JP4095760B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device such as a MOS transistor, and is particularly suitable for application to a semiconductor device using silicide (salicide) technology.
[0002]
[Prior art]
In recent years, with the progress of higher integration of semiconductor elements, further miniaturization of electrodes, wirings, and the like is required. Since miniaturization of electrodes and wiring leads to an increase in resistance, as a countermeasure against this, silicide, which is a compound of silicon and a refractory metal such as tungsten (W) or titanium (Ti), is used as an electrode or wiring material. Technology has been proposed.
[0003]
Further, in the MOS transistor, there is a so-called salicide technique, which is a solid-phase reaction silicide in which silicidation is selectively and self-aligned on the gate electrode and source / drain surfaces of polycrystalline silicon. Thereby, the wiring resistance of the gate electrode and the parasitic resistance of the source / drain are simultaneously reduced, thereby realizing a VLSI transistor with less wiring delay and conductance deterioration.
[0004]
[Problems to be solved by the invention]
When using silicide technology, especially salicide technology for MOS transistors, a resist mask for patterning is formed prior to this, or impurities are introduced by ion implantation. In order to prevent organic contamination or damage due to ion implantation, a thin thermal oxide film is formed on the surface of the target silicon layer or silicon substrate.
[0005]
This thermal oxide film is removed by wet etching or the like using a dilute hydrofluoric acid solution immediately before the silicide (salicide) process. At this time, the thermal oxide film itself is also altered by organic contamination or ion implantation (SiO ₂ → SiO _x (X <2)) is generated and may not be sufficiently removed. Even if the thermal oxide film is formed, it is not possible to sufficiently achieve prevention of organic contamination or damage due to ion implantation, and organic contamination and damage often penetrate the silicon surface through the thermal oxide film. .
[0006]
Thus, although a thermal oxide film is formed for the purpose of removing the organic contamination and damage to clean the silicon surface, it is difficult to achieve sufficient cleaning. When the silicon surface is contaminated, the silicidation is hindered, resulting in a problem that the reliability of the MOS transistor is significantly lowered.
[0007]
Therefore, the present invention has been made in view of the above problems, and removes contamination of a semiconductor layer (silicon layer) due to organic contamination typified by resist / air pollution or damage caused by ion implantation, and sufficient surface cleaning. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can realize silicide (salicide) on the surface of the silicon layer.
[0008]
[Means for Solving the Problems]
As a result of intensive studies, the present inventor has conceived the following aspects of the invention.
[0009]
The method for manufacturing a semiconductor device according to the present invention mainly includes a pre-process for siliciding the surface of a semiconductor layer, for example, a silicon layer, using a refractory metal when forming a semiconductor element, for example, a MOS transistor. is there. In this pre-process, an oxygen gas radical and an etching gas radical are allowed to act on the surface of the silicon layer to perform oxidation treatment and etching treatment.
[0010]
In the present invention, on the surface of the semiconductor layer (silicon layer), an oxide layer containing organic contamination and damage existing on the surface is formed by oxidation treatment, or on the other hand, the oxide layer is removed by etching treatment on the other side. Is done. Thereby, organic contamination and damage on the surface of the semiconductor layer are removed together with the oxide layer, and the surface is cleaned.
[0011]
In this case, specifically, the oxygen gas and the etching gas are radicalized using plasma.
[0012]
As a specific process of the step, it is preferable to perform the oxidation process and the etching process simultaneously after the oxidation process.
[0013]
In this case, first, the former oxidation treatment improves the quality of the oxide film formed in order to mitigate damage caused by organic contamination or ion implantation of the semiconductor layer (silicon layer) (SiO _x (X <2) → SiO ₂ ). In addition, decomposition and sublimation of organic substances in the oxide film are promoted. By the subsequent oxidation treatment and etching treatment, as described above, an oxidation layer containing organic contamination and damage existing on the surface is formed on the one hand or formed, while the oxidation layer is removed by the etching treatment on the other hand. The surface of the semiconductor layer is cleaned.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments to which the present invention is applied will be described in detail with reference to the drawings. Here, as a semiconductor device, a so-called salicide structure MOS transistor is illustrated, and its configuration is disclosed together with a manufacturing method.
FIG. 1 is a schematic cross-sectional view showing the manufacturing method of the MOS transistor of this embodiment in the order of steps, and FIGS. 2 and 3 are schematic views showing the main steps of this embodiment.
