JP4571807B2 - Light receiving element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a light receiving element including a translucent conductive film containing an impurity for reducing resistance that is electrically connected to a constant potential line and blocks external noise, and a method of manufacturing the same.

  In a light-receiving element such as a photodiode or phototransistor that converts an optical signal into an electric signal, a translucent conductive film electrically connected to a constant potential line such as a ground potential, for example, as a countermeasure against malfunction due to external noise such as electromagnetic waves It is known to coat with.

  As an example of a conventional light receiving element, a cross-sectional view of a photodiode is shown in FIG.

  A conventional photodiode 1 includes an n-type epitaxial layer 4 grown on a surface including an n-type buried layer 3 provided on a p-type silicon substrate 2, and an n-type epitaxial layer 4 provided to partition an element formation region. p-type element isolation layer 5, n-type diffusion layer 6 reaching n-type buried layer 3, p-type diffusion layer 7 formed on the surface of n-type epitaxial layer 4 in the element formation region, and provided on these surfaces A thin silicon oxide film 8, a polysilicon layer 9 which is a translucent conductive film formed on the silicon oxide film 8 so as to cover the region of the p-type diffusion layer 7, and a silicon nitride film 10 provided on these surfaces And electrodes 11a, 11b, 11c connected to the n-type diffusion layer 6, the p-type diffusion layer 7, and the polysilicon layer 9 through contact holes provided in the silicon nitride film 10 and the silicon oxide film 8, respectively. On the surface A girder thick silicon nitride film 12, and an electrode 11c and the polysilicon layer 9 and electrically connected to the light-shielding aluminum 13 through a contact hole formed in the silicon nitride film 12.

  Here, the polysilicon layer 9 is maintained at the ground potential through the light shielding aluminum 13, and serves as a noise shield that blocks the influence of external noise.

  Further, impurities such as phosphorus are introduced into the polysilicon layer 9 to reduce the resistance. (For example, see Patent Documents 1 and 2.)

  Next, the manufacturing method of said photodiode 1 is shown in FIGS. 9 to 13 are cross-sectional views showing the order of steps.

  First, as shown in FIG. 9A, arsenic is implanted into a predetermined region of the p-type silicon substrate 2 to form an n-type buried layer 3.

  Next, as shown in FIG. 9B, an n-type epitaxial layer 4 is grown.

  Next, as shown in FIG. 9C, after a silicon oxide film 14 is grown, a photoresist mask 15 having an opening in a portion that becomes an n-type diffusion layer is formed thereon using a general photolithography method. After forming, the silicon oxide film 14 is etched.

  Next, as shown in FIG. 10D, phosphorus is implanted using the silicon oxide film 14 and the photoresist mask 15 as a mask, and then high-temperature annealing is performed to form the n-type diffusion layer 6.

  Thereafter, the photoresist mask 15 and the silicon oxide film 14 are sequentially removed.

  Next, as shown in FIG. 10E, after a thin silicon oxide film 8 is grown on the surface, a portion that becomes a p-type element isolation layer is opened thereon by using a general photolithography method. A photoresist mask 16 is formed and boron is implanted to form the p-type element isolation layer 5. The silicon oxide film 8 is formed for the purpose of insulating the upper and lower sides and reducing damage during impurity implantation.

  Thereafter, the photoresist mask 16 is removed.

  Next, as shown in FIG. 11 (f), using a general photolithography method, a photoresist mask 17 having an opening at a portion to become a p-type diffusion layer is formed, and phosphorus is implanted to form a p-type diffusion layer. 7 is formed.

  Thereafter, the photoresist mask 17 is removed.

  Next, as shown in FIG. 11G, a polysilicon film 9a is formed by chemical vapor deposition (CVD).

  Next, as shown in FIG. 12H, phosphorus is introduced into the polysilicon film 9a using a thermal diffusion method (or ion implantation method) or the like, and the resistance is lowered so that external noise can be quickly dropped to the ground potential. Plan. However, here, some of the introduced phosphorus may pass through the thin silicon oxide film 8 and undesirably diffuse into the underlying layer.

  Next, as shown in FIG. 12I, the polysilicon film is patterned by using a general photolithography method and etching method to form a polysilicon layer 9 as a translucent conductive film.

