以下，基於本發明之較佳之實施例對本發明進行說明。本發明之濺鍍靶材係含有選自由In、Ga、Zn、Sn及Al所組成之群中之至少1種氧化物者。該氧化物可為銦之氧化物、鎵之氧化物、鋅之氧化物、錫之氧化物或鋁之氧化物中之任1種。或者，該氧化物可為選自由In、Ga、Zn、Sn及Al所組成之群中之任意2種以上之元素之複合氧化物。作為複合氧化物之具體例，可列舉In-Ga氧化物、In-Zn氧化物、Zn-Sn氧化物、In-Ga-Zn氧化物、In-Zn-Sn氧化物、In-Al-Zn氧化物、In-Ga-Zn-Sn氧化物、In-Al-Zn-Sn氧化物等，但不限於該等。本發明之濺鍍靶材較佳為含有選自由In、Ga、Zn、Sn及Al所組成之群中之至少1種氧化物，且不含該等元素以外之過渡金屬元素。 本發明之濺鍍靶材係由含有上述氧化物之燒結體構成。該燒結體及濺鍍靶材之形狀並無特別限制，可採用例如平板模具及圓筒形等先前公知之形狀，但於以下之說明中，列舉作為本發明中效果最大之形狀之氧化物圓筒形燒結體及氧化物圓筒形濺鍍靶材為例。圓筒形以外之形狀之情形時，亦同樣地使用以下之說明。 ＜氧化物圓筒形燒結體＞ 氧化物圓筒形燒結體係含有選自由In、Ga、Zn、Sn及Al所組成之群中之至少1種氧化物之燒結體。氧化物圓筒形燒結體之相對密度未特別限制，相對密度越高，對濺鍍裝置之真空系統之影響越小，而有利於形成良好之薄膜。就該觀點而言，相對密度較佳為90%以上，進而較佳為95%以上，更佳為98.0%以上。相對密度藉由下述之實施例所揭示之方法測定。 ＜氧化物圓筒形濺鍍靶材＞ 氧化物圓筒形濺鍍靶材由上述氧化物圓筒形燒結體構成。氧化物圓筒形濺鍍靶材係藉由對氧化物圓筒形燒結體適當地進行加工而製作。例如藉由進行切削加工等而製作。氧化物圓筒形濺鍍靶材之大小未特別限制，外徑較佳為140 mm以上170 mm以下，內徑較佳為110 mm以上140 mm以下，長度較佳為50 mm以上。長度視用途而適當地確定。 本發明之氧化物圓筒形濺鍍靶材之特徵之一在於抑制作為其中所含之雜質之鐵之混入量。詳細而言，本發明之濺鍍靶材較佳為表面不具有源於鐵之面積1000 μm2
以上之變色部。或者，本發明之濺鍍靶材於表面具有源於鐵之面積1000 μm2
以上之變色部之情形時，其比率較佳為0.02個/1200 cm2
以下。若本發明之濺鍍靶材中混入鐵，則其混入部位呈現與未混入鐵之部位不同之顏色。因此，於本發明中，稱鐵之混入部位為變色部。於濺鍍靶材之表面存在鐵之混入部位之情形時，可藉由外觀觀察確認變色部。就該意義而言，亦將濺鍍靶材之表面所觀察到之變色部稱為「表面變色部」。變色部係由例如Fe2
O3
或Fe3
O4
等鐵之氧化物構成，無論具有何種化學構造，均會給由本發明之濺鍍靶材所製造之TFT之性能帶來不利作用。因此，構成變色部之鐵具有何種化學構造並非本發明中之本質問題，問題在於存在含有鐵之變色部。再者，於本發明中提及「鐵」時，亦包括於合金或氧化物等中作為成分而含有之鐵。 本發明者首次發現：若於本發明之濺鍍靶材中未混入鐵，或即便混入有鐵但其混入量為特定值以下，則可有效地防止使用本發明濺鍍靶材製造之TFT之性能降低。就該觀點而言，濺鍍靶材之表面不具有源於鐵之面積1000 μm2
以上之變色部，或於表面具有源於鐵之面積1000 μm2
以上之變色部之情形時，其比率較佳為0.02個/1200 cm2
以下，進而較佳為0.01個/1200 cm2
以下。變色部之最小面積設為1000 μm2
之理由在於：只要變色部之面積為1000 μm2
以下，則即便於藉由濺鍍而鐵混入膜之情形時，其量亦不影響TFT特性之性能降低。即便於表面具有面積為1000 μm2
以上之變色部之情形時，只要其比率為0.02個/1200 cm2
以下，則有可能存在於濺鍍靶材之內部之鐵之混入量充分少，即便藉由濺鍍而鐵混入膜，其量亦不影響TFT特性之性能降低。 濺鍍靶材上之變色部之特定及個數之計測係藉由目視觀察外表面而進行，其面積之測定係使用可計測刻度之microscope等顯微鏡進行測定。關於用以使濺鍍靶材不具有變色部之方法、或者即便具有變色部，亦將其量抑制於特定值以下之方法，於下文進行敍述。 ＜氧化物圓筒形濺鍍靶＞ 藉由利用接合材將上述氧化物圓筒形濺鍍靶材接合於基材，可獲得氧化物圓筒形濺鍍靶。基材通常具有可接合圓筒形濺鍍靶材之圓筒形狀。基材之種類並無特別限制，可適當地選擇使用先前所使用之基材。作為基材之材料，例如可列舉不鏽鋼、鈦及銅等。接合材之種類亦無特別限制，可適當地選擇使用先前所使用之接合材。作為接合材，例如可列舉銦製焊料等。 氧化物圓筒形濺鍍靶材可於1根基材之外側接合1根，亦可於同一軸線上並排接合2根以上。於並排接合2根以上之情形時，各氧化物圓筒形濺鍍靶材間之間隙即分割部之長度通常為0.05 mm以上0.5 mm以下。分割部之長度越短，濺鍍時越難以產生電弧，但於未滿0.05 mm之情形時，存在因接合步驟或濺鍍中之熱膨脹而導致靶材彼此碰撞、破碎之情況。基材及氧化物圓筒形濺鍍靶材之接合方法亦無特別限制，可採用與先前所知之方法相同之方法。 ＜氧化物圓筒形燒結體之製造方法＞ 氧化物圓筒形燒結體較佳為藉由包括將原料粉末粉碎、分級及混合之步驟之方法而製造。於該步驟之任一階段中，均有可能混入作為雜質之鐵。詳細而言，鐵於上述粉碎、分級及混合中之至少一個步驟中混入或原本含於原料粉末。無論因何種理由而混入時，有利的是進行由磁鐵吸引去除鐵之磁選。再者，於本發明中，「磁選」係指去除鐵等附著於磁鐵之雜質之步驟。藉由進行磁選，不僅限於鐵，當然亦可去除Ni及其合金或氧化物、Co及其合金或氧化物等附著於磁鐵之其他雜質。 本製造方法亦可包括製作含有上述原料粉末及有機添加物之漿料之步驟。或者，本製造方法亦可包括製作含有磁選後之上述原料粉末及有機添加物之漿料之步驟。於任一情形時，有利的是進行由磁鐵吸引去除含於漿料中之鐵之磁選。又，本製造方法亦可包括由磁選前之上述漿料或磁選後之上述漿料製造造粒粉之步驟，於該情形時，有利的是對所製造之造粒粉進行磁選，由磁鐵吸引去除鐵。 於本製造方法中，較佳為自準備原料粉末至成形氧化物圓筒形成形體之步驟之間實施至少1次藉由磁力之磁選。具體而言，例如可列舉如下等： (A)原料粉末之磁選； (B)於包括實施將原料粉末粉碎、分級、混合等處理之步驟之情形時，處理後之粉末之磁選； (C)於包括製作含有原料粉末及有機添加物之漿料之步驟之情形時，漿料之磁選； (D)於包括由上述漿料製造造粒粉之步驟之情形時，造粒粉之磁選。於上述中，特佳為進行(C)漿料之磁選。如漿料般以分散於溶劑之狀態實施磁選時，所含有之鐵易於靠近磁鐵，磁選效率較高而有利。於對漿料進行磁選之情形時，漿料之黏度較佳為於磁選時之溫度下為200 mPa・s以下。若漿料之黏度超過200 mPa・s，則存在漿料難以通過磁選機之情況，又，存在含於漿料之鐵難以靠近磁鐵之傾向。由於以上之理由，漿料之黏度進而較佳為100 mPa・s以下，特佳為80 mPa・s以下。漿料之黏度之下限值未特別規定，但通常為1 mPa・s以上。 又，各步驟中之磁選次數並不限定於1次。例如進而對實施過磁選之漿料進行磁選等，實施複數次磁選，藉此可提高磁選效率，故而有利。 氧化物圓筒形燒結體可根據以下所述之方法有效率地製造。然而，氧化物圓筒形燒結體之製造方法除上述關於磁選之製造條件外無特別限制，並不限定於以下所述之製造方法。氧化物圓筒形燒結體之製造方法中之較佳之態樣包括：步驟1，其係由含有原料粉末及有機添加物之漿料製造造粒粉；步驟2，其係對上述造粒粉進行CIP(Cold Isostatic Pressing，冷均壓)成形而製作圓筒形成形體；步驟3，其係對上述成形體進行脫脂；及步驟4，其係煅燒上述脫脂後之成形體。以下，說明各個步驟。 ＜步驟1＞ 於步驟1中，由含有原料粉末及有機添加物之漿料製造造粒粉。作為原料粉末，例如可使用In2
O3
粉末、Ga2
O3
粉末、ZnO粉末、SnO2
粉末及Al2
O3
粉末中之任1種或任意2種以上之粉末之混合粉末。於使用混合粉末之情形時，各粉末之混合比率係根據本氧化物圓筒形燒結體中之構成元素之含量而適當地確定。例如，於最終所獲得之燒結體以原子比計為In：Ga：Zn：O＝1：1：1：4之情形時，以燒結體中之In、Ga、Zn、O之含量以原子比計成為1：1：1：4之方式，確定含於原料粉末之各原料粉末之比率。又，可單獨使用已預先反應、固溶之粉末，於該情形時，例如最終所獲得之燒結體以原子比計為In：Ga：Zn：O＝1：1：1：4時，可單獨使用含量以原子比計為In：Ga：Zn：O＝1：1：1：4之IGZO粉末。於本製造方法中，原料粉末中之各元素之比率可視為與最終所獲得之燒結體及靶材中之各元素之比率相同。 於本發明中，供於製造造粒粉之上述氧化物粉末之混合粉末亦稱為「原料粉末」。或者，於單獨使用上述氧化物粉末之情形時，將該單獨粉末亦稱為「原料粉末」。In2
O3
粉末、Ga2
O3
粉末、ZnO粉末、SnO2
粉末及Al2
O3
粉末中之任意2種以上組合而成之混合粉末及單獨粉末之由BET(Brunauer-Emmett-Teller，布厄特)法測定出之比表面積分別通常為1 m2
/g以上40 m2
/g以下。 於使用混合粉末作為原料粉末之情形時，各氧化物粉末之混合方法無特別限制，例如，可將各氧化物粉末及氧化鋯球放入坩堝進行球磨機混合。由球磨機進行混合後，藉由篩將氧化鋯球與混合粉末分離。 原料粉末可使用乾式磁選機(例如日本Magnetic股份有限公司製之CG-150HHH)而交付至磁選處理。磁選機之磁力越強，可越有效地去除鐵。鐵混入之一個原因係用於裝置或器具之不鏽鋼一般而言磁力較低，故而較理想為將磁選機之磁力設定為較強，具體而言，較佳為3000 G以上，更佳為7000 G以上，進而較佳為10000 G以上，如此可更有效地去除鐵。 添加於磁選前或磁選後之原料粉末之有機添加物係用於較佳地調整漿料或成形體之性狀之物質。作為有機添加物，例如可列舉黏合劑、分散劑及塑化劑等。黏合劑係為了於成形體中將原料粉末結合以提高成形體之強度而添加。作為黏合劑，可使用於公知之粉末燒結法中獲得成形體時通常所使用之黏合劑。作為黏合劑，例如可列舉聚乙烯醇。分散劑係為了提高漿料中之原料粉末之分散性而添加。作為分散劑，例如可列舉聚羧酸銨、聚丙烯酸銨等。塑化劑係為了提高成形體之可塑性而添加。作為塑化劑，例如可列舉聚乙二醇(PEG)及乙二醇(EG)等。 製作含有原料粉末及有機添加物之漿料時所使用之分散介質無特別限制，可根據目的，自水及醇等水溶性有機溶劑中適當地選擇使用。製作含有原料粉末及有機添加物之漿料之方法無特別限制，例如可使用將原料粉末、有機添加物、分散介質及氧化鋯球放入坩堝進行球磨機混合之方法。 已製作之漿料可使用濕式磁選機(例如日本Magnetic股份有限公司製之磁力濾器)而交付至磁選處理。關於磁力，可採用與先前所述之利用乾式磁選機對原料粉末進行磁選時相同之條件。 使用磁選前或磁選後之漿料製造造粒粉之方法無特別限制。例如可使用噴霧乾燥法、滾動造粒法、擠出造粒法等。該等中，就造粒粉之流動性較高，易於製造成形時易於壓碎之造粒粉等方面而言，較佳為使用噴霧乾燥法。噴霧乾燥法之條件無特別限制，可適當地選擇通常用於原料粉末之造粒之條件而實施。 藉由造粒而獲得之造粒粉可使用乾式磁選機(例如日本Magnetic股份有限公司製之CG-150HHH)而交付至磁選處理。關於磁力，可採用與先前所述之藉由乾式磁選機對原料粉末進行磁選及藉由濕式磁選機對漿料進行磁選時相同之條件。 ＜步驟2＞ 於步驟2中，對步驟1所獲得之顆粒進行CIP成形(冷均壓成形)製作圓筒形成形體。CIP成形時之壓力通常為800 kgf/cm2
