Patent Document

FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to a semiconductor device manufacturing apparatus for manufacturing a semiconductor device by performing an etching process, a CO 2  plasma process, and so forth. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventionally, in a manufacturing process of a semiconductor device, a circuit pattern is formed by performing a series of processes such as an etching process for etching an interlayer insulating film or the like formed on a substrate such as a semiconductor wafer and an asking process for removing a photoresist layer, which is used as a mask in the etching process, by oxygen plasma or CO 2  plasma. 
         [0003]    Recently, a low dielectric insulating film (so-called a Low-k film) having a lower dielectric constant than that of a conventionally used SiO 2  film has been used as the interlayer insulating film. A film called a carbon-containing silicon oxide film or the like containing silicon, carbon, oxygen and hydrogen (hereinafter, referred to as a “SiCOH” film) has received recent interest for its usage as a low dielectric insulating film. As compared to the SiO 2  film having a dielectric constant of about 4, the SiCOH film having a dielectric constant equal to or less than about 2.7 is a very useful film to be used as the interlayer insulating film because it has a sufficient mechanical strength. Further, a p-SiCOH film made of a porous SiCOH film may be also employed. 
         [0004]    However, if the above-mentioned p-SiCOH film or the like is exposed to plasma in the etching process or the ashing process, it would be damaged, resulting in problems such as performance deterioration or reliability degradation because of an increase of hygroscopic property or dielectric constant. Such a damage is deemed to be inflicted because a dielectric constant is increased by removing carbon from the low dielectric insulating film and the low dielectric insulating film comes to contain moisture by absorbing water readily. 
         [0005]    In this regard, there is known a method for recovering the damaged low dielectric insulating film by performing a silylation process for silylating the low dielectric insulating film by contacting the low dielectric insulating film with vapor of a silylating agent (for example, TMSDMA (Dimethylaminotrimethylsilane)) or the like after the etching or the ashing process (see, for example, Patent Document 1). 
         [0006]    Patent Document 1: Japanese Patent Laid-open Publication No.  2006 - 49798   
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    When recovery of the damage (increase of hygroscopic property or dielectric constant) on the low dielectric insulating film by the etching or ashing is attempted, the damage can be recovered to some extent by the above-stated silylation process in case that the low dielectric insulating film is etched by plasma etching using an etching gas such as CF 4  and a photoresist layer used as a mask in the etching process is later asked by oxygen plasma. 
         [0008]    However, in case that the ashing process is performed not by the oxygen plasma but by CO 2  plasma, the recovery of the damage cannot be accomplished sufficiently even if the silylation process is conducted because damages inflicted on the low dielectric insulating film are deemed to be different in two cases where the ashing is performed by the oxygen plasma and by the CO 2  plasma. 
         [0009]    That is, when the ashing is performed by the oxygen plasma, the damage that the low dielectric insulating film suffers is mainly oxidation. Meanwhile, when the ashing is performed by the CO 2  plasma, the damage inflicted on the low dielectric insulating film is deemed to include formation of a film (containing C, F, O and the like as composition) impeding silylation on the surface of the low dielectric insulating film as well as oxidation thereof. Further, it is deemed that when the ashing is conducted by the CO 2  plasma, F components originated from CF 4  used in the etching process may remain or diffuse in the low dielectric insulating film, whereby polarity of the low dielectric insulating film increases, resulting in absorption of moisture and consequent increase of dielectric constant. 
         [0010]    Moreover, when the ashing is performed by the oxygen plasma, though the damage on the low dielectric insulating film can be recovered to some extent by the silylation process, the oxidizing power of the oxygen plasma is so strong that the damage inflicted on the low dielectric insulating film reaches even a deep layer portion as well as a surface portion thereof and an oxidized portion is densified. Thus, it is required to perform the ashing by using the CO 2  plasma having a smaller oxidizing power to thereby limit the damage inflicted on the low dielectric insulating film to a vicinity of its surface portion. Moreover, as in the case of the CO 2  plasma ashing, the above-mentioned damage caused by the CO 2  plasma may be also generated when using the CO 2  plasma in other processes, but not limited to the CO 2  plasma ashing process, such as a cleaning process for removing adhered deposits after the plasma etching process. 
         [0011]    In view of the foregoing, the present disclosure provides a semiconductor device manufacturing method and a semiconductor device manufacturing apparatus capable of obtaining a low dielectric insulating film in a good state by recovering a damage such as an increase of hygroscopic property or dielectric constant of the low dielectric insulating film exposed to CO 2  plasma, thus improving performance and reliability of a semiconductor device. 
         [0012]    In accordance with one aspect of the present invention, there is provided a semiconductor device manufacturing method including: an etching process for etching a low dielectric insulating film formed on a substrate; a CO 2  plasma process for exposing the substrate to CO 2  plasma after the etching process; and a UV process for irradiating UV to the low dielectric insulating film after the CO 2  plasma process. 
         [0013]    In the semiconductor device manufacturing method, the CO 2  plasma process may be a CO 2  plasma asking process for removing a photoresist layer used as an etching mask in the etching process. 
         [0014]    In the semiconductor device manufacturing method, the CO 2  plasma process may be a cleaning process for removing deposits generated in the etching process. 
         [0015]    The semiconductor device manufacturing method may further include a silylation process for silylating the low dielectric insulating film after the CO 2  plasma process. 
         [0016]    In accordance with another aspect of the present disclosure, there is provided a semiconductor device manufacturing apparatus including: an etching processing mechanism for performing an etching process that etches a low dielectric insulating film formed on a substrate; a CO 2  plasma processing mechanism for performing a CO 2  plasma process that exposes the substrate to CO 2  plasma after the etching process; a polarization reducing mechanism for performing a polarization reducing process that reduces polarization in the low dielectric insulating film after the CO 2  plasma process; and a transfer mechanism for transferring the substrate. 
         [0017]    The semiconductor device manufacturing apparatus may further include a silylation processing mechanism for performing a silylation process that silylates the low dielectric insulating film after the polarization reducing process. 
