1313931 九、發明說明： 【發明所屬之技術領域】 本發明有關一種影像感測器及其製法，特別是有關一種互補 式金氧半導體電晶體影像感測器及其製法。1313931 IX. Description of the Invention: [Technical Field] The present invention relates to an image sensor and a method of fabricating the same, and more particularly to a complementary MOS transistor image sensor and a method of fabricating the same.
【先前技姻J[Previous marriage J
互補式金氧半導體電晶體影像感測器(CM0S image sensor CIS)和载子偶合裝置（charge_eGUp】e(j deviees，CCDs)都 為普及。 疋t知技射常用來將光轉換為電子訊_光學電路元件，兩 者的應崎㈣很敍，包括有掃郎、攝雜、以及照相機 ，等’但是因為載子偶合裝置受限於價位高以及體積大的問 題所以目則市面上以互補式金氧半導體電晶體影像感測器較 由於互補式錄半導體電晶體影像感測器Complementary MOS transistor image sensor (CIS) image sensor (CIS) and carrier coupling device (charge_eGUp) e (j deviees, CCDs) are popular. 疋t know the technology commonly used to convert light into electronic news _ Optical circuit components, both of which are well-known, including the sweeping, the miscellaneous, and the camera, etc. 'But because the carrier coupling device is limited by the high price and large volume, the market is complementary. The MOS transistor image sensor is more than the complementary recording semiconductor transistor image sensor
請參考第1圖， 第1圖為習知之互補式金氧半導體電晶體 1313931 - (CM〇S)影像感測器(lmage sensor) 100之剖面示意圖。如第j 圖所示，影像感測器100包括一像素陣列區102、一光學專區 (optical black region) 1〇4、及一邏輯區1〇6，分別製作於一半導 體基底11〇上。半導體基底110 &含複數個、淺溝隔離(shall〇w trench isolation) 112以及複數個感光二極體114，各感光二極體 114與至少一相對應之金氧半導體電晶體(未示出）電相連。淺溝 隔離112係用來作為任兩相鄰之感光二極體114之間的絕緣體 私 （insulator)。 一平坦化層116形成於半導體基底n〇上，以覆蓋感光二極 體114與淺溝隔離112，接著於平坦化層116上形成圖案化金 屬層118、120、及122。於圖案化金屬層上形成平坦化層124， 平坦化層124可為多層結構，例如由高密度電漿(Wgh density plasma)方法製得之氧化矽層（簡稱HDP層)與利用電漿增強式 _ 化學氣相沉積方法由乙基正矽酸鹽製得之氧化矽層（簡稱 PETE0S 層（plasma enhanced tetraethyl ortho silicate layer))所組 成。再於平坦化層124上形成保護層(passivation layer) 130，並 沈積頂氧化層132，以防止水氣進入元件區中。 然後，由複數個紅色、綠色、藍色(R/G/B)濾光圖案所構成 彩色濾光陣列（color filter array，CFA) 134位於像素陣列區 102之頂氧化層132上方。一黑色層136位於光學黑區1〇4之 頂氧化層132上方。並於CFA與黑色層之上及之間形成平坦層 1313931 138。並於平坦化層138上方具有複數個微透鏡(micrdens) 140。一頂氧化層142位於最上方，保護微透鏡14〇。位於邏輯 區106的金屬層122則裸露於外部，做為電相連之接合墊。 但是，習知之互補式金氧半導體電晶體影像感測器在製造 時，在製作完成保護層130之後，往往使得感光二極體表面上 具有不少的懸空鍵(dangling bond)，而產生漏電流，亦即暗電流 之問題餐知之解決方式是利用氫氣回火(annealing)之方式， 如第2圖所示之回火步驟131，使氫原子移動至感光二極體之 表面與懸空鍵反應，以鈍化懸空鍵。但是，由於具有遮光用的 圖案化金屬層120，其金屬會與氫氣反應，妨礙懸空鍵的鈍化。 因此，仍會產生許多暗電流。 因此，仍需要一種新穎的影像感測元件之結構及製法以解決 暗電流的問題。 【發明内容】 本發明之一目的係提供一種製造影像感測元件之方法，以製得 具有改善之暗電流之影像感測元件，並且在光學黑區仍具有良好 的遮光效果。 本發明之另一目的係提供一種影像感測元件，其具有較低的暗 電流’並且在光學黑區仍然可具有良好的遮光效果。 1313931 依據本發明之製造影像感測元件之方法包括下列步驟。首 先’ ^供一半導體基底。半導體基底包含有一像素陣列(pixel array)區、一邏輯區、及一光學黑區位於像素陣列區與邏輯區之 間。像素陣列區包括—光感測單元陣列(photo sensing unit array) 及複數個隔離區以隔離各光感測單元。然後’於半導體基底上 形成一第一平坦化層(planarize(i layer)，覆蓋光感測單元陣列。 於位於像素陣列區及邏輯區之第一平坦化層上形成一圖案化金 屬層。於半導體基底上形成一第二平坦層，且第二平坦化層覆 蓋圖案化金屬層。於低於400oC下，於位於光學黑區之第二平 坦化層上形成一光學黑層。於位於像素陣列區之第二平坦層上 形成一彩色濾光陣列。於光學黑層及彩色濾光陣列上形成一第 二平坦層。於第三平坦層上形成複數個微透鏡(micr〇lens)，其 中微透鏡係設置於相對應之彩色濾光陣壯方。最後，移除位 於邏輯區之金屬層上方之各層，以曝露位於邏龍之金屬層以 做為接合塾。 、一像素陣Please refer to FIG. 1 , which is a schematic cross-sectional view of a conventional complementary MOS transistor 1313931 - (CM 〇 S) image sensor (lmage sensor) 100. As shown in FIG. j, the image sensor 100 includes a pixel array region 102, an optical black region 1〇4, and a logic region 1〇6, which are respectively fabricated on the half conductor substrate 11〇. The semiconductor substrate 110 & includes a plurality of, shallow trench isolation 112 and a plurality of photodiodes 114, each of the photodiodes 114 and at least one corresponding MOS transistor (not shown) ) Electrically connected. The shallow trench isolation 112 is used as an insulator between any two adjacent photodiodes 114. A planarization layer 116 is formed over the semiconductor substrate n to cover the photodiode 114 and the shallow trench isolation 112, and then the patterned metal layers 118, 120, and 122 are formed on the planarization layer 116. A planarization layer 124 is formed on the patterned metal