以上。壓力越高，可獲得越緻密之成形體，藉此可使成形體高密度化及高強度化。 ＜步驟3＞ 於步驟3中，對步驟2所製作之成形體進行脫脂。脫脂一般而言藉由加熱成形體而進行。脫脂溫度通常較佳為600℃以上800℃以下，進而較佳為700℃以上800℃以下，更佳為750℃以上800℃以下。脫脂溫度越高，成形體之強度越高，但若超過800℃則存在發生成形體之收縮之情況，故而較佳為於800℃以下進行脫脂。 ＜步驟4＞ 於步驟4即煅燒步驟中，煅燒步驟3所脫脂之成形體。用於煅燒之煅燒爐無特別限制，可使用先前用於氧化物燒結體之製造之煅燒爐。煅燒溫度通常較佳為1300℃以上1700℃以下。煅燒時間以煅燒溫度為該範圍內為條件，通常為3小時以上30小時以下。煅燒環境通常為大氣或氧氣環境。 藉由對由以上步驟而製造出之氧化物圓筒形燒結體實施切削加工等，可獲得濺鍍靶材。藉由將該濺鍍靶材接合於基材可獲得濺鍍靶。如此獲得之濺鍍靶較佳地用於氧化物半導體之製造。關於該濺鍍靶，鐵之混入得以抑制，由此，使用該濺鍍靶而製造之氧化物半導體之特性不易受損。因此，藉由使用該濺鍍靶，可提高氧化物半導體元件之製造良率。 實施例 以下，藉由實施例進而詳細地說明本發明。然而，本發明之範圍並不限於該實施例。 以下所述之實施例及比較例中所獲得之氧化物燒結體之評價方法如下所示。 1.相對密度 氧化物燒結體之相對密度係基於阿基米德法而測定。具體而言，用體積(氧化物燒結體之水中質量/計測溫度下之水比重)除以氧化物燒結體之空中質量，將相對於基於下式(1)之理論密度ρ(g/cm3
)之百分比之值設為相對密度(單位：%)。 式(1)中，C1
～Ci
分別表示燒結體之結構物質之以氧化物換算之含量(質量%)，ρ1
～ρi
表示對應於C1
～Ci
之結構物質之氧化物之密度(g/cm3
)。 [式1]2.漿料之黏度 採取通過磁選機前之漿料而測定漿料之黏度。漿料之黏度使用螺旋黏度計(MALCOM股份有限公司製之PC-10C)測定。 3.由鐵形成之表面變色部 於氧化物燒結體中混入鐵，鐵露出於靶表面之情形時，含有鐵之部分被氧化而變紅。並非全部鐵析出於氧化物表面，但於本發明中將出現於表面之變色部之比率作為標準，而作為所混入之鐵之量之相對評價。關於變色部，藉由目視確認於靶表面1 m2
中產生幾處面積1000 μm2
以上之變色部。 ＜實施例1＞ 將藉由BET法測定之比表面積均為5 m2
/g之In2
O3
粉末、Ga2
O3
粉末、ZnO粉末以In：Ga：Zn：O之原子比成為1：1：1：4之方式調配，而獲得混合粉末。將該混合粉末於坩堝中藉由氧化鋯球進行球磨機混合，製作IGZO原料粉末。 藉由球磨機混合後，利用篩而分離氧化鋯球及原料粉末，使用乾式磁選機將原料粉末交付至磁選處理(12000 G)。於交付至磁選處理後之原料粉末中添加相對於該原料粉末為0.3質量%之聚乙烯醇(黏合劑)、0.5質量%之聚羧酸銨(分散劑)、0.3質量%之聚乙二醇(塑化劑)及50質量%之水(分散介質)，進行球磨機混合而製作漿料。漿料之黏度為200 mPa・s以下。 使用濕式磁選機將該漿料交付至磁選處理(10000 G)。其後，將漿料供給於噴霧乾燥裝置，於霧化轉數14000 rpm、入口溫度200℃、出口溫度80℃之條件下進行噴霧乾燥，製造造粒粉。使用乾式磁選機將所製造出之造粒粉交付至磁選處理(12000 G)。 使磁選處理後之造粒粉一面振實一面填充於圓筒形狀之胺基甲酸乙酯橡膠模具。胺基甲酸乙酯橡膠模具之內徑為225 mm(壁厚10 mm)，長度為400 mm，且內部配置有外徑150 mm之圓柱狀之芯(心軸)。將胺基甲酸乙酯橡膠模具密閉後，以800 kgf/cm2
之壓力進行CIP成形，製造圓筒形成形體。 其次，對成形體進行加熱脫脂。脫脂溫度為600℃，脫脂時間為10小時，升溫速度為20℃/h。於煅燒溫度1500℃、煅燒時間12小時、升溫速度300℃/h之條件下煅燒脫脂過之成形體。環境設為大氣。煅燒結束後，於50℃/h之降溫速度下冷卻所獲得之煅燒物。 如此獲得之燒結體之相對密度為99.7%。對所獲得之燒結體進行切削加工，獲得外徑153 mm、內徑135 mm、長度250 mm之IGZO圓筒形濺鍍靶材。切削加工係藉由如下操作進行，即，使用磨石加工外徑，由治具保持外徑而對內徑進行加工之後，由治具保持內徑進行外徑之精加工。如此，製造100根IGZO圓筒形濺鍍靶材，藉由目視觀察外表面，結果面積1000 μm2
以上之表面變色部之產生為0個/1200 cm2
。製造條件及表面變色部之產生率之結果示於以下之表1。 使用銦作為接合材將所製造出之IGZO圓筒形濺鍍靶材接合於鈦製基材，獲得不存在1000 μm2
以上之表面變色部之IGZO圓筒形濺鍍靶。 ＜實施例2＞ 除未將原料粉末交付至磁選處理以外，以與實施例1相同之方法製造IGZO圓筒形濺鍍靶材。關於該濺鍍靶材，進行與實施例1相同之評價。其結果示於表1。 ＜實施例3＞ 除未將原料粉末及漿料交付至磁選處理以外，以與實施例1相同之方法製造IGZO圓筒形濺鍍靶材。關於該濺鍍靶材，進行與實施例1相同之評價。其結果示於表1。 所製造之IGZO圓筒形濺鍍靶材中，使用銦作為接合材將不存在1000 μm2
以上之表面變色部之靶材接合於鈦製基材，獲得不存在1000 μm2
以上之表面變色部之IGZO圓筒形濺鍍靶。 ＜實施例4＞ 除未將原料粉末及造粒粉交付至磁選處理以外，以與實施例1相同之方法製造IGZO圓筒形濺鍍靶材。關於該濺鍍靶材，進行與實施例1相同之評價。其結果示於表1。 ＜實施例5＞ 除未將漿料及造粒粉交付至磁選處理以外，以與實施例1相同之方法製造IGZO圓筒形濺鍍靶材。關於該濺鍍靶材，進行與實施例1相同之評價。其結果示於表1。 ＜比較例1＞ 除完全不進行磁選處理以外，以與實施例1相同之方法製造IGZO圓筒形濺鍍靶材。關於該濺鍍靶材，進行與實施例1相同之評價。其結果示於表1。 [表1]
由表1所示之結果表明：交付至磁選處理過之各實施例之濺鍍靶材之源於鐵之表面變色部之量非常少，相對於此，未進行磁選而獲得之比較例1之濺鍍靶材，觀察到源於鐵之表面變色部多於各實施例。 [產業上之可利用性] 藉由本發明，可防止薄膜中混入鐵，可提高氧化物半導體元件之製造良率。Hereinafter, the present invention will be described based on preferred embodiments of the present invention. The sputtering target of the present invention contains at least one oxide selected from the group consisting of In, Ga, Zn, Sn, and Al. The oxide may be any one of an oxide of indium, an oxide of gallium, an oxide of zinc, an oxide of tin, or an oxide of aluminum. Alternatively, the oxide may be a composite oxide of any two or more elements selected from the group consisting of In, Ga, Zn, Sn, and Al. Specific examples of the composite oxide include In-Ga oxide, In-Zn oxide, Zn-Sn oxide, In-Ga-Zn oxide, In-Zn-Sn oxide, and In-Al-Zn oxidation. The material, In-Ga-Zn-Sn oxide, In-Al-Zn-Sn oxide, or the like, but is not limited thereto. The sputtering target of the present invention preferably contains at least one oxide selected from the group consisting of In, Ga, Zn, Sn, and Al, and does not contain transition metal elements other than the elements. The sputtering target of the present invention is composed of a sintered body containing the above oxide. The shape of the sintered body and the sputtering target is not particularly limited, and a conventionally known shape such as a flat plate mold or a cylindrical shape can be used. However, in the following description, the oxide round which is the most effective shape in the present invention is listed. A cylindrical sintered body and an oxide cylindrical