JP5143395B2 - Method for forming resist on wafer - Google Patents

Description

  The present invention relates to a method for forming a resist on a wafer, and more particularly to a method for uniformly applying a resist to a wafer.

  The manufacturing process of the thin film magnetic head includes a stacking process on a wafer using a semiconductor process technology. In the step of laminating on a wafer, like many other semiconductor devices, a photoresist (hereinafter referred to as a resist) is used for the purpose of patterning a formed film and forming a film having a predetermined planar shape. Is frequently used. FIG. 14 is a conceptual diagram showing a resist coating method using a spin coating method. In the spin coating method, after the resist R is dropped onto the center of the wafer W, the wafer W is rotated, and the resist R is diffused over the entire surface of the wafer W using centrifugal force.

  Since many elements are simultaneously formed on the wafer, it is important to apply the resist uniformly. For this reason, Patent Document 1 discloses a technique for dropping a resist while moving a nozzle for discharging the resist at a constant speed along the radial direction from the central portion to the peripheral portion of the wafer. This document also describes a technique for moving the nozzle at a constant speed along the radial direction from the peripheral part to the central part of the substrate.

Patent Document 2 discloses a technique for dropping a resist while reducing the viscosity of the resist with time in a state where the nozzle position is fixed to the center of the wafer in order to make the resist film thickness uniform and prevent the resist from dropping from the wafer. Is disclosed. Resist dropped on the wafer in the initial stage reaches the outer periphery of the wafer by centrifugal force, but because of its high viscosity, it tends to stay on the outer periphery of the wafer, preventing it from falling off the wafer, and saving resist It becomes. The viscosity is adjusted by controlling the amount of thinner mixed with the resist.
JP 2000-350955 A JP 2002-045772 A

  In the spin coating method, when the surface of the wafer onto which the resist is dropped is flat, a film having a uniform film thickness is easily obtained, and a part of the wafer is hardly left uncoated. However, in the thin film magnetic head laminating process, many steps or irregularities are formed on the wafer in the middle of the process for creating a shunt pattern, etc., and resist is often applied in that state. See). When the resist is applied to the wafer surface with many steps, the movement of the resist is obstructed by the convex portion, and the resist does not diffuse uniformly in all the directions of the wafer. As a result, the resist tends to spread radially along a large number of linear diffusion routes extending in the radial direction, resulting in a portion where the resist does not spread partially. This phenomenon becomes prominent when the resist has a low viscosity, or when the resist contains a solvent that is difficult to wet or a highly volatile solvent. A portion where the resist is not spread causes pattern defects after exposure and development. The phenomenon that the wafer surface is not partially covered with the resist is not dramatically improved even if the amount of the resist dropped is increased. This is because once the resist has a tendency to diffuse radially on the wafer surface, the resist moves to the outer periphery of the wafer according to the locus even if the resist dropping amount is increased. As a result, the dropped resist falls from the wafer without covering the portion not covered with the resist.

  In the technique described in Patent Document 1, since the resist is dropped while rotating the wafer, the resist is likely to diffuse on the outer peripheral portion of the wafer, but conversely, the resist is less likely to remain in the central portion. For this reason, an uncoated portion is likely to occur in the wafer central portion, and pattern defects in the wafer central portion are likely to occur. Since the technique described in Patent Document 2 needs to adjust the viscosity of the resist with time, it not only increases the number of processes, but also requires a complicated mixing apparatus. As shown in the patent document, it may be possible to store resists having a plurality of viscosities in separate tanks in advance, but equipment costs such as a switching device are required. Although it is conceivable to change the viscosity by adjusting the temperature of the resist, there is a similar problem because a temperature adjusting device is required for each temperature (for each viscosity).

  The present invention has been made to solve such problems of the prior art, and an object of the present invention is to provide a method for uniformly and uniformly forming a resist on an uneven wafer surface.

