Method for removing residual polymer after etching

Abstract

The invention provides a method for removing residual polymer after etching, which comprises the following steps of: providing an etched wafer on which the residual polymer exists, and placing the wafer in a photoresist removing chamber; heating the photoresist removing chamber, and accessing high voltage to the photoresist removing chamber so as to provide a plasma environment; applying a second pressure to the photoresist removing chamber, and introducing water vapor into the photoresist removing chamber to soften the polymer; third pressure is applied to the photoresist removing cavity, oxygen and nitrogen are introduced into the photoresist removing cavity so as to remove and extract the polymer, and the second pressure is higher than the third pressure; and repeatedly executing the step of applying the second pressure and the third pressure to the photoresist removing chamber until the polymer on the wafer is removed. According to the method for removing the residual polymer after etching, the polymer removal effect is remarkable, and the multi-layer treatment mode ensures that even the polymer on the surface of a complex structure can be thoroughly removed.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a method for removing residual polymer after etching. Background Art

[0002] The aluminum pad etching process is a key step in the semiconductor manufacturing process. The process mainly involves using specific gases (such as BCl 3 ) bombards the photoresist, thereby generating Cl-containing - Organic polymers are formed on the wafer, which protect the sidewalls during etching. After etching, the wafer needs to be transferred to the stripping chamber for a dry stripping step to remove the remaining photoresist and the residual polymers generated during the etching process. In the existing thick etching process, due to the deep sidewalls, it is difficult to completely remove the polymers on the etched sidewalls. These residual polymers will have an adverse effect on the subsequent system voltage withstand test and solder joint push-pull force test, thereby affecting the overall reliability of the device.

[0003] In order to deal with this problem, the industry currently generally adopts dry stripping combined with subsequent wet pickling to try to remove the polymer residues on the side walls. However, the actual effect of this method is not ideal. In order to remove the polymer as completely as possible, additional dry stripping and wet pickling steps are often required. Although adding steps can improve the effect of polymer removal to a certain extent, it also brings new problems. For example: temperature changes may cause the polymer to harden further, making it more difficult to remove. Dry stripping combined with subsequent wet pickling has cumbersome steps and increases manufacturing costs and time costs. Summary of the invention

[0004] In view of the problems existing in the prior art in removing residual polymers, the present application provides a method for removing etching polymer residues, comprising the following steps:

[0005] S1: providing an etched wafer with residual polymer on it, and placing the wafer in a degumming chamber;

[0006] S2: raising the temperature of the degumming chamber and connecting a high voltage to the degumming chamber to provide a plasma environment;

[0007] S3: applying high pressure to the degumming chamber and introducing water vapor into the degumming chamber to soften the polymer;

[0008] S4: applying low pressure to the degumming chamber, and introducing oxygen and nitrogen into the degumming chamber to remove and pump away the polymer;

[0009] S5: Repeat steps S3-S4 until the polymer on the wafer is completely removed.

[0010] Preferably, the wafer comprises an insulating layer, a metal interconnection layer is formed on the insulating layer, the metal interconnection layer is etched to form a connection pad, and the polymer is attached to the side wall of the connection pad.

[0011] Preferably, the metal interconnection layer includes an aluminum layer or a copper layer, and the corresponding connection pad includes an aluminum pad or a copper pad.

[0012] Preferably, step S2 further comprises: applying pressure to the debonding chamber; and introducing oxygen into the debonding chamber.

[0013] Preferably, in step S2, the debonding chamber is subjected to a temperature-raising treatment so that the temperature of the debonding chamber is between 250° C. and 300° C.; and a voltage power between 1200W and 1500W is applied to the debonding chamber.

[0014] Preferably, the first pressure applied to the desinfection chamber is between 1800 mTorr and 2200 mTorr; the flow rate of the oxygen is between 4000 sccm and 5000 sccm; and the processing time is between 80 s and 120 s.

