七級衍射光柵結構及其制備方法、晶圓光刻對準方法
【技術領域】
[0001] 本發明涉及集成電路制造技術領域，尤其涉及一種提高晶圓光刻對準的七級衍射 光柵結構及其制備方法，此外本發明還涉及一種晶圓光刻對準方法。
【背景技術】
[0002] 高精度光刻對準是微納器件制作所持續面臨的重要問題，目前常用的精確對準結 構是光柵圖形結構，基于相位光柵原理，當單色探測光垂直入射到該光柵圖形結構時，反射 光在不同角度存在各級衍射光，通過特定光學結構將不同衍射級次光強分離，可以實現遠 小于對準結構尺寸的精確的光柵定位目的。
[0003] 目前集成電路芯片制造公司在193nm光刻過程中比較常用的光柵圖形結構為同時 包含較強第1級衍射光和第7級衍射光的AH74結構。組成該光柵圖形結構的光柵精細結構單 元的俯視圖和側視圖如圖1所示，其中，〇〇指俯視圖，該俯視圖中〇和π表示探測光垂直照射 到該光柵圖形結構時的反射光在同一近鄰高度位置的相位，所謂近鄰高度位置，指光從衍 射結構出射時的近場光學有效高度，通常與光波長量級相當；為便于計算和理解，本發明將 光柵圖形結構的頂層高度位置作為相位監測的近鄰高度位置。01和02是同一光學衍射結構 對應的相位相反的兩種側視圖。由于光學相位0和π是相對值，因此01和02結構所對應的衍 射級次和衍射光強完全相同。
[0004] 圖1所示的ΑΗ74結構的第0、1、2、3、4、5、6、7級衍射光強的晶圓質量WQ分別為： 45.5、25、1.5、2.8、2.4、1、13.3、32.7。可見，其第1級衍射光10為25，第7級衍射光10為32.7。 同時，其最大的衍射光WQ為0級衍射光，由于0級衍射光會干擾其它衍射級次的光強，因此， ΑΗ74結構中較強的0級衍射光會導致其它衍射級次的對比度較低，降低了 ΑΗ74結構的對準 精度。在某些特定光刻工藝過程中，例如刻蝕或化學機械拋光等造成ΑΗ74對準標記發生部 分損壞而導致第7級衍射光強很弱，此時有可能采用第3級和第5級衍射光進行精對準，但是 ΑΗ74的第3和第5級衍射光WQ分別只有2.8和1，不利于在此情形下的光刻對準。在某些應用 條件下，例如在光柵圖形結構上層涂覆高吸光材料涂層時，反射到探測器中的衍射光強將 非常低，甚至無法在探測器中收集到足夠強的衍射光強，在這種情況下，為了實現晶圓對 準，需要在光刻工藝中對覆蓋光柵圖形結構的晶圓頂層高吸收涂層進行部分去除等開孔操 作，從而造成了額外使用一塊掩模版，或必須更換頂層涂層材料等不利影響。
【發明內容】
[0005] 有鑒于此，本發明提供了一種提高光柵衍射光強的七級衍射光柵結構及其制備方 法，以提高光刻對準精度，同時增大光刻時在光柵圖形結構上涂覆材料及其厚度的可選擇 范圍，從而為集成電路向更小技術節點研發和量產提供精確對準保證。
[0006] 此外，本發明還提供了一種晶圓光刻對準方法。
[0007] 為了達到上述發明目的，本發明采用了如下技術方案：
[0008] -種七級衍射光柵結構，包括：
[0009] 晶圓；
[0010] 形成于所述晶圓上的光柵圖形結構；
[0011] 其中，所述光柵圖形結構由一個光柵精細結構單元組成或者由多個光柵精細結構 單元循環排列組成，所述光柵精細結構單元的寬度為一個光柵周期，所述光柵精細結構單 元在寬度方向上等分為28個區域，所述28個區域的每個區域上設置有第一圖形結構1st或 第二圖形結構2nd;
[0012] 所述第一圖形結構1st和第二圖形結構2nd在光柵圖形結構的寬度方向上按照不 同順序排列形成不同的光柵精細結構單元，所述光柵精細結構單元為第一光柵精細結構單 元、第二光柵精細結構單元、第三光柵精細結構單元、第四光柵精細結構單元、第五光柵精 細結構單元、第六光柵精細結構單元或第七光柵精細結構單元；
[0013] 所述第一光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0014] 所述第二光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 1st}；
[0015] 所述第三光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0016] 所述第四光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 1st 1st}；
[0017] 所述第五光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0018] 所述第六光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0019] 所述第七光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0020] 其中，第一圖形結構1st和第二圖形結構2nd在同一近鄰高度位置下的光學相位相 差:π〇
[0021] 可選地，所述晶圓為空白晶圓或者已經制作好前層圖形的晶圓。
[0022] 可選地，所述光柵周期為16微米或者17.6微米。
[0023] 可選地，所述結構還包括：
[0024] 覆蓋在所述光柵圖形結構上的至少一層材料層。
[0025] -種七級衍射光柵結構的制備方法，包括：
[0026]提供晶圓；
[0027] 對所述晶圓進行光刻和刻蝕，以在所述晶圓上形成光柵圖形結構；
[0028] 其中，所述光柵圖形結構由一個光柵精細結構單元組成或者由多個光柵精細結構 單元循環排列組成，所述光柵精細結構單元的寬度為一個光柵周期，所述光柵精細結構單 元在寬度方向上等分為28個區域，所述28個區域的每個區域上分別設置有第一圖形結構 1st或第二圖形結構2nd;
[0029] 所述第一圖形結構1st和第二圖形結構2nd在光柵圖形結構的寬度方向上按照不 同順序排列形成不同的光柵精細結構單元，所述光柵精細結構單元為第一光柵精細結構單 元、第二光柵精細結構單元、第三光柵精細結構單元、第四光柵精細結構單元、第五光柵精 細結構單元、第六光柵精細結構單元或第七光柵精細結構單元；
[0030] 所述第一光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0031] 所述第二光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 1st}；
[0032] 所述第三光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0033] 所述第四光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 1st 1st}；
[0034] 所述第五光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 2nd 2nd 1st lst2nd 2nd 2nd 2nd 2nd 2nd 2nd 1st 2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd}；
[0035] 所述第六光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 1st 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0036] 所述第七光柵精細結構單元的結構為：{1st 1st 1st 1st 1st 1st 1st 1st 1st lst2nd 2nd 1st 1st 2nd 2nd 1st 1st 2nd 2nd 2nd 2nd 2nd 2nd 1st 1st 2nd 2nd}；
[0037] 其中，第一圖形結構1st和第二圖形結構2nd在同一近鄰高度位置下的光學相位