JP2016213407A - Dry etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry etching method which enables the achievement of a superior etching rate and the machining with a high aspect ratio.SOLUTION: A dry etching method comprises the steps of: supplying a gas into a vacuum chamber 2 so that the total amount of the gas supplied per minute becomes 1.0×10cmor more at a static gas pressure in a range of 0.1-1.0 Pa with a mean free path of ions formed in a plasma generation chamber 10 made longer than a sheath thickness; guiding ions to a material to be processed in the vacuum chamber 2; and turning the gas into radicals to etch a target face of the material to be processed with a plasma density in the vicinity of the material to be processed made 10mor more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a dry etching method. Specifically, the present invention relates to a dry etching method capable of realizing an excellent etching rate and capable of processing with a high aspect ratio.

  The use of a stacked integrated circuit (3D-IC) formed by stacking a plurality of chips is attracting attention. In stacked integrated circuits, chips are connected via through silicon vias (TSV: Through Silicon Via), and high integration is possible without depending on the rules of miniaturization so far. In addition, downsizing, high speed, multi-functionality, and power saving can be realized.

  The TSV is formed by forming a TSV through-hole in a silicon wafer, forming a seed layer in the through-hole, and filling copper or the like serving as an electrode by electroplating. By forming the seed layer, it becomes easy to fill the through holes with copper or the like serving as an electrode.

  Here, it is considered that an etching method generally called a Bosch process is advantageous for processing a through hole for TSV. The Bosch process is a dry etching method in which etching of silicon and deposition of a polymer for protecting sidewalls are alternately repeated, and etching with a high aspect ratio is possible.

  In the Bosch process, it is possible to form through-holes with a high aspect ratio by repeating the process of etching the bottom surface of the holes and the protective film forming process for the purpose of protecting the sidewalls of the etching holes in units of several seconds by repeatedly replacing different gases. However, when gas replacement takes a long time, irregularities called scallops are formed on the side wall of the through hole. In the scalloped area, a shadowed part occurs when the through-hole is viewed from the normal direction of the wafer surface, where the seed layer formed by a process such as sputtering is not formed on the side wall of the through-hole, and the electrode material is adhered. Defects may occur. As a result, there is a possibility that voids are generated in the electrode during the plating formation and the quality of the TSV is deteriorated.

  There is also a method of reducing the gas replacement time interval and reducing the scallop, but when forming a hole with a high aspect ratio, the net etching process takes a long time. Therefore, the production efficiency of TSV falls and it is difficult to adopt industrially.

  Further, in the dry etching method that does not perform gas replacement in place of the Bosch process, it has been difficult to obtain etching holes with a high aspect ratio when obtaining a high etching rate.

  Under such circumstances, there exists an etching apparatus that attempts to achieve both a high etching rate and a hole having a high aspect ratio. For example, an etching apparatus described in Patent Document 1 has been proposed.

  Here, the etching apparatus described in Patent Document 1 includes an insulating first chamber provided with a helicon wave type plasma generation unit, and a conductive second chamber. The first chamber and the second chamber communicate with each other through the opening.

  An inert gas is introduced into the first chamber, and the inert gas is turned into plasma by the action of the helicon wave type plasma generator. A reactive gas is introduced into the second chamber, and the reactive gas is excited by plasma electrons in the first chamber to generate active species.

  The active species in the second chamber are drawn to the mounting table side having a negative potential due to the self-bias effect, and are adsorbed on the oxide film of the wafer. Furthermore, ion irradiation of an inert gas is performed along the electric field direction toward the mounting table, and the active species react with the oxide film by ion assist, and chemical etching is promoted in a low-pressure atmosphere.

Japanese Patent Laid-Open No. 6-89880

D. L. Flamm et al .: J. Appl. Phys 52, 3633 (1981)

  However, the etching apparatus described in Patent Document 1 does not provide an etching rate that can achieve the production efficiency necessary for industrially manufacturing TSVs.

  Further, it is considered that there is room for improvement in terms of forming a through hole having a high aspect ratio and excellent anisotropy.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a dry etching method capable of realizing an excellent etching rate and capable of processing with a high aspect ratio.

  Estimating the total amount of radicals, the specification of the plasma source for obtaining the plasma density, the design guideline of the vacuum system for obtaining the total amount of radicals, and the optimum shape of the through-holes, which are the premise of the configuration of the present invention to achieve the above object The conversion will be described below.

  Here, a control guideline of a plasma process for realizing a silicon etching rate of 50 μm / min using a dry etching method to which the present invention is applied will be described.

(1) Estimation of total radical amount As a through hole for TSV necessary for mass production of stacked integrated circuits, a through hole shape having a diameter of 20 μm and a depth of 50 μm is assumed, and it is set to be able to be formed in one minute. The processing speed of conventional dry etching of silicon wafers by fluorine radicals is at most 5.0 μm / min in the Bosch process, and in order to improve this to 50 μm / min, supply of radicals, which is the rate limiting reaction of dry etching, is performed. It is necessary to increase the amount.

The etching rate ER _si of silicon by fluorine radicals is calculated by the following [Equation 1] from the description in Non-Patent Document 1.

When a through-hole shape having a diameter of 20 μm and a depth of 50 μm is processed in one minute, ER _si = 50 μm / min. Further, assuming that the room temperature is 25 ° C. (up to 300 K) and the ion assist effect is 10, the necessary fluorine radical density is expressed by the following [Equation 2]. In addition, about the ion assist effect, the description of the nonpatent literature 1 was referred.

  Considering that the radical generation efficiency from the gas is several tens of percent, assuming that the radical generation efficiency is 65%, the gas density required for one minute to obtain the fluorine radical density of [Formula 2] is It is expressed by the following [Equation 3].

