WO2022095456A1 - Method for grinding diamond substrate - Google Patents

Abstract

A method for grinding a diamond substrate, the method comprising grinding the diamond substrate by means of a grinding disk on which a soft abrasive capable of performing a solid phase chemical reaction with diamond is consolidated, and applying a transverse ultrasonic vibration with an amplitude of 1-20 μm and a frequency of 30-50 kHz along the radial direction of the grinding disk. By means of the transverse-ultrasonic-vibration-assisted friction contact between the soft abrasive and the diamond, the rate of the solid phase chemical reaction between the diamond and the soft abrasive in a contact area is promoted, and the grinding efficiency is greatly improved.

Description

A kind of grinding method of diamond substrate technical field

The invention belongs to the technical field of semiconductor material processing, in particular to a method for grinding a diamond substrate.

Background technique

Due to its high hardness, high wear resistance, good electrical insulation, low friction coefficient, high thermal conductivity, low thermal expansion coefficient, strong light transmission ability, good chemical stability and other superior properties, diamond is regarded as the most valuable material in the 21st century. It is a promising engineering material, and is widely used in high-tech fields such as machining, aerospace and military industry, and microelectronics. Diamond is an ultra-wide bandgap semiconductor material with unique electrical, optical, and acoustic properties. Devices prepared from new materials represented by diamond have excellent performance and have broad application prospects in many aspects. It can improve the working temperature limit of power devices, so that they can work in harsher environments; it can improve the power and efficiency of the devices, and improve the performance of equipment; it can broaden the luminous spectrum and realize full-color display. With the advancement of wide bandgap technology and the gradual maturity of material technology and device technology, its importance will gradually emerge. In the high-end field, it will gradually replace the first and second generation semiconductor materials and become the master of the electronic information industry.

Since diamond is a superhard material, it is very difficult to grind a diamond substrate in the traditional mechanical grinding process, whether using free abrasives or fixed abrasives, which is not only inefficient, but also prone to large damage. Therefore, some scholars have proposed a method for chemical mechanical grinding of diamond. The principle is to use the friction between the soft abrasive particles such as lanthanum and cerium with strong chemical activity and the diamond surface during the grinding process to gradually increase the temperature of the contact area. Under the coupling action of temperature and pressure, solid-phase reaction occurs between diamond and soft abrasive grains in the contact area to form a soft reaction layer (passivation layer), and then the soft abrasive grains remove the reaction layer mechanically. Numerous studies have shown that solid-phase reactive milling can obtain nanoscale smooth surfaces with very little damage or even no damage. However, in the process of solid-phase reaction grinding, due to the slow solid-phase reaction rate between diamond and soft abrasives, the grinding efficiency is low, which has become the bottleneck of the development of diamond solid-phase reaction grinding technology.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects of the prior art and provide a method for grinding a diamond substrate.

The technical scheme of the present invention is as follows:

A method for grinding a diamond substrate, comprising: grinding the diamond substrate with a grinding disc consolidating soft abrasives capable of solid-phase chemical reaction with diamond, and simultaneously applying an amplitude of 1-20 μm and a frequency of 1-20 μm along the radial direction of the grinding disc. It is a transverse ultrasonic vibration of 30-50kHz to increase the relative motion trajectory between the soft abrasive and the diamond substrate surface, increase the contact area between the soft abrasive and the diamond substrate surface, and improve the interface energy of the solid-phase chemical reaction between the soft abrasive and the diamond substrate. , and accelerate the removal of the passivation layer generated by the solid-phase chemical reaction with soft abrasives.

In a preferred embodiment of the present invention, the soft abrasive includes at least one of boron nitride, diamond, boron carbide and aluminum oxide.

In a preferred embodiment of the present invention, the particle size of the soft abrasive is 5-25 μm.

In a preferred embodiment of the present invention, the soft abrasive is bonded and cured into an abrasive block by auxiliary materials.

Further preferably, the auxiliary material includes a binding agent.

More preferably, the bonding agent includes resin bonding agent, ceramic bonding agent and metal bonding agent.

In a preferred embodiment of the present invention, the material of the base of the grinding disc is metal.