sputtering target are exemplified. In the case of a shape other than a cylindrical shape, the following description is also used in the same manner. <Oxide Cylindrical Sintered Body> The oxide cylindrical sintered system contains a sintered body of at least one oxide selected from the group consisting of In, Ga, Zn, Sn, and Al. The relative density of the oxide cylindrical sintered body is not particularly limited, and the higher the relative density, the smaller the influence on the vacuum system of the sputtering apparatus, and it is advantageous to form a good film. From this point of view, the relative density is preferably 90% or more, more preferably 95% or more, and still more preferably 98.0% or more. The relative density was determined by the method disclosed in the examples below. <Oxide Cylindrical Sputtering Target> The oxide cylindrical sputtering target is composed of the above-described oxide cylindrical sintered body. The oxide cylindrical sputtering target is produced by appropriately processing the oxide cylindrical sintered body. For example, it is produced by performing a cutting process or the like. The size of the oxide cylindrical sputtering target is not particularly limited, and the outer diameter is preferably 140 mm or more and 170 mm or less, the inner diameter is preferably 110 mm or more and 140 mm or less, and the length is preferably 50 mm or more. The length is appropriately determined depending on the use. One of the characteristics of the oxide cylindrical sputtering target of the present invention is to suppress the amount of iron mixed as an impurity contained therein. In detail, the sputtering target of the present invention preferably has a color-changing portion whose surface does not have an area of 1000 μm 2 or more derived from iron. Alternatively, when the sputtering target of the present invention has a discolored portion derived from an iron region of 1000 μm 2 or more on the surface, the ratio is preferably 0.02/1200 cm 2 or less. When iron is mixed in the sputtering target of the present invention, the mixed portion exhibits a color different from that of the portion where iron is not mixed. Therefore, in the present invention, the mixed portion of the iron is referred to as a discolored portion. When there is a place where iron is mixed on the surface of the sputtering target, the discolored portion can be confirmed by visual observation. In this sense, the discolored portion observed on the surface of the sputter target is also referred to as a "surface discolored portion". The discolored portion is composed of an oxide of iron such as Fe 2 O 3 or Fe 3 O 4 , and any chemical structure thereof adversely affects the performance of the TFT produced by the sputtering target of the present invention. Therefore, the chemical structure of the iron constituting the discolored portion is not an essential problem in the present invention, and there is a problem in that a discolored portion containing iron is present. In addition, when "iron" is mentioned in the present invention, iron contained as a component in an alloy or an oxide or the like is also included. The present inventors have found for the first time that if iron is not mixed in the sputtering target of the present invention, or if the amount of iron mixed therein is less than or equal to a specific value, the TFT manufactured by using the sputtering target of the present invention can be effectively prevented. Performance is reduced. From this point of view, when the surface of the sputtering target does not have a discolored portion originating from an area of iron of 1000 μm 2 or more, or when the surface has a discolored portion originating from an area of iron of 1000 μm 2 or more, the ratio is higher. Preferably, it is 0.02 / 1200 cm 2 or less, and further preferably 0.01 / 1200 cm 2 or less. Discoloration of minimum area portion is set to 1000 μm 2 in that justification: as long as the portion of the area of discoloration of 1000 μm 2 or less, even when by sputtering in the case of the mixed film of iron in an amount not affect the performance of the TFT characteristics decrease . In other words, when the surface has a discolored portion having an area of 1000 μm 2 or more, if the ratio is 0.02/1200 cm 2 or less, the amount of iron present in the inside of the sputtering target may be sufficiently small, even if it is borrowed. Iron is mixed into the film by sputtering, and the amount thereof does