Preparation method of wafer surface copper layer and preparation method of semiconductor device
By rinsing the edge zone from the front and back side simultaneously during the preparation process of the electroplating copper layer on the wafer surface, the problem of increasing RC delay caused by the oxidation of the edge zone of the electroplating copper layer on the wafer surface is solved, and more stable rotation and More thorough cleaning improves the performance of semiconductor devices.
Patent Information
- Application Number
- CN202411595265.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-02-11
AI Technical Summary
In the prior art, the electroplated copper layer on the wafer surface is prone to oxidation in the edge region, resulting in an increase in parasitic resistance and thus increasing the RC delay.
During the preparation process of electroplating copper layer on the wafer surface, the edge area is simultaneously flushed from the front and the second cleaning liquid from the back to ensure that the edge area maintains pressure balance during the post-corrosion cleaning process, and thus remove residual corrosion liquid .
It effectively reduces the oxidation phenomenon of the edge region of the electroplating copper layer on the wafer surface, reduces the problem of increasing RC delay, and improves the performance of semiconductor devices.
Smart Images
Figure CN119419172A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor processing and manufacturing, and in particular to a method for preparing a copper layer on a wafer surface and a method for preparing a semiconductor device. Background Art
[0002] With the development of semiconductor technology, the line width and line spacing between interconnects in semiconductor devices are getting smaller and smaller. As a result, the parasitic capacitance and parasitic resistance between adjacent traces cause RC delay, which has become a major problem affecting device performance. Using metal copper as the filling metal at the trace position has less RC delay than other metals. At the same time, metal copper lamp methods are diverse and the cost is relatively low, making it a mainstream choice.
[0003] In many devices, a copper layer needs to be formed on the surface of the wafer. Electroplating is the mainstream method for depositing a copper layer. The current electroplating copper layer method is prone to partial oxidation in the edge area of the wafer where the copper layer is exposed, which will affect the parasitic resistance of the copper layer and increase the RC delay.
[0004] Therefore, a solution is needed to solve the problem of increased RC delay caused by this. Summary of the invention
[0005] In view of this, the present invention provides a method for preparing a copper layer on a wafer surface and a method for preparing a semiconductor device, so as to solve the problem that the electroplated copper layer on the wafer surface increases the RC delay of the secondary layer.
[0006] The invention provides a method for preparing a copper layer on the surface of a wafer, comprising the following steps: providing a wafer; the wafer comprising a bare wafer or a wafer with a plurality of structural film layers formed on the surface; electroplating a copper film on a surface of one side of the wafer to form an initial copper layer; the initial copper layer completely covers the surface of the wafer, including the edge area of the wafer; using a corrosive liquid to rinse the initial copper layer located on the surface of the edge area, removing the part of the initial copper layer, exposing the edge area of the wafer, and using the remaining initial copper layer as a copper plating layer; using a cleaning liquid to rinse the exposed edge area of the wafer, removing the residual corrosive liquid; annealing and curing; wherein the step of using a cleaning liquid to rinse the exposed edge area of the wafer comprises: using a first cleaning liquid to rinse the exposed edge area of the wafer from the front side of the wafer; and simultaneously using a second cleaning liquid to rinse the edge area of the wafer from the back side of the wafer.
[0007] Optionally, the position where the first cleaning liquid is used to rinse the wafer is the first rinse position; the position where the second cleaning liquid is used to rinse the wafer is the second rinse position; the horizontal distance between the first rinse position and the center of the wafer is less than or equal to 2 mm; the horizontal distance between the second rinse position and the center of the wafer is less than or equal to 2 mm.
[0008] Optionally, the difference between the flow rate of the first cleaning liquid and the flow rate of the second cleaning liquid is -0.4 L / min to 1.6 L / min.
[0009] Optionally, the flow rate of the first cleaning liquid is 1.5±0.5 L / min; the flow rate of the second cleaning liquid is 0.9±0.5 L / min.
[0010] Optionally, a difference between an angle between a spray direction of the first cleaning liquid and the wafer and an angle between a spray direction of the second cleaning liquid and the wafer is less than or equal to 50°.
[0011] Optionally, the angle between the spraying direction of the first cleaning liquid and the wafer is 90°±2°; the angle between the spraying direction of the second cleaning liquid and the wafer is 40°±2°.
[0012] Optionally, the time for the first cleaning liquid and the second cleaning liquid to simultaneously rinse the edge area of the wafer is 15s±3s.
