TW550831B - Photo sensor and method of forming the same - Google Patents

Abstract

A method of forming a photo sensor in a photo diode is provided. The photo diode is formed in a semiconductor wafer. The semiconductor wafer includes a substrate with a first conductive type, and an insulating layer surrounding the photo sensor. A first ion implantation process, utilizing dopants with a second conductive type, is performed to form a plurality of first doped regions in the surface of the photo sensor. A second ion implantation process, utilizing dopants with the second conductive type, is performed to form a second doped region in the surface of the photo sensor. The second doped region is overlapped with a portion of each of the first doped regions.

Description

550831 V. Description of the invention (1) Field of the invention The present invention provides a method for making a light sensing area of a photodiode, in particular a photodiode with better sensing sensitivity to short-wavelength light. Manufacturing method of body light sensing area. Background: Complementary metal-oxide semiconductor (CMOS) image sensors are a common solid-state image sensing device, and CMOS image sensors have gradually replaced carrier coupling devices. (Charge-coupled device, CCD) trend. This is because the CMOS image sensor is manufactured using a traditional semiconductor process, so it has the advantages of lower manufacturing cost and smaller component size. In addition, the C M 0 S image sensor also has high quantum efficiency. And low-noise (read-out noise) and other advantages, it has been widely used in personal computer cameras (PC camera) and digital cameras (digital camera) and other electronic products. A typical CMOS image sensor includes a photodiode to sense the intensity of light, and three metal oxide semiconductor (meta 1-ο X ide semiconductor, MOS) transistors, which are used as reset elements. (reset M0S), current source follower, and row selector. Among them, photodiodes are mainly

550831 V. Description of the invention (2) Process signal data according to the photocurrent generated by the photo-sensing area, for example, the leakage current (Π ight current) generated by the photo-sensing area in the light receiving state represents the signal (si gna 1), The dark current generated by the light sensing area when it is not in the light state represents noise, so the photodiode can use the strength of the signal-to-noise ratio to process the signal data. Please refer to FIG. 1. FIG. 1 is a schematic diagram of a conventional photodiode light-sensing area on a semiconductor wafer. As shown in FIG. 1, the semiconductor wafer 10 includes a Shi Xi substrate 12, a P-type well 14 is located on the Shi Xi substrate 12, and a light sensing area 16 is defined on the surface of the p-type well 14. And a shallow trench isolation (around the photo-sensing area 16) to isolate the photo-sensing area 6 from other electronic components to avoid short circuits.

The province knows that the method of making the light sensing area 6 is to use an ion implantation process to form an _ ion doped area 2 on the surface of the P-type well 14. For example, arsenic (as) is used as the substrate. The setting is about 80 KeV, so that the doped region 20 has an energy pick-up, plant, and degree. However, since the doped region 20 and the P-type well 14 are different: the M center will generate a depleted region (depietión regi〇n) in the PN junction region where the doped region 20 and the P-type well 14 are adjacent to each other. ) 22, as the area where the photodiode is sensed by the pre-polar body. Because the conventional method uses the ancient ^ rv ^ ^ ^ ^ on j, the reductant I and the high-energy arsenic atom are used as the burden to form the doped region 20. Due to the order of t, The doped region 2 is connected to the p-type well 1 4

