Surface strengthening process for semiconductor wafers
By employing ozone water ultrasonic cleaning, laser treatment, and plasma deposition processes, the problems of insufficient mechanical strength and thermal stability of wafer surfaces have been solved, achieving efficient wafer surface strengthening and improving device reliability and yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI WELNEW MICRO ELECTRONICS
- Filing Date
- 2025-05-28
- Publication Date
- 2026-05-22
AI Technical Summary
Traditional wafer surface treatment processes suffer from problems such as insufficient mechanical strength, chemical damage, poor thermal stability, and corrosion resistance defects, making it difficult to meet the miniaturization and high integration requirements of semiconductor devices.
The wafer surface is strengthened by using ozone water ultrasonic cleaning combined with high-purity nitrogen purging, followed by laser treatment and radio frequency plasma deposition, and finally methane plasma treatment to form a dense silicon nitride layer and a dynamically cross-linked DLC network.
It significantly improves the mechanical strength, surface hardness and electrical stability of wafers, reduces surface roughness and thermal stress, and improves device reliability and yield.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wafer processing technology and relates to a surface strengthening process for semiconductor wafers. Background Technology
[0002] As semiconductor devices evolve towards miniaturization and high integration, the surface properties of wafers have an increasingly significant impact on device reliability and process yield. Traditional surface treatment processes face the following limitations: First, insufficient mechanical strength. Existing technologies such as chemical mechanical polishing or wet etching are prone to subsurface damage, leading to microcracks, lattice distortion, and other problems, reducing the wafer's bending and impact resistance. Second, susceptibility to corrosion defects. While wet cleaning processes can remove surface contaminants, highly corrosive reagents such as hydrofluoric acid may over-etch the wafer surface, resulting in uneven passivation layer thickness. Furthermore, traditional surface treatment processes suffer from insufficient thermal stability. Although high-temperature annealing can repair wafer surface defects, it can cause wafer warping and doped region diffusion shift, with thermal stress issues being particularly prominent for ultra-thin wafers. Therefore, there is an urgent need to develop a wafer surface strengthening process that combines low damage, high uniformity, and low cost to meet the processing requirements of semiconductor materials. Summary of the Invention
[0003] The purpose of this invention is to provide a surface strengthening process for semiconductor wafers.
[0004] The objective of this invention can be achieved through the following technical solutions:
[0005] A surface strengthening process for semiconductor wafers, the specific steps of which are as follows:
[0006] S1: Ozone water ultrasonic cleaning is used to remove organic contaminants from the surface of the semiconductor wafer, and then high-purity nitrogen gas is used to purge the surface of the semiconductor wafer to obtain semiconductor wafer A;
[0007] S2: Semiconductor wafer A is placed in a vacuum chamber for laser processing, with an energy density of 0.5–1.2 J / cm². 2 The scanning speed is 30-50 mm / s, and the overlap rate is 20%, to obtain semiconductor wafer B;
[0008] S3: Perform radio frequency plasma deposition on semiconductor wafer B, introduce a mixed gas at a pressure of 50-70 Pa and a power of 200-220 W, to obtain semiconductor wafer C;
[0009] S4: The semiconductor wafer C is then treated with methane plasma containing methylsilane, and the pulse bias voltage is -500V to obtain the semiconductor wafer.
[0010] As a preferred embodiment of the present invention, the concentration of ozone water in S1 is 60-80 ppm.
[0011] As a preferred embodiment of the present invention, the ultrasonic power in S1 is 80-100W and the frequency is 26-30kHz.
[0012] As a preferred embodiment of the present invention, the nitrogen purging rate in S1 is 3.0 to 4.0 L / min, and the nitrogen purging time is 15 to 30 s.
[0013] As a preferred embodiment of the present invention, the pressure in the vacuum cavity in S2 is ≤10. -3 Pa.
[0014] As a preferred embodiment of the present invention, the laser processing in S2 uses a 248nm KrF excimer laser.
[0015] As a preferred embodiment of the present invention, the mixed gas in S3 is SiH4 / NH3 / He mixed in a volume ratio of (1.5~1.8):(1~1.2):(5~6).
