KR100826651B1 - Method for forming contact in semiconductor device - Google Patents

Abstract

A method for forming a contact of a semiconductor device is provided to implement excellent morphology, low contact resistance, and excellent electro migration characteristic by performing a CVD aluminum process using TMAAB(Trimethylaminealane borane) as a precursor. An interlayer dielectric(310) formed on a semiconductor substrate(300) is etched to form a contact hole. A first aluminum layer(330) is formed in the contact hole by using TMAAB as a precursor. A second aluminum layer(340) is formed so that the contact hole is gap-filled. The first aluminum layer is formed through a CVD process. When the first aluminum layer is formed, the semiconductor substrate is loaded in a reactive chamber. The TMAAB precursor is injected into the reactive chamber. The aluminum layer is deposited by increasing temperature of the reactive chamber and performing a thermal decomposition of the precursor.

Description

Method for forming contact in semiconductor device

1 is a diagram showing the chemical structural formula of MPA.

2 is a diagram showing the chemical structure of TMAAB.

3 is a graph showing the number of particles according to precursors for CVD aluminum deposition.

Figure 4 is a graph showing the deposition rate according to the deposition temperature and the lower film when depositing CVD aluminum using TMAAB.

5A to 5C are atomic force microscope (AFM) photographs of CVD aluminum films deposited using TMAAB as a precursor.

FIG. 6 is a graph showing a glazing incidence angle XRD result of a CVD aluminum film deposited using TMAAB as a precursor.

FIG. 7 is a diagram illustrating Secondary Ion Mass Spectrometry (SIMS) profiles of CVD aluminum films deposited using TMAAB and MPA as precursors, respectively.

8 is a graph showing the specific resistance of the CVD aluminum film deposited using TMAAB and MPA as precursors, respectively.

9 and 10 are cross-sectional views illustrating a process of depositing a CVD aluminum film using TMAAB as a precursor.

11 to 13 are cross-sectional views illustrating a method of forming a contact of a semiconductor device using a CVD aluminum process according to an embodiment of the present invention.

14 is a graph showing contact resistance of contacts formed by a CVD aluminum process and a tungsten plug process.

FIG. 15 is a graph illustrating an operation speed of a device when a contact is formed using a CVD aluminum process and a tungsten plug process.

16 shows electromigration (EM) characteristics of CVD aluminum contacts and tungsten plugs.

The present invention relates to a method for forming a contact of a semiconductor device, and more particularly, to a method for forming a contact of a semiconductor device using CVD aluminum (Al).

As the minimum feature size of the semiconductor memory device is drastically reduced to 60 nm or less, the contact hole filling environment is getting worse. Therefore, the importance of the process of reliably filling contact holes or vias, which is one of the factors that determine the contact resistance or the operating speed of the device, becomes more important. Conventionally, the tungsten (W) plug process using tungsten has been mainly used for the filling of contact holes, but the tungsten plug process has a large number of processes and is complicated, and the specific resistance of the tungsten thin film itself is larger than that of aluminum (Al). There is this.

In order to improve this problem, studies on an aluminum plug process for filling contact holes using aluminum (Al) deposited by a chemical vapor deposition process as a wetting payer have been actively conducted. However, as the size of the contact hole decreases, the step coverage characteristics of the CVD aluminum film used as the wetting layer become poor, so that in the subsequent step, PVD (Physical Vapor Deposition) aluminum is deposited and an overhang at the entrance of the contact hole is performed. There is a problem that (overhang) occurs.

Recently, research has been actively conducted as a warm-aluminum process using CVD aluminum as a seed layer provides good contact hole filling characteristics. Precursors of CVD aluminum that are being studied recently are dimethylethylamine alane (DMEAA, C ₄ H ₁₄ AlN), and methylpyrrolidine alane (MPA, C ₅ H ₁₄ AlN). Alane (AlH ₃ ) series, such as dominate. The allene-based precursor has an advantage of low carbon incorporation in the aluminum thin film.

However, the precursors of the allene-based precursors, which have been used in the past, have low gas stability and thus easily form polymers, thereby causing major particles during thin film deposition. Particles generated during aluminum deposition cause bridges in the etching process for forming metal wires, thereby causing device defects and lowering yields.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method for forming a contact for a semiconductor device capable of reliably filling contact holes using new precursors for depositing CVD aluminum to improve device characteristics.

According to an aspect of the present invention, there is provided a method of forming a contact for a semiconductor device, the method comprising: forming a contact hole by etching an interlayer insulating layer formed on a semiconductor substrate, and forming trimethylaminealane borane in the contact hole; Forming a first aluminum film using TMAAB) as a precursor, and forming a second aluminum film to fill the contact hole.

