CN106937474B

CN106937474B - Inductively coupled plasma processor

Info

Publication number: CN106937474B
Application number: CN201511012715.XA
Authority: CN
Inventors: 周旭升; 黄智林
Original assignee: Advanced Micro Fabrication Equipment Inc Shanghai
Current assignee: Advanced Micro Fabrication Equipment Inc Shanghai
Priority date: 2015-12-31
Filing date: 2015-12-31
Publication date: 2020-07-31
Anticipated expiration: 2035-12-31
Also published as: CN106937474A

Abstract

An inductively coupled plasma processor, comprising: the side wall of the reaction cavity and an insulating material window positioned above the side wall of the reaction cavity are jointly surrounded to form the reaction cavity, the reaction cavity comprises a base, a substrate to be processed is fixed above the base, and a radio frequency induction device is arranged above the insulating material window; the inductance coil device is communicated to a first radio frequency power supply through a first matcher; the inductance coil device is characterized by comprising a first part and a second part surrounding the first part, wherein a shielding plate is arranged between the inductance coil device and the insulation material window, the shielding plate under the first part of the inductance coil device has a first opening ratio, the shielding plate under the second part of the inductance coil device has a second opening ratio, and the first opening ratio is larger than the second opening ratio.

Description

Inductively coupled plasma processor

Technical Field

The invention relates to the technical field of semiconductor manufacturing, in particular to a Faraday shield plate of an inductively coupled plasma processor.

Background

Plasma processors are widely used in the semiconductor industry for high precision processing of substrates to be processed, such as plasma etching, Chemical Vapor Deposition (CVD), and the like. Some plasma processing processes require high-concentration plasma, for example, silicon etching processes such as deep-hole silicon etching (TSV) are typical, and the depth of a through hole to be etched needs more than 100um, so that only a high-concentration plasma processing cavity can achieve an etching effect with economic value, and an inductively coupled plasma processor has the advantage of high plasma concentration, and is widely applied. Referring to fig. 1, which is a typical structure of an inductively coupled plasma processor, the plasma processor includes a reaction chamber 100, and the chamber 100 includes a base 14 at the bottom, the base 14 being used for supporting a substrate to be processed, and a bottom electrode. A radio frequency power supply 10 supplies a low frequency radio frequency power (2 Mhz) to a radio frequency matcher 12, outputs the low frequency radio frequency power to a base station 14 after impedance matching, and a confinement ring 18 is further arranged around the base station for preventing plasma in a reaction chamber from leaking to an exhaust system below to form pollution. The top of the reaction chamber 100 includes an inlet ring 29 for reactant gas inlet piping and thermal isolation. Above the top of the reaction chamber is included an insulating material window 28, typically made of quartz. The insulating material window 28 may be a circular flat plate as shown in fig. 1 or a dome shape which is upwardly bulged, an inductance coil 24 is disposed above the insulating material window 28, the coil 24 is connected to a high frequency rf matching device 22 through at least two

rf cables

23a, 23b, the high frequency rf matching device receives rf power outputted from a high frequency rf power source 20 (13.56 Mhz), and finally ignites the reaction gas in the reaction chamber 100 for plasma processing. A grounded shield 30 surrounds the inductor coil and directs the rf energy to diffuse into the external space. The shielding case 30 is provided with a plurality of airflow channels to allow the airflow to carry away heat generated by the rf power fed into the inductive coil 24.

Inductively coupled reactors have the advantage of high plasma concentration but also have a number of disadvantages:

1. the plasma concentration is not uniformly distributed, the magnetic field generated by the inductive coil 24 enters the reaction chamber downwards, the strength of the generated induced electric field is determined by the alternating magnetic flux in the region, and the peripheral region surrounds the central region, so the peripheral magnetic flux is far greater than the central region, therefore, the plasma concentration in the peripheral region is higher than that in the central region in the reaction chamber 100, and the corresponding etching speed is also the peripheral high-voltage central region. The etch rate profile shown in fig. 2 shows that the etch rate is significantly higher in the edge region of the substrate than in other portions.

2. The magnetic field generated by the inductor penetrates through the insulating material window 28 and enters the reaction chamber, but the inductor itself as a conductor can also form capacitive coupling with the underlying pedestal 14 and the grounded reaction chamber 100, the capacitive coupling can cause the plasma sheath on the lower surface of the insulating material window 28 to become thicker, and more energetic particles bombard the insulating material window 28, which can cause particles to fall down from the insulating material window 28 to the underlying substrate to cause contamination. So that a faraday shield 25 is provided between the inductor 24 and the window 28 of insulating material in the prior art, as shown in figure 2 of US5540800, the area of the faraday shield 80 is very large, covering all the space between the inductor and the window of insulating material. However, at the instant of plasma ignition, inductively coupled plasma processors actually require the use of the direct electric field generated by capacitive coupling, so that a sufficient area of slot or hole-shaped opening must be provided in the faraday shield to allow the direct electric field to be generated between the inductive coil and the lower electrode. The faraday shield of the resulting inductive coupling coil requires a small area of opening for long term plasma processing, but requires additional opening area for plasma ignition, or increased cost and system complexity, separate means for plasma ignition. The design of the opening area size is an irreconcilable contradiction, and an acceptable numerical range can be found only according to the requirements of an actual processor.

