Wet drying method for wafer with graphic structure

Abstract

The invention discloses a wet drying method for a wafer with a graphic structure, which comprises the following steps of: carrying out wet cleaning on the wafer with the graphic structure, and after the wet cleaning is finished, filling a cleaning solution in an interval region between the graphic structures. The flowing supercritical gas is adopted to dry the wafer, and in the drying process, the included angle between the flowing direction of the supercritical gas and the extending direction of the graphic structure ensures that the supercritical gas can smoothly flow from one side of the interval area to the other opposite side, so that the cleaning liquid in the interval area is completely replaced. According to the method, the effect of replacing the cleaning liquid in the interval areas between the pattern structures can be improved, complete replacement of the cleaning liquid is achieved, and meanwhile it is guaranteed that the pattern structures are not collapsed or damaged.

Description

Technical Field

[0001] This invention relates to a method for manufacturing semiconductor integrated circuits, and more particularly to a wet drying method for wafers with patterned structures. Background Art

[0002] In semiconductor manufacturing processes, wet drying is a crucial step in the wet cleaning process. Its core objective is to achieve high-integrity dehydration of the wafer surface microstructure, eliminating the risk of defects caused by residual water stains. Currently, the mainstream drying technologies include three routes: isopropanol displacement drying (IPA Dry), spin drying, and Marangoni surface tension gradient drying.

[0003] For wafer cleaning with patterned structures, existing traditional cleaning processes face technical challenges, such as difficulty in effectively diffusing the cleaning solution into the interior of trenches with high aspect ratios, and high difficulty in removing contaminants such as particles.

[0004] Due to factors such as surface tension and capillary forces, high aspect ratio structures are prone to collapse and adhesion during the drying process. The order of surface tension is: H2O2 > IPA > Hot IPA > SCCO2 = 0.

[0005] The capillary force F is related to the contact angle θ and the surface tension γ; the surface tension should be minimized as much as possible.

[0006] As integrated circuit feature sizes shrink, drying processes need to overcome the pattern collapse problem caused by capillary effects in high aspect ratio structures. Therefore, new drying technologies have emerged, such as Meniscus Re-configuration (MRC). MRC heats the back side of the wafer to bring the surface area of ​​the interphase material (IPA) as close as possible to its boiling point of 82.4°C, while precisely controlling the temperature to prevent boiling over. This achieves drying without pattern collapse or damage. However, it ultimately falls under the category of IPA drying. Although the surface tension of IPA is much lower than that of water, pattern collapse and damage still occur under certain conditions, especially in the drying of ultra-high aspect ratio wafers. Another existing drying method includes a supercritical carbon dioxide drying (SCD) technology. SCD technology adjusts the state of carbon dioxide to a supercritical state by pressurizing and controlling the temperature, and then uses it to replace IPA. After the supercritical carbon dioxide replaces the IPA, it will vaporize from the wafer surface. The surface tension of carbon dioxide gas can approach zero, so it can greatly reduce the pattern collapse problem caused by high aspect ratio patterns during the drying process. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a wet drying method for wafers with patterned structures, which can improve the effect of replacing the cleaning fluid in the gap regions between the patterned structures and achieve complete replacement of the cleaning fluid, while ensuring that the patterned structures do not collapse or break.

[0008] To solve the above-mentioned technical problems, the present invention provides a wafer wet drying method with a patterned structure, comprising the following steps:

[0009] The wafer with the patterned structure is subjected to wet cleaning, and after the wet cleaning is completed, the spacer regions between the patterned structures are filled with cleaning solution.

[0010] The wafer is dried by flowing supercritical gas. During the drying process, the angle between the flow direction of the supercritical gas and the extension direction of the pattern structure ensures that the supercritical gas can flow smoothly from one side of the spacer region to the opposite side, so as to completely replace the cleaning solution in the spacer region.

[0011] A further improvement is that the cleaning fluid includes IPA.

[0012] A further improvement is that the supercritical gas includes supercritical carbon dioxide.

[0013] A further improvement is that the drying is carried out in a drying chamber.

[0014] A further improvement is that the drying chamber includes a supercritical gas spray inlet and a supercritical gas spray outlet, and the flow direction of the supercritical gas is along the direction from the supercritical gas spray inlet to the supercritical gas spray outlet.

[0015] A further improvement is that the wafer has a positioning notch, and the angle between the flow direction of the supercritical gas and the extension direction of the patterned structure can be adjusted by adjusting the angle of the positioning notch.

[0016] A further improvement is to adjust the angle of the positioning notch before the wafer enters the drying chamber; or to adjust the angle of the positioning notch after the wafer enters the drying chamber.

