JP2012094900A - Bcn based insulating film, method of producing the same and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device in which a BCN film can be deposited using a non-corrosive organic aminoboron based gas in place of a conventional BClgas, for example, a BCN film having a stabilized low dielectric constant and a high hardness (Young's modulus) can be deposited using tris(dimethylamino)boron by plasma CVD.SOLUTION: In a method of producing an insulating film, a boron carbon nitride (BCN) based insulating film is deposited using an organic aminoboron based gas. The organic aminoboron based gas is tris(dimethylamino)boron. The BCN based insulating film has a dielectric constant of 2.5 or lower and an elastic modulus (Young's modulus) of 8 GPa or higher.

Description

 The present invention relates to a BCN-based insulating film, a manufacturing method thereof, and a semiconductor device, and more particularly to a BCN-based insulating film having a low dielectric constant, a manufacturing method thereof, and a semiconductor device.

In silicon semiconductor integrated circuits, 65-nm generation system LSIs and 1-Gbit memories have already been produced, and further finer devices are being developed from 45 nm to 32 nm generation. This device development has progressed with the advantage that high-speed operation can be improved by reducing the size of the transistor, but in recent years, the wiring within the device has become longer due to the increased degree of integration and the wiring resistance is separated from the wiring. An electrical signal delay phenomenon due to the capacitance of the insulating layer that has been encountered has encountered the problem of degrading the high-speed operation of the device.
In order to solve this problem, wiring metal (aluminum) and wiring interlayer insulating film (SiO2 (relative dielectric constant k to 4)), which has been conventionally used, are made into a metal having a lower electric resistivity and an insulator material having a lower dielectric constant. Research and development is underway to make changes. The wiring metal was changed from aluminum to copper. On the other hand, with regard to lowering the dielectric constant of the interlayer dielectric film, SiOF, SiOC, and SiC in which fluorine or carbon is added to SiO ₂ have been attracting attention and research and development have been conducted. SiOC is mainly used.

The development of a low dielectric constant film having k <2.2 is eagerly desired for the development of next-generation silicon integrated devices. Due to the trend of practical years for low dielectric constant film (Low-K film) of system LSI using Cu wiring, development of Low-K film for 45 nm generation was promoted in FY2006. It has been studied by forming pores in the insulating film of the system to reduce the dielectric constant. However, such a porous Low-K film has various problems to be solved with respect to introduction into a silicon integrated device as well as development of a film forming method.

The problems with porous Low-k films are: 1) low mechanical strength, 2) high water absorption, 3)
The thermal conductivity is low, and 4) the coefficient of thermal expansion is higher than that of other insulating films. Each problem is described in detail below.
1) Due to the low mechanical strength, in the CMP (Chemical Mechanical Polishing) process used when forming the Cu wiring, the Low-K film is deformed without being able to withstand the load, and the adhesion with the base film is poor. This causes problems such as peeling.
2) Since it becomes easy to absorb water by making it porous, the dielectric constant increases. This is because the dielectric constant of water is as high as about 80. In addition, when the Cu wiring is formed, there also arises a problem that the Cu plating solution penetrates into the porous film through a portion not sufficiently covered with the barrier film.
3) Since the current density is about 105 A / cm ² inside the high-performance CPU, a highly heat-conductive material is desired for the wiring interlayer film to also serve as a heat sink. However, the porous material may reduce the thermal conductivity of the material to about 1/10.
4) In an annealing process when manufacturing an LSI, a void (gap) is generated around the Cu wiring due to a difference in thermal expansion coefficient between the interlayer insulating film and the wiring material Cu. When a multilayer wiring is formed, heat treatment is applied to each layer, so that expansion and contraction are repeated and wiring stress migration is likely to occur.
In addition, there are many problems with the current porous film such that the low-k film on the processed surface is altered by a dry etching gas at the time of groove processing or a chemical solution for polymer removal treatment.
Under such circumstances, the BCN film material is a promising material having excellent physical properties with respect to the above-mentioned four items which are problems in porous low-k. In particular, a BN film containing boron (B) is hard and widely used as a cutting material, and a BCN film containing C also has a Young's modulus of 10
It has been reported that it becomes 0 GPa or more (Non-Patent Document 1).
When considering the dielectric constant of the BCN-based material, the molecular polarizability volume is also a reference, as in the case of the SiOC-based Low-k film. In order to reduce the dielectric constant, it is necessary to reduce the component of orientation polarization. For example, a single bond of C—C has a smaller polarizability than a double bond of C═C, and is suitable for a low dielectric constant material. Will be. Therefore, it is desirable to form a film with a single bond in order to reduce the dielectric constant.

