JP2003007679A - Dry etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry etching method for forming the sidewall shape of a groove into a desired shape, and achieving superior etching, for example, even if the width of the groove is different. SOLUTION: A substrate is arranged in one of a pair of counter electrodes provided in an etching chamber, an apparatus for supplying high-frequency power to both the counter electrodes for etching using plasma is used, etching is made by plasma etching using a gas containing at least Cl2 and HBr, and grooves 104a and 104b are formed, as shown in Figure 1 (b) via a mask layer, such as a silicon nitride layer 103 on a silicon substrate 101 which is shown in Figure 1 (a). Then, the high-frequency power to be applied to the counter electrode on a side where the substrate is arranged is adjusted, thus controlling the shape of sidewalls 105a and 105b of the grooves 104a and 104b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for manufacturing a semiconductor device, and more particularly to a dry etching method for etching a single crystal silicon in shallow trench isolation (STI) to form a trench having a desired shape. The present invention relates to an etching method.

[0002]

2. Description of the Related Art In recent years, so-called shallow trench isolation (STI) has been widely used as an element isolation technique in the field of manufacturing semiconductor devices.

Such STI requires a trench etching step for forming a groove in a single crystal silicon by anisotropic etching. This trench etching step has hitherto been performed with Cl ₂ and O ₂ . This is performed by plasma etching using a mixed gas as an etching gas.

It is also known to carry out such a trench etching process by plasma etching using an etching gas composed of a mixed gas of HBr, Cl ₂ and oxygen.

[0005]

In the above-described STI, for example, SiO ₂ is formed in a groove formed in single crystal silicon.
It is necessary to embed a dielectric material such as Therefore, in order to surely and easily fill the dielectric material, the side wall of the groove is often formed in a tapered shape with a predetermined angle so as to gradually widen from the groove bottom toward the upper opening.

However, the side wall shape of the groove is, for example,
Even within a single wafer, there is a tendency to change due to the difference in the positions of the central part and the peripheral portion, the difference in the width of the grooves, etc., and it is difficult to make the sidewall shape of all grooves the desired shape. There was a problem.

The present invention has been made in consideration of such a conventional situation. Even when the width of the groove is different, the side wall shape of the groove can be set to a desired shape and good etching can be performed. The present invention is intended to provide a dry etching method that can be used.

[0008]

According to a first aspect of the present invention, there is provided a dry etching method for forming a groove having a desired shape on a silicon single crystal through a mask layer, the pair being provided in an etching chamber. The substrate is placed on one of the opposite electrodes of the substrate, and an etching gas is introduced into the etching chamber by using a device that supplies high frequency power to both of the opposite electrodes to perform etching by plasma. The sidewall shape of the groove is controlled by adjusting the high frequency power applied to the opposite electrode on the side.

According to a second aspect of the present invention, in the dry etching method according to the first aspect, the etching gas is a mixed gas of a gas containing at least Cl and a gas containing Br.

According to a third aspect of the present invention, in the dry etching method according to the second aspect, the gas containing Cl is Cl.
It is characterized by being ₂ .

According to a fourth aspect of the present invention, in the dry etching method according to the first or second aspect, the gas containing Br is HBr.

According to a fifth aspect of the present invention, in the dry etching method according to any one of the first to fourth aspects, the etching gas contains oxygen.

According to a sixth aspect of the present invention, in the dry etching method according to any one of the first to fifth aspects, the total flow rate of the etching gas is adjusted to control the sidewall shape of the groove. .

According to a seventh aspect of the present invention, in the dry etching method according to any one of the first to sixth aspects, the amount of Cl _{2 in} the etching gas is adjusted to control the side wall shape of the groove. Is characterized by.

According to an eighth aspect of the present invention, in the dry etching method according to any one of the first to seventh aspects, the high frequency power applied to the counter electrode on the side where the substrate is arranged is
It is characterized in that it is in the range of 0.157 to 1.57 W / cm ² .

According to a ninth aspect of the present invention, in the dry etching method according to any one of the first to eighth aspects, a plurality of types of grooves having different groove widths are formed on the substrate.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged schematic view showing a part of a vertical cross section of a semiconductor wafer (silicon substrate) for explaining one embodiment of the present invention.

