JP2008041845A - Method for manufacturing integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein the etching rate is reduced since polymer is formed, when the upper layer of a photodetector is etched. <P>SOLUTION: In this method for manufacturing an integrated circuit; an upper layer is formed on a substrate having a light-receiving section, and an aperture is formed in the region of the upper layer, corresponding to the light-receiving section. The upper layer is etched on the etching conditions plural number of times, and oxygen plasma treatment is carried out, after at least one etching condition has been finished. Consequently, the polymer that is formed, when the etching has been carried out can be removed, and the treatment time can be reduced for the etching treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a manufacturing method for forming an integrated circuit on a semiconductor substrate or the like, and more particularly, to an etching method for an upper layer stacked on a substrate.

  In recent years, optical disks such as CD (Compact Disk) and DVD (Digital Versatile Disk) have come to occupy a large position as information recording media. These optical disk reproducing devices irradiate laser light along a track of the optical disk by an optical pickup mechanism and detect the reflected light. Then, the recorded data is reproduced based on the change in the reflected light intensity.

  Since the data rate read from the optical disk is very high, the photodetector for detecting the reflected light is composed of a semiconductor element using a PIN photodiode having a high response speed. A weak photoelectric conversion signal generated in the light receiving portion of the semiconductor element is amplified by an amplifier and output to a signal processing circuit at a subsequent stage. Here, from the viewpoint of ensuring the frequency characteristics of the photoelectric conversion signal and suppressing noise superposition, the wiring length between the light receiving unit and the amplifier is configured to be as short as possible. From this viewpoint and from the viewpoint of reducing the manufacturing cost of the photodetector, it is preferable that the light receiving section and the circuit section including the amplifier and the like are formed on the same semiconductor chip.

  FIG. 7 is a schematic cross-sectional view of a photodetector in which a light receiving unit and a circuit unit are disposed adjacent to each other on the same semiconductor substrate. A PIN photodiode structure is formed in the semiconductor substrate 2 in the region corresponding to the light receiving portion 4, and a circuit element such as a transistor is formed in the region corresponding to the circuit portion 6. A film 11 is formed.

  The photodetector in FIG. 7 has a two-layer wiring structure. As the wiring structure layer 10, a first interlayer insulating film 12, a first aluminum (Al) layer 14, a second interlayer insulating film 16, A 2Al layer 18 and a third interlayer insulating film 20 are sequentially stacked.

  The first Al layer 14 and the second Al layer 18 are each patterned using a photolithography technique. For example, the wiring 22 and the planarization pad 24 are formed in the circuit unit 6 by the first Al layer 14, and the wiring 26 and the planarization pad 28 are formed in the circuit unit 6 by the second Al layer 18. A light shielding layer and an Al layer 30 for light shielding are laminated on the wiring structure layer 10 of the circuit unit 6, and a silicon oxide film 32 and a silicon nitride film 34 are sequentially laminated as a protective film. Incidentally, the interlayer insulating film is formed using materials such as SOG (Spin on Glass), BPSG (Borophosphosilicate Glass), and TEOS (Tetra-ethoxy-silane).

  The upper structure layer 38 including the wiring structure layer 10 is also stacked on the semiconductor substrate 2 of the light receiving unit 4. In order to increase the efficiency of light incident on the semiconductor substrate 2 in the light receiving portion 4, it is preferable to remove the upper structural layer 38. Therefore, in the surrounding circuit portion 6, the upper structure layer 38 is left, and the light receiving portion 4 is selectively etched back to form an opening 36 of the upper structure layer 38 in the light receiving portion 4.

  Here, in the light receiving portion 4, each of the Al layers is previously removed by patterning when the upper structure layer 38 is laminated, and the interlayer insulating films 12, 16, 20, etc. are laminated on the light receiving portion 4. That is, as the Al layer is removed, the upper structure layer 38 of the light receiving unit 4 can be depressed more than the surrounding circuit unit 6. As described above, due to the surface of the upper structure layer 38 being not flat, the bottom surface of the opening is not flat as shown in FIG. 7, and the amount of incident light in the surface of the light receiving portion 4 may be uneven. There is sex.

  In order to avoid this, a polysilicon film is formed under the upper structure layer 38, and this is used as the light receiving portion pad 47 to etch back the opening. By using the light receiving portion pad 47, there is a certain effect in making the etching depth uniform in the opening surface.

