Patent Publication Number: US-2023137963-A1

Title: Exposure device and method

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates to a semiconductor manufacturing device and more particularly relates to an exposure device and method. 
     Description of Related Art 
     Photolithography etches and forms a geometric structure on a photoresist layer by exposure and development, and then transfers the pattern formed on a mask to a substrate by etching, wherein the substrate is a silicon wafer or silicon carbide wafer commonly used in semiconductors or a printed circuit board generally used in electronic components. During the manufacturing process, the mask is one of the important components to determine the exposure pattern. However, the mask needs to go through complicated procedures such as design, testing and verification, which may take several months to complete, and thus prolonging the manufacturing process of the semiconductor components. 
     In order to overcome the problems of the mask, maskless lithography gradually gains favour in the market. As the name suggests, maskless lithography does not use any for exposure in order to form a pattern by the photoresist, thus omitting the mask and achieving the effect of maskless exposure. At present, maskless lithography is widely used in the production for small quantity and diverse variety of components, such as inductors, passive components, microelectromechanical systems (MEMS), etc. 
     In general, traditional common maskless exposure machines generate exposure patterns on the photoresist layer through a liquid crystal on silicon (LCOS) device or a digital micromirror device (DMD), but such method has the following drawbacks. For example, the liquid crystal modulation speed of LCOS is slow and the method requires a long exposure time, which does not meet the market requirements for the production of semiconductor components. 
     With reference to  FIGS.  1 A and  1 B  for the schematic views of developing a photoresist layer using the digital micromirror device (DMD) after exposure, the photoresist layer  11  is disposed on a wafer  10 , and the digital micromirror device (DMD) is used to perform the exposure to a predetermined area  13  of the photoresist layer  11 . In  FIG.  1 B , after the development, a part of the photoresist layer  11  is removed to form a pattern  12 . However, due to diffraction, the light is often not 100% concentrated in the area to be exposed, and the area not to be exposed is often partially irradiated (especially near the edge of the area to be exposed). Therefore, the actually formed pattern  12  has an edge  14  unlike the one of the predetermined area  13  perpendicular to the wafer  10 , but the formed pattern  12  is deviated. The edge  14  may be an inclined plane and the area of edge  14  may be smaller than or greater than the predetermined area  13 , so that the pattern  12  cannot be accurately formed at the predetermined position. In other words, if the DMD is used for exposure, the phase cannot be changed, so that it will be unable to set the shape of the pattern accurately or sharply, and the development result will not be as expected (or will have a poor yield), especially in thick photoresist exposure. 
     Therefore, how to solve the problem is worthy of consideration by related manufacturers and those having ordinary skill in the art. 
     SUMMARY 
     In view of the drawbacks of the related art, it is a primary objective of the present disclosure to provide an exposure device that controls a laser by the method of adjusting the phase and amplitude to achieve the effects of controlling the pattern more precisely or sharply and overcoming the drawbacks of the traditional maskless exposure which can only adjust the amplitude. 
     To achieve the aforementioned and other objectives, this disclosure discloses an exposure device for projecting a laser on a photoresist layer, and the exposure device includes a laser source, a first spatial light modulator, a second spatial light modulator and a controller. The laser source is provided for emitting a laser. The first spatial light modulator is irradiated by the laser and includes a plurality of first pixels, each being used for reflecting the laser after the phase of the laser irradiated on the first spatial light modulator is modulated first pixel. The second spatial light modulator is irradiated by the laser reflected by the first spatial light modulator and includes a plurality of second pixels, each being used for reflecting the laser after the amplitude of the laser irradiated on the second spatial light modulator is modulated. Wherein, the laser reflected by the second spatial light modulator is irradiated on the photoresist layer to form an exposure pattern, and the exposure pattern includes a plurality of third pixels, and the first pixel, the second pixel, and the third pixel correspond with one another. 
