Particle control method of PVD (Physical Vapor Deposition) carbon film equipment

Abstract

The invention provides a particle control method of PVD (Physical Vapor Deposition) carbon film equipment. The particle control method comprises the following steps: S1, sputtering a carbon film on a substrate; s2, forming a silicon carbide passivation layer on the surface of the target material; s3, the carbon film particles react with oxygen and are removed; s4, the surface state of the target material is recovered to the initial state; and S5, repeating the steps S1 to S4. According to the method, after the carbon film is formed on the substrate through sputtering, the silicon carbide passivation layer is formed on the surface of the target material, so that when oxygen reacts with carbon particles in plasma, the carbon target cannot react and is consumed, the consumption of the target surface can be effectively reduced, and if the passivation layer does not exist, the surface of the target is not damaged. And the target surface is consumed when oxygen is subsequently introduced to react with the carbon particles. According to the particle control method, the carbon particles gradually accumulated in the vacuum cavity in the carbon film sputtering process in the cavity can be remarkably reduced.

Description

Technical Field

[0001] The present invention relates to a particle control method, and particularly to a particle control method for a PVD carbon film device. Background Art

[0002] In the SiC device process, due to the low diffusion coefficient of impurities, ion implantation technology is the key process for doping. In order to activate the implanted dopants and eliminate the damage defects caused by the implantation process, it is necessary to perform activation annealing on SiC at high temperature. For the SiC lattice with high bond energy, annealing at a temperature above 1600 °C is required to obtain a certain degree of electrical activation. However, at such a high activation annealing temperature, Si is easily sublimated from the SiC surface and redeposited on the wafer surface in the forms of Si, Si2C, SiC2, etc., forming step clusters, resulting in an increase in surface roughness. In order to protect the surface during high-temperature annealing, it is necessary to perform a surface protection treatment before annealing, such as covering a carbon film on the surface. It has been found that the carbon film can successfully inhibit the roughening of the surface.

[0003] Physical vapor deposition is an important method for preparing carbon films, and magnetron sputtering is one of the most commonly used methods. The advantages of preparing carbon films by physical vapor deposition methods are fast film formation speed and good adhesion, but the particle size performance is poor. After continuous sputtering of multiple wafers, as carbon particles gradually accumulate, a large number of particles in the vacuum sputtering atmosphere will cause a significant increase in the surface roughness of the SiC wafer during subsequent high-temperature annealing, thereby seriously affecting the device performance.

[0004] In the prior art, in order to improve the particle stability in the PVD equipment cavity, Chinese Patent No. CN201910937932.1 discloses a device for improving the particle stability in the reaction cavity of a PVD equipment. By installing a fan outside the reaction cavity of the PVD equipment and a fan control system, the temperature data information of different parts of the bell-shaped cover body is transmitted to the controller in real time. After the controller analyzes and processes the temperature data information, it adjusts the rotation speed of the fan in real time to adjust the heat dissipation effect of the fan on the bell-shaped cover body. Although the particle performance in the cavity environment can be improved by controlling the temperature in the cavity to an ideal temperature, this way of controlling the cavity temperature can only make the residual particles adhere to the shielding member without being affected by temperature and resulting in poor adhesion, and cannot fundamentally reduce the number and size of particles. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art and provide a particle control method for a PVD carbon film device. The particle control method of the present invention can significantly reduce the carbon particles gradually accumulating in the vacuum cavity during the sputtering of the carbon film in the cavity. Among them, the preparation of the target surface passivation layer can effectively reduce the consumption of the target surface. Without the passivation layer, introducing oxygen in the subsequent steps will also consume the target surface.

[0006] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is: a method for controlling particles of a PVD carbon film device, comprising the following steps: Step S1, sputtering a carbon film: Transfer the substrate to the stage in the vacuum sputtering cavity, and use a DC magnetron sputtering target to form a carbon film on the substrate, and then remove the substrate from the vacuum sputtering cavity; Step S2, forming a silicon carbide passivation layer: Transfer an undoped pure silicon wafer to the stage, apply a radio frequency power P0 with a certain frequency to the stage, and silicon atoms are gradually etched out. At the same time, input a DC power P1 to the target, so that silicon atoms combine with carbon atoms sputtered by DC, and the sputtering time is recorded as t1. After sputtering, a layer of silicon carbide passivation layer is formed on the surface of the target; Step S3, reacting carbon film particles with oxygen and removing them: Keep the radio frequency power and frequency applied to the stage unchanged, introduce oxygen to fully react with the carbon particles in the cavity to form carbon dioxide gas, which is then pumped away; Step S4, restoring the surface state of the target: Input an asymmetric bipolar pulse power P2 to the target, and P2≥P1, and the sputtering time t2=t1, to remove the passivation layer on the surface of the target, and the state of the target is restored to the initial state again; Step S5, repeat steps S1 - S4.

