Method for preventing wafer from being oxidized during high-temperature operation

Abstract

The invention discloses a method for preventing a wafer from being oxidized during high-temperature operation, and belongs to the technical field of wafer processing. The method comprises the steps that soaking liquid is prepared, and the soaking liquid comprises liquid and volatile matter of the liquid; the target suction cup is placed in liquid and volatile matter thereof to be soaked for a target time length, the target suction cup is provided with a plurality of through gaps, and the liquid and the volatile matter thereof can be reserved in the gaps and / or on the target suction cup within the target time length; taking out the target suction cup and processing the target suction cup; and the target wafer is placed on the treated target suction cup for high-temperature operation, and the liquid and volatile matter remaining in the gap and / or on the target suction cup can be subjected to an oxidation-reduction reaction with air so as to consume oxygen in the air. Through the mode, oxygen in the air and the electrode of the wafer can be prevented from being subjected to oxidation-reduction reaction in the de-bonding stage, so that the wafer processing efficiency and the wafer qualification rate are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wafer processing, and in particular relates to a method for preventing wafer oxidation during high-temperature operation. Background Art

[0002] In the semiconductor manufacturing and packaging industry, temporary wafer bonding is a key process used to achieve thinning of the back side of the device wafer. After wafer bonding, the back side is usually subjected to processes such as grinding, polishing, and back metallization. Common back electrode metals are gold electrodes or silver electrodes, and gold electrodes or silver electrodes are achieved through evaporation or sputtering processes. Because silver electrodes are less resistant to oxidation than gold electrodes, in the subsequent high-temperature debonding process, due to the influence of the high temperature environment, the electrodes are easily reacted with oxygen or other oxidizing substances, causing oxidation and discoloration of the silver layer, which in turn causes changes in resistivity, etc., affecting device performance and yield.

[0003] In the existing wafer debonding process, although various measures have been taken to reduce the high-temperature oxidation problem of the silver layer, there are still problems such as unsatisfactory protection effect and insufficient durability. Especially in the high-temperature hot slip debonding technology, how to effectively suppress the oxidation and discoloration of the silver layer at high temperature, while ensuring that the debonding process proceeds smoothly without causing damage to the wafer itself and its silver-plated layer, is a technical problem that needs to be solved urgently. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is how to prevent oxidation of the back electrode of the wafer when the wafer is debonded.

[0005] In order to solve the above technical problems, the present invention provides a method for preventing oxidation of wafers during high temperature operation, the method comprising:

[0006] configuring an immersion liquid, wherein the immersion liquid comprises a liquid and a volatile substance thereof;

[0007] placing a target suction cup in the liquid and its volatiles and soaking them for a target time, wherein the target suction cup has a plurality of gaps arranged therethrough, and the liquid and its volatiles can remain in the gaps and / or on the target suction cup for the target time;

[0008] taking out the target suction cup and processing the target suction cup;

[0009] The target wafer is placed on the processed target suction cup to perform a debonding operation, and the liquid and its volatiles remaining in the gap and / or on the target suction cup can undergo a reduction reaction with the air to consume oxygen in the air.

[0010] In one embodiment, the processing of the target suction cup includes: placing the suction cup in an oven for baking, so that the surface of the suction cup can remain dry.

[0011] In one embodiment, the temperature in the oven ranges from greater than or equal to 100° C. to less than or equal to 150° C.

[0012] In one embodiment, the baking time is greater than or equal to 5 minutes and less than or equal to 15 minutes.

[0013] In one embodiment, placing the target suction cup in the liquid and its volatiles and soaking them for a target time comprises:

[0014] Providing a fixture for placing the target suction cup, the fixture comprising a placement frame having a plurality of placement slots, and a handle connected to the placement frame;

[0015] Fixing the target suction cup in the placement groove;

[0016] The handle is pulled to immerse the entire placement frame into the liquid and its volatiles, so that the liquid level of the liquid and its volatiles is higher than the top of the target suction cup, or the liquid level of the liquid and its volatiles is flush with the top of the target suction cup.

[0017] In one embodiment, the method further comprises:

[0018] Before the target suction cup is placed in the liquid and its volatiles for immersion, the target suction cup is cleaned to remove impurities in the gaps of the target suction cup.

[0019] In one embodiment, the cleaning of the target suction cup is specifically performed as follows:

[0020] Placing the target suction cup in a cleaning tank of a cleaning device, wherein a cleaning liquid is placed in the cleaning tank;

[0021] The cleaning device is started.

