Wafer degassing method

Abstract

The invention provides a wafer degassing method, the wafer degassing method is executed on equipment with a pre-pumping cavity and a baking cavity, the pre-pumping cavity and the baking cavity are respectively provided with an independent cavity, and the wafer degassing method comprises the following steps: placing a wafer in the pre-pumping cavity for pre-baking for a first time length; the vacuum arm is used for transferring the pre-baked wafer into the baking cavity for baking and degassing for a second time period, the temperature is directly or gradually increased to the baking and degassing temperature in the pre-baking process, and the pre-vacuumizing cavity is vacuumized synchronously in the pre-baking process or after pre-baking is completed, so that the pre-baked wafer is subjected to baking and degassing for a second time period; the vacuumizing method comprises the steps of continuously vacuumizing or circularly executing inert gas filling and vacuumizing operations. According to the invention, the occupation time of the wafer in the baking cavity can be reduced, the productivity bottleneck is eliminated, and the equipment output rate is improved. In addition, release and discharge of impurity gas on the wafer can be accelerated, surface warping of the wafer can be improved, and the production yield can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a wafer degassing method. Background Art

[0002] As linewidths in front-end chip manufacturing processes continue to shrink, advanced packaging equipment is also evolving towards smaller dimensions. This poses greater challenges in processing small linewidths, process control, and increasing production capacity. Advanced packaging is increasingly using wafers with organic materials such as PI and PBO. These specialized wafers release significant amounts of impurity gases and water vapor when heated, typically requiring a long bake-out process of 20-30 minutes to fully remove the impurities and degas, thereby ensuring low Rc (contact resistance). Conventional single-wafer bake-out chambers are no longer sufficient to meet the production capacity requirements of advanced packaging, leading to the development of multi-wafer bake-out chambers. Limited by their volume, multi-wafer bake-out chambers can typically only accommodate approximately 25 wafers. For PVD sputtering tools used for packaging, the process time in PVD sputtering chambers is relatively short (2-3 minutes), while the process time in bake-out degassing chambers can exceed 20 minutes. Therefore, more efficient degassing solutions are needed to further eliminate the production bottleneck caused by the lengthy bake-out process.

[0003] In addition, EWLB (embedded wafer-level ball grid array) wafers, commonly used in advanced packaging, involve multi-layer stacking (such as silicon substrates, glass substrates, redistribution layers, solder balls, etc.). Due to the significant differences in the thermal expansion coefficients of different materials, large internal stresses are generated during (heating / cooling) temperature changes, resulting in significant wafer warpage (up to + / -5mm). Moreover, EWLB often uses ultra-thin wafers (such as around 100μm or even thinner). The mechanical strength of the thinned wafers is reduced, making them more susceptible to greater warpage (up to + / -7mm) due to uneven stress distribution. Existing multi-wafer baking methods are difficult to effectively improve the wafer warpage problem. In view of this, to ensure process quality and product performance, it is necessary to implement more refined and precise control of the process flow of EWLB wafers during heating and cooling.

[0004] It should be noted that the above technical background is merely provided to provide a clear and complete description of the technical solutions of the present invention and to facilitate understanding by those skilled in the art. Simply because these solutions are described in the technical background section of the present invention, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a wafer degassing method to solve the problems of the existing multi-wafer baking degassing method, such as low equipment output due to the long time the wafers are in the baking chamber, and difficulty in improving wafer surface warping.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a wafer degassing method, which is performed on a device having a pre-evacuation chamber and a baking chamber, wherein the pre-evacuation chamber and the baking chamber each have an independent cavity. The wafer degassing method comprises the following steps:

[0007] Placing the wafer into the pre-evacuation chamber for a first pre-bake period;

[0008] The pre-baked wafers are transferred to the baking chamber using a vacuum arm for a second baking and degassing period.

[0009] During the pre-baking process, the temperature is directly or gradually raised to the baking and degassing temperature.

[0010] Optionally, the pre-vacuum chamber is evacuated synchronously during the baking process or after the pre-baking is completed. The evacuation method includes continuous evacuation or cyclic execution of evacuation and filling with inert gas.

[0011] Optionally, during the baking and degassing process, an inert gas is introduced into the baking chamber with a gas flow rate of 50-200 sccm.

[0012] Optionally, multiple wafers are baked and degassed simultaneously during the baking and degassing process.

[0013] Optionally, the temperature is directly or gradually increased to 150° C. during the pre-baking process.

[0014] Optionally, the first duration is shorter than the second duration.

[0015] Optionally, the pre-baking process further includes the steps of gradually filling the pre-evacuation chamber with inert gas, and baking the chamber under pressure for a certain period of time after each filling of the inert gas.

[0016] Optionally, the wafer degassing method also includes a step of transferring the wafer that has completed baking and degassing to a buffer chamber with an independent cavity for cooling. The cooling process is natural cooling or gradual cooling, and inert gas is gradually filled into the buffer chamber during the gradual cooling process, and the pressure is maintained and cooled for a certain period of time after each filling of inert gas.

[0017] As described above, the wafer degassing method provided by the present invention has the following beneficial effects: the wafer degassing method provided by the present invention increases the pre-baking of the wafer in the pre-evacuation chamber, so that the wafer continues to release impurity gases after the wafer reaches the baking degassing temperature in the pre-evacuation chamber, as well as during the subsequent wafer transfer and entry into the baking chamber. This can reduce the time the wafer occupies the baking chamber, eliminate production capacity bottlenecks, and improve equipment output. In addition, the present invention also uses a variety of methods such as gradual heating, continuous reciprocating "inflation + vacuuming" operations in the pre-evacuation chamber, and gradual cooling, which not only helps to accelerate the release and discharge of impurity gases (mainly CO, nitrogen, H2O) on the wafer, but also helps to improve wafer surface warping and improve production yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An exemplary flow chart of a wafer degassing method provided by the present invention is shown.