         [0018]    In the semiconductor device manufacturing apparatus, the silylation processing mechanism and the polarization reducing mechanism may be installed in a single chamber so as to perform the polarization reducing process and the silylation process in the same chamber. 
         [0019]    In the semiconductor device manufacturing apparatus, the chamber may include therein: a silylating agent vapor supply mechanism for supplying vapor of a silylating agent into the chamber; and a nitrogen gas supply unit for supplying a nitrogen gas into the chamber, independently of the silylating agent vapor supply mechanism. 
         [0020]    In the semiconductor device manufacturing apparatus, the transfer mechanism may be installed in a vacuum chamber to transfer the substrate under a vacuum atmosphere. 
         [0021]    In accordance with still another aspect of the present disclosure, there is provided a semiconductor device manufacturing method including: a mask forming process for forming an etching mask, which has a preset circuit pattern, on a surface of a low dielectric insulating film formed on a substrate; an etching process for forming a groove or a hole in the low dielectric insulating film by etching the low dielectric insulating film through the etching mask; a CO 2  plasma process for removing the etching mask by using CO 2  plasma after the etching process; and a UV process for irradiating UV to the low dielectric insulating film after the CO 2  plasma process. 
         [0022]    The semiconductor device manufacturing method may further include a silylation process for silylating the low dielectric insulating film after the UV process. 
         [0023]    The semiconductor device manufacturing method may further include a metal burying process for filling the groove or the hole with a conductive metal after the silylation process. 
         [0024]    In accordance with the present disclosure, there is provided a semiconductor device manufacturing method and a semiconductor device manufacturing apparatus capable of obtaining a low dielectric insulating film in a good state by recovering a damage such as an increase of hygroscopic property or dielectric constant of the low dielectric insulating film exposed to CO 2  plasma, thus improving performance and reliability of a semiconductor device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The disclosure may best be understood by reference to the following description taken in conjunction with the following figures: 
           [0026]      FIG. 1  is a plane view illustrating a schematic configuration of a semiconductor device manufacturing apparatus in accordance with an embodiment of the present disclosure; 
           [0027]      FIG. 2  is a cross sectional view illustrating a schematic configuration of a UV processing unit of the semiconductor device manufacturing apparatus of  FIG. 1 ; 
           [0028]      FIG. 3  is a cross sectional view illustrating a schematic configuration of a silylation processing unit of the semiconductor device manufacturing apparatus of  FIG. 1 ; 
           [0029]      FIG. 4  is a flowchart illustrating a process sequence of a semiconductor device manufacturing method in accordance with an embodiment of the present disclosure; 
           [0030]      FIGS. 5A to 5E  are diagrams illustrating wafer states in each process of  FIG. 4 ; 
           [0031]      FIG. 6  is a graph showing a wafer analysis result by a fourier transform infrared spectrometer; 
           [0032]      FIG. 7  is a graph showing a measurement result of a dielectric constant of a low dielectric insulating film; 
           [0033]      FIG. 8  is a graph showing a measurement result of a leakage current density of a low dielectric insulating film; 
           [0034]      FIG. 9  is a graph showing a measurement result of a moisture amount of a low dielectric insulating film; 
           [0035]      FIG. 10  is a graph showing a measurement result of an amount of fluorine components of a low dielectric insulating film; 
           [0036]      FIG. 11  is a cross sectional view illustrating a schematic configuration of a processing unit for performing a UV process and a silylation process; 
           [0037]      FIG. 12  is a flowchart for describing a process sequence for forming a groove wiring having a single damascene structure; 
           [0038]      FIGS. 13A to 13H  are diagrams schematically illustrating a change in the shape of the groove wiring formed according to the process sequence of  FIG. 12 ; 
           [0039]      FIG. 14  is a flowchart for describing a process sequence for forming a groove wiring having a dual damascene structure; 
           [0040]      FIGS. 15A to 151  are diagrams schematically illustrating a change in the shape of the groove wiring formed according to the process sequence of  FIG. 14 ; 
           [0041]      FIG. 16  is a flowchart for describing another process sequence for forming a groove wiring having a single damascene structure; and 
           [0042]      FIGS. 17A to 17H  are diagrams schematically illustrating a change in the shape of the groove wiring formed according to the process sequence of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    Hereinafter, embodiments of a semiconductor device manufacturing method and a semiconductor device manufacturing apparatus in accordance with the present disclosure will be described in detail with reference to the accompanying drawings. 
         [0044]      FIG. 1  is a plane view illustrating a schematic configuration of a semiconductor device manufacturing apparatus  100  in accordance with an embodiment of the present invention. The semiconductor device manufacturing apparatus  100  includes an etching processing unit  51  for performing a plasma etching process on a substrate (a semiconductor wafer in the present embodiment); an ashing processing unit  52  for performing an ashing process using CO 2  plasma; an UV processing unit  53  for performing an UV process; and a silylation processing unit  54  for performing a silylation process. These processing units  51  to  54  are installed at four sides of a hexagonal wafer transfer chamber  55 , respectively. 
         [0045]    Further, load lock chambers  56  and  57  are respectively installed at two remaining sides of the wafer transfer chamber  55 . A wafer loading/unloading chamber  58  is provided at a load lock chambers  56  and  57 ′ side opposite to the wafer transfer chamber  55 , and three ports  59  to  61  for holding three carriers C capable of accommodating wafers 
         [0046]    W therein are provided at a wafer loading/unloading chamber  58 ′ side opposite to the load lock chambers  56  and  57 . 
