JP2009164406A - Forming method of pit for substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a pit of detailed and sufficient depth without inviting remarkable increase of manufacturing cost. <P>SOLUTION: A multilayer resist consisting of a lower photoresist layer, a nitride silicon layer and an upper photoresist layer, is formed on the surface of a sapphire substrate in a first step. A plurality of detailed pits are formed on an upper photoresist layers by the effect of laser beam radiation and developer in second and third steps. The detailed pits are formed on the nitride silicon layer through vapor etching by 100% of chlorofluocarbon (CF<SB>4</SB>. flon 14) in a fourth step. In a fifth step, the pit is formed on the lower photoresist layer through the vapor etching by 100% of oxygen (O<SB>2</SB>). In a sixth step, the pit is formed on the sapphire substrate through the vapor etching by the mixed gas of Cl<SB>2</SB>/CH<SB>4</SB>/Ar. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for forming fine pits by gas etching on the surface of a high hardness substrate such as a sapphire substrate.

  In the LED, the ratio of the light that can be extracted to the outside with respect to the light generated in the light emitting layer, that is, the improvement of the light extraction efficiency is an important issue. For this reason, various measures have been taken. One of them is the surface of a substrate made of sapphire or the like formed into a concavo-convex shape, and a layer made of a semiconductor material having a different refractive index is formed through a buffer layer or directly concavo-convex. There has been proposed a structure in which a semiconductor crystal layer including a light emitting layer is stacked thereon by being embedded and grown. According to this structure, light propagating in the lateral direction can be efficiently extracted to the outside.

In order to produce such a structure, it is necessary to form a plurality of pits on a high-hardness substrate such as sapphire to make it uneven. As a method of forming a plurality of pits on a high-hardness substrate, for example, Patent Documents 1 and 2 show. The method disclosed in Patent Document 1 directly irradiates a high-hardness substrate with a high-energy laser beam to form pits at the irradiated location. In the method disclosed in Patent Document 2, a photoresist layer is formed on a high-hardness substrate, pits are formed in the photoresist by laser irradiation and development, and etching is performed. A pit is formed below.
JP 2004-1114075 A JP 2007-134742 A

  However, in the method disclosed in Patent Document 1, since a high-energy laser is required, the laser processing apparatus becomes large and a large work space is required. In addition, due to the high energy, there is a problem that the cost of the laser processing apparatus is increased and the manufacturing cost is increased. Furthermore, in order to improve the light extraction efficiency, it is necessary to make the pits formed on the substrate of high hardness as fine as possible. However, in the laser spot, the pits are formed only at the central portion where the laser intensity is high. Then, a pit with sufficient depth cannot be created. In other words, if a deep pit is to be formed, the pit diameter increases accordingly, and eventually a fine pit cannot be formed.

  On the other hand, in the method disclosed in Patent Document 2, it is necessary to reduce the reaction trace of the photoresist in order to make the pit fine, and the pit reaching the high hardness substrate by reducing the reaction trace of the photoresist is reduced. In order to make it, the photoresist must be thinned. However, if the photoresist is thinned, the etching must be completed before the photoresist is affected by the etching, so that a problem arises in that pits of sufficient depth cannot be formed.

  The present invention has been made in view of the above problems, and the object thereof is a method for forming fine pits on a substrate having high hardness such as sapphire, which is fine and sufficient without causing a significant increase in manufacturing cost. It is an object of the present invention to provide a pit forming method capable of forming a pit having a depth.

  In order to achieve the above object, the present invention is characterized in that a multilayer resist having an uppermost layer capable of forming reaction traces or pits by laser light irradiation and a gas-etchable layer formed under the uppermost layer. Irradiating a laser beam to the uppermost layer of the resist-coated substrate on which the multilayer resist is formed by the multilayer resist forming step and forming the multilayer resist on the substrate surface, or on the uppermost layer A first pit forming step for forming pits in the uppermost layer by irradiating a laser beam on the uppermost layer and then forming a pit in the uppermost layer by the first pit forming step. A second pit forming step in which an etching gas is allowed to act on the upper surface of the resist-coated substrate to form pits in the gas-etchable layer; An etching gas different from the etching gas used in the second pit forming step is allowed to act on the upper surface of the resist-coated substrate in which pits are formed in the gas-etchable layer by the 2-pit forming step, thereby forming pits on the substrate. 3 pit formation step.