     This disclosure further provides an exposure method, including the steps of: 
     (a) emitting a laser to a first spatial light modulator, wherein the first spatial light modulator includes a plurality of first pixels; 
     (b) using the first spatial light modulator to change the phase of the laser modulated by each of the first pixels; 
     (c) using the first spatial light modulator to irradiate the laser to a second spatial light modulator after the phase of the laser is modulated, wherein the second spatial light modulator includes a plurality of second pixels; 
     (d) using the second spatial light modulator to change the amplitude of the laser modulated by the second pixel; and 
     (e) using the second spatial light modulator to irradiate the laser to a photoresist layer to form an exposure pattern after the amplitude of the laser is modulated, wherein the exposure pattern includes a plurality of third pixels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A and  1 B  are schematic views showing the exposure and development of a photoresist layer using MDM; 
         FIG.  2 A  is a schematic view of an exposure device of this disclosure; 
         FIG.  2 B  is a schematic block diagram of an exposure device of this disclosure; 
         FIG.  3 A  is a schematic view of a first spatial light modulator which is a liquid crystal on silicon (LCOS) device in accordance with some embodiment of this disclosure; 
         FIG.  3 B  is a schematic perspective view of a first spatial light modulator of this disclosure; 
         FIG.  4    is a schematic perspective view of a second spatial light modulator of this disclosure; 
         FIG.  5    is a schematic view of forming an exposure pattern of this disclosure; 
         FIG.  6 A  is a schematic view of a first pixel of this disclosure; 
         FIG.  6 B  is a schematic view of forming an exposure pattern formed by a laser of this disclosure; 
         FIG.  6 C  is a schematic view showing the light intensity of a third pixel at a time point of this disclosure; 
         FIG.  7 A  is a flow chart of an exposure method of this disclosure; and 
         FIG.  7 B  is a flow chart of detecting the phase and light intensity in the exposure method of this disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     This disclosure will now be described in more detail with reference to the accompanying drawings that show various embodiments of this disclosure. 
     This disclosure provides an exposure device and an exposure method, and uses a spatial light modulator to modulate the phase and amplitude of a laser, and makes use of the lasers with different phases and amplitudes to interfere and offset each other to form a more accurate exposure pattern. With reference to  FIGS.  2 A,  2 B and  7 A  for the schematic views of an exposure device  100 , the structure of the exposure device  100  and an exposure method of this disclosure respectively, the exposure device  100  includes a laser source  110 , a beam expander  112 , a first spatial light modulator  120 , a second spatial light modulator  130 , a sensor  140 , a controller  150  and a projection lens  160 . 
     Firstly, the Step S 11  is carried out to emit a laser  111  to a first spatial light modulator  120 . The laser source  110  as described in the Step S 11  is provided for emitting the laser  111 . The first spatial light modulator  120  is installed on the path of the laser  111  and irradiated by the laser  111 . The beam expander  112  is installed between the laser source  110  and the first spatial light modulator  120  and disposed on the path of the laser  111 , so that the laser  111  passes through the beam expander  112  and irradiates the first spatial light modulator  120 . When the laser  111  passes through the beam expander  112 , the irradiation radius of the laser  111  will be expanded to increase the area of the first spatial light modulator  120  which is irradiated by the laser  111 . In some embodiment, when the laser  111  passes through the beam expander  112 , the laser  111  will cover the entire first spatial light modulator  120 . In this embodiment, the first spatial light modulator  120  is a liquid crystal on silicon (LCOS) device, so that the first spatial light modulator  120  includes a plurality of first pixels  201 , each being used for reflecting the laser  11  after the phase of the laser  111  irradiated on the first spatial light modulator  120  is modulated, and the phase of the reflected laser  111   a  can be changed. Then, Step S 12  is proceeded, and the first spatial light modulator  120  changes the phase of the laser modulated by each first pixel  201 . 
