Abstract:
The present invention provides a method for manufacturing contact holes in a CMOS device by using a gate-last process, comprising: forming high-K dielectrics/metal gates (HKMG) of a first type MOS; forming and metalizing lower contact holes of the source/drain of a first type MOS and a second type MOS as well as forming HKMG of a second type MOS simultaneously, wherein the lower contact holes of the source/drain are filled with the same material as that used by the metal gate of the second type MOS; forming and metalizing contact holes of metal gates of a first type MOS and a second type MOS as well as upper contact holes of the source/drain, wherein the upper contact holes of the source/drain are aligned with the lower contact holes of the source/drain. The method reduces the difficulty of contact hole etching and metal deposition, simplifies the process steps, and increases the reliability of the device.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for manufacturing a semiconductor device, particularly to a method for manufacturing contact holes in a CMOS device. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the traditional MOS transistor process, polysilicon is commonly used as the gate material, but with continuous reduction in the device geometry, a higher gate leakage current is caused due to reduction in the thickness of the polysilicon gate/gate oxidation layer. The feature size of the existing device enters 32 nm node, at this scale, a solution of substituting the high-K dielectrics/metal gate (HKMG) structure for the gate oxidation layer/polysilicon gate structure has been put forward. It is reported by Intel that the gate leakage current may be reduced to one tenth of what it has been when high-K dielectric materials are used. So far, application of high-K dielectrics/metal gate structure becomes an inexorable trend for the development of the integrated circuit of generation of techniques of 32 nm and below. 
         [0003]    However, in terms of the process of manufacturing a transistor of HKMG structure, two camps, which are the school of gate-first process represented by IBM and the school of gate-last process represented by Intel, respectively, exist within the industry. The gate-first integration scheme is similar to the existing polysilicon gate/gate oxidation layer process, but the metal gate is vulnerable to multiple thermal processing including high temperature junction annealing, thereby causing drift of electrical properties. In the gate-last integration, the polysilicon gate will be substituted by the metal gate subsequently through the following thermal processing and relevant processes. The gate-last process has an advantage that all processes within the metal silicide working procedure will not have an effect on the high-K insulating material or metal gate. For now, the gate-last integration scheme is a unique HKMG technology that is applied to product. 
         [0004]    The existing method for manufacturing a CMOS device of HKMG structure by using a gate-last process is that, when the HKMG structures of an NMOS and a PMOS are manufactured and the contact holes are etched as shown in  FIG. 1 , since the depth to width ratio d/w of the contact hole of source/drain S/D is gradually increased with continuous reduction in the width w of the contact hole, from 32 nm node, the complicated process including two photolithographes and two etchings is forced to be used. Meanwhile, deposition of interconnection metal in such contact holes also becomes difficult. This will inevitably lead to a great increase in the manufacturing cost. Furthermore, as shown in the FIGURE, another disadvantage is that, while performing metal deposition to the source/drain contact hole, the deposited metal (typically W or Cu) may easily enter into the device per se to destroy the performance of the device since the contact hole is straightly down to the thinner metal silicide layer on the source/drain. 
       SUMMARY OF THE INVENTION 
       [0005]    The technical problem to be solved by present invention is to provide a new method for manufacturing contact holes by using a gate-last process, which reduces the difficulty of contact hole etching and metal deposition, simplifies the process steps, and increases the reliability of the device. 
         [0006]    To solve the above technical problem, in accordance with the embodiment of the present invention, there is provided a method for manufacturing contact holes in a CMOS device by using a gate-last process, comprising: 
         [0000]    forming high-K dielectrics/metal gates (HKMG) of a first type MOS;
 
forming and metalizing lower contact holes of the source/drain of a first type MOS and a second type MOS, and forming HKMG of a second type MOS simultaneously, wherein the lower contact holes of the source/drain are filled with the same material as that used by the metal gate of the second type MOS;
 
forming and metalizing contact holes of metal gates of a first type MOS and a second type MOS as well as the upper contact holes of the source/drain, wherein the upper contact holes of the source/drain are aligned with the lower contact holes of the source/drain; and
 
wherein the type of the first type MOS is opposite to that of the second type MOS.
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    To understand the present invention well and to show how it is effected, the accompanying drawings will now be referenced through the embodiments, wherein: 
           [0008]      FIG. 1  is a schematic diagram illustrating the structure of the contact hole of a CMOS device manufactured by a gate-last process at present. 
           [0009]      FIG. 2  is a schematic diagram illustrating formation of a source/drain and a CMOS device including the high-K dielectric layer and polysilicon gate. 
           [0010]      FIG. 3  is a schematic diagram of a CMOS device having the PMOS HKMG structure formed. 
           [0011]      FIG. 4  is a schematic diagram of a CMOS device having the NMOS polysilicon gate removed. 
           [0012]      FIG. 5  is a schematic diagram of a CMOS device having the positions of contact holes of the source/drain exposed by photolithography. 
