JP2001284319A - Dry etching process and method of manufacturing semiconductor including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing a side deposition by a reaction product and improving the throughput, when a high melting point material such as Ir and Pt is subjected to dry etching by using a mixture gas of chlorine and argon. SOLUTION: The values of an etching rate and a resist selection ratio, when a structure where a SiO2 film 2, a Ti film 3 and the high melting point material film 4 are deposited sequentially on a Si substrate 1 is subjected to dry etching, by using five etching parameters of a photoresist mask 5 are set to optimum conditions by increasing and by decreasing for example, chlorine concentration, the total gas flow rate, pressure, plasma source power and bias power as shown in a table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dry etching process, and more particularly to a dry etching process for a material having low reactivity with an etchant gas represented by a high melting point material such as Ir.

[0002]

2. Description of the Related Art Conventionally, when etching a high melting point material represented by Ir or the like by using a mixed gas with a chlorine gas or an argon gas, a reaction product adheres to a mask side wall (side deposition), and In addition, there is a problem that the etching rate is low and the throughput is poor. In order to solve this problem, for example, in Japanese Patent Application Laid-Open No. Hei 10-98162, side deposits are prevented and the rate is increased by controlling the photoresist shape and appropriately adjusting the chlorine concentration. In JP-A-7-130712, the temperature of a sample is set to 350
℃ or higher to prevent side deposits and raise the rate.
In addition, many types of gas have been studied, such as adding chlorine-based gas or fluorine-based gas instead of chlorine.

[0003]

However, in the conventional method, in order to obtain the optimum etching conditions, there are many materials which are examined by paying attention to parameters such as gas type and temperature, and must be set at the time of dry etching. It seems that little consideration has been given to the optimal conditions of the etching parameters such as the concentration of the gas, the total flow rate of the gas, and the pressure.

Accordingly, the present invention provides an etching gas
In a dry etching of a high melting point material using a photoresist mask using a mixed gas of chlorine and argon,
It is intended to provide a method for optimizing etching parameters such as gas concentration, total gas flow rate, pressure, plasma source power, and bias power.

[0005]

According to the dry etching process of the present invention, in the step of dry-etching a high melting point material represented by Ir or the like using a photoresist mask, an etching rate between the material to be etched and the photoresist mask is determined. The value of the resist selectivity expressed by the ratio of
No deposit is generated on the mask side wall at the end of dry etching,
In addition, the etching parameter value is determined so that the photoresist mask width does not decrease.

According to this, etching parameters such as total gas flow rate, pressure, and plasma source power can be set to optimal conditions.

According to a second aspect of the present invention, in the dry etching process, chlorine or a mixed gas of chlorine and argon is used as an etching gas in the dry etching process.

According to this, in the step of dry-etching a high-melting point material represented by Ir or the like using a photoresist mask, the total gas flow rate, pressure, and plasma when using versatile chlorine or argon are used. Etching parameters such as source power can be optimized.

According to a third aspect of the present invention, when dry-etching Ir, etching conditions with a resist selectivity of 0.30 to 0.42 are used.

According to this, it is possible to set the values of the etching parameters such as the total gas flow rate, the pressure, and the plasma source power that give the optimum Ir etching conditions.

According to a fourth aspect of the present invention, when dry etching Pt, etching conditions with a resist selectivity of 0.40 to 0.55 are used. It is possible to set values of etching parameters such as a total gas flow rate, a pressure, and a plasma source power that provide an optimal Pt etching condition.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) An embodiment of the present invention will be described with reference to the drawings.

First, as shown in FIG.
An iO ₂ thermal oxide film 2 is formed to a thickness of 600 nm, a Ti film 3 is deposited thereon by sputtering to a thickness of 20 nm, and an Ir film 4 as a high melting point material film is deposited thereon to a thickness of 200 nm. Thereafter, the photoresist 5 is coated to a thickness of 1.2 μm by spin coating, and a pattern is formed by exposure and development.
Here, the structure under Ir does not necessarily need to be the above-mentioned structure, and is chemically stable during dry etching.
It suffices if adhesion with r can be ensured. Further, the structure under Ir may not be formed.

Next, FIG. 2 shows an etching apparatus. A plasma source 6 and a lower electrode 7 are arranged as shown in the figure, and an etching gas is supplied from a gas outlet (not shown) immediately below the plasma source 6 and exhausted by a vacuum pump (not shown). The plasma source power is power supplied to the plasma source 6, and the bias power is power supplied to the lower electrode 7. The sample 8 in FIG. 1 is held on the lower electrode 7 by an electrostatic chuck. At this time, the temperature of the lower electrode is 60 ° C. As a plasma source, I
Any high-density plasma source such as CP may be used.

