Patent Publication Number: US-2002001906-A1

Title: Method of manufacturing a gate in a semiconductor device

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The invention relates generally to a method of manufacturing a gate in a semiconductor device. More particularly, the invention relates to a method of manufacturing a gate in a semiconductor device, which can prevent a gate leakage current and obtain a low threshold voltage, by forming a TiAlN film between a gate insulating film and a metal gate.  
       [0003] 2. Description of the Prior Art  
       [0004] In the process of manufacturing DRAMs and logic devices, etc., which have been mass-produced, a silicon oxide (SiO 2 ) film has been widely used as a gate insulating film. As the design rule is reduced, however, it has become apparent that the thickness of the silicon oxide film to be formed cannot be reduced below the range of 25 Å to 30 Å because of a tunneling limit. For example, in a design rule of 0.1, the thickness of the gate insulating film is expected to be in the range of 25 Å to 30 Å. Due to increase in an off-current by a direct tunneling, however, there is a possibility that it may adversely affect the operation of a device. In particular, in case of a memory device, there is a need for a method of reducing a leakage current. For this, a study has been made in which an insulating material having a high dielectric constant is used.  
       [0005] For example, a tantalum oxide film (Ta 2 O 5 ), a titanium oxide film (TiO 2 ), an aluminum oxide film (Al 2 O 3 ), etc., which are used as a dielectric film of a capacitor, are used as the gate insulating film. The aluminum oxide film (Al 2 O 3 ) has more than 2.5 times the dielectric constant than the silicon oxide film. As the integration degree of a semiconductor device increases, however, when the thickness is formed in the range of 25 Å to 30 Å, there is a possibility that its application is problematic because the value of the dielectric constant is lowered as the thickness is reduced. In order to overcome this problem, if metal is used as the gate material instead of polysilicon, an insulating film having a thickness in the range of 25 Å to 30 Å can be formed without significant problems.  
       [0006] However, in case where the gate is formed with a W/WN or W/TiN structure, if it is combined with an aluminum oxide film or a tantalum oxide film having an effective charge of −2 to 3×10 12 /cm 2 , because the work function of the gate ranges from 4.55 to 4.8 eV, there is a possibility that the following problem may occur. Specifically, as the flat band voltage in the capacitor ranges from 0.2 to 0.3V and the threshold voltage ranges from 1.0 to 1.1V, being greater about 0.5V as compared the 0.4 to 0.6V ranges which is necessary in the level of a sub-micron device, it will be difficult to apply it to a metal gate structure and an insulating film structure having a high dielectric constant.  
       SUMMARY OF THE DISCLOSED METHOD  
       [0007] A method of manufacturing a gate in a semiconductor device capable of preventing a leakage current in the process of manufacturing a high-integration high-speed device is disclosed.  
       [0008] A method of manufacturing a gate in a semiconductor device capable of obtaining a low threshold voltage in the process of manufacture a high-integration high-speed device is disclosed.  
       [0009] A method of manufacturing a gate in a semiconductor device capable of improving reliability of a high-integration high-speed device is also disclosed.  
       [0010] The disclosed method of manufacturing a gate in a semiconductor device comprises the steps of forming a gate insulating film and a TiAlN film on a semiconductor substrate, forming a metal layer and an insulating film on the TiAlN film, patterning the insulating film, and then etching the metal layer, the TiAlN film and the gate insulating film using the patterned insulating film as a mask, thus forming a gate, and removing the insulating film. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] The disclosed method will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:  
     [0012]FIGS. 1A and 1B are cross-sectional view of explaining a method of manufacturing a gate in a semiconductor device. 
    