not affect the performance degradation of the TFT characteristics. The measurement of the specific number and the number of the discolored portions on the sputter target is performed by visually observing the outer surface, and the measurement of the area is performed using a microscope such as a microscope capable of measuring the scale. A method for suppressing the sputtering target from having a discolored portion or a method of suppressing the amount of the discoloration portion to a specific value or less is described below. <Oxide Cylindrical Sputtering Target> An oxide cylindrical sputtering target can be obtained by bonding the above-described oxide cylindrical sputtering target to a substrate by using a bonding material. The substrate typically has a cylindrical shape that can engage a cylindrical sputter target. The type of the substrate is not particularly limited, and the substrate previously used can be appropriately selected and used. Examples of the material of the substrate include stainless steel, titanium, copper, and the like. The kind of the bonding material is also not particularly limited, and the bonding material previously used can be appropriately selected and used. As the bonding material, for example, solder made of indium or the like can be cited. The oxide cylindrical sputtering target may be bonded to one outer side of one substrate, or two or more may be joined side by side on the same axis. When two or more are joined side by side, the gap between the respective cylindrical sputtering targets, that is, the length of the divided portion is usually 0.05 mm or more and 0.5 mm or less. The shorter the length of the divided portion, the more difficult it is to generate an arc during sputtering, but when it is less than 0.05 mm, the target collides and breaks due to thermal expansion during the bonding step or sputtering. The joining method of the substrate and the oxide cylindrical sputtering target is also not particularly limited, and the same method as the previously known method can be employed. <Method for Producing Oxide Cylindrical Sintered Body> The oxide cylindrical sintered body is preferably produced by a method including a step of pulverizing, classifying, and mixing the raw material powder. At any stage of this step, it is possible to mix iron as an impurity. In detail, iron is mixed or originally contained in the raw material powder in at least one of the above-described pulverization, classification, and mixing. When it is mixed for any reason, it is advantageous to perform magnetic separation by attracting and removing iron by a magnet. Further, in the present invention, "magnetic separation" means a step of removing impurities such as iron attached to a magnet. By performing magnetic separation, it is not limited to iron, and it is of course possible to remove Ni and its alloys or oxides, Co and its alloys or oxides and other impurities attached to the magnet. The production method may also include the step of producing a slurry containing the above-mentioned raw material powder and organic additive. Alternatively, the production method may include the step of preparing a slurry containing the magnetic material and the organic additive after magnetic separation. In either case, it is advantageous to perform magnetic separation by attraction of the magnet to remove iron contained in the slurry. Further, the production method may further include a step of producing a granulated powder from the slurry before magnetic separation or the slurry after magnetic separation, and in this case, it is advantageous to magnetically select the granulated powder to be produced and attract the magnet. Remove iron. In the present manufacturing method, it is preferred to perform at least one magnetic separation by magnetic force between the steps of preparing the raw material powder and forming the shaped body of the shaped oxide cylinder. Specifically, for example, the following may be mentioned: (A) magnetic separation of the raw material powder; (B) magnetic separation of the treated powder when the step of pulverizing, classifying, mixing, and the like of the raw material powder is carried out; (C) The magnetic separation of the slurry in the case of the step of preparing a slurry containing the raw material powder and the organic additive; (D) the magnetic separation of the granulated powder in the case of the step of producing the granulated powder from the above-mentioned