阅读说明：本技术 一种晶圆级异质结构的平坦化工艺方法 (Planarization process method for wafer-level heterostructure ) 是由 张姗 赵广宏 许姣 汪郁东 陈春明 张洪涛 申占霞 金小锋 于 2019-09-18 设计创作，主要内容包括：本发明提供一种晶圆级异质结构的平坦化工艺方法,实现基片表面为异种材质,非单一材质,特别是由金属材质和胶类材质的组成的表面结构的减薄抛光。减薄抛光的主要步骤有机械减薄、机械抛光、化学机械抛光。本发明解决了由于异质结构的硬度、密度不同,造成在平坦化过程中异质结构的切削速率不同,导致晶圆基片表面异质结构的高度差较大问题。采用本发明工艺方法,平坦化后的晶圆基片表面整体平整度可控制在(3～10)μm以内,其表面异质结构间高度差在1μm以内,表面金属材质区域的粗糙度小于1nm。(The invention provides a flattening process method of a wafer-level heterostructure, which realizes the thinning and polishing of a surface structure of a substrate, which is made of heterogeneous materials, non-single materials and particularly made of metal materials and glue materials. The main steps of thinning and polishing comprise mechanical thinning, mechanical polishing and chemical mechanical polishing. The invention solves the problem that the height difference of the heterostructure on the surface of the wafer substrate is larger due to different cutting rates of the heterostructure in the planarization process caused by different hardness and density of the heterostructure. By adopting the process method, the integral flatness of the surface of the wafer substrate after planarization can be controlled within (3-10) mu m, the height difference between surface heterogeneous structures is within 1 mu m, and the roughness of a surface metal material area is less than 1 nm.)

1. A planarization process method of a wafer level heterostructure is characterized by comprising the following steps:

(1) mechanically grinding, forming a heterostructure on the surface of the wafer substrate through micro-process processing, mechanically thinning the surface of the wafer substrate by using a chip thinning machine, removing the surface thickness, and reducing the height difference between the heterostructure on the surface of the wafer substrate;

(2) thickness measurement, namely measuring the thickness of the wafer surface heterostructure after mechanical grinding by adopting a thickness gauge; if the difference value of the measured thicknesses between the surface heterogeneous structures exceeds the preset thickness, repeating the step (1) until the measured thicknesses meet the requirements;

(3) mechanical polishing, namely using a chip thinning machine to mechanically polish the surface of the wafer after mechanical grinding, and further reducing the height difference of the heterogeneous structure on the surface of the wafer substrate;

(4) thickness measurement, namely measuring the thickness of the wafer surface heterostructure after mechanical polishing by adopting a thickness gauge; if the difference value of the measured thicknesses between the surface heterogeneous structures exceeds the preset thickness, repeating the step (3) until the measured thicknesses meet the requirements;

(5) chemical mechanical polishing, namely performing chemical mechanical polishing on the surface of the wafer substrate after mechanical grinding and polishing by using chemical mechanical polishing equipment to ensure that the heights of the heterogeneous structures on the surface of the wafer substrate are consistent, and the surface of the wafer substrate becomes a plane;

(6) and (5) thickness measurement, namely measuring the height difference between the heterogeneous structures on the surface of the wafer substrate after chemical mechanical polishing by adopting a probe type contourgraph, if the preset thickness is met, flattening the wafer-level heterogeneous structures, and otherwise, repeating the step (5) until the requirement is met.

2. The process of claim 1, wherein: the wafer-level heterostructure comprises a surface metal material (1), a surface glue material (2) and a substrate wafer (3); the surface metal material (1) is a plurality of cylinders which are distributed in a honeycomb shape and are vertical to the substrate wafer (3), surface glue materials (2) are arranged between every two adjacent cylinders, and height difference exists between the surface metal material (1) and the surface glue materials (2).

3. The process of claim 2, wherein: and removing the wafer substrate after mechanical grinding, mechanical polishing and chemical mechanical polishing to obtain a total thickness of more than 1 μm.

4. The process of claim 2, wherein: and (3) measuring the thickness of the heterostructure on the surface of the wafer substrate after mechanical grinding in the step (2), and controlling the height difference of the heterostructure on the surface of the wafer within 20 mu m.

