200840166 九、發明說明 【發明所屬之技術領域】 本發明係關於注入鎖定式雷射、干涉儀、曝光設備及 裝置製造方法。 【先前技術】 圖 7顯示習知注入鎖定式雷射（見 J.Rahn， ” Feedback stabilization of an i nj e c t i ο η - s e e d e d Nd : Y AG las er”App· Opt ·，24，940(1985))的簡要配置之示意圖。 圖7所示之注入鎖定式雷射採用最小化建立時間的注入鎖 疋式雷射方法。 用於產生脈波光之脈波振盪器Ο —般爲環型以避免頻 譜電洞燒毀的任何影響。PZT支架4裝載脈波振盪器0的 輸出耦合器。PZT控制器（PZT放大器）5準確地驅動 PZT支架4。增益介質3可利用例如，Ti :藍寶石晶體。 以例如Nd : YAG製成之激發光源2可被使用以光束照亮 晶體來激發晶體，使得晶體吸收光束。 種子雷射1係用於注入鎖定之注入式光源，且使用在 一半最大値具有足夠窄的全寬度之單縱向模式光源。自種 子雷射1輸出之種子雷射光被注入脈波振盪器〇，使得其 匹配脈波振盪器0的橫向模式。種子雷射1可使用例如， 外部振盪型半導體雷射。 注入鎖定意指隨著振盪器的光學路徑長度而鎖定注入 振盪器之窄頻帶雷射光的波長。所注入窄頻帶雷射光的光 -4- 200840166 子扮演引起用於最初脈波振盪器的受激射出的部份。此有 助於脈波振盪器同時於窄頻帶集中激發能量。 當脈波振盪器0的光學路徑長度係種子雷射1的振盪 波長的整倍數，注入鎖定的效率是較高且建立時間係最短 。在其它條件下，因爲振盪器產生相對於種子雷射1的損 失，建立時間係長的。 建立時間意指自泵雷射射出直到脈波光振盪的時間。 上述原理被使用於基於建立時間之振盪器控制。 爲檢測建立時間，激發光源光檢器3 2及脈波光光檢 器33被插置在振盪器附近。自光檢器32及33之輸出被 傳送至控制電路3 4。控制電路3 4基於自兩個光檢器3 2及 3 3輸出之信號來計算建立時間，基於建立時間的改變產生 誤差信號，且執行PID濾波用於反饋誤差信號。 所濾波信號被傳送至PZT控制器5。PZT控制器5基 於此信號驅動PZT支架4來控制注入鎖定。 不幸的是，當除了振盪器長度外，因素（例如，泵雷 射強度顫動或指向顫動）改變建立時間時，使用建立時間 之習知控制方法可能產生控制誤差。更壞的是，雜訊是很 可能混合於基於自雷射輸出來計算建立時間之處理電路。 此使其難以產生具有高SN的誤差信號。此產生鎖定控制 誤差，導致諸如強度或波長顫動之雷射特性劣化。 【發明內容】 本發明提供具有良好波長穩定性之注入鎖定式雷射' -5- 200840166 使用該注入鎖定式雷射之干涉儀及曝光設備。 依據本發明的第一形態，提供一種注入鎖定式雷射， 包含：種子雷射；振盪器，自該種子雷射輸出之光的某一 分量注入該振盪器作爲種子雷射光；頻率轉換器，其使自 該種子雷射輸出之該光的另一分量的頻率移位；光檢器， 其檢測藉由合成自該振盪器輸出之光及自該頻率轉換器輸 出之光所獲得的光；及控制器，其基於含於自該光檢器輸 出的信號之差拍信號分量來控制該振盪器的光學路徑長度 〇 依據本發明的第二形態，提供一種注入鎖定式雷射， 包含：種子雷射；振盪器，自該種子雷射輸出之光的某一 分量注入該振盪器作爲種子雷射光；頻率轉換器，其使自 該振盪器輸出之光的頻率移位；光檢器，其檢測藉由合成 自該種子雷射輸出之該光的另一分量及自該頻率轉換器輸 出之光所獲得的光；及控制器，其基於含於自該光檢器輸 出的信號之差拍信號分量來控制該振盪器的光學路徑長度 〇 自示範性實施例的以下說明並參照附圖，本發明的更 多特徵將更爲清楚。 【實施方式】 以下參照附圖將說明本發明的較佳實施例。 〔第一實施例〕 -6 - 200840166 圖1爲顯示依據本發明的第一實施例的注入鎖 射的簡要配置之示意圖。自種子雷射1輸出之光束 藉由半鏡Ml分成兩個光束B2及B3。被半鏡Ml 光束B2係在被鏡M2反射之時注入脈波振盪器〇。 盪器〇較佳地爲環形以避免電洞燃燒的任何影響。 質3被容納於脈波振盪器〇，且可以配置在脈波振 外側的激發光源（泵雷射）2射出之雷射光來照射 〇的內側予以激發。PZT支架4裝載振盪器Ο的輸 鏡Μ 3。包括放大器控制P Z T支架4之P Z T控制器 其可能準確地控制振盪器〇的光學路徑長度。 自種子雷射1輸出且透射穿過半鏡Ml之光束 經由鏡M4及M5導引至作爲轉頻器之聲光調變器 )6。具有頻率fA0M的電壓信號被供應至聲光調變 聲光效應將透射穿過聲光調變器6的光束改變成複 繞射光束。該複數階的這些繞射光束產生nxfA0M ( )的頻移。 來自該複數階的這些繞射光束中，僅第+ 1階 空間地擷取，且藉由纖維耦合器7a耦接至纖維分 的第一輸入端子。例如，纖維分束器8爲偏振保留 型，該型包括兩個輸入端子（第一及第二輸入端子 輸出端子。 以相同方式，自脈波振盪器〇的輸出係藉由半 部份地分束，且藉由纖維耦合器7b耦接至纖維分 的第二輸入端子。 定式雷 B1係 反射之 脈波振 增益介 盪器〇 振盪器 出牵禹合 5。使 B3係 (AOM 器6 〇 數階的 :η :階 光束被 束器8 單模式 )及一 鏡Μ 6 束器8 -7- 200840166 纖維分束器8適於空間地重疊來自種子雷射1及脈波 振盪器Ο之輸出。偏振保留型纖維分束器亦適於最大化兩 個光束間的差拍信號振幅，以及防止由於例如對纖維的應 力改變之偏振的改變。當然，取代纖維分束器，半鏡或類 似物可被使用來重疊光束。 纖維分束器8的輸出端子連接至光檢器9。光檢器9 將自纖維分束器8輸出的光的強度轉換成電信號。因爲纖 維分束器8合成自種子雷射1輸出且經由聲光調變器6移 頻之光及自脈波振盪器Ο輸出的光，自光檢器9輸出之信 號係由以下方程式所給定：200840166 IX. Description of the Invention [Technical Field] The present invention relates to an injection-locked laser, an interferometer, an exposure apparatus, and a device manufacturing method. [Prior Art] Fig. 7 shows a conventional injection-locked laser (see J. Rahn, " Feedback stabilization of an i nj ecti ο η - seeded Nd : Y AG las er" App· Opt ·, 24, 940 (1985) Schematic diagram of a brief configuration. The injection-locked laser shown in Figure 7 employs an injection-locked laser method that minimizes settling time. The pulse wave oscillator used to generate pulsed light is generally ring-shaped to avoid any effects of spectral hole burnout. The PZT bracket 4 is loaded with the output coupler of the pulse oscillator 0. The PZT controller (PZT amplifier) 5 accurately drives the PZT bracket 4. The gain medium 3 can utilize, for example, a Ti: sapphire crystal. The excitation light source 2 made of, for example, Nd:YAG can be used to illuminate the crystal with a light beam to excite the crystal so that the crystal absorbs the light beam. The Seed Laser 1 is used to inject a locked injection source and uses a single longitudinal mode source with a sufficiently narrow full width at half maximum. The seed laser light from the seed laser 1 output is injected into the pulse oscillator 〇 so that it matches the lateral mode of the pulse oscillator 0. The seed laser 1 can use, for example, an external oscillation type semiconductor laser. Injection locking means locking the wavelength of the narrowband laser light injected into the oscillator with the optical path length of the oscillator. The light injected into the narrow-band laser light -4- 200840166 The sub-player causes the stimulated portion for the initial pulse oscillator. This helps the pulse oscillator to simultaneously excite energy in a narrow band. When the optical path length of the pulse oscillator 0 is an integral multiple of the oscillation wavelength of the seed laser 1, the efficiency of the injection locking is higher and the settling time is the shortest. Under other conditions, the settling time is long because the oscillator produces a loss relative to the seed laser 1. Settling time means the time from the pump laser to the pulse wave oscillation. The above principles are used for oscillator control based on settling time. To detect the settling time, the excitation source photodetector 32 and the pulse wave photodetector 33 are interposed near the oscillator. The outputs from the photodetectors 32 and 33 are transmitted to the control circuit 34. The control circuit 34 calculates the settling time based on the signals output from the two photodetectors 3 2 and 3 3, generates an error signal based on the change in the settling time, and performs PID filtering for feeding back the error signal. The filtered signal is transmitted to the PZT controller 5. The PZT controller 5 drives the PZT bracket 4 based on this signal to control the injection lock. Unfortunately, when factors other than the length of the oscillator (e.g., pump laser intensity flicker or pointing flutter) change the settling time, conventional control methods using settling time may produce control errors. Worse, the noise is likely to be mixed with processing circuitry that calculates setup time based on the laser output. This makes it difficult to generate an error signal with a high SN. This produces a lock control error that causes degradation of the laser characteristics such as intensity or wavelength jitter. SUMMARY OF THE INVENTION The present invention provides an injection-locked laser with good wavelength stability. -5- 200840166 Interferometer and exposure apparatus using the injection-locked laser. According to a first aspect of the present invention, there is provided an