KR20070071109A - Method for fabricating interconnecting contact in semiconductor device - Google Patents

Abstract

A method for forming an interconnecting contact of a semiconductor device is provided to improve sidewall coating quality by depositing a conductive wetting layer with different pressures at a first and a latter deposition stages. An insulating layer(230) having a contact hole(235) is formed on a semiconductor substrate(100). A conductive wetting layer(400) extended to an inner wall of the contact hole is deposited. Second pressure of a process chamber at a first deposition stage for depositing the conductive wetting layer is higher than first pressure thereof at a latter deposition stage. Therefore, the conductive wetting layer is prominently deposited on a bottom of the contact hole at the first deposition stage, but on a sidewall of the contact hole at the latter deposition stage. A contact gap-fill layer is deposited on the conductive wetting layer.

Description

Method for fabricating interconnecting contact in semiconductor device

1 and 2 are cross-sectional views schematically illustrating a method of forming a connection contact of a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a diagram schematically illustrating a self ionizing plasma sputter (SIP) device used for depositing a titanium layer according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor devices, and more particularly, to a method for forming a contact contact capable of improving sidewall coverage of a wetting layer.

As design rules of semiconductor devices are reduced, contact embedding characteristics are becoming worse. Accordingly, in order to effectively fill holes for high aspect ratio contacts with a fine line width, a tungsten contact forming method for depositing tungsten by chemical vapor deposition (CVD) has been introduced.

However, as semiconductor devices, such as graphic memory devices, require higher operating speeds, for example, operating speeds of 667 MHz or higher, there is a demand for lowering the resistance of connection contacts. . Tungsten has a relatively high resistivity of about 20 mu OMEGA cm or more, limiting the demand for lower contact resistance. Thus, attempts have been made to form contact structures that can lower contact resistance.

Aluminum (Al) may be considered as a conductive material having a lower resistivity than tungsten, but preferential introduction of a wetting layer is required to deposit aluminum. Such a wetting layer may consider a titanium (Ti) layer deposited by a self ionized plasma (SIP) sputter.

In SIP sputtering, a magnetron is locally introduced into a partial region on the upper side of a target to increase ionization of metal atoms. Depending on the arrangement of the individual magnets constituting the magnetron and the strength of the magnetic field, this local ionization can be increased, increasing the separation distance between the target and the wafer, and increasing the chamber pressure during deposition. Through the reduction, the linearity of the metal ions onto the wafer is increased.

Accordingly, the SIP sputter may be evaluated to have a relatively good property deposited on the bottom of the contact hole, for example, bottom coverage, but a relatively poor property deposited on the sidewall of the contact hole, for example, sidewall applicability. . This is due to the SIP sputter mainly increasing the linearity of the ions to be deposited, through localized ionization of atoms falling off the target.

Therefore, when the wetting layer is deposited using the SIP sputter to be applied in the contact hole, if the applicability to the sidewall of the contact hole is poor due to the deposition property of the SIP sputtering, the embedding of aluminum deposited on the wetting layer will be poor. Can be. Accordingly, the filling property of the contact hole becomes poor due to the generation of voids or the like, and accordingly, the contact resistance may be undesirably increased.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method for forming a contact of a semiconductor device capable of lowering contact resistance by improving sidewall applicability of a wetting layer introduced under a contact.

One aspect of the present invention for achieving the above technical problem is, forming an insulating layer having a through contact hole on a semiconductor substrate, a process chamber in which the semiconductor substrate is deposited, a pedestal introduced into the process chamber ( a self-ionizing plasma sputter device comprising a pedestal, a target introduced opposite the pedestal, and a magnetron introduced at a local location above the target to enhance ionization, mounted on the pedestal to the contact hole. Depositing a conductive wetting layer extending therein, wherein the second pressure at the end of the deposition of the wetting layer is higher than the first pressure of the chamber at the beginning of the deposition of the wetting layer so that the second pressure The deposition of the wetting layer predominantly induces the bottom portion of the contact hole and the deposition of the wetting layer later in the deposition Derived predominantly chosen in the hole portion and the side wall presents a contact connection method for forming a semiconductor device including a step, and depositing a buried contact of an aluminum layer over the wetting layer to deposit the said wetting layer.