         [0047]    The etching processing unit  51 , the ashing processing unit  52 , the UV processing unit  53 , the silylation processing unit  54  and the load lock chambers  56  and  57  are connected to the respective sides of the wafer transfer chamber  55  via gate valves G, as shown in  FIG. 1 , so that they are allowed to communicate with the wafer transfer chamber  55  when the gate valves G are opened and they can be isolated from the wafer transfer chamber  55  when the gate valves G are closed. Further, the gate valves G are also installed at positions where the load lock chambers  56  and  57  are connected to the wafer loading/unloading chamber  58 , so that the load lock chambers  56  and  57  are allowed to communicate with the wafer loading/unloading chamber  58  when the gate valves G are opened and they can be isolated from the wafer loading/unloading chamber  58  when the gate valves G are closed. 
         [0048]    In the wafer transfer chamber  55 , there is provided a wafer transfer mechanism  62  which performs loading and unloading of a wafer W with respect to the etching processing unit  51 , the ashing processing unit  52 , the UV processing unit  53 , the silylation processing unit  54 , and the load lock chambers  56  and  57 . The wafer transfer mechanism  62  is positioned substantially at the center of the wafer transfer chamber  55 , and it includes a rotatable extendible/retractable unit  63  that can make retracting, extending and rotating motions. At leading ends of the rotatable·extendible/retractable unit  63 , there are provided two blades  64   a  and  64   b  for holding the wafer W, and the two blades  64   a  and  64   b  are fixed to the rotatable extendible/retractable unit  63  such that they can be oriented in an opposite direction to each other. Moreover, the interior of the wafer transfer chamber  55  is maintained at a specific vacuum level. 
         [0049]    A non-illustrated HEPA filter is provided in a ceiling portion of the wafer loading/unloading chamber  58 . Clean air which has passed the HEPA filter is supplied into the wafer loading/unloading chamber  58  in a down-flow state to ensure that the tasks of loading and unloading the wafer W are carried out in a clean-air atmosphere under an atmospheric pressure. Each of the wafer loading/unloading chamber  58 &#39;s three ports  59 ,  60  and  61  for holding the carriers C is provided with a non-illustrated shutter. The carriers C, each accommodating wafers W therein or remaining empty, are directly installed on the ports  59 ,  60  and  61 , and the shutters are then opened so that the carriers C are allowed to communicate with the wafer loading/unloading chamber  58  while introduction of exterior air is prevented. Furthermore, an alignment chamber  65  is provided on a lateral side of the wafer loading/unloading chamber  58 , and alignment of the wafer W is performed therein. 
         [0050]    Disposed in the wafer loading/unloading chamber  58  is a wafer transfer mechanism  66  which performs loading and unloading of the wafer W with respect to the carriers C and the load lock chambers  56  and  57 . The wafer transfer mechanism  66  has a multi-joint arm structure and is capable of moving along a rail  68  in an arrangement direction of the carriers C. The wafer transfer mechanism  66  is configured to transfer the wafer W by holding the wafer W with a hand provided at a leading end thereof. The entire system including the wafer transfer mechanisms  62  and  66  is controlled by a control unit  69 . 
         [0051]    Among the aforementioned processing units, each of the etching processing unit  51  and the asking processing unit  52  may be implemented by, for example, a capacitively coupled plasma processing apparatus which generates plasma by applying a high frequency power between parallel plate electrodes provided in a processing chamber. Since such a plasma processing apparatus is well-known, detailed description thereof will be omitted herein. 
         [0052]      FIG. 2  is a longitudinal cross sectional view illustrating a schematic configuration of the UV processing unit  53 . The UV processing unit  53  includes a chamber  31  for accommodating the wafer W therein, and the chamber  31  is provided with an opening  32  through which the wafer W is loaded and unloaded. The opening  32  is connected with the wafer transfer chamber  55  via the gate valve G. 
         [0053]    Disposed in the chamber  31  is a hot plate  33  for mounting the wafer W and capable of heating the wafer W to a preset temperature. A UV lamp  34  for irradiating UV to the wafer W is installed in a ceiling portion of the chamber  31  to face the hot plate  33 . Further, a gas exhaust pipe  35  for evacuating the inside of the chamber  31  and a nitrogen gas supply pipe  36  for supplying a nitrogen gas into the chamber  31  are connected to the chamber  31  to allow the UV irradiation to be carried out in the chamber  31  under a vacuum atmosphere or in a nitrogen gas atmosphere. 
         [0054]      FIG. 3  is a longitudinal cross sectional view illustrating a schematic configuration of the silylation processing unit  54 . The silylation processing unit  54  includes a chamber  41  for accommodating the wafer W therein, and the chamber  41  is provided with a non-illustrated opening through which the wafer W is loaded and unloaded. The opening for the loading and unloading of the wafer W is connected to the wafer transfer chamber  55  via the gate valve G. A hot plate  42  is installed in the chamber  41 , and a nitrogen gas containing a silylating agent such as TMSDMA vapor is supplied into the chamber  41  from a vicinity of the hot plate  42 . 
         [0055]    In the silylation processing unit  54  of  FIG. 3 , though liquid TMSDMA is vaporized by a vaporizer  43  and is contained in the nitrogen gas in a vaporizer  43 , it may be also possible to supply only a vaporized TMSDMA gas (that is, TMSDMA vapor) into the chamber  41 . As will be described later, since the inside of the chamber  41  is maintained at a preset vacuum level when the TMSDMA is supplied into the chamber  41 , the introduction of the TMSDMA gas into the chamber  41  can be readily carried out by using a pressure difference between the vaporizer  43  and the chamber  41 . 
         [0056]    The temperature of the hot plate  42  can be controlled within a range of, e.g., about 50° to 200°, and pins  44  for supporting the wafer W are provided on the surface of the hot plate  42 . Since the wafer W is not directly placed on the hot plate  42 , contamination of the rear surface of the wafer W can be prevented. A gas exhaust port  47  is provided at a substantially central portion of a ceiling portion of the chamber  41  to exhaust the TMSDMA-containing nitrogen gas supplied into the chamber  41 , and the gas exhaust port  47  is connected with a vacuum pump  49  via a pressure controller  48 . 
         [0057]    Further, the silylation processing unit  54  includes a non-illustrated water vapor supply mechanism so that a nitrogen gas containing a certain concentration of water vapor (or only the water vapor) can be supplied into the chamber  41 . 
