Novel device for polishing and unloading wafer with wax

Abstract

The utility model discloses a novel wafer wax polishing and unloading device which comprises a pure water cooling system, a pure water filtering system, a spraying pipeline, a ceramic disc used for wafer CMP (chemical mechanical polishing) processing and a wafer unloading knife used for taking down a wafer from the ceramic disc. The pure water cooling system comprises a cooling barrel used for cooling ultrapure water from the room temperature to the low temperature. After wax polishing, the wafer unloading fragment rate is greatly reduced, the wafer unloading fragment rate of a substrate wafer with the thickness smaller than 1 mm is improved to 0%, and the wafer unloading fragment rate of a substrate wafer with the thickness smaller than 0.5 mm is improved to be close to 0%; one group of wafer unloading device meets at least two polishing lines (one polishing line produces fifty thousand wafers per month), and the raw material cost corresponding to each wafer during CMP (Chemical Mechanical Polishing) is reduced by 1-5 yuan, so that at least one hundred thousand yuan can be saved by one group of wafer unloading device per month; the edge collapse process capability of the geometrical morphology of the wafer after CMP is stabilized at 400-600 nm, and focusing of the wafer in the photoetching process is facilitated.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor wafer CMP, in particular to a novel wafer wax polishing and unloading device. Background Art

[0002] Chemical mechanical polishing (CMP) is a key step in wafer manufacturing. Its function is to reduce the unevenness of the wafer surface. CMP is a process technology that smoothes the surface of integrated circuit devices and makes it highly flat through the organic combination of the physical grinding effect of nano-particles and the chemical corrosion effect of polishing liquid. Currently, the CMP process is mainly used in integrated circuits to precisely polish the surface of the wafer, and can achieve a local flatness difference of 100 to 1000A° (equivalent to 10 to 100nm at the atomic level) and ultra-high flatness.

[0003] Traditional CMP is divided into two categories:

[0004] 1. Wax-free polishing:

[0005] The wafer is adsorbed on the carrier using a polyurethane porous adsorption pad for polishing. Figure 3-7 As shown, although the problem of chip breakage does not occur, the cost of the polyurethane porous adsorption pad is high and the service life is short, which makes the cost of wax-free polishing high.

[0006] 2. Wax polishing:

[0007] Before wax polishing, first apply liquid wax [artificial or natural resin + solvent (isopropyl alcohol is more commonly used)] evenly on the back of the wafer, then bake the wafer at high temperature to evaporate the solvent in the liquid wax and melt the resin in the liquid, and then attach the wafer to the ceramic plate for CMP polishing. Figure 8-10 As shown, the cost of traditional wax polishing is lower than that of wax-free polishing, but the problem of chip breakage is prone to occur when unloading the chip.

[0008] Moreover, no matter it is wax-free polishing or wax-polishing, the edge of the polished surface of the wafer will have a certain degree of edge collapse after polishing, such as Fig.11 Therefore, we need to propose a novel device for wafer wax polishing and unloading. Utility Model Content

[0009] The utility model aims to provide a novel wafer unloading device for wax polishing. After wax polishing, the chip breakage rate of unloading is greatly reduced: the chip fragmentation rate of wafers with a substrate thickness of less than 1 mm is improved to 0%, and the chip fragmentation rate of wafers with a thickness of less than 0.5 mm is improved to nearly 0%; a group of unloading devices can meet at least two polishing lines (one polishing line produces 50,000 wafers per month), and the raw material cost corresponding to each wafer during CMP is reduced by 1-5 yuan, so that a group of unloading devices can save at least 100,000 yuan per month; the geometric morphology collapse process capability of the wafer after CMP is stabilized at 400-600nm, which is beneficial to the focusing of the wafer during the photolithography process, so as to solve the problems raised in the above-mentioned background technology.

