JP2000331992A - Method for manufacturing semiconductor device - Google Patents

Abstract

[PROBLEMS] To enable anisotropic etching without deteriorating a material film containing an organic component, and to perform etching without using fluorocarbon gas in consideration of global warming environmental issues. It is to provide a way to do it. SOLUTION: Assuming that at least silicon, carbon, oxygen and a halogen element are contained and the element ratio of silicon, carbon, oxygen and a halogen element is silicon: carbon: oxygen: halogen element = A: B: C: D, 2A + 2B <2C + D
The material film (the first insulating film 12 and the second insulating film 15) satisfying the following relationship contains at least one or more of carbon monoxide, hydrogen, nitrogen, ammonia, water, and a rare gas. This is a manufacturing method in which etching is performed using gas plasma, and the etching is performed by decomposing a material film with plasma and gasifying the material film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having an etching process for an interlayer insulating film material containing silicon, carbon, oxygen and fluorine.

[0002]

2. Description of the Related Art It is known that an inter-wiring capacitance that increases with miniaturization of a semiconductor device increases the delay time of the semiconductor device and lowers the operation speed. At present, silicon oxide having a relative dielectric constant of about 4.0 is often used as an insulating material. In order to reduce the capacitance between wirings, it is necessary to use a so-called low dielectric constant material having a low dielectric constant as an insulating material between wirings.

Various materials such as fluororesin and organic SOG (Spin on glass) have been proposed as low dielectric constant insulating materials. On the other hand, the material used for the interlayer insulating film includes chemical mechanical polishing (hereinafter referred to as CMP).
It is necessary to have mechanical strength that can withstand nical polishing and good workability when dry etching is performed. The fluororesin has a relative dielectric constant of 2.
Although it is one of the few materials that can achieve about 0 or less, its mechanical strength is insufficient, and it is difficult to use it as it is as an interlayer insulating film material. On the other hand, organic SOG is commercial
Although it has mechanical strength that can withstand P, it has a relatively high dielectric constant among low dielectric constant materials.

Therefore, mechanical strength can be increased by mixing organic SOG with fluororesin. However, since the mixed material of fluororesin and organic SOG contains an SOG component, it is difficult to perform dry etching. As in the case of processing silicon oxide, processing is generally performed by etching using a fluorocarbon gas and an oxygen gas.

[0005]

However, in a plasma generated using a gas obtained by adding oxygen based on a fluorocarbon gas, a large amount of active halogen (especially fluorine) and oxygen are generated. These active species easily react with the organic component, and since the active state lasts for a long time, the active species easily penetrate to the inside of the film structure and easily invade the organic component. That is, the problems in the conventional method are that the organic component easily reacts with the active species generated by the etching plasma to make it difficult to perform anisotropic etching, and that the film material itself is deteriorated.

Further, in the conventional method, there is a problem that the selectivity to inorganic materials such as silicon oxide and silicon nitride is poor, and if these materials are used for a mask material or an underlayer, it is difficult to process them into a desired shape. is there.

For the reasons described above, silicon, carbon,
It is not suitable to process a material containing oxygen and fluorine by etching using a fluorocarbon gas.

[0008] In addition, the current technology has serious environmental problems. Fluorocarbon gas is said to have a high global warming potential and to cause destruction of the ozone layer, and there is a movement to regulate the amount of use and eventually discontinue production entirely. To cope with this problem and develop a semiconductor device in the future, it is essential to develop a technology for processing an insulating material without using a fluorocarbon gas. Alternatively, it is essential to develop an insulating material that can be processed without using a fluorocarbon gas.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a method of manufacturing a semiconductor device which has been made to solve the above-mentioned problems, and which comprises at least silicon, carbon, oxygen and a halogen element, and includes silicon, carbon, oxygen and a halogen element. The element ratio of the elements is silicon: carbon: oxygen: halogen = A: B:
C: A material film satisfying a relationship of 2A + 2B <2C + D as D is etched using plasma of a gas containing at least one or more of carbon monoxide, hydrogen, nitrogen, ammonia, water and a rare gas. It is characterized by:

In the above-described method of manufacturing a semiconductor device, etching proceeds by causing fluorine and carbon contained in the material film to react with the SOG component by the energy of ion incidence. The composition of the material film contains at least silicon, carbon, oxygen and a halogen element, and the element ratio of silicon, carbon, oxygen and the halogen element is silicon: carbon: oxygen: halogen element = A: B: C: D = 2A + 2B < By satisfying the relationship of 2C + D, etching can be performed without using a halogen compound or oxygen gas. In other words, etching is performed by breaking the bond chains of the material film by plasma to decompose and gasify.