The sample shown in FIG. 1 is etched by the etching apparatus shown in FIG. The etching gas is chlorine or a mixed gas of chlorine and argon. The etching parameters are plasma source power, bias power, chlorine concentration, total gas flow rate, and pressure, and the etching is performed by changing these parameters for each sample. The etching end point is detected by an optical end point monitor.

In particular, the pressure is 0.3 Pa to 1.0 Pa, the plasma source power is 600 W to 1000 W, the bias power is 300 W to 550 W, the chlorine concentration is 20 to 80%, and the total gas flow is 50 sccm to 200 sccm. As an example, plasma source power = 900 W, bias power = 450 W, chlorine concentration = 40%, total gas flow rate = 150 s
ccm, pressure = 0.6 Pa.

After that, the photoresist mask 5 is removed by O ₂ plasma.

In the case of Ir, conditions under which etching can be performed without side deposits are determined only by the ratio of the Ir etching rate to the photoresist etching rate (Ir etching rate / photoresist etching rate, hereinafter referred to as resist selectivity). If the resist selectivity is 0.42 or less, etching can be performed without the side deposit. Further, the shape of Ir after etching is substantially the same as long as the resist selectivity is the same. Conditions in which the resist selectivity is above 0.42 include, for example, plasma source power = 900 W, bias power = 450 W, chlorine concentration = 20
%, Total gas flow = 100 sccm, pressure = 0.6 Pa, plasma source power = 900 W, bias power = 450 W, chlorine concentration = 40%, total gas flow = 50 sc
cm, pressure = 0.3 Pa. The condition that the resist selectivity is 0.42 or less is, for example, plasma source power = 1000 W, bias power = 450 W, chlorine concentration = 40%, total gas flow rate = 100 sccm, pressure = 0.
6 Pa conditions, plasma source power = 900 W, bias power = 450 W, chlorine concentration = 40%, total gas flow =
The conditions are 100 sccm and pressure = 1.0 Pa. If the chlorine concentration is 20% or less, it is difficult to reduce the resist selectivity to 0.42 or less. Therefore, the chlorine concentration is preferably 20% or more.

On the other hand, if the resist selectivity is too small, the resist receding becomes large, and the mask size is reduced.
The etching size is reduced. Therefore, considering this, it can be said that favorable etching conditions are when the resist selectivity is between 0.30 and 0.42. However, this etching condition is such that the thickness of the photoresist 5 is 1.2 u.
In the case where the thicknesses of the m and Ir films 4 are 200 nm, and when the respective thicknesses are changed from those described above, the resist selectivity conditions for etching without side deposition are different.

Next, the above results will be described. When the Ir film 4 being etched begins to be etched, FIG.
As shown in (a), a side deposit 9 mainly composed of Ir is generated on the side surface. At this time, since Ir hardly reacts with chlorine, most of it is cut off by physical etching using chlorine plasma and argon plasma. on the other hand,
The photoresist 5 reacts with the chlorine plasma and is etched in a tapered manner from the upper side where the side deposit is thin.

As the etching proceeds further, as shown in FIG. 3 (b), the entire photoresist has a taper, and the side deposit becomes physically easily etched, so that etching without the side deposit can be performed.

FIGS. 4A and 4B show typical shapes after etching. FIG. 4A shows etching without a tapered side deposit. FIG. 4 (b)
Since the etching rate of the photoresist is low, the etching of Ir is completed before the photoresist becomes the state of FIG. 3B. Here, even under the condition having the same photoresist etching rate as that of FIG. 4B, if the Ir etching rate is slower, FIG.
The state shown in FIG. 2B is obtained, and etching can be performed without side deposit. Therefore, the condition that can be etched without side deposit is
It is determined by the ratio between the etching rate of the photoresist 5 and the etching rate of the Ir film 4, that is, the resist selectivity. Further, if the thickness of the photoresist before etching is small, the state shown in FIG. 3B is quickly obtained. Therefore, depending on the thickness of the photoresist 5 or the thickness of the Ir film 4, the conditions under which the etching can be performed without side deposition are as follows. different.

The above properties are not limited to Ir but also apply to compounds such as high melting point metals having low reactivity with chlorine and ferroelectrics. In the case of Pt, the selectivity is 0.40-0.
The range of 55 is a favorable etching condition.

As described above, each of the above five etching parameters may be adjusted and set so as to be in the range of the selectivity without causing the photoresist reduction without the side deposit. However, if the selectivity is the same, the same etched shape can be obtained.

Example 2 Next, an experiment was conducted to increase the etching rate without generating side deposits.
Table 1 shows a change in the Ir etching rate and a change in the resist selectivity when the value of each parameter is increased.