  Next, as shown in FIG. 13J, after a silicon nitride film 10 is formed on the surface including the polysilicon layer 9, this silicon nitride film 10 and silicon are etched using a general photolithography method and etching method. Contact holes are provided in the oxide film 8, and electrodes 11a and 11b connected to the n-type diffusion layer 6 and the p-type diffusion layer 7 and electrodes 11c connected to the polysilicon layer 9 are formed through the contact holes, respectively.

Finally, as shown in FIG. 13 (k), a silicon nitride film 12 is formed on the surface including the electrodes 11a, 11b, and 11c, and this silicon nitride film 12 is formed using a general photolithography method and etching method. A contact hole is provided, and the light shielding aluminum 13 is formed on the silicon nitride film 12, and the light shielding aluminum 13 and the electrode 11c are electrically connected through the contact hole to complete.
Japanese Patent Laid-Open No. 4-85885 JP 59-125673 A

  However, in the photodiode 1 as described above, phosphorus introduced into the polysilicon layer 9 for the purpose of reducing the resistance as described above may pass through the thin silicon oxide film 8 and diffuse to the base. In order to prevent this, if a new insulating film or the like is formed, the number of processes is increased and the translucency may be deteriorated.

  An object of the present invention is to provide a light receiving element capable of preventing impurities introduced into a light transmissive conductive film from diffusing into a base without newly increasing the number of steps or deteriorating the light transmissive property, and a method for manufacturing the same. Is to provide.

The light receiving element of the present invention includes a semiconductor substrate, a first semiconductor layer of the first conductivity type provided on the semiconductor substrate, and a second conductivity type partially formed on the surface of the element formation region of the first semiconductor layer. The second semiconductor layer, the silicon oxide layer provided on the semiconductor substrate, and the silicon oxide layer located on the second semiconductor layer are electrically connected to the constant potential line to block external noise. A light-receiving element including a conductive polysilicon layer including an impurity for resistance , and the light- transmitting film includes a position between the conductive polysilicon layer and the silicon oxide layer. The light receiving element is provided with a polysilicon oxide layer .

The method for manufacturing a light receiving element of the present invention includes a semiconductor substrate, a first semiconductor layer of a first conductivity type provided on the semiconductor substrate, and a first semiconductor layer partially formed on a surface of an element formation region of the first semiconductor layer. A second conductive type second semiconductor layer, a silicon oxide layer provided on a semiconductor substrate, and a silicon oxide layer located on the second semiconductor layer are electrically connected to a constant potential line to reduce external noise. In a method of manufacturing a light receiving element including a light- transmitting film made of polysilicon containing impurities for reducing resistance, the light- transmitting film is formed by chemical vapor deposition, and the chemical vapor deposition is performed. In the method, oxygen is temporarily added to the reaction gas during the step of growing the light- transmitting film to form an oxidized polysilicon layer on a part of the light-transmitting film, and after the light-transmitting film is formed. an impurity for reducing the resistance, the transparent film on the polysilicon oxide layer A method for producing a light-receiving element, characterized in that the inlet.

  According to the light receiving element of the present invention, since the light-transmitting conductive film has at least one oxide layer as an impurity diffusion preventing film, impurities are introduced into the light-transmitting conductive film for the purpose of reducing resistance. Can also prevent impurities from diffusing into the substrate. Further, since a new insulating film is not provided separately from the translucent conductive film, the translucency is not deteriorated. The oxide layer may be formed of a reliable insulator such as polysilicon oxide.

  According to the method for manufacturing a light receiving element of the present invention, when forming a light-transmitting conductive film by a chemical vapor deposition (CVD) method, oxygen is temporarily added and at least one layer is formed inside the light-transmitting conductive film. Since an oxide layer as an impurity diffusion prevention film is formed, it is not necessary to newly increase the number of steps.

  A cross-sectional view of a photodiode is shown in FIG. 1 as an example of the light receiving element of the present invention. The same parts as those in FIG.

