Method for improving photoresist coating uniformity of wafer

Abstract

The invention provides a method for improving wafer photoresist coating uniformity, which comprises the following steps: photoresist coating is carried out on a wafer on which a circuit pattern is formed, the number of times of photoresist coating is at least two, and the subsequent photoresist coating is carried out before the previous photoresist curing; and pre-baking the wafer coated with the photoresist to obtain a photoresist layer with uniform thickness. According to the method, multiple times of photoresist coating are carried out on the wafer on which the circuit pattern is formed, so that the uniformity of the photoresist thickness can be effectively improved, the problem of circuit damage caused by excessive etching due to the fact that a local area is too thin is avoided, and the qualified rate of wafer processing is greatly improved; according to the method, multiple times of coating are continuously carried out, the problems of photoresist layering and poor uniformity caused by successive curing are avoided, and pollution possibly caused by dust can be reduced and the adhesiveness of photoresist can be improved through pre-baking treatment on the photoresist layer and reduction of the solvent content; the method is simple to operate, low in production cost and wider in application range.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor photolithography and relates to a method for improving the uniformity of wafer photoresist coating. Background Art

[0002] With the rapid development of semiconductor technology, wafers, as the basic materials in the semiconductor field, undergo a series of processes to form tiny circuit structures, and then cut, package, and test to make chips, which are necessary steps for wafer application, and then used to prepare various semiconductor devices. The photolithography process is one of the key steps in processing wafers into chips. It is necessary to define the photolithography pattern through coating, exposure, and development, and then form the corresponding circuit layout through etching. The uniformity of photoresist coating will directly affect the subsequent processing steps, and then affect the yield of chip production.

[0003] In the front-end production process of wafer processing, photoresist needs to be evenly coated on the chip surface so that the chip can be patterned using an exposure machine and the circuit is defined after etching. Due to the height difference of the circuit layout on the wafer, the wafer surface is uneven. Therefore, in the back-end production process of the wafer, when photoresist is coated again, it is easy to cause uneven thickness distribution after photoresist coating. Local areas are not even enough to resist etching and cannot play a role in protecting the circuit. The defined circuit is destroyed, resulting in the processed chip not meeting the requirements or even being scrapped. Based on this, when photoresist is coated again on a wafer with a circuit layout, corresponding improvement measures need to be adopted to prevent the circuit from being etched.

[0004] CN 102376541A discloses a method for adjusting the uniformity of key dimensions in integrated circuit manufacturing, the method comprising: forming a test pattern on a test mask, uniformly coating a photoresist of the same thickness on a lens. The test pattern on the test mask is transferred to a wafer through exposure, development, and etching, the key dimensions of the central area and the edge area of ​​the wafer after development or etching are tested, the photoresist thickness of the central area and the edge area of ​​the wafer is determined according to the key dimensions of the two, and the coating parameters of the photoresist are adjusted so that the morphology reaches the photoresist thickness of the central area and the edge area required by the wafer. In the method, the photolithography of the wafer belongs to the front-end production step, at which time the circuit pattern has not been formed on the wafer, and the photoresist coating when the wafer surface is uneven is not involved, and the key of the method is to control the different photoresist thicknesses of the central area and the edge area of ​​the wafer, rather than the control of the photoresist coating uniformity, and the specific coating process parameters are not disclosed.

[0005] CN 117215153A discloses a photoresist coating method, device, electronic device and storage medium for wafers, the method comprising: placing a target wafer in an argon plasma atmosphere for surface pretreatment before photoresist coating, the target wafer comprising a titanium nitride film layer; coating the target wafer after surface pretreatment with photoresist, and then baking the target wafer after photoresist coating to obtain a baked target wafer. The method focuses on modifying the titanium nitride film layer after wafer pretreatment, and aims to solve the problem of high edge roughness of photoresist patterns. The steps of photoresist coating and how to ensure the uniformity of photoresist coating are not emphasized, and the wafer does not form a circuit pattern before photoresist coating, so there is no problem of photoresist coating under uneven surface.

[0006] In summary, in order to improve the uniformity of wafer photoresist coating, especially for wafers with uneven surfaces, it is necessary to improve the photoresist and its coating process to ensure the uniformity of photoresist coating, so as to avoid the problem of circuit damage caused by excessive etching due to the photoresist thickness being too thin in local areas, and to improve the qualified rate of wafer processing. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for improving the uniformity of photoresist coating on wafers. The method can effectively improve the uniformity of photoresist thickness by performing multiple photoresist coatings on wafers with formed circuit patterns, avoid the problem of circuit damage caused by excessive etching due to excessive thinness in local areas, greatly improve the processing qualification rate, and effectively reduce production costs.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for improving the uniformity of wafer photoresist coating, the method comprising the following steps:

[0010] (1) coating a wafer with a circuit pattern formed thereon with photoresist, wherein the photoresist coating is performed at least twice, and the latter photoresist coating is performed before the former photoresist coating is cured;

[0011] (2) Pre-baking the wafer after photoresist coating in step (1) to obtain a photoresist layer with uniform thickness.