In the present invention, the first aluminum film is formed by chemical vapor deposition (CVD). The forming of the first aluminum film may include loading a semiconductor substrate into the reaction chamber, injecting the trimethylaminealane borane (TMAAB) precursor into the reaction chamber, and adjusting the temperature of the reaction chamber. It may be made to increase the aluminum film is deposited by thermal decomposition of the precursor. At this time, in the step of increasing the temperature of the reaction chamber, it is possible to increase the temperature of the reaction chamber to 300 ~ 450 ℃.

Before the forming of the first aluminum layer, the method may further include forming a wetting layer on an inner wall of the contact hole. The wetting layer may be formed by depositing a titanium (Ti) film by a sputtering method.

The method may further include performing precleaning on the semiconductor substrate on which the contact hole is formed, before forming the first aluminum layer.

The second aluminum film is formed using a physical vapor deposition (PVD) method. The forming of the second aluminum film is performed at the temperature of 300 to 450 ° C. in-situ with the forming of the first aluminum film.

The second aluminum film may be formed using an aluminum (Al) -copper (Cu) target.

After the forming of the second aluminum film, heat treatment may be performed on the semiconductor substrate on which the second aluminum film is formed. The heat treatment may be performed for 30 seconds to 150 seconds at a temperature of 400 ~ 650 ℃.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below.

In the present invention, a conventional methylpyrrolidine alane (hereinafter referred to as MPA) and a new precursor, trimethylaminealane borane (hereinafter referred to as TMAAB), which are precursors for depositing CVD aluminum, are referred to. By comparison, we propose a method of forming aluminum contacts using the superior properties of TMAAB.

In the deposition of aluminum thin film using chemical vapor deposition (CVD) process, an aluminum compound called precursor (precursor) is used as a raw material, and in the process of depositing a metal thin film, the characteristics and selection of precursors determine the success or failure of CVD deposition process. It is an important factor. Currently, in the contact hole filling process of a semiconductor device, an aluminum thin film is mainly formed by an CVD method using an allene (AlH ₃ ) -based aluminum precursor, and a deposition mechanism is pyrolysis. That is, after the precursor of allene (AlH ₃ ) series is adsorbed to the semiconductor substrate at a temperature of about 150 ~ 200 ℃, the aluminum (Al)-nitrogen (N) bond and aluminum (Al)-hydrogen (H) by thermal decomposition As the bond breaks, an aluminum thin film is deposited. In general, when the A and B gas are deposited by atomic layer deposition (ALD) by periodic repetition, the step coverage characteristics may be improved to form a conformal thin film. ₃ ) A series of precursors are deposited by pyrolysis and it is difficult to use the ALD method because there is only one feed gas.

TMAAB  Precursor CVD Aluminum film  characteristic

TMAAB is one of allaneic compounds such as MPA, a well known aluminum precursor. Since the allene-based compound does not have an aluminum (Al) -carbon (C) bond, it has an advantage of low carbon incorporation of the deposited aluminum thin film.

1 is a diagram showing the chemical structure of MPA, MPA has an allene (AlH ₃ ) group in which three hydrogen (H) is bonded to aluminum (Al). Because allene (AlH ₃ ) groups have low stability to temperature, they are easily released during the process to form (AlH ₃ ) _X polymers.

2 is a diagram showing the chemical structure of TMAAB. Since TMAAB also contains an allane (AlH ₃ ) group, boron (B) is bonded to hydrogen (H) bonded with aluminum (Al) (AlH ₃ ) _X The production of polymers can be suppressed. Therefore, the gas stability (stability) with the change of temperature or the passage of time is excellent, the generation of particles is suppressed when forming metal wiring.

3 is a graph showing the number of particles according to precursors for CVD aluminum deposition.

As shown, it can be seen that when TMAAB was used as the precursor, the number of particles generated during the deposition of the aluminum film was significantly less than when MPA was used as the precursor. Particle formation during deposition of CVD aluminum using an allene compound-based precursor is known to be due to allene (AlH ₃ ) being very unstable, highly reactive, and highly polymerizable. Therefore, referring to the results of FIG. 3, since TMAAB contains allene (AlH ₃ ), since boron (B) is bonded to hydrogen (H) which is bonded to aluminum (Al), allene (AlH ₃₎ ) _X It can be seen that the number of particles is significantly lower when depositing aluminum because the production of polymer is suppressed.

Figure 4 is a graph showing the deposition rate according to the deposition temperature and the lower film when depositing CVD aluminum using TMAAB.