  8 and 9 are schematic views for explaining a conventional method for manufacturing a photodetector in which an opening is formed after forming a polysilicon film corresponding to the position of the light receiving portion 4, and the light receiving portion in the main process. 4 is a schematic cross-sectional view in the vicinity of 4. A silicon oxide film 40 is formed as a base layer on the semiconductor substrate 2 on which the PIN photodiode, transistor, etc. are formed, and a polysilicon film 41 is deposited on the surface (FIG. 8A).

  A photoresist is applied on the polysilicon film 41 to form a photoresist film 42. The photoresist film 42 is exposed using a photomask 43 configured to allow light to pass through a region corresponding to the light receiving portion (FIG. 8B). Thereafter, a development process is performed to form a photoresist film 42 'that remains at a position corresponding to the light receiving portion (FIG. 8C).

  Using this photoresist film 42 'as an etching mask, the polysilicon film 41 is removed by etching to form a light receiving portion pad 44 made of a polysilicon film in a region corresponding to the light receiving portion (8 (d)).

  After removing the photoresist film 42 'on the light receiving portion pad 44, the upper structure layer 45 is laminated (FIG. 8E).

  Next, a photoresist is applied on the upper structure layer 45 to form a photoresist film 46 (FIG. 9A). The photoresist film 46 is exposed using a photomask 47 that shields the region corresponding to the light receiving portion (FIG. 9B). Thereafter, a development process is performed to form a photoresist film 46 'having an opening at a position corresponding to the light receiving portion (FIG. 9C).

  Next, the upper layer composed of the base layer 40, the light receiving portion pad 44, and the upper structure layer 45 is etched. In order to etch the upper layer, etching is performed using a magnetron reactive ion etching (hereinafter referred to as magnetron RIE) apparatus using the photoresist film 46 'as an etching mask.

  First, the upper structure layer 45 (silicon oxide film) and the light receiving portion pad 44 are etched by anisotropic etching.

  During the etching process in which the upper structure layer 45 and the light receiving pad 44 are etched by anisotropic etching, the photoresist film 46 ′ reacts with carbon and fluorine contained in the etching gas. Therefore, a polymer 47, which is a polymer made of carbon or fluorine, is formed on the surface of the light receiving portion pad 44 (FIG. 9B).

  When etching is performed while changing the etching conditions in the state where the polymer 47 is formed, the etching rate is significantly reduced by the polymer 47 (FIG. 9C).

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an integrated circuit manufacturing method capable of forming a light receiving portion having high flatness.

  The present invention is an integrated circuit manufacturing method in which an upper layer is formed on a substrate having a light receiving portion, and an area corresponding to the light receiving portion of the upper layer is opened, and the upper layer is etched under a plurality of etching conditions. The plurality of etching conditions include anisotropic etching, and oxygen plasma treatment is performed after completion of at least one anisotropic etching.

  Further, the plurality of etching conditions include isotropic etching, and oxygen plasma treatment is performed after anisotropic etching and before isotropic etching.

  The upper layer includes a base layer, a light receiving portion pad, and an upper structural layer, and is characterized in that the base layer, the light receiving portion pad, and the upper structural layer are stacked in this order from the substrate having the light receiving portion.

  In addition, anisotropic etching, oxygen plasma treatment, and isotropic etching are performed on the light receiving portion pad.

  In addition, anisotropic etching, oxygen plasma treatment, and anisotropic etching are performed on the light receiving portion pad.

  According to the present invention, it is possible to improve the flatness of the bottom surface of the opening.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  This embodiment is a photodetector mounted on an optical pickup mechanism of a reproducing apparatus for an optical disc such as a CD or a DVD.

  FIG. 1 is a schematic plan view of a semiconductor element which is a photodetector according to the present embodiment. The photodetector 50 is formed on a semiconductor substrate made of silicon, and includes a light receiving portion 52 and a circuit portion 54. The light receiving unit 52 includes, for example, four PIN photodiodes (PD) 56 arranged in a 2 × 2 manner, and receives light incident on the substrate surface from the optical system by dividing the light into 2 × 2 four sections. The circuit unit 54 is disposed, for example, around the light receiving unit 52. The circuit unit 54 includes, for example, circuit elements such as a CMOS 58, and an amplifier circuit and other signal processing circuits for the output signal from the light receiving unit 52 are formed on the same semiconductor chip as the light receiving unit 52 using these circuit elements. Can do. Although not shown in FIG. 1, wirings connected to circuit elements and wirings connected to the diffusion layer constituting the light receiving unit 52 are arranged in the circuit unit 54. These wirings are formed by patterning an Al film stacked on a semiconductor substrate.