[0012] In the present invention, when photoresist coating is performed on a wafer with an uneven surface on which a circuit pattern has been formed, the resistor coating process needs to be improved for the purpose of protecting the circuit pattern. On the basis of increasing the number of photoresist coatings, multiple coatings are ensured to be performed continuously to avoid the problem of photoresist stratification and poor uniformity due to sequential curing. Then, by pre-baking the photoresist layer, the solvent content is reduced to reduce the possibility of dust pollution, while improving the adhesion of the photoresist on the wafer substrate, ensuring the uniformity of the photoresist coating thickness, avoiding the problem of over-etching, ensuring the integrity of the circuit pattern after etching, and effectively improving the qualified rate of the product. The method is simple to operate, low in production cost, and has a wider range of applications.

[0013] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] As a preferred technical solution of the present invention, the wafer in step (1) has been subjected to at least one photolithography process, for example, once, twice, three times, etc., and the surface has been etched to form a circuit pattern.

[0015] Preferably, the surface of the wafer on which the circuit pattern is formed in step (1) is uneven, wherein the depth of the groove is 0.12 to 0.18 μm, for example, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm or 0.18 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the height of the protrusion is 0.16 to 0.24 μm, for example, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm or 0.24 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0016] As a preferred technical solution of the present invention, the wafer is surface treated before the photoresist coating in step (1).

[0017] Preferably, the surface treatment comprises: first cleaning with a diluent, and then heating the adhered material to steam bake the wafer surface.

[0018] Preferably, the diluent comprises any one of propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate or N-methylpyrrolidone, or a combination of at least two thereof. Typical but non-limiting examples of the combination include: a combination of propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, a combination of propylene glycol monomethyl ether acetate and N-methylpyrrolidone, a combination of propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate and N-methylpyrrolidone, and the like.

[0019] Preferably, the adhesive substance includes hexamethyldisilazide, and the heating temperature is 110-130°C, for example, 110°C, 115°C, 118°C, 120°C, 122°C, 125°C or 130°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the baking time is 45 to 60 seconds, for example 45 seconds, 48 ​​seconds, 50 seconds, 52 seconds, 55 seconds, 58 seconds or 60 seconds, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] In the present invention, the surface treatment of the adhesive material can effectively remove moisture from the wafer surface, enhance the adhesion between the photoresist and the surface, and change the wafer surface from hydrophilic to hydrophobic.

[0022] As a preferred technical solution of the present invention, the composition of the photoresist used in the photoresist coating in step (1) includes phenolic resin, sensitizer and solvent.

[0023] Preferably, the phenolic resin comprises cresol-formaldehyde resin or novolac.

[0024] Preferably, the sensitizer includes tetramethylammonium hydroxide, and the solvent includes any one or a combination of at least two of propylene glycol methyl ether acetate, acetone, ethanol or isopropanol. Typical but non-limiting examples of the combination include: a combination of propylene glycol methyl ether acetate and acetone, a combination of acetone and ethanol, a combination of ethanol and isopropanol, a combination of acetone, ethanol and isopropanol, and the like.

[0025] Preferably, the content of phenolic resin in the photoresist is 15-30wt%, for example, 15wt%, 18wt%, 20wt%, 22wt%, 24wt%, 25wt%, 27wt% or 30wt%, the content of sensitizer is 2-3wt%, for example, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.7wt%, 2.8wt% or 3wt%, and the content of solvent is 65-85wt%, for example, 65wt%, 65wt%, 68wt%, 70wt%, 72wt%, 75wt%, 78wt%, 80wt%, 82wt% or 85wt%, but is not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are equally applicable.

[0026] In the present invention, the photoresist components are selected so that the resin polymer can undergo structural changes when irradiated, the sensitizer can control the chemical reaction of the polymer phase, and the solvent can make the spinning proceed smoothly and form a thin film on the wafer surface.

[0027] As a preferred technical solution of the present invention, the photoresist coating in step (1) is performed by spin coating, and the photoresist coating is performed twice, namely, a first photoresist coating and a second photoresist coating.

[0028] Preferably, during the primary photoresist coating, the glue dripping starts after the wafer rotation speed reaches 400-600r / min, for example, 400r / min, 450r / min, 500r / min, 550r / min or 600r / min, etc., until the rotation speed reaches 3500-5000r / min and stabilizes, for example, 3500r / min, 3800r / min, 4000r / min, 4200r / min, 4500r / min, 4800r / min or 5000r / min, etc., but is not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are equally applicable.

[0029] Preferably, the glue dripping speed of the primary photoresist coating is 1.5-2.5 mL / s, for example, 1.5 mL / s, 1.6 mL / s, 1.8 mL / s, 2 mL / s, 2.2 mL / s, 2.4 mL / s or 2.5 mL / s, and the glue dripping amount is 3-4 mL, for example, 3 mL, 3.2 mL, 3.4 mL, 3.5 mL, 3.6 mL, 3.8 mL or 4 mL, but is not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are equally applicable.

