1267136 玖、發明說明 〔發明所屬之技術領域〕 本發明係關於發光二極齡 兀錢體、雷射二極體等元件所使用 之氮化鎵系化合物半導體之齡^ 十寺^乾蝕刻方法，特別是關於使用 反應性電漿之被處理物的乾軸刻方法。 〔先前技術〕 爲了對m-v族化合物材料實施濕餓刻，—般是使用 鹽酸、硫酸、氫氟㈣其等_合液，但減鎵幾乎不溶 解於這些賴中。因此，氮切之類，-般是採用乾蝕 刪不是賴刻來進彳了。其中，使臓應性電漿之乾触刻 ’由於關速度高、實難佳，與其有關硏究開發相當 熱門。 在使用反應性電漿之乾蝕刻方面，反應氣體的組成乃 決定蝕刻速度及品質之重要因素。可應用於氮化鎵半導體 蝕刻之反應氣體，已被報告的有CF4氣體（日本專利特開平 1 - 204425號公報）、CC12F2氣體、cci4氣體、CF4氣體（日 本專利特開平3 - 108779號公報）、BCl3氣體（日本專利特開 平4 - 34929號公報）、SiCyCL的混合氣體（日本專利特開 平8 - 17803號公報）、CL/H2的混合氣體、BCl3/Ar的混合 氣體（Semiconductor Science and Technology，英國，1983 年，8 卷，2 號，pp.310-312)、BCl3/SiCl4 的混合氣體（Applied Physics Letters，64(7)(美國），1994 年 2 月 14 曰，pp.887-888)、SiCl4 氣 體、SiCl4/SiF4 的混合氣體（Applied Physics Letters,63(20)(美 國）,1993 年 11 月 15 日，pp.2777-2779)。 1267136 〔發明內容〕 發明所要解決之誤顆 上述習知方法所使用之反應氣體中，有些容易發生蝕 刻殘渣、蝕刻凹坑而無法獲得平滑的蝕刻面。另一方面， 依據特開平8 - 17803號公報，藉由使用3丨(：14/^2的混合氣 體可解決上述問題而獲得平滑蝕刻面。但，一般使用氯氣 電漿來進行氮化鎵系化合物半導體之乾蝕刻時，當反應室 內的真空度不足的情形，起因於殘留氧、殘留水分或氮化 鎵之結晶缺陷而容易發生蝕刻面之粗糙、蝕刻凹坑。爲止 該現象，在電漿處理前必須使反應室內形成l(T4Pa級的空 真空。 又氮化鎵系化合物半導體，通常是將氮化鎵系化合物 積層在藍寶石基板或氧化鋁基板上來進行蝕刻加工。這時 ，不僅是氮化鎵系化合物層，有時甚至須加工至基板爲止 ，一般而言要蝕刻藍寶石基板或氧化鋁基板般的鋁氧化物 很困難。 本發明係爲解決上述課題而構成者，其目的係提供出 被處理物之乾蝕刻方法，能以低電力面密度的高頻電力進 行蝕刻，不受氮化鎵之結晶缺陷量的影響，能以10_ 3級之 較低真空度（高壓）獲得平滑蝕刻面，且連藍寶石基板或氧化 鋁基板般之鋁氧化物也能蝕刻。 用以解決課顆之丰段 爲了解決上述課題之本發明的被處理物乾餽刻方法， 其特徵在於，係藉由反應氣體所產生之電漿來進行蝕刻， 7 1267136 該反應氣體含有氯氣與化學式CxHyClz(x、y、z爲正整數)所 代表的化合物氣體。 發明之實施形態及效果 本案發明人等發現出，在產生電漿來進行氮化鎵系化 合物半導體的乾蝕刻時，藉由使用氯氣與化學式CxHyClz(x 、y、z爲正整數）所代表的化合物氣體所混合成之反應氣體 ，能以低電力面密度的高頻電力高效率地進行蝕刻，在10 -3Pa級之較低真空度（高壓）下，仍能獲得無粗糙、無殘渣 、無蝕凹坑等之平滑蝕刻面。 如此般，依本發明的方法具備能以低電力面密度的高 頻電力高效率地進行蝕刻之好處。 上述化學式所代表的化合物，可列舉如氯仿（CHC13)、 二氯甲烷（CH2C12)等。其中之氯仿，針對氮化鎵系化合物半 導體之InGaN的蝕刻特別有利。以往藉由與C1反應來除去 In時，由於InCl的昇華溫度爲180°C，故必須以更高溫（例 如200°C左右）來進行蝕刻。相對於此，使用氯仿時，氯仿 的CH基會和In反應，即使在低溫仍能效率良好地進行蝕 刻。又，使用氯仿時，必須考慮所謂氟氯碳化物限制。另 一方面，二氯甲烷則不受氟氯碳化物限制的拘束，而有容 易處理的好處。 又，使用上述反應氣體之蝕刻方法，針對通常使用之 藍寶石基板或氧化鋁基板般之鋁氧化物也能適用。藉由該 方法，在藍寶石基板或氧化鋁基板上，也能獲得無粗糙、 無殘渣、無蝕凹坑等之平滑蝕刻面。又，在蝕刻氮化鎵系 1267136 化合物層後，由於能使用同樣的反應氣體來進一步蝕刻藍 寶石基板或氧化鋁基板，因此該方法針對必須加工至基板 爲止的用途確實是良好的乾蝕刻方法。 用來實施該方法之裝置，包含平行平板電極型、感應 耦合型等各種型式的電漿蝕刻裝置均可採用。在平行平板 電極型的情形，可將上部電極接地，而使下部電極連接至 高頻電源。 〔實施方式〕 (實施例1) 使用氮化鎵系化合物半導體之元件基板，依本發明之 乾餽刻方法進行蝕刻實驗。圖1係槪略顯示該實驗所用之 元件基板的截面構成。該元件基板20，係在藍寶石基板21 上，積層η型GaN層22(厚2.4// m)、具有多重量子井構造 (MQM)之 GaN 活性層 23(厚 0.1//m)、p 型 GaN 層 24(厚 0·2〜0.3/z m)、Si〇2所形成之遮罩層25而構成。 圖2顯示實驗用的電漿蝕刻裝置之槪略構成。該裝置 屬感應耦合型（ICP)，係在密閉的反應室11中設置平板狀的 下部電極12，在反應室11上部（外部）透過石英板Η而設 置激勵線圏15。激勵線圏15爲立體漩渦形（倒龍捲風形）的 線圈，自線圈中央供給高頻電力，使線圈外周之末端接地 。下部電極12亦連接於高頻電源13。 使用該裝置進行以下實驗。首先，在反應室11之下部 電極12上裝載元件基板20，排出反應室11內的空氣，使 反應室內的壓力成爲2xi0_3pa。之後，對反應室11分別 1267136 以 50sccm、5sccm、20sccm 的流量供給 Cl2 氣體、CH2C12 氣 體及Ar氣體，使反應室11內的壓力成爲0.6Pa。接著，對 激勵線圏15供給200W的高頻電力，對下部電極12供給電 力密度爲〇.37W/cm2之高頻電力，以產生反應氣體之電漿 26。藉由該電漿26進行鈾刻之結果，在GaN層係獲得 181nm/分的蝕刻速度。如此般，藉由使用Cl2氣體與CH2C12 氣體所組成之反應氣體，就算在低電力面密度的高頻電力 下仍能進行高效率的蝕刻。 如上述般，進行蝕刻直到從Si02遮罩層25的下面算起 0.5# m爲止的深度後，從反應室11取出元件基板20，以 掃描型電子顯微鏡（SEM)觀察蝕刻面。圖3顯示蝕刻面的影 像。根據該影像看來，相對於Si02遮罩層25的表面，GaN 層的蝕刻面之壁面呈大致垂直，可知係進行高異向性的蝕 刻。又，在GaN層完全看不到粗糙、殘渣、蝕刻凹坑等， 而獲得極爲平滑的蝕刻面。 又，本實施例雖是採用依據ICP之乾蝕刻，但依據RIE 等其他的乾蝕刻方法也能實施本發明。 (實施例2) 使用和實施例1同樣的裝置，對實施例1所用之元件 基板，進行從3丨02層25至藍寶石基板21爲止之乾蝕刻。 首先，在反應室11之下部電極12上裝載元件基板20 ，排出反應室11內的空氣，使反應室內的壓力成爲2X10一 3Pa。之後，對反應室11分別以50sccm、5sccm的流量供給 Cl2氣體、CH2C12氣體，使反應室11內的壓力成爲0.6Pa。 1267136 接著，對激勵線圈15供給200W的高頻電力，對下部電極 12供給電力密度爲0.74W/cm2之高頻電力，以產生反應氣 體之電漿26。