[0019] Figure 2 The graph shows the relationship between the CO / nitrogen partial pressure and baking time of the PI wafer when baked in a multi-wafer baking chamber, as measured by RGA (residual gas analyzer); among them, curve ① is the wafer that only received multi-wafer baking, and curve ② is the wafer that received both pre-evacuation chamber pre-baking and multi-wafer baking chamber baking.

[0020] Figure 3 The graph shows the relationship between the H2O partial pressure and baking time of PI wafers baked in a multi-wafer baking chamber, as measured by RGA (residual gas analyzer); among them, curve ① is the wafer that only received multi-wafer baking, and curve ② is the wafer that received both pre-evacuation chamber pre-baking and multi-wafer baking.

[0021] Figure 4 Shown is a comparison chart of wafer warpage data obtained in different embodiments using the wafer degassing method provided by the present invention. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional views showing the device structure will not be partially enlarged according to the general proportion, and the schematic views are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0023] It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be varied arbitrarily, and the component layout may be more complex. To minimize the illustrations, not all structures are labeled in the drawings.

[0024] The present invention provides a wafer degassing method, which is performed on a device having a pre-evacuation chamber and a baking chamber. The pre-evacuation chamber and the baking chamber each have independent cavities, do not interfere with each other and can be used independently of each other.

[0025] The pre-evacuation chamber is provided with at least one heating device. For example, in some examples, the pre-evacuation chamber is only provided with an infrared baking device (or infrared heating device), and the infrared baking device contains, for example, more than two bulbs or tubes for baking. The infrared baking device is, for example, arranged directly above the pre-evacuation chamber, and the heat (infrared light) generated by it passes through the glass transparent cover on the top of the wafer pre-evacuation chamber to bake the wafer. The baking bulbs or tubes in the infrared baking device can be placed in parallel, in an arc shape, or in a hemispherical shape to obtain the best baking temperature uniformity on the wafer. The baking bulbs or tubes in the infrared baking device can reach a temperature of 150-250°C within 20s, and the maximum baking temperature can reach 300°C. In the case where only an infrared baking device is provided, the carrier in the pre-evacuation chamber is only used to carry the wafer and does not have a heating function.

[0026] In other examples, the pre-evacuation chamber is equipped with only a bottom heater, which is located below the wafer pre-evacuation chamber. The bottom heater is equipped with a heating wire or heating ring, with a maximum baking temperature of 300°C. The bottom heater is also interspersed with multiple ejector pins. Driven by a drive device, the ejector pins can be raised or lowered to release or place the wafer on the surface of the bottom heater.

[0027] In some other examples, the pre-vacuum chamber is provided with an infrared baking device located directly above the pre-vacuum chamber and a bottom heater located at the bottom of the cavity. The specific settings of the two heating devices can be referred to the above content and will not be repeated for the sake of brevity.

[0028] In addition to the heating device, the pre-evacuation chamber also has a vacuum line connected to a vacuum pump so that the pre-evacuation chamber can be evacuated when necessary. In addition, the pre-evacuation chamber is also provided with a gas filling line connected to an inert gas source, and inert gases such as argon and / or nitrogen can be filled into the pre-evacuation chamber when necessary. The gas filling line can be provided with an MFC (mass flow controller) and a control valve. The pre-evacuation chamber can be single or multiple. When there are multiple pre-evacuation chambers, the multiple pre-evacuation chambers can be stacked up and down and / or arranged in parallel on the same horizontal plane, without specific limitation.

[0029] The wafer degassing method of this embodiment is applicable to any of the above-mentioned pre-evacuation chambers. However, the specific degassing operations may differ depending on the structure of the pre-evacuation chamber, which will be described in detail later.

[0030] The baking chamber is preferably a multi-wafer baking chamber, capable of baking and degassing multiple wafers simultaneously. For example, in some embodiments, the baking chamber is equipped with a tray capable of holding multiple wafers in parallel and at intervals, and a heating device surrounding the wafers. The heating device within the baking chamber can be an infrared or resistance heater, capable of reaching a heating temperature of 150°C or above, without limitation.

[0031] In addition to the pre-evacuation chamber and the baking chamber, the equipment for performing the wafer degassing method of the present invention also includes a buffer chamber that is connected to both the pre-evacuation chamber and the baking chamber and has an independent cavity, an atmospheric arm for transferring external wafers to the pre-evacuation chamber, and a vacuum arm for transferring pre-baked wafers from the pre-evacuation chamber to the baking chamber. The vacuum arm operates in a vacuum environment and can fix the wafer based on vacuum adsorption, which helps to further promote the release of water vapor and impurity gases in the wafer during the wafer transfer process. In addition, the equipment may also include several process chambers connected to the buffer chamber. When there are more than two process chambers, different process chambers can be used to perform the same or different process treatments. For example, some process chambers can be used to perform process operations before degassing, and some process chambers can be used to perform process operations after degassing. This can make the connection between the degassing process and other processes smoother and tighter, reduce the time and contamination risk of wafers in different process flows, help improve equipment output and yield, and reduce production costs.

[0032] The general process of the wafer degassing method of the present invention can be referred to Figure 1 As shown, it at least includes the steps of:

[0033] S1: Place the wafer into the pre-evacuation chamber for a first pre-bake period;

[0034] S2: Use the vacuum arm to transfer the pre-baked wafers to the baking chamber for the second baking and degassing.