[0030] Preferably, after the first photoresist coating and glue dripping are completed, the rotation is maintained for 22 to 35 seconds for glue spinning, for example, 22 seconds, 24 seconds, 25 seconds, 26 seconds, 30 seconds, 32 seconds, 34 seconds or 35 seconds, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and a second photoresist coating is performed before curing.

[0031] In the present invention, the photoresist is in liquid state when sprayed, and is sprayed once more before the photoresist is cured, which can ensure the uniformity of the photoresist distribution and avoid the problem of stratification after curing caused by too long an interval. The coating effect at the grooves on the circuit pattern is also better, avoiding the problem of the local photoresist thickness being too thin.

[0032] As a preferred technical solution of the present invention, the rotation speed of the secondary photoresist coating is 3500-5000r / min, for example, 3500r / min, 3800r / min, 4000r / min, 4200r / min, 4500r / min, 4800r / min or 5000r / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the glue dripping speed of the secondary photoresist coating is 1.5-2.5 mL / s, for example, 1.5 mL / s, 1.6 mL / s, 1.8 mL / s, 2 mL / s, 2.2 mL / s, 2.4 mL / s or 2.5 mL / s, and the glue dripping amount is 3-4 mL, for example, 3 mL, 3.2 mL, 3.4 mL, 3.5 mL, 3.6 mL, 3.8 mL or 4 mL, but is not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are equally applicable.

[0034] Preferably, after the secondary photoresist coating and glue dripping are completed, the rotation is maintained for 30 to 45 seconds for glue spinning, for example, 30 seconds, 32 seconds, 34 seconds, 36 seconds, 38 seconds, 40 seconds, 42 seconds or 45 seconds, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, until the photoresist is initially cured.

[0035] Preferably, the solvent content of the photoresist after initial curing is 10 to 30 wt%, for example 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 27 wt% or 30 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] As a preferred technical solution of the present invention, the thickness of the initially cured photoresist layer obtained after the photoresist coating in step (1) is 2.2 to 3.2 μm, for example, 2.2 μm, 2.4 μm, 2.5 μm, 2.7 μm, 3.0 μm or 3.2 μm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the overall thickness deviation of the preliminarily cured photoresist layer is controlled within ±0.3%, for example, -0.3%, -0.2%, -0.1%, 0%, 0.1%, 0.2% or 0.3%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the wafer after photoresist coating is transferred to a soft baking module for pre-baking.

[0039] As a preferred technical solution of the present invention, the pre-baking temperature in step (2) is 90-120°C, for example, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the pre-baking time is 0.5 to 2 min, for example, 0.5 min, 0.75 min, 1 min, 1.25 min, 1.5 min, 1.75 min or 2 min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the solvent content in the photoresist layer after the pre-bake is reduced to below 6wt%, for example 6wt%, 5.5wt%, 5wt%, 4.5wt%, 4wt%, 3.5wt% or 3wt%, and the thickness thereof is reduced by 10-20% compared with that before the pre-bake, for example 10%, 12%, 14%, 16%, 18% or 20%, but is not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are also applicable.

[0042] In the present invention, the pre-baking treatment can evaporate the solvent in the photoresist layer, so that the photoresist layer after coating reaches an ideal thickness, which can basically reach 2.0 to 2.8 μm, such as 2.0 μm, 2.1 μm, 2.2 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm or 2.8 μm, etc. The solvent content is reduced, which can avoid dust contamination and reduce the film stress formed by high-speed rotation, thereby improving the adhesion of the photoresist on the substrate.

[0043] As a preferred technical solution of the present invention, the thickness of the photoresist layer after etching in step (2) is 1.2 to 1.8 μm, for example, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm or 1.8 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] As a preferred technical solution of the present invention, the method comprises the following steps:

[0045] (1) The wafer is subjected to at least one photolithography process, and the surface is etched to form a circuit pattern. The surface of the wafer is uneven, wherein the depth of the groove is 0.12 to 0.18 μm, and the height of the protrusion is 0.16 to 0.24 μm. The wafer is subjected to surface treatment, and the surface treatment comprises: first cleaning with a diluent, and then heating an adhesive substance to steam bake the wafer surface, wherein the diluent comprises any one of propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, or N-methyl pyrrolidone, or a combination of at least two thereof, and the adhesive substance comprises hexamethyldisilazane, and the heating temperature is 110 to 130° C. and the baking time is 2 hours. The time is 45 to 60 seconds; then photoresist coating is performed, wherein the composition of the photoresist used in the photoresist coating includes phenolic resin, sensitizer and solvent, the phenolic resin includes cresol resin or phenolic varnish, the sensitizer includes tetramethyl ammonium hydroxide, the solvent includes any one or a combination of at least two of propylene glycol methyl ether acetate, acetone, ethanol or isopropanol, the content of phenolic resin in the photoresist is 15 to 30wt%, the content of sensitizer is 2 to 3wt%, and the content of solvent is 65 to 85wt%, the photoresist coating adopts spin coating method, and the number of photoresist coating is twice, namely, one photoresist coating and two photoresist coating;