[0013] Optionally, in the process of cleaning the exposed edge area of the wafer with the cleaning liquid, the rotation speed of the wafer is 500 r / min±100 r / min.
[0014] Optionally, the corrosive liquid is a mixed solution of sulfuric acid and hydrogen peroxide; the first cleaning liquid includes high-purity water; and the second cleaning liquid includes high-purity water.
[0015] The present invention also provides a method for preparing a semiconductor device, the semiconductor device comprising a substrate wafer, a copper-plated layer formed on one side surface of the substrate wafer; the copper-plated layer is formed using the method for preparing a copper layer on the surface of a wafer provided by the present invention.
[0016] The beneficial effects of the present invention are:
[0017] The method for preparing the copper layer on the surface of the wafer provided by the present invention adds a second cleaning liquid rinsing step for rinsing the edge area from the back of the wafer, so that during the post-etching cleaning process, during the front rinsing process, the back side also has pressure for recoil, so that the edge area of the rotating wafer can maintain pressure balance during the rinsing process, and then the rotation remains stable. Stable rotation can make the residual etching liquid be removed more thoroughly, and then the oxidation phenomenon of the exposed edge area in the subsequent process is greatly reduced, so that the problem of increased RC delay associated with the electroplated copper layer on the surface of the wafer can be greatly alleviated.
[0018] The method for preparing a semiconductor device provided by the present invention forms a copper-plated layer on the surface of a wafer by the method for preparing a copper layer on the surface of a wafer provided by the present invention, and adds a second cleaning liquid rinsing step for rinsing the edge area from the back of the wafer, so that during the post-etching cleaning process, during the front rinsing process, the back side also has pressure for recoil, so that the edge area of the rotating wafer can maintain pressure balance during the rinsing process, and thus the rotation remains stable. Stable rotation can make the residual etching liquid be removed more thoroughly, and thus greatly reduce the oxidation of the exposed edge area in the subsequent process, so that the problem of increased RC delay associated with the electroplated copper layer on the surface of the wafer can be greatly alleviated. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] 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.
[0020] Figure 1 It is a schematic diagram of the state when the initial copper layer is formed on the surface of the wafer;
[0021] Figure 2 A schematic diagram of a state in which an initial copper layer is processed to form a copper-plated layer;
[0022] Figure 3 is a schematic diagram of the copper plating layer and the exposed edge area of the wafer;
[0023] Figure 4 This is a photo showing oxidation in the exposed edge area;
[0024] Figure 5 A schematic diagram of conventional post-etching cleaning;
[0025] Figure 6 A schematic diagram of post-etching cleaning in a method for preparing a copper layer on a wafer surface according to an embodiment of the present invention;
[0026] Figure 7 The figure is a schematic flow chart of a method for preparing a copper layer on a wafer surface according to an embodiment of the present invention. DETAILED DESCRIPTION
[0027] As mentioned previously, the electroplating process can cause oxidation on the exposed wafer edge area. Figure 3 , Figure 4 ,exist Figure 4 In the photo, corresponding to Figure 3There are some white areas at the edge area 100A of the wafer, which are the oxidized areas of the wafer. These oxidized areas increase the resistance of the wires, reduce the current transmission speed, and thus increase the RC delay of the copper plating layer.
[0028] The inventors found that this is due to the imbalance of wafer pressure during the post-etching cleaning step during the electroplating process, which results in incomplete removal of the etching solution and residues, which react with the wafer (usually Si wafer) in the subsequent steps to produce an oxidized area. Figure 1-Figure 3 as well as Figure 5 The conventional copper electroplating process to form a copper layer on the surface of a wafer includes the following steps:
[0029] refer to Figure 1 , providing a wafer 100; electroplating a copper film on one side surface of the wafer 100 to form an initial copper layer 200; the initial copper layer 200 completely covers the surface of the wafer 100, including an edge region 100A of the wafer; the position of the edge region 100A is referenced Figure 3 .
[0030] refer to Figure 2 , while the wafer is rotating, the initial copper layer 200 located on the surface of the edge area 100A is washed with an etching solution to remove the initial copper layer 200 so that the edge area 100A of the wafer 100 is exposed, and the remaining initial copper layer 200 is used as a copper plating layer 210;
[0031] refer to Figure 5 , while the wafer is rotating, cleaning the exposed edge area of the wafer with a cleaning solution 300 to remove residual etching solution;
[0032] In the above process, since the edge area 100A is only rinsed with the cleaning liquid 300 on the front side, the wafer 100 is only subjected to the rinsing pressure on one side during the rotation process, and the pressure on the upper and lower sides of the horizontal plane of the wafer is unbalanced, so it is difficult to maintain a stable surface of the wafer. Therefore, it is difficult to completely rinse and remove the residual corrosive liquid during the rinsing process along with the rotation, resulting in a small amount of retention, which reacts with the wafer in the subsequent steps to cause partial oxidation.
