High-density crack-defect-free thin film and preparation method thereof

Abstract

The invention belongs to the technical field of thin film material preparation, and relates to a high-density crack-defect-free thin film and a preparation method thereof.The preparation method comprises the steps that firstly, surface cleaning and modification are conducted on a wafer, specifically, under the air pressure of 50-100 Pa, the power of 250-350 W, the temperature of 280-350 DEG C and the inert gas flow of 2000-2500 sccm, plasma bombardment is conducted on the wafer for 10-20 seconds; 2) performing enhanced ion bombardment on the wafer for 50-100 seconds under the conditions that the air pressure is 30-50 Pa, the power is 500-600 W, the temperature is 280-350 DEG C and the inert gas flow is 2500-3000 sccm; 3) bombarding the wafer for 30-100 seconds by using the plasma under the conditions that the air pressure is 100-150Pa, the power is 150-350W, the temperature is 280-350 DEG C, the flow of the inert gas is 2000-2500sccm, and the flow of the active gas is 100-300sccm; 2) thin film deposition: depositing a stable layer: forming the stable layer on the wafer; depositing a growth layer: forming the growth layer on the stable layer; and depositing a compact layer: forming the compact layer on the growth layer. The defect of film formation cracks caused by unbalanced release of local stress of a film layer can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of film material preparation, and relates to a film and a preparation method thereof, in particular to a high-density crack-free film and a preparation method thereof. Background Art

[0002] Ion chemical vapor deposition (ICCVD) is a thin film growth technology that utilizes plasma for low-temperature deposition and is widely used in the semiconductor field. However, due to material properties, planar defects are prone to appearing on wafers during the grinding and cutting process. During deposition, improper process control and other factors can lead to electrostatic adsorption between the carrier and the wafer surface. This can cause particles to adsorb before or during deposition, leading to cracks in the film formation process. Because these cracks are covered by photoresist under yellow light, they are difficult to detect during inspection. However, during the subsequent etching process, ion bombardment can cause the cracks to detach cells, forming clustered cavities that seriously affect the quality and performance of the finished product.

[0003] Therefore, how to reduce film crack defects during thin film deposition and improve the quality of the thin film is an urgent problem to be solved in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-density crack-free film and a preparation method thereof. The present invention is a new heterogeneous layer deposition film process that can reduce film crack defects caused by unbalanced local stress release in the film layer. A specific plasma surface treatment method is introduced before the deposition process to regulate the electrostatic adsorption effect of the chip, weaken the adsorption efficiency of particles on the chip surface, and improve the stress release between the deposited film layer and the chip. At the same time, the chip surface is micro-roughened to increase the bonding force between the film and the chip, further improve the adhesion and stability of the film, ensure the integrity of the deposited film layer, and improve the consistency of the graphics within the chip after the composite structure is graphically transferred.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a high-density crack-free film, characterized by comprising the following steps:

[0007] 1) Cleaning and modifying the wafer surface, which specifically includes:

[0008] 1) Plasma bombards the wafer for 10-20 seconds at a pressure of 50-100 Pa, a power of 250-350 W, a temperature of 280-350°C, and an inert gas flow rate of 2000-2500 sccm;

[0009] 2) Enhanced ion bombardment of the wafer for 50-100 seconds at a pressure of 30-50 Pa, a power of 500-600 W, a temperature of 280-350°C, and an inert gas flow rate of 2500-3000 sccm;

[0010] 3) Plasma bombards the wafer for 30-100 seconds at a pressure of 100-150 Pa, a power of 150-350 W, a temperature of 280-350°C, a flow rate of 2000-2500 sccm of inert gas and 100-300 sccm of reactive gas;

[0011] 2) Thin film deposition, which specifically includes:

[0012] Deposition of stabilization layer: forming a stabilization layer on the wafer;

[0013] Deposition growth layer: forming a growth layer on the stable layer;

[0014] Deposition of dense layer: A dense layer is formed on the growth layer.