Therefore, there is a need in the art for a new method or apparatus for improving the uniformity of plasma distribution in a reaction chamber to improve the uniformity of plasma processing results while solving the design difficulty of a faraday shield on an inductively coupled plasma processing apparatus.

Disclosure of Invention

The invention solves the problem of reducing particle pollution and simultaneously improving the uniformity of the processing effect of an inductively coupled plasma processing device, and provides an inductively coupled plasma processor, which comprises the following components: the side wall of the reaction cavity and an insulating material window positioned above the side wall of the reaction cavity are jointly surrounded to form the reaction cavity, the reaction cavity comprises a base, a substrate to be processed is fixed above the base, and a radio frequency induction device is arranged above the insulating material window; the inductance coil device is communicated to a first radio frequency power supply through a first matcher; the base is communicated to a second radio frequency power supply through a second matcher; the inductance coil device is characterized by comprising a first part and a second part surrounding the first part, wherein a shielding plate is arranged between the inductance coil device and the insulation material window, the shielding plate under the first part of the inductance coil device has a first opening ratio, the shielding plate under the second part of the inductance coil device has a second opening ratio, and the first opening ratio is larger than the second opening ratio.

The first aperture ratio is larger than 50%, the second aperture ratio is smaller than 10%, and the optimal first aperture ratio reaches 100%, namely, no shielding plate is arranged in the area below the first part of the inductance coil device.

The shielding plate below the second part of the inductance coil device is in a ring shape formed by metal conductors, the shielding plate comprises open grooves which are radially and evenly distributed on the ring, the open grooves divide the ring into conducting strips which are evenly distributed, and the conducting strips are mutually connected and fixed through connecting parts which are positioned on the inner side or the outer side of the ring.

The inductance coil device can be an inductance coil, the inner side lead of the inductance coil forms a first part of the inductance coil device, the outer side lead of the inductance coil forms a second part of the inductance coil device, and the first part and the second part of the inductance coil device are connected in series. The inductor winding arrangement may also be formed by two inductor windings, including a first and a second inductor winding, the first inductor winding forming a first part of the inductor winding arrangement and the second inductor winding forming a second part of the inductor winding arrangement. The first inductance coil and the second inductance coil are connected to the first matcher through cables at two ends of each inductance coil, and the power of a first radio frequency power supply which is introduced into the first inductance coil and the second inductance coil is independently adjustable. The inductively coupled plasma processor operation includes a plasma ignition step and a plasma processing step, wherein the power input by the first inductive coil in the plasma processing step is less than the power input in the plasma ignition step.

An air inlet ring is arranged above the side wall of the reaction cavity and between the insulating material windows and is used for leading reaction gas to enter the reaction cavity from the top of the side wall.

The lower surface of the insulating material window is plated with a plasma corrosion resistant material layer, the plasma corrosion resistant material layer comprises yttrium oxide, the thickness of the plasma corrosion resistant material layer is greater than 50um, and the void ratio is less than 3%.

Drawings

FIG. 1 is a schematic diagram of a prior art inductively coupled plasma processor;

FIG. 2 is a graph of etch rate distribution in a prior art inductively coupled plasma processor;

FIG. 3a is a schematic diagram of an inductively coupled plasma processor of the present invention;

FIG. 3b is a top view of a Faraday shield of the present invention;

FIG. 4 is a graph of etch rate distribution in an inductively coupled plasma processor in accordance with the present invention;

figure 5 is a schematic diagram of a second embodiment of an inductively coupled plasma processor of the present invention.

Detailed Description

Referring to fig. 3a, a schematic diagram of an inductively coupled plasma processor is shown, the basic structure of the present invention is similar to that of the prior art shown in fig. 1, and the main difference is that the faraday shield 26 of the present invention shields only the peripheral portion of the inductive coil. The faraday shield 26 is made of a conductor, which may be a metal such as aluminum, copper, etc., or other good conductor. The annular faraday shield 26 shown in fig. 3b, which is a top view of the faraday shield 26 and includes a plurality of open slots on the inside to isolate the shield conductors from each other and form a complete circular conductor only around the outside, is patterned such that the electric field generated outside the inductor 24 is shielded by the shield 26. If the faraday shield plate is electrically floated, the magnetic field generated by the inductance coil 24 can be partially counteracted, the vertical magnetic field can induce a current loop on the shield plate when passing through the shield plate 26, the current can become heat consumption, and the current can also generate an induced magnetic field, the magnetic fields are opposite to the magnetic field generated by the inductance coil 24, so that the magnetic fields can be counteracted with each other, and the magnetic field intensity fed into the reaction cavity by the magnetic field generated by the inductance coil in the edge area can be finally weakened. When the faraday shield 26 of the present invention is grounded, since the whole shield has the same potential, the induced current cannot be generated and the induced magnetic field having the opposite direction cannot be generated, and the magnetic field fed into the reaction chamber 100 cannot be reduced due to the shielding of the shield 26.