Here, as described in [Equation 3], 10 ¹⁷ cm ^-3 is the gas pressure (p), the molecular number density (n), the absolute temperature (T), and the gas represented by the Boltzmann constant (k). When calculated from the state equation, p = 1 kPa. Here, T to 300K was set. That is, it can be seen that the supply of gas particles of 10 ¹⁷ cm ⁻³ per minute is necessary as a gas supply amount necessary to realize ER _si = 50 μm / min. Further, in consideration of the possibility that the radical generation efficiency does not reach 65%, 10 times the amount of radical equivalent to 10 ¹⁸ cm ⁻³ was supplied per minute as a gas supply with a margin. That is, 10 ¹⁸ cm ¹³ per minute was determined as a necessary gas particle supply amount as a guide for designing an apparatus capable of achieving ER _si = 50 μm / min.

Since the general ionization degree of a capacitively coupled plasma (CCP) system, which is a typical plasma source, is 10 ⁻³ %, the gas particle supply rate is 10 ¹⁸ cm ⁻³ per minute. Considering the case, the plasma density necessary to obtain the fluorine radical density is the value of the following [Equation 4].

  However, in order to obtain the plasma density represented by [Equation 4] by a general CCP method, high output power of 10 kW or more is required, power supply facilities are expensive, and plasma is generated efficiently. Is difficult. Even if plasma can be generated, the steady gas pressure becomes high, an ion scattering phenomenon accompanying collision of ions and neutral particles occurs, and the probability that ions enter the through-hole side wall increases. Similarly, when the steady gas pressure is increased, the probability that radicals are incident on the side wall of the through hole is also increased. That is, it becomes difficult to increase the anisotropy of the through hole processed by etching.

(2) Specifications of plasma source for obtaining high plasma density From the above points, it is necessary to have a plasma generation source that can generate plasma with high density even with a power of several kW and can keep the steady gas pressure low. It becomes. More specifically, a plasma generation method capable of achieving a plasma density of 10 ¹⁸ (m ⁻³ ) and a steady gas pressure of 0.1 to 1.0 Pa that can ensure both the anisotropy of the formed through holes are satisfied. It is necessary to use a plasma source. The range of the stationary gas pressure of 0.1 to 1.0 Pa is a gas pressure obtained from the examination so far, in which ion and radical scattering hardly occur, and the shape of the through hole having a diameter of 20 μm and a depth of 50 μm can be processed. It is a range.

  In addition, when the steady gas pressure is increased to increase the gas supply amount, the mean free path of ions and radicals is shortened, and a scattering phenomenon that facilitates etching of the side wall of the through hole is likely to occur. Formation becomes difficult. Therefore, it is required to reduce the steady gas pressure.

  As a plasma source that satisfies the above conditions depending on the type of plasma source, there is a Helicon Wave Plasma (HWP) method or an Electron Cyclotoron Resonance (ECR) method. These plasma sources can increase the density of plasma in a range where the steady gas pressure is low.

(3) Vacuum system design guidelines for obtaining the total amount of radicals Next, the vacuum system for supplying 10 ¹⁸ cm ^-3 per minute, which is the gas particle supply amount required for 1 minute, into the vacuum vessel as described above. explain. First, there is a gas residence time (τ) as an amount representing the ease of gas flow in the vacuum vessel. Assuming that a gas gas supply amount of 10 ¹⁸ cm ⁻³ (corresponding to filling up to 167 Pa per minute) is obtained at a steady gas pressure of 0.1 Pa per minute, 167 Pa / 0 It can be seen that it is necessary to perform gas replacement in the vacuum vessel 1670 times per second at 1 Pa. That is, the gas residence time τ (sec) is calculated as 1/1670 to 0.5 msec. Here, the gas residence time was calculated by setting the gas particle supply rate to 10 ¹⁸ cm ⁻³ per minute and the steady gas pressure to 0.1 Pa, but the gas supply rate is used to obtain a desired etching rate. It can also be set as a gas equivalent amount (for example, 10 ¹⁷ cm ⁻³ per minute). Similarly, a steady gas pressure can also be set (when obtaining 50 μm / min, the pressure is 1.0 Pa or more). When 10 ¹⁷ cm ⁻³ gas particles are introduced per minute, the steady gas pressure is 1.0 Pa, and the gas residence time τ is calculated, τ (sec) to 60 msec is obtained.

  Subsequently, when the gas pressure p (Pa) and the volume V (L) of the vacuum vessel are given, the flow rate (Q) of the gas introduced to achieve the etching rate of 50 μm / min is considered. The steady gas pressure p (Pa) with respect to the flow rate of the introduced gas is expressed by the following [Equation 5].

  In the above [Equation 5], in the normal case, q is 1/1000 or less of Q and can be almost ignored, and therefore can be approximated as p to Q / S. Here, since the residence time τ (sec) is expressed by the equation τ = V / S, the following [Equation 6] is obtained.

  Here, in order to obtain τ to 0.5 msec, assuming that the steady gas pressure p = 0.1 Pa and the vacuum vessel capacity is V to 0.5 L (a cylindrical vacuum vessel having a diameter of about 80 mm and a height of about 100 mm). The gas flow rate Q (Pa · L / s) to be calculated is Q to 100 (Pa · L / s) from the formula [6]. Further, when converted as 1 Pa · L / s = 0.582 sccm, it is Q to 60 sccm. The gas flow rate Q is an amount determined when the vacuum container capacity is assumed, and is a gas supply amount supplied per unit time required for obtaining an etching rate of 50 μm / min and an etching rate of 50 μm / min. The gas flow rate is not limited as long as it satisfies the use of the plasma source for obtaining the radical generation rate necessary for obtaining the rate.