[0007] Further, in step S1, the target is a carbon target with a diameter of 320 - 321 mm, and the distance between the target and the stage is 40 - 60 mm.

[0008] Further, in step S1, first pre-sputter the target for 1 - 3 min, set the substrate temperature to 25 - 200 °C during pre-sputtering, and keep the vacuum degree of the vacuum sputtering cavity at 1.0×10 -8 -5.0×10 -8 Torr, and the sputtering power is 500 - 1000 W; Then, introduce argon with a flow rate of 15 - 30 sccm into the vacuum sputtering cavity until the pressure of the vacuum sputtering cavity is 1.0 - 2.1 mTorr, sputter the target for 6 - 10 min, and the sputtering power is 1000 - 3000 W.

[0009] Further, in step S2, transfer an undoped pure silicon wafer to the stage, introduce argon with a flow rate of 30 - 60 sccm, the reaction pressure in the cavity is 2.2 - 4.4 mTorr, apply a radio frequency power of 2 - 27.12 MHz to the stage, the power P0 = 100 - 1000 W, and at the same time input a DC power of P1 = 50 - 200 W to the target, and the time t1 is maintained for 10 - 30 s.

[0010] Further, in step S3, a radio frequency power of 2 - 27.12 MHz is applied to the stage, with the power P0 = 100 - 1000 W, the input power of the target being zero. Oxygen with a flow rate of 80 - 100 sccm is introduced into the vacuum chamber, the opening degree of the pump gate valve is adjusted to 50% - 80%, the chamber pressure is 20 - 40 mTorr, and the reaction time is 5 - 10 min, so that oxygen fully reacts with the carbon particles in the chamber to form carbon dioxide gas, which is then pumped away by the pump.

[0011] Further, in step S4, argon with a flow rate of 30 - 60 sccm is introduced, the reaction pressure of the vacuum chamber is 2.2 - 4.4 mTorr, an asymmetric bipolar pulse with an input power P2 = 50 - 200 W is applied to the target, the pulse frequency is 100 - 350 kHz, the duty cycle is 50% - 60%, and the pulse sputtering time t2 is 10 - 30 s.

[0012] The beneficial effects brought by the technical solution provided by the embodiment of the present invention are as follows: After a carbon film is sputtered on the substrate in the present invention, a silicon carbide passivation layer is formed on the surface of the target. This enables the carbon target itself not to react and be consumed when oxygen reacts with carbon particles in the plasma. It can effectively reduce the consumption of the target surface. Without the passivation layer, the target surface would also be consumed when oxygen is introduced later to react with carbon particles. The particle control method of the present invention can significantly reduce the carbon particles gradually accumulated in the vacuum chamber during the process of sputtering the carbon film. Specific Embodiments

[0013] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0014] Embodiment 1 A particle control method for a PVD carbon film device includes the following steps: Step S1, sputtering a carbon thin film: Based on the SJI - SEMI Depomerits P188 Pro PVD device, a carbon target with a purity of 99.998% is selected, the diameter of the target is 320 mm, and the distance between the target and the wafer stage is 50 mm; First, the wafer temperature is set to 25 °C, the chamber base vacuum is maintained at 1.0×10 -8 Torr, a sputtering power of 500 W is used, and the target is pre - sputtered for 3 min; Next, transfer the wafer into the DC magnetron sputtering vacuum chamber, introduce argon gas with a flow rate of 15 sccm, set the chamber reaction pressure to 1.1 mTorr, the target input power to 1500 W, and the sputtering time to 8 min. After depositing the carbon film, transfer the wafer out of the vacuum chamber.

[0015] Step S2, form a silicon carbide passivation layer: Transfer the undoped pure silicon wafer onto the stage, introduce argon gas with a flow rate of 30 sccm, set the chamber reaction pressure to 2.2 mTorr, apply a radio frequency power with a frequency of 13.56 MHz to the stage, with a power of 500 W, and at the same time input a DC current of 100 W to the target. Maintain for 30 s, so that silicon atoms combine with carbon atoms on the target surface to form a silicon carbide passivation layer on the target surface.