layer. The planarization layer 124 may be a multi-layer structure, such as a yttrium oxide layer (HDP layer) prepared by a high-density plasma (Wgh density plasma) method and using plasma enhanced type. _ Chemical vapor deposition method consists of a ruthenium oxide layer (abbreviated as PETO0S layer (plasma enhanced tetraethyl ortho silicate layer). A passivation layer 130 is formed on the planarization layer 124, and a top oxide layer 132 is deposited to prevent moisture from entering the element region. Then, a color filter array (CFA) 134 composed of a plurality of red, green, and blue (R/G/B) filter patterns is disposed above the top oxide layer 132 of the pixel array region 102. A black layer 136 is over the top oxide layer 132 of the optical black region 1〇4. A flat layer 1313931 138 is formed on and between the CFA and the black layer. And there are a plurality of microlenses 140 above the planarization layer 138. A top oxide layer 142 is located at the top to protect the microlens 14〇. The metal layer 122 located in the logic region 106 is exposed to the outside as a bonding pad for electrical connection. However, the conventional complementary MOS transistor image sensor is manufactured, and after the protective layer 130 is completed, the surface of the photosensitive diode is often provided with a plurality of dangling bonds to generate leakage current. The problem of dark current is solved by means of hydrogen annealing, such as the tempering step 131 shown in Fig. 2, to move the hydrogen atoms to the surface of the photosensitive diode and react with the dangling bond. To passivate the dangling key. However, since the patterned metal layer 120 for light shielding has a metal which reacts with hydrogen gas, it hinders the passivation of the dangling bonds. Therefore, many dark currents are still generated. Therefore, there is still a need for a novel image sensing element structure and method to address the problem of dark current. SUMMARY OF THE INVENTION One object of the present invention is to provide a method of fabricating an image sensing element to produce an image sensing element having improved dark current and still have a good light blocking effect in the optical black region. Another object of the present invention is to provide an image sensing element that has a lower dark current ' and still has a good light blocking effect in the optical black area. 1313931 A method of making an image sensing element in accordance with the present invention includes the following steps. First, 'for a semiconductor substrate. The semiconductor substrate includes a pixel array region, a logic region, and an optical black region between the pixel array region and the logic region. The pixel array region includes a photo sensing unit array and a plurality of isolation regions to isolate the respective photo sensing units. Then, a first planarization layer is formed on the semiconductor substrate to cover the photo sensing unit array. A patterned metal layer is formed on the first planarization layer located in the pixel array region and the logic region. Forming a second planarization layer on the semiconductor substrate, and the second planarization layer covers the patterned metal layer. Form an optical black layer on the second planarization layer on the optical black region below 400 ° C. Forming a color filter array on the second flat layer of the region, forming a second flat layer on the optical black layer and the color filter array, and forming a plurality of microlenses on the third flat layer, wherein the micro-lens The lens system is disposed on the corresponding color filter array. Finally, the layers above the metal layer of the logic area are removed to expose the metal layer located in the logic dragon as a joint 塾.