         [0058]    If an interlayer insulating film, which has been damaged by the etching process or asking process or whose surface has become hydrophilic, is taken out to the atmospheric atmosphere, moisture would be absorbed by the interlayer insulating film and thus its dielectric constant would increase. In the semiconductor manufacturing apparatus  100  of the present embodiment, by performing a damage recovery process within the semiconductor manufacturing apparatus  100  without exposing the wafer W to the atmospheric atmosphere after the completion of the etching and asking processes, the increase of the dielectric constant due to the moisture absorption can be prevented. In the semiconductor manufacturing apparatus  100 , however, since the wafer W after the etching process is transferred from the etching processing unit  51  to the silylation process unit  54  in the vacuum atmosphere and thus a portion damaged by the etching does not absorb moisture at all. Accordingly, there is a concern that a silylation reaction may not occur readily. 
         [0059]    In this regard, the silylation processing unit  54  is configured to be capable of supplying water vapor into the chamber  41  and enabling a proper absorption reaction at the damaged portion intentionally, thus facilitating a silylation reaction. Further, since the silylation reaction may be suppressed as opposed to the original intention if the absorption reaction progresses excessively, the supply of the water vapor needs to be controlled so as not to cause such suppression of the reaction. 
         [0060]    Now, an embodiment of a semiconductor device manufacturing method using the above-described semiconductor device manufacturing apparatus  100  will be explained.  FIG. 4  is a flowchart illustrating a process sequence of the semiconductor device manufacturing method in accordance with the embodiment of the present invention, and  FIGS. 5A to 5E  are enlarged diagrams illustrating cross sectional views of a wafer processed in respective steps of  FIG. 4 . 
         [0061]    As depicted in  FIG. 5A , a wafer W is provided with a low dielectric insulating film (Low-k film)  71  formed on a base layer  70  made of silicon or the like by coating, CVD, or the like. A photoresist film  72  is formed on the low dielectric insulating film  71 , and the photoresist film  72  serves as a mask having a preset pattern formed by an exposure and development process or the like. The wafer W in this state is loaded into the semiconductor device manufacturing apparatus  100 . 
         [0062]    In the semiconductor device manufacturing apparatus  100 , the wafer W is first loaded into the etching processing unit  52  by the wafer transfer mechanism  62  in the wafer transfer chamber  55  and is etched therein by, e.g., CF 4  plasma or the like (step  1  of  FIG. 4 ). By this etching process, a hole (or groove)  73  which reaches the base layer is formed in the low dielectric insulating film  71  by using the photoresist film  72  as a mask, as depicted in  FIG. 5B . Here, a reference numeral  71   a  in  FIG. 5B  indicates a damaged portion of the low dielectric insulating film  71  which is caused by the plasma etching. 
         [0063]    Subsequently, the wafer W is transferred from the etching processing unit  51  into the ashing processing unit  52  by the wafer transfer mechanism  62  in the wafer transfer chamber  55 . Then, in the ashing processing unit  52 , an ashing process by, e.g., CO 2  plasma is conducted (step  2  of  FIG. 4 ). By this ashing process, the photoresist mask  72  used as the mask in the etching process is removed, as illustrated in  FIG. 5C . In the ashing process, a damage different from that caused in the etching process is inflicted on the damaged portion  71   a  again. 
         [0064]    Thereafter, the wafer W is transferred from the ashing processing unit  52  into the UV processing unit  53  by the wafer transfer mechanism  62  in the wafer transfer chamber  55 . Then, in the UV processing unit  53 , a UV process for irradiating UV to the wafer W (low dielectric insulating film  71 ) is performed, as shown in  FIG. 5D  (step  3  of  FIG. 4 ). The UV process by the UV processing unit  53  is carried out by irradiating UV to the entire surface of the wafer W while heating the wafer W to, e.g., about 300°. This UV process may be performed in a vacuum atmosphere or in a nitrogen gas atmosphere. 
         [0065]    Subsequently, the wafer W is transferred from the UV processing unit  53  into the silylation processing unit  54  by the wafer transfer mechanism  62  in the wafer transfer chamber  55 . Then, a silylation process is performed in the silylation processing unit  54  (step  4  of  FIG. 4 ). The silylation process by the silylation processing unit  54  is carried out by exposing the wafer W to the silylating agent such as the TMSDMA vapor or the like, as illustrated in  FIG. 5E . Processing conditions for the silylation process may be selected depending on the kind of the silylating agent. For example, the temperature of the vaporizer  43  may be appropriately set to range from a room temperature to about 50°C.; the flow rates of the silylating agent and the N 2  gas (purge gas) may be appropriately set to be in the range of about 0.1 to 1.0 g/min and in the range of about 1 to 10 L/min, respectively; a processing pressure may be appropriately set to range from about 666 to 95976 Pa (5 to 720 Torr); and the temperature of the hot plate  42  may be appropriately set to range from a room temperature to about 200° C. 
         [0066]    After the completion of the silylation process, the wafer W is transferred into the load lock chamber  56  or  57  by the wafer transfer mechanism  62  in the wafer transfer chamber  55  and then is unloaded from the load lock chamber  56  or  57  into a normal pressure atmosphere. 
         [0067]    In the above-described processes, the sidewall of the hole (or groove)  73  formed in the low dielectric insulating film  71  is damaged by the etching process using the CF 4  plasma or the like and the asking process using the CO 2  plasma or the like. To elaborate, the damaged portion may react with moisture, whereby a methyl group would decrease and a hydroxyl group would increase in the vicinity of the sidewall of the hole (or groove)  73 , resulting in an increase of dielectric constant. If such damaged portion remains at the sidewall of the hole (or groove)  73 , a parasitic capacitance may be increased between wirings when the wirings are formed later by filling the hole (or groove)  73  with a metal material, resulting in such problems as a signal delay, a deterioration of insulation between the wiring, and the like. Though the damaged portion  71   a  is schematically illustrated in  FIGS. 5B and 5C , a boundary between the damaged portion  71   a  and an undamaged portion is not actually as clear as shown in  FIGS. 5B and 5C . 
