Abstract:
A method of manufacturing a semiconductor device comprising the steps of: preparing a flexible substrate which includes a base substrate having a light transmission property and an interconnecting pattern formed on one surface of the base substrate, the flexible substrate allowing a light to pass through a region other than the interconnecting pattern; recognizing a position of the interconnecting pattern by viewing the flexible substrate from a surface opposite to the surface on which the interconnecting pattern is formed through the base substrate; recognizing positions of electrodes formed on a semiconductor chip from a direction identical to that in recognizing the interconnecting pattern; and aligning the interconnecting pattern with the electrodes to connect the flexible substrate to the semiconductor chip by the face down bonding.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention relates to a semiconductor device and a method of manufacturing the same, an apparatus for manufacturing a semiconductor device, a circuit board and an electronic instrument. 
   2. Description of Related Art 
   As the electronic devices are recently manufactured to be more miniaturized, there is a demand for semiconductor device packages suitable for a high-density mounting. To answer these demands, surface-mounted packages such as Ball Grid Array (BGA) and Chip Scale/Size Package (CSP) have been developed. With this surface-mounted package, a semiconductor chip is mounted by the face-down bonding on a substrate on which an interconnecting pattern is formed. 
   In order to make a positional alignment of the interconnecting pattern with electrodes of the semiconductor chip, a conventional method of manufacturing the surface-mounted package uses an optical system. Specifically, the optical system is placed between a surface having electrodes of a semiconductor chip and a surface having an interconnecting pattern of a substrate, and images of both surfaces are taken by a camera, thus detecting the positions of the interconnecting pattern and electrodes. According to this method, because the optical system is complicated, errors in positioning are apt to occur, so that a degradation of mounting precision is brought about. 
   SUMMARY OF THE INVENTION 
   The present invention was made to solve the above problem, and an object of the present invention is to provide a method of manufacturing a semiconductor device which improves the mounting precision, the semiconductor device manufactured by the method, an apparatus for manufacturing the semiconductor device, a circuit board, and an electronic instrument. 
   (1) According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device that comprises a flexible substrate including a base substrate that has a light transmission property and an interconnecting pattern formed on one surface of the base substrate, and a semiconductor chip that is connected to the flexible substrate and provided with electrodes, the method comprising the steps of: 
   detecting a position of at least one of the electrodes and interconnecting pattern by a detection means that is provided on a side opposite to a side on which the semiconductor chip is provided; and 
   electrically connecting the interconnecting pattern to the electrodes. 
   (2) In this method of manufacturing a semiconductor device, positions of the interconnecting pattern and the electrodes may be detected by the detection means by viewing from a surface of the flexible substrate opposite to a surface on which the interconnecting pattern is formed. 
   Since the substrate having a light transmission property is used, the interconnecting pattern can be recognized from the reverse surface of the flexible substrate. When the surface on which the interconnecting pattern is formed and the surface on which the electrodes are formed are arranged parallel to each other, the recognition can be made without changing the direction of the detection means. Moreover, by moving the flexible substrate and the semiconductor chip in a direction parallel to these surfaces, the face down bonding can be performed after the recognition. As a result, it is possible to enhance a mounting precision without using a complicated optical system. 
   (3) In this method of manufacturing a semiconductor device, the flexible substrate may be a two-layered flexible substrate in which the interconnecting pattern is formed on the base substrate without using adhesive. 
   Generally-used adhesive inhibits light to transmit through the flexible substrate. By using the two-layered substrate that does not use such generally-used adhesive, the interconnecting pattern can be recognized through the surface opposite to that where the interconnecting pattern is formed. 
   (4) In this method of manufacturing a semiconductor device, the interconnecting pattern may be formed on the base substrate by sputtering. 
   As described above, by forming the interconnecting pattern on the substrate by sputtering, the interconnecting pattern can be easily recognized from the side opposite to that where the interconnecting pattern is formed. 
   (5) In this method of manufacturing a semiconductor device, the base substrate may be formed of polyethylene terephthalate. 
   Polyethylene terephthalate is an example of a material that has the light transmission property. 
   (6) In this method of manufacturing a semiconductor device, the detection means may comprise a camera; positions of the interconnecting pattern and the electrodes may be detected by the camera; and the camera may take an image of one of the flexible substrate having the interconnecting pattern and the semiconductor chip having the electrodes first, and then takes an image of the other. 
   (7) In this method of manufacturing a semiconductor device, the camera may move in a direction parallel to surfaces on which the interconnecting pattern and the electrodes are formed to take an image of one of the interconnecting pattern and the electrodes. 