化層上’及一光學黑層位於第二平垣化層上 依據本發明之影像感測元件，包括一半導體基底 列區、一邏輯區、及一光學黑區。傻去睡me# 1313931 依據本發明之製造影像感測元件之方法，於光學黑區並不形成 如習知技術所使用之遮光金屬層，而是在形成保護層之後及形成 衫色濾光陣列之前，形成-含有金屬之光學黑層，具有良好遮光 政果。因此於回火以純化懸空鍵之製程中，由於沒有習知之遮光 金屬層的阻礙，能夠使光學黑區的懸空鍵鈍化更多，而且，在此 之後可於較低溫度下以包括金屬之材料製作光學黑層，以製得具 有改善之暗電流之影像感測元件。 【實施方式】 請參閱第3圖，第3圖顯示依據本發明之影像感測元件 2〇〇。影像感測元件200包括一半導體基底21〇、一像素陣列區 202、一邏輯區206、及一光學黑區204。像素陣列區202係位 於半導體基底210上，包括一光感測單元陣列2丨4。邏輯區2〇6 係位於半導體基底21〇上，包括周邊電路。光學黑區2〇4係位 於半導體基底上之像素陣列區202與邏輯區2〇6之間，包括一 光感測單元215位於半導體基底21〇上、一第一平坦化層216 位於光感測單元215上、一第二平坦化層224位於第一平坦化 層216上' 及一光學黑層236位於第二平坦化層224上。 值得注意的是，光學黑層236包括一於低溫(例如小於4〇〇〇c) 下製得之金屬層。此金屬層可包括鈦，或是鈦與鈦氮化物之組 1313931 依據本發明之方法製得之影像感測元件具有相對較低之暗 電流。請參閱第10至21圖，其顯示影像感測元件上各部位之 暗電流量測結果，縱座標是暗電流的量，以每秒電子數(e/s)來 表示’橫座標是影像感測元件之行編號。 第10至13圖分別顯示習知技術所得之影像感測元件之像素 陣列區、像素陣列區右端之光學黑區、像素陣列區下端之光學 黑區、及影像感測元件右下角之光學黑區之暗電流量測結果。 此影像感測元件於光學黑區使用金屬遮光層，並於製造時，在 ，成金屬遮光層之後，才進行氫氣回火(氫氣：氮氣=Μ : 2〇 (流 夏比)）’以消除懸空鍵。第1G及12圖之曲線於兩邊明顯想起， 顯示在邊緣部位之暗電流大，第U至13圖之曲線顯示於光學 黑區測得之暗電流之值很大，並且像素陣列區與光學黑區之暗 電流值相差大。 第14至17圖分別顯不習知技術所得之影像感測元件之像素 陣列區、像素陣右端之光學黑區、像素陣顺下端之光學 黑區、及影像感測元件右下角之光學黑區之暗電流量測結果。 此影像感測7G件於絲黑區㈣金屬遮光層，並於製造時，在 形成金屬遮光層之後，才進行氫氣回火(使用較高的氫氣漢度， 氫氣.氛氣-2 . 20(流量比)），以消除懸空鍵。第1<4及16圖之 曲線於兩邊仍她起，顯示在邊料位之暗電流仍較大，第15 與17圖之曲線顯示於光學黑區測得之暗電流之值仍在約2〇〇〇 16 1313931 至4000 e/s之多，並且像素陣列區與光學黑區之暗電流值相差大。 第18至21圖分別顯示依據本發明所得之影像感測元件之像 素陣列區、像素陣列區右端之光學黑區、像素陣列區下端之光 學黑區、及影像感測元件右下角之光學黑區之暗電流量測結 果。依據本發明之影像感測元件於光學黑區，於製造時，進行 氫氣回火(氫氣：氮氣=2 : 20 (流量比))以消除懸空鍵時，並不 具有金屬遮光層，因此能去除較多的懸空鍵。圖中顯示測得之 暗電流明顯較習知之技術為小。第18與2G圖之曲線於兩端已 無明顯的翹起，顯示邊緣處的暗電流與其内部的暗電流並無明 顯差別。而如第19至21圖所示，於光學黑區測得之暗電流之 值已降低至約1000至約2〇〇〇 e/s，並且像素陣列區與光學黑區 之暗電流值之相差減少。可知依據本發明之方法所製得之影像 感測元件可具有改善之暗電流。 ^ 以上所述僅為本發明之較佳實施例，凡依本發明申請專利範 圍所做之均等變化與修飾，皆應屬本發明之涵蓋範圍。 【圖式簡單說明】 第1圖為習知之CMOS影像感測器之剖面示意圖。 第2圖顯示習知技術之氫氣回火方法。 第3圖顯示依據本發明之影像感測元件。 第4至9圖顯示依據本發明之影像感測元件之製法。 1313931 第10至21圖顯示習知與依據本發明之影像感測元件上各部位 之暗電流量測結果。 【主要元件符號說明】 100 習知之CMOS影像感測器 200 依據本發明之影像感測元件 102 、 202 像素陣列區 104、204 光學黑區 106 ' 206 邏輯區 110 、 210 半導體基底 112 淺溝隔離 114 感光二極體 116、216 平坦化層 118、120、122、218、222 圖案化金屬層 124 > 224 平坦化層 126、226 HDP層 128、228 PETEOS 層 130 ' 230 保護層 131 回火步驟 132、142、242、244 頂氧化層 134 、 234 彩色濾光陣列 136 ' 236 光學黑層 138 、 238 平坦化層 1313931 140 、 240 微透鏡 212 > 213 隔離區 214 光感測單元陣列 215 光感測單元 231 氫回火 232 氧化層 » 19The image layer and the optical black layer are located on the second planarization layer. The image sensing device according to the present invention comprises a semiconductor substrate region, a logic region, and an optical black region. Stupid to sleep me# 1313931 According to the method of manufacturing an image sensing element of the present invention, the light-shielding metal layer used in the prior art is not formed in the optical black region, but after forming the protective layer and forming the shirt color filter array Previously, the formation of an optical black layer containing metal had a good shading effect. Therefore, in the process of tempering to purify the dangling bonds, since there is no obstruction of the conventional light-shielding metal layer, the dangling bonds of the optical black region can be passivated more, and thereafter, the material including the metal can be used at a lower temperature. An optical black layer is fabricated to produce an image sensing