[0027]

[Table 1]

Basically, as shown in the results of Table 1, the chlorine concentration is increased while paying attention to the resist selectivity so that no side deposit is generated and the size of the photoresist mask is not reduced. , Increase gas total flow, decrease pressure, increase plasma source power, increase bias power,
At least one operation may be performed. Of course, a plurality may be combined. Particularly effective methods are described below.

Since high-melting-point materials such as Ir are mainly physically etched by sputtering, bias power greatly contributes to the etching rate. Therefore, to increase the etching rate, first,
After increasing the bias power, if the selection ratio becomes a condition where the side deposit remains, the selection ratio is adjusted by changing any of the chlorine concentration, the total gas flow rate, and the plasma source power. These three parameters do not contribute much to increasing the etching rate from a certain value,
It contributes to the resist selectivity. This is because the increase of the above three types of parameter values has the effect of increasing the chlorine plasma density. However, since high melting point materials such as Ir are mainly subjected to physical etching, if the chlorine plasma density is higher than a certain level, It is considered that this is because the etching rate does not change much, and the other photoresist is mainly etched by a chemical reaction, so that as the chlorine plasma density increases, the etching rate increases. As can be seen from Table 1, since the etching rate and the selectivity decrease as the pressure increases, the pressure is adjusted to be as high as possible at the beginning, and is adjusted when the selectivity cannot be adjusted with the above three parameters.

For example, plasma source power = 900 W,
The conditions of bias power = 300 W, chlorine concentration = 40%, total gas flow rate = 150 sccm, and pressure = 0.6 Pa fall within the range of the resist selectivity at which the Ir film 4 of the first embodiment can be favorably etched. At this time, the etching rate of the Ir film 4 is about 150 nm / min. When the bias power is set to 450 W to increase the etching rate and the chlorine concentration is set to 60% to adjust the selectivity, an etching rate of about 200 nm / min can be obtained. When the bias power is set to 450 W and the total gas flow rate is set to 200 sccm, about 195 nm / min can be obtained.

This method can be applied to high melting point materials other than Ir. In the case of Pt, the relationship between the etching rate and each parameter is exactly the same as in the case of Ir shown in Table 1, and therefore, exactly the same method can be applied.

(Embodiment 3) Next, application examples of Embodiments 1 and 2 will be described. In considering mass production of semiconductor devices, it is important to increase the yield in addition to increasing the etching rate and the throughput. For this purpose, it is better to have a wide margin for the etching conditions. Ir
Resist selectivity to obtain good etching of 0.3
Since it is 0 to 0.42, if the etching rate is increased under the condition of the resist selectivity of 0.36, favorable etching conditions with the widest margin can be obtained.

For example, plasma source power = 900 W,
When the bias power is 450 W, the chlorine concentration is 40%, the total gas flow rate is 150 sccm, and the pressure is 0.6 Pa, etching can be performed at a resist selectivity of 0.36 and an etching rate of about 200 nm / min.

[0034]

As described above, according to the dry etching process of the present invention, in the dry etching of a high melting point material using a photoresist mask, etching parameters such as pressure and plasma source power for providing optimum etching conditions. Can be obtained by setting the resist selection ratio to an optimum value.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sample before dry etching in Examples 1, 2, and 3 in the present invention.

FIG. 2 is a cross-sectional view of a dry etching apparatus used in dry etching processes of Examples 1, 2, and 3 in the present invention.

FIG. 3 is a cross-sectional view of a sample during dry etching in Examples 1, 2, and 3 according to the present invention.

FIG. 4 is a cross-sectional view of a sample after dry etching in Example 1 of the present invention.

[Explanation of Codes] 1. Si substrate 2. SiO ₂ film 3. Ti film 4. High melting point material film Photoresist 6. Plasma source 7. Lower electrode 8. Sample 9. Side depot

Claims (5)

[Claims] In a step of dry-etching a high melting point material represented by Ir or the like using a photoresist mask, a value of a resist selectivity represented by a ratio of an etching rate between a material to be etched and the photoresist mask is changed. A dry etching process characterized in that the values of the etching parameters are determined so that a deposit does not occur on the mask side wall at the end of the dry etching and the photoresist mask width does not decrease. 2. The dry etching process according to claim 1, wherein chlorine or a mixed gas of chlorine and argon is used as an etching gas. 3. The dry etching process according to claim 1, wherein when dry-etching Ir, etching conditions with a resist selectivity of 0.30 to 0.42 are used. 4. The dry etching process according to claim 1, wherein, when dry etching Pt, etching conditions with a resist selectivity of 0.40 to 0.55 are used. 5. A semiconductor manufacturing method including a dry etching process using any one of claims 1 to 4.