           [0013]      FIG. 6  is a schematic diagram of a CMOS device having the surface insulation layer etched and the lower contact holes of the source/drain exposed. 
           [0014]      FIG. 7  is a schematic diagram of a CMOS device having performed metal filling to the lower contact holes of the source/drain as well as the NMOS gate structure having the polysilicon removed. 
           [0015]      FIG. 8  is a schematic diagram of a CMOS device having the upper contact holes of the source/drain and the gate contact holes formed. 
           [0016]      FIG. 9  is a schematic diagram of a CMOS device having the upper contact holes of source/drain as well as the gate contact holes metalized. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    One or more aspects of the embodiments of the present invention will be described with reference to the accompanying drawings, where identical elements will be generally indicated by identical reference numerals throughout the drawings. In the following descriptions, many specific details are elaborated for the purpose of explanation so as to facilitate thorough understanding of one or more aspects of the embodiments of the present invention. However, it may be apparent to those skilled in the art that they may use few of these specific details to implement one or more aspects of the embodiments of the present invention. 
         [0018]    In addition, although the specific features or aspects of an embodiment are merely disclosed by one of the implementing modes, such specific features or aspects may be incorporated with one or more other features or aspects of other implementing modes that may be advantageous to and desired by any given or specific application. 
         [0019]    There is provided a substrate, which may be of any type known in the field of electronics, such as bulk silicon, Semiconductor-On-Insulator (SOI), full depletion, partial depletion, FIN type or any other type. 
         [0020]    As shown in  FIG. 2 , isolation trench  1  and the active region of the device are located by using a CMOS process (photolithography, etching), and high-K dielectric layer  10  and sacrificial polysilicon gate electrode layer  20  are sequentially deposited. Wherein the material of high-K dielectric layer  10  may be ZrO 2 , HfO 2 , Al 2 O 3 , HfSiO, HfSiON and/or combination thereof. In another embodiment, after the isolation trench and active region of the device are located, the sacrificial gate oxidation layer (not shown in the FIGURE) instead of the high-K dielectric layer  10  as shown in  FIG. 2  is deposited, then the sacrificial polysilicon gate electrode layer  20  is deposited, wherein the sacrificial gate oxidation layer is SiO 2  or SiON. 
         [0021]    After manufacturing sidewall  3 , source/drain ion implantation and annealing are performed to form a source/drain region (S/D), then metal silicide  5  is formed on the silicon surface of the source/drain region and the polysilicon gate electrode, wherein the metal silicide is NiPt metal silicide, preferably the metal silicide has a thickness of 20 nm. 
         [0022]    Lower insulation layer  30  is deposited, the deposited lower insulation layer, the thickness of which is greater than that of the gate step, completely covers the gate step. Generally, the lower insulation layer comprises two layers, that is, a lower SIN and an upper SiO 2 , preferably the SIN has a thickness of 50 nm and the SiO, has a thickness of 300 nm. 
         [0023]    Lower insulation layer  30  is planarized by Chemical Mechanical Planarization (CMP) with the portion higher than the polysilicon gate removed. 
         [0024]    The sacrificial polysilicon gate electrode layer region of a PMOS is exposed by photolithography. 
         [0025]    Sacrificial polysilicon gate electrode layer  20  of a PMOS is removed by using a wet or dry etching. In another embodiment, in a case where the sacrificial gate oxidation layer instead of the high-K dielectric layer  10  is deposited before forming the source/drain region, the sacrificial polysilicon gate electrode layer and the sacrificial gate oxidation layer below (not shown) are needed to be removed together, wherein the sacrificial gate oxidation layer is SiO 2  or SiON. 
         [0026]    The PMOS gate is filled with PMOS metal gate material  40  by deposition and planarized by Chemical Mechanical Planarization (CMP), to thereby obtain the HKMG structure of the PMOS, as shown in  FIG. 3 . Wherein deposition of the PMOS metal gate material  40  is performed by sequentially depositing material with the appropriate work function and metal filling material (not shown in lamination in the FIGURE) by using Atomic Layer Deposition (ALD) or sputtering process, more preferably, the material with appropriate work function is TiN, and the metal filling material is TiAl, Al or W. In another embodiment, in a case where the sacrificial polysilicon gate oxidation layer and the sacrificial gate oxidation layer below (not shown) are removed, the PMOS high-K dielectric layer material and PMOS metal gate material  40  are sequentially deposited, wherein the material of high-K dielectric layer includes ZrO 2 , HfO 2 , Al 2 O 3 , HfSiO, HfSiON and/or combination thereof. 
         [0027]    The sacrificial polysilicon gate electrode layer region of an NMOS is exposed by photolithography. 
