Package for accommodation of semiconductor element and method of manufacturing the same

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a semiconductor device storage package containing a semiconductor device that transmits and receives light through a sapphire window, and a method for manufacturing the same.

【0002】

[Conventional technology]

Conventionally, sapphire (single crystal alumina: Al) has been used as a material for a light transmitting window of a semiconductor element storage package (hereinafter referred to as a semiconductor package) that houses a semiconductor element such as a CCD (Charge Coupled Device) that exchanges light with the outside.₂O₃) Is used, and sapphire has characteristics such as colorless transparency, high hardness, and high melting point, and is useful as a light transmitting window of a semiconductor package. In particular, in a semiconductor package that requires high light transmission, it is heavily used as a sapphire window for a light transmitting window, and is brazed to a ceramic lid of the semiconductor package.

【0003】

When brazing a sapphire window, a metallizing layer for joining is adhered to a peripheral portion on one main surface side of the sapphire window such as a disk shape, and the sapphire window is joined via the metallizing layer. The metallized layer is a peripheral portion of a sapphire window whose surface has been previously polished with a metal paste obtained by pasting a metal material having a high melting point such as molybdenum (Mo), manganese (Mn), or Mo-Mn alloy. It is formed by depositing on a paste with a predetermined width and baking it in a furnace at a high temperature of about 1400 ° C in a reducing atmosphere (Japanese Patent Laid-Open No. 55-95345, Japanese Patent Application Laid-Open No. 59-94854, See Kaihei 7-106459 (see).

【0004】

FIG. 6 shows a specific configuration of the sapphire window coated with the metallized layer. In the figure, 12 is a disk-shaped sapphire window, and 13 is a metallized layer adhered to the peripheral edge of the sapphire window, and the width is set so as not to cover the light transmitting region through which light passes. Further, FIG. 7 is a perspective view of the semiconductor package. In the figure, 11 is a substantially rectangular parallelepiped semiconductor package, 14 is a container body having an opening on the upper surface and accommodating a semiconductor element inside, and 15 is an alumina ceramic or the like. It is a lid.

【0005】

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional semiconductor package, the heated metal paste is scattered when the metallized layer for joining the sapphire window is baked in the furnace, and the scattered metal paste is burned into the light transmitting region in the center of the sapphire window, resulting in light. There was a problem that the transparency deteriorated. Further, when this metal paste is baked in a furnace, foreign matter peeled off from the furnace wall may adhere to the light transmitting region of the sapphire window and burn, which has the same problem as described above.

【0006】

Such a problem is, for example, in the case of a semiconductor package in which a sapphire window is used as a window for transmitting and receiving an optical signal via an optical fiber, the light coupling efficiency between the optical signal and the semiconductor element is impaired, and the semiconductor package for CCD is also a problem. In the case of, it had an adverse effect such as appearing as a black spot on the image detected by the CCD.

【0007】

Then, in order to remove the metal paste and foreign matter burned in the light transmitting region of the sapphire window, there is a method of scraping off the surface of the sapphire window by polishing or the like, but in this case, the metallized layer for brazing should not be removed. Therefore, the work of removing the metal paste and foreign matter was very difficult, and even if it could be removed, it took a lot of time and was not practical.

【0008】

In addition, when the production volume of a semiconductor package using a sapphire window is small enough to be prototyped, a good sapphire window with no metal paste or foreign matter burned in the light transmitting region of the sapphire window is manually selected. Although work has been carried out, this sorting requires a great deal of time, and such work has not been practical when mass-producing semiconductor packages with sapphire windows.

【0009】

Therefore, for the purpose of obtaining a sapphire surface having extremely good light transmission without scraping off the metallized layer for brazing by polishing, a predetermined portion is formed on the peripheral edge of one main surface side of the sapphire window before polishing. A groove or step is formed over the entire circumference with a width, and a metallized layer is adhered to the groove or step, and the surface of the metallized layer and one main surface of the sapphire window are polished so as to be substantially flush with each other. By doing so, it is possible to effectively prevent metal paste, foreign matter, etc. from adhering to the light transmitting region, and to produce a semiconductor package with a sapphire window with extremely good light transmission with high yield and high productivity. The applicant proposed a manufacturing method (Japanese Patent Application No. 11-363443).