The method for forming a resist on a wafer according to the present invention relates to a method for forming a resist on a wafer on which a step or unevenness is formed. The method about the central axis by rotating the wafer after dropping a resist in the center around the center axis of the wafer or resist dropping Shinano in the center of the wafer, is the Lau Fine wafers of the wafer in the Rukoto further rotating the wafer without dropping the resist after rotation, the outer peripheral portion of the wafer, a first coating step of forming a raised part of the dropped resist, followed by a first coating step And a second application step of dropping the resist onto the wafer by rotating the wafer about the central axis and changing the dropping position of the resist from the central portion toward the outer peripheral portion of the wafer. .

  First, the resist is dropped onto the center of the wafer and diffuses to the outer periphery of the wafer by the rotation of the wafer. By this step, the central portion of the wafer is entirely covered with the resist, and an uncoated portion in the central portion is hardly generated, and a raised portion is formed on the outer peripheral portion. When the resist diffuses toward the outer peripheral portion, the resist is easily trapped by the convex portion of the wafer surface, and at this point, an uncoated portion is generated in a range excluding the central portion and the outer peripheral portion of the wafer. Probability is high. Next, by rotating the wafer and dropping the resist while changing the dropping position, the uncoated portions other than the central portion and the outer peripheral portion of the wafer are easily covered with the resist. This is because the resist moves along a trajectory completely different from the trajectory of the resist formed when the resist is dropped from the central portion. In addition, since the raised portion is formed on the outer peripheral portion of the wafer in the first coating step, there is little possibility that the resist flows out of the wafer. For this reason, the whole area of the wafer is uniformly covered with the resist.

  The second coating step preferably includes diffusing the dropped resist by further rotating the wafer around the central axis after the dropping of the resist is completed. This further promotes resist diffusion and further reduces the uncoated portion of the resist on the wafer.

  Subsequent to the second dropping step, a film thickness adjusting step of adjusting the film thickness of the resist by rotating the wafer around the central axis may be provided.

  It is desirable that the rotation speed of the wafer in the film thickness adjustment step be larger than the rotation speed of the wafer in the second dropping step. This facilitates the diffusion of the resist toward the outer periphery of the wafer and facilitates obtaining a desired film thickness.

  The first application step may include diffusing the dropped resist to the outer peripheral portion by increasing the number of rotations of the wafer after completion of the resist dropping. In addition, the first application step is to drop the resist while the wafer is stationary, to diffuse the dropped resist to the outer peripheral portion by rotating the wafer after the dropping of the resist is completed, May be included.

  The second coating step preferably includes continuously changing the resist dropping position from the central portion to the outer peripheral portion of the wafer.

  As described above, according to the present invention, it is possible to provide a method for uniformly and uniformly forming a resist on an uneven wafer surface.

  First, in a method of manufacturing a thin film magnetic head used in a general hard disk device, a stacking process of a portion related to a reading element will be described with reference to FIGS. In each figure, FIG. X (a) is a plan view (where x is a figure number (x = 1 to 12), the same applies hereinafter), and FIG. X (b) is cut along line xb-xb in FIG. X (a). FIG. 5 is a cross-sectional view taken along line xc-xc in FIG. X (a), and FIG. X (d) is a cross-sectional view cut along line xd-xd in FIG. X (a). In addition, a large number of elements are formed on an actual wafer, but in each drawing, only one element portion is cut out.

  (Step 1) First, as shown in FIG. 1, an insulating layer 2 made of alumina is formed on a substrate 1 made of Altic. The sensor element 11 (see FIG. 8) needs to be protected from damage caused by ESD (Electro-Static Discharge). Therefore, in order to make the sensor element 11 and the substrate 1 equipotential, plugs 8b and 17b (see FIG. 12) are provided between the lower magnetic shield layer 7 and the upper magnetic shield layer 16 surrounding the sensor element 11 from above and below and the substrate 1. ). As one procedure for that purpose, a resist 3 is formed on the insulating layer 2 and a photo pattern 4b is formed in a portion where the plugs 8b and 17b are formed. Similarly, the write head (not shown) needs to be protected from ESD damage. Therefore, it is desirable to provide plugs 8a and 17a (see FIG. 12) between the write head and the substrate 1 in order to make the write head and the substrate 1 have the same potential. As one procedure for that purpose, a photo pattern 4a is formed at a site where the plugs 8a and 17a are formed.