Page 6 550831 V. Description of the invention (3) The empty area 2 2 formed after the combination will relatively produce a relatively narrow joint width, so that the actual light receiving area of the light sensing area (real active region decreases, even if it pays two) Zone 2 2 reduces the photocurrent that can be sensed when the photodiode is receiving light and reduces the signal-to-noise ratio, thereby weakening the signal sensitivity of the photodiode. In addition, the ion cloth with high energy is planted. The doped region 20 formed by the implantation process also has a relatively deep bonding depth. Therefore, when the photodiode is irradiated with short-wavelength light (such as blue light), the short-wavelength light will affect the Shi Xi wafer. The penetration depth is shallow, which makes the photocurrent that can be sensed by the pN junction area of the photodiode is too small, which causes the photodiode to have poor sensitivity to short-wavelength light. And the ion implantation process with high implantation energy It may also lead to the destruction of the lattice structure on the surface of the doped region 20, which greatly increases the probability of surface recombination of the photocharges, which causes the life time of the photocharges to be seriously attenuated. Responds to the signal sensitivity of the photodiode. SUMMARY OF THE INVENTION The object of the present invention is to provide a method to effectively improve the photodiode. According to the purpose of the present invention, a semiconductor wafer is produced. The signal sensing degree of the sensing area. A preferred embodiment of the invention is to first provide a bread containing a first conductive type

Page 7 550831

^ = The surface of the substrate around the photo-sensing area, ^ = the surface of the photo-sensing area f ", in order to use the second conductive type doped second separation; fabricating f with two or more- Doped region, and then perform sensing on the surface of the sensing region to use the second conductivity type dopant in the light i-doped dlπ-second doped region, and make the second doped region and each of the gains Partial regions of the & are overlapped. Several ΐ: ί ϊ = is formed in the substrate using the first ion implantation process.

Therefore, by increasing the contact area between each of the first doped regions and the soil, the light sensing area of the photodiode can be effectively increased, thereby improving the signal sensitivity of the photodiode. In addition, the first doped region of the present invention overlaps the region above each of the first doped regions. Therefore, the empty H formed by the second doped region and the substrate adjacent to it is disposed adjacent to the surface of the substrate. Position to effectively increase the sensitivity of the photodiode to gray short-wavelength light (such as blue light). Detailed description of the invention Please refer to FIGS. 2 to 5. FIGS. 2 to 5 are schematic diagrams of a method for fabricating a light sensing region of a photodiode on a semiconductor wafer surface according to the present invention. As shown in FIG. 2, the semiconductor wafer 30 includes a P-type substrate 32 and a plurality of insulating layers 38, such as a shallow trench isolation structure, provided on the surface of the p-type substrate 32 to define the position of the light sensing area. . In a preferred embodiment of the present invention, the surface of the P-type substrate 32 further includes a p-type epitaxial silicon layer 34, and an insulating layer.

Page 8 550831 V. Description of the invention (5) There is another P-well 36 under the 8 to use the P-well 36 to prevent the bonding current generated in the light sensing area from spreading to adjacent sensing elements. Causes cross talk. As shown in FIG. 3, a photolithography process is then used to form a photoresist layer 40 on the surface of the P-type substrate 32 to define the positions of a plurality of lightly doped regions in the photo-sensing region. Next, a first ion implantation process is performed, using N-type modification, such as arsenic (As) or phosphorus (P), to dope the P-type substrate 32 to form a plurality of doped regions. 42. After that, the photoresist layer 40 on the surface of the semiconductor wafer 30 is completely removed. As shown in FIG. 4, another photolithography process is next used to form a photoresist layer 4 4 on the surface of the p-type substrate 32 to define a heavy-area position in the light sensing area. Next, using the photoresist layer 44 as a mask, a second hetero-implantation process is performed to form a doped region 46 on the surface of the photo-sensing region, and the doped region 46 overlaps the region above the doped region 42. On the next day, the energy of the two-ion implantation process in the 1 township should be less than that of the first ion-implantation process so that the replacement area 4 6 and the P-type stupid crystal fragment 3 4 can be connected to the hole.