injection-locked laser comprising: a seed laser; an oscillator, a component of light output from the seed laser being injected into the oscillator as seed laser light; a frequency converter, It shifts the frequency of another component of the light output from the seed laser; a photodetector that detects light obtained by synthesizing light output from the oscillator and light output from the frequency converter; And a controller that controls an optical path length of the oscillator based on a beat signal component of the signal output from the photodetector. According to a second aspect of the present invention, an injection-locked laser is provided, comprising: a seed a laser; a component of the light output from the seed laser is injected into the oscillator as a seed laser; a frequency converter that shifts the frequency of light output from the oscillator; a photodetector Detecting light obtained by synthesizing another component of the light output from the seed laser and light output from the frequency converter; and a controller based on a difference between signals output from the photodetector Oscillator signal component for controlling the optical path length square from the following description of exemplary embodiments with reference to the drawings and, more features of the invention will become apparent. [Embodiment] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. [First Embodiment] -6 - 200840166 Fig. 1 is a schematic view showing a brief configuration of injection locking according to a first embodiment of the present invention. The beam from the output of the seed laser 1 is split into two beams B2 and B3 by a half mirror M1. The half mirror M1 beam B2 is injected into the pulse oscillator 在 while being reflected by the mirror M2. The rafter is preferably annular to avoid any effects of hole burning. The mass 3 is housed in the pulse oscillator 〇, and can be excited by the laser light emitted from the excitation light source (pump laser) 2 disposed outside the pulse wave to illuminate the inside of the erbium. The PZT bracket 4 is loaded with an oscillator Ο of the mirror Μ 3. The P Z T controller including the amplifier control P Z T bracket 4 may accurately control the optical path length of the oscillator 〇. The light beam output from the seed laser 1 and transmitted through the half mirror M1 is guided to the acousto-optic modulator as a frequency converter via the mirrors M4 and M5. A voltage signal having a frequency fA0M is supplied to the acousto-optic modulation. The acousto-optic effect changes the beam transmitted through the acousto-optic modulator 6 into a complexed beam. The diffracted beams of the complex order produce a frequency shift of nxfA0M ( ). Of the diffracted beams from the complex order, only the +1th order space is taken and coupled to the first input terminal of the fiber sub-fiber by the fiber coupler 7a. For example, the fiber splitter 8 is of a polarization-retaining type, which includes two input terminals (first and second input terminal output terminals. In the same manner, the output from the pulse oscillator 系 is divided by half And the fiber coupler 7b is coupled to the second input terminal of the fiber component. The fixed Ray B1 system reflects the pulse wave oscillator and the oscillator 出 oscillator pulls out the coupling 5. The B3 system (AOM 6 〇 Number of steps: η: order beam is bundled by the beam 8 single mode) and a mirror Μ 6 beamer 8 -7- 200840166 The fiber beam splitter 8 is adapted to spatially overlap the output from the seed laser 1 and the pulse oscillator The polarization-retaining fiber splitter is also suitable for maximizing the beat signal amplitude between the two beams and preventing changes in polarization due to, for example, changes in the stress of the fiber. Of course, instead of a fiber splitter, a half mirror or the like It can be used to overlap the light beam. The output terminal of the fiber splitter 8 is connected to the photodetector 9. The photodetector 9 converts the intensity of the light output from the fiber splitter 8 into an electrical signal because the fiber splitter 8 synthesizes From the seed laser 1 output and via the acousto-optic modulator 6 And light from the optical frequency of the pulse wave outputted from the oscillator Ο, the signal output from the photo-detector 9 lines given by the following equation:
Kt) = ISeed + Ipulse(t) +2VIseedIpulse(t) C〇S (27T(^lse - fseed + f·) · t) =工seed + 工〇 exp (—(t / a)2) +2VW〇 exp (-(t / a)2 / 2) cos (2;i(fpulse - fseed + fA0M) . t) ...(1) 其中Iseed係種子雷射強度，Ipulse係脈波振盪器輸出 ，fseed係種子雷射光頻，及fpulse係脈波雷射中央光頻。 以下，由方程式（1 )給定之信號I ( t )將被稱爲差拍信 號。圖2爲解說藉由模擬所獲得之差拍信號I ( t )的圖表 〇 分析器1 0自差拍信號I ( t )擷取誤差信號。分析器 1 0中的過程將被敘述。Kt) = ISeed + Ipulse(t) +2VIseedIpulse(t) C〇S (27T(^lse - fseed + f·) · t) = work seed + work order exp (—(t / a)2) +2VW〇 Exp (-(t / a)2 / 2) cos (2;i(fpulse - fseed + fA0M) . t) (1) where isse seed laser intensity, Ipulse pulse oscillator output, fseed The seed laser light frequency, and the fpulse pulse wave laser central optical frequency. Hereinafter, the signal I(t) given by equation (1) will be referred to as a beat signal. 2 is a graph illustrating the beat signal I(t) obtained by the simulation. The analyzer 10 takes the error signal from the beat signal I(t). The process in analyzer 10 will be described.