  (Step 2) Next, as shown in FIG. 2, holes 5a and 5b are formed in the insulating layer 2 using ion milling, RIE (Reactive Ion Etching), wet etching, or the like. Thereafter, the photoresist 3 is peeled from the insulating layer 2 using NMP (N-Methyl-2-Pyrrolidone) or a general organic solvent.

  (Step 3) Next, as shown in FIG. 3, in order to form the lower magnetic shield layer 7 of the sensor element 11, the seed layer 6 is formed by sputtering, vapor deposition or the like.

  (Step 4) Next, as shown in FIG. 4, after forming the pattern frame 31 with a photoresist, the lower magnetic shield layer 7 is formed below the portion where the sensor element 11 is formed by electroplating. At the same time, plugs 8a and 8b are formed in and above the holes 5a and 5b. Thereafter, the pattern frame 31 is peeled from the seed layer 6 by the same method as described above.

  (Step 5) Next, as shown in FIG. 5, a masking cover pattern 9 is formed using a photoresist in a region connecting the lower magnetic shield layer 7 and the plug 8b. This is to leave a part of the seed layer 6 as a shunt pattern and remove the other part in order to make the lower magnetic shield layer 7 and the plug 8b equipotential.

  (Step 6) Next, as shown in FIG. 6, a portion of the seed layer 6 that is not covered with the masking cover pattern 9, the lower magnetic shield layer 7, or the plugs 8a and 8b is used by ion milling or the like. Remove.

  (Step 7) Next, as shown in FIG. 7, an insulating layer 9 made of alumina is formed by sputtering or the like, and then the insulating layer 9, the lower magnetic shield layer 7 and the like are formed using CMP (Chemical Mechanical Polishing). The top surfaces of the plugs 8a and 8b are flattened.

  (Step 8) Next, as shown in FIG. 8, the sensor element 11 and the lead part 12 are formed. The sensor element 11 is a reading sensor composed of a dozen or more kinds of laminated films. The lead portion 12 is a conductor for supplying a sense current to the sensor element 11. A shunt pattern 13 for making the substrate 1 and the writing sensor equipotential is also formed at this stage.

  (Step 9) Next, as shown in FIG. 9, an interlayer insulating film 14 made of alumina or the like is formed, and holes 35a and 35b similar to the holes 5a and 5b are formed. Next, a seed layer 15 similar to the seed layer 6 is formed by sputtering or the like. Thereafter, a pattern frame 32 is formed with a photoresist, and the upper magnetic shield layer 16 is formed above the portion where the sensor element 11 is formed by electroplating. At the same time, plugs 17a and 17b are formed in and above the holes 35a and 35b. Thereafter, the pattern frame 32 is peeled from the seed layer 15 by the same method as described above.

  (Step 10) Next, as shown in FIG. 10, a masking cover pattern 18 is formed using a photoresist in a region connecting the upper magnetic shield layer 16 and the plug 17b. This is to leave a part of the seed layer 6 as a shunt pattern in order to make the upper magnetic shield layer 16 and the plug 17b equipotential. Similarly, masking cover patterns 19 and 20 are formed in the vicinity of the plug 17b using a photoresist. This is to leave a part of the seed layer 6 near the plug 17b as a shunt pattern in order to make the writing element equipotential with the substrate 1.

  (Step 11) Next, as shown in FIG. 10, the portion of the seed layer 15 not covered with the masking cover patterns 18 to 20 is removed by ion milling or the like.

  (Step 12) Finally, as shown in FIG. 12, an insulating layer 21 made of alumina is formed by sputtering or the like, and then the top surfaces of the insulating layer 21 and the plugs 17a and 17b are flattened using CMP. Thereafter, the write head portion is continuously formed using the conventional technique.

