A method for calculating a photoresist coating thickness

Abstract

The application discloses a photoresist coating thickness calculation method. According to the photoresist coating thickness calculation method, the thickness measurement value and the thickness theoretical value of the photoresist coating formed under different rotating speeds are fitted to form a fitting equation, and the thickness of at least one layer of photoresist coating formed under any rotating speed is calculated by using the fitting equation, thereby improving the calculation precision of the photoresist coating. The thickness measurement value of each nth layer of photoresist coating and the thickness theoretical value of each nth layer of photoresist coating are fitted to obtain a total thickness theoretical correction value of the photoresist coating, and finally the precise calculation of the multi-photoresist coating film thickness is realized, the wafer waste caused by blind speed adjustment and slice confirmation is avoided, and the cost is greatly saved. The required photoresist coating thickness can also be quickly and accurately prepared, and the product circulation and development time are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a photoresist coating thickness calculation method. BACKGROUND

[0002] With the rapid development of electronic industry, higher requirements are put forward for the design and manufacturing process of integrated circuits, such as higher integration, continuously shrinking critical dimension (CD), multifunctional integration, etc. As the only process for generating patterns in semiconductor manufacturing, the stability and accuracy of the lithography process directly affect the product yield.

[0003] As a barrier layer in subsequent etching process or implantation process, the thickness of photoresist needs to be adjusted according to actual requirements to avoid the medium being etched through or the implantation penetrating the photoresist layer affecting the device performance. For example, in MEMS / BCD / IGBT special processes, deep trench etching and high dose implantation are widely used, which have higher requirements for the thickness of photoresist, generally greater than 2 μm; if photoresist is used as a protective layer after PAD, such as polyimide, the thickness requirement is generally greater than 10 μm. With the continuous development of electronic industry, special device chips in the manufacturing process will inevitably have higher requirements for the thickness of photoresist under the premise of ensuring resolution, such as greater than 20 μm. When the thickness of the formed single-layer photoresist cannot meet the requirements, multiple layers of photoresist can be formed to make the cumulative thickness of the photoresist meet the process requirements.

[0004] However, since the measurement of the thickness of the photoresist coating is usually destructive, it is necessary to propose a photoresist coating thickness calculation method to realize accurate calculation of the thickness of the photoresist coating. SUMMARY

[0005] In the summary section, a series of simplified concepts are introduced, which will be further described in detail in the specific embodiment section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solution, nor to attempt to determine the protection scope of the claimed technical solution.

[0006] The present application provides a photoresist coating thickness calculation method, comprising:

[0007] providing at least two substrates;

[0008] completing n times of photoresist coating, each of the substrates forms n layers of photoresist coating stacked in turn from bottom to top, the photoresist coating rotation speed of different substrates is different, and the photoresist coating rotation speed of each layer of photoresist coating on the same substrate is the same or different;

[0009] The thickness measurement value of the nth photoresist coating layer on each substrate is the thickness measurement value of each nth photoresist coating layer formed at different rotating speeds.

[0010] The thickness theoretical value of the nth photoresist coating layer on each substrate is the thickness theoretical value of each nth photoresist coating layer formed at different rotating speeds.

[0011] The fitting equation about the thickness theoretical correction value of the nth photoresist coating layer is obtained by fitting the thickness measurement value of each nth photoresist coating layer and the thickness theoretical value of each nth photoresist coating layer.

[0012] The total thickness theoretical correction value of the n photoresist coating layers on the substrate formed after the n photoresist coating is completed is calculated by using the fitting equation.

[0013] Wherein, n is a positive integer greater than or equal to 1.

[0014] Further, the fitting equation about the thickness theoretical correction value of the nth photoresist coating layer is obtained by fitting the thickness measurement value of each nth photoresist coating layer and the thickness theoretical value of each nth photoresist coating layer, further comprising:

[0015] The fitting is linear fitting or binomial fitting.

[0016] Further, the thickness measurement value of the nth photoresist coating layer on each substrate is the thickness measurement value of each nth photoresist coating layer formed at different rotating speeds, further comprising:

[0017] The n photoresist coating layers are sequentially stacked from the first photoresist coating layer, the second photoresist coating layer, and the nth photoresist coating layer in order from the top surface of the substrate.

[0018] After the first photoresist coating is completed, the measured thickness of the photoresist coating layer on each substrate is the thickness measurement value of the first photoresist coating layer on each substrate, which is the thickness measurement value of the first photoresist coating layer formed at different rotating speeds.

