Device for improving plasma high-temperature nitriding uniformity

Abstract

The utility model discloses a device for improving plasma high-temperature nitriding uniformity, which comprises a process chamber, a focusing ring is arranged in the middle of the process chamber, and a focusing through hole for plasma to pass through is arranged in the middle of the focusing ring. Compared with the prior art, the focusing ring structure has the advantages that plasmas can pass through the focusing through hole of the focusing ring, and plasmas in other areas are blocked by the focusing ring body and cannot pass through, so that the concentration of the plasmas in the central area of the process cavity can be improved, the concentration of the plasmas at the edge of the process cavity is reduced, and the quality of the process cavity is improved. Therefore, a more uniform nitriding film effect is realized.

Description

Technical Field

[0001] This utility model relates to a device for improving the uniformity of high-temperature plasma nitriding, and belongs to the field of semiconductor equipment technology. Background Technology

[0002] With the rapid development of integrated circuits, the radial dimensions of wafers are becoming larger and larger. Currently, wafer manufacturing with a diameter of 300mm is the mainstream. The increase in wafer size will inevitably lead to an increase in the size of the process chamber, which makes it more difficult to maintain a uniform environment in the process chamber.

[0003] In semiconductor manufacturing, nitriding is commonly used to form protective layers, insulating layers, and for surface modification. Plasma high-temperature nitriding involves using a high-frequency radio frequency source to dissociate a nitrogen source in a chamber to generate plasma, which then reacts with the high-temperature wafer surface to form a nitrided film. The uniformity of the film formation is a crucial indicator of a plasma nitriding system, determining the accuracy of the patterning in subsequent processes. However, due to the non-uniform distribution of plasma within the reaction chamber, film thickness inhomogeneity can easily occur during nitriding, directly impacting the performance and production yield of the final device.

[0004] In semiconductor manufacturing, high-temperature nitriding is a crucial step in forming high-quality thin films. However, in actual production, the uneven distribution of plasma concentration within the chamber often leads to uneven thickness of the final nitrided film. This non-uniformity directly affects the electrical performance and reliability of the device, thereby reducing production yield. Specifically, under the action of a vacuum pump, the plasma flow rate at the edges is higher than at the center, resulting in a plasma concentration distribution that is low in the center of the chamber and high at the edges. This uneven distribution makes it difficult to achieve uniformity in the nitrided film thickness at the wafer center compared to the edges.

[0005] Traditional nitriding processes typically improve uniformity by adjusting parameters such as gas flow rate and temperature, but these methods have limited effectiveness and cannot fundamentally solve the problem of uneven plasma concentration distribution. Uniformity can also be improved by changing the entire chamber structure, but this method requires a complete replacement of the chamber, increasing costs and making the operation more complex.

[0006] Therefore, developing a device to improve the uniformity of high-temperature plasma nitriding and to precisely control the plasma concentration distribution has become an urgent problem for those skilled in the art. Utility Model Content

[0007] The present invention addresses the aforementioned shortcomings by providing a device for improving the uniformity of high-temperature plasma nitriding.

[0008] The above-mentioned objective of this utility model is achieved through the following technical solution: a device for improving the uniformity of high-temperature plasma nitriding, comprising a process chamber, characterized in that: a focusing ring is provided in the middle of the process chamber, and a focusing through hole for plasma to pass through is provided in the middle of the focusing ring.

[0009] Furthermore, the focusing ring is fixed by a support member, which is fixed to the inner wall of the process chamber.

[0010] Furthermore, the process chamber is provided with a process gas inlet and matching system at the top and an exhaust port at the bottom. The process chamber is provided with an RF source at the top and the RF source is connected to an RF power supply through the matching system. The process chamber is provided with a high-temperature substrate for placing wafers at the bottom.

[0011] Furthermore, the focusing ring is made of any one of aluminum alloy, quartz, or ceramic, with quartz being the preferred material.