  The present invention is suitable for forming a plurality of fine pits having a width of about 400 nm and a depth of about 400 nm on a high hardness substrate such as a sapphire substrate. The cross-sectional shape (cross-sectional shape orthogonal to the depth direction) of the pits formed on the substrate is preferably circular, but may be extended long.

  In the present invention, first, in the multilayer resist forming step, the multilayer resist including the uppermost layer capable of forming reaction traces or pits by laser light irradiation and the gas-etchable layer formed under the uppermost layer is the substrate surface. Formed on top. A substrate with a resist is manufactured by this multilayer resist forming step. Note that the uppermost layer only needs to react with laser light irradiation, and does not mean that gas etching is impossible.

  Subsequently, in the first pit formation step, the uppermost layer of the resist-coated substrate is irradiated with laser light, or the laser beam is irradiated and then a developer is applied to the uppermost layer, whereby pits are formed on the uppermost layer. Is formed. In this case, by forming the uppermost layer as a thin photoresist, pits that reach a fine and gas-etchable layer can be formed in the uppermost layer. The pit formed in the uppermost layer is desirably an opening penetrating the uppermost layer. In general, a pit means a concave portion, but in the present invention, it is a concave portion regarded as a resist-attached substrate, and includes a through-opening in each layer.

  Subsequently, in the second pit forming step, pits are formed in a layer below the uppermost layer by applying an etching gas to the upper surface of the resist-coated substrate using the uppermost layer as a mask. That is, an etching gas acts on a layer (a gas-etchable layer) below the pit formed in the uppermost layer to form a pit. Accordingly, fine pits can be formed in the layer below the uppermost layer. This pit is also desirably an opening penetrating the gas-etchable layer, but may be one having a little bottom.

  Subsequently, in the third pit formation step, an etching gas different in kind from the etching gas used in the second pit formation step is allowed to act on the upper surface of the resist-coated substrate using a gas-etchable layer as a mask. A pit is formed. In other words, the etching gas acts on the upper surface of the substrate through the pits formed in the multilayer resist remaining on the substrate (not all layers need to remain), and pits (recesses) are formed in the substrate. . In this case, in the previous step, a gas-etchable layer (mask layer) in which fine pits are formed on the substrate surface can be formed thick. A pit having a sufficient depth can be formed on the substrate before the influence is exerted.

  As a result, fine pits having a sufficient depth can be formed even on a high-hardness substrate. In addition, although the number of resist layers is increased as compared with the conventional one, a laser processing apparatus having a normal laser beam intensity can be used, so that the manufacturing cost is not significantly increased.

  Another feature of the present invention is that in the multilayer resist forming step, the gas-etchable layer is formed of at least two layers, and the uppermost layer of the gas-etchable layer has a reaction mark or pit formed by laser light irradiation. This is because it is formed of a layer that is not formed.

  According to the present invention, the pit formation of the uppermost layer by laser light irradiation and development does not affect the gas-etchable layer, so that a good-shaped pit can be formed in the gas-etchable layer.

  According to another feature of the present invention, the multilayer resist forming step includes forming the gas-etchable layer into two layers, an upper layer and a lower layer, and the second pit forming step is performed by the first pit forming step. A first etching gas is allowed to act on the upper surface of the resist-coated substrate having pits formed in the uppermost layer, and pits are formed in the upper layer of the gas-etchable layer, and gas etching is performed by the upper pit forming step. A lower layer pit forming step in which a second etching gas different from the first etching gas is allowed to act on the upper surface of the resist-coated substrate in which pits are formed on the upper layer of the possible layer, and pits are formed below the gas-etchable layer; It is to include.

  In this invention, the gas-etchable layer is formed of two layers, an upper layer and a lower layer. In the second pit formation step, an upper layer pit formation step and a lower layer pit formation step are performed. In the upper layer pit forming step, pits are formed in the upper layer of the gas-etchable layer by applying a first etching gas to the upper surface of the resist-coated substrate using the uppermost layer as a mask. Accordingly, fine pits can be formed on the upper layer of the gas-etchable layer. This pit is also desirably an opening that penetrates the upper layer of the gas-etchable layer, but it may be one that leaves a little bottom.