The junction depth between the region 42 and the P-type wormwood layer 34. :: The dopant in the Yupin hybrid cloth planting process can be the same as that used in the first ion cloth planting process, that is, using N-type dopants, such as arsenic atoms or phosphorous shell materials, but the first ion cloth The concentration of the dopant in the planting process is the concentration of the dopant in the planting process.丨 ΉDual ion cloth

550831

As shown in FIG. 5, an annealing process is finally performed to make the doping regions in the doped regions 42 and-46 into the P-type epitaxial silicon layer 34 in the doped regions. 4 2 is adjacent to the P-type epitaxial silicon layer 3 4 and the doped: P-type spar stone layer 3 4 is adjacent to the area to form a plurality of empty regions 4 8 and 70 into the light sensing region. 3 Since the present invention uses the first ion implantation process to form a plurality of doped regions 42 in the p-type epitaxial silicon layer, the p-type epitaxial silicon layer can be connected to the p-type epitaxial silicon layer 3 by adding the doped region 42 The contact area between 4 can effectively increase the sense: the photosensitive area of the body, that is, the area of the empty area, to increase the nine currents and improve the signal sensitivity of the photodiode. In addition, the present invention also provides a doped region 46 on the surface of the γ-type epitaxial silicon layer 34, so that a p-type epitaxial silicon layer 34 adjacent to the γ-type epitaxial silicon layer 34 can be formed under the doped region. The long empty region effectively improves the sensitivity of the photodiode to short-wavelength light (eg, blue light). Furthermore, the doped region 46 is overlaid on the plurality of doped regions 42 due to the photodiode structure of the present invention. Therefore, the doped region 46 can be used as a wire connecting the light sensing region, and each doped region 4 2 can obtain the same voltage. In this way, the doped regions 4 2 on both sides of the empty region 4 8 Having the same voltage 'can therefore make the empty region 48 a completely empty region (ie, an open state), and obtain a capacitance value of approximately zero to increase the light collection region and reduce the dark current. In the case of increasing the photocurrent of the empty region 48 and reducing its capacitance value, the light of the photodiode &

550831 V. Description of the invention (7) The sub conversion gain (photon conversion gain) is also increased to effectively improve the performance of the photodiode. Please refer to FIG. 6. FIG. 6 is a schematic structural diagram of a light-sensing area of a photo-polar body according to another embodiment of the present invention. This embodiment simplifies the production process by integrating the photodiode process and the MOS transistor process. As shown in FIG. 6, a semiconductor wafer 50 includes a P-type substrate 52, a light-sensing region 54 and a logic circuit region 56 disposed on the surface of the P-type substrate 52, and a light-sensing region 54 and a logic circuit. A plurality of insulating layers 62 are provided between the regions 56, such as a shallow trench isolation structure. The light sensing area 54 is used to form a photodiode, and the logic circuit area 56 is used to form a MOS transistor. In order to improve the electrical performance of the photodiode, the present invention may optionally include a P-type stupid stone layer 58 on the P-type substrate 52, and a plurality of p-type wells 60 under the insulating layer 62. The light sensing region 5 4 includes a plurality of lightly doped regions 6 4, a heavily doped region 6 6 covers the surface of the lightly doped region 6 4, and a plurality of p-type epitaxial silicon layers 5 8 adjacent thereto. The empty region 7 2 formed by the N-type dopants in the doped regions 6 4 and 6 6. The logic circuit area 56 includes a gate 68, and a lightly doped drain (LDD) 70 disposed on both sides of the gate 68 in a p-type stupid evening layer 58. It is worth noting that the doped region 66 and the lightly doped drain μ are formed through the same ion implantation process to reduce the destruction of the lattice structure on the surface of the doped region 66 and reduce the surface recombination and leakage of photocharge Current phenomenon, and integrate the process of photodiode and Mos transistor to reduce production

550831

cost. Compared with the complex surface in Xi base and the photosensitive surface of its adjacent polar body, the origin region is located near the short-wavelength light region, so the current can be increased and the photons can be converted into oral cavity. The invention uses the first-several lightly doped regions, so the contact area between the substrates in the graying process can be increased by ^ = the product of each light source is added, and the light sensitive photodiode is added to the light sensitive two light source. Remixing • Flora is superimposed on each rank: i: degree. The position of the substrate surface adjacent to the heavily doped region can effectively increase the photosensitivity; And because each empty area is; = κ the first area and & low leakage current '$ to increase the photoelectric embodiment, all applications according to the present invention should be covered by the patent of the present invention

What has been described above are only equivalent changes and modifications to the scope of the preferred patent scope of the present invention.

