1. Field of the Invention
The present invention relates to a manufacturing method for devices to be fabricated on a substrate, and a dicing method. More particularly, the present invention is a manufacturing method including a dicing process in which devices are cut off after the surfaces of the devices are protected with a protective film, and a dicing method.
2. Description of the Related Art
For example, manufacturing processes required for manufacturing multiple devices, which are fabricated on a substrate, for example, semiconductor devices or micro-electromechanical system (MEMS) devices include a dicing process in which the devices are separated. For example, some MEMS devices have a microscopic hole, channel, or a movable part. These devices are fragile due to low mechanical strength and may have flowed surfaces. Consequently, even in the dicing process, the devices may be broken due to vibration from cutting with a dicing saw. Moreover, the faces of the devices may be damaged by fine powder produced during cutting. Therefore, a dicing process has been proposed in which the faces of the devices are protected prior to dicing.
Japanese Unexamined Patent Publication No. 2000-349416 discloses a method in which, for example, after a thermal peel-apart adhesive tape is attached to the face of a semiconductor substrate, in which numerous MEMS devices are fabricated, in order to protect the face of the semiconductor substrate, dicing is performed and after the completion of the dicing, the thermal peel-apart adhesive tape is heated in order to sufficiently reduce adhesive strength, and then peeled off. However, when the face of a substrate is protected with an adhesive tape, if a movable member is fabricated on the face of the substrate, unless the adhesive tape is peeled off uniformly, the movable member may be adversely affected.
Japanese Unexamined Patent Publication No. 10-239346 discloses a method in which: after a semiconductor substrate in which numerous devices each including a movable part and a void are fabricated, is immersed in a resist solution in order to protect the face of the semiconductor substrate, with the resist cured, dicing is performed, and after dicing, the resist on the face of the substrate is removed using a resist peeling agent.
Japanese Unexamined Patent Publication No. 11-160570 discloses a method in which: when dicing is performed in order to dissociate numerous optical couplers which are fabricated on a substrate and each of which includes a dielectric block, a photo-resist is applied in advance to the light incidence surface or light reflecting surface of each dielectric block in order to form a protective film, and after dicing, the protective film is removed using a resist remover.
Problems using a resist as a protective film will be described with reference to
In a dicing process, semiconductor substrate 51 is diced together with photo-resist 53 using a dicing saw while water is sprayed on a cutting position. Thereafter, the photo-resist 53 is dissolved with a solvent and thus removed.
An art in which a resist is not adopted as a protective agent has been unveiled. Japanese Unexamined Patent Publication No. 2001-44143 discloses a method in which: liquefied carbon dioxide is sprayed on a substrate so that dry ice will form on the substrate; in this state, dicing is performed while microparticles of dry ice are sprayed; and after dicing, while a stationary stage is cooled to room temperature, the microparticles of dry ice are further sprayed in order to remove shavings and the dry ice layer. However, when the dry ice is used, a dicing machine and a semiconductor substrate in which devices are fabricated have to be kept at a very low temperature. Moreover, since the semiconductor substrate is alternately brought to room temperature and a very low temperature, the devices may be adversely affected.
Japanese Unexamined Patent Publication No. 59-92356 discloses a method in which a thermally dissoluble polymeric resin, in other words, a resin that is a polymer which is dissolved into monomers when heated is used as a reinforcement resin for the surface of a semiconductor substrate. The reinforcement resin is fully decomposed and removed with heat dissipated during die bonding. However, heating must be used for removal of the thermally dissoluble polymeric resin. Furthermore, Japanese Unexamined Patent Publication No. 59-92356 has not discussed the issue of remaining fine powder produced during cutting.
The present invention addresses the foregoing problems. An object of the present invention is to provide a device manufacturing method and a dicing method capable of reliably removing fine powder without leaving a protective agent residue, which is used to protect the face of a substrate during dicing, even after removal.
In order to accomplish the above object, a device manufacturing method in accordance with the present invention includes: a device fabrication step of fabricating multiple devices in a substrate; a volatile protective agent application step of applying a volatile protective agent to at least the face of the substrate in which the devices are fabricated; a dicing step of separating the devices from the substrate in which the devices are fabricated; a cleaning step for cleaning the surface of the volatile protective agent after the completion of the dicing step; and a volatile protective agent evaporation step for evaporating the volatile protective agent after the cleaning step.
The volatile protective agent application step is a process for applying a volatile protective agent to both sides of a substrate in which devices are fabricated. The volatile protective agent application step may include a process in which: the volatile protective agent is applied to a dummy substrate; the back of the substrate in which the devices are fabricated is placed on the volatile protective agent; and the volatile protective agent is applied to the face of the substrate in which the devices are fabricated.