【0010】

However, in such a configuration, the surface of the metallized layer around the sapphire window is polished, so that the unevenness that exerts the anchor effect on the surface of the metallized layer is reduced. As a result, the anchoring effect of the brazing material on the metallized layer becomes smaller, and a gap is generated between the brazing material and the metallized layer with the passage of time. There was a problem that it was damaged.

【0011】

Therefore, the present invention has been completed in view of the above problems, and an object of the present invention is to effectively prevent metal paste, foreign matter, etc. from adhering to the light transmitting region, and to achieve an extremely good light transmitting sapphire window. It is an object of the present invention to provide a semiconductor element storage package capable of manufacturing a semiconductor package with a sapphire with high yield and high productivity, and firmly holding a bond of a sapphire window to a lid for a long period of time.

【0012】

[Means for solving problems]

The semiconductor element storage package of the present invention includes a container body having an opening formed on the upper surface and accommodating the semiconductor element inside, a lid body provided on the upper surface of the container body and having a window portion made of ceramics, and the above. In a semiconductor device storage package including a sapphire window having a sapphire window on which one main surface side peripheral edge is brazed to the window portion, the sapphire window is formed with a groove or a step portion having a predetermined width over the entire circumference of the sapphire window. In addition, the groove portion or the step portion is coated with a metallized layer to a thickness less than the depth thereof, and the main surface is polished.

【0013】

According to the above configuration, the present invention can effectively and efficiently prevent metal paste, foreign matter, etc. from adhering to the light transmitting region of the sapphire window, and a semiconductor package with a sapphire window having good light transmission is expensive. The yield makes it possible to manufacture the sapphire window with high productivity, and it is possible to firmly hold the bond of the sapphire window to the lid for a long period of time. That is, the bonding of the sapphire window brazed to the semiconductor package can be strengthened, and the metal paste, foreign matter, etc. can be effectively prevented from being seized in the light transmission region, and as a result, the light transmission is very good. It is possible to easily produce a semiconductor package with a sapphire window, which is excellent in mass productivity.

【0014】

In the present invention, the depth of the groove or the step is preferably 50 to 200 μm, and the width of the groove or the step is 250 μm or more outside the light transmitting region in the center of the sapphire window.

【0015】

Further, in the present invention, it is preferable that the arithmetic mean roughness of the surface of the metallized layer is 1 to 5 μm. As a result, the anchoring effect on the brazing material on the surface of the metallized layer is improved, the bonding strength of the sapphire window is increased, and deterioration of the bonding strength over time can be prevented.

【0016】

The method for manufacturing a semiconductor element storage package of the present invention includes a step of accommodating a semiconductor element inside a container body having an opening on the upper surface, and attaching a lid made of ceramics and having a window portion in the opening. In a method for manufacturing a semiconductor device storage package, which comprises a step of brazing a peripheral edge portion of one main surface side of a sapphire window to the window portion, the sapphire window is specified on the peripheral edge portion of one main surface side. A groove or a step portion is formed over the entire circumference with a width, a metallized layer is adhered to at least the groove portion or the step portion in the main surface to a thickness less than the depth thereof, and after polishing the main surface, the said It is characterized by being brazed to the window.

【0017】

With such a configuration, the present invention can effectively and efficiently prevent metal paste, foreign matter, etc. from adhering to the light transmitting region of the sapphire window, and a semiconductor package with a sapphire window having good light transmission. It is possible to produce the sapphire window with high yield and high productivity, and it is possible to firmly hold the bond of the sapphire window to the lid for a long period of time.

【0018】

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail below. 1 (a) to 1 (c) are cross-sectional views showing an example of an embodiment of the semiconductor package with a sapphire window of the present invention, respectively, and FIGS. 2 (a) and 2 (b) are for the semiconductor package of the present invention. It is sectional drawing and plan view of the sapphire window. In these figures, 1 is a substantially rectangular parallelepiped semiconductor package, 2 is a sapphire window, and 3 is a semiconductor element such as a CCD or a flash memory. The semiconductor package 1 and the sapphire window 2 form a container for accommodating the semiconductor element 3 inside.