藉由該電漿26進行蝕刻之結果，在Si02遮 罩層獲得36nm/分、在GaN層獲得263nm/分、在藍寶石基 板獲得15nm/分的蝕刻速度。 如上述般，進行蝕刻直到從n- GaN層22的下面算起 0.1//m爲止的深度後，從反應室11取出元件基板20，以 掃描型電子顯微鏡（SEM)觀察蝕刻面。圖4顯示蝕刻面的影 像。圖5顯示圖4之藍寶石基板部的過蝕刻狀態之擴大 SEM影像。根據該影像看來，相對於Si02遮罩層25的表面 ，GaN層的蝕刻面之壁面呈大致垂直，可知係進行高異向 性的蝕刻。又，雖然通常藍寶石基板的加工非常困難，但 本實施例中，不僅是GaN層、甚至連藍寶石基板面也完全 看不到粗糙、殘渣、蝕刻凹坑等，而獲得極爲平滑的蝕刻 面。又，就算是針對氧化鋁基板，也能進行和藍寶石基板 同樣的加工。 〔圖式簡單說明〕 (一）圖式部分 圖1係槪略顯示實驗用的元件基板之截面構成。 圖2係顯示實驗用的電漿蝕刻裝置之槪略構成圖。 圖3係顯示藉由實施例1的處理所得之蝕刻面的SEM 影像。 圖4係顯示藉由實施例2的處理所得之蝕刻面的SEM 影像。 11 1267136 圖5係圖4之藍寶石基板部之過蝕刻狀態的擴大SEM 影像。 (二）元件代表符號 20…元件基板 21…藍寶石基板 22…η型GaN層 23…GaN活性層（多重量子井構造） 24…p型GaN層 25…Si〇2遮罩層1267136 玖 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 , , , , , , , , , , , , , , , , , , , , , , , , , , , , , In particular, it relates to a dry axis etching method using a processed object of a reactive plasma. [Prior Art] In order to carry out wet hunting of the m-v compound material, it is generally the use of hydrochloric acid, sulfuric acid, hydrofluoric acid (tetra), etc., but the reduction of gallium is hardly dissolved in these. Therefore, nitrogen cutting, etc., is generally done by dry etching. Among them, the dryness of the coked plasma is very popular because of the high speed and the difficulty of development. In the dry etching using reactive plasma, the composition of the reactive gas is an important factor in determining the etching speed and quality. A reaction gas which can be applied to a gallium nitride semiconductor etching has been reported as a CF4 gas (Japanese Patent Laid-Open No. Hei 1-204425), a CC12F2 gas, a cci4 gas, and a CF4 gas (Japanese Patent Laid-Open No. Hei-3-108779) , BCl3 gas (Japanese Patent Laid-Open No. Hei 4-34929), a mixed gas of SiCyCL (Japanese Patent Laid-Open No. Hei 8-17803), a mixed gas of CL/H2, and a mixed gas of BCl3/Ar (Semiconductor Science and Technology, United Kingdom, 1983, Vol. 8, No. 2, pp. 310-312), Mixed gas of BCl3/SiCl4 (Applied Physics Letters, 64(7) (United States), February 14, 1994, pp. 887-888) , SiCl4 gas, mixed gas of SiCl4/SiF4 (Applied Physics Letters, 63 (20) (United States), November 15, 1993, pp. 2777-2779). 1267136 SUMMARY OF THE INVENTION In the reaction gas used in the above conventional method, some of the reaction gases used in the conventional method are likely to be etched and etched, and a smooth etched surface cannot be obtained. On the other hand, according to Japanese Laid-Open Patent Publication No. Hei 08-17803, a smooth etching surface can be obtained by using a mixed gas of 3 丨 (: 14/^2). However, a chlorine gas plasma is generally used for the GaN system. In the dry etching of a compound semiconductor, when the degree of vacuum in the reaction chamber is insufficient, crystal defects due to residual oxygen, residual moisture, or gallium nitride are likely to occur, and the etching surface is likely to be rough and etched. This phenomenon is in the plasma. Before the treatment, it is necessary to form l (T4Pa-class empty vacuum in the reaction chamber. Further, a gallium nitride-based compound semiconductor is usually formed by laminating a gallium nitride-based compound on a sapphire substrate or an alumina