首先，分析器10A/D轉換脈波差拍信號I ( t ) 。A/D 轉換較佳地係藉由例如激發光源（泵雷射）2的Q開關時 -8- 200840166 序來觸發。基於後續FFT (快速傅立葉轉換）過程取樣數 較佳爲2n。 接著，分析器1 〇分析差拍信號I ( t )的頻率。分析 器1 〇執行差拍信號I ( t )的FFT。方程式（1 )被傅立葉 轉換成以下方程式z 1(f) = aV7i(I0 θχρΗβπί)2) +V2IseedI7 exp(~2(a^f - (^ulse - fseed + fA〇M) ) )2)) 圖3例示由方程式（2 )給定之傅立葉轉換。顯而易 知地如自方程式（2 ) ，fA0M周圍的頻譜顯示來自脈波振 盪器〇的脈波光及來自種子雷射1的光之間的頻差。爲自 脈波振盪器〇擷取脈波光的頻率資訊，AOM6的調頻fA0M (頻移量）必須是足夠地大於脈波光的頻譜寬度。 分析器1 〇計算頻譜的加權平均。因爲以下理由，分 析器1 〇不是使用峰値位置而是頻譜的加權平均。亦即， 於峰値位置’ F F Τ的解析度限制誤差信號的解析度，且波 長穩定性於例如干涉儀的應用中僅影響頻譜的加權平均之 改變。 於實際系統中，由於光檢器9或分析器10中的A/D 轉換所產生的雜訊，雜訊資料可混合於必須是通常不受任 何頻譜分量影響之區，導致加權平均的計算誤差。此問題 可藉由預先決定等於系統雜訊位準的臨界値以及考慮到僅 具有高於此臨界値的雜訊位準的資料而實施計算來避免。 因爲不依賴脈頻的頻譜分量存在於D C位準周圍，這係需 要預先指定加權平均的計算區以避免此影響。因此，自種 -9- 200840166 子雷射1輸出之光的頻率fseed及自脈波振盪器輸出的頻率 fpulse間之差異（fpulse-fseed )係由以下方程式給定： Σ / i=i0 …（3) N-1 ^ulse - Seed - 4工(A) i = i0 因此獲得僅含有頻差資訊而未含有正負號資訊之結果 。然而，基於PZT支架4移動的方向及頻差改變的方向’ 正負號決定係可能，因此沒有問題發生在反饋系統上。再 者，即使聲光調變器6的調頻顫動變成測量誤差，其係太 小以致不會影響一般光頻穩定性且因此是可忽略的。 最後，分析器10D/A轉換頻差（fpu丨se-fseed )，且輸 出轉換結果作爲類比誤差信號。因爲依據第一實施例之信 號係脈波雷射，誤差信號被保持直到下一脈波被產生。 分析器1 0爲每一脈波較佳地執行此過程以增加脈波 振盪器〇的控制頻率。當使用FPGA (現場可程式閘陣列 )所形成之分析器1〇時，分析器1〇可在約例如l〇kHz的 重複頻率實施分析。 自分析器10輸出之誤差信號被傳送至PZT控制器5 。此信號於PZT控制器5進行PID補償，然後傳送（反饋 )至PZT支架4。 於第一實施例中，脈波振盪器〇被控制使得脈波光的 振盪波長變成等於種子雷射1的振盪波長。因爲脈波振盪 器Ο的光學路徑長度被保持在種子雷射1的光學路徑長度 的整倍數，此獲得穩定注入鎖定。依據第一實施例，這係 可能依據脈波差拍信號而直接擷取波長差。此容許準確注 -10- 200840166 入鎖定控制免於激發光源的強度顚動的任何影響。 〔第二實施例〕 圖4爲顯示依據本發明的第二實施例的注入鎖定式雷 射的簡要配置之示意圖。自種子雷射1輸出之光束B 1係 藉由半鏡Ml分成兩個光束B2及B3。被半鏡Ml反射之 光束B2係經由鏡M2而注入脈波振盪器〇。脈波振盪器〇 較佳地爲環形以避免電洞燃燒的任何影響。由Ti :藍寶石 晶體製成之增益介質3係容納於脈波振盪器〇。增益介質 3可以激發光源（泵雷射）2射出的第二諧波從外部照射 振盪器〇來擷取，激發光源（泵雷射）2係以例如Nd : YAG製成且具有相當於Ti :藍寶石的吸收帶之波長。PZT 支架4裝載振盪器Ο的輸出稱合鏡M3。包括放大器之 PZT控制器5控制PZT支架4。此使其可能準確地控制振 盪器Ο的光學路徑長度。 種子雷射1所射出且透射穿過至半鏡Μ1之光束B 3 係在被鏡Μ4反射之時導至半鏡Μ6，且分成兩個光束Β4 及Β5。 透射穿過半鏡Μ6之光束Β5係在由鏡Μ7所反射時導 引至電光調變器1 1，使得其在頻率fm進行脈波調變。之 後，光束B5被透射穿過偏振光分束器12及λ /4板13且 導引至參考共振器14。光檢器15係設置在偏振光分束器 1 2的相對側上，且檢測供自參考共振器1 4之光量。 於第二實施例中，種子雷射1的振盪波長係以下述方 -11 - 200840166 式而穩定化。第二實施例採用Pound-Dr ever方法。在藉由 電光調變器11在頻率fm之調變後，雷射光束B6具有由 以下方程式所給定之複數振幅： 〇0 E(t) « E〇 2 Jn(^J βχρ(2πί(ν0 + n^t) ) {1 + φ(ί) } ...(4) η = —〇〇 其中ν 〇係種子雷射1射出之雷射光的中心光頻，Φ (t )係來自中心光頻的相移，及 Φ m係藉由電光調變器 1 1所獲得之調變深度。 被參考共振器1 4所反射之光的轉移函數H r ( V )係 由以下方程式所給定： + βχρ(-2π1ν/ν ) _ ...(5) 1 - ΓΧΓ2 θχρ(-2πιν/νΓ) 其中r 1及r2係參考共振器1 4的鏡的振幅反射比，ν 係種子雷射1所射出之光的頻率，及v F係參考共振器1 4 的 FSR。 被光檢器1 5所接收之光的強度信號係由方程式（4 ) 及（5 )的乘積所給定。僅在來自此信號的調頻fm振盪之 分量的擷取產生： 工⑼=|E〇f I； {Hr(v + nfm)H:(v + (η - DfJJDUJexp^^t) η = -〇〇 + Hr(v + nfm)H:(v + (η + l)4)Jn((|)m)Jn+1(<|)m) exp(-2Tiifmt) } ···(6) 此強度信號在頻率fm被解調以獲得由以下方程式所 給定之解調信號： -12- 200840166 V(V) = -1 |e0|2 Im Σ {Hr(v + n^)H；(v -f (n -f 1) n = -〇o .·· (7) 當V ( ) =N u f+ 5 v時，V ( z；)顯示相對於5 i； 至〇附近的頻率誤差之線性特性且因此可被使用作爲頻率 穩定化的誤差信號。解調器1 6將光強度信號解調成誤差 信號，且執行例如控制PID的濾波過程。解調結果被反饋 至種子雷射1的波長調變端子。 以上述方式，包括參考共振器14之穩定單元使用參 考共振器1 4的振盪波長作爲參考使種子雷射1的振盪波 長穩定化。因爲參考共振器14的頻率改變產生誤差，由 於諸如振動、溫度、及雜訊的干擾，其係需要充份考量光 學路徑長度的改變。更特別，重要的是提供高剛性機械結 構及低振動安裝環境，以及將注入鎖定式雷射容納於具有 隔音材料的空調室。 P 〇 u n d - D r e v e r方法具有誤差信號的S N依賴參考共振 器1 4的細緻度之條件。因此需要選擇具有足夠高反射比 之參考共振器1 4的鏡，且亦足以調整參考共振器1 4。 被半鏡M6所反射之種子雷射1的光束B4被導引至 AOM6。由於聲光效應，AOM6自透射穿過其中的光束接 收具有頻率f Α Ο Μ之電壓信號以產生複數階的繞射光束。 該複數階的這些繞射光束產生nxfA0M的頻移。 自該複數階的這些繞射光束’僅+第1階光束被空間 地擷取且藉由纖維耦合器7a耦接至纖維分束器8的第一 -13- 200840166 輸入端子。纖維分束器8例如，偏振保留單模式型，該型 包括兩個輸入端子（第一及第二輸入端子）及一輸出端子 〇 以相同方式，來自脈波振盪器Ο的輸出係藉由半鏡 M6部份地分束，且藉由纖維耦合器7b耦接至纖維分束器 8的第二輸入端子。光檢器9將自纖維分束器8輸出之光 的強度轉換成電信號，且將其傳送至分析器1 〇。 分析器1 〇藉由如第一實施例的相同過程相對於脈波 振盪器◦產生反饋信號。此信號係經由PZT控制器（PZT 放大器）5反饋至脈波振盪器〇的PZT支架4。 以上方式中，脈波振盪器Ο被控制使得脈波振盪器0 的振盪頻率與種子雷射1的振盪頻率一致。 如上述，種子雷射1使用參考共振器1 4的振盪波長 作爲參考使波長穩定化。因此，控制來保持種子雷射1及 脈波振盪器0的振盪波長恆定以達到脈波雷射光波長的準 確穩定。 〔第三實施例〕 圖5爲顯示依據本發明的第三實施例的注入鎖定式雷 射的簡要配置之示意圖。依據本發明的第三實施例之干涉 儀結合依據第二實施例之注入鎖定式雷射。 依據本發明的第三實施例之干涉儀適於，例如，檢查 內建於諸如半導體曝光設備的曝光設備之投射光學系統的 成像性能。曝光設備使用例如，KrF或ArF的準分子雷射 -14- 200840166 作爲照明光源。爲此理由，投射光學系統被設計在照明光 的波長顯示最佳成像性能。用於檢查投射光學系統的成像 性能之檢查設備同樣地使用大致等於照明光的波長來執行 檢查。將例示第三實施例用於具有193 nm的最佳波長的投 射光學系統之檢測設備。 首先，將解說振盪波長調整方法。作爲檢查設備之干 涉儀在例示於第二實施例之注入鎖定式雷射的輸出部包含 波長轉換單元1 7。波長轉換單元1 7將入射光的波長縮短 至1 /4，且使用非線性光學效應來輸出轉換的波長。爲了 將自波長轉換單元17輸出之光波長設定在193 nm，其係 需要穩定進入波長轉換單元1 7之光的波長，亦即，自注 入鎖定式雷射輸出之光的波長在772nm。 半鏡Μ 8取代依據第二實施例之鏡Μ 7。自種子雷射1 之輸出係部份地透射穿過半鏡Μ8，且在由鏡Μ9所反射時 而導引至波長計30。目種子雷射1輸出之光束亦被分束且 導引至脈波振盪器Ο (注入鎖定）、ΑΟΜ6 (差拍檢測） 及外部參考共振器1 4 (波長穩定），如第二實施例。 精確校準標準具被內建於波長計30且因此可在次微 微米或更小的等級量測絕對波長値。電腦29連接至波長 計3 0 ’計算自種子雷射1的設定波長的波長移位量，且將 計算結果傳送至加法器3 1。 加法器3 1實施用於自電腦29送出的波長移位量之 PID計算以使用波長計3 0作爲參考來產生反饋信號。加 法器3 1然後使用參考共振器丨4作爲參考自解調器1 6將 -15- 200840166 反饋信號加至反饋信號（波長反饋信號），且將總和反饋 至種子雷射1的波長調變端子。 波長反饋信號及頻率反饋信號被送至種子雷射1。當 波長反饋信號的控制頻率被設定足夠小於頻率反饋信號的 控制頻率時，這係可能最小化波長反饋信號及頻率反饋信 號間之干涉的任何影響。 以上述方式，依據第三實施例，包括參考共振器1 4 及波長計3 0之波長穩定單元達到頻率穩定化及種子雷射1 的中心波長的絕對値的保證。因此，依據第三實施例，如 於第二實施例控制脈波振盪器0的光學路徑長度（振盪長 度）達到頻率穩定及脈波光源的中心波長的保證。 波長轉換單元1 7將自脈波振盪器〇輸出的光的波長 縮短至1/4，亦即，193 nm。1/4的係數於波長轉換中在物 理上是固定的，且自波長轉換單元1 7輸出之光的波長係 僅由進入波長轉換單元1 7之光的波長來決定。因此， 1 93 nm脈波亦進行頻率穩定及中心波長的保證。 接著將解說波長計。自波長轉換單元1 7樹出之光束 通過聚光透鏡1 8，且然後透射穿過具有等於或小於繞射限 制的尺寸之針孔1 9，藉此使波形成形。透射穿過針孔1 9 之光束係在展開時透射穿過半鏡20，藉由準直器透鏡21 準直成準直光束，且導至TS透鏡23。TS透鏡23被設計 使得最後表面的曲率半徑變成等於自最後表面至焦點位置 的距離。除了最後表面外，以抗反射膜塗佈TS透鏡23。 由於空氣及玻璃間的折射比差，導至T S透鏡2 3的最後表 -16- 200840166 面之光束的約5% ，且沿著入射光學路徑返回。TS透鏡的 最後表面將被稱爲TS表面，而被TS表面反射之光束將被 稱爲參考光束。TS透鏡23被固定在相移單元22上，且 可藉由相移單元22中的PZT元件被驅動於光軸方向。 透射穿過TS表面之光束暫時會聚在曝光設備的投射 光學系統24的物體平面上，且然後在展開時導至投射光 學系統24。在自投射光學系統24射出後，光束會聚在投 射光學系統24的影像點。具有與投射光學系統24的影像 點重合之曲率的中心之球面RS鏡25被插置在影像側上。 RS鏡2 5的反射表面係以玻璃製成而無任何塗佈，且如同 TS表面具有約5 %的反射比。會聚在影像點之光束在被 RS表面反射時沿著相同光學路徑返回。以下RS鏡的反射 表面將被稱爲RS表面，而被RS表面反射之光束將稱爲 測試光束。 參考光束及測試光束再次透射穿過TS透鏡23，且準 直成準直光束。之後，這些光束再次導引至準直器透鏡21 且當會聚時被半鏡20所反射。空間濾波器26被插置在半 鏡2 0的相反側上之焦點位置。在藉由空間濾波器2 6切除 任何不需要高頻範圍之後，測試光束及參考光束被導至成 像透鏡2 7，準直至準直光束，且導至影像感知器（例如， C CD ) 28。影像感知器28感知測試光束及參考光束的干 涉帶，且將所感知影像資訊傳送至電腦29。 干涉帶係由以下方程式所给定： -17- 200840166 工⑻=Lef + 工㈣ + 2^efItest COS (2 · 27l(W(r) + L / λ)) • · · (8) 其中lef係參考光束的強度，Itest係測試光束的強度 ’ w ( r )係投射光學系統24的波形，L係TS表面及RS 表面間的光學路徑長度，及Λ係雷射光的波長.。 基於干涉帶之準確波形測量可採用相移方法。相移方 法基於被給定已知相移之複數干涉帶的影像來計算波形。 電腦29與影像感知器28的影像傳送時間同步地施加 電壓至相移單元22以沿著光軸驅動TS透鏡23，藉此獲 得想要相移。 測試透鏡的波形W ( r )由以下方程式所给定： W(r) = tan'^Isir) / Ic(r) ) / (2 · 2π) - φ ...(9) 其中Ic及Is分別係改變干涉帶的餘弦分量及正弦分 量，該等干涉帶係在相移之時自該數個干涉帶影像擷取， 及Φ係初始相位項。 發生於波形測量之誤差的主因子係在相移時干涉帶的 改變。觀察如自方程式（8)，干涉帶的改變亦發生在雷 射光的波長λ的改變之時，或由於例如載台振動，TS表 面及RS表面間的光學路徑長度L的改變之時。 用於半導體曝光設備之大型投射光學系統需要只要數 米m的光學路徑長度L。使其不可能忽略波長改變的影響 。因爲第三實施例獲得準確波長穩定性，可比起習知技術 ，更準確地測量波形。 -18- 200840166 藉由連接波長計3 0、解調器1 6及分析器1 0至電腦 2 9，在相移測量期間可監視雷射波長之改變。爲此理由， 當波長改變係大時發出警告以及將其反饋至測量値以容許 更準確地量測。 〔第四實施例〕 圖6爲顯示依據本發明的第四實施例的曝光設備的簡 要配置之示意圖。依據本發明的第四實施例之曝光設備結 合依據第三實施例的干涉儀。 雖然相移單兀22及TS透鏡23被插置於圖6中的曝 光用光的光學路徑，它們於實際曝光中自光學路徑退縮。 亦於曝光中’晶圓載台40被驅動使得不是球面RS鏡25 而是曝光目標晶圓（亦稱爲基板）被設置在投射光學系統 24的影像側上。 準分子雷射3 6射出之光束係經由傳輸系統導引至不 相干單元3 7。不相干單元3 7使入射光束成形且在同時減 小空間相干性。自不相干單元3 7射出之光束被導引至照 明光學系統3 8以使照度均勻且產生想要有效光源，且然 後照亮配置在光罩載台3 9上之光罩（亦稱爲原形或掩膜 )。投射光學系統24將藉由光罩圖案所繞射的入射光束 縮小並投射至配置在晶圓載台4 0上之晶圓以轉移光罩圖 案至晶圓表面。在圖案轉移後，晶圓載台40自曝光區一 步一步地移至下一曝光區以使其曝光。 現將解說測量投射光學系統24的波形像差的方法。 -19- 200840166 波形像差測量使用第二實施例所述之干涉儀。干涉儀光源 保持設定等於準分子雷射3 6的波長之穩定波長。相移單 元22及TS透鏡23係於半導體曝光期間自退縮位置驅動 ，且插置在投射光學系統24的想要物體點。再者，光罩 載台39被驅動以使配置在物體點之光罩退縮。RS鏡25 被設定在晶圓載台40的晶圓固持單元周圍。當晶圓載台 40被驅動時，RS鏡25的曲率的中心變成與投射光學系統 24上的物體點共軛。上述程序容許影像感知器（CCD相 機）28傳送測試光及參考光束的干涉帶。波形係使用相移 單元22藉由相移方法來測量，如於第三實施例。 因爲第四實施例可使用具有準確穩定地波長之雷射作 爲光源，波形可在半導體曝光設備準確地測量。由使用測 量結果來最佳化投射光學系統的波形像差，成像性能可被 最佳化。使其可能轉移非常精細圖案。 於以上實施例，差拍信號係藉由聲光調變器6使自種 子雷射1射出的光的頻率移位以及合成該頻移光與自振盪 器0射出的光而獲得。然而，本發明未受限於該配置。例 如，差拍信號可藉由聲光調變器6使自振盪器Ο射出的光 的頻率移位以及合成該頻移光與自種子雷射1射出的光而 獲得。 