  FIG. 2 is a schematic cross-sectional view showing the structure of the light receiving unit 52 and the circuit unit 54 in a cross section perpendicular to the semiconductor substrate through the straight line A-A ′ shown in FIG. 1. This cross section shows the structures of two PDs 56 of the light receiving unit 52, the CMOS 58 of the circuit unit 54, and wirings and interlayer insulating films stacked on the semiconductor substrate 60 on which they are formed.

  In the photodetector 50, an epitaxial layer 72 having an impurity concentration lower than that of the P-sub layer 70 and having a high specific resistance is formed on one main surface of the P-sub layer 70 which is a p-type silicon substrate into which a p-type impurity is introduced. The stacked semiconductor substrate 60 is used. The P-sub layer 70 constitutes an anode common to the PDs 56 and is applied with a ground potential from the back surface of the substrate, for example. The isolation region 74 is applied with a ground potential by the wiring 76 provided on the substrate surface side, and constitutes an anode together with the P-sub layer 70.

  The epitaxial layer 72 constitutes the i layer of the PD 56 in the light receiving portion 52. In the light receiving portion 52, the above-described isolation region 74 and cathode region 78 are formed on the surface of the epitaxial layer 72.

  A silicon oxide film 80 constituting a gate oxide film or a local oxide film (LOCOS) is formed on the surface of the semiconductor substrate 60, and a gate electrode 82 such as a MOSFET constituting the CMOS 58 is formed on the gate oxide film, for example, polysilicon. Or tungsten (W) or the like. Further, a silicon oxide film 84 as a base layer is formed on the surface of the substrate so as to cover it.

  After the silicon oxide film 84 is formed, a light receiving portion pad made of a polysilicon film is formed at a position corresponding to the light receiving portion 52. As will be described later, the light receiving portion pad is used as an etching stopper when the wiring structure layer 90 is etched back to form the opening 86 at the position of the light receiving portion 52. Therefore, the light receiving portion pad is formed to extend outward from the opening of the opening 86.

  After the formation of the light receiving portion pad, an upper structural layer made of a wiring structure, a protective film or the like is formed on the semiconductor substrate 60. The photodetector 50 has a two-layer wiring structure. As a wiring structure layer 90, a first interlayer insulating film 92, a first Al layer 94, a second interlayer insulating film 96, a second Al layer 98, Three interlayer insulating films 100 are sequentially stacked. The first Al layer 94 and the second Al layer 98 are each patterned using a photolithography technique. For example, the wiring 76 and the planarization pad 102 are formed in the circuit unit 54 by the first Al layer 94, and the wiring 104 and the planarization pad 106 are formed in the circuit unit 54 by the second Al layer 98.

  Here, the planarization pads 102 and 106 are disposed in the gaps between the wirings 76 and 104, respectively, and suppress unevenness of the surfaces of the interlayer insulating films 96 and 100 stacked on the first Al layer 94 and the second Al layer 98, respectively. To do. The interlayer insulating film is formed using a material such as SOG, BPSG, or TEOS.

  On the wiring structure layer 90 of the circuit portion 54, an Al layer 110 for light shielding is laminated, and a silicon oxide film 112 is sequentially laminated as a protective film.

  Here, in order to increase the efficiency of light incident on the PD 56 of the light receiving portion 52, the wiring structure layer 90 and the stacked layer, that is, the upper structural layer 128 are etched back, and an opening is formed in a region corresponding to the light receiving portion 52. 86 is formed. Thus, by etching the wiring structure layer 90 in the light receiving portion 52 and providing the opening 86, the light transmittance to the PD 56 is improved, and the amplitude of the photoelectric conversion signal by the laser reflected light is ensured.