[0016] As a preferred embodiment of the present invention, the radio frequency plasma deposition rate in S3 is 0.5 to 0.6 nm / s.
[0017] As a preferred embodiment of the present invention, the methane plasma in S4 contains 3-5% methylsilane by volume.
[0018] As a preferred embodiment of the present invention, the methane plasma deposition temperature in S4 is 130-150°C and the processing time is 8-12 min.
[0019] First, the surface strengthening process of this invention utilizes ozone water combined with ultrasonic cleaning. The strong oxidizing properties of ozone molecules selectively decompose organic contaminants such as photoresist residue and grease, avoiding the introduction of metal ion impurities. The cavitation effect generated by ultrasound forms microjets and shock waves in the liquid, further removing inorganic particles through mechanical exfoliation, achieving dual purification through chemical dissolution and physical exfoliation. The controlled ozone concentration ensures the removal of organic matter in a short time while avoiding excessive etching of the silicon substrate by excessive active oxygen. Subsequent directional nitrogen purging rapidly removes residual liquid film, preventing the formation of watermarks that increase the interface state density. Simultaneously, an inert atmosphere barrier is constructed, effectively inhibiting the adsorption reaction of hydroxyl groups on the wafer surface with CO2 / H2O in the air after cleaning, providing an atomically clean substrate for subsequent thin film deposition.
[0020] Laser shallow repair technology in a vacuum environment achieves non-thermally fusible surface treatment using excimer lasers. By precisely controlling the laser energy density, a controlled phase transition is induced in the wafer surface through photon-phonon coupling. The amorphous oxide layer absorbs photon energy and undergoes lattice rearrangement, transforming into a dense nanocrystalline structure, while simultaneously eliminating microcracks introduced by plasmon etching. A dynamic focusing system is employed during laser scanning, controlling the grain size through real-time feedback to avoid warping caused by temperature gradients in traditional thermal annealing processes. Laser treatment reduces wafer surface roughness while simultaneously increasing surface hardness.
[0021] A high-density amorphous silicon nitride barrier layer was formed on the wafer surface using radio frequency plasma chemical vapor deposition (RF plasma chemical vapor deposition) with a SiH4 / NH3 / He mixture in a volume ratio of 3:2:5. During deposition, pulsed bias voltage control optimized ion bombardment energy, increasing film density while maintaining hydrogen content within a suitable range to balance internal stress. This film effectively reduces the sodium ion diffusion coefficient, significantly improving barrier performance compared to traditional thermal oxide layers. It effectively blocks the penetration and migration of alkali metal ions in subsequent high-temperature processes, ensuring the stability of the device's threshold voltage.
[0022] Methylsilane is introduced as a precursor during methane plasma treatment. The active hydrogen produced by its decomposition reacts with sp in the diamond-like carbon (DLC) network. 3 Hybridized carbon atoms undergo hydrogenation to form a Si-CH dynamic cross-linked structure. When surface scratches occur, silanol groups undergo condensation reactions with unsaturated bonds in the DLC film, achieving chemical bond reconstruction in the defect region. This self-healing mechanism significantly improves the scratch repair rate, and the surface hardness after repair does not show a significant decrease compared to the original DLC film, attributed to the enhanced energy dissipation caused by the increased cross-linking density. The dynamic cross-linked network also reduces the coefficient of friction, significantly improving scratch resistance during wafer transport.
[0023] The beneficial effects of this invention are:
[0024] The semiconductor surface strengthening process of this invention first employs ozone-ultrasonic cleaning, utilizing both oxidative decomposition and cavitation stripping for dual purification, coupled with nitrogen isolation protection, to ensure atomic-level substrate cleanliness, laying the foundation for subsequent processes. Excimer laser non-thermal melting treatment achieves nanoscale lattice reconstruction, eliminating microcracks while reducing surface roughness and increasing hardness, without thermal stress warping. Plasma deposition of a high-density silicon nitride layer significantly enhances sodium ion blocking performance, ensuring device electrical stability. Methylsilane-enhanced DLC networks form a dynamic cross-linked structure, enabling scratch self-healing without significant hardness reduction after repair, effectively improving scratch resistance during wafer transport. This semiconductor surface strengthening process of the present invention can significantly improve the yield and reliability of semiconductor devices. Detailed Implementation
[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.