[0015] Preferably, in step S3, the second pressure applied to the desizing chamber is between 3000mTorr and 5000mTorr; the flow rate of water vapor introduced into the desizing chamber is between 450sccm and 5550sccm; and the processing time is between 30s and 50s.

[0016] Preferably, step S4 further comprises introducing water vapor into the degumming chamber, wherein the flow rate of the water vapor is between 280 sccm and 320 sccm, so as to soften the residual polymer.

[0017] Preferably, in step S4, the third pressure applied to the desinfection chamber is between 1000mTorr and 2000mTorr; the flow rate of the oxygen is between 3000sccm and 4000sccm; the flow rate of the nitrogen is between 180sccm and 220sccm; and the processing time is between 30s and 50s.

[0018] Preferably, the following steps are repeated at least twice:

[0019] Applying a second pressure to the degumming chamber and introducing water vapor into the degumming chamber to soften the polymer;

[0020] A third pressure is applied to the debonding chamber, and oxygen and nitrogen are introduced into the debonding chamber to remove and pump away the polymer.

[0021] As described above, the method for removing residual polymer after etching provided by the present invention has at least the following beneficial technical effects:

[0022] The polymer removal effect is remarkable. After multi-level treatment, high-pressure water vapor treatment and low-pressure mixed gas treatment, and cyclic operation, the residual polymer on the wafer surface can be treated from multiple dimensions. High-pressure water vapor can penetrate deep into the polymer to promote hydrolysis reaction, while low-pressure mixed gas treatment can continuously decompose and remove polymers under optimized reaction environment. This multi-level treatment method ensures that even polymers on complex structure surfaces (such as the sidewalls of aluminum pads) can be completely removed.

[0023] The process flow is simple. The method for removing residual polymer provided by the present invention applies high pressure and low pressure to the degumming chamber in combination with each other, and the steps are simple; at the same time, the temperature is kept constant to avoid temperature changes that cause the polymer to further harden and become difficult to remove.

[0024] In addition, from a chemical point of view, the hydrogen ions (H + ) and hydroxide ions (OH-) can interact with the chemical bonds in the polymer and destroy its molecular structure. Moreover, the efficiency of this chemical reaction is further enhanced by introducing different gases into the plasma environment, so that the polymer can be efficiently converted into volatile products and removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart showing a method for removing residual polymer after etching.

[0026] Figure 2a-2b Shown is the step of etching the wafer.

[0027] Figure 3a-3b Shown is a cross-sectional view of a wafer after residual polymer is removed using a prior art method.

[0028] Figure 4a-4b The cross-sectional view of the wafer after the residual polymer is removed by the method provided by this embodiment is shown.

[0029] Reference numerals

[0030] 1. Wafer; 00. Device layer; 10. Insulation layer; 20. Metal interconnect layer; 21. Connection pad; 30. Photoresist; 40. Polymer. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention through specific examples, and 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, and 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.

[0032] It should be noted that the diagrams provided in this embodiment are only schematic illustrations of the basic concept of the present invention. Although the diagrams only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity, positional relationship and proportion of each component in actual implementation can be changed at will under the premise of realizing the technical solution of this party, and the layout form of the components may also be more complicated. It should be pointed out here that the "high pressure" and "low pressure" mentioned in the present invention are relative concepts, relative to "low pressure" and "medium pressure".

[0033] This embodiment provides a method for removing residual polymer after etching, such as Figure 1 As shown, it is a flow chart of a method for removing residual polymer after etching; specifically comprising the following steps:

[0034] S1: providing an etched wafer with residual polymer on it, and placing the wafer in a degumming chamber.

[0035] like Figure 2a-2b As shown, it shows the step of etching the wafer 1. Figure 2a As shown, the wafer 1 includes an insulating layer 10 and a metal interconnection layer 20 located on the insulating layer 10. A photoresist 30 is evenly applied on the metal interconnection layer 20, and the wafer 1 is etched to obtain a Figure 2b The wafer structure shown in FIG. 1 is a wafer 1 in which the metal interconnect layer 20 is etched to form a connection pad 21 . During the etching process, a polymer 40 is formed and remains on the sidewall of the connection pad 21 .