slurry. Among the above, it is particularly preferable to carry out magnetic separation of the (C) slurry. When the magnetic separation is carried out in a state of being dispersed in a solvent as in the case of a slurry, the iron contained therein is likely to be close to the magnet, and the magnetic separation efficiency is high and advantageous. In the case of magnetically selecting the slurry, the viscosity of the slurry is preferably 200 mPa·s or less at the time of magnetic separation. When the viscosity of the slurry exceeds 200 mPa·s, there is a case where it is difficult for the slurry to pass through the magnetic separator, and there is a tendency that iron contained in the slurry hardly approaches the magnet. For the above reasons, the viscosity of the slurry is preferably 100 mPa·s or less, and particularly preferably 80 mPa·s or less. The lower limit of the viscosity of the slurry is not particularly specified, but is usually 1 mPa·s or more. Further, the number of magnetic separations in each step is not limited to one. For example, it is advantageous to perform magnetic separation or the like on the slurry subjected to the magnetic separation to perform a plurality of magnetic separations, whereby the magnetic separation efficiency can be improved. The oxide cylindrical sintered body can be efficiently produced according to the method described below. However, the method for producing the oxide cylindrical sintered body is not particularly limited except for the above-described production conditions for magnetic separation, and is not limited to the production method described below. Preferred aspects of the method for producing an oxide cylindrical sintered body include: Step 1, which is a granulated powder from a slurry containing a raw material powder and an organic additive; and Step 2, which is carried out on the granulated powder. CIP (Cold Isostatic Pressing) is formed to form a cylindrical formed body; Step 3 is to degrease the molded body; and Step 4 is to calcine the above-mentioned degreased molded body. Hereinafter, each step will be described. <Step 1> In the step 1, a granulated powder is produced from a slurry containing a raw material powder and an organic additive. As the raw material powder, for example, a mixed powder of any one or a mixture of two or more kinds of In 2 O 3 powder, Ga 2 O 3 powder, ZnO powder, SnO 2 powder, and Al 2 O 3 powder can be used. In the case of using a mixed powder, the mixing ratio of each powder is appropriately determined depending on the content of the constituent elements in the cylindrical sintered body of the present oxide. For example, in the case where the sintered body finally obtained is In:Ga:Zn:O=1:1:1:4 in atomic ratio, the content of In, Ga, Zn, O in the sintered body is atomic ratio. The ratio of each raw material powder contained in the raw material powder was determined in a manner of 1:1:1:4. Further, a powder which has been previously reacted and solid-solved may be used alone. In this case, for example, when the sintered body finally obtained is in the ratio of In:Ga:Zn:O=1:1:1:4 in atomic ratio, it may be used alone. An IGZO powder having an atomic ratio of In:Ga:Zn:O=1:1:1:4 was used. In the present production method, the ratio of each element in the raw material powder can be regarded as the same as the ratio of each element in the sintered body and the target obtained finally. In the present invention, the mixed powder of the above oxide powder for the production of the granulated powder is also referred to as "raw material powder". Alternatively, when the above oxide powder is used alone, the individual powder is also referred to as "raw material powder". BET (Brunauer-Emmett-Teller, cloth) is a mixture of two or more kinds of In 2 O 3 powder, Ga 2 O 3 powder, ZnO powder, SnO 2 powder, and Al 2 O 3 powder. The specific surface area measured by the Utter method is usually 1 m 2 /g or more and 40 m 2 /g or less. In the case where a mixed powder is used as the raw material powder, the method of mixing the respective oxide powders is not particularly limited. For example, each of the oxide powder and the zirconia balls may be placed in a crucible and mixed in a ball mill. After mixing by a ball mill, the zirconia balls were separated from the mixed powder by a sieve. The raw material powder can be delivered to a magnetic separation treatment using a dry magnetic separator (for example, CG-150HHH manufactured by Japan