JPH01179324A - Microwave plasma treatment apparatus and its method - Google Patents

Abstract

PURPOSE:To enhance the treatment efficiency and to enhance a throughput by a method wherein a gradient of a magnetic flux density in a position where ECR is generated is set to a gradient of a magnetic field density used to obtain a speed at which an ion species reaches a substrate within a half-life period of electron energy of an ion species contributing to a treatment operation of the substrate. CONSTITUTION:A thermal oxide film is formed on a silicon wafer as a substrate 1 to be treated; after that, polycrystalline silicon is deposited; a patterning operation is executed; this polycrystalline silicon is etched. SF6 is introduced through a reaction-gas supply nozzle 5 near a microwave introduction window 8 inside a plasma generation chamber; microwaves 6 are propagated by using a waveguide tube 7 and are introduced into the plasma generation chamber 4 through the microwave introduction window 8; a magnetic field is generated by means of a coaxial-type ECR magnetic-field generation coil 9 and an additional magnetic field coil 13 which have been installed around the plasma generation chamber 4 and a treatment chamber 2; an electric current whose direction is opposite to that of the coil 9 and the coil 13 flows to an additional magnetic-field generation coil 14; a line of magnetic force in the opposite direction is generated; by this setup, a gradient in an ECR position of a magnetic flux density distribution inside the plasma generation chamber 4 and the treatment chamber 2 is changed; an etching operation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microwave plasma processing method and an apparatus thereof, and in particular to strong anisotropic etching, highly efficient sputter etching, planarization film formation, or plasma processing. The present invention relates to a microwave plasma processing method and apparatus suitable for doping.

[Conventional technology]

Conventional magnetic field microwave plasma processing methods and apparatuses are disclosed in Japanese Patent Application Laid-open No. 54-141729 and Japanese Patent Application Laid-open No. 56-1348.
As described in No. 0 and JP-A-57-164986, the speed and amount of ions reaching the substrate are controlled by a grid in front of the substrate or by applying a variable frequency wave or DC potential to the substrate. Ta.

[Problem to be solved by the invention]

The above conventional technology uses an electric field to consider the speed and amount of ions that reach the substrate, but it uses a magnetic field to increase the speed and amount of highly active ions that reach the substrate. This point was not taken into account. In the method described in JP-A-55-141729, in which a grid for extracting ions is installed in front of the substrate, ions that pass through the center of one grid lattice enter the substrate perpendicularly. Although the probability is high, other ions receive a strong attraction from the lattice side on one side of the grid, so their traveling direction deviates from the substrate direction, and the overall amount of ions reaching the substrate is small. The amount of ions reaching is even smaller. In addition, since the ions are subjected to a force in the opposite direction after passing through the grid, the speed of the ions reaching the substrate does not increase, resulting in etching and sputtering.

Doping efficiency was not high. Also, JP-A-56-1
In the method described in No. 3480, in which a high frequency or DC potential is applied to the substrate to increase the vertical arrival speed and amount of ions, the E
Because the CR points were fried, the excitation degree of ions entering the ion sheath thinly formed on the 5th substrate was largely lost, and the etching, sputtering, and doping efficiencies were not high. In addition, if the potential value applied to the substrate is increased in order to increase the processing efficiency of the ions that have entered the ion sheath, a large local discharge will be induced between the inner wall of the vacuum chamber and the substrate, and the substrate will be significantly damaged. However, there is a problem in that the interior of the container is also significantly contaminated by scattered substances, and there is a limit to increasing the efficiency of etching, sputtering, and doping by applying a bias potential to the substrate.

An object of the present invention is to improve the above-mentioned disadvantages by appropriately controlling the speed and amount of highly excited ions reaching the substrate using a magnetic field, thereby improving etching and sputtering.

It is an object of the present invention to provide a microwave plasma processing method and an apparatus thereof, which improve doping efficiency and also improve planarization film formation rate.

[Means to solve the problem]

The above problem is solved in a microwave plasma processing method using electron cyclotron resonance (ECR).

This can be achieved by using a method of processing the substrate from the microwave introduction window (in other words, by using such a device).