[0036] Generally, the insulating layer 10 is silicon dioxide or borophosphosilicate glass (BPSG). Specifically, in the present embodiment, borophosphosilicate glass is selected as the insulating layer 10, because borophosphosilicate glass has a relatively high resistivity and good insulating properties; and during the high-temperature annealing process, it exhibits fluidity and can fill the unevenness on the surface of the wafer 1, providing a good foundation for the subsequent deposition of the metal interconnect layer 20. Generally, the metal interconnect layer 20 includes one or a combination of two of an aluminum layer, a copper layer or a tungsten layer. Specifically, in the present embodiment, the metal interconnect layer 20 is a thick aluminum layer, and the corresponding connection pad 21 is a thick aluminum pad. Generally, the thickness of the thick aluminum layer is between 2 μm and 25 μm. Specifically, the wafer 1 also includes a device layer 00. Specifically, during the main etching process of the aluminum pad, a specific gas (such as BCl 3) bombards the photoresist 30, thereby generating Cl-containing - of organic polymers 40.

[0037] The wafer 1 after etching is transferred to a de-etching chamber. Optionally, dry etching is used to remove the photoresist 30 and part of the polymer 40 on the surface of the wafer 1.

[0038] S2: raising the temperature of the debonding chamber and connecting a high voltage to the debonding chamber to provide a plasma environment.

[0039] Create a reaction environment and perform preliminary treatment. Generally, the temperature of the degumming chamber is increased to 250°C to 300°C. Specifically, in this embodiment, the temperature of the degumming chamber is increased to 250°C. The wafer 1 is heated to the degumming chamber temperature so that the molecular thermal motion of the polymer 40 is intensified, which helps the subsequent gas introduction and the reaction of the polymer 40 to occur more easily. Apply 1200W to 1500W of energy to the electrode at the top of the degumming chamber. Specifically, apply 1400W of energy to the degumming chamber to form a plasma environment. The high-energy particles in the plasma collide with the polymer 40, breaking the chemical bonds of the polymer 40 and further destroying the structure of the polymer 40, making it easier to react with the subsequent gas.

[0040] Specifically, in this process, it also includes applying a first pressure to the degumming chamber and introducing oxygen into the degumming chamber. Generally, the first pressure applied to the degumming chamber is between 1800mTorr and 2200mTorr; the flow rate of oxygen is between 4000sccm and 5000sccm. Specifically, the first pressure applied to the degumming chamber is between 1800mTorr and 1800mTorr, and the flow rate of oxygen introduced is between 4000sccm. The applied pressure is used to maintain the gas concentration and distribution state in the degumming chamber to ensure that the reaction gas can fully contact the residual polymer on the surface of the wafer. At the same time, the pressure will also affect the adsorption and dissociation behavior of the gas molecules on the surface of the polymer 40, and promote the reaction. Oxygen can react with the polymer 40 under high temperature, high pressure and plasma environment to oxidize carbon, hydrogen and other elements in the polymer 40 molecules into volatile products such as carbon dioxide and water vapor, thereby preliminarily removing part of the polymer 40. In addition, oxygen can also react with the photoresist 30 that may exist in the stripping chamber to clean the chamber environment and the wafer surface, but oxygen and nitrogen will not react with substances other than the photoresist 30 and the polymer 40 and will not cause damage to the wafer.

[0041] The processing time of step S2 is between 80s and 120s. Specifically, in this embodiment, the processing time of S2 is between 120s.

[0042] S3: applying a second pressure to the degumming chamber and introducing water vapor into the degumming chamber to soften the polymer.

