Abstract:
A semiconductor apparatus comprises a support substrate having through holes filles with conductor adapted to a first pitch; a capacitor formed on or above said support substrate; a wiring layer formed on or above said support substrate, leading some of said through holes filles with conductor upwards through said capacitor, having branches, and having wires of a second pitch different from said first pitch; and plural semiconductor elements disposed on or above said wiring layer, having terminals adapted to the second pitch, and connected with said wiring layer via said terminals. A semiconductor apparatus, in which semiconductor elements having a narrow terminal pitch, a support having through wires at a wider pitch, and a capacitor are suitably electrically connected to realize the decoupling function with reduced inductance and large capacitance.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This invention is based on and claims priority of Japanese patent application 2001-329687, filed on Oct. 26, 2001, the whole contents of which are incorporated herein by reference. This application is a divisional of prior application Ser. No. 10/092,525 filed Mar. 8, 2002, the benefit of which is claimed under 35 U.S.C. § 120. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a semiconductor apparatus having plural parts packaged in one module, particularly a semiconductor apparatus having capacitors connected outside semiconductor elements for improving high frequency characteristics. It also relates to a production process thereof.  
         [0004]     In this specification, in the case where plural semiconductor devices are arranged as a module to constitute a semiconductor apparatus, the respective semiconductor devices are called semiconductor elements. LSIs such as CPU are also called semiconductor elements.  
         [0005]     2. Description of the Related Art  
         [0006]     In recent years, the system-in-packages, in which existing chips are combined and connected at high densities to realize desired functions, are increasingly used. Compared with the case of integrating all functions on one chip, the development period can be shortened, and the cost performance can be improved.  
         [0007]     Furthermore, semiconductor elements such as digital LSIs are advancing to be higher in speed and lower in power consumption. Because of the lower power consumption, the supply voltage declines. For example when the load impedance changes suddenly, the supply voltage is likely to vary. If the supply voltage varies, the semiconductor element is functionally disordered. So, the role of the decoupling capacitors for inhibiting the variation of supply voltage is important.  
         [0008]     Since semiconductor elements are growing to be higher in speed, the influence of high frequency ripple is increasing. It is desired that the decoupling capacitors can also efficiently absorb the high frequency ripple component.  
         [0009]     Because of the above, it is desired to lower the equivalent series resistance (ESR) and equivalent series inductance (ESL) of the capacitors. For this purpose, it is desired to minimize the wiring lengths between the semiconductor chips and the capacitors.  
         [0010]     In the system-in-package, for connecting decoupling capacitors or the like to semiconductor chips or circuit substrate, there are known such techniques as (1) resin buildup technique, (2) thick ceramic film technique and (3) thin film multilayer technique.  
         [0011]     (1) In the resin buildup technique, with a printed board used as the substrate, an insulation layer, passive element layer and wiring layer are built up on it, and capacitors are formed immediately below semiconductor chips and are connected by means of through wires. If an organic insulation layer is used as the insulation layer, the cost can be reduced, and the process can be carried out at low temperature. Furthermore, the thermal stress caused by heat cycles after mounting can be decreased, if the difference between the passive elements and the insulation layer in thermal expansion coefficient is kept small.  
         [0012]     If capacitors are disposed immediately below semiconductor chips, ESL can be lowered, but the pitch of through wires in the capacitor support is as relatively large as 50 to 200 μm. The obtained capacitances of the capacitors are hundreds of picofarads per square centimeter, and this is insufficient as decoupling capacitors at high frequency.  
         [0013]     (2) In the thick ceramic film technique, a low loss ceramic material is used as a substrate and an insulation layer, and a dielectric layer and a resistance layer are burned integrally. Capacitors can be formed immediately below semiconductor chips, and can be connected by means of through wires. The structure is excellent in parts-accommodating capability and low in dielectric loss (tanδ). So, the transmission loss at high frequency is small.  
         [0014]     The obtained capacitance is tens of nanofarads per square centimeter, and the function as decoupling capacitors at high frequency is insufficient. Since the ceramics shrink in volume when burned, the dimensional dispersion becomes large. So, the through wire pitch in the capacitor support is as large as about 100 to 200 μm.  
         [0015]     (3) In the thin film multilayer technique, a low dielectric constant resin is used as an insulation layer, and silicon or glass is used as a substrate. Resistances and capacitors can be formed in the layer, and the capacitors can be connected immediately below semiconductor chips by means of through wires.  
         [0016]     If the process is carried out at high temperature, capacitors having large capacitance of hundreds of nanofarads per square centimeter can be obtained.  