  The photodiode 101 of the present invention includes an n-type epitaxial layer 4 grown on a surface including an n-type buried layer 3 provided on a p-type silicon substrate 2, and an element formation region provided on the n-type epitaxial layer 4. P-type element isolation layer 5, n-type diffusion layer 6 reaching n-type buried layer 3, p-type diffusion layer 7 formed on the surface of n-type epitaxial layer 4 in the element formation region, and provided on these surfaces A thin silicon oxide film 8, a polysilicon layer 102 which is a translucent conductive film formed on the silicon oxide film 8 so as to cover the region of the p-type diffusion layer 7, and a silicon nitride film provided on these surfaces 10 and electrodes 11a, 11b and 11c connected to the n-type diffusion layer 6, the p-type diffusion layer 7 and the polysilicon layer 102 through contact holes provided in the silicon nitride film 10 and the silicon oxide film 8, respectively. A thick silicon nitride film 12 provided on the surface including, and an electrode 11c and the polysilicon layer 102 and electrically connected to the light-shielding aluminum 13 through a contact hole formed in the silicon nitride film 12.

  Here, the polysilicon layer 102 is maintained at the ground potential through the light shielding aluminum 13, and serves as a noise shield that blocks the influence of external noise.

  A polysilicon oxide layer 103 as an impurity diffusion preventing film, which is a feature of the present invention, is formed on a part of the lower surface side of the polysilicon layer 102.

  The remaining portion of the polysilicon layer 102 excluding the portion of the oxidized polysilicon layer 103 is doped with impurities such as phosphorus to reduce the resistance.

  Next, a method for manufacturing the photodiode 101 is shown in FIGS. 2 to 6 are cross-sectional views showing the order of the steps, and the same parts as those in FIGS.

  First, as shown in FIG. 2A, arsenic is implanted into a predetermined region of the p-type silicon substrate 2 to form an n-type buried layer 3.

  Next, as shown in FIG. 2B, an n-type epitaxial layer 4 is grown.

  Next, as shown in FIG. 2C, after a silicon oxide film 14 is grown, a photoresist mask 15 having an opening at a portion to become an n-type diffusion layer is formed thereon using a general photolithography method. After forming, the silicon oxide film 14 is etched.

  Next, as shown in FIG. 3D, phosphorus is implanted using the silicon oxide film 14 and the photoresist mask 15 as a mask, and then high-temperature annealing is performed to form the n-type diffusion layer 6.

  Thereafter, the photoresist mask 15 and the silicon oxide film 14 are sequentially removed.

  Next, as shown in FIG. 3E, after a thin silicon oxide film 8 is grown on the surface, a portion that becomes a p-type element isolation layer is opened thereon by using a general photolithography method. A photoresist mask 16 is formed and boron is implanted to form the p-type element isolation layer 5. The silicon oxide film 8 is formed for the purpose of insulating the upper and lower sides and reducing damage during impurity implantation. .

  Thereafter, the photoresist mask 16 is removed.

  Next, as shown in FIG. 4F, using a general photolithography method, a photoresist mask 17 having an opening at a portion to become a p-type diffusion layer is formed, and phosphorus is implanted to form a p-type diffusion layer. 7 is formed.

  Thereafter, the photoresist mask 17 is removed.

  Next, as shown in FIG. 4G, a polysilicon film 102a is formed by chemical vapor deposition (CVD). Here, in an initial stage of growing the polysilicon film 102a, an amount of oxygen capable of forming an oxide layer is temporarily added to the reaction gas. As a result, a polysilicon oxide film 103a is formed on a part of the lower surface side of the polysilicon film 102a.

  Next, as shown in FIG. 5H, phosphorus is introduced into the polysilicon film 102a using a thermal diffusion method (or ion implantation method) or the like, and the resistance is lowered so that external noise can be quickly dropped to the ground potential. Plan. At this time, since the polysilicon film 103a as an impurity diffusion preventing film is formed on a part of the lower surface side of the polysilicon film 102a, there is no fear that phosphorus diffuses into the base.

  Next, as shown in FIG. 5I, the polysilicon film is patterned using a general photolithography method and etching method to form a polysilicon layer 102 and a polysilicon oxide film 103 as a light-transmitting conductive film. To do.

  Next, as shown in FIG. 6J, after the silicon nitride film 10 is formed on the surface including the polysilicon layer 102, this silicon nitride film 10 and silicon are etched by using a general photolithography method and etching method. Contact holes are formed in the oxide film 8, and electrodes 11a and 11b connected to the n-type diffusion layer 6 and the p-type diffusion layer 7 and electrodes 11c connected to the polysilicon layer 102 are formed through the contact holes, respectively.