     With reference to  FIG.  3 A  for the schematic view of a liquid crystal on silicon (LCOS) device uses as the first spatial light modulator in accordance with some embodiment of this disclosure, the liquid crystal on silicon (LCOS) device used as the first spatial light modulator  120  includes a substrate layer  210 , a complementary metal oxide semiconductor (CMOS) layer  220 , a reflective layer  230 , two alignment layers  240 ,  240 ′, a liquid crystal layer  250 , a transparent electrode layer  260  and a cover glass  270 . The CMOS layer  220  includes a CMOS circuit layer  221  and a plurality of pixel electrodes  222 , and the reflective layer  230  is disposed on the CMOS layer  220 , and the alignment layer  240  is disposed above the reflective layer  230 , and the liquid crystal layer  250  is disposed between the two alignment layers  240 ,  240 ′. The transparent electrode layer  260  is disposed above the alignment layer  240 ′, and the transparent electrode layer  260  has a plurality of transparent electrodes (not shown in the figure), each being configured to be corresponsive to one of the pixel electrodes  222 . In other words, the transparent electrode and the pixel electrode  222  are configured in pairs. The cover glass  270  covers the top of the transparent electrode layer  26  for protecting each component in the liquid crystal on silicon (LCOS) device, in addition to receiving external light. Further, the top of the cover glass  270  has an anti-reflective layer  280  such as an anti-reflective coating. 
     With reference to  FIG.  3 B  for the perspective view of a liquid crystal on silicon (LCOS) device uses as a first spatial light modulator  120  of this disclosure, the viewing plane of the liquid crystal on silicon (LCOS) device is divided into a plurality of first pixels  201 , each being configured to be corresponsive to one of the pixel electrodes  222  and the transparent electrode. In this embodiment, the liquid crystal on silicon (LCOS) device receives an external control signal through the CMOS circuit layer  221  to control the electrical property of the transparent electrode on the pixel electrode  222  and the transparent electrode layer  260 , so that the liquid crystal  251  in the liquid crystal layer  250  corresponding to each pixel electrode can rotate, and after light enters into the liquid crystal on silicon (LCOS) device, the light is affected by the rotated liquid crystal  251  and the phase of the light will be changed. In addition, the direction of the liquid crystal  251  corresponding to each first pixel  201  is controlled by the pixel electrode  222  and the transparent electrode, so that the phase of the light emitted by each first pixel  201  can be controlled. 
     In  FIGS.  2 A and  7 A , the Step S 13  is carried out to irradiate a laser  111  to the second spatial light modulator  130  after the first spatial light modulator  120  modulates the phase of the laser  111   a . The second spatial light modulator  130  is installed on the path of the laser  111   a  reflected by the first spatial light modulator  120 . In addition, the second spatial light modulator  130  includes a plurality of second pixels, each second being used for reflecting the laser  111   a  after the amplitude of the laser  111   a  is modulated. In this embodiment, the second spatial light modulator  130  is a digital micromirror device (DMD) that can reflect the laser  111   a , and the amplitude of the reflected laser  111   b  will be changed. Therefore, when the Step S 14  is carried out, the second spatial light modulator  130  changes the amplitude of the laser  111   b  modulated by the second pixel. 
     With reference to  FIG.  4    for the schematic view of a second spatial light modulator in accordance with some embodiment of this disclosure, the second spatial light modulator  130  further includes a plurality of second pixels, which are micromirrors  320  in this embodiment, and these micromirrors  320  are installed on a substrate  310 . In this embodiment, each micromirror  320  corresponds to one of the first pixels  201  on the first spatial light modulator  120  (as shown in  FIG.  3 B ). Each micromirror  320  can control and change an angle, so that the micromirror  320  has the ON or OFF effect. For example, when the angle relative to the horizontal plane is positive 12°, the micromirror  320  is turned on, and when it is negative 12°, the micromirror  320  is turned off, and the frequency of turning on/off the micromirror  320  can also be controlled. By adjusting the different frequency of switching on and off the micromirrors  320 , the laser  111   a  can be reflected, so that the laser  111   a  reflected by the micromirror  320  with different switching frequencies can accumulate different energies, so as to the effect of adjusting the amplitude (i.e.: the intensity) of the laser  111   a  irradiated on the photoresist layer  20 . After being reflected by the second spatial light modulator  130 , the laser  111   b  is projected onto the photoresist layer  20  through the projection lens  160  to form an exposure pattern  400  as shown in  FIG.  5   . 