substrate. In this case, not only nitriding is performed. The gallium-based compound layer may be processed to a substrate, and it is generally difficult to etch a sapphire substrate or an aluminum oxide-like aluminum oxide. The present invention has been made to solve the above problems, and its object is to provide The dry etching method of the processed material can be etched with high-frequency power with low power surface density, and is not affected by the amount of crystal defects of gallium nitride, and can be 10_ The lower vacuum (high pressure) of the third stage obtains a smooth etched surface, and the aluminum oxide like the sapphire substrate or the aluminum oxide substrate can be etched. The solution for solving the above problems is solved by the method of solving the problem. The dry matter feeding method is characterized in that etching is performed by a plasma generated by a reaction gas, and the reaction gas contains a compound gas represented by chlorine gas and a chemical formula CxHyClz (x, y, z are positive integers). EMBODIMENT AND EFFECT OF THE INVENTION The inventors of the present invention have found that when a plasma is generated to perform dry etching of a gallium nitride-based compound semiconductor, chlorine gas and a chemical formula CxHyClz (x, y, and z are positive integers) are used. The reaction gas in which the compound gas is mixed can be efficiently etched with high-frequency power having a low power surface density, and at a lower vacuum (high pressure) of 10 -3 Pa, no roughness, no residue, no A smooth etched surface such as an etch pit. Thus, the method according to the present invention has the advantage of being able to efficiently perform high-frequency power with low power surface density. Examples of the compound of the table include chloroform (CHC13), dichloromethane (CH2C12), etc. Among them, chloroform is particularly advantageous for etching of InGaN of a gallium nitride-based compound semiconductor, and conventionally, when In is removed by reaction with C1, Since the sublimation temperature of InCl is 180 ° C, it is necessary to perform etching at a higher temperature (for example, about 200 ° C.) In contrast, when chloroform is used, the CH group of chloroform reacts with In, and it is efficiently performed even at a low temperature. Etching is performed. Further, when chloroform is used, the so-called CFC limitation must be considered. On the other hand, methylene chloride is not restricted by the chlorofluorocarbon limit, and has the advantage of being easy to handle. The etching method can also be applied to an aluminum oxide such as a sapphire substrate or an alumina substrate which is usually used. By this method, a smooth etched surface free from rough, residue-free, etch-free pits or the like can be obtained also on the sapphire substrate or the alumina substrate. Further, after etching the gallium nitride-based 1267136 compound layer, the sapphire substrate or the alumina substrate can be further etched using the same reaction gas. Therefore, this method is a good dry etching method for applications that must be processed to a