[0012] Furthermore, the focusing ring is positioned 8-15 mm above the high-temperature substrate, preferably 10 mm. Positions that are too high or too low cannot effectively control the plasma concentration on the wafer surface.

[0013] Furthermore, the inner diameter of the focusing ring is 280-330 mm, preferably 300 mm.

[0014] The advantages of this invention compared to the prior art are: the focusing ring structure allows plasma to pass through the focusing aperture of the focusing ring, while plasma in other areas is blocked by the focusing ring body and cannot pass through. This can increase the plasma concentration in the central area of ​​the process cavity and reduce the plasma concentration at the edge of the process cavity, thereby achieving a more uniform nitriding film effect. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model.

[0016] Figure 2 This is a top view of the focusing ring in this utility model.

[0017] Figure 3 This is a graph showing the total radial pressure of the wafer mesa at its original size.

[0018] Figure 4 The radial total pressure charts of the wafer mesa after reducing the inner diameter of the focusing via of the focusing ring by 10 mm and 20 mm. Wherein: Figure 4 a is a graph showing the radial total pressure of the wafer mesa after the inner diameter of the focusing hole of the focusing ring is reduced by 10 mm; Figure 4 b is a graph showing the radial total pressure of the wafer mesa after the inner diameter of the focusing hole of the focusing ring is reduced by 20mm.

[0019] Figure 5 The radial total pressure diagrams of the wafer mesa after increasing the inner diameter of the focusing via of the focusing ring by 10mm and 20mm are shown. Wherein: Figure 5 a is a graph showing the radial total pressure of the wafer mesa after the inner diameter of the focusing hole of the focusing ring is increased by 10 mm; Figure 5 b is a graph showing the radial total pressure of the wafer mesa after the inner diameter of the focusing hole of the focusing ring is increased by 20mm. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings.

[0021] like Figure 1 As shown, an apparatus for improving the uniformity of high-temperature plasma nitriding includes a process chamber 8. The top of the process chamber 8 is provided with a process gas inlet 2 and a matching system 9, and the bottom is provided with an exhaust port 7. The upper part of the process chamber 8 is provided with a radio frequency source 1, and the lower part of the process chamber 8 is provided with a high-temperature substrate 6 for placing a wafer 5. A focusing ring 3 is provided in the middle of the process chamber 8. The focusing ring 3 has a focusing through hole in the middle for plasma to pass through. The focusing ring 3 is fixed by a support member 4, which is fixed to the inner wall of the process chamber 8.

[0022] During operation, process gas enters the process chamber 8 through process gas inlet 2. A high-frequency current, generated by the radio frequency source 1 and matching system 9, dissociates the process gas to produce plasma. The process gas is either ammonia (NH3) or nitrogen (N2). The plasma passes through the focusing aperture of the focusing ring 3, fixed by the support 4, and reaches the surface of the wafer 5. The high-temperature substrate 6 uniformly heats the wafer 5, and the nitrogen plasma reacts with the silicon on the wafer surface, completing the nitriding process. Excess exhaust gas is discharged through the exhaust port 7. Specifically, the plasma cannot penetrate any part other than the focusing aperture of the focusing ring 3.

[0023] like Figure 2 As shown, the focusing ring 3 is coaxial with the chamber, with an outer diameter of 500 mm and an inner diameter of 310 mm. The focusing ring 3 is located on the support 4, and the distance between its lower surface and the upper surface of the high-temperature substrate 6 is 10 mm. The plasma concentration in the process chamber 8 can be adjusted by changing the inner diameter of the focusing ring 3.

[0024] like Figure 3 As shown, the radial total pressure of the wafer mesa at the original size of the focusing ring 3 shows a trend of higher pressure at the center than at the edge. The difference between the maximum and minimum values ​​is 0.352 mTorr, indicating that the ion concentration at the center of the wafer is lower than that at the edge, resulting in poor film uniformity.