[0035] In the pre-baking process, the temperature is directly or gradually raised to the baking and degassing temperature, and the pre-vacuum chamber is vacuumed synchronously during the pre-baking process or after the pre-baking is completed. The vacuuming method includes continuous vacuuming or cyclically performing the operations of filling inert gas and vacuuming.

[0036] That is, in some examples, the pre-evacuation chamber can be evacuated at the same time as the pre-baking heating device is turned on. In other examples, after the heating device is turned on for a period of time, the pre-evacuation chamber is evacuated after the wafer has completed the pre-baking for the required time. The vacuuming method can be continuous exhaust by a vacuum pump, and in other examples, the pre-evacuation chamber can be evacuated to a certain pressure and then filled with inert gases such as nitrogen or argon, and then the pre-evacuation chamber can be evacuated, or the pre-evacuation chamber can be evacuated for a period of time and then filled with inert gases, and this process can be performed multiple times, that is, the pre-evacuation chamber is cyclically evacuated + filled, so that the pressure in the pre-evacuation chamber produces periodic oscillations, which helps to accelerate the discharge of impurity gases (such as CO, H2O, nitrogen, etc.) in the wafer. The amount, time and / or exhaust power and time of the inert gas filled in each cycle can be the same or different. It is preferred to gradually increase the cavity pressure to help the wafer gradually adapt to the pressure changes in the cavity and reduce wafer damage. For example, in a preferred embodiment, the pre-vacuum chamber is first evacuated to 1mT-10mT, and then the evacuation is stopped and inert gas is filled into the pre-vacuum chamber until the chamber pressure rises to 50mT-200mT, and then the evacuation is repeated, and the cycle is repeated.

[0037] Preferably, in step S1, the wafer is placed in the pre-evacuation chamber using an atmospheric arm. The pre-evacuation chamber may have only an infrared heating device, or only a bottom heater, or both heating devices, and the required heating device can be selectively turned on according to different needs. In some examples, for example, if an infrared heating device is used for non-contact heating, the heating device can be directly turned on to the required high power so that the heating device quickly reaches the preset temperature, which is preferably 150°C. In other examples, such as when a bottom heater is used for contact heating, the power of the heating device can be increased in stages so that the heating device gradually heats up until it reaches 150°C, so that the wafer gradually adapts to the temperature change and reduces wafer damage.

[0038] In a preferred example, the first duration is less than the second duration. For example, the first duration is within 5 minutes as a whole, and the second duration is within 10 minutes (including 10 minutes). The sum of the first duration and the second duration is less than the duration required for baking and degassing only in the baking chamber in the prior art. It is not appropriate for the first duration and the second duration to be too short or too long, and they need to be set according to the specific operation. For example, in some examples, pre-baking is performed in a pre-evacuation chamber with only an infrared baking device, that is, the wafer is pre-baked only from the front side of the wafer, and the time is preferably 90-150 seconds, for example, 90, 100, 110, 120, 130, 140, 150 or any value in this range, preferably 120 seconds. In other examples, the back side of the wafer is pre-baked in a pre-evacuation chamber with only a bottom heater, and the pre-baking can be divided into two stages. The first stage is a heating stage in which the ejector pin lifts the wafer and the wafer is not in direct contact with the bottom heater. The second stage is a heating stage in which the ejector pin descends and the wafer is placed on the surface of the bottom heater. The time of the first stage is preferably 10-60 seconds, preferably 30 seconds, and the time of the second stage is preferably 60-120 seconds, preferably 90 seconds. The power of the bottom heater in these two stages can remain unchanged. In other examples, the back side of the wafer is pre-baked in a pre-evacuation chamber with only a bottom heater. It is also divided into the first stage in which the wafer is lifted by the ejector pin and the wafer is not in direct contact with the bottom heater, and the second stage in which the ejector pin is lowered and the wafer is placed on the surface of the bottom heater. From the perspective of efficiency and effect, the first stage is preferably 10-60 seconds, preferably 25 seconds. However, in the second stage, the heating power of the bottom heater is gradually increased to increase the baking temperature rise rate and baking temperature. In this case, the second time can be appropriately shortened, for example, preferably 10-60 seconds, preferably 25 seconds.

[0039] In some other examples, the front and back sides of the wafer are pre-baked simultaneously in a pre-evacuation chamber having an infrared baking device and a bottom heater. Both heating devices are in the turned-on state. The wafer is first pre-baked for 10-60 seconds (preferably 30 seconds) with the ejector pins lifting it up, and then the wafer is lowered to the surface of the bottom heater and pre-baked for another 10-60 seconds (preferably 30 seconds). During the pre-baking process, the power of the infrared baking device and / or the bottom heater can be gradually increased.

[0040] In some examples, the pre-baking process also includes the steps of gradually filling the pre-vacuum chamber with inert gas, and baking at a pressure-maintaining time for a certain period of time after each filling of inert gas. For example, when the heating device in the pre-vacuum chamber is turned on, the pre-vacuum chamber is filled with inert gas in stages, and stabilized for a certain period of time after each filling of inert gas, so that the wafer can better adapt to the gradually increasing chamber pressure, improve the pre-baking efficiency, promote wafer degassing, and help prevent wafer damage caused by sudden changes in chamber pressure, and improve the adhesion between film layers. The inflation control and pressure-maintaining baking time of each stage should not be too short or too long. In a preferred example, the inert gas is filled for the first time, so that the pressure in the pre-vacuum chamber reaches 0.5Torr, the inflation is stopped, and the pressure is maintained and baked for 30 seconds; then the gas is inflated again for 5 seconds, so that the pressure in the chamber rises to 1Torr, the inflation is stopped, and the pressure is maintained and baked for 30 seconds. For example, if the aforementioned pre-bake is divided into a first stage and a second stage, then after the second stage pre-bake of a preset duration, the pre-evacuation chamber is filled with inert gas and stabilized for a predetermined period of time to perform a pressure-holding bake. This operation can be performed multiple times. Preferably, from multiple perspectives such as degassing efficiency, preventing wafer warpage, and avoiding wafer damage, each filling time is preferably no more than 10 seconds (preferably 5 seconds), and the pressure-holding bake time after filling with inert gas is preferably no more than 60 seconds (preferably 30 seconds). The total pre-bake time, including the filling and pressure-holding bake stages, is still preferably kept within 5 minutes.