[0010] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a new type of wafer wax polishing and wafer unloading device, comprising a pure water cooling system, a pure water filtration system, a spray pipeline, a ceramic disk for wafer CMP processing, and a wafer unloading knife for removing the wafer from the ceramic disk, the pure water cooling system, the pure water filtration system, and the spray pipeline are connected in sequence, the pure water cooling system comprises a cooling barrel for cooling ultrapure water from room temperature to low temperature, a coil for circulating cooling water is installed inside the cooling barrel, the pure water filtration system adopts a resin mixed bed filtration device, the ceramic disk is attached with a wax layer solidified by heavy crystallization, the wafer after CMP processing is completed, the wafer unloading knife is used to split the wax layer to peel the wafer from the ceramic disk, and the nozzle at the end of the spray pipeline is aligned with the wafer.

[0011] Preferably, the coil is a stainless steel coil, the surface of the coil is coated with a Teflon coating, and the temperature of the cooling water flowing inside the coil is 3-7°C.

[0012] Preferably, the lower end of the outer wall of one side of the cooling barrel is connected to a water inlet for introducing ultrapure water, and the upper end of the outer wall of the other side of the cooling barrel is provided with a water outlet for discharging ultrapure water. The water resistivity of the ultrapure water just entering the cooling barrel is greater than or equal to 18MΩ.cm, and the water temperature of the ultrapure water just entering the cooling barrel is 21-25°C.

[0013] Preferably, the ultrapure water at 21-25°C is cooled to 3-7°C after coil refrigeration, and the water quality of the cooled ultrapure water is reduced to a water resistivity greater than or equal to 16MΩ.cm. The low-temperature ultrapure water cooled to 3-7°C flows into the resin mixed bed filter device from the water outlet.

[0014] Preferably, the resin mixed bed filtration device comprises an inlet pipe for low-temperature ultrapure water to enter, a mixed bed container for improving the quality of ultrapure water, and an outlet pipe for discharging the filtered ultrapure water to a spray pipeline, wherein the mixed bed container is a mixed bed filled with cationic resin and anionic resin;

[0015] Cationic resin is used to remove cationic substances in ultrapure water, and anionic resin is used to remove anionic substances in ultrapure water. The water resistivity of ultrapure water after mixed bed container filtration is increased to 18MΩ.cm.

[0016] Preferably, the front side of the wafer is located directly below the nozzle, and the back side of the wafer is attached to the ceramic plate through a wax layer. The wax layer is rapidly cooled to 5-9°C after being sprayed with ultrapure water at a low temperature of 3-7°C, so that the wax layer is heavily crystallized and solidified. The solidified wax layer has cleavage properties, and the needle penetration of the wax layer is 0-3 [(200g*60sec.)<at 25℃> ].

[0017] Preferably, the thickness of the wafer is less than 1 mm, and the thickness of the wax layer is 1-100 μm.

[0018] Compared with the prior art, the beneficial effects of the utility model are:

[0019] 1. The utility model has a greatly reduced chip breakage rate after wax polishing: the chip breakage rate of wafers with a thickness of less than 1mm is improved to 0%, and the chip breakage rate of wafers with a thickness of less than 0.5mm is improved to nearly 0%;

[0020] 2. A set of unloading devices of the utility model can meet the needs of at least two polishing lines (one polishing line produces 50,000 lenses per month), and the raw material cost corresponding to each lens during CMP is reduced by 1-5 yuan, so a set of unloading devices can save at least 100,000 yuan per month;

[0021] 3. The geometric morphology collapse process capability of the wafer after CMP of the utility model is stable at 400-600nm, which is beneficial to the focusing of the wafer during the photolithography process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of tablet unloading using cooling ultrapure water and a tablet unloading knife according to the utility model;

[0023] Figure 2 It is a schematic diagram of the deformation of the wafer when unloading the wafer according to the utility model;

[0024] Figure 3 This is a schematic diagram of mounting a film with traditional wax-free polishing;

[0025] Figure 4 This is a polishing diagram of traditional wax-free polishing;

[0026] Figure 5 This is a schematic diagram of the traditional wax-free polishing before removing the film;

[0027] Figure 6 This is a schematic diagram of the traditional wax-free polishing process;

[0028] Figure 7This is a schematic diagram of the traditional wax-free polishing after unloading;

