determine the specific condition of the suction pen. The OISF process involves humidifying and oxidizing lightly doped silicon wafers in a furnace tube for 2 hours at a temperature of 1100°C, followed by etching with an etching solution. When OISF traces are clearly visible under visual inspection, it is determined that the device cannot be used further and microscopic examination is not required. Under visual inspection, OISF traces are visible but not clear. Microscopic examination is used to assist in the determination. If the OISF density is >400 particles / cm², it is determined that the product cannot continue to be used; if the OISF density is <400 particles / cm², it is determined that the product can continue to be used.
2. The method for eliminating pen marks on the back of a super-sealed product after the outer edge has been extended, as described in claim 1, is characterized in that: The cleaning method for the suction pen is to repeatedly apply the suction pen to a clean silicon wafer surface and observe it with a spotlight until the suction marks on the suction pen disappear, at which point the suction pen is clean.
3. The method for eliminating pen marks on the back of a super-sealed product after the outer edge has been extended, as described in claim 1, is characterized in that: It also includes a cleaning tank for cleaning the suction pen, the top of which is equipped with a hanging bracket for suspending the suction pen, and the hanging bracket is equipped with hooks for suspending the suction pen by means of a hanging ring.