Film deposition method and film deposition system for depositing a halogen compound film, and magnesium fluoride film

Abstract

This invention provides film deposition method and film deposition system for depositing a halogen compound film, which are capable of depositing such a film while suppressing abuse that occurs due to deficiency of a halogen element even if the halogen element is dissociated from a film material. Specifically, the halogen compound film is deposited through a process including: evaporating a film material comprising a halogen compound by means of an evaporation source 3 ; ionizing the evaporated film material with a radio frequency power outputted from a radio frequency power supply unit 11 and supplied through a substrate holder 2 ; and causing the ionized film material to deposit on the substrate 5. In this process a bias voltage outputted from a bias power supply unit 12 and applied to the substrate holder 2 causes halogen ions dissociated from ions of the halogen compound to be incorporated into the film being deposited on the substrate 5.

What is claimed is:  
     
         1 . A film deposition method for depositing a halogen compound film, comprising the steps of: 
 placing a substrate on an obverse side of a bias supply electrode disposed in a vacuum chamber;    evaporating a film material comprising a halogen compound;    supplying a radio frequency voltage to the bias supply electrode used as one of electrodes to generate plasma in the vacuum chamber; and    applying to the bias supply electrode a bias voltage varying in the form of a wave having a negative mean value and a maximum value exceeding a self-bias caused by the radio frequency voltage,    whereby the evaporated film material is ionized and deposited on the substrate to deposit the halogen compound film on the substrate.    
     
     
         2 . The method according to  claim 1 , wherein the maximum value of the bias voltage is a positive voltage.  
     
     
         3 . The method according to  claim 1 , wherein the bias voltage is applied by a power supply.  
     
     
         4 . The method according to  claim 1 , wherein the bias voltage applied is based on a voltage generated in a matching circuit provided for matching an impedance on a power supply side associated with the radio frequency voltage to that on a vacuum chamber side.  
     
     
         5 . The method according to  claim 1 , wherein:  
     
     
         6 . The method according to  claim 1 , wherein the film material comprising the halogen compound is evaporated and ionized in a clustered fashion by cluster ion generating means.  
     
     
         7 . The method according to  claim 1 , wherein a substrate holder holding the substrate on its back surface in the vacuum chamber is formed of an electrically-conductive material and is used also as the bias supply electrode.  
     
     
         8 . The method according to  claim 1 , wherein: 
 an electron beam evaporation source is further provided comprising a crucible holding a material same as the halogen compound to be evaporated, an electron gun for evaporating the halogen compound held in the crucible by heating with an electron beam, and a shutter spaced a predetermined distance from the crucible in a direction toward the substrate; and    the halogen compound in the crucible is evaporated by heating with the electron beam, while direct impingement of the halogen compound thus evaporated upon the substrate is obstructed with the shutter, whereby the evaporated halogen compound is guided sidewardly of the shutter and the crucible.    
     
     
         9 . The method according to  claim 1 , wherein the halogen compound is magnesium fluoride (MgF 2 ).  
     
     
         10 . The method according to  claim 1 , wherein the bias voltage has a frequency ranging between 100 kHz and 2.45 GHz.  
     
     
         11 . An apparatus for forming a halogen compound film, comprising: 
 a vacuum chamber;    a bias supply electrode disposed in the vacuum chamber and having an obverse side for receiving a substrate thereon;    an evaporation source for evaporating a film material of the halogen compound film to be formed on the substrate;    a radio frequency power supply for supplying a radio frequency voltage to the bias supply electrode used as one of electrodes to generate plasma in the vacuum chamber; and    a bias power supply for applying to the bias supply electrode a bias voltage having a frequency ranging between 100 kHz and 2.45 GHz and varying in the form of a wave having a negative mean value and a positive maximum value.    
     
     
         12 . A magnesium fluoride film obtainable by a method comprising the steps of: placing a substrate on an obverse side of a bias supply electrode disposed in a vacuum chamber; evaporating magnesium fluoride; supplying a radio frequency voltage to the bias supply electrode used as one of electrodes to generate plasma in the vacuum chamber; and applying to the bias supply electrode a bias voltage having a frequency ranging between 100 kHz and 2.45 GHz and varying in the form of a wave having a negative mean value and a positive maximum value, thereby forming the magnesium fluoride film on the substrate.  
     
     
         13 . A magnesium fluoride film having a crystal grain diameter not less than 3 nm and not more than 10 nm.