5. The process of claim 2, wherein: and (4) measuring the thickness of the heterostructure on the surface of the wafer substrate after mechanical polishing in the step (4), and controlling the height difference of the heterostructure on the surface of the wafer within 10 mu m.

6. The process of claim 2, wherein: and (4) measuring the thickness of the heterogeneous structure on the surface of the wafer substrate after the chemical mechanical polishing in the step (6), wherein the height difference of the heterogeneous material structure on the surface of the wafer is controlled within 1 micrometer, the integral flatness of the surface of the wafer substrate is controlled within 5 micrometers, and the roughness of a structure area with the surface made of metal is controlled within 1 nm.

7. The process of claim 1, wherein: before the mechanical grinding in the step (1), the method further comprises the following steps:

the automatic sheet sticking method comprises the following steps of (1) sticking sheets, opening automatic sheet sticking equipment, heating a hot plate to a set temperature, putting a glass plate on the hot plate, heating for 3min, then coating the whole glass plate with wax, putting a substrate to be processed in the center of the glass plate, sticking sheets, and taking out the glass plate and the substrate from the automatic sheet sticking equipment after the sheets are stuck;

calibrating a disc, opening the wafer thinning machine, wherein the distance between an arm at one side of a swing arm and the edge of the cast iron disc is 1-3 cm, the disc calibration is carried out by adopting a steel disc calibrator, the disc calibration time is 30-60 min, and the rotating speed of the cast iron disc is 40-80 r/min;

and when mechanical grinding is carried out, the bonded substrate is placed in the center of a wafer sucking tool, vacuum sucking is carried out, proper grinding fluid is selected according to the process requirements for grinding, the grinding rotating speed is 30-60 r/min, the substrate is ground to the corresponding thickness, the substrate is taken down after grinding is finished, the substrate is washed clean by deionized water, and the substrate is swept and cleaned by a nitrogen gun.

8. The process of claim 1, wherein: and (3) during mechanical polishing, dismounting a cast iron disc of the wafer thinning machine, replacing the cast iron disc with a polishing disc, mounting a swing arm and a polishing solution cylinder, mounting the ground substrate on a wafer suction tool, adding a balancing weight on the wafer suction tool at the rotating speed of 40-80 r/min, and dropwise adding a cerium oxide suspension with the particle size of 3 mu m onto the polishing disc by using polishing solution.

9. The process of claim 1, wherein: when the chemical mechanical polishing in the step (5) is carried out, the method specifically comprises the following steps:

repairing a disc of chemical mechanical polishing equipment, starting the chemical mechanical polishing equipment, installing a disc repairing device, and repairing the disc by using deionized water under the pressure of-15 to-5 pounds for 20-40 min;

chemical mechanical polishing, lift off and repair a set ware, settle wafer centre gripping frock, adsorb the substrate after the mechanical polishing to the frock on, adopt the polishing solution to carry out chemical mechanical polishing to the wafer, polishing dish rotational speed 40 ~ 80 revolutions per minute, centre gripping frock rotational speed 30 ~ 60 revolutions per minute, the polishing solution ratio is, the polishing solution: hydrogen peroxide: 1:1:2 of water, 20-40 min of polishing time and-20 to-10 pounds of polishing pressure.

10. The process of claim 9, wherein: the polishing solution is silicon oxide polishing solution.

Technical Field

The invention relates to a flattening process method of a wafer-level heterostructure structure, in particular to a thinning and polishing process of a device structure surface consisting of a plurality of layers of stacked metal materials and photoresist materials on the surface of a semiconductor wafer substrate.

Background

With the rapid development of semiconductor technology, the size of electronic devices is gradually reduced, and the structure is more complicated. The design of multilayer stacked structural devices is becoming more and more widely used. When the number of stacked layers of the wafer substrate is increased, the surface fluctuation of the substrate is more remarkable. The main negative effect of surface relief is that the line width dimension is out of control during photolithography, and the subsequent process is difficult to make patterns on the photoresist with uneven surface thickness, which directly affects the use performance of the device.

The semiconductor wafer flattening process includes grinding and polishing homogeneous or heterogeneous structure on the surface of wafer substrate to eliminate material in certain thickness and ensure the structure height of the wafer substrate surface to be identical and the surface to be one plane.