[0046] During the primary photoresist coating, the wafer rotation speed reaches 400-600r / min before glue dripping begins, and the rotation speed reaches 3500-5000r / min and becomes stable. The glue dripping speed of the primary photoresist coating is 1.5-2.5mL / s, and the glue dripping amount is 3-4mL. After the glue dripping of the primary photoresist coating is completed, the rotation is maintained for 22-35s for glue spinning, and a secondary photoresist coating is performed before curing; the rotation speed of the secondary photoresist coating is 3500-5000r / min, the glue dripping speed of the secondary photoresist coating is 1.5-2.5mL / s, and the glue dripping amount is 3-4mL. After the glue dripping is completed, the rotation is maintained for 30-45s for glue spinning until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 10-30wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 2.2-3.2μm, and the overall thickness deviation is controlled within ±0.3%;

[0047] (2) Transferring the wafer coated with photoresist in step (1) to a soft baking module for pre-baking, wherein the pre-baking temperature is 90 to 120° C., the pre-baking time is 0.5 to 2 min, the solvent content in the photoresist layer after the pre-baking is reduced to below 6 wt %, and the thickness thereof is reduced by 10 to 20% compared with that before the pre-baking, and the thickness of the photoresist layer after etching is 1.2 to 1.8 μm.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The method of the present invention can effectively improve the uniformity of photoresist thickness by coating the wafer with circuit patterns multiple times, avoid the problem of circuit damage caused by excessive etching due to excessive thinness in local areas, and greatly improve the qualified rate of wafer processing to more than 95%;

[0050] (2) The method of the present invention increases the number of photoresist coatings and ensures that multiple coatings are performed continuously, thereby avoiding the problem of photoresist delamination and poor uniformity caused by sequential curing. The method can also reduce the solvent content by pre-baking the photoresist layer to reduce the possibility of dust contamination and improve the adhesion of the photoresist on the wafer substrate.

[0051] (3) The method of the present invention is simple to operate, has low production cost, and has a wider scope of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a photoresist slicing effect diagram after the wafer photoresist is coated provided by Example 1 of the present invention;

[0053] Figure 2 This is a slicing effect diagram of the remaining photoresist after the wafer photoresist is coated and etched provided by Example 1 of the present invention;

[0054] Figure 3 This is a diagram showing the slicing effect of the photoresist after the wafer photoresist is coated according to Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0055] In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0056] The specific implementation of the present invention provides a method for improving the uniformity of photoresist coating on a wafer, the method comprising the following steps:

[0057] (1) coating a wafer with a circuit pattern formed thereon with photoresist, wherein the photoresist coating is performed at least twice, and the latter photoresist coating is performed before the former photoresist coating is cured;

[0058] (2) Pre-baking the wafer after photoresist coating in step (1) to obtain a photoresist layer with uniform thickness.

[0059] The following are typical but non-limiting embodiments of the present invention:

[0060] Embodiment 1:

[0061] This embodiment provides a method for improving the uniformity of wafer photoresist coating, the method comprising the following steps:

[0062] (1) The wafer is subjected to a photolithography process, and the surface is etched to form a circuit pattern. The surface of the wafer is uneven, wherein the depth of the groove is 0.15 μm and the height of the protrusion is 0.2 μm. The wafer is subjected to surface treatment, and the surface treatment comprises: firstly cleaning with a diluent, and then heating the adhesive substance hexamethyldisilazane to steam bake the wafer surface, wherein the diluent is N-methylpyrrolidone, the heating temperature is 120° C., and the baking time is 50 s; then photoresist coating is performed, and the composition of the photoresist used in the photoresist coating comprises phenolic resin, sensitizer and solvent, wherein the phenolic resin is cresol formaldehyde resin, the sensitizer is tetramethylammonium hydroxide, and the solvent is propylene glycol methyl ether acetate. The content of the phenolic resin in the photoresist is 22.5 wt %, the content of the sensitizer is 2.5 wt %, and the content of the solvent is 75 wt %. The photoresist coating is performed by spin coating, and the number of times of the photoresist coating is two, namely, one photoresist coating and two photoresist coating;

[0063] During the primary photoresist coating, the wafer speed reaches 500r / min and then glue dripping begins, until the speed reaches 4200r / min and stabilizes, the glue dripping speed of the primary photoresist coating is 2.0mL / s, the glue dripping amount is 3.5mL, and after the glue dripping is completed, the rotation is maintained for 30s to spin the glue, and a secondary photoresist coating is performed before curing; the rotation speed of the secondary photoresist coating is 4200r / min, the glue dripping speed of the secondary photoresist coating is 2.0mL / s, the glue dripping amount is 3.5mL, and after the glue dripping is completed, the rotation is maintained for 40s to spin the glue until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 20wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 2.7μm, and the overall thickness deviation is controlled within ±0.2%;

[0064] (2) The wafer coated with photoresist in step (1) is transferred to a soft baking module for pre-baking. The pre-baking temperature is 100° C. and the pre-baking time is 1 min. After the pre-baking, the solvent content in the photoresist layer is reduced to 5wt%, and the thickness thereof is reduced by 15% compared with that before the pre-baking. The thickness of the photoresist layer after etching is 1.5 μm.