  In the manufacturing process described above, there are a large number of steps 1, 4, 5, 9, and 10 where the resist is applied. Of these steps, in step 5, the plugs 8a and 8b protrude, and in step 10, the plugs 17a and 17b protrude, and it is necessary to apply the resist in a state where the unevenness of the wafer surface is large. Therefore, when the resist is applied using the conventional technique, the flow of the resist toward the outer peripheral surface of the wafer is hindered by the convex portions (plugs 8a, 8b, 17a, 17b) on the wafer surface, resulting in a problem that the resist is not applied uniformly.

  In the embodiment of the present invention, in these steps, the resist is applied according to the following multiple scanning method. Table 1 is a table showing the procedure of the resist coating method according to the embodiment of the present invention. Table 2 is a table showing a resist coating method according to the prior art for comparison with the present embodiment. The shaded parts in each table are different processes. FIG. 13 is a conceptual diagram showing the state of the wafer corresponding to steps c to g in Table 1.

  (Step a) First, the wafer W is loaded into a predetermined wafer holder (not shown). The wafer holder is an apparatus for holding the wafer W in a rotatable manner and applying a resist to the wafer surface. Conventional equipment can be used as it is. The nozzle 25 for supplying the resist R is at the origin (standby position), and the wafer W is also stationary. When the wafer W is in the state of step 5, the reading element of the thin film magnetic head is formed in a later process. When the wafer is in the state of step 10, a number of reading elements are already formed. The following steps can be similarly applied regardless of the state of the wafer.

  (Step b) Next, with the wafer W mounted on the wafer holder, the nozzle 25 is moved to the center of the wafer W.

  (Step c: First Application Step) Next, as shown in FIG. 13A, the first resist dropping is performed on the wafer center. Specifically, the resist R is diffused to the outer peripheral portion of the wafer W by centrifugal force by rotating the wafer W around the central axis C at a low speed while dropping the resist R on the central portion of the wafer. The rotation speed of the wafer W is preferably 100 rpm or less. This is because the resist R falls from the outer peripheral portion of the wafer W if the rotational speed is increased too much. However, if the rotation speed is too low, the resist R is not sufficiently diffused in the radial direction, and a raised portion 41 described later is hardly formed. The resist R may be dropped while the wafer W is stationary. In this case as well, the resist R gradually diffuses to the outer peripheral portion of the wafer W as the amount of dropping the resist R increases. When the resist R is dropped while the wafer W is stationary, the resist stays in the central portion of the wafer W for a relatively long time, so that an unapplied portion hardly occurs in the central portion, and the resist can be applied uniformly. The steps c to g are a series of operations, and may be performed continuously or at intervals.

  (Step d) Next, as shown in FIG. 13B, after the resist dropping is completed, the rotation speed is kept as it is for several seconds to several tens of seconds, so that the resist R applied to the central portion is removed from the outer periphery of the wafer W. Spread further to the part (spread rotation). The rotational speed of the wafer W may be increased from step c. The resist R that has reached the outer peripheral portion is held on the outer peripheral portion of the wafer W by surface tension. Thereafter, by maintaining the same number of rotations, the resist R that continues to diffuse toward the outer peripheral portion is held at the outer peripheral portion, and the crown (where the resist R has accumulated thicker than the central portion of the wafer at the outer peripheral portion of the wafer W). A raised portion 41) is formed. The number of rotations of the wafer W is preferably set so as to promote the diffusion of the resist R so that the raised portion 41 is formed and the resist R does not flow out from the outer periphery of the wafer W. Is good. The purpose of this step is to form the raised portion 41 on the outer peripheral portion of the wafer W. Accordingly, the resist R is trapped by the plugs 8a and 8b or the plugs 17a and 17b on the wafer at the intermediate portion (intermediate region between the central portion and the outer peripheral portion) of the wafer W that becomes the path through which the resist R diffuses. There is a possibility that there is an uncoated part. When the resist R is dropped while the wafer W is stationary in step c, the dropped resist R is diffused to the outer peripheral portion by rotating the wafer W after the dropping of the resist R is completed.