         [0068]    In the present embodiment, the UV process by the UV processing unit  53  and the silylation process by the silylation processing unit  54  are performed to recover the damage of the low dielectric insulating film  71 . By recovering the damage of the low dielectric insulating film  71 , it is possible to form a wiring having highly advantageous electrical characteristics, thus enabling an improvement of reliability of a semiconductor device. 
         [0069]    Further, in the above-described embodiment, though the above-stated respective processes are performed by a single apparatus, i.e., by the semiconductor device manufacturing apparatus  100  including the etching processing unit  51 , the asking processing unit  52  and the UV processing unit  53  and the silylation processing unit  54  integrated as one body, it may be also possible to perform the respective processes by individual apparatuses. For example, it may be possible to perform the etching process and the ashing process by a single apparatus and to perform the UV process and the silylation process by a UV process apparatus and a silylation process apparatus. 
         [0070]      FIG. 6  is a graph showing an analysis result of a wafer on which an etching process of a low dielectric insulating film, an ashing process by CO 2  plasma, an UV process and a silylation process were performed in accordance with the above-described embodiment; and a wafer on which a conventional method of performing only an etching process of a low dielectric insulating film, an ashing process by CO 2  plasma and a silylation process was carried out without performing a UV process. The analysis was performed by using a fourier transform infrared spectrometer. As depicted in  FIG. 6 , as for the wafer on which the UV process was performed, it is found out that SiOH or SiF (portion indicated by (1) in the graph) decreases near a wave number of about 950 cm −1 , whereas SiO (portion indicated by (2) in the graph) increases near a wave number of about 1060 cm −1 . From this result, it is supposed that there occurred a condensation reaction. In the experiment, a porous MSQ (Methyl Silses Quioxane) was used as the low dielectric insulating film. 
         [0071]    Further, in the present embodiment, it is believed that not only a simple condensation reaction of Si—OH+Si—OH→Si—O—Si (siloxane structure)+H 2 O but also reactions similar to the condensation reaction such as a reaction of Si—F+SiOH→Si—O—Si+HF and a reaction of Si—F+Si—F→Si—O—Si+F 2  also occur at the same time, so that Si—F components in the low dielectric insulating film as well as Si—OH components therein decrease, thereby reducing polarization in the low dielectric insulating film greatly and thus enabling improvement of characteristics of the low dielectric insulating film. 
         [0072]      FIG. 7  shows, in sequence from the top, measurement results of dielectric constants (k values) of low dielectric insulating films in respective cases of performing only an etching process and an ashing process; only a UV process after the etching and the ashing processes; only a silylation process (LKR) after the etching and the ashing processes; and both the UV process and the silylation process (LKR) after the etching and the ashing processes. Further, the dielectric constant of the low dielectric insulating film was about 2.4 before the etching process and the ashing process, and a porous MSQ (Methyl Silses Quioxane) was used as the low dielectric insulating film. 
         [0073]    As depicted in  FIG. 7 , it was proved that though the dielectric constant of the low dielectric insulating film cannot be reduced when only the silylation process (LKR) is performed after the etching process and the ashing process, the dielectric constant of the low dielectric insulating film can be decreased by performing the UV process. Furthermore, in the example shown in  FIG. 7  (the second one from the top), the dielectric constant of the low dielectric insulating film is reduced by performing only the UV process without performing the silylation process. However, the UV process is basically not a reaction for allowing a film to have a hydrophobic property, so that the insulating film&#39;s portion whose dielectric constant is reduced by the UV process may be dissolved in a hydrofluoric acid based solution or the like which may be used in a post process. For the reason, the hydrophobic property of the film surface desirably needs to be as high as possible, and it is therefore desirable to perform the silylation process (LKR) as well as the UV process. 
         [0074]      FIG. 8  shows, in sequence from the top, measurement results of leakage current densities in respective cases of performing only the etching process and the ashing process; only the UV process after the etching and the ashing processes; only the silylation process (LKR) after the etching and the ashing processes; and both the UV process and the silylation process (LKR) after the etching and the ashing processes. Further, the left side of  FIG. 8  indicates a case of applying an electric field of about 1 MV/cm and the right side thereof indicates a case of applying an electric field of about 2 MV/cm. Further, the measurements of the leakage current densities and the above-stated dielectric constants were carried out by performing the above-described respective processes on the low dielectric insulating film formed on the entire surface of the wafer; forming an electrode made of a aluminum film on the surface thereof by using a sputtering method; and then applying a voltage between the front surface and the rear surface of the wafer. Further, a porous MSQ (Methyl Silses Quioxane) was used as the low dielectric insulating film. 
         [0075]    As depicted in  FIG. 8 , it was proved that though the leakage current is slightly reduced when only the silylation process (LKR) is performed after the etching process and the asking process, the leakage current can be more greatly reduced by as much as about one digit place by performing the UV process. 
         [0076]    Moreover, if a loss of a current flowing in a circuit is caused by the leakage current, current consumption increases. Further, since there is a likelihood that a defect may have been generated at a position where the leakage current flows, a degradation of the circuit such as diffusion of Cu wiring into the insulating film or the like may be caused with the lapse of time. Moreover, if a current flows in a circuit which is not originally supposed to flow the current therein, a malfunction of the circuit may be resulted. In view of the mentioned reasons, it is desirable to reduce the leakage current. 
         [0077]      FIG. 9  shows, in sequence from the top, measurement results of moisture amounts in low dielectric insulating films in respective cases of performing only the etching process and the ashing process; only the UV process after the etching and the ashing processes; only the silylation process (LKR) after the etching and the ashing processes; and both the UV process and the silylation process (LKR) after the etching and the ashing processes. The moisture amount was computed by measuring the amount of desorption gas when the temperature of the wafer W was increased by 1° C. every second by employing mass spectrometry (mass=18 (H 2 O)). Further, a porous MSQ (Methyl Silses Quioxane) was used as the low dielectric insulating film. 