In other words, the present invention reduces the gradient of magnetic flux density at the location where ECR occurs to such a gradient that the ionic species reaches the substrate within the half-life of the electronic energy of the ionic species that contributes to processing the substrate. It is characterized by the fact that

Furthermore, in other words, one aspect of the present invention is that the gradient of magnetic field density -d
A feature is that the absolute value of BZ/dZ is set to 100 (Gauss/cm) or more, preferably 150 [Gauss/cm] or more.

It will be done. The ion has a coordinate Z in the direction of the magnetic field line, which is ECR#
A momentum is given that is proportional to the value of the gradient -cf, /dz of the magnetic flux density B (with the direction of the lines of magnetic force being positive). Therefore, in a microwave plasma processing apparatus using a magnetic field, which has a magnetic flux density distribution in which the magnetic flux density decreases almost monotonically from the microwave introduction window toward the substrate, the larger the distribution of magnetic flux that reaches the substrate, the longer the substrate will last within its lifetime. The amount of highly excited ions reaching . Therefore, by increasing the gradient, etching, sputtering, doping rate,
Furthermore, it is possible to improve the flattening film formation speed in which a film is formed by superimposing etching and sputtering. That is, it is important to ensure that the ionic species reaches the substrate within the half-life of the electronic energy of the ionic species that contributes to the process. In addition, since no electric field is used, there will be no damage to the substrate or contamination within the chamber due to large local discharges induced between the substrate and the inner wall of the vacuum chamber. Since the amount of ions that arrive is greatly increased, the efficiency is increased.

〔Example〕

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of the main parts of a microwave plasma processing apparatus according to an embodiment of the present invention. This device is a plasma generation chamber 4
, a microwave waveguide 7, (the oscillator of the microwave 6 is omitted in the figure), an ECR magnetic field coil 9 and an additional magnetic field coil 13, 14, a processing chamber 2. Exhaust port 12 (exhaust port 12 has an exhaust system such as an exhaust pump connected to it), ring-shaped reaction gas supply nozzles 5 and 11 (pump valve etc. for supplying reaction gas to each nozzle) ), the board support stand 3. Consists of.

The plasma generation chamber 4 has a diameter of 370 (nn+)φ and a length of 20
It is made of transparent quartz with a size of 0 [n+m), and the top of the conical shape serves as a microwave introduction window 8. The magnetic field coil 9 for ECR is installed around the plasma generation chamber, the maximum magnetic flux density of the plasma generation chamber is 2.6 (K Gauss), and each divided coil (9 is divided into 3) is adjusted individually. By this, the magnetic flux density can be controlled and the plasma flow 1
0 control is possible.

The processing chamber 2 is made of stainless steel and has a diameter of 370 (nm). The substrate support stand 3 installed in the processing chamber 2 has a diameter of 1
20 (mml) made of alumina, and its position can be varied in the plasma flow direction. Additional magnetic field coils 13 and 14 are installed around the processing chamber 2. Fig. 2 shows the magnetic flux density in the direction of microwave propagation. By adjusting the current values and current directions of the ECR magnetic field coil 9 and additional magnetic field coils 13 and 14, distributions such as A and B shown in Fig. 2 can be created. By adjusting the position of the stand 3, the distance between the board and the ECR position 15 can be controlled.

The ECR position is shown by a dotted line near the reaction gas supply nozzle 11 in FIG.

Example 1 A silicon wafer (diameter 10010 mm) was used as the substrate 1 to be processed.
After forming a thermal oxide film with a thickness of 10100 (n) on 0 (φ), polycrystalline silicon was deposited to a thickness of 500 (nm) and patterned with a resist, and this polycrystalline silicon was etched. 30 [mQ/mi inlet] of SFe was introduced through the reaction gas supply nozzle 5 near the microwave introduction window 8 in the plasma generation chamber, and 2
．． A microwave 6 of 45 GHz is propagated through a waveguide 7 and passed through a microwave introduction window 8 into the plasma generation chamber 4.
The coaxial ECR magnetic field generating coil 9 and additional magnetic field coil 13 installed around the plasma generation chamber 4 and processing chamber 2 generate a magnetic field strength of 875 (Gauss).
The additional magnetic field generating coil 1
4, an ECR magnetic field generating coil 9 and an additional magnetic field coil 1
By passing a current in the opposite direction to the current flowing in the plasma generation chamber 4 and generating lines of magnetic force in the opposite direction, the gradient in the ECR position of the magnetic flux density distribution in the plasma generation chamber 4 and the processing chamber 2 is changed, and etching is performed. did. 02 is supplied from the reaction gas supply nozzle 11. The pressure inside the processing chamber 2 was set to 2 (mTorr) by an exhaust system. Figure 3 (a
) and (b) are the magnetic flux density gradient (dBZ/dZ (Gauss/ Cm).The substrate to be processed 1 is located 10 minutes from the ECR position.
(separated by cm). The vertical etching speed Vp is E
When the gradient value dBZ/dZ of the magnetic flux density distribution in the CR position becomes -100 [Gauss/cm] or less, it increases, and vice versa.

