本文關(guān)鍵詞：高能物理實驗中低噪聲頂層金屬CMOS像素傳感器設(shè)計　出處：《華中師范大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 高能物理實驗 頂層金屬 像素傳感器 低噪聲 模擬讀出 數(shù)字讀出

【摘要】：隨著核物理和粒子物理研究的不斷推進(jìn),以無中微子雙貝塔衰變0vββ和暗物質(zhì)尋找為典型代表的低本底(低事件率、低電荷漂移速率)、低噪聲實驗逐漸成為高能物理領(lǐng)域未來的研究主流和熱點(diǎn)。沒有氣體電荷雪崩增益且以氣體或高壓低溫下的液體為媒介的時間投影室被視為低本底、低噪聲實驗研究的理想探測器。能夠滿足該應(yīng)用需求且具有更高靈敏度的時間、空間及能量分辨率的低噪聲、高密度、大陣列像素傳感器是未來高能物理實驗研究迫切需要的。本文主要研究工作是針對低本底、低噪聲的電荷讀出背景,研究開發(fā)出集直接電荷收集與信號處理于一體的像素傳感器芯片,旨在解決無氣體電荷雪崩增益的時間投影室中直接收集和測量電荷的問題。其具體研究內(nèi)容和創(chuàng)新點(diǎn)體現(xiàn)在如下幾個方面:1.提出了全新的直接電荷收集像素陣列的傳感器結(jié)構(gòu):將芯片最頂層的金屬層開窗成裸露的電極(Topmetal),并在其周圍設(shè)計隔離的同層金屬環(huán)(Guardring)結(jié)構(gòu)。裸露電極用來直接收集電荷,金屬環(huán)與裸露電極之間的電勢差可形成聚焦電場,提高電荷收集效率。用這種傳感器結(jié)構(gòu)設(shè)計的Topmetal-Ⅱ-芯片進(jìn)行了單個Alpha track的物理實驗,結(jié)果表明:該芯片能夠在室溫空氣環(huán)境下,直接觀測到由241Am Alpha電離周圍空氣產(chǎn)生的單條電荷徑跡。并且,在77 K液氮環(huán)境下也觀測到芯片能直接收集電荷。2.解決了模擬讀出過程中行列選擇切換對電荷靈敏放大器(CSA)輸出干擾的關(guān)鍵技術(shù)問題:模擬讀出時行列選擇切換會引入電荷注入導(dǎo)致CSA輸出震蕩,為此,在CSA與行列選擇開關(guān)之間設(shè)計了一級源跟隨電路,有效隔離了電荷注入干擾。通過優(yōu)化單個像素版圖寄生參數(shù),減小了 CSA輸入及反饋電容,增大了電荷轉(zhuǎn)換增益,從而提高了模擬讀出的信噪比。采用該技術(shù)的Topmetal-Ⅱ-芯片在室溫空氣環(huán)境和77 K液氮環(huán)境下的電學(xué)測試結(jié)果表明:模擬讀出工作穩(wěn)定,且等效電荷噪聲(ENC)分別為13.9 e-和12.6 e-。3.提出了片內(nèi)閾值補(bǔ)償方法,提高了像素間閾值電壓的一致性:在像素內(nèi)部增設(shè)數(shù)模轉(zhuǎn)換器(DAC),獨(dú)立補(bǔ)償每個像素的比較器閾值電壓,減小了像素間因CSA輸出噪聲、比較器輸出失調(diào)噪聲以及工藝誤差共同導(dǎo)致的閾值電壓的離散度。Topmetal-Ⅱ-閾值掃描測試結(jié)果表明:采用該補(bǔ)償后,像素陣列閾值電壓基準(zhǔn)電平的離散度減小了 7.5倍,即從35.9mV減小至4.8 mV。且在Topmetal-Ⅱ-的光學(xué)成像實驗中,觀察到了良好的成像效果,從而驗證了數(shù)字讀出通道設(shè)計的正確性。4.提出了通過可調(diào)截止頻率濾波器降低CSA偏置電壓噪聲,從而進(jìn)一步提高信噪比的方法。在Topmetal-Ⅱ-的基礎(chǔ)上,采用此方法設(shè)計了多像素的Topmetal-Ⅱa和單點(diǎn)大像素的Topmetal-S芯片。Topmetal-Ⅱa和Topmetal-S在室溫空氣環(huán)境下的初步電學(xué)測試結(jié)果表明:Topmetal-Ⅱa模擬讀出ENC相比于Topmetal-Ⅱ-減小了 1.5 e-,即從13.9 e-減小至12.4 e-;模擬讀出的直流電平波動噪聲減小了 22%,即從1.2 mV減小至0.936 mV;Topmetal-S模擬讀出ENC為28.7e-,達(dá)到了預(yù)期的30e-以內(nèi)。目前,Topmetal-Ⅱ-芯片已在蘭州重離子加速器和伯克利88-inch回旋加速器上成功實現(xiàn)了無損傷、高位置分辨和高精度時間分辨的束流監(jiān)控系統(tǒng),它即將被應(yīng)用于下一代癌癥治療和加速器儲存環(huán)上的束流監(jiān)控;噪聲更低的Topmetal-Ⅱa芯片將會進(jìn)一步提升該束流監(jiān)控系統(tǒng)的性能;Topmetal-S單顆芯片的電學(xué)測試已近尾聲,由127顆1 mm電極尺寸的Topmetal-S芯片拼成的“正六邊形”大電極陣列正在研發(fā)中,它即將應(yīng)用到Ovββ實驗中。
[Abstract]:With the development of the nuclear physics and particle physics research progresses, the low background in neutrinoless double beta decay of 0V beta and dark matter for the typical (low event rate, low noise, low charge drift rate) has gradually become the field of high energy physics experiment for future research and the mainstream hot spots. No time projection chamber gas charge avalanche in order to gain and gas or high pressure low temperature liquid medium is regarded as a low background, an experimental study on low noise detector. It can meet the application requirements and has a higher sensitivity of the time, space and energy resolution, low noise, high density, high pixel sensor array is the future research of high energy physics experiments urgently need. This paper is mainly aimed at low background charge, low noise readout background, the research and development of a set of direct charge pixel sensor chip collection and signal processing in one, to Direct collection and measurement of charge time projection chamber to solve no gas charge avalanche gain in question. The specific research contents and innovations in the following aspects: 1. proposed a new sensor structure direct charge collection of pixel array chip: the top layer metal window into the bare electrode (Topmetal), the same layer a metal ring around the design and isolation (Guardring) structure. The exposed electrode used to directly collect charge, potential