[0029] Figure 8 This is a schematic diagram of traditional wax polishing, wax dripping and wax application;

[0030] Fig. 9 This is a schematic diagram of traditional wax polishing, wax baking and wax sticking;

[0031] Fig.10 This is a schematic diagram of traditional wax polishing;

[0032] Fig.11 Schematic diagram of edge collapse of the polished surface of a wafer after conventional CMP polishing;

[0033] Fig.12 This is a schematic diagram of unloading the film with traditional wax polishing;

[0034] Fig.13 Schematic diagram of the deformation of the wafer when unloading with traditional wax polishing. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0036] like Figure 3-4 As shown, during wax-free polishing, the wafer is adsorbed on the carrier using a polyurethane porous adsorption pad for polishing. However, because the polyurethane adsorption pad is flexible, the compression rate during polishing is greater than 20%, and the wafer is prone to serious edge collapse after polishing. Moreover, after each wax-free polishing, the elastic recovery rate of the polyurethane porous adsorption pad deteriorates, resulting in a deterioration in the geometric morphology of the wafer after polishing (the process capability is generally 800 to 1000nm). Therefore, during wax-free polishing, the polyurethane porous adsorption pad has strict life control, which brings about the high cost of the polyurethane porous adsorption pad. Generally, the life of each polyurethane porous adsorption pad is about 20 times, corresponding to the cost of the polyurethane porous adsorption pad consumed by each wafer for wax-free polishing of about 5 to 50 yuan.

[0037] However, it is easy to remove the wafer by wax-free polishing. You only need to use low-pressure pure water spray to flush the back of the wafer to separate the wafer from the polyurethane porous adsorption pad. This process is relatively safe and reliable, and the wafer will not break into pieces. Figure 5-7 shown.

[0038] like Figure 8-10As shown, during wax polishing, the solidified wax film on the wafer is fixed on the carrier for polishing, and the wax film is solid. During polishing, the compression rate of the solid wax film is less than 5%, and the wafer is less likely to have serious edge collapse after polishing. Moreover, after each wax polishing, the wafer will be removed from the ceramic plate, and the ceramic plate needs to be cleaned with a wax removal solvent and ultrasonic cleaning again. The cleaned ceramic plate will be used again. Therefore, the geometric morphology of each wafer after wax polishing is theoretically highly consistent from batch to batch (the process capability is generally 400 to 600nm). The wax and wax removal cleaning costs for each wafer consumed during wax polishing are approximately 1 to 3 yuan.

[0039] However, it is difficult to remove the film after wax polishing. The liquid wax commonly used in the industry has a final softening temperature of 70-80℃ after solidification. At room temperature of 23±2℃, the wax layer is slightly crystallized and solidified, and the needle penetration is 3-10[(200g*60sec.)<at25℃> ], which is more difficult to be split by the tablet unloading knife.

[0040] When unloading after wax polishing CMP polishing, the overall probability of all types of wafers being broken is about 0.2%. With the development of the microelectronics industry, in order to reduce costs, the thickness of substrate wafers has evolved from less than 1mm to less than 0.5mm or even less than 0.3mm. The probability of wafers less than 0.5mm in thickness being broken when unloading is 1%

[0041] The traditional wax polishing unloading process is as follows Figure 12-13 As shown in the figure, because there is a certain probability of chip fragmentation when unloading after wax polishing, which leads to increased costs, some advanced CMP processes use wax-free polishing operations to avoid fragmentation, but overall the CMP cost is increased, but at the same time the geometric morphology of the chip after CMP polishing is sacrificed, which is not conducive to focusing the chip during the photolithography process.