[0019] After the n photoresist coating is completed, the measured thickness of the photoresist coating layer on each substrate is the thickness measurement value of the nth photoresist coating layer on each substrate, which is the thickness measurement value of the nth photoresist coating layer formed at different rotating speeds.

[0020] Further, the calculation of the thickness theoretical value of the nth photoresist coating layer on each substrate, i.e. the thickness theoretical value of each nth photoresist coating layer formed at different rotating speeds, further comprises:

[0021] The following equation is used to calculate the thickness theoretical value of the nth photoresist coating layer:

[0022] D n 2 ×ω n =d n 2 ×ω′ n

[0023] wherein,

[0024] ω n represents a pre-defined known photoresist coating reference rotating speed of the nth photoresist coating layer;

[0025] ω′ n represents an arbitrary photoresist coating rotating speed for forming the nth photoresist coating layer;

[0026] D n represents a thickness measured value of the nth photoresist coating layer formed at the rotating speed of ω n

[0027] d n represents a thickness theoretical value to be calculated of the nth photoresist coating layer formed at the rotating speed of ω′ n

[0028] Further, the fitting comprises a linear fitting to determine a linear relationship fitting coefficient related to the thickness measured value of the nth photoresist coating layer and the thickness theoretical value of the nth photoresist coating layer, to obtain a linear relationship fitting equation for the thickness theoretical correction value of the nth photoresist coating layer:

[0029]

[0030] wherein,

[0031] a represents a first linear relationship fitting coefficient, and is a constant;

[0032] b represents a second linear relationship fitting coefficient, and is a constant;

[0033] ω n represents a pre-defined known photoresist coating reference rotating speed of the nth photoresist coating layer;

[0034] ω′ n represents an arbitrary photoresist coating rotating speed for forming the nth photoresist coating layer;

[0035] D​​n represents the thickness measurement value of the photoresist coating layer formed at ω n represents the thickness measurement value of the photoresist coating layer formed at ω

[0036] y n represents the thickness theoretical correction value of the nth layer photoresist coating layer to be calculated, which is formed at ω' n represents the thickness theoretical correction value of the nth layer photoresist coating layer to be calculated, which is formed at ω'

[0037] Further, the fitting includes a binomial fitting to determine binomial relationship fitting coefficients related to the thickness measurement value of the nth layer photoresist coating layer and the thickness theoretical value of the nth layer photoresist coating layer, to obtain a binomial relationship fitting equation for the thickness theoretical correction value of the photoresist coating layer of the nth layer photoresist coating layer:

[0038]

[0039] wherein,

[0040] A represents a first binomial relationship fitting coefficient and is a constant;

[0041] B represents a second binomial relationship fitting coefficient and is a constant;

[0042] C represents a third binomial relationship fitting coefficient and is a constant;

[0043] ω n represents a photoresist coating reference rotation speed of the nth layer photoresist coating layer which is known in advance;

[0044] ω' n represents an arbitrary photoresist coating rotation speed for forming the nth layer photoresist coating layer;

[0045] D n represents the thickness measurement value of the photoresist coating layer formed at ω n represents the thickness measurement value of the photoresist coating layer formed at ω

[0046] y n represents the thickness theoretical correction value of the nth layer photoresist coating layer to be calculated, which is formed at ω' n represents the thickness theoretical correction value of the nth layer photoresist coating layer to be calculated, which is formed at ω'

[0047] Further, the total thickness theoretical correction value of the n layers of photoresist coating layers formed on the substrate after completing n times of photoresist coating calculated by using the fitting equation further includes:

[0048] The total thickness theoretical correction value of the n layers of photoresist coating layers formed on any substrate after completing n times of photoresist coating is calculated according to the following relationship:

[0049]

[0050] wherein,

[0051] Y n represents a total thickness theoretical correction value of the n layers of photoresist coating layers formed after n times of photoresist coating on any substrate to be calculated;

[0052] y n represents a thickness correction value of the n-th layer of photoresist coating layer.

[0053] Further, the substrate comprises a semiconductor substrate, and the semiconductor substrate comprises semiconductor elements and / or semiconductor structures.

[0054] Further, the step of forming n layers of photoresist coating layers stacked in sequence from bottom to top on each of the substrates comprises:

[0055] The n times of photoresist coating is completed by using a spin coating process.

[0056] The photoresist coating is solidified to form the photoresist coating layer.

[0057] Further, the rotation speed ranges from 500 r / min to 10000 r / min.