  Finally, as shown in FIG. 6 (k), a silicon nitride film 12 is formed on the surface including the electrodes 11a, 11b, and 11c, and this silicon nitride film 12 is formed using a general photolithography method and etching method. A contact hole is provided, and the light shielding aluminum 13 is formed on the silicon nitride film 12, and the light shielding aluminum 13 and the electrode 11c are electrically connected through the contact hole to complete.

  In the above example, oxygen is added at the initial stage of the growth of the polysilicon film 102a and the oxidized polysilicon layer 103a is formed on a part of the lower surface side. As shown in FIG. 7A, oxygen is added to an intermediate stage of the growth of the polysilicon film to form a polysilicon oxide layer 103 in a part of the middle of the polysilicon layer 102 as shown in FIG. You can also.

  Further, as shown in FIG. 7B, oxygen is added to the initial stage and the intermediate stage of the growth of the polysilicon film, and two layers of oxidized poly oxide are formed on a part of the lower surface side of the polysilicon layer 102 and a part of the middle. A silicon layer 103 can also be formed. This improves the effect as an impurity diffusion preventing film.

  In the above example, the photodiode formed on the silicon substrate has been described. However, the present invention is not limited to this, and may be a photodiode formed on a compound semiconductor substrate such as GaAs. Needless to say, the same effect can be obtained not only with a photodiode but also with a phototransistor or the like.

  The present invention can be applied to a light receiving element that can prevent an impurity for reducing resistance introduced into a light-transmitting conductive film from diffusing into a base and a manufacturing method thereof.

Sectional drawing of the photodiode as an example of the light receiving element of this invention Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the light receiving element of this invention Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the light receiving element of this invention Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the light receiving element of this invention Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the light receiving element of this invention Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the light receiving element of this invention Sectional drawing of the modification of the photodiode as an example of the light receiving element of this invention Cross-sectional view of a photodiode as an example of a conventional light receiving element Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the conventional light receiving element Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the conventional light receiving element Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the conventional light receiving element Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the conventional light receiving element Sectional drawing which shows the process order of the manufacturing method of the photodiode as an example of the conventional light receiving element

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photodiode as an example of a conventional light receiving element 2 p-type silicon substrate 3 n-type buried layer 4 n-type epitaxial layer 5 p-type element isolation layer 6 n-type diffusion layer 7 p-type diffusion layer 8, 14 Silicon oxide film 9 Polysilicon layer 9a Polysilicon film 10 Silicon nitride film 11a, 11b, 11c Electrode 12 Silicon nitride film 13 Light shielding aluminum 15, 16, 17 Photoresist mask 101 Photodiode 102 as an example of light receiving element of the present invention 102 Polysilicon layer 102a Polysilicon film 103 Oxide polysilicon layer 103a Oxide polysilicon film

Claims (4)

A semiconductor substrate, a first conductivity type first semiconductor layer provided on the semiconductor substrate, and a second conductivity type second semiconductor layer partially formed on a surface of an element formation region of the first semiconductor layer And a silicon oxide layer provided on the semiconductor substrate and a silicon oxide layer provided on the second semiconductor layer, and electrically connected to a constant potential line to cut off external noise. And a translucent film including a conductive polysilicon layer containing impurities for the light- transmitting film, the translucent film includes a gap between the conductive polysilicon layer and the silicon oxide layer. A light receiving element , wherein a polysilicon oxide layer is provided at a position . The light receiving element according to claim 1, wherein the light receiving element is a photodiode. A semiconductor substrate, a first conductivity type first semiconductor layer provided on the semiconductor substrate, and a second conductivity type second semiconductor layer partially formed on a surface of an element formation region of the first semiconductor layer And a silicon oxide layer provided on the semiconductor substrate and a silicon oxide layer provided on the second semiconductor layer, and electrically connected to a constant potential line to cut off external noise. In the manufacturing method of a light receiving element comprising a light-transmitting film made of polysilicon containing impurities for forming the light-transmitting film, the light-transmitting film is formed by a chemical vapor deposition method. During the step of growing the light-transmitting film, oxygen is temporarily added to the reaction gas to form a polysilicon oxide layer on a part of the light-transmitting film, and low after the light-transmitting film is formed. Impurities for resistance are formed on the oxidized polysilicon layer. The manufacturing method of the light-receiving element and introducing the KiToruhikari membrane. The method for manufacturing a light receiving element according to claim 3, wherein the light receiving element is a photodiode.

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