[0042] See also Figure 1-2 The utility model provides a technical solution: a novel device for unloading wafers after wax CMP polishing, which is used for unloading wafers after wax CMP polishing, comprising a pure water cooling system, a pure water filtration system, a spray pipeline, a ceramic disc for wafer CMP processing, and a wafer unloading knife for removing the wafer from the ceramic disc, the pure water cooling system, the pure water filtration system, and the spray pipeline are connected in sequence, the pure water cooling system comprises a cooling barrel for cooling ultrapure water from room temperature to low temperature, a coil for circulating cooling water is installed inside the cooling barrel, the pure water filtration system adopts a resin mixed bed filtration device, the ceramic disc is attached with a wax layer solidified by heavy crystallization, the wafer after CMP processing is completed, the wafer unloading knife is used to split the wax layer to peel the wafer from the ceramic disc, the nozzle at the end of the spray pipeline is aligned with the wafer, and the low-temperature ultrapure water sprayed by the nozzle is sprayed on the wafer.

[0043] The pure water cooling system is used to cool the ultrapure water supplied from the factory from room temperature 23±2℃ to 5±2℃. The pure water filtration system is used to filter out impurities and pollutants in the ultrapure water after cooling. The spray pipeline is used to transport the filtered low-temperature ultrapure water to the ceramic plate to cool the wax layer.

[0044] The coil is a stainless steel coil, the surface of the coil is coated with a Teflon coating, the temperature of the cooling water flowing inside the coil is 3-7°C, and the coil achieves cooling of ultrapure water.

[0045] The lower end of the outer wall of one side of the cooling barrel is connected to a water inlet for introducing ultrapure water, and the upper end of the outer wall of the other side of the cooling barrel is provided with a water outlet for discharging ultrapure water. The water resistivity of the ultrapure water just entering the cooling barrel is greater than or equal to 18MΩ.cm, and the water temperature of the ultrapure water just entering the cooling barrel is 21-25°C.

[0046] The ultrapure water at 21-25℃ is cooled by the coil and the water temperature is reduced to 3-7℃. The water quality of the ultrapure water after cooling is reduced to a water resistivity greater than or equal to 16MΩ.cm. The low-temperature ultrapure water cooled to 3-7℃ flows into the resin mixed bed filter device from the water outlet.

[0047] The resin mixed bed filtration device includes a water inlet pipe for low-temperature ultrapure water to enter, a mixed bed container for improving the water quality of ultrapure water, and a water outlet pipe for discharging the filtered ultrapure water to a spray pipeline. The mixed bed container is a mixed bed filled with cationic resin and anionic resin.

[0048] The resin mixed bed filter device may also include a control system and a regeneration device. The control system is used to control and monitor the working status of the entire resin mixed bed filter device, such as the water inlet flow rate, the water outlet flow rate, the regeneration process of the resin bed, etc. Cationic resins and anionic resins need to be regenerated after a certain period of time and usage to restore their adsorption and ion exchange capabilities. The regeneration device usually includes a regeneration solution storage tank, a regeneration solution pump and other equipment to introduce the regeneration solution into the mixed bed container to flush and regenerate the resin.

[0049] Cationic resin is used to remove cationic substances in ultrapure water, and anionic resin is used to remove anionic substances in ultrapure water. The water resistivity of ultrapure water after mixed bed container filtration is increased to 18MΩ.cm.

[0050] Traditional wax polishing does not cool the wax layer. Since the softening temperature of the wax layer is generally 70-80°C, the wax layer at room temperature is solidified, but the hardness is not enough, and the needle penetration is about 3-10 [(200g*60sec.)<at 25℃> ], it is difficult to be split by the wafer unloading knife, and the wafer bends during unloading, the elastic deformation is greater than 10mm, and the wafer is easily broken.

[0051] The front side of the wafer is located directly below the nozzle, and the back side of the wafer is attached to the ceramic plate through a wax layer. After being sprayed with ultrapure water at a low temperature of 3-7°C, the wax layer is rapidly cooled to 5-9°C to achieve heavy crystallization and solidification of the wax layer. The solidified wax layer has cleavage properties, and the needle penetration of the wax layer is 0-3 [(200g*60sec.)<at25℃> ], the wax layer is easily split by the unloading blade. The wafer is bent during unloading, and the elastic deformation is less than 5mm, so the wafer is not easy to break.

[0052] The thickness of the wafer is less than 1 mm, and the thickness of the wax layer is 1-100 μm.