〔其它實施例〕 接著將說明使用上述曝光設備之裝置製造方法。圖8 爲解說整個半導體裝置製造過程的順序之流程圖。於步驟 -20- 200840166 1 (電路設計），半導體裝置的電路被設計。於步驟2 (光 罩製作），光罩係基於所設計電路圖案而製作。於步驟3 (晶圓製造），晶圓係使用諸如矽的材料而製造。於步驟 4稱爲預處理之（晶圓處理），將實際電路係使用光罩及 晶圓而藉由微影術形成在晶圓上。於稱爲後處理之步驟5 (組裝），半導體晶片係使用製造於步驟4的晶圓而形成 的。此步驟包括諸如組裝（切割及接合）及封裝（晶片封 包）之過程。於步驟6 (檢驗），包括步驟5所製造的半 導體裝置的操作檢查測試及耐久性測試之檢驗被實施。半 導體裝置係於步驟7以這些處理之完成並運送。 圖9爲解說晶圓處理的詳細順序之流程圖。於步驟1 1 (氧化），晶圓表面被氧化。步驟1 2 ( CVD )，絕緣膜係 形成在晶圓表面上。步驟1 3 (電極形成），電極係藉由沉 積而形成在晶圓上。步驟1 4 (離子植入），離子被植入晶 圓。步驟15 ( CMP )，絕緣膜係由CMP所平面化。於步 驟1 6 (抗蝕過程），光敏劑被施加至晶圓。步驟1 7 (曝 光），上述曝光設備係使用來經由其上形成有電路圖案的 掩膜使以光敏劑塗佈的晶圓曝光以形成潛在影像圖案在抗 触劑上。步驟1 8 (顯影），形成在晶圓上的抗蝕劑之潛在 影像圖案被顯影以形成抗蝕圖案。步驟1 9 (蝕刻），在抗 蝕影像下方的層或基板被蝕刻穿過抗蝕圖案開敞的部份。 步驟20 (抗蝕移除），在蝕刻後留下的任何無需抗蝕劑被 移除。藉由重複這些步驟，電路圖案的多層結構係形成在 晶圓上。 -21 - 200840166 雖然已參照示範性實施例說明本發明，將瞭解到’本 發明未受限於所揭示的示範性實施例。以下請求項的範圍 將符合最寬廣詮釋以含蓋所有此種修改以及等效結構與功 能。 【圖式簡單說明】 圖1爲顯示依據本發明的第一實施例的注入鎖定式雷 射的簡要配置之示意圖； 圖2爲解說藉由模擬所獲得之差拍信號〗（t )的圖表 > 圖3爲解說差拍信號的傅立葉轉換之圖表； 圖4爲顯示依據本發明的第二實施例的注入鎖定式雷 射的簡要配置之示意圖； 圖5爲顯示依據本發明的第三實施例的注入鎖定式雷 射的簡要配置之示意圖； 圖6爲顯示依據本發明的第四實施例的曝光設備的簡 要配置之示意圖； 圖7爲顯示習知注入鎖定式雷射的簡要配置之示意圖 圖8爲解說整個半導體裝置製造過程的順序之流程圖 ;及 圖9爲解說晶圓處理的詳細順序之流程圖。 【主要元件符號說明】 -22- 200840166 B1 :光束 B2 :光束 B 3 :光束 Μ1 :半鏡 〇 :脈波振盪器 M2 ··鏡 M3 :輸出耦合鏡 Μ4 :鏡 Μ5 :鏡 Μ 6 :半鏡 fAOM :調頻 η :階First, the analyzer 10A/D converts the pulse beat signal I(t). The A/D conversion is preferably triggered by, for example, the Q-switch of the excitation source (pump laser) 2 -8-200840166. The number of samples based on the subsequent FFT (Fast Fourier Transform) process is preferably 2n. Next, the analyzer 1 〇 analyzes the frequency of the beat signal I ( t ). The analyzer 1 〇 performs an FFT of the beat signal I ( t ). Equation (1) is Fourier transformed into the following equation z 1(f) = aV7i(I0 θχρΗβπί)2) +V2IseedI7 exp(~2(a^f - (^ulse - fseed + fA〇M) ) )2)) 3 illustrates the Fourier transform given by equation (2). Obviously, as from equation (2), the spectrum around fA0M shows the frequency difference between the pulsed light from the pulse oscillator and the light from the seed laser 1. In order to extract the frequency information of the pulse wave from the pulse oscillator, the frequency modulation fA0M (frequency shift amount) of the AOM6 must be sufficiently larger than the spectral width of the pulse wave light. Analyzer 1 〇 calculates the weighted average of the spectrum. For the following reasons, Analyzer 1 does not use the peak position but the weighted average of the spectrum. That is, the resolution of the peak position 'F F 限制 limits the resolution of the error signal, and the wavelength stability affects only the weighted average of the spectrum changes in applications such as interferometers. In an actual system, due to the noise generated by the A/D conversion in the photodetector 9 or the analyzer 10, the noise data can be mixed in an area that must be generally unaffected by any spectral components, resulting in a weighted average calculation error. . This problem can be avoided by pre-determining the critical threshold equal to the system noise level and considering the data with only the noise level above this threshold. Since the spectral components that do not rely on the pulse frequency exist around the D C level, it is necessary to specify a weighted average calculation area in advance to avoid this effect. Therefore, the difference between the frequency fseed of the self-spray -9-200840166 sub-laser 1 output and the frequency fpulse from the pulse oscillator output (fpulse-fseed) is given by the following equation: Σ / i=i0 ...( 3) N-1 ^ulse - Seed - 4 (A) i = i0 Therefore, the result is obtained only with frequency difference information and without positive and negative information. However, based on the direction in which the PZT carriage 4 moves and the direction in which the frequency difference changes, the positive and negative signs are possible, so no problem occurs on the feedback system. Moreover, even if the FM jitter of the acousto-optic modulator 6 becomes a measurement error, it is too small to affect the general optical frequency stability and is therefore negligible. Finally, the analyzer 10D/A converts the frequency difference (fpu丨se-fseed) and outputs the conversion result as an analog error signal. Since the signal according to the first embodiment is a pulse laser, the error signal is held until the next pulse is generated. The analyzer 10 preferably performs this process for each pulse to increase the control frequency of the pulse oscillator 〇. When an analyzer formed by an FPGA (Field Programmable Gate Array) is used, the analyzer 1 can perform analysis at a repetition frequency of, for example, 10 kHz. The error signal output from the analyzer 10 is transmitted to the PZT controller 5. This signal is PID compensated by the PZT controller 5 and then transmitted (feedback) to the PZT bracket 4. In the first embodiment, the pulse oscillator 〇 is controlled such that the oscillation wavelength of the pulse wave light becomes equal to the oscillation wavelength of the seed laser 1. Since the optical path length of the pulse oscillator 被 is maintained at an integral multiple of the optical path length of the seed laser 1, this results in a stable injection lock. According to the first embodiment, it is possible to directly extract the wavelength difference based on the pulse beat signal. This allows for accurate injections. -10- 200840166 In-lock control is immune to any effects of excitation source intensity turbulence. [Second Embodiment] Fig. 4 is a view showing a schematic configuration of an injection-locked laser according to a second embodiment of the present invention. The beam B 1 output from the seed laser 1 is split into two beams B2 and B3 by a half mirror M1. The light beam B2 reflected by the half mirror M1 is injected into the pulse oscillator 经由 via the mirror M2. The pulse oscillator 〇 is preferably annular to avoid any effects of cavity burning. A gain medium 3 made of Ti: sapphire crystal is housed in a pulse wave oscillator. The gain medium 3 can excite the second harmonic emitted by the light source (pump laser) 2 to be extracted from the external illumination oscillator, and the excitation light source (pump laser) 2 is made of, for example, Nd:YAG and has the equivalent Ti: The wavelength