     In  FIGS.  2 A and  7 A , the Step S 15  is carried out, and the laser  111   b  modulated by the second spatial light modulator  130  is irradiated on the photoresist layer  20  to form an exposure pattern  400 . After the laser passes through the first spatial light modulator  120 , the phase of the laser emitted by each first pixel  201  can be adjusted. In addition, the laser passes through the second spatial light modulator  130 , the adjusted laser is irradiated on the photoresist layer  20  with an intensity distribution, so as to have bright and dark distributions on the surface of the photoresist layer  20  and form an exposure pattern  400  as shown in  FIG.  5   . 
     With reference to  FIG.  5    for the schematic view of the exposure pattern  400 , the exposure pattern  400  can be regarded as being formed by a plurality of third pixels  401  arranged in an array, and the third pixel  401  includes a third dark-area pixel  410  and a third bright-area pixel  420 , and each third pixel  401  corresponds to one of the first pixels  201  on the first spatial light modulator  120  and one of the micromirrors  320  on the second spatial light modulator  130 . 
     The first pixel  201  corresponding to the third pixel  401  includes a plurality of first dark-area pixels and a plurality of first bright-area pixels, and the third dark-area pixel  410  corresponds to the first dark-area pixel, and the third bright-area pixel  420  corresponds to the first bright-area pixel. The phases of the laser modulated by at least two first bright-area pixel of the adjacent first dark-area pixels differ by 180° with each other. 
     With reference to  FIG.  6 A  for the schematic view of a first pixel, only three first pixels  201  are shown in  FIG.  6 A  for simplicity, and the first pixel includes one first dark-area pixel  2011  and two adjacent first bright-area pixels  2012   a ,  2012   b . In this embodiment, the first bright-area pixels  2012   a ,  2012   b  are disposed on the left and right sides of the first dark-area pixel  2011  respectively. After the first bright-area pixels  2012   a ,  2012   b  modulate the lasers, the phases of the modulated lasers differ by 180° with each other. In other words, the phases of the lasers modulated by the first bright-area pixel  2012   a ,  2012   b  differ by 180° with each other. 
     With reference to  FIG.  6 B  for the schematic view of the exposure pattern formed by the laser, the laser reflected by the first bright-area pixel  2012   a  is projected onto the third bright-area pixel  420 , and the laser reflected by the first bright-area pixel  2012   b  is projected onto the third bright-area pixel  420 ′. 
     With reference to  FIG.  6 C  for the schematic view showing the light intensity of the third pixel at a time point, the curve  601  shows the light intensity of the laser reflected by the first bright-area pixel  2012   a  and projected onto the third bright-area pixel  420 . The curve  602  shows the light intensity of the laser reflected by the first bright-area pixel  2012   b  and projected onto the third bright-area pixel  420 ′. Due to the light diffraction, a part of the laser is projected onto the third dark-area pixel  410 . The laser reflected by the first bright-area pixel  2012   a ,  2012   b  has a phase difference of 180°, so that the phase of the laser projected onto the third bright-area pixels  420 ,  420 ′ are in opposite states, and the lasers diffracted onto the third dark-area pixel  410  will be interfered and offset with each other due to the lasers reflected by the first bright-area pixels  2012   a ,  2012   b . In this way, the light projected on the third dark-area pixel  410  can be effectively reduced, and further, when the exposure pattern is formed, the distinction between the third bright-area pixel  420  and the third dark-area pixel  410  can be clearer. The micromirror  320  corresponding to the third pixel  401  of the third dark-area pixel  410  has a deflection angle, so that the reflected laser will not irradiate on the third dark-area pixel  410 . On the contrary, the deflection angle of the micromirror  320  corresponding to the third pixel  401  of the third bright-area pixel  420  can irradiate the reflected laser on the third bright-area pixel  420 . 
     With reference to  FIGS.  2 A and  7 A  again, a sensor  140  of one of the embodiments is installed between the second spatial light modulator  130  and the photoresist layer  20  and provided for detecting the phase and light intensity of the laser  111   b  emitted from the second spatial light modulator  130  in the Step S 16 . In addition, a projection lens  160  is installed on the path of the laser  111   b  reflected from the second spatial light modulator  130 , and the laser  111   b  passes through the projection lens  160  and then projects onto the photoresist layer  20  to form the exposure pattern  400  on the photoresist layer  20 . 