In a preferred embodiment of the present invention, the moving direction of the transverse ultrasonic vibration is perpendicular to and in the same plane as the sliding direction of the soft abrasive on the surface of the diamond substrate, so that the soft abrasive makes a sinusoidal curve on the surface of the diamond substrate sports.

In a preferred embodiment of the present invention, the sliding speed of the soft abrasive on the surface of the diamond substrate is 1-20 m/s.

In a preferred embodiment of the present invention, the transverse ultrasonic vibration is applied to a grinding disc or a diamond substrate.

The beneficial effects of the present invention are:

1. The present invention adopts transverse ultrasonic vibration to assist the frictional contact between the soft abrasive and the diamond, which promotes the rate of solid-phase chemical reaction between the diamond and the soft abrasive in the contact area, and greatly improves the grinding efficiency.

2. The transverse ultrasonic vibration in the present invention not only improves the trajectory of the soft abrasive and the surface of the diamond substrate, but also improves the surface contact area between the soft abrasive and the diamond substrate, thereby improving the solid-phase chemical reaction between the soft abrasive and the diamond. rate.

3. The transverse ultrasonic vibration in the present invention can increase the interface energy of the reaction between the soft abrasive and the diamond contact surface, thereby increasing the interface temperature of the solid-phase chemical reaction between the soft abrasive and the diamond, resulting in an increase in the solid-phase chemical reaction rate.

4. The transverse ultrasonic vibration in the present invention can accelerate the mechanical removal, that is, accelerate the removal of the product (passivation layer) by the soft abrasive, so that the new contact surface and the soft abrasive continue to undergo a solid-phase chemical reaction, thereby increasing the rate of the solid-phase chemical reaction. .

Description of drawings

FIG. 1 is a schematic diagram of a solid-phase chemical reaction in an embodiment of the present invention.

2 is a schematic structural diagram of a metal grinding wheel grinding disc combined with soft abrasives in an embodiment of the present invention, and the arrows in the figure are the directions of transverse ultrasonic vibration.

FIG. 3 is a schematic diagram of the motion trajectory of the soft abrasive assisted by transverse ultrasonic vibration in an embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be further illustrated and described below through specific embodiments in conjunction with the accompanying drawings.

Example 1

As shown in Figure 1, a method for grinding a diamond substrate is to use a metal grinding wheel grinding disc (as shown in Figure 2) that consolidates the soft abrasive that can react with diamond in a solid state to grind the diamond substrate to make the diamond substrate soft. Under the action of grinding pressure and friction, the abrasive has a solid-phase chemical reaction with the surface of the diamond substrate, and at the same time, a transverse ultrasonic vibration with an amplitude of 1-20μm and a frequency of 30-50kHz is applied along the radial direction of the grinding disc (applied to the grinding disc or diamond substrate). As shown in Figure 3, the movement direction of the transverse ultrasonic vibration is perpendicular to the sliding direction of the soft abrasive on the surface of the diamond substrate and is in the same plane, so that the soft abrasive moves sinusoidally on the surface of the diamond substrate, and the soft abrasive The sliding speed of the abrasive on the surface of the diamond substrate is 1-20 m/s. The amplitude and frequency of the above-mentioned transverse ultrasonic vibration and the sliding speed of the soft abrasive can be adjusted and selected as required.

The invention adopts transverse ultrasonic vibration to assist the frictional contact between the soft abrasive and the diamond, promotes the solid-phase chemical reaction rate between the diamond and the soft abrasive in the contact area, and greatly improves the grinding efficiency. The transverse ultrasonic vibration not only improves the trajectory of the soft abrasive and the surface of the diamond substrate, but also increases the surface contact area between the soft abrasive and the diamond substrate, thereby increasing the rate of solid-phase chemical reaction between the soft abrasive and the diamond. The interface energy of the reaction between the soft abrasive and the diamond contact surface, thereby increasing the interface temperature of the solid-phase chemical reaction between the soft abrasive and the diamond, resulting in an increase in the rate of the solid-phase chemical reaction; it can accelerate mechanical removal, that is, to accelerate the effect of the soft abrasive on the product (passivation layer) Removal, so that the new contact surface and the soft abrasive particles continue to undergo a solid-phase chemical reaction, thereby increasing the rate of the solid-phase chemical reaction.