The deposition rates 10 and 20 of aluminum on the titanium (Ti) and titanium nitride (TiN) films deposited by the sputtering method increased with increasing temperature, and the deposition rates became saturated at temperatures of about 150 ° C or higher. On the other hand, the deposition rate 30 of aluminum on a tetradimethylamino titanium (TDMAT) CVD titanium nitride (TiN) film was drastically reduced at temperatures above 150 ° C. Usually, when depositing an aluminum film using the precursor of an allene series, it is known that aluminum is deposited by providing the electron of the board | substrate with hydrogen (H) of an allene group. Substrate dependence of TMAAB at such a high temperature can be explained by the difference in absorption rate according to the type of substrate. The activation energy in the surface reactions was 8.07 kcal / mol for sputtered titanium (Ti), 30.94 kcal / mol for sputtered titanium titanide (TiN), and 31.4 kcal / mol for TDMAT CVD-TiN, respectively. Therefore, the activation energy in the sputtered Ti is the lowest.

5A to 5C are atomic force microscope (AFM) photographs of CVD aluminum films deposited using TMAAB as precursors, and are atomic force micrographs of CVD aluminum films deposited on a sputtered Ti film, a sputtered TiN film, and a TDMAT CVD TiN film, respectively. .

Although the morphology of the CVD aluminum film on the sputtered Ti film (see FIG. 5A) is relatively good, the morphology of the CVD aluminum film deposited on the sputtered TiN film and the TDMAT CVD TiN film is very poor and even abnormal deposition. This can also be seen.

FIG. 6 is a graph showing glazing incidence angle XRD results of CVD aluminum films deposited using TMAAB as a precursor, respectively, with a sputtered Ti film 40, a sputtered TiN film 50, and a TDMAT CVD TiN. The results in the film 60 are shown.

As shown, (111) crystal growth appeared in the CVD aluminum film deposited on the sputtered Ti film.

5A to 6, it can be seen that the TMAAB precursor can form the aluminum film having the best properties on the Ti film rather than the TiN film.

FIG. 7 is a diagram illustrating a secondary ion mass spectrometry (SIMS) profile of a CVD aluminum film deposited by using TMAAB and MPA as precursors, and reference numeral “70” denotes MPA when TMAAB is used as a precursor. It shows the case used as.

8 is a graph showing the specific resistance of the CVD aluminum film deposited using TMAAB and MPA as precursors, respectively. Reference numeral "90" indicates a case where TMAAB is used as a precursor, and "100" indicates a case where MPA is used as a precursor.

Boron peaks were detected in CVD aluminum using TMAAB precursors. However, the specific resistance of CVD aluminum using TMAAB is as low as 3.5 µΩ / cm. This indicates that the addition of boron (B) in the aluminum film did not affect the specific resistance of the CVD aluminum film.

Therefore, when a CVD aluminum film is deposited on a titanium film by using TMAAB as a precursor, an aluminum film having excellent morphology and low resistivity with little particle generation can be formed.

TMAAB  Using precursor CVD Aluminum film  And contact  formation

9 and 10 are cross-sectional views illustrating a process of depositing a CVD aluminum film using TMAAB as a precursor.

Referring to FIG. 9, a cross-sectional view of an aluminum film deposited using a TMAAB precursor on a semiconductor substrate, in which a TMAAB precursor is injected into a reaction chamber to adsorb the TMAAB precursor 210 onto a surface of the semiconductor substrate 200. Indicates.

Referring to FIG. 10, the PMAAB precursor adsorbed on the surface of the semiconductor substrate is thermally decomposed due to the subsequent supply of reaction energy, and thus the aluminum film 220 is deposited.

11 to 13 are cross-sectional views illustrating a method of forming a contact of a semiconductor device using a CVD aluminum process according to an embodiment of the present invention.

Referring to FIG. 11, an insulating film, such as an oxide film, is deposited on the semiconductor substrate 300 to form an interlayer insulating film 310. Although not shown for convenience of description and description, the semiconductor substrate 300 is formed with a lower structure, for example, a transistor including a gate, a source / drain, and / or a bit line.

Next, a contact hole for exposing the lower conductive layer 302 is formed by etching the interlayer insulating layer 310 in the region where the contact is to be formed by performing a photo and etching process. The lower conductive layer 302 may be a source / drain of the transistor, and in some cases, may be a wiring layer such as a bit line. Next, a wetting layer 320 is formed on the inner wall of the contact hole to assist the deposition of CVD aluminum. As mentioned above, the wetting layer 320 may be formed of a titanium (Ti) film by using a sputtering method.

Before the wetting layer 320 is formed, a precleaning process may be performed on the semiconductor substrate on which the contact hole is formed, thereby further improving the deposition characteristics of CVD aluminum in a subsequent step.

Referring to FIG. 12, an aluminum film 330 is deposited on the semiconductor substrate on which the wetting layer 320 is formed by using a CVD method. In this case, TMAAB is used as a precursor for depositing an aluminum film. First, TMAAB is injected into a reaction chamber loaded with a semiconductor substrate and adsorbed onto the surface of the wetting layer 320, and then the temperature of the reaction chamber is increased to about 300 to 450 ° C. Then, the CVD aluminum film 330 is deposited while the aluminum (Al) -nitrogen (N) bond and the aluminum (Al) -hydrogen (H) bond are broken by thermal decomposition of the TMAAB precursor.