C. Morant, D.M. Caseres, J .; M.M. Sanz and E.M. Elizalde, Diamond and Relat. Mater. 16 (2007) 1441. Japanese Patent Laying-Open No. 2005-210136

So far, SiOC-based porous LowK films have been studied. However, since the mechanical strength and hardness are low, there is a problem that the mechanical strength of CMP and mechanical damage during wire bonding cannot be tolerated. Therefore, the dielectric constant is 2 while maintaining the hardness (10 Gpa or more in Young's modulus).
. Less than 3 Low-k materials are desired.

In the preparation of a BCN film, conventionally, BCl ₃ gas has been used to introduce boron (B) (for example, Patent Document 1). However, when used as an interlayer insulating film for LSI wiring, the contained chlorine (Cl) component may corrode Cu wiring or the like. Further, in the conventional mixed gas system, in addition to the BN single bond, depending on the film forming conditions, a CC double bond or a BN triple bond (the dielectric constant increases because the polarization volume ratio is high) occurs. It is difficult to stably form a film having a low dielectric constant.

An object of the present invention is to provide an insulating film capable of maintaining the reliability of wiring without corroding wiring (for example, Cu wiring) and a method for manufacturing the same.

An object of this invention is to provide the insulating film which can maintain a low dielectric constant stably, and its manufacturing method.

An object of this invention is to provide the insulating film which has high mechanical strength, and its manufacturing method.

The present invention uses a non-corrosive organic aminoboron-based gas instead of BCl ₃ gas to make BC
It is characterized by forming an N film. Examples of the organic aminoboron gas include trisdimethylaminoboron (TMAB) and dimethylaminoboron. TMAB is preferable because the methyl group of CH ₃ may be incorporated into the film relatively stably.

  As a film formation method, for example, film formation may be performed by plasma CVD.

In addition, the chemical formula of trisdimethylaminoboron (TMAB) is B [N (CH ₃ ) ₂ ] ₃
The bond energy between the atoms constituting the gas is strong in the order of BN <CN <CH. Therefore, when decomposed by plasma, the BN and CN bond portions are first cut,
In the state where CH3 (methyl group) remains, it is taken into the BCN film. Thereby, a space is created in the vicinity of CH3 in the film, and the dielectric constant can be stably reduced.

The invention according to claim 1 is an insulating film manufacturing method for forming a boron nitride carbon (BCN) -based insulating film using trisdimethylaminoboron and N ₂ .

  The invention according to claim 2 is the method for manufacturing an insulating film according to claim 1, wherein the BCN film is formed by using a PACVD method.

  The invention according to claim 3 is the method for manufacturing an insulating film according to claim 1 or 2, wherein the trisdimethylaminoboron supplies gas by heating a gas cylinder, gas piping, and mass flow controller to 50 ° C. or higher.

The invention according to claim 4, the flow rate ratio of N ₂ and TMAB supplied as the gas 2: 1 to 1: 1 an insulating film according to claim 1, wherein any one of claims 1 to 3, It is a manufacturing method.

  The invention according to claim 5 is the insulating film manufacturing method according to any one of claims 1 to 4, wherein the RF power in the CVD method is 40 W or less.

The invention according to claim 6 is the method for producing an insulating film according to any one of claims 1 to 5, wherein annealing at 300 to 400 ° C. is performed in an N ₂ gas atmosphere for 30 minutes.

The invention according to claim 7 is the method for manufacturing an insulating film according to any one of claims 1 to 6, wherein CH ₄ gas is mixed for forming the BCN film.

The invention according to claim 8 is the method for manufacturing an insulating film according to claim 6, wherein H ₂ gas is used for the annealing treatment.

  The invention according to claim 9 is a BCN-based insulating film manufactured by the method according to claim 1 according to any one of claims 1 to 8.

  The invention according to claim 10 is a semiconductor device having the insulating film according to claim 9 as an insulating film between wiring layers.

According to an eleventh aspect of the present invention, there is provided a structure in which a conductive layer is filled in the wiring groove provided in the insulating film according to claim 9 and the via hole provided in the BCN-based insulating film corresponding to the wiring groove. It is a semiconductor device having.
The invention according to claim 12 is the semiconductor device according to claim 11, wherein the via hole is formed by dry etching using a fluorocarbon gas.

According to the present invention, residual Cl due to BCl3 gas does not exist in the interlayer insulating film, so that Cu
Wiring reliability can be maintained without corroding the wiring. In addition, C in the BCN film
Since H3 is structurally incorporated, a low dielectric constant can be stably maintained.

The BCN film is formed by PACVD (Plasma-assisted chemical va
The film was formed using a por deposition method. Trisdimethylaminoboron (T
MAB) The gas flow rate is 0.5 to 5 sccm, the N2 gas flow rate is 0.5 to 5 sccm, the film formation temperature is 300 ° C. to 400 ° C., the film formation pressure is 0.1 to 0.5 Torr, and the RF power is 1
Experiments were performed in the range of 0 to 100W. In order to prevent the TMAB gas from being liquefied inside the pipe, it is desirable to supply the gas by heating the gas cylinder, the gas pipe, and the mass flow controller to 50 ° C. or higher.