of the absorption band of sapphire. The PZT bracket 4 is loaded with an output of the oscillator 称 mirror M3. A PZT controller 5 including an amplifier controls the PZT bracket 4. This makes it possible to accurately control the optical path length of the oscillator Ο. The beam B 3 emitted by the seed laser 1 and transmitted through the half mirror 1 is guided to the half mirror 6 when reflected by the mirror 4, and is split into two beams Β4 and Β5. The beam Β 5 transmitted through the half mirror 6 is guided to the electro-optic modulator 1 1 when reflected by the mirror 7 so that it is pulse-modulated at the frequency fm. Thereafter, the light beam B5 is transmitted through the polarization beam splitter 12 and the λ /4 plate 13 and guided to the reference resonator 14. The photodetector 15 is disposed on the opposite side of the polarization beam splitter 12, and detects the amount of light supplied from the reference resonator 14. In the second embodiment, the oscillation wavelength of the seed laser 1 is stabilized by the following formula -11 - 200840166. The second embodiment employs the Pound-Dr ever method. After modulation by the electro-optical modulator 11 at the frequency fm, the laser beam B6 has a complex amplitude given by the following equation: 〇0 E(t) « E〇2 Jn(^J βχρ(2πί(ν0 + n^t) ) {1 + φ(ί) } ...(4) η = —〇〇 The center optical frequency of the laser light emitted by the ν 〇 seed laser 1 is Φ (t ) from the central optical frequency The phase shift, and the Φ m is the modulation depth obtained by the electro-optic modulator 11. The transfer function H r ( V ) of the light reflected by the reference resonator 14 is given by the following equation: Βχρ(-2π1ν/ν ) _ (5) 1 - ΓΧΓ2 θχρ(-2πιν/νΓ) where r 1 and r2 are the amplitude reflectances of the mirror of the reference resonator 14 and are emitted by the ν-seed laser 1 The frequency of the light, and the FSR of the v F-based reference resonator 14. The intensity signal of the light received by the photodetector 15 is given by the product of equations (4) and (5). The acquisition of the component of the frequency-modulated fm oscillation of the signal produces: (9)=|E〇f I; {Hr(v + nfm)H:(v + (η - DfJJDUJexp^^t) η = -〇〇+ Hr(v + nfm)H:(v + (η + l)4)Jn((|)m)Jn+1(<|)m) exp(-2Tiifmt) } ···(6) The intensity signal is demodulated at frequency fm to obtain a demodulated signal given by the following equation: -12- 200840166 V(V) = -1 | e0|2 Im Σ {Hr(v + n^)H;(v - f (n -f 1) n = -〇o . (7) When V ( ) =N u f+ 5 v, V ( z;) shows the linearity of the frequency error with respect to 5 i; And thus can be used as an error signal for frequency stabilization. The demodulator 16 demodulates the light intensity signal into an error signal and performs a filtering process such as controlling the PID. The demodulation result is fed back to the wavelength adjustment of the seed laser 1. In the above manner, the stabilizing unit including the reference resonator 14 stabilizes the oscillation wavelength of the seed laser 1 using the oscillation wavelength of the reference resonator 14 as a reference. Since the frequency change of the reference resonator 14 produces an error due to, for example, Vibration, temperature, and noise interference, which need to fully consider the change in optical path length. More specifically, it is important to provide a high-rigid mechanical structure and a low-vibration installation environment, as well as to accommodate the injection-locked laser in soundproofing. Air conditioning room for materials. P 〇und - D rever method is wrong The S N of the difference signal depends on the condition of the fineness of the reference resonator 14. Therefore, it is necessary to select the mirror of the reference resonator 14 having a sufficiently high reflectance, and it is also sufficient to adjust the reference resonator 14. The beam B4 of the seed laser 1 reflected by the half mirror M6 is guided to the AOM 6. Due to the acousto-optic effect, the AOM 6 receives a voltage signal having a frequency f Α Μ from the light beam transmitted therethrough to generate a complex-order diffracted beam. The diffracted beams of the complex order produce a frequency shift of nxfA0M. These diffracted beams ' from the complex order only + the first order beam are spatially extracted and coupled to the first -13-200840166 input terminal of the fiber splitter 8 by the fiber coupler 7a. The fiber splitter 8 is, for example, a polarization-retained single mode type including two input terminals (first and second input terminals) and an output terminal 〇 in the same manner, the output from the pulse oscillator 系 is by a half The mirror M6 is partially split and coupled to the second input terminal of the fiber splitter 8 by a fiber coupler 7b. The photodetector 9 converts the intensity of the light output from the fiber splitter 8 into an electric signal and transmits it to the analyzer 1 〇. The analyzer 1 generates a feedback signal with respect to the pulse oscillator 〇 by the same process as the first embodiment. This signal is fed back to the PZT holder 4 of the pulse oscillator 经由 via a PZT controller (PZT amplifier) 5. In the above manner, the pulse oscillator Ο is controlled such that the oscillation frequency of the pulse oscillator 0 coincides with the oscillation frequency of the seed laser 1. As described above, the seed laser 1 stabilizes the wavelength using the oscillation wavelength of the reference resonator 14 as a reference. Therefore, control is made to keep the oscillation wavelengths of the seed laser 1 and the pulse oscillator 0 constant to achieve accurate stabilization of the pulse laser light wavelength. [THIRD EMBODIMENT] Fig. 5 is a view showing a schematic configuration of an injection-locked laser according to a third embodiment of the present invention. The interferometer according to the third embodiment of the present invention incorporates the injection-locked laser according to the second embodiment. The interferometer according to the third embodiment of the present invention is adapted, for example, to check the imaging performance of a projection optical system built in an exposure apparatus such as a semiconductor exposure apparatus. The exposure