[0041] In some examples, the baking and degassing process can be performed in a vacuum environment. In other examples, an inert gas such as nitrogen or argon can be introduced into the baking chamber during the baking and degassing process, preferably at a gas flow rate of 50-200 sccm. The baking and degassing time is preferably 8-12 minutes, preferably 10 minutes.

[0042] In some examples, the wafer degassing method further includes the step of transferring the wafer that has completed baking and degassing to a buffer chamber for cooling. The cooling process can be constant temperature cooling, for example, the wafer is placed on a cooling plate in the buffer chamber for a period of time, during which the temperature of the cooling plate remains unchanged, so that the wafer is cooled. In other examples, the cooling temperature of the cooling device can be gradually lowered to gradually cool the wafer. And in a further example, in the gradual cooling process, inert gas is gradually filled into the buffer chamber, and after each inert gas is filled, the pressure is maintained and cooled for a certain period of time. That is, each time a certain amount of inert gas is filled into the buffer chamber, the pressure in the chamber is increased to a certain level, and then the gas is stopped, and the pressure is maintained and cooled for a certain period of time; then the gas is re-filled, and the pressure in the chamber is further increased, and then the gas is stopped again, and the pressure is maintained and cooled for a certain period of time again, so that the wafer gradually adapts to the changes in temperature and pressure, which helps to improve the wafer warping. For example, in some examples, the cooling process includes first allowing the wafer to cool naturally for 10-60 seconds (preferably 25 seconds) when it is off the cooling plate, and then allowing the wafer to fall onto the surface of the cooling plate and gradually increasing the cooling rate to accelerate the cooling of the wafer. This process takes 10-60 seconds (preferably 25 seconds). Afterwards, the buffer chamber can be filled with inert gas and stabilized for a certain period of time to perform pressure-maintaining cooling. This operation can be performed multiple times. For example, the time for each filling of inert gas does not exceed 10 seconds, preferably 5 seconds. The stabilization time after filling with inert gas is preferably 10-60 seconds, preferably 30 seconds. The total cooling time is preferably controlled within 2 minutes.

[0043] Preferably, the baking and degassing in step S2 is a multi-wafer operation, that is, multiple wafers are baked and degassed simultaneously. The specific degassing method can adopt existing methods, which will not be described in detail. Because the wafers are pre-baked in the pre-evacuation chamber in this embodiment, the degassing process time of the wafers in the baking chamber can be significantly shortened compared to the existing method of baking and degassing only in the baking chamber.

[0044] In addition to its application in front-end wafer processing, the wafer degassing method of the present invention is particularly suitable for degassing wafers containing organic materials such as PI (polyimide) and PBO (poly(p-phenylene benzobisoxazole)). For example, it is suitable for degassing wafers used in back-end packaging operations such as EWLB. These wafers can experience severe surface warpage due to internal stress caused by multiple process steps and differences in thermal expansion coefficients between materials. Therefore, the present invention is particularly suitable for improving this effect.

[0045] The wafer degassing method provided by the present invention increases the pre-baking of the wafer in the pre-vacuum chamber, so that the wafer continues to release impurity gases after the pre-vacuum chamber is baked to the baking degassing temperature, as well as during the subsequent wafer transfer and entry into the baking chamber. This can reduce the time the wafer occupies in the baking chamber, eliminate production capacity bottlenecks, and improve equipment output. At the same time, the pre-vacuum chamber and the baking chamber are independent of each other. By means of vacuuming the pre-vacuum chamber and other means, the wafer completes primary purification during the pre-baking process in the pre-vacuum chamber, which helps to avoid bringing water vapor and impurity gases into the baking chamber, reduces wafer damage, and improves wafer warping. In addition, the present invention also uses a variety of methods such as gradually increasing the temperature, continuously reciprocating "inflation + vacuuming" operations in the pre-vacuum chamber, and gradually cooling the temperature, which not only helps to accelerate the release and discharge of impurity gases (mainly CO, nitrogen, H2O) on the wafer, but also helps to further improve the surface warping of the wafer and improve production yield.

[0046] In order to make the technical solutions and advantages of the present invention more prominent, the present invention is described in more detail below with reference to specific embodiments.

[0047] Comparative Example

[0048] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber;

[0049] Step 2: The vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0050] Step 3: After the chamber bottom pressure reaches E-5 Torr, the vacuum arm removes the wafer from the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0051] Step 4: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0052] Step 5: When the baking degassing timer reaches the set time (for example, 20 minutes), the wafer is taken out with a vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees). The degassing process ends here.

[0053] Example 1

[0054] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (the pre-evacuation chamber only has an infrared baking device, which is initially closed).

[0055] Step 2: The infrared baking device lights up, starts pre-baking the wafer, and starts the pre-baking timer;

[0056] Step 3: At the same time as Step 2 begins, the vacuum pump begins to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0057] Step 4: During the pre-bake process, use a high-power, rapid temperature-raising method. For example, use 50% of the full power output to quickly raise the wafer temperature to 150°C in about 20 seconds. After 120 seconds, turn off the infrared baking device and stop pre-bake.

