Background
In a semiconductor manufacturing process, an Inductively Coupled Plasma (ICP) generator can obtain high-density plasma at a low working pressure, and because the ICP generator has the advantages of simple structure, low cost, and independent control of a radio frequency source for generating the plasma and a radio frequency source of a substrate bearing table, the ICP generator is widely applied to processes of plasma etching, physical vapor deposition, plasma chemical vapor deposition, a micro-electro-mechanical system, a light emitting diode and the like.
Fig. 1 is a structural diagram of a conventional ICP apparatus. As shown in fig. 1, the ICP apparatus includes a chamber 1, an insulating cylinder 4 disposed at the top of the chamber 1, and an intake cover plate 5 disposed at the top of the insulating cylinder 4. The radio frequency coil 3 is arranged around the outside of the insulating cylinder 4 and is connected with an upper radio frequency power supply 9 through an upper matcher 8. A susceptor 10 is disposed in the chamber 1 for supporting a substrate, and the susceptor 10 is connected to a lower rf power supply 12 through a lower adapter 11. An intake port 6 is provided in the intake cover 5, and an exhaust port 7 is provided at the bottom of the chamber 1. In addition, a shielding case 2 is covered around the radio frequency coil 3 and the air inlet cover plate 5, and the shielding case 2 is grounded to shield radio frequency.
As shown in fig. 2, the process of performing the precleaning process using the ICP apparatus includes first introducing a process gas (e.g., argon) with a large flow rate into the chamber through the gas inlet 6, and adjusting the exhaust amount of the exhaust port 7 to maintain the pressure in the chamber at 10mT or more; then, the upper rf power supply 9 is turned on, which feeds rf energy into the rf coil 3 through the upper matcher 8, the rf energy penetrates the insulating cylinder 4 in the form of electromagnetic waves, enters the chamber, and excites argon gas, thereby generating plasma. Subsequently, the lower RF power supply 12 is turned on, which feeds RF energy into the susceptor 10 in the chamber through the lower matcher 11 to attract ions in the plasma to move downward, bombarding the surface of the substrate. At which point the priming step is complete. And then, reducing the flow of the process gas, adjusting the exhaust amount of the exhaust port 7 to reduce the pressure in the cavity to be below 1mT (generally 0.5-0.8 mT), starting the process until the process is finished, closing the air inlet 6 when the process is finished, and exhausting residual air in the cavity through the exhaust port 7.
The practical application of the pre-cleaning process by adopting the ICP device inevitably has the following problems:
first, since the pressure in the chamber needs to be maintained at 10mT or more in the glow starting step to introduce seed electrons required for discharging the process gas, normal glow starting is ensured, which results in a short free path of various particles and poor ion directionality, thereby causing a reduction in process uniformity.
Secondly, the substrate is damaged by a higher starting voltage because the starting region under the high-pressure condition is closer to the substrate to be processed.
Thirdly, when the process is carried out, the air pressure in the cavity is a gradually reduced change process so as to ensure the uniformity of the process, but the change of the air pressure is not beneficial to the stability of the whole process, and even the phenomenon of glow breaking can occur.
Fourthly, as a high-voltage glow starting step is required to be carried out independently, the consumed process time is long, and the production efficiency is reduced.
Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art, and provides plasma processing equipment and a pre-cleaning process, which can improve the process uniformity and the process stability, reduce the substrate damage and improve the process efficiency.
To achieve the object of the present invention, a plasma processing apparatus is provided
(filling after claims have been finalized)
The invention has the following beneficial effects:
according to the plasma processing equipment provided by the invention, the seed electrons required by the discharge of the process gas are introduced into the reaction chamber by using the ignition device, so that the normal starting can be realized without using higher chamber pressure, and therefore, the short free path of various particles and the poor ion directionality caused by higher chamber pressure can be avoided, and the process uniformity can be further improved. Meanwhile, high-pressure starting is not needed, so that the process time can be shortened, the process efficiency is improved, and the pressure of the cavity can be more stable in the process of the process, so that the process stability can be improved. In addition, the area of the ignition device for generating the plasma in the reaction chamber is far away from the base, so that the damage to the substrate can be reduced, and the product yield can be improved.