The conventional mechanical thinning and polishing mode is carried out on a standard wafer thinning machine, and is realized by adopting a mode of oppositely grinding a grinding disc and a substrate, wherein the grinding material is a mixture of micron-sized aluminum oxide and a special dispersing solvent. The removal rate of grinding is faster, and different grinding time is set according to different structural layers. Aiming at the substrate with a single surface structure, the substrate has better thinning uniformity, roughness and smoothness. However, the surface structure of the substrate is two or more different materials, especially the metal material and the rubber material, and due to the difference of the hardness of the two materials, the cutting rate of the rubber material is faster than that of the metal material, so that the metal structure on the surface of the substrate is higher than that of the rubber structure, the integral flatness of the substrate is poor, and the thinning uniformity is poor.

In the chemical mechanical polishing, a wafer is clamped by a rotary polishing head and is pressed on the rotary polishing pad under certain pressure, polishing liquid consisting of abrasive particles and chemical solution flows between the wafer and the polishing pad, and the surface of the wafer is flattened under the combined action of chemistry and machinery. Aiming at substrates made of different materials, particularly metal materials and rubber materials, the influence of chemical solution polishing on the metal materials is larger than that of the rubber materials, the chemical solution polishing mainly cuts the metal materials on the surface, and further the height difference of the metal materials and the rubber materials is reduced. However, the chemical mechanical polishing is affected by the chemical influence, so that the cutting rate is slow, and a lot of working hours are consumed for the wafer substrate with large difference of surface structure height. In addition, the surface stress of the substrate is large due to the overlong thinning and polishing, which affects the stability of the substrate. Therefore, it is not feasible to perform the chemical mechanical polishing process on the surface of the substrate with the removal amount larger than 20 μm.

Patent CN104128879A proposes a process for thinning and polishing hard materials, which is characterized in that a synthetic copper disc grinding disc and grinding fluid are used; the polished surface of the hard material to be thinned is fully contacted with a synthetic copper disc grinding disc, and the hard material is subjected to home operation; the synthetic copper disc grinding disc rotates to thin and polish the hard material; and when the synthetic copper disc grinding disc rotates, the grinding fluid is dripped simultaneously. Aiming at the method, the surface material is a single hard material, the substrate with the same material on the surface can not be covered, and the process processing can not be carried out on the substrate with two different materials (metal materials and glue materials) on the surface; in addition, the index of the thinning and polishing process of the single hard material is too low, and the hard material is thinned and polished, so that the surface flatness of the product can be effectively controlled within 5 mu m, the removal rate of the product reaches 2-3.5 mu m/min, and the surface roughness of the product is less than 0.2 mu m. For subsequent micromachining processes such as photoetching, bonding and the like, the flatness of the subsequent micromachining processes is 5 microns, so that the uniformity of photoetching glue, the line precision of photoetching patterns, the bonding compactness and the like are greatly influenced.

CN1255741A discloses a method for planarization of a surface, which is characterized in that before planarization of the surface of a semiconductor wafer by chemical mechanical polishing, a layer of spin-on glass is coated on the insulating layer, a thermal baking step is performed to make the surface of the semiconductor wafer relatively flat, and then the surface of the semiconductor wafer is polished by chemical mechanical polishing. Aiming at the method, the problem that the surface of a substrate is not flat after surface chemical mechanical polishing due to the fact that a loose element area on the surface of the substrate is faster in cutting speed than a dense element area in the chemical mechanical polishing process is mainly solved. The compensation leveling operation is carried out on the surface of the substrate by coating a layer of spin-on glass on the upper surface of the substrate. And baking the substrate to solidify the substrate, and relieving the height difference caused by different cutting rates of a loose element area and a dense element area on the surface of the substrate in chemical mechanical polishing. The method is not applicable to a structure with uniformly distributed surfaces, a layer of spin-on glass is coated on the surface of the substrate and is baked at high temperature, and the method cannot be completely applicable to the service performance of a wafer substrate device and the temperature born by the wafer substrate device. The article also does not show the height difference between different element regions on the surface after the method is adopted.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method is suitable for the wafer substrate with a surface structure which is made of different materials and has non-single surface structure components, can effectively improve the flatness of the surface of the substrate, reduce the height difference between heterogeneous structures on the surface, optimize the surface roughness, and simultaneously ensure the effective removal rate of the wafer substrate aiming at the planarization process of the wafer substrate with large-size thickness and high flatness requirement.