As shown in FIG. 1A, a silicon dioxide layer 102 having a thickness of, for example, about 9 nm and a thickness of, for example, 160 n are provided on a semiconductor wafer (silicon substrate) 101.
A silicon nitride layer 103 having a thickness of about m is formed, and these are patterned into a predetermined shape so as to have an opening for forming a groove, which constitutes a so-called hard mask.

In the present embodiment, the hard mask made of the above silicon nitride layer 103 and the like is used,
A semiconductor wafer 101 made of single crystal silicon is etched by plasma etching using a gas containing at least Cl ₂ and HBr as an etching gas, and as shown in FIG. , 104b are formed.

The above-mentioned grooves 104a and 104b are each formed to have a predetermined width, and the groove 104 shown on the left side of the drawing is formed.
The width of a is 0.24 μm, for example, and the width of the groove 104b shown on the right side in the figure is 1.00 μm, which are different. Also, these grooves 104a, 104b
The side walls 105a and 105b are formed so as to have substantially the same Taber angles and are formed to have substantially the same depth.

FIG. 2 schematically shows an example of the configuration of the plasma processing apparatus used in the embodiment of the present invention.
As shown in the figure, the plasma processing apparatus 1 is configured as a capacitively coupled parallel plate etching apparatus in which electrode plates are vertically parallel and face each other, and a high frequency power source is connected to both of them.

The etching apparatus 1 has a chamber 2 formed into a cylindrical shape made of aluminum, the surface of which is anodized (anodized), and the chamber 2 is grounded. Chamber 2
A substantially columnar susceptor support 4 for mounting a wafer W is provided on the bottom of the inside of the susceptor support 4 with an insulating plate 3 made of ceramic or the like interposed therebetween.
A susceptor 5 that constitutes a lower electrode is provided. A high pass filter (HPF) 6 is connected to the susceptor 5.

A temperature control medium chamber 7 is provided inside the susceptor support 4, and the temperature control medium is introduced into the temperature control medium chamber 7 through an introduction pipe 8 and circulated to bring the susceptor 5 to a desired temperature. Can be controlled.

The susceptor 5 is formed in a disk shape having a convex upper central portion, and an electrostatic chuck 11 having substantially the same shape as the wafer W is provided thereon. The electrostatic chuck 11 has a structure in which an electrode 12 is interposed between insulating materials.
When a DC voltage of, for example, 1.5 kV is applied from the DC power supply 13 connected to 2, the wafer W is electrostatically attracted by the Coulomb force.

The insulating plate 3, the susceptor support 4, the susceptor 5, and the electrostatic chuck 11 are used to supply a heat transfer medium, such as He gas, to the back surface of the wafer W that is the object to be processed. A gas passage 14 is formed, and heat is transferred between the susceptor 5 and the wafer W via this heat transfer medium, so that the wafer W is maintained at a predetermined temperature.

An annular focus ring 15 is arranged around the upper edge of the susceptor 5 so as to surround the wafer W placed on the electrostatic chuck 11. The focus ring 15 is made of an insulating material such as ceramics or quartz to improve the uniformity of etching.

An upper electrode 21 is provided above the susceptor 5 so as to face the susceptor 5 in parallel.
The upper electrode 21 is supported on the upper portion of the chamber 2 via an insulating material 22, constitutes an opposed surface to the susceptor 5, and has an electrode plate 24 made of, for example, quartz and having a large number of ejection holes 23. It is composed of a conductive material that supports the electrode 24, for example, an electrode support 25 made of aluminum whose surface is anodized. The distance between the susceptor 5 and the upper electrode 21 is adjustable.

A gas introduction port 26 is provided at the center of the electrode support 25 in the upper electrode 21, and a gas supply pipe 27 is connected to the gas introduction port 26. Further, the gas supply pipe 27 is connected to the gas supply pipe 27. A processing gas supply device 30 is connected via a valve 28, a mass flow controller 29, and an etching gas for plasma etching is supplied from the processing gas supply device 30. Although only one processing gas supply system including the processing gas supply device 30 and the like is shown in FIG. 2, a plurality of these processing gas supply systems are provided.
Gas such as Br, Cl ₂ and O ₂ can be supplied into the chamber 2 by independently controlling the flow rate.