         [0017]     If a semiconductor process is used, the through wire pitch in the support can be made as small as about 20 to 50 μm. The thermal stress caused by heat cycles after mounting can be decreased if the difference between passive elements and the insulation layer in thermal expansion coefficient is kept small.  
         [0018]     Semiconductor elements are growing further higher in operation speed, lower in power consumption and larger in area. The transistors and wires in each semiconductor element become finer and finer. The number of terminals of a semiconductor element is also increasing, and the pitch between terminals is diminishing. There is a limit in narrowing the through wire pitch in the support of decoupling capacitors in accompany with the pitch of terminals of a semiconductor element.  
         [0019]     If capacitors are mounted near, not immediately below, semiconductor elements, capacitors with large capacitance can be realized at low cost. However, since the wires must be routed longer, the high frequency characteristics become worse. It becomes difficult to install decoupling capacitors suitable for semiconductor elements acting at high speed at a frequency of more than GHz.  
         [0020]     As described above, the system-in-package encounters a restriction in suitably connecting semiconductor elements, electronic parts such as capacitors, and a circuit substrate.  
       SUMMARY OF THE INVENTION  
       [0021]     An object of this invention is to provide a semiconductor apparatus, in which semiconductor elements having a narrow terminal pitch, a support having through wires at a wider pitch, and capacitors are suitably electrically connected to realize a decoupling function with lowered inductance and large capacitance.  
         [0022]     Another object of this invention is to provide a system-in-package that can be adapted to finer semiconductor elements.  
         [0023]     A further object of this invention is to provide a semiconductor apparatus containing plural semiconductor elements to be used in such a system-in-package.  
         [0024]     From one aspect of this invention, there is provided a semiconductor apparatus, comprising a support substrate having through holes filles with conductor in conformity with a first pitch, capacitors formed on or above said support substrate, a wiring layer formed on or above said support, leading some of said through wires upwards via said capacitors, having branches and having wires in conformity with a second pitch, and plural semiconductor elements disposed on or above said wiring layer, having terminals in conformity with the second pitch and connected with the wiring layer via said terminals.  
         [0025]     From another aspect of this invention, there is provided a process for producing a semiconductor apparatus, comprising the steps of (a) forming through holes at a first pitch in a support substrate, (b) forming an insulation layer on side walls of said through holes, (c) filling through holes filled with conductor in the through holes provided with said insulation film, (d) forming capacitors connected with at least some of said through holes filled with conductor, and wires connected with said through holes filled with conductor or said capacitors and having a second pitch, on said support substrate, and (e) connecting plural semiconductor elements having terminals in conformity with said second pitch, with said wires.  
         [0026]     In this way, a system-in-package having decoupling capacitors with good performance can be formed.  
         [0027]     The wires on or above the support substrate of the capacitors can be used to connect the semiconductor elements with each other. It becomes easy to directly connect terminals disposed at a narrow pitch with each other. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIGS. 1A through 1T  are sectional views showing a process for producing an intermediate laminate according to an embodiment of the present invention.  
         [0029]      FIGS. 2A and 2B  are a plan view and a partial sectional view schematically showing the constitution of a system-in-package. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     An embodiment of this invention is described below in reference to the drawings.  
         [0031]      FIG. 2A  shows a constitution example of a system-in-package SiP. A circuit substrate  50  is mounted with circuit parts  52 - 1  through  52 - 5  including plural semiconductor elements.  
         [0032]     The semiconductor elements are, for example, an arithmetic processing unit, digital signal processor, memory, high frequency IC, input/output interface, etc. Another circuit part  53  is, for example, a SAW filter.  
         [0033]     On the circuit substrate  50 , wires are formed, and between the circuit substrate  50  and the semiconductor elements  52 - 1  through  52 - 5  (and circuit part  53 ), an intermediate laminate  51  containing capacitors and wires is connected. A process for producing the intermediate laminate  51  containing capacitors and wires is described below.  
         [0034]     As shown in  FIG. 1A , for example, a 6-inch Si wafer  11  is mirror-ground to have a thickness of 300 μm, and about 0.5 μm thick silicon oxide layers  12  and  13  are formed on both sides of the wafer by thermal oxidation.  
         [0035]     Insulation layers such as silicon oxide layers can also be formed by means of low-pressure chemical vapor deposition or sputtering instead of thermal oxidation. The insulation layer should act as an etching stopper when the Si substrate is dry-etched, and is not limited to silicon oxide in material. For example, the insulating layer can be, an oxynitride layer, or a laminate of an oxide layer and a nitride layer.  