[0043] High-pressure water vapor treatment. Generally, a second pressure is applied to the degumming chamber, and the second pressure is between 3000mTorr and 5000mTorr; the water vapor flow rate introduced into the degumming chamber is between 450sccm and 5550sccm. Specifically, in the present embodiment, the second pressure applied to the degumming chamber is between 3000mTorr; and the water vapor flow rate introduced is between 450sccm. The high-pressure environment helps the water vapor to penetrate deeper into the polymer 40, increases the contact opportunity between the water vapor and the polymer 40, and causes the polymer molecular chains to undergo a hydrolysis reaction under the combined action of high pressure and water vapor. The hydrolysis reaction destroys the chemical bonds in the polymer molecules, reduces their molecular weight and structural stability, thereby weakening the bonding force between the polymer and the side wall of the aluminum pad, softening the polymer, and making it easier for the polymer to detach from the side wall.

[0044] In addition, water vapor can effectively hydrolyze the polymer under this high pressure, breaking down the polymer molecules into smaller fragments or monomers, while at the same time ～ ) under the action of H 2 O+e - →H + +OH - , water vapor is decomposed into H + and OH ～ , further participate in chemical reactions, such as H + +Cl - →HCl(g), the generated HCl(g) can be subsequently extracted to remove the polymer.

[0045] The processing time of step S3 is between 30s and 50s. Specifically, in this embodiment, the processing time of S3 is 50s.

[0046] S4: applying a third pressure to the degumming chamber, and introducing oxygen and nitrogen into the degumming chamber to remove and pump away the polymer, wherein the second pressure is higher than the third pressure.

[0047] Low-pressure mixed gas treatment. Generally, a third pressure is applied to the degumming chamber, and the third pressure is between 1000mTorr and 2000mTorr; the flow rate of water vapor introduced into the degumming chamber is between 280sccm and 320sccm; the flow rate of oxygen is between 3000sccm and 4000sccm; the flow rate of nitrogen is between 180sccm and 220sccm; specifically, in this embodiment, the third pressure applied to the degumming chamber is 1000mTorr; the flow rate of water vapor introduced is between 280sccm; the flow rate of oxygen introduced is between 3000sccm; the flow rate of nitrogen introduced is between 180sccm. The low-pressure environment is conducive to the rapid discharge of reaction products (volatile gas HCl(g), decomposed small molecules, etc.) from the degumming chamber, reducing the adsorption of reaction products on the wafer surface and the possibility of secondary reactions, and also helps to maintain the stability of the plasma.

[0048] In the plasma environment, oxygen continues to react with the residual polymer to further decompose the polymer molecules, converting them into more volatile products and discharging them from the chamber. At the same time, oxygen can also react with some intermediate products produced in the pressure water vapor treatment step in the previous step S3 to ensure the complete removal of the polymer. Nitrogen acts as a diluent gas. It can adjust the gas composition and reaction activity in the chamber to prevent excessive concentrations of reactive gases such as oxygen from causing overreaction or damage to the wafer. At the same time, nitrogen will also participate in some energy transfer and reaction processes in the plasma, stabilize the plasma state, and help to remove the polymer evenly. In a low-pressure environment, water vapor continues to soften the polymer surface, synergizing with the previous high-pressure water vapor treatment step to further promote the decomposition and detachment of the polymer. At the same time, a small amount of water vapor can maintain a certain humidity in the chamber, which is conducive to maintaining the chemical reaction and preventing incomplete reaction or other adverse effects due to excessive drying.

[0049] The processing time of step S4 is between 30s and 50s. Specifically, in this embodiment, the processing time of S4 is 50s.

[0050] S5: Repeat steps S3 to S4 until the polymer on the wafer is completely removed.

[0051] Repeat steps S3 to S4, and through multiple cycles, the degree of treatment of the residual polymer can be gradually deepened. Generally, steps S3 to S4 are repeated at least twice for the same wafer. Specifically, in this embodiment, steps S3 to S4 are repeated four times. Each cycle will further destroy the structure of the polymer, so that the residual amount is gradually reduced. After multiple cycles, it can be ensured that even the polymer on the deeper sidewalls or other difficult-to-remove locations can be completely removed.