【0019】

The semiconductor package 1 of the present invention is a container for accommodating a semiconductor element 3, and is a metal material such as a copper (Cu) -tungsten (W) alloy or an iron (Fe) -nickel (Ni) -cobalt (Co) alloy. And aluminum oxide (Al₂O₃) It is composed by joining parts made of ceramic materials such as ceramics and aluminum nitride (AlN) ceramics, or by replacing parts made of metal materials with ceramic materials and integrally molding them.

【0020】

As shown in FIG. 1A, for example, the semiconductor package 1 has a mounting portion for mounting the semiconductor element 3 on the surface, and has a high thermal conductivity for dissipating heat generated by the semiconductor element 3 during operation. A heat radiating plate (base or bottom plate) 1a made of Cu-W alloy, Fe-Ni-Co alloy, etc. is used, and a frame shape is formed on the upper surface of the heat radiating plate 1a so as to surround the semiconductor element 3. In addition, a frame body 1b made of Fe-Ni-Co alloy, Fe-Ni alloy, etc. is joined via a brazing material such as silver brazing material. Further, on the upper surface of the frame 1b, a lid 1c made of ceramics such as alumina ceramics having a coefficient of thermal expansion similar to that of the sapphire window 2 and a window 4 opened in the substantially central portion thereof is made of a brazing material such as silver wax. It is joined through.

【0021】

The heat radiating plate 1a is manufactured into a predetermined shape by subjecting an ingot of an alloy such as a Cu-W alloy or a Fe-Ni-Co alloy to a conventionally known metal processing such as rolling or punching. Further, the frame body 1b is manufactured into a predetermined shape by performing the same metal processing as the heat radiating plate 1a using a Fe-Ni-Co alloy, a Fe-Ni alloy, or the like.

【0022】

Further, the heat radiating plate 1a and the frame 1b have a metal having excellent corrosion resistance and excellent wettability with a brazing material on the surface thereof, specifically, a Ni layer having a thickness of 0.5 to 9 μm and a thickness of 0.5 to 9 μm. When the Au layer is sequentially adhered by the plating method, it is possible to effectively prevent the heat radiating plate 1a and the frame 1b from being oxidatively corroded, and the semiconductor element 3 can be firmly adhered and fixed to the upper surface of the heat radiating plate 1a. Therefore, it is preferable to coat the surface of the heat radiating plate 1a or the frame 1b with a metal layer such as a Ni layer of 0.5 to 9 μm or an Au layer of 0.5 to 9 μm by a plating method.

【0023】

When the heat radiating plate 1a and the frame body 1b are made of a ceramic material, for example, as shown in FIG. 1 (b), a container body 1d in which the heat radiating plate 1a part and the frame body 1b part are integrally formed is used. Further, as shown in FIG. 1C, a portion in which the portion of the heat radiating plate 1a, the portion of the frame body 1b, and the portion of the lid body 1c are integrally molded may be used. In this case, the opening on the upper surface of the container body coincides with the window portion of the lid portion.

【0024】

On the other hand, ceramics such as alumina ceramics for the lid 1c include, for example, aluminum oxide (alumina: Al).₂O₃), Silicon oxide (SiO)₂), Magnesium oxide (MgO), calcium oxide (CaO) and other raw material powders are mixed with an appropriate organic solvent and solvent to form a paste, which is then processed into a sheet by the well-known doctor blade method or calendar roll method. A ceramic green sheet (ceramic raw sheet) is obtained by molding into a ceramic green sheet, and then appropriate punching processing such as providing a through hole for the window 4 is performed on the ceramic green sheet, and the ceramic green sheet is placed up and down. It is manufactured by stacking multiple sheets and firing at a high temperature of about 1600 ° C.

【0025】

Further, the lid body 1c of the present invention is a peripheral portion on the main surface side of one of the peripheral portions to be joined to the upper surface of the frame body 1b, and a peripheral portion of the window portion 4 on one of the main surfaces, which is sapphire. A metallized layer 2b for brazing is formed at a portion joined to the peripheral edge of the window 2, and on the metallized layer 2b, a Ni layer and an Au layer are formed as in the case of the heat radiating plate 1a and the frame 1b. Are sequentially coated by the plating method.