The above purpose of the invention is mainly realized by the following technical scheme:

a planarization process method of a wafer level heterostructure comprises the following steps:

(1) mechanically grinding, forming a heterostructure on the surface of the wafer substrate through micro-process processing, mechanically thinning the surface of the wafer substrate by using a chip thinning machine, removing the surface thickness, and reducing the height difference between the heterostructure on the surface of the wafer substrate;

(2) thickness measurement, namely measuring the thickness of the wafer surface heterostructure after mechanical grinding by adopting a thickness gauge; if the difference value of the measured thicknesses between the surface heterogeneous structures exceeds the preset thickness, repeating the step (1) until the measured thicknesses meet the requirements;

(3) mechanical polishing, namely using a chip thinning machine to mechanically polish the surface of the wafer after mechanical grinding, and further reducing the height difference of the heterogeneous structure on the surface of the wafer substrate;

(4) thickness measurement, namely measuring the thickness of the wafer surface heterostructure after mechanical polishing by adopting a thickness gauge; if the difference value of the measured thicknesses between the surface heterogeneous structures exceeds the preset thickness, repeating the step (3) until the measured thicknesses meet the requirements;

(5) chemical mechanical polishing, namely performing chemical mechanical polishing on the surface of the wafer substrate after mechanical grinding and polishing by using chemical mechanical polishing equipment to ensure that the heights of the heterogeneous structures on the surface of the wafer substrate are consistent, and the surface of the wafer substrate becomes a plane;

(6) and (5) thickness measurement, namely measuring the height difference between the heterogeneous structures on the surface of the wafer substrate after chemical mechanical polishing by adopting a probe type contourgraph, if the preset thickness is met, flattening the wafer-level heterogeneous structures, and otherwise, repeating the step (5) until the requirement is met.

Furthermore, the wafer-level heterostructure comprises a surface metal material, a surface glue material and a substrate wafer; the surface metal material is a plurality of cylinders which are distributed in a honeycomb shape and are vertical to the substrate wafer, surface glue materials are arranged between every two adjacent cylinders, and height difference exists between the surface metal material and the surface glue materials.

Further, the total thickness of the removed wafer substrate after mechanical grinding, mechanical polishing and chemical mechanical polishing is more than 1 μm.

Further, the height difference of the wafer surface heterostructure is controlled within 20 μm after the mechanical grinding in the step (2) is performed on the wafer substrate surface heterostructure thickness measurement.

Further, in the step (4), the height difference of the heterostructure on the surface of the wafer is controlled within 10 μm in the thickness measurement of the heterostructure on the surface of the wafer substrate after mechanical polishing.

Further, in the step (6), the thickness of the heterostructure on the surface of the wafer substrate after the chemical mechanical polishing is measured, the height difference of the heterostructure on the surface of the wafer is controlled within 1 μm, the integral flatness of the surface of the wafer substrate is controlled within 5 μm, and the roughness of the structure region with the surface made of metal is controlled within 1 nm.

Further, before the mechanical grinding in step (1), the method further comprises:

the automatic sheet sticking method comprises the following steps of (1) sticking sheets, opening automatic sheet sticking equipment, heating a hot plate to a set temperature, putting a glass plate on the hot plate, heating for 3min, then coating the whole glass plate with wax, putting a substrate to be processed in the center of the glass plate, sticking sheets, and taking out the glass plate and the substrate from the automatic sheet sticking equipment after the sheets are stuck;

calibrating a disc, opening the wafer thinning machine, wherein the distance between an arm at one side of a swing arm and the edge of the cast iron disc is 1-3 cm, the disc calibration is carried out by adopting a steel disc calibrator, the disc calibration time is 30-60 min, and the rotating speed of the cast iron disc is 40-80 r/min;

and when mechanical grinding is carried out, the bonded substrate is placed in the center of a wafer sucking tool, vacuum sucking is carried out, proper grinding fluid is selected according to the process requirements for grinding, the grinding rotating speed is 30-60 r/min, the substrate is ground to the corresponding thickness, the substrate is taken down after grinding is finished, the substrate is washed clean by deionized water, and the substrate is swept and cleaned by a nitrogen gun.