[0065] In this embodiment, the above method is used to coat the photoresist. The photoresist slicing effect after the wafer is coated with photoresist is shown in the figure. Figure 1 As shown in the figure, the slicing effect of the remaining photoresist after photoresist coating and etching is shown in Figure 2 shown.

[0066] In this embodiment, Figure 1 and Figure 2It can be seen that the photoresist coating method mentioned above has good thickness uniformity after coating, and the thinnest part is 2.2μm thick. Even after etching, there is still a large residual photoresist thickness, which avoids damage to the circuit pattern due to local over-etching. The product qualification rate is high, which can reach 96%.

[0067] Embodiment 2:

[0068] This embodiment provides a method for improving the uniformity of wafer photoresist coating, the method comprising the following steps:

[0069] (1) The wafer is subjected to a photolithography process, and a circuit pattern is formed by etching the surface. The surface of the wafer is uneven, wherein the depth of the groove is 0.12 μm and the height of the protrusion is 0.16 μm. The wafer is subjected to surface treatment, and the surface treatment includes: firstly cleaning with a diluent, and then heating the adhesion substance hexamethyldisilazane to steam bake the wafer surface, wherein the diluent is propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate in a mass ratio of 7:3, the heating temperature is 110° C., and the baking The time is 60s; then photoresist coating is performed, wherein the composition of the photoresist used in the photoresist coating includes phenolic resin, sensitizer and solvent, the phenolic resin includes cresol acetaldehyde resin, the sensitizer is tetramethylammonium hydroxide, the solvent is acetone, the content of phenolic resin in the photoresist is 30wt%, the content of sensitizer is 3wt%, and the content of solvent is 67wt%, the photoresist coating adopts spin coating method, and the number of photoresist coating is twice, namely, one photoresist coating and two photoresist coating;

[0070] During the first photoresist coating, the wafer speed reaches 450r / min and then glue dripping begins, and the speed reaches 3500r / min and stabilizes. The glue dripping speed of the first photoresist coating is 1.5mL / s, the glue dripping amount is 3mL, and the rotation is maintained for 25s for glue spinning after the glue dripping is completed, and the second photoresist coating is performed before curing; the rotation speed of the second photoresist coating is 3500r / min, the glue dripping speed of the second photoresist coating is 1.5mL / s, the glue dripping amount is 3mL, and the rotation is maintained for 30s for glue spinning after the glue dripping is completed until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 30wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 2.3μm, and the overall thickness deviation is controlled within ±0.3%;

[0071] (2) The wafer coated with photoresist in step (1) is transferred to a soft baking module for pre-baking. The pre-baking temperature is 90° C. and the pre-baking time is 2 min. After the pre-baking, the solvent content in the photoresist layer is reduced to 6 wt %, and the thickness is reduced by 20% compared with that before the pre-baking. The thickness of the photoresist layer after etching is 1.2 μm.

[0072] In this embodiment, the photoresist coating method is adopted, which can effectively improve the uniformity of the photoresist thickness, avoid the damage of the circuit pattern caused by local over-etching, and the product qualification rate is high, which can reach 95.6%.

[0073] Embodiment 3:

[0074] This embodiment provides a method for improving the uniformity of wafer photoresist coating, the method comprising the following steps:

[0075] (1) The wafer is subjected to a photolithography process, and the surface is etched to form a circuit pattern. The surface of the wafer is uneven, wherein the depth of the groove is 0.18 μm and the height of the protrusion is 0.24 μm. The wafer is subjected to surface treatment, and the surface treatment comprises: firstly cleaning with a diluent, and then heating the adhesive substance hexamethyldisilazane to steam bake the wafer surface, wherein the diluent is propylene glycol monomethyl ether, the heating temperature is 130° C., and the baking time is 45 s; then photoresist coating is performed, and the composition of the photoresist used in the photoresist coating comprises phenolic resin, sensitizer and solvent, wherein the phenolic resin is phenolic varnish, the sensitizer is tetramethylammonium hydroxide, and the solvent is ethanol. The content of the phenolic resin in the photoresist is 15wt%, the content of the sensitizer is 2wt%, and the content of the solvent is 83wt%. The photoresist coating is performed by spin coating, and the number of times of the photoresist coating is two, namely, one photoresist coating and two photoresist coating;