That is, since the relationship of 2A + 2B <2C + D is satisfied, the material film is formed of carbon monoxide (CO), carbon difluoride (CF ₂ ), and silicon difluoride (SiF ₂ ).
And oxygen and fluorine. These active species facilitate the etching.

As described above, since it is not necessary to use a halogen compound or oxygen as an etching gas, there is no deterioration of the material and the etching is performed anisotropically. Further, the etching proceeds by the active species released from the material film which is the material to be etched, so that the selectivity to the underlying material is increased. In addition, carbon monoxide, nitrogen, hydrogen,
By using a plasma of a gas containing at least one or a plurality of ammonia, water, and a rare gas, the sputtering effect of the mask material is suppressed, so that a desired processed shape is easily obtained.

Further, since the material film can be etched without using the fluorocarbon gas, the environmental problem relating to the fluorocarbon gas can be solved at the same time.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of an embodiment according to the present invention will be described with reference to a manufacturing process diagram of FIG.

As shown in FIG. 1A, a substrate 11 on which a semiconductor device (not shown) and wiring (not shown) are formed.
Above, a mixed material of a fluororesin represented by the chemical formula (1) and an organic SOG represented by the chemical formula (2) for use as an insulating material [for example, trade name ST-F (Hitachi Chemical)] Is formed to a thickness of, for example, 400 nm.

[0016]

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[0017]

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As an example, the first insulating film 12 is formed by applying a precursor onto the substrate 11 by a spin coating method,
Curing was performed at 75 ° C. to form a film. This first insulating film 1
The ST-F used in No. 2 is 2A + 2B <2C, based on the principle of a processing method described later, where silicon: carbon: oxygen: halogen (fluorine) = A: B: C: D in element number ratio.
A material having an element number ratio satisfying the inequality [1] of + D is used. The ST-F used here satisfied the above inequality [1] and had a ratio of silicon: carbon: oxygen: fluorine ： 1: 6: 2: 10. Note that the material that can be used for the first insulating film 12 is a mixed material of the fluororesin represented by the above chemical formula (1) and the organic SOG represented by the above chemical formula (2), and silicon, carbon, or the like. Any material may be used as long as it contains the element ratios of oxygen, fluorine and fluorine at the ratio defined by the inequality [1].

Next, on the first insulating film 12, an intermediate layer 13 serving as a hard mask when the first insulating film 12 is etched is formed of, for example, silicon oxide. Subsequently, an opening 14 for forming a connection hole in the intermediate layer 13 is formed by using a usual lithography technique and an etching technique.

Further, a second insulating film (material film) 15 is formed on the intermediate layer 13 including the opening 14. The second insulating film 15 is formed of, for example, the same material as the first insulating film 12 and has a thickness of 400 nm. Next, a mask layer 16 serving as a mask when the second insulating film is etched is formed of, for example, silicon oxide on the second insulating film 15. Subsequently, a groove pattern 17 for forming a wiring groove is formed in the mask layer 16 by using a usual lithography technique and an etching technique.

Next, as shown in FIG. 1B, first, the second insulating film 15 is etched using the mask layer 16 as an etching mask. Then, a wiring groove 18 is formed in the second insulating film 15. In this etching, the intermediate layer 1
3 functions as an etching stopper.

Further, as shown in FIG. 1C, the first insulating film 12 is etched using the intermediate layer 13 as an etching mask to form a connection hole 19. In this etching, the etching of the first insulating film 12 proceeds from the opening 14 formed in the intermediate layer 13 to form a connection hole 19.

