A cleaning method and apparatus for controlling the thickness of etch by-product deposition on a quartz lid

Abstract

This invention discloses a cleaning method and apparatus for controlling the deposition thickness of etching byproducts on a quartz cap. The quartz cap has a double-layer structure, with a conductive mesh disposed between the two layers. The conductive mesh is closer to the process chamber and is connected to a DC power supply. In cleaning mode, a bias voltage is set by the DC power supply to activate plasma, attracting ions to react with the byproducts for etching. This effectively reduces the deposition thickness of byproducts in the reaction chamber, especially on the quartz cap, and avoids process fluctuations caused by byproduct accumulation.

Description

Technical Field

[0001] This invention relates to the field of semiconductor etching technology, and more specifically to a cleaning method and apparatus for controlling the deposition thickness of etching byproducts on a quartz cap. Background Technology

[0002] In existing semiconductor etching equipment, during normal etching processes, the main RF power supply feeds energy into the process cavity to excite plasma, and then the lower RF power supply feeds energy for etching. In this case, etching byproducts are continuously deposited on the quartz cover side facing the process cavity. The deposited byproducts reduce the main RF power feed efficiency, causing changes in etching performance. On the other hand, the deposition of etching byproducts is non-uniform and non-dense. When process conditions change, byproducts may fall onto the substrate surface, causing microscopic defects. This situation is more likely to occur when the byproducts are thicker.

[0003] CN109585247A discloses a plasma processing apparatus, comprising: a processing chamber including a lower electrode arranged below an upper surface of an electrostatic chuck and located between a plurality of sidewalls of the processing chamber, wherein the upper surface of the electrostatic chuck is configured to receive a workpiece; a first radio frequency power generator electrically connected to a radio frequency antenna; a sidewall voltage generator electrically connected to a sidewall electrode; and a second radio frequency power generator electrically connected to the lower electrode. A cleaning method of the plasma processing apparatus includes introducing a processing gas into a processing chamber, wherein the processing chamber has a byproduct along a plurality of sidewalls of the processing chamber; generating a plasma from the processing gas using a radio frequency (RF) signal; connecting a lower electrode disposed within the sidewalls of the processing chamber to a first potential; simultaneously applying a bias voltage having a second potential to a sidewall electrode to induce ion bombardment of the byproduct, wherein the value of the second potential is greater than the value of the first potential; and discharging the processing gas from the processing chamber.

[0004] CN101996840B discloses a plasma processing device, which includes a process chamber, an upper electrode, a lower electrode, and a liner disposed inside the process chamber and surrounding the inner wall of the chamber. The upper electrode is connected to an upper electrode radio frequency power supply to obtain radio frequency power, and the lower electrode is connected to a lower electrode radio frequency power supply to obtain radio frequency power. The process chamber is a double-layer structure including an inner wall and a liner. The liner is connected to a liner radio frequency power supply capable of providing radio frequency power to it. Under the action of the radio frequency power, the liner generates a radio frequency bias voltage to attract plasma to bombard reaction byproducts on the liner. The chamber cleaning method includes the following steps: 10) providing the liner with a liner radio frequency power supply capable of providing radio frequency power to it; 20) exciting the process gas injected into the chamber into plasma by means of the radio frequency power loaded by the upper electrode radio frequency power supply and / or the lower electrode radio frequency power supply; 30) performing plasma processing / treatment on the workpiece to be processed by means of the plasma formed by the process gas; at the same time, guiding the plasma to appropriately bombard the liner by loading radio frequency power to the liner through the liner radio frequency power supply to remove the reaction byproducts deposited on the liner of the process chamber.

[0005] Both of the above-mentioned existing technologies are for cleaning sidewall byproducts.

[0006] Existing inductively coupled plasma (ICP) etching machines work by feeding energy into the process cavity via a planar coil above the cavity, followed by etching using a bias voltage generated by a lower radio frequency (RF). During etching, the self-bias voltage of the RF causes etching on the substrate surface. Most byproducts deposit above the process cavity, with a smaller portion depositing on the sidewalls and liner. Because the sidewalls and liner have a floating potential relative to the plasma, their deposition rate is very slow, resulting in a smaller amount of byproducts. Furthermore, the location of these byproducts significantly affects the process. When byproducts are on the sidewalls, their impact on the process primarily affects the cleanliness of the process cavity. When byproducts are located above the process cavity, they not only affect the cleanliness of the process cavity but also the efficiency of plasma energy feeding from the upper RF coil into the process cavity. This means that the byproducts above have a greater impact on the process. At the same time, since the coil energy is fed from above, cleaning the byproducts above under these circumstances is more difficult. The cleaning solution given in the literature is to apply the lower RF to the sidewall or liner. This is because the sidewall and liner are metal and can be applied directly. However, since the upper part of the process cavity requires RF energy feeding, a metal window cannot be used. Generally, quartz material is used, so the lower RF cannot be applied directly.

