Semiconductor nitriding equipment cavity cleaning process

Abstract

The invention provides a process for cleaning a cavity of semiconductor nitriding equipment. The process comprises the following steps: step 1, a plasma oxidation process; step 2, plasma nitriding process; step 3, cyclically executing the steps 1-2, wherein the number of cycles N is greater than or equal to 1; 4, the temperature in the cavity is increased, the thermal expansion coefficients of the silicon nitride film and the silicon oxide film are different, and breakage of the composite film is accelerated due to thermal expansion; and step 5, reducing the temperature in the cavity, and stripping the composite film from the cavity due to cold shrinkage. According to the invention, the thermal expansion coefficients of silicon nitride and silicon oxide are different, so that stripping of the cavity can be accelerated to achieve the purpose of cleaning.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing equipment, and in particular relates to a semiconductor nitridation equipment cavity cleaning process. Background Art

[0002] Plasma nitridation of semiconductor thin films is an important process, mainly used to prepare high-performance semiconductor devices. This process uses ammonia or nitrogen to generate plasma under magnetic and electric field induction. The formed nitrogen ions and nitrogen-containing active molecules / atoms diffuse to the pre-formed ultra-thin silicon oxide surface through the surface potential, replacing the position of oxygen in the partially broken silicon-oxygen bonds, and fixing the relatively stable silicon-nitrogen bonds that have been formed in the subsequent thermal annealing step. The plasma nitridation process has the advantages of good process controllability and reproducibility, and the formed SIN (Si3N4) has high nitrogen content and good uniformity, which can meet the high requirements of semiconductor devices for the gate oxide layer.

[0003] However, during plasma nitridation, a layer of nitride film (Si3N4) will be deposited in the cavity. The long process will lead to particle contamination, affecting the yield. The pure silicon nitride film cannot be completely removed after high and low temperature cycle purge, and there will be residues, which will aggravate the particle contamination. How to ensure the cleanliness of the cavity is very important and is the main problem in the existing technology. Summary of the invention

[0004] The purpose of the present invention is to provide a semiconductor nitridation equipment cavity cleaning process, which can accelerate cavity peeling to achieve the purpose of cleaning by utilizing the different thermal expansion coefficients of silicon nitride and silicon oxide. The technical solution adopted is:

[0005] A semiconductor nitridation equipment cavity cleaning process, based on the semiconductor nitridation equipment, includes the following steps:

[0006] Step 1: Plasma oxidation process:

[0007] N is introduced into the cavity where the silicon nitride film is deposited. x O y The gas is excited by the radio frequency coil to form a plasma, and the plasma containing the O radical reacts with the silicon nitride to generate silicon oxide, and the silicon oxide is deposited on the surface of the silicon nitride film; x≥0, y≥1;

[0008] Wherein, by controlling the reaction conditions, part of the silicon nitride reacts with the plasma containing the O radical to form a composite film;

[0009] Step 2: Plasma nitriding process:

[0010] N is introduced into the cavity where the composite film is deposited. a H bThe gas is excited by the radio frequency coil to form a plasma, and the N-based plasma reacts with the silicon oxide in the composite film to generate silicon nitride, and the silicon nitride is deposited on the surface of the silicon oxide film in the composite film; a≥1, b≥0;

[0011] wherein, by controlling the reaction conditions, part of the silicon oxide reacts with the N-based plasma to form a composite film;

[0012] Step 3, loop through steps 1 and 2, with the number of loops N ≥ 1;

[0013] Step 4: Raise the temperature in the cavity. The thermal expansion coefficients of silicon nitride and silicon oxide are different, and the composite film breaks faster due to thermal expansion.

[0014] Step 5: Lower the temperature in the cavity, and the composite film will be peeled off from the cavity due to shrinkage caused by cooling.

[0015] Preferably, O2 is used in step 1, and the reaction conditions in step 1 include:

[0016] Cavity temperature: 300-500℃;

[0017] O2 flow rate: 100-300sccm;

[0018] O2 pressure: greater than 30Pa;

[0019] RF power: less than 500W;

[0020] Plasma excitation time: 30-90s;

[0021] Among them, during the formation process of the silicon nitride film deposited on the cavity, the cavity temperature is: 300-500°C, the process gas flow rate is: 100-300sccm, the process gas pressure is: 10-30Pa, the RF power is: 500-700W, and the plasma excitation time is: 120-180s.

[0022] Preferably, in step 1, the O2 pressure range is 30-50Pa; the RF power pressure range is 300-500W.

[0023] Preferably, NH3 is used in step 2, and the reaction conditions in step 2 include:

[0024] Cavity temperature: 300-500℃;

[0025] NH3 flow rate: 100-300sccm;

[0026] NH3 pressure: 10-30Pa;

[0027] RF power: 500-700W;

[0028] Plasma excitation time: 60-120s.

[0029] Preferably, in step 4, after heating, the cavity temperature is 700-900° C., and the temperature is maintained for 0-1 h.

[0030] Preferably, in step 5, after cooling, the cavity temperature is 100-200°C.

[0031] Preferably, step 5 further comprises the following steps:

[0032] Pass 1000-3000 sccm N2 to purge and then evacuate, repeat M times, M≥10.

[0033] Compared with the prior art, the advantages of the present invention are:

[0034] The silicon nitride film is modified to generate a composite film. Since the thermal expansion coefficients of silicon nitride and silicon oxide in the composite film are different, the peeling of the cavity byproduct (nitride film) is accelerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a process flow chart of the semiconductor nitridation equipment chamber cleaning process of this embodiment.

[0036] Figure 2 This is a general process flow chart for cleaning the chamber of semiconductor nitridation equipment.

[0037] Figure 3 This is a process flow chart for over-cleaning the chamber of semiconductor nitridation equipment. DETAILED DESCRIPTION

[0038] The semiconductor nitridation equipment chamber cleaning process of the present invention will be described in more detail below in conjunction with the schematic diagram, wherein a preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein while still achieving the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art, and not as a limitation of the present invention.

[0039] like Figure 1 , a semiconductor nitridation equipment cavity cleaning process, based on the thermal expansion coefficient of silicon nitride film is 2.8-3.2*10 -6 / K, the thermal expansion coefficient of silicon oxide film is 2.2-2.6*10 -6 / K, the different thermal expansion coefficients of the two can be used.

[0040] 1) Process plasma nitriding

[0041] The process gas is introduced into the chamber. The nitrogen source gas can be but not limited to nitrogen (N2), ammonia (NH3), etc. It is excited by the plasma through the RF coil and diffused to the wafer surface for nitridation. At the same time, a layer of byproduct film (SIN) will also be deposited on the cavity.

[0042] The thin film produced as a byproduct of the process over a long period of time will peel off and produce particle contamination. These particles may adhere to the surface of the wafer and cause the performance and yield of the equipment to decrease.

[0043] Therefore, it is necessary to clean the cavity regularly. The different thermal expansion coefficients of silicon nitride film and silicon oxide film can be used to accelerate cavity peeling to achieve the purpose of cleaning.

[0044] Process plasma nitriding conditions: temperature: 300-500°C, flow rate: 100-300sccm, pressure: 10-30Pa, power: 500-700W, time: 120-180s.

[0045] It is known from the prior art that Figure 1 As shown, the semiconductor nitridation device on which the method is based has a structure as follows:

[0046] The process chamber is a quartz chamber, including a plasma generation space and a wafer processing space. A transfer gate is arranged on the chamber.

[0047] A carrier is arranged at the lower part of the cavity, and the carrier is arranged in the wafer processing space inside the process chamber. A heater is integrally embedded in the carrier to heat the wafer by electricity.

[0048] A resonant RF coil is provided at the upper part of the cavity, and the resonant coil is arranged to surround the outer circumference of the plasma generation chamber. A radio frequency (RF) sensor, a high frequency power supply, and a matcher capable of performing an impedance matching operation or an output frequency matching operation on the high frequency power supply are connected to the resonant coil. Not shown in the figure. The matcher is configured to adjust the impedance of the high frequency power supply or the frequency of the RF power output by the high frequency power supply according to the reflected wave information input by the RF sensor to minimize the reflected wave.

[0049] A process gas through hole is opened at the top of the cavity, and the process gas enters the cavity through the process gas through hole, and forms plasma after being excited by the radio frequency coil. A vacuum through hole is opened at the bottom of the cavity, which is connected to a vacuum pump to control the pressure in the cavity.

[0050] 2) The first cleaning process is plasma oxidation, which modifies the byproduct film deposited on the chamber.

[0051] First, the temperature in the chamber is equal to the process temperature of 300-500°C, and 100-300 sccm of oxygen is introduced. The oxygen source gas can be but is not limited to O2 gas, N2O gas, NO gas, NO2 gas, O3 gas, etc.;

[0052] The pressure is controlled to be greater than 30Pa, preferably 30-50Pa;

[0053] The radio frequency power is less than 500W, preferably 300-500W;

[0054] The plasma is excited for 30-90 seconds to complete the modification of the by-product film.

[0055] Increasing the pressure, reducing the power, and shortening the time are all aimed at suppressing the oxidation ability of the by-product film, ensuring that the by-product film will not be completely oxidized, and making it easier to form a film containing a nitride layer and an oxide layer.

[0056] like Figure 3 If the oxidation process pressure is less than 30Pa or the RF power is greater than 500W or the plasma excitation time is greater than 90s, the silicon nitride film will be completely oxidized. The pure silicon oxide film cannot be completely removed after high and low temperature cycle purge, and there will be residues, and particle contamination will be aggravated afterwards.

[0057] like Figure 1 As shown in the figure, after the first cleaning process, the thickness of the composite film is slightly greater than the thickness of the byproduct film on the cavity. The reasons are as follows:

[0058] O2 dissociates into O* ions and combines with broken Si-Si, Si-N, etc. to form Si-O, Si-ON and other composite films. Due to oxygen injection, the thickness of the composite film is slightly larger than the thickness of the byproduct film on the cavity.

[0059] You can choose to change one condition or combine them to increase pressure, reduce power, or shorten time.

[0060] 3) Cleaning The second step is plasma nitridation, which is to further modify the film after oxidation modification.

[0061] First, the temperature in the chamber is equal to the process temperature of 300-500°C, and 100-300sccm of nitrogen is introduced. The nitrogen source gas can be but is not limited to N2 gas, NH3 gas, etc.

[0062] The pressure is equal to the process pressure 10-30Pa, the RF power is equal to the process power 500-700W, and the plasma is excited for 60-120s to complete the modification of the by-product film.

[0063] The purpose of shortening the time is to suppress the nitridation ability of silicon oxide in the by-product film, to ensure that the by-product film is not completely nitrided, and to more easily form a film including a nitride layer and an oxide layer.

[0064] 4) The cleaning first step plasma oxidation and the cleaning second step plasma nitridation are cycled N times, N≥1.

[0065] The by-product film is modified to form a composite film layer including a nitride layer and an oxide layer.

[0066] 5) Then raise the temperature of the cavity to more than 500°C.

[0067] The preferred temperature is 700-900°C and the temperature is stable for 0-1h. The thermal expansion coefficients of the silicon nitride film and the silicon oxide film are different, so the composite film layer will accelerate fracture due to thermal expansion.

[0068] Then cool the chamber to less than 300°C, preferably 100-200°C, so that the composite film layer will shrink and peel off due to the cold. At the same time, introduce 1000-3000sccmN2 to purge and then evacuate, cycle M times, M≥10, accelerate the peeling of the byproducts in the chamber, and purge the peeled products to achieve the purpose of cleaning.

[0069] like Figure 2 According to a specific example, a pure silicon nitride film cannot be completely removed after high and low temperature cycle purge, and there will be residues, and particle contamination will be aggravated afterwards.

[0070] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A semiconductor nitridation equipment cavity cleaning process, characterized in that: Semiconductor nitride-based devices include the following steps: Step 1: Plasma oxidation process: N is introduced into the cavity where the silicon nitride film is deposited. x O y The gas is excited by the radio frequency coil to form a plasma, and the plasma containing the O radical reacts with the silicon nitride to generate silicon oxide, and the silicon oxide is deposited on the surface of the silicon nitride film; x≥0, y≥1; Wherein, by controlling the reaction conditions, part of the silicon nitride reacts with the plasma containing the O radical to form a composite film; Step 2: Plasma nitriding process: N is introduced into the cavity where the composite film is deposited. a H b The gas is excited by the radio frequency coil to form a plasma, and the N-based plasma reacts with the silicon oxide in the composite film to generate silicon nitride, and the silicon nitride is deposited on the surface of the silicon oxide film in the composite film; a≥1, b≥0; wherein, by controlling the reaction conditions, part of the silicon oxide reacts with the N-based plasma to form a composite film; Step 3, loop through steps 1 and 2, with the number of loops N ≥ 1; Step 4: Raise the temperature in the cavity. The thermal expansion coefficients of silicon nitride and silicon oxide are different, and the composite film breaks faster due to thermal expansion. Step 5: Lower the temperature in the cavity, and the composite film will be peeled off from the cavity due to shrinkage caused by cooling.

2. The semiconductor nitridation equipment chamber cleaning process according to claim 1, characterized in that: O2 is used in step 1, and the reaction conditions in step 1 include: Cavity temperature: 300-500℃; O2 flow rate: 100-300sccm; O2 pressure: greater than 30Pa; RF power: less than 500W; Plasma excitation time: 30-90s; Among them, during the formation process of the silicon nitride film deposited on the cavity, the cavity temperature is: 300-500°C, the process gas flow rate is: 100-300sccm, the process gas pressure is: 10-30Pa, the RF power is: 500-700W, and the plasma excitation time is: 120-180s.

3. The semiconductor nitridation equipment chamber cleaning process according to claim 2, characterized in that: In step 1, the O2 pressure range is 30-50Pa; the RF power pressure range is 300-500W.

4. The semiconductor nitridation equipment chamber cleaning process according to claim 1, characterized in that: NH3 is used in step 2, and the reaction conditions in step 2 include: Cavity temperature: 300-500℃; NH3 flow rate: 100-300sccm; NH3 pressure: 10-30Pa; RF power: 500-700W; Plasma excitation time: 60-120s.

5. The semiconductor nitridation equipment chamber cleaning process according to claim 1, characterized in that: In step 4, after heating, the cavity temperature is 700-900°C, and the temperature is maintained for 0-1h.

6. The semiconductor nitridation equipment chamber cleaning process according to claim 1, characterized in that: In step 5, after cooling, the cavity temperature is 100-200°C.

7. The semiconductor nitridation equipment chamber cleaning process according to claim 1, characterized in that: Step 5 also includes the following steps: Pass 1000-3000 sccm N2 to purge and then evacuate, repeat M times, M≥10.

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