  Subsequently, in the lower layer pit formation step, pits are formed in the lower layer of the gas-etchable layer by applying a second etching gas to the upper surface of the resist-coated substrate using the upper layer of the gas-etchable layer as a mask. . This pit is also desirably an opening penetrating the lower layer of the gas-etchable layer, but may be one that leaves a little bottom. The lower layer of the gas-etchable layer is used as a mask when the substrate is gas-etched in the third pit formation step. In this case, the third pit is formed in the lower layer when the lower layer pit formation step is completed by appropriately setting the etching selectivity between the lower layer and the upper layer in the second etching gas (lower layer etching rate / upper layer etching rate). The thickness required as a mask when the substrate is gas-etched in the step can be ensured. As a result, fine pits having a sufficient depth can be formed even on a high-hardness substrate.

  Another feature of the present invention is that the uppermost layer on which reaction traces or pits are formed by the laser beam irradiation and the lower layer of the gas-etchable layer are formed of the same resist material. According to the present invention, the types of resist materials to be used can be reduced, and the manufacturing cost can be suppressed.

  Another feature of the present invention is that the substrate is a sapphire substrate. According to the present invention, a substrate on which pits are formed can be applied, for example, to an LED substrate, and the range of use is widened.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing a method for forming fine pits (hereinafter referred to as a fine pit forming method) on a sapphire substrate which is one of the high-hardness substrates as the embodiment, and FIG. It is the flowchart which represented 1 step divided into substeps. Moreover, FIG. 3 (FIG. 3A, FIG. 3B) is sectional drawing showing the formation state of the sapphire substrate and resist layer in each step.

  The fine pit forming method is roughly divided into a first step S1 to a seventh step S7, and will be described in order from the first step S1. In addition, the specific numerical value shown in the following description is a numerical value appropriate for finally forming a cross-sectional pit having a diameter of 300 nm to 500 nm and a depth of 300 nm to 500 nm on the sapphire substrate.

<First Step S1>
The first step S <b> 1 is a step of forming a plurality of resist layers (hereinafter referred to as a multilayer resist 20) on the surface of the sapphire substrate 10. The first step S1 includes three sub steps (S11 to S13).
<Sub-step S11>
First, the sapphire substrate 10 is set on a spin coater (rotary coating apparatus), and a photoresist is applied on the surface of the sapphire substrate 10. The coating amount is adjusted so that the thickness of the photoresist after pre-baking becomes 2000 nm to 4000 nm. Next, the sapphire substrate 10 coated with the photoresist is pre-baked with a hot plate. Pre-baking is performed at 135 to 230 ° C. for 5 to 10 minutes.

  The photoresist layer 21 thus formed on the surface of the sapphire substrate 10 is hereinafter referred to as a lower photoresist layer 21. The lower photoresist layer 21 becomes unresponsive to light by pre-baking (generally called hard baking) under the above-described temperature conditions. Various types of photoresist can be used. In this embodiment, OFPR-800LB manufactured by Tokyo Ohka Kogyo Co., Ltd. is used.

<Sub-step S12>
When the sub-step S11 is completed, the sapphire substrate 10 on which the lower photoresist layer 21 is formed is loaded into a CVD apparatus, and the silicon nitride Si ₃ N ₄ film 22 is formed on the lower photoresist layer 21 by vapor phase growth. To form. Vapor phase growth is performed so that the thickness of the silicon nitride Si ₃ N ₄ film 22 is about 100 nm. Hereinafter, the silicon nitride Si ₃ N ₄ film 22 formed on the lower photoresist layer 21 is referred to as a silicon nitride layer 22.

<Sub-step S13>
When the sub-step S12 is completed, the sapphire substrate 10 on which the silicon nitride layer 22 is formed is set on a spin coater (rotary coating apparatus), and a photoresist is applied on the silicon nitride layer 22. The coating amount is adjusted so that the thickness of the photoresist after pre-baking is 200 nm to 1000 nm. Next, the sapphire substrate 10 coated with the photoresist is pre-baked with a hot plate. Pre-baking is performed at 90 to 135 ° C. for 5 to 10 minutes.

  The photoresist layer 23 thus formed on the silicon nitride layer 22 is hereinafter referred to as an upper photoresist layer 23. Since the upper photoresist layer 23 is pre-baked under the low temperature condition described above, it becomes a layer capable of forming a reaction trace with respect to the laser beam. Further, since the upper photoresist layer 23 is a layer for forming fine pits by laser light irradiation, which will be described later, its thickness is thin and limited to the above-mentioned dimensions. Although various types of photoresists can be used, in this embodiment, OFPR-800LB manufactured by Tokyo Ohka Kogyo Co., Ltd., which is the same photoresist used in sub-step S11, is used.