[0058] According to the photoresist coating layer thickness calculation method provided by the present application, the thickness measurement value and the thickness theoretical value of the photoresist coating layer formed at different rotation speeds are fitted to form a fitting equation, and the thickness of at least one layer of photoresist coating layer formed at any rotation speed is calculated by using the fitting equation, thereby improving the calculation precision of the photoresist coating layer. Based on the fitting of the thickness measurement value of each n-th layer of photoresist coating layer and the thickness theoretical value of each n-th layer of photoresist coating layer, the total thickness theoretical correction value of the photoresist coating layer is obtained, and finally the precise calculation of the multi-photoresist coating layer film thickness is realized, thereby avoiding the wafer waste caused by blind adjustment of the rotation speed and slice confirmation of the thickness, greatly saving the cost. The required photoresist coating layer thickness can also be quickly and accurately prepared, and the product circulation and development time are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0059] The following drawings of the present application are hereby incorporated as a part of the present application for the purpose of understanding the present application. The embodiments of the present application and the description thereof shown in the drawings are used to explain the principles of the present application.

[0060] In the drawings:

[0061] Figure 1 It is a flowchart of the photoresist coating layer thickness calculation method of one embodiment;

[0062] Figure 2 It is a schematic diagram of a semiconductor device of one embodiment;

[0063] Figure 3 It is a curve diagram of linear fitting of the thickness theoretical value and the thickness measurement value of the first layer of photoresist coating layer of one embodiment;

[0064] Figure 4 Graph of binomial fit of thickness theoretical values versus thickness measured values for a first layer of photoresist coating of one embodiment;

[0065] Figure 5 Graph of binomial fit of thickness theoretical values versus thickness measured values for a second layer of photoresist coating of one embodiment. DETAILED DESCRIPTION

[0066] In the following description, numerous specific details are set forth to provide a more thorough understanding of the present application. However, it will be apparent to one of skill in the art upon

[0067] It should be understood that the present application can be practiced with the elements in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions can be exaggerated for clarity. Identical reference numerals have been used, where applicable, to designate corresponding elements.

[0068] It will be understood that when an element or layer is referred to as being "on" or "adjacent" or "connected" or "coupled" to another element or layer, it can be directly on, adjacent, connected or coupled to the other element or layer or one or more intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on," "directly adjacent," "directly connected" or "directly coupled" to another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application.

[0069] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is inverted, then a dependent element or feature described as "below" or "beneath" another element or feature is oriented "above" or "over" the other element or feature. Thus, the exemplary term "below" or "beneath" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0070] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0071] For a thorough understanding of the present application, reference should be made to the following detailed description, in conjunction with the accompanying drawings, in which:

[0072] In order to realize the accurate calculation of the photoresist coating thickness, the present application provides a photoresist coating thickness calculation method, as shown in the following formula: Figure 1 The method comprises the following steps:

[0073] Step S101: providing at least two substrates;

[0074] Step S102: completing n times of photoresist coating, each of the substrates is formed with n layers of photoresist coating which are stacked from bottom to top, the photoresist coating rotation speeds of different substrates are different, and the photoresist coating rotation speeds of each layer of photoresist coating on the same substrate are the same or different;

[0075] Step S103: measuring the thickness measurement value of the nth layer of photoresist coating on each substrate, i.e. the thickness measurement value of each nth layer of photoresist coating formed under different rotation speeds;

[0076] Step S104: calculate the theoretical thickness of the nth photoresist coating layer on each substrate, i.e. the theoretical thickness of each nth photoresist coating layer formed at different rotating speeds;

[0077] Step S105: based on the thickness measurement of each nth photoresist coating layer and the theoretical thickness of each nth photoresist coating layer, fitting is performed to obtain a fitting equation for the thickness theoretical correction value of the nth photoresist coating layer;

[0078] Step S106: using the fitting equation, the total thickness theoretical correction value of the n photoresist coating layers on the substrate after n times of photoresist coating is calculated;

[0079] Wherein, n is a positive integer greater than or equal to 1.

[0080] First, step S101 is performed, as shown in FIG. 1, at least two substrates 100 are provided. Figure 2

[0081] Exemplarily, the substrate 100 can include semiconductor elements such as single crystal, polycrystalline or amorphous structure silicon or silicon germanium, and can also include hybrid semiconductor structures such as silicon carbide, indium antimonide, indium arsenide, indium phosphide, gallium arsenide or gallium antimonide, alloy semiconductors or combinations thereof, and can also be silicon-on-insulator (SOI), silicon-on-silicon-on-insulator (SSOI), silicon-on-silicon germanium-on-insulator (S-SiGeOI), silicon germanium-on-insulator (SiGeOI) and germanium-on-insulator (GeOI) and the like. In an embodiment, the substrate 100 can be a silicon substrate injected with P-type or N-type impurity ions, and the specific doping concentration is not limited in the embodiment, and the substrate 100 can be formed by epitaxial growth or can be a wafer substrate.