substrate. The apparatus for carrying out the method can be used in various types of plasma etching apparatuses including a parallel plate electrode type and an inductive coupling type. In the case of a parallel plate electrode type, the upper electrode can be grounded and the lower electrode can be connected to a high frequency power supply. [Embodiment] (Example 1) An etching test was carried out in accordance with the dry feed method of the present invention using an element substrate of a gallium nitride compound semiconductor. Fig. 1 is a schematic view showing the cross-sectional configuration of a component substrate used in the experiment. The element substrate 20 is formed on a sapphire substrate 21, an n-type GaN layer 22 (having a thickness of 2.4/m), a GaN active layer 23 having a multiple quantum well structure (MQM) (thickness 0.1/m), and p-type GaN. The layer 24 (thickness 0·2 to 0.3/zm) and the mask layer 25 formed of Si〇2 are formed. Fig. 2 shows a schematic configuration of a plasma etching apparatus for experiments. This device is an inductive coupling type (ICP) in which a flat-shaped lower electrode 12 is provided in a sealed reaction chamber 11, and an excitation coil 15 is provided through an upper portion (outer) of the reaction chamber 11 through a quartz plate. The excitation coil 15 is a three-dimensional spiral (inverted tornado) coil, and high-frequency power is supplied from the center of the coil to ground the end of the outer circumference of the coil. The lower electrode 12 is also connected to the high frequency power source 13. The following experiment was performed using this device. First, the element substrate 20 is placed on the lower electrode 12 of the reaction chamber 11, and the air in the reaction chamber 11 is discharged to bring the pressure in the reaction chamber to 2 xi0_3pa. Thereafter, Cl2 gas, CH2C12 gas, and Ar gas were supplied to the reaction chamber 11 at a flow rate of 50 sccm, 5 sccm, and 20 sccm, respectively, so that the pressure in the reaction chamber 11 became 0.6 Pa. Next, 200 W of high-frequency power is supplied to the excitation coil 15 and high-frequency power having a power density of 37.37 W/cm 2 is supplied to the lower electrode 12 to generate a plasma 26 of the reaction gas. As a result of the uranium engraving by the plasma 26, an etching rate of 181 nm/min was obtained in the GaN layer. In this way, by using a reaction gas composed of Cl2 gas and CH2C12 gas, high-efficiency etching can be performed even under high-frequency power with low power surface density. As described above, etching was performed until the depth of 0.5 Å from the lower surface of the SiO 2 mask layer 25, and then the element substrate 20 was taken out from the reaction chamber 11, and the etched surface was observed by a scanning electron microscope (SEM). Figure 3 shows the image of the etched surface. According to the image, the wall surface of the etched surface of the GaN layer was substantially perpendicular to the surface of the SiO 2 mask layer 25, and it was found that the etching was performed with high anisotropy. Further, roughness, residue, etching