  Thus, in the first step S1, as shown in FIG. 3A (S1), the multilayer resist 20 including the lower photoresist layer 21, the silicon nitride layer 22, and the upper photoresist layer 23 is formed on the surface of the sapphire substrate 10. . Hereinafter, the sapphire substrate 10 on which the multilayer resist 20 is formed is referred to as a substrate 1 with resist.

  This first step S1 corresponds to the multilayer resist forming step in the present invention. The upper photoresist layer 23 corresponds to the uppermost layer in which reaction traces or pits can be formed by laser light irradiation in the present invention, and the silicon nitride layer 22 and the lower photoresist layer 21 are gas-etchable layers in the present invention. Among them, the silicon nitride layer 22 corresponds to the upper layer of the gas-etchable layer in the present invention, and the lower photoresist layer 21 corresponds to the lower layer of the gas-etchable layer in the present invention.

<Second Step S2>
The second step S2 is a step of forming a reaction mark 23a in the upper photoresist layer 23 by laser light irradiation.
When the first step S1 is completed, the resist-coated substrate 1 is set in a laser processing apparatus, and a pulsed laser beam is irradiated perpendicularly to the upper surface of the multilayer resist 20, thereby cross-sectioning the upper photoresist layer 23 at regular intervals. A circular reaction mark 23a is formed (see FIG. 3A (S2)). Since the influence of the laser beam irradiation is hardly exerted on the silicon nitride layer 22, the reaction trace 23 a is formed only on the upper photoresist layer 23. The laser processing apparatus used in the second step S2 will be described later.

<Third Step S3>
The third step S3 is a step of removing the reaction trace 23a and forming pits 23p in the upper photoresist layer 23.
When the second step S2 is completed, the resist-coated substrate 1 is then immersed in a container containing a developer for several minutes to remove the reaction trace 23a (see FIG. 3 (S3)). Thereafter, the resist-coated substrate 1 is taken out from the container, washed to remove the developer, and dried. A developer corresponding to a photoresist may be used. In this embodiment, NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd., which is a developer corresponding to OFPR-800LB manufactured by Tokyo Ohka Kogyo Co., Ltd., is used. In this case, the silicon nitride layer 22 formed under the upper photoresist layer 23 hardly changes even when the developer is immersed.

  The upper photoresist layer 23 is formed thin as described above. Therefore, the fine pits 23p having a good shape can be formed in the upper photoresist layer 23 by the second and third steps S2 and S3. The pits 23p are openings having a circular cross section that penetrates the upper photoresist layer 23. The second step S2 and the third step S3 correspond to the first pit formation step of the present invention.

<Fourth Step S4>
The fourth step S4 is a step of forming pits 22p in the silicon nitride layer 22 by gas etching.
When the third step S3 is completed, the substrate with resist 1 is loaded into an etching apparatus, and an etching gas is applied in a direction perpendicular to the upper surface of the multilayer resist 20 using the upper photoresist layer 23 as a mask. As a result, pits 22p are formed in the silicon nitride layer 22 at portions facing the pits 23p of the upper photoresist layer 23 (see FIG. 3B (S4)). The pits 22p are openings having a circular cross section that penetrates the silicon nitride layer 22. The etching gas simultaneously etches the upper photoresist layer 23 and the silicon nitride layer 22, but pits can be formed in the silicon nitride layer 22 before the upper photoresist layer 23 is lost and the mask function is lost. An etching gas may be used. In this embodiment, 100% carbon tetrafluoride (CF ₄ , Freon 14) is used. In this example, the selectivity between the upper photoresist layer 23 and the silicon nitride layer 22 is approximately 1: 1.

  In this case, in the previous second and third steps S2 and S3, the silicon nitride layer 22 is hardly changed by laser light irradiation and developer immersion. Similarly, fine pits 22p having a good shape can be formed.

<Fifth Step S5>
The fifth step S5 is a step of forming pits 21p in the lower photoresist layer 21 by gas etching.
When the fourth step S4 is completed, the substrate with resist 1 is loaded in the same etching apparatus (or loaded in another etching apparatus), and another etching gas is applied in multiple layers using the silicon nitride layer 22 as a mask. The resist 20 is applied in a direction perpendicular to the upper surface of the resist 20. As a result, pits 21p are formed at portions of the lower photoresist layer 21 facing the pits 22p of the silicon nitride layer 22 (see FIG. 3B (S5)). The pits 21p are openings having a circular cross section that penetrates the lower photoresist layer 21.