[0015]
First, as shown in FIG. 1A, for example, an element formation region is defined in a p-type silicon semiconductor substrate 1. Here, a thick field oxide film 2 is formed in the element isolation region by a so-called LOCOS method, and element isolation is performed.
[0016]
Subsequently, thermal oxidation is performed on the defined element formation region to form a thin gate insulating film 3 having a thickness of about 10 nm on the surface of the semiconductor substrate 1.
[0017]
Subsequently, after depositing a polycrystalline silicon film (not shown) with a film thickness of about 180 nm on the entire surface by, eg, CVD, a photoresist (not shown) is applied on the polycrystalline silicon film, and the electrode shape is formed by photolithography. To process. Then, using the photoresist as a mask, the polycrystalline silicon film and the gate insulating film 3 are anisotropically etched and patterned to form a gate electrode 4 made of the polycrystalline silicon film.
[0018]
Subsequently, after removing the photoresist by ashing or the like, a silicon oxide film is deposited on the entire surface so as to cover the photoresist 11 by, eg, CVD, and the entire surface is anisotropically etched (etched using the gate electrode 4 as a mask). In this way, the sidewall 5 is formed leaving the silicon oxide film only on the side surface of the gate electrode 4.
[0019]
Next, as shown in FIG. 1B, for the purpose of protecting the damage of the surface of the semiconductor substrate 1 and the surface of the gate electrode 4 in a later ion implantation process, the element is exposed at the side of the gate electrode 4 in the element formation region. The surface of the semiconductor substrate 1 and the surface of the gate electrode 4 are thermally oxidized to form a thin protective oxide film 6 having a thickness of about 5 nm.
[0020]
Subsequently, using the gate electrode 4 and the sidewall 5 as a mask, an n-type impurity, in this case, phosphorus (P) is applied to the surface layer of the semiconductor substrate 1 through the protective oxide film 6 with an acceleration energy of 600 keV and a dose of 3 × 10 ¹⁵ / cm. Source / drain 7 is formed on the surface layer of the semiconductor substrate 1 on both sides of the gate electrode 4 and the sidewalls 5 by performing ion implantation under the condition ² and annealing.
[0021]
Here, as shown in FIG. 2A, even if the protective oxide film 6 is formed, organic contamination caused by damage 21 on the surface of the semiconductor substrate 1 and the surface of the gate electrode 4 due to ion implantation, the atmosphere thereof, or the like. 22 exists. Therefore, in the present embodiment, plasma processing using oxygen (O ₂ ) gas and C ₂ F ₆ gas as reaction gases is performed as a pre-process for performing salicide.
[0022]
Specifically, first, O ₂ gas is radicalized by plasma by oxidation treatment using O ₂ gas as a reaction gas for about 60 seconds, and acts on the protective oxide film 6 on the semiconductor substrate 1 and the gate electrode 4. .
[0023]
At this time, as shown in FIG. 2B, the quality of the protective oxide film 6 is improved by oxygen radicals (reforming from SiO _x (X <2) to normal SiO ₂ by ion implantation or the like). At the same time, decomposition and sublimation of the organic matter in the protective oxide film 6 are promoted.
[0024]
Subsequently, Yuki added C ₂ F ₆ gas used as an etching gas to O ₂ gas, as a reaction gas a mixed gas of O ₂ gas and C ₂ F ₆ gas, O ₂ gas into radicals by a plasma, the semiconductor substrate 1 and the surface of the gate electrode 4 and the protective oxide film 6 on these surfaces.
[0025]
At this time, as shown in FIG. 2C, the protective oxide film 6 is removed by etching with fluorine radicals of C ₂ F ₆ . Subsequently, as shown in FIG. 3A, each surface is again oxidized by oxygen radicals to form an oxide film 24 (including a small amount of organic contamination and a damaged layer). Thereby, the oxidation of the damage layer existing on each surface after the removal of the protective oxide film 6 and the decomposition and sublimation of the organic matter are promoted. Further, as shown in FIG. 3B, the oxide film 24 formed on each surface in the above process is removed by etching with fluorine radicals.
[0026]
That is, this series of steps (FIGS. 2 (c), 3 (a) and 3 (b)) is an oxide film containing organic contamination and damage due to oxidation treatment by plasma excitation using the reaction gas as the above mixed gas. And the removal of the oxide film by etching process are performed almost simultaneously, and this process is repeated several times according to various conditions such as plasma excitation operating time to remove organic contamination and damage as much as possible. Is done. In this example, the oxide film is etched by about 6 nm and the silicon layer is etched by about 5 nm by simultaneous processing of oxidation and etching.