[0026] Example 1
[0027] A surface strengthening process for semiconductor wafers, the specific steps of which are as follows:
[0028] S1: The organic contaminants on the surface of the semiconductor wafer were removed by ultrasonic cleaning with 70ppm ozone water. The ultrasonic power was 90W and the frequency was 28kHz. Then, the surface of the semiconductor wafer was purged with high-purity nitrogen at a rate of 3.5L / min for 20s to obtain semiconductor wafer A.
[0029] S2: Semiconductor wafer A is placed in a vacuum chamber for laser processing. A 248nm KrF excimer laser is used for laser processing, and the pressure in the vacuum chamber is ≤10. -3 Pa, energy density 0.8 J / cm³ 2 The scanning speed was 40 mm / s, and the overlap rate was 20%, to obtain semiconductor wafer B;
[0030] S3: Perform radio frequency plasma deposition on semiconductor wafer B by introducing a mixed gas, wherein the mixed gas is SiH4 / NH3 / He mixed in a volume ratio of 1.6:1.1:5.5, the pressure is 60Pa, the power is 210W, and the deposition rate is 0.55nm / s to obtain semiconductor wafer C.
[0031] S4: The semiconductor wafer C is then treated with methane plasma containing 4% methylsilane by volume, with a pulse bias of -500V, a deposition temperature of 140℃, and a treatment time of 10min to obtain the semiconductor wafer.
[0032] Example 2
[0033] A surface strengthening process for semiconductor wafers, the specific steps of which are as follows:
[0034] S1: The organic contaminants on the surface of the semiconductor wafer were removed by ultrasonic cleaning with ozone water at a concentration of 60 ppm. The ultrasonic power was 80 W and the frequency was 26 kHz. Then, the surface of the semiconductor wafer was purged with high-purity nitrogen at a rate of 3.0 L / min for 15 s to obtain semiconductor wafer A.
[0035] S2: Semiconductor wafer A is placed in a vacuum chamber for laser processing. A 248nm KrF excimer laser is used for laser processing, and the pressure in the vacuum chamber is ≤10. -3 Pa, energy density 0.5 J / cm³ 2 The semiconductor wafer B was obtained by scanning at a speed of 30 mm / s and an overlap rate of 20%.
[0036] S3: Perform radio frequency plasma deposition on semiconductor wafer B by introducing a mixed gas, wherein the mixed gas is SiH4 / NH3 / He mixed in a volume ratio of 1.5:1:5, the pressure is 50Pa, the power is 200W, and the deposition rate is 0.5nm / s to obtain semiconductor wafer C.
[0037] S4: The semiconductor wafer C is then treated with methane plasma containing 3% methylsilane by volume, with a pulse bias of -500V, a deposition temperature of 130℃, and a treatment time of 8min to obtain the semiconductor wafer.
[0038] Example 3
[0039] A surface strengthening process for semiconductor wafers, the specific steps of which are as follows:
[0040] S1: The organic contaminants on the surface of the semiconductor wafer were removed by ultrasonic cleaning with ozone water at a concentration of 80 ppm. The ultrasonic power was 100 W and the frequency was 30 kHz. Then, the surface of the semiconductor wafer was purged with high-purity nitrogen at a rate of 4.0 L / min for 30 s to obtain semiconductor wafer A.
[0041] S2: Semiconductor wafer A is placed in a vacuum chamber for laser processing. A 248nm KrF excimer laser is used for laser processing, and the pressure in the vacuum chamber is ≤10. -3 Pa, energy density 1.2 J / cm³ 2 The semiconductor wafer B was obtained by scanning at a speed of 50 mm / s and an overlap rate of 20%.
[0042] S3: Perform radio frequency plasma deposition on semiconductor wafer B by introducing a mixed gas, wherein the mixed gas is SiH4 / NH3 / He mixed in a volume ratio of 1.8:1.2:6, the pressure is 70Pa, the power is 220W, and the deposition rate is 0.6nm / s to obtain semiconductor wafer C.