         [0028]    Sacrificial polysilicon gate electrode layer  20  of an NMOS is removed by using a wet or dry etching, as shown in  FIG. 4 . In another embodiment, in a case where the sacrificial gate oxidation layer instead of the high-K dielectric gate is deposited before forming the source/drain region, the sacrificial polysilicon gate electrode layer and the sacrificial gate oxidation layer below (not shown) are needed to be removed together, wherein the sacrificial gate oxidation layer is SiO 2  or SiON. 
         [0029]    The position of the source/drain is exposed by photolithography to form a Photoresist (PR) pattern, then the gate structure having the sacrificial polysilicon gate electrode layer of an NMOS removed is also filled with photoresist, as shown in  FIG. 5 . 
         [0030]    The exposed lower insulation layer  30  is etched down to the metal silicide on the surface of the source/drain, so as to form lower contact holes of the source/drain, the structure obtained is as shown in  FIG. 6 . 
         [0031]    The lower contact holes of the source/drain and the NMOS gate obtained by removing the NMOS sacrificial polysilicon gate electrode layer  20  are simultaneously deposited and filled with the NMOS metal gate material  50 , then they are planarized by CMP, thus the etching and metalizing of the NMOS HKMG structure and the lower contact holes of the source/drain can be simultaneously performed, as shown in  FIG. 7 . The advantageous effect by doing so is that the depth to width ratio (dl/w) of the lower contact hole of source/drain is decreased with respect to the depth to width ratio (d/w) of the contact hole of source/drain as shown in  FIG. 1 , thus the difficulty of etching and depositing metal is decreased. On the other hand, the lower contact holes of the source/drain are deposited with the same metal material as that of the NMOS gate structure, the process is simplified. In a preferred embodiment, the step of depositing NMOS metal gates comprises two substeps, that is, sequentially depositing the material with appropriate work function and metal filling material (not shown in lamination in the FIGURE), more preferably, the material with appropriate work function is TiN, and the metal filling material is TiAl, Al or W. Furthermore, the metal gate deposition may select the techniques such as sputtering, ALD. In an another embodiment, in a case where the sacrificial gate oxidation layer instead of the high-K dielectric gate  10  is deposited before forming the source/drain region, and the gate polysilicon and the silicon oxidation layer below are removed together, it is also needed to use photolithography, etching and deposition process to form an NMOS high-K gate dielectric layer before depositing NMOS metal gate material to lower contact holes of the source/drain and the NMOS gate obtained by removing the NMOS sacrificial polysilicon gate electrode layer  20 , wherein the material of the NMOS high-K gate dielectrics may be ZrO 2 , HfO 2 , Al 2 O 3 , HfSiO, HfSiON and/or combination thereof. 
         [0032]    Upper insulation layer  60  is deposited on the surface of the device. 
         [0033]    Upper insulation layer  60  is photolithographed and etched to obtain the upper contact holes of the source/drain as well as PMOS and NMOS metal gate contact holes, the structure obtained is as shown in  FIG. 8 . 
         [0034]    Isolation layer materials Ti and TiN are sequentially deposited (not shown). 
         [0035]    Interconnection metal  70  is deposited to fill the etched metal gate contact holes and the upper contact holes of the source/drain and planarize the portions higher than the upper insulation layer by Chemical Mechanical Planarization (CMP), as shown in  FIG. 9 . The advantageous effect by doing so is that the depth to width ratio (d2/w) of the upper contact hole of source/drain is decreased with respect to the depth to width ratio (d/w) of the contact hole of source/drain as shown in  FIG. 1 , thus the difficulty of etching and depositing metal is decreased. Meanwhile, the contact holes of the source/drain are divided into two parts to be manufactured, so that the interface of the upper contact hole and the lower contact hole is lifted to the surface of the gate structure, which is advantageous to lower the chance of short circuit between the source/drain contact holes and the gate, so as to better protect the gate structure. In another preferred embodiment, the interconnection metal of the upper contact hole of the source/drain is preferably TiAl, W or Cu. In a further preferred embodiment, the interconnection metal of the upper contact hole of the source/drain and the interconnection metal of the lower contact hole of the source/drain select the same material, which is advantageous to reduce the contact resistance of the interface of the upper contact hole and the lower contact hole of the source/drain and whereby enhance the performance of the device. 
         [0036]    It should be understood that the above embodiment and the involved figures are merely schematically illustrated. As known to those skilled in the art, more or less elements as shown in the figures may be comprised in the structure, but they would not influence the scope of the embodiment of the present invention. In addition, although in the above embodiment the PMOS metal gate structure is first manufactured, whereas the lower contact hole of the source/drain and the NMOS metal gate structure are manufactured simultaneously, it will be apparent to those skilled in the art they may be manufactured in an reversed order, that is, the NMOS metal gate structure is first manufactured, whereas the lower contact hole of the source/drain and the PMOS metal gate structure are manufactured simultaneously. The scope of the present invention includes any other embodiments and applications that may use the above structures and methods. Therefore, the scope of the present invention shall be determined by referring to the scope of the attached claims as well as the scope of the equivalents that are assigned with such claims.