At the start of etching in the fifth step S5, the upper photoresist layer 23 remaining on the silicon nitride layer 22 also functions as a mask. However, it is removed by gas etching at an early stage, and substantially the silicon nitride layer 22 Is used as a mask. The etching gas simultaneously etches the silicon nitride layer 22 and the lower photoresist layer 21. However, the pits 21p can be formed in the lower photoresist layer 21 before the silicon nitride layer 22 is lost and the mask function is lost. An etching gas may be used. In this embodiment, 100% oxygen (0 ₂ ) is used. In this example, the selectivity between the lower photoresist layer 21 and the silicon nitride layer 22 (the etching rate of the lower photoresist layer 21 / the etching rate of the silicon nitride layer 22) is approximately 50: 1.

  Thereby, fine pits 21p having the same cross-sectional shape as the pits 22p formed in the silicon nitride layer 22 can be formed in the lower photoresist layer 21. In addition, the remaining multilayer resist 20 (the lower photoresist layer 21 and the silicon nitride layer 22) can have a necessary thickness as a mask when the sapphire substrate 10 is subjected to gas etching in the sixth step described later.

  The fourth step S4 and the fifth step S5 correspond to the second pit formation step in the present invention. The fourth step S4 corresponds to the upper layer pit forming step in the present invention, and the fifth step S5 corresponds to the lower layer pit forming step in the present invention.

<Sixth Step S6>
The sixth step S6 is a step of forming pits 10p on the sapphire substrate 10 by gas etching.
When the fifth step S5 is completed, the substrate with resist 1 is loaded in the same etching apparatus (or loaded in another etching apparatus), and another etching gas is applied in multiple layers using the lower photoresist 21 as a mask. It acts in a direction perpendicular to the surface of the resist 20. Thereby, the pit 10p is formed in the site | part which faces the pit 21p of the lower photoresist layer 21 in the sapphire substrate 10 (refer FIG. 3B (S6)).

Any etching gas may be used as long as the pit 10p can be formed on the sapphire substrate 10. Since the sapphire substrate 10 is a high-hardness substrate, a mixed gas of Cl ₂ / CH ₄ / Ar having a large etching power is used in this embodiment. Therefore, although the multilayer resist 20 is also etched by this etching gas, since the lower photoresist layer 21 is formed as thick as 2000 nm to 4000 nm, before the etching in the lower photoresist layer 21 reaches the surface of the sapphire substrate 10, The etching of the sapphire substrate 10 can be finished. For this reason, on the sapphire substrate 10, deep pits having the same planar shape as the pits formed on the multilayer resist 20, that is, fine pits having a sufficient depth can be formed. This sixth step S6 corresponds to the third pit formation step of the present invention.

<Seventh Step S7>
The seventh step S7 is a step of removing the multilayer resist 20 (in this case, the lower photoresist layer 21) formed on the sapphire substrate 10.
The lower photoresist layer 21 remains on the surface of the sapphire substrate 10 for which the sixth step S6 has been completed. Therefore, in the seventh step S7, the sapphire substrate 10 with the lower photoresist layer 21 remaining is dipped in a container containing a stripping solution for several minutes to remove the lower photoresist layer 21 from the sapphire substrate 10 (FIG. 3B ( See S7). Thereafter, the sapphire substrate 10 is taken out from the container, washed to remove the stripping solution and dried. A stripping solution corresponding to a photoresist may be used, and in this embodiment, Tokyo Ohka Kogyo 104, which is a stripping solution compatible with Tokyo Ohka Kogyo's OFPR-800LB, is used.

  According to the method for forming fine pits on the high-hardness substrate described above, since the upper photoresist layer 23 which is the uppermost layer for forming the multilayer resist 20 is formed thin, the upper photoresist layer 23 is formed by laser light irradiation. Pits 23p that reach a minute and immediately lower layer can be formed. Since a layer (a silicon nitride layer 22 in the present embodiment) in which no reaction trace is formed with respect to laser light irradiation is provided as a layer immediately below the upper photoresist layer 23, the same layer (in this embodiment, the silicon nitride layer 22) Fine pits 22p having the same cross-sectional shape as the pits 23p of the upper photoresist layer 23 can be formed in the second silicon nitride layer 22).

  Furthermore, since the etching selectivity is set large in the fifth step S5, when the sapphire substrate 10 is gas-etched in the sixth step in the lowermost layer of the multilayer resist 20 (the lower photoresist layer 21 in the present embodiment). The necessary thickness for the mask can be secured.