According to the pre-cleaning process provided by the invention, the surface of the substrate is cleaned by adopting the plasma processing equipment provided by the invention, so that the problems of short free path of various particles and poor ion directionality caused by high chamber pressure can be avoided, the process uniformity can be improved, the process time can be shortened, the process efficiency can be improved, and in addition, the chamber pressure can be more stable in the process of carrying out the process, and the process stability can be improved.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the plasma processing apparatus and the precleaning process provided by the present invention will be described in detail below with reference to the accompanying drawings.
Referring to fig. 3 to 4B, the plasma processing apparatus includes a reaction chamber, a rf coil 23, an upper rf source, a lower rf source, an air inlet device, and an ignition device 33, wherein the reaction chamber is defined by a cavity 21, an insulating cylinder 24 disposed at the top of the cavity 21, and an air inlet cover 25 disposed at the top of the insulating cylinder 24. The gas inlet means comprises a gas inlet 26 provided in the gas inlet cover 25 for feeding process gases into the reaction chamber. An exhaust port 27 is provided at the bottom of the chamber 21 for exhausting the exhaust gas. The radio frequency coil 23 is disposed around the outside of the insulating cylinder 26, which is electrically connected to the upper radio frequency source. The upper rf source includes an upper matching unit 28 and an upper rf source 29 for applying rf energy to the rf coil 23, and the rf energy is fed into the reaction chamber through the insulating cylinder 24 to excite the process gas in the reaction chamber to form plasma. In addition, a susceptor 30 for supporting a substrate is provided in the reaction chamber, and the susceptor 30 is electrically connected to the lower rf source. The lower rf source includes a lower matching unit 31 and a lower rf source 32 for applying a negative bias to the susceptor 30, which forms an electric field capable of controlling the movement of the plasma toward the substrate. In addition, a shielding case 22 is covered around the radio frequency coil 23 and the air intake cover 25, and the shielding case 22 is grounded to shield radio frequency.
The ignition device 33 is fixed to the chamber lid 25 by a flange 252 for introducing seed electrons required for discharging the process gas into the interior of the reaction chamber. The seed electrons are first electrons that can excite the process gas to form a plasma in the glow starting stage in order to maintain a normal discharge of the plasma in the process stage. The initial electrons are ionized under the excitation of an external radio frequency electric field to generate self-sustaining discharge plasma, namely, normal starting is realized, the starting process is very short, and the plasma capable of stably discharging is quickly obtained.
As can be seen from the above, the ignition device 33 is used for starting without using a high chamber pressure, so that it is possible to avoid that the free path of various particles is short and the directionality of ions is poor due to the high chamber pressure, and further, the process uniformity can be improved. Meanwhile, high-pressure starting is not needed, so that the process time can be shortened, the process efficiency is improved, and the pressure of the cavity can be more stable in the process of the process, so that the process stability can be improved.
In addition, the area where the ignition device 33 generates plasma in the reaction chamber is located near the gas inlet cover plate 25 and is far away from the base 30, so that the damage to the substrate can be reduced, and the product yield can be improved.
The structure of the ignition device 33 provided in the embodiment of the present invention will be described in detail below. Specifically, as shown in fig. 4A and 4B, the ignition device 33 includes a pair of ignition electrodes 331 and an ignition controller 332, wherein the ignition controller 332 is disposed above the intake cover 25 to control the ignition electrodes 331 to perform pulse discharge. A flange opening 251 is provided in the intake cover plate 25, and the input end (upper end) of the ignition electrode 331 is electrically connected to the ignition controller 332; the output end (lower end) of the ignition electrode passes vertically downward through the flange opening 251 and extends to the interior of the reaction chamber. During the ignition process, the ignition controller 332 applies a pulse voltage to the output terminals of the two ignition electrodes 331, and since the output terminals of the two ignition electrodes 331 are located inside the reaction chamber, a current flows through the process gas inside the reaction chamber, so as to excite the process gas to form a plasma. Ignition controller 332 may be a conventional starter, which is generally composed of a pulse discharge control circuit, such as the circuit shown in fig. 4B.