         [0078]    As depicted in  FIG. 9 , it was proved that though the moisture amount is slightly reduced when only the silylation process (LKR) is performed after the etching process and the ashing process, the moisture amount can be reduced to about ⅓ by performing the UV process. 
         [0079]    Furthermore, since moisture increases the mobility of electric charges, it causes an increase of a leakage current between wirings. If a film absorbs moisture, it implies that the film has a structure readily allowing a movement of electric charges. Further, since water itself has a high dielectric constant, it may cause an increase of the dielectric constant of the low dielectric insulating film. In addition, since the moisture serves as a factor that oxidizes a metal wiring such as Cu, it may leads to an increase of wiring resistance, resulting in an increase of power consumption. In consideration of the above-mentioned reasons, it is desirable to reduce the moisture amount in the low dielectric insulating film. 
         [0080]      FIG. 10  shows, in sequence from the top, measurement results of the amount of fluorine components of low dielectric insulating films in respective cases of performing only the etching process and the ashing process; only the UV process after the etching and the ashing processes; only the silylation process (LKR) after the etching and the ashing processes; and both the UV process and the silylation process (LKR) after the etching and the ashing processes. The amount of fluorine components was computed by measuring an amount of desorption gas when the temperature of the wafer W was increased by 1° C. every second by employing mass spectrometry (mass=19 (F)). Further, a porous MSQ (Methyl Silses Quioxane) was used as the low dielectric insulating film. 
         [0081]    As depicted in  FIG. 10 , it was proved that though the fluorine components are not reduced when only the silylation process (LKR) is performed after the etching process and the ashing process, the fluorine components can be reduced to about ⅔ by performing the UV process. 
         [0082]    Since fluorine has high electronegativity, it is highly likely that the polarity of the film structure of the low dielectric insulating film may be increased if the fluorine remains in the low dielectric insulating film. Thus, by attracting moisture, the dielectric constant may increase, whereby the dielectric constant of the insulating film itself is highly likely to increase. Further, in case that the fluorine remains in the low dielectric insulating film, there is a likelihood that the fluorine may be ionized by a slight amount of water in the atmospheric atmosphere or the insulating film with the lapse of time, resultantly dissolving the low dielectric insulating film. In view of the forgoing reasons, it is desirable to reduce the fluorine components in the low dielectric insulating film. 
         [0083]      FIG. 11  illustrates a configuration of a UV processing unit  53   a  configured to perform a UV process and a silylation process (LKR) in a single chamber. The UV processing unit  53   a  includes a chamber  31  for accommodating a wafer W therein, and the chamber  31  is provided with an opening  32  through which the wafer W is loaded and unloaded. The opening  32  is connected with the wafer transfer chamber  55  via the above-described gate valve G. 
         [0084]    Inside the chamber  31 , there is installed a hot plate  33  for holding the wafer W and heating the wafer to a preset temperature. A UV lamp  34  for irradiating UV to the wafer W is installed in a ceiling portion of the chamber  31  to face the hot plate  33 . Further, a nitrogen gas supply pipe  36  for supplying a nitrogen gas into the chamber  31  is connected to the ceiling portion inside the chamber  31 , and a TMSDMA vapor supply pipe  136  for supplying vapor of a silylating agent (TMSDMA in the present embodiment) into the chamber  31  is also connected to the ceiling portion inside the chamber independently of the nitrogen gas supply pipe  36 . In addition, a gas exhaust pipe  35  for evacuating the inside of the chamber  31  is also connected to the chamber  31 . 
         [0085]    In the UV processing unit  53   a  configured as described above, a UV process can be performed in the chamber  31  under a vacuum atmosphere or a nitrogen gas atmosphere. Further, a silylation process can be consecutively performed in the same chamber  31  under a mixed atmosphere of a nitrogen gas and TMSDMA vapor by introducing the TMSDMA vapor from the TMSDMA vapor supply pipe  136  while concurrently introducing the nitrogen gas from the nitrogen gas supply pipe  36 . 
         [0086]    Further, since the nitrogen gas supply pipe  36  and the TMSDMA vapor supply pipe  136  are separated, a highly pure nitrogen gas atmosphere without containing the TMSDMA vapor mixed therein can be generated promptly, and the nitrogen gas/TMSDMA vapor mixed atmosphere can also be generated promptly. Accordingly, processing time can be reduced when the UV process and the silylation process (LKR) are consecutively carried out. 
         [0087]    Now, application of the present invention to a wiring process using a single damascene method will be explained in accordance with an embodiment of the present invention with reference to  FIG. 12  and  FIGS. 13A to 13H .  FIG. 12  is a flowchart for illustrating a process sequence for forming a groove wiring having a single damascene structure and  FIGS. 13A to 13H  are diagrams schematically showing a change of the shape of the groove wiring formed in each process of  FIG. 12 . 
         [0088]    First, there is prepared a wafer W (wafer W itself is not illustrated) including an insulating film  170  in which a lower wiring (Cu wiring)  172  is formed with a barrier metal layer  171  therebetween and a stopper film  173  made of, e.g., a SiN film or a SiC film formed on the surface of the insulating film  170 . An interlayer insulating film  174  made of a low dielectric insulating film (for example, porous MSQ or the like) is formed on the stopper film  173  of the wafer W (step  101 ,  FIG. 13A ). 
         [0089]    Then, an antireflection film  175   a  and a resist film  175   b  are sequentially formed on the interlayer insulating film  174 , and by performing an exposure and development process, the resist film  175   b  becomes a resist mask with a preset pattern (step  102 ,  FIG. 13B ). 
         [0090]    Then, an etching process for etching the interlayer insulating film  174  is performed by using the resist mask, whereby a via  178   a  that reaches the stopper film  173  is formed in the interlayer insulating film  174  (step  103 ,  FIG. 13C ). 