         [0036]     As shown in  FIG. 1B , a resist mask PR 1  made of a photo resist material is formed on the silicon oxide layer  12 . Using the resist mask PR 1  as an etching mask and CF 4  as a main etching gas, the silicon oxide layer  12  is etched to form openings  14 . The openings  14  are formed according to the pattern of through wires to be formed. At this stage, the resist mask PR 1  may be removed.  
         [0037]     Then, using the resist mask PR 1  or the patterned silicon oxide layer  12   a  as an etching mask, and using SF 6  and C 4 F 8  as main etching gases, dry etching is carried out for anisotropic etching of the Si substrate  11 . This etching automatically stops at the lower silicon oxide layer  13 . As a result, via holes  14  through the silicone oxide layer  12   a  and the Si substrate  11   a  are formed. If the resist mask PR 1  has not been removed, it is removed after completion of etching.  
         [0038]     As shown in  FIG. 1C , the Si substrate  11   a  is thermally oxidized to form a silicon oxide layer  15   a  of about 1 μm thick in the regions where the Si surface is exposed. The portions of the silicon oxide layer  13  remaining at the bottoms of the via holes, remain to have the original thickness (about 0.5 μm). The upper and lower silicon oxide layers on the Si substrate  11   a  are further oxidized to become silicon oxide layers  15   b  and  15   c  having a thickness of more than about 1 μm.  
         [0039]     As shown in  FIG. 1D , a Ti layer  16  of about 0.2 μm thick and a Pt layer  17  of about 1.0 μm thick are formed on the back surface of the substrate by sputtering. The Pt layer  17  is a seed layer for the plating to be carried out later. The Ti layer  16  is an adhesive layer for promoting the adhesion of the Pt layer  17  to the Si substrate. In the case where the seed layer has good adhesiveness, the adhesive layer may be omitted. The seed layer (and the adhesive layer) can also be formed by, for example, CVD or printing instead of sputtering.  
         [0040]     Wet etching using a buffered hydrofluoric acid solution as an etchant is carried out to remove the portions of the silicon oxide layer  13  at the bottoms of the via holes. In this case, the other silicon oxide layers are also etched, but they are not removed entirely but partially remain due to the difference of thickness.  
         [0041]     The etching with a buffered hydrofluoric acid solution is followed by wet etching using a diluted hydrofluoric acid nitric acid mixed solution as an etchant, to etch the portions of the Ti layer  16  exposed at the bottoms of the via holes. As a result, the Pt layer  17  is exposed at the bottoms of the via holes. The portions of the Ti layer are molten instantaneously when the etching starts. Even if the etchant has a nature of etching also the silicon oxide layers, the thickness of the silicon oxide layers removed while the Ti layer is etched is very limited. The silicon substrate  11   a  remains covered with the silicon oxide layers.  
         [0042]     Dry etching may also be carried out instead of wet etching. Also in this case, even if the portions of the silicon oxide layer  13  at the bottoms of the via holes, are completely removed by etching, other silicon oxide layers  15   a ,  15   b  and  15   c  remain at least partially.  
         [0043]     As a result, plural through holes can be formed in the Si substrate. At the bottoms of the through holes, the seed layer for plating is exposed, and the side walls of the through holes are covered with the insulation layer. The upper surface of the Si substrate is also covered with the insulation layer.  
         [0044]     As shown in  FIG. 1E , electroplating is carried out to form a Pt plating layer on the Pt layer  17  in the via holes  14 , for forming via conductors  18  filling or packing the via holes.  
         [0045]     In the case where the via holes are small in diameter, the through holes filled with conductor can also be formed by CVD instead of plating. In this case, the seed layer is not especially necessary, and for example, CVD can be carried out in the state of  FIGS. 1B  or  1 C.  
         [0046]     As shown in  FIG. 1F , the upper surface of the Si substrate is flattened or planarized by chemical mechanical polishing(CMP). The upper surfaces of the through holes filled with conductor  18  become flush with the upper surface of the surrounding insulation layer  15   b . Similarly, CMP is carried out also for the lower surface of the Si substrate, to expose the insulation layer  15   c  and the through holes filled with conductor  18 . As a result, a support substrate S having through holes filled with conductor  18  can be obtained.  