difference between the metal ring and the exposed electrode can be formed by the focusing field, improve the charge collection efficiency. Using this sensor structure design of single chip Topmetal- II - Alpha track physics experiment, the results show that the chip in air environment, directly observed by 241Am Alpha ionization ambient air produced by single charge track. And, in 77 K liquid nitrogen environment also observed chip Direct collection charge.2. solved in the process of selecting analog readout ranks of charge sensitive amplifier (CSA) output: the key technical problems of interference when selecting analog readout ranks will introduce the charge injection to CSA output shocks, therefore, in the CSA and switch between the ranks of a source follower circuit, effectively isolating the charge injection interference. Through the optimization of a single pixel layout parasitic parameters, reduce the CSA input and feedback capacitance, increases the charge conversion gain, thereby improving the analog readout signal-to-noise ratio. By using the technology of Topmetal- II - chip in air at room temperature and liquid nitrogen environment 77 K under the environment of the electrical test results show that the analog readout is stable and, the equivalent noise charge (ENC) proposed threshold compensation method of chip are respectively 13.9 e- and 12.6 e-.3., improve the consistency between pixels within the pixel threshold voltage: department number Analog converter (DAC), the comparator threshold voltage compensation of each pixel independently, reduces pixel for CSA output noise, dispersion of.Topmetal- II - threshold voltage of the comparator output offset noise and process error due to the threshold scan test results show that the compensated pixel array threshold voltage reference level dispersion decreases 7.5 times, the optical imaging experiments from 35.9mV reduced to 4.8 mV. and Topmetal- II - in the observed good imaging effect, which verifies the correctness of the.4. digital readout channel design is put forward through the adjustable cut-off frequency of CSA filter to reduce the noise of bias voltage, so as to further improve the signal-to-noise ratio. Based on Topmetal- - II, designed by the method of Topmetal- multi pixel II A and single pixel Topmetal-S chip.Topmetal- II A and Topmetal-S in air ring Preliminary test results show that the electrical environment: Topmetal- II a analog readout ENC compared to Topmetal- II - reduced by 1.5 e-, from 13.9 e- reduced to 12.4 e-; analog DC level readout noise fluctuation is reduced by 22%, which is reduced from 1.2 mV to 0.936 mV; Topmetal-S ENC analog readout 28.7e-, to achieve the desired the less than 30e-. At present, Topmetal- II - chip has been in Lanzhou heavy ion accelerator and cyclotron Berkeley 88-inch successfully realized no damage, high position resolution and high precision time resolved beam monitoring system, it will be applied to the next generation of cancer treatment and the accelerator storage ring beam monitoring; low noise Topmetal- II A chip will further enhance the beam performance of monitoring system; electrical testing of Topmetal-S single chip is nearing completion, by 127 1 mm hexagon electrode size Topmetal-S chip made " "The large electrode array is being developed, and it will be applied to the Ov beta beta experiment.

【學(xué)位授予單位】：華中師范大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TP212

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相關(guān)期刊論文 前1條

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本文編號：1401478