  The gas flow rate Q introduced above is 60 sccm, which is lower than the value of Q = 100 sccm, which is a typical standard for the amount of gas used in the etching process, and can be used industrially. It is used.

In the present invention, a vacuum system capable of satisfying a gas particle supply amount of 10 ¹⁸ cm ⁻³ (or 10 ¹⁷ cm ⁻³ per minute) required for one minute and a steady gas pressure of 0.1 to 1.0 Pa is provided. It is important to be realized, and as described above, the volume of the vacuum container having a volume of V to 0.5 L is not limited to a small one. For example, even in a vacuum container having a large volume, an etching rate of 50 μm / min can be realized by using a vacuum system having an effective exhaust speed that satisfies the above gas supply amount and steady gas pressure. is there.

  As an advantage of using a small vacuum container with a small volume, even when the steady gas pressure is set to 0.1 to 1.0 Pa, it can be put into the container per minute without using a vacuum pump with a large displacement. The total amount of gas can be increased. Since the total amount of gas that can be introduced into the container per minute can be easily obtained without using a pump with a large displacement, the total amount of radicals necessary for obtaining a high etching rate can be easily obtained.

(4) Optimization of the shape of the through hole Although the above-described content makes it possible to obtain a high etching rate, in the present invention, it is also important to form a through hole having a high aspect ratio. In order to efficiently form deep through-holes with a small diameter, it is necessary to reduce the elastic scattering frequency of ions due to collisions between ions and gas neutral particles, and to guide ions to the bottom of the through-holes at a straight incident angle. There is.

  Specifically, by making the gas pressure in the vacuum vessel as low as possible, the collision frequency between the ions and the neutral particles of the gas is lowered, thereby making it difficult for elastic scattering of ions to occur. The pressure is preferably as low as possible. If the pressure is within the range of a stationary gas pressure of 0.1 to 1.0 Pa, elastic scattering of ions is less likely to occur. However, in order to obtain a high density by a Helicon Wave Plasma (HWP) system or an Electron Cyclotoron Resonance (ECR) system, a steady gas pressure of about 0.1 Pa is required.

  In addition, by forming a linear magnetic field in the vacuum vessel and making ions incident substantially perpendicular to the wafer surface, the ion trajectory that enhances the ion assist effect can be controlled, and ions are efficiently guided to the bottom of the through hole. Can do. As a result, high-speed etching of a highly anisotropic through hole is possible.

In view of the above points, in order to achieve the above object, the dry etching method of the present invention uses the mean free path of ions generated by a plasma generating part for generating electromagnetic field excited plasma in a vacuum chamber to the surface of the material to be processed. In order that the steady gas pressure is in the range of 0.1 to 1.0 Pa and the total amount of gas supplied per minute is 1.0 × 10 ¹⁷ cm ⁻³ or longer A gas supply step of supplying a gas into the vacuum chamber; an ion induction step of guiding ions generated by the plasma generation unit to a material to be processed located on a sample support placed in the vacuum chamber; A plasma density in the vicinity of the material is set to 10 ¹⁸ m ⁻³ or more, and an etching process step is performed in which the gas is radicalized to etch the surface of the material to be processed.

Here, it is necessary for processing at a high etching rate by a gas supply process in which the mean free path of ions generated by the plasma generation unit that generates electromagnetic field excited plasma in the vacuum chamber is longer than the sheath thickness generated on the surface of the material to be processed. An ion density capable of realizing a high ion assist effect can be obtained. More specifically, a radical density for realizing an etching rate of ER _si = 50 μm / min, which is a value of an etching rate per minute when a silicon wafer is processed with fluorine radicals, can be obtained.
The mean free path of ions is the average value of the distance that ions generated in the plasma can travel without being disturbed by the collision with the scattering source. The sheath thickness is a thickness of a space in which a sheath electric field near the wafer to be processed acts. Since the mean free path of ions is longer than the sheath thickness generated on the surface of the material to be processed, ion scattering does not occur in the sheath, and a sufficient etching reaction can be efficiently obtained in the vicinity of the bottom surface of the through hole. Become.

  A gas supply step of supplying gas into the vacuum chamber with a steady gas pressure in the range of 0.1 to 1.0 Pa allows the plasma density necessary for a desired radical generation amount to be determined by a helicon wave excitation plasma method or an electron cyclotron resonance plasma method. The anisotropy of the through hole formed and formed can be increased. When using an etching apparatus having a small vacuum container with a small volume, it was generally said that plasma collided with the wall surface of the apparatus and disappeared, resulting in a decrease in plasma density. If plasma can be generated with high density by the above method in the steady gas pressure range, it is possible to secure a plasma generation component that compensates for the disappearance of the plasma. Therefore, by using the above method, a sufficient amount of plasma can be secured even in a small apparatus, and the plasma can be densified. In addition, since the gas pressure is reduced and ion scattering due to collision between the gas and ions is less likely to occur, the formed through-hole can be made highly anisotropic.

  Here, when the steady gas pressure is less than 0.1 Pa, in the helicon wave excitation plasma method or the electron cyclotron resonance plasma method, the ionization frequency between the electrons and the gas decreases, and the plasma generation amount becomes insufficient. On the other hand, when the steady gas pressure exceeds 1.0 Pa, ions and radicals are easily scattered even if the plasma generation amount is sufficient, and the anisotropy of the formed through-holes becomes insufficient.

In addition, the radical density necessary for obtaining a higher etching rate by the gas supply step of supplying gas into the vacuum chamber so that the total amount of gas supplied per minute is 1.0 × 10 ¹⁷ cm ⁻³ or more. Can be obtained. More specifically, a radical density for realizing an etching rate of ER _si = 50 μm / min or more can be obtained.