In order to form the wiring groove 18 and the connection hole 19 by continuously etching the second insulating film 15 and the first insulating film 12, for example, a general electron cyclotron resonance (hereinafter, referred to as ECR) is used. ECR is Electron Cyc
A plasma etching apparatus was used, argon was used as an etching gas, the pressure of the etching atmosphere was set to 1 Pa, the microwave power was set to 1 kW, and the bias RF power was set to 300 W. The etching reaction under these conditions is as shown in chemical formula (3).

[0024]

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In order to advance the reaction of the chemical formula (3), silicon and carbon are converted into silicon difluoride (SiF
₂ ), it is necessary to vaporize in the form of carbon monoxide (CO) and carbon difluoride (CF ₂ ). For that, the first
The ratio of the numbers of elements contained in the insulating film 12 and the second insulating film 15 of Si: C: O: F = A: B: C: D is 2A + 2B <
It is necessary to satisfy the inequality [1] of 2C + D. Etching can be performed even if the inequality [1] is not satisfied, but care must be taken because silicon and carbon components are likely to remain. In this case, a small amount (for example, less than 3%) of oxygen may be added to the etching plasma so that the first insulating film 12 and the second insulating film 15 are not deteriorated.

In the etching using argon, as shown in FIG. 2A, the shoulder of the mask layer 16 serving as a hard mask is sputtered, and the width of the wiring groove 18 is widened. Therefore, in order to prevent deformation of the mask layer 16 due to sputtering, carbon monoxide (CO) was used as an etching gas. For example, when etching was performed using a mixed gas of carbon monoxide and argon as an etching gas, sputtering of the mask layer 16 could be suppressed as shown in (2) of FIG. However, due to oxygen active species generated from carbon monoxide,
The fluororesin components of the second insulating film 15 and the first insulating film 12 slightly decreased, and the mechanical strength of the material decreased. Therefore, when a mixed gas of nitrogen (N ₂ ), hydrogen (H ₂ ), and argon (Ar) is used as the etching gas, the mask layer 16
Of the second insulating film 15 and the first insulating film 12
No damage was found, and good etching was performed.

Next, an example of the etching conditions for the second insulating film 15 and the first insulating film 12 will be described below.

The first example of the etching conditions is as follows. A parallel plate magnetron plasma etching apparatus is used, argon is used as an etching gas (supply flow rate is 50 sccm, for example), the pressure of the etching atmosphere is 8 Pa, and the etching power is 1. It was set to 5 kW. When etching is performed under these etching conditions, the etching rate is 4
00 nm / min. Hereinafter, sccm indicates a volume flow rate (cm ³ / min) in a standard state.

When etching is performed under the etching conditions of the first example, the mask layer 16 serving as a hard mask is reduced by sputtering. These etching conditions can be applied when the thickness of the film to be etched is as thin as, for example, 300 nm or less, or when the mask layer 16 can be formed sufficiently thick.

A second example of the above etching conditions is that a parallel plate magnetron plasma etching apparatus is used, helium is used as an etching gas (supply flow rate is, for example, 50 sccm), the pressure of the etching atmosphere is 16 Pa, and the etching power is 1. It was set to 5 kW. When etching was performed under these etching conditions, the etching rate was 300 nm / min.

When the etching is performed under the etching conditions of the second example, the etching rate is lower than that of the first example, but the amount of sputtering of the mask layer 16 is small because helium is light. However, since plasma is difficult to discharge only with helium alone, it is necessary to increase the pressure of the etching atmosphere as in this example. Alternatively, discharge can be maintained by using a gas obtained by adding about 1% of argon to helium as an etching gas.

A third example of the above etching conditions is that a parallel plate magnetron plasma etching apparatus is used, and argon (supply flow rate is, for example, 50 sccm) and oxygen (supply flow rate is, for example, 1 sccm) are used as etching gases. The pressure of the etching atmosphere was set to 8 Pa, and the etching power was set to 1.5 kW. When etching is performed under these etching conditions, the etching rate is 700 n.
m / min.