And (3) further, when mechanical polishing is carried out in the step (3), a cast iron disc of the wafer thinning machine is detached, a polishing disc is replaced, a swing arm and a polishing liquid charging barrel are installed, the ground substrate is installed on a wafer sucking tool, a balancing weight is additionally arranged on the wafer sucking tool, the rotating speed is 40-80 r/min, and the polishing liquid is dropwise added onto the polishing disc through cerium oxide turbid liquid with the particle size of 3 microns.

Further, when the chemical mechanical polishing in the step (5) is performed, the following steps are specifically performed:

repairing a disc of chemical mechanical polishing equipment, starting the chemical mechanical polishing equipment, installing a disc repairing device, and repairing the disc by using deionized water under the pressure of-15 to-5 pounds for 20-40 min;

chemical mechanical polishing, lift off and repair a set ware, settle wafer centre gripping frock, adsorb the substrate after the mechanical polishing to the frock on, adopt the polishing solution to carry out chemical mechanical polishing to the wafer, polishing dish rotational speed 40 ~ 80 revolutions per minute, centre gripping frock rotational speed 30 ~ 60 revolutions per minute, the polishing solution ratio is, the silicon oxide polishing solution: hydrogen peroxide: 1:1:2 of water, 20-40 min of polishing time and-20 to-10 pounds of polishing pressure.

Compared with the prior art, the invention has the beneficial effects that:

the invention adopts a processing method combining mechanical grinding, mechanical polishing and chemical mechanical polishing, and utilizes the mechanical grinding and polishing to carry out primary planarization treatment on the initial state of the wafer substrate, thereby quickly removing the metal structure on the surface, roughly thinning the metal and the glue substances to the same level, ensuring the basic surface flatness and roughness of the wafer before the chemical mechanical polishing, and reducing the height difference between the heterogeneous structures on the surface. The advantage of high mechanical grinding and polishing speed is utilized to improve the thinning rate. In preparation for further chemical mechanical polishing of the wafer. Chemical mechanical polishing, which adopts mechanical action and polishing liquid with certain chemical removal action with a polishing product to act on the surface of a polished substrate simultaneously, so that the chemical action and the mechanical action act on the surface of the substrate in a synergistic manner, a high-pattern structure is removed at a higher speed to obtain a uniform surface heterostructure, and the influence of different grinding speeds among the surface heterostructures on the surface of the substrate can be effectively reduced. The height difference of the heterostructure on the surface of the wafer substrate obtained finally is within 1 mu m, the roughness of the surface is less than 1nm, and the integral flatness of the surface is within (3-10) mu m.

Drawings

FIG. 1 is a schematic top view of a wafer substrate heterostructure surface according to the present invention.

FIG. 2 is a cross-sectional view of a wafer substrate heterostructure surface according to the present invention.

FIG. 3 is a cross-sectional view of a wafer substrate heterostructure surface after mechanical lapping and polishing in accordance with the present invention.

FIG. 4 is a schematic cross-sectional view of a wafer substrate heterostructure surface after chemical polishing in accordance with the present invention.

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

As shown in fig. 1 and 2, the wafer level heterostructure includes a surface metal material 1, a surface glue material 2 and a base wafer 3; the surface metal material 1 is a plurality of cylinders which are distributed in a honeycomb shape and are vertical to the substrate wafer 3, the surface glue material 2 is arranged between the adjacent cylinders, and the height difference exists between the surface metal material 1 and the surface glue material 2. Due to different hardness and density of the heterostructure, the cutting rate of the heterostructure is different in the planarization process, and the problem of larger height difference of the heterostructure on the surface of the wafer substrate is caused.

(1) And (3) sticking, opening automatic sticking equipment, heating a hot plate to a set temperature (50-120) DEG C, placing a glass plate on the hot plate, heating for 3min, then coating the whole glass plate with wax, placing a substrate to be processed in the center of the glass plate, covering a cover, locking, and starting a sticking function. And after the bonding is finished, taking out the glass plate and the substrate from the automatic bonding unit.

(2) And (3) calibrating the disc, opening the wafer thinning machine, selecting a proper grinding liquid, installing the swing arm, wherein the distance between the arm at one side of the swing arm and the edge of the cast iron disc is (1-3) cm, calibrating the disc by adopting a steel disc calibrator, wherein the disc calibrating time is (30-60) min, and the rotating speed of the cast iron disc is (40-80) r/min.