Preferably, the ignition device 33 further comprises an electrode driving mechanism (not shown) for driving the ignition electrode 331 to move, so that the output end of the ignition electrode 331 moves into or out of the reaction chamber. In the ignition stage, the output end of the ignition electrode 331 can be driven by the electrode driving mechanism to move into the reaction chamber, so as to ignite the plasma. After the ignition is completed, the output end of ignition electrode 331 is driven out of the interior of the reaction chamber by using an electrode driving mechanism to avoid disturbance of the plasma by the portion of ignition electrode 331 located inside the reaction chamber. Of course, in practical applications, even if the ignition electrode 331 disturbs the plasma, it will not affect the normal operation of the process. The electrode driving mechanism can adopt a motor and a corresponding transmission mechanism to drive the ignition electrode 331.
It should be noted that the reaction chamber is not limited to the above structure adopted in this embodiment, and in practical applications, the reaction chamber may also adopt any other structure, and the above ignition device may be fixed on the top chamber wall of the reaction chamber of any structure in a similar or other manner as this embodiment.
It is further noted that the plasma processing apparatus provided by the embodiment of the present invention can be used for performing a precleaning process on the substrate to remove impurities on the surface of the substrate. Alternatively, it can be used for other processes.
It should be noted that, in the present embodiment, the gas inlet device includes the gas inlet 26 disposed on the top of the gas inlet cover plate 25, but the present invention is not limited thereto, and in practical application, the gas inlet device may also adopt any other structure and be disposed at any position of the reaction chamber, as long as the process gas can be delivered into the reaction chamber.
As another technical solution, fig. 5 is a block flow diagram of a precleaning process according to an embodiment of the invention. Referring to fig. 5, a precleaning process is further provided according to an embodiment of the present invention, in which the plasma processing apparatus provided by the embodiment of the present invention is used to clean the surface of the substrate to remove impurities on the surface of the substrate. The pre-cleaning process comprises the following steps:
s1, the gas inlet device (i.e., the gas inlet 26) is opened to supply the process gas into the reaction chamber, and the pressure of the reaction chamber is maintained at a predetermined pressure.
S2, starting the ignition device 33, the upper radio frequency source and the lower radio frequency source according to a preset sequence;
s3, turning off the ignition device 33;
s4, cleaning the surface of the substrate;
s5, closing the upper radio frequency source and the lower radio frequency source;
and S6, closing the air inlet device.
Preferably, the predetermined pressure is less than 10mT in order to avoid affecting process uniformity. Further preferably, the preset pressure is 1 mT.
In the above step S2, the preset sequence may be:
simultaneously turning on the ignition device 33, the upper radio frequency source and the lower radio frequency source; or, the ignition device is started first, and then the upper radio frequency source and the lower radio frequency source are started simultaneously; or the ignition device, the upper radio frequency source and the lower radio frequency source are sequentially started. The ignition device 33 can be used to generate plasma in the reaction chamber in a region far away from the base by sequentially starting the ignition device, the upper radio frequency source and the lower radio frequency source, so that substrate damage can be reduced, and the product yield can be improved.
According to the pre-cleaning process provided by the embodiment of the invention, the surface of the substrate is cleaned by adopting the plasma processing equipment provided by the embodiment of the invention, so that the problems that the free path of various particles is short and the directionality of ions is poor due to high chamber pressure can be avoided, the process uniformity can be improved, the process time can be shortened, the process efficiency can be improved, and in addition, the chamber pressure can be more stable in the process of carrying out the process, so that the process stability can be improved.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.