[0033] Therefore, the inventors provide a method for preparing a copper layer on a wafer surface and a method for preparing a semiconductor device to solve the problem that the RC delay of the electroplated copper layer increases due to oxidation of the edge area.
[0034] 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. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.
[0035] Embodiment 1
[0036] refer to Figure 7 and Figure 6 ,as well as Figure 1-Figure 3 This embodiment provides a method for preparing a copper layer on a wafer surface, comprising the following steps:
[0037] A wafer 100 is provided; the wafer 100 includes a bare wafer or a wafer with a plurality of structural film layers formed on the surface; when the wafer 100 is a bare wafer, the copper layer on the wafer surface is formed on the surface of the bare wafer; when the wafer 100 is a wafer with a plurality of structural film layers formed on the surface, the copper layer on the wafer surface is formed on the surface of the outermost structural film layer.
[0038] A copper film is electroplated on one side of the wafer 100 to form an initial copper layer 200; the initial copper layer 200 completely covers the surface of the wafer 100, including the edge area 100A of the wafer 100 (the position of the edge area 100A is referenced to Figure 3 );
[0039] The initial copper layer 200 located on the surface of the edge region 100A is washed with an etching solution to remove the initial copper layer 200 so that the edge region 100A of the wafer 100 is exposed, and the remaining initial copper layer 200 is used as a copper plating layer 210;
[0040] Cleaning the exposed edge region 100A of the wafer 100 with a cleaning solution 300 to remove residual etching solution;
[0041] Annealing and curing;
[0042] Among them, the step of using the cleaning liquid 300 to clean the exposed edge area 100A of the wafer 100 includes: using the first cleaning liquid 310 to rinse the exposed edge area 100A of the wafer 100 from the front side of the wafer 100; and using the second cleaning liquid 320 to rinse the edge area 100A of the wafer 100 from the back side of the wafer 100.
[0043] The method for preparing the copper layer on the surface of the wafer provided by the present invention adds a second cleaning liquid rinsing step of rinsing the edge area 100A from the back of the wafer 100, so that during the post-etching cleaning process, during the front rinsing process, the back side also has pressure for recoil, so that the edge area 100A of the rotating wafer 100 can maintain pressure balance during the rinsing process, and thus the rotation remains stable. Stable rotation can make the residual etching liquid be removed more thoroughly, and thus greatly reduce the oxidation phenomenon of the exposed edge area 100A in the subsequent process, so that the problem of increased RC delay associated with the electroplated copper layer on the surface of the wafer 100 can be greatly alleviated.
[0044] Furthermore, the position where the first cleaning liquid rinses the wafer is the first rinsing position; the horizontal distance between the first rinsing position and the center of the wafer is less than or equal to 2 mm; the horizontal distance between the second rinsing position and the center of the wafer is less than or equal to 2 mm. That is, the rinsing points on the upper and lower sides are basically in the same horizontal position and opposite in vertical position, and are both located near the center of the wafer 100.
[0045] Specifically, the situation when the corrosive liquid is flushed is as follows Figure 5 As shown, the cleaning liquid cleans the edge area 100A as shown in FIG. Figure 6 As shown, the cleaning liquid near the center of the wafer 100 spreads to the edge of the wafer 100 as the wafer rotates, and washes away the etching liquid on the edge area 100A.
[0046] In this way, the upper and lower pressure positions of the rinsing position are basically opposite and are located near the center of the wafer, so that the wafer can be kept level as much as possible during the rinsing process, and the upper and lower pressures are balanced. It is easier to achieve balance and make it easier to keep the wafer stable.
[0047] Further, in some embodiments, the difference between the flow rate of the first cleaning liquid 310 and the flow rate of the second cleaning liquid 320 is -0.4L / min to 1.6L / min. That is, the difference between the flow rate of the first cleaning liquid 310 and the flow rate of the second cleaning liquid 320 falls within the above numerical range. When the flow rate difference is within the above range, the wafer can be more easily kept stable, and the final oxidation phenomenon is greatly reduced; if it exceeds the above range, the wafer is not stable enough and oxidation is still prone to occur.