(3) And (2) grinding, namely placing the bonded substrate in the step (1) at the center of a wafer sucking tool, sucking the substrate by using vacuum, selecting proper grinding fluid according to process requirements for grinding, wherein the grinding rotating speed is 30-60 r/min, grinding the wafer to a corresponding thickness, taking down the wafer after grinding, washing the wafer by using deionized water, and purging the wafer by using a nitrogen gun.

(4) And (4) thickness measurement, namely measuring the thickness of the ground substrate in the step (3) by using a thickness gauge to obtain the thickness of the substrate with preset requirements, wherein the height difference of the heterostructure on the surface of the substrate is controlled within 20 mu m. And (4) if the measured thickness is too large, repeating the step (3) until the measured thickness meets the requirement.

(5) And (3) mechanically polishing, namely dismounting a cast iron disc of the wafer thinning machine, replacing the cast iron disc with a polishing disc, mounting a swing arm and a polishing solution feed cylinder, mounting the ground substrate in the step (3) on a wafer sucking tool, adding a balancing weight on the wafer sucking tool at the rotating speed of (40-80) r/min, and dropwise adding a cerium oxide suspension with the particle size of 3 mu m on the polishing disc by using polishing solution.

(6) And (3) measuring the thickness of the substrate after mechanical polishing in the step (5) by using a thickness gauge to obtain the thickness of the substrate which is required to be preset, and controlling the height difference of the heterostructure on the surface of the substrate to be within 10 mu m, as shown in figure 3.

The invention carries out primary planarization treatment on the initial state of the wafer substrate by utilizing mechanical grinding and polishing, quickly removes the metal structure on the surface, roughly thins the metal and the glue substances to the same level, ensures the basic surface flatness and roughness of the wafer before carrying out chemical mechanical polishing and reduces the height difference between the heterogeneous structures on the surface.

The advantage of high mechanical grinding and polishing speed is utilized to improve the thinning rate. In preparation for further chemical mechanical polishing of the wafer.

(7) And (3) discharging, opening the automatic wafer sticking unit equipment, heating the hot plate to the set temperature of 50-120 ℃, putting the substrate in the step (6), taking down the substrate after 10-20 min, drying by a nitrogen gun, and putting the substrate in a special box.

(8) Repairing a disc by Chemical Mechanical Polishing (CMP) equipment, starting the CMP equipment, installing a disc repairing device, and repairing the disc by using deionized water under the pressure of (-15 to-5) lb for 20 to 40 min;

(9) chemical mechanical polishing, unloading the disc repairing device, installing a wafer clamping tool, adsorbing the substrate to the tool in the step (7), performing chemical mechanical polishing on the wafer by adopting polishing solution, wherein the rotation speed of the polishing disc (40-80) is rotated/min, the rotation speed of the clamping tool (30-60) is rotated/min, and the proportion of the polishing solution is silicon oxide polishing solution: hydrogen peroxide: 1:1:2 of water, 20-40 min of polishing time and (-20-10) lb of polishing pressure.

Chemical mechanical polishing, which adopts mechanical action and polishing liquid with certain chemical removal action with a polishing product to act on the surface of a polished substrate simultaneously, so that the chemical action and the mechanical action act on the surface of the substrate in a synergistic manner, a high-pattern structure is removed at a higher speed to obtain a uniform surface heterostructure, and the influence of different grinding speeds among the surface heterostructures on the surface of the substrate can be effectively reduced.

(10) And (4) taking down the substrate in the step (9), washing the substrate with deionized water, and purging with a nitrogen gun.

(11) And (3) checking, namely measuring the height difference between the surface heterogeneous structures of the polished substrate chemical mechanical wafer in the step (10) by using a probe type contourgraph, wherein the height difference is less than 1 micrometer, the integral flatness is controlled to be (3-10) micrometers, and the roughness of the surface is less than 1 nm. And placing in a special box for subsequent processing, as shown in figure 4.

The total thickness of the removed wafer substrate after mechanical grinding, mechanical polishing and chemical mechanical polishing is larger than 1 mu m.

The following examples of the present invention are given:

the planarization process for the wafer level heterostructure of the present embodiment is implemented as follows.