  In addition, the ions are directly incident on the surface to be processed of the material to be processed by the ion induction process for inducing the ions generated by the plasma generation unit to the material to be processed located on the sample support table disposed in the vacuum chamber. The anisotropy of the through-hole formed can be increased. Moreover, when the steady gas pressure is in a low range, the incident efficiency of ions to the bottom surface of the through hole can be increased and the etching rate can be improved.

In addition, the plasma density in the vicinity of the material to be processed located on the sample support is set to 10 ¹⁸ m ⁻³ or more, and the gas is made highly efficient by an etching process that performs radical processing of the gas to etch the surface to be processed. It becomes possible to carry out an etching process by radicalization. That is, a radical density necessary for processing at a high etching rate can be obtained. More specifically, a radical density for realizing an etching rate of ER _si = 50 μm / min or more can be obtained.

Here, when the plasma density in the vicinity of the material to be processed located on the sample support is less than 10 ¹⁸ m ⁻³ , a radical amount sufficient to realize an etching rate of ER _si = 50 μm / min is not generated, An etching process having a high etching rate cannot be performed.

Further, as in the above example, assuming that the vacuum container capacity is V to 0.5 L (a cylindrical vacuum container having a diameter of about 80 mm and a height of about 100 mm), and the gas residence time is 0.5 msec in the gas supply process. In the case of the following, a higher radical density can be obtained than is necessary for processing at a high etching rate. More specifically, it is possible to sufficiently supply the total gas supply amount required for one minute required to realize an etching rate of ER _si = 50 μm / min.

  In addition, when a vacuum system capable of high-speed evacuation is provided and the flow rate of gas introduced in the gas supply process is 100 sccm or less, the amount of gas used can be reduced, and the manufacturing cost required for processing can be reduced. Become.

When the plasma generator generates plasma using the helicon wave excitation plasma method or the electron cyclotron resonance plasma method, the output is 1 kW to several kW, and the steady gas pressure is in the range of 0.1 to 1.0 Pa. In addition, plasma having a plasma density of 10 ¹⁸ m ⁻³ or more can be generated. Here, the helicon wave excitation plasma system includes one having an inductively coupled plasma system plasma source.

  In addition, the ion induction process draws the magnetic field lines generated in the plasma generation unit and the vacuum chamber into the sample support table via the magnetic field drawing unit provided on the sample support table, so that the ions are substantially perpendicular to the sample support table. In the case of being incident on the surface, the incident direction of ions can be controlled to improve the anisotropy of the formed through hole. More specifically, the plasma density is increased so that ions can enter the bottom of the etching hole, and the anisotropy and etching rate of the formed through hole are increased.

  Also, when the ion induction process controls ions by applying a high-frequency electric field to the sample support, if the steady gas pressure is in a low range, the incident speed of ions toward the sample support is increased and ion sputtering is performed. The etching rate due to the effect can be improved.

  The dry etching method according to the present invention is a method capable of realizing an excellent etching rate and capable of processing with a high aspect ratio.

It is the schematic which shows an example of the dry etching apparatus in which the dry etching method to which this invention is applied is possible. It is the schematic which shows a part of structure of a dry etching apparatus. It is the figure which showed the vacuum chamber in cross section. It is the schematic diagram which expanded a part of vacuum chamber. It is explanatory drawing of a magnetic force line when a stage is arrange | positioned near a magnetic coil. It is explanatory drawing of a magnetic force line when the magnetic force line drawing member is provided in the stage. It is a figure which shows the positioning of the various plasma generation sources in the relationship between a steady gas pressure and a plasma density.

Hereinafter, embodiments of the present invention will be described with reference to the drawings to facilitate understanding of the present invention.
FIG. 1 is a schematic view showing an example of a dry etching apparatus capable of performing a dry etching method to which the present invention is applied. In addition, the structure shown below is an example of the apparatus which implements the method to which this invention is applied, and the content of this invention is not limited to this.

  A dry etching apparatus 1, which is an example of a dry etching apparatus capable of performing the dry etching method to which the present invention shown in FIG. 1 is applied, includes a vacuum chamber 2, a high frequency coupling antenna 3, a magnetic coil 4, and a stage 5.

  The dry etching apparatus 1 also has a gas exhaust section (not shown) connected to the plasma termination plate 6 and a vacuum pump that exhausts the gas in the vacuum chamber 2. In FIG. 1, the direction of the gas supplied by the symbol X indicates the direction of the gas exhausted by the symbol Z. The symbol Y indicates the direction of the lines of magnetic force formed by the magnetic coil 4.

  In this configuration, an inert gas (Ar, Kr, Xe, etc.) or a fluorine-based process gas is introduced into the vacuum chamber 2 through a hollow tube connected to the plasma termination plate 6. Further, the introduced process gas is evacuated through the gas exhaust part, so that the inside of the vacuum chamber 2 is maintained at a constant steady gas pressure.

  The high frequency coupling antenna 3 is connected to a matching box 7 and a high frequency power source 8. The high-frequency coupling antenna 3 is supplied with high-frequency power from a high-frequency power supply 8 and adjusts the element values of the circuit elements in the matching box 7 to obtain impedance matching to generate a high-frequency electromagnetic field in the vacuum chamber 2, thereby generating process gas. Is turned into plasma.

  Further, the magnetic coil 4 generates lines of magnetic force in the vacuum chamber 2. The charged particles in the plasma are transported substantially parallel to the magnetic lines of force toward the sample placed on the stage 5 while spirally moving so as to wrap around the magnetic lines of force, and the sample is etched.

  Further, the lines of magnetic force generated by the magnetic coil 4 are substantially orthogonal to the stage surface of the stage 5. For this reason, ions fly along the lines of magnetic force and enter the base surface of the stage 5 substantially perpendicularly. As a result, a smooth sidewall of the etching hole is realized, that is, the formed through hole has high anisotropy, and the etching rate is improved.