[0076] During the primary photoresist coating, the wafer speed reaches 550r / min and then glue dripping begins, and the speed reaches 5000r / min and stabilizes. The glue dripping speed of the primary photoresist coating is 2.5mL / s, the glue dripping amount is 4mL, and the rotation is maintained for 35s for glue spinning after the glue dripping is completed, and the secondary photoresist coating is performed before curing; the rotation speed of the secondary photoresist coating is 5000r / min, the glue dripping speed of the secondary photoresist coating is 2.5mL / s, the glue dripping amount is 4mL, and the rotation is maintained for 45s for glue spinning after the glue dripping is completed until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 10wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 3.2μm, and the overall thickness deviation is controlled within ±0.15%;

[0077] (2) The wafer coated with photoresist in step (1) is transferred to a soft baking module for pre-baking. The pre-baking temperature is 120° C. and the pre-baking time is 0.5 min. After the pre-baking, the solvent content in the photoresist layer is reduced to 3wt%, and the thickness thereof is reduced by 10% compared with that before the pre-baking. The thickness of the photoresist layer after etching is 1.8 μm.

[0078] In this embodiment, the above method is used for photoresist coating, which can effectively improve the uniformity of photoresist thickness, avoid damage to circuit patterns caused by local over-etching, and achieve a high product qualification rate of 95.8%.

[0079] Embodiment 4:

[0080] This embodiment provides a method for improving the uniformity of wafer photoresist coating, the method comprising the following steps:

[0081] (1) The wafer is subjected to two photolithography processes, and the surface is etched to form a circuit pattern. The surface of the wafer is uneven, wherein the depth of the groove is 0.16 μm and the height of the protrusion is 0.22 μm. The wafer is subjected to surface treatment, and the surface treatment includes: firstly cleaning with a diluent, and then heating the adhesive material hexamethyldisilazane to steam bake the wafer surface, wherein the diluent is N-methylpyrrolidone, the heating temperature is 115° C., and the baking time is 55 s; then photoresist coating is performed, The photoresist used in the photoresist coating comprises a phenolic resin, a sensitizer and a solvent, the phenolic resin comprises a cresol formaldehyde resin and a cresol acetaldehyde resin in a mass ratio of 1:1, the sensitizer is tetramethylammonium hydroxide, the solvent is isopropanol, the content of the phenolic resin in the photoresist is 27.2wt%, the content of the sensitizer is 2.8wt%, and the content of the solvent is 70wt%, the photoresist coating adopts a spin coating method, and the photoresist coating is performed twice, namely, one photoresist coating and a second photoresist coating;

[0082] During the first photoresist coating, the wafer speed reaches 400r / min and then glue dripping begins, until the speed reaches 4000r / min and stabilizes, the glue dripping speed of the first photoresist coating is 1.8mL / s, the glue dripping amount is 3.6mL, and after the glue dripping is completed, the rotation is maintained for 28s to spin the glue, and a second photoresist coating is performed before curing; the rotation speed of the second photoresist coating is 4800r / min, the glue dripping speed of the second photoresist coating is 1.8mL / s, the glue dripping amount is 3.6mL, and after the glue dripping is completed, the rotation is maintained for 36s to spin the glue until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 15wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 3.0μm, and the overall thickness deviation is controlled within ±0.25%;

[0083] (2) The wafer coated with photoresist in step (1) is transferred to a soft baking module for pre-baking. The pre-baking temperature is 110° C. and the pre-baking time is 0.75 min. After the pre-baking, the solvent content in the photoresist layer is reduced to 4 wt %, and the thickness thereof is reduced by 12% compared with that before the pre-baking. The thickness of the photoresist layer after etching is 1.6 μm.

[0084] In this embodiment, the above method is used for photoresist coating, which can effectively improve the uniformity of photoresist thickness, avoid damage to circuit patterns caused by local over-etching, and achieve a high product qualification rate of 95.4%.

[0085] Embodiment 5:

[0086] This embodiment provides a method for improving the uniformity of wafer photoresist coating, the method comprising the following steps:

[0087] (1) The wafer is subjected to two photolithography processes, and the surface is etched to form a circuit pattern. The surface of the wafer is uneven, wherein the depth of the groove is 0.14 μm and the height of the protrusion is 0.18 μm. The wafer is subjected to surface treatment, and the surface treatment includes: firstly cleaning with a diluent, and then heating the adhesion substance hexamethyldisilazane to steam bake the wafer surface, wherein the diluent is propylene glycol monomethyl ether acetate, the heating temperature is 125° C., and the baking time is 48 s; then Performing photoresist coating, wherein the photoresist used in the photoresist coating comprises a phenolic resin, a sensitizer and a solvent, wherein the phenolic resin is a phenolic varnish, the sensitizer is tetramethylammonium hydroxide, the solvent is propylene glycol methyl ether acetate, the content of the phenolic resin in the photoresist is 17.8wt%, the content of the sensitizer is 2.2wt%, and the content of the solvent is 80wt%, the photoresist coating adopts a spin coating method, and the photoresist coating is performed twice, namely, a first photoresist coating and a second photoresist coating;