[0017] A further improvement is that the flow direction of the supercritical gas is parallel to the extension direction of the patterned structure.

[0018] A further improvement is that, after the complete replacement of the cleaning liquid is completed during the drying process, the supercritical gas is also vaporized to complete the drying.

[0019] For wafers with patterned structures, this invention sets the angle between the supercritical gas and the extension direction of the patterned structure during the drying process. The angle needs to ensure that the supercritical gas can flow smoothly from one side of the spacer region to the opposite side. Since the supercritical gas flows smoothly in the spacer region, that is, it can enter from the opening on one side of the extension direction of the spacer region and flow out from the opening on the other side, it can ensure that the supercritical gas can flow simultaneously in the region from the bottom to the top of the spacer region. Therefore, it can ensure that the cleaning liquid from the bottom to the top of the spacer region can be well replaced without replacement residue. Therefore, the cleaning liquid in the spacer region can be completely replaced in the end.

[0020] In addition, after the cleaning fluid replacement is completed, since the surface tension of supercritical gases such as supercritical carbon dioxide tends to zero, the problem of pattern collapse caused by removing supercritical gases, such as by removing supercritical gases through vaporization, can be eliminated. Attached Figure Description

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0022] Figure 1 This is a schematic diagram of wafer movement before and after drying in an existing wet drying method for wafers with graphic structures;

[0023] Figure 2 This is a schematic diagram of IPA displacement during the drying process of existing wet drying methods for wafers with patterned structures;

[0024] Figure 3 This is a flowchart of a wafer wet drying method with a patterned structure according to an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of wafer movement before and after drying in a wafer wet drying method with a graphic structure according to an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of IPA replacement during the drying process of a wafer wet drying method with a graphic structure according to an embodiment of the present invention. Detailed Implementation

[0027] The embodiments of the present invention are improvements on the existing SCD. Before describing the embodiments of the present invention in detail, the existing SCD method will be described as follows:

[0028] The existing SCD machine design typically places a wafer with a certain thickness of IPA liquid film inside a cuboid cavity, introduces supercritical carbon dioxide from one side of the cavity, and maintains a certain flow rate to flow over the wafer surface. When it comes into contact with the IPA on the wafer surface, it completes the replacement, and then together with the IPA, it is discharged from the other side of the cavity. The supercritical carbon dioxide is continuously introduced and discharged until the IPA on the wafer surface is completely replaced.

[0029] This replacement process does not take into account the orientation characteristics of the pattern. The wafer is placed randomly (or at a fixed, non-adjustable angle) within the drying chamber. This design leads to situations where, under certain operating conditions, the flow direction of supercritical carbon dioxide across the wafer surface is perpendicular (or intersecting) with the trench direction of the pattern. The orientation characteristics of the pattern hinder its flow across the wafer surface, thus reducing the efficiency of IPA replacement. This is particularly evident in wafers with unidirectional wall-like patterned structures.

[0030] like Figure 1 The diagram shown illustrates the wafer movement before and after drying in an existing wet drying method for wafers with patterned structures; as shown... Figure 2 The diagram shown illustrates the IPA replacement process during the drying process of an existing wet drying method for wafers with patterned structures. The existing wet drying method for wafers with patterned structures includes the following steps:

[0031] Step S1: The wafer 101 with patterned structure 101a is wet-cleaned. After the wet cleaning is completed, the spacer region 101b between the patterned structures 101a is filled with cleaning solution 107.

[0032] Depend on Figure 1 It can be seen that after the wet cleaning is completed, the extension direction of the graphic structure 101a is the extension direction of the double arrow line AA.

[0033] The cleaning fluid 107 includes IPA.

[0034] Step S2: The wafer 101 is dried using flowing supercritical carbon dioxide 105. Before entering the drying chamber 102, the extension direction of the pattern structure 101a of the wafer 101 remains unchanged, and is still the extension direction of the double-arrow line AA.

[0035] The drying chamber 102 includes a supercritical carbon dioxide 105 spray inlet and a supercritical carbon dioxide 105 spray outlet, and the flow direction of the supercritical carbon dioxide 105 is along the direction from the supercritical carbon dioxide 105 spray inlet to the supercritical carbon dioxide 105 spray outlet. Figure 1In the drying chamber 102, the supercritical carbon dioxide 105 spray inlet is located on the side 103 of the drying chamber 102, and the supercritical carbon dioxide 105 spray outlet is located on the side 104 of the drying chamber 102.