550831 Brief description of the diagram Brief description of the diagram Figure 1 shows the structure of the light sensing area of a conventional photodiode. FIG. 2 to FIG. 5 are schematic diagrams of a method for fabricating a light sensing region of a photodiode according to the present invention. FIG. 6 is a schematic structural diagram of a light sensing region of a photodiode according to another embodiment of the present invention. Explanation of symbols in the figure 10 Semiconductor wafer 12 Cutting substrate 14 P-type well 16 Photo-sensing area 18 Shallow trench isolation 20 Doped area 22 Empty area 30 Semiconductor wafer 32 P-type substrate 34 P-type epitaxial silicon layer 36 P-type well 38 Insulating layer 40 Photoresist layer 42 First doped region 44 Photoresist layer 46 Second doped region 48 Empty region 50 Semiconductor wafer 52 P-type substrate 54 Photo-sensing region 56 Logic circuit region 58 P-type epitaxial silicon layer 60 P Well 62 Insulating layer 64 First doped region 66 Second doped region 68 Gate 70 Lightly doped electrode

Claims (1)

550831 VI. Scope of patent application1. A method for manufacturing a light sensing area of a photo diode. The photodiode system is fabricated on a semiconductor wafer, and the semiconductor surface includes There is a substrate of a first conductivity type, and an insulation ^ = on the surface of the substrate and surrounding the photo-sensing area. The method includes the following steps: = 3: ion implantation process, using a second conductive Doping of the type forms a plurality of _ doped regions on the u surface; and the ion implantation process 1 uses the doped surface of the second conductive type to form a second doped region, and the second doped region is combined with a Part of the repair area overlaps. 2. As in the method of claim 1 in the scope of patent application, the dopants of the second doped region and the adjacent doped regions are a plurality of empty regions (depletiQn regiGn). ~ The base phase acts to form a method of 2 t, the first range of the benefit range, wherein the first conductive type + is -N "electrical type, and the second conductive type is a p-type conductive type: It is the first conductive type in method 1 of Λ Fan㈣ item 1. ¥ book type, and the second conductive type is an N-type conductive ^ type For example, the method of applying for the first item of the patent scope, wherein the substrate surface is & 550831 An epitaxial silicon layer is included, and each of the first doped regions and ytterbium are formed in the epitaxial silicon layer. μ-doped region is all: the concentration of dopant concentration of Cheng Danping's conversion process from the first ion implantation process to the second ion implantation process. 6. If the dopant concentration of the process in the patent application range is less than 7. According to the method of the scope of application for patent, the surface further includes a logic circuit area, and at least one lightly doped drain electrode is formed in the second semiconductor wafer table circuit area. The implantation process is based on the logic Drain, LDD) 〇1§htly doped 8 · If the method of applying for the patent in the first paragraph of the dry encirclement method, the fire process, using the refreshing person μ · · ·, the method also includes a human surface application technique ( driving-in) This 箆 -change her impurity in the Guangqi A 播 杂 miscellaneous area 9. If the method of the scope of patent application No. 8 is used, i is open, occupying the first private miscellaneous area in Xixi Each of the empty regions 岣 becomes a completely empty region, and each of the empty regions has a capacitance value of approximately zero to increase the light collection region and reduce the dark current, thereby increasing the photocurrent (ph0). t〇current) and photon conversion gain (photon conve; rsi () ri gair〇. I 〇 Method, wherein the second doped region is used as an electrical wire connected to the light sensing region. II. A method of making a light sensing region of a photodiode, the light sensing Page 15 / 、 The scope of the patent application is set in _ _ and the predetermined area i Step: Perform a stack of several first N-types, perform a first-second N-type temple surface formation to LDD). 