In the experiment, N ₂ was deposited at ₂ ccm, TMAB at 1 ccm, the growth pressure was 0.2 Torr, the deposition temperature was 350 ° C., and the RF power was 10 to 1000 W. The composition ratio is 3 for B
5 to 40%, C is 20 to 25%, and N is 30 to 40% (% is% by weight). In addition, atomic%
Then, B: 33 to 47% C: 13 to 28% N: 14 to 32%.

The flow rate ratio between N ₂ and TMAB is preferably 2: 1 to 1: 1. By setting it within this range, there is an advantage that the plasma can be stably formed and the target film composition can be obtained more reliably.
Also, after N2 gas is first introduced and the plasma is stabilized (about 30 to 60 seconds), T
Introducing MAB is also preferable for obtaining a desired film composition more reliably.

From the experiments, the relative permittivity (k value) of the BCN film tended to be smaller as the RF power was lower. FIG. 1 shows a conventional BCl3 gas and a TMAB gas of the present invention (RF power: 20 W).
) Shows the relative dielectric constant (k value). The film formation using the TMAB gas was performed at 20 W, and there was only a change of about ± 0.5 around k = 2.08. In contrast, the conventional B
The Cl3 film has k = 1.9 units at the minimum value, but as a whole, ± 2 around k = 2.14.
. There is a variation of about 0, and the k value varies.

The preferred range of RF power is 20W-60W. In this range, there is an advantage that the CH3 of TMAB is easily taken into the film without being decomposed, and a double or triple bond having a large polarization volume fraction is difficult to be formed. More preferably, it is 40W or less, More preferably, it is 30W or less.

In addition, by performing annealing at 350 ° C. for 30 minutes in an N ₂ gas atmosphere, TMA
The k value of the BCN film made of B gas was reduced to the center value k = 1.94 with little variation.

The conventional BCN film growth conditions are N ₂ (1.0 sccm), CH ₄ (0.5 scc).
m), BCl ₃ (0.8 sccm), H ₂ (1.0 sccm), RF power (80 W),
The film forming temperature was 390 ° C.

The analysis reveals that the elemental composition ratio in the BCN film by the TMAB gas decreases as the RF power decreases, and the ratio of B and N decreases and C increases. The reason for the high C ratio at low RF power is that when the RF power is low, the C—H bond is not decomposed and the methyl group (
In the state of CH3), it is presumed to be taken into the film. Therefore, conventional BCl ₃
FT-IR (Fourier tr) of BCN film for gas deposition and BCN film for TMAB gas deposition
FIG. 2 shows the result of measurement with an infrared Infrared Spectrophotometer.

A peak is observed in the TMAB gas in the vicinity of 2962 cm −1 indicating the C—H stretching mode of the methyl group (due to the methyl group CH ₃ ), but this peak is not observed when the BCl ₃ gas is used. The presence of this peak suggests that the methyl group of the C—H bond has been incorporated into the film without being decomposed, and it is assumed that the structure is relatively stable with a large amount of space. Is done. On the other hand, when BCl3 gas is used, there is no methyl group, and conversely, C—C is present in the film.
In some cases, a double bond or a BN triple bond is formed. In film formation of BCl3 gas system,
Depending on conditions, such multiple bonds are often observed by FT-IR.

In preparation of the BCN film, in order to control the C concentration in the film in addition to TMAB gas and N ₂ gas,
H ₄ gas may be mixed. Further, H ₂ gas may be used for the annealing treatment.

Next, the strength of the BCN film was measured using a nanoindenter. FIG. 3 shows the relationship with the relative dielectric constant on the vertical axis and the Young's modulus on the horizontal axis. Currently used SiOC-based porous films and organic films have a Young's modulus of 10 Gpa or less.
Young's modulus is 26.5 Gpa and 32.1 Gpa, even if the film forming conditions are changed, it is almost 20-40.
It is in the range of Gpa. Therefore, this BCN film has a k value of 2.5 or less and a Young's modulus of 10 Gp.
It is possible to keep a above a. However, if it is too high (too hard), too much stress is applied to the Cu wiring and stress migration occurs in the wiring. 10
0 Gpa or less is preferable, and 80 Gpa or less is more preferable.

FIG. 4 shows a wiring structure formed by the dual damascene method using the interlayer insulating film according to the embodiment of the present invention. The dual damascene method is a method in which the via 11 and the trench wiring 12 are simultaneously opened, and the conductive material is buried in the via 11 and the trench wiring 12 at the same time, so that the planarization process is completed once.