Magnetic Co., Ltd.). The stronger the magnetic force of the magnetic separator, the more effectively the iron can be removed. One reason why iron is mixed is that the stainless steel used for the device or the appliance is generally low in magnetic force, so it is preferable to set the magnetic force of the magnetic separator to be strong, specifically, preferably more than 3000 G, more preferably 7000 G. The above is further preferably 10000 G or more, so that iron can be removed more effectively. The organic additive added to the raw material powder before or after magnetic separation is used for a substance which preferably adjusts the properties of the slurry or the shaped body. Examples of the organic additive include a binder, a dispersant, and a plasticizer. The binder is added in order to combine the raw material powders in the molded body to increase the strength of the molded body. As the binder, a binder which is usually used in obtaining a molded body in a known powder sintering method can be used. As a binder, polyvinyl alcohol is mentioned, for example. The dispersant is added to increase the dispersibility of the raw material powder in the slurry. Examples of the dispersant include ammonium polycarboxylate and ammonium polyacrylate. The plasticizer is added to increase the plasticity of the molded body. Examples of the plasticizer include polyethylene glycol (PEG) and ethylene glycol (EG). The dispersion medium to be used in the production of the slurry containing the raw material powder and the organic additive is not particularly limited, and may be appropriately selected from water-soluble organic solvents such as water and alcohol depending on the purpose. The method of producing the slurry containing the raw material powder and the organic additive is not particularly limited, and for example, a method in which a raw material powder, an organic additive, a dispersion medium, and a zirconia ball are placed in a crucible and mixed in a ball mill can be used. The prepared slurry can be delivered to a magnetic separation process using a wet magnetic separator (for example, a magnetic filter manufactured by Japan Magnetic Co., Ltd.). Regarding the magnetic force, the same conditions as those previously described for magnetic separation of the raw material powder by the dry magnetic separator can be employed. The method of producing the granulated powder using the slurry before or after the magnetic separation is not particularly limited. For example, a spray drying method, a rolling granulation method, an extrusion granulation method, or the like can be used. Among these, it is preferable to use a spray drying method in terms of high fluidity of the granulated powder and easy production of granulated powder which is easily crushed during molding. The conditions of the spray drying method are not particularly limited, and can be suitably selected by appropriately selecting the conditions for granulation of the raw material powder. The granulated powder obtained by granulation can be delivered to a magnetic separation treatment using a dry magnetic separator (for example, CG-150HHH manufactured by Japan Magnetic Co., Ltd.). As for the magnetic force, the same conditions as those previously described for magnetic separation of the raw material powder by a dry magnetic separator and magnetic separation of the slurry by a wet magnetic separator can be employed. <Step 2> In the step 2, the pellet obtained in the step 1 was subjected to CIP molding (cold pressure equalization molding) to prepare a cylindrical formed body. The pressure at which the CIP is formed is usually 800 kgf/cm 2 or more. The higher the pressure, the denser the molded body can be obtained, whereby the molded body can be made denser and higher in strength. <Step 3> In Step 3, the molded body produced in the step 2 is degreased. Degreasing is generally carried out by heating the shaped body. The degreasing temperature is usually preferably 600 ° C or more and 800 ° C or less, more preferably 700 ° C or more and 800 ° C or less, and still more preferably 750 ° C or more and 800 ° C or less. The higher the degreasing temperature, the higher the strength of the molded body. However, if it exceeds 800 ° C, the formed body shrinks. Therefore, it is preferable to carry out degreasing at 800 ° C or lower. <Step 4> In the step 4, that is, the calcination step, the molded body degreased in the step 3 is calcined. The calciner for