  Note that the light receiving portion pad disposed under the wiring structure layer 90 is etched back in the step of forming the opening 86, and the portion existing on the bottom surface of the opening 86 is removed. For this reason, in FIG. 2, the light receiving portion pad on the bottom surface portion of the opening 86 no longer exists, and only the extended portion 114 outward from the opening 86 remains.

  After the opening 86 is formed, a silicon nitride film 116 is deposited. The silicon nitride film 116 covers the top surface of the silicon oxide film 112 and the side wall surface and bottom surface of the opening 86. The silicon nitride film 116 formed on the upper surface constitutes a protective film together with the silicon oxide film 112. Further, the silicon nitride film 116 formed on the side wall surface of the opening 86 covers the interlayer insulating film exposed on the side wall surface, and suppresses moisture from entering the wiring structure layer 90. Thereby, the deterioration of the wirings 76 and 104 is prevented. On the other hand, the silicon nitride film 116 formed on the bottom surface of the opening 86 has a function as an antireflection film that suppresses reflection of incident light from the bottom surface of the opening 86 to the PD 56.

  Next, a manufacturing method of the photodetector 50 will be described with reference to FIG. FIG. 3 is a schematic diagram for explaining a manufacturing method of the present photodetector in which the opening 86 is formed after forming the light receiving part pad corresponding to the position of the light receiving part 52, and in the vicinity of the light receiving part 52 in the main process. A schematic cross-sectional view is shown.

  First, a silicon oxide film 84 is formed as a base layer on the semiconductor substrate 60 on which the above-described PD 56, CMOS 58, etc. are formed. The silicon oxide film 84 is formed by being deposited by, for example, a CVD method. Further, a polysilicon film 120 is formed on the silicon oxide film 84 by a CVD method or the like (FIG. 3A).

  A photoresist film 122 is formed on the polysilicon film 120 by applying a photoresist. The photoresist film 122 is exposed using a photomask 124 configured to transmit light in a region corresponding to the light receiving portion 52 (FIG. 3B).

  Thereafter, development processing is performed to remove the unexposed region of the photoresist film 122, thereby forming a photoresist film 122 'that remains at a position corresponding to the light receiving portion 52 (FIG. 3C).

  The polysilicon film 120 is etched using the photoresist film 122 ′ thus formed as an etching mask to selectively leave the polysilicon film 120 in a region corresponding to the light receiving portion 52, thereby forming the light receiving portion pad 126. (FIG. 3 (d)).

After removing the photoresist film 122 ′ on the light receiving portion pad 126, an upper structure layer 128, for example, SiO ₂ is laminated (FIG. 3E). Lamination of each constituent layer of the upper structural layer 128 can be performed using a CVD method or a PVD method.

  Here, among the layers stacked as the upper structure layer 128, each Al layer is patterned and removed from the light receiving portion 52. Therefore, the upper structure layer 128 has a thickness at the light receiving portion 52 thinner than a thickness at a peripheral circuit portion at a stage where the interlayer insulating films 96 and 100 are laminated and at a stage where all the layers are laminated.

  Next, a photoresist is applied on the upper structure layer 128 to form a photoresist film 130. The photoresist film 130 is exposed using a photomask 132 (FIG. 3F).

  Thereafter, development processing is performed. The photomask 132 is configured to transmit light through a region corresponding to the light receiving unit 52. Therefore, the photoresist film 130 is exposed to a region corresponding to the light receiving portion 52, and the region is removed by development processing. As a result, a photoresist film 130 'having an opening 136 at a position corresponding to the light receiving portion 52 is formed (FIG. 3G).

  Next, the upper structure layer 128 is etched using the photoresist film 130 'as an etching mask. In the present embodiment, in order to form an opening in the upper structure layer 128, three-stage etching is performed using a magnetron RIE apparatus shown in FIG. 4 as an etching apparatus.

  Here, the magnetron RIE apparatus will be described with reference to the schematic diagram of FIG.

The reaction chamber 140 that performs plasma treatment contains a conductive material and is fixed to a ground potential. The reaction chamber 140 is provided with a gas inlet for introducing an etching gas and an outlet for discharging the etching gas and the residue decomposed by the etching (not shown). The lower electrode 146 is connected to a high frequency power source (13.56 MHz) 148 as a bias source. On the lower electrode 146, a substrate 150 that has been subjected to the pre-etching process is installed. The upper electrode 144 is grounded. A permanent magnet (die ball ring) 142 is disposed on the side wall outside the reaction chamber, and generates a magnetic field in the reaction chamber.