[0015] Preferably, in the step 1), the steps 2) and 3) are repeated alternately 2-3 times and nitrogen gas is introduced for 10 seconds at 1000 sccm after each repetition.

[0016] Preferably, in step 1) when cleaning and modifying the surface of the wafer, the inert gas used is nitrogen or argon, and the active gas is hydrogen.

[0017] Preferably, RF ignition is performed before the wafer surface is cleaned and modified in step 1), specifically, the plasma is ignited and stabilized for 5-10 seconds at a pressure of 50-100 Pa, a RF power of 50-200 W, a temperature of 280-350° C., and an inert gas flow rate of 1000-2000 sccm.

[0018] Preferably, the wafer is preheated before the RF ignition, specifically by heating the wafer to 280-350° C. at a rate of 5-10° C. / min and maintaining the temperature in a vacuum state for 60-120 seconds.

[0019] Preferably, the depositing stabilization layer is specifically performed by depositing for 20-50 seconds under the conditions of 50-80 Pa pressure, 250-350 W power, 280-350° C. temperature, 2000-2500 sccm N 2 , 50-100 sccm SiH 4 and 2000-2500 sccm N 2 O to form a stabilization layer on the wafer.

[0020] Preferably, the deposited growth layer is specifically deposited for 1000-1500 seconds under the conditions of 150-200 Pa pressure, 300-400 W power, 280-350° C. temperature, 2000-2500 sccm N 2 , 150-200 sccm SiH 4 and 1500-2000 sccm N 2 O to form a growth layer on the stabilization layer.

[0021] Preferably, the depositing of the dense layer is specifically: sputtering and cleaning for 20-50 seconds under the conditions of 70-120 Pa pressure, 250-300 W power, 280-350° C. temperature, 2000-2500 sccm N2, 100-150 sccm SiH4 and 2000-2500 sccm N2O to form a dense layer on the growth layer.

[0022] Preferably, the wafer is a sapphire wafer.

[0023] In addition, the present invention also provides a high-density crack-free film, characterized in that it is prepared using the preparation method described above.

[0024] Compared with the prior art, the high-density crack-free film and the preparation method thereof of the present invention have one or more of the following beneficial technical effects:

[0025] 1. The present invention reduces the energy and reaction activity of the wafer surface through special gas ionization cleaning and electrostatic adsorption control. The -OH groups after hydrogen passivation form strong covalent bonds with the sediment, reducing the electrostatic adsorption effect on the wafer surface. The micro-roughened surface increases the bonding force between the film and the wafer, improves the adhesion and stability of the film, and ensures the integrity of the deposited film layer.

[0026] 2. The special gas ionization cleaning technology adopted in the present invention is simple and easy to use, low in cost, will not cause damage to the coating equipment, and is easy to integrate with the existing plasma chemical vapor deposition technology.

[0027] 3. The present invention improves the quality and performance of the coating and reduces the occurrence of cavity and crack defects. Experimental results show that the surface cluster defects of the silicon dioxide film prepared by the technology provided by the present invention are significantly reduced, and the quality of the film is significantly improved. Compared with the traditional process, the defect rate is reduced by 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a flow chart of a method for preparing a high-density crack-free film.

[0029] Figure 2 It is a flow chart of wafer pre-processing of the present invention.

[0030] Figure 3is a flow chart of thin film deposition of the present invention. DETAILED DESCRIPTION

[0031] Before describing in detail any embodiment of the present invention, it should be understood that the present invention is not limited in its application to the construction and arrangement details of the components set forth in the following description or illustrated in the following figures. The present invention is capable of other embodiments and can be practiced or carried out in various ways. In addition, it should be understood that the words and terms used herein are for descriptive purposes and should not be considered restrictive. The use of "including" or "having" and their variations herein is intended to cover the items and their equivalents set forth below and additional items. Unless otherwise specified or limited, the terms "mounted", "connected", "supported" and "coupled" and their variations are used broadly and cover direct mounting and indirect mounting, connection, support and coupling. In addition, "connected" and "coupled" are not limited to physical or mechanical connections or couplings.