calcination is not particularly limited, and a calciner previously used for the production of an oxide sintered body can be used. The calcination temperature is usually preferably 1300 ° C or more and 1700 ° C or less. The calcination time is based on the calcination temperature within the range, and is usually from 3 hours to 30 hours. The calcination environment is usually an atmospheric or oxygen environment. The sputtering target can be obtained by performing a cutting process or the like on the oxide cylindrical sintered body produced by the above steps. A sputtering target can be obtained by bonding the sputtering target to a substrate. The sputtering target thus obtained is preferably used for the production of an oxide semiconductor. With regard to the sputtering target, the incorporation of iron is suppressed, whereby the characteristics of the oxide semiconductor produced by using the sputtering target are not easily impaired. Therefore, by using the sputtering target, the manufacturing yield of the oxide semiconductor device can be improved. EXAMPLES Hereinafter, the present invention will be described in detail by way of examples. However, the scope of the invention is not limited to the embodiment. The evaluation methods of the oxide sintered bodies obtained in the examples and comparative examples described below are as follows. 1. Relative Density The relative density of the oxide sintered body was measured based on the Archimedes method. Specifically, the volume (the mass of the water in the oxide sintered body / the specific gravity of the water at the measured temperature) divided by the air mass of the oxide sintered body will be relative to the theoretical density ρ (g/cm 3 based on the following formula (1) The value of the percentage is set to the relative density (unit: %). In the formula (1), C 1 to C i each represent the content (% by mass) of the structural substance of the sintered body in terms of oxide, and ρ 1 to ρ i represent the oxide of the structural substance corresponding to C 1 to C i . Density (g/cm 3 ). [Formula 1] 2. Viscosity of the slurry The viscosity of the slurry was measured by passing the slurry before the magnetic separator. The viscosity of the slurry was measured using a spiral viscometer (PC-10C manufactured by MALCOM Co., Ltd.). 3. The surface discolored portion formed of iron is mixed with iron in the oxide sintered body, and when iron is exposed on the surface of the target, the portion containing iron is oxidized to become red. Not all of the iron is deposited on the surface of the oxide, but in the present invention, the ratio of the discolored portion appearing on the surface is taken as a standard, and as a relative evaluation of the amount of iron to be mixed. With respect to the discolored portion, it was confirmed by visual observation that a plurality of discolored portions having an area of 1000 μm 2 or more were generated in the target surface of 1 m 2 . <Example 1> In 2 O 3 powder, Ga 2 O 3 powder, and ZnO powder having a specific surface area of 5 m 2 /g as measured by the BET method, the atomic ratio of In:Ga:Zn:O was 1: Mix in a 1:1:4 manner to obtain a mixed powder. The mixed powder was mixed in a crucible by a zirconia ball in a ball mill to prepare an IGZO raw material powder. After mixing by a ball mill, the zirconia balls and the raw material powder were separated by a sieve, and the raw material powder was delivered to a magnetic separation treatment (12000 G) using a dry magnetic separator. To the raw material powder which was delivered to the magnetic separation treatment, 0.3% by mass of polyvinyl alcohol (binder), 0.5% by mass of ammonium polycarboxylate (dispersant), and 0.3% by mass of polyethylene glycol were added to the raw material powder. (Plasticizer) and 50% by mass of water (dispersion medium) were mixed in a ball mill to prepare a slurry. The viscosity of the slurry is 200 mPa·s or less. The slurry was delivered to a magnetic separation process (10000 G) using a wet magnetic separator. Thereafter, the slurry was supplied to a spray drying apparatus, and spray-dried under the conditions of an atomization revolution of 14,000 rpm, an inlet temperature of 200 ° C, and an outlet temperature of 80 ° C to produce a granulated powder. The produced granulated powder was delivered to a magnetic separation process (12000 G) using a dry magnetic separator. The granulated powder after the magnetic separation treatment was filled