         [0091]    Subsequently, an asking process for removing the antireflection film  175   a  and the resist film  175   b  is performed by CO 2  plasma (step  104 ,  FIG. 13D ). In  FIGS. 13C and 13D , a reference numeral  179   a  indicates a damaged portion. 
         [0092]    Then, there is performed a modification process for modifying polymer residues or the like remaining on the wafer W after the etching or the ashing process, thus rendering them water soluble (step  105 ). Thereafter, a cleaning process for removing the modified polymer residues or the like is conducted (step  106 ). 
         [0093]    As stated, the sidewall of the via  178   a  formed in the interlayer insulating film  174  is damaged by the etching process, the ashing process, or the subsequent washing process. To elaborate, the damaged portion reacts with moisture, whereby a methyl group decreases and a hydroxyl group increases in the vicinity of the sidewall of the via  178   a,  resulting in an increase of dielectric constant. If the via  178   a  is later filled with a metal material to form a groove wiring in the state that such a damaged portion exists on the sidewall of the via  178   a,  a parasitic capacitance between wirings would be increased, resulting in problems such as a signal delay, a deterioration of insulation between the groove wirings, and so forth. Though the damaged portion  179   a  is schematically illustrated in  FIGS. 13C and 13D , a boundary between the damaged portion  179   a  and an undamaged portion is not actually as clear as shown in  FIGS. 13C and 13D . 
         [0094]    Subsequently, a UV process for irradiating UV to the wafer W is performed (step  107 ), and a silylation process is then carried out (step  108 ), whereby the damaged portion  179   a  of the interlayer insulating film  174  is recovered ( FIG. 13E ). 
         [0095]    Afterward, an etching process for removing the stopper film  173  is performed (step  109 ), and a cleaning process for removing etched residues is then conducted (step  110 ,  FIG. 13F ). 
         [0096]    The sidewall of the via  178   a  formed in the interlayer insulating film  174  may be damaged by this etching process or the cleaning process again, so that a damaged portion  179   b  is formed. Thus, a UV process for irradiating UV to the wafer W is subsequently conducted (step  111 ), and a silylation process is then carried out (step  112 ), whereby the damaged portion  179   b  of the interlayer insulating film  174  is recovered ( FIG. 13G ). As described, it may be possible to perform the UV process and the silylation process for damage recovery even in case that only the etching process is performed on the interlayer insulating film  174  without conducting an asking process by CO 2  plasma or the like. In such a case, it may be also desirable to perform only the silylation process without performing the UV process. 
         [0097]    Thereafter, a barrier metal film and a Cu seed layer (i.e., plating seed layer) are formed on the inner wall of the via  178   a  (step  113 ). Then, the via  178   a  is filled with a metal  176  such as copper by electroplating (step  114 ). Afterward, an annealing process of the metal  176  buried in the via  178   a  is performed by heating the wafer W, and a planarization process is performed by a CMP method (step  115 ,  FIG. 13H ). 
         [0098]    In accordance with the above-described groove wiring forming method, even in case that the sidewall of the via  178   a  formed in the interlayer insulating film is damaged by etching, ashing or cleaning, the damaged portion can be recovered by the UV process and the silylation process. Thus, a groove wiring having advantageous electrical characteristics can be formed, so that the reliability of the semiconductor device can be improved. 
         [0099]    Though the above description has been provided for the case of performing the UV process and the silylation process after the cleaning process is completed, it may be possible to perform the UV process and the silylation process after a certain process in the event that a damage has been inflicted or is likely to be inflicted on the interlayer insulating film  174  by that process. For example, it may be also desirable to perform the UV process and the silylation process immediately after the ashing process of step  104  instead of or in addition to performing those processes after the cleaning process. 
         [0100]    Now, another method for forming a groove wiring in an interlayer insulating film formed on a wafer W will be explained with reference to  FIG. 14  and  FIGS. 15A to 151 .  FIG. 14  is a flowchart for illustrating a process sequence for forming a groove wiring having a dual damascene structure and  FIGS. 15A to 151  are diagrams schematically showing a change of the shape of the groove wiring formed in each process of  FIG. 14 . 
         [0101]    First, there is prepared a wafer W (wafer W itself is not illustrated) including an insulating film  170  in which a lower wiring (Cu wiring)  172  is formed with a barrier metal layer  171  therebetween and a stopper film  173  made of, e.g., a SiN film or a SiC film formed on the surface of the insulating film  170 . An interlayer insulating film  174  made of a low dielectric insulating film (for example, porous MSQ or the like) is formed on the stopper film  173  of the wafer W (step  201 ,  FIG. 15A ). 
         [0102]    Then, an antireflection film  175   a  and a resist film  175   b  are sequentially formed on the interlayer insulating film  174 . Thereafter, a resist mask having a preset pattern is obtained by exposing and developing the resist film  175   b  (step  202 ,  FIG. 15B ). 
         [0103]    Then, an etching process is performed by using the resist film  175   b  as an etching mask, whereby a via  178   a  that reaches the stopper film  173  is formed (step  203 ,  FIG. 15C ). In  FIG. 15C , a reference numeral  179   a  indicates a damaged portion generated by the etching process. 
         [0104]    Subsequently, an ashing process is performed by CO 2  plasma, whereby the antireflection film  175   a  and the resist film  175   b  are removed (step  204 ), and a cleaning process for removing polymer residues or the like generated by the previous etching process or ashing process is carried out (step  205 ). 
         [0105]    Thereafter, a UV process for irradiating UV to the wafer W is performed (step  206 ), and a silylation process is subsequently carried out (step  207 ), whereby the damaged portion  179   a  of the interlayer insulating film  174  is recovered ( FIG. 15D ). 