apparatus uses, for example, KrF or ArF excimer laser -14-200840166 as an illumination source. For this reason, the projection optical system is designed to exhibit optimal imaging performance at the wavelength of the illumination light. The inspection apparatus for inspecting the imaging performance of the projection optical system similarly performs the inspection using a wavelength substantially equal to the illumination light. The third embodiment will be exemplified for a detecting apparatus of a projection optical system having an optimum wavelength of 193 nm. First, the oscillation wavelength adjustment method will be explained. The interferometer as the inspection apparatus includes the wavelength conversion unit 17 in the output portion of the injection-locked laser exemplified in the second embodiment. The wavelength conversion unit 17 shortens the wavelength of incident light to 1/4 and outputs a converted wavelength using a nonlinear optical effect. In order to set the wavelength of the light output from the wavelength conversion unit 17 at 193 nm, it is necessary to stabilize the wavelength of light entering the wavelength conversion unit 17, that is, the wavelength of light self-injected into the locked laser output is 772 nm. The half mirror 8 replaces the mirror 7 according to the second embodiment. The output from the seed laser 1 is partially transmitted through the half mirror 8 and directed to the wavelength meter 30 as reflected by the mirror 9. The beam of the target seed laser 1 output is also split and directed to the pulse oscillator Ο (injection lock), ΑΟΜ 6 (beat detection), and external reference resonator 14 (wavelength stable) as in the second embodiment. The precision calibration etalon is built into the wavelength meter 30 and thus the absolute wavelength 値 can be measured on a sub-micron or smaller scale. The computer 29 is connected to the wavelength meter 3 0 ' to calculate the wavelength shift amount from the set wavelength of the seed laser 1, and transmits the calculation result to the adder 31. The adder 31 implements a PID calculation for the wavelength shift amount sent from the computer 29 to generate a feedback signal using the wavelength meter 30 as a reference. The adder 3 1 then adds the -15-200840166 feedback signal to the feedback signal (wavelength feedback signal) using the reference resonator 丨4 as a reference self-demodulator 16 and feeds the sum back to the wavelength modulation terminal of the seed laser 1. . The wavelength feedback signal and the frequency feedback signal are sent to the seed laser 1. When the control frequency of the wavelength feedback signal is set to be sufficiently smaller than the control frequency of the frequency feedback signal, it is possible to minimize any influence of interference between the wavelength feedback signal and the frequency feedback signal. In the above manner, according to the third embodiment, the wavelength stabilizing unit including the reference resonator 14 and the wavelength meter 30 achieves the guarantee of the frequency stabilization and the absolute 中心 of the center wavelength of the seed laser 1. Therefore, according to the third embodiment, the optical path length (oscillation length) of the pulse wave oscillator 0 is controlled to achieve the frequency stabilization and the center wavelength of the pulse wave source as in the second embodiment. The wavelength conversion unit 17 shortens the wavelength of light output from the pulse oscillator 至 to 1/4, that is, 193 nm. The coefficient of 1/4 is physically fixed in wavelength conversion, and the wavelength of light output from the wavelength conversion unit 17 is determined only by the wavelength of light entering the wavelength conversion unit 17. Therefore, the 1 93 nm pulse wave is also guaranteed for frequency stabilization and center wavelength. Next, the wavelength meter will be explained. The beam from the wavelength conversion unit 17 passes through the collecting lens 18 and is then transmitted through a pinhole 19 having a size equal to or smaller than the diffraction limit, thereby shaping the waveform. The beam of light transmitted through the pinholes 1 9 is transmitted through the half mirror 20 when unfolded, collimated by the collimator lens 21 into a collimated beam, and directed to the TS lens 23. The TS lens 23 is designed such that the radius of curvature of the final surface becomes equal to the distance from the last surface to the focus position. The TS lens 23 is coated with an anti-reflection film in addition to the final surface. Due to the difference in refractive ratio between the air and the glass, it leads to about 5% of the beam of the last surface of the Ts lens 23, and returns along the incident optical path. The final surface of the TS lens will be referred to as the TS surface, and the beam reflected by the TS surface will be referred to as the reference beam. The TS lens 23 is fixed to the phase shifting unit 22, and is driven in the optical axis direction by the PZT element in the phase shifting unit 22. The light beam transmitted through the TS surface temporarily converges on the object plane of the projection optical system 24 of the exposure apparatus and is then directed to the projection optical system 24 when deployed. After being emitted from the self-projecting optical system 24, the light beams converge at the image point of the projecting optical system 24. A spherical RS mirror 25 having a center of curvature coincident with the image point of the projection optical system 24 is interposed on the image side. The reflective surface of the RS mirror 25 is made of glass without any coating and has a reflectance of about 5% as the TS surface. Light beams that converge at the image point return along the same optical path as they are reflected by the RS surface. The reflective surface of the following RS mirror will be referred to as the RS surface, and the beam reflected by the RS surface will be referred to as the test beam. The reference beam and the test beam are again transmitted through the TS lens 23 and collimated into a collimated beam. These beams are then directed again to the collimator lens 21 and are reflected