[0053] When using this device to unload the film, the ultrapure water supplied by the factory is transported to the cooling barrel of the pure water cooling system. At this time, the water resistivity of the ultrapure water is greater than or equal to 18MΩ.cm. The ultrapure water at 21-25℃ is cooled by the coil and the water temperature drops to 3-7℃. The water quality of the ultrapure water after cooling is reduced to a water resistivity greater than or equal to 16MΩ.cm. Then the low-temperature ultrapure water at 3-7℃ flows into the resin mixed bed filtration device from the water outlet. The water resistivity of the ultrapure water after filtration in the mixed bed container is increased to 18MΩ.cm, and the water temperature is still 3-7℃.

[0054] Then low-temperature ultrapure water is sprayed onto the wafer and wax layer through the spray pipeline. The wax layer after spraying is rapidly cooled to 5-9°C, achieving heavy crystallization and solidification of the wax layer. The brittle wax layer can be easily split by the unloading blade.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A novel device for unloading wafers after wax polishing, characterized in that: It includes a pure water cooling system, a pure water filtration system, a spray pipeline, a ceramic disk for CMP processing of wafers, and a wafer removal knife for removing the wafers from the ceramic disk. The pure water cooling system, the pure water filtration system, and the spray pipeline are connected in sequence. The pure water cooling system includes a cooling barrel for cooling ultrapure water from room temperature to low temperature. A coil for circulating cooling water is installed inside the cooling barrel. The pure water filtration system adopts a resin mixed bed filtration device. The ceramic disk is attached with a wax layer that is heavily crystallized and solidified, and the wafer removal knife is used to split the wax layer to peel the wafer from the ceramic disk. The nozzle at the end of the spray pipeline is aligned with the wafer.

2. A novel wafer wax polishing and unloading device according to claim 1, characterized in that: The coil is a stainless steel coil, the surface of the coil is coated with a Teflon coating, and the temperature of the cooling water flowing inside the coil is 3-7°C.

3. A novel wafer wax polishing and unloading device according to claim 1, characterized in that: The lower end of the outer wall of one side of the cooling barrel is connected to a water inlet for introducing ultrapure water, and the upper end of the outer wall of the other side of the cooling barrel is provided with a water outlet for discharging ultrapure water. The water resistivity of the ultrapure water just entering the cooling barrel is greater than or equal to 18MΩ.cm, and the water temperature of the ultrapure water just entering the cooling barrel is 21-25°C.

4. A novel wafer wax polishing and unloading device according to claim 3, characterized in that: The ultrapure water at 21-25℃ is cooled by the coil and the water temperature is reduced to 3-7℃. The water quality of the ultrapure water after cooling is reduced to a water resistivity greater than or equal to 16MΩ.cm. The low-temperature ultrapure water cooled to 3-7℃ flows into the resin mixed bed filter device from the water outlet.

5. A novel wafer wax polishing and unloading device according to claim 1, characterized in that: The resin mixed bed filtration device includes a water inlet pipe for low-temperature ultrapure water to enter, a mixed bed container for improving the water quality of ultrapure water, and a water outlet pipe for discharging the filtered ultrapure water to a spray pipeline. The mixed bed container is a mixed bed filled with cationic resin and anionic resin. Cationic resin is used to remove cationic substances in ultrapure water, and anionic resin is used to remove anionic substances in ultrapure water. The water resistivity of ultrapure water after mixed bed container filtration is increased to 18MΩ.cm.

6. A novel wafer wax polishing and unloading device according to claim 5, characterized in that: The front side of the wafer is located directly below the nozzle, and the back side of the wafer is attached to the ceramic plate through a wax layer. After being sprayed with ultrapure water at a low temperature of 3-7°C, the wax layer is rapidly cooled to 5-9°C to achieve heavy crystallization and solidification of the wax layer. The solidified wax layer has cleavage properties, and the needle penetration of the wax layer is 0-3 [(200g*60sec.)<at25℃> ].

7. A novel wafer wax polishing and unloading device according to claim 1, characterized in that: The thickness of the wafer is less than 1 mm, and the thickness of the wax layer is 1-100 μm.

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