On the other hand, an exhaust pipe 31 is provided at the bottom of the chamber 2.
Is connected to the exhaust pipe 31, and an exhaust device 35 is connected to the exhaust pipe 31. The exhaust device 35 is equipped with a vacuum pump such as a turbo molecular pump, so that the chamber 2 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. Further, a gate valve 32 is provided on the side wall of the chamber 2,
With the gate valve 32 opened, the wafer W is transferred to and from the adjacent load lock chamber (not shown).

The upper electrode 21 has a first high frequency power source 40.
Are connected, and a matching unit 41 is inserted in the power supply line. A low pass filter (LPF) 42 is connected to the upper electrode 21. The first high frequency power supply 40 has a frequency in the range of 50 to 150 MHz, and by applying such a high frequency, it is possible to form a high density plasma in the chamber 2 in a preferable dissociation state. As a result, plasma processing under a low pressure condition can be performed as compared with the conventional case. The frequency of the first high frequency power source 40 is preferably 50 to 80 MHz, and typically, the condition of 60 MHz shown in the figure or in the vicinity thereof is adopted.

A second high frequency power supply 50 is connected to the susceptor 5 as the lower electrode, and a matching unit 51 is inserted in the power supply line. The second high-frequency power supply 50 has a frequency in the range of several hundreds to ten and several MHz, and by applying a frequency in this range, the wafer W, which is the object to be processed, is damaged. It is possible to give proper ionic action without. Second high frequency power supply 50
For the frequency of, the conditions such as the illustrated 13.56 MHz or 800 KHz are typically adopted.

Next, a process of etching a wafer W made of a silicon single crystal to form a trench by the plasma processing apparatus 1 having the above structure will be described.

First, as described above, the wafer W on which the mask layer composed of the silicon dioxide layer 102 and the silicon nitride layer 103 is formed is loaded into the chamber 2 from the load lock chamber (not shown) by opening the gate valve 32. Then, it is placed on the electrostatic chuck 11. And high voltage DC power supply 1
By applying a DC voltage from No. 3, the wafer W is electrostatically attracted to the electrostatic chuck 11.

Then, the gate valve 32 is closed, the chamber 2 is evacuated to a predetermined degree of vacuum by the exhaust mechanism 35, the valve 28 is opened, and the processing gas supplier 30 is opened.
From the etching gas for the main etching, eg H
While adjusting the flow rate of Br and Cl ₂ or HBr, Cl ₂ and O ₂ by the mass flow controller 29, the processing gas supply pipe 27, the gas introduction port 26, the hollow portion of the upper electrode 21, and the discharge hole of the electrode plate 24. Through 23, the wafer W is uniformly ejected as shown by the arrow in FIG.

At the same time, the pressure in the chamber 2 becomes
A high frequency voltage is applied from the first high frequency power source 40 and the second high frequency power source 50 to the upper electrode 21 and the susceptor 5 as the lower electrode, which is maintained at a predetermined pressure, for example, a pressure of about 13.3 Pa, and etching gas is applied. Into plasma,
The wafer W is etched.

In the graphs of FIGS. 3 and 4, the vertical axis is the taper angle, and the horizontal axis is the lower power (power supplied to the lower electrode). In the etching of the 8-inch diameter wafer W using the etching processing apparatus 1, FIG. 3 shows the relationship between the power supplied from the second high-frequency power source 50 to the susceptor 5 as the lower electrode and the taper angle of the side wall of the groove. In FIG. 3, the groove width is 0.24 μm.
4 shows the case where the groove width is 1.00 μm.

In FIGS. 3 and 4, solid lines A and C indicate the central portion of the wafer W, and dotted lines B and D indicate the taper angles of the grooves in the peripheral portion of the wafer W.

The etching conditions are as follows: etching gas: Cl ₂ (flow rate 15 SCCM) + HBr (flow rate 285 SCCM) + O ₂ (flow rate 2.5 SCCM) Pressure: 13.3 Pa Upper electrode applied high frequency power: 1000 W Electrode distance: 80 mm Back He (Center / edge): 399/399 Pa Chamber temperature (top / bottom / wall): 60/60/50 ° C. Etching time: 47 seconds.

As shown in the graph of FIG. 3, in the case of the narrow groove 104a having a groove width of 0.24 μm, the taper angle tends to increase linearly as the lower power increases.
On the other hand, as shown in the graph of FIG. 4, the groove width is 1.00.
In the case of the groove 104b having a wide μm, the taper angle hardly changes even if the lower power is changed.