[0032] Furthermore, on the first hand, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore the above terms cannot be understood as limitations on the present invention; on the second hand, the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" cannot be understood as a limitation on the quantity.

[0033] Figure 1 The flow chart of the method for preparing a high-density crack-free film of the present invention is shown. Figure 1 As shown, the method for preparing a high-density crack-free film of the present invention comprises the following steps:

[0034] 1. Wafer pretreatment

[0035] The present invention can remove impurities attached to the wafer surface through wafer pretreatment, while micro-roughening the wafer surface, releasing the stress between the wafer and the original position of the impurities, and can electrically modify the wafer surface to form saturated dangling bonds, thereby reducing electrostatic adsorption and improving the adhesion and stability of the film.

[0036] like Figure 2 As shown, the wafer pre-processing specifically includes:

[0037] 1. Preheat the chip.

[0038] The wafer is heated to 280-350°C at a constant rate of 5-10°C / min and maintained in a vacuum state (≤1×10-3Pa) for 60-120 seconds to preheat the wafer and ensure that the wafer temperature distribution is uniform and stable.

[0039] 2. RF starting.

[0040] At 50-100 Pa pressure, 50-200 W RF power, 280-350°C temperature, and 1000-2000 sccm inert gas (e.g., argon or nitrogen), the plasma is ignited and stabilized for 5-10 seconds. During RF ignition, the RF power is turned on to generate plasma and transport it toward the wafer. Low-power ignition achieves stable voltage and current in a short time. The RF power setting range avoids ignition failures caused by excessive impedance.

[0041] 3. Surface cleaning and modification.

[0042] Surface cleaning and modification are used to remove impurities attached to the wafer surface and to clean and modify the wafer surface, which specifically includes:

[0043] 1) Plasma bombards the wafer for 10-20 seconds at a pressure of 50-100 Pa, a power of 250-350 W, a temperature of 280-350° C., and an inert gas (eg, nitrogen or argon) flow rate of 2000-2500 sccm.

[0044] In the present invention, the power and the inert gas flow are gradually increased after the RF ignition, which can avoid excessive impedance. The inert gas is ionized into ions and active particles through ionization, bombarding the wafer surface to remove particles (metal impurities, organic impurities, inorganic impurities, etc.) on the wafer surface.

[0045] 2) Enhance ion bombardment of the wafer for 50-100 seconds at a pressure of 30-50 Pa, a power of 500-600 W, a temperature of 280-350° C., and an inert gas (eg, nitrogen or argon) flow rate of 2500-3000 sccm.

[0046] In the present invention, by increasing the power and inert gas flow rate, the ion density can be enhanced, fully bombarding the wafer surface, improving the bombardment intensity and efficiency. Plasma bombardment can also promote micro-roughening of the wafer surface and increase the bonding strength between the film and the wafer.

[0047] 3) Plasma bombards the wafer for 30-100 seconds at a pressure of 100-150 Pa, a power of 150-350 W, a temperature of 280-350° C., a flow rate of 2000-2500 sccm of inert gas (eg, nitrogen or argon) and a flow rate of 100-300 sccm of reactive gas (eg, hydrogen).

[0048] In the present invention, by introducing an appropriate amount of reactive gas (for example, hydrogen), ionization generates plasma, and hydrogen molecules are ionized into hydrogen ions (H+) and electrons (e-) under the effect of the plasma, and may be accompanied by the generation of a small amount of hydrogen free radicals (H·). The wafer surface is directed to carry out plasma bombardment, and the hydrogen ions and hydrogen free radicals bombard the surface of the wafer with higher energy density under the effect of the electric field. This bombardment process can not only remove residual impurities and pollutants on the wafer surface together with the inert ions, but more importantly, it allows the wafer surface to undergo a reduction reaction to remove trace oxides (such as the natural oxide layer) on the wafer surface, reduce the surface oxygen content, and expose a fresh Al atomic layer. The dangling bonds of the fresh atomic layer (i.e., the atomic valence electrons that are not bonded to other atoms) combine with the hydrogen atoms to form stable chemical bonds, thereby reducing the energy and reaction activity on the surface. The Al-OH groups after the hydrogen passivation form strong covalent bonds with the Si-O bonds in the sediment, and the adhesion is improved, providing a more uniform and stable substrate for subsequent silicon dioxide film deposition.