[0025] like Figure 4 As shown, based on the original dimensions, the inner diameter R of the focusing ring 3 is reduced by pointing towards the center of the ring. Figure 4 a and Figure 4b represents the total radial pressure on the wafer mesa after shrinking by 10 mm and 20 mm, respectively. The difference between the maximum and minimum values ​​is reduced to 0.018 mTorr and 0.024 mTorr, respectively, indicating improved uniformity. The radial pressure on the wafer surface is most uniform when the inner diameter of the focusing ring is 300 mm.

[0026] like Figure 5 As shown, the inner diameter R of the focusing ring 3 is enlarged inwards from the center of the ring, while maintaining the original dimensions. Figure 5 a and Figure 5 b represents the total radial pressure of the wafer mesa after expansion by 10mm and 20mm, respectively. The difference between the maximum and minimum values ​​is reduced to 0.057mTorr and 0.093mTorr, respectively, indicating improved uniformity.

[0027] Further explanation of this utility model:

[0028] 1. The focusing ring is generally made of any one of aluminum alloy, quartz, or ceramic, with quartz being the preferred material.

[0029] 2. The focusing ring is positioned 8-15 mm above the high-temperature substrate, preferably 10 mm. Positioning it too high or too low will not effectively control the plasma concentration on the wafer surface.

[0030] 3. The inner diameter of the focusing ring can be selected from 280-330mm, preferably 300mm. If the inner diameter is too small, the plasma concentration at the wafer edge will be too low, and the edge thickness will be less than that at the center; while if the inner diameter is too large, the plasma concentration at the wafer edge will be too high, and the edge thickness will be greater than that at the center.

[0031] 4. The temperature of the high-temperature substrate can be selected from 500-800℃, preferably 600℃. High temperature helps to increase the thickness of the nitride film and can reduce the damage caused by plasma to the wafer surface.

[0032] 5. The process gas is either nitrogen or ammonia, with ammonia being preferred. Compared to nitrogen, nitrogen dissociates more easily, while ammonia dissociates to produce nitrogen and hydrogen plasma. Nitrogen plasma is used for high-temperature nitriding, while hydrogen plasma can combine with impurity elements to generate gas, which is then removed, thus improving the purity of the wafer surface.

[0033] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the description and drawings of this utility model, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An apparatus for improving the uniformity of high-temperature plasma nitriding, comprising a process chamber, characterized in that: A focusing ring is provided in the middle of the process chamber, and a focusing through hole is provided in the middle of the focusing ring for plasma to pass through. A high-temperature substrate for placing wafers is provided in the lower part of the process chamber, and the focusing ring is located 8-15 mm above the high-temperature substrate.

2. The device for improving the uniformity of high-temperature plasma nitriding according to claim 1, characterized in that: The focusing ring is fixed by a support member, which is fixed to the inner wall of the process chamber.

3. The device for improving the uniformity of high-temperature plasma nitriding according to claim 1, characterized in that: The process chamber is equipped with a process gas inlet and matching system at the top and an exhaust port at the bottom. An RF source is located at the top of the process chamber and is connected to an RF power supply through the matching system.

4. The apparatus for improving the uniformity of high-temperature plasma nitriding according to claim 1, characterized in that: The focusing ring is made of any one of aluminum alloy, quartz, or ceramic.

5. The apparatus for improving the uniformity of high-temperature plasma nitriding according to claim 4, characterized in that: The focusing ring is made of quartz.

6. The apparatus for improving the uniformity of high-temperature plasma nitriding according to claim 1, characterized in that: The focusing ring is located 10 mm above the high-temperature substrate.

7. The apparatus for improving the uniformity of high-temperature plasma nitriding according to claim 1, characterized in that: The inner diameter of the focusing ring is 280-330 mm.

8. The apparatus for improving the uniformity of high-temperature plasma nitriding according to claim 7, characterized in that: The inner diameter of the focusing ring is 300 mm.

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