Therefore, in the example shown in FIGS.
100 W (0.314 W / cm) ²)
Both the groove 104a with a narrow groove width and the groove 104b with a wide groove width
The taper angles of can be controlled to be substantially the same.

In the graphs of FIGS. 5 and 6, the vertical axis represents the taper angle and the horizontal axis represents the upper power (power supplied to the upper electrode).
FIG. 5 shows the relationship between the power supplied from the first high-frequency power supply 40 to the upper electrode 21 and the taper angle of the side wall of the groove in the etching of the 8-inch diameter wafer W using the etching processing apparatus 1. FIG. If the groove width is 0.24 μm,
FIG. 6 shows the case where the groove width is 1.00 μm.

In FIGS. 5 and 6, solid lines E and G indicate the central portion of the wafer W, and dotted lines F and H indicate the taper angles of the grooves in the peripheral portion of the wafer W.

As shown in the graphs of FIGS. 5 and 6, even if the upper power is changed, no significant change in the taper angle is observed. Therefore, when controlling the taper angle, the lower power is changed as described above. It can be seen that it is effective to perform the control by adjusting.

If the lower power is too high, the etching rate is increased and the selectivity with respect to the mask layer such as silicon nitride is lowered, so that the maximum power is preferably about 500 W. Further, if it is much lower than 100 W and less than 50 W, the etching rate will decrease, so the lower power is about 50 to 500 W for a wafer having an 8-inch diameter, and therefore, as the power per unit area. , 0.157 to 1.57 W / cm ²
It is preferable to set it as the range.

In the graph of FIG. 7, the ordinate represents the etching depth (and thus the etching rate), and the abscissa represents the ratio of Cl _{2 in} the etching gas (Cl ₂ flow rate / total flow rate). 8-inch diameter wafer W using
₂ shows the relationship between the etching depth and the ratio of Cl ₂ in the etching of No. ₂ , the solid line I shows the case where the groove width is 0.24 μm, and the dotted line J shows the case where the groove width is 1.00 μm.

In the graph of FIG. 8, the vertical axis represents the taper angle,
The horizontal axis represents the ratio of Cl _{2 in} the etching gas (Cl ₂ flow rate / total flow rate), and the taper angle and C
The relationship of the ratio of l ₂ is shown. The solid line K indicates that the groove width is 0.2.
In the case of 4 μm, the dotted line L shows the case where the groove width is 1.00 μm.

The etching conditions are as follows: etching gas: Cl ₂ + HBr (total flow rate 200 SCCM) O ₂ addition (flow rate 1.6 SCCM) Pressure: 13.3 Pa Upper electrode applied high frequency power: 1000 W Lower electrode applied high frequency power: 200 W Between electrodes Distance: 80 mm Back He (center / edge): 399/399 Pa Chamber temperature (top / bottom / wall): 60/60/50 ° C. Etching time: 83 seconds.

As shown in the graphs of FIGS. 7 and 8, by changing the ratio of Cl _{2 in} the etching gas, the etching rate changes and the taper angle also changes. Further, as shown in the graph of FIG. 8, the taper angle changes when the groove width is 0.24 μm (solid line K).
And the case where the groove width is 1.00 μm (dotted line L) are not uniform.

Therefore, for example, when the ratio of Cl ₂ in the etching gas is changed so that the required etching rate and taper angle are obtained, the groove having a narrow groove width and the groove having a wide groove width are different from each other. The taper angle is likely to increase. In such a case, as described above, by adjusting the lower voltage, it is possible to control so as to eliminate the difference in taper angle.

In the graph of FIG. 9, etching is performed on a wafer W having a diameter of 8 inches using the etching processing apparatus 1 with the vertical axis representing the etching depth (thus substantially the etching rate) and the horizontal axis representing the total flow rate of the etching gas. Shows the relationship between the etching depth and the total flow rate of the etching gas. When the solid line M has a groove width of 0.24 μm, the dotted line N shows
The case where the groove width is 1.00 μm is shown.