[0058] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0059] Step 6: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0060] Step 7: When the baking degassing timer reaches the set time (~10 minutes), the wafer is taken out by the vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees). The degassing process ends here.

[0061] Example 2

[0062] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (only the infrared baking device is in the closed state at the beginning);

[0063] Step 2: The infrared baking device lights up, starts pre-baking the wafer, and starts the pre-baking timer;

[0064] Step 3: At the same time as Step 2 begins, the vacuum pump begins to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0065] Step 4: During the pre-bake timing process, gradually increase the heating power. For example, first use 20% of full power for 30 seconds (maintaining 20% ​​of full power for 30 seconds, the time for adjusting the power is negligible, the same below), then use 40% of full power for 30 seconds, and finally use 50% of full power for 60 seconds. By using a gradual and slow temperature increase method to reduce thermal stress and wafer warpage, turn off the infrared baking device after the time is up and stop baking;

[0066] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0067] Step 6: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0068] Step 7: When the baking degassing timer reaches the set time (~10 minutes), the wafer is taken out by the vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees). The degassing process ends here.

[0069] Example 3

[0070] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (only the bottom heater is in the heating state and the temperature is set at 150°C).

[0071] Step 2: Place the wafer on the wafer ejector pins, without contacting the bottom heater, and begin a slow pre-bake of the wafer for 30 seconds. Lower the wafer ejector pins, allowing the wafer to fall onto the bottom heater surface, and gradually increase the wafer baking heating rate for 90 seconds (including the 1-2 seconds wafer lowering time, the same below).

[0072] Step 3: After the pre-bake timer reaches the set time, the wafer ejector pin rises and pushes the wafer up again, stopping the baking;

[0073] Step 4: After the baking is stopped, the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0074] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0075] Step 6: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0076] Step 7: When the baking degassing timer reaches the set time (~10 minutes), the wafer is taken out by the vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees). The degassing process ends here.

[0077] Example 4

[0078] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (which is also equipped with an infrared baking device and a bottom heater. The bottom heater is in a heating state and the temperature is set at 150°C).

[0079] Step 2: Place the wafer on the wafer ejector pins without contacting the bottom heater and begin slow pre-baking the wafer for 30 seconds. At the same time, the infrared baking device is turned on, and the heating power is 20% of the full power for 30 seconds.

[0080] Lower the wafer ejector pins and place the wafer onto the bottom heater surface. Gradually increase the wafer baking temperature rate over a 90-second period. Simultaneously, increase the power of the infrared baking device to 40% of full power for the first 30 seconds and 50% of full power for the last 60 seconds.

[0081] Here, the front and back sides of the wafer are baked simultaneously, and the temperature is slowly increased to further reduce thermal stress and reduce wafer warpage;

[0082] Step 3: At the same time as Step 2 begins, the vacuum pump begins to evacuate the wafer pre-evacuation chamber through the vacuum pipeline. When the chamber pressure drops to the specified pressure (e.g., 1-10 mT), the vacuum pump stops pumping. Then, an inert gas (e.g., argon or nitrogen) is immediately filled into the wafer pre-evacuation chamber through the gas charging pipeline until the chamber pressure rises to the specified pressure (e.g., 50-200 mT). This cycle repeats, and the wafers are quickly baked and the impurity gases released after wafer baking are discharged through continuous gas charging and vacuum pumping.

[0083] Step 4: When the pre-bake timer reaches the set time (~2 minutes), the wafer ejector pin rises to lift the wafer, and the infrared baking device is turned off to stop baking;

[0084] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0085] Step 6: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0086] Step 7: When the baking degassing timer reaches the set time (~10 minutes), the wafer is taken out by the vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees). The degassing process ends here.

[0087] Example 5

[0088] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (only the bottom heater is on, the bottom heater is in the heating state, and the temperature is set at 150°C). Then the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline.

[0089] Step 2: Place the wafer on the wafer ejector pins without contacting the bottom heater and start slow pre-bake of the wafer for 25 seconds.

[0090] Lower the wafer ejector pin and let the wafer fall onto the bottom heater surface. Gradually increase the wafer baking heating rate and baking temperature for 25 seconds.

[0091] Close the high vacuum valve of the pre-evacuation chamber, and then fill the pre-evacuation chamber with argon through the MFC. First, fill for 5 seconds until the pressure in the chamber reaches 0.5 Torr, then stop filling and bake at this pressure for 30 seconds; then fill again for 5 seconds until the pressure in the chamber reaches 1 Torr, then stop filling and bake at this pressure for 30 seconds;

[0092] Step 3: After the pre-bake timer reaches the set time, the wafer ejector pin rises and pushes the wafer up again, stopping the baking;

[0093] Step 4: After the baking is stopped, the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0094] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0095] Step 6: After the wafer enters the multi-wafer baking chamber, the baking degassing timer starts, and 50-200 sccm of inert gas (argon or nitrogen) is continuously introduced;

[0096] Step 7: When the baking degassing timer reaches the set time (~10 minutes), the wafer is taken out by the vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees). The degassing process ends here.

[0097] Example 6

[0098] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (only the bottom heater is on, the bottom heater is in the heating state, and the temperature is set at 150°C). Then the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline.

[0099] Step 2: Place the wafer on the wafer ejector pins without contacting the bottom heater and start slow pre-bake of the wafer for 25 seconds.

[0100] Lower the wafer ejector pin and let the wafer fall onto the bottom heater surface. Gradually increase the wafer baking heating rate and baking temperature for 25 seconds.