  As a result, according to the present embodiment, fine pits 10p having a sufficient depth can be formed in the sapphire substrate 10. Further, since the sapphire substrate 10 is not directly irradiated with laser light to form pits, a high-energy laser processing apparatus is not required, and the manufacturing cost is not significantly increased. Note that the present invention is not limited to the numerical values of these embodiments, and by appropriately selecting the thickness, type, number of layers, type of etching gas, and the like of the resist layer, the width of 300 nm is particularly applied to a high-hardness substrate. The present invention can be effectively applied to the formation of fine pits having a depth of ˜800 nm and a depth of 100 nm to 500 nm. Further, the present invention is applied when the etching rate of the substrate to be formed with pits is smaller than the etching rate of the photoresist, and is not limited to the application to the sapphire substrate.

  Next, the laser processing apparatus used in 2nd step S2 is demonstrated. FIG. 4 is an overall schematic diagram of the laser processing apparatus used in the second step S2. This laser processing apparatus includes a table 31 as a support member that fixes and supports the resist-coated substrate 1 and a processing head 40 that irradiates a laser beam toward the upper surface of the resist-coated substrate 1 to laser-process the resist-coated substrate 1. I have. The table 31 is formed in a circular shape and is driven by a spindle motor 32 and a feed motor 33.

  The spindle motor 32 rotationally drives the table 31 through the rotation shaft 32a by the rotation. The spindle motor 32 incorporates an encoder 32b that detects the rotation of the motor 32, that is, the table 31, and outputs a rotation detection signal indicating the rotation. The encoder 32 b detects the rotation of the spindle motor 32 and outputs a rotation detection signal representing the rotation to the spindle motor control circuit 41. The spindle motor control circuit 41 is controlled by a controller 60 which will be described later, and controls the spindle motor 32 to rotate at a rotation speed designated by the controller 60 using a rotation detection signal supplied from the encoder 32b.

  The feed motor 33 rotates the screw rod 34 to move the table 31 in the radial direction. The screw rod 34 is connected to one end of the screw rod 34 so as to rotate integrally with the rotation shaft of the feed motor 33, and is screwed to a nut (not shown) fixed to the support member 35 at the other end. The support member 35 fixedly supports the spindle motor 32 and is only allowed to move in the radial direction of the table 31. Therefore, when the feed motor 33 rotates, the spindle motor 32, the table 31, and the support member 35 move in the radial direction of the table 31 by the screw mechanism including the screw rod 34 and the nut.

  Also incorporated in the feed motor 33 is an encoder 33a that detects the rotation of the feed motor 33 and outputs a rotation detection signal similar to the encoder 32b. The rotation detection signal is output to the radial position detection circuit 43 and the feed motor control circuit 44. The radial position detection circuit 43 has a count circuit that counts the rotation detection signal from the encoder 33a, detects the radial position of the table irradiated with laser light based on the count value of the count circuit, and determines the radial position. A detection signal is output. The initial setting of the count circuit is performed in cooperation with the feed motor control circuit 44 according to an instruction from the controller 60.

  That is, in the initial stage, the controller 60 instructs the feed motor control circuit 44 to move the support member 35 to the initial position and the radial position detection circuit 43 to perform initial setting. In response to this instruction, the feed motor control circuit 44 rotates the feed motor 33 to move the support member 35 to the initial position. This initial position is a drive limit position of the support member 35 driven by the feed motor 33. The radial position detection circuit 43 continues to input a rotation detection signal from the encoder 33a while the support member 35 is moving. When the support member 35 reaches the initial position and the rotation of the feed motor 33 stops, the radial position detection circuit 43 detects the stop of the input of the rotation detection signal from the encoder 33a and sets the count value of the built-in count circuit as “ Reset to “0”. At this time, the radius position detection circuit 43 outputs a signal for stopping the output to the feed motor control circuit 44, whereby the feed motor control circuit 44 stops outputting the drive signal to the feed motor 33.

  The feed motor control circuit 44 drives and controls the feed motor 33 in accordance with an instruction from the controller 60 to move the irradiation position of the laser beam to a designated radial position of the table 31 or move the table 31 in the radial direction at a designated speed. Or Specifically, the feed motor control circuit 44 feeds using the radial position detected by the radial position detection circuit 43 when the movement of the irradiation position of the laser beam to the radial position designated by the controller 60 is instructed. The rotation of the motor 33 is controlled, and the feed motor 33 is rotated until the detected radial position becomes equal to the radial position designated by the controller 60. When the feed motor control circuit 44 is instructed to move the irradiation position of the laser beam in the radial direction of the table 31 at the moving speed designated by the controller 60, the feed motor control circuit 44 uses the rotation detection signal from the encoder 33a to The movement speed in the radial direction is calculated, and the rotation of the feed motor 33 is controlled so that the calculated movement speed becomes equal to the movement speed designated by the controller 60.