First, an insulating layer 14 to be a layer in which the via 11 and the trench wiring 12 are embedded is prepared. Insulating layer 14
Uses the BCN film of the present invention as a low dielectric constant material (Low-k material).
Next, resist patterning for opening the via portion is performed on the insulating layer 14 by photolithography, and CF _x -based gas (C _n F _m gas: n and m are integers), for example, C ₄ F ₈ gas The insulating layer 14 is dry etched. Other than these, CF ₄ , CHF ₃ , CH ₂ F ₂ , CH ₃
An etching gas such as F may be used. Further, the trench wiring 12 is also subjected to resist patterning, and the insulating layer 14 is dry-etched with a CF _x gas. In this case, etching is performed up to the depth of the groove, and the etching is stopped halfway. Via 11 and wiring trench 12
After forming, the residue is removed by a cleaning process using a chemical solution.

A TaN film, Ru film or TaN / Ta laminated film is used as the via metal 13 and the insulating layer 14.
Is deposited on the entire exposed surface by sputtering or CVD. A Cu film to be a seed is deposited by sputtering, and the plated Cu film 12 is embedded in the via and the trench wiring. For planarization, the surplus plated Cu film is removed by chemical mechanical polishing (Chemical Mechanical Polishing).
Polishing Method, hereinafter referred to as CMP method. 4), the structure shown in FIG. 4 is formed. The buried metal is Cu-Al alloy, Cu-Mg alloy, Ag, A
g alloy may also be used.

When the planarizing process using CMP is soft against frictional force, shearing force, etc., a so-called “dishing” indentation is formed in a portion having a wide wiring pattern. Further, “erosion” is caused in a densely packed region. For this reason, in order for the flattening process to be performed satisfactorily, the insulating layer 14 must have an appropriate mechanical strength.

In the case of the CMP process, the mechanical properties required for the surface film exposed to the flattening process are estimated to have a Young's modulus of about 10 GPa or more, but the BCN according to the embodiment of the present invention is used.
The film has a mechanical strength of Young's modulus of 25 GPa or more and has a sufficient resistance. In addition, the dielectric constant is about 2.2, which is sufficiently smaller than that of a normal porous Low K film and the like, and can be expected to exhibit sufficient electrical characteristics as a part of the device.

The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications and improvements of the damascene method for forming a wiring within the scope of the present invention are within the scope of the present invention. Needless to say, it can be done.

It is a figure which shows the difference in the dielectric constant of the BCN film | membrane by a conventional method and this invention. It is a diagram illustrating the difference in FT-IR spectra of the BCN film according to Example (TMAB) conventional method (BCl ₃₎ and the present invention. It is a figure which shows the Young's modulus and relative dielectric constant of various low dielectric constant films. It is a schematic diagram explaining the wiring structure which concerns on the Example of this invention.

11: Metal embedded in via (Cu film)
12: Metal embedded in wiring trench (Cu film)
13: Barrier metal film (TaN film)
14: Wiring interlayer insulating film (BCN film)
15: Barrier insulating film (SiCN film)
16: Wiring interlayer insulating film (BCN film)
17: Wiring part (Cu film)

Claims (12)

An insulating film manufacturing method for forming a boron nitride carbon (BCN) -based insulating film using trisdimethylaminoboron and N ₂ . The method for manufacturing an insulating film according to claim 1, wherein the BCN film is formed using a PACVD method. The insulating film manufacturing method according to claim 1, wherein the trisdimethylaminoboron is supplied with gas by heating a gas cylinder, a gas pipe, and a mass flow controller to 50 ° C. or more. Method for producing 1 an insulating film according to claim 1, wherein any one of claims 1 to 3 is: flow ratio 2 of N ₂ and TMAB supplied as the gas: 1 to 1. The method for manufacturing an insulating film according to claim 1, wherein an RF power in the CVD method is 40 W or less. The insulating film manufacturing method according to claim 1, wherein annealing is performed at 300 to 400 ° C. for 30 minutes in an N ₂ gas atmosphere. The method for manufacturing an insulating film according to any one of claims 1 to 6, wherein CH ₄ gas is mixed for forming the BCN film. The method for manufacturing an insulating film according to claim 6, wherein H ₂ gas is used for the annealing treatment. A BCN-based insulating film manufactured by the method according to claim 1. A semiconductor device comprising the insulating film according to claim 9 as an insulating film between wiring layers. 10. A semiconductor device having a structure in which a conductive layer is filled in a wiring groove provided in an insulating film according to claim 9 and a via hole provided in the BCN insulating film corresponding to the wiring groove. The semiconductor device according to claim 11, wherein the via hole is formed by dry etching using a fluorocarbon gas.

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