by the half mirror 20 when converging. The spatial filter 26 is interposed at a focus position on the opposite side of the half mirror 20. After the unwanted high frequency range is removed by the spatial filter 26, the test beam and the reference beam are directed to the imaging lens 27, to the collimated beam, and to the image sensor (e.g., CCD) 28. The image sensor 28 senses the interference bands of the test beam and the reference beam and transmits the sensed image information to the computer 29. The interference band is given by the following equation: -17- 200840166 (8)=Lef + work (4) + 2^efItest COS (2 · 27l(W(r) + L / λ)) • · · (8) where lef is The intensity of the reference beam, the intensity of the Itest test beam ' w ( r ) is the waveform of the projection optical system 24, the length of the optical path between the L-series TS surface and the RS surface, and the wavelength of the lanthanide laser light. An accurate waveform measurement based on the interference band can employ a phase shift method. The phase shifting method calculates a waveform based on an image of a complex interference band given a known phase shift. The computer 29 applies a voltage to the phase shifting unit 22 in synchronization with the image transfer time of the image sensor 28 to drive the TS lens 23 along the optical axis, thereby obtaining a desired phase shift. The waveform W ( r ) of the test lens is given by the following equation: W(r) = tan'^Isir) / Ic(r) ) / (2 · 2π) - φ (9) where Ic and Is respectively The cosine component and the sinusoidal component of the interference band are changed, and the interference bands are extracted from the plurality of interference band images at the phase shift, and the Φ system initial phase term. The principal factor of the error that occurs in the waveform measurement is the change in the interference band at phase shift. As observed from equation (8), the change in the interference band also occurs at the time of the change of the wavelength λ of the laser light, or when the optical path length L between the TS surface and the RS surface is changed due to, for example, the vibration of the stage. A large projection optical system for a semiconductor exposure apparatus requires an optical path length L of only several meters. Make it impossible to ignore the effects of wavelength changes. Since the third embodiment achieves accurate wavelength stability, waveforms can be measured more accurately than conventional techniques. -18- 200840166 By changing the wavelength meter 30, the demodulator 16 and the analyzer 10 to the computer 2 9, the change in the laser wavelength can be monitored during the phase shift measurement. For this reason, a warning is issued when the wavelength change is large and is fed back to the measurement 値 to allow for more accurate measurement. [Fourth embodiment] Fig. 6 is a view showing a schematic configuration of an exposure apparatus according to a fourth embodiment of the present invention. The exposure apparatus according to the fourth embodiment of the present invention is combined with the interferometer according to the third embodiment. Although the phase shifting unit 22 and the TS lens 23 are inserted into the optical path of the light for exposure in Fig. 6, they are retracted from the optical path in the actual exposure. Also in the exposure, the wafer stage 40 is driven so that it is not the spherical RS mirror 25 but the exposure target wafer (also referred to as the substrate) is disposed on the image side of the projection optical system 24. The beam emitted by the excimer laser 3 6 is directed to the incoherent unit 37 via the transmission system. The incoherent unit 37 shapes the incident beam and simultaneously reduces spatial coherence. The light beam emitted from the incoherent unit 37 is directed to the illumination optical system 38 to make the illumination uniform and produce the desired effective light source, and then illuminate the photomask (also referred to as the prototype) disposed on the mask stage 39. Or mask). The projection optical system 24 reduces and projects the incident light beam diffracted by the reticle pattern onto the wafer disposed on the wafer stage 40 to transfer the reticle pattern to the wafer surface. After the pattern transfer, the wafer stage 40 is moved from the exposure area to the next exposure area step by step to expose it. A method of measuring the waveform aberration of the projection optical system 24 will now be explained. -19- 200840166 Waveform aberration measurement uses the interferometer described in the second embodiment. The interferometer source maintains a stable wavelength equal to the wavelength of the excimer laser 36. The phase shifting unit 22 and the TS lens 23 are driven from the retracted position during semiconductor exposure and are inserted into a desired object point of the projection optical system 24. Furthermore, the reticle stage 39 is driven to retract the reticle disposed at the object point. The RS mirror 25 is set around the wafer holding unit of the wafer stage 40. When the wafer stage 40 is driven, the center of the curvature of the RS mirror 25 becomes conjugate with the object point on the projection optical system 24. The above procedure allows the image sensor (CCD camera) 28 to transmit the interference bands of the test light and the reference beam. The waveform is measured by the phase shifting method using the phase shifting unit 22 as in the third embodiment. Since the fourth embodiment can use a laser having an accurate and stable wavelength as a light source, the waveform can be accurately measured at the semiconductor exposure apparatus. The imaging performance can be optimized by using the measurement results to optimize the waveform aberration of the projection optical system. Make it possible to transfer very fine patterns. In the above embodiment, the beat signal is obtained by shifting the frequency of the light emitted from the seed laser 1 by the acousto-optic modulator 6 and synthesizing the frequency-shifted light and the light emitted from the oscillator 0. However, the invention is not limited to this configuration. For example, the beat signal can