  FIG. 2 is a schematic view showing a part of the configuration of the dry etching apparatus. FIG. 2 shows an example of the shapes and positional relationships of the high-frequency coupling antenna 3, the magnetic coil 4, and the stage 5. FIG. 3 is a cross-sectional view of the vacuum chamber. FIG. 4 is an enlarged schematic view of a part of the vacuum chamber.

  As shown in FIG. 2, in the vacuum chamber 2, a plasma generation chamber 10 and a plasma processing chamber 11 are formed between the plasma termination plate 6 and the stage 5. The plasma termination plate 6 is provided at a position near the plasma generation chamber 10. The stage 5 is connected to the stage shaft 9.

  The stage 5 is provided at a position near the plasma processing chamber 11. With the above configuration, the process gas flows through the plasma generation chamber 10 and the plasma processing chamber 11.

  The vacuum chamber 2 has a linear cylindrical shape with a diameter of 70 mm and a height of 1000 mm. The vacuum chamber 2 is made of an insulating material that transmits electromagnetic waves. The vacuum chamber 2 is provided with a plasma generation chamber 10 and a plasma processing chamber 11 at different locations along the axial direction of the cylinder. The plasma generation chamber 10 and the plasma processing chamber 11 are formed in the same cylindrical vacuum chamber 10 with the same diameter.

  Furthermore, the vacuum exhaust system including the vacuum suction pump can be operated in a wide pressure range. The amount of radicals supplied per unit time in the plasma generation chamber 10 by adjusting the vacuum suction of such an evacuation system and the process gas supply from the hollow tube connected to the plasma terminal plate 6, and the plasma generation chamber The refresh rate of the process gas within 10 can be controlled.

  On the outer peripheral surface of the plasma generation chamber 10, the high frequency coupling antenna 3 is disposed coaxially with the central axis of the plasma generation chamber 10. The high frequency coupling antenna 3 is supplied with high frequency power of a predetermined frequency from a high frequency power supply via a matching circuit. The high frequency coupling antenna 3 is composed of a double loop antenna.

  The high-frequency coupling antenna 3 excites a high-frequency electric field in the plasma generation chamber 10 by electromagnetic induction, and converts the process gas flowing in the plasma generation chamber 10 into plasma. The high frequency coupling antenna 3 applies, for example, an electromagnetic wave up to several kW in a region of several MHz to several hundred MHz. The high frequency coupling antenna 3 is desirably cooled by a water cooling method or the like.

  A ring-shaped magnetic coil 4 larger than the diameter of the vacuum vessel is disposed outside the plasma generation chamber 10 and on the outer periphery of the high frequency coupling antenna 3 coaxially with the central axis of the plasma generation chamber 10. The magnetic coil 4 is composed of a solenoid coil.

  The magnetic coil 4 generates lines of magnetic force in the plasma generated in the plasma generation chamber 10. At least a part of the lines of magnetic force generated in the plasma, for example, the line of magnetic force in the vicinity of the central axis of the cylindrical vacuum vessel is a straight line parallel to the central axis of the plasma generation chamber 10. The plasma in the plasma generation chamber 10 is excited with a helicon wave (Whistler wave), which is a kind of electromagnetic wave, by the magnetic field applied by the magnetic coil 4.

  In the dry etching apparatus 1, the mean free path of ions generated in the plasma generation chamber 10 is longer than the sheath thickness. Specifically, the vacuum chamber 2 is depressurized within a steady gas pressure range of 0.1 to 1.0 Pa, where the probability that the ions collide with gas particles (collision rate) before colliding with the wafer is below a certain level. Yes.

The pressure and magnetic field intensity in the vacuum chamber 2 are adjusted so that the hole parameter of ions is sufficiently larger than 1 immediately above the wafer, and the mean free path of ions is between the high frequency coupling antenna 3 and the stage 5. It is secured more than the distance. The hole parameters of ions can be adjusted by controlling the pressure and magnetic field in the vacuum chamber 2. The Hall parameter h is expressed by the following [Equation 7] using the cyclotron frequency ω _c / 2π and mainly the collision frequency ν of ions and neutral particles.

  Here, the shape of the vacuum chamber 2 is not limited to a cylindrical shape, and various shapes such as a square shape and a tapered cylindrical structure can be employed.

  Further, the size of the vacuum chamber 2 is not necessarily limited to a cylindrical shape having a diameter of 70 mm and a height of 1000 mm. That is, the present invention is not limited to a small apparatus having a small vacuum part volume. However, the use of a small device has the following advantages.

  In general, it has been said that when the apparatus is downsized, the plasma does not increase because the plasma collides with the side wall of the chamber and disappears. However, the electromagnetic field excitation plasma generation source employed in the dry etching method to which the present invention is applied increases the plasma density by using the electromagnetic field excitation plasma generated by the high frequency excitation antenna that has impedance matching even if the apparatus is downsized. Can be kept in density. In the case of a small apparatus, when the steady gas pressure and the pumping speed of the vacuum pump are made constant, the amount of gas that can be introduced into the container per minute increases. By increasing the amount of gas supply that can be introduced into the container per minute, the total amount of radicals necessary for obtaining a high etching rate can be obtained. In addition, since the gas refresh rate is shortened, a high-speed process with a vacuum pump with a low exhaust speed is possible. Even when a large vacuum vessel is used, the present invention can be implemented if the exhaust speed of the vacuum pump used for exhaust is high.