[0036] After the wafer 101 is placed in the drying chamber 102, supercritical carbon dioxide 105 is flowed for drying. Since the angle of the wafer 101 is not adjusted, the flow direction of the supercritical carbon dioxide 105 and the extension direction of the patterned structure 101a will differ significantly during the drying process, for example, they may intersect perpendicularly. In this case, the patterned structure 101a will hinder the flow of supercritical carbon dioxide 105 on the patterned surface of the wafer 101, thus reducing the efficiency of IPA replacement. This is particularly evident on wafers with a unidirectional wall-like patterned structure.

[0037] Figure 2 In the above, step S2 is divided into multiple sub-steps for understanding. In the first step S2a, the wavy shape 109 indicates that the flow of supercritical carbon dioxide 105 is obstructed, and the cleaning fluid 107 in the top region of the interval region 101b is replaced by supercritical carbon dioxide 105.

[0038] In step S2b, as the flow time of the supercritical carbon dioxide 105 increases, the cleaning fluid 107 in the bottom region of the interval region 101b will also be replaced by the supercritical carbon dioxide 105, but some cleaning fluid will still remain 107a.

[0039] In step S2c, after the supercritical carbon dioxide 105 is vaporized, the cleaning liquid residue 107a cannot be removed, so complete drying cannot be achieved.

[0040] like Figure 3 The diagram shown is a flowchart of a wet drying method for a wafer 201 with a patterned structure 201a according to an embodiment of the present invention; as shown Figure 4 The diagram shown is a schematic representation of the movement of the wafer 201 before and after drying in a wet drying method for a wafer 201 with a patterned structure 201a according to an embodiment of the present invention; as shown... Figure 5 The diagram shown is a schematic representation of IPA replacement during the wet drying process of a wafer 201 with a patterned structure 201a according to an embodiment of the present invention. The wet drying method for a wafer 201 with a patterned structure 201a according to an embodiment of the present invention includes the following steps:

[0041] Step S101: The wafer 201 with patterned structure 201a is wet-cleaned. After the wet cleaning is completed, the spacer region 201b between the patterned structures 201a is filled with cleaning solution 207.

[0042] Depend on Figure 4It can be seen that after the wet cleaning is completed, the extension direction of the graphic structure 201a is the extension direction of the double arrow line AA.

[0043] In this embodiment of the invention, the cleaning fluid 207 includes IPA.

[0044] Step S102: The supercritical gas 205 dries the wafer 201. During the drying process, the angle between the flow direction of the supercritical gas 205 and the extension direction of the pattern structure 201a ensures that the supercritical gas 205 can flow smoothly from one side of the spacer region 201b to the opposite side, so as to completely replace the cleaning liquid 207 in the spacer region 201b.

[0045] In this embodiment of the invention, the flow direction of the supercritical gas 205 is parallel to the extension direction of the patterned structure 201a, that is, the angle between the flow direction of the supercritical gas 205 and the extension direction of the patterned structure 201a is 0 degrees. In other embodiments, the angle between the flow direction of the supercritical gas 205 and the extension direction of the patterned structure 201a can also be greater than 0 degrees, as long as the supercritical gas 205 can flow through the interval region 201b.

[0046] Figure 4 In the diagram, arrow 206 indicates the flow direction of the supercritical gas 205.

[0047] During the drying process, the extension direction of the pattern structure 201a is the direction corresponding to the double-arrow line BB. Figure 4 It can be seen that the double-headed arrows AA and BB have different directions.

[0048] In this embodiment of the invention, the supercritical gas 205 includes supercritical carbon dioxide.

[0049] The drying is carried out in the drying chamber 202.

[0050] The drying chamber 202 includes a supercritical gas 205 spray inlet and a supercritical gas 205 spray outlet, and the flow direction of the supercritical gas 205 is along the direction from the supercritical gas 205 spray inlet to the supercritical gas 205 spray outlet. Figure 4 In the process, the supercritical gas 205 spray inlet is located on the side 203 of the drying chamber 202, and the supercritical gas 205 spray outlet is located on the side 204 of the drying chamber 202.

[0051] The wafer 201 has a positioning notch 301, and the angle between the flow direction of the supercritical gas 205 and the extension direction of the patterned structure 201a can be adjusted by adjusting the angle of the positioning notch 301.

[0052] In this embodiment of the invention, the angle of the positioning notch 301 is adjusted before the wafer 201 enters the drying chamber 202. Figure 4 In the above, step S102' corresponds to the step of adjusting the angle of the positioning notch 301 before entering the drying chamber 202. The arrow arc 302 indicates that the angle of the positioning notch 301 is adjusted. After adjustment, the extension direction of the graphic structure 201a is changed from the direction corresponding to the double arrow line AA to the direction corresponding to the double arrow line BB.