When the etching is performed under the etching conditions of the third example, oxygen volatilizes carbon (C) in the material to be etched in the form of carbon monoxide (CO) as compared with the first example. Therefore, the etching rate is high. Since the processing is completed in a short time, the amount of sputtering of the mask layer 16 is small.
However, since the etching proceeds by oxidizing the fluororesin component, the etching becomes slightly isotropic, and the mask layer 16
The side etching progressed below. In this side etching, the amount of added oxygen is extremely small (for example, a supply flow rate of 0.2
sccm to 0.5 sccm) and the substrate temperature is -80 ° C.
By performing the etching with the degree, the occurrence of the side etching can be suppressed.

A fourth example of the above etching condition is that a parallel plate magnetron plasma etching apparatus is used, and argon (supply flow rate is 50 sccm) and carbon monoxide (supply flow rate is 50 sccm) are used as etching gases. The pressure of the etching atmosphere was set to 8 Pa, and the etching power was set to 1.5 kW. When etching was performed under these etching conditions, the etching rate was 370 nm / min.

When etching is performed under the etching conditions of the fourth example, carbon (C) generated from carbon monoxide forms a deposited film on the mask layer 16 as compared with the first example. In addition, the amount of sputtering of the mask layer 16 is small. Deposition caused by carbon also occurred on the pattern side wall, and had a function of preventing side etching. However, when the substrate temperature was 50 ° C. or higher, side etching was observed due to oxygen generated from carbon monoxide (CO). Therefore, it is desirable to process at a temperature lower than room temperature (for example, 30 ° C.).

The fifth example of the above etching condition is ECR
(Electron Cycrotron Resonance) Using a plasma etching apparatus, nitrogen (supply flow rate is, for example, 50 sccm) and helium (supply flow rate is, for example, 5 sccm) are used as etching gases.
0 sccm), the pressure of the etching atmosphere was set to 1 Pa, and the etching power was set to 3.0 kW. When etching was performed under these etching conditions, the etching rate was 200 nm / min.

When the etching was performed under the etching conditions of the fifth example, the carbon (C) in the film and the nitrogen (N) in the plasma formed CN and deposited, as compared with the first example. As a result, side etching was suppressed and a slightly tapered processed shape was obtained.

A sixth example of the above etching conditions is that an ECR plasma etching apparatus is used, and nitrogen (a supply flow rate is, for example, 50 sccm) and hydrogen (a supply flow rate is, for example, 50 sccm) are used as an etching gas, and the pressure of an etching atmosphere is set. 1 Pa, etching power 3.0 kW
Set to. When etching was performed under these etching conditions, the etching rate was 200 nm / min.

When the etching was carried out under the etching conditions of the sixth example, the deposited C
Since a part of N was volatilized as HCN, the etching rate was increased, and the processed shape became almost vertical.

The seventh example of the etching conditions is as follows. A helicon wave plasma etching apparatus is used, and an etching gas is used by using ammonia (supply flow rate is, for example, 50 sccm) and helium (supply flow rate is, for example, 50 sccm) as an etching gas. Was set to 1 Pa, and the etching power was set to 2.0 kW. When etching is performed under these etching conditions, the etching rate is 350 nm /
Minutes.

When the etching is performed under the etching conditions of the seventh example, the etching proceeds by the same mechanism as in the sixth example. At this time, since the ammonia (NH ₃ ) is easily dissociated in the plasma to form active species as compared with nitrogen (N ₂ ) and hydrogen (H ₂ ), the etching rate is set to the fifth or sixth example. Faster than.

In each of the above examples, neon can be used instead of argon or helium. However, a heavy rare gas such as krypton or xenon, which is a similar rare gas, is not preferable because sputtering of the mask layer 16 becomes intense. In addition, nitrogen (N ₂ ) and hydrogen (H
₂ ) is difficult to dissociate in plasma and generate active species. Therefore, when nitrogen (N ₂ ) or hydrogen (H ₂ ) is used as an etching gas, a high etching rate such as an ECR plasma etching apparatus or a helicon wave plasma etching apparatus is used. It is desirable to perform etching using a high-density plasma etching apparatus. Although ammonia is used only in the seventh example, E
Ammonia can also be used as one of the etching gases when performing etching with a CR plasma etching apparatus or a parallel plate type plasma etching apparatus.