[0007] This shows that current ICP equipment cannot effectively remove byproducts deposited on quartz caps. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by providing a cleaning method and apparatus for controlling the deposition thickness of etching byproducts on a quartz cap. This apparatus and cleaning method can effectively remove byproducts deposited on the sidewalls of the chamber and the upper quartz cap, effectively avoiding process fluctuations caused by byproduct deposition.

[0009] A first aspect of the present invention provides an apparatus for controlling the deposition thickness of etching byproducts on a quartz cover, comprising a process chamber, an upper electrode, a lower electrode, and a quartz cover disposed above the process chamber. The upper electrode is connected to an upper electrode radio frequency power supply to obtain radio frequency power, and the lower electrode is connected to a lower electrode radio frequency power supply to obtain radio frequency power. The quartz cover has a double-layer structure, and a conductive mesh is disposed between the two layers of the quartz cover. The conductive mesh is closer to the process chamber side and is connected to a DC power supply.

[0010] In a preferred embodiment, the thickness ratio of the upper and lower quartz caps is (7-10):1.

[0011] In a preferred embodiment, the conductive mesh has a size of 1mm×1mm and a light transmittance of >85%; the width of the conductive mesh lines is 30-60μm and the thickness is 100-300nm; preferably, the width is 50μm and the thickness is 200nm.

[0012] In a preferred embodiment, the conductive mesh wires are made of a material with a conductivity >10. 4 The conductive material with a strength of S / m is preferably ITO or Ag.

[0013] In a preferred embodiment, the DC power supply is equipped with a filter and is capable of generating a bias voltage of 50-300 V.

[0014] In one preferred embodiment, a coil is provided on the upper surface of the quartz cover.

[0015] In a preferred embodiment, a laser interferometer is also provided on the outside of the coil of the quartz cover to detect the thickness of the by-product deposition layer.

[0016] A second aspect of the present invention provides a process for etching using the above-described equipment, comprising the following steps: Energy is fed into the process cavity by the upper RF power supply to excite plasma, and then energy is fed into the lower RF power supply for etching. Process; The deposition thickness of by-products in the process chamber is detected. When the preset threshold is reached, the non-open chamber cleaning process is started, including: passing cleaning gas into the process chamber, feeding energy into the process chamber from the upper radio frequency power supply to excite plasma, starting the DC power supply to feed energy into the conductive grid, and forming a bias voltage on the side of the quartz cover near the process chamber, so that the plasma is activated and moves towards the by-products and reacts. The gaseous products after the reaction are discharged from the reaction chamber.

[0017] In a preferred embodiment, the frequency of the RF power supply is 13.56 MHz.

[0018] As a preferred embodiment, the preset threshold ranges from 100 to 300 μm.

[0019] In a preferred embodiment, the cleaning gas is a mixture of SF6 and O2 in a volume ratio of 4:1.

[0020] In a preferred embodiment, the bias voltage is 50-300 V, preferably 200 V.

[0021] The beneficial effects of this invention are: (1) The present invention can effectively reduce the maintenance time of the machine and improve the machine utilization rate; (2) The present invention can control the thickness of by-products, reduce the impact of continuous machine operation on etching effect, and improve etching stability; (3) The present invention enables byproducts to always be in a low deposition thickness state, reducing the impact of byproducts on radio frequency conduction efficiency and improving the effective utilization rate of radio frequency energy; (4) The present invention can effectively reduce the probability of by-products falling off and reduce the micro-proportion of finished products. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device used in an embodiment of the present invention; Among them, 1-upper electrode RF power supply, 2-coil, 3-upper quartz cover, 4-laser interferometer, 5-DC power supply, 6-lower quartz cover, 7-conductive grid, 8-stage, 9-lower electrode RF power supply, 10-process cavity. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1The diagram shown is a schematic representation of the first specific embodiment of the plasma processing device provided by the present invention. The plasma processing device includes a process chamber 10, an upper electrode, a lower electrode, and a quartz cover disposed above the process chamber 10. The upper electrode is connected to an upper electrode radio frequency power supply 1 to obtain main radio frequency power, and the lower electrode is connected to a lower electrode radio frequency power supply 9 to obtain radio frequency power. The quartz cover has a double-layer structure, with a conductive mesh 7 disposed between the two layers of the quartz cover and connected to a DC power supply 5.

[0025] In one specific implementation, the quartz cover is divided into an upper quartz cover 3 and a lower quartz cover 6, with a conductive mesh 7 embedded between the two quartz covers. The thickness ratio of the upper quartz cover 3 to the lower quartz cover 6 is (7-10):1, preferably 8:1, which ensures that the conductive mesh is closer to the process cavity 10 to better activate the plasma to react with the byproducts on the quartz cover.

[0026] In one specific implementation, the conductive mesh has a size of 1mm × 1mm and a light transmittance > 85%; the width of the conductive mesh lines is 30-60μm, preferably 50μm; and the thickness is 100-300nm, preferably 200nm. The conductive mesh material is required to have a conductivity > 10. 4 S / m, preferably ITO or Ag.