The etching speed in the horizontal direction decreases when the gradient value dBZ/dZ is approximately -100 [Gauss/cm] or less. From this, we can make the slope steeper (gradient value dBZ/dZ< -
100 [Gauss/cm]) It can be seen that the anisotropy of Nisruto and etching becomes stronger. Figure 4(a).

(b) similarly shows polycrystalline silicon with gradient value dBZ/d
Set Z to about -100 (Gauss/cm) and attach substrate 1.
This figure shows the dependence of VP and Vh on the distance when etching is performed with different distances between the ECR region and the ECR region. It can be seen that when the ECR point approaches the substrate within ), the etching anisotropy becomes stronger. Based on these results, anisotropic etching can be efficiently achieved by making the slope of the magnetic flux density distribution on the ECR point steeper and locating the ECR point closer to the substrate within the mean free path distance of the plasma species. I understand. Furthermore, the slope value dBZ/dZ is -15C) (Gauss/cm)
The following is desirable.

Example 2 In this example, the substrate to be processed 1 is a silicon wafer patterned with resist at a distance of 10 (
cm), and a first gas introduction pipe 5 is installed in the plasma generation chamber 4.
40 (mQ/m1n) of CCU 4 was introduced through the tube, and the experiment was conducted at a pressure of 1 (mTorr). Other conditions are the same as in Example 1. FIGS. 5(a) and 5(b) show the substrate 1
FIG. 3 is a diagram showing the dependence of the etching rate Vp in the direction perpendicular to the substrate and the angle θ of the groove with respect to the direction perpendicular to the substrate measured using an electron microscope on the gradient value of the magnetic flux density. The groove described here is formed on the silicon substrate 1 as shown in FIG.
This is the portion 103 sandwiched between the polycrystalline silicon film pattern 102 deposited on top and the resist pattern 101, and the angle θ is the angle formed by the normal line between the side wall of the silicon film pattern 102 and the silicon substrate 1 in the figure. be. Etching speed V, dBZ/dZ is -100CGauss/c
It can be seen that the angle θ increases as dBZ/dZ decreases from -100. From these results, when the gradient value dBZ/dZ of the magnetic flux density distribution is made smaller than -100 (steeper the gradient), the anisotropy of etching becomes stronger, and even grooves with a large aspect ratio can be etched well. I understand.

Example 3 An oxide film with a thickness of 1000 [nm] was deposited on a silicon wafer as the substrate 1 to be processed, patterned with resist, and anisotropically etched using RF plasma etching to form an oxide film. Sputter etching was performed using a substrate on which a step was formed. 40 m of Ar was passed through the first gas introduction pipe 5 into the plasma generation chamber.
Q/ml was introduced. Other conditions are the same as in Example 2. FIGS. 6(a) and 6(b) are diagrams showing the dependence of the sputtering rate V in the direction perpendicular to the substrate and the sputtering rate 2 in the horizontal direction with respect to the substrate on the magnetic flux density gradient. When the gradient value dBZ/dZ of the magnetic flux density becomes smaller than -100, the velocity in the vertical direction and the horizontal direction of the substrate increases for both Vp and Vh.
It has been found that sputtering efficiency increases at this time.

Example 4 As the substrate 1 to be processed, an n-type (sheet resistance value 12 [Ω/c
Using a substrate patterned with resist on a silicon wafer (m2)), B2 is introduced through the first gas introduction pipe 5.
40 (m Q /m1n) of H8 was introduced and the pressure Q, 5
(mTorr) for 30 minutes. Other conditions are the same as in Example 2.