  In addition, the plasma generation chamber 10 and the plasma processing chamber 11 do not necessarily have the same diameter in the same cylindrical vacuum chamber 2. However, in the present invention, the plasma generation chamber 10 and the plasma processing chamber 11 are the same cylindrical shape because the plasma confinement effect due to the axial magnetic field lines generated by the magnetic coil can reduce the disappearance of the plasma on the side wall surface of the vacuum vessel. The vacuum chamber 2 may be formed with the same diameter.

  Further, the insulator forming the vacuum chamber 2 is not limited, but the higher the volume resistivity, the better. For example, heat-resistant glass, quartz glass, ceramic tubes, etc. with a reduced coefficient of thermal expansion can be used.

  The type of the high-frequency coupling antenna 3 is not limited to the double loop antenna, and various types of excitation antennas such as single, helical, and boswell can be used.

  Further, the magnetic coil 4 does not necessarily need to be constituted by a solenoid coil, and it is sufficient if it generates magnetic lines of force in the plasma generated in the plasma generation chamber 10. For example, a permanent magnet or the like magnetized in the same axial direction as the central axis of the plasma generation chamber 10 can be used instead of the solenoid coil.

  The magnetic coil 4 converges and diverges in the axial direction if the magnetic field lines B near the central axis of the vacuum cylindrical container that is generated in the plasma generation chamber 10 and transports the plasma do not intersect the inner wall of the vacuum chamber 2. Magnetic field lines B may be generated in a magnetic field configuration.

  As shown in FIG. 3, a stage 5 as a sample support is disposed in the plasma processing chamber 11. The stage surface of the stage 5 is disposed so as to intersect perpendicularly with the magnetic field applied by the magnetic coil 4. A wafer 12 to be etched is placed on the upper surface of the stage 5.

  Further, on the opposite side of the stage 5 from the mounting surface of the wafer 12, a bias voltage applying electrode 13 and a permanent magnet 14 as a magnetic line drawing member are arranged. Further, the stage 5 has a temperature adjustment mechanism capable of adjusting the temperature within a predetermined temperature range.

  The bias voltage application electrode 13 is connected to a high frequency power source via a blocking capacitor outside the vacuum chamber 2 and a matching box, and applies an RF bias by applying a high frequency power of 13.56 MHz, for example. By adjusting the bias voltage, the incident speed of ions can be adjusted.

  As shown in FIG. 4, the magnetic field lines B generated by the magnetic coil 4 are configured to be orthogonal to the stage surface of the stage 5. Usually, the magnetic field lines B of the magnetic field generated by the ring-shaped magnetic coil 4 diverge as the distance from the magnetic coil 4, so it is difficult to arrange the stage 5 so that all the magnetic field lines B are orthogonal to the base surface. Here, by providing the permanent magnet 14, the magnetic field lines B can be drawn into the stage 5.

  The range in which the magnetic field is drawn by the permanent magnet 14 is set so as to include the range where the wafer 12 is placed on the stage surface of the stage 5. By making the magnetic field lines B perpendicular to the stage surface of the stage 5, ions are incident on the stage surface of the stage 5 substantially perpendicularly. As a result, ions enter the bottom of the etching hole formed in the wafer 12, and an etching hole having a smooth side wall shape and a size faithful to the mask can be formed. In addition, the momentum transport effect between ions and neutral particles contributes to the improvement of the etching rate.

  Here, the magnetic force line drawing member does not necessarily need to be constituted by the permanent magnet 14, and it is sufficient if the magnetic force lines generated by the magnetic coil 4 can be drawn. For example, a solenoid coil arranged so as to be concentric with the stage 5 may be employed.

  Moreover, the stage 5 does not necessarily need to have a temperature adjustment mechanism. However, the stage 5 has a temperature adjustment mechanism because the wafer heated by etching can be cooled to reduce the thermal damage of the wafer and the etching reaction rate can be controlled by heating the stage 5. It is preferable. Moreover, as a temperature control range, the adjustment in the range of -100 degreeC-100 degreeC can be considered, for example.

  As a structure in which the magnetic field lines B are orthogonal to the stage surface of the stage 5, the structure shown in FIG. In the structure shown in FIG. 5, by arranging the stage 5 near the magnetic coil 4, the ratio of the lines of magnetic force B incident perpendicularly to the stage surface of the stage 5 is increased.

  The stage 5 is disposed at a position closer to the magnetic coil 4 than the position P1 at which the magnetic field lines B start to diverge. As a result, the magnetic lines of force B are incident substantially vertically and uniformly from the center to the periphery of the wafer 12. In addition, in FIG. 6, the mode of the magnetic force line at the time of arrange | positioning the permanent magnet 14 as a magnetic force line drawing member mentioned above is shown as a comparison.

  The dry etching apparatus 1 described above employs a helicon wave excitation plasma method as a plasma generation source. However, in the dry etching method to which the present invention is applied, an electron cyclotron resonance plasma (ECR) method is used as a plasma generation source. Is also possible.

  When the ECR method is used as a plasma generation source, a plasma density equivalent to that of the helicon wave method can be obtained when the steady gas pressure is in the range of 0.1 to 1.0 Pa. Since the ECR system has a divergent magnetic field configuration, it is common to use a diffusion chamber in order to reduce the disappearance of plasma. Similarly to the structure described above, it is also possible to arrange a permanent magnet as a magnetic force line drawing member on the stage so that the magnetic force lines are drawn vertically to the stage.