[0043] S4: The semiconductor wafer C is then treated with methane plasma containing 5% methylsilane by volume, with a pulse bias of -500V, a deposition temperature of 150℃, and a treatment time of 12min to obtain the semiconductor wafer.
[0044] Comparative Example 1
[0045] Without the ozone cleaning step in S1, the remaining steps are the same as in Example 1.
[0046] Comparative Example 2
[0047] In S1, the ozone concentration is reduced to 40 ppm, and the remaining steps are the same as in Example 1.
[0048] Comparative Example 3
[0049] The laser energy density in S2 is 0.3 J / cm². 2 The scanning speed was 50 mm / s, and the remaining steps were the same as in Example 1.
[0050] Comparative Example 4
[0051] In S3, no methylsilane is added to the methane plasma, and the remaining steps are the same as in Example 1.
[0052] Comparative Example 5
[0053] Without step S2, the remaining steps are the same as in Example 1.
[0054] Performance testing
[0055] The hardness of the semiconductor wafers prepared in the examples and comparative examples was measured using nanoindentation. An indenter was pressed into the material surface under a very small load, and the hardness value was calculated using the formula H = P. max / A, where P max The maximum load is given by A, the contact area by H, and the hardness value by H. Semiconductor wafers were cut into 1cm × 1cm samples. A fused silica calibrated nanoindenter was used to ensure accurate indenter area function. The loading rate was set to 0.5 mN / s, the holding time to 10 s, and the unloading rate to 1 mN / s.
[0056] Hardness (GPa) Example 1 11.7 Example 2 11.4 Example 3 10.9 Comparative Example 1 8.5 Comparative Example 2 9.3 Comparative Example 3 7.8 Comparative Example 4 8.9 Comparative Example 5 10.4
[0057] As can be seen from the examples and comparative data, the semiconductor wafers obtained by the surface strengthening method of the present invention have good hardness.
[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.
Claims
1. A surface strengthening process for semiconductor wafers, characterized in that, The specific steps of the surface strengthening treatment process are as follows: S1: Ozone water ultrasonic cleaning is used to remove organic contaminants from the surface of the semiconductor wafer, and then high-purity nitrogen gas is used to purge the surface of the semiconductor wafer to obtain semiconductor wafer A; S2: Semiconductor wafer A is placed in a vacuum chamber and non-thermally fusible surface treatment is achieved using an excimer laser with an energy density of 0.5–1.2 J / cm². 2 The scanning speed is 30-50 mm / s, and the overlap rate is 20%, to obtain semiconductor wafer B; S3: Perform radio frequency plasma deposition on semiconductor wafer B, introduce a mixed gas at a pressure of 50-70 Pa and a power of 200-220 W, to obtain semiconductor wafer C; S4: The semiconductor wafer C is then treated with methane plasma containing methylsilane, and the pulse bias voltage is -500V to obtain the semiconductor wafer. The mixed gas in S3 is SiH4 / NH3 / He mixed in a volume ratio of (1.5~1.8):(1~1.2):(5~6); The methane plasma in S4 contains 3-5% methylsilane by volume. The methane plasma deposition temperature in S4 is 130–150°C, and the processing time is 8–12 min.
2. The surface strengthening process for a semiconductor wafer according to claim 1, characterized in that, The concentration of ozone water in S1 is 60-80 ppm.
3. The surface strengthening process for a semiconductor wafer according to claim 1, characterized in that, The ultrasonic power in S1 is 80-100W, and the frequency is 26-30kHz.
4. The surface strengthening process for a semiconductor wafer according to claim 1, characterized in that, The nitrogen purging rate in S1 is 3.0–4.0 L / min, and the nitrogen purging time is 15–30 s.
5. The surface strengthening process for a semiconductor wafer according to claim 1, characterized in that, The pressure in the vacuum cavity of S2 is ≤10. -3 Pa.
6. The surface strengthening process for a semiconductor wafer according to claim 1, characterized in that, The laser processing in S2 uses a 248nm KrF excimer laser.
7. The surface strengthening process for a semiconductor wafer according to claim 1, characterized in that, The radio frequency plasma deposition rate in S3 is 0.5–0.6 nm / s.