  By generating a magnetic field in the reaction chamber in this way, the gas pressure can be reduced and the ion energy can be lowered while increasing the plasma density, and the plasma density can be increased near the electrode surface by combining the magnetic field and the electric field. Can do.

  Next, an etching method using the magnetron RIE apparatus of the photodetector 50 will be described with reference to FIG. FIG. 5 is a schematic diagram for explaining the manufacturing method of the present photodetector in which the opening 86 is formed after forming the light receiving part pad corresponding to the position of the light receiving part 52, as in FIG. A schematic cross-sectional view in the vicinity of the light receiving portion 52 is shown.

  First, as an upper structure layer etching step, the upper structure layer up to the light receiving portion pad is etched using the photoresist film 130 'having the opening 136 at a position corresponding to the light receiving portion 52 as a mask (FIG. 5A). At this time, it is preferable that the etching does not reach the light receiving portion pad.

  In the upper structure layer etching step, it is desirable to etch the opening 86 by a method that is less likely to spread than the opening 132 in order to make the light receiving part pad 126 function as a light receiving part pad suitably for etch back of the opening 86. From this viewpoint, it is desirable to perform anisotropic etching.

  The thickness of the upper structure layer 128 above the light receiving portion pad 126 is 1.5 to 2 μm, which is very thick compared to the film thickness of the light receiving portion pad 0.1 to 0.2 μm. In order to shorten it, it is desirable to select a condition with a high etching rate for the silicon oxide film constituting the upper structure layer 128.

Considering these points, it is desirable to select a gas containing CF ₄ as the etching gas, for example, a mixed gas containing CHF ₃ and CF ₄ is preferably used.

  Next, as the light receiving portion pad etching step, the upper structure layer 128 and the light receiving portion pad 126 are etched using the photoresist film 130 'as a mask (FIG. 5B). At this time, the etching is performed so as not to reach the silicon oxide film 84.

  Similarly to the upper structure layer etching process, the light receiving part pad etching process is also less likely to spread the etching of the opening 86 than the opening 136 in order to make the light receiving part pad 126 function as an etching stopper with respect to the etch back of the opening 86. It is desirable to carry out by a method. From this viewpoint, it is desirable to perform anisotropic etching.

  Here, since no metal wiring is formed in the opening of the upper structure layer, as shown in FIG. 3G, immediately after the upper structure layer etching step, the film thickness and side edges of the central portion of the opening 86 are obtained. When the film thickness of the part is compared, the film thickness of the side end part is increased.

  When a film having a shape having a difference in film thickness is etched as described above, the film thickness of the side end portion is thicker than that of the central portion even after the etching.

Therefore, in the light receiving portion pad etching step, the selectivity between the upper structural layer 86 and the light receiving portion pad 126 is higher than that in the upper structural layer etching step in order to reduce the film thickness difference (the upper structural layer 86 receives the light. The etching conditions are switched to a higher etching rate than the part pad 126.

  For example, by switching the gas, the etching rate is faster in the silicon oxide film than in the polysilicon. Therefore, as shown in FIG. 5B, when etching the polysilicon at the center, the silicon oxide film at the side edge is etched faster than the polysilicon, so the film thickness at the center and the side edge. The difference is relaxed.

Considering these points, it is desirable to select a gas containing CO ₂ as the gas used in the light receiving portion pad etching process, for example, a mixed gas composed of CO ₂ and CHF ₃ is desirable.

  Next, as a base layer etching step, the light receiving portion pad 126 and the silicon oxide film 84 are etched so as not to reach the semiconductor substrate using the photoresist film 130 'as a mask (FIG. 5C).

  In the underlayer etching process, as in the light receiving portion pad etching step, the light receiving portion pad 126 has a higher selection ratio than the underlayer 84 in order to reduce the difference in film thickness (the light receiving portion pad 126 is the silicon that is the underlayer). The etching condition is switched to an etching condition that is faster than that of the oxide film 84.

  By switching in this way, when the silicon oxide film 84 at the center of the opening 86 is etched, the polysilicon at the side end is quickly etched, so as shown in FIG. And the difference in film thickness at the side edges is further alleviated.