   (8) According to a second aspect of the present invention, there is provided a semiconductor device manufactured by the above-described method. 
   (9) According to a third aspect of the present invention, there is provided a semiconductor device comprising a semiconductor chip and a flexible substrate that includes a base substrate and an interconnecting pattern formed on the base substrate, 
   wherein the base substrate has a light transmission property; and 
   wherein the interconnecting pattern on the base substrate is electrically connected to electrodes formed on the semiconductor chip. 
   (10) The semiconductor chip may be connected to the interconnecting pattern by the face down bonding. 
   (11) According to a fourth aspect of the present invention, there is provided an apparatus for manufacturing a semiconductor device, comprising: 
   a first transportation means for transporting a flexible substrate; 
   a second transportation means for transporting a semiconductor chip; and 
   a detection means for position detecting, 
   wherein the detection means is located on a side opposite to a side on which the semiconductor chip is provided to detect a position of an interconnecting pattern formed on the flexible substrate or a position of electrodes formed on the semiconductor chip. 
   (12) According to a fifth aspect of the present invention, there is provided a circuit board on which the above-described semiconductor device is mounted. 
   (13) According to a sixth aspect of the present invention, there is provided an electronic instrument comprising the above-described circuit board. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A  to  1 C illustrate a method of manufacturing a semiconductor device according to the embodiment of the present invention; 
       FIG. 2  shows a tape carrier as an example of a flexible substrate; 
       FIG. 3  shows a modification of the embodiment in accordance with the present invention; 
       FIG. 4  shows a circuit board on which the semiconductor device of the embodiment is mounted; and 
       FIG. 5  shows an electronic instrument comprising a circuit board on which the semiconductor device of the embodiment is mounted. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   A preferred embodiment of the present invention will be described with reference to the accompanying drawings below. 
     FIGS. 1A  to  1 C show a method of manufacturing a semiconductor device according to the embodiment of the present invention. In this embodiment, there is provided a flexible substrate  10  as shown in FIG.  1 A. The flexible substrate  10  includes a base substrate  12  and an interconnecting pattern  14 . 
   The base substrate  12  is made of, for example, an organic material or a resinous material, and has a flexibility. Furthermore, as long as the base substrate  12  has a light transmission property and allows visible light to pass therethrough, there is no limitation to transmittance of the base substrate  12 . Also, as long as the basic circuit board  12  has a flexibility and light transmission property, there is no limitation to materials of the base substrate  12 . Polyethylene terephthalate (PET) is, for example, taken as a material having a high light transmittance. Alternatively, polyimide resin may be employed. Since the base substrate  12  employing polyimide is colored, its thickness should preferably be 75 μm or less, more preferably 50 μm or less. A heat resistance engineering plastic film such as polyether sulfone (PES) or polyether ether ketone (PEEK) may also be employed as a material of the base substrate  12 . Since these materials are transparent or light in color though they are colored, there is no problem in thickness in many cases. 
   The interconnecting pattern  14  is formed on one surface of the base substrate  12 . Besides the interconnecting pattern  14  formed on one surface of the base substrate  12 , another interconnecting pattern may be formed on the other surface thereof, but the interconnecting pattern on the other surface is not a constitutional feature of the present invention. 
   The interconnecting pattern  14  can be formed in a manner that a film made of an electrical conductive material such as copper is formed on the base substrate  12  by sputtering or the like and then the film is patterned by etching. In this case, the interconnecting pattern  14  is formed immediately on the base substrate  12 , thus producing a two-layered substrate without intervention of adhesive. In general, the adhesive has a light screen property. Since the flexible substrate  10  does not include any adhesive having the light screen property, the interconnecting pattern  14  can be recognized visually from the reverse side through the base substrate  12 . More specifically, the interconnecting pattern  14  can be visually recognized through the base substrate  12 , from the reverse side opposite to the surface on which the interconnecting pattern  14  is formed. If polyimide resin is used in the base substrate  12 , the base substrate  12  is colored. Therefore, in order to facilitate pattern recognition from the reverse side to the surface where the interconnecting pattern  14  is formed, the above-described two-layered substrate, especially the one formed by sputtering copper or the like on polyimide resin is more preferable. If the base substrate  12  is formed of PET having a high light transmittance, the interconnecting pattern  14  can be more easily recognized, so that it is also possible to select a three-layered substrate including adhesive. 