[0027]
When the semiconductor substrate 1 is carried out of the chamber, some natural oxidation or organic contamination 23 occurs on the exposed surface of the semiconductor substrate 1 and the surface of the gate electrode 4 as shown in FIG. Then, the natural oxide film 25 formed at this time is removed by wet etching using a dilute hydrofluoric acid solution.
[0028]
Through the above steps, the surface of the semiconductor substrate 1 and the surface of the gate electrode 4 are cleaned to a degree sufficient for silicidation (salicide).
[0029]
By the way, when performing the above-described plasma excitation, it is preferable to avoid direct contact of the plasma with the surface as much as possible from the viewpoint of protecting the surface of the silicon layer that is the target of action by radical species. Therefore, for example, plasma is generated at a location sufficiently separated from the surface, the generation location and the surface are separated by an opened metal film, and radical species generated by the plasma act on the surface from the opening. It is preferable to do. At this time, although it may be difficult to impart sufficient kinetic energy or the like to the radical species, sufficient energy for the reaction can be obtained, for example, by mixing about several percent of water vapor with the reaction gas.
[0030]
Subsequently, as shown in FIG. 1C, a refractory metal, for example, Co, Ti, W or the like (Co in this case) is sputtered to a thickness of about 10 nm on the entire surface, and between the semiconductor substrate 1 and Co and the gate electrode. A silicide layer 13 is formed by a solid phase reaction between Si and Co between 4 and Co to form a salicide structure. Thereafter, Co in the unreacted portion is removed.
[0031]
Then, as shown in FIG. 1D, the formation of the interlayer insulating film 14 covering the entire surface, the formation of the contact hole 15 exposing a part of the surface of the gate electrode 4 and the source / drain 7, and the buried gate of the contact hole 15 A salicide MOS transistor is completed through the formation of the wiring 16 made of Al or the like that is electrically connected to the electrode 4 and the source / drain 7.
[0032]
As described above, according to the MOS transistor manufacturing method of this embodiment, the contamination of the semiconductor layer (silicon layer) due to organic contamination typified by resist / air pollution and damage due to ion implantation is removed, and a sufficient surface is obtained. It is possible to realize cleaning and to reliably silicide (salicide) the surface of the silicon layer.
[0033]
In order to confirm the above-described effect of the present embodiment, the gate electrode is obtained using as a sample the case where the pre-silicidation process according to the present embodiment is performed and the comparative example in which only the protective oxide film is formed and removed without performing this step. The resist mask used when patterning was used as an ion implantation mask as it was, and after ion implantation of impurities, the surface of the gate electrode was silicided. As a result, as shown in the SEM photograph of FIG. 4, in the comparative example shown in FIG. 4A, black spots are particularly confirmed at the resist mask coating portion (indicated by (A) in the figure). This black dot indicates that the removal of organic contamination, damage, etc. is insufficient, and thus it can be seen that there are many unreacted portions of silicidation in this comparative example. On the other hand, in the present embodiment shown in FIG. 4B, no black point is confirmed, and it can be seen that sufficient silicidation is realized.
[0034]
In the above description of the embodiment, an example is given in which oxygen gas radicals and etching gas radicals are used, but ion active species generated from oxygen gas plasma may be used instead of radicals. In the case of ionic active species, it is advantageous in that the oxidation treatment can be easily and deeply performed even in a state where high temperature or the like is not applied as compared with the case of using radicals.
[0035]
In this embodiment, the salicide technology of the MOS transistor has been exemplified. However, the present invention is not limited to this, and can be applied to, for example, cleaning the surface of a silicon layer exposed by forming a contact hole / via hole. It is.
[0036]
Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.
[0037]
(Supplementary Note 1) A method of manufacturing a semiconductor device in which when forming a semiconductor element, silicidation using a refractory metal is performed on the surface of a silicon layer,
A method for manufacturing a semiconductor device, characterized in that as a pre-process for silicidation, oxygen gas radicals and etching gas radicals are allowed to act on the surface of the silicon layer to perform oxidation treatment and etching treatment.
[0038]
(Supplementary note 2) The method of manufacturing a semiconductor device according to supplementary note 1, wherein the step is performed by radicalizing oxygen gas and etching gas with plasma.
[0039]
(Additional remark 3) The said semiconductor element is a MOS transistor, The said process is performed as a pre-process of salicidation, The manufacturing method of the semiconductor device of Additional remark 1 characterized by the above-mentioned.