[0022] In one embodiment, the cleaning device is an ultrasonic or megasonic cleaning device.

[0023] In one embodiment, the target chuck is a silicon carbide chuck.

[0024] The technical solution provided by the present invention has the following advantages: by placing the target suction cup in a liquid for immersion and soaking the target for a long time, liquid and its volatiles can be retained in the gap of the target suction cup and / or on the target suction cup, and then the target suction cup is taken out and processed, and then a debonding operation is performed; during the debonding process, the liquid and its volatiles retained in the gap of the target suction cup and / or on the target suction cup can first undergo a redox reaction with the air, thereby consuming oxygen in the air, and then consuming a small amount of oxygen in the air remaining between the electrode and the suction cup, so as to prevent the oxygen in the air from undergoing a redox reaction with the electrode of the wafer during the high-temperature stage of debonding, thereby improving the processing efficiency of the wafer and the qualified rate of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic flow chart of a method for preventing oxidation of wafers during high temperature operation in an embodiment of the present invention;

[0027] Figure 2 It is a schematic diagram of a process of placing a target suction cup in a liquid and soaking it for a target time in an embodiment of the present invention;

[0028] Figure 3 This is the state diagram of the suction cup after baking;

[0029] Figure 4 This is the effect of the wafer surface after debonding using the soaked target chuck;

[0030] Figure 5 The wafer surface effect after debonding without using the soaked target chuck. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0033] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0034] This embodiment provides a method for preventing oxidation of wafers during high temperature operations, which is applicable to the wafer debonding step. In other embodiments, the method can also be used in scenarios where wafers undergo high temperature operations. This embodiment only takes the debonding operation as an example for specific description.

[0035] Since one side of some wafers is silver-plated, the silver-plated layer is adsorbed by the suction cup, and the other side of the wafer is a carrier, which needs to be released by thermal sliding. When the wafer is debonded, the debonding environment temperature is generally between 100℃ and 300℃. At such high temperatures, the silver-plated layer is easily damaged by oxidation, which not only affects the subsequent packaging of the wafer, but also affects the electrical properties of the electronic components on the wafer. For example, for the same wafer, the reverse leakage current and capacitance of the diode before and after oxidation are different; when there is an oxide film on the surface of the wafer, the resistance value on the metal wire will also change.

[0036] In order to prevent the above phenomenon from happening, the prior art adopts the method of removing the vacuum of the silicon carbide chuck only after the temperature of the wafer is lowered after the wafer is debonded, so as to prevent the silver coating of the wafer from being oxidized. However, if the above process needs to be completed, the waiting time is long, which in turn affects the overall production efficiency.

[0037] Please combine Figure 1 Therefore, the applicant creatively proposes a method for preventing oxidation of wafers during high temperature operation, which method at least includes the following steps:

[0038] Step S101: preparing an immersion liquid, wherein the immersion liquid includes a liquid and a volatile substance;

[0039] Step S102: placing the target suction cup in the liquid and its volatiles and soaking them for a target time, the target suction cup having a plurality of gaps arranged therethrough, and the liquid and its volatiles can be retained in the gaps and / or on the target suction cup for the target time;

[0040] Step S103: taking out the target suction cup and processing the target suction cup;

[0041] Step S104: placing the target wafer on the processed target suction cup to perform a debonding operation, and the liquid and volatiles thereof remaining in the gap and / or on the target suction cup can undergo an oxidation-reduction reaction with the air to consume oxygen in the air.

[0042] From the above, it can be seen that since the wafer and the target suction cup are located in the cavity during the debonding stage, and the silver-plated layer of the wafer is adsorbed on the target suction cup, the air between the target suction cup and the silver-plated layer of the wafer can first undergo an oxidation reaction with the liquid and its volatiles remaining in the gap of the target suction cup and / or on the target suction cup, thereby consuming the oxygen in the air in the cavity, thereby preventing the silver-plated layer of the wafer from undergoing an oxidation-reduction reaction with oxygen, thereby ensuring the processing efficiency of the wafer.

[0043] In the present embodiment, the target suction cup is a porous suction cup, for example, a silicon carbide porous suction cup. In addition, a plurality of gaps are provided throughout the target suction cup, and the apertures of the plurality of gaps are fine, so that the adsorption force applied to the wafer is small. In addition, a plurality of gaps are distributed on the target suction cup so that the adsorption force on various parts of the wafer tends to be uniform, and will not cause damage to the wafer. At the same time, the condensation of the adsorption force of the plurality of gaps can stably adsorb the wafer. In addition, since a plurality of gaps are provided, when the target suction cup is immersed in liquid, the liquid and its volatiles can enter into the gaps and remain in the gaps to react with oxygen in the air in the subsequent debonding operation.