         [0106]    Then, a protective film  181  is formed on the surface of the interlayer insulating film  174  (step  208 ). Then, an antireflection film  182   a  and a resist film  182   b  are sequentially formed on the protective film  181 , and the resist film  182   b  is subjected to an exposure and development process using a preset pattern, so that the resist film  182   b  becomes a resist mask having the preset pattern (step  209 ,  FIG. 15E ). The protective film  181  can be formed by spin-coating a preset liquid chemical. The protective film  181  is optional, and thus it may be possible to form the antireflection film  182   a  and the resist film  182   b  directly on the interlayer insulating film  174 . 
         [0107]    Subsequently, an etching process is performed by using the resist mask made of the resist film  182   b,  whereby a trench  178   b  is formed in the interlayer insulating film  174  (step  210 ,  FIG. 15F ). Then, the resist film  182   b  and the antireflection film  182   a  are removed by an ashing process using CO 2  plasma (step  211 ). A reference numeral  179   b  shown in  FIG. 15F  is a damaged portion caused by the etching process in step  210 . 
         [0108]    Thereafter, a cleaning process for removing polymer residues generated by the previous etching or ashing process, the protective film  181 , and the like are carried out (step  212 ). Afterward, a UV process for irradiating UV to the wafer W is conducted (step  213 ), and a silylation process is subsequently performed (Step  214 ), whereby the damaged portion  179   b  of the interlayer insulating film  174  is recovered ( FIG. 15G ). 
         [0109]    Subsequently, an etching process for removing the stopper film  173  and a subsequent residue removing process are conducted (step  215 ). Then, a UV process for irradiating UV to the wafer W is performed (step  216 ), and a silylation process is then conducted (step  217 ), whereby damaged portions formed at the via  178   a  and the trench  178   b  by the etching process are recovered ( FIG. 15H ).  FIG. 15H  illustrates a state after the completion of the silylation process. 
         [0110]    Afterward, a barrier metal film and a Cu seed layer are formed on the inner walls of the via  178   a  and the trench  178   b;  a plug is formed by filling the via  178   a  and the trench  178   b  with a metal  176  such as copper by electroplating; an annealing process of the metal  176  buried in the via  178   a  and the trench  178   b  is performed by heating the wafer W; and a planarization process is performed by a CMP method (step  218 ,  FIG. 15I ). 
         [0111]    Now, still another method for forming a groove wring in an interlayer insulating film formed on a wafer W will be explained with reference to  FIGS. 16  and  FIGS. 17A to 17H .  FIG. 16  is a flowchart for illustrating another process sequence for forming a groove wiring having a dual damascene structure, and  FIGS. 17A to 17H  are diagrams schematically showing a change of the shape of the groove wiring formed in each process of  FIG. 16 . 
         [0112]    First, there is prepared a wafer W (wafer W itself is not illustrated) including an insulating film  170  in which a lower wiring (Cu wiring)  172  is formed with a barrier metal layer  171  therebetween and a stopper film  173  made of, e.g., a SiN film or a SiC film formed on the surface of the insulating film  170 . An interlayer insulating film  174  made of a low dielectric insulating film (for example, porous MSQ or the like), a hard mask layer  186 , an antireflection film  187   a  and a resist film  187   b  are sequentially formed on the stopper film  173  of the wafer W, and a resist mask is obtained by exposing and developing the resist film  187   b  by using a preset pattern (step  301 ,  FIG. 17A ). 
         [0113]    Then, an etching process is performed by using the resist film  187   b  as an etching mask (step  302 ) to thereby pattern the hard mask layer  186 , and the antireflection film  187   a  and the resist film  187   b  are then removed (step  303 ,  FIG. 17B ). 
         [0114]    Subsequently, an antireflection film  188   a  and a resist film  188   b  are sequentially formed on the hard mask layer  186 , and a resist mask is obtained by exposing and developing the resist film  188   b  by using a preset pattern (step  304 ,  FIG. 17C ). 
         [0115]    Thereafter, a via  178   a  that reaches the stopper film  173  is formed by using the resist mask made of the resist film  188   b  (step  305 ,  FIG. 17D ). Then, the resist film  188   b  and the antireflection film  188   a  are removed by an ashing process using CO 2  plasma or the like and a polymer residue removing·cleaning process is conducted (step  306 ,  FIG. 17E ). 
         [0116]    In case that a damaged portion is generated at the interlayer insulating film  174  after the ashing process and the polymer residue removing·cleaning process, a UV process and a silylation process may be conducted subsequently. 
         [0117]    Since the hard mask layer  186  having the preset pattern is exposed after the completion of step  306 , a trench  178   b  is formed by performing an etching process while using the hard mask layer  186  as an etching mask (step  307 ). At this time, if a damaged portion is generated at the interlayer insulating film  174 , a UV process and a silylation process can be immediately performed. 
         [0118]    Then, the hard mask layer  186  is removed by an asking process using CO 2  plasma or a liquid chemical process (step  308 ,  FIG. 17F ). For example, a UV process and a silylation process are conducted after the removal of the hard mask layer  186  (step  309 ), whereby a damaged portion generated at the interlayer insulating film  174  in or before step  308  can be recovered. Further,  FIG. 17F  shows a state after the damage is recovered. 
         [0119]    Thereafter, an etching process for removing the stopper film  173  and a residue removing·cleaning process are conducted (step  310 ,  FIG. 17G ), and a UV process and a silylation process are carried out again to recover a damaged portion generated at the via  178   a  and the trench  178   b  because of the etching process or the like (step  311 ). 
         [0120]    Then, a barrier metal film and a Cu seed layer are formed on the inner walls of the via  178   a  and the trench  178   b,  and a plug is formed by filling the via  178   a  and the trench  178   b  with a metal  176  such as copper by electroplating, and an annealing process of the metal  176  buried in the via  178   a  and the trench  178   b  is performed by heating the wafer W, and a planarization process is performed by a CMP method (step  312 ,  FIG. 17H ). 
         [0121]    While the invention has been described with respect to the embodiments, it will be understood by those skilled in the art that various changes and modifications may be made.

Technology Category: h