Figures 7(a) and (b) show the concentration Gp at the depth where the concentration of boron B, which is a doping species, in the vertical direction of the substrate is half, and the horizontal direction where the concentration of B in the horizontal direction of the substrate is at the half-value position. FIG. 7 is a diagram showing the dependence of the concentration CH on the magnetic field strength distribution gradient value with respect to distance. From these results, it can be seen that when the gradient of the magnetic flux density is made steeper (the absolute value of dBZ/dZ is increased), the amount of doping especially in the direction perpendicular to the substrate increases.

Example 5 As the substrate to be processed 1, AQ was deposited on a silicon wafer, patterned with a resist, Afl was etched with RF plasma, and the resist was removed using a substrate using a CVD method in which a sputtering method was superimposed. , flattening film formation was performed. Into the plasma generation chamber 4, 40 (m Q
The other conditions were the same as in Example 2, except that 40 (m Q /win) of Ar and 6 (m fl 7 m1n) were introduced into the processing chamber 2 through the waste introduction pipe 11. FIG. 8(a) is a diagram schematically showing the flattening film formation situation at this time, and FIG.
FIG. 7 is a diagram showing the dependence of the ratio of the width of the height h2 of the protrusion on the stepped portion to the depth hl of the stepped portion of the AQ pattern on the magnetic flux density gradient. Reaction time is 20 minutes.

From this result, we can make the gradient of magnetic flux density steeper (dBZ/d
It can be seen that when the absolute value of Z is increased, the efficiency of planarization film formation by sputtering superimposition becomes higher.

Example 6 The same substrate as used in Example 5 was used as the substrate 1 to be processed, and CHF was supplied from the first gas introduction pipe 5 instead of Ar.
Planarization film formation was performed by introducing 6 s (m Q 7m1n) and using the same conditions as in Example 5 except for the other conditions. FIG. 9(a) is a diagram schematically showing the situation at this time. 9th
Figure (b) shows the depth hi of the step part of the AQ pattern with a width of 2 μm.
It is a figure showing the ratio of the height h2 on the stepped portion to the height h2. Reaction time is 20 minutes. From this result, it was found that when the gradient of the magnetic flux density is made steeper, the efficiency of planarization film formation by the superimposed method using anisotropic etching becomes higher.

As described above, according to this embodiment, in the microwave plasma processing method and apparatus, the gradient of the magnetic flux density distribution at the position where ECR occurs is set to dBZ/dZ<100 [Gauss
/cm), it is possible to increase the speed and amount of highly excited ion species reaching the substrate, making the etching strongly anisotropic, improving sputtering efficiency, and improving doping efficiency. Furthermore, it has been found that the efficiency of flattening film formation can be improved in a film formation process in which etching and sputtering are superimposed on plasma CVD.

Note that in planarization film formation, a method in which etching and sputtering are alternately performed during film formation is also effective, instead of a method in which etching and sputtering are superimposed.

〔Effect of the invention〕

According to the present invention, in microwave plasma processing, the processing efficiency is improved, so that there is an effect that the throughput is improved. Further, since the plasma processing does not require heating the substrate to be processed, it can be used in a wide range of electronic device manufacturing processes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a microwave plasma processing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing examples of magnetic flux density distribution when the magnetic flux density gradient is varied, and FIG. 3(a) , (b
), Figures 4(a) and 4(b) respectively show the dependence of the etching velocity VP in the vertical direction of the substrate and the velocity Vh in the horizontal direction on the magnetic flux density gradient and the ECR point-substrate ratio when performing reactive ion etching. Figure 5 is a diagram showing the dependence of the etching speed in the vertical direction of the substrate and the magnetic flux density gradient of the inclination θ of the etched surface with respect to the vertical direction when grooves are formed by reactive ion etching. , 6th
Figures (a) and (b) show the dependence of sputtering speeds VP and Vh on the magnetic flux density gradient in sputter etching. Figures 7(a) and (b) show the doping efficiency cp, C with respect to the magnetic flux density gradient during plasma doping.
FIG. Figures 8(a), (b) and 9(a), (b) are schematic views of the planarization situation when sputtering or anisotropic etching is superimposed, and diagrams showing the planarization efficiency. It is. FIG. 10 is a schematic diagram for explaining the inclination θ of the etched surface.

