Patent Publication Number: US-2006011577-A1

Title: Method for post-treatment of semi-finished product after dry etching process

Description:
FIELD OF THE INVENTION  
      The present invention generally relates to a post-treatment method which is carried out after a dry etching process in semiconductor manufacturing, and more particularly to a method for post-treatment of a semi-finished product after completion of a dry etching process for removing a residue formed during the dry etching process.  
     GENERAL BACKGROUND  
      Dry etching techniques are widely used in the semiconductor industry. Usually, a process for manufacturing a semiconductor generally includes the steps of coating a photo resist layer on a semiconductor layer that is formed on a substrate, exposing the photo resist layer using a mask and developing the photo resist layer to form a pattern on the photo resist layer, etching the semiconductor layer by a dry etching process using a gas containing for example oxygen (O 2 ), sulfur hex fluoride (SF 6 ) and carbon tetrafluoride (CF 4 ), and removing the remaining photo resist to form a patterned semiconductor layer.  
      However, a lot of residues such as polymers are often formed on the semiconductor layer during the dry etching process. These may cause faulty electrical connections in the finished semiconductor product. Therefore, a HF acid solution generally has to be utilized to remove the residues. Alternatively, the residues may be removed by way of ultraviolet radiation. However, the above-described methods increase costs. In order to economize on cleaning, another method commonly referred to as an ash treatment process has been developed.  
       FIG. 11  to  FIG. 13  show a conventional process for ash treatment of a semi-finished product after a dry etching process. As shown in  FIG. 11 , a semi-finished product is provided. The semi-finished product includes a silicon oxide substrate  1 , a silicon oxide layer  2  formed on the silicon oxide substrate  1 , and a patterned photo resist layer  3  formed on the silicon oxide layer  2 .  
      As shown in  FIG. 12 , the silicon oxide layer  2  is etched by a gas containing CF 4  and trifluoromethane (CHF 3 ) so as to remove a part of the silicon oxide layer  2  which is not covered by the photo resist layer  3 . However, an unwanted fluorocarbon layer  6  is also formed in this process.  
      The treated substrate is then placed into a chamber, for performing of an ash treatment process using a plasma of O 2 . As shown in  FIG. 13 , the fluorocarbon layer  6  and the photo resist layer  3  are removed by the ash treatment process, with the silicon oxide substrate  1  and the silicon oxide layer  2  remaining.  
      By using the plasma of O 2  to remove the fluorocarbon layer  6  and the photo resist layer  3  at the same time, the processing process is simplified, and the costs are reduced.  
      However, during the ash treatment process, the plasma of O 2  is generally incapable of removing the fluorocarbon completely. Therefore the remaining fluorocarbon residue and other polymers may still cause faulty electrical connections in the finished semiconductor product. Moreover, the polymer residues may also contaminate the chamber. Accordingly, the chamber may need to be cleaned unduly frequently.  
      What is needed, therefore, is a method for post-treatment of a semi-finished product after a dry etching process to remove residues formed during the dry etching process, such method overcoming the above-described deficiencies.  
     SUMMARY  
      In a preferred embodiment, a post-treatment method of a semi-finished product after a dry etching process includes the steps of: providing the semi-finished product after completion of a dry etching process, the semi-finished product having a residue formed during the dry etching process; placing the semi-finished product in a chamber having an inlet and an outlet; introducing an SF 6  gas into the chamber via the inlet to effect a reaction between the SF 6  gas and the residue so as to produce a reaction gas; and discharging any remaining SF 6  gas and the reaction gas out of the chamber via the outlet.  
      The SF 6  gas can completely react with the residue from the dry etching process and results residue gas pumped out by a vacuum system. It can entirely eliminate the residue over the contact hole and on the inside surface of the dry etching chamber, and can avoid electrical connection errors and improve the efficiency of manufacture. It also can clean the dry etching chamber and prolong the use life of the dry etching chamber.  
      Other advantages and novel features of preferred embodiments will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  to  FIG. 5  are schematic, cross-sectional views showing successive stages in a method for forming a source electrode and a drain electrode by a dry etching process in accordance with a first embodiment of the present invention.  