    
     DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS  
     [0013] In the disclosed method, a TiAlN film as a barrier layer is formed between a gate insulting film and a metal gate. As the TiAlN film is formed by PVD method or CVD method, the work function of the TiAlN film is reduced compared to that of a TiN film. Therefore, a low threshold voltage can be obtained in a gate insulating film having a high dielectric constant such as Al 2 O 3  or Ta 2 O 5  having a negative effective charge. This employs the characteristic in which, in case of a TiAlN film having a solid solution characteristic of TiN and AlN, AlN having a wide band gap (˜5 eV) and electron affinity ranging from about 1.5 to about 2 eV is added to form a barrier layer having a metal characteristic, and the work function at this time is reduced compared to that of TiN. Also, the TiAlN film has an advantage since it has a good oxidization-resistant compared to TiN.  
     [0014] The disclosed method will be described in detail by way of a preferred embodiment with reference to accompanying drawings.  
     [0015] Referring now to FIGS. 1A and 1B, a method of manufacturing a gate in a semiconductor device will be explained.  
     [0016]FIG. 1A shows a cross-sectional view of a device in which a gate insulating film  12 , a TiAlN film  13 , a metal layer  14  and an insulating film  15  are sequentially formed on a semiconductor substrate  11 .  
     [0017] The gate insulating film  12  is formed in thickness ranging from about 3 Å to about 20 Å using a silicon oxide film or an oxide film having a high dielectric constant. The silicon oxide film is formed by means of a thermal oxidization process at a temperature ranging from about 600° C. to about 900° C. The oxide film having a high dielectric constant may employ a Al 2 O 3  film, a Ta 2 O 5  film, a TiO 2  film, a ZrO 2  film, a HfO 2  film, a mixture oxide film of 3-elements series such as ZrAlO, HfAlO, ZrSiO 4 , HfSiO 4 , etc. Also, before the oxide film having a high dielectric constant is formed, a silicon oxide film may be formed in thickness ranging from about 3 Å to about 10 Å. Meanwhile, in order to improve the characteristic of the oxide film having a high dielectric constant, a rapid thermal process in the temperature ranging from about 500° C. to about 800° C. for a time period ranging from about 10 seconds to about 5 minutes, a thermal process ranging from about 10 seconds to about 100 minutes or a UV/O 3  process may be performed.  
     [0018] The TiAlN film  13  may be formed through the process by which N 2  at a flow rate ranging from about 15 sccm to about 80 sccm and Ar at a flow rate ranging from about 5 sccm to about 25 sccm are implanted, a target of TiAl x  (x=0.05˜0.35) is mounted into the chamber keeping the temperature therein in the range from about −30° C. to about 500° C. and a power ranging from about 500 W to about 7 kW is then applied, or the process by which a target of TiAlN (AlN=0.05˜0.35) is mounted under inert gases such as Ar, Xe, Kr, etc., and a DC or a RF bias is applied. Also, the TiAlN film  13  is formed using a CVD method, using TiCl 4  and TDMAT as a source material of Ti, AlCl 3 , TMA[Al(CH 3 ) 3 ] as a source material of Al, and NH 3 , ND 3  and N 3  as a source material of N so that the composition of AlN can range from about 5% to about 35%. Also, the CVD deposition may be performed by means of thermal nitrification method at the temperature ranging from about 450° C. to about 700° C.  
     [0019] Meanwhile, the TiAlN film  13  may be deposited by means of ALD (atomic layer deposition) method. For this, with the substrate is kept at a temperature ranging from about 150° C. to about 450° C., after a Ti source is added, a nitrogen source is added to deposit a TiN and after an Al source is added, a nitrogen source is added to deposit AlN. At this time, the composition ratio of AlN within the thin film is determined by the number of addition of AlN to the total number of addition.  
     [0020] After the TiAlN film  13  is formed, a rapid thermal oxidization process is performed in order to increase oxidization resistance within the thin film, which uses a rapid thermal process and is performed for about 10 to about 30 seconds when it is ramped up to the temperature ranging from about 500° C. to about 650° C. under an oxygen atmosphere. At this time, oxygen is mainly collected at the grain boundary within the thin film and the total amount of oxygen ranges from about 1% to about 3%.  
     [0021] The metal layer  14  is formed of any one of a W film, a Ta film, a WN film, a TaN film, an Al film, a TiSix film, a CoSix film and a NiSi film and is formed in thickness ranging from about 500 Å to about 1500 Å.  
     [0022] The insulating film  15  is formed of a SiO2 film, a Si3N4 film or a SiON film and is formed in thickness ranging from about 300 Å to about 2000 Å.  
     [0023] Referring now to FIG. 1B, after the insulating film  15  is patterned, the metal layer  14 , the TiAlN film  13  and the gate insulating film  12  are sequentially etched and patterned using the patterned insulating film  15  as a mask. Then, the patterned insulating film  15  is removed to form a gate.  
     [0024] As mentioned above, the present invention can obtain a low threshold voltage while preventing generating a leakage current by forming a TiAlN film between a gate insulating film and a metal gate. Thus, it can improve reliability of a high-integration high-speed device.  
     [0025] The present invention has been described with reference to a particular embodiment in connection with a particular application. Those having ordinary skill in the art and access to the teachings of the present invention will recognize additional modifications and applications within the scope thereof.  
     [0026] It is therefore intended by the appended claims to cover any and all such applications, modifications, and embodiments within the scope of the present invention.