         [0047]     As shown in  FIG. 1G , a Ti layer of about 0.1 μm thick and a Pt layer of about 0.2 μm thick are formed in this order as a lower electrode layer  20  on the surface of the support substrate S by sputtering at a substrate temperature of 400° C. A resist mask PR 2  is formed on the lower electrode layer  20 , and using the resist mask PR 2  as a mask, the lower electrode layer  20  is patterned by milling using Ar ions. The milling can also be combined with etching. Then, the resist mask PR 2  is removed.  
         [0048]     Each of the lower electrodes  20  includes a first portion  20   a  having a wide-area and a cut-away portion and a second portion  20   b  within the cut-away portion. The second portion  20   b  is formed of the same electrode layer and destined to be an extracting electrode for wire leading in the cut-away portion, while being separated from the first portion.  
         [0049]     As shown in  FIG. 1H , a (Ba, Sr)TiO 3  (BST) thin film  21  is formed on the substrate to cover the lower electrode  20 , for example, at a substrate temperature of 550° C., at an Ar gas flow rate of 80 sccm, at an O 2  gas flow rate of 10 sccm, at a vacuum degree of 30 mTorr, with 300 W power applied for a processing time of 1 hour. Under these conditions, a 0.2 μm thick BST dielectric film having a dielectric constant of 500 and a dielectric loss of 2% can be obtained.  
         [0050]     As the material having a high dielectric constant, for example, SrTiO 3  or BaTiO 3  can also be used. It is preferred to use an oxide dielectric containing at least one of Ba, Sr and Ti and having a high dielectric constant. The dielectric film can be formed by sputtering, or also sol-gel method or CVD.  
         [0051]     On the dielectric film  21 , a resist pattern PR 3  is formed, and a buffered hydrofluoric acid solution (NH 4 F:HF=6:1) is used for etching, to expose the surfaces of the leading electrodes and connection areas of the capacitor electrodes. Then, the resist pattern PR  3  is removed.  
         [0052]     As shown in  FIG. 11 , a Pt layer  22  of about 0.2 μm thick is formed by sputtering at a substrate temperature of 400° C. On the Pt layer  22 , a resist pattern PR 4  is formed. The Pt layer  22  is selectively removed by milling using Ar ions. As a result, an upper electrode pattern and a through conductor pattern are formed. Then, the resist pattern PR 4  is removed.  
         [0053]     As a result, the lower electrode and the upper electrode sandwiching a BST dielectric layer form a capacitor. Furthermore, in the region free from the  15  dielectric layer, the lower electrodes and the upper electrodes form through holes filled with conductor. It is preferred that the capacitor electrodes in contact with the oxide dielectric film are made of oxidation resistant material such as Au or Pt, or such material as Pt, Ir, Ru, Pd which keep conductivity even if oxidized, or their oxides.  
         [0054]     As shown in  FIG. 1J , a photosensitive polyimide resin layer  23  is coated to cover the upper electrodes  22 . It is desirable that the polyimide has a thermal expansion coefficient of 10 ppm/° C. or less in the in-plane direction. Then, the thermal stress by heat cycles after mounting can be decreased.  
         [0055]     The photosensitive polyimide layer  23  is selectively exposed using, for example, a reticle and developed, to remove the polyimide layer in the wire-forming regions. The polyimide layer can also be patterned by any other method.  
         [0056]     As shown in  FIG. 1K , a Cu layer  25  is formed by electroplating on the surface of the Pt layer exposed within the openings of the polyimide layer  23 . After capacitors using an oxide dielectric layer are formed, it is preferred to use Cu as wires. Then, as required, CMP is carried out to flatten or planarize the surface of the Cu layer  25  and the polyimide layer  23 .  
         [0057]     As shown in  FIG. 1L , a Cu layer of about 0.2 μm thick is formed as a first wiring layer  26  on the polyimde layer  23  and the leading electrodes  25  by sputtering. The sputtering can be replaced with electroless plating or a combination of electroless plating and electroplating. A resist mask is formed, and ion milling is carried out to pattern the first wiring layer  26 .  
         [0058]     As shown in  1 M, the pattern of the first wiring layer has a pitch and line width corresponding to, for example, one halves of the pitch and line width of the through holes filled with conductor  18 . For example, if the through holes filled with conductor have a pitch of 50 mm and a line width of 20 mm, the pattern of the first wiring layer has a pitch of 25 mm and a line width of 10 mm.  
         [0059]     After patterning the first wiring layer  26 , a photosensitive polyimide resin is applied to form an insulation layer  28  for insulating the first wires  26  from each other. It is preferred that the polyimide resin has a thermal expansion coefficient of 10 ppm/° C. or less in the in-plane direction, like the aforesaid polyimide. In the case where the first wiring layer  26  is not flush with the polyimide layer  28 , it is preferred to flatten them by CMP, etc. As a result, the first wiring layer pattern is formed.  