Moreover, the volatile protective agent application step may include a step of attaching an adhesive tape to the back of a substrate in which devices are fabricated, and applying a volatile protective agent to the face of the substrate.
Preferably, after the volatile protective agent is applied, the substrate in which the devices are fabricated should be retained at a temperature equal to or lower than the melting point of the volatile protective agent until at least the cleaning step is completed.
At the cleaning step, the surface of a volatile protective agent may be cut using a liquid to which high-frequency ultrasonic waves are applied.
The liquid to which high-frequency ultrasonic waves are applied may be cooling water used to cool a dicing chuck which immobilizes the substrate during dicing.
At the cleaning step, the surface of a volatile protective agent may be dissolved using a liquid whose temperature is higher than the melting point of the volatile protective agent.
At the volatile protective agent evaporation step, a substrate covered with a volatile protective agent is evaporated in an atmospheric pressure environment or at room temperature.
At the volatile protective agent evaporation step, a substrate covered with a volatile protective agent is evaporated in a depressurized atmosphere.
A dicing method in accordance with the present invention is a dicing method for substrates including: a step of placing a substrate on a base; a step of applying a volatile protective agent to the face of the substrate; a step of solidifying the volatile protective agent; a step of dicing the substrate together with the volatile protective agent; a step of cleaning the surface of the volatile protective agent; and a step of dissolving or vaporizing the volatile protective agent.
According to a device manufacturing method and a dicing method in which the present invention is implemented, the face of a substrate can be prevented from being damaged. Moreover, fine powder or dust stemming from a dicing step will not adhere to the substrate. Furthermore, a volatile protective agent is evaporated and thus removed while being left intact. Therefore, unlike a method in which a resist protective agent is employed, a residue of the protective agent is not left. Consequently, production of a defective device can be prevented, and a product yield can be improved.
a is an enlarged top view of devices having microscopic holes and being manufactured according to the manufacturing method of the embodiment;
b is an enlarged top view of devices having microscopic holes and being manufactured according to a conventional manufacturing method;
A process of covering both sides of a substrate, in which numerous devices are fabricated, with a volatile protective agent will be described below. In the present embodiment, a dummy substrate is used to support a substrate.
A volatile protective agent 22 is applied to dummy substrate 21. A method of applying the volatile protective agent is not limited to any specific one. A known application method employing a dispenser may be adopted. Volatile protective agent 22 protects the back of a substrate 11 (see
Substrate 11 is placed on volatile protective agent 22 applied to dummy substrate 21 shown in
When hexamethylcyclotrisiloxane whose melting point is 65° C. is adopted as a volatile protective agent, a hot plate is used to retain dummy substrate 22 and substrate 11 at the temperature equal to or higher than the melting point of hexamethylcyclotrisiloxane.
Hexamethylcyclotrisiloxane is applied to dummy substrate 21, while dummy substrate 21 is placed on the hot plate and retained at the temperature equal to or higher than the melting point of 65° C. Substrate 11 is placed on dummy substrate 21, and hexamethylcyclotrisiloxane is further applied to the face of substrate 11. Thereafter, the temperature of the hot plate is lowered to be equal to or lower than 65° C. After hexamethylcyclotrisiloxane is solidified, the substrate covered with hexamethylcyclotrisiloxane is placed on the dicing chuck.
When substrate 11 is covered with the protective agent, substrate 11 is ready for dicing. According to a known method, substrate 11 is diced using a dicing saw while cutting water or cooling water is sprayed on the cutting point.
The jet nozzle unit 41 has multiple nozzles 42 lined. Once jet nozzle unit 41 is moved in a direction orthogonal to the line of nozzles 42, the entire surface of the volatile protective agent 22 can be cleaned. Only one jet nozzle may be used and swept lengthwise and sideways. As water to be jetted out of jet nozzles 42, cooling water supplied from a chiller 32 and used to cool the chuck 31 that holds a substrate is used. As shown in
Consequently, the thickness of the surface of a protective agent shaved with water jets can be controlled by adjusting an amount of water and time to be jetted out of jet nozzles 42.
If volatile protective agent 22 can be thickly applied, after dicing, water whose temperature exceeds the melting point of the volatile protective agent 22 may be flowed in order to dissolve the surface of volatile protective agent 22. Thus, fine powder remaining on the surface may be removed.
Thereafter, cooling of the dicing chuck 31 by the chiller 32 is stopped, and the substrate covered with volatile protective agent 22 is left intact at ambient temperature. Since the vapor pressure of octamethylcyclotetrasiloxane that is volatile protective agent 22 is high, the volatile protective agent evaporates. This results in devices whose surfaces are not damaged, in which fine powder is not mixed, and on which no residue is left. In order to facilitate evaporation of volatile protective agent 22, the substrate covered with volatile protective agent 22 should be disposed in a depressurized environment in order to speed up evaporation. When hexamethylcyclotrisiloxane whose melting point is 65° C. is used, the vapor pressure thereof is so high that hexamethylcyclotrisiloxane is evaporated under atmospheric pressure in a room-temperature environment. Even in this case, when hexamethylcyclotrisiloxane is disposed in the depressurized environment, it is evaporated more quickly. However, for quicker evaporation, the volatile protective agent may be heated.