     In some embodiment, the sensor  140  includes a plurality of beam splitters  143 ,  143 ′, a light intensity sensor  142 , and a phase sensor  141 . The beam splitter  143 ′ is installed between the second spatial light modulator  130  and the projection lens  160  and provided for dividing the incident laser  111   b  into a first laser  111   b ′ and a second laser  111   b ″. Further, the ratio of the light intensity of the first laser  111   b ′ to the light intensity of the second laser  111   b ″ is 99:1, i.e. the beam splitter  143 ′ will project 1% of the divided laser into a light intensity sensor  142  and a phase sensor  141 . In some embodiment as shown in  FIG.  2 A , the second laser  111   b ″ is split by a beam splitter  143 , and projected to light intensity sensor  142  and the phase sensor  141 . The sensor  140  receives the second laser  111   b ″ through the light intensity sensor  142  and the phase sensor  141  to generate a sensing signal. 
     With reference to  FIGS.  2 B to  7 B ,  FIG.  7 B  shows a flow chart of detecting the phase and light intensity in the exposure method of this disclosure, and the controller  150  is electrically connected to the laser source  110 , the first spatial light modulator  120 , the second spatial light modulator  130  and the sensor  140 . The controller  150  is a programmable logic controller or a computer device with a control program. The controller  150  is provided for receiving a sensing signal, and controlling the light intensity and phase of the laser outputted by the laser source  110  according to the sensing signal, and the control method includes the following steps: 
     S 161 : The beam splitter  143 ′ is used to divide the laser  111   b  into a first laser  111   b ′ and a second laser  111   b ″, wherein the first laser  111   b ′ is the laser irradiated on the photoresist layer  20  as described in the Step S 15 . 
     S 162 : The second laser  111   b ″ is projected on a light intensity sensor  142  and a phase sensor  141 , and another beam splitter  143  is used to drive the second laser  111   b ″ to enter into the light intensity sensor  142  and the phase sensor  141  separately. 
     S 163 : The light intensity sensor  142  detects the light intensity of the second laser  111   b″.    
     S 164 : The phase sensor  141  is used to detect the phase of the second laser  111   b″.    
     S 165 : The first light modulator  120  and the second light modulator  130  are controlled according to the phase and light intensity of the second laser  111   b ″, and the formed exposure pattern  400  is corrected. 
     In some embodiment, the steps S 15  and S 16  (which are the steps S 161 ˜S 165 ) are performed synchronously. While the exposure pattern  400  is being formed, the exposure pattern  400  formed by the laser can be dynamically adjusted through the steps S 161 ˜S 165 , and the exposure pattern  400  can be continuously corrected during the exposure process, further ensuring that the exposure pattern  400  matches the expected pattern. 
     More specifically, the controller  150  compares the laser parameter measured by the sensor  140  with a predetermined laser parameter, and if the measured laser parameter does not match the predetermined laser parameter, the controller  150  will control the laser source  110  to adjust the light intensity and phase of the incident laser, until the laser parameter measured by the sensor  140  matches the predetermined laser parameter. 
     In some embodiment, the controller  150  further includes an input interface  151  provided for an operator to enter a predetermined laser parameter. In addition, the input interface  151  is also provided for the operator to input a desired exposure pattern, so that the controller  150  can further operate the first spatial light modulator  120  and the second spatial light modulator  130  to form the desired exposure pattern on the photoresist layer  20  according to the data of inputted exposure pattern. 
     The exposure device and method of this disclosure have the advantages of forming a more precise or sharp exposure pattern, improving the yield of development, and overcoming the drawbacks of the related art by means of modulating the of the phase and amplitude of the laser and using the mutual interference and offset of the laser between pixels. 
     Although the invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments that will be apparent to persons skilled in the art. This invention is, therefore, to be limited only as indicated by the scope of the appended claims.