[0053] In other embodiments of the present invention, the angle of the positioning notch 301 can be adjusted after the wafer 201 enters the drying chamber 202, and the arrow arc 303 indicates that the angle of the positioning notch 301 is adjusted.

[0054] In this embodiment of the invention, after the complete replacement of the cleaning liquid 207 is completed during the drying process, the supercritical gas 205 is also vaporized to complete the drying.

[0055] Depend on Figure 5 As shown, the drying process in step S102 is a time-dependent process. Figure 5 Step S102 is further broken down into steps S102a, S102b, and S102c. After step S102a, the cleaning liquid 207 in the top region of the interval region 201b is replaced by the supercritical gas 205. After step S102b, all the cleaning liquid 207 in the interval region 201b is replaced by the supercritical gas 205. After step S102c, the supercritical gas 205 is completely vaporized, and the drying process is completed.

[0056] For a wafer 201 with a patterned structure 201a, this embodiment of the invention sets the angle between the supercritical gas 205 and the extension direction of the patterned structure 201a during the drying process. The angle needs to ensure that the supercritical gas 205 can flow smoothly from one side of the spacer region 201b to the opposite side. Since the supercritical gas 205 flows smoothly in the spacer region 201b, that is, it can enter from the opening on one side of the extension direction of the spacer region 201b and flow out from the opening on the other side, it can ensure that the supercritical gas 205 can flow simultaneously in the region between the bottom and the top of the spacer region 201b. Therefore, it can ensure that the cleaning liquid 207 from the bottom to the top of the spacer region 201b can be well replaced without replacement residue. Therefore, the cleaning liquid 207 in the spacer region 201b can be completely replaced in the end.

[0057] In addition, after the cleaning fluid 207 is replaced, since the surface tension of supercritical gas 205, such as supercritical carbon dioxide, tends to zero, the problem of pattern collapse caused by removing supercritical gas 205, such as by removing supercritical gas 205 through vaporization, can be eliminated.

[0058] The method of this invention innovatively adapts the characteristics of the wafer pattern to the placement angle of the wafer during the drying process. The angle can be adjusted before the wafer enters the drying chamber and can also be adjusted inside the drying chamber. This avoids flow obstruction caused by the supercritical carbon dioxide flow direction being perpendicular to the wall pattern, thereby improving the supercritical carbon dioxide replacement IPA effect. It can improve the supercritical carbon dioxide replacement efficiency while ensuring that the pattern does not collapse or break.

[0059] The present invention has been described in detail above through specific embodiments, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A wet drying method for wafers with patterned structures, characterized in that, Including the following steps: The wafer with the patterned structure is subjected to wet cleaning, and after the wet cleaning is completed, the spacer regions between the patterned structures are filled with cleaning solution; The wafer is dried using a flowing supercritical gas. During the drying process, the angle between the flow direction of the supercritical gas and the extension direction of the patterned structure ensures that the supercritical gas can flow smoothly from one side of the spacer region to the opposite side, so as to completely replace the cleaning solution in the spacer region.

2. The wafer wet drying method with a patterned structure as described in claim 1, characterized in that: The cleaning fluid includes IPA.

3. The wafer wet drying method with a patterned structure as described in claim 1, characterized in that: The supercritical gas includes supercritical carbon dioxide.

4. The wafer wet drying method with a patterned structure as described in claim 1, characterized in that: The drying process takes place in a drying chamber.

5. The wafer wet drying method with a patterned structure as described in claim 4, characterized in that: The drying chamber includes a supercritical gas spray inlet and a supercritical gas spray outlet, and the flow direction of the supercritical gas is along the direction from the supercritical gas spray inlet to the supercritical gas spray outlet.

6. The wet drying method for wafers with patterned structures as described in claim 5, characterized in that: The wafer has a positioning notch, and the angle between the flow direction of the supercritical gas and the extension direction of the patterned structure can be adjusted by adjusting the angle of the positioning notch.

7. The wet drying method for wafers with patterned structures as described in claim 6, characterized in that: The angle of the positioning notch is adjusted before the wafer enters the drying chamber; or, the angle of the positioning notch is adjusted after the wafer enters the drying chamber.

8. The wet drying method for wafers with patterned structures as described in claim 6, characterized in that: The flow direction of the supercritical gas is parallel to the extension direction of the graphic structure.

9. The wet drying method for wafers with patterned structures as described in claim 1, characterized in that: In the drying process, after the cleaning liquid is completely replaced, the supercritical gas is vaporized to complete the drying.

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