[0040]
(Additional remark 4) The said oxidation process and the said etching process are performed simultaneously, The manufacturing method of the semiconductor device of Additional remark 1 characterized by the above-mentioned.
[0041]
(Supplementary note 5) The method for manufacturing a semiconductor device according to supplementary note 1, wherein the oxidation treatment and the etching treatment are performed simultaneously after the oxidation treatment.
[0042]
(Additional remark 6) When forming a semiconductor element, the radical of oxygen gas and the radical of etching gas are made to act on the surface of the silicon layer on the surface of the semiconductor layer, and an oxidation treatment and an etching treatment are performed. Production method.
[0043]
(Supplementary note 7) The method for manufacturing a semiconductor device according to supplementary note 6, wherein the oxidation treatment and the etching treatment are performed by radicalizing oxygen gas and etching gas with plasma.
[0044]
(Additional remark 8) The said oxidation process and the said etching process are performed as a pre-process of silicidation of the said semiconductor layer, The manufacturing method of the semiconductor device of Additional remark 6 characterized by the above-mentioned.
[0045]
(Additional remark 9) The said oxidation process and the said etching process are performed simultaneously, The manufacturing method of the semiconductor device of Additional remark 6 characterized by the above-mentioned.
[0046]
(Supplementary note 10) The method for manufacturing a semiconductor device according to supplementary note 6, wherein the oxidation treatment and the etching treatment are performed simultaneously after the oxidation treatment.
[0047]
(Supplementary Note 11) A method of manufacturing a semiconductor device in which when forming a semiconductor element, silicidation using a refractory metal is performed on the surface of a silicon layer,
Before performing the silicidation,
Forming a thin oxide film on the surface of the silicon layer by heat treatment;
A step of applying a predetermined treatment to the silicon layer through the oxide film, and generating oxygen gas radicals to act on the oxide film;
A method of manufacturing a semiconductor device, comprising: a step of causing radicals of oxygen gas and radicals of etching gas to act on the surface of the silicon layer and simultaneously performing oxidation treatment and etching treatment.
[0048]
(Additional remark 12) The manufacturing method of the semiconductor device of Additional remark 11 characterized by performing radicalization of oxygen gas and etching gas with plasma.
[0049]
(Additional remark 13) The said semiconductor element is a MOS transistor, The said each process is performed as a pre-process of salicidation, The manufacturing method of the semiconductor device of Additional remark 11 characterized by the above-mentioned.
[0050]
【The invention's effect】
According to the present invention, organic contamination typified by resist / air pollution and contamination of the semiconductor layer (silicon layer) due to damage caused by ion implantation are removed, and sufficient surface cleaning is realized to ensure the surface of the silicon layer. It becomes possible to turn into silicide (salicide).
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a method of manufacturing a MOS transistor according to an embodiment in the order of steps.
FIG. 2 is a schematic view showing a state of a silicon layer surface in the main process of the embodiment.
FIG. 3 is a schematic diagram showing the state of the surface of the silicon layer in the main process of this embodiment, following FIG. 2;
FIG. 4 is a photomicrograph showing the state of the silicon layer surface according to the present embodiment (and the silicon layer surface according to the comparative example) by SEM (scanning electron microscope).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Field oxide film 3 Gate insulating film 4 Gate electrode 5 Side wall 6 Protective oxide film 7 Source / drain 11 Photoresist 12 Natural oxidation and organic contamination 13 Silicide layer 14 Interlayer insulating film 15 Contact hole 16 Wiring 21 Damage 22 Organic Pollution 23 Some natural oxidation / organic contamination 24 Oxide film 25 Natural oxide film

Claims (2)

Forming a gate electrode on a semiconductor substrate containing silicon;
Forming a sidewall including a silicon oxide film on the sidewall of the gate electrode;
Next, forming an oxide film on the surface of the semiconductor substrate;
Ion implantation into the semiconductor substrate through the oxide film;
A step of performing oxygen plasma treatment on the oxide film;
Removing the oxide film by plasma treatment using a mixed gas of oxygen gas and C ₂ F ₆ gas;
Next, forming a metal film on the entire surface of the semiconductor substrate;
And a step of reacting the metal film with the silicon by subjecting the semiconductor substrate to a heat treatment. The method of manufacturing a semiconductor device according to claim 1, wherein the mixed gas further contains water vapor.

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