[0027] In one specific implementation, when the thickness of the conductive mesh line is about 200 nm, the skin depth of the coil 2 of the upper electrode is about 17.9 μm under the main radio frequency of 13.56 MHz, and the thickness of the conductive mesh 7 is much smaller than the skin depth, this means that the low-frequency magnetic field can penetrate the conductive mesh 7, which is much smaller than its skin depth, with almost no attenuation.

[0028] When the above equipment is in operation, the upper electrode RF power supply 1 excites ICP plasma to perform the etching process. For example, when etching sapphire, a CHF3 / BCl3 mixed gas is used as the working gas. Energy is fed into the process chamber 10 by the upper electrode RF power supply 1 to excite the plasma, and then energy is fed into the lower electrode RF power supply 9 for normal etching. At this time, the thickness of by-products is detected in real time by the laser interferometer 4. When the by-products accumulate to a certain thickness d1, for example, a preset threshold can be specified such as 100μm or 300μm, triggering the start of the cleaning process to clean the process chamber 10 without opening the chamber.

[0029] The cleaning method includes the following steps: (1) Introduce cleaning gas (such as SF6 / O2 ratio of 4:1) into process chamber 10, feed energy into process chamber 10 from upper electrode RF power supply 1 to excite plasma, control chamber pressure to 5-10 Pa, and control plasma sheath thickness to above 1 mm. (2) Energy is fed into the conductive grid 7 by the DC power supply 5 with a filter. A bias voltage is formed on the side of the quartz cover near the process chamber, which activates the plasma and causes it to move towards the byproducts and react with them to generate gaseous products that are then removed. The reaction equation is: Byproduct (AlCl x )+F →AlF3↑+Cl2↑.

[0030] (3) The laser interferometer 4 monitors the thickness of the deposited layer. When the thickness is ≤d2, such as 10μm, the cleaning process will automatically stop. The cleaning process is expected to take 3-5 minutes.

[0031] When the etched product on the stage 8 has very high microscopic requirements, it can be cleaned after each run, and the by-products are cleaned up before the next run.

[0032] This invention can effectively remove byproducts deposited in the process chamber 10, especially on the quartz cap, so that the byproducts are always in a low deposition thickness state, optimize the process fluctuations caused by byproduct accumulation, and improve etching stability.

[0033] In summary, the above embodiments are merely illustrative examples of preferred embodiments of the present invention and do not encompass all aspects of the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention; therefore, the scope of protection of the present invention is defined by the claims.

Claims

1. An apparatus for controlling the deposition thickness of etching byproducts on a quartz cap, comprising a process chamber, an upper electrode, a lower electrode, and a quartz cap disposed above the process chamber, wherein the upper electrode is connected to an upper electrode radio frequency power supply to obtain radio frequency power, and the lower electrode is connected to a lower electrode radio frequency power supply to obtain radio frequency power, characterized in that, The quartz cover has a double-layer structure with a conductive mesh between the two layers. The conductive mesh is closer to the process chamber and is connected to the DC power supply.

2. The device according to claim 1, characterized in that, The thickness ratio of the upper and lower quartz caps is (7-10):

1.

3. The device according to claim 1, characterized in that, The conductive mesh has a size of 1mm×1mm and a light transmittance of >85%; the width of the conductive mesh lines is 30-60μm and the thickness is 100-300nm; preferably, the width is 50μm and the thickness is 200nm.

4. The device according to claim 1, characterized in that, The conductive mesh wire is made of a material with a conductivity >10. 4 The conductive material with a strength of S / m is preferably ITO or Ag.

5. The device according to claim 1, characterized in that, The DC power supply is equipped with a filter and is capable of generating a bias voltage of 50-300 V.

6. The device according to claim 1, characterized in that, A laser interferometer is also provided on the outer side of the upper surface of the quartz cover to detect the thickness of the by-product deposition layer.

7. A process for etching using the apparatus according to any one of claims 1-6, comprising the following steps: Energy is fed into the process cavity by the upper RF power supply to excite plasma, and then energy is fed into the lower RF power supply for etching. Process; The thickness of byproducts deposited within the detection chamber is monitored. Once a preset threshold is reached, a non-open-chamber cleaning process is initiated, including: A cleaning gas is introduced into the process chamber, and energy is fed into the process chamber by the upper radio frequency power supply to excite the plasma. The DC power supply is started to feed energy into the conductive grid. The quartz cover forms a bias voltage on the side close to the process chamber, so that the plasma is activated and moves towards the by-products and reacts. The gaseous products after the reaction are discharged from the reaction chamber.

8. The process according to claim 7, characterized in that, The frequency of the RF power supply is 13.56 MHz.

9. The process according to claim 7, characterized in that, The preset threshold range is 100-300μm; the cleaning gas is a mixture of SF6 and O2 in a volume ratio of 4:

1.

10. The process according to claim 7, characterized in that, The bias voltage is 50-300 V, preferably 200 V.

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