in a cylindrical shape of a urethane rubber mold while being solidified. The urethane rubber mold has an inner diameter of 225 mm (wall thickness 10 mm), a length of 400 mm, and a cylindrical core (mandrel) with an outer diameter of 150 mm. After the urethane rubber mold was sealed, CIP molding was carried out at a pressure of 800 kgf/cm 2 to produce a cylindrical formed body. Next, the formed body is heated and degreased. The degreasing temperature was 600 ° C, the degreasing time was 10 hours, and the heating rate was 20 ° C / h. The degreased molded body was calcined under the conditions of a calcination temperature of 1500 ° C, a calcination time of 12 hours, and a temperature increase rate of 300 ° C / h. The environment is set to atmosphere. After the completion of the calcination, the obtained calcined product was cooled at a temperature drop rate of 50 ° C / h. The sintered body thus obtained had a relative density of 99.7%. The obtained sintered body was subjected to a cutting process to obtain an IGZO cylindrical sputtering target having an outer diameter of 153 mm, an inner diameter of 135 mm, and a length of 250 mm. The cutting process is performed by machining the outer diameter using a grindstone, and after the inner diameter is processed by the jig holding the outer diameter, the inner diameter of the jig is used to finish the outer diameter. Thus, 100 IGZO cylindrical sputtering targets were produced, and the outer surface was visually observed, and as a result, the surface discoloration portion having an area of 1000 μm 2 or more was generated to be 0/1200 cm 2 . The results of the production conditions and the production rate of the surface discolored portion are shown in Table 1 below. The produced IGZO cylindrical sputtering target was bonded to a titanium substrate using indium as a bonding material to obtain an IGZO cylindrical sputtering target in which no surface discoloration portion of 1000 μm 2 or more was present. <Example 2> An IGZO cylindrical sputtering target was produced in the same manner as in Example 1 except that the raw material powder was not delivered to the magnetic separation treatment. The same evaluation as in Example 1 was carried out on the sputtering target. The results are shown in Table 1. <Example 3> An IGZO cylindrical sputtering target was produced in the same manner as in Example 1 except that the raw material powder and the slurry were not supplied to the magnetic separation treatment. The same evaluation as in Example 1 was carried out on the sputtering target. The results are shown in Table 1. In the manufactured IGZO cylindrical sputtering target, a target having no surface discoloration portion of 1000 μm 2 or more is bonded to a titanium substrate by using indium as a bonding material, and a surface discoloration portion having no more than 1000 μm 2 is obtained. IGZO cylindrical splash target. <Example 4> An IGZO cylindrical sputtering target was produced in the same manner as in Example 1 except that the raw material powder and the granulated powder were not supplied to the magnetic separation treatment. The same evaluation as in Example 1 was carried out on the sputtering target. The results are shown in Table 1. <Example 5> An IGZO cylindrical sputtering target was produced in the same manner as in Example 1 except that the slurry and the granulated powder were not supplied to the magnetic separation treatment. The same evaluation as in Example 1 was carried out on the sputtering target. The results are shown in Table 1. <Comparative Example 1> An IGZO cylindrical sputtering target was produced in the same manner as in Example 1 except that the magnetic separation treatment was not performed at all. The same evaluation as in Example 1 was carried out on the sputtering target. The results are shown in Table 1. [Table 1] The results shown in Table 1 indicate that the amount of the surface discolored portion derived from the surface of the sputter target of each of the magnetically-treated sputtering examples was extremely small, whereas the comparative example 1 obtained without magnetic separation was obtained. When the target was sputtered, it was observed that the surface discoloration portion derived from iron was more than the respective examples. [Industrial Applicability] According to the present invention, iron can be prevented from being mixed into the film, and the production yield of the oxide semiconductor device can be improved.