[0082] Exemplarily, the substrate 100 also includes an isolation structure, which is a shallow trench isolation (STI) structure or a local oxidation of silicon (LOCOS) isolation structure, and the isolation structure divides the silicon substrate into different active regions, and various semiconductor devices such as NMOS and PMOS can be formed in the active regions. Various well structures are also formed in the substrate 100, which are omitted in the illustration for simplicity.

[0083] Exemplarily, the substrate 100 can also be a multilayer structure including an interlayer dielectric layer or a buried layer. The interlayer dielectric (ILD) can include various forms of insulating silicon dioxide, such as BPSG, PSG, FSG, USG, TEOS, thermal oxidation silicon dioxide, wet oxidation silicon dioxide, silicon-rich silicon dioxide SRO or a combination of multiple layers of films thereof. The buried layer can include a composite structure composed of an anti-reflective layer and a hard mask layer, or other materials or structures that can be used as a buried layer, such as polysilicon, silicon nitride, silicon carbide or metal film layers, etc.​

[0084] Next, step S102 is performed, as shown, n times of photoresist coating is completed, each of the substrates 100 forms n layers of photoresist coating layers stacked in turn from bottom to top, the photoresist coating rotation speeds of different substrates 100 are different, and the photoresist coating rotation speeds of each layer of photoresist coating layers on the same substrate 100 are the same or different. Figure 2

[0085] Exemplarily, the step of forming n layers of photoresist coating layers stacked in turn from bottom to top on each of the substrates 100 comprises:

[0086] The n times of photoresist coating is completed by using a spin coating process;

[0087] The photoresist coating is solidified to form the photoresist coating layer.

[0088] Further, the rotation speed ranges from 500 r / min to 10000 r / min.

[0089] Exemplarily, the photoresist coating layer is formed by using a spin coating process, that is, the substrate 100 is first rotated at a lower speed, at this time, the photoresist nozzle is moved to a position above the center or a position close to the center of the substrate 100, and the photoresist is sprayed on the surface of the substrate 100. The amount of the sprayed photoresist is determined according to the thickness of the photoresist layer to be formed. The heat curing temperature of the photoresist is 50℃-800℃, and the heat curing time is 30s-6h.

[0090] In the embodiment of the present application, the number of substrates is four, the amount of the photoresist sprayed by the photoresist nozzle each time is fixed, the photoresist coating rotation speeds on the four substrates are different, the four substrates are respectively rotated at four photoresist coating rotation speeds of 1500 r / min, 3300 r / min, 3900 r / min and 4500 r / min, and then the photoresist is heated and solidified to form a first layer of photoresist coating layer 201 on each substrate. The spin coating and solidification steps are repeated to form a second layer of photoresist coating layer 202 on the first layer of photoresist coating layer 201. The spin coating and solidification steps are continuously repeated to form n layers of photoresist coating layers. The photoresist coating rotation speeds of each layer of photoresist coating layers on the same substrate are the same or different.

[0091] In one embodiment, on the same substrate, the photoresist coating rotation speed of the first layer of photoresist coating layer 201 is the same as that of the second layer of photoresist coating layer 202, and the photoresist coating rotation speeds of each substrate for forming the second layer of photoresist coating layer 202 are different.

[0092] ​In one embodiment, the first photoresist coating layer 201 and the second photoresist coating layer 202 are formed on the same substrate, and the photoresist coating speed of the first photoresist coating layer 201 is different from the photoresist coating speed of the second photoresist coating layer 202, and the photoresist coating speed of the second photoresist coating layer 202 of each substrate is also different.

[0093] Next, steps S103 and S104 are performed: measuring the thickness measurement value of the nth photoresist coating layer on each substrate, i.e., the thickness measurement value of each nth photoresist coating layer formed at different speeds; calculating the thickness theoretical value of the nth photoresist coating layer on each substrate, i.e., the thickness theoretical value of each nth photoresist coating layer formed at different speeds.

[0094] The measurement of the thickness measurement value of the nth photoresist coating layer on each substrate, i.e., the thickness measurement value of each nth photoresist coating layer formed at different speeds, further includes:

[0095] The n photoresist coating layers are sequentially stacked from the top surface of the substrate upward, including the first photoresist coating layer 201, the second photoresist coating layer 202, and the nth photoresist coating layer in ascending order.