[0052] During the cycle process, the number of cycles can be adjusted according to actual conditions (such as monitoring changes in the amount of polymer residue through optical detection and other means) to achieve the best removal effect, while avoiding unnecessary damage to the wafer due to excessive processing, improving the flexibility and controllability of the process, and ensuring the quality and performance of the final product.

[0053] like Figure 3a , 3b The cross-sectional view of the wafer is shown after the residual polymer after etching is removed using the prior art method. Figure 3a The cross-sectional view of the wafer at the corner of the connection pad 21 and the insulating layer 10 is shown; Figure 3b A cross-sectional view of the wafer showing the sidewall of the connection pad 21; Figure 3a , 3b It can be seen that the circled area indicates that there is still residual polymer. This indicates that the technical effect of the method for removing residual polymer in the prior art is not ideal. Figure 4a , 4b The cross-sectional view of the wafer after removing the residual polymer after etching provided by this embodiment is shown; it can be seen from the figure that the method provided by this embodiment can effectively remove the residual polymer, and it can be clearly seen from the figure that the damage to the wafer surface is relatively small.

[0054] 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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for removing residual polymer after etching, characterized in that: The following steps are involved: S1: providing an etched wafer with residual polymer on it, and placing the wafer in a degumming chamber; S2: heating the degumming chamber and connecting a high voltage to the degumming chamber to provide a plasma environment; S3: applying a second pressure to the degumming chamber and introducing water vapor into the degumming chamber to soften the polymer; S4: applying a third pressure to the degumming chamber, and introducing oxygen and nitrogen into the degumming chamber to remove and pump away the polymer, wherein the second pressure is higher than the third pressure; S5: Repeat steps S3-S4 until the polymer on the wafer is completely removed.

2. The method for removing residual polymer after etching according to claim 1, characterized in that: The wafer comprises an insulating layer, a metal interconnection layer is formed on the insulating layer, the metal interconnection layer is etched to form a connection pad, and the polymer is attached to the side wall of the connection pad.

3. The method for removing residual polymer after etching according to claim 2, characterized in that: The metal interconnection layer includes an aluminum layer or a copper layer, and the corresponding connection pad includes an aluminum pad or a copper pad.

4. The method for removing residual polymer after etching according to claim 1, characterized in that: Step S2 also includes: applying a first pressure to the debonding chamber; and introducing oxygen into the debonding chamber.

5. The method for removing residual polymer after etching according to claim 1, characterized in that: In step S2, the temperature of the debonding chamber is raised to a temperature between 250° C. and 300° C.; a voltage power between 1200W and 1500W is applied to the debonding chamber.

6. The method for removing residual polymer after etching according to claim 4, characterized in that: The first pressure applied to the stripping chamber is between 1800 mTorr and 2200 mTorr; the flow rate of the oxygen is between 4000 sccm and 5000 sccm; The processing time is between 80s and 120s.

7. The method for removing residual polymer after etching according to claim 1, characterized in that: In step S3, the second pressure applied to the stripping chamber is between 3000mTorr and 5000mTorr; the flow rate of water vapor introduced into the stripping chamber is between 450sccm and 5550sccm; and the processing time is between 30s and 50s.

8. The method for removing residual polymer after etching according to claim 1, characterized in that: Step S4 further includes introducing water vapor into the degumming chamber, wherein the flow rate of the water vapor is between 280 sccm and 320 sccm, so as to soften the residual polymer.

9. The method for removing residual polymer after etching according to claim 1, characterized in that: In step S4, the third pressure applied to the stripping chamber is between 1000mTorr and 2000mTorr; the flow rate of the oxygen is between 3000sccm and 4000sccm; the flow rate of the nitrogen is between 180sccm and 220sccm; and the processing time is between 30s and 50s.

10. The method for removing residual polymer after etching according to claim 1, characterized in that: Repeat the following steps at least twice: Applying a second pressure to the degumming chamber and introducing water vapor into the degumming chamber to soften the polymer; A third pressure is applied to the debonding chamber, and oxygen and nitrogen are introduced into the debonding chamber to remove and pump away the polymer.

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