Next, the mechanism of etching the second insulating film 15 and the first insulating film 12 will be described below.

In the etching of the second insulating film 15 and the first insulating film 12, the etching proceeds by the reaction between the carbon component and the SOG component and the fluorine component and the SOG component contained in the films. . That is, when the ions become perpendicular in the plasma and enter perpendicularly, the chemical bond in the material to be etched is broken, and CF _x (x = 1, 2, 2
3) or F is liberated. Some of the liberated CF _x (mainly CF ₂₎ is eventually exhausted as it volatilizes. The remaining CF _x and F react with the first insulating film 12, SOG component in the second insulating film 15, etching proceeds. When this reaction is collectively represented by a chemical formula, it is as shown in the chemical formula (3).

When a gas containing hydrogen such as hydrogen (H ₂ ) or ammonia (NH ₃ ) is used as an etching gas, SiH ₄ is also generated and vaporized.

Through the course of the chemical formula (3), the SOG component, which could not be etched without using a fluorine compound gas, is processed at the same etching rate as before without using a fluorine compound gas. It becomes possible. For that purpose, it is necessary to set plasma conditions that can supply sufficient ion energy. For example, to release CF _x and F at the first stage of the reaction, an ion energy of more than ten eV is sufficient. In order to obtain a practical energy rate, 100 eV which is an order of magnitude higher than that
Degree is required. This level of ion energy can be sufficiently generated by a commonly available etching apparatus.

In the above description, a material film containing fluorine as a halogen element has been described, but the same effect can be obtained even if the material film contains chlorine. In this case,
The etching reaction proceeds in a state where chlorine is replaced instead of fluorine.

As the etching gas, a gas obtained by vaporizing water in addition to carbon monoxide, hydrogen, nitrogen, ammonia, and a rare gas can be used.

[0049]

As described above, according to the present invention,
A material film containing a halogen element such as silicon, carbon, oxygen, fluorine, or chlorine can be etched with good anisotropy without deteriorating the material film. In addition, a hard mask used for etching can be suppressed from being sputtered, and can be processed into a good shape. Further, since a fluorocarbon gas is not used as an etching gas, it is possible to provide an etching method corresponding to environmental problems.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram illustrating an example of an embodiment according to the present invention.

FIG. 2 is a schematic sectional view illustrating a state of a mask layer in etching.

[Explanation of symbols]

12: first insulating film (material film), 15: second insulating film (material film)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M104 DD08 DD20 EE12 EE18 HH14 5F004 AA02 AA16 BA14 CA02 CA03 DA00 DA22 DA23 DA24 DA25 DA26 DB00 DB24 EA06 EB03 5F033 QQ09 QQ10 QQ13 QQ15 QQ25 QQ28 QQ30 RR04 RR04 RR04 RR04 RR04 AA10 AC03 AF04 AG01 AH02

Claims (4)

[Claims] 1. The method according to claim 1, wherein the silicon, carbon, oxygen and halogen elements include at least silicon, carbon, oxygen and a halogen element, and the element ratio of the silicon, carbon, oxygen and halogen elements is silicon: carbon: oxygen: halogen element = A: B:
Etching a material film satisfying the relationship of 2A + 2B <2C + D as C: D using plasma of a gas containing at least one or more of carbon monoxide, hydrogen, nitrogen, ammonia, water and a rare gas A method of manufacturing a semiconductor device. 2. The method according to claim 1, wherein the etching is performed by decomposing the material film with the plasma and gasifying the material film. 3. The material film according to claim 1, A fluorine resin component having a composition represented by the following formula: 2. The method for manufacturing a semiconductor device according to claim 1, comprising a mixture of an organic SOG component represented by the formula: 4. The material film according to claim 1, A fluorine resin component having a composition represented by the following formula: 3. The method of manufacturing a semiconductor device according to claim 2, comprising a mixture of an organic SOG component represented by: