CN115781493A - Method for polishing semiconductor structure - Google Patents
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- CN115781493A CN115781493A CN202111054537.2A CN202111054537A CN115781493A CN 115781493 A CN115781493 A CN 115781493A CN 202111054537 A CN202111054537 A CN 202111054537A CN 115781493 A CN115781493 A CN 115781493A
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Abstract
The embodiment of the disclosure provides a grinding method of a semiconductor structure, which includes: providing a semiconductor substrate, wherein the semiconductor substrate is provided with a functional film layer; providing a grinding pad, and spraying first grinding liquid on the grinding pad; placing the semiconductor substrate on a grinding pad, and grinding the functional film layer; separating the semiconductor substrate from the polishing pad, and spraying a first cleaning solution on the polishing pad to clean the polishing pad; spraying a second grinding fluid on the cleaned grinding pad; placing the semiconductor substrate on a grinding pad, and grinding the functional film layer again; wherein the first polishing liquid is different from the second polishing liquid. The grinding method disclosed by the invention is used for grinding the semiconductor substrate twice, the grinding pad does not need to be replaced in the middle, the cost is saved, the operation is simpler, and the grinding effect is more accurate.
Description
Technical Field
The present disclosure relates to the field of semiconductor manufacturing technologies, and in particular, to a method for polishing a semiconductor structure.
Background
Chemical Mechanical Polishing (CMP) is a commonly used process in semiconductor manufacturing processes, and is used for polishing the roughness of a semiconductor film layer to improve the roughness and make the surface of the semiconductor film layer smoother. As the size of devices in semiconductors is more and more reduced with the progress of semiconductor technology, higher precision is required for the manufacturing of the size of the devices in semiconductors, and therefore, CMP has been expected to be able to more precisely change the height of the concave-convex structure or the step in the film layer of the semiconductor, rather than merely improve the uniformity of the film layer in the semiconductor.
In the prior art, in order to achieve the above-mentioned expectations, different polishing liquids are often used to polish the semiconductor structure, but after each time the polishing liquids are replaced, the semiconductor needs to be continuously polished on different polishing pads, which increases the consumption and cost of the polishing pads and complicates the operation.
The above information disclosed in this background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The present disclosure is directed to a method for polishing a semiconductor structure, in which a semiconductor substrate is polished twice without replacing a polishing pad, so that the method is cost-effective, simpler to operate, and more precise in polishing effect.
A method for polishing a semiconductor structure is provided, which comprises the following steps: providing a semiconductor substrate, wherein the semiconductor substrate is provided with a functional film layer; providing a grinding pad, and spraying a first grinding liquid on the grinding pad; placing the semiconductor substrate on the grinding pad, and grinding the functional film layer; separating the semiconductor substrate from the grinding pad, and spraying a first cleaning solution to the grinding pad to clean the grinding pad; spraying a second grinding fluid on the cleaned grinding pad; placing the semiconductor substrate on the grinding pad, and grinding the functional film layer again; wherein the first polishing fluid is different from the second polishing fluid.
According to an exemplary embodiment of the present disclosure, the functional film layer includes: a first film layer comprising a plurality of film layer patterns; and the second film layer is formed on the first film layer and filled between the film layer patterns.
According to an exemplary embodiment of the present disclosure, the placing the semiconductor substrate on the polishing pad and polishing the functional film layer includes: grinding the second film layer by using the first grinding liquid to enable the surface of the second film layer to be flush with the surface of the first film layer; the step of placing the semiconductor substrate on the grinding pad and grinding the functional film layer again comprises the following steps: and grinding the first film layer by using the second grinding liquid to enable the surface of the first film layer to be lower than the surface of the second film layer.
According to an exemplary embodiment of the present disclosure, the placing the semiconductor substrate on the polishing pad and polishing the functional film layer includes: grinding the second film layer by using the first grinding liquid to remove the second film layer with a first preset thickness; the step of placing the semiconductor substrate on the grinding pad and grinding the functional film layer again comprises the following steps: and continuously grinding the second film layer with the first preset thickness removed by using the second grinding liquid to enable the surface of the second film layer to be lower than the surface of the first film layer.
According to an exemplary embodiment of the present disclosure, the step of placing the semiconductor substrate on the polishing pad and polishing the functional film layer is a single film layer, and the step of polishing the functional film layer includes: grinding the functional film layer by using the first grinding liquid to remove the functional film layer with a second preset thickness; the step of placing the semiconductor substrate on the grinding pad and grinding the functional film layer again comprises the following steps: and continuously grinding the functional film layer with the second preset thickness by using the second grinding liquid.
According to an exemplary embodiment of the present disclosure, the first cleaning solution is deionized water and/or a surfactant.
According to an exemplary embodiment of the present disclosure, the surfactant is a combination of one or more of a cationic surfactant, a nonionic surfactant, and an anionic surfactant.
According to an exemplary embodiment of the present disclosure, the pH of the first polishing liquid is greater than the pH of the second polishing liquid.
According to an exemplary embodiment of the present disclosure, the polishing particles of the first polishing liquid are different from the polishing particles of the second polishing liquid in kind.
According to an exemplary embodiment of the present disclosure, the first polishing liquid has a pH a 1 The pH value of the second grinding liquid is A 2 The pH value of the first cleaning solution is B 1 ，A 1 And A 2 Average value of A v ＝(A 1 +A 2 ) /2 if A 1 ＞A 2 Then A is v -3(A 1 -A v )/4≤B 1 ≤A v +3(A 1 -A v ) (ii)/4; if A 2 ＞A 1 Then A is v -3(A 2 -A v )/4≤B 1 ≤A v +3(A 2 -A v ) (ii)/4; wherein A is 1 、A 2 、A v 、B 1 Are all positive numbers.
According to an exemplary embodiment of the present disclosure, B1= Av.
According to an exemplary embodiment of the present disclosure, the flow rate of the first cleaning liquid is at least 500ml/min, and the cleaning time of the first cleaning liquid is greater than or equal to 3 seconds.
According to an exemplary embodiment of the present disclosure, the first polishing liquid and the second polishing liquid each have a flow rate of 50 to 500ml/min.
According to an exemplary embodiment of the present disclosure, the functional film layer is at least one of a shallow trench isolation, an oxide layer, a metal tungsten layer, a metal copper layer, a polysilicon layer, a silicon nitride layer, and a back surface of a semiconductor substrate.
According to an exemplary embodiment of the present disclosure, the method further comprises: separating the functional film layer which is ground again from the grinding pad, and spraying a second cleaning solution on the grinding pad to clean the grinding pad; spraying a third grinding fluid on the cleaned grinding pad; placing the semiconductor substrate on the grinding pad, and continuously grinding the functional film layer; if the functional layer still needs to be continuously ground after being ground, the method is repeated until the functional film layer is ground.
According to an exemplary embodiment of the present disclosure, the Nth polishing liquid has a pH A N The pH value of the N +1 th grinding liquid is A N+1 The pH value of the Nth cleaning solution is B N ，A N And A N+1 Average value of (A) Av' = (A) N +A N+1 ) 2, if A N ＞A N+1 Then Av' -3 (A) N -Av’)/4≤B N ≤Av’+3(A N -Av')/4; if A N+1 ＞A N Then Av' -3 (A) N+1 -Av’)/4≤B N ≤Av’+3(A N+1 -Av')/4; wherein N is a positive integer and is more than or equal to 2; a. The N 、A N+1 、Av’、B N Are all positive numbers.
According to an exemplary embodiment of the present disclosure, the method further comprises: after the semiconductor substrate is polished, separating the semiconductor substrate from the polishing pad; and spraying a cleaning solution after grinding on the grinding pad to clean the grinding pad.
According to the technical scheme, the method has at least one of the following advantages and positive effects:
according to the polishing method disclosed by the embodiment of the disclosure, after the semiconductor substrate is polished by the first polishing liquid, the semiconductor substrate is separated from the polishing pad, the polishing pad is cleaned by the cleaning liquid, the second polishing liquid can be sprayed on the polishing pad to continuously polish the semiconductor substrate, the polishing pad does not need to be replaced, the cost is saved, the operation is simpler, and the polishing effect is more accurate.
Drawings
The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
FIG. 1 is a flow chart of a method for polishing a semiconductor structure in an exemplary embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a semiconductor structure being polished by spraying a first polishing liquid according to an exemplary embodiment of the disclosure;
FIG. 3 is a schematic illustration of spraying a first cleaning solution in an exemplary embodiment of the present disclosure;
FIG. 4 is a schematic diagram of spraying a second slurry to polish a semiconductor structure according to an exemplary embodiment of the disclosure;
FIG. 5 is a schematic view of a semiconductor structure to be polished in an exemplary embodiment of the present disclosure;
FIG. 6 is the semiconductor structure of FIG. 5 after polishing with a first polishing slurry;
FIG. 7 is the semiconductor structure of FIG. 6 after polishing with a second polishing slurry;
FIG. 8 is a schematic view of a semiconductor structure to be polished in another exemplary embodiment of the present disclosure;
FIG. 9 is the semiconductor structure of FIG. 8 after polishing with a first polishing slurry;
FIG. 10 is the semiconductor structure of FIG. 8 after polishing with a second polishing slurry;
FIG. 11 is a schematic view of a semiconductor structure to be polished in another exemplary embodiment of the present disclosure;
FIG. 12 is the semiconductor structure of FIG. 11 after polishing with a first polishing slurry;
FIG. 13 is the structure of the semiconductor structure of FIG. 12 after polishing with the second polishing slurry.
Description of reference numerals:
1. a semiconductor substrate; 11 11',11", functional film layer; 111 111', a first film layer; 112 112', a second film layer; 2. a polishing pad; 3. a grinding disk; 4. a first polishing liquid spray head; 5. a second grinding fluid spray head; 6. a first cleaning liquid spray head.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many 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 will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted.
In the following description of various exemplary embodiments of the disclosure, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration various exemplary structures in which aspects of the disclosure may be practiced. It is to be understood that other specific arrangements of parts, structures, example devices, systems, and steps may be utilized and structural and functional modifications may be made without departing from the scope of the present disclosure. Moreover, although the terms "over," "between," "within," and the like may be used in this specification to describe various example features and elements of the disclosure, these terms are used herein for convenience only, e.g., in accordance with the orientation of the examples in the figures. Nothing in this specification should be construed as requiring a specific three dimensional orientation of structures in order to fall within the scope of this disclosure. Furthermore, the terms "first," "second," and the like in the claims are used merely as labels, and are not numerical limitations of their objects.
The flow charts shown in the drawings are merely illustrative and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.
In addition, in the description of the present disclosure, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise. "above" and "below" are terms of art that indicate orientation, and are used for clarity of description only and are not limiting.
As shown in fig. 1 to 13, an embodiment of the present disclosure provides a method for polishing a semiconductor structure. Fig. 1 is a flowchart of a polishing method of a semiconductor structure according to an embodiment of the disclosure, fig. 2 to 4 are schematic diagrams of stages in the polishing method according to an embodiment of the disclosure, and fig. 5 to 13 are schematic structural diagrams of the semiconductor structure at different polishing stages according to different embodiments. As shown in fig. 1, a method for polishing a semiconductor structure according to an embodiment of the present disclosure includes:
step S200: a semiconductor substrate 1 is provided, and the semiconductor substrate 1 has functional film layers 11, 11',11 ″.
Step S400: a polishing pad 2 is provided, and a first polishing liquid is sprayed on the polishing pad 2.
Step S600: the semiconductor substrate 1 is placed on the polishing pad 2, and the functional film layers 11, 11',11 ″ are polished.
Step S800: the semiconductor substrate 1 is detached from the polishing pad 2, and a first cleaning solution is sprayed to the polishing pad 2 to clean the polishing pad 2.
Step S1000: the second polishing liquid is sprayed on the cleaned polishing pad 2.
Step S1200: the semiconductor substrate 1 is placed on the polishing pad 2, and the functional film layers 11, 11',11 ″ are polished again. Wherein the first polishing liquid is different from the second polishing liquid.
In the polishing method of the embodiment of the disclosure, after the semiconductor substrate 1 is polished by the first polishing liquid, the semiconductor substrate 1 is separated from the polishing pad 2, and the cleaning liquid is used to clean the polishing pad 2, so that the second polishing liquid can be sprayed on the polishing pad 2 to continue polishing the semiconductor substrate 1, the polishing pad 2 does not need to be replaced, the cost is saved, the operation is simpler, and the polishing effect is more accurate.
The method for polishing a semiconductor structure according to the embodiment of the present disclosure is described in detail below.
Step S200: a semiconductor substrate 1 is provided, and the semiconductor substrate 1 has functional film layers 11, 11',11 ″.
The semiconductor substrate 1 may include a semiconductor substrate on which shallow trench isolations are formed with an active region therebetween. The semiconductor substrate is also provided with a word line structure and a bit line structure, the word line structure and the bit line structure are arranged at different heights of the semiconductor substrate, and the word line structure and the bit line structure are both connected with the active region. The word line structure may include a high-k dielectric layer, a polysilicon layer, a work function layer, a word line metal layer, and the like.
The material of the semiconductor substrate of the embodiments of the present disclosure may be silicon, silicon carbide, silicon nitride, silicon-on-insulator-stack, silicon germanium-on-insulator, or the like. The semiconductor substrate can also be implanted with certain doping particles according to design requirements to change electrical parameters.
As shown in fig. 5, 8 and 11, which respectively show the structure of the semiconductor substrate 1 to be polished in different embodiments. The functional film layer 11, 11',11 ″ of the semiconductor substrate 1 may be at least one of a shallow trench isolation, an oxide layer, a metal tungsten layer, a metal copper layer, a polysilicon layer, and a silicon nitride layer, and may also be a back surface of the semiconductor substrate. It is also understood that the functional film layers 11, 11',11 ″ are those layers of the semiconductor substrate 1 that need to be planarized by grinding.
Referring to fig. 5 and 8, the functional film layers 11, 11',11 ″ may include two film layers, a first film layer 111, 111' and a second film layer 112, 112', respectively. The first film layers 111 and 111' include a plurality of film layer patterns, and the second film layers 112 and 112' are formed on the first film layers 111 and 111' and filled between the film layer patterns. As shown in fig. 5, the first layers 111 and 111 'are silicon oxide, and the second layers 112 and 112' are metal layers, such as tungsten and copper. As shown in fig. 6, the first layers 111, 111 'are silicon, and the second layers 112, 112' are silicon oxide, such as the above-mentioned shallow trench isolation. Of course, the first film layer 111, 111 'or the second film layer 112, 112' may also be a dielectric layer, such as silicon nitride, which is not limited herein. As shown in fig. 11, the functional film layers 11, 11',11 "may also be a single film layer.
Step S400: a polishing pad 2 is provided, and a first polishing liquid is sprayed on the polishing pad 2.
In the embodiment of the present disclosure, the semiconductor substrate 1 is polished using a chemical mechanical polishing process. Chemical mechanical polishing is a process in which a chemical reaction process and a mechanical polishing process work together. In the chemical mechanical polishing, a rotatable polishing disk 3 is provided, a polishing pad 2 is disposed on the polishing disk 3, the semiconductor substrate 1 is placed on the polishing pad 2, and the functional film 11, 11',11 ″ to be polished faces the polishing pad 2, a polishing head (not shown) is provided above the semiconductor substrate 1, and a certain pressure is applied to the surface of the semiconductor substrate 1 opposite to the polishing pad 2, so that the functional film 11, 11',11 ″ of the semiconductor substrate 1 is tightly attached to the polishing pad 2. The polishing disc 3 rotates to drive the polishing pad 2 to rotate, and meanwhile, the polishing head drives the semiconductor substrate 1 and the polishing pad 2 to rotate in the same direction, so that the functional film layers 11, 11',11 ″ of the semiconductor substrate 1 and the surface of the polishing pad 2 generate mechanical friction. In the grinding process, the functional film layers 11, 11',11 ″ are removed to a certain degree through a series of complicated mechanical and chemical actions, so that the purpose of flattening the functional film layers 11, 11',11 ″ of the semiconductor substrate 1 is achieved.
As shown in fig. 2, after providing the polishing pad 2, the first polishing liquid is uniformly sprayed onto the polishing pad 2 by the first polishing liquid spray head 4, the semiconductor substrate 1 is placed on the polishing pad 2, and polishing is performed by the first polishing particles in the first polishing liquid.
Step S600: the semiconductor substrate 1 is placed on the polishing pad 2, and the functional film layers 11, 11',11 ″ are polished.
Step S800: the semiconductor substrate 1 is separated from the polishing pad 2, and a first cleaning solution is sprayed to the polishing pad 2 to clean the polishing pad 2.
As shown in fig. 3, after the first polishing with the first polishing liquid, the semiconductor substrate 1 is lifted off the polishing pad 2. The first cleaning liquid is sprayed to the polishing pad 2 by the first cleaning liquid spray head 6 to wash the polishing pad 2 and remove the first polishing liquid to clean the polishing pad 2.
The first cleaning solution may be deionized water and/or a surfactant. In some embodiments, the surfactant may be a combination of one or more of a cationic surfactant, a nonionic surfactant, and an anionic surfactant, as long as the polishing pad 2 can be cleaned, and is not particularly limited herein.
Step S1000: the second polishing liquid is sprayed on the cleaned polishing pad 2.
As shown in fig. 4, the second polishing liquid is uniformly sprayed onto the cleaned polishing pad 2 by the second polishing liquid nozzle 5 to perform a second polishing on the functional layer of the semiconductor substrate 1.
Step S1200: the semiconductor substrate 1 is placed on the polishing pad 2, and the functional film layers 11, 11',11 ″ are polished again.
In the embodiment of the present disclosure, the first polishing of the functional film layer 11, 11',11 ″ of the semiconductor substrate 1 with the first polishing liquid can remove the functional film layer 11, 11',11 ″ with a predetermined thickness, and the second polishing of the functional film layer 11, 11',11 ″ of the semiconductor substrate 1 with the second polishing liquid can finish the functional film layer 11, 11',11 ″ and improve the polishing precision, for example, the concave-convex structure or the step height in the functional film layer 11, 11',11 ″ can be precisely changed during the second polishing.
In order to achieve the above object, in the embodiments of the present disclosure, the first polishing liquid is different from the second polishing liquid. It is specifically understood that the types of the abrasive particles of the first and second slurries may be different, for example, the abrasive particles of the first slurry may be silicon dioxide, and the abrasive particles of the second slurry may be cerium dioxide; the first polishing liquid and the second polishing liquid may have different pH values. In some embodiments, the pH of the first slurry is greater than the pH of the second slurry. For example, the pH of the first polishing liquid may be 7.5 to 9, and may be in an alkaline range, specifically, 7.8, 8, 8.2, 8.5, or 8.8, which is not particularly limited herein. The pH of the second polishing liquid may be 5 to 6.5, and is in an acidic range, specifically, 5.5, 5.8, 6, 6.2, or 6.4, which is not particularly limited herein. That is, the abrasive particles of the first polishing liquid and the second polishing liquid may be the same, but the pH values thereof may not be the same.
In one embodiment, the first polishing solution can be a silicon dioxide polishing solution with a pH of 8.5, and the second polishing solution can be a cerium dioxide polishing solution with a pH of 5.5. In another embodiment, the first polishing liquid may be a silica polishing liquid with a pH of 8, and the second polishing liquid may also be a silica polishing liquid with a pH of 6. In another embodiment, the first polishing solution may be a ceria polishing solution with a pH of 7.8, and the second polishing solution may also be a ceria polishing solution with a pH of 5.8.
The abrasive particles in the first polishing liquid and the second polishing liquid may have a size (diameter) of 20 to 500nm. Specifically, it may be 100, 200, 300 or 400nm, and is not particularly limited herein. However, the size of the second polishing particles may be smaller than that of the first polishing particles according to the polishing requirements, so that the second polishing can achieve more precise polishing of the functional film layers 11, 11',11 ″ and improve the polishing precision.
In some embodiments, the pH of the first cleaning solution is in the range of: the pH value of the first polishing liquid and the average value of the pH value of the second polishing liquid are added or subtracted between the value obtained by subtracting three quarters of the average value of the maximum value of the pH value of the first polishing liquid and the pH value of the second polishing liquid. For the sake of understanding, let the pH of the first polishing slurry be A 1 The pH value of the second grinding fluid is A 2 The pH value of the first cleaning solution is B 1 ，A 1 And A 2 Average value of A v ＝(A 1 +A 2 ) /2 if A 1 ＞A 2 Then A is v -3(A 1 -A v )/4≤B 1 ≤A v +3(A 1 -A v ) (ii)/4; if A 2 ＞A 1 Then A is v -3(A 2 -A v )/4≤B 1 ≤A v +3(A 2 -A v ) [ 4 ] wherein A 1 、A 2 、A v 、B 1 Are all positive numbers. Therefore, the pH value of the first cleaning liquid is between the pH value of the first grinding liquid and the pH value of the second grinding liquid, so that the first cleaning liquid not only has a cleaning effect, but also has a transition effect of the two grinding liquids, and the stability of the second grinding liquid is ensured.
In one embodiment, if A 1 Is 8,A 2 Is 6, then A v Then 7, the pH value B of the first cleaning solution 1 B is more than or equal to 7-3 (8-7)/4 1 7+3 (8-7)/4 or less, namely B is 6.25 or more 1 7.75. Ltoreq. In which range B1 can be 6.5, 7.0, 7.2 or 7.5, without limitation.
In one embodiment, the pH of the first cleaning solution is B 1 B1= Av, which is an average value of the pH of the first polishing liquid and the pH of the second polishing liquid, in the above example, B1 is 7.0.
In one embodiment, the first cleaning solution has a flow rate of at least 500ml/min, such as 600ml/min, 800ml/min, 1000ml/min, 1200ml/min or 1400ml/min, and the cleaning time of the first cleaning solution is greater than or equal to 3 seconds, such as 4 seconds, 6 seconds or 8 seconds, and may be longer. The flow rate and cleaning time of the first cleaning liquid may be set according to actual conditions, and are not particularly limited herein.
In one embodiment, the flow rates of the first polishing liquid and the second polishing liquid are 50 to 500ml/min, specifically, 80ml/min, 100ml/min, 200ml/min, 300ml/min, or 400ml/min, respectively, and are not limited herein.
The following describes in detail various methods of polishing the semiconductor substrate 1.
As shown in fig. 5, the functional film 11 of the semiconductor substrate 1 includes two films. The first film 111 is a dielectric layer, such as silicon oxide, the second film 112 is a metal layer, such as W or Cu, and the second film 112 is located on the first film 111 and filled between the film patterns of the first film 111. In addition, a TiN layer is filled between the patterns of the second film layer 112 and the first film layer 111, that is, the metal layer and the TiN layer form a word line metal layer in the semiconductor structure, and the two layers can be ground together. In this embodiment, it is desirable to polish the first film layer 111 lower than the second film layer 112. As shown in fig. 6, the second film layer 112 is polished by the first polishing slurry, so that the surface of the second film layer 112 is flush with the surface of the first film layer 111. After the semiconductor substrate 1 is lifted off the polishing pad 2 and cleaned by the first cleaning solution, as shown in fig. 7, the first film layer 111 is polished by the second polishing solution so that the surface of the first film layer 111 is lower than the surface of the second film layer 112. The second grind is finer than the first grind. In this embodiment, the pH values and flow rates of the first polishing liquid, the second polishing liquid and the first cleaning liquid are the same as those described in the above embodiment.
As shown in fig. 8, the functional film layer 11' of the semiconductor substrate 1 includes two layers. The first film 111 'may be silicon, and silicon nitride is shown to be formed on the silicon, in this embodiment, silicon and silicon nitride may be classified as the first film 111', and the second film 112 may be a dielectric layer, such as silicon oxide. The second film 112 is disposed on the first film 111 'and filled between the film patterns of the first film 111'. In this embodiment, it is desirable to polish the second layer 112 to be lower than the first layer 111'. As shown in fig. 9, the second film layer 112 is polished by the first polishing liquid to remove the second film layer 112 with a first predetermined thickness, for example, the first predetermined thickness may be 10 to 100nm, for example, 20nm, 40nm, 60nm, or 80nm, which may be set according to actual requirements, and is not limited herein. After the semiconductor substrate 1 is lifted off the polishing pad 2 and cleaned by the first cleaning solution, as shown in fig. 10, the second film layer 112 with the first predetermined thickness removed is continuously polished by the second polishing solution, so that the surface of the second film layer 112 is lower than the surface of the first film layer 111'. The second grind is finer than the first grind. In this embodiment, the pH values and flow rates of the first polishing liquid, the second polishing liquid, and the first cleaning liquid are the same as those described in the above embodiment.
In the above embodiment, the semiconductor substrate 1 having two functional film layers 11 and 11' is polished. In other embodiments, the functional film layer 11 "may also be a single layer film layer. As shown in fig. 11, the functional film layer 11 ″ of the semiconductor substrate 1 includes a single layer film. In this embodiment, it is desirable to polish the single layer film to a certain thickness and planarize it. The single-layer film may be a polysilicon film layer, a dielectric layer, a metal layer or a semiconductor substrate, and is not particularly limited herein. As shown in fig. 12, the functional film 11 ″ is polished by the first polishing liquid to remove the functional film 11 ″ with a second predetermined thickness, which may be 1-100 nm, for example, 20nm, 40nm, 60nm or 80nm, and may be set according to actual requirements, which is not limited herein. After the semiconductor substrate 1 is lifted off the polishing pad 2 and cleaned by the first cleaning solution, the functional film layer 11 ″ with the second predetermined thickness removed is polished by the second polishing solution as shown in fig. 13. The second grinding is finer than the first grinding. The functional film layer 11 ″ of different materials may have different pH values, different flow rates, and different abrasive particles of the first polishing liquid, the second polishing liquid, and the first cleaning liquid. For example, if the functional film 11 ″ is polysilicon, acidic silicon dioxide can be selected as the first polishing particles, the pH of the first polishing solution is 5-6, and the polishing rate is greater than or equal to 50nm/min, so that the removal amount reaches the second predetermined thickness. The second grinding particles can still be selected from silicon dioxide, the pH value of the second grinding fluid can be adjusted to 2-3, the grinding speed is less than or equal to 5nm/min, and the grinding quantity is 1-10 nm, so that the functional film layer 11' is finely ground, the surface defects of the functional film layer are removed, and the planarization is realized.
While some functional layers 11, 11',11 "may not achieve the desired effect through two polishing operations, in some embodiments of the present disclosure, a third polishing operation, a fourth polishing operation, or more polishing operations may be performed after the second polishing operation without replacing the polishing pad 2. Between each two polishing, the semiconductor substrate 1 is detached from the polishing pad 2 and washed with a cleaning solution.
In one embodiment, the grinding method may further include: spraying a third grinding fluid on the cleaned grinding pad 2; placing the semiconductor substrate 1 on a grinding pad 2, and continuously grinding the functional film layers 11, 11 'and 11'; if the functional layer still needs to be ground after being ground, the method is repeated until the functional film layers 11, 11 'and 11' are ground.
Specifically, let the pH of the Nth polishing liquid be A N The pH value of the N +1 th grinding liquid is A N+1 The pH value of the Nth cleaning solution is B N ，A N And A N+1 Average value of (A) Av' = (A) N +A N+1 ) /2 if A N ＞A N+1 Then Av' -3 (A) N -Av’)/4≤B N ≤Av’+3(A N -Av')/4; if A N+1 ＞A N Then Av' -3 (A) N+1 -Av’)/4≤B N ≤Av’+3(A N+1 -Av')/4. Wherein N is a positive integer and is more than or equal to 2; a. The N 、A N+1 、Av’、B N Are all positive numbers. The pH values of the nth polishing liquid, the (N + 1) th polishing liquid and the nth cleaning liquid can be set by referring to the pH values of the first polishing liquid, the second polishing liquid and the first cleaning liquid, and other parameters such as the flow rates of the nth polishing liquid, the (N + 1) th polishing liquid and the nth cleaning liquid can be referred to the first polishing liquid, the second polishing liquid and the first cleaning liquid,or adjusted according to the actual situation, which is not described herein again.
In some embodiments, the grinding method of the present disclosure may further comprise: after the semiconductor substrate 1 is polished, the semiconductor substrate 1 is separated from the polishing pad 2; the post-polishing cleaning solution is sprayed to the polishing pad 2 to clean the polishing pad 2. The post-polishing cleaning solution is used for cleaning the polishing pad 2 after polishing, and when polishing is performed twice, the pH of the post-polishing cleaning solution may be between the pH of the second polishing solution and 7 (inclusive of 7) because the second polishing solution is generally acidic. After multiple polishing (e.g., N +1 times polishing), the cleaning solution after polishing may have a pH between pH of the N +1 th polishing solution and 7 (including 7).
In summary, in the polishing method of the present disclosure, after the semiconductor substrate 1 is polished by the first polishing liquid, the semiconductor substrate 1 is separated from the polishing pad 2, and the polishing pad 2 is cleaned by the cleaning liquid, the second polishing liquid can be sprayed on the polishing pad 2 to continue polishing the semiconductor substrate 1, and when the semiconductor structure is polished for multiple times, the polishing pad 2 does not need to be replaced, so that the cost is saved, the operation is simpler, and the polishing effect is more precise.
It is to be understood that the disclosure is not limited in its application to the details of construction and the arrangements of the components set forth in the specification. The present disclosure is capable of other embodiments and of being practiced and carried out in various ways. The foregoing variations and modifications are within the scope of the present disclosure. It should be understood that the disclosure disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present disclosure. The embodiments described in this specification illustrate the best mode known for carrying out the disclosure and will enable those skilled in the art to utilize the disclosure.
Claims (17)
1. A method of polishing a semiconductor structure, comprising:
providing a semiconductor substrate, wherein the semiconductor substrate is provided with a functional film layer;
providing a grinding pad, and spraying first grinding liquid on the grinding pad;
placing the semiconductor substrate on the grinding pad, and grinding the functional film layer;
separating the semiconductor substrate from the grinding pad, and spraying a first cleaning solution to the grinding pad to clean the grinding pad;
spraying a second grinding liquid on the cleaned grinding pad;
placing the semiconductor substrate on the grinding pad, and grinding the functional film layer again;
wherein the first polishing fluid is different from the second polishing fluid.
2. The method of claim 1, wherein the functional film layer comprises:
a first film layer comprising a plurality of film layer patterns;
and the second film layer is formed on the first film layer and filled between the film layer patterns.
3. The method of claim 2, wherein the placing the semiconductor substrate on the polishing pad and polishing the functional film layer comprises: grinding the second film layer by using the first grinding liquid to enable the surface of the second film layer to be flush with the surface of the first film layer;
the step of placing the semiconductor substrate on the grinding pad and grinding the functional film layer again comprises the following steps: and grinding the first film layer by using the second grinding liquid to enable the surface of the first film layer to be lower than the surface of the second film layer.
4. The method of claim 2, wherein the placing the semiconductor substrate on the polishing pad and polishing the functional film layer comprises: grinding the second film layer by using the first grinding liquid to remove the second film layer with a first preset thickness;
the step of placing the semiconductor substrate on the grinding pad and grinding the functional film layer again comprises the following steps: and continuously grinding the second film layer with the first preset thickness removed by using the second grinding liquid to enable the surface of the second film layer to be lower than the surface of the first film layer.
5. The method of claim 1, wherein the functional film layer is a single film layer, the placing the semiconductor substrate on the polishing pad, and the polishing the functional film layer comprises: grinding the functional film layer by using the first grinding liquid to remove the functional film layer with a second preset thickness;
the step of placing the semiconductor substrate on the grinding pad and grinding the functional film layer again comprises the following steps: and continuously grinding the functional film layer with the second preset thickness by using the second grinding liquid.
6. The method of claim 1, wherein the first cleaning fluid is deionized water and/or a surfactant.
7. The method of claim 6, wherein the surfactant is a combination of one or more of a cationic surfactant, a nonionic surfactant, and an anionic surfactant.
8. The method of claim 1, wherein the pH of the first polishing fluid is greater than the pH of the second polishing fluid.
9. The method according to claim 1, wherein the abrasive particles of the first polishing liquid are of a different type from the abrasive particles of the second polishing liquid.
10. The method of claim 1, wherein the first slurry has a pH A 1 The pH value of the second grinding liquid is A 2 The first mentionedThe pH value of a cleaning solution is B 1 ，A 1 And A 2 Average value of A v ＝(A 1 +A 2 ) /2 if A 1 ＞A 2 Then A is v -3(A 1 -A v )/4≤B 1 ≤A v +3(A 1 -A v ) (ii)/4; if A 2 ＞A 1 Then A is v -3(A 2 -A v )/4≤B 1 ≤A v +3(A 2 -A v )/4；
Wherein A is 1 、A 2 、A v 、B 1 Are all positive numbers.
11. The method of claim 10, wherein B1= Av.
12. The method of claim 1, wherein the flow rate of the first cleaning fluid is at least 500ml/min and the cleaning time of the first cleaning fluid is greater than or equal to 3 seconds.
13. The method according to claim 1, wherein the flow rates of the first polishing liquid and the second polishing liquid are 50 to 500ml/min, respectively.
14. The method of claim 1, wherein the functional film layer is at least one of a shallow trench isolation, an oxide layer, a metal tungsten layer, a metal copper layer, a polysilicon layer, a silicon nitride layer, and a back surface of a semiconductor substrate.
15. The method of claim 1, further comprising:
separating the functional film layer which is ground again from the grinding pad, and spraying a second cleaning solution on the grinding pad to clean the grinding pad;
spraying a third grinding fluid on the cleaned grinding pad;
placing the semiconductor substrate on the grinding pad, and continuously grinding the functional film layer;
if the functional layer still needs to be continuously ground after being ground, the method is repeated until the functional film layer is ground.
16. The method of claim 15, wherein the nth polishing slurry has a pH of a N The pH value of the N +1 th grinding liquid is A N+1 The pH value of the Nth cleaning solution is B N ，A N And A N+1 Average value of (A) Av' = (A) N +A N+1 ) /2 if A N ＞A N+1 Then Av' -3 (A) N -Av’)/4≤B N ≤Av’+3(A N -Av')/4; if A N+1 ＞A N Then Av' -3 (A) N+1 -Av’)/4≤B N ≤Av’+3(A N+1 -Av’)/4；
Wherein N is a positive integer and is more than or equal to 2; a. The N 、A N+1 、Av’、B N Are all positive numbers.
17. The method of any one of claims 1 to 16, further comprising:
after the semiconductor substrate is polished, separating the semiconductor substrate from the polishing pad;
and spraying a cleaning solution after grinding on the grinding pad to clean the grinding pad.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111054537.2A CN115781493A (en) | 2021-09-09 | 2021-09-09 | Method for polishing semiconductor structure |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111054537.2A CN115781493A (en) | 2021-09-09 | 2021-09-09 | Method for polishing semiconductor structure |
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