[0044] Specifically, in step S101, the immersion liquid is a reducing agent, and the reducing agent includes propylene glycol methyl ether acetate CAS No. 108-65-6 and a phenolic resin derivative CAS No. 9065-82-1, and the ratio range is 40:1-2:1. Other reagents can also be added according to actual conditions to achieve the purpose of allowing the reduction reaction to occur. No specific limitation is made here, and it depends on the actual situation.

[0045] Furthermore, the ratio of the above-mentioned propylene glycol methyl ether acetate CAS No. 108-65-6 and the phenolic resin derivative CAS No. 9065-82-1 may also be in other ranges as long as the purpose of the reduction reaction can be achieved.

[0046] Alternatively, the above-mentioned reducing agent can be configured according to actual needs, and different proportions or the same proportion of reducing agent and other reagents can be configured to achieve the reduction reaction, which is not specifically limited here and depends on the actual situation.

[0047] In step S102, the target suction cup is immersed in the liquid and its volatiles for a target time, and the target time can make the liquid and its volatiles remain in the target suction cup. In this embodiment, the target time is 30 minutes. In other embodiments, the target time can also be 25 minutes, 35 minutes, 40 minutes, etc., but should not be less than 20 minutes, which is not specifically limited here and is determined according to actual conditions.

[0048] In step S103, the target suction cup is processed. Specifically, the target suction cup is processed by placing the suction cup in an oven for baking so that the surface of the suction cup can remain dry. The purpose of this step is to prevent liquid from contaminating the surface of the wafer and affecting subsequent operations.

[0049] In this step, the baking of the target suction cup should not only make the surface of the target suction cup dry, but also ensure that there is liquid and its volatiles in the gap of the target suction cup to react with oxygen in the air during the debonding step, thereby preventing the silver plating layer of the wafer from being oxidized. For example, the baking temperature can be set to 120℃ and the baking time can be set to 10 minutes. The state after baking can be seen in Figure 3 , the above-mentioned purpose of "making the surface of the target suction cup dry, while ensuring that liquid and its volatiles remain in the gap of the target suction cup to react with oxygen in the air during the debonding step" can be achieved. In other embodiments, the baking temperature and baking time can also be increased or decreased accordingly, and are not specifically limited, as long as the above-mentioned purpose is achieved.

[0050] In one embodiment, the temperature in the oven is 120°C and the baking time is 10 minutes. In other embodiments, the temperature in the oven may be 100°C, in which case the baking time is 15 minutes; or the temperature in the oven may be 150°C, in which case the baking time is 5 minutes. It can be seen that as the temperature in the oven increases, the baking time decreases; conversely, as the temperature in the oven decreases, the baking time increases, thereby ensuring that after baking, the surface of the target suction cup is dry and liquid remains in the target suction cup.

[0051] Please combine Figure 2 , and placing the target suction cup in the liquid and immersing it for the target time includes:

[0052] Step S201: providing a fixture for placing a target suction cup, the fixture comprising a placement frame having a plurality of placement slots, and a handle connected to the placement frame;

[0053] Step S202: fix the target suction cup in the placement slot;

[0054] Step S203: Pull up the handle to immerse the entire placement frame into the liquid and its volatiles, so that the liquid level of the liquid and its volatiles is higher than the top of the target suction cup, or the liquid level of the liquid and its volatiles is flush with the top of the target suction cup.

[0055] By providing a fixture, as many target suction cups as possible can be immersed in a reasonable space, thereby improving the wafer processing efficiency. In addition, the placement groove is arranged along the height direction of the frame, so that the target suction cup can be vertically placed in the liquid and its volatiles for immersion, so that the liquid and its volatiles can fully contact with more target suction cups, thereby improving the immersion efficiency.

[0056] The method for preventing wafer oxidation during high temperature operation also includes: before the target suction cup is placed in the liquid and its volatiles for immersion, the target suction cup is cleaned to remove impurities in the gap of the target suction cup.