In consideration of these points, it is desirable to perform etching by selecting a gas containing SF ₆ as the gas used in the underlayer etching process, and for example, it is desirable to select a mixed gas containing SF ₆ or NF ₃ .

  Note that isotropic etching is preferably performed in the base layer etching step. By performing isotropic etching, physical damage on the bottom surface of the opening is suppressed, and the flatness is further improved. When performing isotropic etching, a chemical dry etching apparatus or the like may be used.

  When the etch back for forming the opening 86 is completed, the photoresist 130 ′ is removed. Then, silicon nitride is deposited by using, for example, a CVD method, and a silicon nitride film 116 is formed on the upper surface of the upper structure layer 128 and the side wall surface and the bottom surface of the opening 86. This forms the basic structure of the photodetector 50 shown in FIG.

  By performing the above three-stage etching process, the flatness of the bottom surface of the opening is improved, and the uniformity of the amount of incident light within the light receiving surface can be improved.

  In this embodiment, the opening is formed by a three-stage etching process. However, during the light receiving part pad etching process in which the light receiving part pad 126 is etched by anisotropic etching, the photoresist film 130 ′ and the etching gas are used. The contained carbon and fluorine react. Therefore, after the light receiving portion pad etching process, a polymer 129 which is a polymer made of carbon or fluorine is formed on the surface of the light receiving portion pad 126 (FIG. 5C).

When such a polymer 129 is formed, the etching rate is remarkably reduced when the underlayer etching process is performed, and it takes a very long time to etch into a predetermined shape.

  In addition, since the polymer 129 is not uniformly formed in the opening, depending on the position of the opening, there may be a place where the polymer is etched or a place where the polymer is not etched, and the flatness on the surface of the opening will vary.

  For these reasons, after the light receiving portion pad etching process is completed, the polymer is removed by oxygen plasma treatment.

  By performing the oxygen plasma treatment, carbon and fluorine contained in the polymer react with oxygen. Carbon and fluorine that have reacted with oxygen become COx and FOx and are discarded to the outside. As a result, the polymer can be removed from the surface of the light receiving portion pad 126.

  In this embodiment, a plasma dry etcher shown in FIG. 6 is used to perform oxygen plasma treatment.

  Here, the plasma dry etcher will be described with reference to the schematic diagram of FIG. The reaction chamber 160 that performs plasma treatment contains a conductive material and is fixed to a ground potential. The reaction chamber 160 is provided with a gas inlet for introducing oxygen and an outlet (not shown) for discharging oxygen and residues resulting from separation and decomposition. The lower electrode 164 is installed insulated from the reaction chamber 160 via an insulator. In addition, the substrate 150 that has completed the second etching step is placed on the lower electrode 164. The upper electrode 162 is connected to a high frequency power source (13.56 MHz) 166 as a bias source provided on the upper portion of the reaction chamber 166 via an insulator.

  By performing plasma treatment using this apparatus, the polymer can be removed reliably, and the next underlayer etching process can be reliably performed.

  In this embodiment, the oxygen plasma treatment is performed after the light receiving portion pad etching process is completed. This is because anisotropic etching has a large physical energy, so that the photoresist film 130 ′ is scraped and a polymer is easily formed on the surface of the light receiving portion pad 126 and the sidewall of the opening. Furthermore, since isotropic etching is chemical etching, physical energy is small, and it is more susceptible to a decrease in etching rate due to the polymer than anisotropic etching.

  Therefore, the etching treatment time can be effectively shortened by performing the plasma treatment after the anisotropic etching and before the isotropic etching.

  In order to improve the flatness of the light receiving portion using the light receiving portion pad 126, the etching condition is set such that the selection ratio between the upper structural layer 86 and the light receiving portion pad 126 is higher than that in the upper structural layer etching step. It is necessary to lengthen the processing time. However, if the etching processing time is lengthened, the polymer is easily formed on the light receiving portion pad 126.

  Therefore, it is effective to perform plasma treatment after etching a film whose etching rate is slow under etching conditions with high selectivity.

  Furthermore, oxygen plasma treatment may be performed while anisotropic etching is being performed on the light receiving portion pad 126, and anisotropic etching may be performed again.