Claims (1)

[Claims] 1. In a microwave plasma processing method for processing a predetermined substrate with plasma generated by electron cyclotron resonance using microwaves, the gradient of the magnetic field strength at the position where the electron cyclotron resonance occurs is A microwave plasma processing method characterized in that the magnetic field density gradient is set such that the ion species reach the substrate at a speed within the half-life of the electronic energy of the ion species contributing to the processing of the substrate. 2. The microwave plasma processing method according to claim 1, wherein the absolute value of the gradient value of the magnetic field strength at the position where the electron cyclotron resonance occurs is 100 Gauss/cm or more. Processing method. 3. The microwave plasma processing method according to claim 1, wherein the absolute value of the gradient value of the magnetic field strength at the position where the electron cyclotron resonance occurs is 150 Gauss/cm or more. Processing method. 4. In the microwave plasma processing method according to claim 1, the ion species include a gas consisting of molecules containing at least one halogen atom at a position where electron cyclotron resonance occurs, an oxidizing gas, and a rare gas. A microwave plasma treatment method characterized in that it is produced by introducing at least one type of gas. 5. The microwave plasma processing method according to claim 1, wherein the distance between the position where the electron cyclotron resonance occurs and the substrate is the mean free path distance of the ion species. Plasma treatment method. 6. The microwave plasma processing method according to claim 1, wherein the processing of the substrate is a deposition processing. 7. The microwave plasma processing method according to claim 1, wherein the processing of the substrate is an etching process. 8. The microwave plasma processing method according to claim 1, wherein the processing of the substrate is sputtering processing. 9. The microwave plasma processing method according to claim 1, wherein the treatment of the substrate is doping treatment. 10. The microwave plasma processing method according to claim 1, wherein the processing of the substrate is a combination of deposition processing and etching processing. 11. The microwave plasma processing method according to claim 1, wherein the processing of the substrate is a processing in which a deposition processing and a sputtering processing are superimposed. 12. The microwave plasma processing method according to claim 1, wherein the processing of the substrate is a processing in which a deposition processing and a doping processing are superimposed. 13. In the microwave plasma processing method according to claim 4, the one type of gas is SF_6, CCl_4, Ar, B_
A microwave plasma processing method characterized in that the gas consists of 2H_8, O_2 and CHF_3. 14. In a microwave plasma processing apparatus having a vacuum vessel having at least a microwave introduction window, a gas supply means, and a gas exhaust means, and a magnetic field generation section for applying a magnetic field into the vacuum vessel, When the coordinate is Z (substrate direction is positive) and the magnetic flux density on the coordinate is B_Z, the magnetic flux density B on the Z coordinate that causes electron cyclotron resonance
The slope of _Z is dB_Z/dZ, dB_Z/dZ<-10
A microwave plasma processing apparatus characterized by having a magnetic flux density distribution of 0 [Gauss/cm]. 15. A microwave plasma processing apparatus comprising a vacuum vessel having at least a microwave introduction window, a gas supply means, and a gas exhaust means, and a magnetic field generation section for applying a magnetic field into the vacuum vessel, the magnetic field generation section comprising: At least two or more are installed in parallel in the direction of the center axis of the device so as to surround the vacuum container, and at least one of them generates lines of magnetic force in the opposite direction to the lines of magnetic force generated in other magnetic field generating parts. Microwave plasma processing equipment featuring: 16. The gradient dB_Z/dZ of the magnetic flux density B_Z on the z-coordinate that causes the electron cyclotron resonance is expressed as dB_Z/
Sequence with dZ<-100 and dB_Z/dZ≧-
16. The microwave plasma processing apparatus according to claim 15, wherein the microwave plasma processing apparatus has alternating sequences of 100 and 100. 17. The microwave plasma processing apparatus according to claim 16, characterized in that the distance between the position where electron cyclotron resonance occurs and the substrate is equal to or less than the mean free path distance of gas molecules used in the processing. 18. A support stand for supporting the object to be processed, a vacuum container having the support stand inside and a microwave introduction window, a means for introducing or discharging a predetermined gas into the vacuum container, and a means for applying a magnetic field to the inside of the vacuum container. In a microwave plasma processing apparatus having means for generating a magnetic field, the magnetic field in the vacuum container is formed by combining a first magnetic field of unipolarity and a second magnetic field of opposite polarity. Features of microwave plasma processing equipment.