(1) And (3) sticking, opening the automatic sticking equipment, heating the hot plate to the set temperature of 90 ℃, placing the glass plate on the hot plate for heating for 3min, then coating the whole glass plate with wax, placing the substrate to be processed in the center of the glass plate, covering the cover, locking and starting the sticking function. And after the bonding is finished, taking out the glass plate and the substrate from the automatic bonding unit. And (3) measuring the thickness of the bonded substrate by using a thickness gauge to obtain the initial thickness, and measuring by using a five-point method, wherein the overall thickness of the surface is about (230-300) mu m.

(2) And (3) calibrating a disc, opening the wafer thinning machine, selecting an alumina grinding fluid, installing a swing arm, wherein the distance between the arm at one side of the swing arm and the edge of the cast iron disc is 3cm, calibrating the disc by adopting a steel disc calibrator, wherein the disc calibration time is 40min, and the rotating speed of the cast iron disc is 40 r/min.

(3) Grinding, namely placing the bonded substrate in the step (1) in the center of a wafer sucking tool, sucking the substrate by vacuum, selecting an aluminum oxide grinding fluid according to the process requirement for grinding, wherein the grinding speed is 30 revolutions per minute, grinding the wafer to the thickness of 200 mu m, taking down the wafer after grinding, washing the wafer by using deionized water, and purging the wafer by using a nitrogen gun.

(4) And (3) thickness measurement, namely measuring the thickness of the ground substrate in the step (3) by using a thickness gauge to obtain the thickness of the substrate with the preset requirement of (200-220) mu m, and controlling the height difference of the heterostructure on the surface of the substrate within 20 mu m. And (4) if the measured thickness is too large, repeating the step (3) until the measured thickness meets the requirement.

(5) And (3) mechanically polishing, namely dismounting a cast iron disc of the wafer thinning machine, replacing the cast iron disc with a polishing disc, mounting a swing arm and a polishing solution feed cylinder, mounting the ground substrate in the step (3) on a wafer sucking tool, adding a balancing weight on the wafer sucking tool at the rotating speed of 50 r/min, and dropwise adding a cerium oxide suspension with the particle size of 3 mu m on the polishing disc by using polishing solution.

(6) And (3) measuring the thickness of the substrate after mechanical polishing in the step (5) by using a thickness gauge, wherein the obtained thickness of the substrate is in the range of (180-185) mu m, and the height difference of the heterostructure on the surface of the substrate is controlled within 10 mu m.

(7) And (4) discharging, opening the automatic wafer sticking unit equipment, putting the substrate in the step (6) when the hot plate is heated to the set temperature of 90 ℃, taking down the substrate after 10min, drying by a nitrogen gun, and putting the substrate in a special box.

(8) Repairing a Chemical Mechanical Polishing (CMP) device, starting the CMP device, installing a disc repairing device, and repairing the disc by using deionized water under the pressure of-10 pounds for 30 min;

(9) chemical mechanical polishing, unloading the disc repairing device, installing a wafer clamping tool, adsorbing the substrate to the tool in the step (7), and performing chemical mechanical polishing on the wafer by adopting polishing solution, wherein the rotating speed of the polishing disc is 40 r/min, the rotating speed of the clamping tool is 30 r/min, and the proportion of the polishing solution is silicon oxide polishing solution: hydrogen peroxide: water 1:1:2, polishing time 20min, polishing pressure-10 lbs.

(10) And (4) taking down the substrate in the step (9), washing the substrate with deionized water, and purging with a nitrogen gun.

(11) And (4) checking, namely measuring the height difference between the surface heterogeneous structures of the polished substrate chemical mechanical wafer in the step (10) by using a probe type profilometer, wherein the height difference is less than 1 mu m, the integral flatness is controlled to be 5 mu m, and the roughness of the surface is less than 1 nm. Placing in a special box for subsequent processing.

From the above results, it can be seen that the wafer substrate after mechanical grinding, mechanical polishing and chemical mechanical polishing of the present invention greatly reduces the height difference of the surface heterostructure to less than 1 μm. In addition, the flatness of the surface of the substrate is improved and can be controlled within (3-10) mu m. The surface roughness of the wafer is measured by using an atomic force microscope, and the maximum roughness value is only 0.8nm by adopting a five-point measurement method.

The surface quality of the wafer substrate after planarization is greatly improved compared with that prepared by the prior planarization methods.

Those skilled in the art will appreciate that the details of the invention not described in detail in this specification are well within the skill of those in the art.