  The processing head 40 includes a laser light source 40a, a collimating lens 40b, a polarizing beam splitter 40c, a quarter wavelength plate 40d, an objective lens 40e, a convex lens 40f, a cylindrical lens 40g, a four-divided photo detector 40h, a focus actuator 40i, and the like. The laser beam from 40a is condensed on the surface of the substrate 1 with resist and the reflected light from the substrate 1 with resist is received. The laser light source 40 a is driven and controlled by a light emission signal supply circuit 45 and a laser drive circuit 46 that are controlled by the controller 60. The light emission signal supply circuit 45 inputs data representing a machining pattern (pit shape) from the controller 60 and supplies a pulse train signal corresponding to the data to the laser drive circuit 46. The laser drive circuit 46 is controlled by the controller 60 to supply a drive signal corresponding to the pulse train signal from the light emission signal supply circuit 45 to the laser light source 40a.

  Further, the reflected light by the laser light applied to the resist-coated substrate 1 is guided to and received by the four-divided photodetector 40h. The four-divided photodetector 40 h supplies a focus error signal generation circuit 48 with a light reception signal composed of four signals via the HF signal amplification circuit 47. The focus error signal generation circuit 48 generates a focus error signal based on the light reception signal detected by the four-divided photodetector 40 h and amplified by the HF signal amplification circuit 47 and outputs the focus error signal to the focus servo circuit 49. The focus servo circuit 49 generates a focus servo signal based on the focus error signal and supplies it to the drive circuit 50. The drive circuit 50 drives and controls the focus actuator 40i in the processing head 40 in accordance with the focus servo signal so that the laser light is focused on the surface of the substrate 1 with resist. The focus actuator 40i is provided in the processing head 40 and displaces the objective lens 40e in the optical axis direction of the laser light.

  The controller 60 is configured by a computer including a storage device such as a CPU, a ROM, a RAM, and a hard disk. The controller 60 executes the program according to instructions from the input device 61 such as a keyboard and a mouse, thereby controlling the laser processing apparatus. Operate. The controller 60 is also connected with a display device 62 for visually informing the operator of the operation instructions and the operation status.

  The substrate 1 with a resist has a disk shape, and is set on the table 31 via a substrate fixing jig 70 as shown in FIG. The substrate fixing jig 70 is provided with fixing holes 70 h for fixing and aligning a plurality of substrates (4 in this embodiment) around the central axis of the table 31 in the circumferential direction. Placed on. As shown in FIG. 6, the substrate 1 with resist is inserted into the fixing hole 70 h of the substrate fixing jig 70 with the multilayer resist 20 formation surface side facing up. A plurality of suction holes 31 a are formed on the upper surface of the table 31, and a negative pressure is generated in the suction holes 31 a by the operation of a suction device (not shown) so that the substrate fixing jig 70 and the substrate 1 with resist are attached to the table 31. Fix to the top by suction.

  In this laser processing apparatus, the controller 60 outputs control signals to the spindle motor control circuit 41, the feed motor control circuit 44, and the laser drive circuit 46, thereby sending the table 31 in the radial direction while rotating the table 31, and the processing head 40. A pulsed laser beam is irradiated from the above. Therefore, reaction traces 23a or fine pits 23p can be formed on the upper photoresist layer 23 on the plurality of resist-coated substrates 1 with one table 31. In the present embodiment, the table 31 is moved in the radial direction. However, the machining head 40 may be moved in the radial direction of the table 31.

  As described above, in this embodiment, when the resist-coated substrate 1 is irradiated with laser light in the second step S2, a plurality of resist-coated substrates 1 are arranged on the table 31 in the circumferential direction around the central axis of the table. Since the relative position of the table 31 and the processing head 40 is changed in the radial direction of the table 31 while rotating the table, the processing efficiency is very good.

  As mentioned above, although embodiment of this invention was described in detail, in implementing this invention, it is not limited to the said embodiment, A various deformation | transformation is possible unless it deviates from the objective of this invention.