FIG. 7 shows a diagram in which various plasma generation sources are classified by steady gas pressure and plasma density. In the dry etching method to which the present invention is applied, a helicon wave excitation plasma method denoted by reference numeral 15 as a plasma generation source capable of realizing a plasma density of 10 ¹⁸ m ⁻³ in a range of a steady gas pressure of 0.1 to 1.0 Pa, or , The electron cyclotron resonance plasma (ECR) system indicated by reference numeral 16 is employed. Reference numeral 17 is an inductively coupled plasma (ICP) system, reference numeral 18 is a beamed-ICP system or MSC-ICP (Multi Spiral Coil: MSC) system with improved ICP, reference numeral 19 is a Magnetically Enhanced-CCP system, and reference numeral 20 is a capacity. A coupled plasma (CCP) system, reference numeral 21 indicates a high power impulse magnetron sputtering (HIPIMS) system or a magnetron system.

  In the dry etching apparatus 1 configured as described above, the process gas is introduced into the plasma generation chamber 10 from the hollow tube connected to the plasma terminal plate 6 and simultaneously evacuated from the gas exhaust unit (not shown). Thus, the steady gas pressure is maintained in the range of 0.1 to 1.0 Pa in the plasma generation chamber 10 and the plasma processing chamber 11.

Further, the gas residence time of the process gas in the vacuum chamber 2 is 0.5 to 60 msec, and the total amount of the process gas supplied per minute is set to realize an etching rate of ER _si = 50 μm / min or more. 1.0 × 10 ¹⁷ cm ⁻³ or more.

In this state, when a predetermined magnetic field is formed in the plasma generation chamber 10 by the magnetic coil 4 while applying a high frequency signal of a predetermined high frequency voltage to the plasma generation chamber 10 by the high frequency coupling antenna 3, The electromagnetic field excitation plasma of helicon plasma is excited. At this time, the plasma density in the vicinity of the wafer 12 can be 10 ¹⁸ m ⁻³ .

  The charged particles in the electromagnetic field excited plasma are transported substantially parallel to the magnetic force lines B toward the wafer 12 placed on the stage 5 of the plasma processing chamber 11 while spirally moving so as to wrap around the magnetic force lines B. Thereby, the wafer 12 is etched.

  Further, by changing the RF bias applied to the stage 5 according to the processing gas and atmosphere to be used, ion acceleration in the sheath can be controlled, and appropriate plasma processing according to the wafer 12 can be realized. .

  The etching of the wafer 12 proceeds in principle by the reaction between radicals and the surface to be etched, but when ions are incident on the surface to be etched, the etching is accelerated by the ion assist effect.

  Etching acceleration due to the ion assist effect also occurs depending on the case where the ion incidence speed at the sheath end and the voltage drop in the sheath increase, so that the etching speed can be accelerated as the ion entry speed into the wafer 12 is increased. Since the etching with ion assist proceeds with anisotropy in the ion collision direction, the sidewall shape of the etching hole can be formed smoothly by aligning the ion assisting ion entry direction.

  Also, in the direction of etching by radicals, if the steady gas pressure is high, radical scattering occurs, and the probability of oblique incidence increases and etching anisotropy decreases. However, by reducing the steady gas pressure, radicals and ions are reduced. The probability of incidence of particles on the side wall surface of the through-hole due to scattering of light is reduced, and favorable anisotropic etching can be realized.

  In the dry etching method to which the present invention is applied, the supply of gas particles as a radical source is increased, and the steady gas pressure is lowered to such an extent that the probability of ion scattering due to collision with the gas particles is reduced. Etching can be realized.

  The ions move in the direction of travel and rotate clockwise to move parallel to the magnetic field lines B. The ions are spirally moved around the magnetic field lines B around the magnetic flux along the magnetic field direction, and are transported in a direction parallel to the magnetic field if no scattering occurs.

  As a result, the collision rate with which ions collide with other gas particles before reaching the bottom of the etching hole is suppressed, which contributes to high-speed etching and reduces collision of ions with the vacuum chamber side wall. , Plasma loss is reduced.

  Moreover, since the density of the charged particles (here, ions) of the electromagnetic field excitation plasma increases as the magnetic flux density increases, the number of charged particles of the plasma entering the wafer increases. This increases the probability of plasma charged particles entering the wafer and increases the etching rate.

  Between the plasma generation chamber 10 and the stage 5, there is a linear magnetic field or a converging magnetic field, and ions are initially determined by the potential of the plasma sheath (a few millimeters directly above the wafer) from the plasma generation chamber 10 to the stage 5. Incident with velocity. This improves the wafer etching rate.

  Further, a bias voltage applying electrode 13 for applying a high frequency RF bias to the stage 5 is provided. This RF bias is also generated in a direction substantially perpendicular to the stage surface of the stage 5, and due to the potential difference between the RF bias and the above-described plasma potential, the ion entry speed is further increased, and the etching speed of the wafer 12 is further improved. .

Since the dry etching apparatus 1 forms TSV through holes at a high speed of 50 μm / min or more by etching, the gas supply amount supplied per unit time is increased as compared with the conventional case (normally 100 to 100 μm / min). 1000 times). Specifically, the total amount of gas that is supplied with the process gas in one minute is 1.0 × 10 ¹⁷ cm ⁻³ or more.

  As the amount of gas supplied per unit time increases, the amount of radicals generated with plasma generation also increases. And when the amount of radicals increases, an etching rate will improve.

  However, even if the gas supply amount is increased, if the steady gas pressure is high, the mean free path of ions is shortened and the etching rate is lowered. Therefore, in the dry etching apparatus 1, the steady gas pressure in the vacuum chamber 2 is made lower than before by increasing the gas refresh rate of the vacuum chamber 2. Specifically, the steady gas pressure is maintained in the range of 0.1 to 1.0 Pa.

On the other hand, the diameter of the cylindrical vacuum chamber 2 may be shorter than the gas mean free path in the chamber. The dry etching apparatus 1 uses the helicon wave type plasma generation method, and can reduce the probability that the plasma collides with the side wall and disappears by guiding the ions to the wafer with a linear magnetic field. Because.
As described above, an ECR method can also be adopted as the plasma generation source.