element with improved dark current. [Embodiment] Please refer to Fig. 3, which shows an image sensing element 2 according to the present invention. The image sensing device 200 includes a semiconductor substrate 21, a pixel array region 202, a logic region 206, and an optical black region 204. The pixel array region 202 is located on the semiconductor substrate 210 and includes a photo sensing cell array 2丨4. The logic region 2〇6 is located on the semiconductor substrate 21〇, including peripheral circuits. The optical black area 2〇4 is located between the pixel array area 202 and the logic area 2〇6 on the semiconductor substrate, and includes a photo sensing unit 215 on the semiconductor substrate 21〇, and a first planarization layer 216 in the light sensing. A second planarization layer 224 is disposed on the first planarization layer 216 and an optical black layer 236 is disposed on the second planarization layer 224. It is noted that the optical black layer 236 includes a metal layer produced at a low temperature (e.g., less than 4 〇〇〇 c). The metal layer may comprise titanium or a group of titanium and titanium nitride. 1313931 The image sensing element produced in accordance with the method of the present invention has a relatively low dark current. Please refer to pictures 10 to 21, which show the dark current measurement results of various parts on the image sensing element. The ordinate is the amount of dark current, expressed in electrons per second (e/s). 'The horizontal coordinate is the image sense. The line number of the component. 10 to 13 respectively show the pixel array area of the image sensing element obtained by the prior art, the optical black area at the right end of the pixel array area, the optical black area at the lower end of the pixel array area, and the optical black area of the lower right corner of the image sensing element. Dark current measurement results. The image sensing element uses a metal light-shielding layer in the optical black area, and at the time of manufacture, hydrogen gas tempering (hydrogen: nitrogen=Μ: 2〇 (flow ratio)) is eliminated after the metal light shielding layer is formed. Dangling key. The curves of Figures 1G and 12 are apparent on both sides, showing that the dark current is large at the edge, and the curves of U to 13 show that the dark current measured in the optical black area is large, and the pixel array area and the optical black The dark current values of the zones vary greatly. Figures 14 to 17 show the pixel array area of the image sensing element obtained by the prior art, the optical black area at the right end of the pixel array, the optical black area of the lower end of the pixel array, and the optical black area of the lower right corner of the image sensing element. Dark current measurement results. This image senses 7G parts in the black area (4) metal light-shielding layer, and at the time of manufacture, after the formation of the metal light-shielding layer, hydrogen tempering is performed (using a higher hydrogen gas degree, hydrogen gas atmosphere - 2. 