be obtained by shifting the frequency of the light emitted from the oscillator by the acousto-optic modulator 6 and synthesizing the frequency-shifted light and the light emitted from the seed laser 1. [Other Embodiments] Next, a method of manufacturing a device using the above exposure apparatus will be described. Figure 8 is a flow chart illustrating the sequence of the entire semiconductor device fabrication process. In step -20- 200840166 1 (circuit design), the circuit of the semiconductor device is designed. In step 2 (mask manufacturing), the mask is made based on the designed circuit pattern. In step 3 (wafer fabrication), the wafer is fabricated using materials such as tantalum. In step 4, it is called pre-processing (wafer processing), and the actual circuit is formed on the wafer by lithography using a mask and a wafer. In a step 5 (assembly) called post-processing, a semiconductor wafer is formed using the wafer fabricated in step 4. This step includes processes such as assembly (cutting and bonding) and packaging (wafer packaging). In the step 6 (inspection), the inspection of the operation inspection test and the durability test including the semiconductor device manufactured in the step 5 is carried out. The semiconductor device is completed and shipped in step 7 with these processes. Figure 9 is a flow chart illustrating the detailed sequence of wafer processing. In step 1 1 (oxidation), the surface of the wafer is oxidized. In step 1 2 (CVD), an insulating film is formed on the surface of the wafer. In step 1 3 (electrode formation), the electrodes are formed on the wafer by deposition. Step 1 4 (Ion Implantation), ions are implanted into the crystal. In step 15 (CMP), the insulating film is planarized by CMP. In step 1 6 (resist process), a photosensitizer is applied to the wafer. In step 1 7 (exposure), the exposure apparatus described above is used to expose a wafer coated with a photosensitizer to form a latent image pattern on the anti-contact agent via a mask having a circuit pattern formed thereon. Step 1 8 (development), the latent image pattern of the resist formed on the wafer is developed to form a resist pattern. Step 1 9 (etching), the layer or substrate under the resist image is etched through the open portion of the resist pattern. Step 20 (resist removal), any unwanted photoresist left after etching is removed. By repeating these steps, the multilayer structure of the circuit pattern is formed on the wafer. The present invention has been described with reference to the exemplary embodiments, and it is understood that the invention is not limited by the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation to cover all such modifications and equivalent structures and functions. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a brief configuration of an injection-locked laser according to a first embodiment of the present invention; FIG. 2 is a diagram illustrating a beat signal (t) obtained by simulation. 3 is a diagram illustrating a Fourier transform of a beat signal; FIG. 4 is a schematic diagram showing a brief configuration of an injection-locked laser according to a second embodiment of the present invention; and FIG. 5 is a view showing a third embodiment according to the present invention. FIG. 6 is a schematic diagram showing a schematic configuration of an exposure apparatus according to a fourth embodiment of the present invention; FIG. 7 is a schematic diagram showing a brief configuration of a conventional injection-locked laser. 8 is a flow chart illustrating the sequence of the entire semiconductor device manufacturing process; and FIG. 9 is a flow chart illustrating the detailed sequence of wafer processing. [Description of main component symbols] -22- 200840166 B1 : Beam B2 : Beam B 3 : Beam Μ 1 : Half mirror 〇: Pulse oscillator M2 · · Mirror M3 : Output coupling mirror Μ 4 : Mirror 5 : Mirror 6 : Half mirror fAOM: frequency modulation η: order
Iseed ·’種子雷射強度 I p u 1 s e :脈波振盪器輸出 fseed :種子雷射光頻 fpUlse :脈玻雷射中央光頻 FFT :快速傅立葉轉換 FPGA :現場可程式閘陣列 M7 :鏡 ^ 〇 :中心光頻 Φ m :調變深度 Φ ( t ):相移 fm :調頻Iseed · 'Seed laser intensity I pu 1 se : Pulse oscillator output fseed : Seed laser optical frequency fpUlse : Pulse glass laser central optical frequency FFT : Fast Fourier transform FPGA : Field programmable gate array M7 : Mirror ^ 〇: Center optical frequency Φ m : modulation depth Φ ( t ): phase shift fm : frequency modulation
Hr ( v):轉移函數 -23- 200840166 rl、r2 :振幅反射比 V :頻率 B6 :雷射光束 Μ 6 :半鏡 MU Iref :強度 11 e s t ·強度 L :光學路徑長度 W ( r ):波形 Ic :餘弦分量 Is :正弦分量 Φ :初始相位項 1 :種子雷射 2 :激發光源（泵雷射） 3 :增益介質 4 : PZT支架 5 : PZT控制器 6 :聲光調變器 7a :纖維耦合器 ’ 7b :纖維耦合器 8 :纖維分束器 9 :光檢器 1 〇 :分析器 1 1 :電光調變器 -24 200840166 1 2 :偏振 13 ： λ /4 1 4 :參考 1 5 :光檢 1 6 :解調 1 7 :波長 1 8 :聚光 1 9 :針孔 2 0 :半鏡 21 :準直 22 :相移 2 3 ： TS 鋟 24 :投射 2 5 :球面 26 :空間 27 :成像 2 8 :影像 2 9 :電腦 3 0 :波長 3 1 :加法 3 2 :激發 3 3 :脈波 3 4 :控制 3 6 ··準分 光分束器 板 共振器 器 器 轉換單元 透鏡 器透鏡 單元 :鏡 光學系統 RS鏡 濾波器 透鏡 感知器 計 器 光源光檢器 光光檢器 電路 子雷射 -25 200840166 3 7 :不相干單元 3 8 :照明光學系統 39 :光罩載台 4 0 :晶圓載台 -26Hr ( v): transfer function -23- 200840166 rl, r2 : amplitude reflectance V : frequency B6 : laser beam Μ 6 : half mirror MU Iref : intensity 11 est · intensity L : optical path length W ( r ): waveform Ic: cosine component Is: sinusoidal component Φ: initial phase term 1: seed laser 2: excitation source (pump laser) 3: gain medium 4: PZT bracket 5: PZT controller 6: acousto-optic modulator 7a: fiber Coupler '7b: Fiber Coupler 8: Fiber Beamsplitter 9: Photodetector 1 〇: Analyzer 1 1 : Electro-optic modulator-24 200840166 1 2 : Polarization 13 : λ /4 1 4 : Reference 1 5 : Optical inspection 1 6 : Demodulation 1 7 : Wavelength 1 8 : Concentration 1 9 : Pinhole 2 0 : Half mirror 21 : Collimation 22 : Phase shift 2 3 : TS 锓 24 : Projection 2 5 : Spherical 26 : Space 27 : Imaging 2 8 : Image 2 9 : Computer 3 0 : Wavelength 3 1 : Addition 3 2 : Excitation 3 3 : Pulse 3 4 : Control 3 6 · Quasi-split beam splitter plate resonator converter unit lens lens Unit: Mirror optical system RS mirror filter Lens sensor meter Light source photodetector Light photodetector circuit sub-laser-25 200840166 3 7 : Irrelevant unit 3 8 : Illumination optical system 39 : Light Cover stage 4 0 : wafer stage -26