[0096] After the first photoresist coating is completed, the measured thickness of the photoresist coating layer on each substrate is the thickness measurement value of the first photoresist coating layer 201 on each substrate, i.e., the thickness measurement value of the first photoresist coating layer 201 formed at different speeds.

[0097] After the nth photoresist coating is completed, the thickness of the photoresist coating layer on each substrate is subtracted from the thickness measurement value of the first photoresist coating layer to the nth-1 photoresist coating layer on each corresponding substrate, respectively, to obtain the thickness measurement value of the nth photoresist coating layer on each substrate, i.e., the thickness measurement value of the nth photoresist coating layer formed at different speeds.

[0098] When the photoresist is uniformly spin-coated on the substrate 100, its thickness D can be roughly calculated by a formula related to the speed ω:

[0099] D=kω b (1)

[0100] wherein,

[0101] k represents the initial viscosity function of the photoresist;

[0102] ω represents the speed;

[0103] b represents the volatility of the solvent.

[0104] Further, b is usually taken as -1 / 2.

[0105] However, since the application range of formula (1) is fluid, and the photoresist is not in a fluid state after the curing step, the coating thickness of the photoresist calculated according to formula (1) deviates greatly from the actual measured value. According to formula (1), the following can be obtained:

[0106] D n 2 ×ω n = d n 2 ×ω' n (2)

[0107] wherein,

[0108] ω n represents a photoresist coating reference speed of a known nth photoresist coating layer given in advance;

[0109] ω' n represents an arbitrary photoresist coating speed for forming the nth photoresist coating layer;

[0110] D n represents a thickness measurement value of the nth photoresist coating layer formed at the speed of ω n ;

[0111] d n represents a thickness theoretical value of the nth photoresist coating layer formed at the speed of ω' n to be calculated.

[0112] In one embodiment, only the first photoresist coating layer 201 is formed on the substrate 100.

[0113] In order to improve the accuracy of the calculation of the photoresist coating thickness, the thickness measurement value D1 of the first photoresist coating layer 201 formed at the reference speed ω1 is first confirmed by film thickness measurement or slicing, and then the thickness theoretical value d1 of the first photoresist coating layer 201 formed at the speed ω'1 is calculated according to formula (2).

[0114] In one embodiment, when forming the first photoresist coating layer on four substrates respectively, four rotation speeds of 1500 r / min, 3300 r / min, 3900 r / min and 4500 r / min are respectively used for spin coating, i.e. the photoresist coating rotation speed of the first photoresist coating layer on the first substrate is 1500 r / min, the photoresist coating rotation speed of the first photoresist coating layer on the second substrate is 3300 r / min, the photoresist coating rotation speed of the first photoresist coating layer on the third substrate is 3900 r / min, and the photoresist coating rotation speed of the first photoresist coating layer on the fourth substrate is 4500 r / min, and the photoresist used is polyimide. Any one of 1500 r / min, 3300 r / min, 3900 r / min or 4500 r / min is selected as the photoresist coating reference rotation speed, for example 3300 r / min, and the thickness measurement value of the first photoresist coating layer 201 formed at the photoresist coating reference rotation speed is confirmed to be 5.142 μm by film thickness measurement or slicing. Then the thickness theoretical value of the first photoresist coating layer 201 formed at other rotation speeds (1500 r / min, 3900 r / min or 4500 r / min) is calculated by using formula (2), and the thickness measurement value of the first photoresist coating layer 201 formed at other rotation speeds (1500 r / min, 3900 r / min or 4500 r / min) is confirmed by film thickness measurement or slicing, see Table 1:

[0115] Table 1

[0116]

[0117] In another embodiment, referring to Figure 2 , the first photoresist coating layer 201 and the second photoresist coating layer 202 are formed on the substrate 100. The photoresist coating rotation speed for forming the first photoresist coating layer 201 and the photoresist coating rotation speed for forming the second photoresist coating layer 202 on the same substrate are the same or different, and the photoresist coating rotation speeds for forming the second photoresist coating layer 202 on different substrates are different.