The wetting layer may be deposited including a titanium layer.

The forming of the contact buried layer may include chemical vapor deposition of a first aluminum layer on the titanium layer, and physical vapor deposition of a second aluminum layer on the first aluminum layer.

The first pressure of the chamber at the beginning of the deposition of the wetting layer may be applied at most 3 mTorr, and the second pressure of the chamber after the deposition of the wetting layer may be applied at most 20 mTorr.

The direct current (DC) power applied to the target at the beginning of the deposition of the wetting layer is applied at least 12 kW, and the direct current (DC) power applied to the target after the deposition of the wetting layer is applied at most to less than 12 kW. Can be.

According to the present invention, when depositing a titanium layer with a self-ionizing plasma (SIP) sputter with a wetting layer introduced under the contact, the initial pressure is lowered and the late pressure is higher than the sidewalls of the titanium layer. The applicability can be improved. Accordingly, it is possible to provide a method for forming a contact of a semiconductor device capable of lowering the contact resistance of the contact buried layer deposited on the wetting layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should not be construed that the scope of the present invention is limited by the embodiments described below. Embodiments of the invention are preferably to be interpreted as being provided to those skilled in the art to more fully describe the invention.

An embodiment of the present invention provides a contact formation method in which a titanium (Ti) layer is introduced into a wetting layer of a contact filling layer when the contact hole is filled with a contact filling layer including an aluminum layer. In order to more stably increase the sidewall coverage of the contact hole of the titanium wetting layer, the titanium layer is deposited using a self-ionizing plasma (SIP) sputter, but the process chamber initial pressure during the sputtering deposition is relatively lowered. And the process chamber late pressure during the late deposition proceeds relatively higher. Accordingly, the sidewall applicability of the titanium layer can be relatively further increased.

SIP sputtering may be performed on sputter equipment of an endura system manufactured by Applied Material, Inc. (USA). Such a SIP sputter may basically consist of a chamber structure in which a titanium target introduced into the process chamber is introduced opposite the pedestal on which the wafer is mounted. At this time, the SIP sputter may be configured such that a magnetron source that increases metal ionization through local ionization is introduced into a local region above the target.

Such SIP sputter equipment is increasing the straightness of sputtered ions through magnet arrangement of magnetrons, magnetic phase strength, target-wafer spacing or / or very low deposition pressures. SIP sputters typically use high power with a DC power of at least 15 kW or more and tens of kW for target sputtering, and very low chamber pressures of approximately 2 mTorr or less.

In the embodiment of the present invention, when depositing the Ti wet layer in the contact hole by using the SIP sputtering equipment, the pressure of the process chamber is changed from a relatively low pressure to a high pressure during the deposition process, so that the contact hole of the Ti layer is deposited. It increases the degree of deposition on the sidewalls, i.e. sidewall applicability. At this time, the initial pressure is maintained at a very low pressure, such as at most 3 mTorr or less, and the later pressure is set to a pressure several times higher than the initial pressure, for example, at least 20 mTorr or more.

By setting the chamber pressure in the late deposition relatively high in this manner, the mean free path of the sputtered Ti ions can be reduced to induce deposition on the sidewalls. Since the average free path may be expressed as a value proportional to kT / (Pπσ ² ), the chamber pressure P, the process temperature T, the particle diameter σ, and the like may be considered as variables.

In this case, the increase in the temperature T may induce outgassing in the insulating layer exposed to the sidewalls of the contact holes, which may degrade the sidewall applicability of the titanium layer. In addition, when titanium is deposited by increasing the deposition temperature, formation of TiAl ₃ and aggregation may be caused by a reaction with aluminum which is preferably deposited subsequently, and thus deterioration of characteristics as a wetting layer is expected.

As the average free path decreases with increasing deposition pressure, the applicability of the contact hole bottom portion is somewhat reduced, but as a trade-off relationship, the top portion and sidewall applicability of the contact hole can be relatively improved. Accordingly, the contact hole improvement method according to the embodiment of the present invention can effectively implement the role of the Ti layer as a wetting layer of Al to be subsequently deposited, thereby realizing the improvement of the contact filling property of Al.