[0101] Close the high vacuum valve of the pre-evacuation chamber, and then fill the pre-evacuation chamber with argon through the MFC. First, fill for 5 seconds until the pressure in the chamber reaches 0.5 Torr, then stop filling and bake at this pressure for 30 seconds; then fill again for 5 seconds until the pressure in the chamber reaches 1 Torr, then stop filling and bake at this pressure for 30 seconds;

[0102] Step 3: After the pre-bake timer reaches the set time, the wafer ejector pin rises and pushes the wafer up again, stopping the baking;

[0103] Step 4: After the baking is stopped, the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0104] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0105] Step 6: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0106] Step 7: When the baking and degassing timer reaches the set time (~10 minutes), the wafer is removed by the vacuum arm and sent to the lower multi-wafer buffer chamber (which can accommodate more than 3 wafers). The wafer is allowed to cool naturally by natural cooling to prevent large wafer warping due to excessive cooling.

[0107] Step 8: When the wafer is cooled naturally for a set time (~2 minutes), the wafer is taken out by a vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees), and the degassing process ends here.

[0108] Example 7

[0109] Step 1: The atmospheric arm takes the wafer out of the wafer carrier and places it into the wafer pre-evacuation chamber (only the bottom heater is on, the bottom heater is in the heating state, and the temperature is set at 150°C). Then the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline.

[0110] Step 2: Place the wafer on the wafer ejector pins without contacting the bottom heater and start slow pre-bake of the wafer for 25 seconds.

[0111] Lower the wafer ejector pin and let the wafer fall onto the bottom heater surface. Gradually increase the wafer baking heating rate and baking temperature for 25 seconds.

[0112] Close the high vacuum valve of the pre-evacuation chamber, and then fill the pre-evacuation chamber with argon through the MFC. First, fill for 5 seconds until the pressure in the chamber reaches 0.5 Torr, then stop filling and bake at this pressure for 30 seconds; then fill again for 5 seconds until the pressure in the chamber reaches 1 Torr, then stop filling and bake at this pressure for 30 seconds;

[0113] Step 3: After the pre-bake timer reaches the set time, the wafer ejector pin rises and pushes the wafer up again, stopping the baking;

[0114] Step 4: After the baking is stopped, the vacuum pump starts to evacuate the wafer pre-evacuation chamber through the vacuum pipeline;

[0115] Step 5: The vacuum arm takes the wafer out of the wafer pre-evacuation chamber and then sends it to the multi-wafer baking chamber;

[0116] Step 6: After the wafer enters the multi-wafer baking chamber, the baking and degassing timing begins;

[0117] Step 7: When the baking and degassing timer reaches the set time (~10 minutes), the wafer is taken out with a vacuum arm and sent to a multi-wafer buffer chamber (which can hold more than 3 wafers): first place the wafer on the wafer ejector pin without touching the bottom cooling plate, and slowly cool the wafer naturally for 25 seconds; then lower the wafer ejector pin, and the wafer falls onto the surface of the bottom cooling plate, gradually increasing the wafer cooling rate for 25 seconds; then close the high vacuum valve of the multi-wafer buffer chamber, and fill the pre-evacuation chamber with argon through the MFC. First, fill for 5 seconds to raise the pressure in the chamber to 0.5 Torr, then stop filling and maintain pressure and cool for 30 seconds; finally, fill again for 5 seconds to raise the pressure in the chamber to 1 Torr, then stop filling and maintain pressure and cool for 30 seconds. This can effectively prevent the wafer from warping due to excessive cooling by adopting a multi-step cooling method with a slow cooling speed at first and then a fast cooling speed.

[0118] Step 8: When the wafer cooling timer reaches the set time (~2 minutes), the wafer is taken out by the vacuum arm and sent to the next process chamber (usually a low-temperature pre-cleaning chamber with a base temperature below zero degrees), and the degassing process ends here.

[0119] According to measured data, for wafers containing PI, if only multi-wafer baking and degassing are performed according to the method in the comparative example, it usually takes about 20 minutes of baking, and the WPH (wafer per hour) is 18.7; however, if the pre-baking in the pre-evacuation chamber + multi-wafer baking and degassing method of the present invention is adopted, it can usually save about 10 minutes of degassing time, that is, the second step (multi-wafer baking and degassing) only requires about 10 minutes of degassing time (the degassing time of the second step can be shortened by 50%), and the WPH can be increased to 24.6, an increase of more than 30%.

[0120] Figure 2 and Figure 3 Curve ② shows that by adopting the present invention, the time for the cavity bottom pressure to reach 5E-8Torr is shorter. That is, by adopting the present invention, the impurity gas can reach the cavity bottom pressure in a relatively short time, which can greatly shorten the degassing time of the wafer in the baking chamber and help improve the output rate of the equipment.

[0121] In addition, reference Figure 4 As shown, by adopting the method of the present invention, adding continuous "inflation + vacuuming" and / or "inflation + pressure-maintaining cooling" steps during the baking and degassing process can effectively improve the warping of the wafer surface and improve the adhesion of the film layer. The inert gas injected helps to improve the temperature uniformity of the wafer and improve the production yield.

[0122] It should be noted again that the above embodiments are merely exemplary. The steps in the different embodiments described above can be combined arbitrarily, provided they do not conflict with each other. In particular, a cooling step can be added to the aforementioned embodiments that do not include one. For example, by adding the cooling step of Embodiment 6 or 7 after the baking and degassing steps of Embodiments 1 to 5, the wafer warpage can be further improved. Furthermore, the various process parameters in the above embodiments can be adjusted arbitrarily within the scope of the present invention to achieve similar results. For the sake of brevity, these parameters will not be described in detail.