   Through holes  18  are formed in the base substrate  12 , and the interconnecting pattern  14  is provided over the through holes  18 . Specifically, the interconnecting pattern  14  is formed so as to cover the through holes  18 . Therefore, the interconnecting pattern  14  can be electrically connected to a surface of the base substrate  12  opposite to the surface on which the interconnecting pattern  14  is formed by utilizing these through holes  18 . Thus, external electrodes  34  (see  FIG. 1C ) electrically connected to the interconnecting pattern  14  can be formed on the surface of the base substrate  12  opposite to the surface on which the interconnecting pattern  14  is formed. It should be noted that the inner surfaces of the through holes  18  may be plated with an electrically conductive substance such as gold or copper. 
   There are lands  16  formed on the interconnecting pattern  14 , thus facilitating the connection to the electrodes  32  of the semiconductor chip  30 . It should be noted that bumps may be formed on the lands  16 . 
   As described above, the flexible substrate  10  may be formed in a shape of a separated fragment, or a tape carrier  20  shown in  FIG. 2  may be used to provide the flexible substrates. The tape carrier  20  comprises a substrate  22  in a tape form and interconnecting patterns  24  formed on at least one surface of the substrate  22 . This tape carrier  20  is prepared in a state where it is wound on a reel (not shown). The substrate  22  has sprocket holes  26  formed continuously in the longitudinal direction on both ends in the width direction of the substrate  22 . The sprocket holes  26  are formed so as to gear with sprockets  104  (see  FIG. 1A ) when the tape carrier  20  is wound off. 
   A manufacturing apparatus used in this embodiment comprises a first transportation means such as sprockets  104  which transport the flexible substrate  10 , a second transportation means such as an attraction jig  102  which transports the semiconductor chip  30 , and a detection means such as a camera  100  which performs a position detection. 
   In this embodiment, the flexible substrate  10  and the semiconductor chip  30  are arranged as shown in FIG.  1 A. In  FIG. 1A , the surface of the flexible substrate  10  on which the interconnecting pattern  14  is formed and the surface of the semiconductor chip  30  on which the electrodes  32  are formed are arranged parallel to each other, and they will face each other if the flexible substrate  10  and the semiconductor chip  30  move in a direction parallel to these surfaces to come close to each other. In other words, another surface of the flexible substrate  10  opposite to the surface on which the interconnecting pattern  14  is formed faces the same direction as the surface of the semiconductor chip  30  on which the electrodes  32  are formed, but the flexible substrate  10  and the semiconductor chip  30  do not overlap each other in this figure when they are viewed from a direction perpendicular to these surfaces. 
   Furthermore, the flexible substrate  10  and the semiconductor chip  30  are held by a sliding means (not shown) so as to be freely movable in a direction parallel to these surfaces. 
   In  FIG. 1A , the camera  100  is located in a direction perpendicular to the surface of the flexible substrate  10  opposite to the surface on which the interconnecting pattern  14  is formed and also perpendicular to the surface of the semiconductor chip  30  on which the electrodes  32  are formed, and the camera  100  faces one of these surfaces. Note that the camera is fixed. 
   If the camera  100  is located on the side opposite to the surface of the flexible substrate  10  on which the interconnecting pattern  14  is formed, the camera can recognize the position of the interconnecting pattern  14  through the base substrate  12 , because the base substrate  12  has a light transmission property as described. 
   The camera  100  takes an image of one of the interconnecting pattern  14  and the electrodes  32  that comes within the range of the camera  100 . Thus, the position of the interconnecting pattern  14  or the electrodes  32  is recognized. When an image of the flexible substrate  10  is taken, a detection means (for example the camera  100 ) recognizes the positions of the lands  16  to which the electrodes  32  are connected. Specifically, basic information such as the shape of the interconnecting pattern  14  and the lands  16 , or the positions of the lands  16  on the interconnecting pattern  14  has been previously stored in a memory means. Then, an image of the interconnecting pattern  14  is taken through the base substrate  12 . The positions of the lands  16  are recognized based on the basic information and image information relating to the interconnecting pattern  14  obtained by the camera  100 . If a strict precision is needed, the position of the lands may be recognized by taking images of positioning marks previously provided independently of the lands in the same step where the interconnecting pattern is formed through the base substrate  12  and by calculating the positions of the lands on the basis of the information about the positioning marks. This recognition is performed by a computation means, and data relating to the recognized positions may be stored in a memory means. 
   After the flexible substrate  10  or the semiconductor chip  30  is taken by the camera  100  and its position is recognized, the one is moved away in a direction parallel to the surface thereof to be out of the range of the camera  100 , and the other one of the flexible substrate  10  and the semiconductor chip  30  that has not been taken yet moves to come within the range of the camera  100 . Subsequently, the interconnecting pattern  14  or the electrodes  32  are similarly recognized by the camera  100 . If data of direction and distance relating to the movement of the flexible substrate  10  and the semiconductor chip  30  is stored, the positional data of the interconnecting pattern  14  and the electrodes  32  can be utilized thereafter. 