In the process of plasma ignition of the inductively coupled plasma processor of the present invention, firstly, the reaction gas is introduced into the reaction chamber 100 through the gas inlet ring 29, and the reaction gas can also pass through other parts such as the downward nozzle in the middle of the insulating material window. After the reaction gas is introduced, the high-frequency rf power source 20 feeds rf energy into the inductor coil 24 through the matching unit 22, wherein electric field coupling is generated between the internal coil, which is not shielded by the shielding plate 26, and the lower susceptor 14 or the sidewall of the reaction chamber 100, and the high-frequency electric field ignites a local plasma in the reaction chamber. After the plasma is ignited, the electric field induced in the reaction chamber by the magnetic field generated by the inductive coil 24 further ionizes the reaction gas to generate more ions, and a high-concentration plasma is maintained. Since the shielding plate 26 of the present invention only shields the inductive coil located in the peripheral region, the plasma concentration corresponding to the central region in the reaction chamber 100 is slightly increased due to the electric field coupling compared with the prior art without reducing the reaction, and the plasma concentration in the peripheral region in the reaction chamber is shielded due to the electric field generated by the inductive coil, so the plasma concentration is close to the prior art. Therefore, the partial region shielding plate 26 adopting the structure of the invention can reduce the plasma concentration of the edge region relative to the neutral region, and the effect of the invention can just optimize the defect of the inherent uneven concentration distribution of the inductive coupling plasma processor. Meanwhile, because the ignition of the plasma is realized by the inductance coil in the central area, the shielding electric field only needs to be considered in the peripheral area, and a large-area opening is not reserved for ignition, so the opening area on the shielding plate 26 can be smaller than that of the contrast technology, the shielding effect of the electric field is better, and the plasma concentration in the area below the coil 24 is further reduced. As shown in fig. 4, which is a distribution graph of the etching rate after the faraday shield 26 of the present invention is adopted, it can be seen that the etching rate non-uniformity at the edge region (near 100 mm) of the substrate is significantly reduced compared to that shown in fig. 2, and the overall etching rate uniformity is significantly improved.

The induction coil which is not shielded in the inductively coupled plasma processor is positioned in the center or middle area of the insulating material window, correspondingly, the plasma concentration of the center or middle area of the lower surface of the insulating material window in the reaction cavity is far lower than that of the peripheral area because of the natural plasma distribution form of the inductively coupled plasma reactor, and the reaction gas is introduced from the gas inlet ring 29 at the top of the side wall of the reaction cavity, so that the high-concentration plasma and the reaction gas are further determined to be both in the peripheral area, and when reaching the substrate, the peripheral plasma is diffused to the middle area only through long-distance diffusion from top to bottom, and finally the effect of uniform plasma concentration on the surface of the whole substrate is achieved. Therefore, the plasma concentration generated in the central area of the lower surface of the insulating material window is very low, the thickness of the corresponding sheath layer is small, weak bombardment generated by ions can not generate a large amount of particles to fall onto the lower substrate, and the substrate processing quality is ensured.

In the inductively coupled plasma processor, the outer diameter of the inductance coil is larger than that of the substrate to be etched below, so that if the peripheral area of the inductance coil is not shielded by an electric field, electric field lines in the edge area of the substrate are obliquely and upwardly coupled to the periphery of the inductance coil, so that the through hole opening in the edge area of the substrate is inclined in the etching process, further, the next deposition cannot be carried out, and a semiconductor device in the edge area fails. The invention completely shields the area which leads the electric field lines to incline, only keeps the vertically coupled electric field lines, and does not influence the appearance of the etched through hole.

Referring to fig. 5, which shows a second embodiment of the present invention, the inductor coil further comprises a second inductor coil 27 located at the central region in addition to the inductor coil 24, and the inductor coil 27 is connected to the matching unit through two

rf cables

25a and 25b and is supplied with rf power from the rf power source 20. The shield plate 26 is not provided below the second coil 27, and the shield plate 26 shields the lower side of the inductor 24. The current passing through the inductive coil 24 and the second inductive coil 27 can be independently controlled, when the plasma needs to be ignited by capacitive coupling at first, more power is passed through the second coil 27 located at the center, and less power is passed through the inductive coil 24 located at the periphery, and as the power is not shielded by the shielding plate 26, the radio frequency power of the second coil 27 can be completely fed into the lower part to ignite the plasma smoothly. The rf power fed to the second coil 27 may be reduced or even turned off after ignition while the power fed to the inductive coil 24 is increased or maintained to maintain a high concentration of plasma in the lower reaction chamber 100.