[0123] In summary, the wafer degassing method provided by the present invention increases the pre-baking of the wafer in the pre-vacuum chamber, so that the wafer continues to release impurity gases after the wafer is baked in the pre-vacuum chamber and reaches the baking degassing temperature, as well as during the subsequent wafer transfer and entry into the baking chamber. This can reduce the time the wafer occupies in the baking chamber, eliminate production capacity bottlenecks, and improve equipment output. At the same time, the pre-vacuum chamber and the baking chamber are independent of each other. By means of vacuuming the pre-vacuum chamber and other means, the wafer completes primary purification during the pre-baking process in the pre-vacuum chamber, which helps to avoid bringing water vapor and impurity gases into the baking chamber, reduces wafer damage, and improves wafer warping. In addition, the present invention also uses a variety of methods such as gradually increasing the temperature, continuously and repeatedly performing "inflation + vacuuming" operations in the pre-vacuum chamber, and gradually cooling the temperature, which not only helps to accelerate the release and discharge of impurity gases (mainly CO, nitrogen, H2O) on the wafer, but also helps to improve the warping of the wafer surface, improve the adhesion of the film layer, and improve the production yield.

[0124] Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0125] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A wafer degassing method, characterized in that: The wafer degassing method is performed on a device having a pre-evacuation chamber and a baking chamber, wherein the pre-evacuation chamber and the baking chamber each have an independent cavity. The wafer degassing method includes the following steps: Placing the wafer into the pre-evacuation chamber for a first pre-bake period; The pre-baked wafers are transferred to the baking chamber by a vacuum arm for a second period of baking and degassing. During the pre-baking process, the temperature is directly or gradually raised to the baking and degassing temperature, and the pre-vacuum chamber is evacuated synchronously during the pre-baking process or after the pre-baking is completed. The vacuuming method includes continuous vacuuming or cyclically performing vacuuming and filling with inert gas operations.

2. The wafer degassing method according to claim 1, wherein: During the pre-bake process, the temperature is directly or gradually raised to 150° C., the first duration is less than the second duration, and the wafer degassing method further satisfies some of the following conditions: 1) Multiple wafers are baked and degassed simultaneously during the baking and degassing process; 2) The pre-baking process also includes the steps of gradually filling the pre-evacuation chamber with inert gas and maintaining the pressure and baking for a certain time after each filling of the inert gas; 3) During the baking and degassing process, an inert gas is introduced into the baking chamber with a gas flow rate of 50-200 sccm.

3. The wafer degassing method according to claim 1 or 2, characterized in that: The wafer degassing method also includes the step of transferring the wafer that has completed baking and degassing to a buffer chamber with an independent cavity for cooling. The cooling process is constant temperature cooling or gradual cooling, and inert gas is gradually filled into the buffer chamber during the gradual cooling process, and the pressure is maintained and cooled for a certain period of time after each filling of inert gas.

4. The wafer degassing method according to claim 1 or 2, characterized in that: The wafer degassing method comprises: Use the atmospheric arm to place the wafer into the pre-evacuation chamber; Only the infrared baking device located directly above the wafer is turned on, and its temperature is quickly raised to 150°C to pre-bake the wafer, and the pre-bake timer is started. During this process, the pre-vacuum chamber is also evacuated. After 90-150 seconds, turn off the infrared baking device and stop pre-baking; Transfer the wafer to the baking chamber and start baking and degassing. After 10 minutes, the degassing process is completed and the wafer is transferred out of the baking chamber using a vacuum arm.

5. The wafer degassing method according to claim 1 or 2, characterized in that: The wafer degassing method comprises: Use the atmospheric arm to place the wafer into the pre-evacuation chamber; Only the infrared baking device located directly above the wafer is turned on, and its temperature is gradually raised to 150°C to pre-bake the wafer, and the pre-bake timer is started. During this process, the pre-vacuum chamber is simultaneously evacuated. After 90-150 seconds, turn off the infrared baking device and stop pre-baking; Transfer the wafer to the baking chamber and start baking and degassing. After 10 minutes, the degassing process is completed and the wafer is transferred out of the baking chamber using a vacuum arm.

6. The wafer degassing method according to claim 1 or 2, characterized in that: The pre-evacuation chamber is provided with a bottom heater, and a plurality of ejector pins are passed through the bottom heater. The wafer degassing method includes: Use the atmospheric arm to place the wafer on the ejector pin of the pre-evacuation chamber without contacting the bottom heater. Only the bottom heater is in the heating state at a temperature of 150°C to slowly pre-bake the wafer. After 10-60 seconds, the ejector pins are lowered and the wafer is placed on the bottom heater surface to continue pre-baking. After 60-120 seconds, the bottom heater is turned off, the ejector pin lifts the wafer, and the pre-vacuum chamber begins to be evacuated. After the pre-vacuum chamber is evacuated to the preset vacuum level, the wafer is transferred from the pre-vacuum chamber to the baking chamber for baking and degassing using a vacuum arm; After 10 minutes, the degassing process is completed and the wafer is transferred out of the baking chamber using a vacuum arm.

7. The wafer degassing method according to claim 1 or 2, characterized in that: The pre-evacuation chamber is provided with an infrared baking device located at the upper part of the chamber and a bottom heater located at the lower part of the chamber, and a plurality of ejector pins are passed through the bottom heater. The wafer degassing method includes: Use the atmospheric arm to place the wafer on the ejector pin of the pre-evacuation chamber without contacting the bottom heater. Only the bottom heater is in the heating state at a temperature of 150°C to slowly pre-bake the wafer. After 10-60 seconds, the infrared baking device is turned on with a power lower than 50% of the full power of the infrared baking device to pre-bake the front and back sides of the wafer simultaneously; After 10-60 seconds, the ejector pins are lowered and the wafer is placed on the bottom heater surface to continue pre-baking. During this process, the power of the infrared baking device is gradually increased. During the pre-baking process, the pre-evacuation chamber is cyclically filled with inert gas and evacuated to quickly pre-bake the wafers and exhaust the impurity gases released after the wafers are pre-baked; When the pre-baking timer reaches the set time, lift the wafer and turn off the infrared baking device to stop pre-baking; The wafer is taken out from the pre-evacuation chamber by a vacuum arm and transferred to the baking chamber for baking and degassing.