   The position of the lands  16  for connection to the electrodes  32  and the position of the electrodes  32  are thus recognized, then they are aligned (see FIG.  1 B). The alignment of the lands  16  and the electrodes  32  can be checked by viewing through the base substrate  12 . It is an important feature of the present invention that the alignment can be made sure by viewing the image thereof before the next connecting step. 
   According to the above-described processes, the alignment of the electrodes  32  with the lands  16  that are connected to the electrodes  32  can be simply performed by the fixed camera  100  without a complicated optical system. 
   Next, the face down bonding for the lands  16  and the electrodes  32  is performed as shown in FIG.  1 B. In this embodiment, a general-purpose bonder for the gang bonding style is used, and the bonding tool  200  presses the flexible substrate  10  from the side opposite to the surface on which the interconnecting pattern  14  is formed toward the semiconductor chip  30 . 
   It should be noted that when the tape carrier  20  is used as the flexible substrate  10  as shown in  FIG. 2 , the alignment is performed for the semiconductor devices as a plurality of units and then the process shown in  FIG. 1B  may be conducted subsequently. 
   After the lands  16  and the electrodes  32  are connected together, the solder taking the ball shape is provided on the interconnecting pattern  14  so as to form the external electrodes  34 . Then, the flexible substrate  10  is punched along the external shape of the semiconductor chip  30 , or alternatively punched to an arbitrary shape, thus obtaining the semiconductor device  36 . 
   As described above, according to the embodiment, the lands  16  and the electrodes  32  that face each other can be easily connected by using the general-purpose bonder. 
   Although the description was made for the example of the automatic position recognition and alignment apparatus (or steps), the present invention can be applied also to a manual alignment apparatus, in which an operator looks a camera image on a screen for alignment, and this brings about a great merit to the present invention. Thus, a bonding with a high precision can be performed using a simple apparatus without an expensive equipment. 
   It should be noted that the present invention is not limited to the above-described embodiment and various modifications can be made therein without departing from spirit and scope of the invention. For example, instead of the processes shown in  FIG. 1A , the process shown in  FIG. 3  may be performed. Specifically, in  FIG. 1A , the position of the camera  100  is stationary, and the flexible substrate  10  and the semiconductor chip  30  move in parallel with each other. In  FIG. 3 , the camera  200  moves in parallel with the flexible substrate  10  and the semiconductor chip  30 , and the positions of them are stationary. The similar effect to that of the above-described embodiment can be achieved also by such structure. The positions of the flexible substrate  10  and the semiconductor chip  30  are stationary when the camera  200  takes the images of them in  FIG. 3 , but it is preferable that they move in parallel with each other at the time of the face down bonding for alignment as shown in FIG.  1 B. 
   In the above-described embodiment, the description was made for the manufacture of the Chip Size/Scale Package (CSP) structure, but the method according to the present invention is not limited to that, and the present invention can be applicable to the mounting of whole Face Down (FD) structures using a substrate having a light transmission property such as the Chip On Flex (COP) structure. Also in this case, the connection process for the semiconductor chip and the substrate is important. 
   In  FIG. 4 , illustrated is the circuit board  1000  on which the semiconductor device  1100  manufactured by the method according to the above described embodiment is mounted. An organic substrate such as a glass epoxy resin substrate is generally used for the circuit board  1000 . An interconnecting pattern formed of, for example, copper is formed on the circuit board  1000  to provide a desired circuit. The interconnecting pattern and the external electrodes of the semiconductor device  1100  are mechanically connected, thus achieving an electrical conductivity between them. 
   It should be noted that the mounting area in the semiconductor device  1100  can be reduced to the mounting area for bare chip mounting. For this reason, when this circuit board  1000  is used in an electronic instrument, the electronic instrument itself can be made more compact. Within the same area, a larger mounting area is available, and higher functionality can also be achieved. 
   As an electronic instrument provided with this circuit board  1000 ,  FIG. 5  shows a notebook personal computer  1200 . 
   Although the present invention is applied to a semiconductor device in the above-described embodiment, the present invention can be applied to various surface-mounted electronic components that require a plurality of external terminals similar to a semiconductor device, whether active or passive. Electronic components include, for example, resistors, capacitors, coils, oscillators, filters, temperature sensors, thermistors, varistors, variable resistors, and fuses.