20 ( Flow ratio)) to eliminate dangling keys. The curves of the first <4 and 16 are still on both sides, showing that the dark current at the edge level is still large, and the curves of Figs. 15 and 17 show that the dark current measured in the optical black area is still about 2 〇〇〇16 1313931 to 4000 e/s, and the difference between the dark current values of the pixel array area and the optical black area is large. The figures 18 to 21 respectively show the pixel array area of the image sensing element, the optical black area at the right end of the pixel array area, the optical black area at the lower end of the pixel array area, and the optical black area of the lower right corner of the image sensing element according to the present invention. Dark current measurement results. The image sensing element according to the present invention is subjected to hydrogen tempering (hydrogen: nitrogen = 2:20 (flow ratio)) at the time of manufacture to eliminate the dangling bond, and does not have a metal light shielding layer, so that it can be removed. More dangling keys. The figure shows that the measured dark current is significantly smaller than the conventional technique. The curves of the 18th and 2G graphs have no obvious tilt at both ends, indicating that the dark current at the edges is not significantly different from the dark current inside them. As shown in Figures 19 to 21, the value of the dark current measured in the optical black region has been reduced to about 1000 to about 2 〇〇〇e/s, and the difference between the dark current values of the pixel array region and the optical black region cut back. It is known that the image sensing elements produced in accordance with the method of the present invention can have improved dark current. The above is only the preferred embodiment of the present invention, and all changes and modifications made in accordance with the scope of the present invention should be covered by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a conventional CMOS image sensor. Figure 2 shows a conventional method of hydrogen tempering. Figure 3 shows an image sensing element in accordance with the present invention. Figures 4 through 9 show the fabrication of image sensing elements in accordance with the present invention. 1313931 Figures 10 through 21 show the results of dark current measurements at various locations on conventional image sensing elements in accordance with the present invention. [Major Component Symbol Description] 100 Conventional CMOS Image Sensor 200 Image Sensing Element 102, 202 Pixel Array Region 104, 204 Optical Black Region 106' 206 Logic Region 110, 210 Semiconductor Substrate 112 Shallow Trench Isolation 114 Photodiode 116, 216 planarization layer 118, 120, 122, 218, 222 patterned metal layer 124 > 224 planarization layer 126, 226 HDP layer 128, 228 PETEOS layer 130 ' 230 protective layer 131 tempering step 132 142, 242, 244 top oxide layer 134, 234 color filter array 136 '236 optical black layer 138, 238 planarization layer 1313931 140, 240 microlens 212 > 213 isolation region 214 light sensing unit array 215 light sensing Unit 231 Hydrogen Tempered 232 Oxide Layer » 19