【0026】

This metallized layer 2b is formed of W, Mo, Mn, etc. For example, a metal paste obtained by adding and mixing an organic solvent and a solvent to a powder of W or the like is conventionally known in advance in a ceramic green sheet for a lid 1c. It is formed by printing and applying to a predetermined pattern by the screen printing method of. Such a lid 1c is joined to the upper surface of the frame 1b via a brazing material such as silver wax, and is attached to the peripheral edge of the window portion 4 on the one main surface side thereof on the one main surface side of the sapphire window 2. The peripheral edge of the sapphire is joined via a brazing material such as a gold (Au) -tin (Sn) alloy brazing material.

【0027】

Further, as shown in FIG. 2, the sapphire window 2 joined to the lid 1c has a stepped portion 2a formed on the peripheral edge of one of the main surfaces having a predetermined width over the entire circumference, and therefore the main surface is formed. Has a metallized layer 2b formed on the step portion 2a and a light transmitting region.

【0028】

In the present invention, the step portion 2a and the metallized layer 2b are specifically formed as follows. For example, by grinding the peripheral edge of the disk-shaped sapphire window 2 on the main surface side with a rotary diamond saw or the like, a stepped portion 2a having a depth of about 150 μm and a width of about 500 μm from the outer peripheral edge is formed. .. After that, a metal paste obtained by adding and mixing an organic solvent and a solvent to Mo / Mn powder (powder obtained by mixing Mo powder and Mn powder) or the like is screen-printed on the entire surface of the main surface on which the step portion 2a is formed. It is printed and applied by a method, etc., and baked in a reducing atmosphere at about 1350 to 1450 ° C for about 4 to 5 hours.

【0029】

At this time, the thickness of the metal paste to be printed and applied to the step portion 2a must be set to a thickness less than the depth corresponding to the step portion 2a. That is, by making the surface of the metallized layer 2b so thick that it does not reach the extension surface of the main surface of the sapphire window 2, the surface of the metallized layer 2b is flattened by polishing when the main surface of the sapphire window 2 is polished. It is possible to facilitate the positioning of the joint position of the sapphire window 2 because the step portion 2a remains stepped. In this case, the metal paste is applied to the step portion 2a by a brush painting method or by immersing the metal paste in the ring-shaped rubber stamp so that the depth is less than the depth of the step portion 2a, and then the rubber stamp is pressed against the step portion 2a. It may be applied by a printing method by transfer or the like.

【0030】

In this way, the main having the stepped portion 2a of the sapphire window 2 is first so that the portion of the metallized layer 2b having a thickness that does not reach the extension surface of the main surface of the sapphire window 2 is not polished on the stepped portion 2a of the sapphire window 2. A metallize layer 2b is formed on the entire surface, the metallize layer 2b on the main surface of the sapphire window 2 (the portion corresponding to the substantially light transmitting region in FIG. 2) is ground and removed, and the very surface of the main surface of the sapphire window 2 is mirror-polished. A means, or a means of first forming the metallized layer 2b only on the step portion 2a and mirror-polishing the very surface of the main surface of the sapphire window 2 can be adopted. Thus, a sapphire window 2 having a clean surface and a metallized layer 2b such as Mo / Mn burned onto the step portion 2a is obtained.

【0031】

Further, the Ni layer and the Au layer are sequentially coated on the metallized layer 2b by a plating method in the same manner as the heat radiating plate 1a and the frame body 1b, and the main surface having the joint portion between the plating layer and the lid 1c. A semiconductor package with a sapphire window is produced by joining the plating layer adhered to the peripheral edge of the window portion 4 of the above via a brazing material such as Au-Sn.

【0032】

The arithmetic mean roughness of the surface of the metallized layer 2b adhered to the step portion 2a is preferably 1 to 5 μm. If it is 1 μm or less, the anchoring effect of the brazing material is impaired and the joint strength deteriorates. If it exceeds 5 μm, the uniformity of the thickness of the plating layer adhered on the metallized layer 2b is impaired, and the bonding strength is similarly deteriorated.