  (Step e: Second Application Step) Next, as shown in FIG. 13C, while the wafer W is rotated about the central axis C, the dropping position of the resist R is changed from the central portion to the outer peripheral portion of the wafer W. Then, the resist R is dropped onto the wafer W. Since the dropping position of the resist R is different from that in step c, the resist can follow a diffusion path different from that in step c. For this reason, the resist R is easily dropped directly on the uncoated portion, and even when the resist R is not directly dropped, the resist R is easily bonded to the nearby coated resist R by surface tension. Furthermore, the effect that the resist R gathered in the outer peripheral portion and the newly supplied resist R are connected by surface tension can be expected. In this way, the uncoated portion is further eliminated by the second coating step. The number of rotations of the wafer W is preferably about the same as step d in order to diffuse the dropped resist.

  The dropping position of the resist R may be changed discretely (in a stepped manner) from the central portion toward the outer peripheral portion. It is preferable because the resist R can be dropped more evenly. In this case, since the resist R is dropped along a spiral path, a portion where the resist is dropped and a portion where the resist is not dropped are mixed at each angular position of the wafer W. However, since the resist R moves toward the outer peripheral portion due to the rotation of the wafer W, it is also diffused into the non-dropping region between the resists.

  In step d, since the nozzle 25 is in the center of the wafer W, it is preferable to move the nozzle 25 from the center toward the outer periphery, but it is also possible to move the nozzle 25 from the outer periphery toward the center. Furthermore, the movement pattern of the nozzle can be appropriately set such that the movement from the central portion to the outer peripheral portion is repeated a plurality of times or the center portion and the outer peripheral portion are reciprocated. At that time, if the resist dropping position is changed every time the nozzle is moved, the effect of eliminating the uncoated portion can be further enhanced.

  (Step f) Next, as shown in FIG. 13D, after the dropping of the resist is completed, the dropped resist R is diffused by further rotating the wafer W around the central axis. At the end of step e, the resist R is diffused over almost the entire area of the wafer W, but there is a possibility that an uncoated portion still remains. In this step, the number of rotations of the wafer W is further increased to promote the diffusion of the resist R, and the uncoated portion is eliminated. Since the resist R is additionally applied in step e, the raised portion 41 is formed higher. Therefore, there is little possibility that the resist R will flow out of the wafer W even if the number of wafer rotations is further increased. Therefore, the wafer rotation speed is preferably set to 100 rpm or more. At the end of step f, the rising portion 41 is used as a dam on the wafer, the resist R is formed with a uniform film thickness inside the rising portion 41, and the uncoated portion is largely eliminated as compared with the prior art, or It has been completely eliminated.

  (Step g: Film Thickness Adjusting Step) Next, as shown in FIG. 13E, the film thickness of the resist R is adjusted by rotating the wafer W around the central axis C. The resist R is further diffused to the outer peripheral side of the wafer W by centrifugal force, and the film thickness of the resist R other than the outer peripheral portion is decreased. Since the resist R has already been applied to the entire area of the wafer W, there is no possibility that the resist R will peel off, and the film thickness will decrease overall. This step can be replaced by step f. Since this step is intended to move the resist R to the outer peripheral portion, it is desirable that the number of rotations is at least equal to step f (100 rpm or more) or higher. It is desirable to determine the specific number of rotations according to the desired film thickness.

  On the other hand, according to the conventional coating method shown in Table 2, steps a and b are the same as in the present embodiment, except that the resist is dropped at step c ′ and the resist is diffused at step e ′. The spread is simply rotated. In this method, a resist is applied around the center of the wafer in step c ', and the resist moves to the outer periphery by the subsequent rotation of the wafer. At that time, the resist diffuses radially along a large number of linear diffusion routes extending in the radial direction, but once the diffusion route is formed, it follows the initial locus even if the amount of dripping of the resist is increased. Therefore, it is difficult to reach the entire area of the wafer.