[0016] Step S3, react carbon film particles with oxygen: Keep the radio frequency power and frequency applied to the stage the same as in Step S2, set the target input power to zero, introduce oxygen gas with a flow rate of 90 sccm into the vacuum chamber, adjust the opening of the pump throttle valve to 50%, set the chamber pressure to 40 mTorr, and maintain the reaction time for 10 min, so that oxygen fully reacts with the carbon particles in the chamber to form carbon dioxide gas, which is then pumped away by the pump.

[0017] Step S4, restore the surface state of the target: Introduce argon gas with a flow rate of 30 sccm, set the chamber reaction pressure to 2.2 mTorr, apply an asymmetric bipolar pulse with an input power of 200 W to the carbon target, with a pulse frequency of 250 kHz and a duty cycle of 50%. The pulse sputtering time is 30 s. After sputtering, the target state returns to the initial state.

[0018] Step S5, repeat Steps S1 - S4.

[0019] After Steps S1 - S4 are cycled 100 times, use a KLA plus 50l r-l particle counter to detect the number of particles on the wafer surface after it is transferred out of the vacuum chamber in Step S1. The number of particles of different sizes is shown in Table 1.

[0020] When the carbon target has been used up to 500 kW·h, use a Jiangfeng Electronics CMM three-coordinate detector to scan the maximum sputtering depth of the target surface, denoted as L1, and measure L1 = 6.02 mm.

[0021] Comparative Example 1 A particle control method for a PVD carbon film device, including the following steps: Step S1, sputter a carbon thin film: Based on the SJI-SEMI Depomerits P188 Pro PVD device, select a carbon target with a target purity of 99.998%, a target diameter of 320 mm, and a distance of 50 mm between the target and the wafer stage; First, set the wafer temperature to 25 °C, keep the background vacuum degree of the cavity at 1.0×10 -8 Torr, use a sputtering power of 500 W, and pre-sputter the target for 3 min; Next, transfer the wafer to the DC magnetron sputtering vacuum cavity, introduce argon gas with a flow rate of 15 sccm, the reaction pressure of the cavity is 1.1 mTorr, the input power of the target is 1500 W, the sputtering time is 8 min, and after the carbon film is prepared, transfer the wafer out of the vacuum cavity.

[0022] Step S2: React carbon film particles with oxygen: Apply a radio frequency power of 13.56 MHz to the stage, the power magnitude is 500 W, the input power of the target is zero, introduce oxygen with a flow rate of 90 sccm into the vacuum cavity, adjust the opening of the pump gate valve to 50%, the cavity pressure is 40 mTorr, and keep the reaction time for 10 min to make oxygen fully react with the carbon particles in the cavity to form carbon dioxide gas and be pumped away by the pump.

[0023] Step S3: Repeat steps S1 - S2.

[0024] After steps S1 to S2 are cycled 100 times, use a KLA plus 50l r-l particle analyzer to detect the number of particles present on the wafer surface after being transferred out of the vacuum cavity in step S1. The number of particles of different sizes is shown in Table 1.

[0025] When the carbon target is used up to 500 kW·h, use a Jiangfeng Electronics CMM three-coordinate detector to scan the maximum sputtering depth of the target surface, denoted as L1, and measure L1 = 5.09 mm.

[0026] Comparative Example 2 A particle control method for a PVD carbon film device, comprising the following steps: Step S1: Sputter a carbon thin film: Based on the SJI-SEMI Depomerits P188 Pro PVD device, select a carbon target with a target purity of 99.998%, a target diameter of 320 mm, and a distance of 50 mm between the target and the wafer stage; First, set the substrate temperature to 25 °C, keep the background vacuum degree of the cavity at 1.0×10 -8 Torr, use a sputtering power of 500 W, and pre-sputter the target for 3 min; Next, transfer the wafer to the DC magnetron sputtering vacuum cavity, introduce argon gas with a flow rate of 15 sccm, the reaction pressure of the cavity is 1.1 mTorr, the input power of the target is 1500 W, the sputtering time is 8 min, and after the carbon film is prepared, transfer the wafer out of the vacuum cavity.

[0027] Step S2: Repeat step S1.

[0028] After step S1 loops 100 times, use a KLA plus 50l r-l particle analyzer to detect the number of particles present on the surface after being transferred outside the vacuum chamber in step S1. The number of particles of different sizes is shown in Table 1.

[0029] Table 1 Number of surface particles when the 101st wafer is coated

[0030] As can be seen from Table 1, the total number of particles with a particle size > 3μm on the surface of the wafers after coating 100 times in Example 1 and Comparative Example 1 are 15 and 25 respectively, which are significantly lower than 304 in Comparative Example 2; the total number of particles with a size ≤ 3μm on the surface of the wafers after coating 100 times in Example 1 and Comparative Example 1 are 25 and 628 respectively, which are significantly lower than 1799 in Comparative Example 2. This shows that in Example 1, carbon particles can be removed by the reaction of oxygen with oxygen in the plasma in step S2. That is, after one complete coating and particle removal step, the number of carbon particles of different sizes in the chamber is greatly reduced.