In the present embodiment, substrate 11 in which devices are fabricated is covered with volatile protective agent 22, and fine powder on the volatile protective agent is removed. Therefore, the possibility that devices fabricated in substrate 11 may be broken during removal of the fine powder or the like can be minimized.
In the present embodiment, volatile protective agent 22 is used to bond substrate 11 to dummy substrate 21. Therefore, when volatile protective agent 22 is evaporated, substrate 11 is isolated from dummy substrate 21.
According to a manufacturing method in which the present embodiment is implemented, the face of a substrate can be prevented from being damaged at a dicing step or a step of removing fine powder. Moreover, fine powder or dust stemming from the dicing step does not adhere to the substrate. Furthermore, a volatile protective agent is evaporated and removed at ambient temperature. Compared with a method that adopts a resist as a protective agent, a residue of the protective agent will not be left in concave parts of a substrate or of micro-fabricated devices. Consequently, generation of a defective device can be prevented and product yield can be improved.
Furthermore, when a resist is adopted as a protective agent, a solvent is needed to remove the protective agent. In the present embodiment, while a volatile protective agent is left intact at ambient temperature, it is removed. The cost for use of the solvent can be saved. Moreover, since it is not necessary to attach a dicing tape to the back of a substrate, the step of peeling off the tape is omitted. Furthermore, devices being damaged or adversely affected by peeling off the tape will not occur.
The method of the present embodiment in which a volatile protective agent is applied to the face of a dummy substrate, a substrate in which devices are fabricated is fixed to the dummy substrate, and the protective agent is applied to the face of the substrate would prove effective especially in a case where the back of the substrate is prone to break. However, if the back of the substrate is strong, and after the substrate is diced with an adhesive tape attached to the back thereof, when the adhesive tape is peeled off, the devices will not be adversely affected. In this case, the adhesive tape may be used to secure the back of the substrate, and the volatile protective agent may be applied to only the face of the substrate.
At step S1, devices are fabricated in substrate 11 made of, for example, a semiconductor (see
At step S2, a volatile protective agent is applied to substrate 11.
At step S21 in
At step S22, substrate 11 is placed on dummy substrate 12. At step S23, volatile protective agent 22 is applied to the face of substrate 11.
At step S24, the temperature of the dicing chuck is lowered to be equal to or lower than the melting point of the volatile protective agent, whereby volatile protective agent 22 is solidified. Substrate 11 is covered entirely by the protective agent and fixed to dummy substrate 21 (see
At step S3, according to a known method, dicing is performed using a dicing saw while cutting water or cooling water is being sprayed on the cutting point. As a result, fine powder 35 adhere to the surface of volatile protective agent 22 and remain (see
At step S4, the surface of volatile protective agent 22 is therefore cleaned by utilizing high-frequency ultrasonic cleaning. Specifically, cleaning water to which ultrasonic waves are applied is sprayed, whereby the surface of volatile protective agent 22 is shaved in order to remove the fine powder or dust (see
At step S5, cooling the dicing chuck is stopped and left intact at room temperature in order to evaporate volatile protective agent 22. This results in devices whose surfaces are not damaged, into which fine powder is not mixed, and in which no residue is left (see
An example of the present invention will be described. Microscopic holes of about 3 μm in diameter are formed in a silicon wafer of about 500 μm thick in order to fabricate bio-MEMS devices. Octamethylcyclotetrasiloxane is uniformly applied as a volatile protective agent so that it will have a thickness of 200 μm. Then, the silicon wafer is cooled in order to solidify the protective agent.
The silicon wafer is diced using a dicing saw. A purified water jet (1.2 l/min) of 0° C. to which high-frequency ultrasonic waves (1 MHz, 60 W) are applied is used to remove only the superficial layer of the protective agent, whereby the fine powder of silicon is removed. Then, the protective agent is evaporated. This results in bio-MEMS devices that have no dust stuck to the surfaces or the perimeters of the microscopic holes and have no residue of the protective agent on the surfaces or the perimeters of the microscopic holes thereof.
b) shows a comparative example in which a conventional resist (model AZ-P4210) is applied to a silicon wafer in which bio-MEMS devices having microscopic holes are fabricated. The resist is removed using an organic solvent after dicing. In the comparative example, as shown in
Number | Date | Country | Kind |
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2006-323006 | Nov 2006 | JP | national |