1 2 · If you apply for special: Miscellaneous areas and the function of the _ form a plural number / 1 3 · If you apply for special: Flora and each phase, 1 4 .If you apply for a special program; In addition, a stupid crystal is included; > 1 5. If the application is special: the dopant of the process is thick > ^ ^ One of the p-type substrates of the wafer is surrounded by an-insulating layer, the method includes Λ column if daughter body planting 帛, in the predetermined N-type doped regions are formed on the surface of the region; and the semiconductor ion implantation process, the mixed region, is formed on the surface of the pre-region with a knife shape, and the semiconductor is far from a predetermined region. A lightly doped drain (Ughtiy doped drain), which is the first term in the range of interest, and the second one is the choice of the doped region "1, where + each of the first type doped regions is fixed. Part V of the miscellaneous area will be exchanged with the adjacent P-type substrate in the 11th range of the P-type substrate: it is the same as that of the stack. The two N-type substitutions: ΐ ί Γ: ί method, where the p-type substrate On the surface, the method of item 11 of the worm-type doped region and the second v-type profit range is that the pot change is smaller than that of the second ion implantation process. --- 16 Method 11 of the scope of patent application for fire-made osmium, the method 1 also includes-degenerate. Wang, used to drive-in the second N-type doped region ^ No. 1 The method according to item 16 of the patent, " Each of the empty regions formed between each of the adjacent and each N-type doped regions becomes a completely allowable region, and C has a capacitance value of approximately zero, To: add the light collection area * low dark current, and then increase the photocurrent phQt. Current and the photon conversion gain (ph〇t〇ri c〇nvef ⑽ S ai η) ° M: as the scope of the patent application The method according to item 丨 丨, wherein the second N-type doped region is used as an electrical wire connecting the light sensing region. ^ 1 9 · The method according to item 丨 丨 in the scope of patent application, wherein the lightly doped It is set in a logic circuit area. ', 〇, · Light-sensing area of a photosensitive monopole' The photosensitive dipole system is fabricated on a semi-V body wafer, and the surface of the semiconductor wafer includes a first conductive type A substrate, and an insulating layer disposed on a surface of the substrate and surrounding the photo-sensing area, the photo-sensing area comprising The first doped region of the plurality of second conductive types is provided on the surface of the light sensing region, and the second doped region of the first conductive type is provided on the surface of the light sensing region. 550831 6. Scope of patent application And the μ μ < ... > and the adjacent region order and each of the first doped region and the substrate are adjacent to each other, and are disposed below the second doped region and each of the adjacent ones. Each of the empty regions between the first doped regions becomes a completely empty region, and each of the empty regions has a capacitance value of approximately zero to increase the light-collecting region and reduce the dark current ', thereby increasing light. Photo current, photon conversion gain, and sensitivity of the photodiode to blue light. 21. The light-sensing area according to claim 20, wherein a doped well of a first conductivity type is provided below the insulating layer. 22. For example, the light sensing area of item 20 of the patent scope, wherein the second conductive type is an N-type conductive type, and the second conductive type is a p-type electrical type. 23. The light sensing area according to claim 20 of the application, wherein the first conductive type is a P-type conductive type, and the second conductive type is an N-type electric plough type. Photo-sensing area, wherein the substrate surface doped area and the second doped area 24. The photo-sensing as described in the patent application No. 20 further includes a stupid layer, and each of the first doped 550831 six, The scope of patent applications are all formed in the epitaxial silicon layer. 25. The light-sensing region according to item 20 of the application, wherein the dopant concentration of each of the first doped regions is smaller than that of the second doped region. 26. The light-sensing region according to item 20 of the patent application scope, wherein the second doped region is used as an electrical wire connected to the light-sensing region. Page 19