         [0060]     As shown in  FIG. 1N , a connection wiring pattern  29  is formed according to the same method as described before.  
         [0061]     As shown in  FIG. 1O , the spaces in the connection wiring pattern are filled with a polyimide layer  30  according to the same method as described before.  
         [0062]     As shown in  FIG. 1P , a Cu layer of about 0.2 μm thick is formed as a second wiring layer  31  according to the same method as described before.  
         [0063]     As shown in  FIG. 1Q , the second wiring layer  31  is patterned according to the same method as described before, and the spaces in the pattern is filled with a polyimide insulation layer  32  as described before. As a result, a second wiring pattern is formed.  
         [0064]     By repeating similar steps, a desired number of wiring layers can be formed.  
         [0065]     As shown in  FIG. 1R , a polyimide layer is formed as a protective film  33  on the surface of the wiring layer according to the same method as described before. Openings are selectively formed in the photosensitive polyimide protective film  33  according to the same method as described before, for forming electrode-leading regions.  
         [0066]     As shown in  FIG. 1S , a Cr layer of about 0.05 μm thick, a Ni layer of about 2 μm thick and a Au layer of about 0.2 μm thick, in this order from the bottom, are laminated on the upper surface of the substrate, to cover the protective layer  33 . The laminate is patterned to form electrode pads  35 .  
         [0067]     A protective film  34  and electrode pads  36  are formed also on the lower surface of the substrate according to the same method described before.  
         [0068]     For example, Pb-5 wt % Sn solder is vapor-deposited through a metal mask on the formed electrode pads  35  and  36 , and a flux is applied. They are heated and molten at 350° C., to form solder bumps  37  and  38  for connection. As a result, an intermediate laminate  51  having capacitors and Wiring layers is formed.  
         [0069]     As shown in  FIG. 1T , semiconductor elements  52  are overlaid on the intermediate laminate  51 , and the bumps are molten for mounting them, to form a module. Only one semiconductor element is shown in the drawing, but as shown in  FIG. 2A , plural semiconductor elements  52  are connected on the intermediate laminate  51 . Then, the intermediate laminate  51  is connected on the circuit board  50 . Alternatively, a module having plural circuit parts mounted on the intermediate laminate can also be offered as a product, and the user can mount it on a circuit board.  
         [0070]      FIG. 2B  schematically shows a portion of wires in a module. On the circuit board  50 , the intermediate laminate  51  is disposed, and on the intermediate laminate  51 , circuit parts  54  including plural semiconductor elements IC 1  and IC 2  are disposed. In the intermediate laminate  51 , there are formed through holes filled with conductor PC formed in the support substrate S, vertical wires WV connected to the through holes filled with conductor PC, electrodes Cl and C 2  of a capacitor connected to the vertical wires WV, and local wires LI 1  and LI 2  for connecting the semiconductor elements with each other.  
         [0071]     The terminal pitch of the semiconductor elements IC 1  and IC 2  is narrower than the terminal pitch of the circuit board  50 . If it is attempted to connect the terminals of the semiconductor elements IC 1  and IC 2  with each other via the wires on the circuit board  50 , the wire pitch must be once expanded. If the wires in the intermediate laminate  51  are used, the semiconductor elements IC 1  and IC 2  can be connected with each other using shorter wires without changing the wire pitch or suppressing the expansion of the wire pitch small.  
         [0072]     In the constitution shown in  FIG. 1T , signal wire TS is arranged vertically from the semiconductor element  52  to the circuit board  50 . Therefore, the wire length is short. Power wires V and G are connected to the semiconductor  52  from the circuit board  50  via each one electrode of a capacitor. The power wires respectively have a branch in the portion above the capacitor, to form a wire pitch adapted to the terminal pitch of the semiconductor element  52 . The opposing capacitor electrodes form a decoupling capacitance between power wires.  
         [0073]     With the above constitution, semiconductor elements having a narrow terminal pitch can be efficiently connected with a circuit board having a wide wire pitch. Furthermore, local wires for connecting the semiconductor elements with each other without passing through the circuit board can also be formed. Capacitors having sufficient capacitances can be formed to achieve the function of decoupling capacitors.  
         [0074]     The present invention has been described along one embodiment, but is not limited thereto. For example, it will be obvious for a those skilled in the art, to make various modifications, improvements and combinations.