8. The wafer degassing method according to claim 1 or 2, characterized in that: The pre-evacuation chamber is provided with a bottom heater located at the lower portion of the chamber, and a plurality of ejector pins are inserted into the bottom heater. The wafer degassing method includes placing the wafer on the ejector pins of the pre-evacuation chamber using an atmospheric arm without contact with the bottom heater, with only the bottom heater in a heating state at a temperature of 150° C., slowly pre-baking the wafer, and starting to evacuate the pre-evacuation chamber. After 10-60 seconds, the ejector pin is lowered and the wafer is placed on the bottom heater surface to continue pre-baking. During this process, the wafer baking heating rate and baking temperature are gradually increased; After 10-60 seconds, close the high vacuum valve of the pre-vacuum chamber, and then fill the pre-vacuum chamber with inert gas. First, fill for 5 seconds until the pressure in the chamber reaches 0.5 Torr, then stop filling and bake at the pressure for 30 seconds. Then fill again for 5 seconds until the pressure in the chamber reaches 1 Torr, then stop filling and bake at the pressure for 30 seconds. Lift the ejector pin to separate the wafer from the bottom heater surface, turn off the bottom heater, and stop pre-bake; After the pre-vacuum chamber is vacuumed, the wafer is taken out of the pre-vacuum chamber using a vacuum arm and then transferred to the baking chamber; While the baking chamber is baking and degassing, 50-200 sccm of inert gas is continuously introduced, and the degassing process is completed after a preset time.

9. The wafer degassing method according to claim 3, wherein: The pre-evacuation chamber is provided with a bottom heater located at the lower part of the chamber, and a plurality of ejector pins are passed through the bottom heater. The wafer degassing method includes: Use the atmospheric arm to place the wafer on the ejector pin of the pre-evacuation chamber without contacting the bottom heater. Only the bottom heater is in the heating state at 150°C. Slowly pre-bake the wafer and start evacuating the pre-evacuation chamber. After 10-60 seconds, the ejector pin is lowered and the wafer is placed on the bottom heater surface to continue pre-baking. During this process, the wafer baking heating rate and baking temperature are gradually increased; After 10-60 seconds, close the high vacuum valve of the pre-vacuum chamber, and then fill the pre-vacuum chamber with inert gas. First, fill for 5 seconds until the pressure in the chamber reaches 0.5 Torr, then stop filling and bake at the pressure for 30 seconds. Then fill again for 5 seconds until the pressure in the chamber reaches 1 Torr, then stop filling and bake at the pressure for 30 seconds. Lift the ejector pin to separate the wafer from the bottom heater surface, turn off the bottom heater, and stop pre-bake; After the pre-vacuum chamber is vacuumed, the wafer is taken out of the pre-vacuum chamber using a vacuum arm and then transferred to the baking chamber; After the preset baking and degassing time is completed, the wafer is taken out by the vacuum arm and sent to the buffer chamber, where it is cooled naturally by natural cooling. After cooling, the wafer is taken out using a vacuum arm and transferred to the next process chamber to complete the degassing process.

10. The wafer degassing method according to claim 3, wherein: The pre-evacuation chamber is provided with a bottom heater located at the lower part of the chamber, and a plurality of ejector pins are passed through the bottom heater. The wafer degassing method includes: Use the atmospheric arm to place the wafer on the ejector pin of the pre-evacuation chamber without contacting the bottom heater. Only the bottom heater is in the heating state at 150°C. Slowly pre-bake the wafer and start evacuating the pre-evacuation chamber. After 10-60 seconds, the ejector pin is lowered and the wafer is placed on the bottom heater surface to continue pre-baking. During this process, the wafer baking heating rate and baking temperature are gradually increased; After 10-60 seconds, close the high vacuum valve of the pre-vacuum chamber, and then fill the pre-vacuum chamber with inert gas. First, fill for 5 seconds until the pressure in the chamber reaches 0.5 Torr, then stop filling and bake at the pressure for 30 seconds. Then fill again for 5 seconds until the pressure in the chamber reaches 1 Torr, then stop filling and bake at the pressure for 30 seconds. Lift the ejector pin to separate the wafer from the bottom heater surface, turn off the bottom heater, and stop pre-bake; After the pre-vacuum chamber is vacuumed, the wafer is taken out of the pre-vacuum chamber using a vacuum arm and then transferred to the baking chamber; After completing the preset baking and degassing time, the wafer is transferred to the buffer chamber for cooling using a vacuum arm. During the cooling process, the wafer is first separated from the cooling plate and slowly cooled naturally for 10-60 seconds. The wafer is then placed on the surface of the bottom cooling plate and the wafer cooling rate is gradually increased for 10-60 seconds. The high vacuum valve of the buffer chamber is then turned off, and inert gas is filled into the buffer chamber. First, the chamber is inflated for 5 seconds to raise the pressure in the chamber to 0.5 Torr, then the inflation is stopped and the pressure is maintained for cooling for 10-60 seconds. Finally, the chamber is inflated again for 5 seconds to raise the pressure in the chamber to 1 Torr, then the inflation is stopped and the pressure is maintained for cooling for 10-60 seconds. After cooling is completed, the wafer is taken out by a vacuum arm and sent to the next process chamber. The degassing process ends here.

Images