[0048] Specifically, in some embodiments, the flow rate of the first cleaning liquid 310 is 1.5±0.5 L / min; the flow rate of the second cleaning liquid 320 is 0.9±0.5 L / min. The flow rate of the first cleaning liquid 310 is usually greater than the flow rate of the second cleaning liquid 320, because the corrosion liquid residue is mainly on the front side of the wafer, and a higher impact force is required to remove it with rotation. The second cleaning liquid 320 mainly provides a certain recoil force, which is not necessarily the same as the flow rate of the first cleaning liquid. In some cases, the flow rate of the second cleaning liquid can also be larger.
[0049] Furthermore, in some embodiments, the difference between the angle between the spray direction of the first cleaning liquid 310 and the wafer 100 and the angle between the spray direction of the second cleaning liquid 320 and the wafer 100 is less than or equal to 50°. The first cleaning liquid 310 and the second cleaning liquid 320 do not have to be completely opposite to each other. The second cleaning liquid 320 mainly provides sufficient recoil force to stabilize the wafer, so the flow rate and angle can achieve a suitable recoil force. If the angle difference is greater than or equal to 50°, it is difficult to achieve a balance between the positive and negative forces of the wafer.
[0050] Specifically, in some embodiments, the angle between the spray direction of the first cleaning liquid and the wafer is 90°±2°; the angle between the spray direction of the second cleaning liquid and the wafer is 40°±2°.
[0051] Furthermore, in some embodiments, the time for the first cleaning liquid and the second cleaning liquid to simultaneously rinse the edge area of the wafer is 15s±3s. If the rinsing time is too short, the effect of removing the residual corrosive liquid is poor; if the rinsing time is too long, on the one hand, it causes waste, and on the other hand, it also increases the risk of long-term stress fatigue damage of the wafer during the rinsing process. Therefore, when the rinsing time is within the range of 15s±3s, a balance can be achieved between ensuring the effect of removing the residual corrosive liquid and avoiding waste and reducing the risk of wafer fatigue damage.
[0052] Further, in some embodiments, during the process of cleaning the exposed edge area of the wafer with the cleaning liquid, the rotation speed of the wafer is 500r / min±100r / min. If the rotation speed is too large or too small, the residual removal effect is likely to be poor. Within the above range, a suitable removal effect can be guaranteed.
[0053] Furthermore, in some embodiments, the corrosive liquid is a mixed solution of sulfuric acid and hydrogen peroxide (H 2 SO 4 +H 2 O 2); the first cleaning liquid 310 includes ultrapure water (DIW); the second cleaning liquid 320 includes ultrapure water (DIW). In some other embodiments, the first cleaning liquid 310 and the second cleaning liquid 320 may be different cleaning liquid compositions, and are not limited to ultrapure water. Those skilled in the art may select according to actual needs.
[0054] In order to show the actual effect of this solution, several groups of experiments were conducted for comparison. The comparison results are shown in Table 1 below:
[0055] Table 1 Comparison of final wafer effects after washing with different front and back cleaning liquid flow rates
[0056] Comparative Example FDIW Flow FDIW angle BDIW traffic BDIW angle Result 1 1.5L / min 90° 0 40° Oxidation 2 1.5L / min 90° 0.3L / min 40° The oxidation area becomes smaller, but the oxidation is still not eliminated 3 1.5L / min 90° 0.4L / min 40° No oxidation 4 1.5L / min 90° 0.9L / min 40° No oxidation 5 1.5L / min 90° 1.4L / min 40° No oxidation 6 1.5L / min 90° 1.5L / min 40° DIW splashback on the front of wafer
[0057] In the above table, FDIW represents the first cleaning liquid on the front side, and BDIW represents the second cleaning liquid on the back side. According to the comparison of the results in the above table, it can be seen that when the flow rate, angle of the first cleaning liquid and the angle of the second cleaning liquid are all the same: when there is no second cleaning liquid flushing on the back side (Comparative Example 1), there is an obvious oxidation area. When the second cleaning liquid flow rate is small (0.3L / min), the oxidation area is reduced (Comparative Example 2). When it is increased to 0.4L / min to 1.4L / min (Comparative Examples 3-5), there is no oxidation phenomenon. When it is increased to 1.5 / min (Comparative Example 6), there will be ultrapure water splashing on the front side of the wafer, which is easy to carry residual corrosive liquid and cause oxidation of the front side of the wafer. Therefore, increasing the flushing of the cleaning liquid on the back side and maintaining the flow rate within the range of 0.4L / min to 1.4L / min can effectively remove the oxidation phenomenon in the edge area of the wafer, thereby avoiding the phenomenon of increased RC delay of the copper plating layer.