[0118] In one embodiment, the spin speed of the photoresist coating forming the first photoresist coating layer 201 and the spin speed of the photoresist coating forming the second photoresist coating layer 202 are the same. The spin speed of the photoresist coating forming the second photoresist coating layer on the first substrate is 1500 r / min, the spin speed of the photoresist coating forming the second photoresist coating layer on the second substrate is 3300 r / min, the spin speed of the photoresist coating forming the second photoresist coating layer on the third substrate is 3900 r / min, and the spin speed of the photoresist coating forming the second photoresist coating layer on the fourth substrate is 4500 r / min. The photoresist used is polyimide. Any one of 1500 r / min, 3300 r / min, 3900 r / min, or 4500 r / min is selected as the reference spin speed of the photoresist coating, and in this embodiment, the first speed of 3300 r / min is still taken as the reference spin speed of the photoresist coating. The total thickness measurement value of the first photoresist coating layer 201 and the second photoresist coating layer 202 is confirmed by film thickness measurement or slicing to be 13.700 μm, and the thickness measurement value of the second photoresist coating layer 202 is obtained by subtracting the thickness measurement value of the first photoresist coating layer 201 in Table 1, which is 5.142 μm. The theoretical thickness value of the second photoresist coating layer 202 formed at other speeds (1500 r / min, 3900 r / min, 4500 r / min) is calculated using formula (2), and the total thickness measurement value D of the first photoresist coating layer 201 and the second photoresist coating layer 202 formed at other speeds (1500 r / min, 3900 r / min, 4500 r / min) is confirmed by film thickness measurement or slicing. The thickness measurement value D2 of the second photoresist coating layer 202 is obtained by subtracting the thickness measurement value D1 of the first photoresist coating layer 201 in Table 1, see Table 2:

[0119] Table 2

[0120]

[0121] By analogy, after completing the nth photoresist coating, the thickness of the photoresist coating on each of the substrates is measured and subtracted from the thickness measurement value of the first photoresist coating layer to the (n-1)th photoresist coating layer on each of the substrates, respectively, to obtain the thickness measurement value D of the nth photoresist coating layer on each of the substrates. n That is, the thickness measurement value of the nth photoresist coating layer formed at different speeds.

[0122] Next, step S105 is performed: fitting based on the thickness measurement value of each nth photoresist coating layer and the theoretical thickness value of each nth photoresist coating layer to obtain a fitting equation for the thickness theoretical correction value of the nth photoresist coating layer.

[0123] Exemplarily, the fitting comprises a linear fitting to determine a linear relationship fitting coefficient related to the thickness measurement value of the nth photoresist coating layer and the thickness theoretical value of the nth photoresist coating layer, to obtain a linear relationship fitting equation about the thickness theoretical correction value of the nth photoresist coating layer, i.e. a linear relationship formula about the thickness theoretical correction value of the nth photoresist coating layer and the photoresist coating speed of the nth photoresist coating layer:

[0124]

[0125] wherein,

[0126] a represents a first linear relationship fitting coefficient, and is a constant;

[0127] b represents a second linear relationship fitting coefficient, and is a constant;

[0128] ω n represents a pre-defined known photoresist coating reference speed of the nth photoresist coating layer;

[0129] ω′ n represents an arbitrary photoresist coating speed of forming the nth photoresist coating layer;

[0130] D n represents a thickness measurement value of the photoresist coating layer formed at the speed of ω n ; and

[0131] y n represents a thickness theoretical correction value of the nth photoresist coating layer to be calculated formed at the speed of ω′ n .

[0132] In one embodiment, the thickness measurement value and the thickness theoretical value of the first photoresist coating layer 201 formed at different speeds in Table 1 are linearly fitted, i.e. a set of thickness measurement values of the first photoresist coating layer 201 and a set of thickness theoretical values of the first photoresist coating layer 201 are linearly fitted to form a curve graph of the linear fitting of the thickness theoretical value and the thickness measurement value of the first photoresist coating layer, as shown in Figure 3 y = 1.9839x - 4.8966.

[0133] Exemplarily, the fitting comprises a binomial fitting to determine a binomial relationship fitting coefficient related to the thickness measurement value of the nth photoresist coating layer and the thickness theoretical value of the nth photoresist coating layer, to obtain a binomial relationship fitting equation about the thickness theoretical correction value of the nth photoresist coating layer, i.e. a binomial equation about the thickness theoretical correction value of the nth photoresist coating layer and the photoresist coating speed of the nth photoresist coating layer:

[0134]

[0135] wherein,

[0136] A represents a first binomial relationship fitting coefficient, and is a constant;

[0137] B represents a second binomial relationship fitting coefficient, and is a constant;

[0138] C represents a third binomial relationship fitting coefficient, and is a constant;

[0139] ω n represents a pre-defined known photoresist coating reference speed of the nth layer of photoresist coating;

[0140] ω′ n represents an arbitrary photoresist coating speed for forming the nth layer of photoresist coating;

[0141] D n represents a thickness measurement value of the photoresist coating formed at the speed of ω n .