  Further, the steady gas pressure in the chamber is such that the above-described Hall parameter h is sufficiently larger than 1 so that the mean free path of ions in the chamber is more than the distance between the high frequency coupling antenna 3 and the stage 5. It is adjusted to the degree.

  As a result, the probability that ions transported to the wafer 12 along the magnetic field lines B will cause ion scattering before reaching the bottom surface of the etching hole of the wafer 12 is reduced as much as possible, and collides with the wall surface of the vacuum chamber. Loss of plasma can be reduced. Thereby, in addition to the increase in the amount of radicals related to etching, the excavation force by ion assist is also improved, and the etching rate is further improved.

  In the dry etching apparatus 1, the lines of magnetic force B generated between the plasma generation chamber 10 and the stage 5 are substantially perpendicular to the stage surface of the stage 5. For this reason, the ions fly along the magnetic field lines B, and enter the base surface of the stage 5 perpendicularly. As a result, a smooth sidewall of the etching hole can be realized.

  Further, the magnetic field lines B intersecting the wafer 12 are substantially perpendicular to the plane of the wafer 12, but once the magnetic field is converged in the middle of the plasma generation chamber 10 and the stage 5, the magnetic flux density near the stage 5 is increased. You may raise compared with the plasma generation chamber 10 vicinity. Increasing the magnetic flux density near the stage 5 increases the plasma density near the stage 5 and improves the etching rate.

  Further, it is preferable to adjust the position of the stage 5 so that the wafer 12 placed on the stage 5 comes to the position of the antinode or node of the electromagnetic wave propagating in the electromagnetic field excited plasma. When the axial boundary (stage 5) is an electrically insulating material (or an electrically insulating material as a whole), the wafer 12 is adjusted so as to be in the antinode position of the electromagnetic wave, and the axial boundary is a conductor material (or the entire material). In this case, the wafer 12 can be adjusted so as to be positioned at the node of the electromagnetic wave.

  Moreover, in the dry etching method to which the present invention is applied, the following points can be adjusted for application to etching rate and fine plasma etching of 100 nm or less.

  First, it is conceivable to adjust the pulse power input using a pulse length (ms or less) considering the particle diffusion time or a pulse length (1 s or less) shortened to suppress the temperature rise. Plasma is generated intermittently by controlling ON / OFF of the pulse power, and the heat generation of the antenna is reduced.

  In addition, the voltage value of the bias voltage can be adjusted to change the speed at which ions are incident on the wafer. In particular, by increasing the bias voltage, the effect of accelerating ions can be increased, and the etching rate can be improved.

  In addition, it is considered that the frequency of the high-frequency power source is adjusted in the range of several MHz to several GHz in accordance with the antenna configuration and the plasma generation source.

  In addition, the amount of gas used can be reduced by adjusting the gas flow rate of the process gas to be supplied in the range of several sccm to 100 sccm.

  Furthermore, the steady gas pressure can be adjusted by adjusting the vacuum conductance by inserting a baffle plate or providing a gate valve opening / closing structure.

  As described above, the dry etching method of the present invention can realize an excellent etching rate and can be processed with a high aspect ratio.

DESCRIPTION OF SYMBOLS 1 Dry etching apparatus 2 Vacuum chamber 3 High frequency coupling antenna 4 Magnetic coil 5 Stage 6 Plasma termination plate 7 Matching box 8 RF power source 9 Stage shaft 10 Plasma generation chamber 11 Plasma processing chamber 12 Wafer 13 Electrode for bias voltage application 14 Permanent magnet 15 Helicon wave excited plasma method 16 Electron cyclotron resonance plasma (ECR) method 17 Inductively coupled plasma (ICP) method 18 Beamed-ICP method or MSC-ICP (Multi Spiral Coil: MSC) method 19 Magnetically Enhanced-CCP method 20 Capacitively coupled plasma ( Capacitively Coupled Plasma (CCP) method 21 HIPIMS (High Power Impulse Magnetron Sputtering) method or Magnetron method

Claims (6)

In the vacuum chamber, the mean free path of ions generated by the plasma generating part for generating electromagnetic field excited plasma is made longer than the sheath thickness generated on the surface of the material to be processed, and the steady gas pressure is in the range of 0.1 to 1.0 Pa. And a gas supply step of supplying gas into the vacuum chamber such that the total amount of gas supplied per minute is 1.0 × 10 ¹⁷ cm ⁻³ or more,
An ion induction step of inducing ions generated by the plasma generation unit to a material to be processed located on a sample support placed in the vacuum chamber;
A dry etching method, comprising: an etching process step in which a plasma density in the vicinity of the material to be processed is set to 10 ¹⁸ m ⁻³ or more, and the gas is radicalized to etch a surface to be processed of the material to be processed. The dry etching method according to claim 1, wherein the gas supply step supplies gas into the vacuum chamber so that a residence time of the gas is 0.5 msec or less. 3. The dry etching method according to claim 1, wherein in the gas supply step, a gas is supplied into the vacuum chamber so that a flow rate of the introduced gas is 100 sccm or less. The dry etching method according to claim 1, wherein the plasma generation unit generates plasma using a helicon wave excitation plasma method or an electron cyclotron resonance plasma method. In the ion induction step, magnetic force lines of magnetic fields generated in the plasma generation unit and the vacuum chamber are drawn into the sample support table via a magnetic line drawing unit provided on the sample support table, and ions are supplied to the sample support table. 5. The dry etching method according to claim 1, 2, 3 or 4, wherein the light is incident substantially perpendicularly. The dry etching method according to claim 1, wherein the ion induction step controls ions by applying a high-frequency electric field to the sample support.