【0033】

The manufacturing method of the sapphire window 2 of the present invention is as follows in steps [1] to [4]. A step portion 2a is formed by grinding on the peripheral edge portion on the one main surface side of the sapphire window 2. The metallized layer 2b is adhered only to the main surface (substantially the portion corresponding to the light transmitting region) of the sapphire window 2 including the step portion 2a, the step portion 2a, or the step portion 2a with a thickness less than the depth corresponding to the step portion 2a. .. The metallized layer on the main surface of the sapphire window 2 is ground and removed so that the metallized layer 2b adhered to the step portion 2a is not ground, and then the very surface of the main surface of the sapphire window 2 is ground or the sapphire window 2 is ground. When the metallized layer is not formed on the main surface of the sapphire window 2, only the very surface of the main surface of the sapphire window 2 is ground. After the metal paste and foreign matter burned on the main surface of the sapphire window 2 are removed, the metallized layer 2b of the step portion 2a is prevented from being polished, and the ground surface of the main surface of the sapphire window 2 is mirror-polished.

【0034】

Here, in the above step [2], when the metallize layer 2b is adhered only to the step portion 2a, the difference (height difference) between the surface of the metallize layer 2b and the main surface of the sapphire window 2 is 20 to 170 μm. At best, if it is less than 20 μm, when the metal paste for the metallized layer 2b is printed and applied, the upper surface of the metal paste layer may protrude from the main surface due to the variation in the printing thickness. As a result, the protruding portion is polished, and a polished portion and a non-polished portion are formed, so that the state of the surface of the Ni plating layer applied to the metallized layer 2b becomes non-uniform. Therefore, the reliability of the wax joint of the sapphire window 2 tends to decrease. On the other hand, if it exceeds 170 μm, it becomes extremely difficult to form it by a normal printing method, and the productivity decreases.

【0035】

Further, in the present invention, the depth of the step portion 2a is preferably 50 to 200 μm, and if it is less than 50 μm, the metal paste layer may protrude from the main surface due to variations in printing thickness, while exceeding 200 μm. In this case, it becomes difficult to print and apply the metal paste to the step portion 2a at this depth, and the productivity is lowered. Therefore, the depth of the step portion 2a is preferably 50 to 200 μm.

【0036】

The thickness of the metallized layer 2b adhered to the step portion 2a is preferably about 5 to 70 μm within a thickness range of less than the depth of the step portion 2a, and if it is less than 5 μm, the metallized layer is adhered. There is a risk that some parts will not be used. On the other hand, if it exceeds 70 μm, the metallized layer 2b may be peeled off due to the stress due to its thickness. More preferably, it is about 10 to 30 μm, in which case the above-mentioned problems can be sufficiently avoided.

【0037】

Further, regarding the polishing of the sapphire window 2 of the present invention, it can be easily identified that the polishing has been performed by observing the surface and the cross section by SEM (Scanning Electron Microscope) photograph.

【0038】

Further, the width of the step portion 2a should be 250 μm or more outside the light transmission region at the center of the sapphire window 2, and if the width is less than 250 μm, the width of the step portion 2a is very narrow, so the semiconductor by the sapphire window 2 The airtightness of the element 3 tends to be impaired. That is, the bondability between the sapphire window 2 and the semiconductor package 1 becomes very weak, and even if the airtightness is good at the beginning of the bond, reliability tests such as temperature cycle test and thermal shock test are performed. When this is done, cracks or the like may occur in the brazing material, and as a result, the airtightness inside the semiconductor package 1 may be broken.

【0039】

On the other hand, when the brazing material joint is formed with a large width so as to cover the light transmitting region of the sapphire window 2, the amount of transmitted light is reduced. In the case of the semiconductor package 1 using 2, the light coupling efficiency between the optical signal and the semiconductor element 3 is impaired. Therefore, the width of the step portion 2a is preferably 250 μm or more outside the light transmission region at the center of the sapphire window 2.

【0040】

As described above, the semiconductor package 1 with the sapphire window 2 of the present invention has a container body made of a metal material or a ceramic material, a lid body 1c made of ceramics and a window portion 4 formed therein, and one main surface of the lid body 1c. It is basically composed of a sapphire window 2 joined to the window part 4. Then, after mounting the semiconductor element 3 in the container body so that it can be electrically connected to the outside, the peripheral edge of the sapphire window 2 is formed in the window portion 4 formed as a through hole in the substantially central portion of the lid 1c. The metallized layer 2b is adhered to the stepped portion 2a formed by cutting out the portion with a predetermined width over the entire circumference with a thickness less than the depth corresponding to the stepped portion 2a. The step portion 2a has, for example, a depth of 50 to 200 μm, a width of 250 μm or more outside the light transmitting region at the center of the sapphire window 2, and a sapphire window via a metallized layer 2b adhered to the step portion 2a. By brazing 2 to the lid 1c, it becomes a semiconductor device as a product.