To reduce the risk of particle fall due to ion bombardment in the area not shielded by the shielding plate 26, a layer of yttria (Y2O 3) which is a plasma-resistant material may be coated on the lower surface of the insulating material window 28, preferably by the technique described in the chinese patent application 201210421403.4 "gas shower head for plasma processing chamber and coating formation method thereof" that has been filed by the applicant, the thickness of the yttria layer may be greater than 50um, and the porosity is less than 3%. After the plating layer is added on the lower surface of the insulating material window 28, the plating layer is thick and compact in structure, and is not easy to be corroded by plasma, so that particles cannot fall off even if a small amount of ions are accelerated and bombarded on the plating layer.

In the first embodiment shown in fig. 3a and the second embodiment shown in fig. 5, the shielding plate is not disposed below the central region of the inductor device, and the shielding plate 26 is disposed in the peripheral region, but according to the principles of the present invention, the shielding plate may be disposed below the central region of the inductor device, but the opening ratio (opening area/(opening area + shielding area)) of the shielding plate in the central region is much larger than that of the shielding plate 26 in the peripheral region, and the two may be independent from each other or integrated into one body. For example, the aperture ratio of the shielding plate in the central region is greater than 50%, and the aperture ratio in the peripheral region is less than 10%, so that the smooth ignition of plasma in the initial stage can be ensured, and the uniformity of the distribution of the plasma below the plasma in the subsequent treatment process can be adjusted.

The invention comprehensively applies the gas inlet structure, the arrangement of the inductance coil and the design of the peripheral Faraday shielding ring, can ensure the reliability of plasma ignition, improve the uniformity of the whole plasma distribution and the appearance of etching holes in the edge area of the substrate, and simultaneously can not increase the generation of particles on an insulating material window, thereby realizing the aim of the invention by using a simple structure and obtaining remarkable effect.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An inductively coupled plasma processor, comprising: the side wall of the reaction cavity and an insulating material window positioned above the side wall of the reaction cavity are jointly surrounded to form the reaction cavity, the reaction cavity comprises a base, a substrate to be processed is fixed above the base, and an inductance coil device is arranged above the insulating material window;

the inductance coil device is communicated to a first radio frequency power supply through a first matcher;

the base is communicated to a second radio frequency power supply through a second matcher;

its characterized in that the inductance coil device includes the first portion and centers on the second part of first portion, wherein including a shield plate between inductance coil device and the insulating material window, the shield plate that corresponds the below at inductance coil device first portion has first aperture opening rate, and the shield plate that corresponds the below at inductance coil device second portion has the second aperture opening rate, and wherein first aperture opening rate is 100%, and the second aperture opening rate is less than 10%, the shield plate is including being a plurality of open slot that the direction of radiation was arranged, a plurality of the open slot separates the shield plate for the polylith conducting strip, the polylith conducting strip is fixed through the connecting portion interconnect that is located the shield plate outside.

2. The inductively coupled plasma processor of claim 1 wherein the inductive coil device is an inductive coil, the inner conductive wire of the inductive coil device forming a first portion of the inductive coil device and the outer conductive wire of the inductive coil device forming a second portion of the inductive coil device, wherein the first portion and the second portion of the inductive coil device are connected in series with each other.

3. The inductively coupled plasma processor of claim 1 wherein the inductive coil arrangement is two inductive coils, including a first inductive coil and a second inductive coil, the first inductive coil forming a first portion of the inductive coil arrangement and the second inductive coil forming a second portion of the inductive coil arrangement.

4. The inductively coupled plasma processor of claim 3 wherein the first inductive coil and the second inductive coil are connected to the first matcher by cables at each end, and wherein the power from the first RF power source to the first inductive coil and the second inductive coil is independently adjustable.

5. The inductively coupled plasma processor of claim 4 wherein the inductively coupled plasma processor operation includes a plasma ignition step and a plasma processing step, wherein the power input by the first inductive coil during the plasma processing step is less than the power input during the plasma ignition step.

6. The inductively coupled plasma processor of claim 1 further comprising an inlet ring above the sidewall of the reaction chamber and between the windows of insulating material for introducing reactant gas into the reaction chamber from the top of the sidewall.

7. The inductively coupled plasma processor of claim 1 wherein the lower surface of the dielectric window is coated with a layer of plasma resistant material comprising yttria, the plasma resistant material having a thickness greater than 50um and a porosity less than 3%.