pits, and the like are not observed at all in the GaN layer, and an extremely smooth etching surface is obtained. Further, although the present embodiment employs dry etching in accordance with ICP, the present invention can be carried out in accordance with other dry etching methods such as RIE. (Example 2) Using the same apparatus as in Example 1, the element substrate used in Example 1 was subjected to dry etching from 3 丨 02 layer 25 to sapphire substrate 21. First, the element substrate 20 is placed on the lower electrode 12 of the reaction chamber 11, and the air in the reaction chamber 11 is exhausted to bring the pressure in the reaction chamber to 2 x 10 - 3 Pa. Thereafter, Cl2 gas and CH2C12 gas were supplied to the reaction chamber 11 at a flow rate of 50 sccm and 5 sccm, respectively, so that the pressure in the reaction chamber 11 became 0.6 Pa. 1267136 Next, 200 W of high-frequency power is supplied to the excitation coil 15, and high-frequency power having a power density of 0.74 W/cm 2 is supplied to the lower electrode 12 to generate a plasma 26 of the reaction gas. As a result of etching by the plasma 26, 36 nm/min was obtained in the SiO 2 mask layer, 263 nm/min was obtained in the GaN layer, and an etching rate of 15 nm/min was obtained in the sapphire substrate. As described above, etching was performed until a depth of 0.1 //m from the lower surface of the n-GaN layer 22, and then the element substrate 20 was taken out from the reaction chamber 11, and the etched surface was observed by a scanning electron microscope (SEM). Figure 4 shows an image of the etched surface. Fig. 5 shows an enlarged SEM image of the over-etched state of the sapphire substrate portion of Fig. 4. From the image, the wall surface of the etched surface of the GaN layer was substantially perpendicular to the surface of the SiO 2 mask layer 25, and it was found that etching was performed with high anisotropy. Further, although the processing of the sapphire substrate is generally very difficult, in the present embodiment, not only the GaN layer but also the sapphire substrate surface is completely free from roughness, residue, etching pits, and the like, and an extremely smooth etching surface is obtained. Moreover, even in the case of an alumina substrate, the same processing as that of the sapphire substrate can be performed. [Simplified description of the drawings] (1) Schematic diagram Fig. 1 is a schematic cross-sectional view showing the component substrate for the experiment. Fig. 2 is a schematic block diagram showing a plasma etching apparatus for experiments. 3 is a SEM image showing an etched surface obtained by the treatment of Example 1. 4 is a SEM image showing an etched surface obtained by the treatment of Example 2. 11 1267136 FIG. 5 is an enlarged SEM image of the over-etched state of the sapphire substrate portion of FIG. 4. (2) Component symbol 20... Component substrate 21... Sapphire substrate 22... η-type GaN layer 23... GaN active layer (multiple quantum well structure) 24... p-type GaN layer 25...Si〇2 mask layer
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