[0057] The specific steps of cleaning the target suction cup are as follows: placing the target suction cup in a cleaning tank of a cleaning device, wherein a cleaning liquid is placed in the cleaning tank; and starting the cleaning device. In this embodiment, the cleaning liquid is a PMA (propylene glycol methyl ether acetate) liquid, and the cleaning device is an ultrasonic or megasonic cleaning device, which improves the wetting speed and effect of the suction cup gap, thereby improving the cleaning efficiency. PMA liquid has a strong solubility for both polar and non-polar substances, thereby further ensuring the cleaning efficiency of the target suction cup.

[0058] The invention is described below with reference to specific embodiments.

[0059] Embodiment 1:

[0060] Place the target suction cup in the liquid and its volatiles to ensure that the target suction cup is completely immersed, so that the target suction cup is immersed in the liquid and its volatiles for 30 minutes. After the immersion time is reached, take out the target suction cup and place it in an oven for baking at a temperature of 120°C for 10 minutes. After baking, take out the target suction cup and install it for debonding. Place the target wafer on the processed target suction cup for debonding. The liquid and its volatiles remaining in the gap and / or on the target suction cup can undergo redox reactions with the air to consume oxygen in the air. Among them, the debonded wafer is as follows Figure 4 shown.

[0061] Comparative Example:

[0062] The unsoaked chuck is directly mounted, and then the wafer is placed on the unsoaked chuck for debonding. During the debonding process, the silver coating of the wafer reacts with oxygen in the air, such as Figure 5 shown.

[0063] To sum up: by placing the target suction cup in the liquid and its volatiles for immersion and soaking the target for a long time, the liquid and its volatiles can remain in the gap of the target suction cup and / or on the target suction cup, and then the target suction cup is taken out and processed, and then the debonding operation is performed; during the debonding process, the liquid and its volatiles remaining in the gap of the target suction cup and / or on the target suction cup can first undergo redox reaction with the air, thereby consuming the oxygen in the air, and then consuming the small amount of oxygen in the air remaining between the electrode and the suction cup, so as to prevent the oxygen in the air from undergoing redox reaction with the electrode of the wafer during the debonding stage, thereby improving the processing efficiency of the wafer and the qualified rate of the wafer.

[0064] Obviously, the embodiments described above are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, ordinary technicians in this field can make other different forms of changes or modifications without creative work, which should fall within the scope of protection of the present invention.

Claims

1. A method for preventing oxidation of wafers during high temperature operation, characterized in that: The method comprises: configuring an immersion liquid, wherein the immersion liquid comprises a liquid and a volatile substance thereof; placing a target suction cup in the liquid and its volatiles and soaking them for a target time, wherein the target suction cup has a plurality of gaps arranged therethrough, and the liquid and its volatiles can remain in the gaps and / or on the target suction cup for the target time; taking out the target suction cup and processing the target suction cup; The target wafer is placed on the processed target suction cup for high temperature operation, and the liquid and its volatiles remaining in the gap and / or on the target suction cup can undergo redox reaction with the air to consume oxygen in the air.

2. The method according to claim 1, characterized in that The processing of the target suction cup includes placing the suction cup in an oven for baking, so that the surface of the suction cup can be kept dry.

3. The method according to claim 2, characterized in that The temperature in the oven ranges from greater than or equal to 100° C. to less than or equal to 150° C.

4. The method according to claim 2, characterized in that: The baking time is greater than or equal to 5 minutes and less than or equal to 15 minutes.

5. The method according to any one of claims 1 to 4, characterized in that The step of placing the target suction cup in the liquid and its volatiles and soaking it for a target time comprises: Providing a fixture for placing the target suction cup, the fixture comprising a placement frame having a plurality of placement slots, and a handle connected to the placement frame; Fixing the target suction cup in the placement groove; The handle is pulled to immerse the entire placement frame into the liquid and its volatiles, so that the liquid level of the liquid and its volatiles is higher than the top of the target suction cup, or the liquid level of the liquid and its volatiles is flush with the top of the target suction cup.

6. The method according to any one of claims 1 to 4, characterized in that The method further comprises: Before the target suction cup is placed in the liquid and its volatiles for immersion, the target suction cup is cleaned to remove impurities in the gaps of the target suction cup.

7. The method according to claim 6, characterized in that The cleaning of the target suction cup is specifically as follows: Placing the target suction cup in a cleaning tank of a cleaning device, wherein a cleaning liquid is placed in the cleaning tank; The cleaning device is started.

8. The method according to claim 7, characterized in that The cleaning equipment is an ultrasonic or megasonic cleaning equipment.

9. The method according to any one of claims 1 to 4, characterized in that The target suction cup is a porous suction cup.

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