In the graph of FIG. 10, the vertical axis represents the taper angle and the horizontal axis represents the total flow rate of the etching gas. In the etching of the 8-inch diameter wafer W using the etching processing apparatus 1, the taper angle and the etching gas are shown. The solid line O shows the case where the groove width is 0.24 μm, and the dotted line P shows the case where the groove width is 1.00 μm. The etching conditions are as follows: etching gas: Cl ₂ + HBr + O ₂ Cl ₂ = 25% (vs Cl ₂ / HBr total flow rate) O ₂ = 0.8% (vs Cl ₂ / HBr total flow rate) Pressure: 13.3 Pa Upper electrode Applied high frequency power: 1000 W High frequency power applied to lower electrode: 200 W Distance between electrodes: 80 mm Back He (center / edge): 399/399 Pa Chamber temperature (top / bottom / wall): 60/60/50 ° C. Etching time: 83 seconds is there.

As shown in the graphs of FIGS. 9 and 10, by changing the total flow rate of the etching gas, the etching rate changes and the taper angle also changes. Further, as shown in the graph of FIG. 10, the taper angle changes when the groove width is 0.24 μm (solid line K).
And the case where the groove width is 1.00 μm (dotted line L) are not uniform.

Therefore, for example, when the total flow rate of the etching gas is changed so that the required etching rate and taper angle can be obtained, the groove having a narrow groove width and the groove having a wide groove width have different taper angles. Will be more likely. In such a case, as described above, by adjusting the lower voltage, it is possible to control so as to eliminate the difference in taper angle.

As described above, according to the dry etching method of the present invention, by adjusting the lower flow rate as well as the total flow rate of the etching gas, the amount (ratio) of Cl _{2 in} the etching gas, the grooves having different groove widths are mixed. Even in such a case, the side wall shape of these grooves can be set to a predetermined shape so as to have a desired taper angle.

Therefore, it is possible to satisfactorily embed the dielectric material thereafter, and it is possible to favorably perform element isolation by STI.

[0057]

As described above in detail, according to the dry etching method of the present invention, even if the width of the groove is different, the side wall shape of the groove can be made into a desired shape, which is excellent. Etching can be performed.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a wafer cross section for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing an example of the configuration of an apparatus used in an embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a lower power and a taper angle of a groove having a groove width of 0.24 μm.

FIG. 4 is a graph showing a relationship between a lower power and a taper angle of a groove having a groove width of 1.00 μm.

FIG. 5 is a graph showing the relationship between the upper power and the taper angle of a groove having a groove width of 0.24 μm.

FIG. 6 is a graph showing the relationship between the upper power and the taper angle of a groove having a groove width of 1.00 μm.

FIG. 7 is a graph showing the relationship between the etching depth and the ratio of Cl ₂ .

FIG. 8 is a graph showing the relationship between the taper angle and the ratio of Cl ₂ .

FIG. 9 is a graph showing the relationship between etching depth and the total flow rate of etching gas.

FIG. 10 is a graph showing the relationship between the taper angle and the total flow rate of etching gas.

[Explanation of symbols]

101 ... Substrate (single crystal silicon), 102 ... Silicon dioxide layer, 103 ... Silicon nitride layer, 104a, 1
04b ... Trench, 105a, 105b ... Side wall.

Claims (9)

[Claims] 1. A dry etching method for forming a groove having a desired shape on a silicon single crystal through a mask layer, wherein a substrate is arranged on one of a pair of counter electrodes provided in an etching chamber. Then, using an apparatus that supplies high frequency power to both of the counter electrodes to perform etching by plasma, introduces an etching gas into the etching chamber, and applies high frequency power to the counter electrode on the side where the substrate is arranged. A dry etching method characterized in that the side wall shape of the groove is controlled by adjusting. 2. The dry etching method according to claim 1, wherein the etching gas is a gas containing at least Cl.
A dry etching method, which is a mixed gas of gases containing Br. 3. The dry etching method according to claim 2, wherein the gas containing Cl is Cl ₂ . 4. The dry etching method according to claim 1, wherein the gas containing Br is HBr. 5. The dry etching method according to claim 1, wherein the etching gas contains oxygen. 6. The dry etching method according to claim 1, wherein the sidewall shape of the groove is controlled by adjusting the total flow rate of the etching gas. 7. The dry etching method according to claim 1, wherein the sidewall shape of the groove is controlled by adjusting the amount of Cl _{2 in} the etching gas. Etching method. 8. The dry etching method according to claim 1, wherein the high frequency power applied to the counter electrode on the side where the substrate is arranged is 0.157 to 1.57 W / cm ² . The dry etching method is characterized by being in the range. 9. The dry etching method according to claim 1, wherein a plurality of types of grooves having different groove widths are formed on the substrate.