[0088] During the first photoresist coating, the wafer speed reaches 600r / min and then glue dripping begins, until the speed reaches 4600r / min and stabilizes, the glue dripping speed of the first photoresist coating is 2.2mL / s, the glue dripping amount is 3.2mL, and after the glue dripping is completed, the rotation is maintained for 22s to spin the glue, and a second photoresist coating is performed before curing; the rotation speed of the second photoresist coating is 3800r / min, the glue dripping speed of the second photoresist coating is 2.2mL / s, the glue dripping amount is 3.2mL, and after the glue dripping is completed, the rotation is maintained for 32s to spin the glue until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 25wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 2.5μm, and the overall thickness deviation is controlled within ±0.15%;

[0089] (2) The wafer coated with photoresist in step (1) is transferred to a soft baking module for pre-baking. The pre-baking temperature is 105° C. and the pre-baking time is 1.5 min. After the pre-baking, the solvent content in the photoresist layer is reduced to 4.5 wt %, and the thickness thereof is reduced by 18% compared with that before the pre-baking. The thickness of the photoresist layer after etching is 1.4 μm.

[0090] In this embodiment, the above method is used for photoresist coating, which can effectively improve the uniformity of photoresist thickness, avoid damage to circuit patterns caused by local over-etching, and achieve a high product qualification rate of 95.5%.

[0091] Comparative Example 1:

[0092] This comparative example provides a method for improving the uniformity of photoresist coating on a wafer. The method is similar to the method in Example 1, with the only difference being that the photoresist coating is performed once in step (1).

[0093] In this comparative example, the above method is used for photoresist coating, and the photoresist slicing effect diagram after the wafer photoresist coating is as follows: Figure 3 shown.

[0094] In this comparative example, Figure 3 It can be seen that when only a single photoresist coating is performed, the photoresist thickness at the circuit pattern groove is extremely thin. Once subsequent etching is performed, over-etching is likely to occur, causing damage to the circuit pattern. At this time, the product qualification rate is only 80%.

[0095] Comparative Example 2:

[0096] This comparative example provides a method for improving the uniformity of photoresist coating on a wafer. The method is similar to the method in Example 1, with the only difference being that in step (1), a second photoresist coating is performed after the photoresist coated once is cured.

[0097] In this comparative example, since the photoresist coated once is cured and then a second photoresist coating is performed, the formed photoresist layer is divided into two layers, and the uniformity of the thickness is difficult to control, resulting in an increase in thickness deviation.

[0098] It can be seen from the above embodiments and comparative examples that the method of the present invention can effectively improve the uniformity of photoresist thickness by performing multiple photoresist coatings on wafers with formed circuit patterns, avoid the problem of circuit damage caused by excessive etching due to excessive thinness in local areas, and greatly improve the qualified rate of wafer processing, which can reach more than 95%; the method ensures that multiple coatings are performed continuously on the basis of increasing the number of photoresist coatings, avoids the problem of photoresist stratification and poor uniformity due to sequential curing, and can also reduce the solvent content by pre-baking the photoresist layer to reduce the possibility of dust pollution and improve the adhesion of the photoresist on the wafer substrate; the method is simple to operate, low in production cost, and has a wider range of applications.

[0099] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the method of the present invention, addition of auxiliary steps, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for improving the uniformity of wafer photoresist coating, It is characterized in that The method comprises the following steps: (1) coating a wafer with a circuit pattern formed thereon with photoresist, wherein the photoresist coating is performed at least twice, and the latter photoresist coating is performed before the former photoresist coating is cured; (2) Pre-baking the wafer after photoresist coating in step (1) to obtain a photoresist layer with uniform thickness.

2. The method according to claim 1, It is characterized in that The wafer in step (1) has been subjected to at least one photolithography process, and the surface has been etched to form a circuit pattern; Preferably, the surface of the wafer on which the circuit pattern has been formed in step (1) is uneven, wherein the depth of the grooves is 0.12 to 0.18 μm, and the height of the protrusions is 0.16 to 0.24 μm.

3. The method according to claim 1 or 2, It is characterized in that Step (1) performing surface treatment on the wafer before photoresist coating; Preferably, the surface treatment comprises: first cleaning with a diluent, then heating the adhered material to steam bake the wafer surface; Preferably, the diluent comprises any one of propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate or N-methylpyrrolidone or a combination of at least two thereof; Preferably, the adhesive substance includes hexamethyldisilazide, and the heating temperature is 110-130° C.; Preferably, the baking time is 45 to 60 seconds.

4. The method according to any one of claims 1 to 3, It is characterized in that The composition of the photoresist used in the photoresist coating in step (1) includes phenolic resin, sensitizer and solvent; Preferably, the phenolic resin comprises cresol-formaldehyde resin or novolac; Preferably, the sensitizer includes tetramethylammonium hydroxide, and the solvent includes any one or a combination of at least two of propylene glycol methyl ether acetate, acetone, ethanol or isopropanol; Preferably, the content of the phenolic resin in the photoresist is 15-30 wt %, the content of the sensitizer is 2-3 wt %, and the content of the solvent is 65-85 wt %.