【0041】

Thus, the present invention can effectively and efficiently prevent metal paste, foreign matter, etc. from adhering to the light transmitting region of the sapphire window, and can provide a semiconductor package with a sapphire window having good light transmission with a high yield. It is possible to manufacture the sapphire window with high productivity, and it is possible to firmly hold the bond of the sapphire window to the lid for a long period of time.

【0042】

The present invention is not limited to the above embodiment, and various changes may be made without departing from the gist of the present invention.

【0043】

For example, in the above embodiment, the step portion 2a shown in FIG. 2, that is, the step portion 2a cut out from the outer peripheral edge of the sapphire window 2 toward the center side of the main surface with a predetermined width over the entire circumference has been described. As another embodiment of the invention, as shown in FIG. 3, a groove portion 2a'in which the peripheral edge portion of the sapphire window 2 is notched over the entire circumference may be formed with a width not reaching the outer peripheral edge. The effect of the invention can be obtained.

【0044】

Further, in the above embodiment, the sapphire window 2 is joined to the upper surface of the lid 1c, but it may be joined to the lower surface of the lid 1c as shown in FIG. In this case, the height of the semiconductor package 1 can be lowered by the thickness of the sapphire window 2, which is very effective for miniaturization. Further, although the sapphire window 2 has a disk shape, it may be a polygon such as a quadrangle as shown in FIG. However, in this case, stress tends to be concentrated on the corners at the time of joining, and the bondability tends to be weak. Therefore, it is desirable to give R (radius of curvature) to the corners to form a rounded shape.

【0045】

[Effect of the invention]

In the present invention, the sapphire window has a groove or a step portion formed on the peripheral edge portion having a predetermined width over the entire circumference, and a metallized layer is adhered to the groove portion or the step portion to a thickness less than the depth thereof, and the main surface. By polishing the sapphire window, it is possible to effectively and efficiently prevent metal paste, foreign matter, etc. from adhering to the light transmitting region of the sapphire window, and a semiconductor package with a sapphire window having good light transmission is expensive. The yield makes it possible to manufacture the sapphire window with high productivity, and further, it is possible to firmly hold the sapphire window bonded to the lid for a long period of time.

【0046】

Further, when such a sapphire window is brazed to a semiconductor package, the brazed joint can be firmly held, the light transmission is very good, and the semiconductor package with a sapphire window having excellent mass productivity can be obtained. Easy to produce.

【0047】

In the method for manufacturing a package for storing a semiconductor element of the present invention, in a sapphire window, a groove or a step portion having a predetermined width is formed on the peripheral edge portion on one main surface side, and at least the groove portion or the step portion in the main surface is formed. By applying a metallized layer to a thickness less than that depth, polishing the main surface, and then brazing to the window, the brazing bond can be firmly held and the light transmission is very good. In addition, it is possible to easily produce a semiconductor package with a sapphire window, which has a high yield and excellent mass productivity.

[Simple explanation of drawings]

[Figure 1]

(a) to (c) are cross-sectional views showing various embodiments of the semiconductor package of the present invention, respectively.

[Figure 2]

The sapphire window for the semiconductor package of FIG. 1 is shown, (a) is a cross-sectional view of the sapphire window, and (b) is a plan view of the sapphire window.

[Fig. 3]

Other embodiments of the sapphire window of the present invention are shown, (a) is a sectional view of the sapphire window, and (b) is a plan view of the sapphire window.

[Fig. 4]

It is sectional drawing which shows the other embodiment of the semiconductor package of this invention.

[Fig. 5]

(a) and (b) are a cross-sectional view and a plan view showing another embodiment of the sapphire window for the semiconductor package of the present invention.

[Fig. 6]

(a) and (b) are a cross-sectional view and a plan view of a sapphire window for a conventional semiconductor package.

[Fig. 7]

It is a perspective view of the conventional semiconductor package.

[Explanation of symbols]

1: Semiconductor package 1c: Lid 2: Sapphire window 2a: Step 2b: Metallized layer 3: Semiconductor element 4: Window