  On the other hand, in this embodiment, the first dropping is performed at the center of the wafer, and the second dropping is performed while continuously changing the position from the center of the wafer in the outer peripheral direction. It diffuses without being constrained by the existing trajectory, and is effectively applied even to uncoated portions. In addition, since the raised portion 41 is formed on the outer periphery of the wafer in the first dropping, the diffused resist and the resist constituting the raised portion 41 are combined with each other by the surface tension, which is also effective for the uncoated portion near the outer peripheral portion. To be applied. Since the first dropping is performed on the center of the wafer, the resist is uniformly formed even in the central portion of the wafer where an uncoated portion or an insufficient film thickness portion is likely to occur. Since the raised portion 41 also functions as a dam, the dropped resist can stay in the wafer without waste, and a state where the entire surface of the wafer is covered with the resist is formed. Thereafter, by controlling the number of rotations of the wafer so as to obtain a desired film thickness, the entire wafer surface can be covered with a resist having a predetermined film thickness, and the occurrence of pattern defects can be effectively prevented.

  The method for forming a resist on a wafer in the manufacturing process of the thin film magnetic head has been described above. This method is not only in the manufacturing process of the thin film magnetic head, but also in the manufacturing process of a general semiconductor device. Needless to say, the present invention can be similarly applied when forming a resist.

It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the lamination process of the part which concerns on the reading element of a thin film magnetic head. It is a conceptual diagram which shows the condition of the wafer corresponding to step cg of Table 1. FIG. It is a conceptual diagram which shows the application | coating method of the resist using a spin coating method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Insulating layer 3 Resist 6,15 Seed layer 7 Lower magnetic shield layer 8a, 8b Plug 9, 18, 19, 20 Masking cover pattern 11 Sensor element 12 Lead part 13 Shunt pattern 16 Upper magnetic shield layer 17a, 17b Plug 25 Nozzle 31, 32 Pattern frame 41 Swelling part W Wafer R Resist

Claims (8)

A method of forming a resist on a wafer having a step or unevenness,
Around the wafer after dropping a resist in the center of the wafer by rotating around the central axis of the wafer, or resist dropping Shinano in the center of the wafer La previous SL wafer of the central axis of the wafer in the Rukoto is further rotated the wafer without dropping the resist after rotation, the outer peripheral portion of the wafer, a first coating step of forming a raised part of the dropped the resist,
Subsequent to the first coating step, the resist is dropped onto the wafer by rotating the wafer around the central axis while changing the resist dropping position from the central portion toward the outer periphery of the wafer. A second application step,
A method for forming a resist on a wafer.   2. The resist according to claim 1, wherein the second coating step includes diffusing the dropped resist by further rotating the wafer around the central axis after finishing the dropping of the resist. 3. Forming method.   3. The resist formation according to claim 1, further comprising a film thickness adjusting step of adjusting the film thickness of the resist by rotating the wafer around the central axis following the second dropping step. Method.   The resist forming method according to claim 3, wherein the rotation speed of the wafer in the film thickness adjustment step is larger than the rotation speed of the wafer in the second dropping step.   5. The method according to claim 1, wherein the first coating step includes diffusing the dropped resist to the outer peripheral portion by increasing the number of rotations of the wafer after the dropping of the resist is completed. 2. The resist forming method according to item 1. The first application step includes
Dropping the resist while the wafer is stationary;
Diffusing the dropped resist to the outer peripheral portion by rotating the wafer after the dropping of the resist is completed;
The resist formation method of any one of Claim 1 to 4 containing this.   The resist forming method according to claim 1, wherein the second applying step includes continuously changing the dropping position of the resist from the central portion to the outer peripheral portion of the wafer.   The resist forming method according to claim 1, wherein the wafer is a wafer on which a number of reading elements of a thin film magnetic head are formed or to be formed.

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