5. The method according to any one of claims 1 to 4, It is characterized in that The photoresist coating in step (1) is performed by spin coating, and the photoresist coating is performed twice, namely, a first photoresist coating and a second photoresist coating; Preferably, during the primary photoresist coating, the wafer rotation speed reaches 400-600 r / min before the glue dripping starts, and the rotation speed reaches 3500-5000 r / min and stabilizes; Preferably, the glue dripping speed of the photoresist coating is 1.5-2.5 mL / s, and the glue dripping amount is 3-4 mL; Preferably, after the first photoresist coating and glue dripping are completed, the rotation is maintained for 22 to 35 seconds to perform glue spinning, and a second photoresist coating is performed before curing.

6. The method according to any one of claims 1 to 5, It is characterized in that The rotation speed of the secondary photoresist coating is 3500-5000 r / min; Preferably, the glue dripping speed of the secondary photoresist coating is 1.5-2.5 mL / s, and the glue dripping amount is 3-4 mL; Preferably, after the secondary photoresist coating and glue dripping are completed, the rotation is maintained for 30 to 45 seconds to perform glue spinning until the photoresist is initially cured; Preferably, the solvent content of the photoresist after preliminary curing is 10-30 wt %.

7. The method according to any one of claims 1 to 6, It is characterized in that The thickness of the initially cured photoresist layer obtained after the photoresist coating in step (1) is 2.2 to 3.2 μm; Preferably, the overall thickness deviation of the preliminarily cured photoresist layer is controlled within ±0.3%; Preferably, the wafer after photoresist coating is transferred to a soft baking module for pre-baking.

8. The method according to any one of claims 1 to 7, It is characterized in that The pre-baking temperature in step (2) is 90-120° C. Preferably, the pre-baking time is 0.5 to 2 minutes; Preferably, after the pre-bake, the solvent content in the photoresist layer drops to below 6 wt %, and the thickness thereof is reduced by 10-20% compared with that before the pre-bake.

9. The method according to any one of claims 1 to 8, It is characterized in that The thickness of the photoresist layer after etching in step (2) is 1.2 to 1.8 μm.

10. The method according to any one of claims 1 to 9, It is characterized in that The method comprises the following steps: (1) The wafer is subjected to at least one photolithography process, and the surface is etched to form a circuit pattern. The surface of the wafer is uneven, wherein the depth of the groove is 0.12 to 0.18 μm, and the height of the protrusion is 0.16 to 0.24 μm. The wafer is subjected to surface treatment, and the surface treatment comprises: first cleaning with a diluent, and then heating an adhesive substance to steam bake the wafer surface, wherein the diluent comprises any one of propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, or N-methyl pyrrolidone, or a combination of at least two thereof, and the adhesive substance comprises hexamethyldisilazane, and the heating temperature is 110 to 130° C. and the baking time is 2 hours. The time is 45 to 60 seconds; then photoresist coating is performed, wherein the composition of the photoresist used in the photoresist coating includes phenolic resin, sensitizer and solvent, the phenolic resin includes cresol resin or phenolic varnish, the sensitizer includes tetramethyl ammonium hydroxide, the solvent includes any one or a combination of at least two of propylene glycol methyl ether acetate, acetone, ethanol or isopropanol, the content of phenolic resin in the photoresist is 15 to 30wt%, the content of sensitizer is 2 to 3wt%, and the content of solvent is 65 to 85wt%, the photoresist coating adopts spin coating method, and the number of photoresist coating is twice, namely, one photoresist coating and two photoresist coating; During the primary photoresist coating, the wafer rotation speed reaches 400-600r / min before glue dripping begins, and the rotation speed reaches 3500-5000r / min and stabilizes. The glue dripping speed of the primary photoresist coating is 1.5-2.5mL / s, and the glue dripping amount is 3-4mL. After the glue dripping of the primary photoresist coating is completed, the rotation is maintained for 22-35s to spin the glue, and a secondary photoresist coating is performed before curing; the rotation speed of the secondary photoresist coating is 3500-5000r / min, the glue dripping speed of the secondary photoresist coating is 1.5-2.5mL / s, and the glue dripping amount is 3-4mL. After the glue dripping is completed, the rotation is maintained for 30-45s to spin the glue until the photoresist is initially cured, and the solvent content of the photoresist after the initial curing is 10-30wt%; the thickness of the initially cured photoresist layer obtained after the photoresist coating is 2.2-3.2μm, and the overall thickness deviation is controlled within ±0.3%; (2) Transferring the wafer coated with photoresist in step (1) to a soft baking module for pre-baking, wherein the pre-baking temperature is 90 to 120° C., the pre-baking time is 0.5 to 2 min, the solvent content in the photoresist layer after the pre-baking is reduced to below 6 wt %, and the thickness thereof is reduced by 10 to 20% compared with that before the pre-baking, and the thickness of the photoresist layer after etching is 1.2 to 1.8 μm.

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