The above-mentioned soft abrasives include at least one of boron nitride, diamond, boron carbide and aluminum oxide, and have a particle size of 5-25 μm, which can be selected as required, as shown in Table 1 below. The above-mentioned soft abrasive is bonded and solidified into a grinding block by auxiliary materials including a binder, and the binder includes a resin bond, a ceramic bond and a metal bond. The concentration of the soft abrasive in the bond can be adjusted and selected as required. The rigidity of the metal grinding wheel grinding disc can also be adjusted according to the surface shape accuracy requirements of the machined parts.

Table 1 Principles and critical conditions of solid-phase chemical reaction between several main soft abrasives and diamond

The above-mentioned transverse ultrasonic vibration is used to assist the solid-phase chemical reaction, and the motion trajectory, motion contact area and friction surface temperature of the soft abrasive are calculated as follows:

(1) The motion trajectory is calculated as follows:

Abrasive particle motion equation: X=v _B *t

Y=acosωt

Velocity equation: X direction: v _B

Y direction: v(t)=aωsinωt

Then the displacement of the next cycle of vibration is:

The displacement of the next cycle without vibration is:

L=v _B *T

Then the trajectory increases the efficiency:

Assuming a=μm f=30-50kHz v _B =1-20m/s D _{abrasive grain} =5μm

When the speed V _s and the amplitude a are constant, the relationship between the trajectory increasing efficiency and the frequency f is as follows:

a=20μm, Vs =1m/s	Displacement L without vibration	Displacement L 1 under vibration	Increase rate η 1
f=30kHz	33.33333	88.99637	166.9891%
f=35kHz	28.57143	86.93542	204.2740%
f=40kHz	25.0000	85.52523	242.1009%
f=45kHz	22.2222	84.51523	280.3185%
f=50kHz	20.0000	83.76550	318.8275%

When the speed V _s and the frequency f remain unchanged, the relationship between the trajectory increasing efficiency and the amplitude a is as follows:

V s = 1m/s, f = 40kHZ	Displacement L without vibration	Displacement L 1 under vibration	Increase rate η 1
a=1μm	25	25.39023	1.560910%
a=5μm	25	33.01646	32.06582%
a=10μm	25	48.78747	95.18988%
a=15μm	25	66.74728	166.9891%
a=20μm	25	85.52523	242.1009%

When the amplitude a and the frequency f are unchanged, the relationship between the trajectory increasing efficiency and the speed V _s is as follows:

a=20μm, f=40kHZ	Displacement L without vibration	Displacement L 1 under vibration	Increase rate η 1
V s =1m/s	25	85.52523	242.1009%
V s =5m/s	125	152.2544	21.80349%
V s = 10m/s	250	265.1126	6.045047%
V s = 15m/s	375	385.3157	2.750852%
V s = 20m/s	500	507.8045	1.560910%

It can be seen from the above three tables that the increase rate of the motion trajectory of abrasive particles under ultrasonic vibration and without vibration increases with the increase of ultrasonic frequency and amplitude, and decreases with the increase of sliding speed.

(2) The contact area of motion is calculated as follows:

For abrasive particles with different particle sizes, when their moving speed, ultrasonic frequency and amplitude are constant, their moving trajectory is also unchanged, but their moving contact area is changed.

Assuming a=15μm f=50kHz T=1/fω=2πfD _{abrasive grains} =5-25μm

v _a = aω = 15 × 10 ^-6 × 2πf = 1.8852m/s v _B = 1m/s

The moving contact area is calculated by Matlab as follows:

It can be seen from the above table that with the increase of the particle size of the abrasive particles, the increase rate of the contact area of the abrasive particles with the diamond under ultrasonic vibration and without vibration gradually decreases. This is because as the particle size of the abrasive grains increases, the overlap ratio of the contact area with the diamond will continue to increase during the movement. However, the increase of the overlap ratio will reduce the rate of solid-phase reaction between the abrasive grains and the diamond. On the other hand, the particle size of the abrasive particles should not be too small. If the particle size is too small, the distance between the abrasive particles will be too small, which will weaken the ability of the grinding wheel to accommodate and remove chips.