[0058] Embodiment 2
[0059] This embodiment provides a method for preparing a semiconductor device, wherein the semiconductor device includes a substrate wafer, and a copper-plated layer is formed on one side of the substrate wafer; the copper-plated layer is formed using the method for preparing a copper layer on the surface of a wafer provided in the above-mentioned embodiment 1.
[0060] In the method for preparing a semiconductor device provided in this embodiment, the copper-plated layer on the surface of the wafer is formed by the method for preparing the copper layer on the surface of the wafer provided by the present invention, and a second cleaning liquid rinsing step is added to rinse the edge area from the back of the wafer, so that during the post-etching cleaning process, during the front rinsing process, the back side also has pressure for recoil, so that the edge area of the rotating wafer can maintain pressure balance during the rinsing process, and thus the rotation remains stable. Stable rotation can make the residual etching liquid be removed more thoroughly, thereby greatly reducing the oxidation of the exposed edge area in the subsequent process, which can greatly alleviate the problem of increased RC delay associated with the electroplated copper layer on the surface of the wafer.
[0061] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.
Claims
1. A method for preparing a copper layer on a wafer surface, characterized in that: The following steps are involved: Providing a wafer; the wafer includes a bare wafer or a wafer with a plurality of structural film layers formed on the surface; Electroplating a copper film on one side of the wafer to form an initial copper layer; the initial copper layer completely covers the surface of the wafer, including the edge area of the wafer; Using a corrosive liquid to wash the initial copper layer located on the surface of the edge area, removing the portion of the initial copper layer, exposing the edge area of the wafer, and using the remaining initial copper layer as a copper plating layer; Cleaning the exposed edge area of the wafer with a cleaning solution to remove residual etching solution; Annealing and curing; Wherein, the step of using a cleaning liquid to clean the exposed edge area of the wafer includes: Rinse the exposed edge area of the wafer from the front side of the wafer using a first cleaning solution; At the same time, a second cleaning liquid is used to rinse the edge area of the wafer from the back side of the wafer.
2. The method for preparing a copper layer on a wafer surface according to claim 1, characterized in that: The position where the first cleaning liquid rinses the wafer is a first rinsing position; The position where the second cleaning liquid rinses the wafer is a second rinsing position; The horizontal distance between the first flushing position and the center of the wafer is less than or equal to 2 mm; A horizontal distance between the second flushing position and the center of the wafer is less than or equal to 2 mm.
3. The method for preparing a copper layer on a wafer surface according to claim 2, wherein: The difference between the flow rate of the first cleaning liquid and the flow rate of the second cleaning liquid is -0.4 L / min to 1.6 L / min.
4. The method for preparing a copper layer on a wafer surface according to claim 3, characterized in that: The flow rate of the first cleaning liquid is 1.5±0.5L / min; The flow rate of the second cleaning liquid is 0.9±0.5 L / min.
5. The method for preparing a copper layer on a wafer surface according to claim 2, characterized in that: A difference between an angle between a spray direction of the first cleaning liquid and the wafer and an angle between a spray direction of the second cleaning liquid and the wafer is less than or equal to 50°.
6. The method for preparing a copper layer on a wafer surface according to claim 5, characterized in that: The angle between the spray direction of the first cleaning liquid and the wafer is 90°±2°; The included angle between the spraying direction of the second cleaning liquid and the wafer is 40°±2°.
7. The method for preparing a copper layer on a wafer surface according to claim 2, characterized in that: The time for the first cleaning liquid and the second cleaning liquid to simultaneously rinse the edge area of the wafer is 15s±3s.
8. The method for preparing a copper layer on a wafer surface according to claim 2, characterized in that: During the process of cleaning the exposed edge area of the wafer using the cleaning solution, the rotation speed of the wafer is 500 r / min±100 r / min.
9. The method for preparing a copper layer on a wafer surface according to any one of claims 1 to 8, characterized in that: The corrosive liquid is a mixed solution of sulfuric acid and hydrogen peroxide; The first cleaning solution includes high-purity water; The second cleaning solution includes high-purity water.
10. A method for preparing a semiconductor device, characterized in that: The semiconductor device comprises a substrate wafer, and a copper plating layer is formed on one side surface of the substrate wafer; The copper plating layer is formed using the method for preparing a copper layer on a wafer surface as described in any one of claims 1 to 9.