  As a result, the polymer can be removed before the unevenness of the polymer itself becomes large at the time of etching the light-receiving portion pad, so that variations in flatness on the surface of the opening can be effectively suppressed.

  In this embodiment, the light receiving pad made of polysilicon is selected as the light receiving pad. However, the present invention is not limited to this, and a metal such as Al or a refractory metal, or an insulating film such as a silicon nitride film is used. It may be used.

  Even when a light receiving part pad different from polysilicon is used, the upper structure layer etching process is performed under an etching condition in which the etching speed of the upper structure layer is high, and the light receiving part pad etching process receives light from the upper structure layer and the light receiving part. Etching conditions with a high selection ratio of the part pads are selected, and an etching condition with a high selection ratio with the light-receiving part pads is selected in the base layer etching step. Thereby, the flatness of the bottom surface of the opening is improved, and the uniformity of the amount of incident light within the light receiving surface can be improved.

  Further, in the present embodiment, the light receiving part pad etching step and the upper structure layer etching step have different etching conditions, but the same etching conditions may be used.

  In this embodiment, an etching method using a magnetron RIE apparatus is shown. However, the present invention is not limited to this, and other methods such as an inductively coupled plasma (ICP) apparatus may be used.

  Moreover, in this embodiment, it is not restricted to this which performed oxygen plasma processing after completion | finish of a light-receiving part pad etching process, You may perform plasma processing after base layer etching.

It is a schematic plan view of the semiconductor element which is a photodetector concerning this embodiment. It is typical sectional drawing which shows the structure of the light-receiving part of the photodetector which is this embodiment, and a circuit part. It is a schematic diagram explaining the formation method of the opening part in the photodetector of this embodiment. It is the schematic of the etching apparatus used by this embodiment. It is a schematic diagram explaining the formation method of the opening part in the photodetector of this embodiment. It is the schematic of the plasma processing apparatus used by this embodiment. It is typical sectional drawing which shows the structure of the light-receiving part and circuit part of the conventional photodetector. It is a schematic diagram explaining the formation method of the opening part in the conventional photodetector. It is a schematic diagram explaining the formation method of the opening part in the conventional photodetector.

Explanation of symbols

50 photodetectors, 52 light receiving parts, 54 circuit parts,
56 PIN photodiode, 58 CMOS, 60 semiconductor substrate,
70 P-sub layer, 72 epitaxial layer, 74 isolation region, 76,104 wiring, 78
Cathode region, 80, 84, 112 silicon oxide film, 82 gate electrode, 86 opening, 90 wiring structure layer, 92 first interlayer insulating film, 94 first Al layer,
96 second interlayer insulating film, 98 second Al layer, 100 third interlayer insulating film,
102, 106 planarization pad, 110 light-shielding Al layer, 114 extended portion,
116 silicon nitride film, 120 polysilicon film,
122, 130 photoresist film, 124 photomask,
126 light receiving pad, 128 superstructure layer, 129 polymer,
132 photomask, 136 aperture, 140,160 reaction chamber, 142 permanent magnet,
144, 162 Upper electrode, 146, 164 Lower electrode,
148,166 High frequency power supply, 150 substrates.

Claims (5)

Forming an upper layer on a substrate having a light receiving portion;
An integrated circuit manufacturing method for opening a region corresponding to the light receiving portion of the upper layer,
Etching the upper layer under a plurality of etching conditions,
The plurality of etching conditions include anisotropic etching,
An integrated circuit manufacturing method comprising performing oxygen plasma treatment after completion of at least one anisotropic etching. The plurality of etching conditions include isotropic etching,
The integrated circuit manufacturing method according to claim 1, wherein oxygen plasma treatment is performed after the anisotropic etching and before the isotropic etching. The upper layer comprises a base layer, a light receiving pad, and an upper structure layer,
3. The method of manufacturing an integrated circuit according to claim 1, wherein a base layer, a light receiving part pad, and an upper structure layer are laminated in this order from the substrate having the light receiving part.   4. The integrated circuit manufacturing method according to claim 3, wherein anisotropic etching, oxygen plasma treatment, or isotropic etching is performed on the light receiving portion pad.   4. The integrated circuit manufacturing method according to claim 3, wherein anisotropic etching, oxygen plasma treatment, and anisotropic etching are performed on the light receiving portion pad.

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