  For example, in the present embodiment, a reaction mark 23a is formed on the upper photoresist layer 23 by laser light irradiation in the second step S2, and a developer is applied in the third step S3, thereby causing the upper photoresist layer 23 to react. Although the pits 23p are formed, the step of removing reaction traces with a developer may be omitted by using a resist material in which the pits 23p are formed by laser light irradiation. In this case, the third step S3 can be omitted, and the pits 10p can be formed on the sapphire substrate 10 more efficiently.

In the present embodiment, in the seventh step S7, the lower photoresist layer 21 remaining on the sapphire substrate 10 is removed using a stripping solution, but the substrate 1 with resist is put into the same etching apparatus. While loaded (or loaded into another etching apparatus), 100% oxygen (0 ₂ ), which is the etching gas used in the fifth step S5, may be applied to the lower photoresist layer 21 to be removed. . In this case, since the sapphire substrate 10 is not etched with 100% oxygen (0 ₂ ), the etching gas may be allowed to act longer than the time during which the remaining lower photoresist layer 21 can be removed.

  In the present embodiment, the laser processing apparatus employs a configuration in which a plurality of resist-coated substrates 1 are placed on a table and irradiated with laser light at a time. However, the present invention is not limited to this, and any laser processing is possible. The device can be used.

It is a flowchart which shows the pit formation method of the board | substrate of this invention. It is the flowchart which divided and showed the 1st step of the pit formation method of the board | substrate of this invention to a substep. It is sectional drawing for every step (first half) of a board | substrate with a resist. It is sectional drawing for every step (latter half) of a board | substrate with a resist. It is a schematic system block diagram of the laser processing apparatus used at a 2nd step. It is explanatory drawing showing the setting method to the table of a board | substrate with a resist. It is a schematic perspective view showing the state where the board | substrate with a resist was set to the table.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate with a resist, 10 ... Sapphire substrate, 10p ... Pit (fine pit), 20 ... Multi-layer resist, 21 ... Lower photoresist layer, 21p ... Pit, 22 ... Silicon nitride layer, 22p ... Pit, 23 ... Upper photoresist Layer, 23a ... reaction trace, 23p ... pit, 31 ... table, 32 ... spindle motor, 33 ... feed motor, 40 ... processing head, 60 ... controller, 70 ... substrate fixing jig, 70h ... fixing hole.

Claims (5)

A multilayer resist forming step of forming on the substrate surface a multilayer resist having an uppermost layer capable of forming reaction traces or pits by laser light irradiation and a gas-etchable layer formed under the uppermost layer;
By irradiating the uppermost layer of the resist-coated substrate on which the multilayer resist is formed in the multilayer resist forming step with a laser beam, or irradiating the uppermost layer with a laser beam and then applying a developer to the uppermost layer. A first pit forming step of forming pits in the uppermost layer by acting;
A second pit forming step of forming an pit in the gas-etchable layer by causing an etching gas to act on the upper surface of the resist-coated substrate in which the pit is formed in the uppermost layer by the first pit forming step;
An etching gas different from the etching gas used in the second pit formation step is allowed to act on the upper surface of the resist-coated substrate in which pits are formed in the gas-etchable layer in the second pit formation step, thereby forming pits on the substrate. And a third pit forming step. A method for forming a pit on a substrate.   In the multilayer resist forming step, the gas-etchable layer is formed of at least two layers, and the uppermost layer of the gas-etchable layer is formed of a layer in which no reaction mark or pit is formed by laser light irradiation. The method for forming pits on a substrate according to claim 1. The multilayer resist forming step includes:
The gas-etchable layer is formed of two layers, an upper layer and a lower layer,
The second pit formation step includes
An upper layer pit forming step of forming a pit on an upper layer of the gas-etchable layer by causing a first etching gas to act on the upper surface of the resist-coated substrate in which the pit is formed in the uppermost layer by the first pit forming step;
A second etching gas different from the first etching gas is allowed to act on the upper surface of the resist-coated substrate in which pits are formed in the upper layer of the gas-etchable layer in the upper layer pit forming step, and pits are formed in the lower layer of the gas-etchable layer. 3. A method for forming a pit on a substrate according to claim 1, further comprising a lower layer pit forming step for forming the substrate.   4. The pit of the substrate according to claim 3, wherein the uppermost layer in which reaction traces or pits are formed by the laser light irradiation and the lower layer of the gas-etchable layer are formed of the same resist material. Forming method.   The method for forming pits on a substrate according to any one of claims 1 to 4, wherein the substrate is a sapphire substrate.

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