[0049] Preferably, the steps 2 and 3) are repeated 2-3 times for better results, and N2 1000 sccm is introduced for 10 seconds after each repetition. Among them, nitrogen ionization bombardment alone cannot solve the problems of oxide layer reduction and particle adsorption at the same time. At the same time, too long nitrogen ionization time may cause excessive nitridation of the wafer surface, reducing the surface oxidation effect of H2 ionization reduction. The use of alternating bombardment achieves a reduction in defect rate by dynamically switching the reaction mechanism. In the present invention, by repeating steps 2 and 3) 2-3 times, the surface roughness Ra of the wafer will reach 5-15nm (AFM detection, scanning range 10×10μm), and the surface oxygen content will be ≤0.5at%.

[0050] 2. Thin film deposition.

[0051] In the present invention, after the wafer is pretreated, a PECVD process may be used to deposit a thin film, such as a silicon dioxide thin film, on the surface of the pretreated wafer.

[0052] like Figure 3 As shown, the thin film deposition specifically includes:

[0053] 1. Sedimentation of stable layer.

[0054] Under the conditions of 50-80 Pa pressure, 250-350 W power, 280-350° C., 2000-2500 sccm N 2 , 50-100 sccm SiH 4 and 2000-2500 sccm N 2 O, deposition is performed for 20-50 seconds to form a stable layer on the wafer.

[0055] In the present invention, a non-equilibrium plasma is formed during the deposition of the stabilization layer. In the non-equilibrium plasma, electrons react with the deposition reaction gas to cause the reaction gas to decompose and form a mixture of ions and active groups (such as SiH3 + 、H + , O-, OH·, etc.). During the transport of active groups to the film growth surface, secondary reactions occur due to collisions and scattering between atoms, molecules, ions, and electrons in the reactants. The various primary and secondary reaction products that reach the growth surface are adsorbed and react with the surface, which can control the film production rate and combine with saturated dangling bonds on the wafer surface to ensure that the bonding force between atoms on the film surface is enhanced, reducing surface defects and vacancies.

[0056] 2. Sedimentary growth layer.

[0057] The growth layer is formed on the stabilization layer by deposition for 1000-1500 seconds under conditions of 150-200 Pa pressure, 300-400 W power, 280-350° C. temperature, 2000-2500 sccm N 2 , 150-200 sccm SiH 4 , and 1500-2000 sccm N 2 O.

[0058] In the present invention, during the process of depositing the growth layer, the deposition rate can be accelerated by precisely controlling the power, gas pressure, gas flow rate and other process parameters of the radio frequency power supply, thereby facilitating accelerated deposition and growth of the thin film to a desired thickness.

[0059] 3. Deposition of dense layer.

[0060] Sputter cleaning is performed for 20-50 seconds under the conditions of 70-120 Pa pressure, 250-300 W power, 280-350° C. temperature, 2000-2500 sccm N 2 , 100-150 sccm SiH 4 and 2000-2500 sccm N 2 O to form a dense layer on the growth layer.

[0061] In the present invention, during the process of depositing a dense layer, the film production speed can be controlled by precisely controlling process parameters such as the power, gas pressure, and gas flow of the radio frequency power supply, and the film surface is sputtered and cleaned to sputter off loosely bound particles, so that the number of surface particles is less than 20 particles per piece, thereby strengthening the adhesion between the film and the wafer, reducing the recombination rate of non-equilibrium carriers on the surface, and forming a dense and uniform deposited film.