1 and 2 are cross-sectional views schematically illustrating a method of forming a connection contact of a semiconductor device according to an embodiment of the present invention. FIG. 3 is a diagram schematically illustrating a self ionizing plasma sputter (SIP) device used for depositing a titanium layer according to an embodiment of the present invention.

1 and 3, the method of forming a connection contact according to an embodiment of the present invention may be effectively applied to a contact electrically connecting wirings, but may be applied to forming a connection contact of another semiconductor device. .

In detail, the first insulating layer 210 as the interlayer insulating layer ILD may be formed on the semiconductor substrate 100, and the first metal wire 300 may be formed on the first insulating layer 210. The first wiring 300 may include a metal layer such as an aluminum layer.

A contact hole formed as a second insulating layer 230 as an interlayer insulating layer IMD covering the first wiring 300, and aligned with the first metal wiring 300 through the second insulating layer 230. 235). The contact hole 235 may be formed by selectively etching the second insulating layer 230 by a photo process or an etching process.

Before forming the conductive layer filling the contact hole 235, a wetting layer 400 for forming the conductive layer as a metal layer is formed. In this case, when the conductive layer filling the contact hole 235 is formed of an aluminum layer, the contact resistance may be reduced compared to tungsten. When the aluminum layer filling the contact hole 235 is deposited, the first aluminum layer is formed by chemical vapor deposition (CVD) in consideration of the filling property of the contact hole 235, and then, the physical property of which the deposition rate is excellent is excellent. The second aluminum layer by vapor deposition (PVD) may be formed to form contacts or / and wiring.

However, when the CVD-aluminum layer is deposited, the wetting layer 400 is required. When the wetting layer 400 is disconnected to expose the insulating layer 230 forming the sidewall of the contact hole 235, the exposed insulation is exposed. A CVD-aluminum layer may not be deposited or / and grown on the material. It can be understood that this is due to the metal layer deposition characteristics by CVD. Therefore, in order to prevent the occurrence of buried defects during the deposition of the CVD-Al layer, first, the wetting layer 400 needs to be deposited to uniformly extend not only to the bottom of the contact hole 235 but also to the sidewall.

In an embodiment of the present invention, the wetting layer 400 preferably forms a titanium layer. At this time, the titanium layer may be formed to preferably cover the bottom and sidewalls of the contact hole 400 by the SIP sputter 500 as shown in FIG.

The SIP sputter 500 includes a process chamber 510 in which deposition is performed, a pedestal 520 introduced into the process chamber 510 to mount a wafer-like semiconductor substrate 100, and a radio behind the semiconductor substrate 100. A bias power unit 530 for applying a frequency (RF) bias, preferably a planar target 540 of titanium introduced at a position opposite the wafer, and a magnetron introduced at a local position above the target 540. 550, a DC power unit 560 for applying power of DC current DC to the target 540, and a shield 570 introduced on the chamber wall surface. In this case, plasma or / and ions due to sputtering of the target 540 are generated in the chamber internal space 580 to be deposited on the semiconductor substrate 100.

Although SIP sputtering 500 may be evaluated as having significantly superior floor applicability in terms of equipment characteristics, in the embodiment of the present invention, in order to realize an increase in the sidewall applicability of the titanium layer evaluated in a trade-off relationship to floor applicability, SIP sputtering In the initial stage of setting a relatively low chamber pressure, in the later stage to set a relatively high chamber pressure, the deposition of the titanium layer is carried out.

For example, the deposition of the titanium layer is performed by initially applying a pressure inside the chamber 510 of FIG. 3 to a relatively low pressure of about 3 mTorr or less, preferably about 1 to 3 mTorr. At this time, the DC power applied for the sputtering from the target (540 in Fig. 3) is set to at least 12kW or several tens of kW, leading to high ionization efficiency of the sputtered Ti atoms. This initial deposition process can be understood to induce an increase in the bottom coatability by inducing preferential deposition of Ti in the bottom portion of the contact hole (235 of FIG. 1).

Thereafter, the pressure in the chamber 510 is preferably changed to several times higher than the initial pressure, such as about 20 mTorr or less, leading to an increase in the sidewall applicability of the Ti layer. At this time, not only the pressure of the chamber 510 but also the DC power for sputtering may be reduced, for example, to be maintained below 12 kW, for example, approximately 3 kW to less than 12 kW, thereby inducing a reduction in the average free path of the sputtered Ti ions. . That is, the linearity of Ti ions in the bottom direction of the contact hole 235 can be induced. This late deposition process may be understood to induce an increase in sidewall coatability by inducing predominant deposition in the sidewall portion of the contact hole 235.