[0142] y n represents a thickness theoretical correction value of the nth layer of photoresist coating formed at the speed of ω′ n .

[0143] In one embodiment, binomial fitting is performed on the thickness measurement values and thickness theoretical values of the first layer of photoresist coating 201 formed at different speeds in Table 1 to form a binomial fitting graph of the thickness theoretical values and the thickness measurement values of the first layer of photoresist coating 201, as shown in Figure 4 . The binomial equation of the thickness theoretical correction value y1 of the first layer of photoresist coating and the photoresist coating speed x1 of the first layer of photoresist coating is y1 = 0.121x1 2 + 0.5022x1 - 0.6032.

[0144] In one embodiment, binomial fitting is performed on the thickness measurement values and thickness theoretical values of the second layer of photoresist coating 202 formed at different speeds in Table 2 to form a binomial fitting graph of the thickness theoretical values and the thickness measurement values of the second layer of photoresist coating 202, as shown in Figure 5 . The binomial equation of the thickness theoretical correction value y2 of the second layer of photoresist coating and the photoresist coating speed x2 of the second layer of photoresist coating is y2 = -0.0096x2 2 + 1.8726x2 - 6.8108.

[0145] Next, step S106 is performed: calculating the total thickness theoretical correction value of the n layers of photoresist coating on the substrate after n times of photoresist coating using the fitting equation.

[0146] The total thickness theoretical correction value of the n layers of photoresist coating layers formed on the substrate after completing n times of photoresist coating is calculated by using the fitting equation, and the total thickness theoretical correction value of the n layers of photoresist coating layers formed on the substrate after completing n times of photoresist coating is calculated according to the following relationship:

[0147] The total thickness theoretical correction value of the n layers of photoresist coating layers formed on the substrate after completing n times of photoresist coating is calculated according to the following relationship:

[0148]

[0149] Wherein,

[0150] Y n represents the total thickness theoretical correction value of the n layers of photoresist coating layers formed on the substrate after completing n times of photoresist coating to be calculated;

[0151] y n represents the thickness correction value of the n layers of photoresist coating layers.

[0152] In one of the embodiments, the total thickness theoretical correction value of the two layers of photoresist coating layers formed on the substrate after completing twice photoresist coating is calculated according to the following relationship:

[0153] Y2=0.121x1 2 +0.5022x1-0.6032-0.0096x2 2 +1.8726x2-6.8108

[0154] By constructing the physical model of the double photoresist coating layer, the calculation method of the single photoresist coating layer thickness is improved, and the theoretical value is fitted and corrected with the measured value, so as to realize the accurate calculation of the double photoresist coating layer thickness, avoid the wafer waste caused by adjusting the rotating speed and then confirming the thickness, reduce the cost, and save the product development time.

[0155] According to the photoresist coating thickness calculation method provided by the application, the thickness measured value and the thickness theoretical value of the photoresist coating layer formed at different rotating speeds are fitted to form a fitting equation, and the total thickness of the multiple photoresist coating layers formed at any rotating speed is calculated by using the fitting equation. The total thickness of the multiple photoresist coating layers is a total thickness theoretical correction value, which is closer to the actual thickness value of the multiple photoresist coating layers than the thickness value calculated by using a simple multiple relationship, improves the calculation accuracy of the photoresist coating layer, and effectively solves the problem that the calculation film thickness value of the traditional theory deviates greatly from the actual film thickness.