[0062] Experimental results show that the silicon dioxide film prepared by the method for preparing a high-density crack-free film provided by the present invention has significantly reduced surface cluster defects and significantly improved film quality. Compared with traditional processes, the defect rate is reduced by 90%.

[0063] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art may, based on the principles of the present invention, modify or replace the technical solutions of the present invention with equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-density crack-free film, characterized in that: The following steps are involved: 1) Cleaning and modifying the wafer surface, which specifically includes: 1) Plasma bombards the wafer for 10-20 seconds at a pressure of 50-100 Pa, a power of 250-350 W, a temperature of 280-350°C, and an inert gas flow rate of 2000-2500 sccm; 2) Enhanced ion bombardment of the wafer for 50-100 seconds at a pressure of 30-50 Pa, a power of 500-600 W, a temperature of 280-350°C, and an inert gas flow rate of 2500-3000 sccm; 3) Plasma bombards the wafer for 30-100 seconds at a pressure of 100-150 Pa, a power of 150-350 W, a temperature of 280-350°C, a flow rate of 2000-2500 sccm of inert gas and 100-300 sccm of reactive gas; 2) Thin film deposition, which specifically includes: Deposition of stabilization layer: forming a stabilization layer on the wafer; Deposition growth layer: forming a growth layer on the stable layer; Deposition of dense layer: A dense layer is formed on the growth layer.

2. The method for preparing a high-density crack-free film according to claim 1, characterized in that: In the step 1), the steps 2) and 3) are alternately repeated 2-3 times, and nitrogen gas is introduced for 10 seconds at 1000 sccm after each repetition.

3. The method for preparing a high-density crack-free film according to claim 1, wherein: In the step 1) of cleaning and modifying the wafer surface, the inert gas used is nitrogen or argon, and the active gas is hydrogen.

4. The method for preparing a high-density crack-free film according to claim 1, wherein: Before the wafer surface is cleaned and modified in step 1), RF ignition is performed, specifically: plasma is ignited and stabilized for 5-10 seconds at a pressure of 50-100 Pa, a RF power of 50-200 W, a temperature of 280-350° C., and an inert gas flow rate of 1000-2000 sccm.

5. The method for preparing a high-density crack-free film according to claim 4, characterized in that: Before RF ignition, the wafer is preheated by heating the wafer to 280-350°C at a rate of 5-10°C / min and maintaining the temperature in a vacuum state for 60-120 seconds.

6. The method for preparing a high-density crack-free film according to claim 1, wherein: The depositing stabilization layer is specifically: depositing for 20-50 seconds under the conditions of 50-80 Pa pressure, 250-350 W power, 280-350° C. temperature, 2000-2500 sccm N 2 , 50-100 sccm SiH 4 and 2000-2500 sccm N 2 O to form a stabilization layer on the wafer.

7. The method for preparing a high-density crack-free film according to claim 1, wherein: The specific method of the deposition growth layer is: at 150-200Pa pressure, 300-400W power, 280-350℃ temperature, 2000-2500sccm N2, 150-200sccm SiH4 and 1500-2000sccm Under N2O conditions, deposition was performed for 1000-1500 seconds to form a growth layer on the stable layer.

8. The method for preparing a high-density crack-free film according to claim 1, wherein: The deposited dense layer is specifically: at 70-120Pa pressure, 250-300W power, 280-350℃ temperature, 2000-2500sccm N2, 100-150sccm SiH4 and 2000-2500sccm Under N2O conditions, sputter cleaning is performed for 20-50 seconds to form a dense layer on the growth layer.

9. The method for preparing a high-density crack-free film according to any one of claims 1 to 8, characterized in that: The wafer is a sapphire wafer.

10. A high-density crack-free film, characterized in that: The invention discloses a method for preparing the present invention according to any one of claims 1 to 9.

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