The wetting layer 235 of the titanium layer formed by such a deposition process may exhibit not only bottom coating properties but also relatively excellent sidewall coating properties, so that the bottom and sidewalls of the contact holes 235 may be more uniformly coated. Can be.

Referring to FIG. 2, a contact buried layer 450 including an aluminum layer is deposited on the wetting layer 400. At this time, in order to improve the contact embedding property, preferably, the first aluminum layer 451 is deposited by CVD method, and after that, the second aluminum layer 453 is deposited by PVD method to form the contact buried layer 450. Can be. In this case, a step of reflowing the aluminum layers 451 and 453 may be further performed in a subsequent heat treatment process.

As described with reference to FIGS. 1 and 3, the Ti layer of the wetting layer 400 may have improved sidewall applicability, so that the Ti layer may be formed more uniformly on the sidewalls as well as the bottom of the contact hole 235. The first aluminum layer 451 deposited by CVD may be deposited with a relatively high embedding property, excluding the occurrence of buried defects such as voids.

Therefore, the contact, which can be understood as a part of filling the contact hole 235 of the contact buried layer 450, may be composed of aluminum layers 451 and 453, thereby realizing a relatively low contact resistance compared to tungsten contacts. have. In addition, since the Ti wetting layer 400 may be deposited with more uniform coating properties, stable formation of aluminum contacts is possible.

According to the present invention described above, a fine contact, for example, a connection contact having an area of about 0.025 μm ² may be formed including an aluminum layer, thereby reducing contact resistance of the contact.

The Ti wetting layer required for the deposition of the CVD aluminum layer can be formed to more uniformly cover the bottom and sidewalls of the contact hole, thereby improving the contact embedding characteristics of the CVD-Al layer deposited depending on the Ti wetting layer. . An increase in the sidewall coatability of the Ti wetting layer can be realized, thereby enabling a more stable wetting layer.

Accordingly, when performing contact filling using the aluminum layer, it is possible to effectively prevent the occurrence of contact filling defects such as voids and the like. Therefore, more stable contact resistance can be realized.

As mentioned above, although this invention was demonstrated in detail through the specific Example, this invention is not limited to this, It is clear that the deformation | transformation and improvement are possible by the person of ordinary skill in the art within the technical idea of this invention.

Claims (6)

Forming an insulating layer having a through contact hole on the semiconductor substrate; Depositing a conductive wetting layer extending into the contact hole, wherein the second pressure at the end of deposition of the wetting layer is higher than the first pressure of the process chamber of the deposition equipment at the beginning of the deposition of the wetting layer. Depositing the wetting layer predominantly inducing deposition of the wetting layer early in the deposition and at the bottom portion of the contact hole and inducing deposition of the wetting layer predominantly in the sidewall portion of the contact hole later in the deposition; And Forming a contact buried layer of an aluminum layer on the wetting layer. The method of claim 1, Deposition of the wetting layer The process chamber in which deposition of the wetting layer is performed; A pedestal introduced into the process chamber; A target introduced opposite the pedestal; And And a self ionizing plasma (SIP) sputtering device including a magnetron introduced at a local position above the target to increase ionization as the deposition device. The method of claim 2, The direct current (DC) power applied to the target at the beginning of the deposition of the wetting layer is applied at least 12kW The direct current (DC) power applied to the target after the deposition of the wetting layer is applied to at least less than 12kW. The method of claim 1, The wetting layer includes a titanium layer is deposited, characterized in that for depositing a contact of the semiconductor device. The method of claim 4, wherein Forming the contact buried layer Chemical vapor deposition of a first aluminum layer on the titanium layer; And Physical vapor deposition of a second aluminum layer on the first aluminum layer. The method of claim 1, The first pressure of the chamber at the beginning of the deposition of the wetting layer is applied at most 3mTorr and And a second pressure of the chamber at the end of the deposition of the wetting layer is applied at most 20 mTorr.

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