[0156] The present application has been described by way of the above examples, but it should be understood that the above examples are for illustrative and explanatory purposes only, and are not intended to limit the present application to the scope of the described examples. Furthermore, those skilled in the art can understand that the present application is not limited to the above examples, and that various modifications and changes can be made to the present application according to the teachings of the present application, and that these modifications and changes all fall within the scope of the present application claimed. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the thickness of a photoresist coating, characterized in that, include: Provide at least two substrates; After n photoresist coatings are completed, n photoresist coatings are formed on each substrate from bottom to top. The photoresist coating speeds are different for different substrates, and the photoresist coating speeds of each photoresist coating on the same substrate may be the same or different. The thickness of the nth photoresist layer on each of the substrates is measured, which is the thickness of each nth photoresist layer formed at different rotation speeds. Calculate the theoretical thickness of the nth photoresist layer on each of the substrates, which is the theoretical thickness of each nth photoresist layer formed at different rotation speeds; By fitting the measured thickness values ​​of each nth photoresist layer and the theoretical thickness values ​​of each nth photoresist layer, a fitting equation for the theoretical correction value of the thickness of the nth photoresist layer is obtained. The theoretical correction value of the total thickness of the n-layer photoresist coating on the substrate formed after n photoresist coating processes is calculated using the fitting equation. Where n is a positive integer greater than 1; The calculation of the theoretical thickness of the nth photoresist layer on each of the substrates, which is the theoretical thickness of each nth photoresist layer formed at different rotation speeds, further includes: The theoretical thickness of the nth photoresist layer is calculated using the following equation: D n 2 ×ω n =d n 2 ×ω′ n in, ω n This represents the pre-given, known reference rotation speed for coating the nth photoresist layer; ω′ n This represents any photoresist coating speed used to form the nth photoresist layer; D n Indicates at ω n The thickness measurement of the nth photoresist layer formed at a given rotational speed; d n This indicates that the value to be calculated is at ω′. n The theoretical value of the thickness of the nth photoresist layer formed at the rotational speed; The fitting is a linear fitting, used to determine the linear relationship fitting coefficients related to the measured thickness of the nth photoresist layer and the theoretical thickness of the nth photoresist layer, thus obtaining the linear relationship fitting equation for the theoretical correction value of the thickness of the nth photoresist layer: in, 'a' represents the first linear relationship fitting coefficient, and it is a constant; b represents the fitting coefficient of the second linear relationship, and it is a constant; ω n This represents the pre-given, known reference rotation speed for coating the nth photoresist layer; ω′ n This represents any photoresist coating speed used to form the nth photoresist layer; D n Indicates at ω n The thickness measurement of the photoresist coating formed at the rotation speed; y n This indicates that the value to be calculated is at ω′. n The theoretical correction value for the thickness of the nth photoresist layer formed at the rotational speed; or, The fitting is a binomial fitting to determine the binomial relationship fitting coefficients related to the measured thickness value of the nth photoresist layer and the theoretical thickness value of the nth photoresist layer, thereby obtaining the binomial relationship fitting equation for the theoretical correction value of the thickness of the nth photoresist layer: in, A represents the fitting coefficient of the first binomial relationship, and it is a constant; B represents the fitting coefficient of the second binomial relationship, and it is a constant; C represents the fitting coefficient of the third binomial relationship, and it is a constant; ω n This represents the pre-given, known reference rotation speed for coating the nth photoresist layer; ω′ n This represents any photoresist coating speed used to form the nth photoresist layer; D n Indicates at ω n The thickness measurement of the photoresist coating formed at the rotation speed; y n This indicates that the value to be calculated is at ω′. n The theoretical correction value for the thickness of the nth photoresist layer formed at a given rotational speed.

2. The calculation method as described in claim 1, characterized in that, The measurement of the thickness of the nth photoresist layer on each of the substrates, which is the thickness measurement of each nth photoresist layer formed at different rotation speeds, further includes: The n layers of photoresist coatings stacked sequentially are the first layer of photoresist coating, the second layer of photoresist coating, and the nth layer of photoresist coating stacked sequentially from the upper surface of the substrate upwards. After the first photoresist coating is completed, the thickness of the photoresist coating on each of the substrates is the thickness measurement value of the first layer of photoresist coating on each of the substrates, which is the thickness measurement value of the first layer of photoresist coating formed at different rotation speeds. After completing the nth photoresist coating, the thickness of the photoresist coating on each substrate is measured, and the thickness of the first to (n-1)th photoresist coatings on each corresponding substrate is subtracted to obtain the thickness of the nth photoresist coating on each substrate. This thickness is the thickness of the nth photoresist coating formed at different rotation speeds.

3. The calculation method as described in claim 1, characterized in that, The step of calculating the theoretical correction value of the total thickness of the n-layer photoresist coating on the substrate after n photoresist coatings using the fitted equation also includes: The theoretical correction value for the total thickness of the n-layer photoresist coating formed after n photoresist coating processes on any substrate is calculated according to the following formula: in, Y n This represents the theoretical correction value for the total thickness of the n-layer photoresist coating formed after n photoresist coatings are applied to any substrate to be calculated. y n This represents the thickness correction value for the nth photoresist layer.

4. The calculation method as described in claim 1, characterized in that, The substrate includes a semiconductor substrate, which includes semiconductor elements and / or semiconductor structures.

5. The calculation method as described in claim 1, characterized in that, The step of forming n layers of photoresist coatings stacked sequentially from bottom to top on each of the substrates includes: The nth photoresist coating process is completed using spin coating. The photoresist coating is cured to form the photoresist layer.

6. The calculation method as described in claim 1, characterized in that, The speed range is 500 r / min to 10000 r / min.

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