[0031] Table 2 Condition of the carbon target surface after sputtering 500 kW·h

[0032] As can be seen from Table 2, the total thickness of the carbon target is 9 mm. When sputtering 500 kW·h in the same way, the thickness of the lowest part of the remaining target material in Example 1 is 6.02 mm, while the thickness of the lowest part of the remaining target material in Comparative Example 1 is 5.09 mm. This shows that in Example 1, by adding a passivation layer to protect the surface of the carbon target, when removing carbon particles in the vacuum chamber through step S3 later, the loss of the target material is greatly reduced and the target material life is significantly extended.

[0033] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A particle control method for a PVD carbon film device, characterized in that, It includes the following steps: Step S1, sputtering a carbon film: Transfer the substrate to the stage in the vacuum sputtering chamber, and use a DC magnetron sputtering target to form a carbon film on the substrate, and then transfer the substrate out of the vacuum sputtering chamber; Step S2, forming a silicon carbide passivation layer: Transfer an undoped pure silicon wafer to the stage, apply a radio frequency power P0 with a certain frequency to the stage, and silicon atoms are gradually etched out. At the same time, input a DC power P1 to the target, so that silicon atoms combine with carbon atoms sputtered by DC, and the sputtering time is recorded as t1. After sputtering, a layer of silicon carbide passivation layer is formed on the surface of the target; Step S3, reacting carbon film particles with oxygen and removing them: Keep the radio frequency power and frequency applied to the stage unchanged, introduce oxygen to fully react with carbon particles in the chamber to form carbon dioxide gas, which is then pumped away; Step S4, restoring the surface state of the target: Input an asymmetric bipolar pulse power P2 to the target, and P2≥P1, the sputtering time t2=t1, to remove the passivation layer on the surface of the target, and the state of the target is restored to the initial state; Step S5, repeat steps S1 - S4.

2. The particle control method of the PVD carbon film equipment according to claim 1, characterized in that In step S1, the target uses a carbon target with a diameter of 320 - 321 mm, and the distance between the target and the stage is 40 - 60 mm.

3. The particle control method of the PVD carbon film equipment according to claim 1, characterized in that, In step S1, the target is pre-sputtered for 1 - 3 minutes first. During pre-sputtering, the substrate temperature is set to 25 - 200 °C, the vacuum degree of the vacuum sputtering chamber is maintained at 1.0×10 -8 - 5.0×10 -8 Torr, and the sputtering power is 500 - 1000 W; Then, introduce argon with a flow rate of 15 - 30 sccm into the vacuum sputtering chamber until the pressure of the vacuum sputtering chamber is 1.0 - 2.1 mTorr, sputter the target for 6 - 10 min, and the sputtering power is 1000 - 3000 W.

4. The particle control method of the PVD carbon film equipment according to claim 1, characterized in that, In step S2, transfer an undoped pure silicon wafer to the stage, introduce argon with a flow rate of 30 - 60 sccm, the reaction pressure in the chamber is 2.2 - 4.4 mTorr, apply a radio frequency power of 2 - 27.12 MHz to the stage, the power P0 = 100 - 1000 W, and at the same time input a DC power of P1 = 50 - 200 W to the target, and the time t1 is maintained for 10 - 30 s.

5. The particle control method of the PVD carbon film equipment according to claim 1, characterized in that, In step S3, apply a radio frequency power of 2 - 27.12 MHz to the stage, the power P0 = 100 - 1000 W, the input power of the target is zero, introduce oxygen with a flow rate of 80 - 100 sccm into the vacuum chamber, adjust the opening of the pump gate valve to 50% - 80%, the chamber pressure is 20 - 40 mTorr, and the reaction time is 5 - 10 min, so that oxygen fully reacts with carbon particles in the chamber to form carbon dioxide gas and is pumped away.

6. The particle control method of the PVD carbon film equipment according to claim 1, characterized in that, In step S4, introduce argon with a flow rate of 30 - 60 sccm, the reaction pressure in the vacuum chamber is 2.2 - 4.4 mTorr, input an asymmetric bipolar pulse with a power of P2 = 50 - 200 W to the target, the pulse frequency is 100 - 350 kHz, the duty cycle is 50% - 60%, and the pulse sputtering time t2 is 10 - 30 s.

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