(3) The friction surface temperature is calculated as follows:

Assuming a=15μm f=50kHz T=1/fω=2πfD _{abrasive grain} =5μm

v _a = aω = 15 × 10 ^-6 × 2πf = 4.713m/s v _B = 1m/s

Friction surface flash point temperature:

Then the frictional flash point temperature increases the efficiency:

Average friction for the next cycle of vibration:

when

RMS value of vibration velocity in one cycle:

The average value of the vibration velocity in one cycle:

Take valid values as an example:

Take the average as an example:

From the perspective of energy conservation, in one cycle: E _k1 +E ₁ =E _k2 +W _f (E _k1 is the initial kinetic energy, E _k2 is the final kinetic energy, E ₁ is the ultrasonic vibration energy, and W _f is the work of friction) , the surface temperature will increase substantially with the increase of the energy of the interface.

The flash point contact temperature θ _f is generated by the friction between the substrate and the abrasive particles, and the average temperature θ _b is the average temperature of the two sliding contact objects. Then the maximum temperature θ _c of the local surface is: θ _c =θ _f +θ _b

Then the average temperature of the two sliding contact objects increases the efficiency

Then the increase efficiency of surface temperature, taking the effective value as an example: η=η ₂ +η ₃ =64.2686%

Take the average value as an example: η=η ₂ +η ₃ =51.7886%

Note: v _B : sliding velocity; a: amplitude; L ₁ : moving length of abrasive particles under vibration; L: moving length of abrasive particles without vibration; μ: friction coefficient without vibration; μ _f : friction coefficient under vibration; N: load; V: relative velocity; E: elastic modulus; K: thermal conductivity; C: specific heat capacity; ρ: density; H: surface contact hardness; v _a : amplitude of vibration velocity;; v(t): vibration velocity; θ: surface contact temperature without vibration; θ _f : surface contact temperature under vibration.

The above are only the preferred embodiments of the present invention, so the scope of implementation of the present invention cannot be limited accordingly, that is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the description should still be covered by the present invention. In the range.

Industrial Applicability

The invention discloses a method for grinding a diamond substrate, which comprises grinding the diamond substrate with a grinding disc consolidated with soft abrasives capable of solid-phase chemical reaction with diamond, and simultaneously applying an amplitude of 1- Transverse ultrasonic vibration of 20 μm and a frequency of 30-50 kHz. The invention adopts the raw transverse ultrasonic vibration to assist the frictional contact between the soft abrasive and the diamond, promotes the solid-phase chemical reaction rate between the diamond and the soft abrasive in the contact area, greatly improves the grinding efficiency, and has industrial practicability.

Claims (9)

1. A method for grinding a diamond substrate, characterized in that: comprising: grinding the diamond substrate with a grinding disc that consolidates soft abrasives capable of solid-phase chemical reaction with diamond, while applying an amplitude of 1 along the radial direction of the grinding disc -Transverse ultrasonic vibration of 20 μm and a frequency of 30-50 kHz, the particle size of the soft abrasive is 5-25 μm.
2. The grinding method of claim 1, wherein the soft abrasive comprises at least one of boron nitride, diamond, boron carbide and aluminum oxide.
3. The grinding method according to claim 1, wherein the soft abrasive is bonded and solidified into a grinding block by auxiliary materials.
4. The grinding method of claim 1, wherein the material of the base of the grinding disc is metal.
5. The grinding method according to claim 1, wherein the moving direction of the transverse ultrasonic vibration is perpendicular to and in the same plane as the sliding direction of the soft abrasive on the surface of the diamond substrate, so that the soft abrasive is in the same plane on the surface of the diamond substrate. The surface makes a sinusoidal motion.
6. The grinding method according to claim 1, wherein the sliding speed of the soft abrasive on the surface of the diamond substrate is 1-20 m/s.
7. A method for grinding a diamond substrate as claimed in claim 1 or 6, characterized in that the sliding speed of the soft abrasive on the surface of the diamond substrate is 1 m/s, the radial applied amplitude of the grinding disc is 20 μm, and the frequency is 40 kHz.
8. The grinding method according to claim 1, characterized in that the amplitude of the vibration frequency a=15μm, the vibration frequency f=50kHz, the sliding speed v _s =1m/s, and the particle size of the abrasive particles is 5-15μm.
9. The grinding method of claim 1, wherein the transverse ultrasonic vibration is applied to the grinding disc or the diamond substrate.

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