The TMAAB precursors include boron (B) is Alain (AlH _3), because it is combined with hydrogen (H) bond with the aluminum, (AlH ₃₎ If the _X polymer is not generated standing conformal CVD aluminum films 330 of the Is formed.

Referring to FIG. 13, an aluminum film 340 is deposited on the CVD aluminum film 330 by using a PVD method to fill the contact hole. The PVD aluminum film 340 is deposited in-situ in the reaction chamber in which the CVD aluminum film is deposited, and is deposited in one-step at a temperature of about 300 to 450 ° C. When the PVD aluminum layer 340 is deposited, copper migration may be improved by doping the aluminum layer 340 with the aluminum (Al) -copper (Cu) target.

In addition, after depositing the PVD aluminum film, the heat treatment process may be performed in-situ to reflow the deposited PVD aluminum film 340 to further improve contact hole filling characteristics. The heat treatment process is preferably performed for 30 to 150 seconds at a temperature of about 400 ~ 650 ℃.

14 is a graph showing the contact resistances 412, 414, 416 of CVD aluminum contacts and the contact resistance 420 of a tungsten plug.

As shown, it can be seen that the contact resistance of the CVD aluminum process is only about 50% of the contact resistance of the tungsten plug process. In addition, it can be seen that the contact hole filling characteristics and the contact resistance of the CVD aluminum process are different depending on many process conditions, for example, pre-cleaning, wetting layer, deposition temperature, or subsequent PVD aluminum deposition process.

FIG. 15 is a graph illustrating an operation speed of a device when a contact is formed using a CVD aluminum process and a tungsten plug process. In the case of the CVD aluminum process (510), it can be seen that the ratio is higher at the higher speed than the tungsten plug process (520).

In order to confirm the reliability of the CVD aluminum process, it is necessary to confirm the wafer-level electromigration (EM) characteristics.

FIG. 16 illustrates electromigration (EM) characteristics of an aluminum contact formed by a CVD aluminum process and a tungsten plug formed by a tungsten plug process, and show a frequency of failure over time. As can be seen in the figure, the EM properties 610 of the aluminum contacts formed by the CVD aluminum process are superior to the EM properties 620 of the tungsten plugs formed by the tungsten plug process.

As described so far, according to the method for forming a contact of a semiconductor device according to the present invention, by forming a contact for connecting the upper and lower conductive layers by a CVD aluminum process using TMAAB as a precursor, the generation of particles is suppressed and the reliability of the device is reduced. Can improve the production yield. In addition, according to the present invention it is possible to form a contact having excellent morphology, low contact resistance and excellent electromigration characteristics.

The present invention is not limited to the above embodiments, and various modifications can be made by those skilled in the art within the technical spirit of the present invention.

Claims (13)

Forming a contact hole by etching the interlayer insulating film formed on the semiconductor substrate; Forming a first aluminum film using trimethylaminealane borane (TMAAB) as a precursor in the contact hole; And And forming a second aluminum film to fill the contact hole. The method of claim 1, And forming the first aluminum film by chemical vapor deposition (CVD). The method of claim 1, wherein the forming of the first aluminum film comprises: Loading the semiconductor substrate into the reaction chamber; Injecting the trimethylaminealane borane (TMAAB) precursor into the reaction chamber, and Increasing the temperature of the reaction chamber so that an aluminum film is deposited by pyrolysis of the precursor. According to claim 3, In the step of increasing the temperature of the reaction chamber, The method of forming a contact of a semiconductor device, characterized in that for increasing the temperature of the reaction chamber to 300 ~ 450 ℃. The method of claim 1, Before the step of forming the first aluminum film, And forming a wetting layer on an inner wall of the contact hole. The method of claim 5, The wetting layer is formed by depositing a titanium (Ti) film by a sputtering method. The method of claim 1, wherein before forming the first aluminum film, And pre-cleaning the semiconductor substrate on which the contact hole is formed. The method of claim 1, The second aluminum layer is formed by using a physical vapor deposition (PVD) method. The method of claim 8, The forming of the second aluminum film may include forming the first aluminum film and proceeding in-situ. The method of claim 8, The second aluminum film is formed at a temperature of 300 to 450 ℃ contact method of a semiconductor device. The method of claim 8, And forming the second aluminum film using an aluminum (Al) -copper (Cu) target. The method of claim 1, After the forming of the second aluminum film, performing a heat treatment on the semiconductor substrate on which the second aluminum film is formed. The method of claim 12, The heat treatment is a contact forming method of a semiconductor device, characterized in that performed for 30 seconds to 150 seconds at a temperature of 400 ~ 650 ℃.

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