       FIG. 6  to  FIG. 10  are schematic, cross-sectional views showing successive stages in a method for forming a gate electrode by a dry etching process in accordance with a second embodiment of the present invention.  
       FIG. 11  to  FIG. 13  are schematic, cross-sectional views showing successive stages in a conventional process for post-treatment of a semi-finished product after a dry etching process. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  to  FIG. 5  illustrate successive stages in a method for forming a source electrode and a drain electrode by a dry etching process in accordance with a preferred embodiment of the present invention.  
      As shown in  FIG. 1 , a source-drain electrode metal layer  50  is formed on a glass substrate  10 . A passivation layer  40  is formed on and covers the source-drain electrode metal layer  50 .  
      As shown in  FIG. 2 , a photo resist layer  30  is formed on the passivation layer  40 . The photo resist layer  30  is exposed using a photo mask (not shown), and is developed to form a pattern in the photo resist layer  30 .  
      As shown in  FIG. 3 , the passivation layer  40  is etched by using a gas containing O 2 , SF 6  and CF 4  in a dry etching chamber (not shown) to form a contact hole  70 . Meanwhile, a byproduct, i.e. a polymer layer  60 , is generally unavoidably formed on an inner surface of the contact hole  70  and on the photo resist layer  30 . Further, the byproduct may be also deposited on an inside surface of the dry etching chamber.  
      The dry etching chamber includes an inlet and an outlet. An SF6 gas is introduced into the dry etching chamber through the inlet. As shown in  FIG. 4 , the SF 6  gas reacts with the polymer layer  60  and the polymer on the inside surface of the dry etching chamber and produces a SiF 4  gas. Remaining SF 6  gas and the produced SiF 4  gas are discharged out of the dry etching chamber via the outlet, by means of a vacuum system that is connected to the outlet. An amount of the SF 6  gas introduced should be carefully controlled, because the SF 6  gas may further react with the passivation layer  40  and the glass substrate  10  after the polymer layer  60  has been removed.  
      As shown in  FIG. 5 , the glass substrate  10  is immersed into a developer solution to remove the photo resist layer  30 . The glass substrate  10  and the passivation layer  40  remain. The developer solution may be an acidic solution such as a solution containing tetramethylammonium hydroxide solution, or a neutral solution such as a solution containing polyethylene oxide.  
      The SF 6  gas can completely react with the polymer formed during the dry etching process and produce silicon tetrafluoride (SiF 4 ) gas of that is discharged out of the dry etching chamber by the vacuum system. That is, the SF 6  gas can completely remove the polymer from the contact hole  70  and the inside surface of the dry etching chamber. Thus, faulty electrical connections in the finished semiconductor product can be avoided. The SF 6  gas can also clean the dry etching chamber and thus prolong the useful service lifetime of the dry etching chamber.  
       FIG. 6  to  FIG. 10  show successive stages in a method for forming a gate electrode by the dry etching process. The method is similar to the above-described method for forming a source electrode and a drain electrode.  
      As shown in  FIG. 6 , a gate electrode metal layer  51  is deposited on a glass substrate  11 , and an isolation layer  21  and a passivation layer  41  are sequentially deposited on the glass substrate  11  having the gate electrode metal layer  51 . Referring to  FIG. 7 , a patterned photo resist layer  31  is formed on the passivation layer  41  using a photo mask. Referring to  FIG. 8 , a pattern  71  is defined by a dry etching process, with a polymer residue layer  61  being formed. Referring to  FIG. 9 , the polymer residue layer  61  is then removed by a post-treatment process using an SF 6  gas. Referring to  FIG. 10 , the remaining portions of the photo resist layer  31  are then removed.  
      It should be noted that the inventive post-treatment process can be applied to not only the manufacturing of electrodes of transistors, but also to the manufacturing of other semiconductor products where removal of polymer residue is necessary or desirable.  
      It is to be understood, however, that even though numerous characteristics and advantages of the embodiments have been set out in the foregoing description, together with details of the functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.